GMD-Based Hybrid Beamforming for Large Reconfigurable Intelligent Surface Assisted Millimeter-Wave Massive MIMO

TL;DR

This paper proposes a GMD-based hybrid beamforming method for RIS-assisted mmWave MIMO systems, improving spectral efficiency and BER performance by exploiting channel sparsity and LoS angles, with a focus on broadband applications.

Contribution

It introduces a novel GMD-based hybrid beamforming scheme for RIS-assisted mmWave MIMO, leveraging channel sparsity and LoS angles to enhance performance.

Findings

Achieves better BER performance than conventional methods.

Utilizes a simultaneous orthogonal match pursuit algorithm for beam selection.

Provides an initial exploration of broadband hybrid beamforming for RIS-assisted systems.

Abstract

Reconfigurable intelligent surface (RIS) is considered to be an energy-efficient approach to reshape the wireless environment for improved throughput. Its passive feature greatly reduces the energy consumption, which makes RIS a promising technique for enabling the future smart city. Existing beamforming designs for RIS mainly focus on optimizing the spectral efficiency for single carrier systems. To avoid the complicated bit allocation on different spatial domain subchannels in MIMO systems, in this paper, we propose a geometric mean decomposition-based beamforming for RIS-assisted millimeter wave (mmWave) hybrid MIMO systems so that multiple parallel data streams in the spatial domain can be considered to have the same channel gain. Specifically, by exploiting the common angular-domain sparsity of mmWave massive MIMO channels over different subcarriers, a simultaneous orthogonal match pursuit algorithm is utilized to obtain the optimal multiple beams from an oversampling 2D-DFT codebook. Moreover, by only leveraging the angle of arrival and angle of departure associated with the line of sight (LoS) channels, we further design the phase shifters for RIS by maximizing the array gain for LoS channel. Simulation results show that the proposed scheme can achieve better BER performance than conventional approaches. Our work is an initial attempt to discuss the broadband hybrid beamforming for RIS-assisted mmWave hybrid MIMO systems.