1. Network Architecture for General-purpose Sensor Networks
Omprakash Gnawali
CSSE March 17, 2009

2. 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

3. Building Vibrations Forced Vibration Testing
at the Four Seasons Building
in Los Angeles

4. Bridge Vibrations

5. Pursuit Evasion

6. Habitat Imaging
James Reserve, Riverside, CA

7. Sensor Network Applications
Examples
Industrial space
Environment
Infrastructure
Hardware and Software Optimizations
Components
Scenarios

8. Outline Sensor Network Programming a Sensor Network
Tenet: A General-purpose Sensor Network

9. Programming a SensorNet
Programming Abstraction
Services

10. 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

11. Collection Routing Collect data from the network Challenges
From all the nodes
To a small number of “sinks”
Challenges
Link estimation
Dynamics
Tree Routing
CTP, MultihopLQI

12. Collection

13. Reliable Transport Prevent data-loss End-to-end retransmission
Used with Collection
Challenges
Limited RAM
Congestion

14. 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 14

15. 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

16. Timing Timestamps for sensor readings Globally synchronized time
Challenges
Different clock rates on the nodes
Wireless
Approaches
Hardware: GPS
Software: FTSP

17. Sensing and Actuation Sensors Actuators Portable abstraction
Light, Temperature, Accelerometer
Actuators
LED, Relays
Portable abstraction

18. Data Processing Services
Raw data not always needed
Data filters
Specify (un)wanted data
Data processing
Statistics
Transforms, Coefficients

19. General-purpose API Provides Services
Collection routing
Reliable transport
Dissemination
Timing
Sensing and Actuation
Data processing
Allows flexible composition of services

20. Outline Sensor Network Programming a Sensor Network
Tenet: A General-purpose Sensor Network

21. repeat(1s)->sense(LIGHT)->send(RELIABLE)
Tenet
Masters and Motes
Tasks and Responses
Linear data-flow programs
repeat(1s)->sense(LIGHT)->send(RELIABLE)

22. Tenet Services

23. 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

24. Executing Tenet Programs
Applications run on masters, and masters task motes
Motes produce, process data,
and return responses 24

25. Tenet Performance
Tenet applications perform comparably with software optimized for a particular application.

26. Deployments

27. Conclusion Deployments Looking ahead Software reuse
No performance penalty
Looking ahead
General-purpose radio duty-cycling