Research On Non-cooperative Receiving Technique Of Frequency Hopping Communication

Frequency hopping(FH)communication has been widely used in military and civil communications,due to its low probability of interception and detection,anti-interference and anti-fading performance,and high security.The non-cooperative receiving technique of frequency hopping communication has also become a hot research topic.In this paper,some non-cooperative receiving techniques of FH communication are mainly studied,including methods for FH signals detection,classification,parameters estimation and modulation recognition.The main contents and contributions of this paper are as follows:Aiming at the problem that the non-cooperative party receives signal without relevant parameters of the FH signal,the blind detection of frequency hopping signals and blind sorting of frequency hopping network are studied.Aiming at the problem that the traditional time-domain autocorrelation algorithm hardly detects the FH signals when there exists the fixed-frequency interference,the power spectrum elimination and the traditional time-domain autocorrelation joint algorithm is proposed,the power spectrum elimination method is used to suppress the fixed-frequency interference,then use the autocorrelation algorithm to detect it,and its performance is verified by simulation.Based on the idea of blind source separation algorithm,the independent component method is used to sort the FH radio stations,which can achieve the blind source separation of hybrid FH radio stations when the characteristic parameters of the network can not be predicted,and the sorting performance of the independent component method is verified by simulation.Aiming at the problem that the non-cooperative party must solve the communication parties' FH parameters before it can impose interference on the communication parties and obtain information,blind estimation of FH signal parameters and modulation recognition is studied.Firstly,the common time-frequency analysis algorithms are studied,and the different time-frequency analysis methods are compared by the indexes of computation,time-frequency focusing and cross term.Secondly,the hop speed,transition time and frequency hopping pattern are estimated by the STFTSP-LS-Kay algorithm,aiming at the deficiency that the performance of frequency estimation is decreased with the decrease of SNR when using it to estimate the FH signal parameters,the STFTSP-LS-Zoom-FFT algorithm is proposed,using the Zoom-FFT algorithm to estimate the frequency improved the performance of frequency hopping pattern estimation,the simulation results show that the STFTSP-LS-Zoom-FFT algorithm has better performance than the STFTSP-LS-Kay algorithm in the low SNR.Finally,according to the demand of the non-cooperative party to obtain the information of the communication parties,in the precondition of estimating the frequency hopping signal parameters,using higher-order spectral technique to study the recognition of three kinds of modulation methods commonly used in frequency hopping communication: BPSK,QPSK and BFSK.Through above reseach on non-cooperative receiving technique of frequency hopping communication,a typical non-cooperative receiving system is designed,which completes the detection,sorting,parameter estimation,de-hopping,modulation recognition and demodulation and a series of work,and realizes the whole process of non-cooperative reception,the non-cooperative reception performance of the system is tested by simulation.It is proved that the system can complete the non-cooperative reception of the FH signal and recover the communication parties' information.