Optimization of the FHCF Algorithm for QoS in IEEE 802.11e Networks

The IEEE 802.11e standard was proposed to provide QoS capabilities in wireless networks. For the centralized HCF channel access mode (HCCA), the standard proposes a simple reference scheduler which allocates time to stations based on mean data rates for flows. Due to its static mechanism of time allocation based on mean data rates, the scheduler is inefficient for variable bit-rate (VBR) traffic such as video-conferencing or VoIP traffic. The Flexible HCF (FHCF) scheme was proposed for handling VBR traffic by using better queue length estimation for flows. However, FHCF over estimates queue-lengths, allocates time inefficiently and it fails to provide QoS under high load. We propose a modified and highly optimized version of FHCF, the Optimized FHCF (OFHCF). OFHCF is a scheduling algorithm that is more efficient, economical, and provides QoS guarantees for all types of traffic even under heavy load. Simulation results are presented to compare FHCF and OFHCF.