Fairness-Oriented Optimization of NOMA-Enabled Pinching-Antenna Systems Under Blockage and Imperfect CSI

TL;DR

This paper proposes a fairness-oriented design for NOMA-enabled pinching-antenna systems that optimizes antenna placement and power allocation to enhance user SINR under blockage and imperfect CSI conditions.

Contribution

It introduces a joint optimization framework for antenna placement and power allocation in PASS, incorporating a robust SINR evaluation under channel uncertainties.

Findings

Improves minimum user SINR by 7-10 dB over fixed systems.

Develops a conservative SINR evaluation for imperfect CSI.

Uses a tailored PSO algorithm for non-convex optimization.

Abstract

The pinching-antenna system (PASS) has been proposed as a promising solution for mitigating line-of-sight (LoS) blockages by dynamically repositioning pinching antennas (PAs) along a dielectric waveguide. This paper develops a fairness-oriented downlink design for a non-orthogonal multiple access (NOMA)-enabled PASS, where the longitudinal placement of PAs and the NOMA power allocation coefficients are jointly optimized to maximize the minimum user signal-to-interference-plus-noise ratio (SINR) across all users under transmit power and waveguide constraints. A soft-blockage channel model incorporating waveguide attenuation and imperfect channel state information (CSI) is developed. To ensure the feasibility of successive interference cancellation under CSI uncertainty, a conservative SINR evaluation framework is proposed. The resulting non-convex max-min SINR optimization problem is efficiently solved using a tailored particle swarm optimization (PSO) algorithm. Numerical results demonstrate that the proposed design improves the minimum user SINR by approximately 7-10 dB compared with fixed-antenna systems and non-robust optimization baselines under moderate blockage and imperfect CSI.