2014

Submitted by:-

Real Time Communication In

Wireless Sensor Networks (WSN)

WHAT IS WSN?

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.

Routing Protocols for WSNsA number of routing protocols have been

defined for the WSN communication.

These are the following:-i)Floodingii)Gossipingiii)Spiniv)Gear

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.

2)GOSSIPINGGossiping 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.

3)SPINSPIN (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

4)GEARGEAR (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.

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.

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.

 

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.

ApplicationsVarious 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 . 

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.

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.

G. Others:

Acoustic DetectionSeismic DetectionMilitary SurveillanceMedical MonitoringAgriculture SectorMedical Sector