Throughput maximization for wireless powered non-orthogonal multiple access networks with multiple antennas

The non-orthogonal multiple access (NOMA) technique can provide higher spectral efficiency and massive connectivities to wireless networks. The wireless power transfer (WPT) technique is a controllable and promising way to solve the energy scarcity problem of wireless devices. In this paper, we introduce the NOMA and WPT techniques into a multi-user wireless network, where multiple users need to transmit their information to an information receiver within a very limited spectrum and they suffer from the energy scarcity problem. We consider a harvest-then-transmit protocol by dividing each transmission block into two time-slots. In the first time-slot, a power station sends dedicated energy to the users via wireless energy beamforming. In the second time-slot, using their harvested energy in the previous time-slot, the users transmit their information to the information receiver in the NOMA manner. In this network, the throughput can be optimized by jointly optimizing the energy beamforming at the power station, the transmit powers of the users, as well as the time allocation between the two time-slots. We propose an algorithm to find the optimal solution of the throughput maximizing joint energy beamforming and resource allocation problem. Simulation results show that the proposed algorithm achieves higher throughput than the benchmark scheme.