Download Wireless Sensor Networks

Introduction To
Wireless Sensor Networks
Wireless Sensor Networks
A wireless sensor network is a collection of
nodes organized into a cooperative network.
Each node consists of processing capability
may contain multiple types of memory have
an RF transceiver, have a power source
(e.g.,
batteries
and
solar
accommodate various sensors.
cells),
and
Wireless Sensor Networks
Communication Network
A communication network is composed of
nodes, each of which has computing power and
can
transmit
and
receive
messages
communication links, wireless or cabled.
over
Basic Network Topologies

Star Topology

Ring Topology

Bus Topology

Tree Topology

Fully Connected Networks

Mesh Networks
Star Topology
All nodes of the star topology are connected to a single
hub node. The hub requires greater message handling,
routing, and decision-making capabilities than the other
nodes. If a communication link is cut, it only affects one
node. However, if the hub is incapacitated the network
is destroyed.
Ring Topology
In the ring topology all nodes perform the
same function and there is no leader node.
Messages generally travel around the ring in
a single direction.
However, if the ring is cut, all
communication is lost.
Bus Topology
In
the
bus
topology,
messages
are
broadcast on the bus to all nodes. Each
node checks the destination address in the
message
header,
and
messages addressed to it.
processes
the
Tree Topology
In Tree Topology there will be a root node
and the root node has two branches. Each
branch may again contains branches and so
on.
Fully-connected Network
In
a
fully
connected
Network
when
additional nodes are added, the number of
links increases exponentially.
Mesh Network
Mesh networks
are regularly
distributed
networks that generally allow transmission
only to a node’s nearest neighbors. The
nodes
in
these
networks
identical.
Mesh nets can be good models for
large-scale
networks
of
wireless
sensors that are distributed over a
geographic region.
are
generally
Communication Network
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A single network may consist of several
interconnected
subnets
of
different
topologies. Networks are further classified
as Local Area Networks (LAN), e.g. inside
one building, or Wide Area Networks (WAN),
e.g. between buildings.
Wireless Sensor Networks
A wireless sensor network (WSN) is a
wireless
network
distributed
consisting
autonomous
of
spatially
devices
using
sensors to cooperatively monitor physical or
environmental
temperature,
conditions,
sound,
vibration,
such
as
pressure,
motion or pollutants, at different locations.
Wireless Sensor Networks
The
development
networks
military
was
of
originally
applications
surveillance.
wireless
sensor
motivated
such
However,
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as
by
battlefield
wireless
sensor
networks are now used in many civilian
application
and
areas,
habitat
including
environment
monitoring,
healthcare
applications, home automation, and traffic
control.
Sensor Node

Networks of typically small, battery-powered,
wireless devices.
• On-board processing,
• Communication, and
• Sensing capabilities.
Sensors
Storage
Processor
Radio
WSN device schematics
P
O
W
E
R
Sensor Node
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In addition to one or more sensors, each
node
in
a
sensor
network
is
typically
equipped with a radio transceiver or other
wireless communications device, a small
microcontroller,
and
an
energy
usually a battery.
source,
Sensors
Storage
Processor
Radio
WSN device schematics
P
O
W
E
R
Sensor Node
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Sensor Node
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Sensor
Network
Antenna
Server
Interface
electronics, radio
and microcontroller
Soil moisture
probe
Communications
barrier
Sensor field
Mote
Gateway
Internet
Computer Revolution
Original IBM PC (1981)
MICAZ Mote (2005)
4.77 MHz
4 MHz
16-256 KB RAM
128 KB RAM
160 KB Floppies
512 KB Flash
~ $6K (today)
~ $35
~ 64 W
~14 mW
25 lb, 19.5 x 5.5 x 16 inch
0.5 oz, 2.25 x 1.25 x 0.25
inch
Sensor Network
Server
Watershed
Sensor
field
Gateway
Internet
Network Model for WSN
A
wireless
sensor
network
consists
of
hundreds or thousands of low cost nodes
which could either have a fixed location or
randomly
deployed
to
monitor
the
environment. The flowing of data ends at
special
nodes
called
base
stations
(sometimes they are also referred to as
sinks).
Network Model for WSN
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A base station links the sensor network to
another
network
(like
a
gateway)
to
disseminate the data sensed for further
processing. Base stations have enhanced
capabilities over simple sensor nodes since
they must do complex data processing.
Network Model for WSN
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This justifies the fact that bases stations
have workstation/laptop class processors,
and of course enough memory, energy,
storage and computational power to perform
their tasks well.
Usage of Sensor Networks
Environmental Observation:
Sensor
networks
can
be
used
to
monitor
environmental changes. An example could be water
pollution detection in a lake that is located near a
factory that uses chemical substances. Sensor
nodes could be randomly deployed in unknown and
hostile areas and relay the exact origin of a
pollutant.
Other
examples
include
forest
fire
detection, air pollution and rainfall observation in
agriculture.
Usage of Sensor Networks
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Military Monitoring:
Military uses sensor networks for battlefield
surveillance;
sensors
could
monitor
vehicular traffic, track the position of the
enemy.
Usage of Sensor Networks
Building Monitoring:
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Sensors can also be used in large buildings
or factories monitoring climate changes.
Thermostats and temperature sensor nodes
are deployed all over the building’s area. In
addition, sensors could be used to monitor
vibration that could damage the structure of
a building.
Usage of Sensor Networks
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Healthcare:
Sensors
can
be
used
in
biomedical
applications to improve the quality of the
provided care. Sensors are implanted in the
human body to monitor medical problems
like cancer and help patients maintain their
health.
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