1. The PermaSense Project Low-power Sensor Networks for Extreme Environments Jan Beutel, ETH Zurich National Competence Center in Research – Mobile Information and Communication Systems

2. PermaSense – Alpine Permafrost Monitoring Cooperation with Uni Basel and Uni Zurich

3. PermaSense – Aims and Vision Geo-science and engineering collaboration aiming to: –provide long-term high-quality sensing in harsh environments –facilitate near-complete data recovery and near real-time delivery –obtain better quality data, more effectively –obtain measurements that have previously been impossible –provide relevant information for research or decision making, natural hazard early-warning systems

4. To Better Understand Catastrophic Events… Eiger east-face rockfall, July 2006, images courtesy of Arte Television

5. PermaSense Deployment Sites 3500 m a.s.l. A scientific instrument for precision sensing and data recovery in environmental extremes

6. PermaSense – Key Architectural Requirements Support for ~25 nodes Different sensors –Temperatures, conductivity, crack motion, ice stress, water pressure –1-60 min sensor duty-cycle Environmental extremes –−40 to +65° C, ΔT ≦ 5° C/min –Rockfall, snow, ice, rime, avalanches, lightning Near real-time data delivery Long-term reliability – ≧ 99% data yield –3 years unattended lifetime Relation to other WSN projects Comparable to other environmental monitoring projects –GDI [Szewczyk], Glacsweb [Martinez], Volcanoes [Welsh], SensorScope [Vetterli], Redwoods [Culler] Lower data rate Harsher, higher yield & lifetime Data quality/integrity

7. PermaSense Technology

8. PermaSense – System Architecture BackendSensor networkBase station

9. Powerful embedded Linux (Gumstix) 4 GB storage, all data duplicated Solar power (2x 90W, 100 Ah, ~3 weeks) WLAN/GPRS connectivity, backup modem PermaSense – Base Station Overview

10. Base Station with Stacked Mikrotik WLAN Router Gumstix Verdex TinyNode GSM WLAN Router EMP Protectors IP68 Enclosure and Connectors

11. PermaSense – Sensor Node Hardware Shockfish TinyNode584 –MSP430, 16-bit, 8MHz, 10k SRAM, 48k Flash –LP radio: XE1205 @ 868 MHz Waterproof housing and connectors Protective shoe, easy install Sensor interface board –Interfaces, power control –Stabilized measurements –1 GB memory 3-year life-time –Single battery, 13 Ah –~300  A power budget

12. Precision Sensing – Architectural Considerations One platform vs. family of devices? Make vs. buy? –Capabilities for multiple sensors –Extreme low-power –High quality data acquisition (ADC resolution on MSP430 not sufficient) –Reliability in extreme environment Based on existing platform, Dozer low-power protocol –0.167% duty-cycle, 0.032mA Modular, accommodating different sensors on one platform Single, switchable serial bus architecture Strict separation of operating phases (TDMA) [Burri – IPSN2007]

13. Precision Sensing – Sensor Interface Board I Extension: One Serial Bus (Power) control using GPIO Optimized for low-power duty cycling

14. Precision Sensing – Sensor Interface Board II External Memory Data buffering End-to-end validation

15. Precision Sensing – Sensor Interface Board III Power Control and Protection Design for Testbed Integration

16. Dozer Low-Power System Software Integration Dozer ultra low-power data gathering system –Beacon based, 1-hop synchronized TDMA –Optimized for ultra-low duty cycles –0.167% duty-cycle, 0.032mA System-level, round-robin scheduling –“Application processing window” between data transfers and beacons –Custom DAQ/storage routine time jitter slot 1slot 2slot k data transfer contention window beacon time slot 1slot 2slot k Application processing window [Burri – IPSN2007]

17. Validation Using Simultaneous Power Traces

18. PermaDozer – Power Performance Analysis 1/30 sec 1/120 sec 148 uA average power

19. PermaSense Sensors Sensor rods (profiles of temperature and electric conductivity) Thermistor chains Crack meters Water pressure Ice stress Self potential Data: Simple sensors, constant rate sampling, few integer values

