@article{hu_doshi_eun_2024, title={Minimizing File Transfer Time in Opportunistic Spectrum Access Model}, volume={23}, ISSN={["1558-0660"]}, url={https://doi.org/10.1109/TMC.2022.3212926}, DOI={10.1109/TMC.2022.3212926}, abstractNote={We study the file transfer problem in opportunistic spectrum access (OSA) model, which has been widely studied in throughput-oriented applications for max-throughput strategies and in delay-related works that commonly assume identical channel rates and fixed file sizes. Our work explicitly considers minimizing the file transfer time for a given file in a set of heterogeneous-rate Bernoulli channels, showing that max-throughput policy doesn't minimize file transfer time in general. We formulate a mathematical framework for static extend to dynamic policies by mapping our file transfer problem to a stochastic shortest path problem. We analyze the performance of our proposed static and dynamic optimal policies over the max-throughput policy. We propose a mixed-integer programming formulation as an efficient alternative way to obtain the dynamic optimal policy and show a huge reduction in computation time. Then, we propose a heuristic policy that takes into account the performance-complexity tradeoff and consider the online implementation with unknown channel parameters. Furthermore, we present numerical simulations to support our analytical results and discuss the effect of switching delay on different policies. Finally, we extend the file transfer problem to Markovian channels and demonstrate the impact of the correlation of each channel.}, number={1}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Hu, Jie and Doshi, Vishwaraj and Eun, Do Young}, year={2024}, month={Jan}, pages={630–644} }
 @article{doshi_mallick_eun_2023, title={Convergence of Bi-Virus Epidemic Models With Non-Linear Rates on Networks-A Monotone Dynamical Systems Approach}, volume={31}, ISSN={["1558-2566"]}, DOI={10.1109/TNET.2022.3213015}, abstractNote={We study convergence properties of competing epidemic models of the Susceptible-Infected-Susceptible ( $SIS$ ) type. The SIS epidemic model has seen widespread popularity in modelling the spreading dynamics of contagions such as viruses, infectious diseases, or even rumors/opinions over contact networks (graphs). We analyze the case of two such viruses spreading on overlaid graphs, with non-linear rates of infection spread and recovery. We call this the non-linear bi-virus model and, building upon recent results, obtain precise conditions for global convergence of the solutions to a trichotomy of possible outcomes: a virus-free state, a single-virus state, and to a coexistence state. Our techniques are based on the theory of monotone dynamical systems (MDS), in contrast to Lyapunov based techniques that have only seen partial success in determining convergence properties in the setting of competing epidemics. We demonstrate how the existing works have been unsuccessful in characterizing a large subset of the model parameter space for bi-virus epidemics, including all scenarios leading to coexistence of the epidemics. To the best of our knowledge, our results are the first in providing complete convergence analysis for the bi-virus system with non-linear infection and recovery rates on general graphs.}, number={3}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Doshi, Vishwaraj and Mallick, Shailaja and Eun, Do Young}, year={2023}, month={Jun}, pages={1187–1201} }
 @article{doshi_mallick_eun_2021, title={Competing Epidemics on Graphs - Global Convergence and Coexistence}, ISSN={["0743-166X"]}, DOI={10.1109/INFOCOM42981.2021.9488828}, abstractNote={The dynamics of the spread of contagions such as viruses, infectious diseases or even rumors/opinions over contact networks (graphs) have effectively been captured by the well known Susceptible-Infected-Susceptible (SIS) epidemic model in recent years. When it comes to competition between two such contagions spreading on overlaid graphs, their propagation is captured by so-called bi-virus epidemic models. Analysis of such dynamical systems involve the identification of equilibrium points and its convergence properties, which determine whether either of the viruses dies out, or both survive together. We demonstrate how the existing works are unsuccessful in characterizing a large subset of the model parameter space, including all parameters for which the competitiveness of the bi-virus system is significant enough to attain coexistence of the epidemics. In this paper, we fill in this void and obtain convergence results for the entirety of the model parameter space; giving precise conditions (necessary and sufficient) under which the system globally converges to a trichotomy of possible outcomes: a virus-free state, a single-virus state, and to a coexistence state – the first such result.}, journal={IEEE CONFERENCE ON COMPUTER COMMUNICATIONS (IEEE INFOCOM 2021)}, author={Doshi, Vishwaraj and Mallick, Shailaja and Eun, Do Young}, year={2021} }
 @article{chattopadhyay_dai_eun_2021, title={Controlling Metastable Infection Patterns in Multilayer Networks via Interlink Design}, volume={8}, ISSN={["2327-4697"]}, DOI={10.1109/TNSE.2021.3108075}, abstractNote={Recent research on epidemic spreading in networks has uncovered the phenomena of metastable infection patterns, where epidemics can be sustained in localized regions of activity, in contrast to the classical dichotomy between a quick extinction of infections and a network-wide global infection. Our objective in this work is to leverage this localized infection state to achieve controlled spreading in multilayer networks via intelligent design of the interlink structure between the network layers. Following the approach in recent works, the dynamic contact process is approximated by studying the dynamics in local regions around the hubs of the network. This allows us to approximately track the contact process in the near-threshold regime and estimate the mean metastable infection size over the lifetime of the infection. Furthermore, interlinking strategies are devised that can achieve a desired infection size under certain conditions. Theoretically optimal interlink structures can be derived under special cases, whereas greedy strategies are proposed for the general case. We compare the interlinking strategies developed in this work to some popular heuristics and demonstrate their superiority by extensive simulation experiments on both synthetic and real-world networks.}, number={4}, journal={IEEE TRANSACTIONS ON NETWORK SCIENCE AND ENGINEERING}, author={Chattopadhyay, Srinjoy and Dai, Huaiyu and Eun, Do Young}, year={2021}, month={Oct}, pages={3242–3256} }
 @article{hosseinalipour_rahmati_eun_dai_2021, title={Energy-Aware Stochastic UAV-Assisted Surveillance}, volume={20}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2020.3044490}, abstractNote={With the ease of deployment, capabilities of evading the jammers and obscuring their existence, unmanned aerial vehicles (UAVs) are one of the most suitable candidates to perform surveillance. There exists a body of literature in which the inspectors follow a deterministic trajectory to conduct surveillance, which results in a predictable environment for malicious entities. Thus, introducing randomness to the surveillance is of particular interest. In this work, we propose a novel framework for stochastic UAV-assisted surveillance that i) inherently considers the battery constraints of the UAVs, ii) proposes random moving patterns modeled via random walks, and iii) adds another degree of randomness to the system via considering probabilistic inspections. We formulate the problem of interest, i.e., obtaining the energy-efficient random walk and inspection policies of the UAVs subject to probabilistic constraints on inspection criteria of the sites and battery consumption of the UAVs, which turns out to be signomial programming that is highly non-convex. To solve it, we propose a centralized and a distributed algorithm along with their performance guarantee. This work contributes to both UAV-assisted surveillance and classic random walk literature by designing random walks with random inspection policies on weighted graphs with energy limited random walkers.}, number={5}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Hosseinalipour, Seyyedali and Rahmati, Ali and Eun, Do Young and Dai, Huaiyu}, year={2021}, month={May}, pages={2820–2837} }
