Research On TDOA-based Underwater Source Localization Under Multipath Condition

The oceans are the treasure of mankind.In recent years,the exploration and development of marine resources have been increasing.Underwater positioning technology has attracted more and more attention as a key technology for developing and exploring the ocean.while underwater channel is one of the most complex wireless communication channels currently considered.Underwater channel has a series of properties,such as time denaturation,seriously multipath effect,Doppler effect and complex noise,which leads to locating technology underwater more complicated than on land.Due to the multipath effect of underwater acoustic channel,the received signal is often accompanied by many of the multipath signals besides the direct path signal in the underwater positioning technology research and this kind of multipath signal is seen as one of the direct path signal interference in previously researches.However,a number of rencently studies have shown that multipath signals can be used to locate the target nodes under a certain condition.The TDOA positioning technology requires only time synchronization between the receiving nodes and does not require time synchronization between the receiving node and the sending node.Therefore,the TDOA positioning technology is more suitable for passive positioning.Based on the principle of TDOA positioning technology,this paper carry on research on distributed receiving nodes under multi-path conditions to the location of underwater source nodes.The main work of this paper is as follows:(1)The estimated Cramer-Rao lower bound and maximum likelihood estimation of the underwater source node location in the multi-path environment.Firstly,take the derivative of the estimated Cramer-Rao lower bound and maximum likelihood estimation of the underwater source node location in the multi-path environment according to the principle of TDOA location technology,and then take simulation and validation analysis for the above results.From the simulation results it can be seen that multipath signals can be used to improve the positioning precision of the source and target nodes in the case of multipath path reflection interface information under the condition of known and multipath signals can be distinguished.We can found that the receiving node number is proportional to the source node positioning accuracy and the bandwidth of the pulse signal sent by a source node width is proportional to the source node location accuracy through simulation analysis based on control variable method.In addition,the location distribution of the receiving node relative to the source node also has a certain influence on the accuracy of source node positioning.(2)The source node localization algorithm based on TDOA.For the actual situation,this paper proposes a TDOA location algorithm which can matches the signal propagation path on the premise that the receiving node signal is known and the multipath signal with the corresponding signal propagation path is unknown,analysis also carried out on the effectiveness of the proposed algorithm.The simulation results show that the algorithm can be used in target locating the source node,and at the same time the conclusion that using multipath time delay of underwater signal transmission information can improve the accuracy of the source node position estimation can be verified.