Virtual Sectorization to Enable Hybrid Beamforming in mm-Wave mMIMO

TL;DR

This work addresses multi-user mmWave M-MIMO with hybrid beamforming by tackling the high complexity of joint analog–digital beamforming. It introduces a hierarchical clustering-based approach (Hierarchical clustering-PC) tailored for partially connected HBF, using subarray-aware distances and cluster-center vectors derived from the first left singular vectors, with a multi-center extension. In simulations on QuaDRiGa 2.0 channels, the method reduces ADC requirements from $N_{RX}=1024$ to $M=64$ with only about $1.4$ dB loss at $K=8$, and outperforms baseline clustering and single-center schemes by up to ~1.8 dB, approaching fully digital performance. The results demonstrate a practical pathway to sectorized HBF deployments that balance complexity and performance in realistic LOS scenarios.

Abstract

Hybrid beamforming (HBF) is a key technology to enable mm-wave Massive multiple-input multiple-output (mMIMO) receivers for future-generation wireless communications. It combines beamforming in both analog (via phase shifters) and digital domains, resulting in low power consumption and high spectral efficiency. In practice, the problem of joint beamforming in multi-user scenarios is still open because an analog beam can't cover all users simultaneously. In this paper, we propose a hierarchical approach to divide users into clusters. Each cluster consists of users inside a virtual sector produced by the analog beamforming of an HBF-based mMIMO receiver. Thus, inside each sector, a lower-cost digital beamforming serves a limited number of users within the same cluster. Simulations with realistic non-line-of-sight scenarios generated by the QuaDRiGa 2.0 demonstrate that our methods outperform standard FFT-based alternatives and almost achieve SVD-based beamspace performance bound.

Figures (5)

• Figure 1: Sub-array HBF.
• Figure 2: Double beamforming HBF scheme at the receiver.
• Figure 3: Receiver structure with the beamspace transformation.
• Figure 4: Subarrays radiation pattern for 3 clusters.
• Figure 5: Frame error rate (the ratio of codewords received with errors to total received codewords).