| Summary: | Underwater localization is used as a key element in most applications of underwater communications. Despite the global positioning system (GPS) receivers are usually employed in terrestrial wireless sensor networks, they cannot be exploited for underwater localization. In fact, GPS signals are highly attenuated by the water, by being unusable to a depth of more than a couple of meters, and cannot propagate underwater, especially, in the case of the salt water. In place of RF signals, acoustic signals are the most common mode of communication, and the so-called underwater acoustic sensor networks attracted a significant interest due to their great impact on ocean monitoring and exploration. Hydroacoustics, as the study and application of sound in water, is the foundation of underwater localization, but the existing available methods, classified in range-based versus range-free techniques, are affected by several open problems and research challenges. Therefore, an accurate range-based algorithm for localization needs to be developed, and the demand for expeditiously employing the energy of the sensor nodes is still remaining a distinct feature for underwater wireless sensor networks. Because of these argues, an improved interpretation for underwater localization is presented, by first presenting a general localization algorithm, and afterward deploying the ordinary, beacon nodes in order to find the error and accuracy of sensor localization. After that, we present two localization algorithms named as distance-based and angle-based algorithms. We consider a realistic case, where sensor nodes are not time synchronized and the sound speed in water is unknown. The simulation results exhibit that our algorithms compensate for time synchronization, estimate the mean errors in localization and achieve good localization accuracy.
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