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On the Fundamental Tradeoff of Joint Communication and QCD: The Monostatic Case

Sung Hoon Lim, Daewon Seo

TL;DR

The paper tackles the fundamental tradeoff between reliable communication and quickest change detection in a monostatic ISAC system with echo feedback.It introduces the JCCS strategy that uses state-aware, pilot-assisted, feedback-driven coding together with a Subblock CuSum detector to jointly optimize rate and detection delay.A rate-delay region is characterized via state-dependent mutual information and KL divergences, supported by a partial converse showing asymptotic optimality of the detection algorithm within the JCCS framework.Numerical results on binary and Gaussian MIMO channels illustrate tangible gains of closed-loop adaptive coding over open-loop schemes and demonstrate practical design insights for ISAC systems.

Abstract

This paper investigates the fundamental tradeoff between communication and quickest change detection (QCD) in integrated sensing and communication (ISAC) systems under a monostatic setup. We introduce a novel Joint Communication and quickest Change subblock coding Strategy (JCCS) that leverages feedback to adapt coding dynamically based on real-time state estimation. The achievable rate-delay region is characterized using state-dependent mutual information and KL divergence, providing a comprehensive framework for analyzing the interplay between communication performance and detection delay. Moreover, we provide a partial converse demonstrating the asymptotic optimality of the proposed detection algorithm within the JCCS framework. To illustrate the practical implications, we analyze binary and MIMO Gaussian channels, revealing insights into achieving optimal tradeoffs in ISAC system design.

On the Fundamental Tradeoff of Joint Communication and QCD: The Monostatic Case

TL;DR

The paper tackles the fundamental tradeoff between reliable communication and quickest change detection in a monostatic ISAC system with echo feedback.It introduces the JCCS strategy that uses state-aware, pilot-assisted, feedback-driven coding together with a Subblock CuSum detector to jointly optimize rate and detection delay.A rate-delay region is characterized via state-dependent mutual information and KL divergences, supported by a partial converse showing asymptotic optimality of the detection algorithm within the JCCS framework.Numerical results on binary and Gaussian MIMO channels illustrate tangible gains of closed-loop adaptive coding over open-loop schemes and demonstrate practical design insights for ISAC systems.

Abstract

This paper investigates the fundamental tradeoff between communication and quickest change detection (QCD) in integrated sensing and communication (ISAC) systems under a monostatic setup. We introduce a novel Joint Communication and quickest Change subblock coding Strategy (JCCS) that leverages feedback to adapt coding dynamically based on real-time state estimation. The achievable rate-delay region is characterized using state-dependent mutual information and KL divergence, providing a comprehensive framework for analyzing the interplay between communication performance and detection delay. Moreover, we provide a partial converse demonstrating the asymptotic optimality of the proposed detection algorithm within the JCCS framework. To illustrate the practical implications, we analyze binary and MIMO Gaussian channels, revealing insights into achieving optimal tradeoffs in ISAC system design.

Paper Structure

This paper contains 19 sections, 14 theorems, 99 equations, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. Problem Statement
  3. Channel model
  4. Code definition
  5. Performance metrics
  6. Supplementary definitions
  7. Main Results
  8. Achievability
  9. Proposed joint communication and QCD strategy
  10. Communication probability of error analysis
  11. QCD analysis
  12. Numerical Examples
  13. Binary channel example
  14. MIMO Gaussian example
  15. Discussion
  16. ...and 4 more sections

Key Result

Theorem 1

For a post-state set $\mathcal{S}$, a rate-delay pair $(R, \Delta)$ is achievable if for some $\{ptp_{X|S}(x|s), s\in\mathcal{S}\}$, for all $s\in\mathcal{S}$, where $(X_s, {\tilde{Y}}_s) \sim p(x|s)p({\tilde{y}}|x, s)$.

Figures (5)

  • Figure 1: Monostatic model for ISAC. The encoder and QCD detector are the same entity which has access to the channel observation $Y$ via feedback.
  • Figure 2: Binary-input binary-output channel with crossover probabilities $\epsilon_0$, $\epsilon_1$.
  • Figure 3: Achievable region for the BIBO channel example.
  • Figure 4: Achievable region for the Gaussian MIMO channel example.
  • Figure 5: Achievable rate and $\Delta$ vs. beamforming angle for the single post-state MIMO example.

Theorems & Definitions (17)

  • Theorem 1
  • Theorem 2
  • Corollary 1
  • Theorem 3
  • Remark 1
  • Theorem 4
  • Remark 2
  • Lemma 1
  • Lemma 2
  • Theorem 5
  • ...and 7 more