Distortion Behavior of Amplify-and-Forward Cooperative System with Layered Broadcast Coding

Cooperative system has been receiving considerable attention recently as an effective approach to improve transmission reliability in slow fading wireless channels. In this paper, we exploit cooperative diversity in multiple relay networks to improve the performance of Gaussian source transmission with layered broadcast coding. Specifically, we study the distortion performance of two amplify-and-forward (AF) schemes, namely, distributed beamforming and selection AF. First, we analyze their asymptotic performance in terms of the distortion exponent and the expected distortion. We then show that, under stringent delay constraint, there exist SNR thresholds below which the AF systems achieve lower distortion than the direct transmission system.