Beamforming Methods for Multiuser Relay Networks

In this paper, we consider a multiuser relay network under amplify and forward (AF) scheme, where each mobile station (MS) is supported by a unique relay station (RS). While the RSs forwards the scaled signal to the MSs, the interference caused by the multiuser nature of the system propagates via the RSs, which significantly degrades the performance gain of the relay technique. We propose two beamforming methods, zero forcing (ZF) method and maximizing signal to leakage ratio (MSLR) method, to suppress the multiuser interference in the relay networks. ZF method can effectively cancel multiuser interference for all MSs and RSs, while it requires a relatively large number of transmit antennas equipped at the base station (BS). The other method, MSLR, aims to maximize the received signal at each MS and RS, while minimize the energy leaking to other MSs and RSs. The advantage of MSLR method is that it does not impose a condition on the relation between the number of transmit antennas equipped at the BS and the receive antennas at the RSs and MSs. Simulations show that MSLR method has significant performance gains over ZF method.