@article{lee_yu_dai_2024, title={Privacy-Preserving Decentralized Inference With Graph Neural Networks in Wireless Networks}, volume={23}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2023.3279442}, abstractNote={As an efficient neural network model for graph data, graph neural networks (GNNs) recently find successful applications for various wireless optimization problems. Given that the inference stage of GNNs can be naturally implemented in a decentralized manner, GNN is a potential enabler for decentralized control/management in the next-generation wireless communications. Privacy leakage, however, may occur due to the information exchanges among neighbors during decentralized inference with GNNs. To deal with this issue, in this paper, we analyze and enhance the privacy of decentralized inference with GNNs in wireless networks. Specifically, we adopt local differential privacy as the metric, and design novel privacy-preserving signals as well as privacy-guaranteed training algorithms to achieve privacy-preserving inference. We also define the SNR-privacy trade-off function to analyze the performance upper bound of decentralized inference with GNNs in wireless networks. To further enhance the communication and computation efficiency, we adopt the over-the-air computation technique and theoretically demonstrate its advantage in privacy preservation. Through extensive simulations on the synthetic graph data, we validate our theoretical analysis, verify the effectiveness of proposed privacy-preserving wireless signaling and privacy-guaranteed training algorithm, and offer some guidance on practical implementation.}, number={1}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Lee, Mengyuan and Yu, Guanding and Dai, Huaiyu}, year={2024}, month={Jan}, pages={543–558} }
 @article{jin_liu_huang_he_wu_dai_2024, title={Sign-Based Gradient Descent With Heterogeneous Data: Convergence and Byzantine Resilience}, volume={1}, ISSN={["2162-2388"]}, DOI={10.1109/TNNLS.2023.3345367}, abstractNote={Communication overhead has become one of the major bottlenecks in the distributed training of modern deep neural networks. With such consideration, various quantization-based stochastic gradient descent (SGD) solvers have been proposed and widely adopted, among which signSGD with majority vote shows a promising direction because of its communication efficiency and robustness against Byzantine attackers. However, signSGD fails to converge in the presence of data heterogeneity, which is commonly observed in the emerging federated learning (FL) paradigm. In this article, a sufficient condition for the convergence of the sign-based gradient descent method is derived, based on which a novel magnitude-driven stochastic-sign-based gradient compressor is proposed to address the non-convergence issue of signSGD. The convergence of the proposed method is established in the presence of arbitrary data heterogeneity. The Byzantine resilience of sign-based gradient descent methods is quantified, and the error-feedback mechanism is further incorporated to boost the learning performance Experimental results on the MNIST dataset, the CIFAR-10 dataset, and the Tiny-ImageNet dataset corroborate the effectiveness of the proposed methods.}, journal={IEEE TRANSACTIONS ON NEURAL NETWORKS AND LEARNING SYSTEMS}, author={Jin, Richeng and Liu, Yuding and Huang, Yufan and He, Xiaofan and Wu, Tianfu and Dai, Huaiyu}, year={2024}, month={Jan} }
 @article{liu_zhao_hosseinalipour_gao_huang_dai_2024, title={TDRA: A Truthful Dynamic Reverse Auction for DAG Task Scheduling Over Vehicular Clouds}, volume={73}, ISSN={["1939-9359"]}, DOI={10.1109/TVT.2023.3329141}, abstractNote={Vehicular Clouds (VCs) have attracted tremendous attention for offering commendable computing services to vehicles with computation-intensive tasks. Such tasks are often represented as Directed Acyclic Graphs (DAGs) consisting of several interdependent subtasks and directed edges. Processing of DAG tasks often needs pooling the computation resources of vehicles. However, the selfishness of vehicles prevents them from sharing their resources. To this end, we propose a Truthful Dynamic Reverse Auction (TDRA) mechanism to motivate vehicles to participate in service provisioning. To realize TDRA, we first propose an enumeration-based allocation strategy to optimally allocate subtasks among vehicles and obtain a Vickrey-Clarke-Groves (VCG)-based pricing strategy that can ensure the economic properties of individual rationality and truthfulness. Then, to deal with the high computational complexity of obtaining the optimal solution, we develop a near-optimal Dynamic Bilateral Ranking (DBR) allocation strategy to allocate subtasks within polynomial time and design a critical value-based pricing strategy that can also guarantee the two above-mentioned economic properties. Through simulating real-world movement traces of vehicles, we demonstrate that DBR outperforms the existing benchmarks, and verify our theoretical analysis on the economic properties of our developed pricing strategy.}, number={3}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Liu, Zhang and Zhao, Yifeng and Hosseinalipour, Seyyedali and Gao, Zhibin and Huang, Lianfen and Dai, Huaiyu}, year={2024}, month={Mar}, pages={4337–4351} }
 @article{maeng_chowdhury_guvenc_bhuyan_dai_2023, title={Base Station Antenna Uptilt Optimization for Cellular-Connected Drone Corridors}, volume={59}, ISSN={["1557-9603"]}, url={https://doi.org/10.1109/TAES.2023.3237994}, DOI={10.1109/TAES.2023.3237994}, abstractNote={Reliable wireless coverage in drone corridors is critical to enable a connected, safe, and secure airspace. To support beyond-visual-line-of-sight operations of aerial vehicles in a drone corridor, cellular base stations (BSs) can serve as a convenient infrastructure as they are widely deployed to provide seamless wireless coverage. However, antennas in the existing cellular networks are downtilted to optimally serve their ground users, which results in coverage holes at higher altitudes when they are used to serve drones. In this article, we consider the use of additional uptilted antennas at each cellular BS and optimize the uptilt angle to maximize the wireless coverage probability across a given drone corridor. Through numerical results, we characterize the optimal value of the antenna uptilt angle for a given antenna pattern as well as the minimum/maximum altitudes of the drone corridor.}, number={4}, journal={IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS}, author={Maeng, Sung Joon and Chowdhury, Md Moin Uddin and Guvenc, Ismail and Bhuyan, Arupjyoti and Dai, Huaiyu}, year={2023}, month={Aug}, pages={4729–4737} }
 @article{zhang_he_dai_2023, title={Blind Post-Decision State-Based Reinforcement Learning for Intelligent IoT}, volume={10}, ISSN={["2327-4662"]}, DOI={10.1109/JIOT.2023.3242613}, abstractNote={Recent years have witnessed a renewed interest in reinforcement learning (RL) due to the rapid growth of the Internet of Things (IoT) and their associated intelligent information processing and decision-making demands. As the slow learning speed is one of the major stumbling blocks of the classic RL algorithms, substantial efforts have been devoted to developing faster RL algorithms. Among them, post-decision state (PDS) learning is a prominent one, which can often improve the learning speed by orders of magnitude by exploiting the structural property of the underlying Markov decision processes (MDPs). However, conventional PDS learning requires prior information about the PDS transition probability, which may not be always available in practice. To lift this limitation, a novel blind PDS (b-PDS) learning algorithm is proposed in this work by leveraging the generic two-timescale stochastic approximation framework. By introducing an extra estimating procedure about the PDS transition probability, b-PDS learning can achieve a similar improvement of learning speed as conventional PDS learning while excluding the need for prior information. In addition, by analyzing the globally asymptotically stable equilibrium of the corresponding ordinary differential equation (o.d.e.), the convergence and optimality of b-PDS learning are established. Moreover, extensive simulation results are provided to validate the effectiveness of the proposed algorithm. Over the considered random MDPs, it has been observed that, to reach 90% of the best possible time average reward, the proposed b-PDS learning can reduce the learning time by 70% compared to $Q$ -learning and 30% compared to Dyna.}, number={12}, journal={IEEE INTERNET OF THINGS JOURNAL}, author={Zhang, Jingzhe and He, Xiaofan and Dai, Huaiyu}, year={2023}, month={Jun}, pages={10605–10620} }
 @article{reza_rahmati_wu_dai_2023, title={CGBA: Curvature-aware Geometric Black-box Attack}, ISSN={["1550-5499"]}, DOI={10.1109/ICCV51070.2023.00018}, abstractNote={Decision-based black-box attacks often necessitate a large number of queries to craft an adversarial example. Moreover, decision-based attacks based on querying boundary points in the estimated normal vector direction often suffer from inefficiency and convergence issues. In this paper, we propose a novel query-efficient curvature-aware geometric decision-based black-box attack (CGBA) that conducts boundary search along a semicircular path on a restricted 2D plane to ensure finding a boundary point successfully irrespective of the boundary curvature. While the proposed CGBA attack can work effectively for an arbitrary decision boundary, it is particularly efficient in exploiting the low curvature to craft high-quality adversarial examples, which is widely seen and experimentally verified in commonly used classifiers under non-targeted attacks. In contrast, the decision boundaries often exhibit higher curvature under targeted attacks. Thus, we develop a new query-efficient variant, CGBA-H, that is adapted for the targeted attack. In addition, we further design an algorithm to obtain a better initial boundary point at the expense of some extra queries, which considerably enhances the performance of the targeted attack. Extensive experiments are conducted to evaluate the performance of our proposed methods against some well-known classifiers on the ImageNet and CIFAR10 datasets, demonstrating the superiority of CGBA and CGBA-H over state-of-the-art non-targeted and targeted attacks, respectively. The source code is available at https://github.com/Farhamdur/CGBA.}, journal={2023 IEEE/CVF INTERNATIONAL CONFERENCE ON COMPUTER VISION, ICCV}, author={Reza, Md Farhamdur and Rahmati, Ali and Wu, Tianfu and Dai, Huaiyu}, year={2023}, pages={124–133} }
 @article{ozturk_anjinappa_erden_chowdhury_guvenc_dai_bhuyan_2023, title={Channel Rank Improvement in Urban Drone Corridors Using Passive Intelligent Reflectors}, ISSN={["1095-323X"]}, DOI={10.1109/AERO55745.2023.10115741}, abstractNote={Multiple-input multiple-output (MIMO) techniques can help in scaling the achievable air-to-ground (A2G) channel capacity while communicating with drones. However, spatial multiplexing with drones suffers from rank-deficient channels due to the unobstructed line-of-sight (LoS), especially in millimeter-wave (mmWave) frequencies that use narrow beams. One possible solution is utilizing low-cost and low-complexity metamaterial-based intelligent reflecting surfaces (IRS) to enrich the multi path environment, taking into account that the drones are restricted to flying only within well-defined drone corridors. A hurdle with this solution is placing the IRSs optimally. In this study, we propose an approach for IRS placement with a goal to improve the spatial multiplexing gains, and hence, to maximize the average channel capacity in a predefined drone corridor. Our results at 6 GHz, 28 GHz, and 60 GHz show that the proposed approach increases the average rates for all frequency bands for a given drone corridor when compared with the environment with no IRSs present, and IRS-aided channels perform close to each other at sub-6 and mmWave bands.}, journal={2023 IEEE AEROSPACE CONFERENCE}, author={Ozturk, Ender and Anjinappa, Chethan K. and Erden, Fatih and Chowdhury, Md Moin Uddin and Guvenc, Ismail and Dai, Huaiyu and Bhuyan, Arupjyoti}, year={2023} }
 @article{lee_yu_dai_2023, title={Decentralized Inference With Graph Neural Networks in Wireless Communication Systems}, volume={22}, ISSN={["1558-0660"]}, DOI={10.1109/TMC.2021.3125793}, abstractNote={Graph neural network (GNN) is an efficient neural network model for graph data and is widely used in different fields, including wireless communications. Different from other neural network models, GNN can be implemented in a decentralized manner during the inference stage with information exchanges among neighbors, making it a potentially powerful tool for decentralized control in wireless communication systems. The main bottleneck, however, is wireless channel impairments that deteriorate the prediction robustness of GNN. To overcome this obstacle, we analyze and enhance the robustness of the decentralized GNN during the inference stage in different wireless communication systems in this paper. Specifically, using a GNN binary classifier as an example, we first develop a methodology to verify whether the predictions are robust. Then, we analyze the performance of the decentralized GNN binary classifier in both uncoded and coded wireless communication systems. To remedy imperfect wireless transmission and enhance the prediction robustness, we further propose novel retransmission mechanisms for the above two communication systems, respectively. Through simulations on the synthetic graph data, we validate our analysis, verify the effectiveness of the proposed retransmission mechanisms, and provide some insights for practical implementation.}, number={5}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Lee, Mengyuan and Yu, Guanding and Dai, Huaiyu}, year={2023}, month={May}, pages={2582–2598} }
 @article{tian_zhang_yang_jin_dai_2023, title={Distributed Learning Over Networks With Graph-Attention-Based Personalization}, volume={71}, ISSN={["1941-0476"]}, DOI={10.1109/TSP.2023.3282071}, abstractNote={In conventional distributed learning over a network, multiple agents collaboratively build a common machine learning model. However, due to the underlying non-i.i.d. data distribution among agents, the unified learning model becomes inefficient for each agent to process its locally accessible data. To address this problem, we propose a graph-attention-based personalized training algorithm (GATTA) for distributed deep learning. The GATTA enables each agent to train its local personalized model while exploiting its correlation with neighboring nodes and utilizing their useful information for aggregation. In particular, the personalized model in each agent is composed of a global part and a node-specific part. By treating each agent as one node in a graph and the node-specific parameters as its features, the benefits of the graph attention mechanism can be inherited. Namely, instead of aggregation based on averaging, it learns the specific weights for different neighboring nodes without requiring prior knowledge about the graph structure or the neighboring nodes' data distribution. Furthermore, relying on the weight-learning procedure, we develop a communication-efficient GATTA by skipping the transmission of information with small aggregation weights. Additionally, we theoretically analyze the convergence properties of GATTA for non-convex loss functions. Numerical results validate the excellent performances of the proposed algorithms in terms of convergence and communication cost.}, journal={IEEE TRANSACTIONS ON SIGNAL PROCESSING}, author={Tian, Zhuojun and Zhang, Zhaoyang and Yang, Zhaohui and Jin, Richeng and Dai, Huaiyu}, year={2023}, pages={2071–2086} }
 @article{liwang_gao_hosseinalipour_su_wang_dai_2023, title={Graph-Represented Computation-Intensive Task Scheduling Over Air-Ground Integrated Vehicular Networks}, volume={16}, ISSN={["1939-1374"]}, DOI={10.1109/TSC.2023.3270169}, abstractNote={This article investigates vehicular cloud (VC)-assisted task scheduling in an air-ground integrated vehicular network (AGVN), where tasks carried by unmanned aerial vehicles (UAVs) and resources of VCs are both modeled as graph structures. We consider a scenario in which resource-limited UAVs carry a set of computation-intensive graph tasks, which are offloaded to resource-abundant vehicles for processing. We formulate an optimization problem to jointly optimize the mapping between task components and vehicles, and transmission powers of UAVs, while addressing the trade-off between i) completion time of tasks, ii) energy consumption of UAVs, and iii) data exchange cost among vehicles. We show that this problem is a mixed-integer non-linear programming, and thus NP-hard. We subsequently reveal that satisfying constraints related to graph task structure requires addressing the non-trivial subgraph isomorphism problem over a dynamic vehicular topology. Accordingly, we propose a decoupling approach by segregating template searching from transmission power allocation, where a <italic>template</italic> denotes a mapping between task components and vehicles. For template search, we introduce a low-complexity algorithm for isomorphic subgraphs extraction. For power allocation, we develop an algorithm using <inline-formula><tex-math notation="LaTeX">$p$</tex-math><alternatives><mml:math><mml:mi>p</mml:mi></mml:math><inline-graphic xlink:href="gao-ieq1-3270169.gif"/></alternatives></inline-formula>-norm and convex optimization techniques. Extensive simulations demonstrate that our approach outperforms baseline methods in various network settings.}, number={5}, journal={IEEE TRANSACTIONS ON SERVICES COMPUTING}, author={Liwang, Minghui and Gao, Zhibin and Hosseinalipour, Seyyedali and Su, Yuhan and Wang, Xianbin and Dai, Huaiyu}, year={2023}, month={Sep}, pages={3397–3411} }
 @article{li_tong_liu_wang_xie_dai_2023, title={Learning-Based Data Gathering for Information Freshness in UAV-Assisted IoT Networks}, volume={10}, ISSN={["2327-4662"]}, DOI={10.1109/JIOT.2022.3215521}, abstractNote={Unmanned aerial vehicle (UAV) has been widely deployed in efficient data collection for Internet of Things (IoT) networks. Information freshness in data collection can be characterized by the Age of Information (AoI). It is highly challenging to schedule multiple energy-constrained UAVs to improve information freshness especially when the generation instants of sensing samples are unpredictable. To deal with this issue, we leverage state-of-art reinforcement learning (RL) methods to design flight trajectories of UAVs without knowing the sampling mode each sensor node (SN) adopts. Each SN can sample the environment at periodical or random intervals. Multiple energy-constrained UAVs are dispatched to collect update packets from the SNs when flying over them. The UAV trajectory planning problem for AoI minimization is formulated as a Markov decision process (MDP). The objective is to minimize the average AoI of the SNs under the constraints of energy capacity and collision avoidance for the UAVs. Then, we propose two learning algorithms based on the Sarsa and value-decomposition network (VDN), respectively, which allow the UAVs to fulfill data collection tasks requested by the SNs. By learning directly from the environment, the Sarsa-based algorithm can approach the optimal policy asymptotically when certain conditions are satisfied. As one of the most popular multiagent deep RL methods, the VDN-based algorithm enables each UAV to make its own decision independently on its flight and data collection based on the partially observed network information. Simulation results validate the effectiveness of the proposed two learning-based algorithms compared with baseline policies.}, number={3}, journal={IEEE INTERNET OF THINGS JOURNAL}, author={Li, Zhiming and Tong, Peng and Liu, Juan and Wang, Xijun and Xie, Lingfu and Dai, Huaiyu}, year={2023}, month={Feb}, pages={2557–2573} }
 @article{he_he_jin_dai_2023, title={Location Privacy-Aware and Energy-Efficient Offloading for Distributed Edge Computing}, volume={22}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2023.3257197}, abstractNote={Driven by the ever-increasing scale and intensity of the computing tasks arising from various mobile applications, distributed edge computing has fostered wide research interests. It can effectively reduce the task processing delay by partitioning the original large-scale task into several small subtasks and offloading them to multiple edge nodes (ENs) for parallel computing. In edge computing, as the mobile user usually tends to offload computing tasks to closer ENs to save transmit power, the attacker may stealthily infer user location by exploiting this feature. Although there have been some pioneering works on offloading related location privacy, they mainly focused on the scenario where each task can only be offloaded to a single EN, and may not be directly applicable to distributed edge computing. Besides, the privacy issues considered in existing works are mainly based on good heuristics, and there is still a lack of concrete examples of location privacy attacks in edge computing. To the best of our knowledge, the location privacy issue in distributed edge computing still remains largely unexplored in existing literature. With this consideration, a location inference attack based on matrix sequential probability ratio test (MSPRT) is identified in this work. Besides, a countermeasure based on dynamic multi-EN selection is proposed, together with a location privacy-aware and energy-efficient distributed offloading scheme based on the generic Lyapunov optimization framework. Both theoretic analysis and simulations based on real-world channel measurements are employed to validate the feasibility of the identified MPSRT attack and the effectiveness of the proposed defense scheme.}, number={11}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={He, Yulong and He, Xiaofan and Jin, Richeng and Dai, Huaiyu}, year={2023}, month={Nov}, pages={7975–7988} }
 @article{liu_jia_ma_zhou_zhou_zhou_dai_dou_2023, title={Multi-Job Intelligent Scheduling With Cross-Device Federated Learning}, volume={34}, ISSN={["1558-2183"]}, DOI={10.1109/TPDS.2022.3224941}, abstractNote={Recent years have witnessed a large amount of decentralized data in various (edge) devices of end-users, while the decentralized data aggregation remains complicated for machine learning jobs because of regulations and laws. As a practical approach to handling decentralized data, Federated Learning (FL) enables collaborative global machine learning model training without sharing sensitive raw data. The servers schedule devices to jobs within the training process of FL. In contrast, device scheduling with multiple jobs in FL remains a critical and open problem. In this article, we propose a novel multi-job FL framework, which enables the training process of multiple jobs in parallel. The multi-job FL framework is composed of a system model and a scheduling method. The system model enables a parallel training process of multiple jobs, with a cost model based on the data fairness and the training time of diverse devices during the parallel training process. We propose a novel intelligent scheduling approach based on multiple scheduling methods, including an original reinforcement learning-based scheduling method and an original Bayesian optimization-based scheduling method, which corresponds to a small cost while scheduling devices to multiple jobs. We conduct extensive experimentation with diverse jobs and datasets. The experimental results reveal that our proposed approaches significantly outperform baseline approaches in terms of training time (up to 12.73 times faster) and accuracy (up to 46.4% higher).}, number={2}, journal={IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS}, author={Liu, Ji and Jia, Juncheng and Ma, Beichen and Zhou, Chendi and Zhou, Jingbo and Zhou, Yang and Dai, Huaiyu and Dou, Dejing}, year={2023}, month={Feb}, pages={535–551} }
 @article{jin_huang_zhang_dai_2023, title={On the Privacy Guarantees of Gossip Protocols in General Networks}, volume={10}, ISSN={["2327-4697"]}, DOI={10.1109/TNSE.2023.3247626}, abstractNote={Recently, the privacy guarantees of information dissemination protocols have attracted increasing research interests, among which the gossip protocols assume vital importance in various information exchange applications. In this article, we study the privacy guarantees of gossip protocols in general networks in terms of differential privacy and prediction uncertainty. First, lower bounds of the differential privacy guarantees are derived for gossip protocols in general networks in both synchronous and asynchronous settings. The prediction uncertainty of the source node given a uniform prior is also determined. For the private gossip algorithm, the differential privacy and prediction uncertainty guarantees are derived in closed forms in the asynchronous setting. Moreover, considering that these two metrics may be restrictive in some scenarios, the relaxed variants are proposed. It is found that source anonymity is closely related to some key network structure parameters in the general network setting. Then, we investigate information spreading in wireless networks with unreliable communications, and quantify the tradeoff between differential privacy guarantees and information spreading efficiency. Finally, considering that the attacker may not be present at the beginning of the information dissemination process, the scenario of delayed monitoring is studied and the corresponding differential privacy guarantees are evaluated.}, number={6}, journal={IEEE TRANSACTIONS ON NETWORK SCIENCE AND ENGINEERING}, author={Jin, Richeng and Huang, Yufan and Zhang, Zhaoyang and Dai, Huaiyu}, year={2023}, month={Nov}, pages={3114–3130} }
 @article{benmahmoud_meftah_dai_2023, title={On the outage probability of uplink IRS-aided networks: NOMA and OMA}, volume={59}, ISSN={["1874-4907"]}, DOI={10.1016/j.phycom.2023.102077}, abstractNote={In this paper, the outage performance of uplink intelligent reflecting surface (IRS)-aided non-orthogonal and orthogonal multiple-access (NOMA/OMA) networks is investigated. Specifically, we consider a two-user equipment (UE) NOMA/OMA network, in which both UEs have both direct (UE→base station (BS)) and reflected (UE→IRS→BS) links. All the links between the UEs and the IRS/BS are modeled either as a Rayleigh or a Nakagami-m variate. To characterize these networks’ outage performance, new statistics for the effective channel gains of the IRS-NOMA/OMA’s UEs are derived. Based on that, closed-form expressions for the outage probability (OP) for each UE are derived. Monte Carlo simulations’ results are provided to verify the accuracy of the analytical results.}, journal={PHYSICAL COMMUNICATION}, author={Benmahmoud, Slimane and Meftah, El-Hadi and Dai, Huaiyu}, year={2023}, month={Aug} }
 @article{song_an_ding_dai_2023, title={Optimal Relay Probing for UAV Millimeter Wave Communications with Beam Training Overhead}, volume={72}, ISSN={["1939-9359"]}, DOI={10.1109/TVT.2023.3236681}, abstractNote={Blockage in millimeter wave (mmWave) channels can severely degrade the efficiency of air-to-ground (A2G) communications between unmanned aerial vehicles (UAVs) and base stations (BSs). Although relay-aided transmission has proved to be effective in mitigating the negative impact of blockage on mmWave communications, how to efficiently select the optimal relaying UAV for A2G communications remains an open problem. To enable optimal relay selection, the UAV under blockage should probe neighboring UAVs for the quality of their A2G links, which incurs non-negligible beam training overheads. Moreover, most existing studies ignore the impacts of UAV orientations as well as the finite sizes of beam codebooks on the performance of relay selection. In view of these challenges, we study the design of relay probing strategies for UAV mmWave A2G communications to maximize the expected achievable throughput between the UAV under blockage and the BS. Different from existing work, we jointly consider beam training overhead, the limited number of neighboring UAVs, the finite sizes of UAV codebooks, and the orientation of neighboring UAVs in our schematic design. Besides, we derive the closed-form expression for the distribution of achievable throughput when a specific neighboring UAV is adopted as the relay, in order to facilitate the development of the optimal relay probing strategy. Extensive simulation results demonstrate the accuracy of our analysis and the superiority of the obtained relay probing strategy.}, number={6}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Song, Zhe and An, Jianping and Ding, Haichuan and Dai, Huaiyu}, year={2023}, month={Jun}, pages={7351–7363} }
 @article{liu_liwang_hosseinalipour_dai_gao_huang_2023, title={RFID: Towards Low Latency and Reliable DAG Task Scheduling Over Dynamic Vehicular Clouds}, volume={72}, ISSN={["1939-9359"]}, DOI={10.1109/TVT.2023.3266582}, abstractNote={Vehicular cloud (VC) platforms integrate heterogeneous and distributed resources of moving vehicles to offer timely and cost-effective computing services. However, the dynamic nature of VCs (i.e., limited contact duration among vehicles), caused by vehicles' mobility, poses unique challenges to the execution of computation-intensive applications/tasks with a directed acyclic graph (DAG) structure, where each task consists of multiple interdependent components (subtasks). In this paper, we study the scheduling of DAG tasks over dynamic VCs, where multiple subtasks of a DAG task are dispersed across vehicles and processed by vehicles cooperatively. We formulate DAG task scheduling as a 0-1 integer programming problem, aiming to minimize the overall task completion time while ensuring a high execution success rate, which turns out to be NP-hard. To tackle the problem, we develop a <underline>r</underline>anking and <underline>f</underline>oresight-<underline>i</underline>ntegrated <underline>d</underline>ynamic scheduling scheme (RFID). RFID consists of <italic>i)</italic> a <italic>dynamic downward ranking</italic> mechanism that sorts the scheduling priority of different subtasks, while explicitly taking into account the sequential execution nature of DAG; <italic>ii)</italic> a <italic>resource scarcity-based priority changing</italic> mechanism that overcomes possible performance degradations caused by the volatility of VC resources; and <italic>iii)</italic> a <italic>degree-based weighted earliest finish time</italic> mechanism that assigns the subtask with the highest scheduling priority to the vehicle which offers rapid task execution along with reliable transmission links. Simulation results reveal the effectiveness of our proposed scheme in comparison to benchmark methods.}, number={9}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Liu, Zhang and Liwang, Minghui and Hosseinalipour, Seyyedali and Dai, Huaiyu and Gao, Zhibin and Huang, Lianfen}, year={2023}, month={Sep}, pages={12139–12153} }
 @article{pervej_jin_dai_2023, title={Resource Constrained Vehicular Edge Federated Learning With Highly Mobile Connected Vehicles}, volume={41}, ISSN={["1558-0008"]}, DOI={10.1109/JSAC.2023.3273700}, abstractNote={This paper proposes a vehicular edge federated learning (VEFL) solution, where an edge server leverages highly mobile connected vehicles’ (CVs’) onboard central processing units (CPUs) and local datasets to train a global model. Convergence analysis reveals that the VEFL training loss depends on the successful receptions of the CVs’ trained models over the intermittent vehicle-to-infrastructure (V2I) wireless links. Owing to high mobility, in the full device participation case (FDPC), the edge server aggregates client model parameters based on a weighted combination according to the CVs’ dataset sizes and sojourn periods, while it selects a subset of CVs in the partial device participation case (PDPC). We then devise joint VEFL and radio access technology (RAT) parameters optimization problems under delay, energy and cost constraints to maximize the probability of successful reception of the locally trained models. Considering that the optimization problem is NP-hard, we decompose it into a VEFL parameter optimization sub-problem, given the estimated worst-case sojourn period, delay and energy expense, and an online RAT parameter optimization sub-problem. Finally, extensive simulations are conducted to validate the effectiveness of the proposed solutions with a practical 5G new radio (5G-NR) RAT under a realistic microscopic mobility model.}, number={6}, journal={IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Pervej, Md Ferdous and Jin, Richeng and Dai, Huaiyu}, year={2023}, month={Jun}, pages={1825–1844} }
 @article{du_mujumdar_ozdemir_ozturk_guvenc_sichitiu_dai_bhuyan_2022, title={60 GHz Outdoor Propagation Measurements and Analysis Using Facebook Terragraph Radios}, ISSN={["2164-2958"]}, DOI={10.1109/RWS53089.2022.9719957}, abstractNote={The high attenuation of millimeter-wave (mmWave) would significantly reduce the coverage areas, and hence it is critical to study the propagation characteristics of mmWave in multiple deployment scenarios. In this work, we investigated the propagation and scattering behavior of 60 GHz mmWave signals in outdoor environments at a travel distance of 98 m for an aerial link (rooftop to rooftop), and 147 m for a ground link (light-pole to light-pole). Measurements were carried out using Facebook Terragraph (TG) radios. Results include received power, path loss, signal-to-noise ratio (SNR), and root mean square (RMS) delay spread for all beamforming directions supported by the antenna array. Strong line-of-sight (LOS) propagation exists in both links. We also observed rich multipath components (MPCs) due to edge scatterings in the aerial link, while only LOS and ground reflection MPCs in the other link.}, journal={2022 IEEE RADIO AND WIRELESS SYMPOSIUM (RWS)}, author={Du, Kairui and Mujumdar, Omkar and Ozdemir, Ozgur and Ozturk, Ender and Guvenc, Ismail and Sichitiu, Mihail L. and Dai, Huaiyu and Bhuyan, Arupjyoti}, year={2022}, pages={156–159} }
 @article{lee_hosseinalipour_brinton_yu_dai_2022, title={A Fast Graph Neural Network-Based Method for Winner Determination in Multi-Unit Combinatorial Auctions}, volume={10}, ISSN={["2168-7161"]}, DOI={10.1109/TCC.2020.3046883}, abstractNote={The combinatorial auction (CA) is an efficient mechanism for resource allocation in different fields, including cloud computing. It can obtain high economic efficiency and user flexibility by allowing bidders to submit bids for combinations of different items instead of only for individual items. However, the problem of allocating items among the bidders to maximize the auctioneers’ revenue, i.e., the winner determination problem (WDP), is NP-complete to solve and inapproximable. Existing works for WDPs are generally based on mathematical optimization techniques and most of them focus on the single-unit WDP, where each item only has one unit. On the contrary, few works consider the multi-unit WDP in which each item may have multiple units. Given that the multi-unit WDP is more complicated but prevalent in cloud computing, we propose leveraging machine learning (ML) techniques to develop a novel low-complexity algorithm for solving this problem with negligible revenue loss. Specifically, we model the multi-unit WDP as an augmented bipartite bid-item graph and use a graph neural network (GNN) with half-convolution operations to learn the probability of each bid belonging to the optimal allocation. To improve the sample generation efficiency and decrease the number of needed labeled instances, we propose two different sample generation processes. We also develop two novel graph-based post-processing algorithms to transform the outputs of the GNN into feasible solutions. Through simulations on both synthetic instances and a specific virtual machine (VM) allocation problem in a cloud computing platform, we validate that our proposed method can approach optimal performance with low complexity and has good generalization ability in terms of problem size and user-type distribution.}, number={4}, journal={IEEE TRANSACTIONS ON CLOUD COMPUTING}, author={Lee, Mengyuan and Hosseinalipour, Seyyedali and Brinton, Christopher. G. G. and Yu, Guanding and Dai, Huaiyu}, year={2022}, month={Oct}, pages={2264–2280} }
