Wireless Sensor Networks

• A collection of sensing devices that can

communicate wirelessly

• Each device can sense, process, and

talk to its peers

• Typically, centralized collection point

(sink or base station)

Sensor Node deployment and Communication Infrastructure

Internet and Satellite

Task Manager node

Sink A

B

C

D

E

Sensor FieldSensor Node

User

Sensor Node

A sensing node has 3 basic components:

CPU

radio transceiver

sensor array

Sensor Node Architecture

Sensors

A sensor is a small hardware device

which is capable of generating response

to change in physical environment.

Although sensors are of different type

which are application specific but

desired characteristics of a sensor node

are small size and low power consumption

Energy conservation

• Goal: unsupervised operation with

no maintenance

• Nodes need to conserve energy

• Radio is power-hungry!

A WSN typically has little or no

infrastructure. It consists of a

number of sensor nodes (few tens

to thousands) working together to

monitor a region to obtain data

about the environment.

Gateway

Server

Internet

Communication’s

barrier

Sensor field

Soil Moisture etc.

Mote

Applications

WSN applications can be classified into two categories:

•Monitoring

•Tracking

Monitoring applications

•indoor/outdoor environmental monitoring viz., agriculture,

air / water pollution

•health and wellness monitoring, power monitoring, inventory

•location monitoring, factory and process automation viz.,

pipeline

•seismic and structural monitoring.

Tracking objects •animals

•humans

•vehicles.

Health Applications

Sensor networks are also widely used in

health care area. In some modern hospital

sensor networks are constructed to monitor

patient physiological data, to control the drug

administration track and monitor patients and

doctors and inside a hospital. They support

fall detection, unconsciousness detection,

vital sign monitoring and dietary/exercise

monitoring.

WSNs are also used to form BAN(Body Area

Network) which is placed close to body of

patient and is used to monitor patient’s heart

beat rate and breath rate and movements.

Military Applications

Sensor networks can provide variety of

services to military and air force like

information collection, battlefield surveillance,

intrusion detection and attack detection. In

this field of application sensor networks have

quite an advantage over other networks

because enemy attacks can damage or

destroy some of the nodes but nodes failure

in WSN doesn’t affect the whole network.

Intrusion detection

Sensor network can be used as a 2-phase in

Intrusion Detection System. Instead of using

mines intrusion can be detected by

establishing sensor network in that area.

Mines are dangerous to civilians so instead

sensor nodes sense the detection and alarm

the army. The response to prevent intrusion is

now decided by the military.

Enemy Tracking and target classification

Objects moving with significant metallic

content can be detected using specially

designed sensors. So enemies can be tracked

and civilians are ignored. This system

specially helps in detecting armed soldiers

and vehicles.

Battlefield surveillance

Critical areas and borders can be

closely monitored using sensor

networks to obtain information

about any enemy activity in that

area. This provides quick gathering

of information provides time for

quick response.

Battlefield damage assessment

Sensor networks can be deployed

after the battle or attacks to gather

information of damage assessment.

Detection of NBC attacks

Sensor networks can be used as Nuclear,

Biological and Chemical warning system. If

any nuclear biological or chemical agents can

be detected by sensors and embedded alert

system can now send a warning message. It

provides the military critical response time to

check the situation and prevent possible

attacks which can save lives of many.

Targeting system

Sensors can be embedded in weapons.

Exact information about the target like

distance, angle can be collected and

sent to the shooter. So sensors can be

collaborated with the weapons for better

target assessment.

Agricultural Monitoring

WSN in agriculture helps in distributed

data collection, monitoring in harsh

environments, precise irrigation and

fertilizer supply to produce profuse crop

production while diminishing cost and

assisting farmers in real time data

gathering.

The proposed agricultural environment

monitoring server system collects

environmental and soil information on the

outdoors through WSN-based environmental

and soil sensors.

Applications

WSNs can be used for studying the local environment which is helpful in

agriculture. Sensors are used to monitor the

following conditions:

Temperature

Humidity

Soil moisture

Wind speed and direction

Rainfall

Sunshine

Level of CO2

Precision Agriculture

Precision agriculture is a method of farm management that

enables farmers to produce more efficiently through a frugal use

of resources.

Motivation:

•traditionally, a large farm is taken as homogeneous field in

terms of resource distribution and its response to climate

change, weeds, and pests

•accordingly, farmers administer

•fertilizers, pesticides, herbicides, and water resources

•in reality, wide spatial diversity in soil types, nutrient content,

and other important factors

Requirements of precision agriculture technologies

•collect a large amount of data

•over several days

•monitoring the humidity and temperature

conditions in the field

•monitoring the wetness

•determining the potential risk of the disease and

the need for fungicides

Environmental

Applications

Another major area of application of WSN is

environmental monitoring. WSNs are

deployed for habitat monitoring,

flood detections , forest fire detection etc.

Forest Fire detection

Millions of sensor nodes can be

deployed which use distributed sensing

and collaborate with each other to

provide information. So fire can be

detected and exact location of fire origin

can be provided before the fire is

uncontrollable

Flood detection

ALERT systems use sensors for

rain, water level and weather.

