Application based Study on Wireless Sensor Network

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International Journal of Computer Applications (0975 – 8887)
Volume 21– No.8, May 2011
9
Application based Study on Wireless Sensor Network
Kiran Maraiya
Department of Computer
Science and Engineering
National Institute of
Technology Hamirpur,
Hamirpur (H.P.) INDIA
Kamal Kant
Department of Computer
Science and Engineering
ASET, Amity University,
Noida (U.P), India
Nitin Gupta
Department of Computer
Science and Engineering
National Institute of
Technology Hamirpur,
Hamirpur (H.P.) INDIA
ABSTRACT
A wireless sensor network is type of wireless network. Basically
it consist a collection of tiny device are called sensor node,
sensor node has a resource constraint means battery power,
storage and communication capability. These sensor nodes are
set with radio interface with which they communicated with one
another to form a network. Wireless sensor network has very
necessary application like remote has remote environmental
monitoring and target tracking. The goal of our survey is to
present a comprehensive review of the recent literature on
various aspects of WSNs.And also discuss how wireless sensor
network works and advantages and disadvantages over the
traditional network
Keywords
Sensor network, layers, application, traditional network
1. INTRODUCTION
This wireless sensor networks is depends on a simple equation:
Sensing + CPU + Radio = Thousands of possible applications. A
wireless sensor network is type of wireless network. It is small
and infrastructure less .basically wireless sensor network consist
a number of sensor node, called tiny device and these are
working together to detect a region to take data about the
environment. Wireless sensor network has two types: structured
and unstructured. if we talk about unstructured so is a collection
of sensor nodes. And these deployed in adhoc manner into a
region. Once deployed, the network is absent unattended
perform monitoring and reporting functions. In other structured
wireless sensor network, the all sensor nodes are deployed in pre
designed manner. The benefit of structure wireless sensor
network is that some nodes can be deployed with lower network
maintenance and management cost. Fewer nodes can be
deployed now since nodes are placed at specific locations to
provide coverage while ad hoc deployment can have uncovered
regions. Wireless sensor network aim is to provide efficient
connection among the physical environmental condition and
internet worlds. The sensor nodes of the wireless sensor
network is allows random deployment in inaccessible terrains,
this means protocol of the wireless sensor is self organized,
another important feature of the wireless sensor network is
cooperative effort of the sensor nodes. Sensor nodes are
collecting data about environment, after collecting it they
process it and then transmit to the base station. Base station
provides a interface between user and internet. Basic
characteristic of the wireless sensor network are limited energy,
dynamic network topology, lower power, node failure and
mobility of the nodes, short-range broadcast communication and
multi-hop routing and large scale of deployment. In the wireless
sensor network architecture includes both a hardware platform
and an operating system designed. TinyOS is a component based
operating system designed to run in resource constrained
wireless devices. It provides highly well-organized
communication primitives and fine grained concurrency
mechanisms to application and protocol developers. Basically
TinyOS is the use of event based programming in conjunction
with a highly efficient component model. TinyOS enables
system-wide optimization by providing a tight coupling among
hardware and software. TinyOS has been designed to run on a
generalized architecture where a single CPU is shared between
application and protocol processing. Figure 1 show the basic
architecture of the wireless sensor network in which sensor node
deployed in the sensor fields and they communicate with each
other for collect the information from the environment, or
directly send to the base station basically base station act as a
gateway. With the help of gateway data is transmitting to the
internet. Because user is directly connect to the internet.
Figure 1 Architecture of the Wireless Sensor network
2. TYPES OF SENSOR NETWORKS
Wireless sensor networks are deployed on land ,underground,
and underwater. A sensor network faces different challenges and
constraints according to the environment in the sensor network
deployed. There are five types of the wireless sensor network as
discussed by Jennifer et at.[4].
