@article{zou_wang_2023, title={Downlink Decoding Based Accurate Measurement of LTE Spectrum Tenancy}, volume={22}, ISSN={["1558-0660"]}, DOI={10.1109/TMC.2021.3125569}, abstractNote={Mobile networks are embracing Dynamic Spectrum Access (DSA) to unleash data capacities of spectrum holes caused by tidal traffic. Being the largest mobile system, LTE has been standardized to operate in the DSA mode where the knowledge on the spectrum tenancy of LTE systems is required. Although there exists rich literature on spectrum sensing, measurement and modeling, they cannot satisfy the needs of accurately acquiring the spectrum tenancy of LTE systems. This is because most traditional measurements only provide inaccurate tenancy in coarse granularities, and therefore models built upon them are defective. To enable the precise discovery of spectrum assignments of an LTE cell from an outsider perspective, we build U-CIMAN to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</i> n <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> over spectrum occupancy and user <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> nformation in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> obile <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> ccess <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> etworks. The LTE protocol fields parsed by U-CIMAN not only accurately reveal the spectrum occupancy at the same granularity with LTE scheduling, but also provide important details associated with spectrum usage, i.e., rough user locations and traffic types. Besides insightful observations based on measurements enabled by U-CIMAN, we propose to characterize LTE spectrum occupancy using Vector Autoregression that captures the statistical distributions of spectrum tenancy intervals in multiple channels and the correlations among them.}, number={5}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Zou, Rui and Wang, Wenye}, year={2023}, month={May}, pages={2613–2627} }
 @article{wang_wang_wang_2023, title={Remedy or Resource Drain: Modeling and Analysis of Massive Task Offloading Processes in Fog}, volume={10}, ISSN={["2327-4662"]}, DOI={10.1109/JIOT.2023.3245100}, abstractNote={Task offloading, which refers to processing (computation-intensive) data at facilitating servers, is an exemplary service that greatly benefits from the fog computing paradigm, which brings computation resources to the edge network for reduced application latency. However, the resource-consuming nature of task execution, as well as the sheer scale of IoT systems, raises an open and challenging question: whether fog is a remedy or a resource drain, considering frequent and massive offloading operations? This question is nontrivial, because participants of offloading processes, i.e., fog nodes, may have diversified technical specifications, while task generators, i.e., task nodes, may employ a variety of criteria to select offloading targets, resulting in an unmanageable space for performance evaluation. To overcome these challenges of heterogeneity, we propose a gravity model that characterizes offloading criteria with various gravity functions, in which individual/system resource consumption can be examined by the device/network effort metrics, respectively. Simulation results show that the proposed gravity model can flexibly describe different offloading schemes in terms of application and node-level behavior. We find that the expected lifetime and device effort of individual tasks decrease as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$O({}{1}/{N})$ </tex-math></inline-formula> over the network size <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> , while the network effort decreases much slower, even remain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$O(1)$ </tex-math></inline-formula> when load balancing measures are employed, indicating a possible resource drain in the edge network.}, number={13}, journal={IEEE INTERNET OF THINGS JOURNAL}, author={Wang, Jie and Wang, Wenye and Wang, Cliff}, year={2023}, month={Jul}, pages={11669–11682} }
 @article{fei_wang_2023, title={The vulnerability and enhancement of AKA protocol for mobile authentication in LTE/5G networks}, volume={228}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2023.109685}, abstractNote={The Long-Term Evolution (LTE)/5G network connects much of the world’s population to provide subscriber’s voice calls and mobile data delivery, with security provided by the Authentication and Key Agreement (AKA) defined by 3GPP, which makes the LTE/5G network more secure than all its predecessors. Primarily due to the access limitations of LTE systems, the vulnerabilities of AKA protocol and potential attacks have not received much investigation, which is essential to LTE users with a tremendous amount of cellular services. In this study, we focus on two questions: (i) what are the vulnerabilities that can be exploited to carry out attacks in practice? and (ii) how to design an enhanced AKA protocol against such attacks? We examine the detailed procedures of Evolved Packet System (EPS)-AKA protocol by 3GPP, and have identified three types of attacks with respect to catching, location tracking, and jamming. We have designed and implemented attacks with commercial equipment to evaluate their threats in practice. In addition, we propose an enhanced AKA protocol that essentially relies on asymmetric encryption rather than symmetric in the AKA protocol and additional digital signatures to countermeasure these attacks. Finally, we verified our solution through formal verification to prove that our solution can mitigate the newly found vulnerabilities.}, journal={COMPUTER NETWORKS}, author={Fei, Teng and Wang, Wenye}, year={2023}, month={Jun} }
 @article{wang_wang_wang_song_2022, title={Spectrum Activity Surveillance: Modeling and Analysis From Perspectives of Surveillance Coverage and Culprit Detection}, volume={21}, ISSN={["1558-0660"]}, url={https://doi.org/10.1109/TMC.2020.3032434}, DOI={10.1109/TMC.2020.3032434}, abstractNote={Spectrum activity surveillance (SAS) is essential to dynamic spectrum access (DSA)-enabled systems with a two-fold impact: it is a primitive mechanism to collect usage data for spectrum efficiency improvement; it is also a prime widget to collect misuse forensics of unauthorized or malicious users. While realizing SAS for DSA-enabled systems appears to be intuitive and trivial, it is, however, a challenging yet open problem. On one hand, a large-scale SAS function is costly to implement in practice; on the other hand, it is not clear how to characterize the efficacy and performance of monitor deployment strategies. To address such challenges, we introduce a three-factor space, composed of spectrum, time, and geographic region, over which the SAS problem is formulated by a two-step solution: 3D-tessellation for sweep (monitoring) coverage and graph walk for detecting spectrum culprits, that is, devices responsible for unauthorized spectrum occupancy. In particular, our system model transforms SAS from a globally collective activity to localized (even distributed) actions, and strategy objectives from qualitative attributes to quantitative measures. With this model, we design low-cost deterministic strategies for dedicated monitors, which outperform strategies found by genetic algorithms, and performance-guaranteed random strategies for crowd-source monitors, which can detect adversarial spectrum culprits in bounded time.}, number={5}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Wang, Jie and Wang, Wenye and Wang, Cliff and Song, Min}, year={2022}, month={May}, pages={1829–1846} }
 @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{jalooli_song_wang_2019, title={Message coverage maximization in infrastructure-based urban vehicular networks}, volume={16}, ISSN={["2214-2096"]}, DOI={10.1016/j.vehcom.2019.02.001}, abstractNote={The success of vehicular networks is highly dependent on the coverage of messages, which refers to the trajectory of messages over time. Many of the existing works primarily performed in 1-D environments (i.e., straight highways) and/or merely focused on vehicle-to-vehicle (V2V) communications to enhance the coverage in a given road network. Consequently, there still lacks a clear comprehension of using road infrastructures (e.g., roadside units), to improve the message coverage in 2-D environments (i.e., urban areas). In this paper, we study the problem of optimal utilization of roadside units in 2-D environments. Specifically, we develop a message coverage maximization algorithm (MCMA) that carefully deploys the roadside units to achieve the maximum message coverage. Considering that the vehicle density is heterogeneous across the road networks, we study the message coverage for V2V networks by deriving analytical lower bounds of message dissemination distance for areas with different vehicle densities. The MCMA then utilizes the derived lower bounds to estimate the minimum spacing allowed between neighbor roadside units based on the prevailing traffic stream and delay constraint of applications. In addition, we propose a disseminator selection algorithm for infrastructure-based urban vehicular networks to further improve the message coverage. By selecting desired types of applications (i.e., safety and non-safety), we obtain two different roadside unit deployment sets from MCMA for the evaluation purpose. Extensive simulation studies show that MCMA outperforms the alternative algorithms in terms of the message coverage and message dissemination speed. The results also demonstrate that MCMA improves traffic efficiency in a post-crash scenario.}, journal={VEHICULAR COMMUNICATIONS}, author={Jalooli, Ali and Song, Min and Wang, Wenye}, year={2019}, month={Apr}, pages={1–14} }
 @article{wang_pambudi_wang_song_2019, title={Resilience of IoT Systems Against Edge-Induced Cascade-of-Failures: A Networking Perspective}, volume={6}, ISSN={["2327-4662"]}, url={https://doi.org/10.1109/JIOT.2019.2913140}, DOI={10.1109/JIOT.2019.2913140}, abstractNote={Internet of Things (IoT) is a networking paradigm that interconnects physical systems to the cyber world, to provide automation and intelligence via interdependent links between the two domains. Such interdependence renders IoT systems vulnerable to random failures, e.g., broken communication links or crashed cyber instances, because a single incident in one domain can develop into a cascade-of-failures across domains, which dissolves the network structure, and has devastating consequences. To answer how robust an IoT system is, this paper studies its resilience by examining the impact of edge- and jointly-induced cascades, that is, a sequence of failures caused by randomly broken physical links (and simultaneous failing cyber nodes). Resilience of an IoT system is quantified by two new metrics, the critical edge disconnecting probability φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cr</sub> , i.e., the maximum intensity of random failures the system can withstand, and the cascade length τ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cf</sub> , i.e., the lifetime of a cascade. For IoT systems with Poisson degree distributions, we derive exact solutions for the critical disconnecting probability φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cr</sub> , above which an edge-induced cascade will completely fragment the network. We also find that the critical condition φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cr</sub> marks a dichotomy of the expected cascade length E(τ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cf</sub> ): for the super-critical (φ > φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cr</sub> ) scenario, we obtain E(τ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cf</sub> ) ~ exp(1 - φ) through analysis, while for the subcritical scenario, we observe E(τ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cf</sub> ) ~ exp(1/1 - φ) through simulations. With these results, the final outcome of a cascade can be anticipated upon the initial failures, while the reaction window of time-sensitive countermeasures can be obtained before a cascade fully unfolds.}, number={4}, journal={IEEE INTERNET OF THINGS JOURNAL}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Wang, Jie and Pambudi, Sigit and Wang, Wenye and Song, Min}, year={2019}, month={Aug}, pages={6952–6963} }
 @article{wei_lu_wang_2018, title={On Characterizing Information Dissemination During City-Wide Cascading Failures in Smart Grid}, volume={12}, ISSN={["1937-9234"]}, DOI={10.1109/JSYST.2017.2763462}, abstractNote={Although the smart gird is expected to eliminate cascading failures with the help of real-time system monitoring and control, it is yet unknown whether its underlying communication network is fast and reliable enough to achieve this goal. In this paper, we take an in-depth study on this issue by addressing three specific questions: 1) what is the evolution process of information dissemination and fault propagation in the smart grid?; 2) how to quantify the impact of cascading failures?; and 3) what are the conditions that information dissemination becomes either a booster or an adversary in mitigating cascading failures? To answer these questions, we build an innovative framework, the cascading failure with communications framework, to consolidate both communication networks and power grids, and provide quantitative evaluation on the impact of cascading failures. By studying and observing the progress of cascading failures in two city-wide power grids, we find that information dissemination is not always the winner in the race against fault propagation. Particularly, while fast and reliable communications can help in mitigating the consequences of cascading failures, anomalies such as massage delays may weaken its capability. Moreover, severely under-achieved communications, counter-intuitively, can even exacerbate the consequence of cascading failures.}, number={4}, journal={IEEE SYSTEMS JOURNAL}, author={Wei, Mingkui and Lu, Zhuo and Wang, Wenye}, year={2018}, month={Dec}, pages={3404–3413} }
 @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{pambudi_wang_wang_2017, title={From isolation time to node resilience: Impact of cascades in D2D-based social networks}, DOI={10.1109/glocom.2017.8255073}, abstractNote={The ever-increasing traffic demand from social networking service (SNS) users and recent progress in device-to-device (D2D) technology have empowered a new D2D-based SNS paradigm, which enables multimedia content exchange via short-range wireless networking. In this paradigm, a small node failure may trigger a collection of rapidly-spreading isolation events called cascade-of-failures. Unlike existing works that studied the outcome of cascading failures from the spatial and probabilistic perspectives, this paper sheds light on the temporal properties of the cascade-of-failures. To do this, we introduce a maximum isolation time that quantifies the steps needed until the last node is isolated by the cascades, and then show that it scales non-monotonically to the fraction of initial survivors (non-failure nodes) and increases logarithmically with the network size. Then, we use the result to further analyze a node resilience metric, which is the likelihood that a node does not become isolated before its social networking session is finished. These findings, which are validated using numerical simulations, provide a temporal perspective of network performance that is valuable in the design of D2D-based SNSs yet still missing in the literature.}, booktitle={Globecom 2017 - 2017 ieee global communications conference}, author={Pambudi, S. A. and Wang, Wenye and Wang, C.}, year={2017} }