20. PermaSense Sensors – Sensor Rod Example

21. Sensors Rod Data –Temperature and Resistivity

22. PermaSense Sensors – Crack Meter Example

23. Crack Meter Data – Happy Geo-Science Partners

24. Of Testing, Bugfixing and Learning it the Hard Way…

25. Power Optimization – A Squeeze with Implications Regulator uses 17uA quiescent current Bypass used to shutdown regulator -> ~1uA in standby No Bypass increases ADC accuracy: std dev 0.8844 -> 0.0706

26. The Result – Power Quality Increases Data Accuracy After Before

27. Of Sensors, Placement and Power Consumption

28. Testing – Physical Reality Impacting Performance Watchdog Resets time Storage Duration DAQ Duration Ambient Temperature

29. Networked testbed: Deployment-Support Network Power profiling Power trace verification [Woehrle – FORMATS2009] Temperature cycling Sensor calibration Rooftop system break-in PermaSense – Test and Validation Facilities [Beutel – EWSN2007]

30. But Nothing Can Replace Real Field Experience Battery Voltage & Temperature Lost Packets System Outages

31. Node Health Data – Indispensable for Analysis Nodes Reset System Outages # Lost Packets Network Disconnect

32. Understanding the Exact Causes is Hard... Missing EMP protector – broken radio chip? If so is it snow/wind or lightning induced? Long-term software bug – buffer overflow; timing? Misunderstood “feature” of the implementation? Hardware breakdown? Energy-supply dependent? Spring-time behavior based on the environment? Cosmic rays at 3500 m a.s.l. ? Can external effects trigger the reed contact on the reset? … Probably not feasible to test/reproduce this in the lab!

33. Installation – Timeconsuming and Demanding PermaSense installation 2007, images courtesy of Arte Television

34. Pro’s and Con’s of Solar Panels

35. Demo – Live Data at http://tik42x.ee.ethz.ch:22001

36. Key PermaSense Challenges System Integration Correct Test and Validation Actual DataInterdisciplinary Team

37. PermaSense Achievements – Current Status Dozer integration successful –Best-in-class low power –DAQ vs. COM power consumption –Extreme installation effort (time) –Relative relaxation of multihop requirement Continuous data since mid July 2008 Media attention First joint geo-science publications [Gruber etal. – NICOP2008] 148 uA average power

38. Acknowledgements All PermaSense collaborators –Uni Basel, Uni Zurich, EPFL, SLF, ETH Zurich, … Further reading –J. Beutel, S. Gruber, A. Hasler, R. Lim, A. Meier, C. Plessl, I. Talzi, L. Thiele, C. Tschudin, M Woehrle, M. Yuecel: PermaDAQ: A Scientific Instrument for Precision Sensing and Data Recovery in Environmental Extremes. IPSN 2009. –J. Beutel, S. Gruber, A. Hasler, R. Lim, A. Meier, C. Plessl, I. Talzi, L. Thiele, C. Tschudin, M Woehrle, M. Yuecel: Operating a Sensor Network at 3500 m Above Sea Level. IPSN 2009. –A. Hasler, I. Talzi, J. Beutel, C. Tschudin, and S. Gruber, “Wireless sensor networks in permafrost research - concept, requirements, implementation and challenges,” in Proc. 9th Int’l Conf. on Permafrost (NICOP 2008), vol. 1, pp. 669–674, June 2008. –M. Woehrle, C. Plessl, J. Beutel and L. Thiele: Increasing the Reliability of Wireless Sensor Networks with a Unit Testing Framework. EmNets 2007. –J. Beutel, M. Dyer, M. Yücel and L. Thiele: Development and Test with the Deployment-Support Network. EWSN 2007. –K. Aberer, G. Alonso, G. Barrenetxea, J. Beutel, J. Bovay, H. Dubois-Ferriere, D. Kossmann, M. Parlange, L. Thiele and M. Vetterli: Infrastructures for a Smart Earth - The Swiss NCCR-MICS Initiative. Praxis der Informationsverarbeitung und Kommunikation, pages 20-25, Volume 30, Issue 1, January 2007. –N. Burri, P. von Rickenbach, and R. Wattenhofer, “Dozer: ultra-low power data gathering in sensor networks,” in Proc. 6th Int’l Conf. Information Processing Sensor Networks (IPSN ’07), pp. 450–459, ACM Press, New York, Apr. 2007.

39. Project Webpage: http://www.permasense.ch