1. Terrestrial Wireless sensor network.
2. Underground Wireless sensor network.
3. Underwater Wireless sensor network.
4. Multi-media Wireless sensor network.
5. Mobile Wireless sensor network.
Terrestrial WSNs [1] typically consist of hundreds to thousands
of inexpensive sensor nodes deployed in a given region, either in
BS
Target
Internet
User
Sensor node
Sensor field

International Journal of Computer Applications (0975 – 8887)
Volume 21– No.8, May 2011
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an ad hoc or in a pre-planned manner. In ad hoc deployment,
sensor nodes can be dropped from a plane and randomly placed
into the target area. In pre-planned deployment, there is grid
placement, optimal placement, 2-d and 3-d placement models. In
a terrestrial WSN, reliable communication in a dense
environment is very essential. Sensor nodes must be able to
successfully communicate with the base station in terrestrial
WSN, while battery power is a limited. In any case, it is
essential for sensor nodes to conserve energy. Energy of sensor
nodes can be conserved with multi-hop optimal routing, short
transmission range, in-network data aggregation, reducing data
redundancy, minimizing delay and using low duty-cycle
operations in terrestrial WSN.Underground WSNs in which
sensor node covered underground, basically it used for detect
used to monitor underground situation. And sink node are used
for transmit information to the sensor node to the base station.
This wireless senor network is more costly as compare to
terrestrial WSN in terms of equipment, deployment, and
maintenance. Underground sensor nodes are expensive because
proper components must be used for reliable communication
through soil, rocks, water, and other mineral contents. The
underground environment makes wireless communication a
challenge due to signal losses and high levels of attenuation. An
underground WSN requires careful planning energy and cost
considerations during deployment to increase network lifetime.
Underwater WSNs consist of a number of sensor nodes and
vehicles deployed underwater. Unlike terrestrial WSNs,
underwater sensor nodes are more costly and less dense.
independent underwater vehicles are used for searching or
gathering data from sensor nodes. Sensor nodes communicate
via acoustic waves in underwater WSN. Acoustic
communication is a challenge in underwater due to limited
bandwidth, long propagation delay, and signal fading problem.
Underwater WSNs consist of a number of sensor nodes and
vehicles deployed underwater. Unlike terrestrial WSNs,
underwater sensor nodes are more costly and less dense.
independent underwater vehicles are used for searching or
gathering data from sensor nodes. Sensor nodes communicate
via acoustic waves in underwater WSN. Acoustic
communication is a challenge in underwater due to limited
bandwidth, long propagation delay, and signals fading problem.
And also node failure. Sensor node in wireless sensor network
has a capability to take a harsh ocean environment condition.
Sensor node have limited battery power which cannot be
recharges and replace. For energy conservation, underwater
WSNs involve developing efficient underwater communication
and networking techniques. Multi-media WSNs are used to
monitoring and tracking of events in the form of multimedia.
Multi-media WSNs consist of a number of low cost sensor
nodes equipped with cameras and microphones. These sensor
nodes communicate with each other for data retrieval, process,
correlation, and compression over a wireless connection. Multi-
media sensor nodes are deployed in a pre-planned manner into
the atmosphere for coverage guarantee. High bandwidth
demand, high energy consumption, quality of service (QoS)
condition, data processing and compressing techniques and
cross-layer design are challenges in multi-media WSNs. Multi-
media content such as video stream needs high bandwidth in
order to content to be delivered. Therefore, energy consumption
is high for high data rate. High bandwidth and low energy
consumption transmission techniques have to be developed. QoS
is difficult to preserve in a multi-media WSNs due to variable
delay and variable channel capacity. It is essential to get a
certain level of QoS for reliable content delivery. In-network
processing, filtering, and compression of contents can
significantly improve network performance by filtering and
extracting redundant information and merging contents.
Similarly, cross-layer interaction between the layers can
improve the processing and the delivery process. Mobile WSNs
is a collection of sensor nodes that can move on their own and
interact with the physical environment. Mobile nodes have the
ability of sensing, computing, and communication like static
nodes. A key difference is mobile nodes have the ability to
change the position and organize itself in the network. A mobile
WSNs can start with some initial deployment and nodes can
then spread out to gather information. A mobile node can
communicate to another mobile node when they are within the
range of each other and transfer gathered information. Another
key difference is data distribution. In mobile WSNs, data can be
distributed using dynamic routing while fixed routing or
flooding is used in static WSNs. Sensor nodes deployment,
localization, self-organization, navigation and control, coverage,
energy, maintenance, and data process are challenges in mobile
WSNs. Mobile WSNs applications include environment
monitoring, target tracking, search and rescue, and real-time
monitoring of hazardous material etc. Mobile sensor nodes can
achieve a higher degree of coverage and connectivity compared
to static sensor nodes.
