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A MIMO ISAC System for Ultra-Reliable and Low-Latency Communications

Homa Nikbakht, Yonina C. Eldar, H. Vincent Poor

TL;DR

This work tackles joint ISAC for URLLC and eMBB in a bi-static MIMO setting, where URLLC transmissions are triggered by SR sensing outcomes. It introduces a DPC-based coding framework with power-shell codebooks and block-type dependent precancellation to mitigate interference from sensing and eMBB signals, and develops a finite-blocklength rate-reliability-detection trade-off that jointly bounds the eMBB rate, URLLC reliability, and target detection probability. The analysis leverages generalized chi-square and Gaussian approximations to derive performance bounds, and a theorem provides the rate constraint $R_e \le C_e - \sqrt{V_e/n}\,Q^{-1}(\epsilon_e-\Delta_e) - K_e (\log n)/n - (\log M_s)/n$ under reliability and detection constraints. Numerical results show the proposed DPC-based ISAC scheme significantly outperforms power-sharing and time-sharing approaches, delivering higher eMBB rates while satisfying URLLC and sensing requirements, demonstrating practical gains for 6G ISAC scenarios.

Abstract

In this paper, we propose a bi-static multiple-input multiple-output (MIMO) integrated sensing and communication (ISAC) system to detect the arrival of ultra-reliable and low-latency communication (URLLC) messages and prioritize their delivery. In this system, a dual-function base station (BS) communicates with a user equipment (UE) and a sensing receiver (SR) is deployed to collect echo signals reflected from a target of interest. The BS regularly transmits messages of enhanced mobile broadband (eMBB) services to the UE. During each eMBB transmission, if the SR senses the presence of a target of interest, it immediately triggers the transmission of an additional URLLC message. To reinforce URLLC transmissions, we propose a dirty-paper coding (DPC)-based technique that mitigates the interference of both eMBB and sensing signals. For this system, we formulate the rate-reliability-detection trade-off in the finite blocklength regime by evaluating the communication rate of the eMBB transmissions, the reliability of the URLLC transmissions and the probability of the target detection. Our numerical analysis show that our proposed DPC-based ISAC scheme significantly outperforms power-sharing based ISAC and traditional time-sharing schemes. In particular, it achieves higher eMBB transmission rate while satisfying both URLLC and sensing constraints.

A MIMO ISAC System for Ultra-Reliable and Low-Latency Communications

TL;DR

This work tackles joint ISAC for URLLC and eMBB in a bi-static MIMO setting, where URLLC transmissions are triggered by SR sensing outcomes. It introduces a DPC-based coding framework with power-shell codebooks and block-type dependent precancellation to mitigate interference from sensing and eMBB signals, and develops a finite-blocklength rate-reliability-detection trade-off that jointly bounds the eMBB rate, URLLC reliability, and target detection probability. The analysis leverages generalized chi-square and Gaussian approximations to derive performance bounds, and a theorem provides the rate constraint under reliability and detection constraints. Numerical results show the proposed DPC-based ISAC scheme significantly outperforms power-sharing and time-sharing approaches, delivering higher eMBB rates while satisfying URLLC and sensing requirements, demonstrating practical gains for 6G ISAC scenarios.

Abstract

In this paper, we propose a bi-static multiple-input multiple-output (MIMO) integrated sensing and communication (ISAC) system to detect the arrival of ultra-reliable and low-latency communication (URLLC) messages and prioritize their delivery. In this system, a dual-function base station (BS) communicates with a user equipment (UE) and a sensing receiver (SR) is deployed to collect echo signals reflected from a target of interest. The BS regularly transmits messages of enhanced mobile broadband (eMBB) services to the UE. During each eMBB transmission, if the SR senses the presence of a target of interest, it immediately triggers the transmission of an additional URLLC message. To reinforce URLLC transmissions, we propose a dirty-paper coding (DPC)-based technique that mitigates the interference of both eMBB and sensing signals. For this system, we formulate the rate-reliability-detection trade-off in the finite blocklength regime by evaluating the communication rate of the eMBB transmissions, the reliability of the URLLC transmissions and the probability of the target detection. Our numerical analysis show that our proposed DPC-based ISAC scheme significantly outperforms power-sharing based ISAC and traditional time-sharing schemes. In particular, it achieves higher eMBB transmission rate while satisfying both URLLC and sensing constraints.
Paper Structure (24 sections, 7 theorems, 40 equations, 3 figures)

This paper contains 24 sections, 7 theorems, 40 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Problem Setup
  3. Communication Received Signal at the UE
  4. Target Echo Signal Model
  5. Coding Scheme
  6. Codebook construction
  7. Encoding
  8. Encoding at each block $b \notin \mathcal{B}_{\text{arrival}}$
  9. Encoding at each block $b \in \mathcal{B}_{\text{arrival}}$
  10. Decoding
  11. Decoding of URLLC Messages
  12. Decoding the eMBB Message
  13. Main Results
  14. Numerical Analysis
  15. Conclusion
  16. ...and 9 more sections

Key Result

Proposition 1

Given $n, \eta$ and $\mathsf{P}$, let $\mathsf{R}_e := \frac{\log M_{\mathsf{e}}}{n}$ be the eMBB transmission rate. The rate-reliability-detection trade-off is where $\mathcal{P}_X(\mathsf{P})$ is defined in eq:1.

Figures (3)

  • Figure 1: An illustration of the system model: (a) no target is detected, (b) detection of a target, (c) example of transmission blocks with $\eta = 4$.
  • Figure 2: Comparing our DPC-based scheme with power-sharing and time-sharing schemes for $\mathsf{P}= 0.5$, $\ell = 150$, $\eta = 10$, $P_{FA} = 10^{-6}$, $\epsilon_e = 10^{-3}$.
  • Figure 3: Our proposed scheme with different values of the URLLC decoding error probability threshold for $\mathsf{P}= 0.5$, $\ell = 150$, $\eta = 10$, $P_{FA} = 10^{-6}$, $\epsilon_e = 10^{-3}$.

Theorems & Definitions (8)

  • Definition 1
  • Proposition 1
  • Lemma 1
  • Lemma 2
  • Lemma 3
  • Theorem 1
  • Lemma 4
  • Lemma 5