Iterative MMSE Decoder for Trace-Orthogonal Space-Time Coding

Trace-orthogonality is an important property of linear space-time encoders that has emerged relatively recently. In this work we carry out the theoretical performance analysis of a low complexity decoder for trace-orthogonal space-time codes based on the linear MMSE estimator. We derive the diversity order of such a decoder in the case of MIMO systems affected by uncorrelated flat Rayleigh fading, when information symbols are carved from a QPSK constellation, and are encoded using what we term a unitary trace-orthogonal design. Then we propose an iterative decoder that dramatically improves the performance over the linear MMSE decoder. Simulation results give evidence of the effectiveness of the proposed scheme