NLOS identification using a hybrid ToA-signal strength algorithm for underwater acoustic localization

The existence of obstacles in harbors or near shore environments leads to Non-Line-Of-Sight (NLOS) links between two underwater acoustic communication (UWAC) nodes. That is, only echoes of the transmitted signal arrive at the receiving node. Mistaking the first (strong) echo as a Line-Of-sight (LOS) measurement and using it for ranging causes significant degradation of the accuracy level of UWAC-based localization. In this paper, we propose a solution for the NLOS identification problem in underwater acoustic localization. Results from both extensive simulations and sea trial experiments confirm our approach and demonstrate a high detection rate of NLOS measurements.