 @article{chattopadhyay_dai_eun_2020, title={Maximization of Robustness of Interdependent Networks Under Budget Constraints}, volume={7}, ISSN={["2327-4697"]}, DOI={10.1109/TNSE.2019.2935068}, abstractNote={We consider the problem of interlink optimization in multilayer interdependent networks under cost constraints, with the objective of maximizing the robustness of the network against component (node) failures. Diverting from the popular approaches of branching process based analysis of the failure cascades or using a supra-adjacency matrix representation of the multilayer network and employing classical metrics, in this work, we present a surrogate metric based framework for constructing interlinks to maximize the network robustness. In particular, we focus on three representative mechanisms of failure propagation, namely, connected component based cascading failure, load distribution in interdependent networks, and connectivity in demand-supply networks, and propose metrics to track the network robustness for each of these mechanisms. Owing to their mathematical tractability, these metrics allow us to optimize the interlink structure to enhance robustness. Furthermore, we are able to introduce the cost of construction into the interlink design problem, a practical feature largely ignored in relevant literature. We simulate the failure cascades on real world networks to compare the performance of our interlinking strategies with the state of the art heuristics and demonstrate their effectiveness.}, number={3}, journal={IEEE TRANSACTIONS ON NETWORK SCIENCE AND ENGINEERING}, author={Chattopadhyay, Srinjoy and Dai, Huaiyu and Eun, Do Young}, year={2020}, pages={1441–1452} }
 @article{hosseinalipour_mao_eun_dai_2020, title={Prevention and Mitigation of Catastrophic Failures in Demand-Supply Interdependent Networks}, volume={7}, ISSN={["2327-4697"]}, DOI={10.1109/TNSE.2019.2951084}, abstractNote={We propose a generic system model for a special category of interdependent networks, demand-supply networks, in which the demand and the supply nodes are associated with heterogeneous loads and resources, respectively. Our model sheds a light on a unique cascading failure mechanism induced by resource/load fluctuations, which in turn opens the door to conducting stress analysis on interdependent networks. Compared to the existing literature mainly concerned with the node connectivity, we focus on developing effective resource allocation methods to prevent these cascading failures from happening and to mitigate/confine them upon occurrence in the network. To prevent cascading failures, we identify some dangerous stress mechanisms, based on which we quantify the robustness of the network in terms of the resource configuration scheme. Afterward, we identify the optimal resource configuration under two resource/load fluctuations scenarios: uniform and proportional fluctuations. We further investigate the optimal resource configuration problem considering heterogeneous resource sharing costs among the nodes. To mitigate/confine ongoing cascading failures, we propose two network adaptations mechanisms: intentional failure and resource re-adjustment, based on which we propose an algorithm to mitigate an ongoing cascading failure while reinforcing the surviving network with a high robustness to avoid further failures.}, number={3}, journal={IEEE TRANSACTIONS ON NETWORK SCIENCE AND ENGINEERING}, author={Hosseinalipour, Seyyedali and Mao, Jiayu and Eun, Do Young and Dai, Huaiyu}, year={2020}, pages={1710–1723} }
 @inproceedings{lee_kang_eun_2019, title={Non-Markovian Monte Carlo on Directed Graphs}, volume={3}, number={1}, booktitle={Proceedings of the ACM on Measurement and Analysis of Computing Systems (POMACS)}, author={Lee, Chul-Ho and Kang, Min and Eun, Do Young}, year={2019}, month={Mar} }
 @article{lee_tenneti_eun_2019, title={Transient Dynamics of Epidemic Spreading and Its Mitigation on Large Networks}, DOI={10.1145/3323679.3326517}, abstractNote={In this paper, we aim to understand the transient dynamics of a susceptible-infected (SI) epidemic spreading process on a large network. The SI model has been largely overlooked in the literature, while it is naturally a better fit for modeling the malware propagation in early times when patches/vaccines are not available, or over a wider range of timescales when massive patching is practically infeasible. Nonetheless, its analysis is simply non-trivial, as its important dynamics are all transient and the usual stability/steady-state analysis no longer applies. To this end, we develop a theoretical framework that allows us to obtain an accurate closed-form approximate solution to the original SI dynamics on any arbitrary network, which captures the temporal dynamics over all time and is tighter than the existing approximation, and also to provide a new interpretation via reliability theory. As its applications, we further develop vaccination policies with or without knowledge of already-infected nodes, to mitigate the future epidemic spreading to the extent possible, and demonstrate their effectiveness through numerical simulations.}, journal={PROCEEDINGS OF THE 2019 THE TWENTIETH ACM INTERNATIONAL SYMPOSIUM ON MOBILE AD HOC NETWORKING AND COMPUTING (MOBIHOC '19)}, author={Lee, Chul-Ho and Tenneti, Srinivas and Eun, Do Young}, year={2019}, pages={191–200} }
 @inproceedings{xu_lee_eun_2017, title={Challenging the limits: Sampling online social networks with cost constraints}, DOI={10.1109/infocom.2017.8057169}, abstractNote={Graph sampling techniques via random walk crawling have been popular for analyzing statistical characteristics of large online social networks due to simple implementation and provable guarantees on unbiased estimates. Despite the growing popularity, the ‘cost’ of sampling and its true impact on the accuracy of estimates still have not been carefully studied. In addition, the random walk-based methods inherently suffer from the sluggish nature of random walks and the ‘slow-mixing’ structure of social graphs, thereby leading to high correlation in the samples obtained. With these in mind, in this paper, we develop a mathematical framework such that the cost of sampling is properly taken into account, which in turn re-defines a widely used asymptotic variance into a cost-based asymptotic variance. Our new metric enables us to compare a class of sampling policies under the same cost constraint, integrating “random skipping” (bypassing nodes without sampling) into the random walk-based sampling. We obtain an optimal policy striking the right balance between sampling quality (less correlation) and sampling quantity (higher cost per sample), which greatly improves over the usual skip-free crawling-based samplers. We further extend our framework, enabling one to design more sophisticated sampling strategies with an array of control knobs, which all produce unbiased estimates under the same cost constraint.}, booktitle={Ieee infocom 2017 - ieee conference on computer communications}, author={Xu, X. and Lee, C. H. and Eun, D. Y.}, year={2017} }
 @article{chattopadhyay_dai_eun_hosseinalipour_2017, title={Designing Optimal Interlink Patterns to Maximize Robustness of Interdependent Networks Against Cascading Failures}, volume={65}, ISSN={["1558-0857"]}, DOI={10.1109/tcomm.2017.2709302}, abstractNote={In this paper, we consider the optimal design of interlinks for an interdependent system of networks. In contrast to existing literature, we explicitly exploit the information of intra-layer node degrees to design interdependent structures such that their robustness against cascading failures, triggered by randomized attacks, is maximized. Utilizing percolation theory-based system equations relating the robustness of the network to its degree sequence, we characterize the optimal design for the one-to-one structure, with complete interdependence and partial interdependence, under randomized attack. We also extend our study to the one-to-many interdependence structure and the targeted attack model. The theoretically derived optimal interdependence structures have been verified using simulations on scale-free networks.}, number={9}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Chattopadhyay, Srinjoy and Dai, Huaiyu and Eun, Do Young and Hosseinalipour, Seyyedali}, year={2017}, month={Sep}, pages={3847–3862} }
