
Network topology design at 27,000 km/hr - olivernyc
https://blog.apnic.net/2020/02/25/network-topology-design-at-27000-km-hr/
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walrus01
The first generations of Starlink satellites will serve as bent pipes. They're
not doing intersatellite links. This will require dozens of small trunk-link
earth stations around the USA, in the same general region for rural services.

For example an earth station near the fiber in Boise, ID would have visibility
for bent-pipe type relay to the same satellites presently overhead of many
very hard to reach, rural, remote Idaho locations. The remote parts of ID
which are presently only serviced by small geostationary VSAT terminals
(viasat/wildblue/hughesnet etc).

About a year and a half ago Elon Musk fired the part of the starlink team,
based on Redmond WA who wanted to go directly to intersatellite links in the
first generation, most of whom have now ended up at Kuiper.

[https://www.reuters.com/article/us-spacex-starlink-
insight/m...](https://www.reuters.com/article/us-spacex-starlink-insight/musk-
shakes-up-spacex-in-race-to-make-satellite-launch-window-sources-
idUSKCN1N50FC)

This also means that in order to establish service in a particular area it
will require putting in place starlink earth stations in the general region.
Meaning that there might be full satellite coverage over the same latitudes in
Canada, and Russia on the same calendar date, but Canada will receive live
service much earlier.

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erentz
That’s really disappointing to learn. It was the inter-satellite linking part
that make it really interesting (to me) and which promised to provide big
latency improvements over fiber (over longer distances). I wonder if it proved
too hard in practice?

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mhandley
Elon Musk has stated that until they have inter-satellite laser links
deployed, they can get wide area low latency communications by relaying via
ground stations at a high slant angle. I built a simulator and ran an analysis
of this, and actually it works pretty well. My video analysing all this is
here: [https://youtu.be/m05abdGSOxY](https://youtu.be/m05abdGSOxY)

~~~
walrus01
There's a variety of software packages you can use to simulate the ground
footprint of a starlink satellite, from the TLEs (two line elements). Or
Iridium or anything else.

It's a circle many hundreds of km wide. Assuming that an earth station will
have a minimum look angle of about 18 degrees above the horizon, one can
calculate the serviceable area for customer and trunk link spot beams within
the satellite's moving footprint.

The scenario shown in your youtube video has uses for HFT and similar very
latency sensitive applications. But because it's RF, there's no way that a
chain of starlink satellites relaying through multiple ground stations will
compete in raw throughput and capacity with fiber. Remember that a single IT
standard 100GHz grid DWDM channel is a few terahertz wide, and 80 channels can
easily fit in the conventional bands of a long haul DWDM system in just two
strands of fiber.

~~~
mhandley
Yes, that's correct, but the interesting part is not the footprint, but the
latency and variability of the dynamically routed paths you can obtain. That's
what I simulated. I also made some modifications to how you'd normally route
such a network, because the conventional approach wasn't fast enough if you
have a wide choice of groundstations and the topology is continuously
changing. The animations in the video are doing the route calculations in
realtime once per frame of video; I was pretty pleased with those
optimizations. One surprise, for me at least, was that there are paths where
you sometimes want to relay via ground stations, even when the satellites have
inter-satellite laser links. That's in the video towards the end.

Edit: in response to the point you added about bandwidth: that's correct -
there's no way the ground relay path competes with fibre on bandwidth. There
are, however, many potential uses that require low latency and are not high
bandwidth.

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IndrekR
If you enjoyed this, _Eccentric Orbits: The Iridium Story_ by John Bloom is a
good book on the similar topic from few decades back. Spiced with a healthy
bunch of politics, entrepreneurship and action.

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awshepard
Have to second this comment. The Audible version of it had me riveted. A great
story well-told, with a raft of good quotes, such as "People didn’t like game
changers in the 90s anymore than the owners of of the Erie Canal liked the
transcontinental railroad. New technology always leaves a battlefield littered
with bodies."

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sriku
While general purpose satellite internet is nice, I'm wondering (in brainstorm
mode) about whether there are alternative situations for which an architecture
based on such fast moving satellites would be desirable rather than a
challenge.

Below are some unfiltered thoughts on this -

1\. Treat satellites like postboxes. If ground to satellite link is fast, use
it to upload TB of data to these satellites and let them transport it across
oceans and dump them at destinations (article notes it takes 6mins to cross
the Atlantic).

2\. Serve applications off satellites - sort of like CDN edge servers.
Thinking Cloudflare Workers. No idea what their capacities are though.

3\. Distribute updates to devices or end points. Tesla updates?

4\. Make the satellites pick up and drop data between specific ground
stations.

Any intelligent ways to abuse this system?

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rosstex
Yoo, I met the author when I toured ETH Zurich for visit days. If you're
reading this, super excited for you :D

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nthngtshr
Are there any companies that are doing something similar in the bay area?

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walrus01
oneweb, kuiper, starlink, telesat, and SES (o3b) are all hiring. Not
necessarily in the bay area.

