S e n so r N e tw o rk s - University Of Marylandamol/sensors-passport.pdfSensors A device that can...
Transcript of S e n so r N e tw o rk s - University Of Marylandamol/sensors-passport.pdfSensors A device that can...
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Sensor Networks
Prof. Amol Deshpande
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Outline
Brief description of sensor networks
Applications
Sensor Networks: Details
Sensor Networks: Challenges
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Sensors
A device that can “sense” thingssense = measure = instrument
Examples:Traffic Sensors
e.g. traffic camerasLocation Sensors
e.g. cell phones, GPS unitsSensors sensing environmental properties
e.g. temperature, humidity, light etc
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Sensor Networks
A collection of sensing devices that can communicate with each other
Can collectively measure or instrument a large scale phenomenon or property
A network of sensors instruments the San Francisco Bay Area Traffic (http://traffic.511.org/traffic_map.asp)
Zebranet (http://www.princeton.edu/~mrm/zebranet.html)
Increasing number of deployments everywhere
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Applications
We will discuss a few of the applications in detail
Ubiquitous Computing
Habitat Monitoring
Health Care
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Ubiquitous ComputingMark Weiser’s Vision
The most profound technologies are those that disappear. They weave themselves into the fabric of everyday life until they are indistinguishable from it.
Sometimes called pervasive or calm computing
http://www.hiit.fi/u/reti/interests/computer-for-21-century.pdf
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Sal awakens: she smells coffee. A few minutes ago her alarm clock, alerted by her restless rolling before waking, had quietly asked "coffee?", and she had mumbled "yes." "Yes" and "no" are the only words it knows.
At breakfast Sal reads the news. She still prefers the paper form, as do most people. She spots an interesting quote from a columnist in the business section. She wipes her pen over the newspaper's name, date, section, and page number and then circles the quote. The pen sends a message to the paper, which transmits the quote to her office.
Once Sal arrives at work, the foreview [mirror] helps her to quickly find a parking spot. As she walks into the building the machines in her office prepare to log her in, but don't complete the sequence until she actually enters her office.
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Ubiquitous Computing
Computing devices pervasive but hiddenSense their relationship to us and each otherRespond appropriately to our actionsCommunicate among each other to organize and coordinate their actions
Need:To sense a broad set of physical phenomenonTo observe human activity
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Examples...
.. of how sensing is used in ubicomp work
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RFIDs (“Smart Labels”)
Identify objects from distancesmall IC with RF-transponder
Wireless energy supply ~1mmagnetic field (induction)
ROM or EEPROM (writeable)~100 bytes
Cost ~ $0.1 ... $1Consumable and disposable
Flexible tagslaminated with paper
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Activity InferencingIntel Seattle (http://seattleweb.intel-research.net/projects/activity/)
RFID Tags + iGlove Can infer what you are doing
Think ‘invisible man’
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Applications
We will discuss a few of the applications in detail
Ubiquitous Computing
Habitat Monitoring
Health Care
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Habitat Monitoring
Monitor microclimates around animals, birds etc
Need remote sensing
Can help understand the patterns of movement, the climates they like, habitat utilization etc
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Habitat MonitoringGreat Duck Island
Monitor Leach’s Storm Petrel - An elusive seabird
Leach's Storm Petrel
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Sensors Used
4Mhz, 8 bit Atmel RISC uProc40 kbit Radio4 K RAM, 128 K Program Flash, 512 K Data FlashAA battery packMany different types of sensors can be attached
temperature, humidity, light, air pressure, vibration, gps etc
Mica MoteMica Mote
Mica2DotMica2Dot
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Berkeley Motes
Popular sensing devices
Produced now by Crossbow
Can buy for $50 apiece
Many more deployments already exist...
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Applications
We will discuss a few of the applications in detail
Ubiquitous Computing
Habitat Monitoring
Health Care
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Health Care
Nursing HomesElite Care (http://www.elite-care.com)Location sensors, vitals monitoring sensors etc
Personalized database to maintain historyHospitals
Patient monitoring, Doctor tracking
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Health Care
Bio-medical Sensors
Implanted in the body
e.g. glucose level, heart rate monitoring, artificial retina, cancer detectors etc etc
Emerging field
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Outline
Brief description of sensor networks
Applications
Sensor Networks: Platforms
Sensor Networks: Challenges
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Types of Sensor Networks
Incredible Variety
Especially since our broad definition of sensors
Wired vs Wireless
Wireless preferred, but has energy constraints
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Hierarchical Deployment
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Platforms
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Spec
Link 1
Link 2
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MICA2 Mote
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Types of Sensors
• Sensors attach via daughtercard
•Weather–Temperature–Light x 2 (highintensity PAR, lowintensity, fullspectrum)–Air Pressure–Humidity
•Vibration–2 or 3 axisaccelerometers
•Tracking–Microphone (for rangingand acoustic signatures)–Magnetometer
• GPS
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NetworkingSingle hop
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Networkingvs multi-hop
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Technology
TinyOS
An OS that runs on the motes
nesC: C-like programming language
TinyDB
etc...
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Outline
Brief description of sensor networks
Applications
Sensor Networks: Details
Sensor Networks: Challenges
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Challenges
Hardware Platforms
Motes still too big
But some apps need more power
Started with the vision of “smart dust’’
A lot of progress in last few years...
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Challenges
Reliability
Deployments are in extreme conditions
Failures are common
Node failures, communication failures etc
Weird failures... working but not correctly
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Challenges
Programming the tiny devices
TinyOS/nesC help
Not all sensors have identical platforms
Too much variety right now
TinierOS ?
Some even smaller (specs, RFIDs etc)
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ChallengesNetworking
Especially for wireless devices
Reliable networking is tricky
Especially multi-hop
Inherently lossy communication environment
Traditional internet protocols don’t work
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Challenges
ENERGY
Battery-powered
Other alternative used in some cases
Must run unattended for months, if not years
Radio communication most costly
Battery power doesn’t obey Moore’s law
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Challenges
Data management
When data is missing, imprecise, interpreting it becomes tricky
Because of high communication costs, should push computation inside the network
HUGE volumes of data
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Challenges
Security and Privacy
Perhaps the least-looked-at, but most important challenge
Too much data being collected
This will happen whether we like it or not
Who controls it ? Who can see it ?
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Summary
Goal was to give you an idea of one of the exciting new things happening in computer science
Many challenges need to be overcome before the vision becomes reality