Pinching-Antenna Systems with In-Waveguide Attenuation: Performance Analysis and Algorithm Design

TL;DR

This paper analyzes pinching-antenna systems with in-waveguide attenuation, deriving optimal placement, conditions where attenuation impact is negligible, and developing algorithms for multi-user scenarios, showing significant performance improvements over fixed antennas.

Contribution

It provides the first comprehensive analysis of in-waveguide attenuation effects and introduces algorithms for joint beamforming and antenna placement in pinching-antenna systems.

Findings

Optimal antenna placement depends on attenuation coefficient and user distance.

In-waveguide attenuation can be negligible under certain conditions.

Proposed algorithms outperform fixed-antenna baselines in simulations.

Abstract

Pinching-antenna systems have emerged as a promising flexible-antenna architecture for next-generation wireless networks, enabling enhanced adaptability and user-centric connectivity through antenna repositioning along waveguides. However, existing studies often overlook in-waveguide signal attenuation and in the literature, there is no comprehensive analysis on whether and under what conditions such an assumption is justified. This paper addresses this gap by explicitly incorporating in-waveguide attenuation into both the system model and algorithm design, and studying its impact on the downlink user data rates. We begin with a single-user scenario and derive a closed-form expression for the globally optimal antenna placement, which reveals how the attenuation coefficient and the user-to-waveguide distance jointly affect the optimal antenna position. Based on this analytical solution, we further provide a theoretical analysis identifying the system conditions under which the in-waveguide attenuation has an insignificant impact on the user achievable rate. The study is then extended to the multi-user multiple-input multiple-output setting, where two efficient algorithms are developed, based on the weighted minimum mean square error method and the maximum ratio combining method, to jointly optimize beamforming and antenna placement. Simulation results validate the efficacy of the proposed algorithms and demonstrate that pinching-antenna systems substantially outperform conventional fixed-antenna baselines, underscoring their potential for future flexible wireless communications.