Cross-Layer Techniques for Reliable Wireless Video Communication

Designing wireless video communication system is a challenging task due to high error rates of wireless channels, limited and dynamically varying bandwidth availability, and low energy and complexity requirements of portable multimedia devices. Scalable video coders having excellent rate-distortion performance are most suited to cope with time varying bandwidth of wireless networks, but encoded bits are extremely sensitive to channel errors. This chapter presents a reliable video communication system exploring opportunities offered by various network layers for improved overall performance, while optimizing the resources. More specifically, cross-layer approach for Unequal Error Protection (UEP) of scalable video bitstream is the main theme of this chapter. In UEP, the important bits are given a higher protection compared to the other bits. Conventionally, UEP is achieved by using Forward Error Correction (FEC) at the application layer. However, UEP can also be provided at the physical layer using hierarchical modulation scheme. In this chapter, the authors discuss cross-layer design methodology for UEP that rely on interaction between the application layer and the physical layer to achieve reliable and high quality end-to-end performance in wireless environments. The discussion is mainly focused for wavelet coded video, but it is applicable to other embedded bitstreams as well.