Enhancements to IEEE 802.11 MAC to Avoid Packet Collisions

The IEEE 802.11 WLAN standard specifies two different ways in which a wireless station (STA) can gain access to the channel - (i) distributed channel access where each STA can access channel in a probabilistic manner, (ii) access point (AP) coordinated channel access where the AP provides channel access to each STA by polling mechanism. Whilst the former is attractive because of simpler implementation, it suffers from packet collisions which tend to increase as more STAs try to gain access to the channel. On the other hand, AP coordinated channel access is more robust to packet collisions but it requires fairly complex implementation and has substantial overhead compared to distributed mode. In this paper we propose to add minimal intelligence to the enhanced distributed channel access (EDCA) mechanism of IEEE 802.11e to avoid the packet collisions while maintaining its fairness and simplicity. The simulation results show that the proposed scheme leads to significant throughput improvements over EDCA.