Joint Power Allocation and Radiation Optimization in NOMA-Assisted Pinching Antenna Systems

This paper investigates the joint optimization of transmit power allocation and radiation coefficients in a downlink Pinching Antenna System (PASS) with Non-Orthogonal Multiple Access (NOMA). Exploiting PASS-enabled flexible channel adjustment and NOMA’s power-domain multiplexing capability, we formulate a sum-rate maximization problem that jointly optimizes the base station (BS) transmit power and the pinching antenna (PA) radiation powers. Due to the non-convex nature of the problem, it is decomposed into two sub-problems: BS power allocation, for which closed-form solutions are derived, and PA radiation power optimization, addressed via successive convex approximation. The two sub-problems are solved iteratively using alternating optimization until convergence. Furthermore, two decoding order strategies are considered: an exhaustive search scheme and a low-complexity CSI-based approach. Numerical results demonstrate significant sum-rate gains over conventional equal power allocation PASS schemes.