A Broadcasting Relay for Orthogonal Multiuser Channels

This paper introduces broadcasting relay nodes for orthogonal multiuser channels. The underlying idea is that a single relay node is shared by multiple source-destination pairs. In this scheme, the relay node receives the messages of multiple independent sources, and broadcasts a single superimposed signal to multiple destinations. Compared to dedicated relay scenarios, large gains in capacity region and outage capacity is possible with the shared relay scenario. We consider the special case of two pairs, and examine discrete memoryless channels and Gaussian channels assuming degradedness for the relay channels and physically degradedness for the broadcast channel. Upper bounds on capacity are obtained and shown to be achievable. The analysis is also extended to Rayleigh fading channels, where outage regions are investigated.