A Waiting-Time Dependent Backoff Algorithm for QoS Enhancement of Voice over WLAN

As the integration of prevailing Wireless Local Area Network (WLAN) and Voice over Internet Protocol (VoIP) technology, Voice over WLAN (VoWLAN) is expected to experience a dramatic growth in the near future. However, the widely deployed IEEE 802.11 contention-based Media Access Control (MAC) mechanism is unsuitable for voice transmission with strict Quality of Service (QoS) requirements. In this paper, the delay jitter and collision problems in Binary Exponential Backoff (BEB) algorithm are analyzed first. Then, a novel "Waiting-time Dependent Backoff (WDB)" algorithm is proposed to cope with these problems and improve QoS of voice transmission. Simulation results show that WDB can dramatically reduce delay jitter and collision probability, as well as end-to-end delay, while maintaining acceptable drop rate.