Information-Theoretic Relaying for Multicast in Wireless Networks

A two-sender, two-receiver channel model with one relay node is considered for the case of multicast traffic. We examine two different cooperative approaches: relaying, in which the relay time-shares between helping two senders and employs traditional routing on the network layer, and more general encoding schemes in which the relay simultaneously forwards two data streams. Outer bounds are presented and then specialized to bound the performance of any relaying scheme. Two simple encoding schemes that allow for more general relaying are considered and compared to the relaying outer bound. We also consider the performance of an opportunistic network coding scheme that exploits interference at the receivers by interpreting it as a form of a network code.