Abstract
We propose a low-complexity turbo-detector scheme for frequency selective multiple-input multiple-output channels. The detection part of the receiver is based on a List-type MAP equalizer which is a state-reduction algorithm of the MAP algorithm using per-survivor technique. This alternative achieves a good tradeoff between performance and complexity provided a small amount of the channel is neglected. In order to induce the good performance of this equalizer, we propose to use a whitened matched filter (WMF) which leads to a white-noise "minimum phase" channel model. Simulation results show that the use of the WMF yields significant improvement, particularly over severe channels. Thanks to the iterative turbo processing (detection and decoding are iterated several times), the performance loss due to the use of the suboptimum List-type equalizer is recovered.
Highlights
The growing demand for new services at high data rates indicates the need for new techniques to increase channel capacity
The first J taps are processed by the trellis transitions of the List-type equalizer and the remaining taps are processed by a per-survivor processing with S survivors at each state
It is composed of the generalized List-type maximum a posteriori (MAP) equalizer and a single-input single-output (SISO) decoder using the BCJR-MAP algorithm proposed by Bahl et al [3]
Summary
The growing demand for new services at high data rates indicates the need for new techniques to increase channel capacity. In [17], Bauch and Al-Dhahir used a set of shortening filters [18] as prefilters to turbo equalization in order to reduce the number of states of the MAP equalizer The disadvantage of this method is that the noise becomes colored at the outputs of the shortened channel. Thanks to the WMF, the noise at the input of the turbo detector is white This permits to have a good performance without enhancing the complexity of the equalizer. For simplicity, the colored noise is assumed to be white, the soft outputs of the equalizer are degraded, on the first turbo iteration This can affect significantly the performance of the iterative receiver since we know the importance of the equalization at the first iteration for the turbo processing.
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