3mbps on a ship at 5:1 tdma oversubscribed is about 16k a month on c band
Sure, Bro.
Hi Scott,
If it's Iridium they aren't doing 1.5mbps. Iridium has Short Burst
Data (SBD), a messaging service capable of sending and receiving a 2kB
message a couple times a minute and they have RUDICS, a 1200bps or
2400bps (not kbps or mbps) synchronous serial service. They also have
a product which gangs enough RUDICS channels together to get a 56k
modem speed. Higher speed claims are "with compression."
SBD is not used for Internet access, though it can be used for email.
It's messaging, not packet data.
What Iridium does have is coverage. Everywhere. Including both poles.
They use a couple constellations of Low Earth Orbit (LEO) satellites
with honest to god packet routing across the satellites to the ground
stations. You don't need a stabilized high-gain antenna to talk to the
satellites (they're only 500 miles up) and you don't have to be in the
same footprint as a ground station.
Basically, they're flying cell phone towers circa the mid-90's with
microwave relays between them.
This is very different from something like, let's say, Inmarsat.
Inmarsat's satellites sit out at geostationary orbit, 23,000 miles
away. More, they're a "bent-pipe" configuration. Your signal goes up
on one radio frequency, is analog-shifted and comes back down at
another radio frequency to the ground station that shares the
footprint. On the other hand, since they're simple analog amps they've
been able to recognize the kind of gains from tech that improved
9600bps phone lines to 7mbps DSL lines, and because they're not
routing between satellites, each bird they fly has its own complete
bandwidth.
But I suspect an arctic icebreaker isn't using Inmarsat, with or
without a stabilized three-meter antenna. Geostationary satellites
have to fly around the equator. They wouldn't be stationary relative
to the surface if they didn't. So, they kinda have trouble seeing the
poles.
There's also the odd fish like Globalstar. They have LEO satellites
that are bent-pipes. This gives them limited coverage, and it's kinda
weird -- your signal actually hits multiple satellites and ground
stations and has to be deduped. Still, where it works it seems to
work.
Regards,
Bill Herrin
Just to be fast, the article said 1.5Mbps
Also, I completely missed that there was a page 2. It looks like they use
Iridium. Here is some pricing. Just the first thing I found:http://www.sattransusa.com/irprpl.html
Plan Monthly Amount Monthly Allowance Cost per 1000 Bytes
Plan SBD 0 $27.00 0 Bytes $1.15
Plan SBD 12 $35.10 10,000 Bytes $1.05
Plan LBS 8* $28.78 8,000 Bytes $1.78Hi Scott,
If it's Iridium they aren't doing 1.5mbps. Iridium has Short Burst
Data (SBD), a messaging service capable of sending and receiving a 2kB
message a couple times a minute and they have RUDICS, a 1200bps or
2400bps (not kbps or mbps) synchronous serial service. They also have
a product which gangs enough RUDICS channels together to get a 56k
modem speed. Higher speed claims are "with compression."
Russian Satellite Communications Company operates geostationary
satellites as part of intelsat and eutelsat. Molniya insorfar as I'm
aware still exists and is a constellation of high elliptical orbit
communications satellites with a 12 hour orbit, it's specifically
useful over the poles.
in one of the photos on the orignal live journal is an inmarsat terminal
onbaord the vessel.
the ship is the icebreaker yamal which at 23000 tons is a pretty big
platform to mount hardware on.