Power Allocation And Performance Analysis Research Of NOMA Networks Based On Relay

With the rapid development of mobile Internet and Internet of things,a large number of devices are connected to the network,and the era of Internet of things is coming.The existing communication technology can not meet the needs of people.Therefore,it is necessary to study the communication technology with higher spectral efficiency.Non-Orthogonal multiple access(NOMA)is considered as an effective spectrum resource utilization technology.NOMA improves the spectrum efficiency and meets the needs of large-scale access by superposing the signals of different users in the power domain.In NOMA technology,how to allocate power reasonably has a great influence on system performance,and is the hot research direction of NOMA technology.In addition,as a kind of wireless communication technology,open channel makes the security of NOMA network greatly threatened.Due to the above reasons,this paper studies the problem of power allocation in NOMA network,and proposes a spectrum sharing scheme with the help of NOMA relay.At the same time,feasible security schemes are proposed respectively for the NOMA system based on full-duplex multi-antenna relay and half-duplex single antenna relay,and the security performance of the system is analyzed.The main work is summarized as follows:(1)A spectrum sharing scheme assisted by NOMA relay is proposed,in which relay and the secondary receiver with good channel condition is used to assist the signal transmission of the primary receiver.The rate sum of secondary receivers is maximized under the condition that the network works normally.The simulation results show the effectiveness of the proposed scheme.(2)A secure transmission scheme based on a full-duplex multi-antenna NOMA relay is proposed,which is divided into two time slots.In the first time slot,the artificial noise transmitted by the full-duplex relay is used to ensure the security of the private signal.In the second time slot,the security of private signal is guaranteed by the improved decoding order of successive interference cancellation and beamforming optimization,which is converted to convex and solved by an iterative algorithm.The simulation results show the effectiveness of the proposed scheme.(3)A secure transmission scheme of NOMA system assisted by half-duplex single antenna relay is proposed,which is divided into two time slots.In the first time slot,the security is guaranteed by allocating smaller power to the private signal.In the second time slot,the base station transmits signal which is not private as interference to disrupt the eavesdropping,and the security can be guaranteed.At the same time,the outage probability of user which is not private and the secrecy outage probability of private user is calculated.The simulation results show the effectiveness of the proposed scheme.