Wireless Systems for Energy-Efficient Data Acquisition and Position Estimation in Wide Area Networks
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Reddy, Varun Amar
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Abstract
Wide area networks for surveying applications continue to grow in area, density, and traffic. In particular, seismic acquisition presents a challenging application wherein real-time data delivery is expected from thousands of devices called geophones, that are deployed across very large areas to obtain images of the Earth’s subsurface. The data is processed at the sink node and employed in earthquake detection, oil and gas exploration, and urban planning. This thesis provides the foundational framework for designing a standards-compliant and cost-effective wireless data acquisition system for the most challenging and intriguing application – oil and gas exploration.
Unlike typical sensor networks, data generation rates at each of the geophones are relatively high (0.1-1 Mbps), implying an aggregate rate of several Gigabits per second at the sink node for a total of 10,000-30,000 geophones that are deployed across areas as large as 100 square kilometers. An architecture compliant with IEEE 802.11af is proposed for operation in sub-GHz television white spaces, over which data rates of up to 70 Mbps across distances of up to 1 km can be realized. Additional channel access schemes, based on smart polling and time division multiple access techniques, are designed to deliver contention-free access and improved power saving at the geophones. A self-organizing network compliant with the IEEE 802.11ad standard is also proposed as an alternative choice for deployment at this layer. Both architectures provide for a scalable approach wherein coverage can be established across large areas with minimal number of gateway nodes.
In order to relay data from the gateway nodes to the final sink node, a mesh network compliant with various flavors of the IEEE 802.11 standard, unmanned aerial vehicles, and free space optical communication is evaluated with the goal of sustaining real-time acquisition at Gigabit rates. The IEEE 802.11ad standard, which operates in the mm-wave 60 GHz bands, is shown to be the preferable choice for data backhauling. Effective power conservation can be enforced at this stage by formulating an analytical framework that yields optimal values for the number of relay nodes, transmit power, modulation and coding scheme, frame aggregation length, and sleep duration.
The aforementioned schemes for onshore surveys are extended to the case of marine acquisition, and evaluated after accounting for the use of autonomous underwater vehicles. Additionally, the subject of position estimation of the geophones is investigated, and Cramér-Rao bounds on the position error are derived for mm-wave cooperative localization. The proposed system can altogether eliminate the need for GPS modules, by employing a very minimal number of anchor nodes across large areas.
Overall, this thesis lays the groundwork for designing real-time, energy-efficient, scalable, economical, and standards-compliant wireless systems that can find application in seismic acquisition, offshore surveys, large-scale environmental monitoring, meteorological studies, industrial networks, and cellular backhaul.
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Date
2021-04-27
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Dissertation