@article{wang_pambudi_wang_wang_2023, title={Toward Fast and Energy-Efficient Access to Cloudlets in Hostile Environments}, volume={22}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2023.3262311}, abstractNote={Cloudlets, which refer to the edge computing services deployed at the proximity of end devices, are key providers of connectivity, storage, and computation resources to many applications. While access to cloudlets is pervasive in typical settings, it can be difficult in challenging, even hostile environments, such as military or post-disaster scenarios, featuring multi-hop communication and energy-constrained end devices. In these cases, cloudlets may have become the only equipment powerful enough to execute life-critical applications, such as battle-field situation awareness, tactic cooperation, and search-and-rescue missions. Quality of these services is greatly influenced by the minimum time that a packet can be delivered, i.e., the cloudlet access delay (CAD), whose characteristics remain unknown. To address the open question of fast and efficient cloudlet access, we establish a packet mobility model that allows CAD and energy consumption to be analyzed as a function of the initial device-cloudlet distance. We find that the expected CAD scales either linearly or quadratically under distinct types of packet mobility, and the successful access rate (SAR) can be bounded by functions of the delay constraint. Based on these findings, we develop a packet shedding algorithm that saves 24% transmission power, and reduces the average CAD by 2%, while maintaining a similar SAR in simulated cloudlet access environments.}, number={11}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Wang, Jie and Pambudi, Sigit Aryo and Wang, Wenye and Wang, Cliff}, year={2023}, month={Nov}, pages={8320–8335} }
 @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 <italic>cascade-of-failures</italic> across domains, which dissolves the network structure, and has devastating consequences. To answer how robust an IoT system is, this paper studies its <italic>resilience</italic> 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 <italic>critical edge disconnecting probability</italic> <inline-formula> <tex-math notation="LaTeX">$\phi _{cr}$ </tex-math></inline-formula>, i.e., the maximum intensity of random failures the system can withstand, and the cascade length <inline-formula> <tex-math notation="LaTeX">$\tau _{cf}$ </tex-math></inline-formula>, i.e., the lifetime of a cascade. For IoT systems with Poisson degree distributions, we derive exact solutions for the critical disconnecting probability <inline-formula> <tex-math notation="LaTeX">$\phi _{cr}$ </tex-math></inline-formula>, above which an edge-induced cascade will completely fragment the network. We also find that the critical condition <inline-formula> <tex-math notation="LaTeX">$\phi _{cr}$ </tex-math></inline-formula> marks a dichotomy of the expected cascade length <inline-formula> <tex-math notation="LaTeX">$\mathbb {E}(\tau _{cf})$ </tex-math></inline-formula>: for the super-critical (<inline-formula> <tex-math notation="LaTeX">$\phi > \phi _{cr}$ </tex-math></inline-formula>) scenario, we obtain <inline-formula> <tex-math notation="LaTeX">$\mathbb {E}(\tau _{cf}) \sim \exp (1-\phi)$ </tex-math></inline-formula> through analysis, while for the subcritical scenario, we observe <inline-formula> <tex-math notation="LaTeX">$\mathbb {E}(\tau _{cf}) \sim \exp (1/1-\phi)$ </tex-math></inline-formula> 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} }
 @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{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} }
 @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.} }