Rethinking Signaling Design for ISAC: From Pilot-Based to Payload-Based Sensing

TL;DR

This paper explores a paradigm shift in ISAC signaling from pilot-based to payload-based sensing, emphasizing integration within 5G NR structures and demonstrating practical benefits through a V2I case study.

Contribution

It introduces novel payload-based sensing techniques for ISAC, extending beyond pilot signals, and analyzes their implementation within existing 5G NR frameworks.

Findings

Payload-based sensing reduces signaling overhead.

Constellation shaping enhances sensing performance.

Practical V2I case study demonstrates feasibility.

Abstract

Integrated Sensing and Communications (ISAC) is emerging as a key enabler for 6G networks, with signaling design at the core of its evolution. This paper reviews the paradigm shift of ISAC signaling designs from pilot-aided sensing to data payload-based approaches, with a particular focus on how these techniques can be realized within existing 5G NR structures. We commence with the reuse of pilots and reference signals that exploit existing 5G New Radio (NR) structures for sensing. Then, we extend to more advanced approaches that integrate the data payload through novel constellation shaping, modulation bases, and pulse shaping filters. We highlight the opportunities and tradeoffs that arise when extending sensing from sparse pilot and reference signal resources to the full communication frame, emphasizing how constellation properties and modulation choices directly determine sensing performance. To illustrate practical feasibility, a case study on sensing-assisted NR Vehicle-to-Infrastructure (V2I) networks demonstrates how exploiting both reference signals and payload echoes can reduce signaling overhead and enable proactive beam management and handover.