Throughput evaluation and enhancement in 802.11 WLANs with access point

In 802.11 infrastructure mode some stations that are located far away from an access point may face signal fading and interference. In this case, the wireless station changes its data rate to some lower value. In 802.11b protocol, wireless stations can operate at data rates 11, 5.5, 2 and 1 Mbps. From the literature and our simulation we found that when some wireless stations use a lower data rate than others, the performance of all stations is degraded. The throughput of all wireless stations, including fast and slow, ones is decreased to the order of magnitude of the slow station. This is due to the CSMA/CA channel access method used in 802.11, which guarantees that the long term channel access probability is equal for all wireless stations. In this paper, we propose a solution that avoids slow stations from penalizing other ones transmitting at higher rates. The solution is based on using frames of different sizes according to the link data rate.