Next-Generation Multiple Access for Integrated Sensing and Communications

Integrated sensing and communications (ISAC) has received considerable attention from both industry and academia. By sharing the spectrum and hardware platform, ISAC significantly reduces costs and improves spectral, energy, and hardware efficiencies. To support the large number of communication users (CUs) and sensing targets (STs), the design of multiple access (MA) is a fundamental issue in ISAC. MA techniques in ISAC are expected to avoid mutual interference between sensing and communicating functions under the critical constraints of both functions. In this article, we present an overview on approaches of MA for ISAC, from orthogonal transmission strategies to nonorthogonal ones, realized in time, frequency, code, spatial, delay-Doppler, power, and/or multiple domains. We discuss their individual implementation schemes and corresponding resource allocation strategies, as well as highlight future research opportunities.

I. Introduction

Integrated sensing and communications (ISAC) enables the shared use of wireless resources, physical infrastructures, and devices between sensing and communication functionalities to reduce costs and improve the efficiency of spectrum, energy, and hardware. ISAC is also known as radar communication (RadCom), joint communication and radar (JCR), joint radar and communication (JRC), and dual-functional radar-communications (DFRC), which further drives various use cases including but not limited to sensing as a service, in-cabin sensing in smart home, vehicle to everything, smart manufacturing and the industrial Internet of Things (IoT), and environmental monitoring [1], [2], [3].