
SpaceX faces high bar at FCC in bid for rural-broadband funding - samizdis
https://arstechnica.com/tech-policy/2020/06/fcc-has-serious-doubts-that-spacex-can-deliver-latencies-under-100ms/
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xt00
FYI: it takes 1.9ms for light to travel 570km. Given a situation where people
are just streaming Netflix, then the latency should not be an issue, but if
you are browsing a webpage that hits 50 domains downloading random javascript
stuff, it will result in a summation of a bunch of 1.9ms*2 events occurring.
Plus, if people are at an angle to the satellite, or your data hops between
satellites, then you will be seeing additional latency. It would seem like the
optimal approach to web browsing for example would be similar to the Amazon
Silk browser, where you communicate your "intent" of what you want to do like
which webpage you want. Then it renders that webpage in a local instance on
the cloud, then transmits the fully rendered webpage to you in a streaming
sense. That process would likely cause additional latency before you start to
see something show up, but the result is actually a shorter total time to get
your page in front of you.

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FlyingAvatar
This is literally what happens all the time for all Internet users though
wires and fiber on ground-based internet at similar or worse single-hop
latencies.

The number of domains is irrelevant since most of those requests would be
asynchronous. What matters is the number of hops that the traffic needs to
take and the latency for each hop.

1.9ms times any reasonable number of hops would still produce a sub-100ms
latency which is the FCC sites as their requirement, and would be a perfectly
serviceable latency for nearly all Internet use (and is around what most users
experience now).

It is unclear why the FCC would reference "the laws of physics" as a barrier
for StarLink achieving this, as it is unclear how they would be causing any
problems.

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shaklee3
SpaceX does not have cross links. They will need to have several hops up and
back to different satellites before the signal arrives in many cases. It's not
unlikely that when processing time is included, it's well over 100ms.

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FlyingAvatar
If conventional geosynchronous satellite internet can achieve real world
latencies between 600ms and 1200ms, can you describe a scenario where having a
hop time that is 60x faster could not manage to improve this by a factor of
12x?

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shaklee3
Think of it this way: traditional geo satellite has a theoretical latency of
430-500ms in most cases. That means there's AT LEAST another 100ms purely due
to processing delay and other hops, but typically much more.

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Obi_Juan_Kenobi
Naked preference for big telecos on display.

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Shakahs
I don’t think the 100ms limit is to prevent competition, it’s near the max
recommended latency for VOIP and video conferencing. Both of these are
important for rural Americans to have access to.

