@article{rhee_shin_hong_lee_kim_chong_2011, title={On the Levy-Walk Nature of Human Mobility}, volume={19}, ISSN={["1558-2566"]}, DOI={10.1109/tnet.2011.2120618}, abstractNote={We report that human walks performed in outdoor settings of tens of kilometers resemble a truncated form of Levy walks commonly observed in animals such as monkeys, birds and jackals. Our study is based on about one thousand hours of GPS traces involving 44 volunteers in various outdoor settings including two different college campuses, a metropolitan area, a theme park and a state fair. This paper shows that many statistical features of human walks follow truncated power-law, showing evidence of scale-freedom and do not conform to the central limit theorem. These traits are similar to those of Levy walks. It is conjectured that the truncation, which makes the mobility deviate from pure Levy walks, comes from geographical constraints including walk boundary, physical obstructions and traffic. None of commonly used mobility models for mobile networks captures these properties. Based on these findings, we construct a simple Levy walk mobility model which is versatile enough in emulating diverse statistical patterns of human walks observed in our traces. The model is also used to recreate similar power-law inter-contact time distributions observed in previous human mobility studies. Our network simulation indicates that the Levy walk features are important in characterizing the performance of mobile network routing performance.}, number={3}, journal={IEEE-ACM TRANSACTIONS ON NETWORKING}, author={Rhee, Injong and Shin, Minsu and Hong, Seongik and Lee, Kyunghan and Kim, Seong Joon and Chong, Song}, year={2011}, month={Jun}, pages={630–643} }
 @article{hwang_kim_sung_song_2008, title={Performance analysis of IEEE 802.11e EDCA with a virtual collision handier}, volume={57}, ISSN={["1939-9359"]}, DOI={10.1109/TVT.2007.911611}, abstractNote={This paper presents an analytical model of IEEE 802.11e enhanced distributed channel access (EDCA) with a virtual collision handler (VCH). The proposed analytical model provides different access categories (ACs) for supporting the quality of service (QoS) of differentiated services by using different contention window (CW) sizes and arbitration interframe space (AIFS) values in EDCA. The proposed model considers a network of stations, each of which has multiple queues and a VCH for different ACs. Based on the proposed model, we analyze the throughput and delay performance of the EDCA with four different ACs and investigate the effect of the VCH by considering two VCH schemes. The analytical and simulation results show that the proposed analytical model is very accurate for various CW sizes and AIFS values.}, number={2}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Hwang, Ho Young and Kim, Seong Joon and Sung, Dan Keun and Song, Nah-Oak}, year={2008}, month={Mar}, pages={1293–1297} }