29-03-2011, 10:30 AM
PRESENTED BY:
Vamshi Nadipelli
Preethi Tiwari
2007-sensor_Networks.ppt (Size: 8.06 MB / Downloads: 103)
Taking Sensor Networks from the Lab to the Jungle
What is a Sensor Network?
Challenges
Technical
System
Conclusion
Introduction
Chain Home - Britain’s Radar Network WWII
Cold War:
SOSUS – The Pacific Ocean
NORAD – Cheyenne Mountain
National Power Grid
Involves
Devices with multiple sensors
Network via wireless/physical links
Involved Technologies
The Systems involved
Sensor Node Internals
Operating System
Sensor Node Internals
Operating System - TinyOS
Custom built at UC, Berkeley for wireless sensor nodes
Component-based architecture: ensures minimum code size
Component library includes:
Network protocols
Sensor drivers
Data acquisition tools
Distributed services
Physical Size
Applications
Border Monitoring
Battlefield Observation
Forest Fire Detection
Environment and Habitat Monitoring
Infrastructure security
Industrial sensing
Medical Applications
Border Monitoring
Most widely cited application
US-Mexico Border (3100 km)
Requires Full length Surveillance
Detection can be based on sound or vibration
With in a range of 10m
Estimated need of 440,000 sensors
Air dropped biannually (battery life 6months)
Not cost effective
Should distinguish humans from wild animals
Battlefield surveillance
Observing enemy activities in a battle field.
Unmanned aerial vehicles (UAV)
Coverage problem (limited radio range)
10,000 nodes were required to monitor just 1 square kilometer
For large areas:
cost
Many nodes implies large number of UAV’s operating simultaneously.
Forest Fire Detection
A sensor network is more feasible as an early warning system for forests.
Carefully placing nodes (close to vulnerable areas such as hilltops)
Reduce the number of sensors required to cover a large geographic area.
Important aspect is lifetime
Must operate for a very long period of time to discover a comparatively rare event
Environment and Habitat Monitoring
Monitoring nesting
Large number of burrows.
Long time observation
Over 100 sensor nodes.
Long term observation
Migration pattern of zebras
They generally move in wide area
Long term observation
Sensors were integrated on to the zebra’s neck.
Consisted of 2 radios.
Long range (base station)
Short range (neighbors)
These were used to monitor the heart beat, body temperature and frequency of feeding
Infrastructure Security
Medical applications
Heart rate
Oxygen saturation
Enhances emergency medical care.
Challenges
Power
Communication
Hostile Environments
Cost
Technical challenges
Changing network topology:
Node failures
Introduction of additional nodes variations in sensor location
Changes to cluster allocations in response to network demands requires the adaptability of underlying network structures and operations.
Advanced communication protocols
To support high level services and real-time operation
(to adapt rapidly to changes in network conditions).
Resource optimization:
To minimize cost, power and network traffic loads
Ensuring network reliability and adequate sensor resolution for data accuracy.
Limitations:
Power, Memory, processing power, life-time. These physical constraints may be minimized through further technological breakthroughs in materials and sensor hardware designs.
Failure prone:
Individual sensors are unreliable, particularly in harsh and unpredictable environments.
Addressing sensor reliability can reduce the level of redundancy required for a network to operate with the same level of reliability.
Network congestion resulting from dense network deployment:
The quantity of data gathered may exceed the requirements of the network and so evaluation of the data and transmission of only relevant and adequate information needs to be performed.
Self-organization
Ability to adapt to dynamic environments as well as ad hoc distribution and connectivity scenarios.
Self-operating and self-maintaining
This functionality is desired in order to minimize further human interaction beyond network deployment.
Security
It is a critical factor in sensor networks.
An effective compromise must be obtained, between the low bandwidth requirements of sensor network applications and security demands.
Conclusion
Sensor networks are application specific
Key application characteristics
Lifetime, cost, data rate, environment, network topology, user interaction
Must address the system aspects of wireless sensor network design