Rotatable Antenna-Enabled NOMA Downlink Communications

Abstract

This letter investigates rotatable antenna (RA)-enabled downlink non-orthogonal multiple access (NOMA) communications, in which the antenna boresights can be independently adjusted to introduce additional spatial degrees of freedom. Under the successive interference cancellation constraint, we formulate a sum rate maximization problem that jointly optimizes the boresights of RAs, BS beamforming, and power allocation coefficients. To tackle this problem, an alternating optimization framework is developed, in which the BS beamforming and the power allocation coefficient optimization subproblems are handled via successive convex approximation, while the boresights of RAs are optimized via particle swarm optimization. Numerical results show that the proposed RA-enabled NOMA scheme achieves higher sum achievable rates than conventional benchmarks, demonstrating the effectiveness of RA in improving performance in NOMA systems.