Dynamic Subarrays for Hybrid Precoding in Wideband mmWave MIMO Systems

TL;DR

This paper introduces a dynamic subarray hybrid precoding method for wideband mmWave MIMO systems, achieving near fully-digital spectral efficiency and outperforming fixed structures by adapting to long-term channel characteristics.

Contribution

It develops a closed-form hybrid precoding solution for wideband mmWave systems and proposes a dynamic subarray design that adapts to channel conditions, improving performance.

Findings

Achieves spectral efficiency close to fully-digital architectures.

Dynamic subarray design outperforms fixed structures.

Effective in various system and channel conditions.

Abstract

Hybrid analog/digital precoding architectures can address the trade-off between achievable spectral efficiency and power consumption in large-scale MIMO systems. This makes it a promising candidate for millimeter wave systems, which require deploying large antenna arrays at both the transmitter and receiver to guarantee sufficient received signal power. Most prior work on hybrid precoding focused on narrowband channels and assumed fully-connected hybrid architectures. MmWave systems, though, are expected to be wideband with frequency selectivity. In this paper, a closed-form solution for fully-connected OFDM-based hybrid analog/digital precoding is developed for frequency selective mmWave systems. This solution is then extended to partially-connected but fixed architectures in which each RF chain is connected to a specific subset of the antennas. The derived solutions give insights into how the hybrid subarray structures should be designed. Based on them, a novel technique that dynamically constructs the hybrid subarrays based on the long-term channel characteristics is developed. Simulation results show that the proposed hybrid precoding solutions achieve spectral efficiencies close to that obtained with fully-digital architectures in wideband mmWave channels. Further, the results indicate that the developed dynamic subarray solution outperforms the fixed hybrid subarray structures in various system and channel conditions.