Pappas, Thrasyvoulos Northwestern U
There has been much interest in supporting video communication over wireless networks. This is not a simple task due to the stringent Quality of Service (QoS) required by video applications and the many impairments of wireless channels. Two important QoS characteristics for video are the degree of signal distortion and the transmission delay. Wireless channels are lossy, have a timevarying response, and are subject to multi-user interference. Furthermore, since users of a wireless network are mobile, e.ciently utilizing the available energy is a key consideration. The di.culties inherent in wireless video can be addressed at both the physical layer and the source coding layer. We jointly consider a combination of these approaches in a cross-layer framework. Speci.cally, we consider jointly adapting source coding parameters, such as the quantization step-size and prediction mode, along with physical layer resources, such as the transmission rate and power. Our goal is to provide acceptable QoS while taking into account system constraints such as the available energy. We propose a general framework that allows a number of resource/distortion optimal formulations for balancing the requirements of di.erent applications.
