Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Coding-Enhanced Cooperative Jamming for Secret Communication in Fluid Antenna Systems

Hao Xu, Kai-Kit Wong, Wee Kiat New, Guyue Li, Farshad Rostami Ghadi, Yongxu Zhu, Shi Jin, Chan-Byoung Chae, Yangyang Zhang

TL;DR

This work addresses secret communication in a fluid antenna system (FAS)–assisted wiretap channel by allowing the jamming signal from the transmitter to be encoded, enabling the legitimate receiver to decode and cancel the interference while the eavesdropper cannot, even with codebook knowledge. The secrecy rate is maximized by jointly optimizing port selection over $N$ ports and power split $(p_1,p_2)$ under a total power $P$, with per-port secrecy expressions guiding the design. Although the problem is NP-hard due to the discrete port choice, the authors prove that for a fixed port the subproblems admit closed-form solutions, and an overall optimal solution is obtained by sweeping all ports (Algorithm 1). Simulations demonstrate that FAS with the proposed encoding-based jamming substantially improves secrecy rates over conventional FPA and Gaussian-jamming schemes, with larger gains at moderate SNR and when port correlation is managed by increasing the normalized size $W$ of the FAS. The results underscore the practical potential of FAS for secure communications and motivate future work on Eve leveraging FAS and on robust CSI handling.

Abstract

This letter investigates the secret communication problem for a fluid antenna system (FAS)-assisted wiretap channel, where the legitimate transmitter transmits an information-bearing signal to the legitimate receiver, and at the same time, transmits a jamming signal to interfere with the eavesdropper (Eve). Unlike the conventional jamming scheme, which usually transmits Gaussian noise that interferes not only with Eve but also with the legitimate receiver, in this letter, we consider that encoded codewords are transmitted to jam Eve. Then, by employing appropriate coding schemes, the legitimate receiver can successfully decode the jamming signal and then cancel the interference, while Eve cannot, even if it knows the codebooks. We aim to maximize the secrecy rate through port selection and power control. Although the problem is non-convex, we show that the optimal solution can be found. Simulation results show that by using the FAS technique and the proposed jamming scheme, the secrecy rate of the system can be significantly increased.

Coding-Enhanced Cooperative Jamming for Secret Communication in Fluid Antenna Systems

TL;DR

This work addresses secret communication in a fluid antenna system (FAS)–assisted wiretap channel by allowing the jamming signal from the transmitter to be encoded, enabling the legitimate receiver to decode and cancel the interference while the eavesdropper cannot, even with codebook knowledge. The secrecy rate is maximized by jointly optimizing port selection over ports and power split under a total power , with per-port secrecy expressions guiding the design. Although the problem is NP-hard due to the discrete port choice, the authors prove that for a fixed port the subproblems admit closed-form solutions, and an overall optimal solution is obtained by sweeping all ports (Algorithm 1). Simulations demonstrate that FAS with the proposed encoding-based jamming substantially improves secrecy rates over conventional FPA and Gaussian-jamming schemes, with larger gains at moderate SNR and when port correlation is managed by increasing the normalized size of the FAS. The results underscore the practical potential of FAS for secure communications and motivate future work on Eve leveraging FAS and on robust CSI handling.

Abstract

This letter investigates the secret communication problem for a fluid antenna system (FAS)-assisted wiretap channel, where the legitimate transmitter transmits an information-bearing signal to the legitimate receiver, and at the same time, transmits a jamming signal to interfere with the eavesdropper (Eve). Unlike the conventional jamming scheme, which usually transmits Gaussian noise that interferes not only with Eve but also with the legitimate receiver, in this letter, we consider that encoded codewords are transmitted to jam Eve. Then, by employing appropriate coding schemes, the legitimate receiver can successfully decode the jamming signal and then cancel the interference, while Eve cannot, even if it knows the codebooks. We aim to maximize the secrecy rate through port selection and power control. Although the problem is non-convex, we show that the optimal solution can be found. Simulation results show that by using the FAS technique and the proposed jamming scheme, the secrecy rate of the system can be significantly increased.
Paper Structure (7 sections, 2 theorems, 22 equations, 3 figures, 1 algorithm)

This paper contains 7 sections, 2 theorems, 22 equations, 3 figures, 1 algorithm.

Table of Contents

  1. Introduction
  2. System Model and Problem Formulation
  3. Main Results
  4. Simulation Results
  5. Conclusions
  6. Proof of Theorem \ref{['theorem1']}
  7. Proof of Theorem \ref{['theorem2']}

Key Result

Theorem 1

The optimal solution of (max_R_hat) is given by and ${\hat{p}}_2^* = P - {\hat{p}}_1^*$, where $\alpha = \frac{-b - \sqrt{b^2 - 4ac}}{2 a}$ and On the other hand, the optimal solution $({\tilde{p}}_1^*, {\tilde{p}}_2^*)$ of (max_R_tilde) takes the value of $({\tilde{P}}_{1, {\text{lb}}}, 0)$, $({\tilde{P}}_{1, {\text{lb}}}, P - {\tilde{P}}_{1, {\text{lb}}})$, $({\tilde{P}}_{1, {\text{ub}}}, 0)$,

Figures (3)

  • Figure 1: Secrecy rate $R_{\text{EJ}}$ and $R_{\text{GN}}$ versus the SNR $\rho$ with $W = 5$.
  • Figure 2: Secrecy rate $R_{\text{EJ}}$ and $R_{\text{GN}}$ versus $W$ with $\rho = 10$ dB.
  • Figure 3: Secrecy rate $R_{\text{EJ}}$ versus $N$ with $\rho = 10$ dB.

Theorems & Definitions (2)

  • Theorem 1
  • Theorem 2