 @article{gao_liwang_hosseinalipour_dai_wang_2022, title={A Truthful Auction for Graph Job Allocation in Vehicular Cloud-Assisted Networks}, volume={21}, ISSN={["1558-0660"]}, DOI={10.1109/TMC.2021.3059803}, abstractNote={Vehicular cloud computing has been emerged as a promising solution to fulfill users’ demands on processing computation-intensive applications in modern driving environments. Such applications are commonly represented by graphs consisting of components and edges. However, encouraging vehicles to share resources poses significant challenges owing to users’ selfishness. In this paper, an auction-based graph job allocation problem is studied in vehicular cloud-assisted networks considering resource reutilization. Our goal is to map each buyer (component) to a feasible seller (virtual machine) while maximizing the buyers’ utility-of-service, which concerns the execution time and commission cost. First, we formulate the auction-based graph job allocation as a 0-1 integer programming (0-1 IP) problem. Then, a Vickrey-Clarke-Groves based payment rule is proposed which satisfies the desired economical properties, truthfulness and individual rationality. We face two challenges: 1) the abovementioned 0-1 IP problem is NP-hard; 2) one constraint associated with the IP problem poses addressing the subgraph isomorphism problem. Thus, obtaining the optimal solution is practically infeasible in large-scale networks. Motivated by which, we develop a structure-preserved matching algorithm by maximizing the utility-of-service-gain, and the corresponding payment rule which offers economical properties and low computation complexity. Extensive simulations demonstrate that the proposed algorithm outperforms the contrast methods considering various problem sizes.}, number={10}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Gao, Zhibin and Liwang, Minghui and Hosseinalipour, Seyyedali and Dai, Huaiyu and Wang, Xianbin}, year={2022}, month={Oct}, pages={3455–3469} }
 @article{jin_he_dai_2022, title={Communication Efficient Federated Learning With Energy Awareness Over Wireless Networks}, volume={21}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2021.3138394}, abstractNote={In federated learning (FL), reducing the communication overhead is one of the most critical challenges since the parameter server and the mobile devices share the training parameters over wireless links. With such consideration, we adopt the idea of SignSGD in which only the signs of the gradients are exchanged. Moreover, most of the existing works assume Channel State Information (CSI) available at both the mobile devices and the parameter server, and thus the mobile devices can adopt fixed transmission rates dictated by the channel capacity. In this work, only the parameter server side CSI is assumed, and channel capacity with outage is considered. In this case, an essential problem for the mobile devices is to select appropriate local processing and communication parameters (including the transmission rates) to achieve a desired balance between the overall learning performance and their energy consumption. Two optimization problems are formulated and solved, which optimize the learning performance given the energy consumption requirement, and vice versa. Furthermore, considering that the data may be distributed across the mobile devices in a highly uneven fashion in FL, a stochastic sign-based algorithm is proposed. Extensive simulations are performed to demonstrate the effectiveness of the proposed methods.}, number={7}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Jin, Richeng and He, Xiaofan and Dai, Huaiyu}, year={2022}, month={Jul}, pages={5204–5219} }
 @article{yue_jin_wong_dai_2022, title={Communication-Efficient Federated Learning via Predictive Coding}, volume={16}, ISSN={["1941-0484"]}, DOI={10.1109/JSTSP.2022.3142678}, abstractNote={Federated learning can enable remote workers to collaboratively train a shared machine learning model while allowing training data to be kept locally. In the use case of wireless mobile devices, the communication overhead is a critical bottleneck due to limited power and bandwidth. Prior work has utilized various data compression tools such as quantization and sparsification to reduce the overhead. In this paper, we propose a predictive coding based compression scheme for federated learning. The scheme has shared prediction functions among all devices and allows each worker to transmit a compressed residual vector derived from the reference. In each communication round, we select the predictor and quantizer based on the rate–distortion cost, and further reduce the redundancy with entropy coding. Extensive simulations reveal that the communication cost can be reduced up to 99% with even better learning performance when compared with other baseline methods.}, number={3}, journal={IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING}, author={Yue, Kai and Jin, Richeng and Wong, Chau-Wai and Dai, Huaiyu}, year={2022}, month={Apr}, pages={369–380} }
 @article{rahmati_hosseinalipour_yapici_he_guvenc_dai_bhuyan_2022, title={Dynamic Interference Management for UAV-Assisted Wireless Networks}, volume={21}, ISSN={["1558-2248"]}, url={https://doi.org/10.1109/TWC.2021.3114234}, DOI={10.1109/TWC.2021.3114234}, abstractNote={We investigate a transmission mechanism aiming to improve the data rate between a base station (BS) and a user equipment (UE) through deploying multiple relaying UAVs. We consider the effect of interference incurred by another established communication network, which makes our problem challenging and different from the state of the art. We aim to design the 3D trajectories and power allocation for the UAVs to maximize the data flow of the network while keeping the interference on the existing communication network below a threshold. We utilize the mobility feature of the UAVs to evade the (un)-intended interference caused by (un)-intentional interferers. To this end, we propose an alternating-maximization approach to jointly obtain the 3D trajectories and the UAVs transmission powers. We handle the 3D trajectory design by resorting to spectral graph theory and subsequently address the power allocation through convex optimization techniques. We also approach the problem from the intentional interferer’s perspective where smart jammers chase the UAVs to effectively degrade the data flow of the network. We also extend our work to the case for multiple UEs. Finally, we demonstrate the efficacy of our proposed method through extensive simulations.}, number={4}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Rahmati, Ali and Hosseinalipour, Seyyedali and Yapici, Yavuz and He, Xiaofan and Guvenc, Ismail and Dai, Huaiyu and Bhuyan, Arupjyoti}, year={2022}, month={Apr}, pages={2637–2653} }
 @article{yue_jin_wong_dai_2022, title={Federated Learning via Plurality Vote}, volume={12}, ISSN={["2162-2388"]}, DOI={10.1109/TNNLS.2022.3225715}, abstractNote={Federated learning allows collaborative clients to solve a machine-learning problem while preserving data privacy. Recent studies have tackled various challenges in federated learning, but the joint optimization of communication overhead, learning reliability, and deployment efficiency is still an open problem. To this end, we propose a new scheme named federated learning via plurality vote (FedVote). In each communication round of FedVote, clients transmit binary or ternary weights to the server with low communication overhead. The model parameters are aggregated via weighted voting to enhance the resilience against Byzantine attacks. When deployed for inference, the model with binary or ternary weights is resource-friendly to edge devices. Our results demonstrate that the proposed method can reduce quantization error and converges faster compared to the methods directly quantizing the model updates.}, journal={IEEE TRANSACTIONS ON NEURAL NETWORKS AND LEARNING SYSTEMS}, author={Yue, Kai and Jin, Richeng and Wong, Chau-Wai and Dai, Huaiyu}, year={2022}, month={Dec} }
 @article{lee_yu_dai_li_2022, title={Graph Neural Networks Meet Wireless Communications: Motivation, Applications, and Future Directions}, volume={29}, ISSN={["1558-0687"]}, DOI={10.1109/MWC.001.2200023}, abstractNote={As an efficient graph analytical tool, graph neural networks (GNNs) have special properties that are particularly fit for the characteristics and requirements of wireless communications, exhibiting good potential for the advancement of next-generation wireless communications. This article aims to provide a comprehensive overview of the interplay between GNNs and wireless communications, including GNNs for wireless communications (GNN4Com) and wireless communications for GNNs (Com4GNN). In particular, we discuss GNN4Com based on how graphical models are constructed and introduce Com4GNN with corresponding incentives. We also highlight potential research directions to promote future research endeavors for GNNs in wireless communications.}, number={5}, journal={IEEE WIRELESS COMMUNICATIONS}, author={Lee, Mengyuan and Yu, Guanding and Dai, Huaiyu and Li, Geoffrey Ye}, year={2022}, month={Oct}, pages={12–19} }
 @article{nguyen_lee_dai_2022, title={Hybrid Beamforming and Adaptive RF Chain Activation for Uplink Cell-Free Millimeter-Wave Massive MIMO Systems}, volume={71}, ISSN={["1939-9359"]}, DOI={10.1109/TVT.2022.3176389}, abstractNote={In this work, we investigate hybrid analog–digital beamforming (HBF) architectures for uplink cell-free (CF) millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems. We first propose two HBF schemes, namely, decentralized HBF (D-HBF) and semi-centralized HBF (SC-HBF). In the former, both the digital and analog beamformers are generated independently at each AP based on the local channel state information (CSI). In contrast, in the latter, only the digital beamformer is obtained locally at the access point (AP), whereas the analog beamforming matrix is generated at the central processing unit (CPU) based on the global CSI received from all APs. We show that the analog beamformers generated in these two HBF schemes provide approximately the same achievable rates despite the lower complexity of D-HBF and its lack of CSI requirement. Furthermore, to reduce the power consumption, we propose a novel adaptive radio frequency (RF) chain-activation (ARFA) scheme, which dynamically activates/deactivates RF chains and their connected analog-to-digital converters (ADCs) and phase shifters (PSs) at the APs based on the CSI. For the activation of RF chains, low-complexity algorithms are proposed, which can achieve significant improvement in energy efficiency (EE) with only a marginal loss in the total achievable rate.}, number={8}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Nguyen, Nhan Thanh and Lee, Kyungchun and Dai, Huaiyu}, year={2022}, month={Aug}, pages={8739–8755} }
 @article{pervej_guo_kim_parsons_orlik_di cairano_menner_berntorp_nagai_dai_2022, title={Mobility, Communication and Computation Aware Federated Learning for Internet of Vehicles}, ISSN={["1931-0587"]}, DOI={10.1109/IV51971.2022.9827190}, abstractNote={While privacy concerns entice connected and automated vehicles to incorporate on-board federated learning (FL) solutions, an integrated vehicle-to-everything communication with heterogeneous computation power aware learning platform is urgently necessary to make it a reality. Motivated by this, we propose a novel mobility, communication and computation aware online FL platform that uses on-road vehicles as learning agents. Thanks to the advanced features of modern vehicles, the on-board sensors can collect data as vehicles travel along their trajectories, while the on-board processors can train machine learning models using the collected data. To take the high mobility of vehicles into account, we consider the delay as a learning parameter and restrict it to be less than a tolerable threshold. To satisfy this threshold, the central server accepts partially trained models, the distributed roadside units (a) perform downlink multicast beamforming to minimize global model distribution delay and (b) allocate optimal uplink radio resources to minimize local model offloading delay, and the vehicle agents conduct heterogeneous local model training. Using real-world vehicle trace datasets, we validate our FL solutions. Simulation shows that the proposed integrated FL platform is robust and outperforms baseline models. With reasonable local training episodes, it can effectively satisfy all constraints and deliver near ground truth multi-horizon velocity and vehicle-specific power predictions.}, journal={2022 IEEE INTELLIGENT VEHICLES SYMPOSIUM (IV)}, author={Pervej, Md Ferdous and Guo, Jianlin and Kim, Kyeong Jin and Parsons, Kieran and Orlik, Philip and Di Cairano, Stefano and Menner, Marcel and Berntorp, Karl and Nagai, Yukimasa and Dai, Huaiyu}, year={2022}, pages={750–757} }
 @article{he_jin_dai_2022, title={Multi-Hop Task Offloading With On-the-Fly Computation for Multi-UAV Remote Edge Computing}, volume={70}, ISSN={["1558-0857"]}, DOI={10.1109/TCOMM.2021.3129902}, abstractNote={The dramatic growth in computing capability and the inherent mobility of the unmanned aerial vehicles (UAVs) foster the recent surge of interests in incorporating UAVs into edge computing systems to facilitate on-demand deployment and extended coverage. Nonetheless, due to the limited communication capability of the UAVs, single-UAV edge computing systems may still be incompetent when serving remote users. Although the traditional multi-UAV relay network can be a viable solution, it fails to exploit the computing capability of the UAVs. With this consideration, a multi-hop task offloading with on-the-fly computation scheme is proposed in this work to enable a more powerful multi-UAV remote edge computing network. To solve the corresponding joint resource allocation and deployment problem, two efficient algorithms are proposed. One of them can find the global optimal strategy in a special case, while the other can obtain a good local optimal strategy in the general cases. Both algorithms have a complexity only linear in the number of UAVs and admit distributed implementation. In addition to analysis, numerical results are provided to corroborate the effectiveness of the proposed scheme.}, number={2}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={He, Xiaofan and Jin, Richeng and Dai, Huaiyu}, year={2022}, month={Feb}, pages={1332–1344} }
 @article{hosseinalipour_azam_brinton_michelusi_aggarwal_love_dai_2022, title={Multi-Stage Hybrid Federated Learning Over Large-Scale D2D-Enabled Fog Networks}, ISSN={["1558-2566"]}, DOI={10.1109/TNET.2022.3143495}, abstractNote={Federated learning has generated significant interest, with nearly all works focused on a “star” topology where nodes/devices are each connected to a central server. We migrate away from this architecture and extend it through the <italic>network</italic> dimension to the case where there are multiple layers of nodes between the end devices and the server. Specifically, we develop multi-stage hybrid federated learning (<monospace>MH-FL</monospace>), a hybrid of intra-and inter-layer model learning that considers the network as a <italic>multi-layer cluster-based structure.</italic> <monospace>MH-FL</monospace> considers the <italic>topology structures</italic> among the nodes in the clusters, including local networks formed via device-to-device (D2D) communications, and presumes a <italic>semi-decentralized architecture</italic> for federated learning. It orchestrates the devices at different network layers in a collaborative/cooperative manner (i.e., using D2D interactions) to form <italic>local consensus</italic> on the model parameters and combines it with multi-stage parameter relaying between layers of the tree-shaped hierarchy. We derive the upper bound of convergence for <monospace>MH-FL</monospace> with respect to parameters of the network topology (e.g., the spectral radius) and the learning algorithm (e.g., the number of D2D rounds in different clusters). We obtain a set of policies for the D2D rounds at different clusters to guarantee either a finite optimality gap or convergence to the global optimum. We then develop a distributed control algorithm for <monospace>MH-FL</monospace> to tune the D2D rounds in each cluster over time to meet specific convergence criteria. Our experiments on real-world datasets verify our analytical results and demonstrate the advantages of <monospace>MH-FL</monospace> in terms of resource utilization metrics.}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Hosseinalipour, Seyyedali and Azam, Sheikh Shams and Brinton, Christopher G. and Michelusi, Nicolo and Aggarwal, Vaneet and Love, David J. and Dai, Huaiyu}, year={2022}, month={Feb} }
 @article{maeng_yapici_guvenc_bhuyan_dai_2022, title={Precoder Design for Physical-Layer Security and Authentication in Massive MIMO UAV Communications}, volume={71}, ISSN={["1939-9359"]}, url={https://doi.org/10.1109/TVT.2022.3141055}, DOI={10.1109/TVT.2022.3141055}, abstractNote={Supporting reliable and seamless wireless connectivity for unmanned aerial vehicles (UAVs) has recently become a critical requirement to enable various different use cases of UAVs. Due to their widespread deployment footprint, cellular networks can support beyond visual line of sight (BVLOS) communications for UAVs. In this paper, we consider cellular connected UAVs (C-UAVs) that are served by massive multiple-input-multiple-output (MIMO) links to extend coverage range, while also improving physical layer security and authentication. We consider Rician channel and propose a novel linear precoder design for transmitting data and artificial noise (AN). We derive the closed-form expression of the ergodic secrecy rate of C-UAVs for both conventional and proposed precoder designs. In addition, we obtain the optimal power splitting factor that divides the power between data and AN by asymptotic analysis. Then, we apply the proposed precoder design in the fingerprint embedding authentication framework, where the goal is to minimize the probability of detection of the authentication tag at an eavesdropper. In simulation results, we show the superiority of the proposed precoder in both secrecy rate and the authentication probability considering moderate and large number of antenna massive MIMO scenarios.}, number={3}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Maeng, Sung Joon and Yapici, Yavuz and Guvenc, Ismail and Bhuyan, Arupjyoti and Dai, Huaiyu}, year={2022}, month={Mar}, pages={2949–2964} }
 @article{hosseinalipour_dai_2021, title={A Two-Stage Auction Mechanism for Cloud Resource Allocation}, volume={9}, ISSN={["2168-7161"]}, DOI={10.1109/TCC.2019.2901785}, abstractNote={The contemporary literature on cloud resource allocation is mostly focused on studying the interactions between customers and cloud managers. Nevertheless, the recent growth in the customers’ demands and the emergence of private cloud providers (CPs) entice the cloud managers to rent extra resources from the CPs so as to handle their backlogged tasks and attract more customers. This also renders the interactions between the cloud managers and the CPs an important problem to study. In this paper, we investigate both interactions through a two-stage auction mechanism. For the interactions between customers and cloud managers, we adopt the options-based sequential auctions (OBSAs) to design the cloud resource allocation paradigm. As compared to existing works, our framework can handle customers with heterogeneous demands, provide truthfulness as the dominant strategy, enjoy a simple winner determination procedure, and preclude the delayed entrance issue. We also provide the performance analysis of the OBSAs, which is among the first in literature. Regarding the interactions between cloud managers and CPs, we propose two parallel markets for resource gathering, and capture the selfishness of the CPs by their offered prices. We conduct a comprehensive analysis of the two markets and identify the bidding strategies of the cloud managers.}, number={3}, journal={IEEE TRANSACTIONS ON CLOUD COMPUTING}, author={Hosseinalipour, Seyyedali and Dai, Huaiyu}, year={2021}, pages={881–895} }
 @article{lee_ma_yu_dai_2021, title={Accelerating Generalized Benders Decomposition for Wireless Resource Allocation}, volume={20}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2020.3031920}, abstractNote={Generalized Benders decomposition (GBD) is a globally optimal algorithm for mixed integer nonlinear programming (MINLP) problems, which are NP-hard and can be widely found in the area of wireless resource allocation. The main idea of GBD is decomposing an MINLP problem into a primal problem and a master problem, which are iteratively solved until their solutions converge. However, a direct implementation of GBD is time- and memory-consuming. The main bottleneck is the high complexity of the master problem, which increases over the iterations. Therefore, we propose to leverage machine learning (ML) techniques to accelerate GBD aiming at decreasing the complexity of the master problem. Specifically, we utilize two different ML techniques, classification and regression, to deal with this acceleration task. In this way, a cut classifier and a cut regressor are learned, respectively, to distinguish between useful and useless cuts. Only useful cuts are added to the master problem and thus the complexity of the master problem is reduced. By using a resource allocation problem in device-to-device communication networks as an example, we validate that the proposed method can reduce the computational complexity of GBD without loss of optimality and has good generalization ability. The proposed method is applicable for solving various MINLP problems in wireless networks since the designs are invariant for different problems.}, number={2}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Lee, Mengyuan and Ma, Ning and Yu, Guanding and Dai, Huaiyu}, year={2021}, month={Feb}, pages={1233–1247} }
 @article{nguyen_lee_daiieee_2021, title={Application of Deep Learning to Sphere Decoding for Large MIMO Systems}, volume={20}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2021.3076527}, abstractNote={Although the sphere decoder (SD) is a powerful detector for multiple-input multiple-output (MIMO) systems, it has become computationally prohibitive in massive MIMO systems, where a large number of antennas are employed. To overcome this challenge, we propose fast deep learning (DL)-aided SD (FDL-SD) and fast DL-aided <inline-formula> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula>-best SD (KSD, FDL-KSD) algorithms. Therein, the major application of DL is to generate a highly reliable initial candidate to accelerate the search in SD and KSD in conjunction with candidate/layer ordering and early rejection. Compared to existing DL-aided SD schemes, our proposed schemes are more advantageous in both offline training and online application phases. Specifically, unlike existing DL-aided SD schemes, they do not require performing the conventional SD in the training phase. For a <inline-formula> <tex-math notation="LaTeX">$24 \times 24$ </tex-math></inline-formula> MIMO system with QPSK, the proposed FDL-SD achieves a complexity reduction of more than 90% without any performance loss compared to conventional SD schemes. For a <inline-formula> <tex-math notation="LaTeX">$32 \times 32$ </tex-math></inline-formula> MIMO system with QPSK, the proposed FDL-KSD only requires <inline-formula> <tex-math notation="LaTeX">$K = 32$ </tex-math></inline-formula> to attain the performance of the conventional KSD with <inline-formula> <tex-math notation="LaTeX">$K=256$ </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> is the number of survival paths in KSD. This implies a dramatic improvement in the performance–complexity tradeoff of the proposed FDL-KSD scheme.}, number={10}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Nguyen, Nhan Thanh and Lee, Kyungchun and DaiIEEE, Huaiyu}, year={2021}, month={Oct}, pages={6787–6803} }
 @article{chattopadhyay_dai_eun_2021, title={Controlling Metastable Infection Patterns in Multilayer Networks via Interlink Design}, volume={8}, ISSN={["2327-4697"]}, DOI={10.1109/TNSE.2021.3108075}, abstractNote={Recent research on epidemic spreading in networks has uncovered the phenomena of metastable infection patterns, where epidemics can be sustained in localized regions of activity, in contrast to the classical dichotomy between a quick extinction of infections and a network-wide global infection. Our objective in this work is to leverage this localized infection state to achieve controlled spreading in multilayer networks via intelligent design of the interlink structure between the network layers. Following the approach in recent works, the dynamic contact process is approximated by studying the dynamics in local regions around the hubs of the network. This allows us to approximately track the contact process in the near-threshold regime and estimate the mean metastable infection size over the lifetime of the infection. Furthermore, interlinking strategies are devised that can achieve a desired infection size under certain conditions. Theoretically optimal interlink structures can be derived under special cases, whereas greedy strategies are proposed for the general case. We compare the interlinking strategies developed in this work to some popular heuristics and demonstrate their superiority by extensive simulation experiments on both synthetic and real-world networks.}, number={4}, journal={IEEE TRANSACTIONS ON NETWORK SCIENCE AND ENGINEERING}, author={Chattopadhyay, Srinjoy and Dai, Huaiyu and Eun, Do Young}, year={2021}, month={Oct}, pages={3242–3256} }
 @article{tian_zhang_wang_chen_wang_dai_2021, title={Distributed ADMM With Synergetic Communication and Computation}, volume={69}, ISSN={["1558-0857"]}, DOI={10.1109/TCOMM.2020.3027032}, abstractNote={In this article, we propose a novel distributed alternating direction method of multipliers (ADMM) algorithm with synergetic communication and computation, called SCCD-ADMM, to reduce the total communication and computation cost of the system. Explicitly, in the proposed algorithm, each node interacts with only part of its neighboring nodes, the number of which is progressively determined according to a heuristic searching procedure, which takes into account both the predicted convergence rate and the communication and computation costs at each iteration, resulting in a trade-off between communication and computation. Then the node chooses its neighboring nodes according to an importance sampling distribution derived theoretically to minimize the variance with the latest information it locally stores. Finally, the node updates its local information with a new update rule which adapts to the number of communication nodes. We prove the convergence of the proposed algorithm and provide an upper bound of the convergence variance brought by randomness. Extensive simulations validate the excellent performances of the proposed algorithm in terms of convergence rate and variance, the overall communication and computation cost, the impact of network topology as well as the time for evaluation, in comparison with the traditional counterparts.}, number={1}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Tian, Zhuojun and Zhang, Zhaoyang and Wang, Jue and Chen, Xiaoming and Wang, Wei and Dai, Huaiyu}, year={2021}, month={Jan}, pages={501–517} }
 @article{hosseinalipour_rahmati_eun_dai_2021, title={Energy-Aware Stochastic UAV-Assisted Surveillance}, volume={20}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2020.3044490}, abstractNote={With the ease of deployment, capabilities of evading the jammers and obscuring their existence, unmanned aerial vehicles (UAVs) are one of the most suitable candidates to perform surveillance. There exists a body of literature in which the inspectors follow a deterministic trajectory to conduct surveillance, which results in a predictable environment for malicious entities. Thus, introducing randomness to the surveillance is of particular interest. In this work, we propose a novel framework for stochastic UAV-assisted surveillance that i) inherently considers the battery constraints of the UAVs, ii) proposes random moving patterns modeled via random walks, and iii) adds another degree of randomness to the system via considering probabilistic inspections. We formulate the problem of interest, i.e., obtaining the energy-efficient random walk and inspection policies of the UAVs subject to probabilistic constraints on inspection criteria of the sites and battery consumption of the UAVs, which turns out to be signomial programming that is highly non-convex. To solve it, we propose a centralized and a distributed algorithm along with their performance guarantee. This work contributes to both UAV-assisted surveillance and classic random walk literature by designing random walks with random inspection policies on weighted graphs with energy limited random walkers.}, number={5}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Hosseinalipour, Seyyedali and Rahmati, Ali and Eun, Do Young and Dai, Huaiyu}, year={2021}, month={May}, pages={2820–2837} }
 @article{maeng_deshmukh_guvenc_bhuyan_dai_2021, title={Interference Analysis and Mitigation for Aerial IoT Considering 3D Antenna Patterns}, volume={70}, ISSN={["1939-9359"]}, url={https://doi.org/10.1109/TVT.2020.3046121}, DOI={10.1109/TVT.2020.3046121}, abstractNote={Due to dense deployments of Internet of things (IoT) networks, interference management becomes a critical challenge. With the proliferation of aerial IoT devices, such as unmanned aerial vehicles (UAVs), interference characteristics in 3D environments will be different than those in the existing terrestrial IoT networks. In this paper, we consider 3D topology IoT networks with a mixture of aerial and terrestrial links, with low-cost cross-dipole antennas at ground nodes and both omni-directional and cross-dipole antennas at aerial nodes. Considering a massive-access communication scenario, we first derive the statistics of the channel gain at IoT receivers in closed form while taking into account the radiation patterns of both ground and aerial nodes. These are then used to calculate the ergodic achievable rate as a function of the height of the aerial receiver and the cumulative interference. We propose a low-complexity interference mitigation scheme that utilizes 3D antenna radiation pattern with different dipole antenna settings. Our results show that using the proposed scheme, the ergodic achievable rate improves as the height of the aerial receivers increases. In addition, we also show that the ratio between the ground and aerial receivers that maximizes the peak rate increases with the height of the aerial IoT receiver.}, number={1}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Maeng, Sung Joon and Deshmukh, Mrugen A. and Guvenc, Ismail and Bhuyan, Arupjyoti and Dai, Huaiyu}, year={2021}, month={Jan}, pages={490–503} }
 @article{he_jin_dai_2021, title={Joint Service Placement and Resource Allocation for Multi-UAV Collaborative Edge Computing}, ISSN={["1525-3511"]}, DOI={10.1109/WCNC49053.2021.9417565}, abstractNote={Driven by the burgeoning development of unmanned aerial vehicle (UAV) technology, the recently advocated multi-UAV edge computing paradigm is anticipated to greatly enhance the coverage and on-demand deployment capability of the edge networks. One of the prominent advantage of this paradigm is to allow the UAVs to participate in the edge computing process by executing some computing tasks at their onboard processors. To this end, a key prerequisite is that the corresponding computing services must be placed onboard beforehand. Nonetheless, unlike its counterpart for conventional ground edge systems, the service placement issue in multi-UAV edge computing systems remains much less explored. To the best of our knowledge, this work is among the first to consider the joint service placement and resource allocation problem for multi-UAV edge computing. Due to the mutual influence between service placement and resource allocation, this problem turns out to be a computationally intractable mixed-integer nonlinear programming. Fortunately, through our analysis, it is found that this problem can be divided into two subproblems that are submodular and convex, respectively. Based on this observation and the general alternative optimization framework, an efficient joint service placement and resource allocation scheme that can find a reasonably good solution with only a linear complexity is proposed. In addition to the analysis, simulations are conducted to validate the effectiveness of the proposed scheme.}, journal={2021 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE (WCNC)}, author={He, Xiaofan and Jin, Richeng and Dai, Huaiyu}, year={2021} }
 @article{jin_he_dai_2021, title={Minimizing the Age of Information in the Presence of Location Privacy-Aware Mobile Agents}, volume={69}, ISSN={["1558-0857"]}, DOI={10.1109/TCOMM.2020.3035394}, abstractNote={The recent advances in wireless sensor networks and sensing techniques enable various time-sensitive applications that require timely exchange of updates between a Base Station (BS) and ground terminals. In practice, the ground terminals may not be able to communicate with the BS directly due to constraints in transmit power and communication capability, and mobile agents are commonly employed to help collect and deliver the updates. In particular, the emerging mobile crowd sensing (MCS) provides an appealing cost-effective paradigm for such employment. However, in this case, the mobile agents are required to share their locations with the ground terminals and the BS, which incurs location privacy concerns and may deter them from participating in the information delivery process. With this consideration, a location privacy-aware payment mechanism, which can stimulate the mobile agents to report their locations with differential privacy levels desired by the BS, is proposed. Furthermore, considering that the BS usually has a limited budget, it is essential to properly select the set of mobile agents to perform the information collection tasks. Therefore, a cost-efficient mobile agent selection algorithm is proposed. Finally, simulation results are presented to demonstrate the effectiveness of the proposed method.}, number={2}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Jin, Richeng and He, Xiaofan and Dai, Huaiyu}, year={2021}, month={Feb}, pages={1053–1067} }
 @article{su_liwang_hosseinalipour_huang_dai_2021, title={Optimal Position Planning of UAV Relays in UAV-assisted Vehicular Networks}, ISSN={["1550-3607"]}, DOI={10.1109/ICC42927.2021.9500796}, abstractNote={This paper considers unmanned aerial vehicle (UAV)-assisted infrastructure-to-vehicle (I2V) communication employing UAVs as relays to increase the throughput between a roadside unit (RSU) and a vehicular user equipment (VUE). We investigate the UAV position planning problem under both single UAV and multiple cooperative UAVs scenarios while considering the mobility of the VUE, aiming to maximize the data rate of the system. We first consider using a single UAV and prove that the single UAV position planning can be formulated as a convex optimization problem, and then obtain the optimal position of the UAV. Next, we investigate the multiple cooperative UAVs scenario and formulate the joint power control and position planning problem to improve the data rate of the system under a fixed total power consumption. Numerical simulations are provided to verify our theoretical results. Our findings highlight the effects of important system parameters, such as height, transmit power, and the number of UAVs, on the optimal UAV positioning and system performance.}, journal={IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC 2021)}, author={Su, Yuhan and LiWang, Minghui and Hosseinalipour, Seyyedali and Huang, Lianfen and Dai, Huaiyu}, year={2021} }
 @article{ding_dai_guvenc_bhuyan_2021, title={Outage Analysis for Cooperative mmWave UAV Communications With Beam Training Overhead}, volume={10}, ISSN={["2162-2345"]}, url={https://doi.org/10.1109/LWC.2021.3098424}, DOI={10.1109/LWC.2021.3098424}, abstractNote={In this letter, we investigate the tradeoff between reliability and beam training overhead in cooperative millimeter wave (mmWave) unmanned aerial vehicle (UAV) communications. In particular, we analyze how outage probability varies with the number of neighboring UAVs being probed as potential relays for relay selection. Unlike existing work, the limited number of UAV beams as well as UAV orientations are explicitly considered in our analysis. We derive the outage probability in closed form and verify our analysis via simulations. The results facilitate us to understand the fundamental limits of cooperative mmWave UAV communications.}, number={10}, journal={IEEE WIRELESS COMMUNICATIONS LETTERS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Ding, Haichuan and Dai, Huaiyu and Guvenc, Ismail and Bhuyan, Arupjyoti}, year={2021}, month={Oct}, pages={2249–2253} }
