Sum Rate Maximization for NOMA-Assisted Uplink Pinching-Antenna Systems

TL;DR

This work analyzes uplink NOMA with a single pinching antenna on a dielectric waveguide to maximize the system sum rate by jointly optimizing the pinching position $x^{\\text{Pin}}$ and user powers $\\{P_m\\}$. In the absence of QoS constraints, all users transmit at their maxima and a 1D PSO finds near-optimal antenna placement, leveraging a telescoping-rate structure. When QoS guarantees are required, an alternating optimization combines a low-complexity power-allocation step with a modified PSO for antenna positioning to satisfy $R_m^{\\min}$. Numerical results show substantial gains over fixed-antenna and TDMA baselines, with PSO-based solutions closely matching exhaustive-search performance under moderate QoS, highlighting the practical benefits of pinching-antenna aided uplink NOMA.

Abstract

In this paper, we investigate an uplink communication scenario in which multiple users communicate with an access point (AP) employing non-orthogonal multiple access (NOMA). A pinching antenna, which can be activated at an arbitrary point along a dielectric waveguide, is deployed at the AP to dynamically reconfigure user channels. The objective is to maximize the system sum rate by jointly optimizing the pinching-antenna's position and the users' transmit powers. Two scenarios are considered: one without quality-of-service (QoS) guarantees, and the other with QoS guarantees. In the former case, users transmit at full power, and the antenna position is determined using the particle swarm optimization (PSO) algorithm. In the latter, an alternating optimization approach is adopted, where a low-complexity solution is derived for power allocation, and a modified PSO algorithm is applied to optimize the antenna position. Numerical results show that the proposed pinching-antenna-assisted system significantly improves the sum rate compared to the conventional fixed-antenna architecture. Furthermore, the NOMA-based approach consistently outperforms its TDMA-based counterpart. Finally, the proposed PSO-based method achieves near-optimal performance, particularly when the QoS constraints are moderate.

Figures (4)

• Figure 1: Illustration of the considered uplink pinching-antenna system.
• Figure 2: One realization of the objective function with randomly generated values of $x_m$, $y_m$ and $d$, when $M=5$. The red circles denote the corresponding $x_m$ values.
• Figure 3: Achievable sum rate versus the maximum transmit power constraint at the users when $R^{\min}=0.5$ bps/Hz.
• Figure 4: Achievable sum rate versus $R^{\min}$ with $P^{\max}=30$ dBm.