Non-uniform array design for robust LoS MIMO via convex optimization

TL;DR

This paper proposes a convex optimization-based method for designing non-uniform arrays in LoS MIMO systems to maximize capacity over varying transmit distances, outperforming traditional uniform arrays.

Contribution

It introduces a convex relaxation approach for joint non-uniform array design in LoS MIMO, enhancing capacity robustness across distances.

Findings

Non-uniform arrays outperform uniform arrays in capacity.

Convex relaxation effectively solves the array design problem.

Refined solutions improve performance further.

Abstract

The array design problem of multiple-input multiple-output (MIMO) systems in a line-of-sight (LoS) transmit environment is examined. As uniform array configurations at the transmitter (Tx) and receiver (Rx) are optimal at specific transmit distances only, they lead to reduced spectral efficiency over a range of transmit distances. To that end, the joint design of nonuniform Tx and Rx arrays towards maximizing the minimum capacity of a LoS MIMO system across a range of transmit distances is investigated in this paper. By introducing convex relaxation, the joint Tx and Rx array design is cast as a convex optimization problem, which is solved in a iterative manner. In addition, we also implement a local search to obtain a refined solution that achieves an improved performance. It is shown that the non-uniform configurations designed with our proposed approach outperform uniform and non-uniform array designs of the literature in terms of capacity and/or complexity.