3. HOW WIRELESS SENSOR
NETWORKS WORKS
Wireless sensor networks is collection of the small tiny device
called sensor nodes. It may be small and large. That’s why
construct the wireless sensor network is based on sensor nodes.
So entire working of sensor network is depending on sensor
nodes. These nodes are varying in size and totally depend on this
because different sizes of sensor nodes work efficiently in
different fields. Wireless sensor networking have such sensor
nodes which are especially designed in such a typical way that
they have a microcontroller which controls the monitoring, a
radio transceiver for generating radio waves, different type of
wireless communicating devices and also ready with an energy
source like battery. The entire network worked simultaneously
by using different dimensions of sensors and worked on the
phenomenon of multi routing algorithm which is also termed as
wireless ad hoc networking.
4. WIRELESS SENSOR NODE
ARCHITECTURE
For better understanding of sensor network it is important to
know about all the components of sensor node. Common sensor
node architecture is shown in Figure2. The architecture of a
generic wireless sensor node consists of four subsystems [5]. A
computing subsystem consisting of a microprocessor, ALU and
memory, a communication subsystem consisting of a short range
radio for wireless communication, sensing subsystem that links
the node to the physical world and consists of a group of sensors
and actuators, and a power supply subsystem, which houses the
battery and the (optional) DC-DC converter, and powers the rest
of the node. Each subsystem plays an main role in the sensor
node.

International Journal of Computer Applications (0975 – 8887)
Volume 21– No.8, May 2011
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Figure 2 Sensor Node System
Radio: It enables wireless communication among sensor nodes
and outside world. It consists of a short range radio which
usually has a single channel, a low data rate and operates at
unlicensed bands of near 2.4 GHz (global). For efficient energy
consumption, it operates in four different modes: Transmit
Receive, Idle and Standby modes. In case of most radios, it is
observed that when radio operates in Idle mode it consumes
energy almost equal to power consumed in Receive mode [6].
Thus, when it is not transmitting or receiving it is vital to
completely shut down the radio rather than keep it in the Idle
mode to save precious energy. Another influencing factor is that,
when radio changes its operating mode, radio electronics causes
a significant amount of power dissipation in this transient
activity.
Microprocessor: It provides intelligence to the sensor node.
The microprocessor controls the sensors, executes
communication protocols and signal processing algorithms on
the gathered sensor data [7]. To conserve energy,
microprocessor works in four different modes: off, sleep, idle,
and active. In sleep mode, the CPU and most internal peripherals
are turned off, and can only be activated by an external event
(interrupt). In idle mode, the CPU is still inactive, but other
peripherals are active, for example, the internal clock or timer.
In the active mode, multiple sub modes may be defined based on
clock speeds and voltages. Within the active states, the CPU and
all peripherals are active.
Sensor: It translates physical phenomena to electrical signals.
There exists a variety of sensors that measure environmental
parameters such as temperature, light intensity, temperature,
magnetic fields, sound, image, etc. Due to the diversity of
sensors, there is no standard power consumption figure. For a
simple sensor we assume that only the states on and off are
given, and that the energy consumption within both states can be
measured by time. However, more powerful sensors operate in
different states, comparable to the microprocessor. To reduce
energy consumption low power components can be used at the
cost of performance which is not required.
Battery: The battery is an important component in sensor node.
It supplies power to all component of sensor node. Therefore,
sensor nodes lifetime totally depends on battery and network’s
lifetime depends on lifetime of sensor nodes. The amount of
power drained from a battery should be checked. Since Sensor
nodes are usually small, light and cheap and the size of the
battery is limited. (Advancement in Battery technologies much
more slower than semiconductor technologies. For example, the
energy densities of Li-ion batteries only increased 50% from
1994 to 1999. While in the same period of time, the number of
transistors of Intel processors doubles every 24 months.). Sensor
nodes are deployed in unattended environment where battery
replacement is not possible in network which consists of
thousands of nodes. Hence, energy consumption is vital factor to
prolong sensor nodes lifetime.
