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

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

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

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

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

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

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

Sensitivity ~ 3 dB

Loss due to Temperature

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

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

Link Budget Analysis P RX (d) = P n p log10(d 0 /d) RSS [dBm] Distance [m] + L TX (T) + L RX (T) n p =2.3

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

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

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

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

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

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

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

Effect of Temperature on Localization Anchors (GPS) Blind Nodes 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.

Ranging Errors RSS [dBm] pdf d = 10 m d*=11.6m Received power modeled by the log-normal shadowing model: PRX(d) = P LOG-D (d) + ∆;∆~N(0, σ dB ); Maximum Likelihood Estimate: Errors increase with the temperature d* = 21.5m -95 σ dB

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

Effect of Connectivity on Localization

Effect of Connectivity on Localization As temperature reduces connectivity, the number of range estimates decreases The number of “connectivity” measurements does not change Range-BasedConnectivity-Based

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

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.

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

Don’t forget the sunscreen! Thanks