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Enhancing Robustness and Security in ISAC Network Design: Leveraging Transmissive Reconfigurable Intelligent Surface with RSMA

Ziwei Liu, Wen Chen, Qingqing Wu, Zhendong Li, Xusheng Zhu, Qiong Wu, Nan Cheng

TL;DR

The paper tackles secure ISAC design under imperfect CSI by integrating transmissive RIS (TRIS) with RSMA and a time-division sensing-communication framework. It constructs a robust optimization problem that maximizes secrecy sum-rate while ensuring sensing performance and eavesdropping outage constraints, and solves it via a BCD-based approach with SDR, S-procedure, Bernstein inequalities, and SCA to obtain practical beamforming and resource allocations. Key contributions include a tractable convex reformulation of nonconvex constraints, a bounded-uncertainty model for IU channels, and a demonstration that RSMA enables common-stream artificial-noise-like behavior to degrade eavesdroppers without sacrificing LU QoS, yielding notable secrecy-energy-efficiency gains. The results indicate that increasing TRIS elements and employing multi-slot beam scanning enhance both security and sensing accuracy, highlighting the practical viability of TRIS-RSMA ISAC systems for secure, low-power deployments.

Abstract

In this paper, we propose a novel transmissive reconfigurable intelligent surface transceiver-enhanced robust and secure integrated sensing and communication network. A time-division sensing communication mechanism is designed for the scenario, which enables communication and sensing to share wireless resources. To address the interference management problem and hinder eavesdropping, we implement rate-splitting multiple access (RSMA), where the common stream is designed as a useful signal and an artificial noise, while taking into account the imperfect channel state information and modeling the channel for the illegal users in a fine-grained manner as well as giving an upper bound on the error. We introduce the secrecy outage probability and construct an optimization problem with secrecy sum-rate as the objective functions to optimize the common stream beamforming matrix, the private stream beamforming matrix and the timeslot duration variable. Due to the coupling of the optimization variables and the infinity of the error set, the proposed problem is a nonconvex optimization problem that cannot be solved directly. In order to address the above challenges, the block coordinate descent-based second-order cone programming algorithm is used to decouple the optimization variables and solving the problem. Specifically, the problem is decoupled into two subproblems concerning the common stream beamforming matrix, the private stream beamforming matrix, and the timeslot duration variable, which are solved by alternating optimization until convergence is reached. To solve the problem, S-procedure, Bernstein's inequality and successive convex approximation are employed to deal with the objective function and non-convex constraints. Numerical simulation results verify the superiority of the proposed scheme in improving the secrecy energy efficiency and the Cramér-Rao boundary.

Enhancing Robustness and Security in ISAC Network Design: Leveraging Transmissive Reconfigurable Intelligent Surface with RSMA

TL;DR

The paper tackles secure ISAC design under imperfect CSI by integrating transmissive RIS (TRIS) with RSMA and a time-division sensing-communication framework. It constructs a robust optimization problem that maximizes secrecy sum-rate while ensuring sensing performance and eavesdropping outage constraints, and solves it via a BCD-based approach with SDR, S-procedure, Bernstein inequalities, and SCA to obtain practical beamforming and resource allocations. Key contributions include a tractable convex reformulation of nonconvex constraints, a bounded-uncertainty model for IU channels, and a demonstration that RSMA enables common-stream artificial-noise-like behavior to degrade eavesdroppers without sacrificing LU QoS, yielding notable secrecy-energy-efficiency gains. The results indicate that increasing TRIS elements and employing multi-slot beam scanning enhance both security and sensing accuracy, highlighting the practical viability of TRIS-RSMA ISAC systems for secure, low-power deployments.

Abstract

In this paper, we propose a novel transmissive reconfigurable intelligent surface transceiver-enhanced robust and secure integrated sensing and communication network. A time-division sensing communication mechanism is designed for the scenario, which enables communication and sensing to share wireless resources. To address the interference management problem and hinder eavesdropping, we implement rate-splitting multiple access (RSMA), where the common stream is designed as a useful signal and an artificial noise, while taking into account the imperfect channel state information and modeling the channel for the illegal users in a fine-grained manner as well as giving an upper bound on the error. We introduce the secrecy outage probability and construct an optimization problem with secrecy sum-rate as the objective functions to optimize the common stream beamforming matrix, the private stream beamforming matrix and the timeslot duration variable. Due to the coupling of the optimization variables and the infinity of the error set, the proposed problem is a nonconvex optimization problem that cannot be solved directly. In order to address the above challenges, the block coordinate descent-based second-order cone programming algorithm is used to decouple the optimization variables and solving the problem. Specifically, the problem is decoupled into two subproblems concerning the common stream beamforming matrix, the private stream beamforming matrix, and the timeslot duration variable, which are solved by alternating optimization until convergence is reached. To solve the problem, S-procedure, Bernstein's inequality and successive convex approximation are employed to deal with the objective function and non-convex constraints. Numerical simulation results verify the superiority of the proposed scheme in improving the secrecy energy efficiency and the Cramér-Rao boundary.
Paper Structure (28 sections, 2 theorems, 89 equations, 12 figures, 1 table, 1 algorithm)

This paper contains 28 sections, 2 theorems, 89 equations, 12 figures, 1 table, 1 algorithm.

Table of Contents

  1. Introduction
  2. System Model
  3. ISAC Network Models
  4. Channel Model
  5. Communication Channels for LUs
  6. Wiretap Channels for IUs
  7. Radar Sensing Channels for IUs
  8. Signal Model
  9. Quality of Service Evaluation Metrics And Problem Formulation
  10. Secure Communication Performance Metric
  11. Sensing Performance Metric
  12. Detection Probability
  13. Beampattern Approximation
  14. Problem Formulation
  15. Joint Design of Communication and Sensing
  16. ...and 13 more sections

Key Result

Lemma 1

Bernstein-type inequalities bechar2009bernsteintype: Assume that the Gaussian variable ${\bf e} \sim {\cal C}{\cal N}\left( {0,{{\bf{I}}_N}} \right)$, the matrix ${\bf Q} \in \mathbb{H}^{N\times N}$ and ${\bf r}\in\mathbb{C}^{N\times1}$ satisfies $f({\bf e})={\bf e}^H{\bf Q}{\bf e}+2{\rm Re}\left\{{ and where $E^+={\rm{tr}}\left( {\bf{Q}} \right) + \sqrt {2\sigma \left( {\left\| {\bf{Q}} \right\|

Figures (12)

  • Figure 1: TRIS transceiver empowered ISAC networks.
  • Figure 2: The principle and mapping process of TRIS.
  • Figure 3: Frame structure of the ISAC network.
  • Figure 4: Small-scale fading uncertainty.
  • Figure 5: Convergence process: secrecy sum-rate versus number of iterations under different TRIS elements (${\varepsilon _k}=\sqrt{0.01}, {\varepsilon _{m,n}}=0.1\sqrt{\kappa_v}, P_t = 1{\rm mW}$).
  • ...and 7 more figures

Theorems & Definitions (2)

  • Lemma 1
  • Lemma 2