Research On Anti-eavesdropping Technology For Satellite Communication System

At present,with the increasing maturity of the 5th Generation Mobile Communication System(5G),the dimension and breadth of communication technology have been extended and expanded.In the future,the communication network will integrate terrestrial 5G communication and satellite communication.And then realize the integration of sky and earth information network.As the main body of the air-space-ground integrated information network,satellite communication forms complementary advantages with the terrestrial network due to the continuity,breadth and scalability of its services,and gradually embodies its advantages.However,wireless channels are naturally open,and communication satellites are exposed to space orbits for a long time.In the whole air-space network,they face various security threats,including complex electromagnetic environment and attacks and eavesdropping from external malicious nodes.How to design anti-eavesdropping methods for satellite communication and realize reliable and effective information transmission has become a hot research topic.Physical-layer Security(PLS)technology makes use of the randomness and time-varying characteristics of wireless channels to introduce differences between legitimate main channel and eavesdropping channel,so that the quality of legitimate main channel is better than that of eavesdropping channel,and the Security and confidentiality of communication system is guaranteed.Significant achievements have been made in physical layer security of land-based mobile communication.However,the Channel similarity between ground terminal and eavesdropper and the Channel State Information(CSI)of ground eavesdropper are inherent defects in satellite communication link.Therefore,the existing research results are not completely applicable to satellite communication system.Aiming at this inherent defect,this thesis studies the anti-eavesdropping technology suitable for satellite communication with the help of air-space cooperation to increase the spatial freedom of communication.The main work and contributions of this thesis are as follows:Aiming at the problem that the eavesdropper’s CSI is difficult to obtain,combined with the characteristics of satellite channel,a single hop anti eavesdropping method based on dual full duplex cooperative interference is proposed in this thesis.This method does not need the CSI between the ground terminal and the eavesdropper,gets rid of the dependence of the existing satellite communication anti eavesdropping technology on the eavesdropper CSI,and has high robustness.Firstly,a single hop anti eavesdropping model based on dual full duplex cooperative interference is established.On this basis,the expressions of signal to interference noise ratio(SINR)are derived respectively between legitimate terminal and eavesdropper in the case of residual self-interference and complete elimination of selfinterference in full duplex receiver,and then the expression of system security rate is given.Then,under the constraints of system total power and user information rate,the optimal power allocation problem is established,and its optimal closed-form solution is obtained.Finally,the correctness of the theoretical derivation is verified by simulation.The simulation results show that the optimal power allocation scheme proposed in this thesis can significantly improve the system security compared with the equal power allocation scheme.Aiming at the similarity between legitimate channel and eavesdropping channel in satellite ground link,an anti-eavesdropping method based on hybrid amplify and forward(AF)relay transmission and full-duplex jamming technology is proposed in this thesis.In this method,the source node acts as both the source and the "jammer" in the eavesdropping channel.Therefore,even if the channels of legitimate users and eavesdroppers are similar,they can effectively resist eavesdroppers,so as to ensure the confidentiality of the whole system.Firstly,a two-hop anti eavesdropping model based on the joint cooperation of space and earth is established.On this basis,the security capacity expressions of uplink and downlink are derived respectively,in the case of residual self-interference and complete elimination of self-interference in full-duplex relay,and then the security capacity expressions of the system are obtained.Then,a relay selection strategy and an optimal power allocation scheme based on system security capacity are proposed for multi-relay scenarios and the optimal closed-form solution is obtained.Finally,the correctness of the theoretical derivation is verified by simulation.The simulation results show that the relay selection strategy proposed in this thesis is better than the existing relay selection strategies.Compared with the equal power allocation scheme,the optimal power allocation scheme proposed in this thesis can significantly improve the system security.