Abstract
In large multi-user multi-input multi-output systems, the computational cost and circuit scale of base stations (BSs) are effectively reduced using two-stage signal processing consisting of a slow varying outer beamformer (OBF) based on long-term channel statistics and group-specific multi-user detection for instantaneous channel variations. However, the dimensionality reduction of the group-specific beam-domain channel based on the OBF causes significant performance degradation in the subsequent spatial-filtering detection. To compensate for this drawback, this paper introduces a novel layered belief propagation (BP) detector with a concatenated structure of beam- and antenna-domain BP layers for post-stage OBF processing. The proposed detector is designed for improving the convergence of iterative detection by suppressing intra- and inter-group interference in stages. The layered structure provides the advantages of both beam and antenna domains while maintaining low signal-processing complexity. Numerical results show the validity of our proposed method in terms of the bit error rate performance in both the uncoded and coded cases and the computational complexity.
Highlights
Large multi-user multi-input multi-output (MU-MIMO) systems, which are equipped with a large number of antennas on both the transmitter and receiver sides, have been regarded as one of the most promising technologies in the physical layer of wireless communication systems [1]–[5]
As M increases, the required Es/N0 increases more rapidly in “minimum mean square error (MMSE) w/ outer beamformer (OBF)” than in “MMSE” owing to the severe inter-group interference caused by dimensionality reduction in the former
We proposed a novel concatenated beamand antenna-domain layered belief propagation (BP) detector for realizing lowcomplexity, high-accuracy, large-scale MU-MIMO detection based on the OBF
Summary
Large multi-user multi-input multi-output (MU-MIMO) systems, which are equipped with a large number of antennas on both the transmitter and receiver sides, have been regarded as one of the most promising technologies in the physical layer of wireless communication systems [1]–[5]. The most common MF-based BP detector is approximate message passing (AMP) [24]–[26], which is systematically derived from a rigorous approximation of Gaussian BP (GaBP) [21]–[23] in the largesystem limit, where the input and output dimensions, M and N , respectively, are infinity for a given compression rate ρ = N/M These algorithms separate the multiplexed signals using MF and consist of only scalar-wise operations; they can achieve a computational complexity of O(M N ) for each iteration. To resolve the lack of an appropriate MUD scheme as the post-stage of OBF for high-spatial-loading MU-MIMO systems, in this paper, we propose a novel design for a concatenated structure of beam- and antenna-domain BP detectors. The contributions of this paper are summarized as follows1: 1) A novel low-complexity MUD scheme employing concatenated beam- and antenna-domain layered BP based on a given OBF is proposed for high-spatial-loading MU-MIMO systems.
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