[Paper Review] Integrated Sensing and Communications: Towards Dual-functional Wireless Networks for 6G and Beyond

Fan Liu, Yuanhao Cui+5 more|arXiv (Cornell University)|Aug 16, 2021

Indoor and Outdoor Localization Technologies62 citations

TL;DR

This paper provides a comprehensive overview of Integrated Sensing and Communications (ISAC), its history, architecture, performance tradeoffs, waveform/receiver design, and network-level mutual assistance to enable dual-functional wireless networks for 6G and beyond.

ABSTRACT

As the standardization of 5G is being solidified, researchers are speculating what 6G will be. Integrating sensing functionality is emerging as a key feature of the 6G Radio Access Network (RAN), allowing to exploit the dense cell infrastructure of 5G for constructing a perceptive network. In this paper, we provide a comprehensive overview on the background, range of key applications and state-of-the-art approaches of Integrated Sensing and Communications (ISAC). We commence by discussing the interplay between sensing and communications (S&C) from a historical point of view, and then consider multiple facets of ISAC and its performance gains. By introducing both ongoing and potential use cases, we shed light on industrial progress and standardization activities related to ISAC. We analyze a number of performance tradeoffs between S&C, spanning from information theoretical limits, tradeoffs in physical layer performance, to the tradeoff in cross-layer designs. Next, we discuss signal processing aspects of ISAC, namely ISAC waveform design and receive signal processing. As a step further, we provide our vision on the deeper integration between S&C within the framework of perceptive networks, where the two functionalities are expected to mutually assist each other, i.e., communication-assisted sensing and sensing-assisted communications. Finally, we summarize the paper by identifying the potential integration between ISAC and other emerging communication technologies, and their positive impact on the future of wireless networks.

Motivation & Objective

• Motivate the ISAC paradigm as a unification of sensing and communications for next-generation networks.
• Catalog key applications, industry progress, and standardization activities related to ISAC.
• Analyze fundamental and cross-layer tradeoffs between sensing and communication performance.
• Discuss signal processing aspects including ISAC waveform design and receive processing.
• Propose a vision for perceptive networks where sensing and communications mutually assist each other.

Proposed method

• Survey the historical development and convergence of radar and communications toward ISAC.
• Classify ISAC architecture into sensing-centric and communication-centric designs and discuss tradeoffs.
• Outline information-theoretic and PHY-layer performance tradeoffs for ISAC.
• Review ISAC waveform design and receiver processing approaches.
• Introduce the concept of perceptive networks and cross-layer mutual assistance between S&C.
• Highlight industrial progress, use cases, and potential integration with emergent technologies.

Experimental results

Research questions

• RQ1 What are the fundamental performance tradeoffs between sensing and communications in ISAC systems?
• RQ2 How can waveform design and receiver processing be optimized to support dual functionality?
• RQ3 What industrial applications and standardization efforts are shaping ISAC development for 6G?
• RQ4 How can sensing-assisted communications and communication-assisted sensing be realized within perceptive networks?
• RQ5 What is the potential impact of ISAC on beyond-5G/6G architectures and related technologies?

Key findings

• ISAC can achieve integration and coordination gains by sharing wireless resources for dual purposes.
• There is a convergence trend where sensing and communications leverage similar hardware, channels, and signal processing, especially at mmWave with large arrays.
• Hybrid analog-digital (HAD) architectures enable scalable mMIMO/mMIMO radar which supports ISAC front-ends.
• Sensing-assisted beam training, tracking, and resource allocation can significantly reduce signaling overhead in networks.
• Industrial progress and standardization activities indicate growing momentum for ISAC in 6G and beyond.
• Perceptive networks conceptually unify sensing and communications to build ubiquitous, environment-aware services.