Two-Timescale Joint Transmit and Pinching Beamforming for Pinching-Antenna Systems

--Pinching antenna systems (PASS) have been proposed as a revolutionary flexible antenna technology which facilitates line-of-sight links via numerous low-cost pinching antennas with adjustable activation positions over waveguides. This letter proposes a two-timescale joint transmit and pinching beamforming design for the maximization of sum rate of a PASS-based downlink multi-user multiple input single output system. A primal dual decomposition method is developed to decouple the two-timescale problem into two sub-problems: 1) A Karush-Kuhn-T ucker-guided dual learning-based approach is proposed to solve the short-term transmit beamforming design sub-problem; 2) The long-term pinching beamforming design sub-problem is tackled by adopting a stochastic successive convex approximation method. Simulation results demonstrate that the proposed two-timescale algorithm achieves a significant performance gain compared to other baselines. Flexible-antenna techniques such as reconfigurable intelligent surfaces (RISs) [1], movable antennas [2], and fluid antennas [3], have been developed to break the limitation of fixed-channel assumptions in the sixth generation (6G) and beyond wireless network.