Finite-Blocklength ISAC Multiple Access: A Source-Channel Coding Perspective

2026-07-05

AI Summary

This work investigates the fundamental limits of integrated sensing and communication (ISAC) in finite-blocklength multi-access systems under short-packet constraints, aiming to jointly optimize sensing accuracy and communication reliability. By modeling sensing distortion constraints as source coding requirements, the study establishes a unified framework for joint payload recovery and, for the first time, develops a theoretical analysis for finite-blocklength ISAC multi-access systems. Leveraging finite-blocklength information-theoretic tools—including Fano’s inequality, genie-aided single-user bounds, and multi-user converse bounds—the authors derive achievability and converse bounds that reveal the intrinsic coupling between sensing and communication. The results demonstrate that the energy cost of sensing fidelity increases approximately linearly (in dB per decade) as the distortion tolerance tightens, an effect significantly amplified by multi-access load; moreover, joint coding schemes achieve substantial integration gains over optimized orthogonal two-stage approaches.

Abstract

Future networks must serve massive populations of devices that sense and communicate simultaneously under short-packet constraints, yet the fundamental limits of integrated sensing and communication (ISAC) in the finite-blocklength multiple-access regime remain largely undiscovered. This paper closes this gap from a source-channel coding perspective. We prove that satisfying a sensing-distortion constraint is information-theoretically equivalent to a source-coding requirement, which collapses sensing and communication into the joint recovery of a single effective payload within a coded multiple-access framework. Building on this equivalence, we derive a finite-blocklength achievability bound together with a Fano-sum many-user converse and a genie-aided single-user converse, yielding a tight characterization of the minimum energy per bit and the rate-sensing tradeoff. Numerical results reveal that the energy price of sensing fidelity grows almost linearly in dB per decade of distortion tightening and is significantly amplified by the multiple-access load, and that joint encoding of the effective payload strictly outperforms an optimized orthogonal two-phase scheme, demonstrating a genuine integration gain of ISAC at finite blocklength.

Problem

• Integrated Sensing and Communication
• Finite Blocklength
• Multiple Access
• Source-Channel Coding
• Short-Packet Communication

Innovation

• finite-blocklength
• integrated sensing and communication (ISAC)
• source-channel coding
• multiple-access
• energy-per-bit