Frequency-Selective Modeling and Analysis for OFDM-Integrated Wideband Pinching-Antenna Systems

TL;DR

This paper models and analyzes the frequency-selective behavior of OFDM-integrated pinching-antenna systems, revealing how waveguide properties affect communication efficiency and phase alignment across subcarriers.

Contribution

It introduces an electromagnetic-compliant end-to-end channel model for OFDM PASS and analyzes the impact of waveguide characteristics on system performance.

Findings

Operating above waveguide cutoff improves achievable rates.

Near cutoff frequency, CP overhead increases, reducing spectral efficiency.

Waveguide dispersion causes significant phase misalignment and path loss.

Abstract

This letter investigates the integration of pinching-antenna systems (PASS) with orthogonal frequency division multiplexing (OFDM) to ensure their compatibility and to explore the frequency-selective behavior inherent to PASS. First, an end-to-end channel model for OFDM PASS is proposed based on electromagnetic-compliant modeling of waveguides and coupled-mode theory, which includes frequency-dependent waveguide attenuation, dispersion and antenna coupling effect. Furthermore, a critical dependence of the OFDM cyclic prefix (CP) overhead on the proximity of the operating frequency to the waveguide cutoff is revealed. Moreover, the phase misalignment effect across subcarriers in OFDM PASS is derived for an approximate pinching antenna location strategy based on path loss minimization, which reveals the phase misalignment is exacerbated for wider bandwidths and larger array size. Numerical results show that: 1) frequency-selective effects in OFDM PASS lead to substantial variations in subcarrier achievable rates, highlighting the necessity of operating above the waveguide cutoff frequency for effective communications; 2) waveguide dispersion mandates considerable CP overhead when operating near the cutoff frequency, severely impacting the spectral efficiency of OFDM PASS; and 3) the gentle linear waveguide attenuation in a practical PASS significantly more advantageous than the severe logarithmic path loss characteristic of fixed-location antennas.