Repeater-Assisted Capacity Enhancement (RACE) for MIMO Links in a Line-of-Sight Environment

A single on-frequency, full duplex wireless repeater is considered for enhancing the capacity of a long-distance 2 times 2 multiple-input multiple-output (MIMO) wireless link with a dominant line-of-sight (LOS) component. Such links might be used for high-speed communication between buildings or towers. For practical reasons, the aperture sizes of the transmit (TX) and receive (RX) arrays may be limited, which tends to make the rank of the long-distance MIMO channel matrix close to unity. The paper shows that the addition of just one repeater can bring the channel to full rank, approximately doubling the capacity of the link. Typical values of repeater isolation are assumed. For small TX and RX array element spacings, there is considerable robustness in optimal repeater location. Even with some multipath, most of the capacity improvement is retained.