Parameter Estimation And Jamming Technology Of Underwater Acoustic Non-cooperative Direct Sequence Spread Spectrum Signal

Direct Sequence Spread Spectrum(DSSS)communication is widely used for underwater civil and military communication sonar due to its strong anti-interference ability,good concealment,strong multi-path resistance and the capability of multi-site reuse.The DSSS signal has a low power spectral density,which is usually submerged in strong noise.Therefore,the parameter estimation of such signals is difficult especially in doubly selective and noisy UWA channel.Traditional interference methods include full-band jamming suppression,partial-band jamming and single frequency jamming,etc,which are with less demand for parameter estimation.however,there are some disadvantages such as power waste,insufficient interference effect,and easy exposure to themselves.It is clear that the parameter estimation of the DSSS signal becomes the key to implement the high-efficiency communication jamming,which makes the related research to be a hotspot nowadays.A blind estimation method for non-cooperative underwater acoustic DSSS communication signals is proposed.The carrier frequency of the DSSS signal is estimated by squared multiplication.In order to estimate the chip length of DSSS signal,time-delay autocorrelation method is used to estimate it.The two times processing method of power spectrum is used to estimate the PN code period of DSSS signal.For the multipath effect of the underwater acoustic channel,an improved method for the estimation of the two times processing method of power spectrum is proposed,which improves the performance in the complex underwater acoustic channel.Also considering the complex environment of underwater acoustic channel,a PN code estimation method based on triple correlation function of database matching is proposed,which can be better adapted to underwater environment.According to the estimation of the key parameters,a time slot estimation method is proposed for non-cooperative TDMA underwater acoustic communication network.The energy method is used firstly to determine the start position of the DSSS signal in the time slot,and then intercepts a small length of DSSS signal to estimate the key parameters.The estimated PN sequence has a strong correlation with the DSSS signal,and the length of the signal can be estimated,which can avoid the interference from the previous signal to the next signal location estimation.After the time slot estimation,the transmission of the jamming signal will be more pertinent,thus realizing the jamming under the smaller power.Finally,a set of underwater acoustic communication detection and jamming equipment is designed based on LabVIEW.Computer simulation and test in pool are completed to verify the effectiveness of the algorithm.