From: Ulrich Speidel
[mailto:u.speidel@auckland.ac.nz]
Sent: Saturday, March 5, 2022 1:43
AM
To: dickroy@alum.mit.edu; 'David
Lang'
Cc: starlink@lists.bufferbloat.net
Subject: Re: [Starlink] Starlink
Digest, Vol 12, Issue 6
On 5/03/2022 7:38 pm, Dick Roy wrote:
-----Original
Message-----
From: Starlink [mailto:starlink-bounces@lists.bufferbloat.net]
On Behalf Of Ulrich Speidel
Sent: Friday, March 4, 2022 4:14 PM
To: David Lang
Cc: starlink@lists.bufferbloat.net
Subject: Re: [Starlink] Starlink Digest, Vol 12, Issue 6
True,
but Starlink is designed as a high bandwidth, low latency (OK, we
won't
mention their bufferbloat issues again here), and (currently) low
user
density service.
Bandwidth-wise,
good old Shannon and Hartley are agnostic about whether
you
divide your channel between 1 or a million users.
[RR] But they are
assuming a “single” channel in the time domain. When you can
take advantage of other dimensions (eg. space) to create more channels, (aka
SDMA) the capacity goes up!
Taken
as read - but it's beside the point. Shannon-Hartley allows you to do what was
proposed - turning a channel that supplies a small number of users with a lot
of capacity each into one that supplies a large number of users with a little
capacity each, and of course if you add diversity (space, polarisation, ...)
then this applies even more so. But the point is that each communication system
is designed around an expectation of how many users will access it, and that
you can't simply take an existing technology and somehow assume that it will
work with a larger number of users just because it's theoretically possible.
Basically, you can't simply throw more dishys at the problem if you need to
serve more users.
[RR] Actually, to a certain extent it depends on how the “dishys
are/could be connected” and how the satellites overhead are “configured”,
but that’s a story for another day and related to the point about the Maverick
show ))). That said, I agree that systems have to be and are designed/optimized
to handle a specified load (really a range of loads) and can not be expected to
perform as well outside that range, and I agree that anyone who thinks that Shannon
can be simply be ignored (as was tried in the past by a very famous corporation
we all know all too well) is simply delusional. As the saying goes, “you can
not make chicken salad out of chicken feathers!”
--
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Dr. Ulrich Speidel
School of Computer Science
Room 303S.594 (City Campus)
The University of Auckland
u.speidel@auckland.ac.nz
http://www.cs.auckland.ac.nz/~ulrich/
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