3. Abstract:-
Advances in silicon technology have led to the development of
next-generation, low-cost, low-power, multifunctional, sensor
devices.
These devices communicate wirelessly to transmit their
readings. They are called wireless sensors and compact devices
that integrate communication and computation devices into a
single chip.
A sensor network is a collection of communicating sensing
devices or nodes. A large number of sensors can be spread
across a geographical area and networked in many
applications that require unattended operations, hence
producing a wireless sensor network (WSN).
A WSN is a network that is made of hundreds or thousands of
these sensor nodes which are densely deployed in an
unattended environment with the capabilities of sensing,
wireless communications and computations.
4. Routing Protocols for WSNs
A number of routing protocols have been defined for
the WSN communication.
These are the following:-
i)Flooding
ii)Gossiping
iii)Spin
iv)Gear
5. 1)FLOODING:-
In Flooding, a node sends out the received data or the
management packets to its neighbors by broadcasting,
unless a maximum number of hops for that packet are
reached or the destination of the packets is arrived.
DEFICIENCIES:-
Implosion: is the case where a duplicated data or
packets are sent to the same node.
Overlap: if two sensor nodes cover an overlapping
measuring region, both of them will sense/detect the
same data. As a result, their neighbor nodes will
receive duplicated data or messages.
6. 2)GOSSIPING
Gossiping protocol is an alternative to flooding
mechanism. In Gossiping, nodes can forward the
incoming data/packets to randomly selected neighbor
node.
This technique assists in energy conservation by
randomization. Gossiping can solve the implosion
problem.
7. 3)SPIN
SPIN (Sensor Protocols for Information via Negotiation)
is a family of adaptive protocols for WSNs.
Their design goal is to avoid the drawbacks of flooding
protocols mentioned above by utilizing data negotiation
and resource-adaptive algorithms
8. 4)GEAR
GEAR (Geographical and Energy Aware Routing) is a
recursive data dissemination protocol WSNs.
It uses energy aware and geographically informed
neighbor selection Heuristics to route a packet to the
targeted region.
9. Different Networking Technologies for
Wireless Sensor Networks:
A. Bluetooth:
IEEE 802.15.1 standard, popularly known as Bluetooth, offers moderate
data rates at lower energy levels.
It is ideally suited for high end WSN applications that require higher data
rates with harder real time constraints.
Bluetooth is used in star topology.
B. ZigBee:
IEEE 802.15.4 standard, popularly known as ZigBee, offers low data rates
at very low energy levels.
It is ideally suited for applications requiring infrequent smaller data
transfers where battery life is an important issue.
10. C. UWB:
Ultra wide band is a technology for transmitting information spread over a
large bandwidth (>500 MHz).
Ideally suited for short distance, high speed communications with very low
power budget.
As it is based on wide band technology, it can achieve very high geo-location
accuracy to the sub-meter levels.
D. Wi-Fi:
Wi-Fi represents group of WLAN technologies defined under IEEE 802.11
standard body.
Wi-Fi technologies are capable of providing very high throughput (>100
Mbps) at longer range but required very high power budget.
Also, Wi-Fi can locate end point location to the accuracy of several meters
only. Because of this limitation, use of Wi-Fi is mostly restricted to devices
with fixed power supply.
11. Operating systems used in WSN
A. TinyOS:
TinyOS can support concurrent programs with very low memory
requirements.
The OS fits in 400 bytes.
The TinyOS component library includes network protocols, distributed
services, sensor drivers, and data acquisition tools.
B. Contiki OS
Contiki is a lightweight open source OS written in C for WSN sensor
nodes.
Contiki is a highly portable OS.
A typical Contiki configuration consumes 2 kilobytes of RAM and 40
kilobytes of ROM.
12. Applications
Various fields of applications of wireless sensor networks are:
A. Area Monitoring:
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 detects enemy intrusion.
B. Environmental/Earth Monitoring:
The term Environmental Sensor Networks, has evolved to cover
many applications of WSNs to earth science research.
This includes sensing volcanoes, oceans ,glaciers, forests .
13. C. Air pollution Monitoring:
Wireless sensor networks have been deployed in several
cities (Stockholm, London or Brisbane) to monitor the
concentration of dangerous gases for citizens.
These can take advantage of the ad-hoc wireless links
rather than wired installations.
D. Forest fire Detection:
A network of Sensor Nodes can be installed in a forest to
detect when a fire has started.
The nodes can be equipped with sensors to measure
temperature, humidity and gases which are produced by
fire in the trees or vegetation. The early detection is
crucial for a successful action of the firefighters.
14. E. 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.
Through the data gathered it may be possible to know the
occurrence of landslides long before it actually happens.
F. Water Quality Monitoring:
Water quality monitoring involves analyzing water properties in
dams, rivers, lakes & oceans, as well as underground water
reserves.
The use of many wireless distributed sensors enables the
creation of a more accurate map of the water status, and allows
the permanent deployment of monitoring stations in locations
of difficult access.