 @inproceedings{lee_xu_eun_2017, title={On the rao-blackwellization and its application for graph sampling via neighborhood exploration}, DOI={10.1109/infocom.2017.8057071}, abstractNote={We study how the so-called Rao-Blackwellization, which is a variance reduction technique via “conditioning” for Monte Carlo methods, can be judiciously applied for graph sampling through neighborhood exploration. Despite its popularity for Monte Carlo methods, it is little known for Markov chain Monte Carlo methods and has never been discussed for random walk-based graph sampling. We first propose two forms of Rao-Blackwellization that can be used as a swap-in replacement for virtually all (reversible) random-walk graph sampling methods, and prove that the ‘Rao-Blackwellized’ estimators reduce the (asymptotic) variances of their original estimators yet maintain their inherent unbiasedness. The variance reduction can translate into lowering the number of samples required to achieve a desired sampling accuracy. However, the sampling cost for neighborhood exploration, if required, may outweigh such improvement, even leading to higher total amortized cost. Considering this, we provide a generalization of Rao-Blackwellization, which allows one to choose a suitable extent of obtaining Rao-Blackwellized samples in order to achieve a right balance between sampling cost and accuracy. We finally provide simulation results via real-world datasets that confirm our theoretical findings.}, booktitle={Ieee infocom 2017 - ieee conference on computer communications}, author={Lee, C. H. and Xu, X. and Eun, D. Y.}, year={2017} }
 @article{kwak_lee_eun_2016, title={A High-Order Markov-Chain-Based Scheduling Algorithm for Low Delay in CSMA Networks}, volume={24}, ISSN={["1558-2566"]}, DOI={10.1109/tnet.2015.2458703}, abstractNote={Recently, several CSMA algorithms based on the Glauber dynamics model have been proposed for wireless link scheduling, as viable solutions to achieve the throughput optimality, yet simple to implement. However, their delay performance still remains unsatisfactory, mainly due to the nature of the underlying Markov chains that imposes a fundamental constraint on how the link state can evolve over time. In this paper, we propose a new approach toward better queueing delay performance, based on our observation that the algorithm needs not be Markovian, as long as it can be implemented in a distributed manner. Our approach hinges upon utilizing past state information observed by local link and then constructing a high-order Markov chain for the evolution of the feasible link schedules. We show that our proposed algorithm, named delayed CSMA, achieves the throughput optimality, and also provides much better delay performance by effectively “decorrelating” the link state process (and thus resolves link starvation). Our simulation results demonstrate that the delay under our algorithm can be reduced by a factor of 20 in some cases, compared to the standard Glauber-dynamics-based CSMA algorithm.}, number={4}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Kwak, Jaewook and Lee, Chul-Ho and Eun, Do Young}, year={2016}, month={Aug}, pages={2278–2290} }
 @inproceedings{kwak_eun_2016, title={An antithetic coupling approach to multi-chain based CSMA scheduling algorithms}, DOI={10.1109/infocom.2016.7524595}, abstractNote={In recent years, a suite of Glauber dynamics-based CSMA algorithms have attracted great attention due to their simple, distributed implementations with guaranteed throughput-optimality. However, these algorithms often suffer from poor delay performance and the starvation problem. Among several attempts to improve the delay performance, a remarkable improvement has recently been made in a class of CSMA algorithms that utilize multiple instances of the algorithm (or Markov chains). In this paper, we develop a new approach via an antithetic coupling (AC) method, which can further improve the delay performance of those that virtually emulate multiple chains. The key enabler of utilizing AC method lies in our skilful choice of manipulating the driving sequences of random variables that govern the evolution of schedule instances, in such a way that those multiple instances of chains become negatively correlated as oppose to having them run independently. This contributes faster change of the link state, rendering it more like a periodic process and thus leading to better queueing performance. We rigorously establish an ordering relationship for the effective bandwidth of each net-input process to the queue, between our proposed algorithm (AC-CSMA) and other state-of-the-art existing algorithms in the literature, under a mild set of assumptions. The proposed algorithm involves very simple modification onto existing CSMA-based algorithms, and can be implemented in a fully distributed manner without any additional message overhead. Our extensive simulation results also confirm that AC-CSMA always delivers better queueing performance over a variety of network scenarios.}, booktitle={IEEE INFOCOM 2016 - the 35th annual IEEE international Conference on Computer Communications}, author={Kwak, J. and Eun, D. Y.}, year={2016} }
 @article{jeong_yi_cho_eun_chong_2016, title={Energy-Efficient Wi-Fi Sensing Policy Under Generalized Mobility Patterns With Aging}, volume={24}, ISSN={["1558-2566"]}, DOI={10.1109/tnet.2015.2468590}, abstractNote={An essential condition precedent to the success of mobile applications based on Wi-Fi (e.g., iCloud) is an energy-efficient Wi-Fi sensing. Clearly, a good Wi-Fi sensing policy should factor in both inter-access point (AP) arrival time (IAT) and contact duration time (CDT) distributions of each individual. However, prior work focuses on limited cases of those two distributions (e.g., exponential) or proposes heuristic approaches such as Additive Increase (AI). In this paper, we first formulate a generalized functional optimization problem on Wi-Fi sensing under general inter-AP and contact duration distributions and investigate how each individual should sense Wi-Fi APs to strike a good balance between energy efficiency and performance, which is in turn intricately linked with users mobility patterns. We then derive a generic optimal condition that sheds insights into the aging property, underpinning energy-aware Wi-Fi sensing polices. In harnessing our analytical findings and the implications thereof, we develop a new sensing algorithm, called Wi-Fi Sensing with AGing (WiSAG), and demonstrate that WiSAG outperforms the existing sensing algorithms up to 37% through extensive trace-driven simulations for which real mobility traces gathered from hundreds of smartphones is used.}, number={4}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Jeong, Jaeseong and Yi, Yung and Cho, Jeong-Woo and Eun, Do Young and Chong, Song}, year={2016}, month={Aug}, pages={2416–2428} }
 @article{lee_eun_2016, title={Exploiting Heterogeneity for Improving Forwarding Performance in Mobile Opportunistic Networks: An Analytic Approach}, volume={15}, ISSN={["1558-0660"]}, DOI={10.1109/tmc.2015.2407406}, abstractNote={Heterogeneity arises in a wide range of scenarios in mobile opportunistic networks and is one of the key factors that govern the performance of forwarding algorithms. While the heterogeneity has been empirically investigated and exploited in the design of new forwarding algorithms, it has been typically ignored or marginalized when it comes to rigorous performance analysis of such algorithms. In this paper, we develop an analytical framework to quantify the performance gain achievable by exploiting the heterogeneity in mobile nodes' contact dynamics. In particular, we derive a delay upper bound of a heterogeneity-aware static forwarding policy per each given number of message copies and obtain its closed-form expression, which enables our quantitative study on the benefit of leveraging underlying heterogeneity structure in the design of forwarding algorithms. In addition, we develop a dynamic forwarding policy that performs as an extension of the static forwarding policy while proven to improve the delay performance. We then demonstrate that only a small fraction of total (unlimited) message copies, via both static and dynamic forwarding policies, are enough under various heterogeneous network settings to achieve the same delay as that obtained using the unlimited message copies when the networks become homogeneous. We also show that, given the same number of message copies, our dynamic forwarding policy significantly outperforms the `homogeneous-optimal' forwarding policy (up to about 50 percent improvement in the delay performance), especially when the number of message copies allowed in the networks is small.}, number={1}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Lee, Chul-Ho and Eun, Do Young}, year={2016}, month={Jan}, pages={150–162} }
