A prioritization scheme for H.264/AVC video congestion resilience with IEEE 802.11e

Intra-refresh is an efficient technique to mitigate temporal error propagation resulting from network packet losses. However, while including intra-refresh macroblocks (MBs) can prevent error propagation, conversely when network congestion occurs, packets carrying this type of MBs should be dropped at wireless network access time, in preference to dropping packets containing data of other types of MBs. Exploiting this observation, the proposed network access prioritization scheme combines intra-refresh MB lines with the H.264/AVC codec's Flexible Macroblock Ordering (FMO) to enhance congestion resilience. The proposed scheme is shown to improve the resulting video quality by up to 4 dB during periods of congestion. As an application of the proposed algorithm, the paper applies a crosslayer mapping of video traffic to IEEE802.11e access categories. The potential gains are demonstrated both for random packet drops at input buffers and for a wireless sensor network scenario.