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Space-time turbo equalization and symbol detection in frequency selective MIMO channels

A computationally efficient space-time turbo equalization algorithm is derived for frequency selective multiple-input multiple-output (MIMO) channels. The algorithm is an extension of the iterative equalization algorithm by Reynolds and Wang (2001) for frequency selective fading channels. This paper's proposed equalizer performs MIMO channel estimation, multiple user signal detection, and decoding, jointly all in an iterative manner. The iterative channel estimator achieves high accuracy in estimating channel parameters even if only a relatively small number of unique word symbols are available. The multiple user signal detector (MUSD) consists of soft interference cancellers for the multiple users, each followed by a minimum mean square error (MMSE) filter. With this simple structure, the proposed detector achieves a drastic reduction in computational complexity compared with conventional trellis-based turbo equalizers. Simulation results show the proposed equalizer can properly separate multiple user signals in frequency selective MIMO channels.