5. SPECIAL FEATURES OF WIRELESS
SENSOR NETWORKs
This section discusses some unique features of WSNs, which
need to be taken into account when designing management
architectures in WSNs
5.1 Different types of nodes
In the wireless sensor network are three types of sensor nodes:
the normal nodes is reponsile for collecting information or
sensor data. Sensor nodes have resource constraint. That’s why
sensor node have not storing capability for storing large amount
of information or sensor data. It may take simply data
processing if necessary; sink nodes responsible for receiving,
storing, and processing (e.g. aggregation) data from normal
nodes; and gateway nodes that connect sink nodes to external
entities called observers. In addition, actuators can also be
introduced to control or actuate on a monitored region in
Wireless sensor networks.
5.2 Application-Specific
Wireless Sensor Networks are closely application-dependent.
The constrained resources (e.g. processing, storage and
transmission range) limit sensor nodes in WSNs to contain a
wide variety of applications as the traditional network does. The
designs of applications and management architectures in WSNs
are also dependent on application semantics. As a result,
application designers have to develop various complex and
special program to execute node localization, data routing and
data aggregation tailored to specific sensor applications. Thus, it
is not likely that those programs can carry over directly from
one application to another, since the application-specific
requirements on WSNs are varied in terms of resource usage and
communication patterns. Recent WSN research has focused
increasingly on the solutions that can hold the diversity of
various sensor applications by integrating the application
knowledge with management architectures in WSNs.
5.3 Resource Constrains
Resource-constrains of sensor nodes is another unique feature of
WSNs. Sensor nodes usually compose of four basic units as in
Figure 2: a sensing unit, a processing unit, a transceiver unit, and
a power unit. The power unit supports all the activities on a
sensor node, including communication, local data processing,
sensing, etc. The lifetime of a sensor node is mainly determined
by the power supply since battery replacement is not an option
in sensor networks, especially in dangerous environments as
Battery
DC-DC
Radio
Communication
Processin
g Unit
ADC
MCU
Memory
Sensing
Sensors
Protocol
s
OS
Filtering & Data
aggregation
Power Supply

International Journal of Computer Applications (0975 – 8887)
Volume 21– No.8, May 2011
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battlefields or environment monitoring. The longer the lifetime
of a sensor, the more stable the WSN. In order to save power,
redundant activities should be reduced if not eliminated.
5.4 Network Topology
Network Topology represents the actual topology map and the
achieve ability of sensor nodes in the network. Note that the
topology in WSNs may be dynamic due to the nodes changes.
For example, nodes may fail (either from lack of energy or from
physical destruction), and new nodes may join the network.
Therefore, the network must be able to reconfigure itself
periodically.
5.5 Fault Tolerance
Failures are prone to happen in WSNs, which normally include
sensor nodes failure, and communication failures etc. Although
the sensor application may have already measured this in their
design, there is still a need for WSN to have the ability to
reconfigure and recover itself without too much human being
intervene, especially in inaccessible environment condition.
6. PROTOCOL STACK FOR WIRELESS
SENSOR NETWORK
The sensor network protocol stack is much like the traditional
protocol stack, with the following layers: Physical, Data Link,
Network, Transport, and Application as discussed by Elizabeth
[8] and shown in Figure 3. The WSN must also be aware of the
following management planes in order to function efficiently:
Power, Mobility, and Task Management Planes. The Power
Management Plane is responsible for minimizing power
consumption and may turn off functionality to preserve energy.
Mobility plane manages the movement of sensor nodes and
maintains a data route to the sink. The task plane manages the
sensing task assigned to sensor nodes so only those nodes which
are necessary, are assigned sensing task and other node can
focus their energy resource on routing and data aggregation.
Physical Layer: Physical Layer is responsible for frequency
selection, carrier frequency generation, signal detection,
modulation, and encryption. The main work of this layer is to
minimization of energy The minimum output power required to
transmit over a distance d is proportional to d to a power of n,
where n varies from 2 to 4 and is closer to four when the
antennae are near the ground as is typical in WSNs. This is due
to ground-reflected rays, which causes partial signal
cancellation. This problem is overcome by multi-hop
communication and high node density.
Data Link Layer: The Data Link is responsible for the
multiplexing of data streams, data frame detection, medium
access and error control. A WSN must have a specific Medium
Access Control (MAC) protocol to address the issues of power
conservation and data-centric routing. The MAC protocol must
meet two goals. The first is to create a network infrastructure,
which includes establishing communication links among nodes,
and providing the self-organizing capabilities to the network.
