The pinching-antenna systems (PASS) enable blockage mitigation in urban micro (UMi) networks through flexible antenna placement. However, the joint optimization of antenna positions and beamforming precoding is inherently nonconvex and becomes significantly more challenging under user mobility. To address this issue, we propose a bilevel optimization framework for dynamic antenna positioning and beamforming precoding design. In the outer level, a soft actor-critic (SAC) agent learns a continuous control policy for real-time antenna positioning, while in the inner level, zero-forcing (ZF) precoding is applied based on the instantaneous effective channel. Numerical results demonstrate that the proposed framework significantly improves spectral efficiency (SE) and enhances robustness against user mobility and random blockages.
@article{arxiv.2603.00619,
title = {Dynamic Antenna Placement for Mobile Users in Urban Micro Pinching-Antenna Systems},
author = {Qiushi Zhao and Zihan Feng and Ximing Xie and Hao Qin and Yuanwei Liu and Xingqi Zhang},
journal= {arXiv preprint arXiv:2603.00619},
year = {2026}
}