An Optimized Scheduling Scheme to Provide Quality of Service in 802.11e Wireless LAN
802.11 WLAN technology has been widely used recently to transmit heterogeneous data. The transmission of multimedia data has its quality of service (QoS) requirements. Hybrid Coordination Function (HCF) is proposed to provide service differentiation to support real-time transmission by 802.11e working group. HCF is composed of connection-based Enhanced Distributed Coordination Access (EDCA) and contention-free control-based HCF Controlled Channel Access (HCCA). The simple scheduler in HCCA proposed by 802.11e working group generates constant bit rate service, which is not efficient for the multimedia data with variable bit rates. An efficient scheduling scheme for the 802.11e wireless LAN is proposed in this paper. The allocation of the transmission opportunity to each wireless station is based on the optimization performance index and uses the queue length of the wireless station as feedback information. Simulation results demonstrate that the proposed scheduling can achieve a better QoS for different traffic class under heavy traffic load.