Research On Localization Algorithm Of Underwater Wireless Sensor Networks For Range Correction

UWSNs(Underwater Wireless Sensor Networks)are widely used as the extension of WSNs(Wireless Sensor Networks).Because of the complexity of the underwater environment and the particularity of underwater acoustic communication,the technology of node localization,as the basic technology of WSNs,is facing new challenges.Because the error of most localization algorithms is related to the error of distance between nodes,we corrected the distance of ranging-based and non-ranging localization algorithms in this thesis.Then two algorithms of UWSNs for range correction were proposed to reduce the localization error.In the aspect of ranging-based algorithm,aiming at the problem that the large error of ranging that is caused by variable sound velocity and obstacle in underwater,an underwater node localization algorithm based on ranging correction and curved sound ray was designed in this thesis.Firstly,the rationality of the curved sound ray was explained by analyzing propagation characteristics of the underwater acoustic signal.Based on Ao A(Angle of Arrival)and To A(Time of Arrival),a ranging method with parabolic models that is suitable for curved sound ray was proposed.And the method considers both ranging accuracy and real-time performance because it can not only provide more accurate ranging but also calculate the time of ranging without clock synchronization.Then,by comparing the calculation time and measurement time of signal propagation in the process of ranging,under the condition that the noise satisfies Gaussian distribution,the ranging recognition method of non-ideal path caused by obstacle and the ranging correction method of ideal path were proposed.Finally,the projection method and the least square method were used to complete the localization.The simulation results show that the algorithm can effectively reduce the localization error in three aspects: curved sound ray,path recognition,and ranging correction.In the aspect of the non-ranging localization algorithm,we proposed an improved threedimensional DV-Hop(Distance Vector-Hop)algorithm with continuous hop value to solve the problem that the large distance error between nodes could result in inaccurate localization in DV-Hop.Firstly,by the relationship between the localization of two neighboring nodes and the volume of the intersecting sphere composed of the localization and communication radius,the functional relationship between the ratio of the two volumes and the distance between nodes was obtained.Then,combined with the concept of hop in DV-Hop,the definition of continuous hop value was put forward,and its calculation method was given according to the functional relationship.And the method of parameter correction was applied to the calculation method to reduce the error,and five improved relationships of continuous hop value were put forward.Finally,the influence of network environment on parameters was explored by simulation.Then we also determined the parameters value,and which calculation formula of continuous hop value should be used through simulation.And the continuous hop value was used instead of the hop in DV-Hop to reduce the localization error.The simulation results show that compared with DV-Hop algorithm and the improved algorithm,the algorithm effectively reduces the localization error without increasing the complexity of the algorithm and additional hardware.