 @inproceedings{wang_wang_song_2017, title={How durable and stable is file sharing on the move in cellular-assisted D2D communications?}, DOI={10.1109/glocom.2017.8254603}, abstractNote={File sharing is one of the most promising Proximity Service (ProSe) using device-to-device (D2D) communication technology. As the prospective D2D-enabled file sharing rely on mobile peer discovery and connection in physical proximity, the challenges come from the highly dynamic environment as a consequence of the unpredictable user mobility and the temporal-spatial locality of content popularity. A challenging yet open question is \textit{how users could move to fetch target files durably and stably}. In this paper, we characterize mobile file sharing in temporal and spatial domains by \textit{how long time} the service can be active (referred as \textit{service lifetime} $\tau_\text{L}$), \textit{how far} a mobile user can move away while keeping ongoing service (referred as \textit{service distance} $\|D_\text{L}\|$), and \textit{how fast} the ongoing service would be recovered once interruption caused by handover (classified into \textit{bundled handover} and \textit{split handover} in this paper) (referred as \textit{recover delay} $\sigma_\text{HO}$). Answers to these questions offer a straightforward interpretation of the potentials of D2D communications for file sharing on the move. Both theoretical and simulation results suggest that D2D file sharing is more benefit for popular content among group moving users with longer service lifetime and distance and less delay caused by mobile user handover and peer discovery.}, booktitle={Globecom 2017 - 2017 ieee global communications conference}, author={Wang, Y. L. and Wang, Wenye and Song, M.}, year={2017} }
 @inproceedings{wang_wang_wang_2017, title={Modeling and strategy design for spectrum monitoring over a geographical region}, DOI={10.1109/glocom.2017.8254113}, abstractNote={Spectrum monitoring is a prerequisite in dynamic access regulation, policy enforcement, as well as spectrum database establishment. In this paper, we introduce the dimension of geographical space into the spectrum monitoring problem, and studied deployment strategies of multiple monitors, in terms of coverage time and cost. The monitoring problem is modeled as a 3-d continuous sweep coverage problem, whose solution space is then reduced by effectively dividing the spectra-location space, in order to achieve a small coverage time. The cost minimization is then formulated as a Multiple Traveling Salesman problem (MTSP), which is NP-hard. By observing the structure of the strategy space, we propose a solution that attains a reasonable cost, without applying complex optimization algorithms.}, booktitle={Globecom 2017 - 2017 ieee global communications conference}, author={Wang, Jie and Wang, Wenye and Wang, C.}, year={2017} }
 @inproceedings{wei_lu_wang_2017, title={On modeling and understanding vehicle evacuation attacks in VANETs}, DOI={10.1109/icc.2017.7996463}, abstractNote={To secure a Vehicular Ad-hoc Network (VANET), extensive studies have been conducted on developing authentication infrastructures, and identifying misbehaving vehicles. The effectiveness of such efforts heavily depends on the underlying communication network. However, information exchange in the VANET can be severely delayed because of its highly-dynamic and partially-connected topology. Such delay can be potentially exploited by attackers to cause physical impacts to the transportation system. In this paper, we propose and model a new attack, called vehicle evacuation attack, to investigate how the message delay endangers the trustworthiness in VANETs, and further causes physical impacts to cars on the road. Our study demonstrates that there exists a linear relationship between the delay of message dissemination and the impact of the vehicle evacuation attack, which can be used as a guideline on security, reliability, and safety design in real-world VANETs.}, booktitle={2017 ieee international conference on communications (icc)}, author={Wei, M. K. and Lu, Z. and Wang, Wenye}, year={2017} }
 @inproceedings{wang_li_wang_song_2016, title={A locality-based mobile caching policy for D2D-based content sharing network}, DOI={10.1109/glocom.2016.7841510}, abstractNote={As the explosion of Internet traffic is quickly leading to overloaded cellular network, device-to-device (D2D)-based content sharing is proposed as a method to offload mobile data traffic. The performance of D2D-based content sharing is dramatically affected by the success rate of content fetching from nearby devices and quality of content transmission, which is determined by the geographic distribution of mobile devices, the number of devices having contents in their caches, and the condition of D2D links. Hence, a key problem is how to cache various contents in the limited storage of mobile devices for improving the success rate of content fetching. In this paper, we aim to design a caching policy by considering the joint impact of locality of real-world mobile data traffic and device contact pattern to improve the success rate of content fetching. To do this, we first study the characteristics of network traffic and device contact pattern by analyzing traces from realistic networks. Then, we design a locality-based caching policy and derive the content caching probability and hit ratio through mathematical analysis. Through numerical evaluation and trace-driven simulations, we not only quantify how content popularity, content active lifetime, content size, content bit rate, device storage, transmission rate, and closeness centrality affect the content hit ratio, but also provide comparison on hit ratio and storage cost in different caching policy, which is a strong evidence that the joint impacts from characteristics of content and device are the necessary consideration when to design a caching policy.}, booktitle={2016 ieee global communications conference (globecom)}, author={Wang, Y. L. and Li, Y. J. and Wang, Wenye and Song, M.}, year={2016} }
 @article{wei_wang_2016, title={Data-centric threats and their impacts to real-time communications in smart grid}, volume={104}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2016.05.003}, abstractNote={One of the most distinguished challenges in studying the aftermath of cyber attacks in smart grid lies in data-centric threats, which refer to cyber attacks aimed at gaining advantage or sabotage the infrastructure by manipulating the data exchanged in the underlying communication network. Even though such attacks are critical by itself in the information network, they will result in more serious impacts to the power grid. This is because for an information-centric network, distorted or delayed information undermines services and applications, in the case of a power grid, however, these data-centric attacks may result in unstable systems, which may further detrimentally impact the power supplies. In this paper, we study the impacts of data-centric attacks in the real-time communication network of smart gird, and further the consequences caused to the power grid. Our study provides insights to both smart grid security research and operation.}, journal={COMPUTER NETWORKS}, author={Wei, Mingkui and Wang, Wenye}, year={2016}, month={Jul}, pages={174–188} }
 @article{wang_wang_wang_2016, title={Divide and Conquer: Leveraging Topology in Control of Epidemic Information Dynamics}, ISSN={["2576-6813"]}, DOI={10.1109/glocom.2016.7841747}, abstractNote={As online social networks grow in both size and connectivity, epidemic information dynamics in such networks is attracting considerable research interests, due to its impact on both the network and individuals. This paper studies control of malicious information (virus) epidemic with replicable antidote information, taking topological characteristics of the underlying graph into consideration. Specifically, we analytically relate the extinction time of the virus to the diameter and giant component size of the remaining graph after the initial antidote distribution. With this 'divide and conquer' guideline, topology-based antidote distribution approaches are designed, and then examined through simulations in real world network portions.}, journal={2016 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={Wang, Jie and Wang, Wenye and Wang, Cliff}, year={2016} }
 @article{wei_lu_wang_2016, title={Dominoes with Communications: On Characterizing the Progress of Cascading Failures in Smart Grid}, ISSN={["1550-3607"]}, DOI={10.1109/icc.2016.7511048}, abstractNote={Cascading failures are one of the most devastating forces in power systems, which may be initially triggered by minor physical faults, then spread with Domino-like chain-effect, resulting in large-scale blackout. How to prevent cascading failures becomes imperative, as our daily lives heavily depend on stable and reliable power supply. The next-generation power system, namely Smart Grid, is envisioned to facilitate real-time and distributed control of critical power infrastructures, thus effectively forestalling cascading failures. Although cascading failures have been well investigated in the literature, most studies were confined only in the power operation domain with the assumption that communication is always perfect, which is, however, not true for today's communication networks, where traffic congestion and random delay happen. Therefore, an open question is how to characterize cascading failures in the communication-assisted smart grid? To this end, we take an in-depth inspection of cascading failures in smart grid and reveal the interactions between the power system and the communication network. Our results provide insights into the interactions between physical failure propagation and communication message dissemination. In addition, we show that while ideal communications can undoubtedly help prevent cascading failures, under-achieved communications (i.e., communications with severe delay) can, counter-intuitively, exacerbate cascading failures.}, journal={2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC)}, author={Wei, Mingkui and Lu, Zhuo and Wang, Wenye}, year={2016} }
 @inproceedings{pambudi_wang_wang_2016, title={How robust Is a D2D-based messaging service?}, DOI={10.1109/glocom.2016.7841877}, abstractNote={Motivated by the massive and increasing number of online messaging service users, the idea of utilizing short-range device-to-device (D2D) communication has been adapted to the access of instant messaging services on-the-go, introducing a D2D-based messaging service (D2D-Msg) paradigm that promises higher data rate and longer battery life. The quality of message dissemination in such a new paradigm, however, remains largely unknown due to the open nature of the D2D environment. To address this, we define a node survival probability that captures the impact of random and targeted node failures due to the open wireless environment. Further, we define a secondary infection rate R&#8727; that measures how fast message propagates initially, and leverage a framework based on probability generating function to analyze R&#8727; under random and targeted failures. Numerical results show that the D2D-Msg is more robust against random failure, the targeted node failure favors communication graph with narrow degree distribution, and R&#8727; is proportional to the ratio between the number of message-receiving users to all users, which is a good metric for quantifying the D2D-Msg's robustness.}, booktitle={2016 ieee global communications conference (globecom)}, author={Pambudi, S. A. and Wang, Wenye and Wang, C.}, year={2016} }
 @article{wang_wang_wang_2016, title={How the Anti-Rumor Kills the Rumor: Conflicting Information Propagation in Networks}, ISSN={["1550-3607"]}, DOI={10.1109/icc.2016.7511492}, abstractNote={Online Social Networks (OSNs) is taking over television and newspapers, to be the dominant information dissemination option. The growing involvement of individuals create the situation that colliding, even contradicting information coexist and propagate in the same network, which gives rise to an interesting question: how will the conflicting information propagate? To answer this question, the propagation process is described to be an Susceptible-Infected-Cured (SIC) epidemic, and we propose an inference algorithm to study the transient behavior of the competing propagation processes in connected networks. Moreover, we provide an analytic method to derive the conditional infection count distribution for networks with special topologies, as a step further to understand the evolution. A trace collected from the Internet is analyzed to validate our model and methods.}, journal={2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC)}, author={Wang, Jie and Wang, Wenye and Wang, Cliff}, year={2016} }
 @article{pambudi_wang_wang_2016, title={Modeling and Estimating the Structure of D2D-Based Mobile Social Networks}, ISSN={["1550-3607"]}, DOI={10.1109/icc.2016.7511491}, abstractNote={Along with the explosive growth of mobile social network (MSN) users and the advent of device-to-device (D2D) communications, D2D-based MSN (D2D-MSN) has become a promising alternative for exchanging multimedia contents on-the-go. Although the complete structure of a D2D-MSN plays a key role in understanding its performance, such knowledge is not readily available due to the difficulty of collecting connectivity information from the vast amount of users. To model the structure, we define a D2D-MSN network that jointly captures the social connectivity over the MSN and the opportunistic D2D contacts among users. A random walk with self loop (RWSL) scheme that quickly converges to its stationary distribution is proposed to collect a subset of D2D-MSN nodes. An estimator is then introduced to obtain an unbiased estimate of the D2D-MSN graph's joint degree distribution, pi, j, from the set of visited nodes, leading to an unbiased RWSL scheme. The resulting estimate of pi, j can be used as a statistic for creating synthetic graph and generating functions for analyzing robustness of D2D-MSN. Numerical results show that the proposed unbiased RWSL converges faster to its stationary distribution, achieves higher joint degree distribution accuracy, and visits less number of nodes, compared to existing graph exploration schemes.}, journal={2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC)}, author={Pambudi, Sigit Aryo and Wang, Wenye and Wang, Cliff}, year={2016} }
 @article{lu_wang_wang_2016, title={On the Evolution and Impact of Mobile Botnets in Wireless Networks}, volume={15}, ISSN={["1558-0660"]}, DOI={10.1109/tmc.2015.2492545}, abstractNote={A botnet in mobile networks is a collection of compromised nodes due to mobile malware, which are able to perform coordinated attacks. Different from Internet botnets, mobile botnets do not need to propagate using centralized infrastructures, but can keep compromising vulnerable nodes in close proximity and evolving organically via data forwarding. Such a distributed mechanism relies heavily on node mobility as well as wireless links, therefore it breaks down the underlying premise in existing epidemic modeling for Internet botnets. In this paper, we adopt a stochastic approach to study the evolution and impact of mobile botnets. We find that node mobility can be a trigger to botnet propagation storms: the average size (i.e., number of compromised nodes) of a botnet increases quadratically over time if the mobility range that each node can reach exceeds a threshold; otherwise, the botnet can only contaminate a limited number of nodes with average size always bounded above. This also reveals that mobile botnets can propagate at the fastest rate of quadratic growth in size, which is substantially slower than the exponential growth of Internet botnets. To measure the denial-of-service impact of a mobile botnet, we define a new metric, called last chipper time, which is the last time that service requests, even partially, can still be processed on time as the botnet keeps propagating and launching attacks. The last chipper time is identified to decrease at most on the order of 1=√B, where B is the network bandwidth. This result reveals that although increasing network bandwidth can help mobile services, it can, at the same time, indeed escalate the risk of services being disrupted by mobile botnets.}, number={9}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Lu, Zhuo and Wang, Wenye and Wang, Cliff}, year={2016}, month={Sep}, pages={2304–2316} }
