Low-Complexity Hybrid Precoding in Massive Multiuser MIMO Systems

TLDR

Massive MIMO promises significant capacity gains yet suffers from high hardware complexity. This work proposes a low‑complexity hybrid precoding scheme that approaches the performance of full‑complexity zero‑forcing precoding. The phased‑ZF scheme applies phase‑only control at the RF stage followed by low‑dimensional baseband zero‑forcing on the effective channel. Simulations in Rayleigh and millimeter‑wave channels show that even with 2‑bit RF phase quantization the scheme incurs minimal degradation and achieves highly desirable performance.

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.