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Cross-layer design is a promising direction and challenging issue for quality delivery of multimedia over wireless networks. This article proposes a cross-layer design which can substantially enhance the transmission quality of video streaming over 802.11e ad hoc networks. The proposed design consists of two parts: a dispersive video frame importance (DVFI) scheme in the application layer that can correctly label the priorities of video packets, and a comb-shaped quadratic mapping (CQM) algorithm in the medium access control (MAC) layer that can provide a better congestion control mechanism among the multiple access category (AC) queues than 802.11e Enhanced Distributed Channel Access (EDCA) for wireless video delivery. The DVFI value of a video frame is measured from its own transmission loss and the accompanied impact to other coding-dependent video frames, and is accordingly adopted to prioritize the video frame associated packets. When these prioritized video packets arrive at the reserved AC queue in the MAC layer, the CQM algorithm can accordingly provide multi-branched service differentiation among them by dynamically downward mapping less significant video packets to lower-priority ACs based on the instant congestion level of the reserved AC queue, which can thus offer a better channel access resource to those video packets of higher priorities. In addition, the minimum-delay-time rule embedded in the CQM will select a better destiny for those downward mapped video packets among the lower-priority AC queues. Under various video-input-rate and cross-traffic tests, the simulation results show that this study outperforms the existing works, including EDCA, Adaptive Mapping, and Enhanced Adaptive Mapping.

A novel cross-layer design using comb-shaped quadratic packet mapping for video delivery over 802.11e wireless ad hoc networks