Robust and Feasible QoS-Aware mmWave Massive MIMO Hybrid Beamforming

2026-07-14

AI Summary

This work addresses the performance degradation and potential data stream outage in millimeter-wave massive MIMO hybrid beamforming caused by channel state information (CSI) errors under conventional quality-of-service (QoS) provisioning schemes. To enhance robustness, the proposed approach leverages channel eigenvectors to guide RF beamforming and introduces a diagonalized baseband precoding structure to mitigate channel uncertainty. By replacing the original uncertainty region with an effective one, the scheme substantially reduces transmit power requirements. Furthermore, it integrates a low-complexity feasibility criterion with a cutting-plane method to iteratively optimize the design, simultaneously eliminating infeasible streams while satisfying per-stream mean-square-error constraints. Simulation results demonstrate that the proposed method significantly lowers transmit power while guaranteeing QoS, exhibiting strong robustness, high feasibility, and low computational complexity.

Abstract

Hybrid beamforming (HB) with quality-of-service (QoS) provisioning per stream in millimeter waves is indispensable in 5G/6G networks. HB includes baseband and radio frequency (RF) beamforming, and requires error-free channel state information (CSI), which is erroneous in practice. So there is a need for efficient, feasible, robust, and QoS-aware HB. To achieve this, we mitigate CSI uncertainty via baseband beamforming, and we steer the RF beamformer by using the estimates of the channel's eigenvectors. In doing so, we consider the effective channel's uncertainty region instead of the uncertainty region of the channel itself, as the former is smaller than the latter, requiring less transmit power to satisfy the QoS constraint. We also detect and eliminate the infeasible data streams. Our iterative scheme (which is based on the cutting-set method) for baseband beamforming satisfies the mean-squared error (MSE) constraint per stream, where a limited number of constraints are considered instead of infinitely many constraints. In our low-complexity scheme, we derive a simple sufficient condition to check the feasibility of each stream, we diagonalize the effective channel at the baseband precoder, and we use minimum MSE combining at the baseband combiner. Extensive simulations validate our formulations and theoretical derivations.

Problem

• hybrid beamforming
• QoS-aware
• mmWave massive MIMO
• CSI uncertainty
• feasibility

Innovation

• hybrid beamforming
• QoS-aware
• CSI uncertainty
• effective channel
• cutting-set method