The impact of relaying on the capacity of broadcast channels

The capacity of two broadcast systems with relay links is studied in this paper. Both of these systems are extensions of two users degraded broadcast channels, which achieves a rate region of channels and includes the capacity region of original broadcast channel. We then consider another system, the dumb relay broadcast channel, where an additional relay node is introduced into the two users degraded broadcast channel that assists both user. This relay node does not have its own information from the source, and hence is referred to as dumb relay node. From the results an achievable rate region for this channel is derived and is shown to include that for the cooperative broadcast channel.