Flocklab a testbed for distributed synchronized tracing and pro ling of wireless embedded systems
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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 pro ling of wireless embedded systems

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

IPSN 2013

NSLab study group 2013/04/08

Presented by: Yu-Ting


  • Introduction

  • Architecture

  • Benchmark

  • Application


  • 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


  • Introduction

  • Architecture

  • Benchmark

  • Application


9 LEDs



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


This selection is doneby two 8-bitsignal translator

Map slot withtarget boardsby serial ID chiip

For outdoor nodes without Ethernet

More about measuring power
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


  • OS: OpenEmbedded Linux

  • NTP client: Chrony, synchronize every 1-2min with NTP server of FlockLab

Efficient data handling


Backend infrastructure
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


  • Indoor * 26 (in same LAN segment)

  • Outdoor * 4

  • Yellow level: RSSI value when idle


  • Introduction

  • Architecture

  • Benchmark

  • Application

Time accuracy gpio
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

Time accuracy power profiling
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

Power accuracy
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

Limits in capturing gpio events
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)


  • Introduction

  • Architecture

  • Benchmark

  • Application

Analysis of tasks without flocklab
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

Comparative multi platform analysis
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

Finding and fixing bugs
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

Controlling and pro ling applications
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

Measuring clock drift
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

Multi modal monitoring at network scale
Multi-Modal Monitoringat Network Scale