The second goal is to efficiently share communication resources
(frequency) among all the nodes. Traditional MAC protocols fail
to meet these two goals because power conservation is only a
secondary concern in their development. Also, WSNs are
controlled centrally and a much larger number of nodes than
traditional ad-hoc networks. Any MAC layer protocol for WSNs
must overcome the problem of changing topology of the sensor
network due to node failure and redeployment.
Network Layer: The network layer is to provide
internetworking with external networks like other sensor
networks, In one scenario, the sink nodes can be used as a
gateway to other networks. The network layer in a WSN must be
designed with the following considerations in mind: Power
efficiency, WSNs are data-centric networks WSNs have
attribute-based addressing and Sensor nodes are location aware.
The Link layer handles how two nodes talk to each other, the
network layer is responsible for deciding which node to talk to.
Transport Layer: The transport layer comes into play when the
system needs to communicate with the outside world.
Transmitting data from sink to outside user is a problem because
WSNs do not use global identification and attribute based
naming is used for sending the data. Very little research has
been done at the transport layer.
Application Layer: At the application layer, a Sensor
Management Protocol (SMP), SMP is used to make the
hardware and software of lower layers transparent to the sensor
network management applications. The programmers and
system administrators interact with the sensor network using
SMP. Again at application layer the lack of global ids and
infrastructure less nature of sensor networks must be taken into
account. SMP provides the rules for the following to enable
interaction between applications and sensor networks: Data
aggregation, attribute-based naming, and clustering ,Time
synchronization, Moving sensor nodes, Exchange data related to
the location finding algorithms, Authentication, key distribution,
and security, Turning nodes on or off, Querying WSN
configuration status, reconfiguring the WSN. Different
considerations must be taken when developing protocols for
WSNs. Traditional thinking where main focus is on quality of
service must be reversed. In WSNs quality of service must be
compromised to conserve energy and preserve network lifetime.
The thought process must focus on the functionality of the entire
network rather than what is best for each individual node.
Concern must be taken at every level of the protocol stack to
conserve energy, allow nodes to reconfigure the network, and
modify their set of tasks according to the resources available.
6. WIRELESS SENSOR NETWORK
APPLICATIONS
Wireless sensor network has a lots of applications like security,
monitoring, biomedical research, tracking etc.basically these
application are used emergency services. The applications of the
Figure 3 Protocol stack for WSNs
Application
Presentation
Session
Data link
Network
Transport
Physical
Transport
Physical
Data link
Network
Application
Energy, Task, Mobility
Management Plane

International Journal of Computer Applications (0975 – 8887)
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sensor network are categorized into various classes such as
Environmental data collection, Military applications, Security
monitoring, sensor node tracking, health application, home
application, and hybrid networks.
1. Environmental Data Collection
In environmental data collection application, are used collect
various sensor data in a period of time. If a data to be
meaningful so collecting sensor data at regular interval and the
nodes would remain at known locations. In the environmental
data collection application, a large number of nodes
continuously sensing and transmitting data back to a set of base
stations that store the data using traditional methods. In typical
usage scenario, the nodes will be evenly distributed over an
outdoor environment. In environmental monitoring applications
, it is not essential that the nodes develop the optimal routing
strategies on their own. Instead, it may be possible to calculate
the optimal routing topology outside of the network and then
communicate the necessary sensor data to the nodes as required.
This is possible because the physical topology of the network is
relatively constant. While the time variant nature of RF
communication may cause connectivity between two nodes to be
intermittent, the overall topology of the network will be
relatively stable.
2.Military Applications
Most of the elemental knowledge of sensor networks is basic on
the defence application at the beginning, especially two
important programs the Distributed Sensor Networks (DSN) and
the Sensor Information Technology form the Defence Advanced
Research Project Agency (DARPA), sensor networks are
applied very successfully in the military sensing. Now wireless
sensor networks can be an integral part of military command,
control, communications, computing, intelligence, surveillance,
reconnaissance and targeting systems. In the battlefield context,
rapid deployment, self-organization, fault tolerance security of
the network should be required. The sensor devices or nodes
should provide following services: like Monitoring friendly
forces, equipment and ammunition, Battlefield surveillance,
Reconnaissance of opposing forces, Targeting, Battle damage
assessment Nuclear, biological and chemical attack detection
reconnaissance.
