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

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

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

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

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

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

PermaSense Technology

PermaSense – System Architecture BackendSensor networkBase station

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

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

PermaSense – Sensor Node Hardware Shockfish TinyNode584 –MSP430, 16-bit, 8MHz, 10k SRAM, 48k Flash –LP radio: 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

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]

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

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

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

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]

Validation Using Simultaneous Power Traces

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

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

PermaSense Sensors – Sensor Rod Example

Sensors Rod Data –Temperature and Resistivity

PermaSense Sensors – Crack Meter Example

Crack Meter Data – Happy Geo-Science Partners

Of Testing, Bugfixing and Learning it the Hard Way…

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 >

The Result – Power Quality Increases Data Accuracy After Before

Of Sensors, Placement and Power Consumption

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

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]

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

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

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!

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

Pro’s and Con’s of Solar Panels

Demo – Live Data at

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

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

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 –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 –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 –M. Woehrle, C. Plessl, J. Beutel and L. Thiele: Increasing the Reliability of Wireless Sensor Networks with a Unit Testing Framework. EmNets –J. Beutel, M. Dyer, M. Yücel and L. Thiele: Development and Test with the Deployment-Support Network. EWSN –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 –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

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