Index Modulation for Integrated Sensing and Communications: A signal processing perspective [Special Issue on Signal Processing for the Integrated Sensing and Communications Revolution]

A joint design of both sensing and communication can lead to substantial enhancement for both subsystems in terms of size and cost as well as spectrum and hardware efficiency. In the last decade, integrated sensing and communications (ISAC) has emerged as a means to efficiently utilize the spectrum on a single and shared hardware platform. Recent studies focused on developing multifunction approaches to share the spectrum between radar sensing and communications. Index modulation (IM) is one particular approach to incorporating information-bearing communication symbols into the emitted radar waveforms. While IM has been well investigated in communications-only systems, the implementation adoption of the IM concept in ISAC has recently attracted researchers to achieve improved energy/spectral efficiency while maintaining satisfactory radar sensing performance. This article focuses on recent studies on IM-ISAC and presents in detail the analytical background and relevance of the major IM-ISAC applications.