Multiple Repeater Placement for Assisting Long-Range LOS MIMO Links

A wireless MIMO link is considered in a LOS configuration with multiple SISO wireless repeaters assisting. A theoretical analysis is presented in which repeater positions are considered and sufficient conditions proposed and evaluated for maximizing the MIMO multiplexing gain. The assisting repeaters would be useful when space constraints, for example, on a building top, would prohibit the wide element spacings needed by a MIMO terminal to reach full capacity over a long range LOS link. Sufficient conditions include, among other things, mutual orthogonality of steering vectors from one MIMO terminal pointing toward the opposite terminal and toward each of the repeaters. Once n - 1 such repeaters have been properly placed, where n represents the smaller dimension of the channel matrix, the matrix becomes full rank and the multiplexing gain is maximized.