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FlockLab : A Testbed for Distributed, Synchronized Tracing and Profiling of Wireless Embedded Systems

FlockLab : A Testbed for Distributed, Synchronized Tracing and Profiling of Wireless Embedded Systems. IPSN 2013 NSLab study group 2013/04/08 Presented by: Yu-Ting. Outline. Introduction Architecture Benchmark Application. Introduction.

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FlockLab : A Testbed for Distributed, Synchronized Tracing and Profiling of Wireless Embedded Systems

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  1. FlockLab: A Testbed for Distributed, SynchronizedTracing and Profiling of Wireless Embedded Systems IPSN 2013 NSLab study group 2013/04/08 Presented by: Yu-Ting

  2. Outline • Introduction • Architecture • Benchmark • Application

  3. Introduction • A testbed with 30 observers (4 at outdoors) and a set of servers • Support 4 different targets (nodes) • Other than serial port service,these nodes can synchronously: • Trace GPIO • Actuate GPIO • Power profiling • Adjust supply voltage • Much better than multiple logic analyzers, mixed-signal oscilloscopes, and power analyzers

  4. Outline • Introduction • Architecture • Benchmark • Application

  5. 9 LEDs By GPIO or UART Hardware 5V for embedded Com 3.3V for others 1000 USD Step: 0.1V Can also control USB fan foroutdoor nodes Shunt resistor Amplify the volt across shuntby a gain of 100 To profile power CPU: 624MHz RAM: 128MB Flash: 32MB 8GB This selection is doneby two 8-bitsignal translator Map slot withtarget boardsby serial ID chiip For outdoor nodes without Ethernet

  6. More about measuring power • Resolution in power: 10nA • Limit: 160mA (enough) • ADC sample at 56kHz in high-speed mode and 28kHz in high-resolution (SNR = 109dB) mode with 14.3MHz clock source=> resolution in time: 35.7us or 17.85us

  7. Software • OS: OpenEmbedded Linux • NTP client: Chrony, synchronize every 1-2min with NTP server of FlockLab Efficient data handling (caching)

  8. Backend Infrastructure • Time Synchronization server (NTP server)=> sync by another server on campus and PPS by GPS receiver • Web server • Test management server (also stores data) • Database server • Monitoring server

  9. Deployment • Indoor * 26 (in same LAN segment) • Outdoor * 4 • Yellow level: RSSI value when idle

  10. Outline • Introduction • Architecture • Benchmark • Application

  11. Time Accuracy - GPIO • Use GPIO to trace PPS of same GPS clock • Use mixed-signal oscilloscope to actuate GPIO • Pairwise timing error • GPIO tracing VS PPS: normal distribution

  12. Time Accuracy – Power Profiling • SFD rise -> toggle GPIO & turn on LEDSFD fall ->turn off LED • SFD events happen at the same time (< 1us) • Most error of same observer comes from random delay of GPIO event and the following power sample • Error of different observer is comparable topairwise timing error of GPIO events

  13. Power Accuracy • Test by high-precision power analyzer • Target resistance: 259mΩAA batteries: 947mΩ • Calibration: Use linear regression to estimate more accurate constant of offset and gain of current-sense amplifier, and shunt resistor Relative error: observer VS power analyzer

  14. Limits in Capturing GPIO Events • No new events can be captured until the respective flag is cleared • Minimum required interval between consecutive GPIO events to be captured=> depends on the interrupt delay and ISR execution time • SFD events may still loss for small packet(<9bytes)

  15. Outline • Introduction • Architecture • Benchmark • Application

  16. Analysis of Tasks Without FlockLab • Generally speaking, they are: • More intrusive and less accurate • Need to recompile due to code changes • Need to change existing codes for different platform • Power profiling • Energest in Contiki, but also intrusive • Customize yourselves in TinyOS… • End-to-end delay • Timestamps in serial logging, but it’s inaccurate • Run time synchronization protocol=> Multiple protocols may cause performance losses or even failures • Actuate events (controlling) for multiple nodes • Also need time synchronization • Using network simulators like Cooja

  17. Comparative Multi-Platform Analysis • Run CTP on top of LPL: how each platform affects the trade-offs between metrics • Observation • 200ms is best for such topology & traffic load • Tmote Sky is most sensitive, while IRIS is best • The trades are the same

  18. Finding and Fixing Bugs • Bug: the initial results with LPL wake-up intervals of 500 ms and 1s from Tinynodeand Opal nodes were significantly worse • Reason: children were transmitting at most one packet during an LPL wake-up interval, although they had multiple packets ready to be sent

  19. Controlling and Profiling Applications • Purpose • One node to generate a packet every 2s for 260s, from t = 30s to t = 290s • In the mean time, measure the energy consumption • Task 1 is easily done by GPIO actuation • Comparison of task 2 between different methods • FlockLab is non-intrusive and highly accurate

  20. Measuring Clock Drift • Enable FTSP every 3s and get the clock drifts of each node compared with the root • Toggle a GPIO pin every 0.5s • Compare the difference between GPIO timestamp interval and 0.5s with clock drifts • Average over 5min to limit GPIO timing errors

  21. Multi-Modal Monitoringat Network Scale

  22. Q&A

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