Throughput maximization scheme of the IRS-aided wireless powered NOMA systems

The computation complexity of the existing resource allocation schemes to maximize sum throughput is very high for intelligent reflecting surface (IRS)-assisted wireless powered non-orthogonal multiple access (NOMA) system. Therefore, a low complexity resource allocation method to maximize sum throughput is considered by joint optimizing phase shifts and time allocation. Firstly, to reduce the variables that need to be optimized, we derive the problem with only phase shifts as variables, and further deduce optimization problem of phase shifts only for downlink wireless energy transmission (WET) process. Then, the problem of phase shifts for WET process is solved directly by transforming multi-variable optimization problem into that with single variable, and the phase shifts for the uplink wireless information transmission process are got as well with given phase shifts for WET process. Finally, with given phase shifts, the optimal time allocation is obtained by using the function extremum method. Theoretical analysis demonstrates that the proposed scheme has low computational complexity, and the simulation results show that sum throughput of the proposed scheme is no less than that of the existing schemes in the same scenario.