Low Complexity Metric for Joint MLD in Overloaded MIMO System

Abstract

This paper presents a low complexity metric for joint maximum-likelihood detection (MLD) in overloaded multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) systems. In overloaded MIMO systems, a nonlinear detection scheme such as MLD combined with error correction coding achieves superior performance than that of a single signal stream with higher order modulation. However, MLD demands large computational complexity because of multiplications in the selection of candidate signal points. Thus, a Manhattan metric has been used to reduce the complexity. Nevertheless, it is not accurate and causes performance degradation in overloaded MIMO systems. Thus, this paper proposes a new metric that is calculated with summations and bit shifts. New numerical results obtained through computer simulation show that the proposed metric improves bit error rate (BER) performance more than 0.2dB at the BER of 10^(-4) in comparison with a Manhattan metric.