Joint Power Control and Antenna Positioning for Uplink RSMA in Pinching Antenna Systems

This paper investigates a rate-splitting multiple access (RSMA) for uplink pinching antenna system (PASS). Our objective is to maximize the uplink sum rate by jointly optimizing a continuous antenna positioning and user's transmission power. The formulated problem is highly non-convex and difficult to solve directly; to address this challenge, we propose an alternating optimization (AO) framework which decomposes the original problem into two tractable sub-problems, namely (i) power allocation optimization sub-problem and (ii) antenna position optimization sub-problem. Both sub-problems are solved using successive convex approximation (SCA)-based algorithm and solved alternatively until convergence. The RSMA access for PASS is compared with conventional non-orthogonal multiple access (NOMA) and space-division multiple access (SDMA) techniques. The performance of discrete antenna activation with PASS strategy is also examined. Simulation results demonstrate that our proposed framework significantly enhances the achievable sum rate compared to other multiple access methods.