A Survey on Fundamental Limits of Integrated Sensing and Communication

Abstract

The integrated sensing and communication (ISAC), in which the sensing and communication share the same frequency band and hardware, has emerged as a key technology in future wireless systems due to two main reasons. First, many important application scenarios in fifth generation (5G) and beyond, such as autonomous vehicles, Wi-Fi sensing and extended reality, requires both high-performance sensing and wireless communications. Second, with millimeter wave and massive multiple-input multiple-output (MIMO) technologies widely employed in 5G and beyond, the future communication signals tend to have high-resolution in both time and angular domain, opening up the possibility for ISAC. As such, ISAC has attracted tremendous research interest and attentions in both academia and industry. Early works on ISAC have been focused on the design, analysis and optimization of practical ISAC technologies for various ISAC systems. While this line of works are necessary, it is equally important to study the fundamental limits of ISAC in order to understand the gap between the current state-of-the-art technologies and the performance limits, and provide useful insights and guidance for the development of better ISAC technologies that can approach the performance limits. In this paper, we aim to provide a comprehensive survey for the current research progress on the fundamental limits of ISAC. Particularly, we first propose a systematic classification method for both traditional radio sensing (such as radar sensing and wireless localization) and ISAC so that they can be naturally incorporated into a unified framework. Then we summarize the major performance metrics and bounds used in sensing, communications and ISAC, respectively. After that, we present the current research progresses on fundamental limits of each class Manuscript

Integrated Sensing and Communications: Towards Dual-functional Wireless Networks for 6G and Beyond

“…We note that there have been several survey/tutorial papers on ISAC-related topics, e.g., [10] on the general designs of JRC systems, [56] on fundamental limits of ISAC, [58] on the spectral coexistence of radar and communication systems, [59] on the sensing-centric DFRC design, [47] on the mmWave JRC, and [48] on DFRC for autonoumous vehicles. Unlike previous works that depict only part of the picture of ISAC, our overview has demonstrated the panorama of the ISAC theoretical framework, by shedding light on the basic performance tradeoffs, waveform design, and receiver design in ISAC systems, as well as the mutual assistance between S&C at a network level.…”

“…However, the performance of sensing, from information theoretical perspectives, is not as clearly defined as in that of communications. Therefore, new analytical techniques are needed to evaluate ISAC systems [56].…”

“…Finally, z is the Gaussian noise with zero mean and unit variance. Two fundamental problems arise from the model in (56). The first one is what the optimal decision region is for a given constellation in accordance with the maximum likelihood (ML) criterion.…”

“…The study of the toy model (56) shows that, in the regime of mid/high radar INR, one may consider to recover/estimate the radar interference first, and pre-cancel it from the mixed reception y. More importantly, a good ISAC receiver design should exploit the structural information of the S&C signals.…”

Symbiotic Sensing and Communications Towards 6G: Vision, Applications, and Technology Trends

“…In [6], a comprehensive survey on JCAS techniques is provided and a novel network architecture, named perceptive mobile network (PMN), is proposed to show the feasibility that integrates radio sensing into the existing cellular mobile network. Authors in [7] surveyed the recent studies on fundamental limits of ISAC, in which the major performance metrics are summarized, providing useful guideline for the practical network design. In [8], various use cases in ISAC-enabled IoT networks are presented.…”