 @article{sun_wang_li_2016, title={The Impact of Network Size and Mobility on Information Delivery in Cognitive Radio Networks}, volume={15}, ISSN={["1558-0660"]}, DOI={10.1109/tmc.2015.2398420}, abstractNote={There have been extensive works on the design of opportunistic spectrum access and routing schemes to improve spectrum efficiency in cognitive radio networks (CRNs), which becomes an integral component in the future communication regime. Nonetheless, the potentials of CRNs in boosting network performance yet remain to be explored to reach the full benefits of such a phenomenal technique. In this paper, we study the end-to-end latency in CRNs in order to find the sufficient and necessary conditions for real-time applications in finite networks and large-scale deployments. We first provide a general mobility framework which captures most characteristics of the existing mobility models and takes spatial heterogeneity into account. Under this general mobility framework, secondary users are mobile with an mobility radius $\alpha$ , which indicates how far a mobile node can reach in spatial domain. We find that there exists a cutoff point on $\alpha$ , below which the latency has a heavy tail and above which the tail of the latency is bounded by some Gamma distributions. As the network grows large, the latency is asymptotically scalable (linear) with respect to the dissemination distance (e.g., the number of hops or euclidean distance). An interesting observation is that although the density of primary users adversely impacts the expected latency, it makes no influence on the dichotomy of the latency tail in finite networks and the linearity of latency in large networks. Our results encourage CRN deployment for real-time and large applications, when the mobility radius of secondary users is large enough.}, number={1}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Sun, Lei and Wang, Wenye and Li, Yujin}, year={2016}, month={Jan}, pages={217–231} }
 @inproceedings{wang_wang_2016, title={To live or to die: Encountering conflict information dissemination over simple networks}, DOI={10.1109/infocom.2016.7524603}, abstractNote={In an era of networks in which any individual is connected with one another, such as Internet of Things (IoT) and Online Social Networks (OSNs), the networks are evolving into complex systems, carrying a huge volume of information that may provoke even more. An interesting, yet challenging question is how such information dissemination evolves, that is, to continue or to stop. Specifically, we aim to find out the aftermath of epidemic spreading via individuals and conflicting information dissemination. From a holistic, networking view, it is impossible to take every aspect into accounts for complex networks toward these questions. Therefore, we establish a Susceptible-Infectious-Cured (SIC) propagation model to examine two simple network topologies, clique and star, in terms of extinction time and half-life time of information under controllable, epidemic dynamics. For a network of size n, both theoretical and numerical results suggest that extinction time and half-life time are O(log n/n) for clique networks, and O(log n) for star networks. More interestingly, given an initial network state I0, the extinction time is constant (O(1)) for cliques, and O(log I0) for stars; while the half-life time is O(log 1/I0) for both clique and star networks, respectively. In addition, we developed a method to estimate the conditional infection count distribution, which indicates the scope of information dissemination.}, booktitle={IEEE INFOCOM 2016 - the 35th annual IEEE international Conference on Computer Communications}, author={Wang, Jie and Wang, Wenye}, year={2016} }
 @article{lu_wang_wang_2015, title={Camouflage Traffic: Minimizing Message Delay for Smart Grid Applications under Jamming}, volume={12}, ISSN={["1941-0018"]}, DOI={10.1109/tdsc.2014.2316795}, abstractNote={Smart grid is a cyber-physical system that integrates power infrastructures with information technologies. To facilitate efficient information exchange, wireless networks have been proposed to be widely used in the smart grid. However, the jamming attack that constantly broadcasts radio interference is a primary security threat to prevent the deployment of wireless networks in the smart grid. Hence, spread spectrum systems, which provide jamming resilience via multiple frequency and code channels, must be adapted to the smart grid for secure wireless communications, while at the same time providing latency guarantee for control messages. An open question is how to minimize message delay for timely smart grid communication under any potential jamming attack. To address this issue, we provide a paradigm shift from the case-by-case methodology, which is widely used in existing works to investigate well-adopted attack models, to the worst-case methodology, which offers delay performance guarantee for smart grid applications under any attack. We first define a generic jamming process that characterizes a wide range of existing attack models. Then, we show that in all strategies under the generic process, the worst-case message delay is a U-shaped function of network traffic load. This indicates that, interestingly, increasing a fair amount of traffic can in fact improve the worst-case delay performance. As a result, we demonstrate a lightweight yet promising system, transmitting adaptive camouflage traffic (TACT), to combat jamming attacks. TACT minimizes the message delay by generating extra traffic called camouflage to balance the network load at the optimum. Experiments show that TACT can decrease the probability that a message is not delivered on time in order of magnitude.}, number={1}, journal={IEEE TRANSACTIONS ON DEPENDABLE AND SECURE COMPUTING}, author={Lu, Zhuo and Wang, Wenye and Wang, Cliff}, year={2015}, pages={31–44} }
 @article{wei_gong_wang_2015, title={Claim What You Need: A Text-Mining Approach on Android Permission Request Authorization}, ISSN={["2334-0983"]}, DOI={10.1109/glocom.2015.7417472}, abstractNote={Android is one of the most popular mobile operating systems nowadays, whose popularity, however, also attracts even more crafty developers to develop malicious softwares, or malwares, to exploit illegitimate means for profit. As a basic countermeasure, Android enforces the permission request scheme, in which an application (App) is required to present to the user the system resources (permissions) it will access, and ask user's approval before installation. However, this approach has been proven ineffective as it delegates the whole responsibility of decision- making to the user, who usually lacks the professional knowledge to comprehend the interpretation of a permission. Alternatively, many current researches focus on identifying potential malwares based on attributes of individual Apps, such as inspecting their source code, which, unfortunately, fall in another extreme which tend to make the decision for the user. Nevertheless, from the user's perspective, a satisfactory solution should be an approach which assists users to make the decision of the App installation on their own, by providing them with lucid reasons and requiring minimum professional knowledge. Based on the observation that the description of an App is the most direct interface to communicate its functionality to the user, in this paper we are motivated to explore the relationship between the description and the requested permissions of an App, and further build a model to predict proper permissions based on its description. Our evaluation with Apps collected from the Google Play Market shows that our prediction can achieve as high as 87% accuracy. In this regard, provide a user has full understanding of the description of an App, our model can act as an effective reminder to the user if the App tries to stealthily request permissions that are inconsistent with its description, which is a major character commonly exploited by malwares.}, journal={2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={Wei, Mingkui and Gong, Xi and Wang, Wenye}, year={2015} }
 @inproceedings{zhu_chen_wang_2015, title={G2G: Privacy-preserving group matching for proximity-based mobile social networks}, DOI={10.1109/iccchina.2015.7448721}, abstractNote={The explosive development of mobile devices and position systems makes it possible and meaningful for Proximity-based Mobile Social Networks (PMSNs), in which social group networking is among the most prominent features. In order to choose a suitable friend group, a group needs to find another group in vicinity and computes the matching degree based on their attributes. Then, they decide whether to make new social interactions through WiFi/Bluetooth interfaces embedded in their mobile devices according to the matching information. However, since group attributes usually contain some sensitive information, users may have increasing privacy concerns and do not want to reveal them to strangers. In this paper, we propose G2G, a novel privacy-preserving group matching mechanism, which can support group matching with preserving the privacy of all group members by applying permutation function. Considering a few potential attacks, we design an enhanced version G2G+, which can further improve group privacy. By detailed analysis and evaluation, we demonstrate that the proposed schemes have a desirable performance on security, efficiency and communication traffic.}, booktitle={2015 IEEE/CIC International Conference on Communications in China (ICCC)}, author={Zhu, X. Y. and Chen, Z. B. and Wang, Wenye}, year={2015} }
 @article{sun_wang_lu_2015, title={On Topology and Resilience of Large-Scale Cognitive Radio Networks Under Generic Failures}, volume={14}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2015.2404919}, abstractNote={It has been demonstrated that in wireless networks, blackholes, which are typically generated by isolated node failures, and augmented by failure correlations, can easily result in devastating impact on network performance. In order to address this issue, we focus on the topology of Cognitive Radio Networks (CRNs) because of their phenomenal benefits in improving spectrum efficiency through opportunistic communications. Particularly, we first define two metrics, namely the failure occurrence probability p and failure connection function g(·), to characterize node failures and their spreading properties, respectively. Then we prove that each blackhole is exponentially bounded based on percolation theory. By mapping failure spreading using a branching process, we further derive an upper bound on the expected size of blackholes. With the observations from our analysis, we are able to find a sufficient condition for a resilient CRN in the presence of blackholes through analysis and simulations.}, number={6}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Sun, Lei and Wang, Wenye and Lu, Zhuo}, year={2015}, month={Jun}, pages={3390–3401} }
 @article{wei_wang_2015, title={Safety Can Be Dangerous: Secure Communications Impair Smart Grid Stability Under Emergencies}, ISSN={["2334-0983"]}, DOI={10.1109/glocom.2015.7417012}, abstractNote={Smart grid features real-time monitoring and control by integrating advanced communication networks into traditional power grids. This integration, however, makes smart grid vulnerable to cyber attacks, i.e., the anomalies caused by attackers in the communication network can affect ordinary operations of the power grid and result in severe physical damage. To protect smart grid from cyber attacks, many traditional countermeasures, such as message encryption, have been proposed to be directly migrated to fit this system. In this regard, the very first fundamental questions that need to be addressed are how to evaluate and compare the physical impacts of cyber attacks and countermeasures, and whether traditional cyber security countermeasures can result in satisfactory performance in smart grid. Motivated by these questions, we establish a small-scale smart grid prototype, and use both experiments and cross-domain simulations to evaluate and compare the reaction of the power system under cyber attacks, with and without the presence of traditional countermeasures. Our study reveals that traditional countermeasures can not be readily migrated to protect smart grid in particular, and shows that during system emergencies where prompt system reactions are critical, the extra latency caused by message encryption and decryption can result in more than 10 times in the magnitude of voltage collapse. Our work indicates that traditional countermeasures may not fit smart grid, the newly emerging cyber- physical system, which has strict time constraint. Therefore it is essential for researchers to seek solutions to address smart grid specific security threats.}, journal={2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM)}, author={Wei, Mingkui and Wang, Wenye}, year={2015} }
 @inproceedings{wei_wang_2014, title={Greenbench: A benchmark for observing power grid vulnerability under data-centric threats}, DOI={10.1109/infocom.2014.6848210}, abstractNote={Smart grid is a cyber-physical system which inte- grates communication networks into traditional power grid. This integration, however, makes the power grid susceptible to cyber attacks. One of the most distinguished challenges in studying the aftermath of cyber attacks in smart grid lies in data-centric threats. Even though such attacks are critical to the information network, they will result in much more Domino-like impact than they behave in cyber world. This is because for an information- centric network, distorted or delayed information undermines services and applications. But in power grid, these data-centric attacks may result in instable power systems, and further detrimental impact of power supplies. In this paper, we present Greenbench, a benchmark that is designed to evaluate real-time power grid dynamics in response to data-centric attacks. The simulation results provide several counter-intuitive suggestions to both smart grid security research and deployment.}, booktitle={2014 proceedings ieee infocom}, author={Wei, M. K. and Wang, Wenye}, year={2014}, pages={2625–2633} }
 @inproceedings{lu_wang_wang_2014, title={How can botnets cause storms? Understanding the evolution and impact of mobile botnets}, DOI={10.1109/infocom.2014.6848085}, abstractNote={A botnet in mobile networks is a collection of compromised nodes due to mobile malware, which are able to perform coordinated attacks. Different from Internet botnets, mobile botnets do not need to propagate using centralized infrastructures, but can keep compromising vulnerable nodes in close proximity and evolving organically via data forwarding. Such a distributed mechanism relies heavily on node mobility as well as wireless links, therefore breaks down the underlying premise in existing epidemic modeling for Internet botnets. In this paper, we adopt a stochastic approach to study the evolution and impact of mobile botnets. We find that node mobility can be a trigger to botnet propagation storms: the average size (i.e., number of compromised nodes) of a botnet increases quadratically over time if the mobility range that each node can reach exceeds a threshold; otherwise, the botnet can only contaminate a limited number of nodes with average size always bounded above. This also reveals that mobile botnets can propagate at the fastest rate of quadratic growth in size, which is substantially slower than the exponential growth of Internet botnets. To measure the denial-of-service impact of a mobile botnet, we define a new metric, called last chipper time, which is the last time that service requests, even partially, can still be processed on time as the botnet keeps propagating and launching attacks. The last chipper time is identified to decrease at most on the order of 1/ p B, where B is the network bandwidth. This}, booktitle={2014 proceedings ieee infocom}, author={Lu, Z. and Wang, Wenye and Wang, C.}, year={2014}, pages={1501–1509} }
