Research On Shallow Seawater Acoustic Multipath Channel Tracking Method Based On Random Finite Set

Underwater acoustic communications is the only communication method that can realize long-distance underwater transmission,but the variable and complex marine environment will affect the propagation of acoustic signals,resulting in a time-varying and randomness of the underwater acoustic channel.Effective tracking of underwater acoustic multipath channels helps to explore underwater communications environments while improving channel equalization.This research is a hot topic in today's underwater acoustic communications research.The traditional channel tracking method,such as the adaptive tracking method,can only roughly restore the overall information of the channel,and cannot obtain the sub-path information.However,with the continuous development of underwater communications,the importance of underwater acoustic channel parameters in understanding the underwater communications environment and in various researches has become increasingly prominent,such as channel equalization and environmental detection.Therefore,this paper proposes a channel tracking method for directly tracking underwater acoustic multipath parameters in combination with the physical characteristics of shallow seawater acoustic channels.This thesis proposes a multipath channel tracking method based on random finite set and applies it to underwater acoustic single carrier communications system and OFDM(Orthogonal Frequency Division Multiplexing)system.For the multi-path channel tracking method based on random finite set,we first give the time-varying state model of the time delay and the Doppler of the sub-path based on the relative motion between the transceivers.Then,using the Probability Hypothesis Density Filter(PHD)based on the random finite set and its improved method,we transform the traditional multi-target tracking into multi-path parameter tracking,and then obtain the path-related parameters.On this basis,we apply the above channel tracking technology in single-carrier time domain systems and OFDM systems,respectively.The difficulty of the application lies in the acquisition of tracking measurements.In this regard,in the single-carrier time domain system,we use the HFM signal,and the pilot signal is used in the OFDM system to extract the measurement of the sub-path.The tracking signal is reconstructed by using the tracking sub-path information to obtain the error rate of the two systems,and the preliminary application of the proposed tracking method in two typical underwater acoustic communication systems is realized.The simulation results show that the proposed multipath channel tracking method can effectively track the time-varying underwater acoustic multipath channel in shallow sea and obtain the channel characteristic parameters of the sub-path.Especially for the time-varying underwater acoustic channel with high sparsity,the demodulation error of the underwater communication system can be more effectively reduced than the conventional method.In addition,we alsoapply the above tracking method to the existing test data.The lake test data processing shows that the method can obtain better performance when the water acoustic channel path is sparse.The existing sea trial data processing also preliminarily verified the effectiveness of the method.This study can improve the channel equalization technology in underwater acoustic communications and provide a theoretical basis for integrated underwater acoustic communications detection technology.Further performance analysis is subject to subsequent experimental verification.