Network Architecture for General-purpose Sensor Networks

1. Network ArchitectureforGeneral-purpose Sensor Networks Omprakash Gnawali gnawali@usc.edu http://enl.usc.edu/ 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 • 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 • 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. 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. Motes produce, process data, and return responses Executing Tenet Programs Applications run on masters, and masters task motes 24

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

26. Deployments

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