 @article{choi_eun_2016, title={Optimal CSMA Scheduling With Look Ahead Mechanism for Wireless Networks}, volume={5}, ISSN={["2162-2345"]}, DOI={10.1109/lwc.2016.2596745}, abstractNote={Optimal carrier sense multiple access (CSMA) scheduling algorithms such as Q-CSMA suffer from large delay, mainly due to the strong correlations residing in consecutive link schedules. Some previous works have remedied this issue with multiple instances of the scheduler, but the baseline scheduler (Q-CSMA) itself remains untouched. By noticing the inherent inefficiency in the contention mechanism of Q-CSMA, we propose looks ahead (LA)-CSMA algorithm in which each link LA its state update in advance and utilizes this free information during the contention stage. We show that our algorithm achieves optimal throughput with reduced correlation in the service process, thereby leading to significantly smaller delay without any additional overhead.}, number={5}, journal={IEEE WIRELESS COMMUNICATIONS LETTERS}, author={Choi, Jin-Ghoo and Eun, Do Young}, year={2016}, month={Oct}, pages={508–511} }
 @article{lee_kwak_eun_2016, title={Towards Distributed Optimal Movement Strategy for Data Gathering in Wireless Sensor Networks}, volume={27}, ISSN={["1558-2183"]}, DOI={10.1109/tpds.2015.2407893}, abstractNote={In this paper, we address how to design a distributed movement strategy for mobile collectors, which can be either physical mobile agents or query/collector packets periodically launched by the sink, to achieve successful data gathering in wireless sensor networks. Formulating the problem as general random walks on a graph composed of sensor nodes, we analyze how much data can be successfully gathered in time under any Markovian random-walk movement strategies for mobile collectors moving over a graph (or network), while each sensor node is equipped with limited buffer space and data arrival rates are heterogeneous over different sensor nodes. In particular, from the analysis, we obtain the optimal movement strategy among a class of Markovian strategies so as to minimize the data loss rate over all sensor nodes, and explain how such an optimal movement strategy can be made to work in a distributed fashion. We demonstrate that our distributed optimal movement strategy can lead to about two times smaller loss rate than a standard random walk strategy under diverse scenarios. In particular, our strategy results in up to 70 percent cost savings for the deployment of multiple collectors to achieve the target data loss rate than the standard random walk strategy.}, number={2}, journal={IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS}, author={Lee, Chul-Ho and Kwak, Jaewook and Eun, Do Young}, year={2016}, month={Feb}, pages={574–584} }
 @article{lee_eun_2015, title={Characterizing link connectivity in opportunistic networks}, journal={Opportunistic Mobile Social Networks}, author={Lee, C. H. and Eun, D. Y.}, year={2015}, pages={71–97} }
 @inproceedings{xu_chen_eun_2015, title={Modeling time-sensitive information diffusion in online social networks}, DOI={10.1109/infcomw.2015.7179419}, abstractNote={After a piece of information is released in Online Social Networks (OSNs), will it spread to the entire network or reach only a small population of users? In a time window of interest, how many users will forward or comment on this information? Limited effort has been made at this point to develop an effective model to address these issues, as the time-sensitive nature of information spreading and the complexity of network structure make it a very challenging task. In this paper, we propose a continuous-time model for information diffusion with time-varying diffusion (infection) rate to address these issues, and provide an interface between our proposed model and the well-studied SI model with constant diffusion rate. We prove that there exists an elegant time-rescaling relationship between these two cases, such that any available result on the standard SI model can readily carry over to our time-varying case. We then show how the shape of the time-dependent infection rate will influence the temporal evolution of the size of infection and the time until the information reaches a given node on a graph. This also explains why some information stops spreading before reaching the entire population. Simulation results on Digg graph validate our findings.}, booktitle={2015 ieee conference on computer communications workshops (infocom wkshps)}, author={Xu, X. and Chen, X. and Eun, D. Y.}, year={2015}, pages={408–413} }
 @inproceedings{lee_eun_2015, title={On the efficiency-optimal Markov chains for distributed networking applications}, DOI={10.1109/infocom.2015.7218566}, abstractNote={The Metropolis-Hastings (MH) algorithm, in addition to its application for Markov Chain Monte Carlo sampling or simulation, has been popularly used for constructing a random walk that achieves a given, desired stationary distribution over a graph. Applications include crawling-based sampling of large graphs or online social networks, statistical estimation or inference from massive scale of networked data, efficient searching algorithms in unstructured peer-to-peer networks, randomized routing and movement strategies in wireless sensor networks, to list a few. Despite its versatility, the MH algorithm often causes self-transitions of its resulting random walk at some nodes, which is not efficient in the sense of the Peskun ordering - a partial order between off-diagonal elements of transition matrices of two different Markov chains, and in turn results in deficient performance in terms of asymptotic variance of time averages and expected hitting times with slower speed of convergence. To alleviate this problem, we present simple yet effective distributed algorithms that are guaranteed to improve the MH algorithm over time when running on a graph, and eventually reach `efficiency-optimality', while ensuring the same desired stationary distribution throughout.}, booktitle={2015 ieee conference on computer communications (infocom)}, author={Lee, C. H. and Eun, D. Y.}, year={2015} }
 @inproceedings{xu_lee_eun_2014, title={A general framework of hybrid graph sampling for complex network analysis}, DOI={10.1109/infocom.2014.6848229}, abstractNote={Being able to capture the properties of massive real graphs and also greatly reduce data scale and processing complexity, graph sampling techniques provide an efficient tool for complex network analysis. Random walk-based sampling has become popular to obtain asymptotically uniform samples in the recent literature. However, it produces highly correlated samples and often leads to poor estimation accuracy in sampling large networks. Another widely-used approach is to launch random jump by querying randomly generated user/node ID, but also has the drawback of unexpected cost when the ID space is sparsely populated. In this paper, we develop a hybrid graph sampling framework that inherits the benefit of returning immediate samples from random walk-based crawling, while incorporating the advantage of reducing the correlation in the obtained samples from random jump. We aim to strike the right balance between random jump and crawling by analyzing the resulting asymptotic variance of an estimator of any graph nodal property, in order to give guidelines on the design of better graph sampling methods. We also provide simulation results on real network (graph) to confirm our theoretical findings.}, booktitle={2014 proceedings ieee infocom}, author={Xu, X. and Lee, C. H. and Eun, D. Y.}, year={2014}, pages={2795–2803} }
 @inproceedings{kwak_lee_eun_2014, title={A high-order Markov chain based scheduling algorithm for low delay in CSMA networks}, DOI={10.1109/infocom.2014.6848103}, abstractNote={Recently, several CSMA algorithms based on the Glauber dynamics model have been proposed for multihop wireless scheduling, as viable solutions to achieve the throughput optimality, yet simple to implement. However, their delay performance still remains unsatisfactory, mainly due to the nature of the underlying Markov chains that imposes a fundamental constraint on how the link state can evolve over time. In this paper, we propose a new approach toward better queueing delay performance, based on our observation that the algorithm needs not be Markovian, as long as it can be implemented in a distributed manner. Our approach hinges upon utilizing past state information observed by local link and then constructing a high-order Markov chain for the evolution of the feasible link schedules. We show in theory and simulation that our proposed algorithm, named delayed CSMA, achieves the throughput optimality, and also provides much better delay performance by effectively `de-correlating' the link state process (and thus resolves link starvation). Our extensive simulations demonstrate that the delay under our algorithm can be often reduced by a factor of 20 over a wide range of scenarios, compared to the standard Glauber-dynamics-based CSMA algorithm.}, booktitle={2014 proceedings ieee infocom}, author={Kwak, J. and Lee, C. H. and Eun, D. Y.}, year={2014}, pages={1662–1670} }
