Optimization of User Pairing, Beamforming and Phase-shifting for Intelligent Reflecting Surface Assisted Non-Orthogonal Multiple Access Systems
The joint optimization of user pairing, beamforming and phase shifting in a Non-Orthogonal Multiple Access(NOMA) network assisted by Intelligent Reflecting Surface(IRS) is studied in this paper. In the system, each pair is assigned with one beam and the intra-group successive interference cancellation in the signal detection is adopted. A user pairing strategy independent of transmit beamforming and IRS phase shift is proposed, so the user pairing is separated from the joint optimization and the difficulty and complexity in the solving of the optimization is significantly reduced. Then, the transmit beamforming, power allocation and IRS phase shift are jointly optimized to minimize the total transmission power of the base station. The original optimization problem is non-convex. By using the methods such as slack variables, successive convex approximation, semidefinite relaxation and alternative optimization, the original problem is transformed into a convex problem and solved. Simulation results show that the performance of the proposed scheme is better than that of the scheme that one user is assigned with one beam when the number of the transmit antennas is less than that of the users, and is very close to the scheme that one user is assigned with one beam when the number of antennas is more than that of the users, while the computational complexity of the proposed scheme is lower.Compared with the schemes that employ different user pairing strategy, random IRS phase shift, maximum ratio transmission beamforming, or that without IRS, the proposed scheme is always superior in performance.
万方数据
维普