 @article{yapici_rupasinghe_guvenc_dai_bhuyan_2021, title={Physical Layer Security for NOMA Transmission in mmWave Drone Networks}, volume={70}, ISSN={["1939-9359"]}, url={https://doi.org/10.1109/TVT.2021.3066350}, DOI={10.1109/TVT.2021.3066350}, abstractNote={The non-orthogonal multiple access (NOMA) and millimeter-wave (mmWave) transmission enable the unmanned aerial vehicle (UAV) assisted wireless networks to provide broadband connectivity over densely packed urban areas. The presence of malicious receivers, however, compromise the security of the UAV-to-ground communications links, thereby degrading secrecy rates. In this work, we consider a NOMA-based transmission strategy in a mmWave UAV-assisted wireless network, and investigate the respective secrecy-rate performance rigorously. In particular, we propose a protected-zone approach to enhance the secrecy-rate performance by preventing the most vulnerable subregion (outside the user region) from the presence of malicious receivers. The respective secrecy rates are then derived analytically as a function of the particular protected zone, which verifies great secrecy rate improvements through optimizing shape of the protected zone in use. Furthermore, we show that the optimal protected zone shape for mmWave links appears as a compromise between protecting the angle versus distance dimension, which would otherwise form to protect solely the distance dimension for sub-6 GHz links. We also numerically evaluate the impact of transmission power, protected-zone size, and UAV altitude on the secrecy-rate performance improvement for the sake of practical deployments.}, number={4}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Yapici, Yavuz and Rupasinghe, Nadisanka and Guvenc, Ismail and Dai, Huaiyu and Bhuyan, Arupjyoti}, year={2021}, month={Apr}, pages={3568–3582} }
 @article{singh_bhattacherjee_ozturk_guvenc_dai_sichitiu_bhuyan_2021, title={Placement of mmWave Base Stations for Serving Urban Drone Corridors}, DOI={10.1109/VTC2021-Spring51267.2021.9448923}, abstractNote={As the use of unmanned aerial vehicles (UAVs) in various commercial, civil, and military applications increases, it becomes important to study the design of aerial drone corridors that can support multiple simultaneous UAV missions. In this work, we study the placement of base stations (BSs) to serve aerial drone corridors while satisfying specific UAV mission requirements, such as the geometrical waypoints for the UAV to fly through and the minimum data rate to be supported along the mission trajectory. We develop a mathematical model of the drone corridor and propose a brute force algorithm that leverages A* search to meet the quality of service (QoS) requirements of the corridor by choosing the minimal set of BS locations from a pre-determined initial set. Using raytracing simulations, BS placement results are presented for various antenna array sizes in a dense urban region in East Manhattan. It was found that, for the scenario under consideration, a single BS equipped with an 8x8 antenna array is sufficient to satisfy the given QoS requirements of the corridor, while two BSs are required when using 4x4 antenna arrays.}, journal={2021 IEEE 93RD VEHICULAR TECHNOLOGY CONFERENCE (VTC2021-SPRING)}, author={Singh, Simran and Bhattacherjee, Udita and Ozturk, Ender and Guvenc, Ismail and Dai, Huaiyu and Sichitiu, Mihail and Bhuyan, Arupjyoti}, year={2021} }
 @article{maeng_yapici_guvenc_dai_bhuyan_2021, title={Power Allocation for Fingerprint-Based PHY-Layer Authentication with mmWave UAV Networks}, ISSN={["1550-3607"]}, DOI={10.1109/ICC42927.2021.9500273}, abstractNote={Physical layer security (PLS) techniques can help to protect wireless networks from eavesdropper attacks. In this paper, we consider the authentication technique that uses fingerprint embedding to defend 5G cellular networks with unmanned aerial vehicle (UAV) systems from eavesdroppers and intruders. Since the millimeter wave (mmWave) cellular networks use narrow and directional beams, PLS can take further advantage of the 3D spatial dimension for improving the authentication of UAV users. Considering a multi-user mmWave cellular network, we propose a power allocation technique that jointly takes into account splitting of the transmit power between the precoder and the authentication tag, which manages both the secrecy as well as the achievable rate. Our results show that we can obtain optimal achievable rate with expected secrecy.}, journal={IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC 2021)}, author={Maeng, Sung Joon and Yapici, Yavuz and Guvenc, Ismail and Dai, Huaiyu and Bhuyan, Arupjyoti}, year={2021} }
 @article{xiao_lu_xu_zhuang_dai_2021, title={Reinforcement Learning-Based Physical-Layer Authentication for Controller Area Networks}, volume={16}, ISSN={["1556-6021"]}, DOI={10.1109/TIFS.2021.3056206}, abstractNote={In controller area networks (CANs), electronic control units (ECUs) such as telematics ECUs and on-board diagnostic ports must protect the message exchange from spoofing attacks. In this paper, we propose a CAN bus authentication framework that exploits physical layer features of the messages, including message arrival intervals and signal voltages, and applies reinforcement learning to choose the authentication mode and parameter. By applying the Dyna architecture and using a double estimator, this scheme improves the utility in terms of authentication accuracy without changing the CAN bus protocol or the ECU components and requiring knowledge of the spoofing model. We also propose a deep learning version to further improve the authentication efficiency for the CAN bus. The learning scheme applies a hierarchical structure to reduce the exploration time, and uses two deep neural networks to compress the high-dimensional state space and to fully exploit the physical authentication experiences. We provide the computational complexity and the performance analysis. Experimental results verify the theoretical analysis and show that our proposed schemes significantly improve the authentication accuracy as compared with benchmark schemes.}, journal={IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY}, author={Xiao, Liang and Lu, Xiaozhen and Xu, Tangwei and Zhuang, Weihua and Dai, Huaiyu}, year={2021}, pages={2535–2547} }
 @article{bhuyan_guvenc_dai_sichitiu_singh_rahmati_maeng_2021, title={Secure 5G Network for a Nationwide Drone Corridor}, ISSN={["1095-323X"]}, DOI={10.1109/AERO50100.2021.9438162}, abstractNote={5G can provide the multiplicative capacity gains needed to support a large number of drones/UAS (Unmanned Aircraft Systems). 5G cellular networks with newly available millimeter wave (mmWave) frequency bands can provide wireless communication links for control as well as data traffic for drones and drone swarms. Drones are becoming increasingly important for commercial uses such as delivery and transportation as well as for public safety search and rescue of natural disaster victims, surveillance of remote critical infrastructure, surveys of environmental quality in protected regions, and detection of threats during major public events. This paper presents research findings in the following areas critical to validating the effectiveness of providing required 5G access to the drones with security, reliability, and spectral efficiency: 1) Radio coverage for the drone corridor by adding a separate set of antennas for coverage in the air while the conventional set of antennas continues to provide coverage on the ground. Beam transmission and validation with ray-tracing simulations are covered. 2) Optimization of uplink communication from a swarm of drones with a single mmWave beam by grouping the drones with power allocations for non-orthogonal multiple access (NOMA). 3) Optimization of the network lifetime of a swarm of drones resulting in suitable trajectories in the presence of interference. 4) Methods including precoding that can enhance physical layer security with channel information about the interference source. The paper concludes with plans for future research to provide further scientific basis for the proposed cellular drone network.}, journal={2021 IEEE AEROSPACE CONFERENCE (AEROCONF 2021)}, author={Bhuyan, Arupjyoti and Guvenc, Ismail and Dai, Huaiyu and Sichitiu, Mihail L. and Singh, Simran and Rahmati, Ali and Maeng, Sung Joon}, year={2021} }
 @article{zhang_he_wu_dai_2021, title={Spectral Graph Theory Based Resource Allocation for IRS-Assisted Multi-Hop Edge Computing}, ISSN={["2159-4228"]}, DOI={10.1109/INFOCOMWKSHPS51825.2021.9484578}, abstractNote={The performance of mobile edge computing (MEC) depends critically on the quality of the wireless channels. From this viewpoint, the recently advocated intelligent reflecting surface (IRS) technique that can proactively reconfigure wireless channels is anticipated to bring unprecedented performance gain to MEC. In this paper, the problem of network throughput optimization of an IRS-assisted multi-hop MEC network is investigated, in which the phase-shifts of the IRS and the resource allocation of the relays need to be jointly optimized. However, due to the coupling among the transmission links of different hops caused by the utilization of the IRS and the complicated multi-hop network topology, it is difficult to solve the considered problem by directly applying existing optimization techniques. Fortunately, by exploiting the underlying structure of the network topology and spectral graph theory, it is shown that the network throughput can be well approximated by the second smallest eigenvalue of the network Laplacian matrix. This key finding allows us to develop an effective iterative algorithm for solving the considered problem. Numerical simulations are performed to corroborate the effectiveness of the proposed scheme.}, journal={IEEE CONFERENCE ON COMPUTER COMMUNICATIONS WORKSHOPS (IEEE INFOCOM WKSHPS 2021)}, author={Zhang, Huilian and He, Xiaofan and Wu, Qingqing and Dai, Huaiyu}, year={2021} }
 @article{zou_wang_dai_2021, title={Temporal and Spectral Analysis of Spectrum Hole Distributions in an LTE Cell}, ISSN={["2576-6813"]}, DOI={10.1109/GLOBECOM46510.2021.9685339}, abstractNote={Dynamic Spectrum Access (DSA) is proposed to improve spectrum efficiency by enabling opportunistic access of underutilized spectrum resources. The key to successful DSA operations is the correct understanding of spectrum hole distributions. Though huge amounts of studies have been conducted on spectrum tenancy due to the significance of spectrum hole distributions, there are still two overlooked aspects. One is the measurement resolution, and the other is the spectrum distribution in the spectral perspective. Since the spectrum hole analysis relies on the measurement data, we decode the LTE downlink control information to obtain the spectrum tenancy at the same time-frequency granularity with LTE scheduling. We analyze the spectrum hole distributions in fine resolutions along both the temporal and the spectral dimensions, and investigate the performance of two widely used spectrum tenancy models, the Markov and the on/off models, in terms of their capabilities on capturing the distributions of spectrum holes. Our observations include but are not limited to the following. The spectrum holes follow the power law distributions when examined in the LTE scheduling unit from both the time and the frequency perspectives. Both Markov and on/off models should be fitted to the spectrum tenancy along the frequency perspective to achieve their best performance.}, journal={2021 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={Zou, Rui and Wang, Wenye and Dai, Huaiyu}, year={2021} }
 @article{xiao_ding_huang_liu_tang_dai_2021, title={UAV Anti-Jamming Video Transmissions With QoE Guarantee: A Reinforcement Learning-Based Approach}, volume={69}, ISSN={["1558-0857"]}, DOI={10.1109/TCOMM.2021.3087787}, abstractNote={Unmanned aerial vehicles (UAVs) that are widely utilized for video capturing, processing and transmission have to address jamming attacks with dynamic topology and limited energy. In this paper, we propose a reinforcement learning (RL)-based UAV anti-jamming video transmission scheme to choose the video compression quantization parameter, the channel coding rate, the modulation and power control strategies against jamming attacks. More specifically, this scheme applies RL to choose the UAV video compression and transmission policy based on the observed video task priority, the UAV-controller channel state and the received jamming power. This scheme enables the UAV to guarantee the video quality-of-experience (QoE) and reduce the energy consumption without relying on the jamming model or the video service model. A safe RL-based approach is further proposed, which uses deep learning to accelerate the UAV learning process and reduce the video transmission outage probability. The computational complexity is provided and the optimal utility of the UAV is derived and verified via simulations. Simulation results show that the proposed schemes significantly improve the video quality and reduce the transmission latency and energy consumption of the UAV compared with existing schemes.}, number={9}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Xiao, Liang and Ding, Yuzhen and Huang, Jinhao and Liu, Sicong and Tang, Yuliang and Dai, Huaiyu}, year={2021}, month={Sep}, pages={5933–5947} }
 @article{liu_tong_wang_bai_dai_2021, title={UAV-Aided Data Collection for Information Freshness in Wireless Sensor Networks}, volume={20}, ISBN={1558-2248}, DOI={10.1109/TWC.2020.3041750}, abstractNote={In this work, we study the UAV-enabled data collection problem for high information freshness in wireless sensor networks, where one UAV is dispatched to collect information of ground Sensor Nodes (SNs). The information freshness is measured by the Age of Information (AoI) of each SN, which is defined as the sum of the SN’s data uploading time and the UAV’s flight time after leaving this SN. Two optimization problems of age-optimal data collection are formulated to minimize the SNs’ maximal AoI and average AoI, respectively. An iterative SN association and trajectory planning policy is proposed to seek the age-optimal solutions via an iterative two-step procedure. Firstly, SN association is performed based on the affinity propagation clustering method with an appropriate weight to find a set of data Collection Points (CPs) at which the UAV hovers to collect data and schedules which SNs to upload in what order. Based on this result, trajectory planning is performed to find the max-AoI-optimal and ave-AoI-optimal trajectories of the UAV along the CPs using dynamic programming or genetic algorithm. With the optimized clustering weight, the proposed scheme can always strike a balance between the SNs’ uploading time and the UAV’s flight time in various scenarios. Simulation results show that the proposed strategy can improve the freshness of information collected from all the SNs.}, number={4}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Liu, Juan and Tong, Peng and Wang, Xijun and Bai, Bo and Dai, Huaiyu}, year={2021}, month={Apr}, pages={2368–2382} }
 @article{liwang_hosseinalipour_gao_tang_huang_dai_2020, title={Allocation of Computation-Intensive Graph Jobs Over Vehicular Clouds in IoV}, volume={7}, ISSN={["2327-4662"]}, DOI={10.1109/JIOT.2019.2949602}, abstractNote={Graph jobs represent a wide variety of computation-intensive tasks in which computations are represented by graphs consisting of components (denoting either data sources or data processing) and edges (corresponding to data flows between the components). Recent years have witnessed dramatic growth in smart vehicles and computation-intensive graph jobs, which pose new challenges to the provision of efficient services related to the Internet of Vehicles. Fortunately, vehicular clouds (VCs) formed by a collection of vehicles, which allows jobs to be offloaded among vehicles, can substantially alleviate heavy onboard workloads and enable on-demand provisioning of computational resources. In this article, we present a novel framework for VCs that maps components of graph jobs to service providers via opportunistic vehicle-to-vehicle communication. Then, graph job allocation over VCs is formulated as a nonlinear integer programming with respect to vehicles’ contact duration and available resources, aiming to minimize the job completion time and data exchange cost. The problem is addressed for two scenarios: 1) low-traffic and 2) rush-hour scenarios. For the former, we determine the optimal solutions for the problem. In the latter case, given the intractable computations for deriving feasible allocations, we propose a novel low complexity randomized graph job allocation mechanism by considering hierarchical tree-based subgraph isomorphism extraction. The evaluation of the performance of both optimal and proposed randomized algorithms with two greedy-based baseline methods is carried out through extensive simulations.}, number={1}, journal={IEEE INTERNET OF THINGS JOURNAL}, author={LiWang, M. and Hosseinalipour, Seyyedali and Gao, Zhibin and Tang, Yuliang and Huang, Lianfen and Dai, Huaiyu}, year={2020}, month={Jan}, pages={311–324} }
 @article{huang_jin_dai_2020, title={Differential Privacy and Prediction Uncertainty of Gossip Protocols in General Networks}, ISSN={["2576-6813"]}, DOI={10.1109/GLOBECOM42002.2020.9322558}, abstractNote={Recent advances in social media and information technology have enabled much faster dissemination of information, while at the same time raise concerns about privacy leakage after various privacy breaches. Therefore, the privacy guarantees of information dissemination protocols have attracted increasing research interests, among which the gossip protocols assume vital importance in various information exchange applications. Very recently, the rigorous framework of differential privacy has been introduced to measure the privacy guarantees of gossip protocols in the simplified complete network scenario. In this work, we extend the study to general networks. First, lower bounds of the differential privacy guarantees are derived for the gossip protocols in general networks in both synchronous and asynchronous settings. The prediction uncertainty of the source node given a uniform prior is also determined. It is found that source anonymity is closely related to some key network structure parameters in the general network setting. Then, we investigate information spreading in wireless networks with unreliable communications, and quantity the tradeoff between differential privacy guarantees and information spreading efficiency. Finally, considering that the attacker may not be present in the beginning of the information dissemination process, the scenario of delayed monitoring is studied and the corresponding differential privacy guarantees are evaluated.}, journal={2020 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={Huang, Yufan and Jin, Richeng and Dai, Huaiyu}, year={2020} }
 @article{rahmati_hosseinalipour_yapici_guvenc_dai_bhuyan_2020, title={Energy-Efficient Beamforming and Power Control for Uplink NOMA in mmWave UAV Networks}, ISSN={["2576-6813"]}, DOI={10.1109/GLOBECOM42002.2020.9348114}, abstractNote={The integration of unmanned aerial vehicles (UAVs) into the terrestrial communications networks with a variety of tasks is viewed as a key technology for 5G and beyond. In this work, we consider the uplink millimeter-wave (mmWave) transmission between a set of UAVs and a base station (BS), where the UAVs deploy uplink non-orthogonal multiple access (NOMA) in multiple clusters. Furthermore, the BS also serves its own desired ground user equipment (UE) in the presence of many other ground UEs associated with other cells, which share the same frequency band. Considering the limited energy budget of UAVs, we formulate an energy efficiency (EE) problem, and propose a solution aided by the Dinkelbach's algorithm and successive convex approximation (SCA). Using realistic air-to-ground (A2G) and terrestrial channel models, we assess the performance of the proposed algorithm under various circumstances (maximum transmit power for UAVs, quality-of-service (QoS) constraint for the desired UE, etc.), and identify the best use cases.}, journal={2020 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={Rahmati, Ali and Hosseinalipour, Seyyedali and Yapici, Yavuz and Guvenc, Ismail and Dai, Huaiyu and Bhuyan, Arupjyoti}, year={2020} }
 @article{hosseinalipour_brinton_aggarwal_dai_chiang_2020, title={From Federated to Fog Learning: Distributed Machine Learning over Heterogeneous Wireless Networks}, volume={58}, ISSN={["1558-1896"]}, DOI={10.1109/MCOM.001.2000410}, abstractNote={Machine learning (ML) tasks are becoming ubiquitous in today's network applications. Federated learning has emerged recently as a technique for training ML models at the network edge by leveraging processing capabilities across the nodes that collect the data. There are several challenges with employing conventional federated learning in contemporary networks, due to the significant heterogeneity in compute and communication capabilities that exist across devices. To address this, we advocate a new learning paradigm called fog learning, which will intelligently distribute ML model training across the continuum of nodes from edge devices to cloud servers. Fog learning enhances federated learning along three major dimensions: network, heterogeneity, and proximity. It considers a multi-layer hybrid learning framework consisting of heterogeneous devices with various proximities. It accounts for the topology structures of the local networks among the heterogeneous nodes at each network layer, orchestrating them for collaborative/cooperative learning through device-to-device communications. This migrates from star network topologies used for parameter transfers in federated learning to more distributed topologies at scale. We discuss several open research directions toward realizing fog learning.}, number={12}, journal={IEEE COMMUNICATIONS MAGAZINE}, author={Hosseinalipour, Seyyedali and Brinton, Christopher G. and Aggarwal, Vaneet and Dai, Huaiyu and Chiang, Mung}, year={2020}, month={Dec}, pages={41–47} }
 @article{he_jin_dai_2020, title={Joint Power and Deployment Optimization for Multi-UAV Remote Edge Computing}, ISSN={["2576-6813"]}, DOI={10.1109/GLOBECOM42002.2020.9348243}, abstractNote={Driven by the dramatic growth in computing capability and the inherent mobility of the unmanned aerial vehicles (UAVs), the recently advocated UAV edge computing paradigm is expected to enhance the coverage and the on-demand deployment capability of existing terrestrial edge computing systems. Nonetheless, due to the limited onboard resource of the UAV, single- UAV edge computing systems may still be incompetent when serving remote users. Although using multiple UAVs to form a traditional relay network is a viable solution to remote edge computing, it fails to exploit the computing capability of the UAVs. This entails a pressing need to develop multi-UAV remote edge computing mechanisms that allow the UAVs to handle part of the computation tasks using their local processors while conducting multi-hop computation task offloading. To achieve the best performance in such cases, the UAVs have to properly split their power budget for communication and computation and also move to suitable service locations. Nonetheless, finding the optimal UAV power allocation and deployment turns out to be an intractable high-dimensional monotonic optimization problem, even for a mild number of UAVs. To overcome this challenge, a more efficient algorithm that has a complexity only linear in the number of UAVs is developed by exploiting the special structure of this problem. In addition to analysis, numerical results are provided to validate the effectiveness of the proposed scheme.}, journal={2020 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={He, Xiaofan and Jin, Richeng and Dai, Huaiyu}, year={2020} }
 @article{chattopadhyay_dai_eun_2020, title={Maximization of Robustness of Interdependent Networks Under Budget Constraints}, volume={7}, ISSN={["2327-4697"]}, DOI={10.1109/TNSE.2019.2935068}, abstractNote={We consider the problem of interlink optimization in multilayer interdependent networks under cost constraints, with the objective of maximizing the robustness of the network against component (node) failures. Diverting from the popular approaches of branching process based analysis of the failure cascades or using a supra-adjacency matrix representation of the multilayer network and employing classical metrics, in this work, we present a surrogate metric based framework for constructing interlinks to maximize the network robustness. In particular, we focus on three representative mechanisms of failure propagation, namely, connected component based cascading failure, load distribution in interdependent networks, and connectivity in demand-supply networks, and propose metrics to track the network robustness for each of these mechanisms. Owing to their mathematical tractability, these metrics allow us to optimize the interlink structure to enhance robustness. Furthermore, we are able to introduce the cost of construction into the interlink design problem, a practical feature largely ignored in relevant literature. We simulate the failure cascades on real world networks to compare the performance of our interlinking strategies with the state of the art heuristics and demonstrate their effectiveness.}, number={3}, journal={IEEE TRANSACTIONS ON NETWORK SCIENCE AND ENGINEERING}, author={Chattopadhyay, Srinjoy and Dai, Huaiyu and Eun, Do Young}, year={2020}, pages={1441–1452} }
 @article{he_jin_dai_2020, title={Peace: Privacy-Preserving and Cost-Efficient Task Offloading for Mobile-Edge Computing}, volume={19}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2019.2958091}, abstractNote={The limited information processing capability and battery life of mobile devices is becoming a bottleneck in delivering more advanced and high-quality services to the customers. To address this problem, the recently advocated mobile-edge computing (MEC) architecture is promising, where the essential idea is to bring the computation resource to the network edge and allow users to wirelessly offload resource demanding computation tasks to the nearby MEC servers for potentially faster execution and lower battery consumption. Nonetheless, the existing understanding of the privacy aspect of MEC is still far from complete. In this work, a user presence inference attack that invades user privacy by exploiting the feature tasks offloaded from users is identified for MEC. Existing privacy-preserving techniques developed for other applications cannot be applied to defeat this attack in MEC, as they may disrupt the optimal task offloading scheduling and cause severe degradation in user experience. With this consideration, a novel privacy-preserving and cost-efficient (PEACE) task offloading scheme that can preserve user privacy while still ensure the best possible user experience is developed in this work based on the generic Lyapunov optimization framework. The effectiveness of the proposed scheme is validated through both analysis and simulations.}, number={3}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={He, Xiaofan and Jin, Richeng and Dai, Huaiyu}, year={2020}, month={Mar}, pages={1814–1824} }
 @article{he_jin_dai_2020, title={Physical-Layer Assisted Secure Offloading in Mobile-Edge Computing}, volume={19}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2020.2979456}, abstractNote={The wireless offloading feature of the recently advocated mobile-edge computing (MEC) imposes a risk of disclosing private user data to eavesdroppers. Physical-layer security approaches that are built on information theoretic methods can be applied to defend eavesdropping in MEC. Nonetheless, directly incorporating existing physical-layer security technique may introduce extra energy and delay costs to the resource-limited mobile device and thus substantially disrupt the users’ offloading decisions. To fulfill effective secure offloading in MEC, there is a compelling need to properly optimize existing physical-layer security techniques and develop new offloading schemes accordingly. With this consideration, a novel physical-layer assisted secure offloading scheme is proposed in this work, in which the edge server proactively broadcasts jamming signals to impede eavesdropping and leverages full-duplex communication technique to effectively suppress the self-interference. Finding the optimal jamming signal and the corresponding optimal offloading ratio turns out to be a challenging bilevel optimization problem. The special structure of the secure offloading problem is exploited to develop efficient offloading algorithms. Numerical results are presented to validate the effectiveness of the proposed scheme.}, number={6}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={He, Xiaofan and Jin, Richeng and Dai, Huaiyu}, year={2020}, month={Jun}, pages={4054–4066} }
 @article{hosseinalipour_nayak_dai_2020, title={Power-Aware Allocation of Graph Jobs in Geo-Distributed Cloud Networks}, volume={31}, ISSN={["1558-2183"]}, DOI={10.1109/TPDS.2019.2943457}, abstractNote={In the era of big-data, the jobs submitted to the clouds exhibit complicated structures represented by graphs, where the nodes denote the sub-tasks each of which can be accommodated at a slot in a server, while the edges indicate the communication constraints among the sub-tasks. We develop a framework for efficient allocation of graph jobs in geo-distributed cloud networks (GDCNs), explicitly considering the power consumption of the datacenters (DCs). We address the following two challenges arising in graph job allocation: i) the allocation problem belongs to NP-hard nonlinear integer programming; ii) the allocation requires solving the NP-complete sub-graph isomorphism problem, which is particularly cumbersome in large-scale GDCNs. We develop a suite of efficient solutions for GDCNs of various scales. For small-scale GDCNs, we propose an analytical approach based on convex programming. For medium-scale GDCNs, we develop a distributed allocation algorithm exploiting the processing power of DCs in parallel. Afterward, we provide a novel low-complexity (decentralized) sub-graph extraction method, based on which we introduce cloud crawlers aiming to extract allocations of good potentials for large-scale GDCNs. Given these suggested strategies, we further investigate strategy selection under both fixed and adaptive DC pricing schemes, and propose an online learning algorithm for each.}, number={4}, journal={IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS}, author={Hosseinalipour, Seyyedali and Nayak, Anuj and Dai, Huaiyu}, year={2020}, month={Apr}, pages={749–765} }
 @article{hosseinalipour_mao_eun_dai_2020, title={Prevention and Mitigation of Catastrophic Failures in Demand-Supply Interdependent Networks}, volume={7}, ISSN={["2327-4697"]}, DOI={10.1109/TNSE.2019.2951084}, abstractNote={We propose a generic system model for a special category of interdependent networks, demand-supply networks, in which the demand and the supply nodes are associated with heterogeneous loads and resources, respectively. Our model sheds a light on a unique cascading failure mechanism induced by resource/load fluctuations, which in turn opens the door to conducting stress analysis on interdependent networks. Compared to the existing literature mainly concerned with the node connectivity, we focus on developing effective resource allocation methods to prevent these cascading failures from happening and to mitigate/confine them upon occurrence in the network. To prevent cascading failures, we identify some dangerous stress mechanisms, based on which we quantify the robustness of the network in terms of the resource configuration scheme. Afterward, we identify the optimal resource configuration under two resource/load fluctuations scenarios: uniform and proportional fluctuations. We further investigate the optimal resource configuration problem considering heterogeneous resource sharing costs among the nodes. To mitigate/confine ongoing cascading failures, we propose two network adaptations mechanisms: intentional failure and resource re-adjustment, based on which we propose an algorithm to mitigate an ongoing cascading failure while reinforcing the surviving network with a high robustness to avoid further failures.}, number={3}, journal={IEEE TRANSACTIONS ON NETWORK SCIENCE AND ENGINEERING}, author={Hosseinalipour, Seyyedali and Mao, Jiayu and Eun, Do Young and Dai, Huaiyu}, year={2020}, pages={1710–1723} }
 @article{lu_xiao_dai_dai_2020, title={UAV-AIDED CELLULAR COMMUNICATIONS WITH DEEP REINFORCEMENT LEARNING AGAINST JAMMING}, volume={27}, ISSN={["1558-0687"]}, DOI={10.1109/MWC.001.1900207}, abstractNote={Cellular systems have to resist smart jammers that can optimize their selection of jamming channels and powers based on the estimated ongoing network states. In this article, we present an unmanned aerial vehicle (UAV) aided cellular framework against jamming, in which an UAV uses reinforcement learning to choose the relay policy for a mobile user whose serving base station is attacked by a jammer. More specifically, the UAV applies deep reinforcement learning and transfer learning to help cellular systems resist smart jamming without knowing the cellular topology, the message generation model, the server computation model and the jamming model, based on the previous anti-jamming relay experiences and the observed current communication status. The performance bound in terms of the bit error rate and the UAV energy consumption is derived from the Nash equilibrium of the studied dynamic relay game and verified via simulations. Simulation results show that this scheme can reduce the bit error rate and save the UAV energy consumption in comparison with the benchmark.}, number={4}, journal={IEEE WIRELESS COMMUNICATIONS}, author={Lu, Xiaozhen and Xiao, Liang and Dai, Canhuang and Dai, Huaiyu}, year={2020}, month={Aug}, pages={48–53} }
 @article{liwang_dai_gao_du_guizani_dai_2019, title={A COMPUTATION OFFLOADING INCENTIVE MECHANISM WITH DELAY AND COST CONSTRAINTS UNDER 5G SATELLITE-GROUND IOV ARCHITECTURE}, volume={26}, ISSN={["1558-0687"]}, DOI={10.1109/MWC.2019.1800364}, abstractNote={The 5G Internet of Vehicles has become a new paradigm alongside the growing popularity and variety of computation-intensive applications with high requirements for computational resources and analysis capabilities. Existing network architectures and resource management mechanisms may not sufficiently guarantee satisfactory Quality of Experience and network efficiency, mainly suffering from the coverage limitation of road side units, unsatisfactory computational resources and capabilities of onboard equipment, frequently changing network topologies, and ineffective resource management schemes. To meet the demands of such applications, in this article we first establish a novel architecture by integrating the satellite network with the 5G cloud-enabled Internet of Vehicles to efficiently support seamless coverage and efficient resource management. An incentive mechanism based joint optimization problem of opportunistic computation offloading under delay and cost constraints is formulated under the proposed 5G integrated satellite-ground framework, where a vehicular user can either be a service requestor allowed to offload workload to nearby vehicles via vehicle-to-vehicle channels while effectively controlling the cost, or a service provider who provides computing services while protecting profits. As the optimization problem is non-convex and NP-hard, simulated annealing based on the Markov Chain Monte Carlo as well as the metropolis algorithm is applied which can efficaciously obtain both high-quality and cost-effective approximations of global optimal solutions. The effectiveness of the proposed mechanism is corroborated through simulation results.}, number={4}, journal={IEEE WIRELESS COMMUNICATIONS}, author={LiWang, Minghui and Dai, Shijie and Gao, Zhibin and Du, Xiaojiang and Guizani, Mohsen and Dai, Huaiyu}, year={2019}, month={Aug}, pages={124–132} }
