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Robust and Secure Blockage-Aware Pinching Antenna-assisted Wireless Communication

Ruotong Zhao, Shaokang Hu, Deepak Mishra, Derrick Wing Kwan Ng

TL;DR

This work develops a blockage-aware, PA-assisted downlink system to securely and robustly serve multiple users in the presence of multi-antenna eavesdroppers under imperfect CSI. A 3D blockage-aware channel model combined with geometry-aware CSI uncertainty for eavesdroppers enables a robust sum-rate optimization that jointly designs beamforming, artificial noise, PA power-ratios, and PA positions. The authors introduce a block coordinate descent algorithm with S-procedure and majorization-minimization, plus a two-stage PA positioning strategy that separates large-scale placement from small-scale phase alignment, achieving substantial rate and secrecy gains compared with fixed-antenna baselines. Simulations confirm the tightness of the proposed uncertainty bound and show that neglecting blockage degrades performance and secrecy, while adaptive PA positioning enhances legitimate-LoS and suppresses eavesdroppers, reducing artificial-noise requirements.

Abstract

In this work, we investigate a blockage-aware pinching antenna (PA) system designed for secure and robust wireless communication. The considered system comprises a base station equipped with multiple waveguides, each hosting multiple PAs, and serves multiple single-antenna legitimate users in the presence of multi-antenna eavesdroppers under imperfect channel state information (CSI). To safeguard confidential transmissions, artificial noise (AN) is deliberately injected to degrade the eavesdropping channels. Recognizing that conventional linear CSI-error bounds become overly conservative for spatially distributed PA architectures, we develop new geometry-aware uncertainty sets that jointly characterize eavesdroppers position and array-orientation errors. Building upon these sets, we formulate a robust joint optimization problem that determines per-waveguide beamforming and AN covariance, individual PA power-ratio allocation, and PA positions to maximize the system sum rate subject to secrecy constraints. The highly non-convex design problem is efficiently addressed via a low computational complexity iterative algorithm that capitalizes on block coordinate descent, penalty-based methods, majorization-minimization, the S-procedure, and Lipschitz-based surrogate functions. Simulation results demonstrate that sum rates for the proposed algorithm outperforms conventional fixed antenna systems by 4.7 dB, offering substantially improved rate and secrecy performance. In particular, (i) adaptive PA positioning preserves LoS to legitimate users while effectively exploiting waveguide geometry to disrupt eavesdropper channels, and (ii) neglecting blockage effects in the PA system significantly impacts the system design, leading to performance degradation and inadequate secrecy guarantees.

Robust and Secure Blockage-Aware Pinching Antenna-assisted Wireless Communication

TL;DR

This work develops a blockage-aware, PA-assisted downlink system to securely and robustly serve multiple users in the presence of multi-antenna eavesdroppers under imperfect CSI. A 3D blockage-aware channel model combined with geometry-aware CSI uncertainty for eavesdroppers enables a robust sum-rate optimization that jointly designs beamforming, artificial noise, PA power-ratios, and PA positions. The authors introduce a block coordinate descent algorithm with S-procedure and majorization-minimization, plus a two-stage PA positioning strategy that separates large-scale placement from small-scale phase alignment, achieving substantial rate and secrecy gains compared with fixed-antenna baselines. Simulations confirm the tightness of the proposed uncertainty bound and show that neglecting blockage degrades performance and secrecy, while adaptive PA positioning enhances legitimate-LoS and suppresses eavesdroppers, reducing artificial-noise requirements.

Abstract

In this work, we investigate a blockage-aware pinching antenna (PA) system designed for secure and robust wireless communication. The considered system comprises a base station equipped with multiple waveguides, each hosting multiple PAs, and serves multiple single-antenna legitimate users in the presence of multi-antenna eavesdroppers under imperfect channel state information (CSI). To safeguard confidential transmissions, artificial noise (AN) is deliberately injected to degrade the eavesdropping channels. Recognizing that conventional linear CSI-error bounds become overly conservative for spatially distributed PA architectures, we develop new geometry-aware uncertainty sets that jointly characterize eavesdroppers position and array-orientation errors. Building upon these sets, we formulate a robust joint optimization problem that determines per-waveguide beamforming and AN covariance, individual PA power-ratio allocation, and PA positions to maximize the system sum rate subject to secrecy constraints. The highly non-convex design problem is efficiently addressed via a low computational complexity iterative algorithm that capitalizes on block coordinate descent, penalty-based methods, majorization-minimization, the S-procedure, and Lipschitz-based surrogate functions. Simulation results demonstrate that sum rates for the proposed algorithm outperforms conventional fixed antenna systems by 4.7 dB, offering substantially improved rate and secrecy performance. In particular, (i) adaptive PA positioning preserves LoS to legitimate users while effectively exploiting waveguide geometry to disrupt eavesdropper channels, and (ii) neglecting blockage effects in the PA system significantly impacts the system design, leading to performance degradation and inadequate secrecy guarantees.
Paper Structure (19 sections, 3 theorems, 72 equations, 9 figures, 1 algorithm)

This paper contains 19 sections, 3 theorems, 72 equations, 9 figures, 1 algorithm.

Table of Contents

  1. Introduction
  2. System Model
  3. Blockage-Aware System Setup
  4. Channel Model
  5. PA System CSI Uncertainty Models
  6. Waveguide Propagation Model
  7. Problem Statement
  8. Performance Metric
  9. CSI Error Bound Determination
  10. Problem Formulation
  11. Solution for Joint Optimization of $\textbf{w}_k, \textbf{V}$ and $\textbf{P}$
  12. Problem Transformation
  13. S-Procedure
  14. MM Procedure
  15. PA Location Solution
  16. ...and 4 more sections

Key Result

Lemma 1

(Standard S-Procedure hu2021robust): Let a function $f_m\left(\mathrm{\textbf{x}}\right), m\in \{1, 2\}$, be defined as:

Figures (9)

  • Figure 1: A downlink PAs-assisted communication system.
  • Figure 2: Illustration of the ULA of EA $g$, depicting the antenna indexing, blockage regions, and the orientation angle $\theta_g$, with respect to the position $x$-axis.
  • Figure 3: Geometric illustration of a 3D blockage scenario.
  • Figure 4: Illustration of the available power allocation among PAs along the $n$-th dielectric waveguide considering propagation attenuation.
  • Figure 5: Proposed channel error bound when $N = 5$, $M = 2$, and $T = 2$.
  • ...and 4 more figures

Theorems & Definitions (6)

  • proof
  • proof
  • Lemma 1
  • Lemma 2
  • Lemma 3
  • proof