Deployment in Wireless Sensor Networks

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ISSN: 2278


909X

International Journal of Advanced Research in Electronics and Communication Engineering (IJARECE)

Volume 2, Issue 2, February 2013


A
ll Rights Reserved © 2013 IJARECE

108


Deployment in
Wir
eless Sensor Networks

Laki,

Shri

R.N. Shukla





Abstrac
t
:

Recent
year’s

research has opened
challenging and advantageous issues in wireless
sensor networks.
A wireless sensor network
(WSN) consists of spatially distributed
autonomous

sensors to cooperatively monitor the
environment

and to pass their data through the
network to a main location.

The WSN is built of
"nodes"


from a few to several hundreds or even
thousands, where each node is connected to one
(or sometimes several) sens
ors.
This

paper
includes the placement of nod
es in wireless sensor
networks. We

also discuss the topology,
connectivity and matrices
.

Keywords:

coverage, connectivity, mobility based
communication, wireless sensor networks


I.
Introduction



Deployment of
a sensor network in a target area can
be a continuous process, for example to replace
nodes that have been destroyed due to environmental
influence. Deployment establishes an association of
sensor nodes with objects, creatures, or places in
order to augmen
t them with information
-
processing
capabilities. Once
a sufficient number of nodes have

been deployed, the sensor network can be used to
fulfil its task. This task can be issued by an external
entity connected to the sensor network, such as a user
with a P
DA, an aircraft flying by, or some device on
the Internet. In hybrid architectures, the sensing
results Control the sensors to trigger more detailed
monitoring of acertain phenomenon, which is then
repor
ted to the external task issuer.

The network must
be
deployed keeping in mind two main objectives:
coverage

and connectivity.

Coverage

belongs to

the application
-
specific quality
of

information
obtained from the environment by the
networked sensor devices.

Connectivity

pertains to the network topology over
w
hich information routing

can take place.

Other issues, such as equipment costs, energy
limitations, and

the need for robustness, should also
be taken into account
. A wireless sensor network
(WSN) design included many factors such as
transmission errors, n
etwork topology and power

consumption. Developing a

WSN application
introduces several implementation challenges. This
paper describes one of the most fundamental issue
s

in
WSN designing


the deployment
problem. In

the
given fig
.
left is localization


it
s aim is to locate
where the nodes are placed. On the right is
deployment (placement)


its aim is to determine
where the nodes should be placed. In the vast
majority of deployment problems the coverage is

considered, but this is not necessary and depends
on
the application.


















W
e concentrate on optimal node placement. This is
one of the most important design step
s

to selectively
decide the loca
tions of the sensors to optimize the
desirable objectives, e.g., maximize the covered area
or minimize the

energy use. Fundamental questions
in
this:

• How many sensor nodes are needed to meet the
over
-
all system objectives?

• For a given network with a ce
rtain number of
sensor nodes, how do we precisely deploy these
nodes in order to optimize network performance?

• When data sources change or some part of the net
-

work malfunctions, how do we adjust the network
topology and sensor deployment
?



II
.

Wireles
s

sensor netw
orks



The several envisioned applications of WSN
are still

very much under active research and deployment, in
both academic and
industry.
Here

some applications
from different domains

such as ecological habitat
monitoring, military

survei
llance and target tra
c
king,

structural and
seismic monitoring, industrial
and
commercial networked
sensing.
Wireless sensor
networks have attracted a lot of attention for their
broad applications and potentials. Such deployments
will have significant impac
t on both scientific
adventures and our daily life.

Sensor

networks
(WSNs) for the purposes of

environmental
monitoring are becoming increasingly popular due to
their ability to collect information at a high

resolution
across increasingly larger temporal a
nd spatial scales
for a declining cost per unit
area.
The use of these
networks in large
-
scale field applications, which will
allow for

numerous new research possibilities, is
currently still under an

experimental phase. In an
early report discussing WSNs
for environmental
monitoring, outline the general application
requirements of wireless monitoring systems.
Included in these requirements are the reliability and
longevity of the network

nodes and their
WSN

positioning

Localization

Deployment

(placemen
t)



ISSN: 2278


909X

International Journal of Advanced Research in Electronics and Communication Engineering (IJARECE)

Volume 2, Issue 2, February 2013


A
ll Rights Reserved © 2013 IJARECE

109


measurements. The longevity of the system is highly
d
ependent on the battery life of the individual node
s
(or motes) that make up the network.

