Relay MAC Channels: Capacity and Resource Allocation

We investigate the relay multiple access channels (RMAC) with two users and a destination. We determine the lower bound and upper bound on the capacity of RMAC under time-division (TD) decode-and-forward (DF) mode by using superposition modulation. A relay scheme with resource allocation is proposed to achieve the lower bound. Analytical results and simulation results show that the proposed scheme can achieve larger capacity region than that of direct transmission (DT) for the fixed channel gain case. But they provide the same maximum sum capacity. Whereas, the proposed relay scheme can provide higher outage capacity than DT scheme due to the fact that the two sources can share the resources from each other.