Performance Analysis Of Preamble Detection And Recognition In Underwater Acoustic Communication System

In recent years,with the development of Marine industry,various countries pay more and more attention to the research of underwater acoustic communication system.Preamble detection is an important module for an underwater acoustic communication system.Both false detection and miss detection are unacceptable which will cause communication failure and bring undesirable consequences on the lifetime of communication devices.As one of the most complex channel at present,the underwater acoustic channel is characterized by serious multipath effect,obvious Doppler effect and various kinds of interference,which makes it difficult to detect the preamble,and there is no ideal detection performance.This paper studies the detection and recognition of the preamble signal from two aspects,and analyzes the theoretical performance of the proposed methods deeply.The theoretical performance is of great significance to actual underwater acoustic applications.The detection performance of the preamble decreases due to the complex underwater environment and varied interference.Among them,partial-band partial-block-duration(pbpd)interference has a particularly serious impact on the performance of the detector because it is similar to the preamble signal.To solve this problem,a detection algorithm DP-GLRT for pbpd interference is proposed in this paper.The duration and frequency of pbpd interference only accounts for a part of the signal.Based on the characteristic,the optimal detector is designed by using likelihood ratio test when the channel is unknown,and its detection performance is theoretically analyzed.The detection performance is also compared with the simulation performance.It provides a strong guarantee for the application of the detector in the actual underwater acoustic.The performance of the theoretical analysis can effectively guide marine communication experiments.On this basis,we further compared the detection performance of DP-GLRT and traditional detection algorithms under different interference backgrounds using simulation data and marine data.Experiments show that the DP-GLRT detector designed in this paper has strong robustness in both simulation and actual underwater acoustic tests.The underwater acoustic communication network often needs to recognize the signals transmitted by multiple receivers at the same time,which is actually to recognize different preamble signals.In this dissertation,the performance of the leading signal recognition under multiple receivers is studied from two aspects: the single path signal recognition and the unknown multipath attenuation and the underwater acoustic channel signal recognition.For single path channels,the optimal detector under maximum likelihood criterion is given,and its theoretical performance is analyzed.The performance analysis provides guidance for the identification of the preamble signal of the unknown channel.On the other hand,in the actual communication system,because of the multipath and attenuation of the channel,the received signal cannot be exactly the same as the sent signal,that is to say,the received signal is not completely known.Based on this situation,we use the generalized likelihood ratio criterion to design the optimal method of multi-receiver's preamble recognition under unknown channel and analyze its theoretical performance comprehensively and deeply,which provides a strong guarantee for actual underwater acoustic application.The effectiveness of the proposed method is demonstrated by Simulation and experimental data.