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Tripod Localization and Sensing Testbed. Lewis Girod. Goals of this effort. Develop a system to calibrate locations of field-deployed motes Turnkey system Deploy, use, and take down in a day Minimize restrictions on deployment Provide a convenient platform for…

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Presentation Transcript
goals of this effort
Goals of this effort
  • Develop a system to calibrate locations of field-deployed motes
    • Turnkey system
    • Deploy, use, and take down in a day
    • Minimize restrictions on deployment
  • Provide a convenient platform for…
    • testing and evaluating new ranging techniques
    • Acoustic channel measurement?
    • Other kinds of sensing experiments?
tripod design
Tripod Design
  • Resource un-constrained design
  • Runs on batteries for 6 hours
  • Four audio channels
    • 4 fixed microphones
      • Omni-directional, 15Hz-30KHz
    • 1 fixed speaker with a reflector
    • 96 KHz / 24 bit samples
  • CPU
    • 1 GHz P3, 256 MB, 20GB Hard drive
    • Runs on 12V
  • Network
    • 802.11 for inter-tripod network
    • “MoteNIC” to talk to mote network
  • 3-axis orientation sensor
more detail
More detail

Mica2 Mote

USB 802.11 adaptor

Reflector

Car stereo speaker

3-axis orientation sensor from MicroStrain. May be dropped due to cost if found unnecessary.

Behringer ECM8000 microphone, intended for acoustic testing. Very flat response from 15Hz to 20KHz

2x “Audiobuddy” 2 channel microphone preamp, feeding to M-Audio Delta-44 4 channel 96/24 PCI sound card.

30 cm inter-mic spacing

CPU: Currently a ruggedized industrial PC from littlePC.com

questions
Questions
  • Would this kind of platform be helpful to your group?
  • Are there additional / unnecessary features?
    • Is 96 KHz / 24 bit useful to you?
    • Microphone spacing?
  • Microphone preamps
    • Need phantom power
    • The one I selected runs off 9V AC 
    • Rather have it run off a (noisy) DC supply
mote localization in more detail
Mote Localization in More Detail

Relative locations of motes more poorly constrained

  • Inter-mote ranging.. Why not?
    • Additional hardware and software constraints
    • Resource consumption
    • Emitter only is low-cost
  • How important is it?
    • Bi-partite geometry may leave locations of motes poorly determined
    • Other constraints
      • Bearing estimates?
      • Mote connectivity?
tripod system in more detail
Tripod System in more Detail

After motes in blue region are located, move tripods to cover green region

  • Grounding the coordinate system
    • Locate one tripod at origin position, define it as the “origin”
    • Will another fixed point be needed?
  • System feedback to user:
    • System can ask tripods to be moved to improve constraints
    • System indicates when all motes in region are located
  • Cover more ground by moving tripods

Origin

experimental ranging techniques leveraging four channels
Experimental Ranging TechniquesLeveraging Four Channels
  • Bearing estimates
    • Add constraints to multilateration
    • May be helpful to address bi-partite topology
    • Angular inconsistencies across nodes might detect obstructed signals
  • Computed based on detected ranges to each microphone
    • More sophisticated analysis might correlate mic signals
multipath bearing estimation
Multipath Bearing Estimation
  • Bearing estimates of multipath components?
    • Distribution of incoming paths (angle and intensity)
      • Might provide clue about whether path is obstructed
      • Cases with LOS should have much stronger direct path
    • Deduce location of sender in some cases?
      • Estimation using model of reflectors
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