A number of basic questions must be considered
when deploying a wireless

Sensor

network:

1
. Structured

versus randomized deployment: Does
the network involve

(a)
Stru
ctured

placement, either by hand or via
autonomous robotic nodes, or

(b)
Randomly

scattered deployment?

2
. Over
-
deployment versus incremental deployment:
For robustness against

node failures and energy
depletion, should the network be deployed a priori
wit
h redundant nodes, or can nodes be added or
replaced incrementally when

need arises?

3. Network topology: Is the network topology going
to be a simple star topology, or a grid, or an arbitrary
multi
-
hop mesh, or a two
-
level cluster hierarchy?
What kind of

robust connectivity guarantees are
desired?

4. Homogeneous versus heterogeneous deployment:
Are all sensor nodes of

the same type or is there a
mix of high
-

and low
-
capability devices? In case
of
heterogeneous deployments, there may be multiple
gateway/s
ink devices (nodes to which sensor nodes
report their data and through which an external user
can access the sensor network).

5. Coverage metrics: What is the kind of sensor
information desired from the environment and how is
the coverage measured? This co
uld be on the basis of
detection and false alarm probabilities or whether
every event can be sensed by K distinct nodes, etc.


III.
Network topology


The main topologies are given below



1
.

Single
-
hop
star
:

The simplest WSN topology is
the sin
gle
-
hop star

shown in
Fig (
a). Every

node in
this topology communicates its measurements
directly to the gateway.
This

approach can
significantly simplify design, as the networking

concerns ar
e reduced to a minimum.

The

limitation
of this topology is its poor scalabil
ity and robustness
properties. For instance, in larger areas, nodes that
are distant from the gateway will have poor
-
quality
wireless links.

2.

Multi
-
hop mesh and
grid
:

For larger areas and
networks, multi
-
hop routing is necessary. Depending
on how

they ar
e placed, the nodes could form an
arbit
rary mesh graph as in Fig
.
(b)

or they could form
a more structured communication graph such as the
2D grid

structure shown i
n Fig.
(c).

3.
Two
-

tier hierarchical cluster
: Perhaps the most
compelling architecture

for W
SN is a deployment
architecture
where many nodes within each local area

report to

different
cluster heads
. There are a number
of ways in which such a hierarchical
architecture may

be implemented. This approach becomes powerful in
multiple

settings when the

cluster
-
head nodes are
more powerful in terms of

com
putation
. Th
e
advantage of this
approach is that it naturally
decomposes a large network into separate zones
within which data processing and aggregation can be
performed locally. Within each cluster the
re could be
either single
-
hop or multi
-
hop communication.

Once
data reach a cluster
-
head they would then be routed
through the
second tier

network formed by cluster
-
heads to another cluster
-
gateway.
the

second
-
tier
network may utilize a higher bandwidth rad
io or it
c
ould even be a wired network if
the second
-
tier
nodes can all be connected to the wired

Infrastructure
. Having a wired network for the second
tier is relatively easy in building
-
like environments,
but not for random deployments in remote location
s.
In random deployments there may be no designated
cluster
-
heads; these may have to be determined by
some process of self
-
election.




















ISSN: 2278


909X

International Journal of Advanced Research in Electronics and Communication Engineering (IJARECE)

Volume 2, Issue 2, February 2013


A
ll Rights Reserved © 2013 IJARECE

110

















IV.
Connectivity


Network is connected if any acti
ve

node can
communicate with any other active node. Network
connectivity is necessary to ensure that messages are
propagated to the desired base station and the loss of
connectivity if treated as the end of network life. This
property strongly connected wi
th coverage and
energy efficiency. The relationship between coverage
and connectivity results from sensing and
transmission ranges. If the transmission range of a
node is much longer than its sensing range then
connectivity is not an issue, because the cov
erage
ensures there is a way to communicate. Situation is
different if the communication range is less than
sensing

range. The connectivity and coverage can
be
analyzed

by using random graph
theory.

A random graph model is a systematic description of
some
random experiment that can be used to generate
graph instances. These models usually contain a
tuning parameter that varies the average density of
the constructed random graph.

C
onnectivity using power control
:

Whether
randomized or structured deployment i
s performed,
once the nodes are in place there is an additional
tunable parameter that can be used to adjust the
connectivity properties of the deployed network. This
parameter is the radio transmission power setting for
all nodes in the network. This para
meter is the radio
transmission power setting for all nodes in the
netwIncreasing radio transmission power has a
number of interrelated consequences


Some of these are positive, others negative:

1
. It

can extend the communication range, increasing
the num
ber of communicating neighbouring nodes
and improving connectivity in the form of
availability of end
-
to
-
end paths.

