Achieving Near Capacity of Non-Binary LDPC Coded Large MIMO Systems with a Novel Ultra Low-Complexity Soft-Output Detector

Abstract

Recently, it has been proved that both MMSE and MF detectors are near optimal detection for large scale MIMO systems, e.g., MIMO systems with hundreds of antennas. In order to attain near capacity region with reasonable complexity, low-complexity detector with soft-output generation is necessary for coded large MIMO systems. We show in this paper that the non-binary LDPC codes and well-known soft-output MMSE detector can be utilized to significantly reduce the gap to capacity. We also propose a novel soft-output MF-based detector for the non-binary LDPC coded large MIMO systems. With this proposed detector, capacity approaching performance, i.e., the gap to capacity of 1.6 dB, can be achieved with ultra low-complexity detection, e.g., just 0.28% of MMSE detection. Moreover, use of the proposed scheme in large MIMO systems is found to be robust to the presence of imperfect channel estimation and spatial fading correlation which are both the realistic scenarios for large MIMO systems.