 @article{liwang_dai_gao_tang_dai_2019, title={A Truthful Reverse-Auction Mechanism for Computation Offloading in Cloud-Enabled Vehicular Network}, volume={6}, ISSN={["2327-4662"]}, DOI={10.1109/JIOT.2018.2875507}, abstractNote={The growth of smart vehicles and computation-intensive applications poses new challenges in providing reliable and efficient vehicular services. Offloading such applications from vehicles to mobile edge cloud servers has been considered as a remedy, although resource limitations and coverage constraints of the cloud service may still result in unsatisfactory performance. Recent studies have shown that exploiting the unused resources of nearby vehicles for application execution can augment the computational capabilities of application owners while alleviating heavy on-board workloads. However, encouraging vehicles to share resources or execute applications for others remains a sensitive issue due to user selfishness. To address this issue, we establish a novel computation offloading marketplace in vehicular networks where a Vickrey–Clarke–Groves based reverse auction mechanism utilizing integer linear programming (ILP) problem is formulated while satisfying the desirable economical properties of truthfulness and individual rationality. As ILP has high computation complexity which brings difficulties in implementation under larger and fast changing network topologies, we further develop an efficient unilateral-matching-based mechanism, which offers satisfactory suboptimal solutions with polynomial computational complexity, truthfulness and individual rationality properties as well as matching stability. Simulation results show that, as compared with baseline methods, the proposed unilateral-matching-based mechanism can greatly improve the system efficiency of vehicular networks in all traffic scenarios.}, number={3}, journal={IEEE INTERNET OF THINGS JOURNAL}, author={Liwang, Minghui and Dai, Shijie and Gao, Zhibin and Tang, Yuliang and Dai, Huaiyu}, year={2019}, month={Jun}, pages={4214–4227} }
 @article{benmahmoud_dai_2019, title={A unified framework for the performance evaluation of single-branch dual-hop AF relaying in the presence of transceiver hardware impairments}, volume={32}, ISSN={["1874-4907"]}, DOI={10.1016/j.phycom.2018.12.008}, abstractNote={In this paper, a general four-parameter end-to-end signal-to-noise with distortion ratio (SNDR) model for single-branch dual-hop amplify-and-forward (AF) relaying with/without the presence of transceiver hardware impairments is proposed. This model encompasses standard as well as non-standard AF relay configurations for both ideal and non-ideal transceiver hardware cases. A unified framework to evaluate the performance of single-branch dual-hop AF relaying is then formulated. This is accomplished by deriving new closed-form expressions for some statistics of some functions of two independent Gamma random variables. Based on these closed-form expressions, an exact analytical expression for the outage probability (OP) and an upper bound for the ergodic capacity are derived. Monte Carlo simulations’ results are provided to verify the accuracy of the analytical results.}, journal={PHYSICAL COMMUNICATION}, author={Benmahmoud, Slimane and Dai, Huaiyu}, year={2019}, month={Feb}, pages={231–241} }
 @article{he_jin_dai_2019, title={Camouflaging Mobile Primary Users in Database-Driven Cognitive Radio Networks}, volume={8}, ISSN={["2162-2345"]}, DOI={10.1109/LWC.2018.2846621}, abstractNote={The ever-increasing wireless demand has led to the opening of the 3.5 GHz spectrum band to commercial applications and the enforcement of database-driven cognitive radio networks. Along with its advantages, this technological amendment raises new privacy concerns, especially on the primary users (PUs) that are sensitive federal and military devices. Existing studies mainly focus on static PUs while the privacy issue of mobile PUs still remains unresolved. In this letter, a novel scheme that can camouflage mobile PUs through generating low-cost fake trajectories in the database is developed, and its effectiveness is validated by numerical results.}, number={1}, journal={IEEE WIRELESS COMMUNICATIONS LETTERS}, author={He, Xiaofan and Jin, Richeng and Dai, Huaiyu}, year={2019}, month={Feb}, pages={21–24} }
 @article{he_jin_dai_2019, title={Deep PDS-Learning for Privacy-Aware Offloading in MEC-Enabled IoT}, volume={6}, ISSN={["2327-4662"]}, DOI={10.1109/JIOT.2018.2878718}, abstractNote={The rapid uptake of Internet-of-Things (IoT) devices imposes an unprecedented pressure for data communication and processing on the backbone network and the central cloud infrastructure. To overcome this issue, the recently advocated mobile-edge computing (MEC)-enabled IoT is promising. Meanwhile, driven by the growing social awareness of privacy, significant research efforts have been devoted to relevant issues in IoT; however, most of them mainly focus on the conventional cloud-based IoT. In this paper, a new privacy vulnerability caused by the wireless offloading feature of MEC-enabled IoT is identified. To address this vulnerability, an effective privacy-aware offloading scheme is developed based on a newly proposed deep post-decision state (PDS)-learning algorithm. By exploiting extra prior information, the proposed deep PDS-learning algorithm allows the IoT devices to learn a good privacy-aware offloading strategy much faster than the conventional deep ${Q}$ -network. Theoretic analysis and numerical results are provided to corroborate the correctness and the effectiveness of the proposed algorithm.}, number={3}, journal={IEEE INTERNET OF THINGS JOURNAL}, author={He, Xiaofan and Jin, Richeng and Dai, Huaiyu}, year={2019}, month={Jun}, pages={4547–4555} }
 @article{xiao_sheng_liu_dai_peng_song_2019, title={Deep Reinforcement Learning-Enabled Secure Visible Light Communication Against Eavesdropping}, volume={67}, ISSN={["1558-0857"]}, DOI={10.1109/TCOMM.2019.2930247}, abstractNote={The inherent broadcast characteristics of the visible light communication (VLC) channel makes VLC downlinks susceptible to unauthorized terminals in many actual VLC scenarios, such as offices and shopping centers. This paper considers a multiple-input-single-output (MISO) VLC scenario with multiple light fixtures acting as the transmitter, a VLC receiver as the legitimate user, and an eavesdropper attempting to intercept the undisclosed information. To improve the confidentiality of VLC links, a physical-layer anti-eavesdropping framework is proposed to obscure the unauthorized eavesdroppers and diminishes their capability of inferring the information through smart beamforming over the MISO VLC wiretap channel. To cope with the intractable problem of finding the theoretically optimal solution of the secrecy rate and utility for the MISO VLC wiretapping channel, a reinforcement learning (RL)-based VLC beamforming control scheme is proposed to achieve the optimal beamforming policy against the eavesdropper. Furthermore, a deep RL-based VLC beamforming control scheme is proposed to handle the curse of dimensionality for both observation space and action space and avoid the quantization error of the RL-based algorithm. Simulation results show that the proposed learning-based VLC beamforming control schemes can significantly decrease the bit error rate of the legitimate receiver and increase the secrecy rate and utility of the anti-eavesdropping MISO VLC system, compared with the benchmark strategy.}, number={10}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Xiao, Liang and Sheng, Geyi and Liu, Sicong and Dai, Huaiyu and Peng, Mugen and Song, Jian}, year={2019}, month={Oct}, pages={6994–7005} }
 @article{min_wan_xiao_chen_xia_wu_dai_2019, title={Learning-Based Privacy-Aware Offloading for Healthcare IoT With Energy Harvesting}, volume={6}, ISSN={["2327-4662"]}, DOI={10.1109/JIOT.2018.2875926}, abstractNote={Mobile edge computing helps healthcare Internet of Things (IoT) devices with energy harvesting provide satisfactory quality of experiences for computation intensive applications. We propose a reinforcement learning (RL)-based privacy-aware offloading scheme to help healthcare IoT devices protect both the user location privacy and the usage pattern privacy. More specifically, this scheme enables a healthcare IoT device to choose the offloading rate that improves the computation performance, protects user privacy, and saves the energy of the IoT device without being aware of the privacy leakage, IoT energy consumption, and edge computation model. This scheme uses transfer learning to reduce the random exploration at the initial learning process and applies a Dyna architecture that provides simulated offloading experiences to accelerate the learning process. A post-decision state learning method uses the known channel state model to further improve the offloading performance. We provide the performance bound of this scheme regarding the privacy level, the energy consumption, and the computation latency for three typical healthcare IoT offloading scenarios. Simulation results show that this scheme can reduce the computation latency, save the energy consumption, and improve the privacy level of the healthcare IoT device compared with the benchmark scheme.}, number={3}, journal={IEEE INTERNET OF THINGS JOURNAL}, author={Min, Minghui and Wan, Xiaoyue and Xiao, Liang and Chen, Ye and Xia, Minghua and Wu, Di and Dai, Huaiyu}, year={2019}, month={Jun}, pages={4307–4316} }
 @article{huang_dai_2019, title={Multiplex Conductance and Gossip Based Information Spreading in Multiplex Networks}, volume={6}, ISSN={["2327-4697"]}, DOI={10.1109/TNSE.2018.2838104}, abstractNote={In this network era, not only people are connected, different networks are also coupled through various interconnections. This kind of network of networks, or multilayer networks, has attracted research interest recently, and many beneficial features have been discovered. However, quantitative study of information spreading in such networks is essentially lacking. Despite some existing results in single networks, the layer heterogeneity and complicated interconnections among the layers make the study of information spreading in this type of networks challenging. In this work, we study the information spreading time in multiplex networks, adopting the gossip (random-walk) based information spreading model. A new metric called multiplex conductance is defined based on the multiplex network structure and used to quantify the information spreading time in a general multiplex network in the idealized setting. Multiplex conductance is then evaluated for some interesting multiplex networks to facilitate understanding in this new area. Finally, the tradeoff between the information spreading efficiency improvement and the layer cost is examined to explain the user's social behavior and motivate effective multiplex network designs.}, number={3}, journal={IEEE TRANSACTIONS ON NETWORK SCIENCE AND ENGINEERING}, author={Huang, Yufan and Dai, Huaiyu}, year={2019}, pages={391–401} }
 @article{jin_he_dai_2019, title={On the Security-Privacy Tradeoff in Collaborative Security: A Quantitative Information Flow Game Perspective}, volume={14}, ISSN={["1556-6021"]}, DOI={10.1109/TIFS.2019.2914358}, abstractNote={To contest the rapidly developing cyber-attacks, numerous collaborative security schemes, in which multiple security entities can exchange their observations and other relevant data to achieve more effective security decisions, are proposed and developed in the literature. However, the security-related information shared among the security entities may contain some sensitive information and such information exchange can raise privacy concerns, especially when these entities belong to different organizations. With such consideration, the interplay between the attacker and the collaborative entities is formulated as Quantitative Information Flow (QIF) games, in which the QIF theory is adapted to measure the collaboration gain and the privacy loss of the entities in the information sharing process. In particular, three games are considered, each corresponding to one possible scenario of interest in practice. Based on the game-theoretic analysis, the expected behaviors of both the attacker and the security entities are obtained. In addition, the simulation results are presented to validate the analysis.}, number={12}, journal={IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY}, author={Jin, Richeng and He, Xiaofan and Dai, Huaiyu}, year={2019}, month={Dec}, pages={3273–3286} }
 @article{huang_dai_ke_2019, title={Principles of Effective and Robust Innate Immune Response to Viral Infections: A Multiplex Network Analysis}, volume={10}, ISSN={["1664-3224"]}, DOI={10.3389/fimmu.2019.01736}, abstractNote={The human innate immune response, particularly the type-I interferon (IFN) response, is highly robust and effective first line of defense against virus invasion. IFN molecules are produced and secreted from infected cells upon virus infection and recognition. They then act as signaling/communication molecules to activate an antiviral response in neighboring cells so that those cells become refractory to infection. Previous experimental studies have identified the detailed molecular mechanisms for the IFN signaling and response. However, the principles underlying how host cells use IFN to communicate with each other to collectively and robustly halt an infection is not understood. Here we take a multiplex network modeling approach to provide a theoretical framework to identify key factors that determine the effectiveness of the IFN response against virus infection of a host. In this approach, we consider the virus spread among host cells and the interferon signaling to protect host cells as a competition process on a two-layer multiplex network. We focused on two types of network topology, i.e., the Erdős-Rényi (ER) network and the Geometric Random (GR) network, which represent the scenarios when infection of cells is mostly well mixed (e.g., in the blood) and when infection is spatially segregated (e.g., in tissues), respectively. We show that in general, the IFN response works effectively to stop viral infection when virus infection spreads spatially (a most likely scenario for initial virus infection of a host at the peripheral tissue). Importantly, we show that the effectiveness of the IFN response is robust against large variations in the distance of IFN diffusion as long as IFNs diffuse faster than viruses and they can effectively induce antiviral responses in susceptible host cells. This suggests that the effectiveness of the IFN response is insensitive to the specific arrangement of host cells in peripheral tissues. Thus, our work provides a quantitative explanation of why the IFN response can serve an effective and robust response in different tissue types to a wide range of viral infections of a host.}, journal={FRONTIERS IN IMMUNOLOGY}, author={Huang, Yufan and Dai, Huaiyu and Ke, Ruian}, year={2019}, month={Jul} }
 @article{nguyen_lee_dai_2019, title={QR-Decomposition-Aided Tabu Search Detection for Large MIMO Systems}, volume={68}, ISSN={["1939-9359"]}, DOI={10.1109/TVT.2019.2905642}, abstractNote={In the conventional tabu search (TS) detection algorithm for multiple-input multiple-output (MIMO) systems, the cost metrics of all neighboring vectors are computed to determine the best neighbor. This can require an excessively high computational complexity, especially in large MIMO systems because the number of neighboring vectors and the dimension per vector are large. In this study, we propose an improved TS algorithm based on the QR decomposition of the channel matrix (QR-TS), which allows for finding the best neighbor with a significantly lower complexity compared with the conventional TS algorithm. Specifically, QR-TS does not compute all metrics by early rejecting unpromising neighbors, which reduces the computational load of TS without causing any performance loss. To further optimize the QR-TS algorithm, we investigate novel ordering schemes, namely the transmit-ordering (Tx-ordering) and receive-ordering (Rx-ordering), which can considerably reduce the complexity of QR-TS. Simulation results show that QR-TS reduces the complexity approximately by a factor of two compared with the conventional TS. Furthermore, when both Tx-ordering and Rx-ordering are applied, QR-TS requires approximately $60\%\text{ -- }90\%$ less complexity compared with the conventional TS scheme. The proposed algorithms are suitable for both low-order and high-order modulation, and can achieve a significant complexity reduction compared to the Schnorr–Euchner and $K\text{-}$best sphere decoders in large MIMO systems.}, number={5}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Nguyen, Nhan Thanh and Lee, Kyungchun and Dai, Huaiyu}, year={2019}, month={May}, pages={4857–4870} }
 @article{xiao_li_han_dai_poor_2018, title={A Secure Mobile Crowdsensing Game With Deep Reinforcement Learning}, volume={13}, ISSN={1556-6013 1556-6021}, url={http://dx.doi.org/10.1109/tifs.2017.2737968}, DOI={10.1109/tifs.2017.2737968}, abstractNote={Mobile crowdsensing (MCS) is vulnerable to faked sensing attacks, as selfish smartphone users sometimes provide faked sensing results to the MCS server to save their sensing costs and avoid privacy leakage. In this paper, the interactions between an MCS server and a number of smartphone users are formulated as a Stackelberg game, in which the server as the leader first determines and broadcasts its payment policy for each sensing accuracy. Each user as a follower chooses the sensing effort and thus the sensing accuracy afterward to receive the payment based on the payment policy and the sensing accuracy estimated by the server. The Stackelberg equilibria of the secure MCS game are presented, disclosing conditions to motivate accurate sensing. Without knowing the smartphone sensing models in a dynamic version of the MCS game, an MCS system can apply deep Q-network (DQN), which is a deep reinforcement learning technique combining reinforcement learning and deep learning techniques, to derive the optimal MCS policy against faked sensing attacks. The DQN-based MCS system uses a deep convolutional neural network to accelerate the learning process with a high-dimensional state space and action set, and thus improve the MCS performance against selfish users. Simulation results show that the proposed MCS system stimulates high-quality sensing services and suppresses faked sensing attacks, compared with a Q-learning-based MCS system.}, number={1}, journal={IEEE Transactions on Information Forensics and Security}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Xiao, Liang and Li, Yanda and Han, Guoan and Dai, Huaiyu and Poor, H. Vincent}, year={2018}, month={Jan}, pages={35–47} }
 @article{parvez_rahmati_guvenc_sarwat_dai_2018, title={A Survey on Low Latency Towards 5G: RAN, Core Network and Caching Solutions}, volume={20}, ISSN={["1553-877X"]}, url={https://doi.org/10.1109/COMST.2018.2841349}, DOI={10.1109/COMST.2018.2841349}, abstractNote={The fifth generation (5G) wireless network technology is to be standardized by 2020, where main goals are to improve capacity, reliability, and energy efficiency, while reducing latency and massively increasing connection density. An integral part of 5G is the capability to transmit touch perception type real-time communication empowered by applicable robotics and haptics equipment at the network edge. In this regard, we need drastic changes in network architecture including core and radio access network (RAN) for achieving end-to-end latency on the order of 1 ms. In this paper, we present a detailed survey on the emerging technologies to achieve low latency communications considering three different solution domains: 1) RAN; 2) core network; and 3) caching. We also present a general overview of major 5G cellular network elements such as software defined network, network function virtualization, caching, and mobile edge computing capable of meeting latency and other 5G requirements.}, number={4}, journal={IEEE COMMUNICATIONS SURVEYS AND TUTORIALS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Parvez, Imtiaz and Rahmati, Ali and Guvenc, Ismail and Sarwat, Arif I. and Dai, Huaiyu}, year={2018}, pages={3098–3130} }
 @book{advances in mechanics of microstructured media and structures_2018, volume={87}, ISBN={["978-3-319-73693-8"]}, ISSN={["1869-8433"]}, DOI={10.1007/978-3-319-73694-5}, abstractNote={The book offers contributions on micropolar, micromorphic and strain gradient media, media with internal variables, metamaterials, and beam lattices.}, journal={ADVANCES IN MECHANICS OF MICROSTRUCTURED MEDIA AND STRUCTURES}, year={2018}, pages={1–369} }
 @book{he_dai_he_dai_2018, title={Adversary Detection For Cognitive Radio Networks}, ISBN={9783319758671 9783319758688}, ISSN={2191-8112 2191-8120}, url={http://dx.doi.org/10.1007/978-3-319-75868-8}, DOI={10.1007/978-3-319-75868-8}, abstractNote={This brief provides a comprehensive study of the security threats to cognitive radio networks and the corresponding adversary detection problems.}, journal={SpringerBriefs in Electrical and Computer Engineering}, publisher={Springer International Publishing}, author={He, X. and Dai, H. and He, X and Dai, H}, year={2018} }
 @article{he_dai_he_dai_2018, title={Adversary Detection For Cognitive Radio Networks Conclusion and FutureWork}, ISBN={["978-3-319-75867-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75868-8_7}, abstractNote={After reviewing relevant background and preliminaries in Chaps. 1 and 2 , our discussion sets off from an overview of the state-of-the-art of adversary detection techniques against the PUE attack and the Byzantine attack in Chap. 3 . In the subsequent chapters, more detailed case studies of several adversary detection schemes are conducted. Specifically, a link signature assisted PUE attack detection scheme is discussed in Chap. 4 . In Chap. 5 , an HMM-based Byzantine detection scheme is introduced. In this approach, the adversary is detected by inspecting the parameter difference in the corresponding HMM models for the honest SUs and the adversary. In Chap. 6 , a CFC based Byzantine attack detection algorithm was presented. In this approach, two CFC statistics are extracted from the SUs spectrum sensing behaviors and then compared with those of a trusted SU for adversary detection. Lastly, concluding remarks and outlooks for future works are provided in this chapter.}, journal={ADVERSARY DETECTION FOR COGNITIVE RADIO NETWORKS}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={73–74} }
 @article{he_dai_he_dai_2018, title={Adversary Detection For Cognitive Radio Networks Introduction}, ISBN={["978-3-319-75867-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75868-8_1}, abstractNote={The ubiquitous and ever-expanding wireless applications in our modern life quickly eat up the limited spectrum resource and thus impose a strong driving force to the research and development of high spectrum-efficiency wireless technologies. Cognitive radio (CR) is one of such desired technologies. However, due to its fundamental characteristics of open medium, CR networks suffer from many security threats. Without properly address these security issues, the deployment of CR technology in practice may be severely hampered. In this chapter, a brief review of the CR technology is presented, along with an overview of the potential security vulnerabilities in CR networks. The two unique security issues in CR networks, namely, the PUE attack and the Byzantine attack, are discussed in more details.}, journal={ADVERSARY DETECTION FOR COGNITIVE RADIO NETWORKS}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={1–6} }
 @article{he_dai_he_dai_2018, title={Case Study I: Link Signature Assisted PUE Attack Detection}, ISBN={["978-3-319-75867-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75868-8_4}, abstractNote={This chapter aims to present a detailed case study of a link signature assisted PUE attack detection scheme. As discussed in the previous chapter, one of the main hurdles making the design of a PUE attack detection scheme nontrivial is the FCC’s requirement that no change should be made to the PU. Due to this requirement, most of the existing detection methods are designed solely for the SU side. Nonetheless, if one can deploy a nearby helper node that holds similar behavioral and physical properties as the PU and allow it to cooperate with the SU, the PUE detection performance may be further improved without disobeying the FCC’s requirement. To convey this idea, in this chapter, some background on link signature will be introduced first, followed by an illustration of how the helper node can exploit its physical closeness to the PU to accurately authenticate the PU signal. Then, the overall link signature based PUE attack detection algorithm is illustrated.}, journal={ADVERSARY DETECTION FOR COGNITIVE RADIO NETWORKS}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={45–50} }
 @article{he_dai_he_dai_2018, title={Case Study II: HMM-Based Byzantine Attack Detection}, ISBN={["978-3-319-75867-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75868-8_5}, abstractNote={Most of the existing defense schemes against the Byzantine attack discussed in Chap. 3 either assume that the underlying spectrum states at different timeslots are independent or they only focus on the measurements collected in a single timeslot. Nonetheless, for many practical scenarios, the activities of the PUs and the induced spectrum states often follow a Markov process, and hence the spectrum sensing behaviors of the SUs may be better characterized by the HMM. Under this modeling, a novel HMM-based Byzantine attack detection technique can be developed to enforce the robustness of collaborative spectrum sensing. To illustrate this, the HMM-based spectrum sensing behavioral model is presented first, and based on which, the sought-after multi-HMM inference algorithm is introduced. Then, the overall HMM-based Byzantine attack detection scheme is demonstrated along with some numerical results to corroborate its effectiveness.}, journal={ADVERSARY DETECTION FOR COGNITIVE RADIO NETWORKS}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={51–62} }
 @article{he_dai_he_dai_2018, title={Case Study III: CFC-Based Byzantine Attack Detection}, ISBN={["978-3-319-75867-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75868-8_6}, abstractNote={The multi-HMM inference algorithm presented in the previous chapter can effectively assist the Byzantine attack detection when either the percentage of the malicious SUs or their flipping probability is not too high. To further enhance the detection performance, a tailor-designed Byzantine attack detection scheme, termed CFC, will be presented in this chapter. In this method, two natural yet effective CFC statistics that can capture the second-order properties of the underlying spectrum dynamics and the SUs spectrum sensing behaviors are constructed for Byzantine attacker identification. More specifically, we will first briefly clarify the underlying system model and then presents the CFC based Byzantine attack detection algorithm. In addition, performance analysis of this method will also be presented.}, journal={ADVERSARY DETECTION FOR COGNITIVE RADIO NETWORKS}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={63–72} }
 @article{jin_he_dai_2018, title={Collaborative IDS Configuration: A Two-Layer Game-Theoretic Approach}, volume={4}, ISSN={["2332-7731"]}, DOI={10.1109/TCCN.2018.2856207}, abstractNote={To cope with the increasingly sophisticated intrusions, collaborative intrusion detection systems (CIDSs) are proposed in the literature. In particular, intrusion detection systems (IDSs) in collaboration can dynamically share available computational resources among themselves to enhance the overall detection performance. However, due to resource limitation, it is infeasible for the IDSs to respond to all the intrusion detection requests from their collaborative peers. In the meantime, obtaining the optimal IDS configuration in CIDSs is far from trivial. With such consideration, the collaborative IDS configuration problem is formulated as a two-layer stochastic game (SG). To solve this two-layer SG, a centralized Vickrey–Clarke–Groves auction based collaboration scheme and a distributed game-theoretic incentive mechanism are proposed in this paper. The effectiveness of the proposed schemes is validated through both analysis and numerical experiments. The proposed approach can be applied to more general collaborative settings.}, number={4}, journal={IEEE TRANSACTIONS ON COGNITIVE COMMUNICATIONS AND NETWORKING}, author={Jin, Richeng and He, Xiaofan and Dai, Huaiyu}, year={2018}, month={Dec}, pages={803–815} }
 @book{he_dai_2018, title={Dynamic Games for Network Security}, ISBN={9783319758701 9783319758718}, ISSN={2191-8112 2191-8120}, url={http://dx.doi.org/10.1007/978-3-319-75871-8}, DOI={10.1007/978-3-319-75871-8}, abstractNote={This brief collects and systematically presents advanced stochastic game theory research and the underlying game-theoretic and learning tools}, journal={SpringerBriefs in Electrical and Computer Engineering}, publisher={Springer International Publishing}, author={He, Xiaofan and Dai, Huaiyu}, year={2018}, pages={1–74} }
 @article{he_dai_he_dai_2018, title={Dynamic Games for Network Security Conclusion and Future Work}, ISBN={["978-3-319-75870-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75871-8_6}, abstractNote={In this book, we have studied the applications of SG theory in addressing various dynamic network security games, with a particular focus on the techniques of handling scenarios with information asymmetry. In Chap. 1, preliminaries of game theory, MDP, and SG have been reviewed. With these necessary backgrounds, a brief review of existing security applications of the SG framework is provided in Chap. 2. We have further examined several novel techniques for SG with information asymmetry and their security applications. Particularly, the discussions in Chap. 3 focus on dynamic security games with extra information, and the complementary situations where the defender only has incomplete information are examined in Chap. 4 through the lens of Bayesian SG. In Chap. 5, we have studied how the defender can proactively create information asymmetry to enhance security performance. Lastly, in this chapter, summary and perspective for future works will be provided.}, journal={DYNAMIC GAMES FOR NETWORK SECURITY}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={73–74} }
 @article{he_dai_he_dai_2018, title={Dynamic Security Games with Deception}, ISBN={["978-3-319-75870-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75871-8_5}, abstractNote={In the previous two chapters, we have investigated dynamics security games with asymmetric information, in which the extra or the missing information is inherent to the underlying security problems. In this chapter, we switch the gear and further consider the possibility of proactively creating information asymmetry in security games for the defender’s benefit. Particularly, deception will be investigated as a concrete tool to achieve this objective. However, most existing deception techniques are designed for static scenarios. The objective of this chapter is to illustrate a foresighted deception framework that allows the defender to better align its deception strategy with its conventional defense strategy and the dynamics in the environment. In addition, a network protection game is taken as a concrete example to illustrate the advantage of the foresighted deception achieved by the SDG framework over the conventional myopic deception.}, journal={DYNAMIC GAMES FOR NETWORK SECURITY}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={61–71} }
 @article{he_dai_he_dai_2018, title={Dynamic Security Games with Extra Information}, ISBN={["978-3-319-75870-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75871-8_3}, abstractNote={In the previous chapter, we have reviewed existing applications of SG in addressing different dynamic security problems. Nonetheless, most existing works assume equal knowledgeable defender and attacker, whereas, in practice, the defender and the attacker are likely to hold different information about the ongoing security rivalries. Conventional SG based methods developed in existing literature do not fit well to such dynamic security games with information asymmetry. To achieve the best possible defense in such scenarios, new techniques that can adequately manage the information asymmetry are needed. In this chapter, we will focus on scenarios where the defender has extra information and present two novel algorithms, termed minimax-PDS and WoLF-PDS, to solve the corresponding dynamic security games with extra information. After establishing the theoretical basis, we will provide two exemplary applications to illustrate how these two new algorithms can be leveraged to handle dynamic security games with extra information. The first application is concerned with anti-jamming and the second application is concerned with a cloud-based security game.}, journal={DYNAMIC GAMES FOR NETWORK SECURITY}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={25–42} }
 @article{he_dai_he_dai_2018, title={Dynamic Security Games with Incomplete Information}, ISBN={["978-3-319-75870-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75871-8_4}, abstractNote={In this chapter, we continue our exploration of dynamic security games with information asymmetry. As compared to the previous chapter, the discussions in this chapter focus on the complementary scenarios where the defender lacks information about the ongoing security competitions. Such scenarios exist in many practical security problems. The framework of Bayesian SG will be employed in this chapter to model and analyze such incomplete information dynamic security problems. Accordingly, a new algorithm, termed Bayesian Nash-Q, that allows the defender to infer the missing information based on repeated interactions with the attacker and the dynamic environment will be presented. This algorithm is a natural combination of the conventional repeated Bayesian games and the Nash-Q algorithm. For this reason, our discussion starts from reviewing some elementary concepts of Bayesian games, and then the Bayesian SG model and the Bayesian Nash-Q algorithm will be discussed in details.}, journal={DYNAMIC GAMES FOR NETWORK SECURITY}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={43–60} }
 @article{he_jin_dai_2018, title={Leveraging Spatial Diversity for Privacy-Aware Location-Based Services in Mobile Networks}, volume={13}, ISSN={["1556-6021"]}, DOI={10.1109/tifs.2018.2797023}, abstractNote={While providing unprecedented convenience to people’s daily life, location-based services (LBSs) may cause serious concerns on users’ location privacy, when the system is compromised. Although various location privacy protection mechanisms have been developed for LBSs, the ambient physical environment often imposes some fundamental limitations on their performances. As a result, mobile users may experience a spatial diversity in the achievable location privacy when traveling along their routes. However, to the best of our knowledge, an appropriate location privacy metric that can capture the influence of the ambient environment is still missing in the literature. Also, none of the existing location privacy protection methods can properly leverage such spatial diversity. With this consideration, new ambient environment-dependent location privacy metrics are proposed in this paper, together with a stochastic model that can capture their spatial variations along the user’s route. Based on this modeling, a new optimal stopping-based LBS access scheme that allows mobile users to fully leverage the spatial diversity and achieve a substantially better performance is developed. The effectiveness of the proposed scheme is corroborated by both numerical results and simulations over real-world road maps.}, number={6}, journal={IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY}, author={He, Xiaofan and Jin, Richeng and Dai, Huaiyu}, year={2018}, month={Jun}, pages={1524–1534} }
