Performance analysis over QoS strategies for IEEE 802.11 wireless LANs

Summary form only given. Due to its simplicity and robustness, the IEEE 802.11 wireless LAN (WLAN) standard has been accepted widely for many application areas. However, the 802.11 standard was originally proposed with minimal quality of service (QoS) support, and this limitation has drawn increasing concerns as the WLAN technologies are being recommended to offer high-quality and real-time services across the network. While new mechanisms for QoS support have been proposed by the IEEE 802.11e group, further investigations on the new standard in conjunction with the legacy 802.11 configuration are important for having a sustainable improvement on QoS in various working conditions. Within the 802.11 protocol architecture, the medium access control (MAC) sub-layer is responsible for supporting QoS. The legacy 802.11 MAC has two operation modes characterised by the coordination functions: the distributed coordination function (DCF) and the point coordination function (PCF). These two operation modes face vigorous challenges for maintaining QoS in the wireless environment featuring high packet loss rates, large latency, jitter and time varying.