QoS in Wireless LAN: a comparison between Feedback-Based and Earliest Due-Date approaches

The Hybrid Coordination Function is a very powerful mechanism to provide differentiated services in IEEE 802.11 WLANs. In recent years, its adoption in conjunction with centralized scheduling algorithms has lead to many interesting solutions to support services with very sharp delay constraints. Notably, two main approaches have been proposed to face real-time service provisioning, i.e., using the well known earliest due date scheme or feedback control theory. Unfortunately, it is still missing a deep comparison among them. To bridge this gap, we propose herein a novel feedback-based mechanism for infrastructure WLANs and compare it with respect to the most important delay-EDD algorithm, in complex scenarios with video, voice, and best effort flows. Simulation results, obtained using ns-2, demonstrate that (i) both algorithms are able to guarantee upper bounded packet delays, (ii) a more efficient bandwidth usage and a higher network throughput is achieved using the feedback based approach. In particular, it has been shown that the feedback based approach allows a throughput gain ranging from 10% to 20% with respect to delay-EDD.