Abstract
The IEEE802.11 protocol defines access techniques to wireless medium using CSMA/CA, and defines two modes of operation in WLAN DCF and PCF. DCF does not provide any QoS, so that throughput and delay of real-time traffic, such as voice and video cannot be guaranteed over WLAN. IEEE 802.11e introduces a service differentiation mechanism based on prioritized contention access, which causes throughput degradation if the network becomes high loaded by high priority traffic. This paper proposes service differentiation for multiple access categories by using multilevel priority mechanisms in MAC layer, using multilevel priority controllability to network performance according to throughput of each traffic category.