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On Dual-Fed Pinching Antenna Systems with In-Waveguide Attenuation

Ximing Xie, Hao Qin, Fang Fang, Xianbin Wang

Abstract

Pinching antenna systems (PAS) have recently emerged as a promising architecture for flexible and reconfigurable wireless communications. However, their performance is fundamentally constrained by in-waveguide attenuation, which is non-negligible in practical dielectric waveguides and can severely degrade the achievable data rate, particularly for long waveguides. To overcome this limitation, we propose a dual-fed PAS (DF-PAS), in which each waveguide is equipped with two feed points located at the two ends, enabling dynamic feed-point selection based on user locations. This design effectively shortens the in-waveguide propagation distance and mitigates attenuation-induced power loss without modifying the waveguide structure or the PA actuation mechanism. We investigate the DF-PAS in both single- and multi-waveguide scenarios. For the single-waveguide case, we derive closed-form high-SNR approximations of the ergodic rate and obtain closed-form solutions for the optimal PA position and feed-point selection under time-division multiple access (TDMA). We then extend DF-PAS to a multi-waveguide scenario, where we first derive closed-form high-SNR approximations of the ergodic rate and then formulate a joint optimization problem over feed-point selection, PA placement, and beamforming under general orthogonal multiple access (OMA). To solve this problem efficiently, we develop a two-phase optimization framework that integrates greedy feed-point switching, gradient-based PA placement, and WMMSE-based beamforming. Simulation results demonstrate that the proposed DF-PAS consistently outperforms conventional single-fed PAS (SF-PAS) across various network configurations, validating its effectiveness as a practical and scalable solution for mitigating in-waveguide attenuation in PAS-enabled wireless networks.

On Dual-Fed Pinching Antenna Systems with In-Waveguide Attenuation

Abstract

Pinching antenna systems (PAS) have recently emerged as a promising architecture for flexible and reconfigurable wireless communications. However, their performance is fundamentally constrained by in-waveguide attenuation, which is non-negligible in practical dielectric waveguides and can severely degrade the achievable data rate, particularly for long waveguides. To overcome this limitation, we propose a dual-fed PAS (DF-PAS), in which each waveguide is equipped with two feed points located at the two ends, enabling dynamic feed-point selection based on user locations. This design effectively shortens the in-waveguide propagation distance and mitigates attenuation-induced power loss without modifying the waveguide structure or the PA actuation mechanism. We investigate the DF-PAS in both single- and multi-waveguide scenarios. For the single-waveguide case, we derive closed-form high-SNR approximations of the ergodic rate and obtain closed-form solutions for the optimal PA position and feed-point selection under time-division multiple access (TDMA). We then extend DF-PAS to a multi-waveguide scenario, where we first derive closed-form high-SNR approximations of the ergodic rate and then formulate a joint optimization problem over feed-point selection, PA placement, and beamforming under general orthogonal multiple access (OMA). To solve this problem efficiently, we develop a two-phase optimization framework that integrates greedy feed-point switching, gradient-based PA placement, and WMMSE-based beamforming. Simulation results demonstrate that the proposed DF-PAS consistently outperforms conventional single-fed PAS (SF-PAS) across various network configurations, validating its effectiveness as a practical and scalable solution for mitigating in-waveguide attenuation in PAS-enabled wireless networks.
Paper Structure (24 sections, 3 theorems, 71 equations, 6 figures, 1 algorithm)

This paper contains 24 sections, 3 theorems, 71 equations, 6 figures, 1 algorithm.

Table of Contents

  1. Introduction
  2. Related Works
  3. Motivation and Contributions
  4. Organization
  5. Dual-Fed Pinching Antenna System: Single Waveguide Case
  6. In-waveguide Attenuation
  7. Dual-Fed Pinching Antenna System
  8. Performance Analysis
  9. Optimization
  10. Optimal PA Position
  11. Feed-Point Selection
  12. Dual-Fed Pinching Antenna System: Multiple Waveguides Case
  13. Multi-waveguide Dual-Fed Pinching Antenna System
  14. Performance Analysis
  15. Optimization
  16. ...and 9 more sections

Key Result

Lemma 1

At high SNR, the ergodic rate of ${\rm U}_m$ can be approximated as

Figures (6)

  • Figure 1: Power decay along a PTFE waveguide
  • Figure 2: Architecture of the DF-PAS
  • Figure 3: Ergodic rate performance analysis of the single-waveguide scenario: (a) Ergodic data rate versus waveguide length $L_x$, which verifies the accuracy of the derived analytical result \ref{['closed form e rate']} against Monte Carlo simulations; (b) Ergodic data rate versus transmit power $P_0$ under different values of $L_x$; (c) Ergodic data rate versus service area width $L_y$ under different transmit power levels $P_0$.
  • Figure 4: Sum rate optimization of the single-waveguide scenario under TDMA: (a) Sum rate versus transmit power $P_0$; (b) Sum rate versus waveguide length $L_x$; (c) Sum rate versus service area width $L_y$.
  • Figure 5: Ergodic rate performance analysis of the multi-waveguide scenario: (a) Ergodic data rate versus waveguide length $L_x$, which verifies the accuracy of the derived analytical result \ref{['closed form e rate multi waveguide']} against Monte Carlo simulations; (b) Ergodic data rate versus transmit power $P_0$ under different numbers of waveguides $N$; (c) Ergodic data rate versus number of waveguides $N$ under different transmit power levels $P_0$.
  • ...and 1 more figures

Theorems & Definitions (7)

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