Iterative detection based on reduced-rank equalization [mobile radio]

In this paper, we consider an iterative or turbo receiver with linear detection using the Wiener filter (WF), i.e. the optimal linear filter based on the mean square error (MSE) criterion. Multiple antennas at the receiver increase the dimension of the observation vector which results in computationally intense detectors. We extend an optimal but computationally efficient algorithm, originally derived for a single receive antenna, to single-input multiple-output (SIMO) channels. To further reduce computational complexity, we apply the suboptimal low-rank multi-stage Wiener filter (MSWF) and approximate additionally second order statistics of non-stationary random processes by their time-invariant averages. Complexity investigations reveal the enormous capability of the proposed algorithms to decrease computational effort. Moreover, simulation results show that the reduced-rank MSWF behaves near optimum although the rank is drastically reduced to two or even one.