Content-Based Cross-layer Packetization and Retransmission Strategies for Wireless Multimedia Transmission

Existing wireless networks provide dynamically varying resources with only limited support for the Quality of Service required by the bandwidth-intense, loss-tolerant, and delay-sensitive multimedia applications. This variability of resources does not significantly impact data applications (e.g., file transfers), but has considerable consequences for multimedia applications and often leads to unsatisfactory user experience. Recently, the research focus has been to adapt existing algorithms and protocols at the lower layers of the network stack to better support multimedia transmission applications, and conversely, to modify application layer solutions to cope with the varying wireless networks resources. In this paper, we show that significant improvements in wireless multimedia performance can be obtained by deploying a joint application-layer packetization and MAC-layer retransmission strategy. First, we show that packet-size optimizations solely determined at the MAC-layer result in a sub-optimal performance in terms of the multimedia quality. Subsequently, we propose cross-layer strategies that optimize the packetization, prioritization and retransmission strategies based on content characteristics, channel conditions, and the specific features of the deployed video coder. Finally, we investigate the use of content based distortion models for the video, to reduce the complexity of our proposed optimization.