Amplify-and-forward relay stations in correlated line-of-sight indoor MIMO channels

The bandwidth efficiency of Multiple Input - Multiple Output (MIMO) channels is analyzed for point-to-point (P2P) and relay channels. The focus lies on channels with a strong and unobstructed line-of-sight (LOS) signal component between transmitter (Tx) and receiver (Rx), as it is the case in indoor in-room scenarios. The bandwidth efficiency of the resulting correlated P2P MIMO channel is strongly dependent upon the geometrical antenna setup. Especially the angle of arrival (AOA) and the inter-array antenna spacing of uniform linear arrays (ULAs) influence the bandwidth efficiency. Both influences are minimized by the use of distributed simple amplify-and-forward relay stations, while the resulting relay MIMO channel is correlated. In the relay case, the total transmit power spent at the Tx and the relay is limited to the transmit power of the Tx in the P2P case for a fair comparison. Relay stations are capable to enhance the bandwidth efficiency of the pure LOS MIMO channels, while the high bandwidth efficiency of channels with LOS and non line-of-sight (NLOS) signal components is not further increased in the considered scenario.