 @article{xiao_chen_xie_dai_poor_2018, title={Mobile Crowdsensing Games in Vehicular Networks}, volume={67}, ISSN={["1939-9359"]}, DOI={10.1109/tvt.2016.2647624}, abstractNote={Vehicular crowdsensing takes advantage of the mobility of vehicles to provide location-based services in large-scale areas. In this paper, mobile crowdsensing (MCS) in vehicular networks is analyzed and the interactions between a crowdsensing server and vehicles equipped with sensors in an area of interest is formulated as a vehicular crowdsensing game. Each participating vehicle chooses its sensing strategy based on the sensing cost, radio channel state, and the expected payment. The MCS server evaluates the accuracy of each sensing report and pays the vehicle accordingly. The Nash equilibrium of the static vehicular crowdsensing game is derived for both accumulative sensing tasks and best-quality sensing tasks, showing the tradeoff between the sensing accuracy and the overall payment by the MCS server. A Q-learning-based MCS payment strategy and sensing strategy is proposed for the dynamic vehicular crowdsensing game, and a postdecision state learning technique is applied to exploit the known radio channel model to accelerate the learning speed of each vehicle. Simulations based on a Markov-chain channel model are performed to verify the efficiency of the proposed MCS system, showing that it outperforms the benchmark MCS system in terms of the average utility, the sensing accuracy, and the energy consumption of the vehicles.}, number={2}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Xiao, Liang and Chen, Tianhua and Xie, Caixia and Dai, Huaiyu and Poor, H. Vincent}, year={2018}, month={Feb}, pages={1535–1545} }
 @article{zhang_cai_li_zhong_dai_2018, title={One-Bit Quantized Massive MIMO Detection Based on Variational Approximate Message Passing}, volume={66}, ISSN={1053-587X 1941-0476}, url={http://dx.doi.org/10.1109/tsp.2017.2786256}, DOI={10.1109/tsp.2017.2786256}, abstractNote={One-bit quantization can significantly reduce the massive multiple-input and multiple-output (MIMO) system hardware complexity, but at the same time it also brings great challenges to the system algorithm design. Specifically, it is difficult to recover information from the highly distorted samples as well as to obtain accurate channel estimation without increasing the number of pilots. In this paper, a novel inference algorithm called variational approximate message passing (VAMP) for one-bit quantized massive MIMO receiver is developed, which attempts to exploit the advantages of both the variational Bayesian inference algorithm and the bilinear generalized approximated message passing algorithm to accomplish joint channel estimation and data detection in a closed form with first-order complexity. Asymptotic state evolution analysis indicates the fast convergence rate of VAMP and also provides a lower bound for the data detection error. Moreover, through extensive simulations, we show that VAMP can achieve excellent detection performance with low pilot overhead in a wide range of scenarios.}, number={9}, journal={IEEE Transactions on Signal Processing}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Zhang, Zhaoyang and Cai, Xiao and Li, Chunguang and Zhong, Caijun and Dai, Huaiyu}, year={2018}, month={May}, pages={2358–2373} }
 @article{he_dai_he_dai_2018, title={Overview of Adversary Detection in CR Networks}, ISBN={["978-3-319-75867-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75868-8_3}, abstractNote={As discussed in Chap. 1, the PUE attack and the Byzantine attack are two severe security threats unique to the CR networks, and if not properly addressed, the functionality of the entire CR network will be demolished. With this consideration, advocators of the CR technology have devoted substantial research efforts to address these two security problems in the past decade. Most of them focus on how to detect and identify the adversaries; after all, detection and identification is usually the very first step to remove a security threat. The objective of this chapter is to provide an overview of the recent advancements in detecting these two disrupting attacks. Particularly, in the first part of this chapter, we intend to provide a systematic review of the existing PUE attack detection methods, and in the second part of this chapter, we will switch gear towards the Byzantine attack detection schemes.}, journal={ADVERSARY DETECTION FOR COGNITIVE RADIO NETWORKS}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={19–44} }
 @article{he_dai_he_dai_2018, title={Overview of Dynamic Network Security Games}, ISBN={["978-3-319-75870-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75871-8_2}, abstractNote={Due to environmental variations and system fluctuations, the defender often faces a dynamic security competition against the attacker in practice, and two common challenges exist in addressing these dynamic security games: (1) how to deal with the intelligent attacker that may change its strategy based on the deployed defense, and (2) how to properly align the defense strategy with the environmental or system dynamics to achieve the most efficient and effective defense. In literature, the SG framework reviewed in the previous chapter has been considered as a promising mathematical tool to jointly overcome these two challenges and guide the defender towards the best possible defense. In this chapter, a brief survey of the recent efforts in this direction is provided. Specifically, the applications of the SG in addressing security issues in cyber networks, wireless communication networks, and cyber-physical networks are presented, respectively.}, journal={DYNAMIC GAMES FOR NETWORK SECURITY}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={17–23} }
 @article{he_dai_he_dai_2018, title={Preliminaries}, ISBN={["978-3-319-75870-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75871-8_1}, abstractNote={To start our journey in this book, relevant backgrounds on game theory, Markov decision process (MDP), and stochastic game (SG) will be introduced first in this chapter to pave the way for our later exposition. In essence, many security issues can be treated as a game between the defender and the attacker who are intelligent entities that can smartly plan their actions in the security rivalries. For this reason, our discussion in this chapter begins with the presentation of some rudimentary concepts of the classic game theory—a fascinating theory that concerns the modeling and prediction of the behaviors of intelligent entities in strategical interactions. In addition to the interactions with the opponent, practical security problems often involve with different environmental, system, or network dynamics. As a fundamental tool for optimal planning in dynamic environments, the MDP is also reviewed in this chapter. Moreover, as a key framework for addressing various dynamic security games, the SG will be reviewed in this chapter as well.}, journal={DYNAMIC GAMES FOR NETWORK SECURITY}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={1–16} }
 @article{he_dai_he_dai_2018, title={Preliminaries of Analytical Tools}, ISBN={["978-3-319-75867-1"]}, ISSN={["2191-8120"]}, DOI={10.1007/978-3-319-75868-8_2}, abstractNote={This chapter mainly focuses on reviewing some of the important analytic tools used in existing literature for adversary detection in CR networks. Particularly, in the first part of the chapter, two widely employed statistical inference tools, sequential hypothesis testing, and belief propagation are reviewed. In the second part of this chapter, some important machine learning methods are reviewed, including non-parametric Bayesian classification, artificial neural network, and affinity propagation. Throughout the discussions of this chapter, we will focus on introducing the relevant concepts and models, algorithmic procedure as well as important properties of these analytic tools, whereas their applications in adversary detection will be postponed to the next chapter.}, journal={ADVERSARY DETECTION FOR COGNITIVE RADIO NETWORKS}, author={He, Xiaofan and Dai, Huaiyu and He, X and Dai, H}, year={2018}, pages={7–17} }
 @article{xiao_li_dai_dai_poor_2018, title={Reinforcement Learning-Based NOMA Power Allocation in the Presence of Smart Jamming}, volume={67}, ISSN={0018-9545 1939-9359}, url={http://dx.doi.org/10.1109/tvt.2017.2782726}, DOI={10.1109/tvt.2017.2782726}, abstractNote={Nonorthogonal multiple access (NOMA) systems are vulnerable to jamming attacks, especially smart jammers who apply programmable and smart radio devices such as software-defined radios to flexibly control their jamming strategy according to the ongoing NOMA transmission and radio environment. In this paper, the power allocation of a base station in a NOMA system equipped with multiple antennas contending with a smart jammer is formulated as a zero-sum game, in which the base station as the leader first chooses the transmit power on multiple antennas, while a jammer as the follower selects the jamming power to interrupt the transmission of the users. A Stackelberg equilibrium of the antijamming NOMA transmission game is derived and conditions assuring its existence are provided to disclose the impact of multiple antennas and radio channel states. A reinforcement learning-based power control scheme is proposed for the downlink NOMA transmission without being aware of the jamming and radio channel parameters. The Dyna architecture that formulates a learned world model from the real antijamming transmission experience and the hotbooting technique that exploits experiences in similar scenarios to initialize the quality values are used to accelerate the learning speed of the Q-learning-based power allocation, and thus, improve the communication efficiency of the NOMA transmission in the presence of smart jammers. Simulation results show that the proposed scheme can significantly increase the sum data rates of users, and thus, the utilities compared with the standard Q-learning-based strategy.}, number={4}, journal={IEEE Transactions on Vehicular Technology}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Xiao, Liang and Li, Yanda and Dai, Canhuang and Dai, Huaiyu and Poor, H. Vincent}, year={2018}, month={Apr}, pages={3377–3389} }
 @article{he_dai_ning_dutta_2017, title={A Leader-Follower Controlled Markov Stopping Game for Delay Tolerant and Opportunistic Resource Sharing Networks}, volume={35}, ISSN={["1558-0008"]}, DOI={10.1109/jsac.2017.2659581}, abstractNote={In various resource sharing networks, opportunistic resources with dynamic quality are often present for the users to exploit. As many user tasks are delay-tolerant, this favorably allows the network users to wait for and access the opportunistic resource at the time of its best quality. For such delay-tolerant and opportunistic resource sharing networks, the resource accessing strategies developed in the literature suffer from three limitations. First, they mainly focused on single-user scenarios, whereas the competition from other users is ignored. Second, the influence from the resource seller who may take actions to manipulate the resource sharing procedure is not considered. Third, the impact of the actions from both the network users and the resource seller on the resource quality dynamics is not considered either. To overcome these limitations, a leader–follower controlled Markov stopping game (LF-C-MSG) is developed in this paper. The derived Stackelberg equilibrium strategy of the LF-C-MSG can be used to guide the behaviors of both the network users and the resource seller for better performance and resource utilization efficiency. Two exemplary applications of the proposed LF-C-MSG are presented, along with corresponding numerical results to verify the effectiveness of the proposed framework.}, number={3}, journal={IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS}, author={He, Xiaofan and Dai, Huaiyu and Ning, Peng and Dutta, Rudra}, year={2017}, month={Mar}, pages={615–627} }
 @article{chattopadhyay_dai_eun_hosseinalipour_2017, title={Designing Optimal Interlink Patterns to Maximize Robustness of Interdependent Networks Against Cascading Failures}, volume={65}, ISSN={["1558-0857"]}, DOI={10.1109/tcomm.2017.2709302}, abstractNote={In this paper, we consider the optimal design of interlinks for an interdependent system of networks. In contrast to existing literature, we explicitly exploit the information of intra-layer node degrees to design interdependent structures such that their robustness against cascading failures, triggered by randomized attacks, is maximized. Utilizing percolation theory-based system equations relating the robustness of the network to its degree sequence, we characterize the optimal design for the one-to-one structure, with complete interdependence and partial interdependence, under randomized attack. We also extend our study to the one-to-many interdependence structure and the targeted attack model. The theoretically derived optimal interdependence structures have been verified using simulations on scale-free networks.}, number={9}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Chattopadhyay, Srinjoy and Dai, Huaiyu and Eun, Do Young and Hosseinalipour, Seyyedali}, year={2017}, month={Sep}, pages={3847–3862} }
 @inproceedings{chattopadhyay_dai_2017, title={Designing optimal interlink structures for interdependent networks under budget constraints}, DOI={10.1109/icc.2017.7997212}, abstractNote={In this work, we focus on the problem of obtaining the optimal interlink structures, which maximizes the robustness of networks against random node failures, in a cost constrained setting. Using percolation theory based system equations, we have formulated our objective as a constrained optimization problem and designed algorithms serving two key purposes: i) obtaining the budget limits, Bl and Bu, defined as the minimum budget guaranteeing the existence of a feasible and optimal interlink structure, respectively; and ii) obtaining interlink structures for intermediate budgets. Through these algorithms and associated simulation results, we demonstrate the importance of cost in network design. Furthermore, the designed algorithms have close to optimal performance while being much cheaper than cost agnostic network designs.}, booktitle={2017 ieee international conference on communications (icc)}, author={Chattopadhyay, S. and Dai, H. Y.}, year={2017} }
 @inproceedings{hosseinalipour_wang_dai_wang_2017, title={Detection of infections using graph signal processing in heterogeneous networks}, DOI={10.1109/glocom.2017.8254487}, abstractNote={Determining the causality of abnormalities in a network is the prerequisite for developing countermeasures. In this paper, we focus on infection detection in heterogeneous networks. Given a snapshot of the network which demonstrates the condition of the nodes, the goal is to distinguish between random failures and epidemic scenarios. We model the network situation as a graph signal based on the nodes' status. Detection metrics motivated by graph signal processing are introduced for the infection detection problem in hand, and an effective algorithm is proposed to solve it. Simulation results indicate a dramatic improvement in terms of detection probability compared to the current state-of-the-art.}, booktitle={Globecom 2017 - 2017 ieee global communications conference}, author={Hosseinalipour, S. and Wang, Jie and Dai, Huaiyu and Wang, Wenye}, year={2017} }
 @inproceedings{nayak_hosseinalipour_dai_2017, title={Dynamic advertising in VANETs using repeated auctions}, DOI={10.1109/glocom.2017.8254662}, abstractNote={Vehicular ad-hoc networks (VANETs) have been an active area in the research community during the last decade with focus primarily on routing protocols, security aspects and safety. Recent advances in wireless communication and the inherent dynamic nature of VANETs provide excellent opportunity for advertisement dissemination. In this paper, we address the problem of dynamic advertising in VANETs. We consider a city divided into a grid, where the blocks have different vehicular densities that vary over time. Several advertising companies compete for the blocks to broadcast their advertisements in the network. The content dissemination in the network is controlled by a data management unit that receives requests from advertising companies for each block. To solve the problem of block allocation, we adapt the repeated auction scheme for the dynamic setting. Two new metrics are defined to better represent the real- world scenario and fairness in repeated auctions. We propose an algorithm which is a combination of adaptive linear prediction and nonparametric Bayesian belief update, enabling smart bidding and improving the utilities of the competing advertising companies significantly in the long- run. Through simulations, we show that the proposed algorithm achieves better performance than two baselines approaches.}, booktitle={Globecom 2017 - 2017 ieee global communications conference}, author={Nayak, A. and Hosseinalipour, S. and Dai, H. Y.}, year={2017} }
 @inproceedings{he_islam_jin_dai_2017, title={Foresighted deception in dynamic security games}, DOI={10.1109/icc.2017.7996811}, abstractNote={Deception has been widely considered in literature as an effective means of enhancing security protection when the defender holds some private information about the ongoing rivalry unknown to the attacker. However, most of the existing works on deception assume static environments and thus consider only myopic deception, while practical security games between the defender and the attacker may happen in dynamic scenarios. To better exploit the defender's private information in dynamic environments and improve security performance, a stochastic deception game (SDG) framework is developed in this work to enable the defender to conduct foresighted deception. To solve the proposed SDG, a new iterative algorithm that is provably convergent is developed. A corresponding learning algorithm is developed as well to facilitate the defender in conducting foresighted deception in unknown dynamic environments. Numerical results show that the proposed foresighted deception can offer a substantial performance improvement as compared to the conventional myopic deception.}, booktitle={2017 ieee international conference on communications (icc)}, author={He, X. F. and Islam, M. M. and Jin, R. C. and Dai, H. Y.}, year={2017} }
 @article{zhang_zhang_dai_chen_wu_2017, title={Fountain-Coded File Spreading Over Mobile Networks}, volume={16}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2017.2730874}, abstractNote={Spreading a large file consisting of many packets over a mobile network is challenging due to the short meeting duration for each transmission. Moreover, two typical causes of inefficient file spreading are duplicate packet reception at the destination nodes and excessive overhead exchanges. We propose to employ fountain codes at the source node to jointly addresses the three issues: 1) each coded packet can be small enough to fit into the meeting duration; 2) duplicate packet reception is significantly reduced since each coded packet is innovative; and 3) overhead is greatly saved by using file-level ACK instead of packet-level ACK. We conduct performance analysis in terms of the source-to-destination file delay and source-to-destination file spreading time in both non-relaying and relaying scenarios. While packet duplication can be eliminated in the former scenario, there is still a non-trivial duplication probability if relaying is allowed. Therefore, we propose a fountain-coded two-hop relaying (FTTR) protocol to further reduce the packet duplication ratio so that the spreading performance does not degrade with network size. The file spreading time and packet duplication ratio of FTTR are derived in closed form and verified through simulations.}, number={10}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Zhang, Zhaoyang and Zhang, Huazi and Dai, Huaiyu and Chen, Xiaoming and Wu, Dapeng Oliver}, year={2017}, month={Oct}, pages={6766–6778} }
 @inproceedings{li_xiao_dai_poor_2017, title={Game theoretic study of protecting MIMO transmissions against smart attacks}, DOI={10.1109/icc.2017.7996461}, abstractNote={Multiple-input multiple-output (MIMO) systems are threatened by smart attackers, who apply programmable radio devices such as software defined radios to perform multiple types of attacks such as eavesdropping, jamming and spoofing. In this paper, MIMO transmission in the presence of smart attacks is formulated as a noncooperative game, in which a MIMO transmitter chooses its transmit power level and a smart attacker determines its attack type accordingly. A Nash equilibrium of this secure MIMO transmission game is derived and conditions assuring its existence are provided to reveal the impact of the number of antennas and the costs of the attacker to launch each type of attack. A power control strategy based on Q-learning is proposed for the MIMO transmitter to suppress the attack motivation of smart attackers in a dynamic version of MIMO transmission game without being aware of the attack and the radio channel model. Simulation results show that our proposed scheme can reduce the attack rate of smart attackers and improve the secrecy capacity compared with the benchmark strategy.}, booktitle={2017 ieee international conference on communications (icc)}, author={Li, Y. D. and Xiao, L. and Dai, H. Y. and Poor, H. V.}, year={2017} }
 @inproceedings{huang_dai_2017, title={Multiplex conductance and gossip based information spreading in multiplex networks}, DOI={10.1109/isit.2017.8006559}, abstractNote={In this work, we study the information spreading time in multiplex networks, adopting the gossip (random-walk) based information spreading model. A new metric called multiplex conductance is defined based on the multiplex network structure and used to quantify the information spreading time in a general multiplex network in the idealized setting. Multiplex conductance is then evaluated for some interesting multiplex networks to facilitate understanding in this new area. Finally, the tradeoff between the information spreading efficiency improvement and the layer cost is examined to explain the user's social behavior and motivate effective multiplex network designs.}, booktitle={2017 ieee international symposium on information theory (isit)}, author={Huang, Y. F. and Dai, H. Y.}, year={2017}, pages={406–410} }
 @inproceedings{hosseinalipour_dai_2017, title={Options-based sequential auctions for dnamic cloud resource allocation}, DOI={10.1109/icc.2017.7997242}, abstractNote={With growing demands for cloud computing services, the idea of managing limited cloud resources for making a profit has arisen as an important problem. Auction theory is recently considered as a viable way to solve the problem of cloud resource allocation. In this paper, we consider a model for Cloud of Clouds Networks (CCNs) with different types of servers along with customers with heterogeneous demands, in which customers and cloud servers may join and leave the CCN at will. We propose an options-based sequential auction that not only provides a good match with the dynamic structure of the problem, but also solves the entrance time problem and possesses the truthfulness property. We study both first-price and second-price options-based sequential auctions, and model the price matching processes in those auctions as Markov chains. We provide mathematically tractable methods to find the expected value of the CCN manager's revenue, and further show how the proxy agents' patience time affects the CCN manager's revenue.}, booktitle={2017 ieee international conference on communications (icc)}, author={Hosseinalipour, S. and Dai, H. Y.}, year={2017} }
 @inproceedings{he_liu_jin_dai_2017, title={Privacy-aware offloading in mobile-edge computing}, DOI={10.1109/glocom.2017.8253985}, abstractNote={Recently, mobile-edge computing (MEC) emerges as a promising paradigm to enable computation intensive and delay-sensitive applications at resource limited mobile devices by allowing them to offload their heavy computation tasks to nearby MEC servers through wireless communications. A substantial body of literature is devoted to developing efficient scheduling algorithms that can adapt to the dynamics of both the system and the ambient wireless environments. However, the influence of these task offloading schemes to the mobile users' privacy is largely ignored. In this work, two potential privacy issues induced by the wireless task offloading feature of MEC, location privacy and usage pattern privacy, are identified. To address these two privacy issues, a constrained Markov decision process (CMDP) based privacy-aware task offloading scheduling algorithm is proposed, which allows the mobile device to achieve the best possible delay and energy consumption performance while maintain a pre-specified level of privacy. Numerical results are presented to corroborate the effectiveness of the proposed algorithm.}, booktitle={Globecom 2017 - 2017 ieee global communications conference}, author={He, X. F. and Liu, J. and Jin, R. C. and Dai, H. Y.}, year={2017} }
 @article{zhang_li_lee_dai_2017, title={QoS-Based Interference Alignment With Similarity Clustering for Efficient Subchannel Allocation in Dense Small Cell Networks}, volume={65}, ISSN={["1558-0857"]}, DOI={10.1109/tcomm.2017.2737001}, abstractNote={Interference alignment (IA) can remarkably improve the spectral efficiency of dense small cell networks (SCNs) underlaying a macrocell, but its feasibility condition and implementation complexity are restricted by the number of small cell equipments (SUEs). Moreover, the SUEs performing IA may have unsatisfactory quality of service (QoS) requirements as IA only eliminates interference while neglecting the gain of desired signals. In this paper, we propose a centralized efficient subchannel allocation scheme based on IA with similarity clustering in dense SCNs underlaying a macrocell, which aims at maximizing the number of QoS guaranteed SUEs performing IA. The corresponding problem is formulated as a combinatorial optimization problem which is NP-hard. So a low-complexity solution is proposed which includes three phases: similarity clustering for SUEs through graph partitioning, further adjustments of cluster sizes to make IA feasible in each cluster, and subchannel allocation for the formed clusters, each of which is performed with a notably reduced computational complexity. Moreover, the proposed solution greatly reduces the signaling overhead incurred by channel state information estimation. Numerical results show that the proposed solution not only outperforms other related schemes, but also achieves a performance close to the optimal solution.}, number={11}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Zhang, Hao and Li, Hongyan and Lee, Jung Hoon and Dai, Huaiyu}, year={2017}, month={Nov}, pages={5054–5066} }
 @inproceedings{hosseinalipour_nayak_dai_2017, title={Real-time strategy selection for mobile advertising in VANETs}, DOI={10.1109/glocom.2017.8253975}, abstractNote={Vehicular ad-hoc networks (VANETs) has recently attracted a lot of attention due to their great potentials for different applications such as collision avoidance, route finding and autonomous driving. A wide range of coverage and accessibility to the end users in VANETs make them a good target for commercial advertising. This paper addresses the problem of mobile advertising in VANETs. We consider a case where different advertisers compete for the VANET infrastructure. It is assumed that a city is partitioned into a grid of blocks and the central data center manager (CDM) sets the rental price for each block considering the geographical position and the predicted density of vehicles inside the block. The regret-based minimization method is adopted to tackle the problem in response to its dynamic nature. Regret bound of the proposed algorithm and its convergence to the best strategy are shown rigorously. Furthermore, a good potential of the proposed algorithm is revealed through simulations.}, booktitle={Globecom 2017 - 2017 ieee global communications conference}, author={Hosseinalipour, S. and Nayak, A. and Dai, H. Y.}, year={2017} }
 @article{jin_he_dai_dutta_ning_2017, title={Towards Privacy-Aware Collaborative Security: A Game-Theoretic Approach}, DOI={10.1109/pac.2017.32}, abstractNote={With the rapid development of sophisticated attack techniques, individual security systems that base all of their decisions and actions of attack prevention and response on their own observations and knowledge become incompetent. To cope with this problem, collaborative security in which a set of security entities are coordinated to perform specific security actions is proposed in literature. In collaborative security schemes, multiple entities collaborate with each other by sharing threat evidence or analytics to make more effective decisions. Nevertheless, the anticipated information exchange raises privacy concerns, especially for those privacy-sensitive entities. In order to obtain a quantitative understanding of the fundamental tradeoff between the effectiveness of collaboration and the entities' privacy, a repeated two-layer single-leader multi-follower game is proposed in this work. Based on our game-theoretic analysis, the expected behaviors of both the attacker and the security entities are derived and the utility-privacy tradeoff curve is obtained. In addition, the existence of Nash equilibrium (NE) for the collaborative entities is proven, and an asynchronous dynamic update algorithm is proposed to compute the optimal collaboration strategies of the entities. Furthermore, the existence of Byzantine entities is considered and its influence is investigated. Finally, simulation results are presented to validate the analysis.}, journal={2017 1ST IEEE SYMPOSIUM ON PRIVACY-AWARE COMPUTING (PAC)}, author={Jin, Richeng and He, Xiaofan and Dai, Huaiyu and Dutta, Rudra and Ning, Peng}, year={2017}, pages={72–83} }
 @inproceedings{he_dai_ning_dutta_2016, title={A A multi-player Markov stopping game for delay-tolerant and opportunistic resource sharing networks}, DOI={10.1109/infocom.2016.7524350}, abstractNote={Opportunistic resources are often present in various resource sharing networks for the users to exploit, but their qualities often change over time. Fortunately, many user tasks are delay-tolerant, which offers the network users a favorable degree of freedom in waiting for and accessing the opportunistic resource at the time of its best quality. For such delay-tolerant and opportunistic resource sharing networks (DT-ORS-Net), the corresponding optimal accessing strategies developed in existing literature mainly focus on the single-user scenarios, while the potential competition from other peer users in practical multi-user DT-ORS-Net is often ignored. Considering this, a multi-player Markov stopping game (M-MSG) is developed in this work, and the derived Nash equilibrium (NE) strategy of this M-MSG can guide network users to properly handle the potential competition from other peers and thus exploit the time diversity of the opportunistic resource more effectively, which in turn further improves the resource utilization efficiency. Applications in the cloud-computing and the mobile crowdsourcing networks are demonstrated to verify the effectiveness of the proposed method, and simulation results show that using the NE strategy of the proposed M-MSG can provide substantial performance gain as compared to using the conventional single-user optimal one.}, booktitle={IEEE INFOCOM 2016 - the 35th annual IEEE international Conference on Computer Communications}, author={He, X. F. and Dai, Huaiyu and Ning, P. and Dutta, Rudra}, year={2016} }
 @article{gao_chiang_huang_yuan_dai_huang_2016, title={A reverse auction algorithm for carrier allocation in femtocells for multimedia applications}, volume={21}, ISSN={["1743-8233"]}, DOI={10.1504/ijahuc.2016.075377}, abstractNote={An efficient carrier allocation algorithm is important for self-organised networks SONs. SON can significantly improve network performance and user experience which greatly help relieve the heavy loading of the current multimedia applications for mobile environments. This paper proposes a distributed algorithm for carrier allocation using a reverse auction algorithm, wherein the original cells affected by newly added cells self-organise into auction groups to facilitate new carrier allocation. The computational overhead required to adapt to topology changes can be significantly reduced compared with the conventional topology-based approaches that ignore prior assignments. The number of original cells affected by the reallocation is as small as possible in the reverse auction algorithm while optimising carrier allocation. We investigate the algorithm performance in various scenarios. Our results indicate that the reverse auction algorithm exhibits significant advantages compared with traditional approaches, especially in highly dynamic networks where frequent resource re-allocation is needed.}, number={3}, journal={INTERNATIONAL JOURNAL OF AD HOC AND UBIQUITOUS COMPUTING}, author={Gao, Zhibin and Chiang, Hua-Pei and Huang, Lianfen and Yuan, Yannan and Dai, Huaiyu and Huang, Yueh-Min}, year={2016}, pages={171–179} }
 @article{zhang_jiang_li_liu_song_dai_2016, title={Cluster-Based Resource Allocation for Spectrum-Sharing Femtocell Networks}, volume={4}, ISSN={["2169-3536"]}, DOI={10.1109/access.2016.2635938}, abstractNote={Femtocells in two-tier femto-macro networks can enhance indoor coverage and improve overall network performance. Macro networks may share spectrum with overlaid femtocells so as to improve spectral efficiency. However, the deployment of femtocells also brings co-tier and cross-tier interferences, which will significantly degrade system performance. In order to solve this problem efficiently, we propose a distributed scheme to manage wireless resources in this heterogeneous networks. The feasible solution can be obtained by dividing the problem into two sub-problems. First, we propose a femtocells clustering scheme, which uses a mathematical modeling idea based on LINGO, an optimization software that can solve the joint clustering problem for the femtocell access points (FAPs). The proposed branch-and-bound algorithm and the simplex algorithm are used jointly to find the optimal solution by LINGO. The optimality of the proposed clustering algorithm is verified both theoretically and through simulations where the comparison with other algorithms is made. Second, a novel algorithm is proposed to allocate sub-channels to the femtocell users (FUEs). Compared with other related schemes, the proposed channel-allocation algorithm can reduce the interference more effectively and achieve higher data-rate fairness among FUEs. Specifically, according to the situation that the FUEs move in the room, the FUE mobility model is proposed to predict the change tendency of path loss values of the FUEs, which can guarantee the mobile service quality and improve system capacity effectively. Finally, the power of the FAPs is adjusted dynamically through setting the interference threshold to further improve the performance of the system.}, journal={IEEE ACCESS}, author={Zhang, Haibo and Jiang, Dingde and Li, Fangwei and Liu, Kaijian and Song, Houbing and Dai, Huaiyu}, year={2016}, pages={8643–8656} }
 @inproceedings{jin_he_dai_2016, title={Collaborative IDS configuration: A two-layer game-theoretical approach}, DOI={10.1109/glocom.2016.7841671}, abstractNote={As information systems become ubiquitous, Intrusion Detection Systems (IDSs) have assumed increasing importance. As a result, substantial amount of research efforts have been devoted to developing various intrusion detection algorithms. However, there is still no single detection algorithm that can catch all possible attacks. On the other hand, it is infeasible for practical IDSs to run all the detection algorithms simultaneously due to resource limitation, leaving potential opportunities for the adversaries to explore. This resource scarcity problem becomes more severe when the system is in an ill state (e.g., partially compromised). Enabling collaboration among multiple IDSs may be a viable way to mitigate this problem. Particularly, IDSs in the healthy state can share some of their idle computational resources to those in ill states, so as to improve the overall intrusion detection performance. Considering this, the collaborative IDS configuration problem is formulated as a two-layer stochastic game (SG) in this work and a new algorithm is proposed to solve this two-layer SG. Simulation results show that the proposed algorithm can provide an effective collaborative configuration scheme, leading to significant detection performance gain. Some performance analysis has also been given, and the conditions under which there is a guaranteed improvement in expected system performance have been derived.}, booktitle={2016 ieee global communications conference (globecom)}, author={Jin, R. C. and He, X. F. and Dai, H. Y.}, year={2016} }
