Space time turbo equalization with successive interference cancellation for multipath coded MIMO channels
Résumé
This paper addresses the issue of iterative space-time equalization for multiple input multiple output (MIMO) frequency selective fading channels. A new soft equalization concept based on successive interference cancellation (SIC) is introduced for a space-time bit interleaved coded modulation (STBICM) transmission. The proposed equalizer allows to separate intersymbol interference (ISI) and multi-antenna interference (MAI) functions. Soft ISI is successively suppressed using a low-complexity sub-optimum minimum mean square error (MMSE) criterion. The decoupling of ISI and MAI offers more flexibility in the design of the whole space-time equalizer. Different multi-antenna detection criteria can be considered, ranging from simple detectors to the optimal maximum a-posteriori (MAP) criterion. In particular, we introduce two soft equalizers called SIC/SIC and SIC/MAP, and we show that they can provide a good performance/complexity trade-off for many system configurations, compared with other turbo equalization schemes. The paper also introduces an MMSE-based iterative channel state information (CSI) estimation algorithm, and shows that attractive performance can be achieved when the proposed soft-SIC space-time equalizer iterates with the MMSE-based CSI estimator.