Superposition transmission of layered encoded sources over non-orthogonal amplify-forward relay networks

The paper investigates the broadcast of n-layered source codes over a single-relay network using a half-duplex nonorthogonal amplify-forward (HD-NAF) relaying protocol. Taking the distortion exponent, (i.e., the SNR exponent of the average end-to-end distortion) as the performance metric, we consider system operation in the high SNR regime. We first prove that the HD-NAF relay network with an n-layer code is subject to the successively refinable Diversity Multiplexing Tradeoff (DMT) curve, which is exercised to derive a closed-form expression for an achievable upper bound of the system distortion exponent. Rate allocation optimization is conducted to analyze and gain insight into system behavior. Numerical evaluations are performed based on derived analytical formulations, and the performance advantage of single-relay HD-NAF networks is justified in terms of the distortion exponent versus its conventional counterparts. Furthermore, it is observed that increases in the number of encoded layers increases system performance.