Geographical NOMA-Beamforming in Multi-Beam Satellite-Based Internet of Things

In this paper, a geographical non-orthogonal multiple access based multiuser beamforming (NOMA-BF) scheme is investigated to improve spectral efficiency in multi-beam satellite-based Internet of Things (IoT), where the primary user per beam needs to be timely served with a small targeted data rate while other users per beam are opportunistically served by using the NOMA concept. We first design a novel user scheduling to enhance spectrum efficiency. Then, a multi-layer beamforming (BF) is developed to mitigate inter-beam interference, augment the difference of the effective channel gains of the users, and perform inter-beam power allocation in a separate manner. Additionally, a dynamic intra-beam power allocation policy is conceived to further improve spectrum efficiency, while meeting predefined target data rates of the primary NOMA users. Numerical results show the capability of our proposal.