Resource Allocation Algorithms Of Cooperative Noma System Based On Energy Harvesting

With the rapid development of mobile communication technology,users have higher and higher requirements for wireless transmission rate and service quality.Non-orthogonal multiple access technology allows multiple users to share time-frequency resources,effectively improving the system's spectrum resource utilization.In addition,cooperative relay technology can effectively improve the communication quality of cell edge users and expand base station signal coverage.Wireless energy harvesting technology collects energy from radio frequency signals to power energyconstrained mobile devices.Therefore,combining NOMA technology with cooperative relay technology and energy harvesting technology is a current research hotspot.This thesis studies the cooperative CR-NOMA network based on SWIPT energy harvesting,derives the analytical expression of the user interruption probability when the OPS strategy is adopted,and proposes a resource optimization allocation algorithm for energy efficiency issues.The main research contents and innovations of this thesis are as follows:(1)For the cooperative CR-NOMA system based on SWIPT,the analytic expression of the outage probability of cell edge users when OPS strategy is adopted is derived.For the convenience of analysis,this thesis assumes that the interference threshold at the receiving end of the primary cognitive radio user and the interference threshold at the transmitting end of the secondary user are assumed.The maximum transmit power is proportional to the ratio of noise power.Under the condition of high signal-to-noise ratio,the approximate expression of Bessel function and gamma function are used to derive the approximate expression of cell edge user outage probability.The simulation results show that in the cooperative cognitive relay network based on SWIPT,the NOMA scheme can effectively reduce the outage probability of the system,and verifies the accuracy of the outage probability expression derived in this thesis.(2)For the cooperative CR-NOMA system based on SWIPT,a system energy efficiency optimization algorithm adopting OPS strategy is proposed,and the system capacity expressions adopting TS strategy and OPS strategy are respectively derived.Under the constraints of limited collection energy and service quality,An optimization problem with the goal of maximizing energy efficiency is constructed.The objective function is a multi-objective optimization NP-Hard problem.In this thesis,the original problem is transformed into three sub-problems about relay power,NOMA coefficient and division coefficient,which are carried out by the golden section algorithm,the monotonicity determination method of the function,and the genetic algorithm.Solve,and adopt a multi-objective iterative algorithm for joint optimization of the optimal solution of the sub-problem.The simulation results show that,compared with the PS and TS strategies,the OPS strategy can significantly improve the energy transmission efficiency of the system.(3)For the problem of secure transmission in the cooperative CR-NOMA system based on energy self-collection,a secure energy efficiency optimization algorithm based on OPS is proposed.The relay can perform energy self-collection on the forwarded signal to reduce energy consumption.Under the constraints of limited collection energy and user service quality,an optimization problem with the goal of maximizing safety and energy efficiency is constructed.In this thesis,the original NP-Hard problem is transformed into three sub-problems about signal covariance matrix,NOMA coefficient,and partition coefficient.The semi-definite relaxation algorithm is used to solve the nonconvex sub-problem about the emission covariance matrix,and the monotonicity of the function is used to determine NOMA coefficient,using genetic algorithm to solve the partition coefficient.The simulation results show that the OPS strategy and the energy self-collection scheme adopted by the relay can effectively improve the safety and energy efficiency of the system.