Capacity Bounds for MIMO Shared Relay Channel with Half-Duplex Constraint

We consider a shared relay channel (SRC) where a single relay assists the communications between multiple source-destination links under the half-duplex (HD) constraint. Specifically, we derive lower and upper bounds on the capacity of 2-user AWGN MIMO SRC with two source-destination pairs. Two different coding strategies are presented based on superposition coding and on dirty paper coding, respectively. We compare the performance of the proposed SRC coding schemes with that of a TDMA strategy where each source-destination pair communicates in alternative time slots with the assistance of the relay. The proposed coding schemes for SRC results in significant performance improvement over TDMA strategy in terms of both ergodic capacity and outage probability.