MMSE space-time multiuser decision-feedback detection in multiple-antenna SDMA systems over dispersive fading channels

This paper analyzes the performance of space-time decision feedback equalization (STDFE) assisted multiuser detection (MUD) for multiple-antenna space division multiple access (SDMA) systems to improve system capacity over dispersive fading channels. The MUD-STDFE receiver consists of a bank of matched filters and symbol-spaced feedforward filters (FFF) that both spatially and temporally whitens noise and the precursive parts of multiple access interference (MAI), followed by a bank of causal feedback filters (FBF) to cancel postcursive ISI and MAI for each user. The algorithm for computing this multi-dimensional FFF and FBF coefficients is presented, based on minimum mean-squared error (MMSE) optimality criterion. The error probability is estimated accurately and efficiently using the Gauss quadrature rule (GQR). The proposed MUD-STDFE receiver is capable of improving the performance significantly, separating the users and offering a significant performance gain relative to linear MMSE detection in an SDMA system.