MANAGING DISASTER WITH WIRELESS SENSOR NETWORKS INTRODUCTION A wireless sensor network (WSN) is a group of low cost ,low power, multifunctional and small size wireless sensor nodes that cooperate together to sense the environment, process the data and communicate wirelessly over a short distance . The sensors are commonly used to monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at areas of interest. Some of these sensor nodes are able to move on their own, this is achieved by mounting the sensors on mobile platforms. The development of WSN was originally motivated by military application such as battlefield surveillance. However, WSN are now used in many industrial and civilian application areas, including industrial process monitoring and control, machine health monitoring, environment and habitat monitoring, disaster management, healthcare applications, home automation and traffic control. In this paper we will review the MUSALIAR COLLEGE OF ENGINEERING AND TECHNOLOGY 1
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MANAGING DISASTER WITH WIRELESS SENSOR NETWORKS
INTRODUCTION
A wireless sensor network (WSN) is a group of low cost ,low power,
multifunctional and small size wireless sensor nodes that cooperate together
to sense the environment, process the data and communicate wirelessly
over a short distance . The sensors are commonly used to monitor physical
or environmental conditions, such as temperature, sound, vibration,
pressure, motion or pollutants, at areas of interest. Some of these sensor
nodes are able to move on their own, this is achieved by mounting the
sensors on mobile platforms.
The development of WSN was originally motivated by military
application such as battlefield surveillance. However, WSN are now used in
many industrial and civilian application areas, including industrial process
monitoring and control, machine health monitoring, environment and
habitat monitoring, disaster management, healthcare applications, home
automation and traffic control. In this paper we will review the applicability
of WSN in improving and assisting disaster management operations.
. WSN has many possible applications that have not yet been
explored. WSN is a fast growing technology however much written about
WSN is still theory. ’How to deploy WSNs,’ although having much theory
written still currently lacks practical guide. Using our research experience
and the practical real life solutions found when deploying a WSN for the
applications this outlines the steps required when conducting a real world
deployment of a WSN .In the application for WSN most focused on is for
purpose of detecting natural disasters. WSN can be useful to disaster
management in two ways. Firstly, WSN has enabled a more convenient
early warning system and secondly, WSN provides a system able to learn
about the phenomena of natural disasters.
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Natural disasters are increasing worldwide due to the global
warming and climate change .The losses due to these disasters are
increasing in an alarming rate. Hence, it is would be beneficial to detect the
pre-cursors of these disasters, early warn the population, evacuate them,
and save their life. However, these disasters are largely unpredictable and
occur within very short spans of time. Therefore technology has to be
developed to capture relevant signals with minimum monitoring delay.
Wireless Sensors are one of the cutting edge technologies that can quickly
respond to rapid changes of data and send the sensed data to a data analysis
center in areas where cabling is inappropriate.WSN technology has the
capability of quick capturing, processing, and transmission of critical data
in real-time with high resolution. However, it has its own limitations such
as relatively low amounts of battery power and low memory availability
compared to many existing technologies .It does, though, have the
advantage of deploying sensors in hostile environments with a bare
minimum of maintenance. This fulfills a very important need for any real
time monitoring, especially in hazardous or remote scenarios.
EXISTING SYSTEM
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SATELLITE MONITORING
Satellites specifically designed to observe Earth from orbit, similar
to reconnaissance satellites but intended for non-military uses such as
environmental monitoring, meteorology, map making etc. Most Earth
observation satellites carry instruments that should be operated at a
relatively low altitude
There are two main disadvantages of satellite communication. The
first is cost. Developing, launching and maintaining a satellite is extremely
expensive. No further explanation of that is necessary. The second is the
time delay in responding. Communications satellites are typically
positioned so they rotate around the earth at the same rotation rate as the
earth. This is called 'geosynchronous' positioning. The geosynchronous
orbit is far from earth, so the time it takes for the signal to reach the satellite
and then bounce back to earth is about half a second. The delays can be
very annoying on voice calls, as people tend to talk over each other. The
delays are also problem with data exchange, as data response packets are
also delayed which limits the effective bandwidth of the channel. One way
broadcasts, like TV and Radio signals are perfect for satellites as no
response is required.
PROPOSED SYSTEM
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A wireless sensor network (WSN) is a group of low cost, low power,
multifunctional and small size wireless sensor nodes that cooperate together
to sense the environment, process the data and communicate wirelessly
over a short
distance . The sensors are commonly used to monitor physical or
environmental conditions, such as temperature, sound, vibration, pressure,
motion or pollutants, at areas of interest. Some of these sensor nodes are
able to move on their own, this is achieved by mounting the sensors on
mobile platforms.
The development of WSN was originally motivated by military
application such as battlefield surveillance. However, WSN are now used in
many industrial and civilian application areas, including industrial process
monitoring and control, machine health monitoring, environment and
habitat monitoring, disaster management, healthcare applications, home
automation and traffic control . In this paper we will review the
applicability of WSN in improving and assisting disaster management
operations.
