An efficient sphere decoding algorithm for rank-deficient OFDM/SDMA systems

The design of efficient receivers for orthogonal frequency division multiplexing/space division multiple access (OFDM/SDMA) channels remain a challenging task especially when the number of mobile stations (MSs) transmitting exceed base station (BS) antennas. The benchmark performance is achieved by Maximum Likelihood (ML) detector at the cost of computational complexity that exponentially increases with spatial and temporal dimension. As an alternative to reduce complexity without compromising the performance, this paper discusses a simple and effective Fincke and Pohst Sphere Decoding (FP-SD) algorithm which incorporates a pseudo-antenna augmentation scheme to handle a rank-deficient channel. The work also explains how suitable radius selection affects the performance.