Parallel relay broadcast channels

In this paper, we study the achievable rate regions of parallel relay broadcast channels. We present two system models, the parallel unshared-relay broadcast channel and the parallel shared-relay broadcast channel. In the first system, each relay node is peculiar to one of the users and does not assist any other user. In the second system, each relay node is shared by all users and assists all of them. Achievable rate regions for these two different channel models are derived in the discrete memoryless case. We also provide an outer bound on the rate regions, which is tighter than the cut-set bound.