Optimal Channel Search Time for Handoff in the IEEE 802.11 WLANs

In recent years, the IEEE 802.11 wireless local area networks (WLANs) have become a very popular access network technique. However, due to the large handoff latency, most application scenarios are limited to hot spot areas without handoff across different access points (APs). As the advance of many real-time or highly interactive applications such as voice over IP (VoIP), one of burning issues for the WLAN is to reduce the handoff latency. Current studies in the literature have indicated that the latency in searching available APs dominates the handoff latency. Thus, we propose a simple analytical model to calculate the search latency and success probability for the handoff in the IEEE 802.11 WLAN. A new performance metric, namely the "effective search time (EST)", is introduced to evaluate the latency that is required for a station to successfully search a channel from neighboring APs. Based on the developed model, the optimum numbers of the probe request and response transmission for minimizing the EST can be obtained. Our results demonstrate that, in the environment of 100 contending stations, the EST with optimum number of transmissions can be reduced by 30% compared to that in the legacy IEEE 802.11 WLAN

[1]  Oliver W. W. Yang,et al.  Delay analysis of the IEEE 802.11 DCF , 2003, 14th IEEE Proceedings on Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003..

[2]  Periklis Chatzimisios,et al.  Packet delay distribution of the IEEE 802.11 distributed coordination function , 2005, Sixth IEEE International Symposium on a World of Wireless Mobile and Multimedia Networks.

[3]  William A. Arbaugh,et al.  An empirical analysis of the IEEE 802.11 MAC layer handoff process , 2003, CCRV.

[4]  A. Girotra,et al.  Performance Analysis of the IEEE 802 . 11 Distributed Coordination Function , 2005 .

[5]  A. Agrawala,et al.  The IEEE 802.11 active probing analysis and enhancements , 2005, 2005 International Conference on Wireless Networks, Communications and Mobile Computing.

[6]  Zoran Hadzi-Velkov,et al.  Saturation throughput - delay analysis of IEEE 802.11 DCF in fading channel , 2003, IEEE International Conference on Communications, 2003. ICC '03..

[7]  Periklis Chatzimisios,et al.  IEEE 802.11 packet delay-a finite retry limit analysis , 2003, GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489).

[8]  Pravin Varaiya,et al.  Saturation throughput analysis of IEEE 802.11 wireless LANs for a lossy channel , 2005, IEEE Communications Letters.

[9]  Gunnar Karlsson,et al.  Techniques to reduce the IEEE 802.11b handoff time , 2004, 2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577).