I.NEED FOR DISASTER MANAGEMENT
Studies over the recent years have gathered evidences indicating that
the global climate is changing. The changes include the occurrence of
extreme climate phenomenon that may have disastrous consequences to us
human. The Intergovernmental Panel on Climate Change (IPCC) identified
a number of extreme climate phenomenon with high level of likelihood to
occur ;
i. Heat Waves
ii. Floods
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iii. Landslides
iv. Avalanche
v. Soil Erosion
vi. Tropical Cyclones
vii. Drought
viii. Storms.
The effects of the global climate change are clearly felt by many
around the globe. The extreme climates together with uncontrollable human
activities increase the frequencies of disastrous events which affect higher
numbers of people with increasing levels of life threatening damages. Thus
there is the need for more comprehensive regional and local risk reduction
strategies. Thus, it is important for authorities to ensure their risk reduction
strategies include effective prediction, detection, monitoring, alerting, and,
search and rescue systems. The National Security Council (NSC) had laid
out its total disaster risk management strategy into four parts;
i. prevention and mitigation,
ii. Preparedness – prediction and early warning system, awareness
iii. Response – search and rescue, relief, medical
iv. Recovery – analysis, rehabilitation, reconstruction.
The first two parts of the strategy are to be implemented before a
disaster occurs while the other two are implemented after a disaster
happens.
An efficient disaster prediction, monitoring and alerting system
could help the authorities and public to be better prepared to face an
incoming disaster thus reducing the lost of life and properties risks. Another
crucial aspect for reducing the amount of casualties is the search and rescue
operation. We believe that WSN can play an important role in enhancing
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these two aspects of disaster management. A number of studies had shown
the applicability of WSN for functions suitable for these kinds of systems.
A WSN used for disaster detection and alerting system could sense
for any significant changes in the environment and send an appropriate alert
signal, for example sensors sensing water level at a river bank and tilt
meters at a hill side could alert the authorities and public for possible flood
and landslide. In search and rescue application the deployed WSNs can the
disaster area and locate the victims via the numerous sensing modes. The
WSN can then provide the search and rescue teams with the identified
locations of the victims needing rescue. The WSN can also provide the
teams with crucial information such as the surrounding of the disaster site,
obstacles that they need to overcome and avoid, etc. Thus, the search and
rescue teams will be able to plan their operation with higher level of
precision, timeliness and safety for both the victims and their members.
II. DESIGN ISSUES
There are multiple issues to be considered when designing WSN for
disaster management. The first thing to be identified is the type of disaster
to be handled .Different situation called for different system design, for
example air quality monitoring requirement is not the same as search and
rescue operation.
Among the design issues are:
A) Deployment
Deployment is regarding on how the network is being installed.
WSN is typically deployed in two methods predeterministic or randomly. In
predeterministic deployment the location of the sensors is decided first
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before the sensor nodes are deployed. In this method other issues like the
degree of coverage and nodes connectivity are guaranteed. Random
deployment is simpler than the predeterministic deployment where the
sensor nodes are randomly scattered in the region of interest. It allows the
WSN to be deployed over hostile and unreachable environment, for
example the nodes can be dispersed from an unmanned air vehicle (UAV)
over a remote area for forest fire detection.
B) Coverage
In three types of coverage are discussed; blanket coverage, barrier
coverage and sweep coverage. This classification is borrowed from robotic
system. Blanket coverage aims to provide maximum detection rate in a
region of interest whereas for barrier coverage instead of providing
coverage throughout the region of interest the focus is now on ensuring that
the perimeter of the region of interest is fully covered. Both blanket and
barrier coverage can be achieve through static arrangement of the sensor.
For sweep coverage the objective is achieved by moving the sensor nodes
so that the region of interest is swept by the sensors sensing range. There
are other specifications of coverage, such as listed in; area coverage, barrier
coverage and point coverage. Area coverage is on how to cover an area
with the sensors, where the objective is to maximize the coverage
percentage. Coverage percentage is ratio of area covered by at least one
sensor to the total area of the region of interest. Coverage problem can also
be seen as a minimization problem .From the minimization point of view,
the objective is to make sure the total area of the coverage holes in the
network is as small as possible. Area coverage is similar to blanket
coverage. Point coverage is coverage for a set of points of interest.
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Basically this type of coverage is concern only on how to cover a set of
targets or hotspots in an area, instead of the whole area as in area coverage.
Area, blanket and sweep coverage are suitable for disaster management
applications. A disaster prone area can be thoroughly monitor using blanket
coverage whereas sweep coverage can be used for a more active sensing.
