Fair Hierarchical Scheduling with Capability of Handling Channel Failures in a Wireless LAN

This paper proposes and analyzes the performance of a packet scheduling scheme capable of satisfying both real-time Quality-of-Service (QoS) constrains and non-real time best effort service while handling channel errors in IEEE 802.11 WLAN through exploiting a hierarchical EDF-FCFS scheduler featuring an adaptive feedback control mechanism. While the real-time scheduler is derived from the legacy Earliest Deadline First (EDF) scheme, the non-real time scheduler is derived from the ordinary First Come First Served (FCFS) scheme. During runtime operation, with the support of a feedback control mechanism, the Access Point (AP) dynamically switches the two polling schedulers according to the channel status, giving the temporarily unreachable real-time traffic more chances to meet its time constrains while continuing the best effort service for the non-real time traffic. Simulation results show that the proposed hierarchical scheduler efficiently improves the overall WLAN packet success ratio.