Wireless Sensor Network’s Architecture and Applications

The design and development of low-cost, low-power, multifunctional sensor nodes that are small in size and communicate untethered in short distances have become feasible.

To realize the existing and potential applications for WSNs, sophisticated and extremely efficient communication protocols are required. WSNs are composed of a large number of sensor nodes, which are densely deployed either inside a physical phenomenon or very close to it.

Introduction:

Wireless Sensor Networks are networks that consists

of sensors which are distributed in an ad hoc manner.

These sensors work with each other to sense some

physical phenomenon and then the information

gathered is processed to get relevant results.

Wireless sensor networks consists of protocols and

algorithms with self-organizing capabilities.

Sensor networks use source-node processing or hierarchical processing architecture.

Instead of sending the raw data to the nodes responsible for the fusion, sensor nodes use their processing capabilities to locally carry out simple computations and transmit only the required and partially processed data

In a hierarchical processing architecture, processing occurs at consecutive tiers until the information about events of interest reaches the appropriate decision-making and/or administrative point.

Overview of the technology:

A sensor is a device that converts a real-world property (e.g. temperature) into data that a computer can process.

The properties they detect are

Temperature-Temperature

Light-Light / dark

Pressure-Pressure (e.g. someone standing on it)

Water-level-How full / empty a container is

Movement-Movement nearby

Sensor:

The output of a sensor is generally a signal that is

converted to human-readable display at the sensor

location or transmitted electronically over a network for

reading or further processing.

All sensors need to be calibrated with respect

with some reference value or standard device for

accurate measurement.

High Sensitivity: Sensitivity indicates how much the output of the device changes with unit change in input (quantity to be measured). For example the voltage of a temperature sensor changes by 1mV for every 1°C change in temperature than the sensitivity of the sensor is said to be 1mV/°C.

Linearity: The output should change linearly with the input.

High Resolution: Resolution is the smallest change in the input that the device can detect.

Less Noise & Disturbance. Less power consumption.

Classifications of a sensor:

Environmental sensors e.g.: Rain gauge, snow gauge, moisture sensor. Acoustic & Sound sensors e.g.: Microphone and Hydrophone Optical sensors e.g. : Photodiode, Phototransistor, Wave front sensor Proximity & Presences sensors e.g.: Doppler radar, Motion detector Automotive sensors e.g.: Speedometer, Radar gun, Speedometer, fuel ratio

meter.

Types of a sensor:

.

Sensor networks are the key to gathering the information needed by smart environments, whether in buildings, utilities, industrial, home, shipboard, transportation systems automation, or elsewhere.

It consists of multiple detection stations called sensor nodes, each of which is small, lightweight and portable

Every sensor node is equipped with a transducer, micro computer, trans receiver and power source.

The transducer generates electrical signals based on sensed physical effects and phenomena.

The microcomputer processes and stores the sensor output.

The transceiver receives commands from a central computer and transmits data to that computer.

Wireless Sensor Network:

Wireless Sensor Network’s Architecture:

Task Manager

Internet and satellite

Sink

AC

DB

UserSensor Nodes Sensor field

1. The sensor nodes are usually scattered in a sensor field.

2. Each of these scattered sensor nodes has the capability to

collect data and route data back to the sink/gateway and the

end-users.

3. The sink may communicate with the task manager/end-user

via the Internet or satellite or any type of wireless network

(like WiFi, mesh networks, cellular systems, WiMAX, etc.), or

without any of these networks where the sink can be

directly connected to the end-users.

Continued…….

4. In WSNs, the sensor nodes have the dual functionality of

being both data originators and data routers. Hence,

communication is performed for two reasons:

• Source function: Source nodes with event information

perform communication functionalities in order to transmit

their packets to the sink.

• Router function: Sensor nodes also participate in forwarding

the packets received from other nodes to the next destination

in the multi-hop path to the sink.

Three Major components in WSN architecture:

NodeThe spatially distributed measurement nodes interface with sensors to monitor assets or their environment.

