Multi-source multi-destination relay network: constrained optimisation for higher diversity

The authors consider a cooperative communication system where multiple sources transmit data to multiple destinations, being helped by multiple half-duplex relay nodes: relay nodes perform `amplify and forward` as their cooperative technique, with the use of complex weights for forwarding; complex forwarding weights are optimised, based on the obtained channel information, to improve data transmission performance, especially its corresponding diversity order. In particular, the authors investigate the constrained optimisation on the forwarding weights, under the two constraints of interference-free data reception at all destinations and total forwarding power at all relays, to (i) maximise the signal-to-noise ratio (SNR) of any given source`destination pair; (ii) optimise (here maximise the minimum among) the SNRs of all source`destination pairs. Performance (especially diversity order) analysis and Monte-Carlo simulations show the achieved diversity order and the consistence between analytical and numerical results.