Research And Implementation Of Key Technologies Of Physical Layer Security Based On Satellite-to-ground Channel Characteristics

Nowadays,satellite communication network is developing rapidly in China and is widely employed in various industries.Satellite-to-ground communication security is becoming more important.Traditional cryptography-based computing security faces challenges due to the improvement of computing power of computers.Physical layer security guarantees secure transmission by using the characteristics of wireless channels,which has attracted much attention.This thesis mainly studies and implements key technology in physical layer for secure transmission such as identity authentication and secret key generation based on the characteristics of satellite-to-ground channel.Firstly,this thesis analyzes the characteristics of satellite-to-ground channel.Compared with the ground transmission link,satellite-to-ground transmission link has the characteristics of high delay and heavy attenuation.Due to the direct path of the satellite-to-ground channel,the fading of main path obeys Rice distribution.With reference to the channel parameters of classic 5-path Low Earth Orbit(LEO)satellite channel,this paper establishes a satellite-to-ground channel model.This thesis studies the identity authentication technology in physical layer,which is based on the characteristics of channel and watermark information.Due to the reciprocity and uniqueness of the channel,this thesis establishes a binary hypothesis testing model.After obtaining the channel characterstics,the model calculates the multidimensional test statistic for identity judgment.In this thesis,theoretical analysis and derivation of the detection threshold under the condition of constant false alarm probability and minimized cost function are performed.The simulation results show that the authentication rate is more than 90% when the signal-to-noise ratio is 10 dB.Then,this thesis studies the principle of digital spread-spectrum watermarking identity authentication technology based on Orthogonal Frequency Division Multiplexing(OFDM)technology and simulates performance indicators such as authentication rate,watermark error rate and data error rate under typical channel conditions.The results show that the higher watermark spreading code rate and the larger watermark embedding power coefficient lead to the lower watermark bit error rate and the better authentication performance.In addition,this thesis studies secret key generation technology in physical layer,which is also based on characteristics of channel.This thesis studies the classic algorithms of modules such as channel detection,signal preprocessing,channel feature quantization,key agreement and privacy enhancement in the system of secret key generation.Regarding the signal denoising preprocessing,this thesis compares the key disagreement rate generated by the algorithms based on extracting effective channel paths and improved wavelet transform(WT)respectively.Simulation results demonstrate that the initial key disagreement rate reduced by more than 5%.Then,this thesis simulates the performance of classical quantization and negotiation quantization,and compares the performance of key information negotiation algorithms based on interactive information and error correction coding.On the basis of the theoretical analysis and verification,this thesis builds a test platform based on Laboratory Virtual Instrument Engineering Workbench(LabVIEW)and Universal Software Radio Peripheral(USRP).The test performance curve of identity authentication and key transmission is less than 1dB from the theoretical simulation curve,verifying that the satellite-to-ground secure communication test platform has the functions of identification and encrypted communication.