Date of Completion

8-22-2014

Embargo Period

8-21-2014

Keywords

Underwater Acoustic Communications, Networks, Sensor Networks, Localization, Target Tracking, Navigation

Major Advisor

Shengli Zhou

Associate Advisor

Peter Willett

Associate Advisor

Jun-Hong Cui

Field of Study

Electrical Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Underwater sensor networks have seen huge strides within the past decade as they approach viability both technologically and financially; though several issues persist in their implementation. Of interest is localization, a key aspect of sensor networks and navigation. This dissertation looks at several solutions, corresponding to different scenarios:

• Global localization and tracking using surface anchor nodes: In a networking context, supernodes deployed on the surface of a body of water can be equipped with global positioning service (GPS) devices, and can act in a time-synchronized fashion with certainty of their positions. We desire minimizing the use of messaging resources in the network by having only the supernodes transmit information. A solution is developed for an unlimited number of nodes which are capable of receiving the transmissions with no more messaging than if there was one node. The various properties of the algorithm will be tested in full deployments of networks of OFDM modems.

• Network localization through on-demand protocols with asynchronous nodes assuming only a known position: By allowing asynchronous nodes, a larger range of networking scenarios can be addressed. This is accomplished by leveraging a simple reactive beaconing concept to maximize the amount of information that can be obtained by nodes without requiring any transmission from those nodes inside the network. The localization capabilities of the algorithm will be rigorously tested using OFDM acoustic modems deployed in realistic scenarios.

• Single-user localization for instantaneous position estimates: In the previous scenarios, localization takes place over a window of many seconds. For a network with mobile elements, such as autonomous underwater vehicles (AUVs), this can degrade the accuracy of the solution considerably. To solve this, instead of anchors transmitting to a node, the node transmits a single burst to the anchors, who then combine information to compute the exact location of the target node at the time of transmission. This provides a much more accurate method in localizing mobile elements. The dissertation goes beyond a single point-estimate of the node and considers fusing the Doppler-estimation capabilities of OFDM modems with tracking methods to provide a high-accuracy tracking solution.

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