 @inproceedings{lee_kwak_eun_2013, title={Characterizing link connectivity for opportunistic mobile networking: Does mobility suffice?}, DOI={10.1109/infcom.2013.6567009}, abstractNote={With recent drastic growth in the number of users carrying smart mobile devices, it is not hard to envision opportunistic ad-hoc communications taking place with such devices carried by humans. This leads to, however, a new challenge to the conventional link-level metrics, solely defined based on user mobility, such as inter-contact time, since there are many constraints including limited battery power that prevent the wireless interface of each user from being always `on' for communication. By taking into account the process of each user's availability jointly with mobility-induced contact/inter-contact process, we investigate how each of them affects the link-level connectivity depending on their relative operating time scales. We then identify three distinct regimes in each of which (1) the so-called impact of mobility on network performance prevails; (2) such impact of mobility disappears or its extent is not that significant; (3) the user availability process becomes dominant. Our findings not only caution that mobility alone is not sufficient to characterize the link-level dynamics, which in turn can lead to highly misleading results, but also suggest the presence of many uncharted research territories for further exploration.}, booktitle={2013 proceedings ieee infocom}, author={Lee, C. H. and Kwak, J. and Eun, D. Y.}, year={2013}, pages={2076–2084} }
 @article{lee_eun_2013, title={On the Forwarding Performance under Heterogeneous Contact Dynamics in Mobile Opportunistic Networks}, volume={12}, ISSN={["1558-0660"]}, DOI={10.1109/tmc.2012.84}, abstractNote={In this paper, we focus on how the heterogeneous contact dynamics of mobile nodes impact the performance of forwarding algorithms in mobile opportunistic networks (MONs). To this end, we consider two representative heterogeneous network models, each of which captures heterogeneity among node pairs (individual) and heterogeneity in underlying environment (spatial), respectively, and examine the full extent of difference in delay performance they cause on forwarding algorithms through formal stochastic comparisons. We first show that these heterogeneous models correctly capture non-Poisson contact dynamics observed in real traces. We then rigorously establish stochastic/convex ordering relationships on the delay performance of direct forwarding and multicopy two-hop relay protocol under these heterogeneous models and the corresponding homogeneous model, all of which have the same average intercontact time of a random pair of nodes. In particular, we demonstrate that the heterogeneous models predict an entirely opposite ordering relationship in delay performance depending on which of the two heterogeneity structures is captured. We also provide simulation results including the delay performance of epidemic routing protocol to support the analytical findings. Our results thus suggest that the heterogeneity in mobile nodes' contact dynamics should be properly taken into account for the performance evaluation of forwarding algorithms. Our results will also be useful for better design of forwarding algorithms correctly exploiting the heterogeneity structure.}, number={6}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Lee, Chul-Ho and Eun, Do Young}, year={2013}, month={Jun}, pages={1107–1119} }
 @inproceedings{lee_eun_2011, title={Smart sleep: sleep more to reduce delay in duty-cycled wireless sensor networks}, DOI={10.1109/infcom.2011.5935237}, abstractNote={A simple random walk (SRW) has been considered as an effective forwarding method for many applications in wireless sensor networks (WSNs) due to its desirable properties. However, a critical downside of SRW - slow diffusion or exploration over the space, typically leads to longer packet delay and undermines its own benefits. Such slow-mixing problem becomes even worse under random duty cycling adopted for energy conservation. In this paper, we study how to overcome this problem without any sacrifice or tradeoff, and propose a simple modification of random duty cycling, named Smart Sleep, which achieves more power-saving as well as faster packet diffusion (or smaller delay) while retaining the benefits of SRW. We also introduce a class of p-backtracking random walks and establish its properties to analytically explain the fast packet diffusion induced by Smart Sleep. We further obtain a necessary condition to achieve an optimal performance under our Smart Sleep, and finally demonstrate remarkable performance improvement via independent simulation results over various network topologies.}, booktitle={2011 proceedings ieee infocom}, author={Lee, C. H. and Eun, D. Y.}, year={2011}, pages={611–615} }
 @inproceedings{lee_eun_2010, title={A Distributed Wake-up Scheduling for Opportunistic Forwarding in Wireless Sensor Networks}, DOI={10.1109/glocom.2010.5683254}, abstractNote={In wireless sensor networks (WSNs), sensor nodes are typically subjected to energy constraints and often prone to topology changes. While \emph{duty cycling} has been widely used for energy conservation in WSNs, \emph{random walks} have been popular for many delay-tolerant applications in WSNs due to their many inherent desirable properties. In this paper, we consider an opportunistic forwarding under an asynchronous and heterogeneous duty cycling. We first show that its resulting packet trajectory can be interpreted as a continuous-time random walk, and then provide an analytical formula for its end-to-end delay. Since the extremely large end-to-end delay is still undesirable even for most delay-tolerant applications, we develop a \emph{distributed} wake-up scheduling algorithm in which each node autonomously adjusts its (heterogeneous) wake-up rate based \emph{only} on its own degree information so as to improve the worst-case end-to-end delay. In particular, we prove that our algorithm outperforms pure homogeneous duty cycling, where every node uses the same wake-up rate, in its guaranteed asymptotic upper bound of the worst-case delay for \emph{any} graph. In addition, we show that our proposed algorithm brings out more than $35\%$ performance improvement on average when compared with pure homogeneous duty cycling, under various settings of random geometric graphs via numerical evaluations and independent simulation results.}, booktitle={2010 ieee global telecommunications conference globecom 2010}, author={Lee, C. H. and Eun, D. Y.}, year={2010} }
 @inproceedings{kim_eun_2010, title={Age invariant regime for multi-source content update in mobile opportunistic networks}, DOI={10.1109/glocom.2010.5683934}, abstractNote={In the multi-source content update scenario where each mobile node can be both a publisher and subscriber and opportunistic contacts are used for spreading out up-to-date contents, the age of contents would be the main interest in performance evaluation. We can simplify the overall age dynamics in this scenario by two parameters, which are content update rate and contact rate among mobile users. In this paper, we analyze how the age of time-evolving contents changes in publish/subscribe scenario when Poisson update and contact are assumed, and show that there exists an age-invariant regime where the average age does not depend on content update rate or contact rate. We also compare the age-invariant regime in publish/subscribe scenario with that of service provider content update case, and show a stark contact in those regimes. Then, we extend our study into existing mobility models that generate non-Poisson contacts, show that there still exists an age-invariant regime where Poisson assumptions suffice to capture the age dynamics, and specify a general rule of thumb that decides the scope of this regime. Our work that shows the existence of an age-invariant regime is in sharp contact to previous works that highlighted the impact of mobility models under single message scenario.}, booktitle={2010 ieee global telecommunications conference globecom 2010}, author={Kim, S. and Eun, D. Y.}, year={2010} }
