Structural Design of Non-Uniform Linear Arrays for Favorable Propagation in Massive MIMO

TL;DR

This paper proposes a novel design for non-uniform linear arrays in massive MIMO systems to eliminate grating lobes, thereby ensuring favorable propagation conditions across all angles of arrival, which enhances system performance.

Contribution

It introduces a new analysis and design methodology for non-uniform linear arrays that cancels grating lobes and restores favorable propagation in massive MIMO systems.

Findings

Design effectively cancels grating lobes in non-uniform arrays.

Restores favorable propagation for all distinct angles of arrival.

Compatible with hybrid beamforming and multipath channels.

Abstract

Favorable propagation (FP) for massive multiple-input multiple-output (MIMO) systems with uniform and non-uniform linear arrays is considered. A gap in the existing FP studies of uniform linear arrays is identified, which is related to the existence of grating lobes in the array pattern and which results in the FP condition being violated, even under distinct angles of arrival. A novel analysis and design of \textit{non-uniform} linear arrays are proposed to cancel grating lobes and to restore favorable propagation for \textit{all} distinct angles of arrival. This design is consistent with the popular hybrid beamforming paradigm and extends to multipath channels and arrays of directional elements.