QoS-oriented Power Allocation Scheme for Multi-user NOMA System Assisted by RIS

Reconfigurable Intelligent Surface (RIS) can be regarded as a ‘relay’ with special functions in communication network. It can cooperate with Non-Orthogonal Multiple Access (NOMA) system to construct a coordinated information transmission scheme. Considering the different Quality of Service (QoS) requirements of different user devices in the future Internet of Things (IoT) scenarios, a RIS-assisted multi-user NOMA communication system model is proposed. According to the different QoS requirements of two types of users (information users and energy users), a power allocation method based on iterative optimization is designed. This method minimizes the total transmit power of the system by jointly designing the phase-shift matrix of RIS, the beamforming of base station and the order of successive interference cancellation in NOMA system, so as to reduce comprehensively the energy consumption of base station. Simulation results show that compared with the scenario without RIS, RIS-assisted NOMA system can effectively reduce the energy consumption of base station. In the case with RIS, the energy consumption of the proposed power allocation method is significantly lower than that of random phase selection at RIS and zero-forcing beamforming at base station. © 2023 Science Press. All rights reserved.