QoS/QoE Support for H.264/AVC Video Stream in IEEE 802.11ac WLANs

The H.264 video compression technique enjoys the merit of good video quality with high compression rate; therefore, it has been widely applied in delivering video content. In IEEE 802.11ac wireless local area networks, enhanced distributed channel access (ED-CA) is the primarily adopted access control mechanism for multimedia traffic transmission. However, the performance is degraded due to the unpredictable delay caused by its inefficient back-off procedure. To achieve high quality of service/experience, this paper proposes a multi polling controlled access (MP-CA) scheme to guarantee the latency in delivering important video frames while reducing transmission overhead.

We also propose a cross-layer designed quality adjustment strategy to maximize the visual experience. Furthermore, the down-link multi user multiple-input–multiple-output feature in IEEE 802.11ac is exploited to enhance the reliability of MP-CA. Theoretical analysis is provided to show high efficiency of MP-CA. Simulation results indicate that MP-CA has higher throughput, lower packet delay, lower packet loss, and higher peak signal-to-noise ratio than the ED-CA.