Foundations of MIMO Radar Detection Aided by Reconfigurable Intelligent Surfaces

TL;DR

This paper investigates how reconfigurable intelligent surfaces (RIS) can enhance MIMO radar target detection, proposing models, optimization algorithms, and analyzing the benefits of RIS deployment in various configurations.

Contribution

It introduces a comprehensive signal model for RIS-aided MIMO radar, formulates phase shift optimization as a detection probability maximization, and analyzes system performance and deployment strategies.

Findings

RISs improve detection performance.

Near-field deployment of RISs is optimal.

Performance depends on radar-RIS distance and RIS size.

Abstract

A reconfigurable intelligent surface (RIS) is a nearly-passive flat layer made of inexpensive elements that can add a tunable phase shift to the impinging electromagnetic wave and are controlled by a low-power electronic circuit. This paper considers the fundamental problem of target detection in a RIS-aided multiple-input multiple-output (MIMO) radar. At first, a general signal model is introduced, which includes the possibility of using up to two RISs (one close to the radar transmitter and one close to the radar receiver) and subsumes both a monostatic and a bistatic radar configuration with or without a line-of-sight view of the prospective target. Upon resorting to a generalized likelihood ratio test (GLRT), the design of the phase shifts introduced by the RIS elements is formulated as the maximization of the probability of detection in the location under inspection for a fixed probability of false alarm, and suitable optimization algorithms are proposed. The performance analysis shows the benefits granted by the presence of the RISs and shed light on the interplay among the key system parameters, such as the radar-RIS distance, the RIS size, and location of the prospective target. A major finding is that the RISs should be better deployed in the near-field of the radar arrays at both the transmit and the receive side. The paper is concluded by discussing some open problems and foreseen applications.