Feasible HCCA Polling Mechanism for Video Transmission in IEEE 802.11e WLANs

IEEE 802.11e standard defines two Medium Access Control functions to support Quality of Service (QoS) for wireless local area networks: Enhanced Distributed Channel Access (EDCA) and HCF Controlled Channel Access (HCCA). EDCA provides fair prioritized QoS support while HCCA guarantees parameterized QoS for the traffics with rigid QoS requirements. The latter shows higher QoS provisioning with Constant Bit Rate traffics. However, it does not efficiently cope with the fluctuation of the Variable Bit Rate (VBR) video streams since its reference scheduler generates a schedule based on the mean characteristics of the traffic. Scheduling based on theses characteristics is not always accurate as these traffics show high irregularity over the time. In this paper, we propose an enhancement on the HCCA polling mechanism to address the problem of scheduling pre-recorded VBR video streams. Our approach enhances the polling mechanism by feed-backing the arrival time of the subsequent video frame of the uplink traffic obtained through cross-layering approach. Simulation experiments have been conducted on several publicly available video traces in order to show the efficiency of our mechanism. The simulation results reveal the efficiency of the proposed mechanism in providing less delay and high throughput with conserving medium channel through minimizing the number of Null-Frames caused by wasted polls.