Adjustable TXOP mechanism for supporting video transmission in IEEE 802.11e HCCA

Abstract

The basic mechanism of HCCA (HCF Control Channel Access) has been introduced in IEEE 802.11e standard to support the parameterized QoS by allocating a fixed duration based on the requested TSPEC requirements during the admission control process. However, the variable bit rate (VBR) traffic (e.g., MPEG-2 and MPEG-4 video) cannot be surely supported. In this study, the adjustable TXOP mechanism for supporting video transmission, ATMV, has been proposed. The mechanism adaptively adjusts the TXOP duration according to a finite state machine based on feedback queue size information. The mechanism aims for prompt serving burst packets, generated from the incoming video frames, which finally minimizes the packet delay. Both system performance (mean packet delay, TXOP loss factor, and channel occupancy) and video quality (PSNR and MOS values) have been evaluated from five video clips in three categories by using the network simulator, NS2, with EvalVid toolset. The results reveal that the proposed mechanism performs well for rapid movement video category and adequately supports for other video categories.