1. Institut for Technical Informatics 1 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Towards Runtime Support for Energy Awareness in Wireless Sensor Networks Thomas Trathnigg and Reinhold Weiss Institute for Technical Informatics Graz University of Technology Graz, A-8010 Austria {trathnigg,rweiss}@iti.tugraz.at

2. Institut for Technical Informatics 2 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Outline Introduction Measuring Energy in WSNs Measurement Setup Error Analysis Validate PowerTOSSIM Conclusion + Outlook

3. Institut for Technical Informatics 3 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Introduction Lifetime of a wireless sensor network depends on the energy consumption of each node Limited energy-budget –Battery-powered –Energy harvesting Energy-awareness –Energy-aware routing –Dynamic Power Management –…

4. Institut for Technical Informatics 4 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Introduction Monitor the energy consumption of each mote Online monitoring Simulator calibration Requirements –accurate –low-power –small –inexpensive

5. Institut for Technical Informatics 5 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Mica2 Motes ATMEGA 128L –7.3 Mhz 8-bit CPU –128 KB code, 4 KB RAM 433, 868 or 916 Mhz, 76.8 Kbps FSK radio transceiver 512 KB flash for logging Sandwich-on sensor boards Powered by 2 AA batteries

6. Institut for Technical Informatics 6 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Typical Current Profile of Mica2 14-bit 100MHz dual-channel Digitizer (National Instruments) Fast changes in current profile due to cpu and radio state changes Clamp-on current probes „Fuel Gauges“ –Based on peridodical ADC sampling Energy-Driven Sampling –Based on an approach published by Chang et al. –Detecting software hotspots on a PDA

7. Institut for Technical Informatics 7 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Measurement Setup

8. Institut for Technical Informatics 8 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Error Analysis Non-ideal behavior of electrical components –discharge time of capacitor 500ns, 1000:1 ratio at 35mA; 0.1% error Voltage at the mote –voltage drop caused by shunt resistor <2% error Current-sense amplifier –error is below 2% in the range 3 to 66mA Bandwith of current-sense amplifier –fastest current change measured on mica2 mote 2.4mV/  s We expect the error of our setup to be below 5%

9. Institut for Technical Informatics 9 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Calibration + Verfication Determined the amount of energy a ramp depicts (54  J) Verification –Stable voltage supply 3V –Constant current load –60s measurments –Comparision of measurement with calculated result

10. Institut for Technical Informatics 10 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Error of Measurement Setup

11. Institut for Technical Informatics 11 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Validate PowerTOSSIM TinyOS 1.1.15 PowerTOSSIM –Support only for mica2 –used CPU cycle counting mica2 (868MHz) –Deluge disabled Several TinyOS Applications measured for 60s

12. Institut for Technical Informatics 12 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Typical TinyOS Applications

13. Institut for Technical Informatics 13 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Analysis of PowerTOSSIM Divergence Possible reasons –Measurement errors –Inaccuracies in the simulation PowerTOSSIM simulates at 4MHz, mica2 motes operate at 7.38MHz –Power-model of PowerTOSSIM systematic errors values of the power-model may be inaccurate 443MHz vs 868MHz Other hardware differences

14. Institut for Technical Informatics 14 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Energy Consumption of Different Motes No mica2 motes at 443MHz available, so we checked only other hardware differences 8 different mica2 motes 4% max. difference for Blink 3.4% max. difference for CntToRfm

15. Institut for Technical Informatics 15 Thomas Trathnigg Towards Runtime Support for Energy Awareness in WSNs Conclusion + Outlook Approach of energy-based sampling is feasible –size –cost –low-power, should be improved –accuracy range must be increased Improve/calibrate energy model of PowerTOSSIM Redesign of measurement setup –measurement range –low-power –integration on mica2 sensorboard