Traffic Scheduling for MPDCF MAC to Support QoS-Sensitive Data in IEEE 802.11 Wireless LANs

In IEEE 802.11 wireless LAN (WLAN), it is very hard to meet QoS requirements (throughput, delay and loss rate) of multimedia traffic by using Distributed Coordination Function (DCF). In order to support QoS in WLAN, enhanced IEEE 802.11 Medium Access Control (MAC) protocol is discussed in IEEE 802.11 Task Group E. IEEE 802.11e uses the rather complex Hybrid Coordination Function (HCF). In this paper, we propose a simple MultiPolling DCF (MPDCF) mechanism with the advantages of high channel efficiency and QoS support. In our proposed mechanism, an AP can decide the transmission order and duration of QoS-sensitive wireless stations and poll the stations whenever it needs based on the controlled backoff procedure. We propose a scheduling algorithm using the proposed MPDCF to serve real-time traffic with constant and variable bit rates. The simulation results show that QoS requirements of the traffic can be satisfied and the channel utilization is also increased with our scheduling mechanism.