Embedded Networks Laboratory
Network Architecture
for
General-purpose Sensor Networks
Omprakash Gnawali
gnawali@usc.edu
http://enl.usc.edu/
CSSE March 17, 2009
Embedded Networks Laboratory
Sensor Network
• Network of small form-factor sensors
• Resource constraints
– CPU (<10 MHz)
– RAM (<10 KB)
– Low power
• Embedded in the physical world
• Wireless communication
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Embedded Networks Laboratory
Building Vibrations
Forced Vibration Testing
at the Four Seasons Building
in Los Angeles
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Embedded Networks Laboratory
Bridge Vibrations
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Embedded Networks Laboratory
Pursuit Evasion
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Embedded Networks Laboratory
Habitat Imaging
James Reserve, Riverside, CA
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Embedded Networks Laboratory
Sensor Network Applications
• Examples
– Industrial space
– Environment
– Infrastructure
• Hardware and Software Optimizations
– Components
– Scenarios
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Embedded Networks Laboratory
Outline
• Sensor Network
• Programming a Sensor Network
• Tenet: A General-purpose Sensor Network
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Embedded Networks Laboratory
Programming a SensorNet
Programming Abstraction
Services
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Embedded Networks Laboratory
Programming Abstraction
• Node-level API
– “Node x: execute program y”
– Reasoning and Debugging Challenging
• Program the network
– “Network: Collect light readings”
– No fine-grained control
– Network and Node Services
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Embedded Networks Laboratory
Collection Routing
• Collect data from the network
– From all the nodes
– To a small number of “sinks”
• Challenges
– Link estimation
– Dynamics
• Tree Routing
– CTP, MultihopLQI
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Embedded Networks Laboratory
Collection
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Embedded Networks Laboratory
Reliable Transport
•
•
•
•
Prevent data-loss
End-to-end retransmission
Used with Collection
Challenges
– Limited RAM
– Congestion
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Embedded Networks Laboratory
Congestion Collapse
• Four Seasons
building deployment
• Some packets took
more than an hour
to recover while
collecting 10
minutes worth of
data
Loss recovery latency
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Embedded Networks Laboratory
Dissemination
• Delivers data to every node in a network
• Challenges
– Rate
– “Broadcast storm”
• Many uses
– Reconfiguring a network
– Injecting queries and tasks
– Substrate for more complex protocols
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Embedded Networks Laboratory
Timing
• Timestamps for sensor readings
• Globally synchronized time
• Challenges
– Different clock rates on the nodes
– Wireless
• Approaches
– Hardware: GPS
– Software: FTSP
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Embedded Networks Laboratory
Sensing and Actuation
• Sensors
– Light, Temperature, Accelerometer
• Actuators
– LED, Relays
• Portable abstraction
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Embedded Networks Laboratory
Data Processing Services
• Raw data not always needed
• Data filters
– Specify (un)wanted data
• Data processing
– Statistics
– Transforms, Coefficients
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Embedded Networks Laboratory
General-purpose API
• Provides Services
– Collection routing
– Reliable transport
– Dissemination
– Timing
– Sensing and Actuation
– Data processing
• Allows flexible composition of services
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Embedded Networks Laboratory
Outline
• Sensor Network
• Programming a Sensor Network
• Tenet: A General-purpose Sensor Network
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Embedded Networks Laboratory
Tenet
• Masters and Motes
• Tasks and
Responses
• Linear data-flow
programs
repeat(1s)->sense(LIGHT)->send(RELIABLE)
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Embedded Networks Laboratory
Tenet Services
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Embedded Networks Laboratory
Tenet Programs
• Linear data flow language
– natural choice for sensor data processing
• Tasklets specify elementary actions
– sense(), set_leds(), avg()
• Tasklets can be composed to form a task
– sense(LIGHT,10 samples)avg(LIGHT)send()
– repeat(10 mins)get(ROUTING_PARENT)send()
• No branches
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Embedded Networks Laboratory
Executing Tenet Programs
Applications run on masters,
and masters task motes
Motes produce, process data,
and return responses
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Embedded Networks Laboratory
Tenet Performance
400
min
avg
max
350
msg/min
300
250
200
150
100
50
0
Mote-PEG
Tenet-PEG
Tenet applications perform comparably with
software optimized for a particular application.
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Embedded Networks Laboratory
Deployments
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Embedded Networks Laboratory
Conclusion
• Deployments
– Software reuse
– No performance
penalty
• Looking ahead
– General-purpose
radio duty-cycling
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