 @inproceedings{liu_li_yin_dai_2016, title={Connectivity for overlaid wireless networks with outage constraints}, DOI={10.1109/icassp.2016.7472382}, abstractNote={We study the connectivity of overlaid wireless networks where two users can communicate if the signal-to-interference ratio is larger than a threshold subject to an outage constraint. By using percolation theory, we first specify a 2-dimensional connectivity region defined as the set of density pairs-the density of secondary users and the density of primary users- within which the secondary network is percolated. Several interesting properties of this region are also revealed. Our work provides a new perspective for better understanding of the connectivity of large-scale overlaid networks.}, booktitle={International conference on acoustics speech and signal processing}, author={Liu, Y. and Li, C. Z. and Yin, C. C. and Dai, H. Y.}, year={2016}, pages={3771–3775} }
 @inproceedings{chattopadhyay_dai_2016, title={Estimation of robustness of interdependent networks against failure of nodes}, DOI={10.1109/glocom.2016.7841822}, abstractNote={Abstract-We consider a partially interdependent network and develop mathematical equations relating the fractional size of the connected component of the network, surviving the cascading failure, to the intra-layer degree distribution of the nodes. We show that these system equations can be mathematically analyzed and closed form expressions for the metrics of robustness can be obtained for the Erdos-Renyi (ER) model of random graph generation. We have described the application of our analysis technique to networks with general degree distributions. In our analysis, we consider the two extremes of the attack model: randomized attack, where nodes are attacked at random without any knowledge of intra-layer degrees and perfect targeted attack, where nodes are attacked based on the strict descending order of their intra-layer degrees. Our results can enable researchers to gain a better understanding of the robustness of interdependent networks.}, booktitle={2016 ieee global communications conference (globecom)}, author={Chattopadhyay, S. and Dai, H. Y.}, year={2016} }
 @article{he_dai_ning_2016, title={Faster Learning and Adaptation in Security Games by Exploiting Information Asymmetry}, volume={64}, ISSN={["1941-0476"]}, DOI={10.1109/tsp.2016.2548987}, abstractNote={With the advancement of modern technologies, the security battle between a legitimate system (LS) and an adversary is becoming increasingly sophisticated, involving complex interactions in unknown dynamic environments. Stochastic game (SG), together with multi-agent reinforcement learning (MARL), offers a systematic framework for the study of information warfare in current and emerging cyber-physical systems. In practical security games, each player usually has only incomplete information about the opponent, which induces information asymmetry. This paper exploits information asymmetry from a new angle, considering how to exploit information unknown to the opponent to the player's advantage. Two new MARL algorithms, termed minimax post-decision state (minimax-PDS) and Win-or-Learn Fast post-decision state (WoLF-PDS), are proposed, which enable the LS to learn and adapt faster in dynamic environments by exploiting its information advantage. The proposed algorithms are provably convergent and rational, respectively. Also, numerical results are presented to show their effectiveness through three important applications.}, number={13}, journal={IEEE TRANSACTIONS ON SIGNAL PROCESSING}, author={He, Xiaofan and Dai, Huaiyu and Ning, Peng}, year={2016}, month={Jul}, pages={3429–3443} }
 @article{lee_choi_dai_2016, title={Joint User Selection and Feedback Bit Allocation Based on Sparsity Constraint in MIMO Virtual Cellular Networks}, volume={15}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2015.2497702}, abstractNote={In this paper, we jointly consider the user selection and feedback design problems in a virtual cellular network (VCN), where multiple base stations (BSs) share a user set. In many practical systems, the uplink feedback channel is generally shared by multiple users. Thus, the feedback budget allocated to unselected users not only wastes the feedback resources, but harms the system throughput by decreasing the available feedback budget for the selected users. We optimize both the user selection and feedback bit allocation based on long-term average channel information of the users. We first analyze the effects of the quantization error on the average achievable rate of the VCN system. Next, we propose a user selection and feedback bit allocation protocol under each BS's sum feedback rate constraint as well as the sparsity constraint on all users' feedback sizes. We show that the joint optimization problem can be decoupled into several NP-hard subproblems, one for each BS. We describe the brute-force searching algorithm for the optimal solution, and propose an efficient algorithm with significantly reduced computational complexity by relaxing the sparsity constraint on the feedback sizes. As a result, only the selected users exploit the uplink feedback budget, and the system performance is improved.}, number={3}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Lee, Jung Hoon and Choi, Wan and Dai, Huaiyu}, year={2016}, month={Mar}, pages={2069–2079} }
 @article{zhang_dai_zhang_huang_2016, title={Mobile Conductance in Sparse Networks and Mobility-Connectivity Tradeoff}, volume={15}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2015.2513776}, abstractNote={In this paper, our recently proposed mobile-conductance based analytical framework is extended to the sparse settings, thus offering a unified tool for analyzing information spreading in mobile networks. A penalty factor is identified for information spreading in sparse networks as compared to the connected scenario, which is then intuitively interpreted and verified by simulations. With the analytical results obtained, the mobility-connectivity tradeoff is quantitatively analyzed to determine how much mobility may be exploited to make up for network connectivity deficiency.}, number={4}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Zhang, Huazi and Dai, Huaiyu and Zhang, Zhaoyang and Huang, Yufan}, year={2016}, month={Apr}, pages={2954–2965} }
 @inproceedings{xiao_xie_chen_dai_poor_2016, title={Mobile offloading game against smart attacks}, volume={4}, DOI={10.1109/infcomw.2016.7562110}, abstractNote={Mobile devices, such as smartphones, can offload applications and data to the cloud via access points or base stations to reduce energy consumption and improve user experience. However, mobile offloading is vulnerable to smart attackers that use smart and programmable radio devices, such as universal software radio peripherals, to perform multiple types of attacks, such as spoofing and jamming, based on the radio environment and offloading transmissions. In this paper, a mobile offloading game is investigated that consists of three players: a mobile device that chooses its offloading rate, a smart attacker that determines its attack mode, and a security agent that decides whether or not to initiate full protection for the serving access point during the offloading. Nash and Stackelberg equilibria of the offloading game are derived and their existence conditions are discussed. A Q-learning-based mobile offloading strategy is proposed for mobile devices that are unaware of system parameters, such as the channel conditions, in dynamic radio environments. Simulation results show that the proposed offloading strategy can improve the utility of the mobile device and reduce the attack rate of smart attackers.}, booktitle={2016 ieee conference on computer communications workshops (infocom wkshps)}, author={Xiao, L. and Xie, C. X. and Chen, T. H. and Dai, H. Y. and Poor, H. V.}, year={2016}, pages={2281–2291} }
 @article{liu_dai_chen_2016, title={On Throughput Maximization of Time Division Multiple Access With Energy Harvesting Users}, volume={65}, ISSN={["1939-9359"]}, DOI={10.1109/tvt.2015.2428635}, abstractNote={In this paper, we consider a multiple-access channel, where multiple users equipped with energy harvesting batteries communicate to an access point. To avoid consuming extra energy on competition for the channel, the users are supposed to share the channel via time division multiple access (TDMA). In many existing works, it is commonly assumed that the users' energy harvesting processes and storage status are known to all the users before transmissions. In practice, such knowledge may not be readily available. To avoid excessive overhead for real-time information exchange, we consider the scenario where the users schedule their individual transmissions according to the users' statistical energy harvesting profiles. We first study the optimal transmission scheme in the case where each node has an infinite-capacity battery. By optimization theory, we show that, to maximize the average system throughput, all the users should transmit at an identical optimal power, which solely depends on the energy harvesting rate per time slot. We then study the equal-power TDMA scheme in the case where each node is equipped with a battery of finite capacity. The system is formulated as a polling system consisting of multiple energy queues and one server. By the Markov chain modeling method, we derive the performance of equal-power TDMA in this case, in terms of the energy loss ratio and average system throughput. In addition, we develop an algorithm to efficiently compute the optimal transmission power in the finite-capacity battery case. We also consider an equal-time TDMA scheme, which assigns equal-length subslots to each user, and analyze its system performance. It is found that equal-power TDMA always outperforms equal-time TDMA in the infinite-capacity battery case, whereas equal-time TDMA exhibits compatible or even slightly better performance in some scenarios when the batteries have finite capacities.}, number={4}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Liu, Juan and Dai, Huaiyu and Chen, Wei}, year={2016}, month={Apr}, pages={2457–2470} }
 @article{ding_dai_poor_2016, title={Relay Selection for Cooperative NOMA}, volume={5}, ISSN={["2162-2345"]}, DOI={10.1109/lwc.2016.2574709}, abstractNote={This letter studies the impact of relay selection (RS) on the performance of cooperative non-orthogonal multiple access (NOMA). In particular, a two-stage RS strategy is proposed, and analytical results are developed to demonstrate that this two-stage strategy can achieve the minimal outage probability among all possible RS schemes, and realize the maximal diversity gain. The provided simulation results show that cooperative NOMA with this two-stage RS scheme outperforms that based on the conventional max-min approach, and can also yield a significant performance gain over orthogonal multiple access.}, number={4}, journal={IEEE WIRELESS COMMUNICATIONS LETTERS}, author={Ding, Zhiguo and Dai, Huaiyu and Poor, H. Vincent}, year={2016}, month={Aug}, pages={416–419} }
 @article{he_dai_shen_ning_dutta_2016, title={Toward Proper Guard Zones for Link Signature}, volume={15}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2015.2498621}, abstractNote={Motivated by information-theoretic security, link signature (LS)-based security mechanisms exploit the ample channel characteristics between wireless devices for security establishment. Nevertheless, LS is originated from wireless environments and hence may exhibit potential vulnerabilities that can be exploited by adversary in the vicinity. As to this, it is widely believed in existing literature on LS that, a half-wavelength guard zone is sufficient to decorrelate the adversary channel from the legitimate one and thereby secures the legitimate LS. However, such an assumption may not hold universally - in some environments, high channel correlations have been observed for much larger spatial separations. Considering this, a comprehensive understanding of channel correlation in different wireless environments is needed for more confident deployment of LS-based security mechanisms. To this end, various well-established channel correlation models are investigated in this work. A set of important physical factors that have significant influence on LS security are identified, and with the obtained insights, extensive simulations are conducted to explore suitable guard zone sizes for LS in several typical indoor and outdoor environments. Experimental results based on universal software radio peripheral (USRP) platforms and GNURadio are also presented to further support the analysis.}, number={3}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={He, Xiaofan and Dai, Huaiyu and Shen, Wenbo and Ning, Peng and Dutta, Rudra}, year={2016}, month={Mar}, pages={2104–2117} }
 @article{zhang_wu_zhang_dai_kato_2016, title={Virtual-MIMO-Boosted Information Propagation on Highways}, volume={15}, ISSN={1536-1276}, url={http://dx.doi.org/10.1109/twc.2015.2489661}, DOI={10.1109/twc.2015.2489661}, abstractNote={In vehicular communications, traffic-related information should be spread over the network as quickly as possible to maintain a safer transportation system. This motivates us to develop more efficient information propagation schemes. In this paper, we propose a novel virtual-MIMO-enabled information dissemination scheme in which the vehicles opportunistically form virtual antenna arrays to boost the transmission range, and therefore, accelerate information propagation along the highway. We model the information propagation process as a renewal reward process and investigate in detail the information propagation speed (IPS) of the proposed scheme. The corresponding closed-form IPS is derived, which shows that the IPS increases cubically with the vehicle density but will ultimately converge to a constant upper bound. Moreover, increased mobility also facilitates the information spreading by offering more communication opportunities. However, the limited network density essentially determines the bottleneck in information spreading. Extensive simulations are carried out to verify our analysis. We also show that the proposed scheme exhibits a significant IPS gain over its conventional counterpart.}, number={2}, journal={IEEE Transactions on Wireless Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Zhang, Zhaoyang and Wu, Hui and Zhang, Huazi and Dai, Huaiyu and Kato, Nei}, year={2016}, month={Feb}, pages={1420–1431} }
 @article{he_dai_ning_dutta_2016, title={Zero-determinant Strategies for Multi-player Multi-action Iterated Games}, volume={23}, ISSN={1070-9908 1558-2361}, url={http://dx.doi.org/10.1109/lsp.2016.2517640}, DOI={10.1109/lsp.2016.2517640}, abstractNote={Zero-determinant (ZD) strategies that allow a player to unilaterally control the linear combinations of its own and other players' expected rewards in iterated games have recently found wide applications. However, existing ZD strategies mainly focus on some specific scenarios with restrictions on the number of players or actions a player can take. Targeting wider applications and better performance, the ZD strategies along with corresponding existence conditions for general multi-player multi-action iterated games are developed in this work, including existing ones as special cases. In addition, an interesting fact that every player can have at most one master player (that can control the expected reward of the given player) is revealed.}, number={3}, journal={IEEE Signal Processing Letters}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={He, Xiaofan and Dai, Huaiyu and Ning, Peng and Dutta, Rudra}, year={2016}, month={Mar}, pages={311–315} }
 @inproceedings{he_dai_ning_dutta_2015, title={A A stochastic multi-channel spectrum access game with incomplete information}, DOI={10.1109/icc.2015.7249082}, abstractNote={To ensure continuous functioning and satisfactory performance, a wireless communication system has to not only learn and adapt to the unknown and ever-changing wireless environment, but also strategically deal with the usually unfamiliar peers. Incomplete information stochastic game (SG) is a promising model for the corresponding analysis and strategy design. In this work, an exemplary multi-channel spectrum access game (SAG) with unknown environment dynamics and limited information of the other player is considered to illustrate the proposed solution for the corresponding incomplete information SG. To find the best communication strategy in the face of uncertainty, a joint reinforcement learning and type identification algorithm is developed, which is provably convergent under certain technical conditions. Numerical results show that using the proposed algorithm, a wireless user can gradually achieve the same performance as that in the corresponding complete information game.}, booktitle={2015 ieee international conference on communications (icc)}, author={He, X. F. and Dai, Huaiyu and Ning, P. and Dutta, Rudra}, year={2015}, pages={4799–4804} }
 @inproceedings{liu_li_yin_dai_2015, title={A unified framework for wireless connectivity study subject to general interference attack}, DOI={10.1109/icc.2015.7249471}, abstractNote={Connectivity is crucial to ensure information availability and survivability for wireless networks. In this paper, we propose a unified framework to study the connectivity of wireless networks under a general type of interference attack, which can address diverse applications including Cognitive Radio, Jamming attack and shadowing effect. By considering the primary users, jammers and deep fading as unified Interferers, we investigate a 3-dimensional connectivity region, defined as the set of key system parameters - the density of users, the density of Interferers and the interference range of Interferers - with which the network is connected. Further we study the impact of the Interferers' settings on node isolation probability, which is a fundamental local connectivity metric. Through percolation theory, the sufficient and necessary conditions for global connectivity are also derived. Our study is supported by simulation results.}, booktitle={2015 ieee international conference on communications (icc)}, author={Liu, Y. and Li, C. Z. and Yin, C. C. and Dai, H. Y.}, year={2015}, pages={7174–7179} }
 @article{xiao_chen_liu_dai_2015, title={Anti-Jamming transmission Stackelberg game with observation errors}, volume={19}, DOI={10.1109/lcomm.2015.2418776}, abstractNote={As smart jammers that can analyze the ongoing radio transmission with flexible and powerful control on jamming signals throw serious threats on cognitive radio networks, game theory provides a powerful approach to study the interactions between smart jammers and secondary users (SUs). In this work, the power control strategy of an SU against a smart jammer under power constraints is formulated as a Stackelberg game. The jammer as the follower of the game chooses the jamming power according to the observed ongoing transmission, while the SU as the leader determines its transmit power based on the estimated jamming power. The impact of the observation accuracy of the jammer regarding the transmit power of the SU is investigated. The Stackelberg equilibrium of the anti-jamming game is derived and compared with the Nash equilibrium of the game. Simulation results show that the transmission of an SU benefits from the observation error of the jammer with a higher signal-to-interference-plus-noise ratio and utility.}, number={6}, journal={IEEE Communications Letters}, author={Xiao, L. and Chen, T. H. and Liu, J. L. and Dai, H. Y.}, year={2015}, pages={949–952} }
 @inproceedings{lee_dai_2015, title={Beamforming games with quantized CSI in two-user interference channels}, DOI={10.1109/ictc.2015.7354802}, abstractNote={We consider a beamforming game of the transmitters in a two-user multiple-input single-output interference channel using limited feedback and investigate how each transmitter should find a strategy from the quantized channel state information (CSI). In the beamforming game, each transmitter (a player) tries to maximize the achievable rate (a payoff function) via a proper beamforming strategy. With the perfect CSI, each transmitter can know the exact achievable rate region, and hence can find the beamforming strategy corresponding to any point in the achievable rate region. With limited feedback, however, the transmitters can only conjecture the achievable rate region from the quantized CSI, so their optimal strategies may not be optimal anymore. Considering the quantized CSI at the transmitter, we first find the Nash equilibrium in a non-cooperative game. Then, we consider a cooperative game and modify the Nash bargaining solution.}, booktitle={2015 International Conference on ICT Convergence (ICTC)}, author={Lee, J. H. and Dai, H. Y.}, year={2015}, pages={1303–1306} }
 @article{liu_dai_chen_2015, title={Delay Optimal Scheduling for Energy Harvesting Based Communications}, volume={33}, ISSN={["1558-0008"]}, DOI={10.1109/jsac.2015.2391972}, abstractNote={Green communications have been attracting increased research interest recently. Equipped with a rechargeable battery, a source node can harvest energy from ambient environments and rely on this free and regenerative energy supply to transmit packets. Due to the uncertainty of available energy from harvesting, however, intolerably large latency and packet loss could be induced, if the source always waits for harvested energy. To overcome this problem, one Reliable Energy Source (RES) can be resorted to for a prompt delivery of backlogged packets. Naturally, there exists a tradeoff between the packet delivery delay and power consumption from the RES. In this paper, we address the delay optimal scheduling problem for a bursty communication link powered by a capacity-limited battery storing harvested energy together with one RES. The proposed scheduling scheme gives priority to the usage of harvested energy, and resorts to the RES when necessary based on the data and energy queueing processes, with an average power constraint from the RES. Through two-dimensional Markov chain modeling and linear programming formulation, we derive the optimal threshold-based scheduling policy together with the corresponding transmission parameters. Our study includes three exemplary cases that capture some important relations between the data packet arrival process and energy harvesting capability. Our theoretical analysis is corroborated by simulation results.}, number={3}, journal={IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS}, author={Liu, Juan and Dai, Huaiyu and Chen, Wei}, year={2015}, month={Mar}, pages={452–466} }
 @article{he_dai_ning_dutta_2015, title={Dynamic IDS Configuration in the Presence of Intruder Type Uncertainty}, ISSN={["2334-0983"]}, DOI={10.1109/glocom.2015.7417158}, abstractNote={Intrusion detection systems (IDSs) assume increasingly importance in past decades as information systems become ubiquitous. Despite the abundance of intrusion detection algorithms developed so far, there is still no single detection algorithm or procedure that can catch all possible intrusions; also, simultaneously running all these algorithms may not be feasible for practical IDSs due to resource limitation. For these reasons, effective IDS configuration becomes crucial for real-time intrusion detection. However, the uncertainty in the intruder's type and the (often unknown) dynamics involved with the target system pose challenges to IDS configuration. Considering these challenges, the IDS configuration problem is formulated as an incomplete information stochastic game in this work, and a new algorithm, Bayesian Nash-Q learning, that combines conventional reinforcement learning with a Bayesian type identification procedure is proposed. Numerical results show that the proposed algorithm can identify the intruder's type with high fidelity and provide effective configuration.}, journal={2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={He, Xiaofan and Dai, Huaiyu and Ning, Peng and Dutta, Rudra}, year={2015} }
 @inproceedings{he_dai_ning_2015, title={Improving learning and adaptation in security games by exploiting information asymmetry}, DOI={10.1109/infocom.2015.7218560}, abstractNote={With the advancement of modern technologies, the security battle between a legitimate system (LS) and an adversary is becoming increasingly sophisticated, involving complex interactions in unknown dynamic environments. Stochastic game (SG), together with multi-agent reinforcement learning (MARL), offers a systematic framework for the study of information warfare in current and emerging cyber-physical systems. In practical security games, each player usually has only incomplete information about the opponent, which induces information asymmetry. This work exploits information asymmetry from a new angle, considering how to exploit local information unknown to the opponent to the player's advantage. Two new MARL algorithms, termed minimax-PDS and WoLF-PDS, are proposed, which enable the LS to learn and adapt faster in dynamic environments by exploiting its private local information. The proposed algorithms are provably convergent and rational, respectively. Also, numerical results are presented to show their effectiveness through two concrete anti-jamming examples.}, booktitle={2015 ieee conference on computer communications (infocom)}, author={He, X. F. and Dai, H. Y. and Ning, P.}, year={2015} }
 @article{xiao_li_chen_cheng_dai_2015, title={Jamming Games in Underwater Sensor Networks with Reinforcement Learning}, ISSN={["2334-0983"]}, DOI={10.1109/glocom.2015.7417192}, abstractNote={Jamming attacks that can further lead to denial of service attacks have thrown serious threats to underwater sensor networks (UWSNs). However, due to the narrow bandwidth of underwater acoustic signals and time variant propagation environments, jamming in UWSNs cannot be fully addressed by spread spectrum techniques, one type of widely-used antijamming methods in wireless networks for decades. In this work, we investigate jamming attacks in underwater sensor networks. More specifically, the interactions between the underwater sensors and jammers in UWSNs are formulated as an underwater jamming game, in which the players choose their transmit power levels to maximize their individual utilities based on the signal to interference plus noise ratio of the legal signals and transmission costs. The Nash equilibrium (NE) of a static jamming game is presented in a closed-form expression for the jamming scenario with known acoustic channel gains. For the dynamic and unknown underwater environments, we propose a reinforcement learning-based anti-jamming method for UWSNs, in which each sensor chooses its transmit power without knowing the channel gain of the jammers. Simulations are performed to evaluate the NE in the static jamming game in underwater sensor networks and to validate the efficacy of the proposed anti-jamming power control scheme against jamming in dynamic environments.}, journal={2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={Xiao, Liang and Li, Qiangda and Chen, Tianhua and Cheng, En and Dai, Huaiyu}, year={2015} }
 @article{lee_dai_2015, title={Nash Bargaining in Beamforming Games with Quantized CSI in Two-user Interference Channels}, ISSN={["2334-0983"]}, DOI={10.1109/glocom.2015.7417263}, abstractNote={In this paper, we consider a beamforming game of the transmitters in a two-user multiple-input single- output interference channel using limited feedback and investigate how each transmitter should find a strategy from the quantized channel state information (CSI). In the beamforming game, each transmitter (a player) tries to maximize the achievable rate (a payoff function) via a proper beamforming strategy. In our case, each transmitter's beamforming strategy is represented by a linear combining factor between the maximum-ratio transmission (MRT) and the zero-forcing (ZF) beamforming vectors, which is shown to be a Pareto optimal achieving strategy. With the perfect CSI, each transmitter can know the exact achievable rate region, and hence can find the beamforming strategy corresponding to any point in the achievable rate region. With limited feedback, however, the transmitters can only conjecture the achievable rate region from the quantized CSI, so their optimal strategies may not be optimal anymore. Considering the quantized CSI at the transmitter, we first find the Nash equilibrium in a non-cooperative game. Then, in a cooperative (Nash bargaining) game, we find a Nash bargaining solution and test its validity. Finally, we propose three bargaining solutions that improve the validity of the cooperation or the average Nash product. Our proposed bargaining solutions utilize the codebook structure; instead of each quantized channel itself, its Voronoi region is considered.}, journal={2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={Lee, Jung Hoon and Dai, Huaiyu}, year={2015} }
 @inproceedings{shen_liu_he_dai_ning_2015, title={No time to demodulate - fast physical layer verification of friendly jamming}, DOI={10.1109/milcom.2015.7357518}, abstractNote={Jamming attacks are well-known threats to wireless communications, but on the other hand they provide insights for researchers to design novel approaches to protect wireless communications. In recent years, friendly jamming is used by a number of research works to achieve the wireless medium access control. However, in these works, the friendly jammer relies on bit-level information to distinguish the allies' wireless transmissions from the enemies', which requires the received signals to be processed through demodulation steps and thus introduces a non-trivial reaction time delay for the friendly jammer. This reaction delay is undesirable as the transmissions need to be jammed while they are still on the air. To address this problem, we propose fast friendly jamming, which eliminates the need for demodulation and enables the friendly jammer to verify the received signals directly on the physical layer. We have implemented a prototype of the proposed techniques based on GNURadio and USRP, and performed real-world experiments to validate the proposed techniques. The experiment results show that the proposed techniques reduce the normal reaction delay of the friendly jammer by 81.9%-85.7%, and achieve the accurate distinction between allies' and enemies' transmissions.}, booktitle={2015 ieee military communications conference (milcom 2015)}, author={Shen, W. B. and Liu, Y. and He, X. F. and Dai, H. Y. and Ning, P.}, year={2015}, pages={653–658} }
 @article{pandian_sichitiu_dai_2015, title={Optimal Resource Allocation in Random Access Cooperative Cognitive Radio Networks}, volume={14}, ISSN={["1558-0660"]}, DOI={10.1109/tmc.2014.2343968}, abstractNote={Cooperative cognitive radio networks (CCRNs) incorporates cooperative communication into cognitive radio networks, in which, primary users lease their spectrum to secondary users, and in exchange, the primary users leverage secondary users as cooperative relays to enhance their own throughput. Mobile operators offload their Internet traffic to privately owned Wi-Fi access points (APs), much to the inconvenience of non-cellular users served by the APs. However, by employing the CCRN scheme, the mobile operator can lease a licensed channel to the AP, effectively doubling its capacity. In this paper, we propose an implementation of the CCRN framework applied to IEEE 802.11 WLANs. The cooperation is cast as a two-player bargaining game where the two players are the primary users (users of the mobile operator) and the secondary users (users of the AP before spectrum leasing) who bargain for either throughput share or channel access time share. The optimal resource allocation that ensures efficiency as well as fairness among users is provided by the Nash solution. Simulation results show that the users achieve higher throughput via the proposed CCRN scheme, thus providing the mobile operator (e.g., AT&T) and the private Wi-Fi provider (e.g., a Starbucks coffee shop) with incentives for cooperation.}, number={6}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Pandian, Mani Bharathi and Sichitiu, Mihail L. and Dai, Huaiyu}, year={2015}, month={Jun}, pages={1245–1258} }
 @article{liu_li_dai_guo_chen_2015, title={Robust blind image watermarking based on chaotic mixtures}, volume={80}, ISSN={["1573-269X"]}, DOI={10.1007/s11071-015-1946-z}, number={3}, journal={NONLINEAR DYNAMICS}, author={Liu, Niansheng and Li, Huajian and Dai, Huaiyu and Guo, Donghui and Chen, Deming}, year={2015}, month={May}, pages={1329–1355} }
 @article{li_dai_2015, title={Single-Hop Transport Throughput of Secondary Networks in Spectrum Sharing Systems}, volume={14}, ISSN={1536-1233}, url={http://dx.doi.org/10.1109/tmc.2014.2363091}, DOI={10.1109/tmc.2014.2363091}, abstractNote={In order to improve the spectrum efficiency, spectrum sharing systems allow multiple systems to utilize the same spectrum with different priorities. Typically, the primary network performs as a stand-alone network while the secondary one accesses the spectrum only if it does no harm to the primary receivers. In this paper, the configuration of the secondary network is of our interest and we explore its single-hop transport throughput (STT) with outage constraints imposed on both networks. STT is a new metric that inherits the merits of both the traditional transport capacity and transmission capacity, incorporating transmission distance and outage probability into a uniform framework. Given the settings of the primary network, we first evaluate the limit of the secondary STT, single-hop transport capacity (STC). Then, we investigate STT with secondary receivers randomly located in the field of interest. To provide a comprehensive view of achievable secondary network throughputs, three models regarding the selection of receivers are considered: optimally selected, randomly selected, and the nearest neighbors. Our theoretical analysis are well substantiated by numerical and simulation results.}, number={8}, journal={IEEE Transactions on Mobile Computing}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Li, Chengzhi and Dai, Huaiyu}, year={2015}, month={Aug}, pages={1726–1736} }
 @article{chattopadhyay_dai_2015, title={Towards Optimal Link Patterns for Robustness of Interdependent Networks against Cascading Failures}, ISSN={["2576-6813"]}, DOI={10.1109/glocom.2015.7417333}, abstractNote={In this work we consider the optimal design of interconnection links for an interdependent system of networks. In contrast to existing literature, we explicitly exploit the information of intra- layer node degrees to design more robust interdependency structure against cascading failures triggered by random attacks. Built on solid mathematical models, we characterize the optimal design for the one-to-one structure, with complete interdependence and partial interdependence. We also extend the study to the one-to-many structure and targeted attack model. Simulation results are provided to corroborate the theoretical results.}, journal={2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={Chattopadhyay, Srinjoy and Dai, Huaiyu}, year={2015} }
 @article{he_dai_ning_2014, title={Dynamic Adaptive Anti-Jamming via Controlled Mobility}, volume={13}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2014.2320973}, abstractNote={In this paper, the mobility of network nodes is explored as a new promising approach for jamming defense. To fulfill it, properly designed node motion that can intelligently adapt to the jammer's action is crucial. In our study, anti-jamming mobility control is investigated in the context of the single and multiple commodity flow problems, in the presence of intelligent mobile jammers which can respond to the evasion of legitimate nodes as well. Based on spectral graph theory, two new spectral quantities, single- and multi-weighted Cheeger constants and corresponding eigenvalue variants, are constructed to direct motions of the defender and the attacker in this dynamic adaptive competition. Both analytical and simulation results are presented to justify the effectiveness of the proposed approach. Furthermore, the proposed scheme can also be applied in cognitive radio networks to reconfigure the secondary users in the presence of mobile primary users.}, number={8}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={He, Xiaofan and Dai, Huaiyu and Ning, Peng}, year={2014}, month={Aug}, pages={4374–4388} }
