1. College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China 2. Key Laboratory of Ocean Observation-Imaging Testbed of Zhejiang Province, Ocean College, Zhejiang University, Zhoushan 316021, China
在水下媒介中，声速随着水深、温度和盐度而变化。水体的不均匀性导致声线弯折，使得现有基于声信号直线传播假设的定位算法不够精确。为实现水下声学传感网络中的高精度节点定位，本文首先使用线性分割近似方法，提出多层等梯度声速剖面（sound speed profile，SSP）模型。基于此模型，可将声线跟踪问题转化为多项式寻根问题。利用传感器节点处信号多普勒频移的导数，提出一种新的使用到达时间差（time difference of arrival，TDOA）和到达频率差（frequency difference of arrival，FDOA）的水下节点定位算法。通过模拟仿真，可以证明所提算法的有效性。与传统基于直线传播假设的方法相比，所提算法可有效处理声线弯折现象。此外，研究了不同SSP建模误差下的估计精度。总体而言，新提出的方法可以实现准确可靠的节点定位。
Abstract：
In the underwater medium, the speed of sound varies with water depth, temperature, and salinity. The inhomogeneity of water leads to bending of sound rays, making the existing localization algorithms based on straight-line propagation less precise. To realize high-precision node positioning in underwater acoustic sensor networks (UASNs), a multi-layer isogradient sound speed profile (SSP) model is developed using the linear segmentation approximation approach. Then, the sound ray tracking problem is converted into a polynomial root-searching problem. Based on the derived gradient of the signal’s Doppler shift at the sensor node, a novel underwater node localization algorithm is proposed using both the time difference of arrival (TDOA) and frequency difference of arrival (FDOA). Simulations are implemented to illustrate the effectiveness of the proposed algorithm. Compared with the traditional straight-line propagation method, the proposed algorithm can effectively handle the sound ray bending phenomenon. Estimation accuracy with different SSP modeling errors is also investigated. Overall, accurate and reliable node localization can be achieved.
