Study On RSS-based Underwater Acoustic Distance Measurement With Multiple Frequencies

With the deepening of human exploration,development and utilization of marine resources,ocean has been more and more important in strategy,and marine monitoring based on underwater sensor networks has been more and more widely used.As one of the basic,key and essential part,underwater acoustic localization technology has been widely studied.Among all kinds of these technologies,the localization technology based on received signal strength(RSS)is popular and with great potential because of its low cost and easy accessibility.However,in the actual environment,due to the influence of multipath effect,it is easy to make mistakes in the process of mapping distance through RSS,which impairs the localization performance of this technology.In this paper,an underwater acoustic ranging method based on RSS is studied to mitigate the multipath effect.The main work of this paper is as follows:1.Based on the assumption of constant sound speed profile in shallow water,a ranging method based on RSS with multiple frequencies is proposed.Combined a ray tracing method based on image source with the research of interface reflection coefficient,the classical Urick transmission loss model is improved,and a new propagation model considering multipath effect is established.Aiming at the problem that the objective function cannot be solved because there are too many unknown parameters in this new model,a measurement idea with multiple frequencies is proposed.Then the objective function is redefined as the difference between the model and the measured information,and the constraint conditions are according to the prior information in the scene.Finally,by solving the minimum value of this objective function using the interior-point optimization algorithm,the ranging result is obtained.In order to evaluate the performance of this RSS-based method with multiple frequencies,the Cramer-Rao variance lower bound(CRLB)is derived in the numerical analysis firstly.In the numerical simulation,it shows that the ranging performance of this method is very close to CRLB,and improves with the increase of the number of frequency points.Furthermore,in a new simulation using Bellhop toolbox,it shows that the localization performance of the proposed method is obviously better than that of the localization method based on Urick model,and is equivalent to that of localization method based on the compressed sensing.Finally,to verify the feasibility of proposed method,it is implemented in the actual underwater environment.2.Based on the typical sound velocity profile named Munk in the deep sea,the ranging method in shallow water is improved by considering the influence of sound variation.Under the condition of series approximation,the Eikonal equation and transport equation derived from Helmholtz equation are solved.After considering the initial conditions and boundary conditions,the sound field propagation model is obtained.In the simulation using OASES software,the propagation loss of the same scene is obtained and treated as the input measured information after adding noise.Similarly,the ranging results are obtained under certain constraints using the interior-point optimization algorithm.This simulation results show that the ranging performance of this method is improved with the increase of the number of frequency points;and compared with the traditional method based on Urick model,the ranging error of proposed method is reduced by about 2/3,which further verifies the feasibility of proposed method.