Hybrid Beamforming and Resource Allocation Designs for mmWave Multi-User Massive MIMO-OFDM Systems on Uplink

Abstract

In this paper, we investigate hybrid beamforming and resource allocation design problems for uplink millimeter wave (mmWave) multi-user (MU) massive multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. We propose three hybrid beamforming designs with dynamic streams assignment (DSA) integrated into the solution for the formulated resource allocation problem to maximize spectral efficiency. In the analog beamforming stage, three different designs are developed to maximize the channel gains of the equivalent baseband channel at each subcarrier, while the number of data streams is also determined for each mobile station (MS). Specifically, for the first design, the analog beamformers are designed to match the corresponding channel across the entire band for each MS. In the second one, to significantly reduce the complexity of the first design, we can completely avoid the matrix decomposition by selecting the appropriate set of array response vectors. The last design only performs singular value decomposition (SVD) on the channel of the center subcarrier to find the analog beamformers. In the digital beamforming stage, for the interference cancellation, the digital precoder and the combiner are obtained at each subcarrier using the block diagonalization (BD) and the coordinated transmit-receive processing method. We also develop fully-digital beamforming and another three hybrid beamforming schemes based on the existing algorithms as performance benchmarks. By being verified through numerical simulations, the spectral efficiency of the proposed schemes can be significantly improved after dynamically assigning the number of data streams for each MS. Moreover, simulations indicate the first and the third proposed hybrid beamforming designs can achieve a very competitive performance and even outperform the fully-digital design in some situations.

Keywords

• Resource allocation
• hybrid beamforming
• multiple user access
• multiple-input-multiple-output (MIMO)
• orthogonal frequency-division multiplexing (OFDM)
• spectral efficiency