Joint source and relay optimization for multiuser relay system with QoS considerations

In this paper, a joint source and relay optimization problem is studied for a multiuser relay system. Assuming that the channel state information (CSI) at the source and relay is available, an amplify and forward (AF) relaying scheme is proposed to maximize the sum-rate of the system under the constraints that a set of SIR targets should be satisfied at the users. We apply two well-known methods in this paper, namely, the gradient search algorithm and the SIR-balancing algorithm, to design the relay and source matrix. Thus, a convergence-ensured iterative algorithm is proposed to successively optimize the transmit parameters at one node (source or relay) with those at the other node being fixed. Theoretical analysis and Monte Carlo simulations illustrate the performance of the derived scheme.