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

TL;DR

This paper proposes a joint optimization framework for power allocation and radiation pattern design in NOMA-assisted Pinching Antenna Systems, significantly enhancing sum-rate performance through an iterative solution approach.

Contribution

It introduces a novel joint optimization method for power and radiation in NOMA-PASS, employing decomposition and successive convex approximation techniques.

Findings

Substantial sum-rate improvement over equal power schemes.

Effective decomposition of a complex non-convex problem.

Comparison of decoding order strategies shows trade-offs in complexity and performance.

Abstract

This paper explores a joint optimization of transmit power allocation and radiation coefficients in a downlink Pinching Antenna SyStem (PASS) employing Non-Orthogonal Multiple Access (NOMA). By leveraging the PASS-enabled flexible channel adjustment and NOMA's power allocation adaptability, a sum rate maximization problem is formulated with the objective of simultaneously optimizing base station (BS)'s transmit power coefficients and pinching antenna (PA)'s radiation powers. Due to its non-convexity and complexity, the formulated optimization problem is challenging to solve directly. Hence, we decompose the main problem into two sub-problems, namely transmit power allocation sub-problem and PA radiation power allocation sub-problem. In the first sub-problem, closed-form solutions are derived for the BS's power allocation among NOMA users. Meanwhile, in the second sub-problem, we optimize the PA's radiation power utilizing successive convex approximation (SCA). These two sub-problems are solved alternatively using Alternating Optimization (AO) until convergence. It should be noted that decoding order plays a significant role in NOMA-assisted PASS. Hence, two variations of decoding order are considered, namely: i) a high-complexity exhaustive search approach, and, ii) a low-complexity alternative that utilizes pre-determined channel information. Numerical results show that our proposed approach substantially improves the system's sum-rate compared to widely adopted equal power allocation PASS schemes.