3.Security Monitoring
Security monitoring networks are collected of nodes that are
placed at fixed locations throughout an environment that
continually monitor one or more sensors to detect an anomaly. A
key difference between security monitoring and environmental
monitoring is that security networks are not actually collecting
any data. This has a significant impact on the optimal network
architecture. Each node has to frequently check the status of its
sensors but it only has to transmit a data report when there is a
security violation. The immediate and reliable communication of
alarm messages is the primary system requirement. These are
“report by exception” networks. It is confirmed that each node is
still present and functioning. If a node were to be disabled or
fail, it would represent a security violation that should be
reported. For security monitoring applications, the network must
be configured so that nodes are responsible for confirming the
status of each other. One approach is to have each node be
assigned to peer that will report if a node is not functioning. The
optimal topology of a security monitoring network will look
quite different from that of a data collection network. In a
collection tree, each node must transmit the data of all of its
decedents. The accepted norm for security systems today is that
each sensor should be checked approximately once per hour.
Combined with the ability to evenly distribute the load of
checking nodes, the energy cost of performing this check
becomes minimal. A majority of the energy consumption in a
security network is spent on meeting the strict latency
requirements associated with the signaling the alarm when a
security violation occurs. In security networks, a vast majority
of the energy will be spend on confirming the functionality of
neighboring nodes and in being prepared to instantly forward
alarm announcements. Actual data transmission will consume a
small fraction of the network energy.
4. Node tracking scenarios
In which wireless sensor network is the tracking of a tagged
object through a area of space monitored by a sensor network.
There are many condition where one would like to track the
location of important assets or personnel. Current inventory
control systems attempt to track objects by recording the last
checkpoint that an object passed through. However, with these
systems it is not possible to determine the current location of an
object. For example, UPS tracks every shipment by scanning it
with a barcode whenever it passes through routing centers. The
system breaks down when objects do not flow from checkpoint
to checkpoint. In typical work environments it is impractical to
expect objects to be continuously passed through checkpoints.
With wireless sensor networks, objects can be tracked by simply
tagging them with a small sensor node. The sensor node will be
tracked as it moves through a field of sensor nodes that are
deployed in the environment at known locations. Instead of
sensing environmental data, these nodes will be deployed to
sense the RF messages of the nodes attached to various objects.
The nodes can be used as active tags that announce the presence
of a device. A database can be used to record the location of
tracked objects relative to the set of nodes at known locations.
With this system, it becomes possible to ask where an object is
currently, not simply where it was last scanned . Unlike sensing
or security networks, node tracking applications will continually
have topology changes as nodes move through the network.
While the connectivity between the nodes at fixed locations will
remain relatively stable, the connectivity to mobile nodes will be
continually changing.
5. Health Applications
Sensor networks are also widely used in health care area. In
some modern hospital sensor networks are constructed to
monitor patient physiological data, to control the drug
administration track and monitor patients and doctors and inside
a hospital. In spring 2004 some hospital in Taiwan even use
RFID basic of above named applications to get the situation at
first hand. Long-term nursing home [9]: this application is focus
on nursing of old people. In the town farm cameras, pressure
sensors, orientation sensors and sensors for detection of muscle
activity construct a complex network. They support fall
detection, unconsciousness detection, vital sign monitoring and
dietary/exercise monitoring. These applications reduce
personnel cost and rapid the reaction of emergence situation.

International Journal of Computer Applications (0975 – 8887)
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6. Home Application
Along with developing commercial application of sensor
network it is no so hard to image that Home application will step
into our normal life in the future. Many concepts are already
designed by researcher and architects, like “Smart Environment:
Some are even realized. Let’s see the concept “the intelligent
home”:After one day hard work you come back home. At the
front door the sensor detects you are opening the door, then it
will tell the electric kettle to boil some water and the air
condition to be turned on. You sit in the sofa lazily. The light on
the table and is automatically on because the pressure sensor
under the cushion has detected your weight. The TV is also on.
One sensor has monitored that you are sitting in front of it. “I’m
simply roasting. The summer time in Asia is really painful.”
