| The battlefield electromagnetic environment is becoming more complex and facing more challenges as the broad application of military frequency equipment,civilian electric facilities,and active malicious interferences are overwhelming.Therefore,it is necessary to research a communication method to resist substantial interference and adapt to highly harsh electromagnetic conditions.Dual Sequence Frequency Hopping(DSFH)provides a "channel represents message" communication mode,which effectively processes low signalto-noise ratio(SNR)communication signals based on prior knowledge and has a strong anti-interference ability.As a newly invented technology in the nonlinear processing field,Stochastic Resonance(SR)uses the noise energy to improve the SNR of the detected signal,which is suitable for solving communication signal detection under low SNR conditions.SR presents an advantage to suppress the noise alone when the signal frequency is close to the noise.In this paper,the DSFH communication system and SR theory are combined to build a communication signal receiving system.The research is about the noise model construction,SR system construction and performance measurement,DSFH communication system construction and performance measurement based on SR,system dynamic performance,and other related issues aiming to the method feasibility and the system availability,The main contents and innovations are as follows:(1)The noise model matching with battlefield electromagnetic noise environment is constructed.Noise model selection,noise generation,and parameter estimation are studied for the battlefield wireless communication noise environment.Based on the situation that the impulsive noise occupying the main component in battlefield electromagnetic environment,alphα-stable distribution is selected as noise model.Three methods are designed and investigated: Alphα-stable distribution random number generation method,fractional Low Order Moments parameter estimation method,and parameter estimation accuracy verification method.The electromagnetic environment data are collected in a specific working scene.The parameter estimation is carried out based on the actual collected data,and the value property and ranges are obtained.The obtained results realize a quantitative description of the distribution property of battlefield electromagnetic noise,which is the basis for the subsequent performance research and parameter optimization on SR and DSFH communication systems.It is essential to improve the pertinence of research conclusions in this paper.(2)The construction,structure optimization,and performance measurement of the SR system are investigated.Aiming at the SR part of the DSFH communication system,the SR problem of alphα-stable noise and low-frequency periodic signal in the classical bistable system is studied.The method of theoretical analysis and numerical simulation is adopted.The Langevin equation and Fokker-Planck equation of the SR system are constructed.The study introduces the idea of sampling decisions in digital signal processing.It proposes a "fixed time finite difference method" based on decision time,which handles solving the timevarying fractional Fokker-Planck equation.The difference of output signal probability density with or without periodic signal is proved.Using the average SNR improvement as the measurement index,the parameter optimization and performance analysis of the bistable system under different noise conditions are carried out.The influence of noise impulsivity and skewness on SR performance is obtained in a qualitative approach.In this paper,the symmetric and asymmetric tristable systems are introduced into the SR study.The performance comparison results of different nonlinear structures in noise change sensitivity,SNR improvement,controllability,and input signal adaptability are obtained.The results show that the tristable system is more sensitive to noise change,and the bistable system has better controllability and signal adaptability.Under the condition of impulse noise,the SR performance of different nonlinear systems is evaluated for the first time.(3)The structure design and realization,structure optimization,and performance measurement of DSFH communication signal receiving system base on SR are investigated.Combining DSFH with SR theory,for the low frequency and small-signal limitation of SR,the idea of scale change is introduced to establish an SR detection system suitable for the frequency range of DSFH intermediate frequency(IF)signal and the structural parameters of the system are optimized with SNR as measurement index.Based on the probability density difference with or without the IF signal,the detection probability and false alarm probability are calculated.The study also obtains Receiver Operator Characteristic(ROC).The signal receiving methods based on generalized energy polynomial and sign function are proposed,and a multi-point decision mechanism is introduced.The polynomial parameters are optimized based on the maximum offset coefficient.The difference in probability density distribution is further amplified.The system Bit-Error-Rate(BER)is reduced below the available level.By analyzing the relationship between noise conditions,decision points,the BER,the applicable SNR,and the achievable BER level are obtained.Under the condition of impulse noise,the application conditions and performance of the DSFH communication system are examined.Based on the software radio platform,the implementation of DSFH communication system is verified.(4)The dynamic characteristics and communication rate of the DSFH communication system is studied.At present,SR is mainly used to solve signal processing under off-line conditions,which has no requirement for real-time performance.Its dynamic response performance is directly related to the communication rate of the system.Mean First Passage Time(MFPT)is the critical index of SR dynamic response performance,and the solving method of MFPT is studied.Under the condition that the noise can not be expressed analytically,the numerical distribution of MFPT is obtained by the improved path integral method.The study analyzes the relationship between DSFH hopping speed and communication rate and between communication signal period and MFPT.The study also examines the influence of input SNR,DSFH IF signal frequency on MFPT,and decision points on communication rate.The study obtains the IF signal frequency range and communication rate suitable for the system and the system communication rate under impulse noise is first described quantitatively. |
