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Enhanced Connectivity in Ambient Backscatter Communications via Fluid Antenna Readers

Masoud Kaveh, Farshad Rostami Ghadi, Riku Jantti, Kai-Kit Wong, F. Javier Lopez-Martinez

TL;DR

A particle swarm optimization (PSO)-based framework is developed to jointly determine the FAS port selection and modulation coefficient on an optimize-then-average (OTA) basis, which significantly improves the achievable rate compared with conventional single-antenna readers.

Abstract

Ambient backscatter communication (AmBC) enables ultra-low-power connectivity by allowing passive backscatter devices (BDs) to convey information through reflection of ambient signals. However, the cascaded AmBC channel suffers from severe double path loss and multiplicative fading, while accurate channel state information (CSI) acquisition is highly challenging due to the weak backscattered signal and the resource-limited nature of BDs. To address these challenges, this paper considers an AmBC system in which the reader is equipped with a pixel-based fluid antenna system (FAS). By dynamically selecting one antenna position from a dense set of pixels within a compact aperture, the FAS-enabled reader exploits spatial diversity through measurement-driven port selection, without requiring explicit CSI acquisition or multiple RF chains. The intrinsic rate-energy tradeoff at the BD is also incorporated by jointly optimizing the backscatter modulation coefficient under an energy harvesting (EH) neutrality constraint. To efficiently solve this problem, a particle swarm optimization (PSO)-based framework is developed to jointly determine the FAS port selection and modulation coefficient on an optimize-then-average (OTA) basis. Simulation results show that the proposed scheme significantly improves the achievable rate compared with conventional single-antenna readers, with gains preserved under imperfect observations, stringent EH constraints, and different pixel spacings.

Enhanced Connectivity in Ambient Backscatter Communications via Fluid Antenna Readers

TL;DR

A particle swarm optimization (PSO)-based framework is developed to jointly determine the FAS port selection and modulation coefficient on an optimize-then-average (OTA) basis, which significantly improves the achievable rate compared with conventional single-antenna readers.

Abstract

Ambient backscatter communication (AmBC) enables ultra-low-power connectivity by allowing passive backscatter devices (BDs) to convey information through reflection of ambient signals. However, the cascaded AmBC channel suffers from severe double path loss and multiplicative fading, while accurate channel state information (CSI) acquisition is highly challenging due to the weak backscattered signal and the resource-limited nature of BDs. To address these challenges, this paper considers an AmBC system in which the reader is equipped with a pixel-based fluid antenna system (FAS). By dynamically selecting one antenna position from a dense set of pixels within a compact aperture, the FAS-enabled reader exploits spatial diversity through measurement-driven port selection, without requiring explicit CSI acquisition or multiple RF chains. The intrinsic rate-energy tradeoff at the BD is also incorporated by jointly optimizing the backscatter modulation coefficient under an energy harvesting (EH) neutrality constraint. To efficiently solve this problem, a particle swarm optimization (PSO)-based framework is developed to jointly determine the FAS port selection and modulation coefficient on an optimize-then-average (OTA) basis. Simulation results show that the proposed scheme significantly improves the achievable rate compared with conventional single-antenna readers, with gains preserved under imperfect observations, stringent EH constraints, and different pixel spacings.
Paper Structure (7 sections, 22 equations, 5 figures, 1 algorithm)

This paper contains 7 sections, 22 equations, 5 figures, 1 algorithm.

Table of Contents

  1. Introduction
  2. System Model
  3. Problem Formulation
  4. Results and Discussions
  5. Simulation Setup
  6. Result Analysis and Discussion
  7. Conclusion

Figures (5)

  • Figure 1: The considered AmBC system with pixel-based FAS at the reader.
  • Figure 2: Average achievable rate versus average SNR for the proposed FAS-based AmBC with different number of preset positions.
  • Figure 3: Average achievable rate versus average SNR for the proposed FAS-based AmBC with different number of preset positions.
  • Figure 4: Average achievable rate versus CSI error variance for the proposed FAS-based AmBC with different number of preset positions.
  • Figure 5: Average achievable rate versus average received SNR for the pixel-based FAS-aided AmBC with $K=10$ and different inter-pixel spacings $d_\text{i,j}$.