Research On Localization Algorithm Of Underwater Acoustic Sensor Network Under Weak Communication Condition

With the rapid development of underwater acoustic communication and underwater acoustic positioning technologies,underwater acoustic sensor networks(UASN)that integrates information sensing,information transmission and information processing,has been favored by people.After more than ten years of development,UASN has been widely used in civilian and military fields such as marine data collection,marine resource protection,marine exploration,geological disaster prediction and military monitoring.In the above applications,the location information of nodes in UASN is very important,since the data sensed by the node must match the corresponding location tag so such the decision center can effectively communicate or control commands.However,compared with terrestrial sensor networks,the unique underwater acoustic weak communication characteristics of underwater environment make the localization of nodes in UASN more challenging.Based on this,combined with the existing positioning research results of terrestrial sensor networks and UASN,this thesis studied the positioning in UASN under underwater acoustic weak communication characteristics.The research works in this thesis includes the following aspects:(1)For the positioning problem of underwater sensor node under asynchronous clock and stratification effect in static UASN,an asynchronous positioning protocol is designed to eliminate the impact of asynchronous clock on propagation delay and reduce the impact of stratification effect on propagation delay by using the asynchronous clock and stratification effect models.Then,the nonlinear measurement equations about the underwater sensor node are constructed,and an unscented transform(UT)based localization estimator is proposed to reduce the linearization error of the nonlinear measurement equation.Then,the localization ability of sensor node can be improved.(2)For the positioning problem of underwater sensor node under strong noise in static UASN,a consensus-based unscented Kalman filtering(UKF)localization algorithm is proposed to achieve the estimation of underwater sensor node.In order to reduce the impact of communication noise during the collaboration of anchor nodes in different combinations,a localization algorithm based on consistency fusion strategy is adopted.Then,the influence of asynchronous clock,stratification effect and strong noise interference can be reduced in the positioning process of sensor node.(3)For the positioning problem of underwater sensor node under anchor location uncertainties in static UASN,an accurate underwater sensor node positioning algorithm is proposed.Through four phases of data collection,rough position acquisition,localization error estimation and iterative position update,the corresponding localization algorithms are designed by using time difference of arrival measurements to achieve the accurate positioning of underwater sensor node.In addition,the Cramer-Rao lower bound(CRLB)of the proposed algorithm is derived.Then,it is proved that the localization accuracy of the proposed algorithm can reach the theoretical CRLB under certain conditions.(4)For the positioning problem of underwater autonomous mobile node under asynchronous clock,stratification effect and energy constraint in mobile UASN,a localization strategy based on velocity observer and rigid topology is proposed.First,a motion prediction strategy combining UT-based localization estimator and terminal sliding-mode velocity observer is proposed under asynchronous clock and stratification effect.According to the predicted trajectory of mobile node,the minimum rigid graph is constructed by taking the posterior CRLB as the link weight to balance the positioning accuracy and energy consumption,then UKF algorithm is employed to realize the positioning of mobile node.(5)For the positioning problem of underwater passive mobile sensor node under asynchronous clock and anchor location privacy in mobile UASN,according to whether the sensor node actively initiates the positioning request,the privacy preserving localization algorithms of active and ordinary sensor nodes based on motion prediction are proposed respectively with the idea of transmitting noise sum is zero.Thus,active and ordinary sensor nodes can realize their own position estimation without stealing the location privacy of anchor nodes.