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Outage-Constrained Sum Secrecy Rate Maximization for STAR-RIS with Energy-Harvesting Eavesdroppers

Zahra Rostamikafaki, Francois Chan, Claude D'Amours

TL;DR

A novel strategy for enhancing secure wireless communication through the use of a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) in a multiple-input single-output system that outperforms conventional RIS methods in terms of robust security and energy performance.

Abstract

This article proposes a novel strategy for enhancing secure wireless communication through the use of a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) in a multiple-input single-output system. In the presence of energy-harvesting eavesdroppers, the study aims to maximize the secrecy rate while adhering to strict energy harvesting constraints. By dynamically manipulating the wireless environment with the STAR-RIS, the research examines the balance between harvested energy and secrecy rate under two key protocols: energy splitting and mode selection. The study addresses both imperfect and perfect channel state information (CSI) and formulates a complex non-convex optimization problem, which is solved using a penalty concave convex procedure combined with an alternating optimization algorithm. The method optimizes beamforming and STAR-RIS transmission and reflection coefficients to achieve a optimal balance between secure communication and energy harvesting constraints. Numerical simulations show that the proposed approach is effective, even with imperfect CSI, and outperforms conventional RIS methods in terms of robust security and energy performance.

Outage-Constrained Sum Secrecy Rate Maximization for STAR-RIS with Energy-Harvesting Eavesdroppers

TL;DR

A novel strategy for enhancing secure wireless communication through the use of a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) in a multiple-input single-output system that outperforms conventional RIS methods in terms of robust security and energy performance.

Abstract

This article proposes a novel strategy for enhancing secure wireless communication through the use of a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) in a multiple-input single-output system. In the presence of energy-harvesting eavesdroppers, the study aims to maximize the secrecy rate while adhering to strict energy harvesting constraints. By dynamically manipulating the wireless environment with the STAR-RIS, the research examines the balance between harvested energy and secrecy rate under two key protocols: energy splitting and mode selection. The study addresses both imperfect and perfect channel state information (CSI) and formulates a complex non-convex optimization problem, which is solved using a penalty concave convex procedure combined with an alternating optimization algorithm. The method optimizes beamforming and STAR-RIS transmission and reflection coefficients to achieve a optimal balance between secure communication and energy harvesting constraints. Numerical simulations show that the proposed approach is effective, even with imperfect CSI, and outperforms conventional RIS methods in terms of robust security and energy performance.
Paper Structure (13 sections, 29 equations, 6 figures, 2 algorithms)

This paper contains 13 sections, 29 equations, 6 figures, 2 algorithms.

Table of Contents

  1. Introduction
  2. System Model
  3. Signal Model of STAR-RIS Protocols
  4. The Energy Splitting Protocol
  5. The Mode Selection Protocol
  6. Signal Transmissions and Receptions
  7. Optimization Problem Formulation
  8. Addressing the SOP Probabilistic Constraint
  9. Addressing Non-Convexity of Optimization Problem For ES
  10. Addressing Non-Convexity of Optimization Problem For MS
  11. Complexity Analysis
  12. Numerical Results and Discussion
  13. Conclusions

Figures (6)

  • Figure 1: Secure STAR-RIS system model.
  • Figure 2: Average sum secrecy rate versus STAR-RIS number of elements: $P_{\text{max}} = 0$ dBW, $E_{\text{min}}= -20$ dB, $N_t = 4$, $\delta = 0.5$.
  • Figure 3: Average sum secrecy rate versus number of antennas: $P_{\text{max}} = 0$ dBW, $E_{\text{min}}= -20$ dB, $M = 40$, $\delta = 0.5$.
  • Figure 4: Average sum secrecy rate versus min required energy: $P_{\text{max}} = 0$ dBW, $N_t = 4$ dB, $M = 40$, $\delta = 0.5$.
  • Figure 5: Average sum secrecy rate versus power budget: $E_{\text{min}}= -20$ dB, $N_t = 4$, $M = 40$, $\delta = 0.5$.
  • ...and 1 more figures