Performance Analysis Of Cooperative NOMA Communication Systems Based On SWIPT

With the rapid development of mobile Internet and the continuous emergence of new services,mobile data traffic has increased explosively,and the problem of spectrum shortage needs to be solved urgently.Different from the traditional orthogonal multiple access(OMA)technology that the same orthogonal resource block(such as time and frequency)only serves one user,non-orthogonal multiple access(NOMA)technology in power domain uses different power levels to distinguish users,allows multiple users to transmit information at the same time and frequency,and thus effectively improves the utilization of system spectrum resources and supports large-scale connections of cellular networks.Therefore,NOMA is considered to be one of the most promising wireless access technologies in the fifth generation(5G)communication system.In wireless networks,cooperative communication technology has attracted extensive attention because it can provide spatial diversity to reduce fading.Therefore,cooperative communication technology and NOMA technology can be combined to further improve the reliability of information received by cell-edge users.However,in cooperative NOMA systems,using wireless devices as relays will consume their own energy and shorten the battery life.Therefore,how to prolong the life of energy limited wireless devices is also a problem that can not be ignored.Simultaneous wireless information and power transfer(SWIPT)technology aims to realize the parallel transmission of information and energy and provide controllable and stable energy for wireless applications.In this thesis,SWIPT technology is applied to cooperative NOMA systems,and the outage/security outage performance of cooperative NOMA communication systems based on SWIPT is studied.The main works and contributions are as follows:(1)Combining the coordinated multipoint(Co MP)transmission technology with cooperative NOMA,the outage performance of a Co MP-CNOMA network based on SWIPT is studied.The network includes two base stations and three users.Each base station serves its own SWIPT cellcentre user and a common cell-edge user.There is no direct link between the base station and the celledge user.Each base station uses NOMA technology to superposition signals of the cell-centre users and the cell-edge user on the same channel to the cell-centre users,which decode the information of the two users using successive interference cancellation(SIC)technology.The collected energy is used to forward the information of cell-edge user.This thesis deduces the closed expressions of the outage probabilities of the cell-centre users,and the approximate closed expressions of the outage probability of the cell-edge user using the maximum ratio combining(MRC)technology and the selection combining(SC)technology respectively,and analyzes the influence of various factors on the outage performances of the users.The correctness of the derivation and analysis is verified by Monte Carlo simulation.The results show that Co MP-CNOMA network can provide significant performance gain for the cell-edge user compared with traditional cooperative NOMA.(2)For secure communication in the presence of eavesdroppers in wireless communication,the secrecy outage performance of a cooperative NOMA network based on SWIPT is studied.The network includes a base station,multiple cell-centre users,a cell-edge user and an eavesdropper.It is assumed that there is no direct link between the base station and the cell-edge user.This thesis proposes a max-min user selection strategy,where the cell-centre user whose minimum normalized secrecy rate is the highest among all the cell-centre users is selected to assist the cell-edge user communication.The selected cell-centre user and the cell-edge user form a NOMA pair.The selected cell-centre user uses SWIPT for wireless power supply,and uses the collected energy to forward the information of the cell-edge user.In this thesis,the approximate closed expression of system secrecy outage probability under the proposed strategy is derived,and the influence of various factors on system secrecy outage performance is analyzed.The correctness of the theoretical results and analysis is verified by Monte Carlo simulation.The simulation results show that the proposed user selection strategy has better system security than other strategies in the existing literature.