Accurate Shallow and Deep Water Range Estimation for Underwater Networks

Underwater Wireless Sensor Networks (UWSN) are faced with the challenge of estimating distances between nodes for localization purposes. To estimate the range, most researchers opt to model the propagation trajectory of an acoustics signal either as straight lines, or by solving the wave equation and then deriving the distance. The main drawback of the former is oversimplifying the aquatic propagation model by assuming a homogeneous medium, whereas the latter approach is computationally intense and requires knowledge of the water characteristics that alters the signal velocity along the propagation path; examples of which are the sound speed profile and density. Furthermore, ranging techniques for deep water applications differ from shallow water ones due to the different boundary conditions faced in each medium. In this paper, we propose a novel and unified ranging method that is suitable for both deep and shallow waters and implicitly factors the aquatic characteristics. In particular, the proposed method uses a parabolic ranging model that takes advantage of both angle of arrival and departure of newly formed communication links to relatively localize nodes within a network. Basically, we localize nodes by modeling the propagation between each pair of nodes as a parabola that satisfies the angles of arrival and departure and show that that parabolic expansion factors in the reflection, refraction and straight line model. We validate our approach through simulation and compare its performance to contemporary ranging techniques.