GDI Sensor Net RIP GDI Data Analysis Robert Szewczyk December 20, 2002

Global statistics 43 distinct nodes reporting data at various times packets logged in the DB 3 maintenance events, roughly every month Heavy mote losses – 4% daily Best nodes – nearly packets on a pair of AA batteries, over 2.5 months unattended operation

Sample data collected Collected light levels, temperature, relative humidity, thermopile IR and ambient temperature

Sample data – sensor discussion Thermopile sensor -- difficult to gain the confidence in the readings –Good correlation between the ambient temperature readout from the thermopile and the measured temperature »But difficult to scale it –Difficult to determine appropriate signal processing for the IR signal »Low confidence even as a occupancy detector Pressure sensor –Not used in the application, produced even less reliable nodes Humidity sensor –packaging problems – bulky, battery drain when wet –addressed in the next revision of the weather board Temperature sensor –resolution significantly lower than advertised; –reported in a plausible temperatures in a wide range ( deg C) –Very good correspondence with Coast Guard data Light sensor –Known limitations, good baseline indication of mote health

Power Management Expected 6+ 3% duty cycle –Real world performance MUCH worse – best node lasted only 2.5 months Correlation between packet success rate and battery voltage –Boost converter provides less consistency than expected –Batteries can be drained down to 0.8 V per cell, poor reliability below 1.1 V per cell Battery voltage at node 57, the most reliable mote from the initial deployment. Last packet from that node on that set of batteries was received on 9/24; the node reliability declined drastically after 9/22.

Network analysis Several underlying causes for packet loss –Laptop / database crash – connection to the laptop was only available 47% of the time –Low battery levels –Collisions –Environmental conditions – wind blowing antennas out of alignment, rain affecting humidity sensor and short-circuiting the battery Packet loss distribution –Packet loss does not behave like an independent distribution –Work in progress to bin the potential causes of packet loss

Loss distribution

Phase stability

Conclusions First application that stressed low power and unattended long-term operation What we learned –Need a lot of diagnostic information to support long running apps »Gain confidence in the sensor readings »Diagnose and remotely repair faults (if possible); provide bounded downtime »Components addressing many concerns either exist or will soon exists – link layer acks, channel monitoring component, watchdog timer, etc. –Boost converter falls short of expectations »Poor efficiency »Reduced performance on weaker batteries

Conclusions (cont.) Future work –Application redeployment in a more controlled environment –Further root cause analysis –Incorporating the lessons learned into Generic Sensor Kit and second generation weather board Accessing GDI data – –PostgreSQL database »Server: dbsvr.berkeley.intel-research.net »Username: reader »Password: readonly »Database: gdi »Most interesting table: weather

Mote 18: Outside

Mote 26: Burrow 115a

Mote 53: Burrow 115b

Mote 47: Burrow 88a

Mote 40: Burrow 88b

Mote 39: Burrow 84