Joint Coupling Spacing and Beamforming Optimization for Pinching-Antenna Systems

Abstract

Practical implementation of pinching-antenna systems (PASS) is challenging due to hardware limitations in large-scale antenna movement and continuous radiation power adjustment. This paper proposes a practical PASS-enabled downlink multiuser multiple-input multiple-output communication framework with discrete radiation control and localized discrete antenna movement. Specifically, a hardware-compatible discrete coupling-spacing model is adopted to enable adjustable radiation power control for each pinching antenna (PA) through quantized coupling levels. Moreover, a practical PA movement model is considered, where each PA can only move among discrete locations within a limited region determined by the movement speed and duration. The in-waveguide attenuation is also incorporated into the system model to reflect real-world conditions. Based on the proposed framework, we jointly optimize the PA positions, coupling spacing levels, and transmit beamforming to minimize the total average power consumption subject to users' minimum SINR requirements. The resulting problem is a highly coupled mixed-integer nonlinear programming problem due to the coupling between discrete PASS structural variables and continuous transmit beamforming variables. To solve it efficiently, a scalable genetic algorithm-assisted particle swarm optimization framework with second-oorder cone programming-based beamforming algorithm is proposed. Simulation results demonstrate that the proposed design significantly reduces the power consumption compared with existing PASS schemes and MIMO architectures.