Information collected by these

sensors can forecast the possible

flood threats thus providing help for

disaster management.

Pollution Monitoring

WSNs can be deployed for monitoring the

level of pollution and warning generation.

Air Pollution Monitoring Systems are

deployed in cities like London and Brisbane

to monitor the level of pollutants.

These sensor networks look for amount of

poisonous gases and these statistics are

studied to analyze if pollution has increased

and take actions to check pollution

Disaster Management

Applications

WSNs can also be used for other disaster

management like earthquake and landslide

monitoring and disaster assessment.

Disaster monitoring

Motivation

•most of Earth’s changes of

climate are hidden from view

•at present, typical changes are

monitored using expensive

devices that are difficult to move

•the deployment and maintenance

of these devices require expensive

assistance

•data storage must be retrieved on

a periodic basis

WSNs can be very useful for weather / climate monitoring

•a large number of small, cheap,

and self-organizing nodes

•can be deployed to cover a vast

field

Advantage of WSNs in active disaster monitoring

•fast and economical deployment

•possible to achieve high spatial

diversity

•the networks can operate without

requiring stringent maintenance

routines

An important task in active disaster monitoring is to capture discrete events

•eruptions, earthquakes, or tremor

activities

•these events are transient

•occurring several times a day

Therefore, the researchers used the raw data to investigate volcanic activities

the samples must be accurately time

stamped to allow comparisons

between correlated measurements

Conclusion

•WSNs are suitable for capturing

triggered events

•WSNs are inadequate for

capturing complete waveforms for

a long period of time

Pipeline Monitoring

Monitoring gas, water and oil

pipelines

Motivation:

•management of pipelines

presents a formidable challenge

•long length, high value, high

risk

•difficult access conditions

•requires continuous and

unobtrusive monitoring

Pipeline leakages can occur due to excessive deformations

•Earthquakes

•landslides or collisions with an

external force

•corrosion, wear, material flaws

•intentional damage to the

structure

To detect leakages, it is vital to

understand the characteristics of the

substance the pipelines transport

•fluid pipelines generate a hot-spot

at the location of the leak

•gas pipelines generate a cold-spot

due to the gas pressure relaxation

•fluid travels at a higher

propagation velocity in metal

pipelines than in a Polyvinyl

Chloride (PVC)

•a large number of commercially

available sensors to detect and

localize thermal anomalies

•fiber optics sensors

•temperature sensors

•acoustic sensors

The PipeNet prototype

The task is to monitor

•hydraulic and water quality by measuring

pressure and pH

•the water level in combined sewer system

•sewer collectors and combined sewer

outflows

Industrial Sensing

Managing inventory control

Each item in a warehouse may have a sensor

node attached to it. The end users can

find out the exact location of the item with the

help of sensor and tally the number of items

in the same category stored in

the database.

Structural Health

Monitoring

Motivation

events:

•on August 2, 2007, a highway bridge unexpectedly

collapsed in Minnesota

•nine people were killed in the event

•potential causes: wear and tear, weather, and the

weight of a nearby construction project

•in fact, the BBC reported (August 14, 2007) that China

had identified more than 6,000 bridges that were

damaged or considered to be dangerous

these accidents motivate wireless

sensor networks for monitoring

bridges and similar structures

Motivation

traditional inspections

•visual inspection everyday

•labor-intensive, tedious, inconsistent, and

subjective

•basic inspections at least once a year

•detailed inspection at least every five years

on selected bridges

•special inspections according to technical

needs

•the rest require sophisticated tools

expensive, bulky, and power consuming

Underground Mining

Motivation:

one of the most dangerous work

environments in the world incident

of August 3, 2007 at the Crandall

Canyon mine, Utah, USA

•six miners were trapped inside

the coal mine

•their precise location was not

known

•the owners of the mine claimed

a natural earthquake was the

cause while scientists suspect

the mine operations caused

seismic spikes

•a costly and irksome rescue

attempt went underway

Advantages of WSNs over traditional methods

Wide coverage

Long monitoring periods

No individual tracking

Data available directly to researcher’s

location

Land and Aquatic Coverage

Continuous monitoring

WSN Operating

Systems

•TinyOS

•Contiki

•MANTIS

•Btnut

•SOS

•Nano-RK

TinyOS:

•Event-driven programming model

instead of multithreading

•TinyOS and its programs written in

nesC

TinyOS Charactersitics:

•Small memory footprint

non-preemptable FIFO task

scheduling

•Power Efficient

Puts microcontroller to sleep

Puts radio to sleep

•Concurrency-Intensive Operations

Event-driven architecture

Efficient Interrupts and event

handling

•No Real-time guarantees

WSN Simulators

•NS-2

•GloMoSim

•OPNET

•SensorSim

•J-Sim

•OMNeT++

•Sidh

•SENS

WSN Emulators

•TOSSIM

•ATEMU

•Avrora

•EmStar