|Title||:||Analysis of Collisions in Contention-based Wireless Networks|
|Speaker||:||Manas Khatua (Singapore University of Technology and Design)|
|Details||:||Wed, 8 Jun, 2016 2:30 PM @ BSB 361|
|Abstract:||:||Each station of a wireless network (WN) requires access to communication channel which is shared and open to all station in the network. Contention-based approach is one of the most accepted channel access mechanism in WNs. However, frame collision remains one of the fundamental problems of multiple channel access in Contention-based Wireless Networks (CWNs). Collision is managed by sacrificing network performance, but is not fully avoidable yet. The primary reason of this inefficiency is the shared nature and distributed access control of wireless channel. In their current forms, CWNs suffer from limited throughput, higher channel access delay, unfair resource provisioning, and security threat. Motivated by these problems, we explore few alternative design of collision management scheme that can effectively improve the present performance level. We design a semi-distributed backoff (SDB) scheme for avoiding successive collisions for delay sensitive applications. Further, the design of delay-aware distributed dynamic adaptation of contention window (D2D) jointly optimizes the saturation throughput and channel access delay in runtime.
The objective of the work reported in SDB is to provide guaranteed channel access to colliding frames, which, in turn, increases the network throughput and decreases the average medium access delay. The key idea of the SDB scheme is to perform receiver-side backoff, if a station encounters collision even after performing the existing sender-side backoff process. Using the SDB scheme, we design Semi-DCF, a MAC protocol for Wireless LAN, which performs opportunistic migration from random to deterministic backoff. SDB exploits the signature-based collision detection in WN, and leverages this opportunity for disseminating optimal backoff counter for the next round, which, in turn, reduces the idle channel overhead. On the other hand, joint optimization of throughput and channel access delay is the objective of D2D design. The D2D scheme requires two ad-hoc, distributed, and easy to obtain estimates -- delay deviation ratio and channel busyness ratio -- of the present delay level and channel congestion status of the network, respectively. We integrate the D2D scheme with the IEEE 802.11e EDCA MAC protocol for designing the D2D Channel Access (D2DCA) and observing performance improvement. In both the works, we propose two-dimensional Markov chain model for analysing the theoretical performance of the respective protocols. Comparison of results with the benchmark protocols and the maximum throughput limit establishes the effectiveness of the proposed protocols.
Brief Biography: Manas Khatua received his B.Tech. in Computer Science and Engineering from University of Kalyani, M.Tech. in Information Technology from Bengal Engineering and Science University, and Ph.D. from Indian Institute of Technology Kharagpur in the year of 2003, 2007, and 2015 (provisional certificate), respectively. He was an Assistant System Engineer of Tata Consultancy Services, Kolkata and Bhubaneswar, for two and half years, and a Lecturer in the Department of Computer Science and Engineering at Bankura Unnayani Institute of Engineering, West Bengal, for more than two years. He is presently working as Postdoctoral Research Fellow at Singapore University of Technology and Design, Singapore. His research interests include Wireless Networks, Sensor Networks, and Mobile Cloud Computing. He has already published 13 (thirteen) international journal and conference papers in the above mentioned areas and few are in the process of publication. He is a member of IEEE since 2013 and Akhil Bharat Vivekananda Yuva Mahamandal since 1989.