132 research outputs found
Underwater Communication Acoustic Transducers: A Technology Review
This paper provides a comprehensive review on transducer technologies for underwater communications. The popularly used communication transducers, such as piezoelectric acoustic transducers, electromagnetic acoustic transducers, and acousto-optic devices are reviewed in detail. The reasons that common air communication technologies are invalid die to the differences between the media of air and water are addresses. Because of the abilities to overcome challenges the complexity of marine environments, piezoelectric acoustic transducers are playing the major underwater communication roles for science, surveillance, and Naval missions. The configuration and material properties of piezoelectric transducers effects on signal output power, beamwidth, amplitude, and other properties are discussed. The methods of code and decode communication information signals into acoustic waves are also presented. Finally, several newly developed piezoelectric transducers are recommended for future studies
Proposal of a health care network based on big data analytics for PDs
Health care networks for Parkinson's disease (PD) already exist and have been already proposed in the literature, but most of them are not able to analyse the vast volume of data generated from medical examinations and collected and organised in a pre-defined manner. In this work, the authors propose a novel health care network based on big data analytics for PD. The main goal of the proposed architecture is to support clinicians in the objective assessment of the typical PD motor issues and alterations. The proposed health care network has the ability to retrieve a vast volume of acquired heterogeneous data from a Data warehouse and train an ensemble SVM to classify and rate the motor severity of a PD patient. Once the network is trained, it will be able to analyse the data collected during motor examinations of a PD patient and generate a diagnostic report on the basis of the previously acquired knowledge. Such a diagnostic report represents a tool both to monitor the follow up of the disease for each patient and give robust advice about the severity of the disease to clinicians
Model-Driven Based Deep Unfolding Equalizer for Underwater Acoustic OFDM Communications
It is challenging to design an equalizer for the complex time-frequency
doubly-selective channel. In this paper, we employ the deep unfolding approach
to establish an equalizer for the underwater acoustic (UWA) orthogonal
frequency division multiplexing (OFDM) system, namely UDNet. Each layer of
UDNet is designed according to the classical minimum mean square error (MMSE)
equalizer. Moreover, we consider the QPSK equalization as a four-classification
task and adopt minimum Kullback-Leibler (KL) to achieve a smaller symbol error
rate (SER) with the one-hot coding instead of the MMSE criterion. In addition,
we introduce a sliding structure based on the banded approximation of the
channel matrix to reduce the network size and aid UDNet to perform well for
different-length signals without changing the network structure. Furthermore,
we apply the measured at-sea doubly-selective UWA channel and offshore
background noise to evaluate the proposed equalizer. Experimental results show
that the proposed UDNet performs better with low computational complexity.
Concretely, the SER of UDNet is nearly an order of magnitude lower than that of
MMSE
Pulses in the Sand: Impulse Response Analysis of Wireless Underground Channel
Wireless underground sensor networks (WUSNs) are becoming ubiquitous in many areas and designing robust systems requires extensive understanding of the underground (UG) channel characteristics. In this paper, UG channel impulse response is modeled and validated via extensive experiments in indoor and field testbed settings. Three distinct types of soils are selected with sand and clay contents ranging from 13% to 86% and 3% to 32%, respectively. Impacts of changes in soil texture and soil moisture are investigated with more than 1,200 measurements in a novel UG testbed that allows flexibility in soil moisture control. Time domain characteristics of channel such as RMS delay spread, coherence bandwidth, and multipath power gain are analyzed. The analysis of the power delay profile validates the three main components of the UG channel: direct, reflected, and lateral waves. It is shown that RMS delay spread follows a log-normal distribution. The coherence bandwidth ranges between 650 kHz and 1.15MHz for soil paths of up to 1m and decreases to 418 kHz for distances above 10m. Soil moisture is shown to affect RMS delay spread non-linearly, which provides opportunities for soil moisture-based dynamic adaptation techniques. The model and analysis paves the way for tailored solutions for data harvesting, UG sub-carrier communication, and UG beamforming
Pulses in the Sand: Impulse Response Analysis of Wireless Underground Channel
Wireless underground sensor networks (WUSNs) are becoming ubiquitous in many areas and designing robust systems requires extensive understanding of the underground (UG) channel characteristics. In this paper, UG channel impulse response is modeled and validated via extensive experiments in indoor and field testbed settings. Three distinct types of soils are selected with sand and clay contents ranging from 13% to 86% and 3% to 32%, respectively. Impacts of changes in soil texture and soil moisture are investigated with more than 1,200 measurements in a novel UG testbed that allows flexibility in soil moisture control. Time domain characteristics of channel such as RMS delay spread, coherence bandwidth, and multipath power gain are analyzed. The analysis of the power delay profile validates the three main components of the UG channel: direct, reflected, and lateral waves. It is shown that RMS delay spread follows a log-normal distribution. The coherence bandwidth ranges between 650 kHz and 1.15MHz for soil paths of up to 1m and decreases to 418 kHz for distances above 10m. Soil moisture is shown to affect RMS delay spread non-linearly, which provides opportunities for soil moisture-based dynamic adaptation techniques. The model and analysis paves the way for tailored solutions for data harvesting, UG sub-carrier communication, and UG beamforming
Broadband optical wireless communications for the teleoperation of mining equipment
The current level of technological advancement of our civilization serving more than seven
billion human population requires new sources of biotic and abiotic natural resources. The
depletion and scarcity of high-grade mineral deposits in dry land are forcing the Natural Re-
sources industry to look for alternate sources in underwater environments and outer space,
requiring the creation of reliable broadband omnidirectional wireless communication systems
that allows the teleoperation of exploration and production equipment. Within these ob-
jectives, Optical Wireless Communications (OWC) are starting to be used as an alternative
or complement to standard radio systems, due to important advantages that optical wave-
lengths have to transmit data: potential for Terabit/s bit rates, broadband operation in
underwater environments, energy e ciency and better protection against interference and
eavesdropping. This research focus in two crucial design aspects required to implement
broadband OWC systems for the teleoperation of mining equipment: high bandwidth wide
beam photon emission and low noise omnidirectional Free-Space Optical (FSO) receivers.
Novel OWC omnidirectional receivers using guided wavelength-shifting photon concentra-
tion are experimented in over 100 meters range vehicle teleoperation.Master of Science (MSc) in Natural Resources Engineerin
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