Toward a preferred 4 × 4 space-time block code: A performance-versus-complexity sweet spot with linear-filter decoding

We develop a new 4 × 4 Hadamard-precoded quasi-orthogonal space-time block code (QO-STBC) that enables highly effective near-maximum-likelihood (near-ML) reliability-based prioritized symbol detection using linear filters. Approximate block-error-rate minimization is being used to optimize the code rotation angle. Detailed computational complexity evaluation of the decoder in terms of real multiplications and additions shows significant complexity reduction for symbol alphabet sizes of interest. Numerical and simulation studies demonstrate negligible bit-error-rate degradation compared to the state-of-the-art in bit-error-rate by ML decoded 4 × 4 codewords.