HFM Acoustic Preamble Signal Detection Algorithm Based On Match Filter And Waveform Design In Underwater Communication

With the deep exploitation of the ocean,underwater acoustic communication is more and more popular,application of which gra dually expand from the military field to the commercial field and even civilian areas.The preamble signal is an important part of the underwater communication.Underwater data transmission is carried out in the form of data frames.Before transmitting data frames,a preamble signal is transmitted to trigger the detector to receive valid data.Both false detection and miss detection are unacceptable which will cause communication failure.However,strong Doppler shift,violent multipath effects and various kinds of interferences in the marine environment make so much trouble.This paper will try its best to solve this problem through two ways by optimizing detection algorithm and optimizing preamble waveform,and improve the performance of preamble signal de tection in the system.To prevent underwater disturbance from affecting preamble signal detection,this paper proposed a new kind of detection algorithm which has better performance and lower complexity based on existing algorithm.Firstly,this paper analyzes various types of interference which may exist in the marine environment,and then simulates performance and variation of MF,NMF and Page test in those disturbances.Based on NMF and Page test,a new detection algorithm N-PT is proposed.Compared with present methods,N-PT can show relatively stable detection performance under various disturbances.It takes advantages of both NMF and Page test,and at the same time overcome the lack of both.N-PT not only can suppresses the ambient noise through the normalization process,but also fully considers the multi-channel effect of the underwater acoustic channel,accumulates the multipath signal energy to get greater detection performance.To prevent severe Doppler effect in underwater acoustic channel from causing signal frequency offset and affecting the detection performance,we proposed a improved preamble signal waveform based on UD-HFM..In this paper,we first analyze the Doppler invariance of the HFM which is usually used as preamble signal in underwater acoustic communication.Based on which,here comes UD-HFM which is make up of two HFMs with different sweep directions.UD-HFM can calculate the channel Doppler factor while at expense of detection accuracy.Based on which an improved preamble waveform UMD-HFM is proposed.UMD-HFM make simple encode based on UD-HFM,by adding a blank interval it avoid two HFM signals superimposed and affecting the detection results.Experimental make clear that compared with UD-HFM,UMD-HFM can show better detection performance under Gaussian white noise,impulse interference,partial-duration-partial-band interference and similar frequency modulation interference.Finally,in order to verify the performance of the N-PT detection algorithm and the preamble signal UMD-HFM this paper simulates the performance of the UMD-HFM pilot signal under the condition of short-time band limited interference.