MIMO Amplify-and-Forward Relaying in Correlated MIMO Channels

Amplify-and-Forward (AF) is a simple but effective relaying concept for multihop networks that combines transparency regarding modulation format and coding scheme with ease of implementation. Recently, a spatial filter design for MIMO AF relays was proposed that allows for capacity gains when having i.i.d. Rayleigh fading channels and full channel knowledge available at the relay station. In this paper, correlated MIMO channels are considered and spatial filter designs for partial channel knowledge at the relay station are considered. It appears that for correlated MIMO channels, it becomes essential to spatially filter the signal at the relay station in order to avoid implicit beamforming into wrong directions