Distortion Exponents for Multi-Relay Cooperative Networks with Limited Feedback

In this paper, we consider the transmission of a Gaussian source in a multi-relay cooperative network, where limited channel-state feedback is combined with separate source and channel coding to help the transmission. We analyze the end-to-end distortion of the system at a high signal-to-noise ratio (SNR) in terms of the distortion exponent. The achievable distortion exponents of the limited-feedback-based scheme are optimized under various cooperation protocols, including the orthogonal amplify-and-forward (AF)/decode-and-forward (DF) protocols, the nonorthogonal AF/DF protocols, and the slotted AF protocol. Our analysis reveals the impact of the feedback resolution, the bandwidth ratio, the number of relays, and cooperation strategies on the optimized distortion exponent. It is shown that the feedback scheme outperforms the best known nonfeedback strategies for multiple-relay systems with only a few bits of feedback information.