Telemetry for a Coastal Ocean Observing System Part 2

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Telemetry for a Coastal Ocean Observing System -
Part 2 Results further on using the Iridium
System Chris Calloway, Sara Haines, Collin
McKinney, Luke Stearns, Bill Brown, Harvey
Seim SEACOOS / NCCOOS / UNC-CH Dept. of Marine
Science Jeff Jefferson SEACOOS / CAROCOOPS / USC
Baruch Institute for Marine Coastal
Sciences Paul Work SEACOOS / Georgia
Tech-Savannah School of Civil and Environmental
Engineering William Johns SEACOOS / EFSIS / U.
of Miami Rosenstiel School of Marine
Science Cliff Merz, Chad Lembke SEACOOS / COMPS
/ USF College of Marine Science Center for Ocean
Technology http//www.seacoos.org
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SEACOOS and Iridium at UNC-CH
Navy TACTS Towers (ISU originated to POTS FTP)
Research Buoys (ISU originated to POTS FTP)
Slocum Gliders (ISU originated to POTS ZMODEM
proprietary)
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SEACOOS and Iridium at Baruch
Research Buoys (land ISU to ISU ZModem)
Linux 37.8 kb/day Transmission every two hours
(battery recharge time) February 2006 86 call
success March 2006 93 call success Errors
reported via cell phone to on-call technician No
Carrier is highest error count Desire automated
method to determine signal quality at specific
points at specific times
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SEACOOS and Iridium at Georgia Tech
Triaxys Buoys (proprietary AXYS WaveView
software)
Directional (spectral) wave buoy Uses 9505 modem
and newer pancake antenna Also capable of VHF,
INMARSAT D, INMARSAT C, Argos, Orbcomm, GOES and
GSM telemetry Two minute transmissions at 2400
baud
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SEACOOS and Iridium at RSMAS
SWAMP Shallow Water Autonomous Profiler Fixed
ADCP and a buoyant CTD under HF
radar Periodically released to the
surface Winched back to the bottom Profiles of
velocity and T/S Hourly current and 6-hourly CTD
profiles Transmitted every 6 hours. Currently
VHF Iridium under development Ocean Sensors, Inc.
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SEACOOS and Iridium at USF
BSOP Bottom Stationed Ocean Profiler Receives
programmed mission for next surfacing 100 T/S
samples in profile Low drift rate (lt 0.1 nm /
cycle) Position held by stationing on sea
floor Currently Orbcomm Quake modem Iridium in
development (not Quake SBD only two way
required)
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Error Analyses of Two Platforms at UNC with
Common Communications Library
Tower "R4" (100 nm east of St. Simon's Island, GA)
Lookout Shoals (NC) Research Buoy "LSRB"
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Error Analyses of R4 and LSRB
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Higher rate of error at Tower platform after
relocation of antenna mount. Previous error rates
in same neighborhood prior to relocation.
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Most errors make use of the software/hardware
recovery mechanism.
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Tower error distribution is very similar to buoy
error distribution despite much lower file
transfer success rate.
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LSRB Disconnect Errors

• Observations in lab report "no carrier" as major
  cause of Disconnect error
• Win CE 3.0 platform incapable of Disconnect error
  granularity

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R4 Hangup Errors

• Indication of Retry in Progress
• Loss of comms results in myriad RASHangUp return
  codes

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Timeout Error Comparison

• Excellent signal path results in few retry
  attempts due to Iridium
• Poor signal path results in many retry attempts
  due to Iridium

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Obvious Development Path for CommLib

• Monitor Disconnect error rate in real time
• Increase Dial retry limit as Disconnect error
  rate rises
• Introduce Dial retry time delay

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Recommendations

• Automated method to determine signal
  quality Real time Predictive
• Fixed cost solutions for high bandwidth and
  multiple platforms

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http//georidium.org/Members/cbc/april-2006/