Forward capacity of space-time turbo coded CDMA system with turbo reception

In this paper we consider a multiple-input multiple-output (MIMO) downlink multi-cell CDMA system employing BLAST space-time turbo codes (STTuC) over the frequency-selective fading channel. The system performance is measured in terms of system spectral efficiency (bits/s/Hz/cell). A space-time RAKE receiver and a space-time turbo receiver are proposed. The turbo receiver is based on space-time parallel interference cancellation (ST-PIC), which can reconstruct and subtract all the types of interference in the multipath MIMO CDMA channel at the same time. In each iteration, the soft output of the space-time turbo decoder is fed back to improve the PIC´s performance. The simulation shows that the turbo PIC receiver enhances the STTuC CDMA system spectral efficiency by 50% over the RAKE receiver. This result suggests that, with the turbo reception technique, the MIMO CDMA system can serve much more users in a cell or provide much higher rate downlink packed data service to one user.