Kenneth Bannister, Gianni Giorgetti, Sandeep K.S. Gupta

1. Wireless Sensor Networking for “Hot” Applications: Effects of Temperature on Signal Strength, Data Collection and Localization HotEmnets’08 – Charlottesville – 3 June 2008 Kenneth Bannister, Gianni Giorgetti, Sandeep K.S. Gupta IMPACT LAB http://IMPACT.ASU.EDU

2. Outline • Signal Strength Observations • Lab Experiments • Effect of Temperature on: • Link Budget and Communication Range • Network Connectivity and Data Collection • Localization • Conclusions and Future Work

3. Environmental Monitoring Botanical Garden, Phoenix, AZ Daily Variations in RSS “SMART” Container Project Daily Variations in RSS The “SMART” Container

4. Correlation With Temperature Botanical Garden, Phoenix, AZ RSS TEMP “SMART” Container Project RSS The “SMART” Container TEMP

5. Outline • Signal Strength Observations • Lab Experiments • Effect of Temperature on: • Link Budget and Communication Range • Network Connectivity and Data Collection • Localization • Conclusions and Future Work

6. Experimental Setup & Results Effects of temperature on the transmitter Thermal Chamber Attenuators Temperature at the Transmitter/RSS RX Section of the CC2420 POWER AMPLIFIER

7. Temperature Effects on the Receiver Effects of temperature on the receiver Thermal Chamber Attenuators RX Section of the CC2420 DEMODULATOR LNA Amplifies the RF signal from the antenna Measures RSS

8. Sensitivity ~ 3 dB

9. Loss due to Temperature

10. CC2400 and CC2520 DATASHEETS TI CC2400 and CC2520 Datasheets Output Power vs Temperature Output Power vs Temperature CC2400 CC2520 Output Power (dBm) -2.0 dB Output Power (dBm) -3.3 dB Temperature (°C) Temperature (°C) Sensitivity vs Temperature Sensitivity vs Temperature CC2400 Sensitivity (dBm) Sensitivity (dBm) -3.7 dB -1.6 dB CC2520 Temperature (°C) Temperature (°C)

11. Outline • Signal Strength Observations • Lab Experiments • Effect of Temperature on: • Link Budget and Communication Range • Network Connectivity and Data Collection • Localization • Conclusions and Future Work

12. Link Budget Analysis PRX(d) = P0 + 10nplog10(d0/d) + LTX(T) + LRX(T) -40 -50 -60 RSS [dBm] -70 np=2.3 -80 -90 -100 0 25 50 75 100 125 150 Distance [m]

13. Communication Range Depending on the path loss model, losses due temperature cause reduction in range comprised between 40% and 60% the max. value

14. Outline • Signal Strength Observations • Lab Experiments • Effect of Temperature on: • Link Budget and Communication Range • Network Connectivity and Data Collection • Localization • Conclusions and Future Work

15. Network Connectivity @ 25°C SINK NODE Avg. Connectivity = 8.94; Connected nodes = 100%; Avg. Path Length = 2.95.

16. Network Connectivity @ 45°C SINK NODE Avg. Connectivity = 4.57; Connected nodes = 98%. Avg. Path Length = 4.93. Few nodes are disconnected.

17. Network Connectivity @ 65°C SINK NODE Avg. Connectivity = 1.88; Connected nodes = 0%. The sink is disconnected from the rest of the network!

18. Data Collection: Summary • Temperature steadily decreases connectivity • Failure of Critical Links can cause the sink to become disconnected

19. Outline • Signal Strength Observations • Lab Experiments • Effect of Temperature on: • Link Budget and Communication Range • Network Connectivity and Data Collection • Localization • Conclusions and Future Work

20. Effect of Temperature on Localization Location awareness: • Enable Context-Aware Apps • Resource & Services Discovery • Tracking (People, Equipment,...) • Navigation Support • Security (Location-based access) Two Approaches: • Range-Based Localization (e.g. triangulation) • Range-Free Localization (e.g connectivity) • Both Range Estimates and Connectivity can be obtained from radio communication. Blind Nodes Anchors (GPS)

21. Ranging Errors d = 10 m d*=11.6m d* = 21.5m 0.2 pdf σdB 0.1 0 -65 -70 -75 -80 -85 -90 -95 RSS [dBm] • Received power modeled by the log-normal shadowing model: • PRX(d) = PLOG-D(d) + ∆; ∆~N(0, σdB); • Maximum Likelihood Estimate: • Errors increase with the temperature

22. Ranging Errors Temperature will cause to over-estimate the node distances Case 2 Case 1

23. Effect of Connectivity on Localization

24. Effect of Connectivity on Localization 4 1 3 1 2 1 3 2 1 1 2 1 2 1 Range-Based Connectivity-Based http://www.IMPACT.asu.edu • As temperature reduces connectivity, the number of range estimates decreases • The number of “connectivity” measurements does not change

25. Outline • Signal Strength Observations • Lab Experiments • Effect of Temperature on: • Link Budget and Communication Range • Network Connectivity and Data Collection • Localization • Conclusions and Future Work

26. Conclusions and Future Work • Actual measurements only available for the CC2420 radio. Simple model to account for temperature effects on RSS. • Tests with other platforms in progress • Importance of including temperature sensors in node design. • Importance of proper insulation and placement.

27. Impact of Temperature on WSN Design Data Collection Design & Implementation WSN Architecture Localization Applications Routing / Scheduling Services Networking Software OS / HAL Sensors Hardware Link Budget RSS Radio Radio TEMPERATURE Connectivity MCU Energy Capacity Battery Battery Life-time Source: CR2330 Datasheet Panasonic Physical Models Networking Models

28. Don’t forget the sunscreen! Thanks