For existing
neighbours, it can improve link quality (in the
absence of other Interfering traffic).

2
. It can induce additional interference

that reduces
capacity and introduces Congestion.

3
. It can cause an increase in the energy expended.


V.
Coverage

matrices



Connectivity metrics are generally application
independent. In most networks the objective is
simply to ensure that there exists a

path between
every pair of nodes. At most, if robustness is a
concern, the K
-
connectivity (whether there exist
s

K
disjoint paths between any pair of nodes) metric may
be
used. The

choice of coverage metric is much more
diverse and depends highly upon the
application. We
examine two different sets of coverage metrics that
have been considered in several studies:

1
.
The

set of K
-
coverage metrics that measure the
degree of sensor coverage overlap.

2.

The set of path
-
observability metrics
that is

suitable for

applications involving tracking of
moving objects.


K
-
coverage
:

This metric is applicable in contexts
where there is some notion of a region being

covered
by each individual sensor. A field is said to be K
-
covered if every point

in the field is within the

overlapping coverage region of at least K

sensors.





VI.
Mobile

based
communication


A large number of small and simple sensor devices
communicate over short
-
range wireless interfaces to
deliver observations over multiple hops to central
l
ocations called sinks. Sensor nodes, and hence these
appli
cations are limited processing
, storage,
communications capabilities

and limited power
supplies. Numerous challenges are faced while
designing WSNs and protocols, maintaining
connectivity and maximi
zing the network lifetime
over critical considerations. The connectivity is met
by deploying a sufficient number of sensors, or using
nodes with long
-
range communication capabilities to
maintain a connected graph. The network lifetime is
ISSN: 2278


909X

International Journal of Advanced Research in Electronics and Communication Engineering (IJARECE)

Volume 2, Issue 2, February 2013


A
ll Rights Reserved © 2013 IJARECE

111


directly related t
o how long the power services in
sensor nodes will last. The mobile devices can also
be used as an

orthogonal

method to address the
connectivity and lifetime problems in WSNs. In other
scenarios mobile devices can be incorporated into the
design of the WSN

architecture such as airborne and
groundbased vehicles. With communication devices
on mobile platforms, the connectivity and energy
efficiency (network lifetime) problem are addressed
as follows: As for connectivity, mobile platforms can
be used to carry
information between isolated parts of
WSNs. On the other hand, energy efficiency means
that information carried in mobile devices can reduce
the energy consummation of sensor nodes by
reducing multihop communication. In recent years a
number of approaches
exploiting mobility for data
collection in WSNs have been proposed. These
approaches can be categorized with respect to the
properties of sink mobility and the wireless

communications

methods for data transfer.





VII.
Conclusion


In this paper we outline the main properties and
criteria that should be considered while de
ploy the
nodes.





More work is required in order to provid
e the
solution which can be applied in real applications.
We also provide an overview of sensor actuated
networks. More work is required in order to provide
the solutions which can be required in real time
application.


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www.google.com









She qualified GATE
-

2010 Examination with 79.
41
percentile.

She is pursuing M.tech. (2
nd
Year) in
Digital Systems from the department o
f Electronics
and Communicati
on
Engineering
,
M.M.M.
Engineering College Gorakhpur (U.P.) India. Her
main research includes Wireless Communication and
Wireless sensor networks.






He has 10 years
of industrial experience, 25 years of
consultancy experience. He works as
assistant
professor for 16 years, as associate professor for 10
years and then as professor for 3 years in Electronics
Engineering Department, M.M.M. Engineering
College,

Gora
khpur. He is member of ISTE, IE
(INDIA), I
ETE and CISCO. He supervised 16
M.tech
.

D
issertations. He has 24 publications on
various platforms in area of Process

Communication.
His research interests include Process

Communication, Wireless Communication &
Wireless

sensor netwo
rks.

Laki was born in 1989 in
sitapur, uttar Pradesh,
India.
She completed
B.tech degree in
electronics and
communication
engineering

from Dr.
R.M.L. Avadh University
Faizabad (U.P.) India in
2011.


Shri Prof. R.N.
Shukla was born in
1950. He is a gold
medallist for 1st
Rank in B.Tech


in
University. He is dual
M.tech.
In

Ci
rcuits
and Systems and also
in I
ndustrial
Electronics and
process
communication.