Design Of Underwater Acoustic Preamble Signal Detection Method Based On Multipath Extraction

Preamble signal detection is an important part of underwater acoustic communication.The preamble signal detection is to trigger the receiver to switch from standby mode to operation mode.Compared to land,the underwater environment is complex and changeable.The underwater multipath is rich,the Doppler is large,and the channel time-varying is intense,which will affect the detection of the preamble signal.For the waveforms of the preamble signal,the commonly used waveforms are linear frequency modulation signal(LFM)and hyperbolic frequency modulation signal(HFM).The ambiguity function of HFM signal is more smooth and has no obvious fluctuation.The ambiguity map shows smaller main lobe width.Therefore,the HFM signal has better resolution and stronger anti-jamming capability.And HFM signal is Doppler-insensitive,so it is suitable to be used as underwater acoustic preamble signal.This topic is based on the design of HFM signal detection method.Traditional preamble detection methods include matched filter(MF),normalized matched filter(NMF),page test(PT)and so on.These methods have good detection performance in Gaussian white noise.However,under the condition of multipath and various interference,the detection performance is not good.Therefore,in order to improve the detection effect of the preamble signal,two detection methods are proposed: the adaptive iterative approach(IAA)detector and the sparse learning via iterative minimum(SLIM)detector.These two detection methods can more effectively match multiple paths,and have stronger anti-interference ability.Especially,in the case of down-sampling,the two iterative detection methods increase the signal energy,reduce the noise and interference energy by iterations,improve the resolution,detection performance advantages are more obvious.Simulation and experimental data show that under the condition of partial-duration partial-band interference and narrowband interference,the IAA detector has excellent detection performance.And in various common underwater environments,SLIM detector shows excellent detection performance,which is superior to the traditional detection methods.For SLIM detector,by analyzing the influence of the delay matrix and the number of paths on the detector,the optimal parameters of the actual system are proposed.