Channel Condition Based Contention Window Adaptation in IEEE 802.11 WLANs

• Published in: IEEE transactions on communications Vol. 60; no. 2; pp. 469 - 478
• Main Authors: KUNHO HONG, LEE, Sukyoung, KIM, Kyungsoo, KIM, Yoonhyuk
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.02.2012; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Access methods and protocols, osi model; Adaptation models; Algorithms; Applied sciences; backoff; Business and industry local networks; channel access delay; DCF; Delay; Exact sciences and technology; IEEE 802.11; IEEE 802.11 Standards; Networks and services in france and abroad; non-saturated condition; Protocols; Radiation detectors; Studies; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Teleprocessing networks. Isdn; Teletraffic; Throughput; Transmission and modulation (techniques and equipments); Wireless LAN; Access control; IEEE 802.11; Wireless LAN; Wireless telecommunication; DCF; backoff; Information rate; Teletraffic; channel access delay; Information transmission; Simulation; Delay time; IEEE standards; throughput; Personal communication networks; non-saturated condition; Traffic congestion
• ISSN: 0090-6778; 1558-0857
• DOI: 10.1109/TCOMM.2012.012012.100472

In IEEE 802.11 standard, the backoff parameters of its collision avoidance mechanism can be very inefficient and hence, the network becomes far from its optimal behavior. There have been several mechanisms to tune the Contention Window (CW) with the aim to achieve the optimal throughput in the IEEE 802.11 WLAN, however, the mechanisms do not specifically address a proper setting of the backoff parameters under non-saturated conditions. Noting that typical 802.11 networks are usually non-saturated, in this paper, we analytically derive the CW sizes that maximize the WLAN system throughput under both saturated and non-saturated conditions. Then, using the CW sizes derived, we propose a distributed algorithm that enables each station to dynamically adapt its CW according to the channel congestion status. The performance of the proposed algorithm is investigated through simulation. Simulation results indicate that our proposed backoff algorithm provides a remarkable performance improvement in terms of the delay experienced by a packet in the MAC layer, while maintaining an optimal throughput close to the theoretical throughput limit of the IEEE 802.11 Distributed Coordination Function (DCF) access scheme.