Research On Key Technologies Of Physical Layer Security Based On Satellite Channel Characteristics

As an important part of modern communication technology,satellite communication has gradually integrated into people's daily life in recent years,but the openness,mobility,and complexity of its propagation environment make it vulnerable to be attacked by illegal parties.Traditional encryption schemes are mainly concentrated on the upper layers of computer network protocol stacks.However,with the increase of computing speed requirements for future communications,the current security mechanism is limited to a certain extent by the contradiction between computational complexity and communication rate.Based on this,this thesis studies the lightweight physical layer security(PLS)encryption system for the complex and changing environment of satellite communication.The main work includes:This thesis first analyzes the basic principle and implementation feasibility of the secret key generation mechanism based on wireless channel characteristics and introduces three indicators to measure the performance of the system: key disagreement rate,key generation rate,and key randomness.Then,from the perspective of information theory,the secret capacity theoretical formula of the traditional time division duplexing(TDD)system is analyzed,and the existing conclusions are extended to the frequency division duplexing(FDD)system to derive the theoretical formula of secret capacity at this time.The derivation proves that the strong line of sight(LoS)in the wireless propagation environment will decrease the channel changing speed,thereby reducing the secret capacity to a certain extent.Compared with the TDD system,the training sequence in the FDD system has experienced two independent wireless channels in two frequency bands during the forwarding process,so it contains a larger amount of information.Numerical simulation has further verified that the system can obtain a larger secret capacity in FDD and Rayleigh channels.This thesis starts with the existing secret key generation mechanism in a typical channel environment and selects representative implementation solutions in the four links of channel detection,quantization,reconciliation,and privacy amplification in order to analyze and compare.Aiming at the non-ideal channel environment,a denoising scheme based on a modified wavelet transform and a noise suppression scheme based on the effective path are proposed to combat the defect of high initial key disagreement rate in the system.Then,the performance of each implementation is evaluated from the perspectives of complexity,the number of interactions,and effectiveness,and the characteristics and applicable scenarios of different implementations are analyzed.The analysis shows that the key sequence obtained by equiprobable quantization has strong randomness,and the entire process does not require signaling transmission,which is more practical;error correction code reconciliation uses the error correction capability of the codeword itself for error detection,which has fewer numbers of interactions,and easy engineering implementation.This thesis designs an overall scheme of secret key generation system based on the characteristics of satellite channels.The thesis first modeled the satellite channel.Studies show that the satellite channel changes slowly compared to the conventional terrestrial wireless channel due to the existence of LoS.Combining the previous research conclusions,this thesis chooses the algorithm of channel detection based on FDD mode,equiprobable equalization,and error correction code reconciliation,and combines the proposed new pre-processing algorithm to form an overall secret key generation scheme.Finally,the overall scheme is evaluated through numerical simulation analysis,and the performance of the physical layer security encryption mechanism is verified.Finally,the thesis summarizes the research results and clarifies the direction of the follow-up research.