7,181 research outputs found
Data Transmission with Reduced Delay for Distributed Acoustic Sensors
This paper proposes a channel access control scheme fit to dense acoustic
sensor nodes in a sensor network. In the considered scenario, multiple acoustic
sensor nodes within communication range of a cluster head are grouped into
clusters. Acoustic sensor nodes in a cluster detect acoustic signals and
convert them into electric signals (packets). Detection by acoustic sensors can
be executed periodically or randomly and random detection by acoustic sensors
is event driven. As a result, each acoustic sensor generates their packets
(50bytes each) periodically or randomly over short time intervals
(400ms~4seconds) and transmits directly to a cluster head (coordinator node).
Our approach proposes to use a slotted carrier sense multiple access. All
acoustic sensor nodes in a cluster are allocated to time slots and the number
of allocated sensor nodes to each time slot is uniform. All sensor nodes
allocated to a time slot listen for packet transmission from the beginning of
the time slot for a duration proportional to their priority. The first node
that detect the channel to be free for its whole window is allowed to transmit.
The order of packet transmissions with the acoustic sensor nodes in the time
slot is autonomously adjusted according to the history of packet transmissions
in the time slot. In simulations, performances of the proposed scheme are
demonstrated by the comparisons with other low rate wireless channel access
schemes.Comment: Accepted to IJDSN, final preprinted versio
Quick release acoustic sensor holding fixture
Quick-release spring holder secures acoustic sensor to test material surface eliminating adhesive bonding to test material and achieving acoustic emission evaluation from tensile tests. Reusability of sensors reduces test cost
Cooperative Authentication in Underwater Acoustic Sensor Networks
With the growing use of underwater acoustic communications (UWAC) for both
industrial and military operations, there is a need to ensure communication
security. A particular challenge is represented by underwater acoustic networks
(UWANs), which are often left unattended over long periods of time. Currently,
due to physical and performance limitations, UWAC packets rarely include
encryption, leaving the UWAN exposed to external attacks faking legitimate
messages. In this paper, we propose a new algorithm for message authentication
in a UWAN setting. We begin by observing that, due to the strong spatial
dependency of the underwater acoustic channel, an attacker can attempt to mimic
the channel associated with the legitimate transmitter only for a small set of
receivers, typically just for a single one. Taking this into account, our
scheme relies on trusted nodes that independently help a sink node in the
authentication process. For each incoming packet, the sink fuses beliefs
evaluated by the trusted nodes to reach an authentication decision. These
beliefs are based on estimated statistical channel parameters, chosen to be the
most sensitive to the transmitter-receiver displacement. Our simulation results
show accurate identification of an attacker's packet. We also report results
from a sea experiment demonstrating the effectiveness of our approach.Comment: Author version of paper accepted for publication in the IEEE
Transactions on Wireless Communication
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Acoustic sensor
A method of designing and manufacturing an acoustic sensor having a high degree of directivity is disclosed. The sensor includes a rotatable plate that is attached to a substrate with mounts. In one aspect the mounts are freely rotatable and the torque on the plate is measured using detectors disposed on springs that provide a resistance to rotation of the plate. In another aspect the plate is mounted to the substrate with mounts that torsionally deform during rotation of the plate. These detectors measure the torque on the plate according to the torsional deformation of the mounts. Methods of improving the signal to noise ratio of acoustic sensors having multiple detectors are also disclosed.Board of Regents, University of Texas Syste
Micromachines Acoustic Sensor For Monitoring Electrochemical Deposition
Disclosed are micromachined acoustic sensors for monitoring electrochemical deposition, methods for fabricating such sensors, and methods for in-situ monitoring of electrochemical deposition processes using such sensors. An exemplary acoustic sensor includes a deformable silicon membrane, an encapsulated piezoelectric layer formed on the silicon membrane, and surface electrodes formed on the piezoelectric layer. The sensor and a loudspeaker may be used to calibrate an electrochemical deposition process. The acoustic response of the sensor is monitored over time with respect to plating thickness during electroplating of a sample to generate a predictive model defining the plating process. The predictive model may be used to monitor the plating thickness of other samples in real time.Georgia Tech Research Corporatio
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