Alternating Minimization for Hybrid Precoding in Multiuser OFDM mmWave Systems

TL;DR

This paper introduces a novel hybrid precoding structure and an alternating minimization algorithm for multiuser OFDM mmWave systems, achieving near-digital performance with efficient computation and emphasizing the importance of interuser interference cancellation.

Contribution

It proposes a simplified hybrid precoding design for multiuser OFDM mmWave systems and an efficient AltMin algorithm using LASSO formulation for analog precoding.

Findings

Performance close to fully digital precoding achieved

Efficient LASSO-based algorithm developed for analog precoding

Interuser interference cancellation is crucial for system performance

Abstract

Hybrid precoding is a cost-effective approach to support directional transmissions for millimeter wave (mmWave) communications. While existing works on hybrid precoding mainly focus on single-user single-carrier transmission, in practice multicarrier transmission is needed to combat the much increased bandwidth, and multiuser MIMO can provide additional spatial multiplexing gains. In this paper, we propose a new hybrid precoding structure for multiuser OFDM mmWave systems, which greatly simplifies the hybrid precoder design and is able to approach the performance of the fully digital precoder. In particular, two groups of phase shifters are combined to map the signals from radio frequency (RF) chains to antennas. Then an effective hybrid precoding algorithm based on alternating minimization (AltMin) is proposed, which will alternately optimize the digital and analog precoders. A major algorithmic innovation is a LASSO formulation for the analog precoder, which yields computationally efficient algorithms. Simulation results will show the performance gain of the proposed algorithm. Moreover, it will reveal that canceling the interuser interference is critical in multiuser OFDM hybrid precoding systems.