C) Connectivity
Each sensor node in a WSN senses for occurrences of event of
interest, this information need to be relayed to the base station. Therefore
connectivity of the sensors to their base station and also connectivity among
themselves is another important issue to be considered. Typically in WSN,
information is relayed to a base station using multi hop communication,
where the information is transmitted from a node to another node until the
information reaches the base station. However this approach needs a
connected network where at least a spanning tree exists to connect the
nodes to their base station. The problem with this kind of network is that
information would be lost if a link is broken, in addition to that in some
environments obstacle such as a very dense rainforest or other obstruction
will make it difficult to maintain connectivity. In a moving base station is
proposed. The mobile base station collects information by moving across
the monitored area.
D) Mobility
Sensor mobility is another aspect to be considered in designing a
WSN system. Mobility can be classified into two type; uncontrolled and
controlled mobility. For uncontrolled mobility the movement is either
caused by environmental influences such as wind and wave or the mobility
is due to the sensor is embedded to a moving subject. In controlled mobility
the sensor nodes are able to determined where and when to move
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themselves. Controlled mobility is an attractive feature as it allows the
sensors to self maintain the network, to harvest energy, to collect
information using mobile based stations and to compensate for lack of
sensors in providing enough coverage by constantly moving the sensors so
that the chance of target detection is improved . It could also help to allow
the WSN to provide sweep coverage thus minimizing number of missed
detection . On the other hand mobility usually will cause the sensor node to
be bigger and bulkier thus limiting the movement of sensors in narrow or
small spaces
.E) Type of sensors
The last issue to be considered here is the type of sensors to be used
on the sensor nodes. Among the sensors used for disaster management are;
motion detector sensor – sensing any sign of movement, camera – to obtain
visual information, tilt meter – for landslide monitoring, humidity sensor,
temperature sensor, ultrasonic sensors – for water measurement and etc.
Which type of sensors to be chosen is based on the targeted types of
disasters.
III.REQUIREMENT ANALYSIS
This section will describe in detail how to design a real-time
Wireless Sensor Network (WSN), and what are the
considerations/requirements that have to be analyzed for designing the
network for any scenario. The different processes that will contribute to a
WSN design are:
• Analysis of Scenario
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Wireless Sensor Networks (WSN) could be useful in a vast and
diverse amount of applications. The chosen target scenario must be
understood and investigated thoroughly in order to choose the most
appropriate sensors and network. A comprehensive analysis of the scenario
is one of the first steps to undertake when considering the design of the
system. The constraints found (from the analysis of the scenario) determine
and govern the overall size and type of network and sensors required.
Understanding the characteristics of a scenario allows logical links to be
made about how to detect the occurrence of land movement.
• Selection of Geophysical Sensors
The key geophysical sensors such as rain gauge, soil moisture
sensors, pore pressure transducers, strain gauges, tilt meters, and geophones
are identified for measuring the principal parameters. These sensors are
selected based on their relevance in finding the causative geological factors
for disaster. The details of the selected sensors are:
• Placement of Geophysical Sensors
All the chosen geophysical sensors are capable of real-time
monitoring with bare minimum maintenance. A DEP(Deep Earth Probe)
was devised to deploy these many sensors as a stack, attached to a vertical
pipe, in different locations of the landslide prone site. This generalized
design for the DEP, and the sensor placement procedures at the DEP has
been developed and implemented to simplify future deployments. This
design can be adapted for any landslide prone area and potentially for
placing sensors to detect other natural disasters, in other disaster prone
areas.
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• Wireless Sensor Network Requirements
Disaster detection requires wide area monitoring, and real-time,
continuous data collection, processing, and aggregation. Wireless Sensor
Networks (WSNs) are the key emerging technology that has the capability
to real-time, continuous data collection, processing, aggregation with
minimum maintenance. Any wide area monitoring must determine the:
– Maximum number of wireless sensor nodes,
– Maximum number of relay nodes,
– Maximum frequency of data collection from each node per minute,
– Maximum data rate required,
– Maximum power required for sampling, transmitting, processing, and
receiving,
– Maximum tolerance limit of delay,
– Maximum tolerance limit of data packet loss.
• Algorithm Requirements
Wide area monitoring requires efficient algorithm development for
data collection, processing, and transmission. The different criteria to be
analyzed for designing the algorithms are: the total area of deployment,
maximum and minimum transmission range, maximum number of sensor
nodes necessary, maximum number of sensor nodes available, maximum
amount of power available (in the battery), the corresponding transmission
range, data storage capability of each node, availability of constant power
source, maximum bandwidth availability, frequency of data collection and
transmission specific to the application scenario, and the data aggregation
method suitable for the application
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under consideration. Analysis of the above requirements contributes to the
development of required algorithms for designing the network topology,
data collection algorithm, data aggregation algorithm, data dissemination
method, energy optimized network, networks with maximum life time, time
synchronized network, localization techniques etc.
• Network Requirements
The design and development of the complete network architecture
requires the knowledge and understanding of relevant technologies such as