Abstract
Target tracking is one of the broad applications of underwater wireless sensor networks (UWSNs). However, as a result of the temporal and spatial variability of acoustic channels, underwater acoustic communications suffer from an extremely limited bandwidth. In order to reduce network congestion, it is important to shorten the length of the data transmitted from local sensors to the fusion center by quantization. Although quantization can reduce bandwidth cost, it also brings about bad tracking performance as a result of information loss after quantization. To solve this problem, this paper proposes an optimal quantization-based target tracking scheme. It improves the tracking performance of low-bit quantized measurements by minimizing the additional covariance caused by quantization. The simulation demonstrates that our scheme performs much better than the conventional uniform quantization-based target tracking scheme and the increment of the data length affects our scheme only a little. Its tracking performance improves by only 4.4% from 2- to 3-bit, which means our scheme weakly depends on the number of data bits. Moreover, our scheme also weakly depends on the number of participate sensors, and it can work well in sparse sensor networks. In a sensor network, compared with sensor networks, the number of participant sensors increases by 334.92%, while the tracking accuracy using 1-bit quantized measurements improves by only 50.77%. Overall, our optimal quantization-based target tracking scheme can achieve the pursuit of data-efficiency, which fits the requirements of low-bandwidth UWSNs.
Highlights
As we know, more than the 70% of the earth’s surface is covered with seas and oceans
underwater wireless sensor networks (UWSNs) are the extending of wireless sensor networks (WSNs), which are used in terrestrial environments [5,6,7]
The posterior Cramer–Rao lower bound (PCRLB) is defined as the inverse of the Fisher information matrix (FIM), and it provides a lower bound on the mean-square error (MSE)
Summary
More than the 70% of the earth’s surface is covered with seas and oceans. A limited bandwidth leads to low bit rates, in the order of tens of Kb/s [10], which is extremely slow compared with WSNs. in this paper, we improve the data-efficiency of UWSNs during target tracking tasks by reducing the length of data packets transmitted from local sensors to the fusion center. The general quantization method divides the measuring range into several uniform parts [11,12] This kind of quantization method is simple and easy to implement; its tracking performance strongly depends on the number of data bits. On the basis of our optimal quantization algorithm, we propose a corresponding target tracking scheme This achieves the pursuit of data-efficiency, which fits the requirements of low-bandwidth UWSNs. The rest of the paper is organized as follows.
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