PSO based power allocation in multiuser hybrid beamforming mmWave NOMA

Non-Orthogonal Multiple Access (NOMA) is one of the blooming technologies in 5G and beyond wireless networks to support a massive number of users with a huge data rate. In this work, we investigate a multiuser hybrid beamforming millimeter wave (mmWave) downlink NOMA system. Wideband mmWave line of sight (LOS) channel and non-line of sight (NLOS) channels are considered in this study. The first step of the multiuser power allocation problem is user clustering, where users are clustered based on their channel correlation and difference. Subsequently, low complex analog beamforming design and zero forcing digital beamforming design are employed. Finally, we formulate users’ power allocation problem with the objectives of spectral efficiency maximization / energy efficiency maximization based on the constraints of users’ quality of service requirements (QoS) and total available power. Existing research solves the non-convex problem by assuming equal power to all the clusters. Then the problem is decomposed into sub-problems and independently solved for each cluster, which increases the complexity. But, we propose a particle swarm optimization (PSO) based single step low complex algorithm, which achieves a faster convergence rate and grants consistent results. Moreover, the simulation results show that our proposed approach outperforms existing sub-optimal method and the conventional zero forcing time division multiple access scheme (ZF-TDMA).