Research On Underwater Acoustic Doppler Shift Factor Estimation Based On LFM Instantaneous Autocorrelation And Expansion

In the underwater acoustic communication system,the research of Doppler shift factor is always an important subject.In today's era,the technology of land,sea and air has been fully developed.However,the sound speed is relatively slow and affected by the acoustic propagation,environment noise,multipath delay,the Doppler effect in underwater acoustic communication is far greater than the air and land communication.It is necessary to take some measures to estimate and compensate the Doppler frequency shift factor.Therefor,this paper carries on the related technical research and algorithm design,mainly includes:Firstly,this paper introduce the common characteristics of underwater acoustic communication channel and their influence,including the limited communication band,the marine environment noise,multipath delay and Doppler effect.Meanwhile,some common Doppler frequency shift factor estimation and algorithms are described,and the practicability,merits and faults are analyzed in the real underwater acoustic communication.Secondly,in order to solve the contradiction between the estimation accuracy and the computational complexity of the existing Doppler estimation,a new method based on LFM instantaneous autocorrelation and expansion is proposed for the estimation of the frequency shift factor.The linear frequency modulated(LFM)signal is firstly used as the transmitting signal,then the received signal is theoretically analyzed by using the function of instantaneous autocorrelation and expansion.Through these procedures,we can finally get the expression of the Doppler frequency shift factor and the performance expression of algorithm.Thirdly,the CRLB bound is derived according to the basic of signal parameter estimation,and the performance of the new algorithm is analyzed by a large number of simulation experiments.The results show that the new algorithm has a certain estimation accuracy in the case of low computational complexity.In addition,the performance of the proposed method can quickly approach to the CRLB bound under the condition of low SNR and considering multipath effect.