 @article{chiu_eun_2010, title={On the Performance of Content Delivery under Competition in a Stochastic Unstructured Peer-to-Peer Network}, volume={21}, ISSN={["1558-2183"]}, DOI={10.1109/tpds.2010.15}, abstractNote={Peer-to-peer (P2P) network is widely used for transferring large files nowadays. Measurement results show that most downloading peers are patient as the average download session is usually very long. It is sometimes even longer than downloading from a dedicated server using a modem. Existing results in the literature indicate that the stochastic fluctuation and the heterogeneity in the service capacity of each peer are two of the major reasons that make the average download time far longer than expected. In those studies, it has been often assumed that there is only one downloading peer in the network, ignoring the interaction and competition among peers. In this paper, we investigate the impact of the interaction and competition among peers on downloading performance under stochastic, heterogeneous, and unstructured P2P settings, thereby greatly extending the existing results on stochastic P2P networks made only under a single downloading peer in the network. To analyze the average download time in a P2P network with multiple competing downloading peers, we first introduce the notion of system utilization tailored to a P2P network. We investigate the relationship among the average download time, system utilization, and the level of competition among downloading peers in a stochastic P2P network. We then derive an achievable lower bound on the average download time and propose algorithms to give the peers the minimum average download time. Our result can much improve the download performance compared to earlier results in the literature. The performance of the different algorithms is compared under NS-2 simulations. Our results also provide theoretical explanation to the inconsistency of performance improvement by using parallel connections (parallel connections sometimes do not outperform a single connection) observed in some measurement studies.}, number={10}, journal={IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS}, author={Chiu, Yuh-Ming and Eun, Do Young}, year={2010}, month={Oct}, pages={1487–1500} }
 @article{kim_lee_eun_2010, title={Superdiffusive Behavior of Mobile Nodes and Its Impact on Routing Protocol Performance}, volume={9}, ISSN={["1558-0660"]}, DOI={10.1109/TMC.2009.124}, abstractNote={Mobility is the most important component in mobile ad hoc networks (MANETs) and delay-tolerant networks (DTNs). In this paper, we first investigate numerous GPS mobility traces of human mobile nodes and observe superdiffusive behavior in all GPS traces, which is characterized by a ¿faster-than-linear¿ growth rate of the mean square displacement (MSD) of a mobile node. We then investigate a large amount of access point (AP) based traces, and develop a theoretical framework built upon continuous time random walk (CTRW) formalism, in which one can identify the degree of diffusive behavior of mobile nodes even under possibly heavy-tailed pause time distribution, as in the case of reality. We study existing synthetic models and trace-based models in terms of the capability of producing various degrees of diffusive behavior, and use a set of Levy walk models due to its simplicity and flexibility. In addition, we show that diffusive properties make a huge impact on contact-based metrics and the performance of routing protocols in various scenarios, and that existing models such as random waypoint, random direction model, or Brownian motion lead to overly optimistic or pessimistic results when diffusive properties are not properly captured. Our work in this paper, thus, suggests that the diffusive behavior of mobile nodes should be correctly captured and taken into account for the design and comparison study of network protocols.}, number={2}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Kim, Sungwon and Lee, Chul-Ho and Eun, Do Young}, year={2010}, month={Feb}, pages={288–304} }
 @article{cai_eun_2009, title={Crossing Over the Bounded Domain: From Exponential to Power-Law Intermeeting Time in Mobile Ad Hoc Networks}, volume={17}, ISSN={["1558-2566"]}, DOI={10.1109/TNET.2008.2011734}, abstractNote={Intermeeting time between mobile nodes is one of the key metrics in a mobile ad hoc network (MANET) and central to the end-to-end delay of forwarding algorithms. It is typically assumed to be exponentially distributed in many performance studies of MANET or numerically shown to be exponentially distributed under most existing mobility models in the literature. However, recent empirical results show otherwise: The intermeeting time distribution, in fact, follows a power-law. This outright discrepancy potentially undermines our understanding of the performance tradeoffs in MANET obtained under the exponential distribution of the intermeeting time and, thus, calls for further study on the power-law intermeeting time including its fundamental cause, mobility modeling, and its effect. In this paper, we rigorously prove that a finite domain, on which most of the current mobility models are defined, plays an important role in creating the exponential tail of the intermeeting time. We also prove that by simply removing the boundary in a simple two-dimensional isotropic random walk model, we are able to obtain the empirically observed power-law decay of the intermeeting time. We then discuss the relationship between the size of the boundary and the relevant timescale of the network scenario under consideration. Our results thus provide guidelines on the mobility modeling with power-law intermeeting time distribution, new protocols including packet-forwarding algorithms, as well as their performance analysis.}, number={5}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Cai, Han and Eun, Do Young}, year={2009}, month={Oct}, pages={1578–1591} }
 @inproceedings{lee_eun_2009, title={Heterogeneity in contact dynamics: Helpful or harmful to forwarding algorithms in DTNs?}, booktitle={2009 7th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless}, author={Lee, C. H. and Eun, D. Y.}, year={2009}, pages={72–81} }
 @article{won_cai_eun_guo_netravali_rhee_sabnani_2009, title={Multicast Scheduling in Cellular Data Networks}, volume={8}, ISSN={["1558-2248"]}, DOI={10.1109/twc.2009.080330}, abstractNote={Multicast is an efficient means of transmitting the same content to multiple receivers while minimizing network resource usage. Applications that can benefit from multicast such as multimedia streaming and download, are now being deployed over 3G wireless data networks. Existing multicast schemes transmit data at a fixed rate that can accommodate the farthest located users in a cell. However, users belonging to the same multicast group can have widely different channel conditions. Thus existing schemes are too conservative by limiting the throughput of users close to the base station. We propose two proportional fair multicast scheduling algorithms that can adapt to dynamic channel states in cellular data networks that use time division multiplexing: Inter-group Proportional Fairness (IPF) and multicast proportional fairness (MPF). These scheduling algorithms take into account (1) reported data rate requests from users which dynamically change to match their link states to the base station, and (2) the average received throughput of each user inside its cell. This information is used by the base station to select an appropriate data rate for each group. We prove that IPF and MPF achieve proportional fairness among groups and among all users in a group inside a cell respectively. Through extensive packet-level simulations, we demonstrate that these algorithms achieve good balance between throughput and fairness among users and groups.}, number={9}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Won, Hyungsuk and Cai, Han and Eun, Do Young and Guo, Katherine and Netravali, Arun and Rhee, Injong and Sabnani, Krishan}, year={2009}, month={Sep}, pages={4540–4549} }
