The Curse of Beam-Squint in ISAC: Causes, Implications, and Mitigation Strategies

TL;DR

This paper examines the causes and effects of beam-squint in wideband ISAC systems, highlighting its impact on performance and proposing mitigation strategies to improve sensing and communication capabilities.

Contribution

It provides a comprehensive analysis of beam-squint challenges in ISAC and discusses various design approaches and research opportunities for mitigation.

Findings

Beam-squint significantly degrades ISAC performance.

Mitigation strategies can effectively reduce beam-squint effects.

Multiple design perspectives are explored for improved ISAC systems.

Abstract

Integrated sensing and communications (ISAC) has emerged as a means to efficiently utilize spectrum and thereby save cost and power. At the higher end of the spectrum, ISAC systems operate at wideband using large antenna arrays to meet the stringent demands for high-resolution sensing and enhanced communications capacity. However, the wideband implementation entails beam-squint, that is, deviations in the generated beam directions because of the narrowband assumption in the analog components. This causes significant degradation in the communications capacity, target detection, and parameter estimation. This article presents the design challenges caused by beam-squint and its mitigation in ISAC systems. In this context, we also discuss several ISAC design perspectives including far-/near-field beamforming, channel/direction estimation, sparse array design, and index modulation. There are also several research opportunities in waveform design, beam training, and array processing to adequately address beam-squint in ISAC.