Multi-User Scheduling in Hybrid Millimeter Wave Massive MIMO Systems

TL;DR

This paper investigates multi-user scheduling in hybrid millimeter wave massive MIMO systems using a simplified beamforming approach, providing an optimization framework and numerical insights into system performance.

Contribution

It introduces an offline optimization framework for proportional fair multi-user scheduling with per-stream hybrid beamforming in mmWave systems, including a near-optimal solution.

Findings

Performance close to the upper-bound demonstrated by numerical results.

System parameters significantly impact scheduling efficiency.

The proposed solution offers a practical approach for multi-user scheduling in mmWave MIMO.

Abstract

While mmWave bands provide a large bandwidth for mobile broadband services, they suffer from severe path loss and shadowing. Multiple-antenna techniques such as beamforming (BF) can be applied to compensate the signal attenuation. We consider a special case of hybrid BF called per-stream hybrid BF (PSHBF) which is easier to implement than the general hybrid BF because it circumvents the need for joint analog-digital beamformer optimization. Employing BF at the base station enables the transmission of multiple data streams to several users in the same resource block. In this paper, we provide an offline study of proportional fair multi-user scheduling in a mmWave system with PSHBF to understand the impact of various system parameters on the performance. We formulate multi-user scheduling as an optimization problem. To tackle the non-convexity, we provide a feasible solution and show through numerical examples that the performance of the provided solution is very close to an upper-bound. Using this framework, we provide extensive numerical investigations revealing several engineering insights.