 @article{li_wang_2014, title={Message Dissemination in Intermittently Connected D2D Communication Networks}, volume={13}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2014.2317703}, abstractNote={Device-to-device (D2D) communications enable direct communications and information distribution among closely located devices in wireless networks. Many applications of D2D communications require message dissemination to a group of mobile users at certain locations. The challenges of message dissemination come from highly dynamic network environments due to movements of devices. Existing studies on message dissemination have focused on information propagation speed and latency, but the size of the area affected by message dissemination at time t is also critical to D2D communication applications that heavily depend on message dissemination among users in a geographic region. In this paper, we study the fundamental issues in D2D communications: how far the message dissemination can reach by time t (referred as dissemination distance) and how long the dissemination takes to inform nodes located at distanced (referred to as hitting time), especially in dynamic, intermittently connected networks. We first derive analytic bounds of dissemination distance and hitting time under different dissemination mechanisms, providing the spatial and temporal limits of message dissemination. Analytic results are further validated by simulation results of several corresponding dissemination algorithms. Finally, two application scenarios are provided to illustrate how our results serve as guidelines to choose or design appropriate dissemination methods for different D2D communication applications.}, number={7}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Li, Yujin and Wang, Wenye}, year={2014}, month={Jul}, pages={3978–3990} }
 @article{lu_wang_wang_2014, title={Modeling, Evaluation and Detection of Jamming Attacks in Time-Critical Wireless Applications}, volume={13}, ISSN={["1558-0660"]}, DOI={10.1109/tmc.2013.146}, abstractNote={Recently, wireless networking for emerging cyber-physical systems, in particular the smart grid, has been drawing increasing attention in that it has broad applications for time-critical message delivery among electronic devices on physical infrastructures. However, the shared nature of wireless channels unavoidably exposes the messages in transit to jamming attacks, which broadcast radio interference to affect the network availability of electronic equipments. An important, yet open research question is how to model and detect jamming attacks in such wireless networks, where communication traffic is more time-critical than that in conventional data-service networks, such as cellular and WiFi networks. In this paper, we aim at modeling and detecting jamming attacks against time-critical wireless networks with applications to the smart grid. In contrast to communication networks where packets-oriented metrics, such as packet loss and throughput are used to measure the network performance, we introduce a new metric, message invalidation ratio, to quantify the performance of time-critical applications. Our modeling approach is inspired by the similarity between the behavior of a jammer who attempts to disrupt the delivery of a time-critical message and the behavior of a gambler who intends to win a gambling game. Therefore, by gambling-based modeling and real-time experiments, we find that there exists a phase transition phenomenon for successful time-critical message delivery under a variety of jamming attacks. That is, as the probability that a packet is jammed increases from 0 to 1, the message invalidation ratio first increases slightly, then increases dramatically to 1. Based on analytical and experimental results, we design the Jamming Attack Detection based on Estimation (JADE) scheme to achieve robust jamming detection, and implement JADE in a wireless network for power substations in the smart grid.}, number={8}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Lu, Zhuo and Wang, Wenye and Wang, Cliff}, year={2014}, month={Aug}, pages={1746–1759} }
 @article{li_lin_wang_mitton_2014, title={PPNA special issue on "the green, reliability and security of machine-to-machine communications"}, volume={7}, ISSN={["1936-6450"]}, DOI={10.1007/s12083-013-0237-z}, abstractNote={Machine-to-machine communications is an emerging technology that realizes a system of networks, wireless or wired, possibly distributed across the world, for transmitting events captured by low-end machines such as sensors and smart meters to high-end applications and/or personal appliances, where the events are translated into meaningful information. It embraces several major research fields including wireless sensor networks, vehicular networks, smart grid and RFID, emerging as a promising approach to enabling ubiquitous computing environment. Unlike current world-scale humancentric 3G wireless networks, M2M communication network is characterized by the absence of direct human intervention and the rapid increase in size and is therefore imposed with unique requirements. With ever-decreasing cost of deployment of M2M communication devices and access to public wireless data networks, and also thanks to its potential to support a large number of ubiquitous characteristics and achieving better cost efficiency, M2M communications has quickly become a market-changing force for a wide variety of real-time monitoring applications, such as remote patient monitoring, smart homes, utility management, environmental monitoring and industrial automation. However, the flourishing of M2M communications still hinges on fully understanding and managing the existing GRS challenges, i.e., Green (energy efficiency), Reliability and Security. This special issue includes six state-of-the-art contributions on the GRS aspects of M2M communications. The first paper entitled “An Attack-and-Defence Game for Security Assessment in Vehicular Ad Hoc Networks” by Suguo Do, Xiaolong Li, Junbo Du, Haojin Zhu points out that existing risk analysis solutions fail to consider the attack and defense costs and gains in vehicular networks, and thus cannot appropriately model the mutual interaction between the attacker and defender. The authors propose a game theoretical approach for security assessment in Vehicular Ad Hoc Networks (VANETs). They consider both of the rational attacker and defender, and adopt the attack-defense tree to model the attacker’s potential attack strategies and the defender’s corresponding countermeasures. To take the attack and defense costs into consideration, they introduce Return On Attack and Return on Investment to represent the potential gain from launching an attack or adopting a countermeasure in vehicular networks. They investigate the potential strategies of the defender and the attacker by modeling it as an attackdefense game. A detailed analysis on its Nash Equilibrium is provided. The second paper entitled “A Social Network Approach to Trust Management in VANETs” by Zhen Huang, Sushmita Ruj, Marcos Cavenaghi, Milos Stojmenovic, and Amiya Nayak presents several limitations of current trust management schemes in VANETs and proposes ways to counter them. The authors identify that the problem of information cascading and oversampling, which commonly arise in social networks, adversely affects trust management schemes in VANETs. They show that simple voting for decision-making leads to oversampling and gives incorrect results in VANETs. To overcome this problem, they propose a new voting scheme, where each vehicle has different votingweight according to its distance from the event. The vehicle that is closer to the event possesses higher weight. X. Li (*) Huawei Technologies Canada, Ottawa, ON K2K 3J1, Canada e-mail: easylix@gmail.com}, number={3}, journal={PEER-TO-PEER NETWORKING AND APPLICATIONS}, author={Li, Xu and Lin, Xiaodong and Wang, Wenye and Mitton, Nathalie}, year={2014}, month={Sep}, pages={213–214} }
 @article{lu_wang_ma_2013, title={An Empirical Study of Communication Infrastructures Towards the Smart Grid: Design, Implementation, and Evaluation}, volume={4}, ISSN={["1949-3061"]}, DOI={10.1109/tsg.2012.2225453}, abstractNote={The smart grid features ubiquitous interconnections of power equipments to enable two-way flows of electricity and information for various intelligent power management applications, such as accurate relay protection and timely demand response. To fulfill such pervasive equipment interconnects, a full-fledged communication infrastructure is of great importance in the smart grid. There have been extensive works on disparate layouts of communication infrastructures in the smart grid by surveying feasible wired or wireless communication technologies, such as power line communications and cellular networks. Nevertheless, towards an operable, cost-efficient and backward-compatible communication solution, more comprehensive and practical understandings are still urgently needed regarding communication requirements, applicable protocols, and system performance. Through such comprehensive understandings, we are prone to answer a fundamental question, how to design, implement and integrate communication infrastructures with power systems. In this paper, we address this issue in a case study of a smart grid demonstration project, the Future Renewable Electric Energy Delivery and Management (FREEDM) systems. By investigating communication scenarios, we first clarify communication requirements implied in FREEDM use cases. Then, we adopt a predominant protocol framework, Distributed Network Protocol 3.0 over TCP/IP (DNP3 over TCP/IP), to practically establish connections between electric devices for data exchanges in a small-scale FREEDM system setting, Green Hub. Within the real-setting testbed, we measure the message delivery performance of the DNP3-based communication infrastructure. Our results reveal that diverse timing requirements of message deliveries are arguably primary concerns in a way that dominates viabilities of protocols or schemes in the communication infrastructure of the smart grid. Accordingly, although DNP3 over TCP/IP is widely considered as a smart grid communication solution, it cannot satisfy communication requirements in some time-critical scenarios, such as relay protections, which claim a further optimization on the protocol efficiency of DNP3.}, number={1}, journal={IEEE TRANSACTIONS ON SMART GRID}, author={Lu, Xiang and Wang, Wenye and Ma, Jianfeng}, year={2013}, month={Mar}, pages={170–183} }
 @article{wang_lu_2013, title={Cyber security in the Smart Grid: Survey and challenges}, volume={57}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2012.12.017}, abstractNote={The Smart Grid, generally referred to as the next-generation power system, is considered as a revolutionary and evolutionary regime of existing power grids. More importantly, with the integration of advanced computing and communication technologies, the Smart Grid is expected to greatly enhance efficiency and reliability of future power systems with renewable energy resources , as well as distributed intelligence and demand response. Along with the silent features of the Smart Grid, cyber security emerges to be a critical issue because millions of electronic devices are inter-connected via communication networks throughout critical power facilities, which has an immediate impact on reliability of such a widespread infrastructure. In this paper, we present a comprehensive survey of cyber security issues for the Smart Grid. Specifically, we focus on reviewing and discussing security requirements, network vulnerabilities, attack countermeasures , secure communication protocols and architectures in the Smart Grid. We aim to provide a deep understanding of security vulnerabilities and solutions in the Smart Grid and shed light on future research directions for Smart Grid security .}, number={5}, journal={COMPUTER NETWORKS}, author={Wang, Wenye and Lu, Zhuo}, year={2013}, month={Apr}, pages={1344–1371} }
 @article{li_zhao_wang_2013, title={Internode Mobility Correlation for Group Detection and Analysis in VANETs}, volume={62}, ISSN={["1939-9359"]}, DOI={10.1109/tvt.2013.2264689}, abstractNote={Recent studies on mobility-assisted schemes for routing and topology control and on mobility-induced link dynamics have presented significant findings on the properties of a pair of nodes (e.g., the intermeeting time and link life time) or a group of nodes (e.g., network connectivity and partitions). In contrast to the study on the properties of a set of nodes rather than individuals, many works share a common ground with respect to node mobility, i.e., independent mobility in multihop wireless networks. Nonetheless, in vehicular ad hoc networks (VANETs), mobile devices installed on vehicles or held by humans are not isolated; however, they are dependent on each other. For example, the speed of a vehicle is influenced by its close-by vehicles, and vehicles on the same road move at similar speeds. Therefore, the gap between our understanding of the impact of independent mobility and our interest in the properties of correlated mobility in VANETs, along with the real systems altogether, declare an interesting question. How can we measure the internode mobility correlation, such as to uncover the node groups and network components, and explore their impact on link dynamics and network connectivity? Bearing this question in mind, we first examine several traces and find that node mobility exhibits spatial locality and temporal locality correlations, which are closely related to node grouping. To study the properties of these groups on the fly, we introduce a new metric, i.e., dual-locality ratio (DLR), which quantifies mobility correlation of nodes. In light of taking spatial and temporal locality dimensions into account, the DLR can be used to effectively identify stable user groups, which in turn can be used for network performance enhancement.}, number={9}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Li, Yujin and Zhao, Ming and Wang, Wenye}, year={2013}, month={Nov}, pages={4590–4601} }
 @article{xu_wang_2013, title={Scheduling Partition for Order Optimal Capacity in Large-Scale Wireless Networks}, volume={12}, ISSN={["1536-1233"]}, DOI={10.1109/tmc.2012.113}, abstractNote={The capacity scaling property specifies the change of network throughput when network size increases. It serves as an essential performance metric in large-scale wireless networks. Existing results have been obtained based on the assumption of using a globally planned link transmission schedule in the network, which is however not feasible in large wireless networks due to the scheduling complexity. The gap between the well-known capacity results and the infeasible assumption on link scheduling potentially undermines our understanding of the achievable network capacity. In this paper, we propose the scheduling partition methodology that decomposes a large network into small autonomous scheduling zones and implements a localized scheduling algorithm independently in each partition. We prove the sufficient and the necessary conditions for the scheduling partition approach to achieve the same order of capacity as the widely assumed global scheduling strategy. In comparison to the network dimension $(\sqrt{n})$, scheduling partition size $(\Theta (r(n)))$ is sufficient to obtain the optimal capacity scaling, where $(r(n))$ is the node transmission radius and much smaller than $(\sqrt{n})$. We finally propose a distributed partition protocol and a localized scheduling algorithm as our scheduling solution for maximum capacity in large wireless networks.}, number={4}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Xu, Yi and Wang, Wenye}, year={2013}, month={Apr}, pages={666–679} }
 @inproceedings{sun_wang_2013, title={Understanding blackholes in large-scale cognitive radio networks under generic failures}, DOI={10.1109/infcom.2013.6566859}, abstractNote={It has been demonstrated that in wireless networks, Blackholes, which are typically generated by isolated node failures, and augmented by failure correlations, can easily result in devastating impact on network performance. Therefore, many solutions, such as routing protocols and restoration algorithms, are proposed to deal with Blackholes by identifying alternative paths to bypass these holes such that the effect of Blackholes can be mitigated. These advancements are based on an underlying premise that there exists at least one alternative path in the network. However, such a hypothesis remains an open question. In other words, we do not know whether the network is resilient to Blackholes or whether an alternative path exists. The answer to this question can complement our understanding of designing routing protocols, as well as topology evolution in the presence of random failures. In order to address this issue, we focus on the topology of Cognitive Radio Networks (CRNs) because of their phenomenal benefits in improving spectrum efficiency through opportunistic communications. Particularly, we first define two metrics, namely the failure occurrence probability p and failure connection function g(·), to characterize node failures and their spreading properties, respectively. Then we prove that each Blackhole is exponentially bounded based on percolation theory. By mapping failure spreading using a branching process, we further derive an upper bound on the expected size of Blackholes. With the observations from our analysis, we are able to find a sufficient condition for a resilient CRN in the presence of Blackholes through analysis and simulations.}, booktitle={2013 proceedings ieee infocom}, author={Sun, L. and Wang, Wenye}, year={2013}, pages={728–736} }
