Date of Completion
Field of Study
Computer Science and Engineering
Doctor of Philosophy
With recent advancement in underwater robotics and acoustic communications, the concept of mobile underwater acoustic networks (MUANs) has gradually become feasible. The advantage of MUANs lies in their mobility which allows them to adjust the topology easily and therefore adapt to environment changes. Many promising applications are made possible with this class of networks, for example, a network of autonomous underwater vehicles (AUVs) can be used in fishery to herd fish or in the oil industry to monitor undersea pipelines. However, designing a mobile network in an uncertain environment, such as the ocean, is a challenging task.
In this dissertation, we investigate three topics in in MUANs. The first piece of work presents a deployment framework for a typical scenario in Lagrangian oceanography measurement in which uses mobile sensors to collect data. The sensors are redeployed if drifted out of the area. Our proposed framework aims to provide guidance to network designers. For example, with the constructed models for coverage and connectivity, they are able to determine the number of nodes needed to guarantee coverage of 80% or connectivity of at most 4 components with probability of 0.5, for instance.
The second piece of work proposes a MAC protocol, named PMAC, which has real applications in monitoring oil pipelines. The protocol is scheduling-based and is specifically designed for string networks to achieve high performance. Real sea test data shows that the protocol had much higher goodput than an RTS/CTS scheme tested in the same experiment, up to three times more efficient. On top of this, the end-to-end delay is also shorter. In this work, we also point out an important issue yet usually ignored by a majority of studies: the modem processing delay. With this delay, short packets can have adverse effects on network performance if they are not scheduled carefully. Additionally, we derive a closed form formula, considering real modems’ characteristics, for choosing the optimal packet size which can serve as the upper bound on the optimal packet size.
The third piece of work is on a novel underwater navigation method designed for mobile vehicle. Our scheme has many potential applications, for example fish herding or undersea surveillance, because it does not require a vehicle to surface. In our approach, we deploy seamarks, which serve as landmarks at sea, to assist vehicles’ inertial navigation systems. Seamarks are lightweight undersea nodes whose main functionality is to help a vehicle measure round-trip distances. Based on this data, a vehicle executes our estimation algorithm to correct its velocity and position. Simulation results shows that our algorithm is simple enough to implement in practice and requires a reasonable number of measurements.
Le, Son Ngoc, "Navigation, Deployment and Experimentation for Mobile Underwater Acoustic Networks" (2014). Doctoral Dissertations. 595.