Rethinking the fundamental performance limits of integrated sensing and communication systems

TL;DR

This paper develops a unified continuous-time model for integrated sensing and communication systems, introducing a new sensing metric and analyzing performance trade-offs, providing insights for system design.

Contribution

It establishes a continuous-time information model for ISAC, introduces sensing mutual information, and analyzes performance bounds and trade-offs in practical settings.

Findings

SMI bridges mutual information and MSE domains.

Performance bounds are characterized by CMI-SMI and CMI-MSE regions.

Design insights include waveform preferences and resource allocation relationships.

Abstract

Integrated sensing and communication (ISAC) has been recognized as a key enabler and feature of future wireless networks. In the existing works analyzing the performances of ISAC, discrete-time systems were commonly assumed, which, however, overlooked the impacts of temporal, spectral, and spatial properties. To address this issue, we establish a unified information model for the band-limited continuous-time ISAC systems. In the established information model, we employ a novel sensing performance metric, called the sensing mutual information (SMI). Through analysis, we show how the SMI can be utilized as a bridge between the mutual information domain and the mean squared error (MSE) domain. In addition, we illustrate the communication mutual information (CMI)-SMI and CMI-MSE regions to identify the performance bounds of ISAC systems in practical settings and reveal the trade-off between communication and sensing performances. Moreover, via analysis and numerical results, we provide two valuable insights into the design of novel ISAC-enabled systems: i) communication prefers the waveforms of random amplitude, sensing prefers the waveforms of constant amplitude, both communication and sensing favor the waveforms of low correlations with random phases; ii) There exists a linear positive proportional relationship between the allocated time-frequency resource and the achieved communication rate/sensing MSE.