Optimization And Performance Analysis Of Secure Transmission In Wireless Networks Via NOMA

As the future mobile communications network has a series of features such as high speed,low latency,large bandwidth,and ultra-high density,the explosive growth of various demands has brought great challenges to the future technology of wireless mobile communication systems.Non-Orthogonal Multiple Access(NOMA)creatively shifts the power domain of transmission from being allocated to a single user to multiple users,thereby greatly increasing the total amount of wireless access and the corresponding Spectrum utilization.NOMA has become an important technology of new generation wireless network.On the other hand,due to the open and broadcast nature of wireless transmission,potential eavesdroppers are likely to threaten the secure transmission of information.The use of the inherent physical properties of the wireless channel,proper precoding processing at the sender side or adding artificial noise can provide a certain security and reduce the risk of information leakage.Therefore,this paper studies the security transmission optimization and performance analysis of communication network based on NOMA,in order to improve the ability of wireless communication system to resist eavesdroppers.Specifically speaking,the work includes:(1)As for the multi-user downlink NOMA wireless communication network,we aim to jointly optimize the precoding vectors at the transmitter to cope the eavesdropping.First,when the eavesdropping channel state information(CSI)is available at base station,the precoding optimization problem is designed to maximize the sum secrecy rate of the secure users in the network.Then,when the eavesdropping CSI is not available,considering the different locations of the secure user,the modified successive interference cancellation order and joint precoding optimization can be adopted to ensure its security.(2)As for the relay assisted cooperative NOMA wireless communication network,a scheme is proposed to adopt full-duplex relay to assist secure users in forwarding information and preventing eavesdropping.The precoding vector at the relay is designed reasonably to eliminate the adverse effect of artificial noise on the legitimate receivers.The statistical information of related channels is analyzed,and the security outage probability expression of legitimate signals is derived.Then,the optimal power allocation coefficient of the artificial noise is determined to minimize the security outage probability of legitimate users.(3)As for the proposed unified secure transmission framework based on rate splitting multiple access(RSMA),we ensure the secure transmission of private information in RSMA,NOMA and SDMA(Space Division Multiple Access)systems.The precoding vector is optimized to reduce the risk of eavesdropping towards the private information in RSMA system.By adjusting some of the parameters and conditions,the proposed RSMA secure framework not only meets the requirements of secure transmission in NOMA and SDMA systems,but also greatly enhances the transmission performance of other broadcast information in the system.Then,the relevance and differences of three kinds of multiple access networks are studied and compared.