Polar experience with Iridium: Dialup and SBD

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Polar experience with IridiumDial-up and SBD

• David Meldrum and Duncan Mercer
• Scottish Association for Marine Science
• www.sams.ac.uk

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SAMS involvement with Iridium

• Active user
• Deployers of Argos drifters since 1980
• Orbcomm ice drifters since 1999
• Iridium for polar applications
• Development of policy and protocols for the data
  buoy community
• Data Buoy Co-operation Panel
• International body sponsored by IOC and WMO
• Argos Joint Tariff Agreement

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History repeats itself

• Early problems for the Argos user
• Why buy Argos?
• Argos promises to meet user need
• The system works!
• How does it work?
• Will it do a new task?
• Suck it and see
• The system doesnt work
• God Only Knows (GOK)
• Satellite Operator Only Knows (SOOK)
• Whom do you contact?

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One solution

• DBCP (1985)
• Metocean community concerns over quantity/quality
  of Argos buoy data
• Resolutions and recommendations
• No effect on data
• Technical Co-ordinator (1987)
• Based at Argos Toulouse
• Access to all elements of chain, incl GTS
• Access to Argos technical team

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Why is the TC a success?

• Within Argos
• Independent of Argos
• Focussed on user issues
• Good for users
• Good for Argos
• Better support
• Better definition of requirements
• Better roll-out of new products
• Better for image

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How is it funded?

• Salary and expenses from users
• Contributions from DBCP members
• Accommodation and facilities from Argos
• Ballpark cost 100k/year

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CASES Deployment

• Three, pancake ice buoys deployed
• Latitudes between 700N and 720N (1200W)
• SBD packets 892 bytes
• 8 Messages / buoy / day
• 9 buoy-months of data (so far)
• 2000 messages in total

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CASES Buoys
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System Operation

• Turn on Modem
• Wait for system to register to network
• Try to send message
• Test reply for success
• Read and act on inbound messages
• 3 attempts then discard

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Registration Time
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Transmission Time
gt Rate of 740 Baud!
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Lost Messages (dml100)
10 Msg Loss
9 Msg Loss
The Moral of this story ??
12 Msg Loss
KEEP YOUR ANTENNAS POINTING UPWARDS !
3 Msg Loss
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Msg Loss
Received from localhost (HELO sbd.iridium.com)
(127.0.0.1) by 0 with SMTP 1 Jan 2004 144341
-0000 Reply-To ltsbdservice_at_sbd.iridium.comgt From
sbdservice_at_sbd.iridium.com To
iridium_at_sams.ac.uk Subject SBD Msg From Unit
300001001854010 MOMSN 1003 MTMSN 0 Time of
Session (UTC) Thu Jan 1 144338 2004 Session
Status INCOMPLETE CALL Message Size (bytes)
0 Unit Location Lat 69.667585 Long
-120.486450 CEPradius 2
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Msg Loss

• 100 of messages correctly acknowledged
• MOMSN correct count of messages sent
• Problems with mail server Data loss !
• Alternate mail servers in DNS ?
• Get SBD sent to more than one site ?

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Dial Up

• SBD easy but!!
• GreenIce COMMS cost 115k for 6 months

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GreenIce Dial Up

• Dial up problems with NO CONNECT
• Implement ZModem
• Transfer files of 37 kbytes
• Buoys between 840 and 860N
• First 2Weeks -gt Avg Tx Time 120 Secs
• gt 3100 Baud !
• Compression info?

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Our Iridium conclusions

• Excellent potential for higher data volumes
• Real-time interaction with mobile
• 1 or 2 orders of magnitude more energy efficient
  than Argos or Orbcomm
• 20 J/kbyte for larger file sizes
• 10 cents/kbyte for dial-up
• SBD costs
• 1/kbyte for North America and elsewhere
• Easier to implement than dial-up
• Expensive for large datasets!
• Still lots to learn
• Much better tech info/support needed!

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