 @article{cai_eun_ha_rhee_xu_2009, title={Stochastic convex ordering for multiplicative decrease internet congestion control}, volume={53}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2008.10.012}, abstractNote={Window growth function for congestion control is a strong determinant of protocol behaviors, especially its second and higher-order behaviors associated with the distribution of transmission rates, its variances, and protocol stability. This paper presents a new stochastic tool, called convex ordering, that provides an ordering of any convex function of transmission rates of two multiplicative-decrease protocols and valuable insights into high-order behaviors of protocols. As the ordering determined by this tool is consistent with any convex function of rates, it can be applied to any unknown metric for protocol performance that consists of some high-order moments of transmission rates, as well as those already known such as rate variance. Using the tool, it is analyzed that a protocol with a growth function that starts off with a concave function and then switches to a convex function (e.g., an odd order function such as x3 and x5) around the maximum window size in the previous loss epoch, gives the smallest rate variation under a variety of network conditions. Among existing protocols, BIC and CUBIC have this window growth function. Experimental and simulation results confirm the analytical findings.}, number={3}, journal={COMPUTER NETWORKS}, author={Cai, Han and Eun, Do Young and Ha, Sangtae and Rhee, Injong and Xu, Lisong}, year={2009}, month={Feb}, pages={365–381} }
 @article{eun_wang_2008, title={Achieving 100% throughput in TCP/AQM under aggressive packet marking with small buffer}, volume={16}, ISSN={["1558-2566"]}, DOI={10.1109/TNET.2007.904000}, abstractNote={We consider a TCP/AQM system with large link capacity (NC) shared by many flows. The traditional rule-of-thumb suggests that the buffer size be chosen in proportion to the number of flows (N) for full link utilization, while recent research outcomes show that O(radic(N)) buffer sizing is sufficient for high utilization and O(1) buffer sizing makes the system stable at the cost of reduced link utilization. In this paper, we consider a system where the active queue management (AQM) is scaled as O(Nalpha) with a buffer of size O(Nbeta) (0 < alpha < beta < 0.5). By capturing randomness both in packet arrivals and in packet markings, we develop a doubly-stochastic model for a TCP/AQM system with many flows. We prove that, under such a scale, the system always performs well in the sense that the link utilization goes to 100% and the loss ratio decreases to zero as the system size JV increases. Our results assert that the system enjoys benefit of largeness with no tradeoff between full link utilization, zero packet loss, and small buffer size, at least asymptotically. This is in stark contrast to existing results showing that there always exists a tradeoff between full link utilization and the required buffer size. Extensive ns-2 simulation results under various configurations also confirm our theoretical findings. Our study illustrates that blind application of fluid modeling may result in strange results and exemplifies the importance of choosing a right modeling approach for different scaling regimes.}, number={4}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Eun, Do Young and Wang, Xinbing}, year={2008}, month={Aug}, pages={945–956} }
 @article{kim_eun_2008, title={Impact of super-diffusive behavior on routing performance in delay tolerant networks}, ISBN={["978-1-4244-2074-2"]}, ISSN={["1550-3607"]}, DOI={10.1109/icc.2008.554}, abstractNote={Motivated by the recent findings of super-diffusive patterns in mobility traces, we investigate the impact of super- diffusive behavior of mobile nodes on contact-based metrics and performance metrics of routing protocols in delay tolerant networks (DTNs). We show that diffusive properties make huge impact on the performance of routing protocol - message delivery ratio and delay of delivered messages, and existing models such as random waypoint models or Brownian motion models lead to overly optimistic or pessimistic results when diffusive properties are not properly captured. In addition, we point out that existing contact-based metrics are unable to differentiate between varying degrees of routing performance under different diffusive mobility patterns, and then propose to use the number of new contacts as a far more effective metric, especially for scenarios in which message routing/forwarding is built upon contacts among mobile nodes. Our work in this paper suggests that the diffusive behavior of mobile nodes should be taken into account, for the design and the performance evaluation of network protocols in DTNs.}, journal={2008 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, PROCEEDINGS, VOLS 1-13}, author={Kim, Sungwon and Eun, Do Young}, year={2008}, pages={2941–2945} }
 @article{cai_lee_eun_2008, title={Invariance property of isotropic random walk mobility patterns in mobile ad-hoc networks}, ISBN={["978-1-4244-2074-2"]}, ISSN={["1550-3607"]}, DOI={10.1109/icc.2008.410}, abstractNote={The class of isotropic random walk mobility models, including random direction mobility model, random walk mobility model and Brownian motion mobility model, has been widely used in the study of Mobile Ad-Hoc Networks for mobility modeling and control. In this paper, we show an important property for contact time of isotropic random walk mobility models. Specifically, we find that the mean contact time of two mobile nodes following isotropic random walk mobility models is invariant with respect to the step-length distribution under both the simplest distance-based (Boolean) interference model and the more realistic SINR-based interference model. We also study the effect of system parameters on the contact and inter-meeting time of mobile nodes and discuss their higher-order statistics.}, journal={2008 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, PROCEEDINGS, VOLS 1-13}, author={Cai, Han and Lee, Chul-Ho and Eun, Do Young}, year={2008}, pages={2141–2145} }
 @article{chiu_eun_2008, title={Minimizing file download time in stochastic peer-to-peer networks}, volume={16}, ISSN={["1558-2566"]}, DOI={10.1109/TNET.2007.899051}, abstractNote={The peer-to-peer (P2P) file-sharing applications are becoming increasingly popular and account for more than 70% of the Internet's bandwidth usage. Measurement studies show that a typical download of a file can take from minutes up to several hours depending on the level of network congestion or the service capacity fluctuation. In this paper, we consider two major factors that have significant impact on average download time, namely, the spatial heterogeneity of service capacities in different source peers and the temporal fluctuation in service capacity of a single source peer. We point out that the common approach of analyzing the average download time based on average service capacity is fundamentally flawed. We rigorously prove that both spatial heterogeneity and temporal correlations in service capacity increase the average download time in P2P networks and then analyze a simple, distributed algorithm to effectively remove these negative factors, thus minimizing the average download time. We show through analysis and simulations that it outperforms most of other algorithms currently used in practice under various network configurations.}, number={2}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Chiu, Yuh-Ming and Eun, Do Young}, year={2008}, month={Apr}, pages={253–266} }
 @article{kim_lee_eun_2008, title={Super-diffusive behavior of mobile nodes from GPS traces}, volume={12}, ISSN={1559-1662}, url={http://dx.doi.org/10.1145/1374512.1374521}, DOI={10.1145/1374512.1374521}, abstractNote={Mobility is the most important factor in mobile adhoc networks (MANETs) and delay-tolerant networks (DTNs). Mobility models that fail to capture real movement pattern of mobile nodes will result in misleading guidelines on the design of new protocols and their performance evaluations and thus prevent us from making judicious decisions.}, number={1}, journal={ACM SIGMOBILE Mobile Computing and Communications Review}, publisher={Association for Computing Machinery (ACM)}, author={Kim, Sungwon and Lee, Chul-Ho and Eun, Do Young}, year={2008}, month={Jan}, pages={28} }