 @article{liu_dai_guo_2014, title={Security Analysis of MAC Protocol for Mobile Device Identification Based on PARADIS}, DOI={10.1109/sere-c.2014.45}, abstractNote={Authenticating wireless devices based on PARADIS technique draws increasing research interest recently, providing security access services in wireless networks. This paper provides an overview of various schemes for PARADIS identification using physical layer characteristics. Firstly, this work systematizes the existing knowledge on this topic for a better understanding of PARADIS device identification, its implications on the analysis and design of security solutions in wireless mobile networks, and possible applications. Secondly, we review the development progress of PARADIS identification techniques, discuss the merits and demerits of existing PARADIS identification schemes and provide a summary of the current state of the art. Moreover, we propose a new authentication scheme based on PRARDIS and discuss its security and feasibility in the SAE/LTE application. We also highlight the open problems of PRARDIS and motivate future works.}, journal={2014 IEEE EIGHTH INTERNATIONAL CONFERENCE ON SOFTWARE SECURITY AND RELIABILITY - COMPANION (SERE-C 2014)}, author={Liu, Niansheng and Dai, Huaiyu and Guo, Donghui}, year={2014}, pages={237–242} }
 @article{li_dai_2014, title={Throughput Scaling of Primary and Secondary Ad Hoc Networks With Same-Order Dimensions}, volume={63}, ISSN={["1939-9359"]}, DOI={10.1109/tvt.2014.2310424}, abstractNote={In this paper, the scaling law of the network throughput of a special type of heterogeneous networks is studied, where a secondary network composed of cognitive users shares the same resources opportunistically with a primary network of licensed users. Some pioneering works in this area showed that this type of heterogeneous networks performs as well as two stand-alone networks under the dense network model. A key assumption behind this conclusion is that the density of the secondary network is higher than that of the primary network in the order sense, which essentially decouples the two overlaid networks as the secondary network dominates asymptotically. In this paper, we endeavor to investigate this problem with a weaker condition that the dimensions of the two overlaid networks are on the same order, under the extended network model. Our analysis shows that, with the ratio of the two network sizes larger than a threshold, this weaker (and arguably more practical) condition does not degrade either network throughput scaling. Our result further reveals the potential of cognitive radio (CR) technology in real applications.}, number={8}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Li, Chengzhi and Dai, Huaiyu}, year={2014}, month={Oct}, pages={3957–3966} }
 @article{he_dai_ning_2013, title={A Byzantine Attack Defender in Cognitive Radio Networks: The Conditional Frequency Check}, volume={12}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2013.031313.121551}, abstractNote={Security concerns are raised for collaborative spectrum sensing due to its vulnerabilities to the potential attacks from malicious secondary users. Most existing malicious user detection methods are reputation-based, which become incapable when the malicious users dominate the network. On the other hand, although Markovian models characterize the spectrum state behavior more precisely, there is a scarcity of malicious user detection methods which fully explore this feature. In this paper, a new malicious user detection method using two proposed conditional frequency check (CFC) statistics is developed under the Markovian model for the spectrum state. With the assistance of one trusted user, the proposed method can achieve high malicious user detection accuracy (≥ 95%) for arbitrary percentage of malicious users that may even be equipped with more advanced sensing devices, and can thus improve the collaborative spectrum sensing performance significantly. Simulation results are provided to verify the theoretical analysis and effectiveness of the proposed method.}, number={5}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={He, Xiaofan and Dai, Huaiyu and Ning, Peng}, year={2013}, month={May}, pages={2512–2523} }
 @article{shen_ning_he_dai_2013, title={Ally Friendly Jamming: How to Jam Your Enemy and Maintain Your Own Wireless Connectivity at the Same Time}, ISBN={["978-1-4673-6166-8"]}, ISSN={["1081-6011"]}, DOI={10.1109/sp.2013.22}, abstractNote={This paper presents a novel mechanism, called Ally Friendly Jamming, which aims at providing an intelligent jamming capability that can disable unauthorized (enemy) wireless communication but at the same time still allow authorized wireless devices to communicate, even if all these devices operate at the same frequency. The basic idea is to jam the wireless channel continuously but properly control the jamming signals with secret keys, so that the jamming signals are unpredictable interference to unauthorized devices, but are recoverable by authorized ones equipped with the secret keys. To achieve the ally friendly jamming capability, we develop new techniques to generate ally jamming signals, to identify and synchronize with multiple ally jammers. This paper also reports the analysis, implementation, and experimental evaluation of ally friendly jamming on a software defined radio platform. Both the analytical and experimental results indicate that the proposed techniques can effectively disable enemy wireless communication and at the same time maintain wireless communication between authorized devices.}, journal={2013 IEEE SYMPOSIUM ON SECURITY AND PRIVACY (SP)}, author={Shen, Wenbo and Ning, Peng and He, Xiaofan and Dai, Huaiyu}, year={2013}, pages={174–188} }
 @inproceedings{he_dai_ning_2013, title={Dynamic adaptive anti-jamming via controlled mobility}, DOI={10.1109/cns.2013.6682686}, abstractNote={In this paper, the mobility of network nodes is explored as a new promising approach for jamming defense. To fulfill it, properly designed node motion that can intelligently adapt to the jammer's action is crucial. In our study, anti-jamming mobility control is investigated in the context of the single and multiple commodity flow problems, in the presence of intelligent mobile jammers which can respond to the evasion of legitimate nodes as well. Based on spectral graph theory, two new spectral quantities, single- and multi-weighted Cheeger constants and corresponding eigenvalue variants, are constructed to direct motions of the defender and the attacker in this dynamic adaptive competition. Both analytical and simulation results are presented to justify the effectiveness of the proposed approach. Furthermore, the proposed scheme can also be applied in cognitive radio networks to reconfigure the secondary users in the presence of mobile primary users.}, booktitle={2013 IEEE Conference on Communications and Network Security (CNS)}, author={He, X. F. and Dai, H. Y. and Ning, P.}, year={2013}, pages={1–9} }
 @article{li_dai_2013, title={Efficient In-Network Computing with Noisy Wireless Channels}, volume={12}, ISSN={["1536-1233"]}, DOI={10.1109/tmc.2012.185}, abstractNote={In this paper, we study distributed function computation in a noisy multihop wireless network. We adopt the adversarial noise model, for which independent binary symmetric channels are assumed for any point-to-point transmissions, with (not necessarily identical) crossover probabilities bounded above by some constant ε. Each node takes an m-bit integer per instance, and the computation is activated after each node collects N readings. The goal is to compute a global function with a certain fault tolerance in this distributed setting; we mainly deal with divisible functions, which essentially cover the main body of interest for wireless applications. We focus on protocol designs that are efficient in terms of communication complexity. We first devise a general protocol for evaluating any divisible functions, addressing both one-shot (N = O(1)) and block computation, and both constant and large m scenarios. We also analyze the bottleneck of this general protocol in different scenarios, which provides insights into designing more efficient protocols for specific functions. In particular, we endeavor to improve the design for two exemplary cases: the identity function, and size-restricted type-threshold functions, both focusing on the constant m and N scenario. We explicitly consider clustering, rather than hypothetical tessellation, in our protocol design.}, number={11}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Li, Chengzhi and Dai, Huaiyu}, year={2013}, month={Nov}, pages={2167–2177} }
 @article{zhang_zhang_dai_2013, title={Gossip-Based Information Spreading in Mobile Networks}, volume={12}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2013.100113.130619}, abstractNote={In this paper, we analyze the effect of mobility on information spreading in geometric networks through natural random walks. Specifically, our focus is on epidemic propagation via mobile gossip, a variation from its static counterpart. Our contributions are twofold. Firstly, we propose a new performance metric, mobile conductance, which allows us to separate the details of mobility models from the study of mobile spreading time. Secondly, we utilize geometrical properties to explore this metric for several popular mobility models, and offer insights on the corresponding results. Large scale network simulation is conducted to verify our analysis.}, number={11}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Zhang, Huazi and Zhang, Zhaoyang and Dai, Huaiyu}, year={2013}, month={Nov}, pages={5918–5928} }
 @article{he_dai_ning_2013, title={HMM-Based Malicious User Detection for Robust Collaborative Spectrum Sensing}, volume={31}, ISSN={0733-8716}, url={http://dx.doi.org/10.1109/jsac.2013.131119}, DOI={10.1109/jsac.2013.131119}, abstractNote={Collaborative spectrum sensing improves the spectrum state estimation accuracy but is vulnerable to the potential attacks from malicious secondary cognitive radio (CR) users, and thus raises security concerns. One promising malicious user detection method is to identify their abnormal statistical spectrum sensing behaviors. From this angle, two hidden Markov models (HMMs) corresponding to honest and malicious users respectively are adopted in this paper to characterize their different sensing behaviors, and malicious user detection is achieved via detecting the difference in the corresponding HMM parameters. To obtain the HMM estimates, an effective inference algorithm that can simultaneously estimate two HMMs without requiring separated training sequences is also developed. By using these estimates, high malicious user detection accuracy can be achieved at the fusion center, leading to more robust and reliable collaborative spectrum sensing performance (substantially enlarged operational regions) in the presence of malicious users, as compared to the baseline approaches. Different fusion methods are also discussed and compared.}, number={11}, journal={IEEE Journal on Selected Areas in Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={He, Xiaofan and Dai, Huaiyu and Ning, Peng}, year={2013}, month={Nov}, pages={2196–2208} }
 @inproceedings{he_dai_shen_ning_2013, title={Is link signature dependable for wireless security?}, DOI={10.1109/infcom.2013.6566763}, abstractNote={A fundamental assumption of link signature based security mechanisms is that the wireless signals received at two locations separated by more than half a wavelength are essentially uncorrelated. However, it has been observed that in certain circumstances (e.g., with poor scattering and/or a strong line-of-sight (LOS) component), this assumption is invalid. In this paper, a Correlation ATtack (CAT) is proposed to demonstrate the potential vulnerability of the link signature based security mechanisms in such circumstances. Based on statistical inference, CAT explicitly exploits the spatial correlations to reconstruct the legitimate link signature from the observations of multiple adversary receivers deployed in vicinity. Our findings are verified through theoretical analysis, well-known channel correlation models, and experiments on USRP platforms and GNURadio.}, booktitle={2013 proceedings ieee infocom}, author={He, X. F. and Dai, H. Y. and Shen, W. B. and Ning, P.}, year={2013}, pages={200–204} }
 @article{zhang_zhang_dai_2013, title={On the Capacity Region of Cognitive Multiple Access over White Space Channels}, volume={31}, ISSN={["1558-0008"]}, DOI={10.1109/jsac.2013.131105}, abstractNote={Opportunistically sharing the white spaces, or the temporarily unoccupied spectrum licensed to the primary user (PU), is a practical way to improve the spectrum utilization. In this paper, we consider the fundamental problem of rate regions achievable for multiple secondary users (SUs) which send their information to a common receiver over such a white space channel. In particular, the PU activities are treated as on/off side information, which can be obtained causally or non-causally by the SUs. The system is then modeled as a multi-switch channel and its achievable rate regions are characterized in some scenarios. Explicit forms of outer and inner bounds of the rate regions are derived by assuming additional side information, and they are shown to be tight in some special cases. An optimal rate and power allocation scheme that maximizes the sum rate is also proposed. The numerical results reveal the impacts of side information, channel correlation and PU activity on the achievable rates, and also verify the effectiveness of our rate and power allocation scheme. Our work may shed some light on the fundamental limit and design tradeoffs in practical cognitive radio systems.}, number={11}, journal={IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS}, author={Zhang, Huazi and Zhang, Zhaoyang and Dai, Huaiyu}, year={2013}, month={Nov}, pages={2517–2527} }
 @article{dai_zhang_liu_2013, title={Structured Variational Methods for Distributed Inference in Networked Systems: Design and Analysis}, volume={61}, ISSN={1053-587X 1941-0476}, url={http://dx.doi.org/10.1109/tsp.2013.2264463}, DOI={10.1109/tsp.2013.2264463}, abstractNote={In this paper, a variational message passing framework is proposed for distributed inference in networked systems. Based on this framework, structured variational methods are explored to take advantage of both the simplicity of variational approximation (for inter-cluster processing) and the quality of more accurate inference (for intra-cluster processing). To investigate the convergence performance of our inference approach, we distinguish the inter- and intra-cluster inference algorithms as vertex and edge processes, respectively. Based on an analysis on the intracluster inference procedure, the overall performance of structured variational methods, modeled as a mixed vertex-edge process, is quantitatively characterized via a coupling approach. The tradeoff between performance and complexity of this inference approach is also addressed.}, number={15}, journal={IEEE Transactions on Signal Processing}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Dai, Huaiyu and Zhang, Yanbing and Liu, Juan}, year={2013}, month={Aug}, pages={3827–3839} }
 @inproceedings{he_dai_ning_2012, title={A Byzantine attack defender: The Conditional Frequency Check}, DOI={10.1109/isit.2012.6284709}, abstractNote={Collaborative spectrum sensing is vulnerable to the Byzantine attack. Existing reputation based countermeasures will become incapable when malicious users dominate the network. Also, there is a scarcity of methods that fully explore the Markov property of the spectrum states to restrain sensors' statistical misbehaviors. In this paper, a new malicious user detection method based on two proposed Conditional Frequency Check (CFC) statistics is developed with a Markovian spectrum model. With the assistance of one trusted sensor, the proposed method can achieve high malicious user detection accuracy in the presence of arbitrary percentage of malicious users, and thus significantly improves collaborative spectrum sensing performance.}, booktitle={2012 ieee international symposium on information theory proceedings (isit)}, author={He, X. F. and Dai, H. Y. and Ning, P.}, year={2012} }
 @article{zhang_wang_li_dai_2012, title={Channel-aware adaptive resource allocation for multicast and unicast services in orthogonal frequency division multiplexing systems}, volume={6}, ISSN={["1751-8636"]}, DOI={10.1049/iet-com.2012.0111}, abstractNote={To support the multicast and unicast services in the orthogonal frequency division multiplexing system simultaneously, a channel-aware adaptive resource allocation algorithm is proposed to maximise the total throughput of the unicast service while guaranteeing the required quality of service (QoS) for the multicast service. The two-step optimisation scheme is developed to solve the problem based on the perfect channel state information at the base station: first, subcarriers are allocated to the multicast and the unicast services under the assumption that power is divided equally to every subcarrier. Especially, the noisy chaotic neural network with a new parameter set is applied to allocate the subcarriers to the unicast service by elaborately constructing the energy function to fully exploit the multiuser diversity gain, the optimal solution is found successfully through its rich neurodynamics; Secondy, the power averagely allocated to the unicast service is reallocated quickly in a linear water-filling fashion. Compared with existing algorithms the proposed algorithm achieves higher spectrum efficiency and better bit-error rate for the multicast service, also higher throughput for the unicast service.}, number={17}, journal={IET COMMUNICATIONS}, author={Zhang, H. and Wang, X. and Li, F. and Dai, H.}, year={2012}, month={Nov}, pages={3006–3014} }
 @article{li_dai_xiao_ning_2012, title={Communication Efficiency of Anti-Jamming Broadcast in Large-Scale Multi-Channel Wireless Networks}, volume={60}, ISSN={1053-587X 1941-0476}, url={http://dx.doi.org/10.1109/tsp.2012.2206589}, DOI={10.1109/tsp.2012.2206589}, abstractNote={Uncoordinated Frequency Hopping (UFH) and Collaborative UFH (CUFH) are viable countermeasures for jamming attacks without dependency on pre-shared secret keys. In this work we analytically evaluate their communication efficiency in large-scale networks, where the number of nodes n is large and may even exceed the number of channels C. Such a large-system analysis is pertinent to emerging complex networks and systems, and helps us reveal the scaling behavior of the system performance with respect to the network size and other important system parameters. In particular, we show that the average network broadcast delay incurred by UFH scales as O(Clnn) , while that incurred by CUFH scales as O(lnn) when C=o(lnn). This demonstrates a significant improvement achieved by cooperative relays and the feasibility of UFH-based schemes in large-scale networks. In large-scale networks, the number of relays in CUFH needs to be carefully controlled for best performance. In this study the optimal number of relays in CUFH is derived such that the packet reception rate is maximized, and the optimal cooperation gain achieved by CUFH over UFH is quantified. To facilitate the implementation of CUFH, a suboptimal protocol, CUFH-p, is proposed, which achieves the optimal cooperation gain asymptotically. As an intermediate step, we also study an ideal cooperative network, whose results may be of independent interest. Our analytical results are well substantiated by simulations, and our analytical methodology applies largely to general anti-jamming broadcast in multi-channel networks.}, number={10}, journal={IEEE Transactions on Signal Processing}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Li, Chengzhi and Dai, Huaiyu and Xiao, Liang and Ning, Peng}, year={2012}, month={Oct}, pages={5281–5292} }
 @article{xiao_dai_ning_2012, title={Jamming-Resistant Collaborative Broadcast Using Uncoordinated Frequency Hopping}, volume={7}, ISSN={1556-6013 1556-6021}, url={http://dx.doi.org/10.1109/tifs.2011.2165948}, DOI={10.1109/tifs.2011.2165948}, abstractNote={We propose a jamming-resistant collaborative broadcast scheme for wireless networks, which utilizes the Un coordinated Frequency Hopping (UFH) technique to counteract jamming without preshared keys, and exploits node cooperation to achieve higher communication efficiency and stronger jamming resistance. In this scheme, nodes that already obtain the broadcast message serve as relays to help forward it to other nodes. Relying on the sheer number of relay nodes, our scheme provides a new angle for jamming countermeasure, which not only significantly enhances the performance of jamming-resistant broadcast, but can readily be combined with other existing or emerging antijamming approaches in various applications. We present the collaborative broadcast protocol, and analyze its successful packet reception rate and the corresponding cooperation gain for both synchronous and asynchronous relays for a snapshot scenario. We also investigate the full broadcast process based on a Markov chain model and derive a closed-form expression of the average broadcast delay. Simulation results in both single-hop and multihop networks indicate that our scheme is a promising antijamming technique in wireless networks.}, number={1}, journal={IEEE Transactions on Information Forensics and Security}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Xiao, Liang and Dai, Huaiyu and Ning, Peng}, year={2012}, month={Feb}, pages={297–309} }
 @article{xiao_dai_ning_2012, title={MAC Design of Uncoordinated FH-Based Collaborative Broadcast}, volume={1}, ISSN={2162-2337 2162-2345}, url={http://dx.doi.org/10.1109/wcl.2012.041012.120162}, DOI={10.1109/wcl.2012.041012.120162}, abstractNote={Uncoordinated Frequency Hopping (UFH) techniques are promising to address jamming attacks in wireless networks without requiring pre-shared secret keys, and its communication efficiency in the broadcast scenario can be significantly improved through node cooperation. In this letter, we take a first step to investigate efficient Media Access Control (MAC) strategies for the UFH-based collaborative broadcast, and derive closed-form expressions of the channel access probabilities for time-slotted systems to minimize the broadcast delay and to significantly reduce the energy cost. Numerical and simulation results are provided to verify our analysis and reveal some insights.}, number={3}, journal={IEEE Wireless Communications Letters}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Xiao, Liang and Dai, Huaiyu and Ning, Peng}, year={2012}, month={Jun}, pages={261–264} }
 @article{lu_yang_dai_wang_2012, title={Opportunistic Decode-and-Forward Relaying With Beamforming in Two-Wave With Diffuse Power Fading}, volume={61}, ISSN={["1939-9359"]}, DOI={10.1109/tvt.2012.2205028}, abstractNote={In this paper, we propose new opportunistic decode-and-forward (DF) relaying with beamforming for multirelay networks, where an Ns-antenna source communicates with an Nd-antenna destination with the aid of N parallel single-antenna relays. Among these relays, only one relay that correctly decodes the signal from the source and has the highest instantaneous signal-to-noise ratio (SNR) to the destination is selected for transmission. The source employs maximum ratio transmission (MRT) to transmit, whereas the destination performs maximum ratio combining (MRC) to the received signals. To examine the benefits of the proposed scheme, we first derive the exact outage probability for independently but non-identically distributed (i.n.i.d.) two-wave with diffuse power (TWDP) fading channels. We then derive an easy-to-compute expression for the exact outage probability to reduce computational cost. Our results encompass Rayleigh and Rician fading as special cases. We further derive a compact expression for the asymptotic outage probability, which characterizes two factors governing the network performance at high SNRs, i.e., the diversity order and the array gain. We demonstrate that our scheme preserves the maximum diversity order of N × min {Ns, Nd}. Additionally, we derive the optimal power allocation factor, which provides a practical design rule to optimally distribute the total transmission power between the source and the selected relay to minimize the outage probability.}, number={7}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Lu, Yao and Yang, Nan and Dai, Huaiyu and Wang, Xiaoxiang}, year={2012}, month={Sep}, pages={3050–3060} }
 @inproceedings{li_dai_2011, title={On the throughput scaling of cognitive radio ad hoc networks}, DOI={10.1109/infcom.2011.5935063}, abstractNote={Due to the emergence of Cognitive Radio, a special type of heterogeneous networks attracts increasing interest recently, in which a secondary network composed of cognitive users shares the same resources opportunistically with a primary network of licensed users. Network throughput in this setting is of essential importance. Some pioneer works in this area showed that this type of heterogeneous networks performs as well as two stand-alone networks, under the dense network model where the size of a network grows with the node density in a fixed area. A key assumption behind this conclusion is that the density of the secondary network is higher than that of the primary one in the order sense, which essentially decouples the two overlaid networks, as the secondary network dominates asymptotically. In this paper we endeavor to investigate this problem with a weaker condition that the dimensions of the two overlaid networks are on the same order, and consider the extended network model where the size of a network scales with the area with the node density fixed. Surprisingly, our analysis shows that this weaker (and arguably more practical) condition does not degrade either network throughput in terms of scaling law. Our result further reveals the potentials of CR technology in real applications.}, booktitle={2011 proceedings ieee infocom}, author={Li, C. Z. and Dai, H. Y.}, year={2011}, pages={241–245} }
 @inproceedings{li_dai_2011, title={Transport throughput of secondary networks in spectrum sharing systems}, DOI={10.1109/infcom.2011.5935105}, abstractNote={Spectrum sharing systems such as cognitive radio networks have drawn much attention recently due to their potential to resolve the conflict between increasing demand for spectrum and spectrum shortage. Such systems are typically composed of primary and secondary networks; the configuration of the latter depends on spectrum opportunity unexploited in the former. In this paper we explore the characteristics of the single hop transport throughput (STT) of the secondary network with outage constraints imposed on both networks. STT is a new metric that inherits the merits of both the traditional transport capacity and another popular metric, transmission capacity, incorporating transmission distance and outage probability into a uniform framework. We first derive the limit of STT, single hop transport capacity (STC), together with a practical upper bound for it. Then we investigate STT with secondary receivers randomly located in the field of interest. Three models regarding the selection of receivers are considered: optimally selected, randomly selected, or the nearest. Study on these models provides a comprehensive view of achievable secondary network throughput, and offers insights into the configuration of secondary networks. In addition, the broadcast transport throughput (BTT) of the secondary networks is also investigated as an extension of STT, and its similarity with STT in the nearest neighbor model is revealed.}, booktitle={2011 proceedings ieee infocom}, author={Li, C. Z. and Dai, H. Y.}, year={2011}, pages={2732–2740} }
 @article{liu_ning_dai_2010, title={Authenticating Primary Users' Signals in Cognitive Radio Networks via Integrated Cryptographic and Wireless Link Signatures}, ISSN={["1081-6011"]}, DOI={10.1109/sp.2010.24}, abstractNote={To address the increasing demand for wireless bandwidth, cognitive radio networks (CRNs) have been proposed to increase the efficiency of channel utilization; they enable the sharing of channels among secondary (unlicensed) and primary (licensed) users on a non-interference basis. A secondary user in a CRN should constantly monitor for the presence of a primary user's signal to avoid interfering with the primary user. However, to gain unfair share of radio channels, an attacker (e.g., a selfish secondary user) may mimic a primary user's signal to evict other secondary users. Therefore, a secure primary user detection method that can distinguish a primary user's signal from an attacker's signal is needed. A unique challenge in addressing this problem is that Federal Communications Commission (FCC) prohibits any modification to primary users. Consequently, existing cryptographic techniques cannot be used directly. In this paper, we develop a novel approach for authenticating primary users' signals in CRNs, which conforms to FCC's requirement. Our approach integrates cryptographic signatures and wireless link signatures (derived from physical radio channel characteristics) to enable primary user detection in the presence of attackers. Essential to our approach is a {\em helper node} placed physically close to a primary user. The helper node serves as a "bridge" to enable a secondary user to verify cryptographic signatures carried by the helper node's signals and then obtain the helper node's authentic link signatures to verify the primary user's signals. A key contribution in our paper is a novel physical layer authentication technique that enables the helper node to authenticate signals from its associated primary user. Unlike previous techniques for link signatures, our approach explores the geographical proximity of the helper node to the primary user, and thus does not require any training process.}, journal={2010 IEEE SYMPOSIUM ON SECURITY AND PRIVACY}, author={Liu, Yao and Ning, Peng and Dai, Huaiyu}, year={2010}, pages={286–301} }
 @article{li_dai_li_2010, title={Collaborative Quickest Spectrum Sensing via Random Broadcast in Cognitive Radio Systems}, volume={9}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2010.07.091667}, abstractNote={Quickest detection is applied in spectrum sensing in cognitive radio systems when multiple secondary users collaborate with limited communication time slots. When the transmissions of sensing results are not coordinated to avoid confliction, random broadcast is used to exchange information. A necessary condition for the optimal broadcast probability, as a function of the log likelihood ratio of local observation, is obtained using variational analysis. To alleviate the difficulty of computing the optimal broadcast probability, a simple threshold broadcast scheme is proposed. Simulation shows that the proposed threshold broadcast scheme can achieve substantial performance gain (less than 60% in detection delay for the same false alarm rate) over schemes of random broadcast without regulation and single-user spectrum sensing.}, number={7}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Li, Husheng and Dai, Huaiyu and Li, Chengzhi}, year={2010}, month={Jul}, pages={2338–2348} }
 @article{li_dai_zhang_2010, title={Location-Aided Fast Distributed Consensus in Wireless Networks}, volume={56}, ISSN={["1557-9654"]}, DOI={10.1109/tit.2010.2081030}, abstractNote={Existing works on distributed consensus explore linear iterations based on reversible Markov chains, which contribute to the slow convergence of the algorithms. It has been observed that by overcoming the diffusive behavior of reversible chains, certain nonreversible chains lifted from reversible ones mix substantially faster than the original chains. In this paper, the idea of Markov chain lifting is studied to accelerate the convergence of distributed consensus, and two general pseudoalgorithms are presented. These pseudoalgorithms are then instantiated through a class of location-aided distributed averaging (LADA) algorithms for wireless networks, where nodes' coarse location information is used to construct nonreversible chains that facilitate distributed computing and cooperative processing. Our first LADA algorithm is designed for grid networks; for a k × k grid network, it achieves an ε-averaging time of O(k log(ε-1)). Based on this algorithm, in a wireless network with transmission range r, an ε-averaging time of O(r-1 log(ε-1)) can be attained through a centralized algorithm. Subsequently, a distributed LADA algorithm is presented, achieving the same scaling law in averaging time as the centralized scheme in wireless networks for all r satisfying the connectivity requirement; the constructed chain also attains the optimal scaling law in terms of an important mixing metric, the fill time, in its class. Finally, a cluster-based LADA algorithm is proposed, which, requiring no central coordination, provides the additional benefit of reduced message complexity compared with the distributed LADA algorithm.}, number={12}, journal={IEEE TRANSACTIONS ON INFORMATION THEORY}, author={Li, Wenjun and Dai, Huaiyu and Zhang, Yanbing}, year={2010}, month={Dec}, pages={6208–6227} }
 @inproceedings{li_dai_2010, title={Towards efficient designs for in-network computing with noisy wireless channels}, DOI={10.1109/infcom.2010.5462023}, abstractNote={In this paper we study distributed function computation in a noisy multi-hop wireless network, in which $n$ nodes are uniformly and independently distributed in a unit square. We adopt the adversarial noise model, for which independent binary symmetric channels are assumed for any point-to-point transmissions, with (not necessarily identical) crossover probabilities bounded above by some constant &#949;. Each node holds an m-bit integer per instance and the computation is started after each node collects N readings. The goal is to compute a global function with a certain fault tolerance, in this distributed setting; we mainly deal with divisible functions, which essentially covers the main body of interest for wireless applications. We focus on protocol designs that are efficient in terms of communication complexity. We first devise a general protocol for evaluating any divisible functions, addressing both one-shot (N = O(1)) and block computation, and both constant and large $m$ scenarios; its bottleneck in different scenarios is also analyzed. Based on this analysis, we then endeavor to improve the design for two special cases: identity function, and some restricted type-threshold functions, both focusing on the constant m and N scenario.}, booktitle={2010 proceedings ieee infocom}, author={Li, C. Z. and Dai, H. Y.}, year={2010} }
 @article{li_dai_2010, title={Transport Capacity and Connectivity of Cognitive Radio Networks with Outage Constraint}, DOI={10.1109/isit.2010.5513267}, abstractNote={In this paper we study two basic properties, capacity and connectivity, of Cognitive Radio networks. Our goal is to quantitatively characterize the relationship and tradeoff among key system parameters involved in these properties, incorporating channel randomness and interference into the performance analysis. In particular, we explore the characterization of a capacity metric, single-hop transport capacity, with respect to arbitrarily and randomly located receivers, and investigate a fundamental connectivity metric, node isolation probability. The tradeoff between capacity and connectivity is also revealed.}, journal={2010 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY}, author={Li, Chengzhi and Dai, Huaiyu}, year={2010}, pages={1743–1747} }
 @article{zhang_dai_2009, title={A Real Orthogonal Space-Time Coded UWB Scheme for Wireless Secure Communications}, ISSN={["1687-1499"]}, DOI={10.1155/2009/571903}, abstractNote={Recent research reveals that information security and information-hiding capabilities can be enhanced by proper exploitation of space-time techniques. Meanwhile, intrinsic properties of ultra-wideband (UWB) signals make it an outstanding candidate for secure applications. In this paper, we propose a space-time coding scheme for impulse radio UWB systems. A novel real orthogonal group code is designed for multi-antenna UWB signals to exploit the full spatial diversity gain and achieve the perfect communication secrecy. Its performance in a frequency-selective fading channel is analyzed. The transmission secrecy, including low probability of detection (LPD), low probability of intercept (LPI), and anti-jamming performance, is investigated, and some fundamental tradeoffs between these secrecy metrics are also addressed. A comparison of the proposed scheme with the direct sequence spread spectrum (DSSS) technique is carried out, which demonstrates that proper combination of UWB and space-time coding can provide substantial enhancement to wireless secure communications over other concurrent systems.}, journal={EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING}, author={Zhang, Yanbing and Dai, Huaiyu}, year={2009} }
