An Adaptive Multimedia QoS Scheduler for 802.11e Wireless LANs

The IEEE 802.11e standard defines the Hybrid Coordination Function (HCF) which specifies the QoS algorithms in the MAC layer of the next generation 802.11 wireless LAN (WLAN). The HCF is composed of two access functions: A distributed contention-based channel access function (EDCA) providing prioritized QoS and a centralized polling-based channel access function (HCCA) providing parameterized QoS. In this paper, we address the efficient medium access control (MAC) of the mostly variable bit rate (VBR) and bursty multimedia traffic in HCCA and propose a novel application-aware adaptive 802.11e QoS scheduler. The proposed scheduler coordinates the resource allocation of the associated flows using adaptive service intervals, transmit opportunities, and polling order. The service schedule is based not only on the traffic classification done according to the packet size, interval distribution, and the direction but also on the instantaneous buffered traffic conditions. The proposed scheduler is shown to have significant performance gains in terms of multimedia traffic channel utilization, packet loss ratio, delay, and jitter when compared with the other schemes.