Gateway

The acquired data wirelessly transmits to the gateway, which can operate independently or connect to a host system where you can collect, process, analyze, and present your measurement data using software

Software

Data collected is processed, analyzed by using software. Routers are a special type of measurement node that you can use to extend WSN distance and reliability

The architecture of a protocol stack is used by the sink and sensor node.

This protocol stack integrates data with Networking protocols.

It communicates power efficiently through the wireless medium and promotes cooperative efforts of sensor nodes.

Protocol Stack for WSN:

Com

mun

icat

ion

prot

ocol

s

Management protocols

Fig.: Protocol Stack

•It is responsible for frequency selection, carrier frequency generation, signal detection, modulation, and data encryption

PHYSICAL LAYER

•multiplexing of data streams, data frame detection, and medium access and error control

•It ensures reliable point-to-point and point-to-multipoint connections in a communication networkDATALINK LAYER

•The information collected relating to the phenomenon should be transmitted to the sink, which may be located far from the sensor field.

•This requires efficient multi-hop wireless routing protocols between the sensor nodes and the sink node using intermediate sensor nodes as relays.

NETWORK LAYER

Communication protocols:

•when the network is planned to be accessed through the Internet or other external networks.

• power consumption and scalability, and characteristics like data-centric routing, mean sensor networks need different handling in this layer

TRANSPORT LAYER

•It includes the main application as well as several management functionalities

•Time synchronization, localization, topology management

APPLICATION LAYER

Management protocols:

Power Managem

ent

It manages how a sensor node uses it power and manages its power consumption among the three operations(sensing , computation, wireless communication )

Task Managem

ent

It balances and schedules the events i.e., sensing and detecting tasks from a specific area. Depending on the power level some nodes perform the sensing task

Mobility – Managem

ent It detect and registers the movement/mobility of a sensor nodes as a network control primitive

Mesh topology

Star topology

Tree topology

Switched star topology

Peer to peer topology

WSN Topologies:

Industrial automation

Smart home system

Military surveillance

Environmental monitoring

Applications:

Wireless sensor network technology has demonstrated a great potential for industrial, commercial, and consumer applications.

Specifically, in process monitoring and control, process data such as pressure, humidity, temperature, flow, level, viscosity, density and vibration intensity measurements can be collected through sensing units and transferred wirelessly to a control system for operation and management.

Industrial automation:

•cooling down a reactor by adjusting the flow rate through the cooling jacket is a process.• Here, the temperature is the controlled variable.•The temperature value is transmitted to the controller; the controller implements the functions and calculations, transmits the output to control the valve and issues alarm if there are faulty conditions.•Failure of a control loop may cause unscheduled plant shutdown or even severe accidents in process-controlled plants .

Control room

Controller

Temperaturetransmitter Valve

positioner

Fig.: Wired process control system

Controller

Fig.: Wireless process control system

By utilizing WSN technology, sensing and action devices will communicate wirelessly with an access point (e. g., a gateway or router), which is connected to the control station wirelessly (e.g., Ethernet).

Advantages:• No Wiring Constraints•Easy Maintenance•Reduced Cost•Better Performance

wireless sensor networks can be used by the military for a number of purposes such as monitoring militant activities and force protection.

Being equipped with appropriate sensors these networks can enable detection of enemy movement, identification of enemy force and analysis of their movement and progress.

Military surveillance:

Smart Home is the integration of technology and services through home networking for better quality of living.

The smart home integration consists of three major areas physical components, control system, communication system which connects physical components and control system.

Smart home system:

In a smart home system the physical components sense the environment and pass to home control system through home sub networks and home network. Home control system takes the decision and passes the control information to the actuators through home network.

There are many applications in monitoring environmental parameters which share extra challenges of harsh environments and reduced power supply.

They are: Forest fire detection Natural disaster prevention

Environmental Monitoring:

Forest fire detection:

Natural disaster Prevention: