Robust Beamforming for Pinching-Antenna Systems-Based Multi-User Communications

Pinching-antenna systems (PASS)-enabled communications are a promising paradigm. However, obtaining accurate channel state information (CSI) is challenging due to the limited pilots, model mismatch, and other hardware impairments. In this paper, we study the robust beamforming design for PASS-based multi-user communication under the CSI uncertainty. In particular, we model the CSI error using a complex-ball uncertainty set and study the worst-case beamforming design to minimize the transmit power for satisfying users’ minimum achievable rate requirements. To address this problem, the S-procedure is first applied to convert the resulting semi-infinite formulation into a tractable finite set of constraints. Then, an alternating optimization framework is developed to design the baseband beamforming and pinching beamforming. The base-band beamforming subproblem is handled via the semidefinite programming, while a penalty dual decomposition-based method is developed to address the non-convex pinching beamforming subproblem. Finally, the effectiveness of the proposed algorithm is verified through simulations.