 @article{xu_wang_2013, title={Wireless Mesh Network in Smart Grid: Modeling and Analysis for Time Critical Communications}, volume={12}, ISSN={["1536-1276"]}, DOI={10.1109/twc.2013.061713.121545}, abstractNote={Communication networks are an indispensable component in the smart grid power systems by providing the essential information exchange functions among the electrical devices that are located distributively in the grid. In particular, wireless networks will be deployed widely in the smart grid for data collection and remote control purposes. In this paper, we model the smart grid wireless networks and present the communication delay analysis in typical wireless network deployment scenarios in the grid. As the time critical communications are coupled with the power system protections in the smart grid, it is important to understand the delay performance of the smart grid wireless networks. Our results provide the delay bounds that can help design satisfactory wireless networks to meet the demanding communication requirements in the smart grid.}, number={7}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Xu, Yi and Wang, Wenye}, year={2013}, month={Jul}, pages={3360–3371} }
 @inproceedings{wang_lu_wang_huang_2012, title={Development of distributed grid intelligence platform for solid state transformer}, DOI={10.1109/smartgridcomm.2012.6486031}, abstractNote={This paper introduces the development of a platform intended as a distributed controller for grid intelligence (DGI) system at FREEDM Systems Center. This platform serves as both a hard real-time local converter controller and a communication node for distributed deployment of energy management schemes. One of the converter devices it controls is the solid state transformer (SST), one of the key elements to interface renewable energy sources into distribution system in FREEDM Center. Both the hardware design and software structure for SST control are presented in this paper. For the communication part, the Distributed Network Protocol (DNP) 3.0 is adopted to congregate multiple SSTs to balance local generation and demands in a coordinated manner. Experiment results are presented to show that this distributed platform has good performance.}, booktitle={2012 IEEE Third International Conference on Smart Grid Communications (SmartGridComm)}, author={Wang, F. and Lu, X. and Wang, Wenye and Huang, A.}, year={2012}, pages={481–485} }
 @inproceedings{mehta_duel-hallen_wang_2012, place={Piscataway, NJ, USA}, title={Enabling adaptive rate and relay selection for 802.11 mobile ad hoc networks}, url={http://dx.doi.org/10.1109/ICC.2012.6363785}, DOI={10.1109/icc.2012.6363785}, abstractNote={Mobile ad hoc networks (MANETs) are self-configuring wireless networks that lack permanent infrastructure and are formed among mobile nodes on demand. Rapid node mobility results in dramatic channel variation, or fading, that degrades MANET performance. Employing channel state information (CSI) at the transmitter can improve the throughput of routing and medium access control (MAC) protocols for mobile ad hoc networks. Several routing algorithms in the literature explicitly incorporate the fading signal strength into the routing metric, thus selecting the routes with strong channel conditions. While these studies show that adaptation to the time-variant channel gain is beneficial in MANETs, they do not address the effect of the outdated fading CSI at the transmitter. For realistic mobile node speeds, the channel gain is rapidly varying, and becomes quickly outdated due the feedback delay. We analyze the link throughput of joint rate adaptation and adaptive relay selection in the presence of imperfect CSI. Moreover, for an 802.11 network that employs geographic opportunistic routing with adaptive rate and relay selection, we propose a novel method to reduce the effect of the feedback delay at the MAC layer in the presence of Rayleigh fading. This method exploits channel reciprocity and fading prediction and does not require significant modification to the existing 802.11 frame structure. Extensive network simulations demonstrate that the proposed approach significantly improves the throughput, delay, and packet delivery ratio for high mobile velocities relative to previously proposed approaches that employ outdated CSI at the transmitter.}, booktitle={2012 ieee international conference on communications (icc)}, author={Mehta, N. and Duel-Hallen, A. and Wang, Wenye}, year={2012}, pages={4150–4} }
 @inproceedings{li_wang_2012, title={Geo-dissemination in vehicular ad hoc networks}, DOI={10.1109/icc.2012.6364456}, abstractNote={Vehicular Adhoc Networks (VANETs) aim to improve road safety and convenience through vehicle-to-vehicle and vehicle-to-roadside communications. Traffic information and accident warnings are often disseminated to vehicles in certain areas where driving could be affected by hazardous situations. Such message dissemination with destinations confined in specific geographic regions is referred to as Geo-Dissemination. In this paper, we analyze how far a geo-dissemination can possibly reach over a period of time t (denoted as dissemination distance D(t)), and what is the latency for a message to reach locations that are d distance far from the source (denoted as the stopping time τ). Simulations results of two dissemination methods (stateless opportunistic forwarding and GPS-based message broadcasting) are compared with our analytic results.}, booktitle={2012 ieee international conference on communications (icc)}, author={Li, Y. J. and Wang, Wenye}, year={2012} }
 @inproceedings{lu_wang_wang_2012, title={Hiding traffic with camouflage: Minimizing message delay in the smart grid under jamming}, DOI={10.1109/infcom.2012.6195760}, abstractNote={The smart grid is an emerging cyber-physical system that integrates power infrastructures with information technologies. In the smart grid, wireless networks have been proposed for efficient communications. However, the jamming attack that broadcasts radio interference is a primary security threat to prevent the deployment of wireless networks. Hence, spread spectrum systems with jamming resilience must be adapted to the smart grid to secure wireless communications. There have been extensive works on designing spread spectrum schemes to achieve feasible communication under jamming attacks. Nevertheless, an open question in the smart grid is how to minimize message delay for timely communication in power applications. In this paper, we address this problem in a wireless network with spread spectrum systems for the smart grid. By defining a generic jamming process that characterizes a wide range of existing jamming models, we show that the worst-case message delay is a U-shaped function of network traffic load. This indicates that, interestingly, increasing a fair amount of redundant traffic, called camouflage, can improve the worst-case delay performance. We demonstrate via experiments that transmitting camouflage traffic can decrease the probability that a message is not delivered on time in order of magnitude for smart grid applications.}, booktitle={2012 Proceedings IEEE infocom}, author={Lu, Z. and Wang, Wenye and Wang, C.}, year={2012}, pages={3066–3070} }
 @inproceedings{sun_wang_2012, title={On latency distribution and scaling: From finite to large cognitive radio networks under general mobility}, DOI={10.1109/infcom.2012.6195491}, abstractNote={Cognitive Radio Networks (CRNs), as a phenomenal technique to improve spectrum efficiency for opportunistic communications, become an integral component in the future communication regime. In this paper, we study the end-to-end latency in CRNs because many CRN applications, such as military networks and emergency networks, are either time-sensitive or dependent on delay performance. In particular, we consider a general mobility framework that captures most characteristics of the existing models and accounts for spatial heterogeneity resulting from the scenario that some locations are more likely to be visited by mobile nodes (these can be home in the case of people, or garage in the case of vehicles). By assuming that secondary users are mobile under this general framework, we find that there exists a cutoff point on the mobility radius #, which indicates how far a mobile node can reach in the spatial domain, below which the latency has a heavy-tailed distribution and above which the tail distribution is bounded by some Gamma (light-tailed) distribution. A heavy tail of the latency implies a significant probability that it takes long time to disseminate a message from the source to the destination and thus a light-tailed latency is crucial for time-critical applications. Moreover, as the network grows large, we notice that the latency is asymptotically scalable (linear) with the dissemination distance (e.g., the number of hops or Euclidean distance). Another interesting observation is that although the density of primary users adversely impacts the expected latency, it makes no influence on the dichotomy of the tail distribution of the latency in finite networks and the linearity of latency in large networks. Our results encourage the CRN deployment for real-time and large applications, when the mobility radius of secondary users is large enough.}, booktitle={2012 Proceedings IEEE infocom}, author={Sun, L. and Wang, Wenye}, year={2012}, pages={1287–1295} }
 @inproceedings{sun_wang_2012, title={On the connectivity of large multi-channel cognitive radio networks}, DOI={10.1109/icc.2012.6363893}, abstractNote={Cognitive Radio Networks (CRNs) have become promising network components to improve spectrum utilization efficiency, where secondary (unlicensed) users exploit spectrum opportunistically without interfering with the coexisting primary users. A challenging yet open question is how to ensure that information can be disseminated to the entire CRN, which is a prerequisite to applications of wireless networks. In this paper, we address the connectivity of large multi-channel CRNs. Particularly, we study full connectivity and percolation of secondary networks. The former is the existence of a communication path between any two nodes and the latter is the existence of a large component of secondary users. We find that the sufficient and necessary condition to achieve full connectivity is λ = Θ(log n/πr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ), where λ is the density, n is the number and r is the transmission range of secondary users respectively, and P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> is the probability that any two secondary users can communicate with each other without interfering with primary users. We further show that the required density for percolation is a constant, and identify an upper bound on λ, above which the network is percolated and a lower bound on λ below which the network is not percolated. Our results provide a theoretical understanding of connectivity in large multi-channel cognitive radio networks.}, booktitle={2012 ieee international conference on communications (icc)}, author={Sun, L. and Wang, Wenye}, year={2012}, pages={1854–1858} }
 @inproceedings{li_wang_duel-hallen_2012, place={Piscataway, NJ, USA}, title={The latency of gaining alpha-reliability for message dissemination in vehicle-to-vehicle networks}, url={http://dx.doi.org/10.1109/GLOCOM.2012.6504004}, DOI={10.1109/glocom.2012.6504004}, abstractNote={In many Vehicular Ad-hoc Network applications, such as hazard warning and traffic coordination, the message dissemination in unreliable and highly mobile network environment is a key challenge. In order to understand the relationship between dissemination latency and reliability, we analyze the latency of gaining α-reliability that a node correctly receives a message with probability larger than α (0 min (α). Besides dissemination reliability requirement α, t min (α) also depends on node's original distance from the source, node mobility, channel reliability, and traffic flow. Numerical analysis discloses several interesting insights that 1) t min (α) is dominated by the first attempt to send the message to a destination, 2) node mobility has little impact on t min (α) in emergency information dissemination, and 3) transmission range and node density greatly affect dissemination latency and reliability.}, booktitle={2012 ieee global communications conference (globecom)}, author={Li, Y. J. and Wang, Wenye and Duel-Hallen, A.}, year={2012}, pages={5550–5555} }
 @inproceedings{sun_wang_2012, title={Understanding the tempo-spatial limits of information dissemination in multi-channel cognitive radio networks}, DOI={10.1109/infcom.2012.6195489}, abstractNote={Cognitive Radio Networks (CRNs) have emerged to become promising network components for exploiting spectrum opportunistically in order that information can be delivered in circumstances otherwise impossible. Challenging yet open questions are how fast and how far a packet can be delivered in such networks, in temporal and spatial domains, respectively. The answers to these questions offer a straightforward interpretation of the potentials of CRNs for time-sensitive applications. To tackle these questions, we define two metrics, dissemination radius ∥ℒ(t)∥ and propagation speed S(d). The former is the maximum Euclidean distance that a packet can reach in time t, and the latter is the speed that a packet transmits between a source and destination at Euclidean distance d apart, which can be used to measure the transmission delay. Further, we determine the sufficient and necessary conditions under which there exist spatial and temporal limits of information dissemination in CRNs. We find that when information cannot be disseminated to the entire network, the limiting dissemination radius is statistically dominated by an exponential distribution, while the limiting information propagation speed approaches to zero. Otherwise, the dissemination radius approaches to infinity and the propagation speed S(d) is no lower than some constant k for large d. The results are validated through simulations.}, booktitle={2012 Proceedings IEEE infocom}, author={Sun, L. and Wang, Wenye}, year={2012}, pages={1278–1286} }
 @article{wang_xu_khanna_2011, title={A survey on the communication architectures in smart grid}, volume={55}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2011.07.010}, abstractNote={The next-generation electric power systems (smart grid) are studied intensively as a promising solution for energy crisis. One important feature of the smart grid is the integration of high-speed, reliable and secure data communication networks to manage the complex power systems effectively and intelligently. We provide in this paper a comprehensive survey on the communication architectures in the power systems, including the communication network compositions, technologies, functions, requirements, and research challenges. As these communication networks are responsible for delivering power system related messages, we discuss specifically the network implementation considerations and challenges in the power system settings. This survey attempts to summarize the current state of research efforts in the communication networks of smart grid, which may help us identify the research problems in the continued studies.}, number={15}, journal={COMPUTER NETWORKS}, author={Wang, Wenye and Xu, Yi and Khanna, Mohit}, year={2011}, month={Oct}, pages={3604–3629} }
