Research On The Physical Layer Security Transmission Mechanism Of Leo Satellite Based On Noma

In recent years,the rapid development of wireless communication technology has made the mobile communication enter the era of 5G.Great progress has been achieved in terrestrial communication represented by mobile communication,but it cannot meet the requirements of future traffic explosion and globally seamless coverage due to the limit of communication capacity and covera ge.Because of the inherent huge coverage and rich spectrum resources,the satellite communication system can supplement and expand the dense terrestrial network effectively and provide flexible key business services.Owing to the advantages of closer to e arth and small-time delay,the low earth orbit satellite system is attracting people's great interest.The integration of low earth orbit satellite and terrestrial network can become the cornerstone for achieving the predictable global heterogeneous networ k.It needs to be pointed out that the information is easily intercepted by illegal users in such a large-scale open wireless network.Along with the popularization of various wireless services provided by low earth orbit satellite network,much attention has been paid to its safety problems.Due to the heterogeneity and dynamic changes of the satellite network structure,other security technologies need to be considered as effective supplementary solutions based on the realization of the upper encryption o f communication protocol.To serve the needs of large-scale connection of the space-air-ground integrated network and communication security,it is pressing to solve how to achieve the physical security technology.This dissertation is based on the premise that low earth orbit satellites provide services for terrestrial users,it adopts non-orthogonal multiple access and physical layer security technologies to achieve the efficiency and security of satellite networks.The satellite link uses a non-orthogonal multiple access scheme that simultaneously provides services for multiple users to increase the transmission rate.For scenarios where the low earth orbit satellite-to-territory direct transmission link is poor,this dissertation proposes a safe and reliable transmission strategy based on high-altitude platform relay cooperative forwarding.In this scenario,the optimal relay is selected for cooperative forwarding through a reasonable relay selection scheme.At the same time,when the low earth orbit satellite communication link is good,this dissertation introduces territory base stations as the green interference source in the network,and focuses on the safety transmission performance of the satellite-territory hybrid network.This dissertation proposes that satellites and base stations cooperate to transmit security beams,so that the base station can cause interference to eavesdroppers,but minimize the interference to legitimate users.The safe beamforming vector is obtained by using the second-order cone programming iterative algorithm.Furthermore,it is proposed to use the base station as a satellite relay for cooperative forwarding and interference with eavesdroppers.The base station eliminates interference to satellite users by performing zero-forcing precoding on signals transmitted to territory users.The power distribution of the system is optimized by adopting the beetle antennae search algorithm,and a reasonable power distribution plan of the system is given.Simulation results show,the designed safe transmission scheme can guarantee the safety of the system and significantly improve the communication performance of the system.In summary,the efficient and secure transmission scheme designed in this dissertation for low earth orbit satellite communication is feasible.It is of great significance to the development and application of the future space-air-ground integrated network.