A Two-Round Interactive Receiver Cooperation Scheme for Multicast Channels

Abstract : We consider the transmission of a common message from a transmitter to two receivers over a broadcast channel, also called a multicast channel in this case. The two receivers are allowed to cooperate with each other in full-duplex over non-orthogonal cooperation links. We investigate the information-theoretic upper and lower bounds on the broadcast rate. In particular, we propose a two-round cooperation scheme in which the receivers interactively perform compress-forward (CF) and then decode-forward (DF) to improve the achievable rate. Numerical results compare the proposed scheme to existing schemes and the cutset upper bound in the Gaussian case. We show that the proposed scheme outperforms the non-interactive DF and CF schemes as well as the noisy network coding scheme. The gain over the DF scheme becomes larger when the main channel becomes symmetric, while the gain over the CF scheme becomes larger when the main channel becomes asymmetric.