Service time estimation in multiple-rate IEEE 802.11 WLANs with and without opportunistic cooperative mechanism under unsaturated load conditions

Wireless media servers and real-time applications are becoming increasingly popular in most homes. Wireless network latency is a key factor in many applications. The objective of this paper is to derive an analytical framework to estimate the latency in terms of the average service time of the most used multiple-rate wireless link protocol, i.e., IEEE 802.11. A number of analytical models for IEEE 802.11 exists in the literature. However, to the best of the authors´ knowledge, no general analytical model exists that jointly models IEEE 802.11 latency under the assumption of using multiple transmission rates and unsaturated load traffic. Additionally, the proposed model can also be extended to cooperative variants of IEEE 802.11 which exploit the presence of both multiple nodes and multiple transmission rates to improve network performance. In particular, in this paper, the extension to model COBRA MAC, an opportunistic cooperative variant of IEEE 802.11 is presented. The derived model is validated against simulation results, revealing good match between model and simulation. Also, results showing the performance benefits achieved by COBRA MAC over IEEE 802.11 are presented.