 @inproceedings{lu_wang_wang_2011, title={From jammer to gambler: Modeling and detection of jamming attacks against time-critical traffic}, DOI={10.1109/infcom.2011.5934989}, abstractNote={Time-critical wireless applications in emerging network systems, such as e-healthcare and smart grids, have been drawing increasing attention in both industry and academia. The broadcast nature of wireless channels unavoidably exposes such applications to jamming attacks. However, existing methods to characterize and detect jamming attacks cannot be applied directly to time-critical networks, whose communication traffic model differs from conventional models. In this paper, we aim at modeling and detecting jamming attacks against time-critical traffic. We introduce a new metric, message invalidation ratio, to quantify the performance of time-critical applications. A key insight that leads to our modeling is that the behavior of a jammer who attempts to disrupt the delivery of a time-critical message can be exactly mapped to the behavior of a gambler who tends to win a gambling game. We show via the gambling-based modeling and real-time experiments that there in general exists a phase transition phenomenon for a time-critical application under jamming attacks: as the probability that a packet is jammed increases from 0 to 1, the message invalidation ratio first increases slightly (even negligibly), then increases dramatically to 1. Based on analytical and experimental results, we further design and implement the JADE (Jamming Attack Detection based on Estimation) system to achieve efficient and robust jamming detection for time-critical wireless networks.}, booktitle={2011 proceedings ieee infocom}, author={Lu, Z. and Wang, Wenye and Wang, C.}, year={2011}, pages={1871–1879} }
 @inproceedings{xu_wang_2011, title={Information delivery in large wireless networks with minimum energy expense}, DOI={10.1109/infcom.2011.5934950}, abstractNote={Energy efficient communication is a critical research problem in large-scale multihop wireless networks because of the limited energy supplies from batteries. We investigate in this paper the minimum energy required to fulfill various information delivery goals that correspond to the major communication paradigms in large wireless networks. We characterize the minimum energy requirement in two steps. We first derive the lower bounds on the energy consumption for all the possible solutions that deliver the information as required. We then design routing schemes that accomplish the information delivery tasks by using an amount of energy comparable to the lower bounds. Our work provides the fundamental understandings of energy needs and the efficient solutions for energy usages in major communication scenarios, which contribute to the rational dimensioning and wise utilization of the energy resources in large wireless networks.}, booktitle={2011 proceedings ieee infocom}, author={Xu, Y. and Wang, Wenye}, year={2011}, pages={1584–1592} }
 @inproceedings{li_zhao_wang_2011, title={Intermittently connected vehicle-to-vehicle networks: Detection and analysis}, DOI={10.1109/glocom.2011.6134395}, abstractNote={Vehicular Adhoc Networks (VANETs) are dedicated to improve the safety and efficiency of transportation systems through vehicle to vehicle or vehicle to road side communications. VANETs exhibit dynamic topology and intermittent connectivity due to high vehicle mobility. These distinguished features declare a challenging question: how to detect on the fly vehicular networks such that we can explore mobility-assisted message dissemination and topology control in VANETs. As being closely related to network dynamics, vehicle mobility could be explored to uncover network structure. In this paper, we have observed that mobility of vehicle, rather than being random, shows temporal locality (i.e., frequently visiting several communities like home and office), and spatial locality (i.e., velocity constrained by road layout and nearby vehicles). We first examine temporal locality using a campus trace, then measure temporal locality similarity between two vehicles based on the relative entropy of their location preferences. By further incorporating spatial locality similarity, we introduce a new metric, namely dual locality ratio (DLR), which represents the mobility correlation of vehicles. Simulation results show that DLR can effectively identify dynamic vehicular network structures. We also demonstrate applications of DLR for improving performances of data forwarding and clustering in vehicle-to-vehicle networks.}, booktitle={2011 ieee global telecommunications conference (globecom 2011)}, author={Li, Y. J. and Zhao, M. and Wang, Wenye}, year={2011} }
 @inproceedings{lu_lu_wang_ma_2011, title={On network performance evaluation toward the smart grid: A case study of DNP3 over TCP/IP}, DOI={10.1109/glocom.2011.6134406}, abstractNote={The smart grid is the next-generation power system that incorporates power infrastructures with information technologies. In the smart grid, power devices are interconnected to support a variety of intelligent mechanisms, such as relay protection and demand response. To enable such mechanisms, messages must be delivered in a timely manner via network protocols. A cost-efficient and backward-compatible way for smart grid protocol design is to migrate current protocols in supervisory control and data acquisition (SCADA) systems to the smart grid. However, an open question is whether the performance of SCADA protocols can meet the timing requirements of smart grid applications. To address this issue, we establish a micro smart grid, Green Hub, to measure the delay performance of a predominant SCADA protocol, distributed network protocol 3.0 (DNP3) over TCP/IP. Our results show that although DNP3 over TCP/IP is widely considered as a smart grid communication protocol, it cannot be used in applications with delay constraints smaller than 16ms in Green Hub, such as relay protection. In addition, since DNP3 provides reliability mechanisms similar to TCP, we identify that such an overlapped design induces 50%-80% of the processing delay in embedded power devices. Our results indicate that DNP3 over TCP/IP can be further optimized in terms of delay efficiency, and a lightweight communication protocol is essential for time-critical smart grid applications.}, booktitle={2011 ieee global telecommunications conference (globecom 2011)}, author={Lu, X. and Lu, Z. and Wang, Wenye and Ma, J. F.}, year={2011} }
 @inproceedings{zheng_wang_2011, title={On the access time in mobile hybrid networks}, DOI={10.1109/glocom.2011.6133498}, abstractNote={This paper investigates the access time of mobile nodes to infrastructure networks in Mobile Hybrid Networks (MHNs), e.g., sensor-actuator networks, where mobile nodes move around the coexisting infrastructure networks. In such networks, mobile nodes may relay data packets in a hop-by-hop fashion, and eventually deliver packets to the wired networks. Our objective is to study the lower bound of the access time, which implies the minimum time to deliver data packets from low-speed, unreliable wireless networks to the high-speed, reliable infrastructure network. In particular, we propose a theoretical framework to analyze the packet propagation speed in MHNs, and to show that there is a unified lower bound on the access time regardless of data forwarding schemes. When wireless nodes move at an average speed of v and variance σ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> towards an AP, and their density λ is small (e.g., the network is sparse and surely disconnected), we prove that the expected access time is lower bounded by (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> (0)-r) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /σ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> packet mobility is unbiased and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> (0)-r/v for the biased case, where L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> (0) is the distance from the source node to the nearest access point. Here, packet mobility is the mobility of a packet due to both node mobility and data transmissions. We further propose a routing scheme to achieve such theoretical bounds.}, booktitle={2011 ieee global telecommunications conference (globecom 2011)}, author={Zheng, H. Y. and Wang, Wenye}, year={2011} }
 @article{xu_wang_2011, title={The Limit of Information Propagation Speed in Large-Scale Multihop Wireless Networks}, volume={19}, ISSN={["1558-2566"]}, DOI={10.1109/tnet.2010.2057444}, abstractNote={This paper investigates the speed limit of information propagation in large-scale multihop wireless networks, which provides fundamental understanding of the fastest information transportation and delivery that a wireless network is able to accommodate. We show that there exists a unified speed upper bound for broadcast and unicast communications in large-scale wireless networks. When network connectivity is considered, this speed bound is a function of node density. If the network noise is constant, the bound is a constant when node density exceeds a threshold; if the network noise is an increasing function of node density, the bound decreases to zero when node density approaches infinity. As achieving the speed bound places strict requirements on node locations, we also quantify the gap between the actual achieved speed and the desired bound in random networks in which the relay nodes are not located as desired. We find that the gap converges to zero exponentially as node density increases to infinity.}, number={1}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Xu, Yi and Wang, Wenye}, year={2011}, month={Feb}, pages={209–222} }
 @article{xing_wang_2011, title={Toward robust multi-hop data forwarding in large scale wireless networks}, volume={55}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2011.04.014}, abstractNote={Design of robust network topology is an essential issue in large-scale multi-hop wireless networks since data packets are forwarded through intermediate nodes between source and destination, especially in the presence of non-cooperative nodes. Traditionally, topology design aims at generating network topology with high node degree, maximum throughput, and mitigation of malicious attacks. In this paper, we formulate a novel topology control problem as achieving optimal topology which maximizes network robustness against data forwarding distortion (DFD) in which a relay node may be compliant in route discovery, but drop or delay packets as non-cooperative nodes. Such node misbehavior can degrade network performance dramatically, without being detected by routing protocols and countermeasures. Therefore, we propose to design a network topology and data forwarding algorithms, namely PROACtive, in order to distribute data packets among cooperative nodes only, subject to k-connectivity constraint. Through analysis and simulations, we show that there exists a trade-off between achieving network robustness and k-connected with high probability (w.h.p.). By using distributed measurement schemes, data packets can be forwarded with low message complexity Θ(N), and improves network goodput significantly in different network scenarios.}, number={11}, journal={COMPUTER NETWORKS}, author={Xing, Fei and Wang, Wenye}, year={2011}, month={Aug}, pages={2608–2621} }
 @inproceedings{sun_wang_2011, title={on distribution and limits of information dissemination latency and speed in mobile cognitive radio networks}, DOI={10.1109/infcom.2011.5935069}, abstractNote={Dissemination latency and speed are central to the applications of cognitive radio networks, which have become an important component of current communication infrastructure. In this paper, we investigate the distributions and limits of information dissemination latency and speed in a cognitive radio network where licensed users (primary users) are static and cognitive radio users (secondary users) are mobile. We show that the dissemination latency depends on the stationary spatial distribution and mobility capability α (characterizing the region that a mobile secondary user can reach) of secondary users. Given any stationary spatial distribution, we find that there exists a critical value on α, below which the latency and speed are heavy-tailed and above which the right tails of their distribution are bounded by Gamma random variables. We further show that as the network grows to infinity, the latency asymptotically scales linearly with the “distance” (characterized by transmission hops or Euclidean distance) between the source and the destination. Our results are validated through simulations.}, booktitle={2011 proceedings ieee infocom}, author={Sun, L. and Wang, Wenye}, year={2011}, pages={246–250} }
 @inproceedings{kharbash_wang_2010, title={All-terminal network reliability optimization in fading environment via cross entropy method}, DOI={10.1109/icc.2010.5501918}, abstractNote={This paper presents a new algorithm that can be readily applied to solve all-terminal network reliability optimization problem of a wireless network in a fading environment. The optimization problem solved considers finding the optimal topological layout of links at which the all-terminal network reliability is maximized by controlling the nodes' transmission powers. To that end, a link probabilistic model is developed to relate fading, attenuation, interference and nodes' transmission powers to link reliability. Then, the proposed algorithm utilized this probabilistic model to control nodes' transmission power to maximize links reliabilities and hence all-terminal network reliability. The proposed algorithm is based on two major steps that use a global stochastic optimization technique, Cross Entropy (CE) to generate the optimal network topology and control nodes transmission powers such that all-terminal network reliability is maximized. An illustrative example is used to illustrate the proposed algorithm.}, booktitle={2010 ieee international conference on communications - ICC 2010}, author={Kharbash, S. and Wang, Wenye}, year={2010} }
 @inproceedings{xu_wang_2010, title={Characterizing the spread of correlated failures in large wireless networks}, DOI={10.1109/infcom.2010.5462009}, abstractNote={Correlated failures pose a great challenge for the normal functioning of large wireless networks, because an initial local failure may trigger a global sequence of related failures. Given their potentially devastating impact, we characterize the spread of correlated failures in this paper, which lays the foundation for evaluating and improving the failure resilience of existing wireless networks. We model the failure contagiousness as two generic functions: the failure impact radius distribution function f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> (x) and the failure connection function g(x). By using the percolation theory, we determine the respective characteristic regimes of f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> (x) and g(x) in which correlated failures will and will not percolate in the network. As our model represents various failure scenarios, the results are generally applicable in understanding the spread of a wide range of correlated failures.}, booktitle={2010 proceedings ieee infocom}, author={Xu, Y. and Wang, Wenye}, year={2010} }
 @inproceedings{lu_wang_wang_2010, title={On order gain of backoff misbehaving nodes in CSMA/CA-based wireless networks}, DOI={10.1109/infcom.2010.5462002}, abstractNote={Backoff misbehavior, in which a wireless node deliberately manipulates its backoff time, can induce significant network problems, such as severe unfairness and denial-of-service. Although great progress has been made towards the design of countermeasures to backoff misbehavior, little attention has been focused on quantifying the gain of backoff misbehaviors. In this paper, we define and study two general classes of backoff misbehavior to assess the gain that misbehaving nodes can obtain. The first class, called continuous misbehavior, keeps manipulating the backoff time unless it is disabled by countermeasures. The second class is referred to as intermittent misbehavior, which tends to evade the detection by countermeasures by performing misbehavior sporadically. Our approach is to introduce a new performance metric, namely order gain, which is to characterize the performance benefits of misbehaving nodes in comparison to legitimate nodes. Through analytical studies, simulations, and experiments, we demonstrate the impact of a wide range of backoff misbehaviors on network performance with respect to the number of users in CSMA/CA-based wireless networks.}, booktitle={2010 proceedings ieee infocom}, author={Lu, Z. and Wang, Wenye and Wang, C.}, year={2010} }
