Performance Evaluation of Multi-Rate Communication in Wireless LANs

In IEEE 802.11a/b/g wireless LAN, STAs (stations) can select an appropriate transmission rate based upon the received signal strength in order to achieve high throughput. In such a multi-rate environment, however, the total throughput is degraded if an AP (access point) is shared by STAs at both high and low transmission rates simultaneously. This problem is identified as the performance anomaly problem in only IEEE 802.11b, and we closely examine it under the IEEE 802.11a multi-rate environment. Although earlier studies have assumed that this performance anomaly always occurs, we show that it does not occur under a certain environment. First, we describe the mechanism of the performance anomaly, then illustrate the condition under which the performance anomaly does not occur. Finally, we show, through simulation results, the condition under which a performance anomaly may and may not occur in a multirate environment.