You think and turn down the temperature of the air condition. At
the sometime five sensors in every corner in the room are
measuring the temperature. Originally there is also sensor in the
air condition. But it can only get the temperature at the edge of
the machine not the real temperature in the room. So the sensors
in the room will be detecting the environment. The air condition
will turn to sleep mode until all the sensors get the right
temperature. The light on the corridor, in the washing groom and
balcony are all installed with sensor and they can be turned on or
turn out automatically. Even the widows are also attached with
vibratory sensors connected to police to against thief. How nice!
You become nurse and bodyguard at the same time.
7. WIRELESS SENSOR NETWORK
CHALLENGES
WSN is an emerging area. It offers wide variety of applications
and these applications can be implement in real world. To
implement them more efficient protocols and algorithms are
needed. Design a new protocol or algorithm addresses
challenges of this field. To design a better protocol or algorithm,
it is necessary to first clearly understood challenges [9]. These
challenges are summarized below.
Physical Resource Constraints: The most important constraint
in sensor network is the limited battery power of sensor nodes.
Sensor nodes are left in unattended environment where recharge
and replacement of battery is not possible. Sensor node’s
lifetime dependents on battery power. Thus effective lifetime of
sensor network is directly dependent on battery. Hence the
energy consumption is main design issue of a protocol. Limited
computational power and memory size is another constraint due
to that individual sensor node can store and process less amount
of data. So the protocol should be simple and light-weighted.
Limited bandwidth is also a constraint due to this
communication delay can be high.
Ad-hoc Deployment: Sensor nodes are randomly deployed in
required monitoring field without any infrastructure. For an
example, for fire detection in a forest the nodes are typically
dropped in to the forest from a plane. Sensor nodes itself create
connections with other nodes and form an infrastructure. Hence
new protocol or algorithm should be able to handle this ad-hoc
deployment.
Fault-Tolerance: Sensor nodes are prone to failure because of
unattended environment. A sensor node may fail due to
hardware or software problem or energy exhaustion. If few of
sensor nodes fail, working protocol should handle all type of
failures to maintain connectivity and prolong lifetime of
network. For example, routing or aggregation protocol, must
find suitable paths or aggregation point in case of these kinds of
failures.
Scalability: In monitoring field, number of sensor nodes
deployed could be in order of hundreds, thousands or even more.
It depends upon the application. It may possible that initially
deployed sensor nodes are not enough to monitor the
environment. In this situation, protocol that is working upon
network should be scalable and able to accommodate large
number of sensor nodes.
Quality of Service: Some applications like multi-media or time
critical needs QoS. Multi-media application requires enough
good quality of contents (video, audio and image). In time
critical application, the data should be delivered within a certain
period of time from the moment it is sensed; otherwise the data
will be useless. New protocols which are designed for such
applications should handle QoS.
Security: In sensor networks, security is another important and
challenging parameter. An effective and efficient compromise
should be achieved, between security demands for secure
communication and low bandwidth required for communication
in sensor network. Whereas in traditional networks, the focus is
on maximizing channel throughput with secure transmission.
8. WIRELESS SENSOR NETWORKS VS
TRADITIONAL WIRELESS NETWORKS
There are many existing protocols, techniques and concepts
from traditional wireless network, such as mobile ad-hoc
network, cellular network, wireless local area network and
Bluetooth, that are applicable and still used in WSN, but there
are lot of fundamental differences which initiate the need of new
techniques and protocols [12]. Some of the most important
characteristic differences are summarized below: In WSNs,
number of nodes is much higher than any traditional wireless
network. Depending on the application, nodes may be in order
of even millions. Thus, it requires an extremely scalable solution
to make sure sensor network operations without any
interruption. WSNs have large number of sensor nodes due to
this addresses are not assigned to them. Instead of address-
centric sensor networks are data-centric. Operations of sensor
networks are concentrated on data instead of individual sensor
node. Thus, sensor nodes need collaborative efforts. Most of
traditional wireless networks use point-to-point
communications, whereas sensor networks use broadcast
communications. Sensor nodes are much cheaper than nodes in
ad hoc networks. WSNs are event-driven or environment-driven.
