As the demand for broadband multimedia wireless services increases, the need to provide QoS and higher data rate enhancements to the widely deployed IEEE 802.11 wireless LAN has become apparent. However, currently deployed IEEE 802.11 standards have little or no QOS support functions built in to the MAC layer. The IEEE 802.11e EDCF mechanism is currently being developed to provide QoS functions in the MAC layer based on service differentiation and traffic class prioritization. Along with the 802.11e QoS amendment, 802.11n defines advanced ARQ policies designed to increase the channel utilization efficiency by reducing MAC protocol overhead. Although these techniques provide vast improvements over the legacy 802.11 protocol, opportunities exist with in this framework to optimize performance based on the type of traffic being serviced. In this paper a distributed medium access scheme called EDCF, which is adopted in an upcoming standard IEEE 802.11e to allow prioritized medium access for applications with QoS requirements is analyzed and its performance is evaluated using OPNET Modeler.We also investigate the performance optimization of the 802.11 Block AckARQ policy, and discuss adaptive block size algorithm for throughput improvement.

Key words: 8 0 2 . ARQ1 optimization; Block ACK; WLAN;HCF;EDCF;OPNET Modeler