A distributed and spectrally efficient link selection scheme for multiuser multirelay networks with transmit beamforming

A distributed and spectrally efficient link selection scheme for multiuser multirelay cooperative networks with transmit beamforming is proposed and analyzed in terms of outage probability and mean spectral efficiency. More specifically, we consider a network composed by a base station equipped with M antennas which is communicating with one out of L single-antenna mobile stations under the aid of one out of N single-antenna, variable-gain amplify-and-forward relay stations. Either the direct link or the dual-hop relaying link is selected for each communication process by following a distributed link selection scheme. Single-integral expressions for upper and lower bounds of the outage probability and mean spectral efficiency are obtained and validated by Monte Carlo simulations. Furthermore, closed-form expressions derived from the asymptotic analysis of the outage probability reveal that the proposed system achieves full diversity order, which is equal to ML+N. Importantly, it is shown that the mean spectral efficiency is always higher than half of that one attained by direct transmission.