MIMO Detection With High-Level Modulations Using Power Equality Constraints

This paper proposes computationally efficient algorithms for the detection of symbols of high-level modulation constellations in multiple-input-multiple-output (MIMO) systems. The proposed approach is based on replacing the maximum-likelihood constraint with a finite set of power equality constraints (PECs), resulting in a set of nonconvex optimization problems, which can efficiently be solved using the hidden convexity methodology. Next, using specific structural properties of the proposed approach, we develop an ordered PEC algorithm, which provides a significant computational complexity reduction with no performance degradation. Based on that, an improved OPEC algorithm, which incorporates a heuristic local search, is proposed. Numerical results show that the proposed detectors significantly outperform the conventional minimum-mean-square-error (MMSE) detector in terms of bit error rate (BER) performance, with only a slightly higher complexity.