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| Profile of the writer: Dr. Lawrence Materum |
Wireless
communication technologies that never fail and can withstand any disaster are infeasible
to deploy and impractical to design. Instead of making such systems for
disaster risk reduction, the desired approach is to design wireless
communication systems with acceptable performance levels that have mechanisms
that are: (1) proactive—by preventing risks that can cause disasters; and (2) reactive
in two ways: (2.1) by recovering from disaster impacts during and after a
disaster—this is referred to as resilience; and (2.2) by adapting to different
disaster scenarios.
A wireless sensor network (WSN) is a communication
system composed of a base station (a.k.a. access point, gateway, collector,
aggregator) which collects data from nodes wirelessly. This WSN is shown in Fig. 1. The nodes and/or the collector could be fixed
or mobile. Each node has at least 1 sensor—sensor node.
A sensor node is a WSN component.
It is a radio transceiving device with at least one sensor. Fig. 2 illustrates
hardware implementations of sensor nodes.
Examples of types of sensors that can be placed
in sensor nodes are the following.
1.
Acoustic,
sound, vibration
2.
Automotive,
transportation
3.
Chemical
4.
Electric
current, electric potential, magnetic, radio
5.
Flow,
fluid velocity
6.
Force,
density, level
7.
Ionizing
radiation, subatomic particles
8.
Navigation
instruments
9.
Optical,
light, imaging
10.
Position,
angle, displacement, distance, speed, acceleration
11.
Pressure
12.
Proximity,
presence
13.
Thermal,
heat, temperature
Examples of position sensors are
as follows.
1.
Capacitive
sensing
2.
Free
fall sensor
3.
Gravimeter
4.
Gyroscopic
sensor
5.
Impact
sensor
6.
Inclinometer
7.
Inclinometers
8.
LIDAR
9.
Odometer
10.
Photoelectric
sensor
11.
Piezoelectric
accelerometer
12.
Position
sensor
13.
Rangefinder
14.
Rate
sensor
15.
Shock
data logger
16.
Shock
detector
17.
Stretch
sensor
18.
Surface
velocimeter
19.
Tachometer
20.
Tilt
sensor
21.
Ultrasonic
thickness gauge
22.
Variable
reluctance sensor
23.
Velocity
receiver
On
the other hand a collector is another WSN component. It could also serve as a sensor node, but it functions
as the gateway
for coordinating data transmission/reception in the network. Potential sensor node locations are in the
following.
In
natural environments:
1. Bodies of water—for
sensing: flood, tsunami, …
2. Soils—for sensing:
landslides, quakes, …
3. Air—for sensing: pollution,
airborne microbes, …
In
built environments
1. Water supply—for
sensing: quality, leaks, …
2.
Energy grid—for
sensing: damages, supply, …
3. Bridges, roads, dams, plants, hazardous
scenes., etc.—for sensing: safety, compliance, traffic, fires, gas
leaks, …
There
are three important requirements for WSNs being deployed for disaster scenarios.These are: (1) long-range—the
collector must receive data from the farthest
sensor node at a reasonable time;
(2) low
power—sensor nodes must consume very
minimal amount of power such
that its battery should last at least ten years; (3) sufficient
—sensor nodes must be
placed sufficiently to obtain appropriate data. The long-range
feature is
usually handled at the antenna and at the setting of the maximum allowable
transmit power (to avoid interference).
The low-power requirement depends on the
amount of processing and the
environment where the sensor node is placed.
For the
requirement for sufficiency, it remains as one large open
problem since it could be
scenario-specific. So generalizing such scenarios may
not be straightforward.
Challenges to researchers: Here
problems that have been left unaddressed as to the authors’ knowledge are
presented as follows.
1.
In
natural and built environments, how do you position the nodes in order to have sufficient
data for each of the following mechanisms?
a.
Prevention
of disaster risks
b.
Recovery
from disasters
c.
Adaptation
to different disaster scenarios
2.
If
a fraction of the nodes are broken during a disaster, what node data sampling
process would lead to an accurate assessment of the desired mechanisms ?
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