On FR-BDSM approach for next generation mobile communications

In previous studies, the co-channel users (CCUs) in a fixed-relay spatial-multiplexing system are assigned to the same relay station (RS), and this strategy causes serious co-channel interference (CCI) because of short distances between CCUs. To mitigate CCI, a novel spatial multiplexing approach, referred to as fixed-relay beam-division spatial-multiplexing (FR-BDSM), is proposed in the paper. In the FR-BDSM architecture, CCUs are assigned to different relay stations by the optimal CCU allocation algorithm which maximizes the distances between CCUs, hence the CCI is suppressed. To improve orthogonal property of the relay spatial-division channels, an optimal array vector algorithm is investigated. By the optimal array vectors which are found by maximizing the signal to interference ratios (SIRs), the spatial channel between a base station (BS) and its relay stations (RSs) is divided into multiple orthogonal beam-division spatial channels, hence the system capacity is increased.