Abstract

This paper proposes concatenated beam- and antenna-domain belief propagation (BP) based signal detector for realizing low-complexity large multi-user multi-input multi-output (MU-MIMO) detection. As a low-complexity strategy for large-scale MU detection (MUD), group-specific signal detection in the beam domain has been proposed, where user equipments (UEs) are grouped based on the long-term channel statistics at a base station (BS) to design outer beamformer (OBF). In this case, the BP-based algorithm is effective as the subsequent signal detector to compensate for the performance degradation due to the dimensionality reduction caused by the OBF. However, the convergence characteristics of beam-domain BP is degraded as compared to the antenna-domain BP due to increased correlation between the beliefs. To avoid the impairments, we propose a novel concatenated structure of beam- and antenna-domain BP layers, which allows us to benefit from the advantages of both domains while maintaining low signal processing complexity. Numerical results show the validity of our proposed method in terms of the bit error rate (BER) performance both in the coded and uncoded cases and the computational complexity.