Capacity scaling and coverage for repeater-aided MIMO systems in line-of-sight environments

Multiple-input multiple-output (MIMO) technique provides capacity improvement which scales linearly with the number of antennas. However, such improvement cannot be realized in line-of-sight (LOS) environments due to lack of scattering. It had been proposed that if a mobile station can receive signal from multiple repeaters, the artificial multipath could render an equivalent high-rank end-to-end MIMO channel. In this paper, we study whether fixed-location repeaters can induce significant MIMO capacity gain throughout the coverage of a cell in a LOS environment. Our results indicate that, for a wide range of repeater locations and antenna parameters, the majority of the coverage area of a cell can support a high-order capacity scaling factor. We further show that for a capacity scaling factor of 2, the corresponding coverage consists of a small number of simply-connected areas. We present the expressions for the contour of these areas as a function of base station and repeater locations, antenna spacings, and antenna orientations.