 @article{xing_wang_2010, title={On the Survivability of Wireless Ad Hoc Networks with Node Misbehaviors and Failures}, volume={7}, ISSN={["1941-0018"]}, DOI={10.1109/tdsc.2008.71}, abstractNote={Network survivability is the ability of a network to stay connected under failures and attacks, which is a fundamental issue to the design and performance evaluation of wireless ad hoc networks. In this paper, we focus on the analysis of network survivability in the presence of node misbehaviors and failures. First, we propose a novel semi-Markov process model to characterize the evolution of node behaviors. As an immediate application of the proposed model, we investigate the problem of node isolation where the effects of denial-of-service (DoS) attacks are considered. Then, we present the derivation of network survivability and obtain the lower and upper bounds on the topological survivability for k-connected networks. We find that the network survivability degrades very quickly with the increasing likelihood of node misbehaviors, depending on the requirements of disjoint outgoing paths or network connectivity. Moreover, DoS attacks have a significant impact on the network survivability, especially in dense networks. Finally, we validate the proposed model and analytical result by simulations and numerical analysis, showing the effects of node misbehaviors on both topological survivability and network performance.}, number={3}, journal={IEEE TRANSACTIONS ON DEPENDABLE AND SECURE COMPUTING}, author={Xing, Fei and Wang, Wenye}, year={2010}, pages={284–299} }
 @inproceedings{yi_wang_2010, title={On the connectivity analysis over large-scale hybrid wireless networks}, DOI={10.1109/infcom.2010.5462106}, abstractNote={Many real systems are hybrid networks which include infrastructure nodes in multi-hop wireless networks, such as sinks in sensor networks and mesh routers in mesh networks. However, we have very little understanding of network connectivity in such networks. Therefore, in this paper, we consider hybrid networks denoted by H(¿, ß) with ad hoc nodes and base stations and prove how base stations can improve the connectivity of ad hoc nodes in subcritical phase, that is, the ad hoc node density, ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¿</sub> is lower than the critical density ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¿</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sup> . We find that with the existence of a positive density of base stations, i.e., the density of base stations ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ß</sub> > 0 which have the same transmission range as ad hoc nodes, the number of connected ad hoc nodes is ¿(n) with probability nearly 1, where n is the number of ad hoc nodes. However, the size of connected ad hoc component scales linearly with ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ß</sub> when it is lower than c <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> (¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¿</sub> ) with probability nearly 1, which demonstrates a tremendous benefit of using base stations to enhance the connectivity of ad hoc nodes. Further, we study a hybrid network architecture that makes a significant connectivity improvement with transmission range r <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ß</sub> larger than r <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¿</sub> for ad hoc nodes. Therefore, our results provide a theoretical understanding of to what extent ad hoc nodes can benefit from base stations in multi-hop wireless networks.}, booktitle={2010 proceedings ieee infocom}, author={Yi, C. and Wang, Wenye}, year={2010} }
 @inproceedings{lu_lu_wang_wang_2010, title={Review and evaluation of security threats on the communication networks in the smart grid}, DOI={10.1109/milcom.2010.5679551}, abstractNote={The smart grid, generally referred to as the next-generation power electric system, relies on robust communication networks to provide efficient, secure, and reliable information delivery. Thus, the network security is of critical importance in the smart grid. In this paper, we aim at classifying and evaluating the security threats on the communication networks in the smart grid. Based on a top-down analysis, we categorize the goals of potential attacks against the smart grid communication networks into three types: network availability, data integrity and information privacy. We then qualitatively analyze both the impact and feasibility of the three types of attacks. Moreover, since network availability is the top priority in the security objectives for the smart grid, we use experiments to quantitatively evaluate the impact of denial-of-service (DoS) attacks on a power substation network. Our work provides initial experimental data of DoS attacks against a power network and shows that the network performance degrades dramatically only when the DoS attack intensity approaches to the maximum.}, booktitle={Military communications conference, 2010 (milcom 2010)}, author={Lu, Z. and Lu, X. A. and Wang, Wenye and Wang, C.}, year={2010}, pages={1830–1835} }
 @inproceedings{sun_wang_2010, title={Topology-incurred delay for information dissemination in large multi-channel cognitive radio networks}, DOI={10.1109/glocom.2010.5683925}, abstractNote={Cognitive Radio (CR) networks have become an important component of the modern communication infrastructure due to their capability of improving spectrum usage efficiency by exploiting channels opportunistically. In CR networks, the network topology changes very frequently because of the temporarily available channels and dynamic transmitting parameters (e.g. transmission power and transmitting frequency), which may even result in network disconnectivity from time to time. Hence an interesting and open question is that: are there bounds on end-to-end delay between a source-destination pair with Euclidean distance d apart in such networks? These bounds are required for time-critical applications. This paper first investigates the nature of topology-incurred end-to-end delay in large multi-channel CR networks and then identifies the conditions under which the asymptotic topology-incurred delay scales linearly with the Euclidean distance (d); that is, the conditions under which the end-to-end delay is bounded. The results in this paper are validated through extensive simulations and can advance our understanding of CR network performance.}, booktitle={2010 ieee global telecommunications conference globecom 2010}, author={Sun, L. and Wang, Wenye}, year={2010} }
 @article{zhao_wang_2009, title={A unified mobility model for analysis and simulation of mobile wireless networks}, volume={15}, ISSN={["1572-8196"]}, DOI={10.1007/s11276-007-0055-4}, number={3}, journal={WIRELESS NETWORKS}, author={Zhao, Ming and Wang, Wenye}, year={2009}, month={Apr}, pages={365–389} }
 @article{agarwal_wang_2009, title={An Experimental Study of the Performance Impact of Path-Based DoS Attacks in Wireless Mesh Networks}, volume={15}, ISSN={1383-469X 1572-8153}, url={http://dx.doi.org/10.1007/s11036-009-0204-3}, DOI={10.1007/s11036-009-0204-3}, number={5}, journal={Mobile Networks and Applications}, publisher={Springer Science and Business Media LLC}, author={Agarwal, Avesh K. and Wang, Wenye}, year={2009}, month={Aug}, pages={693–709} }
 @article{wang_devetsikiotis_2009, title={Special Issue on Advances in Broadband Wireless Networks}, volume={14}, ISSN={["1383-469X"]}, DOI={10.1007/s11036-009-0159-4}, number={4}, journal={MOBILE NETWORKS & APPLICATIONS}, author={Wang, Wenye and Devetsikiotis, Michael}, year={2009}, month={Aug}, pages={365–367} }
 @article{xu_wang_2009, title={Topology Stability Analysis and Its Application in Hierarchical Mobile Ad Hoc Networks}, volume={58}, ISSN={["1939-9359"]}, DOI={10.1109/TVT.2008.928006}, abstractNote={The hierarchical architecture has been proven effective for solving the scalability problems in large-scale ad hoc networks. The stability of the hierarchical architecture is a key factor in determining the network performance. Although many solutions have been proposed to construct stable clusters, the maximum stability achievable in mobile environments is still unknown. In this paper, we define three metrics for measuring network stability: (1) the cluster lifetime;(2) the intercluster link lifetime; and (3) the end-to-end path lifetime. We model and analyze the maximum of these lifetimes under the constraint of random node mobility. Analytical results provide the fundamental understanding of the bounds on network stability. Inspired by this understanding, we propose a clustering algorithm and a hierarchical routing protocol that work together to achieve the maximum network stability. The analytical results are verified by simulations.}, number={3}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Xu, Yi and Wang, Wenye}, year={2009}, month={Mar}, pages={1546–1560} }
 @article{xu_wang_2008, title={Finding the fastest path in wireless networks}, ISBN={["978-1-4244-2074-2"]}, ISSN={["1550-3607"]}, DOI={10.1109/icc.2008.600}, abstractNote={The timeliness of packet delivery is an important performance measure in wireless networks, especially when urgent messages need to be transported through a network. This paper investigates the fastest packet transportation in light-loaded wireless networks. We show that the end-to-end packet delay depends largely on the locations of the relay nodes that forward the packet and there exists a shortest-delay path theoretically. We also propose a routing algorithm to locate a fast relay path in actual networks to achieve the near-shortest packet delay.}, journal={2008 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, PROCEEDINGS, VOLS 1-13}, author={Xu, Yi and Wang, Wenye}, year={2008}, pages={3188–3192} }
 @article{xing_wang_2008, title={On the devolution of large-scale sensor networks in the presence of random failures}, ISBN={["978-1-4244-2074-2"]}, ISSN={["1550-3607"]}, DOI={10.1109/icc.2008.439}, abstractNote={In battery-constrained large-scale sensor networks, nodes are prone to random failures due to various reasons, such as energy depletion and hostile environment. Random failures can substantially impact the communication connectivity, which in turn impairs the sensing coverage. Redeploying additional sensors is one effective way to maintain the connectivity; however, it may be infeasible and costly to replace failed sensors one by one. When should a redeployment be conducted is an interesting and important question in designing resilient sensor networks. In this paper, we tackle this problem by investigating the devolution process of large-scale sensor networks. We first define a new metric called the first partition time, which is the first time that a network starts to discomposes to multiple isolated small components. Then we analyze the devolution process in a geometric random graph from a percolation-based connectivity perspective and obtain the condition under which the graph is not percolated. Finally, we find out that the lower bound of the first partition time depends on the node lifetime distribution and should be of the order between log (log n) and (log n) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/rho</sup> for rho > 1. This result provides a theoretical upper bound of the latest time that a redeployment has to be carried out.}, journal={2008 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, PROCEEDINGS, VOLS 1-13}, author={Xing, Fei and Wang, Wenye}, year={2008}, pages={2304–2308} }
 @article{tezcan_wang_2008, title={Self-orienting wireless multimedia sensor networks for maximizing multimedia coverage}, ISBN={["978-1-4244-2074-2"]}, ISSN={["1550-3607"]}, DOI={10.1109/icc.2008.421}, abstractNote={The performance of a wireless multimedia sensor network (WMSN) is tightly coupled with the pose of individual multimedia sensors. In particular, orientation of an individual multimedia sensor (direction of its sensing unit) is of great importance for the sensor network applications in order to capture the entire image of the field. In this paper, we study the problem of self-orientation in a wireless multimedia sensor network, that is finding the most beneficial pose of multimedia sensors to maximize multimedia coverage with occlusion-free viewpoints. We first propose a distributed algorithm to detect a node's multimedia coverage and then determine its orientation, while minimizing the effect of occlusions and total overlapping regions in the sensing field. Our approach enables multimedia sensor nodes to compute their directional coverage, provisioning self-configurable sensor orientations in an efficient way. Simulations show that using distributed messaging and self-orientation having occlusion-free viewpoints significantly increase the multimedia coverage.}, journal={2008 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, PROCEEDINGS, VOLS 1-13}, author={Tezcan, Nurcan and Wang, Wenye}, year={2008}, pages={2206–2210} }
 @article{tezcan_wang_2008, title={Self-orienting wireless multimedia sensor networks for occlusion-free viewpoints}, volume={52}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2008.05.014}, abstractNote={Wireless multimedia sensor networks (WMSN) are formations of a large number of compact form-factor computing devices that can capture multimedia content, such as video and audio, and communicate them over wireless channels. The efficiency of a WMSN heavily depends on the correct orientation (i.e., view) of its individual sensory units in the field. In this paper, we study the problem of self-orientation in WMSN, that is finding the most beneficial orientation for all multimedia sensors to maximize multimedia coverage. We propose a new algorithm to determine a node’s multimedia coverage and find the sensor orientation that minimizes the negative effect of occlusions and overlapping regions in the sensing field. Our approach enables multimedia sensor nodes to compute their directional coverage leading to an efficient and self-configurable sensor orientation calculation. By using simulations, we show that the occlusion-free viewpoint approach increases the multimedia coverage significantly. The self-orientation methodology is designed in the form of a distributed algorithm, making it a suitable candidate for deployment in practical systems.}, number={13}, journal={COMPUTER NETWORKS}, author={Tezcan, Nurcan and Wang, Wenye}, year={2008}, month={Sep}, pages={2558–2567} }
 @article{wang_eun_wang_2007, title={A dynamic TCP-Aware call admission control scheme. for generic next generation packet-switched wireless networks}, volume={6}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2007.06064}, abstractNote={Traditional call admission control (CAC) schemes only consider call-level performance and are mainly designed for circuit-switched wireless network. Since future wireless communications will become packet-switched systems, the packet-level features could be explored to improve the system performance. This is especially true when the TCP-type of elastic applications are running over such packet-switched wireless networks, as the elasticity of TCP applications has more tolerance toward the throughput/delay variation than non-elastic traffic does. In order to efficiently utilize the system resource from an admission control perspective, we propose a TCP-aware CAC scheme to regulate the packet-level dynamics of TCP flows. We analyze the system performance under realistic scenarios in which (i) the call holding time for non-elastic traffic like voice is independent of system states and (ii) the call holding time for TCP type of traffic depends on the system state, i.e., on the TCP flow's transmission rate. Extensive simulations are presented under different scenarios to show that the proposed scheme can effectively improve the system performance in terms of call blocking probability, call-level throughput (call/min) and link utilization, in accordance with our theoretical results.}, number={9}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Wang, Xinbing and Eun, Do Young and Wang, Wenye}, year={2007}, month={Sep}, pages={3344–3352} }
 @article{agarwal_wang_2007, title={AN EXPERIMENTAL STUDY ON SECURITY PROTOCOLS IN WLANS}, ISSN={["1860-4862"]}, DOI={10.1007/978-0-387-33112-6_12}, journal={WIRELESS NETWORK SECURITY}, publisher={New York: Springer}, author={Agarwal, Avesh Kumar and Wang, Wenye}, year={2007}, pages={295–322} }
