Extended WDB Algorithm for QoS Enhancement in IEEE 802.11e WLAN

The paper proposes an extended waiting-time dependent backoff (EWDB) algorithm for IEEE 802.11e WLAN as an extension of our previous WDB method. Concerning the QoS limitations of EDCA, EWDB controls backoff window (BW) according to waiting-time (WT), and staggers BW ranges among prioritized services. The algorithm is based on a flexible mathematic model consisting of deterministic function and random function. Backoff functions are respectively designed for voice, video and data. WT-dependent sub-priority is introduced for voice and video. An overlap-restricted backoff function is designed for data traffic. Simulation results show the superiority of EWDB to EDCA in terms of jitter and delay of voice/video, throughput of data, as well as overall collision rate under different network load.