Soft information assisted space-time multiuser detection for highly loaded CDMA

Abstract

This letter presents an effective space-time multiuser detector (MUD) with the assistance of soft information in multipath code division multiple access (CDMA) channels. The space-time MUD considered is a simple, separable spatialtemporal filter which consists of a single spatial filter and a single temporal filter. Based on the soft-decision outputs determined in the previous iteration, the soft information is then exchanged in the alternating updates of either the spatial filters or the temporal filters. Furnished simulations show that the proposed scheme can offer substantial performance improvement compared with previous works, especially in highly loaded scenarios.

Soft Decision Error Assisted Layered Multiuser Detectors for MIMO 2D Spread MC DS-CDMAs

“…T represents the corresponding statistics of the soft decisions [25]; andv g,k−1 is the Gaussian noise vector. Note that becauseȇ g,k−1 is the soft decision error of the (k − 1)th user in the gth group, we only need to remove the corresponding estimated signals of the (1, 1)th, .…”

“…Furthermore, based on the maximum a posteriori (MAP) method, the soft decisionλ(d g,k,i ) for the transmitted symbol d g,k,i can be expressed as follows [1,25]:…”

A two‐stage receiver with soft interference cancellation for space–time block code and spatial multiplexing combined systems

“…Based on the statistical property of the transmitted STBC symbols and the Gaussian noise assumption of the channels, as Reference 23, it can be readily shown that ${\bar {z}}_{j}^{(g)} $ is approximately Gaussian so ${\bar {z}}_{j}^{(g)} = {\bar {m}}_{j}^{(g)} b_{j}^{(g)} + n_{j}^{(g)} $ 17, 18, where ${\bar {m}}_{j}^{(g)} $ is the equivalent strength and $n_{j}^{(g)} $ is the noise with variance ${\bar {\sigma }}_{j}^{(g)^{2} } $ . After some manipulations as given in Appendix A, ${\bar {m}}_{j}^{(g)} $ and ${\bar {\sigma }}_{j}^{(g)^{2} } $ can be shown, respectively, as and where || · || denotes the Euclidean norm.…”

“…After some manipulations as given in Appendix A, ${\bar {m}}_{j}^{(g)} $ and ${\bar {\sigma }}_{j}^{(g)^{2} } $ can be shown, respectively, as and where || · || denotes the Euclidean norm. The soft‐decision output after the filter and the MAP criterion is then given by Reference 17, 18 …”

“…To provide satisfactory performance with reasonable cost, in this paper we propose a soft information‐assisted two‐stage receiver for the combined STBC‐SM MIMO systems. In light of the fact that the soft information approach 17–19 can generally result in a more precise estimate of the interferences, the first stage of the receiver, utilizing the inherent structure of the STBC, consists of a bank of soft generalized sidelobe canceller (GSC)‐based detectors, each for every STBC block. These detectors are an extension of the conventional GSC‐based receiver addressed in Reference 20 to produce soft‐decision outputs, aiming at providing a more precise initial estimate of the transmitted symbols for the follow‐up symbol detection.…”