Distortion exponents of source transmission over two-way relaying cooperative networks

In this paper, we consider the source transmission in a three-node, half-duplex, and two-way relaying network, where two users communicate with the help of one relay. The relay employs the decode-and-forward (DF) based relaying protocol. We study the distortion exponent that characterizes the high signal-to-noise ratio (SNR) behavior of the end-to-end distortion of the reconstructed signal at each user node. We first provide an upper bound on the achievable distortion exponents of two-way relaying communications, which is tight at large bandwidth ratio. We then investigate the performance of various coding and transmission schemes, including the conventional one-way relaying strategies and source-channel coding in two-way relaying with single-rate coding or limited channel state feedback. We derive the achievable distortion exponents of all these schemes and illustrate the effect of the bandwidth ratio, feedback resolution, and relaying strategies on the optimal distortion exponent.