 @inbook{xing_wang_2007, title={On the Resilient Overlay Topology Formation in Multi-hop Wireless Networks}, ISBN={9783540726050 9783540726067}, ISSN={0302-9743 1611-3349}, url={http://dx.doi.org/10.1007/978-3-540-72606-7_1}, DOI={10.1007/978-3-540-72606-7_1}, abstractNote={In this paper, we study the problem of how to design overlay topologies in multi-hop wireless networks such that the overlays achieve perfect resilience, in terms of all cooperative nodes included but misbehaving nodes excluded, and preserve the k-connectivity with high probability. To address this problem, we propose a new distributed topology control protocol called PROACtive. By using PROACtive, every node pro-actively selects its cooperative adjacent nodes as neighbors by mutually exchanging neighbor request and reply messages. As a result, the union of all neighbor sets forms a resilient overlay for a given network. Our analysis finds that the PROACtive protocol is light-weighted with the message complexity of only O(m), where m is the number of links in the original network. Our simulation results validate the effectiveness of PROACtive and show that the overlays generated by our protocol preserve the k-connectivity with high probability (> 90%) and low false positive ratio (< 5%).}, booktitle={NETWORKING 2007. Ad Hoc and Sensor Networks, Wireless Networks, Next Generation Internet}, publisher={Springer Berlin Heidelberg}, author={Xing, Fei and Wang, Wenye}, year={2007}, pages={1–12} }
 @article{agarwal_wang_2007, title={On the impact of quality of protection in wireless local area networks with IP mobility}, volume={12}, ISSN={["1572-8153"]}, DOI={10.1007/s11036-006-0009-6}, number={1}, journal={MOBILE NETWORKS & APPLICATIONS}, author={Agarwal, Avesh K. and Wang, Wenye}, year={2007}, month={Feb}, pages={93–110} }
 @article{wang_xue_2006, title={A cost-minimization algorithm for fast location tracking in mobile wireless networks}, volume={50}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2005.09.035}, abstractNote={Location tracking is one of the most important issues in providing real-time applications over wireless networks due to its effect to quality of service (QoS), such as end-to-end delay, bandwidth utilization, and connection dropping probability. In this paper, we study cost minimization for locating mobile users under delay constraints in mobile wireless networks. Specifically, a new location tracking algorithm is developed to determine the position of mobile terminals under delay constraints, while minimizing the average locating cost based on a unimodal property. We demonstrate that the new algorithm not only results in minimum locating cost, but also has a lower computational complexity compared to existing algorithms. Furthermore, detailed searching procedures are discussed under both deterministic and statistic delay bounds. Numerical results for a variety of location probability distributions show that our algorithm compares favorably with existing algorithms.}, number={15}, journal={COMPUTER NETWORKS}, author={Wang, Wenye and Xue, Guoliang}, year={2006}, month={Oct}, pages={2713–2726} }
 @inproceedings{zhao_wang_2006, title={A novel semi-Markov smooth mobility model for mobile ad hoc networks.}, DOI={10.1109/glocom.2006.940}, abstractNote={Existing random mobility models have their limitations such as speed decay and sharp turn which have been demonstrated by the previous studies. More importantly, mobility models need to mimic the movements that abide by the physical law for accurate analysis and simulations of mobile networks. Therefore, in this paper, we propose a novel mobility model, semi-Markov smooth (SMS) model. Each SMS movement includes three consecutive phases: speed up phase, middle smooth phase, and slow down phase. Thus, the entire motion in the SMS model is smooth and consistent with the moving behaviors in real environment. Through steady state analysis, we demonstrate that SMS model has no average speed decay problem and always maintains a uniform spatial node distribution. The analytical results are validated by extensive simulation experiments. In addition, we compare the simulation results on link lifetime and percentage of node degree with random waypoint model, Gauss-Markov model and the proposed SMS model.}, booktitle={Globecom 2006 - 2006 ieee global telecommunications conference}, author={Zhao, M. and Wang, Wenye}, year={2006} }
 @article{song_wang_2006, title={A simulation study of IP-based vertical handoff in wireless convergent networks}, volume={6}, ISSN={["1530-8677"]}, DOI={10.1002/wcm.415}, abstractNote={Abstract The advances in wireless networks and IP technologies has brought ubiquitous access to all‐IP information into reality. For wireless IP services, IP‐based handoff is a critical issue to the performance of application‐level services. Although mobile IP (MIP) and its extensions, as network layer solutions, have been proposed as de facto standard, transmission throughput degradation due to packet loss, registration delay, and transport layer blocking are unavoidable because of MIP handoff mechanisms. In this paper, we evaluate the performance of a transport layer handoff approach, mobile stream control transmission protocol (mSCTP), and compare it with that of a network layer solution, MIP. mSCTP is based on stream control transmission protocol (SCTP), which is the third general purpose transport layer protocol from IETF. We investigate the use of mSCTP for seamless vertical handoff without any change in IP protocol stack by its multi‐homing feature and dynamic address reconfiguration (DAR) extension. We evaluate the performance of mSCTP and MIP by introducing handoff delay, end‐to‐end transmission throughput, and packet loss, and verify our observations by a simulation study of the two protocols in UMTS/802.11b integrated networks using NS‐2 network simulator. Copyright © 2006 John Wiley & Sons, Ltd.}, number={5}, journal={WIRELESS COMMUNICATIONS & MOBILE COMPUTING}, author={Song, Lung Kee and Wang, Wenye}, year={2006}, month={Aug}, pages={629–650} }
 @article{wang_wang_nilsson_2006, title={Energy-efficient bandwidth allocation in wireless networks: Algorithms, analysis, and simulations}, volume={5}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2006.05018}, number={5}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Wang, Wenye and Wang, Xinbing and Nilsson, Arne. A.}, year={2006}, month={May}, pages={1103–1114} }
 @inproceedings{xing_wang_2006, title={Modeling and analysis of connectivity in mobile ad hoc networks with misbehaving nodes}, DOI={10.1109/icc.2006.254994}, abstractNote={Mobile ad hoc networks are vulnerable to malicious attacks and failures due to their unique features, such as node mobility and dynamic network topology. The design and evaluation of routing protocols and topology control require sound analysis on network connectivity and node behaviors. However, little work has been done on how node misbehaviors affect network connectivity. Modeling and analysis of node misbehavior involves many challenges such as multiple failures caused by selfishness, mobility, and potential Denial of Service attacks. Thus, we propose a novel model to characterize node misbehaviors based on a semi-Markov process. In particular, we analyze the impact of node misbehavior on network connectivity in a mobile ad hoc network stochastically. Numerical results based on analysis and simulations are provided to demonstrate the effectiveness of our approach and results.}, booktitle={2006 ieee international conference on communications, vols 1-12}, author={Xing, F. and Wang, Wenye}, year={2006}, pages={1879–1884} }
 @inproceedings{tezcan_wang_2006, title={effective energy conservation in wireless sensor networks}, DOI={10.1109/icc.2006.255235}, abstractNote={In this paper, we present a two-tiered scheduling scheme that provides effective energy conservation in wireless sensor networks. The effectiveness of this scheme relies on dynamically updated two-tiered scheduling architecture. We aim to prolong network lifetime, while preserving the major requirements of wireless sensor networks: coverage and connectivity. In this approach, sensors are periodically scheduled to sleep in two phases using weighted greedy algorithms. First, we establish a coverage-tier by selecting a set of sensors that covers the sensing field in order to provide fully monitoring of entire field. Sensors that are not selected for the coverage-tier, are put into sleep immediately. Then, a second tier, called connectivity-tier, is formed on top of the coverage-tier to forward the data traffic to sink node. Thus sensors, essential to coverage-tier but not in connectivity-tier may periodically sleep and become active only for sending new sensing measurement and receiving query from the sink to preserve coverage. By this way, we may allow more nodes to sleep with different sleeping behaviors, i.e., continuous sleep or periodic sleep/active. Moreover, fair energy consumption among sensors is achieved by periodically rotating the coverage and connectivity tiers. Through extensive simulations in ns2, we demonstrate that the two-tier scheduling can reduce average energy consumption up to 40% while balancing the residual energy of sensors.}, booktitle={2006 ieee international conference on communications, vols 1-12}, author={Tezcan, N. and Wang, Wenye}, year={2006}, pages={3359–3364} }
 @article{mcnair_tugcu_wang_xie_2005, title={A survey of cross-layer performance enhancements for Mobile IP networks}, volume={49}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2005.06.001}, abstractNote={Among the characteristics of future wireless networks is the desire to support a wide range of wireless users and a diverse set of services from many different types of networks. One of the most often referenced networking protocols for diverse wireless and mobile networking is Mobile IP. Although recent focus has been on developing a micro-mobility architecture for Mobile IP, an emerging need is to enhance the unifying performance of Mobile IP by using a cross-layer, cross-technology, approach to protocol design, in order to serve a wide variety of users, services and networks. This paper provides a survey of recently proposed performance enhancements for Mobile IP and discusses the impact on network-level performance. After a review of the Mobile IP architecture, recent research on reducing handoff latency is discussed, including the use of layer 2 hints. Then, location registration is explored, including new techniques for authentication of mobile users. Finally, an overview of performance analysis models is provided to show the most recent approaches to determining the impact of mobility on a given network.}, number={2}, journal={COMPUTER NETWORKS}, author={McNair, J and Tugcu, T and Wang, WY and Xie, JL}, year={2005}, month={Oct}, pages={119–146} }
 @article{wang_liang_agarwal_2005, title={Integration of authentication and mobility management in third generation and WLAN data networks}, volume={5}, ISSN={["1530-8677"]}, DOI={10.1002/wcm.335}, abstractNote={The successful deployment of wireless local area networks (WLAN) for high speed data transmission and cellular systems for wide coverage and global roaming has emerged to be a complementary platform for wireless data communications. In order to fully exploit potentials in 3G/WLAN integration, authentication of roaming users crossing different networks, must be coupled with mobility management, which is a challenging, yet not resolved issue. The focus of this paper is on state-of-art solutions to Wi-Fi and cellular networks based on IP infrastructure. Moreover, we introduce a new authentication architecture for fast authentication during inter-networking handoff and large-scale heterogeneous networks. We show that the new architecture can reduce authentication latency significantly and be adaptive to user mobility and traffic. Copyright © 2005 John Wiley & Sons, Ltd.}, number={6}, journal={WIRELESS COMMUNICATIONS & MOBILE COMPUTING}, author={Wang, WY and Liang, W and Agarwal, AK}, year={2005}, month={Sep}, pages={665–678} }
 @article{liang_wang_2005, title={On performance analysis of challenge/response based authentication in wireless networks}, volume={48}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2004.10.016}, abstractNote={The emergence of public access wireless networks enables ubiquitous Internet services, whereas inducing more challenges of security due to open mediums. As one of the most widely used security mechanisms, authentication is to provide secure communications by preventing unauthorized usage and negotiating credentials for verification. Meanwhile, it generates heavy overhead and delay to communications, further deteriorating overall system performance. Therefore, it is very important to have an in-depth understanding of the relationship between the security and quality of service (QoS) through the authentication in wireless networks. In this paper, we analyze the impact of authentication on the security and QoS quantitatively. First, a system model based on challenge/response authentication mechanism is introduced, which is wide applied in various mobile environments. Then, the concept of security levels is proposed to describe the protection of communications with regard to the nature of security, i.e., information secrecy, data integrity, and resource availability. Third, traffic and mobility patterns are taken into account for quantitative analysis of QoS. Finally, we provide numerical results to demonstrate the impact of security levels, mobility and traffic patterns on overall system performance in terms of authentication cost, delay, and call dropping probability.}, number={2}, journal={COMPUTER NETWORKS}, author={Liang, W and Wang, WY}, year={2005}, month={Jun}, pages={267–288} }
 @article{akyildiz_wang_2004, title={The predictive user mobility profile framework for wireless multimedia networks}, volume={12}, ISSN={["1558-2566"]}, DOI={10.1109/tnet.2004.838604}, abstractNote={User mobility profile (UMP) is a combination of historic records and predictive patterns of mobile terminals, which serve as fundamental information for mobility management and enhancement of quality of service (QoS) in wireless multimedia networks. In this paper, a UMP framework is developed for estimating service patterns and tracking mobile users, including descriptions of location, mobility, and service requirements. For each mobile user, the service requirement is estimated using a mean-square error method. Moreover, a new mobility model is designed to characterize not only stochastic behaviors, but historical records and predictive future locations of mobile users as well. Therefore, our approach incorporates aggregate history and current system parameters to acquire UMP. In particular, an adaptive algorithm is designed to predict the future positions of mobile terminals in terms of location probabilities based on moving directions and residence time in a cell. Simulation results are shown to indicate that the proposed schemes are effective on mobility and resource management by evaluating blocking/dropping probabilities and location tracking costs in wireless networks.}, number={6}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Akyildiz, IR and Wang, WY}, year={2004}, month={Dec}, pages={1021–1035} }
 @inproceedings{wang_zhao, title={Joint effects of radio channels and node mobility on link dynamics in wireless networks}, booktitle={27th ieee conference on computer communications (infocom), vols 1-5}, author={Wang, W. Y. and Zhao, M.}, pages={1606–1614} }
 @inproceedings{agarwal_wang, title={Measuring performance impact of security protocols in wireless local area networks}, booktitle={2nd International Conference on Broadband Networks (Broadnets 2005)}, author={Agarwal, A. K. and Wang, W. Y.}, pages={625-} }
 @article{li_wang, title={Modeling and analysis of single-hop mobile cloudlet}, journal={Advances in Mobile Cloud Computing Systems}, author={Li, Y. J. and Wang, W. Y.}, pages={231–256} }
 @inproceedings{pambudi_wang_wang, title={On the resilience of D2D-based social networking service against random failures}, booktitle={2016 ieee global communications conference (globecom)}, author={Pambudi, S. A. and Wang, W. Y. and Wang, C.} }
 @inproceedings{xu_wang, title={The speed of information propagation in large wireless networks}, booktitle={27th IEEE Conference on Computer Communications (Infocom), vols 1-5}, author={Xu, Y. and Wang, W. Y.}, pages={403–411} }