Instances of the relay-broadcast channel and cooperation strategies

It is well known that cooperation between users in a communication network can lead to significant performance gains relative to the same network without cooperation. One common model which has been studied recently is the two users degraded broadcast channel (BC) with cooperating decoders. It can be viewed as a special case of the relay-broadcast channel (RBC), where the link from the relay to the other user is a noiseless channel (bit-pipe), that does not interact with the main channel. In this work two extensions of this basic model are suggested and studied: the BC with conferencing and degraded message sets, and the degraded BC with parallel conferencing, where there are parallel relays whose data streams are received by all the users in the channel. Since the data stream of each relay is also received by the other, one relay can allocate part of its rate to help the other relay to distribute its data stream. The capacity region is characterized for the two models.