Using multiple metrics for rate adaptation algorithms in IEEE 802.11 WLANs

IEEE 802.11 Wireless LANs (WLANs) use rate adaptation algorithms (RAAs) to dynamically switch data rates to accommodate the fluctuating wireless channel conditions. Classic RAAs such as ARF and ONOE suffer from rate poisoning and inability to distinguish between collision and packet losses caused by channel errors. Existing approaches in the literature are able to solve only one of the above two issues. In this paper we propose a novel rate adaptation protocol to address both issues for multi-rate wireless networks. The novelty of our approach is to combine the metrics of expected packet transmission time (ETT) and the average number of frozen slots (ANFS) to estimate the quality and level of contention for the current channel. A mathematical model to calculate ETT and ANFS on the fly is presented. Our protocol is simple and practical, which takes into consideration not only link quality and frame loss characteristics, but also impact of collisions during the design. Simulation results show that without the perfect knowledge of current channel condition and any signal strength information, our algorithm can achieve significant performance improvement in terms of end-to-end throughput for different network conditions compared with state-of-the-art link adaptation algorithms.