2. Introduction
• Wireless sensor networks (WSN), are similar to Wireless ad hoc network
(WANET) in the sense that they rely on wireless connectivity and
spontaneous formation of networks so that sensor data can be transported
wirelessly.
• A WSN system incorporates a gateway that provides wireless connectivity
back to the wired world and distributed nodes.
• WSN are spatially distributed autonomous sensors to monitor physical or
environmental conditions, such as temperature, sound, pressure, etc. and to
cooperatively pass their data through the network to a main locations .
• 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.
3. History
• The origins of the research on WSN can be traced back to the Distributed Sensor
Networks (DSN) program at the Defense Advanced Research Projects Agency
(DARPA) at around 1980. By this time, the ARPANET (Advanced Research Projects
Agency Network) had been operational for a number of years, with about 200 hosts at
universities and research institutes ( Chon & Kumar, 2003). A demonstrative
application of DSN was a helicopter tracking system (Myers et al., 1984), using a
distributed array of acoustic microphones by means of signal abstractions and
matching techniques, developed at the Massachusetts Institute of Technology (MIT).
• Even though early researchers on sensor networks had in mind the vision of a DSN,
the technology was not quite ready (Size is large).
• Further, the earliest DSN were not tightly associated with wireless connectivity. Recent
advances in computing, communication and micro electromechanical technology have
caused a significant shift in WSN research and brought it closer to achieving the
original vision.
• The new wave of research in WSN started in around 1998 and has been attracting
more and more attention and international involvement. Further, the sensor nodes have
been much smaller in size (i.e. pack of cards to dust particle) and much cheaper in
price, and thus many new civilian applications of sensor networks such as environment
monitoring, vehicular sensor network and body sensor network have emerged.
4. Working
• 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 transceiver is
a device
comprising both
a transmitter an
da receiver that
are combined
and share
common
circuitry or a
single housing.
A microcontroller contains one or more CPUs
(processor cores) along with memory and
programmable input/output peripherals.
Program memory in the form of Ferroelectric
RAM or OTP ROM is also often included on
chip, as well as a small amount of RAM.
5. Working
• The SensiNet® Services Gateway is a powerful appliance based on the
Intel® Atom ™ processor and provides network management, user
interface, data logging, trending, alarming and communications without any
complicated software to install. A standard browser and network connection
is all that’s required to access and configure the system. The GWAY-2100
also operates as stand-alone data logger with real time views, trending and
e-mail alerts.
6. Classification Of Routing
Protocols
Routing techniques are required for sending data between sensor nodes an
the base stations for communication.
Routing Protocols can be classified :
• Based on Mode of functioning and type of target applications into Proactive,
Reactive and Hybrid.
• Based on Participation style of the nodes into as Direct Communication, Flat
and Clustering Protocols .
• Depending on the Network Structure as Hierarchical, Data Centric and
Location based
7. Direct Communication, Flat and
Clustering Protocols
• In Direct Communication Protocols, any node can send information to the
BS directly.
• When this is applied in a very large network, the energy of sensor nodes
may be drained quickly.
• Its scalability is very small.
• SPIN is an example of this type of protocol.
• In the case of Flat Protocols, if any node needs to transmit data, it first
searches for a valid route to the BS and then transmits the data. Nodes
around the base station may drain their energy quickly.
• Its scalability is average.
• Rumor Routing is an example of this type of protocol.
• According to the clustering protocol, the total area is divided into numbers of
clusters.
• Each and every cluster has a cluster head (CH) and this cluster head
directly communicates with the BS.
• All nodes in a cluster send their data to their corresponding Cluster Head.
• The Threshold sensitive Energy Efficient sensor Network (TEEN) is an
example of a clustering protocol.
8. Advantage/Disadvantage
Advantages
• Wireless sensor networks are used in those harsh and hostile environments where
wired networks can't be deployed. For example in a forest, wireless sensor nodes are
dropped from the air because going down there and deploying a wired setup is not
possible.
• Another advantage is that the wireless sensor networks are scalable. That is why they
are actively being used in applications such as Structural Health Monitoring where
there is a need of dense deployment and with a dense wired set up, it may lead to a
chaos at the time of deployment. Moreover a dense wired set up will prove to be very
costly. On the other hand, wireless sensor nodes can easily be deployed without any
hustle.
Disadvantages
• Limited computation and communication resources are the only disadvantages in
wireless sensor networks. They have limited battery power, limited storage and
computation capabilities, prone to the security attacks and have limited bandwidth to
communicate.
• Less but still human interaction is their.
• Despite of the above disadvantages, sensor networks are being used widely and
considered to be the backbone of the phenomenon we call “Internet of Things”.
