@article{lee_jeong_yi_won_rhee_chong_2015, title={Max Contribution: An Online Approximation of Optimal Resource Allocation in Delay Tolerant Networks}, volume={14}, ISSN={["1558-0660"]}, DOI={10.1109/tmc.2014.2329001}, abstractNote={In this paper, a joint optimization of link scheduling, routing and replication for delay-tolerant networks (DTNs) has been studied. The optimization problems for resource allocation in DTNs are typically solved using dynamic programming which requires knowledge of future events such as meeting schedules and durations. This paper defines a new notion of approximation to the optimality for DTNs, called snapshot approximation where nodes are not clairvoyant, i.e., not looking ahead into future events, and thus decisions are made using only contemporarily available knowledges. Unfortunately, the snapshot approximation still requires solving an NP-hard problem of maximum weighted independent set (MWIS) and a global knowledge of who currently owns a copy and what their delivery probabilities are. This paper proposes an algorithm, Max-Contribution (MC) that approximates MWIS problem with a greedy method and its distributed online approximation algorithm, Distributed Max-Contribution (DMC) that performs scheduling, routing and replication based only on locally and contemporarily available information. Through extensive simulations based on real GPS traces tracking over 4,000 taxies and 500 taxies for about 30 days and 25 days in two different large cities, DMC is verified to perform closely to MC and outperform existing heuristically engineered resource allocation algorithms for DTNs.}, number={3}, journal={IEEE TRANSACTIONS ON MOBILE COMPUTING}, author={Lee, Kyunghan and Jeong, Jaeseong and Yi, Yung and Won, Hyungsuk and Rhee, Injong and Chong, Song}, year={2015}, month={Mar}, pages={592–605} }
 @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} }