Low-Complexity Hybrid Precoding in Massive Multiuser MIMO Systems

TL;DR

This paper introduces a low-complexity hybrid precoding method for massive MIMO systems that closely approximates optimal performance with reduced hardware complexity, suitable for both Rayleigh and mmWave channels.

Contribution

A novel hybrid precoding scheme called phased-ZF (PZF) that uses phase-only RF control and low-dimensional baseband ZF, significantly reducing complexity while maintaining near-optimal performance.

Findings

PZF achieves performance close to full-complexity ZF in simulations.

Limited RF phase quantization (up to 2 bits) causes minimal performance degradation.

Effective in both Rayleigh fading and mmWave channels.

Abstract

Massive multiple-input multiple-output (MIMO) is envisioned to offer considerable capacity improvement, but at the cost of high complexity of the hardware. In this paper, we propose a low-complexity hybrid precoding scheme to approach the performance of the traditional baseband zero-forcing (ZF) precoding (referred to as full-complexity ZF), which is considered a virtually optimal linear precoding scheme in massive MIMO systems. The proposed hybrid precoding scheme, named phased-ZF (PZF), essentially applies phase-only control at the RF domain and then performs a low-dimensional baseband ZF precoding based on the effective channel seen from baseband. Heavily quantized RF phase control up to $2$ bits of precision is also considered and shown to incur very limited degradation. The proposed scheme is simulated in both ideal Rayleigh fading channels and sparsely scattered millimeter wave (mmWave) channels, both achieving highly desirable performance.