Re: [Starlink] Starlink Digest, Vol 12, Issue 6

["Dick Roy" <dickroy@alum.mit.edu>]

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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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