Optimization of Power Constrained Multi-Source Uplink Relay Networks

In this paper, we study the tradeoffs between basestation beamforming and distributed beamforming in the uplink. Here, multiple single-antenna sources access a multiple-antenna destination (basestation) through a network of single-antenna relays. In order to determine the solution, we decouple the problem into that of optimizing a linear decoder at the destination and that of optimizing relay beamforming weights. We find the optimal linear decoder at the destination and the corresponding feasible SINR feasible upperbound when the number of receive antennas at the destination is no less than the number of relays. We then apply a recently developed semidefinite relaxation technique that optimizes the relay weights. The proposed algorithm iteratively optimizes the weight matrix at the relays and the linear decoder at the destination and is able to reach a fixed point in only a few iterations. In addition, the tradeoffs between basestation and relay network complexity are investigated.