Investigation Of Atmospheric Optical Channel Information Transmission And Shared Key Generation

With the popularity of the5 th generation mobile networks(5G)communication,the technology of high-speed and large-capacity transmission has become the research hotspot for current optical communication communities.Wireless optical communication(WOC)has addressed highly attention due to its advantages such as high-speed,high-bandwidth,electromagnetic-interference-free(EMI),and no spectrum application.However,there is an atmosphere on the surface of the earth,which causes attenuation and scintillation effects for light waves.Therefore,it is of great scientific significance and engineering value to investigate the mechanism of information transmission in the atmospheric optical channel.Moreover,today's society is an "Internet" era,and information security is the research theme.Due to the characteristics of reciprocity and time-varying randomness,the atmospheric optical channel satisfies the conditions of the key source.It is also of great theoretical significance and application value to exploit the shared key generation technology of the atmospheric optical channel.In this paper,a series of critical technology research work on the mechanism of information transmission and the technology of shared key generation in the atmospheric optical channel are carried out.Firstly,the mechanism performances between the characteristic parameters of the atmospheric optical channel are investigated,includingatmospheric attenuation,transmittance coefficient,scintillation factor in atmospheric turbulence,atmospheric coherence length,and probability density function(PDF)of channel fading.According to the model,the key parametersofthe atmospheric optical channel are measured in the field experiments,and the experimental analyses are also performed.Then,the influence mechanisms of the characteristic parameters of the atmospheric optical channel on the multi-level-pulse-amplitude modulation(M-PAM)and multiple-phase-shift-keying modulation(M-PSK)information transmission are studied systematically.Based on this,the M-PAM and M-PSK(M=4)information communication systems are developed and constructed,and the relevant experiments are also carried out.Simultaneously,the difficulties of the atmospheric optical channel reciprocity evaluation which based on the optical fiber receiver system are solved.The reciprocity measuring system is also successfully developed.Based on the characteristics of this system,the shared key generation model in atmospheric optical is proposed,and the problems of the quantization algorithm and key negotiation are solved.The detailed research content as follows:(1)The characteristic parameter model of the atmospheric optical channel is exploited theoretically.Firstly,mathematical and physical formulas are used to describe the effects of the atmospheric attenuation and scintillation,the evaluation model of the degree of atmospheric turbulence,and the PDFmodel of the atmospheric optical channel.Moreover,experiments are performed at the Ali Observatory in Tibet and Changchun University of Science and Technology(CUST)for the field measurement of the characteristic parameters about the atmospheric optical channel,which verifies the related theoretical models.Finally,the application and the physical significance of the characteristic parameters of the atmospheric optical channel are also discussed.(2)The effects of atmospheric optical channel on M-PAM information transmission and signal equalization techniques are studied theoretically and experimentally.Firstly,combining the engineering parameters of the avalanche photodiode(APD)detector,an M-PAM information transmission model based on the Gamma-Gamma atmospheric optical channel is given.Furthermore,according to the theoretical model,a numerical simulation analysis is performed.The simulation results show that when transmitting M-PAM information in the atmospheric optical channel,we can choose to optimize engineering parameters to improve the quality of information transmission according to the atmospheric optical channel conditions,such as increasing the APD gain,reducing the system temperature,choosing a suitable light source,and using a optimal modulation order,et.al.Simultaneously,in view of the distortion of M-PAM optical signals in the atmospheric optical channel,an FIR-LMS adaptive equalizer scheme is creatively proposed,and an M-PAM(M = 4)information transmission system is developed for the atmospheric optical channel.Finally,in order to verify the feasibility and effectiveness of the FIR-LMS adaptive equalizer,a related experiment is carried out in the atmospheric simulation turbulence pool.(3)The influence mechanism of the atmospheric optical channel for M-PSK information transmission and signal equalization technology are investigated theoretically and experimentally.Firstly,based on the optical fiber receiving system,a Johnson S_B function is proposed for describing the time-domain distribution of the optical signal received by the fiber,which is verified by the Monte Carlo numerical simulation and field experiment.Then,combining the characteristics of the balanced detector,an M-PSK information transmission model is established based on the Johnson S_B channel fading PDF,and related numerical simulation experiments are also performed.Finally,combining the theoretical model and numerical simulation results,we built an M-PSK(M = 4)information transmission system.In order to solve the key problem of M-PSK optical signal distortion caused by the atmospheric optical channel,a cascaded LMS-LMS adaptive equalization scheme is proposed.We design an experiment about M-PSK information transmission and signal equalization in an atmospheric simulated turbulence pool,which verifies the feasibility and effectiveness of the LMS-LMS adaptive equalizer.(4)The reciprocity mechanism of the atmospheric optical channel is exploited theoretically and experimentally,and the time-varying random characteristics of the atmospheric optical channel are also studied experimentally.By the analysis of the point-receiving light field,the proof of the reciprocity of the atmospheric optical channel is introduced theoretically.Then,in the case of the optical fiber receiving system,the reciprocity of the atmospheric optical channel is proved theoretically.A measured and evaluated model of reciprocity is also proposed.Moreover,the measurement principle diagram of reciprocity is given.According to the principle of reciprocity measurement,an experiment is implemented,and the reciprocity is measured which keeps above 0.83.It is observed that there is a time delay in the measurement system.By offline eliminating the time delay,the system reciprocity is increased by 10%.Subsequently,based on the Johnson S_B PDF,a time-domain light intensity signal generation model is given by employing the stochastic differential equations(SDEs)method,and the influence of the reciprocity measurement system delay on reciprocity is investigated.Finally,according to the time-domain characteristics of the atmospheric optical channel,an adaptive sampling method is used to generate a truly random number from the laser spot,which is verified by using the NIST test method.The results show that the generated sequences meet the characteristics of the truly random number,which proves that the atmospheric optical channel is time-varying random in the time-space domain.(5)The mechanism of the shared key generation of the atmospheric optical channel is investigated theoretically and experimentally.Based on the reciprocity and time-varying random characteristics of the atmospheric optical channel,a shared key generation model for the atmospheric optical channel is established,and a time-domain optical signal generation model is given,which is utilized at Alice and Bob.Then,based on the atmospheric optical channel,the ASBG quantization algorithm model of shared key generation is studied,and related numerical simulation is also performed.In order to improve the shared key generation rate performance of the ASBG algorithm,an MF-AMSBG quantization algorithm is proposed.Subsequently,for further reducing the shared keys inconsistency rate,a key agreement model based on parallel concatenated Low-density-parity-check code(LDPC)is also proposed,and related numerical simulation is performed.Finally,an experimental system for the shared key generation of the atmospheric optical channel is designed.The MF-AMSBG algorithm and the key agreement model are employed to generate shared key sequences,which verifies the feasibility of this model.The results obtained in this dissertation are very beneficial and valuable for the design ofatmospheric optical channel information transmission system and atmospheric optical channel shared key generation system.