Research On Underwater Source Localization Under Multipath Condition

The ocean is of great significance to the development of human society.In recent years,many countries have increased the intensity of exploration and development of the ocean.As the key technology of ocean exploration and development,underwater positioning technology has been paid much attention by researchers.In the positioning of the underwater target,due to the multi-path effect of the underwater acoustic channel,the receiver may receive some multipath signals in addition to the direct path signal.Usually,these multipath signals are regarded as a kind of interference.However,in recent years,some studies have shown that under certain conditions,multipath signals can be used to locate the target.According to the principle of TOA localization,this paper studies the problem of underwater source node localization in multipath environment by using distributed receiving nodes.The main work is as follows:(1)Cramér-Rao Lower Bound(CRLB)and the maximum likelihood estimator(MLE).According to the principle of TOA localization,the CRLB and the MLE are derived for the study of underwater source node localization performance using N distributed receiving nodes in the multipath environment,and the derived results are simulated and analyzed.The simulation results show that the multipath signal can be used to improve the accuracy of the source node position estimation in the case where the geographic information of the multipath reflection interface and the velocity of sound in the water are known.And the larger the bandwidth of the transmitted signal,the more the number of receiving nodes,the higher accuracy of the source node location estimation can achieve.In addition,the simulation results show that the relative distribution of the source node and the receiving nodes will also affect the accuracy of the source node position estimation.(2)TOA localization algorithm based on multipath utilization.A TOA localization algorithm based on multipath signal delay and signal propagation path matching is proposed for the case where the signal delay is known at each receiving node,but the signal propagation path corresponding to each path delay is unknown.The validity of the algorithm is verified by simulation.The simulation results show the feasibility of the algorithm,and it also shows that the accuracy of the position estimation of the source node can be improved by using the multipath delay information.