Information Theoretic Foundations of Joint Communication and Sensing

Project Information

IT-JCAS

Grant agreement ID: 101116550

DOI

10.3030/101116550

EC signature date 12 October 2023

Start date 1 January 2024

End date 31 December 2028

Funded under

• European Research Council (ERC)

Total cost

€ 1 499 618,00

EU contribution

€ 1 499 618,00

Coordinated by

TECHNISCHE UNIVERSITEIT EINDHOVEN
Netherlands

Periodic Reporting for period 1 - IT-JCAS (Information Theoretic Foundations of Joint Communication and Sensing)

Reporting period: 2024-01-01 to 2026-06-30

Summary of the context and overall objectives of the project

The integration of radio communication and sensing services within the same standard and network infrastructure will be a key feature of next-generation wireless technology. It is envisaged that wireless base-stations will simultaneously communicate with active user devices connected to the network and detect, localize and track passive targets within their vicinity; all using the same radio spectrum and hardware. In automotive, vehicles are expected to sense their surroundings and communicate with other vehicles and infrastructure through an integrated radio system. This emerging joint communication and sensing (JCAS) paradigm, currently at the frontier of wireless research, promises to transform diverse domains ranging from automotive and traffic management to industrial automation, agriculture and healthcare.

To realize this vision and unlock the full potential of JCAS, a fundamental theory is required. Communication-centric wireless systems have long relied on information theory to establish performance limits and guide the design of efficient schemes that best utilize scarce radio resources. In sharp contrast, information theory for JCAS is currently in its infancy, and without such a theory, optimal signal and protocol design for next-generation wireless networks will likely remain elusive. The overarching goal of this project is to take the first major steps towards closing this fundamental knowledge gap.

The project is structured around three main thrusts. The first thrust will revisit the notions of efficiency and reliability in sensing and establish fundamental information-theoretic trade-offs. The second thrust focuses on establishing new information-theoretic performance limits and optimal schemes for JCAS systems, where signals serve the dual purpose of communicating and probing. The final thrust extends the analysis to multiple transceivers, targets, and users by introducing a novel network information theory for sensing and JCAS. The results of this project will open a new research frontier in information theory, push the boundaries of current research in related areas, and directly impact the design and development of future JCAS-enabled wireless technology.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the first half of project IT-JCAS, significant progress has been made on the first two of the three project objectives.

On the first objective (WP1), we studied the logarithmic loss as a performance measure for sensing fidelity in a specific class of channels, and used it to derive notions of sensing capacity and sensing reliability function. While extending this framework to more general channel models remains a main challenge for the next phase, the approach has already attracted interest from other research groups, who have adopted the logarithmic loss measure and investigated it further in related settings.

On the second objective (WP2), we obtained a comprehensive characterisation of the fundamental communication-sensing trade-off for JCAS channels with finite-valued sensing parameters. We extended this to continuous parameters through a new approach based on the Expected Cramér–Rao Bound (ECRB), applicable to multi-antenna (MIMO) wireless channels, where we also identified optimal coding schemes. A key insight emerging from this line of work is the central role of constant-composition and cost-constrained codes in achieving optimal communication-sensing trade-offs.

These foundational results were also applied to practical wireless systems. For OFDM systems, the modulation backbone of 5G networks and a likely candidate for 6G as well, we established the exact trade-off between communication rate and ranging reliability and showed that it is governed entirely by the power allocation across subcarriers. In a related line of work, we studied the same setting under a sidelobe-level constraint on the transmit signal, which reflects a practical requirement in radar sensing. Here we established the structure of the optimal signalling schemes, and proposed a simple strategy based on superposition coding that achieves near-optimal performance. We also developed a sensing-aided beam alignment scheme for millimetre-wave systems, where backscattered signals are used to estimate the direction of arrival and improve communication link quality.

The techniques developed in the project have also produced new results in the related areas of source coding, channel decoding and the theory of guessing.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The results of IT-JCAS represent genuine advances beyond the current state of the art.

The use of logarithmic loss as a performance measure for sensing, and the resulting derivation of sensing capacity and reliability function, are new contributions to the field. While the results so far are limited to specific channel models, the approach has attracted interest from other research groups who have adopted it and investigated it further in related settings. The project has delivered a complete characterisation of the fundamental communication-sensing trade-off for a class of JCAS channels, solving a key problem and providing ideal benchmarks against which practical schemes can be evaluated. A key insight is the central role of constant-composition and cost-constrained codes in achieving optimal trade-offs.

Prior works on continuous-parameter JCAS relied on Bayesian Cramér–Rao Bounds (BCRB). We showed that, in the practically relevant regime where the sensing parameter remains fixed during a transmission block, the Expected Cramér–Rao Bound (ECRB) is the correct and tight asymptotic characterisation. This distinction has tangible consequences for both theory and system design. For OFDM systems, the fundamental trade-off between communication rate and ranging reliability had not been previously characterised. Our result establishes this exactly, and identifies conditions under which uniform power allocation is optimal for ranging. Under sidelobe-level constraints, we further established the structure of optimal signalling schemes and proposed a simple superposition-based strategy that achieves near-optimal performance, offering a practical design route for systems that must meet radar sensing requirements.

Beyond the core objectives, techniques developed in IT-JCAS are generating impact in neighbouring areas of information theory, and have opened a new research direction on robust and secure sensing systems. Realising the full impact of these results will require further research to extend the framework to networked settings with multiple users and targets, which is the focus of the remaining phase of the project. Sustained engagement with the wireless standardisation community will also be important, as the performance limits established here are most valuable when they inform the design choices made during the development of 6G.