 @article{zhang_dai_hughes_2009, title={Analysis on the Diversity-Multiplexing Tradeoff for Ordered MIMO SIC Receivers}, volume={57}, ISSN={["1558-0857"]}, DOI={10.1109/TCOMM.2009.0901.060321}, abstractNote={The diversity-multiplexing tradeoff for multiple-input multiple-output (MIMO) point-to-point channels and multiple access channels were first proposed and studied by Zheng and Tse recently. While the optimal tradeoff curves for MIMO channels have been explicitly explored, those corresponding to some suboptimal and practical MIMO schemes are still open. One such important problem is the diversity-multiplexing tradeoff for a V-BLAST type system employing ordered successive interference cancellation (SIC) receivers with zero forcing (ZF) or minimum mean square error (MMSE) processing at each stage. In this paper, we take a novel geometrical approach and rigorously verify that under general settings, the optimal ordering rule for a V-BLAST SIC receiver will not improve its performance regarding diversity-multiplexing tradeoff in point-to- point channels. The same geometrical tool is then applied to MIMO spatial-division multiple access channels, leading to some first results in this area. Particularly, we reveal that when the rates of data streams are fixed (i.e., zero spatial multiplexing gain), the diversity order is not improved by user ordering.}, number={1}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Zhang, Hongyuan and Dai, Huaiyu and Hughes, Brian L.}, year={2009}, month={Jan}, pages={125–133} }
 @article{li_dai_2009, title={Cluster-Based Distributed Consensus}, volume={8}, ISSN={["1558-2248"]}, DOI={10.1109/T-WC.2009.071146}, abstractNote={In this paper, we incorporate clustering techniques into distributed consensus algorithms for faster convergence and better energy efficiency. Together with a simple distributed clustering algorithm, we design cluster-based distributed consensus algorithms in forms of both fixed linear iteration and randomized gossip. The time complexity of the proposed algorithms is presented in terms of metrics of the original and induced graphs, through which the advantage of clustering is revealed. Our cluster-based algorithms are also shown to achieve an Omega(log n) gain in message complexity over the standard ones.}, number={1}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Li, Wenjun and Dai, Huaiyu}, year={2009}, month={Jan}, pages={28–31} }
 @inproceedings{zhang_dai_2009, title={Structured variational methods for distributed inference in wireless ad hoc and sensor networks}, DOI={10.1109/icassp.2009.4960198}, abstractNote={In this paper, a variational message passing framework is proposed for Markov random fields, which is computationally more efficient and admits wider applicability compared to the belief propagation algorithm. Based on this framework, structured variational methods are explored to take advantage of both the simplicity of variational approximation (for inter-cluster processing) and the accuracy of exact inference (for intra-cluster processing). Its performance is elaborated on a Gaussian Markov random field, through both theoretical analysis and simulation results.}, booktitle={International conference on acoustics speech and signal processing}, author={Zhang, Y. B. and Dai, H. Y.}, year={2009}, pages={2773–2776} }
 @inproceedings{li_dai_li_2009, title={adaptive quickest change detection with unknown parameter}, DOI={10.1109/icassp.2009.4960315}, abstractNote={Quickest detection of an abrupt distribution change with an unknown time varying parameter is considered. A novel adaptive approach is proposed to tackle this problem, which is shown to outperform the celebrated Parallel CUSUM Test. Performance is evaluated through theoretical analysis and numerical simulations.}, booktitle={International conference on acoustics speech and signal processing}, author={Li, C. Z. and Dai, H. Y. and Li, H. S.}, year={2009}, pages={3241–3244} }
 @article{zhang_mehta_molisch_zhang_dai_2008, title={Asynchronous interference mitigation in cooperative base station systems}, volume={7}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2008.060193}, abstractNote={Cooperative transmission by base stations (BSs) can significantly improve the spectral efficiency of multiuser, multi-cell, multiple input multiple output (MIMO) systems. We show that contrary to what is often assumed in the literature, the multiuser interference in such systems is fundamentally asynchronous. Intuitively, perfect timing-advance mechanisms can at best only ensure that the desired signal components -but not also the interference components -are perfectly aligned at their intended mobile stations. We develop an accurate mathematical model for the asynchronicity, and show that it leads to a significant performance degradation of existing designs that ignore the asynchronicity of interference. Using three previously proposed linear preceding design methods for BS cooperation, we develop corresponding algorithms that are better at mitigating the impact of the asynchronicity of the interference. Furthermore, we also address timing-advance inaccuracies (jitter), which are inevitable in a practical system. We show that using jitter-statistics-aware precoders can mitigate the impact of these inaccuracies as well. The insights of this paper are critical for the practical implementation of BS cooperation in multiuser MIMO systems, a topic that is typically oversimplified in the literature.}, number={1}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Zhang, Hongyuan and Mehta, Neelesh B. and Molisch, Andreas F. and Zhang, Jin and Dai, Huaiyu}, year={2008}, month={Jan}, pages={155–165} }
 @inbook{zhang_dai_2008, title={Design Fundamentals and Interference Mitigation for Cellular Networks}, booktitle={Advances in Wireless Networks: Performance Modelling, Analysis and Enhancement}, publisher={Nova Science Publishers}, author={Zhang, H. and Dai, H.}, editor={Min, G. and Pan, Y. and Fan, P.Editors}, year={2008} }
 @article{serpedin_li_dogandzic_dai_cotae_2008, title={Distributed signal processing techniques for wireless sensor networks}, ISSN={["1687-6180"]}, DOI={10.1155/2008/540176}, abstractNote={1Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX 77843, USA 2Department of Electrical and Computer Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA 3Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011, USA 4Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695, USA 5Department of Electrical and Computer Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA}, journal={EURASIP JOURNAL ON ADVANCES IN SIGNAL PROCESSING}, author={Serpedin, Erchin and Li, Hongbin and Dogandzic, Aleksandar and Dai, Huaiyu and Cotae, Paul}, year={2008} }
 @article{li_dai_2008, title={Energy-efficient distributed detection via multihop transmission in sensor networks}, volume={15}, ISSN={["1070-9908"]}, DOI={10.1109/LSP.2008.916720}, abstractNote={We investigate three multihop fusion schemes for distributed detection in geographically dispersed sensor networks, multihop forwarding (MF) and Log-likelihood ratio Fusion (LF), which are different in the transmitted messages, fusion rules, and communication structure. Simulation results show that transmission energy is significantly reduced by multihop fusion schemes as compared to direct transmission, with LF outperforming the others. Moreover, it is shown that LF exhibits the most favorable energy scaling law with the network size among these schemes.}, journal={IEEE SIGNAL PROCESSING LETTERS}, author={Li, Wenjun and Dai, Huaiyu}, year={2008}, pages={265–268} }
 @article{dai_gastpar_jindal_xie_2008, title={Theory and applications in multiuser/multiterminal communications}, ISSN={["1687-1499"]}, DOI={10.1155/2008/950951}, abstractNote={Reference EPFL-ARTICLE-169504doi:10.1155/2008/950951View record in Web of Science Record created on 2011-10-17, modified on 2017-05-12}, journal={EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING}, author={Dai, Huaiyu and Gastpar, Michael and Jindal, Nihar and Xie, Liang-Liang}, year={2008} }
 @article{zhou_dai_2007, title={Asymptotic analysis on the interaction between spatial diversity and multiuser diversity in wireless networks}, volume={55}, ISSN={["1941-0476"]}, DOI={10.1109/TSP.2007.896059}, abstractNote={Spatial diversity and multiuser diversity attract much research interest recently. In this paper, through asymptotic analysis of the average system capacity and scheduling gain, we investigate the cross-layer interaction between these two forms of diversity in wireless networks. Rigorous proofs and necessarily stronger results in terms of convergence are provided for some intuitions in this area. Equally important, explicit expressions of scheduling gain and average system capacity in various circumstances that reveal interconnections and fundamental tradeoffs among key system parameters are given, which afford us some insights in system design. Our results are general enough to cover many practical scenarios of interest.}, number={8}, journal={IEEE TRANSACTIONS ON SIGNAL PROCESSING}, author={Zhou, Quan and Dai, Huaiyu}, year={2007}, month={Aug}, pages={4271–4283} }
 @article{li_dai_2007, title={Distributed detection in wireless sensor networks using a multiple access channel}, volume={55}, ISSN={["1941-0476"]}, DOI={10.1109/TSP.2006.887563}, abstractNote={Distributed detection in a one-dimensional (1-D) sensor network with correlated sensor observations, as exemplified by two problems-detection of a deterministic signal in correlated Gaussian noise and detection of a first-order autoregressive [AR(1)] signal in independent Gaussian noise, is studied in this paper. In contrast with the traditional approach where a bank of dedicated parallel access channels (PAC) is used for transmitting the sensor observations to the fusion center, we explore the possibility of employing a shared multiple access channel (MAC), which significantly reduces the bandwidth requirement or detection delay. We assume that local observations are mapped according to a certain function subject to a power constraint. Using the large deviation approach, we demonstrate that for the deterministic signal in correlated noise problem, with a specially chosen mapping rule, MAC fusion achieves the same asymptotic performance as centralized detection under the average power constraint (APC), while there is always a loss in error exponents associated with PAC fusion. Under the total power constraint (TPC), MAC fusion still results in exponential decay in error exponents with the number of sensors, while PAC fusion does not. For the AR signal problem, we propose a suboptimal MAC mapping rule which performs closely to centralized detection for weakly correlated signals at almost all signal-to-noise ratio (SNR) values, and for heavily correlated signals when SNR is either high or low. Finally, we show that although the lack of MAC synchronization always causes a degradation in error exponents, such degradation is negligible when the phase mismatch among sensors is sufficiently small}, number={3}, journal={IEEE TRANSACTIONS ON SIGNAL PROCESSING}, author={Li, Wenjun and Dai, Huaiyu}, year={2007}, month={Mar}, pages={822–833} }
 @article{zhang_dai_2007, title={Energy-efficiency and transmission strategy selection in cooperative wireless sensor networks}, volume={9}, ISSN={["1976-5541"]}, DOI={10.1109/JCN.2007.6182883}, abstractNote={Energy efficiency is one of the most critical concerns for wireless sensor networks. By allowing sensor nodes in close proximity to cooperate in transmission to form a virtual multiple-input multiple-output (MIMO) system, recent progress in wireless MIMO communications can be exploited to boost the system throughput, or equivalently reduce the energy consumption for the same throughput and BER target. However, these cooperative transmission strategies may incur additional energy cost and system overhead. In this paper, assuming that data collectors are equipped with antenna arrays and superior processing capability, energy efficiency of relevant traditional and cooperative transmission strategies: Single-input-multiple-output (SIMO), space-time block coding (STBC), and spatial multiplexing (SM) are studied. Analysis in the wideband regime reveals that, while receive diversity introduces significant improvement in both energy efficiency and spectral efficiency, further improvement due to the transmit diversity of STBC is limited, as opposed to the superiority of the SM scheme especially for non-trivial spectral efficiency. These observations are further confirmed in our analysis of more realistic systems with limited bandwidth, finite constellation sizes, and a target error rate. Based on this analysis, general guidelines are presented for optimal transmission strategy selection in system level and link level, aiming at minimum energy consumption while meeting different requirements. The proposed selection rules, especially those based on system-level metrics, are easy to implement for sensor applications. The framework provided here may also be readily extended to other scenarios or applications.}, number={4}, journal={JOURNAL OF COMMUNICATIONS AND NETWORKS}, author={Zhang, Yanbing and Dai, Huaiyu}, year={2007}, month={Dec}, pages={473–481} }
 @article{dai_zhang_zhou_2007, title={Some Analysis in Distributed MIMO Systems}, volume={2}, ISSN={1796-2021}, url={http://dx.doi.org/10.4304/jcm.2.3.43-50}, DOI={10.4304/jcm.2.3.43-50}, abstractNote={The predicted capacity gain of a traditional co- located MIMO system is often severely limited in realistic propagation scenarios, especially when the number of antennas becomes large. Recently, a generalized paradigm for multiple-antenna communications, distributed MIMO, is proposed as a remedy. In this paper, through asymptotic large-system analysis, we provide solid justifications on the advantages of distributed MIMO over co-located MIMO when communication channels are subject to spatial correlation and shadow fading. We also exploit inherent macrodiversity in distributed MIMO to devise a cost- effective link adaptation scheme that achieves significant performance gain.}, number={3}, journal={Journal of Communications}, publisher={Academy Publisher}, author={Dai, Huaiyu and Zhang, Hongyuan and Zhou, Quan}, year={2007}, month={May} }
 @article{zhou_dai_2006, title={Asymptotic analysis in MIMO MRT/MRC systems}, ISSN={["1687-1499"]}, DOI={10.1155/wcn/2006/45831}, abstractNote={Through the analysis of the probability density function of the squared largest singular value of a complex Gaussian matrix at the origin and tail, we obtain two asymptotic results related to the multi-input multi-output (MIMO) maximum-ratio-transmission/maximum-ratio-combining (MRT/MRC) systems. One is the asymptotic error performance (in terms of SNR) in a single-user system, and the other is the asymptotic system capacity (in terms of the number of users) in the multiuser scenario when multiuser diversity is exploited. Similar results are also obtained for two other MIMO diversity schemes, space-time block coding and selection combining. Our results reveal a simple connection with system parameters, providing good insights for the design of MIMO diversity systems.}, journal={EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING}, author={Zhou, Quan and Dai, Huaiyu}, year={2006} }
 @inproceedings{zhou_dai_2006, title={Asymptotic analysis on spatial diversity versus multiuser diversity in wireless networks}, DOI={10.1109/icc.2006.255017}, abstractNote={Spatial diversity provided by multiple antennas implemented at the physical layer (PHY) can protect a wireless link from harmful fading, while opportunistic scheduling that exploits multiuser diversity at the media access control (MAC) layer can increase the system throughput with the aid of constructive fading in a multiuser wireless network. In this paper, by studying the average system capacity of opportunistic scheduling and scheduling gain (defined as the average system capacity difference between opportunistic scheduling and conventional round-robin scheduling), we investigate the cross-layer interaction between spatial diversity and multiuser diversity. Our analyses focus on the asymptotic scenarios, by allowing either the number of users or the number of antennas, or both, to go to infinity, for which some succinct closed-form expressions can be obtained and the connections among system parameters become clear.}, booktitle={2006 ieee international conference on communications, vols 1-12}, author={Zhou, Q. and Dai, H. Y.}, year={2006}, pages={1464–1469} }
 @article{zhang_dai_2006, title={Fast MIMO transmit antenna selection algorithms: A geometric approach}, volume={10}, ISSN={["1558-2558"]}, DOI={10.1109/LCOMM.2006.060604}, abstractNote={Motivated by matrix determinant properties, this letter develops a fast transmit antenna selection algorithm for MIMO systems: the G-circles method. This novel scheme is shown to achieve many advantages over other existing algorithms}, number={11}, journal={IEEE COMMUNICATIONS LETTERS}, author={Zhang, Hongyuan and Dai, Huaiyu}, year={2006}, month={Nov}, pages={754–756} }
 @inproceedings{zhou_dai_zhang_2006, title={Joint Tomlinson-Harashima Precoding and Scheduling for Multiuser MIMO with Imperfect Feedback}, DOI={10.1109/wcnc.2006.1696462}, abstractNote={In this paper, we propose a crosslayer approach that explores Tomlinson-Harashima precoding (THP) at the physical layer to reduce the multiuser scheduling burden at the MAC layer, and improves the sum rate of the downlink multiuser MIMO system. Our proposed scheme is further evaluated with imperfect feedback, obtained by the long range prediction (LRP) technique. Compared to some existing scheduling schemes, the proposed scheme approaches the performance upper bound in certain scenarios, while incurring much less computation complexity. Significant gains are still maintained with imperfect channel state information (CSI), fed back at a rate much lower than the data rate}, booktitle={2006 ieee wireless communications and networking conference (wcnc 2006), vols 1-4}, author={Zhou, Q. A. and Dai, H. Y. and Zhang, H. Y.}, year={2006}, pages={1233–1238} }
 @article{zhou_dai_2006, title={Joint antenna selection and link adaptation for MIMO systems}, volume={55}, ISSN={["1939-9359"]}, DOI={10.1109/TVT.2005.861211}, abstractNote={Based on the observation that link adaptation and antenna selection problems are often coupled, this paper studies the problem of joint antenna subset selection and link adaptation for MIMO systems. After the formulation of the multidimensional joint optimization problem, the main contribution of this paper lies in the design of efficient algorithms approaching the optimal solution for both uncorrelated and correlated MIMO channels. Specifically, we propose one simplified antenna selection and link adaptation rule based on the expected optimal number of active antennas for uncorrelated MIMO with Raleigh fading, and one for correlated MIMO channels only based on the slowly varying channel correlation information. Our proposed algorithms are verified through numerical results, demonstrating significant gains over traditional MIMO signaling while feasible for practical implementation.}, number={1}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Zhou, Q and Dai, HY}, year={2006}, month={Jan}, pages={243–255} }
 @inbook{dai_jayaweera_poor_reynolds_wang_2006, place={Cambridge, UK}, title={Multiuser Receiver Design}, booktitle={MIMO Wireless Communications}, publisher={Cambridge University Press}, author={Dai, H. and Jayaweera, S. and Poor, H.V. and Reynolds, D. and Wang, X.}, editor={Bilgieri, E. and Calderbank, A.R. and Constantinides, A.G. and Goldsmith, A. and Paulraj, A. and Poor, H.V.Editors}, year={2006} }
 @article{zhang_dai_zhou_hughes_2006, title={On the diversity order of spatial multiplexing systems with transmit antenna selection: A geometrical approach}, volume={52}, ISSN={["1557-9654"]}, DOI={10.1109/TIT.2006.885531}, abstractNote={In recent years, the remarkable ability of multiple-input-multiple-output (MIMO) wireless communication systems to provide spatial diversity or multiplexing gains has been clearly demonstrated. For MIMO diversity schemes, it is well known that antenna selection methods that optimize the postprocessing signal-to-noise ratio (SNR) can preserve the diversity order of the original full-size MIMO system. On the other hand, the diversity order achieved by antenna selection in spatial multiplexing systems, especially those exploiting practical coding and decoding schemes, has not thus far been rigorously analyzed. In this paper, a geometrical framework is proposed to theoretically analyze the diversity order achieved by transmit antenna selection for separately encoded spatial multiplexing systems with linear and decision-feedback receivers. When two antennas are selected from the transmitter, the exact achievable diversity order is rigorously derived, which previously only appears as conjectures based on numerical results in the literature. If more than two antennas are selected, we give lower and upper bounds on the achievable diversity order. Furthermore, the same geometrical approach is used to evaluate the diversity-multiplexing tradeoff in spatial multiplexing systems with transmit antenna selection}, number={12}, journal={IEEE TRANSACTIONS ON INFORMATION THEORY}, author={Zhang, Hongyuan and Dai, Huaiyu and Zhou, Quan and Hughes, Brian L.}, year={2006}, month={Dec}, pages={5297–5311} }
 @inproceedings{zhang_dai_hughes_2006, title={On the diversity-multiplexing Tradeoff for ordered SIC receivers over MIMO channels}, DOI={10.1109/icc.2006.254939}, abstractNote={The diversity-multiplexing tradeoff for MIMO point-to-point channels and multiple access channels are first proposed and studied in [4][5]. While the optimal tradeoff curves for MIMO channels have been explicitly explored, those corresponding to some practical MIMO schemes are still open. One such example, as mentioned in [4][5], is the diversity-multiplexing tradeoff problem for ordered successive interference cancellation (SIC) receivers, which is the focus of this paper. In literature, the impact of the optimal ordering on the diversity order for V-BLAST SIC receivers is analyzed for 2-layer scenarios [2][3][6], but only conjectured for larger number of layers through numerical results [2][7]. In this paper, based on a novel geometrical analysis, we prove that under general settings, any ordering rule for a V-BLAST SIC receiver will not improve its performance regarding diversity-multiplexing tradeoff. Furthermore, extending the study to multiple access channels, we show that the two extreme points of the tradeoff curve remain unchanged regardless of ordering, which motivates us to predict that the whole tradeoff curve is the same as that of fixed-order detectors.}, booktitle={2006 ieee international conference on communications, vols 1-12}, author={Zhang, H. Y. and Dai, H. Y. and Hughes, B. L.}, year={2006}, pages={1368–1373} }
 @article{li_dai_2005, title={Optimal Throughput and Energy Efficiency for Wireless Sensor Networks: Multiple Access and Multipacket Reception}, volume={2005}, ISSN={1687-1499}, url={http://dx.doi.org/10.1155/wcn.2005.541}, DOI={10.1155/wcn.2005.541}, abstractNote={We investigate two important aspects in sensor network design—the throughput and the energy efficiency. We consider the uplink reachback problem where the receiver is equipped with multiple antennas and linear multiuser detectors. We first assume Rayleigh flat-fading, and analyze two MAC schemes: round-robin and slotted-ALOHA. We optimize the average number of transmissions per slot and the transmission power for two purposes: maximizing the throughput, or minimizing the effective energy (defined as the average energy consumption per successfully received packet) subject to a throughput constraint. For each MAC scheme with a given linear detector, we derive the maximum asymptotic throughput as the signal-to-noise ratio goes to infinity. It is shown that the minimum effective energy grows rapidly as the throughput constraint approaches the maximum asymptotic throughput. By comparing the optimal performance of different MAC schemes equipped with different detectors, we draw important tradeoffs involved in the sensor network design. Finally, we show that multiuser scheduling greatly enhances system performance in a shadow fading environment.}, number={4}, journal={EURASIP Journal on Wireless Communications and Networking}, publisher={Springer Nature}, author={Li, Wenjun and Dai, Huaiyu}, year={2005}, pages={670575} }
 @article{dai_mailaender_poor_2004, title={CDMA Downlink Transmission with Transmit Antenna Arrays and Power Control in Multipath Fading Channels}, volume={2004}, ISSN={1687-1499}, url={http://dx.doi.org/10.1155/s1687147204404034}, DOI={10.1155/s1687147204404034}, abstractNote={Wireless code-division multiple-access (CDMA) cellular downlink communications with transmit antenna arrays in multipath fading channels is studied. Various array signal processing techniques at the transmit end are investigated and compared under various settings, in conjunction with power control. No instant downlink channel information is assumed; however, the obtained results are also compared with results assuming ideal feedback. The study is carried out for both circuit-switched and packet-switched systems, where different goals are pursued and different conclusions are drawn. In particular, it is found that the traffic type impacts the algorithm choice in downlink transmission, and that there is no need to seek optimum power control/allocation schemes, which are either too complex or infeasible in practice. Another interesting conclusion is that, even though feedback does not help much for packet-switched systems, it does help for circuit-switched systems, the gain of which increases with the number of antennas.}, number={1}, journal={EURASIP Journal on Wireless Communications and Networking}, publisher={Springer Nature}, author={Dai, Huaiyu and Mailaender, Laurence and Poor, HVincent}, year={2004}, pages={219825} }
 @article{zhang_dai_2004, title={Cochannel Interference Mitigation and Cooperative Processing in Downlink Multicell Multiuser MIMO Networks}, volume={2004}, ISSN={1687-1499}, url={http://dx.doi.org/10.1155/s1687147204406148}, DOI={10.1155/s1687147204406148}, abstractNote={Recently, the remarkable capacity potential of multiple-input multiple-output (MIMO) wireless communication systems was unveiled. The predicted enormous capacity gain of MIMO is nonetheless significantly limited by cochannel interference (CCI) in realistic cellular environments. The previously proposed advanced receiver technique improves the system performance at the cost of increased receiver complexity, and the achieved system capacity is still significantly away from the interference-free capacity upper bound, especially in environments with strong CCI. In this paper, base station cooperative processing is explored to address the CCI mitigation problem in downlink multicell multiuser MIMO networks, and is shown to dramatically increase the capacity with strong CCI. Both information-theoretic dirty paper coding approach and several more practical joint transmission schemes are studied with pooled and practical per-base power constraints, respectively. Besides the CCI mitigation potential, other advantages of cooperative processing including the power gain, channel rank/conditioning advantage, and macrodiversity protection are also addressed. The potential of our proposed joint transmission schemes is verified with both heuristic and realistic cellular MIMO settings.}, number={2}, journal={EURASIP Journal on Wireless Communications and Networking}, publisher={Springer Nature}, author={Zhang, Hongyuan and Dai, Huaiyu}, year={2004}, pages={202654} }
 @article{dai_molisch_poor_2004, title={Downlink Capacity of Interference-Limited MIMO Systems With Joint Detection}, volume={3}, ISSN={1536-1276}, url={http://dx.doi.org/10.1109/twc.2003.821168}, DOI={10.1109/twc.2003.821168}, abstractNote={The capacity of downlink cellular multiple-input multiple-output (MIMO) systems, where co-channel interference is the dominant channel impairment, is investigated in this paper, mainly from a signal-processing perspective. Turbo space-time multiuser detection (ST MUD) is employed for intracell communications and is shown to closely approach the ultimate capacity limits in Gaussian ambient noise for an isolated cell. Then, it is combined with various multiuser detection methods for combating intercell interference. Among various multiuser detection techniques examined, linear minimum-mean-square-error (MMSE) MUD and successive interference cancellation are shown to be feasible and effective. Based on these two multiuser detection schemes, one of which may outperform the other for different settings, an adaptive detection scheme is developed, which together with a Turbo ST MUD structure offers substantial performance gain over the well-known V-BLAST techniques with coding in this interference-limited cellular environment. The obtained multiuser capacity is excellent in the high to medium signal-to-interference ratio scenario. Nonetheless, numerical results also indicate that a further increase in system complexity, using base-station cooperation, could lead to further significant increases of the system capacity. The asymptotic multicell MIMO capacity with linear MMSE MUD preprocessing is also derived, and this analysis agrees well with the simulation results.}, number={2}, journal={IEEE Transactions on Wireless Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Dai, H. and Molisch, A.F. and Poor, H.V.}, year={2004}, month={Mar}, pages={442–453} }
 @article{dai_poor_2003, title={Advanced signal processing for power line communications}, volume={41}, DOI={10.1109/mcom.2003.1200108}, abstractNote={In this article, signal processing techniques to combat the adverse communications environment on power lines are addressed, so as to enable reliable high speed data communications over low-voltage power distribution networks for Internet access and in-home/office networking. It is seen that multicarrier code-division multiple access, multiuser detection, and turbo decoding, having demonstrated their limit-approaching capacity in DSL and wireless communication systems, are readily applied to power line communications. In particular, it is argued that these methods can successfully mitigate the influence of the principal impairments in PLC channels: time-varying channel attenuation, multipath frequency-selective fading, multiple access interference, and background noise. Strategies to deal with the most unfavorable noise source, the impulse noise, are also discussed.}, number={5}, journal={IEEE Communications Magazine}, author={Dai, H. Y. and Poor, H. V.}, year={2003}, pages={100–107} }
 @article{dai_poor_2003, title={Asymptotic spectral efficiency of multicell MIMO systems with frequency-flat fading}, volume={51}, ISSN={["1053-587X"]}, DOI={10.1109/TSP.2003.818201}, abstractNote={The spectral efficiency of multiple-input multiple-output (MIMO) systems operating in multicell frequency-flat fading environments is studied for situations in which co-channel interference is the dominant channel impairment instead of ambient noise. The following detectors are analyzed: the joint optimum detector, a group linear minimum-mean-square-error (MMSE) detector and its generalized version, a group MMSE successive interference cancellation detector, and an adaptive multiuser detector, with the focus on their large-system asymptotic (nonrandom) expressions. Analytical and numerical results based on these asymptotic multicell MIMO spectral efficiencies are explored to gain insights into the behavior of interference-limited multicell MIMO systems.}, number={11}, journal={IEEE TRANSACTIONS ON SIGNAL PROCESSING}, author={Dai, HY and Poor, HV}, year={2003}, month={Nov}, pages={2976–2988} }
 @article{dai_poor_2002, title={Iterative space-time processing for multiuser detection in multipath CDMA channels}, volume={50}, ISSN={1053-587X}, url={http://dx.doi.org/10.1109/tsp.2002.801923}, DOI={10.1109/tsp.2002.801923}, abstractNote={Space-time processing and multiuser detection are two promising techniques for combating multipath distortion and multiple-access interference in code division multiple access (CDMA) systems. To overcome the computational burden that rises very quickly with increasing numbers of users and receive antennas in applying such techniques, iterative implementations of several space-time multiuser detection algorithms are considered here. These algorithms include iterative linear space-time multiuser detection, Cholesky iterative decorrelating decision-feedback space-time multiuser detection, multistage interference canceling space-time multiuser detection, and expectation-maximization (EM)-based iterative space-time multiuser detection. A new space-time multiuser receiver structure that allows for efficient implementation of iterative processing is also introduced. Fully exploiting various types of diversity through joint space-time processing and multiuser detection brings substantial gain over single-receiver-antenna or single-user-based methods. It is shown that iterative implementation of linear and nonlinear space-time multiuser detection schemes discussed in this paper realizes this substantial gain and approaches the optimum performance with reasonable complexity. Among the iterative space-time multiuser receivers considered in this paper, the EM-based (SAGE) iterative space-time multiuser receiver introduced here achieves the best performance with excellent convergence properties.}, number={9}, journal={IEEE Transactions on Signal Processing}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Dai, Huaiyu and Poor, H.V.}, year={2002}, month={Sep}, pages={2116–2127} }
 @article{dai_poor_2002, title={Turbo multiuser detection for coded DMT VDSL systems}, volume={20}, ISSN={0733-8716}, url={http://dx.doi.org/10.1109/49.983354}, DOI={10.1109/49.983354}, abstractNote={In recent years, iterative processing techniques with soft-in/soft-out components have received considerable attention. Such techniques, based on the so-called turbo principle, are exemplified through turbo decoding, turbo equalization, and turbo multiuser detection. Turbo multiuser detection is applied to a discrete multitone (DMT) very-high-rate digital subscriber line system to combat crosstalk signals and to obtain substantial coding gain. The proposed iterative DMT receiver is shown to achieve an overall 7.0 dB gain over the uncoded optimum receiver at a bit error rate of 10/sup -7/ for a channel with severe intersymbol interference and additive white Gaussian noise and with one dominant crosstalk signal. Impulse noise is detrimental to the proposed scheme but can be overcome through erasure decoding techniques, as is shown by example.}, number={2}, journal={IEEE Journal on Selected Areas in Communications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Dai, H. and Poor, V.}, year={2002}, pages={351–362} }
 @article{dai_poor_2001, title={Crosstalk mitigation in DMT VDSL with impulse noise}, volume={48}, ISSN={1057-7122}, url={http://dx.doi.org/10.1109/81.956015}, DOI={10.1109/81.956015}, abstractNote={Crosstalk and impulse noise are two principal sources of degradation in very-high-rate digital subscriber line (VDSL) transmission systems. The traditional single-user data detector for such systems merges crosstalk into the background noise, which is assumed to be white and Gaussian. Recent research has explored the nature of crosstalk signals and shown the potential benefits of multiuser detection (MUD) for VDSL signals with strong crosstalkers. Impulse noise is one of the most difficult transmission impairments to suppress, and is poorly characterized and understood as well. In DSL transmission, impulse noise is typically combated with interleaved forward-error correction (FEC). However, recent data indicate that a significant minority of impulse-noise events are longer than the maximum error-correcting capacities of the default interleaved FEC provided within current ANSI standards. Thus, it is of interest to consider signal processing methods that can jointly mitigate crosstalk and impulse noise. In this paper, we explore such a technique based on a recently developed robust M-detector structure for MUD in non-Gaussian ambient noise.}, number={10}, journal={IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Dai, Huaiyu and Poor, H.V.}, year={2001}, pages={1205–1213} }
 @article{dai_cao_1998, title={Study of IMBE Vocoder with Speech Enhancement}, volume={19}, number={4}, journal={Journal of China Institute of Communications}, author={Dai, H. and Cao, Z.}, year={1998}, month={Apr}, pages={43–49} }