Rotatable Antenna Meets Multiple Access: NOMA or OMA?

2026-06-01

AI Summary

This study addresses the unclear energy efficiency comparison between non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA) in reconfigurable antenna-assisted multiuser systems. It presents the first systematic evaluation of their performance in minimizing transmit power under user rate requirements and antenna rotation constraints. The authors formulate a non-convex optimization problem incorporating directional antenna gain and jointly optimize antenna orientation and power allocation, solving it via particle swarm optimization (PSO). Theoretical analysis and simulations demonstrate that reconfigurable antennas significantly reduce transmit power. Furthermore, NOMA outperforms OMA under asymmetric user distributions, yet may underperform time-division multiple access (TDMA)—a representative OMA scheme—when users are symmetrically located, thereby revealing NOMA’s performance boundaries and strong dependence on deployment geometry.

Abstract

Rotatable antenna (RA) technology has emerged as a promising solution to enhance spectrum efficiency by exploiting additional spatial degrees of freedom (DoFs) in multiple access networks. However, the relative performance superiority among different multiple access schemes remains largely unclear due to the unique capability of RA in reconfiguring the directional gain pattern. In this letter, we conduct a theoretical comparison between non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA) schemes in RA-assisted communication systems in terms of transmit power minimization, subject to constraints on antenna rotational range and users' target rates. To address the associated non-convex optimization problem, a particle swarm optimization (PSO) algorithm is employed to optimize the rotational angle. Simulation results demonstrate that RA-assisted schemes significantly reduce transmit power compared to fixed-antenna benchmarks. Furthermore, RA-assisted NOMA may perform worse than time-division multiple access (TDMA) for symmetric user deployments, while it exhibits superior robustness and energy efficiency in asymmetric scenarios.

Problem

• Rotatable Antenna
• Multiple Access
• NOMA
• OMA
• Transmit Power Minimization

Innovation

• Rotatable Antenna
• NOMA
• OMA
• Power Minimization
• Particle Swarm Optimization