摘要：Wireless Local Area Networks (WLANs) are becoming a popular way of networking computer equipments in the home and office. In order to support differentiated Quality-of- Service (QoS) in WLANs, the IEEE 802.11e Enhanced Distributed Channel Access (EDCA) protocol allocates multiple Access Categories (ACs) with different priorities, inter-frame spaces, and contention window sizes. This paper presents an improved Medium Access Control (MAC) scheme to enhance the QoS of WLANs based on the idea of using the different increasing functions for each AC to enlarge the size of contention window in the case of transmission collision. The performance of this improved scheme under multimedia applications is extensively investigated and compared with the original EDCA using the well- known network simulator NS-2. The results show that this scheme is able to achieve higher throughput and medium utilization as well as lower access delay and packet loss probability than the original EDCA. Moreover, it provides a good prioritization level between multiple ACs.