Sensor networks generate or collect data when any event occurs
or environment changes, while human generates data in
traditional networks. Hence, traffic pattern changes significantly
from time to time. Mobile ad hoc Networks (MANETs) are
designed for distributed computing, while sensor networks are
mostly used to gather information. Data collected by
neighboring sensor nodes is highly correlated. It has also been
observed that the environmental quantities changes very slowly
and some consecutive readings, sensed by sensor nodes are
correlated. It is a unique characteristic of sensor network, which
gives an opportunity to develop energy efficient protocols for
routing and aggregation. These protocols reduce traffic and
redundant data in network and prolong network lifetime. Thus,

International Journal of Computer Applications (0975 – 8887)
Volume 21– No.8, May 2011
15
main focus of sensor network is to extend network lifetime,
where traditional network try to maximizing throughput of a
channel or minimizing node deployment in network.
9. THIS NETWORK HAS CERTAIN
ADVANTAGES ALSO OVER THE
TRADITIONAL NETWORKS
Advantages: The configuration of the wireless sensor network
is nearly zero. Sensor nodes of the wireless sensor network have
low cost as compared to GPRS modems. if we talk about energy
so in which minimum energy consumption as compared to
traditional network and the coverage area is easy to expansion
and reduction. Disadvantages: Wireless sensor network has
lower speed as compared to wired network. It is a less secure
because hacker’s laptop can act as access point. If you
connected to their laptop, they'll read all your information.
Affected by surrounding. Such as walls (blocking), microwave
oven (interference), far distance (attenuation).
10. CONCLUSION
Wireless sensor network is very important wireless network
because it able to monitor the physical and environment
condition, where traditional network is not monitors it. In this
paper we discuss overview of the wireless sensor network, how
differ from the tradition network, and challenges, features,
protocol stack of the sensor network. But wireless sensor
networking has a bright future in the field of computer
networking because we can solve the monitoring problems at an
advanced level in the future with the help of such technology of
networking.
10.1. Acknowledgments
This work was supported in part by a grant from NIT Hamirpur
(himachal Pradesh).
11. REFERENCES
[1] I. Akyildiz, W. Su, Y. Sankarasubramaniam, and E. Cayirci,
“A Survey On Sensor Networks”, IEEE Communications
Magazine, Volume 40, Number 8, pp.102-114, 2002.
[2] Deborah Estrin, R.G., John Heidemann, Satish Kumar. Next
Century Challenges: Scalable Coordination in Sensor
Networks. In ACM/IEEE International Conference on
Mobile Computing and networking. 1999.
[3] Eiko Yoneki, J.B., A Survey of Wireless Sensor Network
Technologies: Research Trends and Middleware'S Role.
2005, University of Cambridge: Cambridge. p. 45.
[4] Jennifer Yick, Biswanath Mukherjee, Dipak Ghosal,
“Wireless sensor network survey,” Computer Networks
Elsevier 52 (2008) 2292–2330.
[5] I.F. Akyildiz, E.P. Stuntebeck, Wireless underground sensor
networks: research challenges, Ad-Hoc Networks 4 (2006)
669–686.
[6] J. Feng, F. Koushanfar, M. Potkonjak,"System-
Architectures for Sensor Networks Issues, Alternatives, and
Directions", IEEE International Conf on Computer Design
(ICCD), Germany, 2002. pp. 226- 231.
[7] D. Culler, D. Estrin, M. Srivastava, "Overview of Sensor
Networks", IEEE Computer, USA, vol 37, pp. 41-49,
August 2004.
[8] A. M. Bratkovski, "Monitoring an environment using RFID
assembly." vol. WO/2006/094085, W. I. P. Organization,
Ed. USA: HEWLETT-PACKARD Development Company,
L. P., 2006, p. 13
[9] I.F. Akyildiz, W. Su, A power aware enhanced routing
(PAER) protocol for sensor networks, Georgia Tech
Technical Report, January 2002, submitted for publication.
[10] P. Bonnet, J. Gehrke, P. Seshadri, Querying the physical
world, IEEE Personal Communications (October 2000) 10–
15.
[11] A. Cerpa, J. Elson, M. Hamilton, J. Zhao, Habitat
monitoring: application driver for wireless communications
technology, ACM SIGCOMM’2000, Costa Rica, April
2001.
[12] R. K. Ghosh , Vijay Garg , M. S. Meitei , S. Raman , A.
Kumar and N. Tewari, “Dense cluster gateway based
routing protocol for multi-hop mobile ad hoc networks,” Ad
Hoc Networks, Vol. 4, No. 2, p.168-185, March, 2006 .