  This paper proposes a novel layered belief propagation (BP) detector with a
concatenated structure of two different BP layers for low-complexity large
multi-user multi-input multi-output (MU-MIMO) detection based on statistical
beams. To reduce the computational burden and the circuit scale on the base
station (BS) side, the two-stage signal processing consisting of slow varying
outer beamformer (OBF) and group-specific MU detection (MUD) for fast channel
variations is effective. However, the dimensionality reduction of the
equivalent channel based on the OBF results in significant performance
degradation in subsequent spatial filtering detection. To compensate for the
drawback, the proposed layered BP detector, which is designed for improving the
detection capability by suppressing the intra- and inter-group interference in
stages, is introduced as the post-stage processing of the OBF. Finally, we
demonstrate the validity of our proposed method in terms of the bit error rate
(BER) performance and the computational complexity.