 @article{cai_eun_2008, title={Tuning up the performance of constant-time distributed scheduling algorithms via majorization}, ISBN={["978-1-4244-2074-2"]}, ISSN={["1550-3607"]}, DOI={10.1109/icc.2008.552}, abstractNote={Scheduling algorithms assign contention probability for each link in wireless ad hoc networks and plays a key role in deciding the system performance. Recently, many low-cost distributed scheduling algorithms are proposed. In this paper, we propose to improve the performance of a class of distributed collision-based scheduling algorithms, called constant-time distributed scheduling algorithms, by exploring the advantage brought by the unevenness of links' contention probabilities. Specifically, we prove that there exists ordering relationship for the success probability of any neighborhood when the contention probability vectors are ordered in the sense of majorization. We show how to modify the existing algorithms so as to find a new contention probability vector that majorizes the original one in a distributed manner. Our simulation results indicate that by using our modified algorithms, the average queue-lengths of a stable system can be reduced by 25% to 50%, while the capacity region remains the same. Our modification to the existing algorithms is extremely simple and entails essentially zero additional cost.}, journal={2008 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, PROCEEDINGS, VOLS 1-13}, author={Cai, Han and Eun, Do Young}, year={2008}, pages={2931–2935} }
 @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{wang_eun_2007, title={Local and global stability of TCP-newReno/RED with many flows}, volume={30}, ISSN={["1873-703X"]}, DOI={10.1016/j.comcom.2006.11.007}, abstractNote={Stability is one of the important issues for a TCP/AQM (Active Queue Management) system. In this paper, we study the local and global stability of TCP-newReno/RED under many flows regime. The existing results of the local stability are mostly for TCP-Reno, not for newReno. These results are obtained based on a small scale model with a few number of flows and thus cannot be blindly applied to a large system with many flows. Moreover, traditional approaches for the global stability based on Lyapunov functions is not suitable for a system with a large amount of flows due to its complexity. Motivated by this, we present a normalized discrete-time model to capture the essential dynamics of TCP-newReno/RED with many flows and obtain its local stability criterion. The normalized model allows us to proceed numerical iterations to analyze the global stability in an efficient manner. Our results show that by properly choosing some 'free' parameters, we can always ensure that a locally stable TCP-newReno/RED system is in fact globally stable. Our results become more accurate as the number of flows increases. Finally, we extend our normalized model to the case of heterogeneous RTTs.}, number={5}, journal={COMPUTER COMMUNICATIONS}, author={Wang, Xinbing and Eun, Do Young}, year={2007}, month={Mar}, pages={1091–1105} }
 @article{eun_2007, title={On the limitation of fluid-based approach for Internet congestion control}, volume={34}, ISSN={["1018-4864"]}, DOI={10.1007/s11235-006-9028-7}, number={1-2}, journal={TELECOMMUNICATION SYSTEMS}, author={Eun, Do Young}, year={2007}, month={Feb}, pages={3–11} }
 @article{eun_wang_2007, title={Performance analysis of TCP/AQM with generalized AIMD under intermediate buffer sizes}, volume={51}, ISSN={["1872-7069"]}, DOI={10.1016/j.comnet.2007.03.005}, abstractNote={For TCP/AQM systems, the issue of buffer sizing has recently received much attention. The classical rule-of-thumb suggests O(N) buffer size to ensure full link utilization when N TCP flows share a bottleneck link of capacity O(N), while recent empirical study shows the buffer of size O(N) is enough to yield high utilization (say, 95%) for large N. However, these results are all limited to the drop-tail scheme and there has been no systematic modeling framework for any buffer sizing between O(N) and O(N). In this paper, we study the limiting behavior of a TCP/AQM system for an intermediate buffer sizing of O(N^@c) (0.5=<@c<1). We develop a stochastic model in a discrete-time setting to characterize the system dynamics and then show that we can have 100% link utilization and zero packet loss probability for a large number of flows when the buffer size is chosen anywhere between O(N) and O(N). Our model is general enough to cover any queue-based AQM scheme with ECN marking (including the drop-tail) and various generalized AIMD (additive-increase-multiplicative-decrease) algorithms for each TCP flow. We also provide arguments showing that the discrete-time based modeling can effectively capture all the essential system dynamics under our choice of scaling (0.5=<@c<1) for buffer size as well as AQM parameters.}, number={12}, journal={COMPUTER NETWORKS}, author={Eun, Do Young and Wang, Xinbing}, year={2007}, month={Aug}, pages={3655–3671} }
 @article{eun_shroff_2005, title={Network decomposition: Theory and practice}, volume={13}, ISSN={["1558-2566"]}, DOI={10.1109/TNET.2005.850218}, abstractNote={We show that significant simplicities can be obtained for the analysis of a network when link capacities are large enough to carry many flows. We develop a network decomposition approach in which network analysis can be greatly simplified. We prove that the queue length at the downstream queue converges to that of a single queue obtained by removing the upstream queue, as the capacity and the number of flows at the upstream queue increase. The precise modes of convergence vary depending on the type of input traffic, i.e., from regulated traffic arrivals to point process inputs. Our results thus help simplify network analysis by decomposing the original network into a simplified network in which all the nodes with large capacity have been eliminated. By means of extensive numerical investigation under various network scenarios, we demonstrate different aspects and implications of our network decomposition approach. Some of our findings are that our techniques perform well especially for the cases when: i) many flows are multiplexed as they enter the queue and/or ii) departing flows are routed to different downstream nodes, i.e., no single flow dominates at any node.}, number={3}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Eun, DY and Shroff, NB}, year={2005}, month={Jun}, pages={526–539} }
 @article{eun_shroff_2004, title={Analyzing a two-stage queueing system with many point process arrivals at upstream queue}, volume={48}, ISSN={["1572-9443"]}, DOI={10.1023/B:QUES.0000039886.54866.c5}, number={1-2}, journal={QUEUEING SYSTEMS}, author={Eun, DY and Shroff, NB}, year={2004}, pages={23–43} }
 @article{eun_shroff_2004, title={Network decomposition in the many-sources regime}, volume={36}, ISSN={["1475-6064"]}, DOI={10.1239/aap/1093962240}, abstractNote={We derive results that show the impact of aggregation in a queueing network. Our model consists of a two-stage queueing system where the first (upstream) queue serves many flows, of which a certain subset arrive at the second (downstream) queue. The downstream queue experiences arbitrary interfering traffic. In this setup, we prove that, as the number of flows being aggregated in the upstream queue increases, the overflow probability of the downstream queue converges uniformly in the buffer level to the overflow probability of a single queueing system obtained by simply removing the upstream queue in the original two-stage queueing system. We also provide the speed of convergence and show that it is at least exponentially fast. We then extend our results to non-i.i.d. traffic arrivals.}, number={3}, journal={ADVANCES IN APPLIED PROBABILITY}, author={Eun, DY and Shroff, NB}, year={2004}, month={Sep}, pages={893–918} }
 @article{eun_shroff_2004, title={Network decomposition in the many-sources regime}, volume={36}, ISSN={0001-8678 1475-6064}, url={http://dx.doi.org/10.1017/S0001867800013173}, DOI={10.1017/S0001867800013173}, abstractNote={We derive results that show the impact of aggregation in a queueing network. Our model consists of a two-stage queueing system where the first (upstream) queue serves many flows, of which a certain subset arrive at the second (downstream) queue. The downstream queue experiences arbitrary interfering traffic. In this setup, we prove that, as the number of flows being aggregated in the upstream queue increases, the overflow probability of the downstream queue converges uniformly in the buffer level to the overflow probability of a single queueing system obtained by simply removing the upstream queue in the original two-stage queueing system. We also provide the speed of convergence and show that it is at least exponentially fast. We then extend our results to non-i.i.d. traffic arrivals.}, number={03}, journal={Advances in Applied Probability}, publisher={Cambridge University Press (CUP)}, author={Eun, Do Young and Shroff, Ness B.}, year={2004}, month={Sep}, pages={893–918} }