Wireless Sensor Networks

WIRELESS SENSOR 
NETWORKS


Introduction


Sensing & Sensors


Classification and Examples of
Sensors


DATA ACQUISITION & ACTUATION


Wireless Sensor Networks


.A wireless sensor network (WSN) consists of
spatially distributed autonomous sensors to monitor
physical or environmental conditions, such as
temperature, sound, vibration, pressure, motion or
pollutants and to cooperatively pass their data
through the network to a main location. The more
modern networks are bi-directional, enabling also to
control the activity of the sensors.
.The development of wireless sensor networks was
motivated by military applications such as battlefield
surveillance; today such networks are used in many
industrial and consumer applications, such as
industrial process monitoring and control, machine
health monitoring, and so on.



.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)
sensors.
.Each such sensor network node has typically
several parts: a radio transceiver with an internal
antenna or connection to an external antenna, a
microcontroller, an electronic circuit for interfacing
with the sensors and an energy source, usually a
battery or an embedded form of energy
harvesting.
.A sensor node might vary in size from that of a
shoebox down to the size of a grain of dust,



Wireless Sensor Networks


WSN


Characteristics of WSN

.Power consumption constrains for nodes using
batteries or energy harvesting
.Ability to cope with node failures
.Mobility of nodes
.Dynamic network topology
.Communication failures
.Heterogeneity of nodes
.Scalability to large scale of deployment
.Ability to withstand harsh environmental
conditions
.Ease of use
.Unattended operation.



Communication in a WSN


Single-hop Vs Multi-hop
communication in sensor
networks


Parameters of sensor nodes

.The cost of sensor nodes is similarly variable,
ranging from hundreds of dollars to a few
pennies, depending on the complexity of the
individual sensor nodes. Size and cost
constraints on sensor nodes result in
corresponding constraints on resources such as
energy, memory, computational speed and
communications bandwidth.
.The topology of the WSNs can vary from a simple
star network to an advanced multi-hop wireless
mesh network.
. The propagation technique between the hops of
the network can be routing or flooding.





 Applications of WSN
.Military,
.Environmental,
.Health (Scanning),
.Space,
.Exploration,
.Vehicular Movement,
.Mechanical stress
levels on attached
objects etc.





 Area Monitoring
.Area monitoring is a common application of
WSNs. In area monitoring, the WSN is deployed
over a region where some phenomenon is to be
monitored. A military example is the use of
sensors to detect enemy intrusion; a civilian
example is the geo-fencing of gas or oil pipelines.
.When the sensors detect the event being
monitored (heat, pressure), the event is reported
to one of the base stations, which then takes
appropriate action (e.g., send a message on the
internet or to a satellite). Similarly, wireless
sensor networks can use a range of sensors to
detect the presence of vehicles ranging from
motorcycles to train cars.



Area Pollution Monitoring

.Wireless sensor networks have been deployed in
several cities (Stockholm, London or Brisbane) to
monitor the concentration of dangerous gases for
citizens.




 Forest fires detection

.A network of Sensor Nodes can be installed in a
forest to control when a fire has started. The
nodes will be equipped with sensors to control
temperature, humidity and gases which are
produced by fire in the trees or vegetation.



Greenhouse monitoring

.Wireless sensor networks are also used to control
the temperature and humidity levels inside
commercial greenhouses. When the temperature
and humidity drops below specific levels, the
greenhouse manager must be notified via e-mail
or cell phone text message, or host systems can
trigger misting systems, open vents, turn on fans,
or control a wide variety of system responses.



Landslide Detection

.A landslide detection system, makes use of a
wireless sensor network to detect the slight
movements of soil and changes in various
parameters that may occur before or during a
landslide. And through the data gathered it may
be possible to know the occurrence of landslides
long before it actually happens.



Industrial Monitoring

 Machine health monitoring

.Wireless sensor networks have been developed
for machinery condition-based maintenance
(CBM)as they offer significant cost savings and
enable new functionalities. In wired systems, the
installation of enough sensors is often limited by
the cost of wiring. Previously inaccessible
locations, rotating machinery, hazardous or
restricted areas, and mobile assets can now be
reached with wireless sensors



Wastewater Monitoring

.Agriculture


 Using wireless sensor networks within the
agricultural industry is increasingly common;
using a wireless network frees the farmer from
the maintenance of wiring in a difficult
environment. Gravity feed water systems can be
monitored using pressure transmitters to monitor
water tank levels, pumps can be controlled using
wireless I/O devices and water use can be
measured and wirelessly transmitted back to a
central control center for billing. Irrigation
automation enables more efficient water use and
reduces waste.



Structural monitoring

.Wireless sensors can be used to monitor the
movement within buildings and infrastructure
such as bridges, flyovers, embankments, tunnels
etc... enabling Engineering practices to monitor
assets remotely with out the need for costly site
visits, as well as having the advantage of daily
data, whereas traditionally this data was collected
weekly or monthly, using physical site visits,
involving either road or rail closure in some
cases. it is also far more accurate than any visual
inspection that would be carried out.