Performance analysis of polling schemes with IEEE 802.11a WLAN

IEEE 802.11 MAC consists of the distributed coordination function, the point coordination function and their coexistence. The DCF provides contention services and the PCF provides contention-free services. Although DCF is the fundamental access protocol of IEEE 802.11, it can not support various classes of traffic while guaranteeing quality of service requirements in general. In fact, the point coordination function is aimed to support QoS related services by using polling schemes. However, it has an inherent problem. The point coordinator has no mechanism to know the queue status of the station buffer and this may cause a lot of troubles. We introduce an enhanced polling scheme to overcome the problem. We compare the enhanced polling scheme with three popular polling schemes, non-preemptive, round-robin and first-in-first-out under various channel situations including error prone environments.