[e2e] Satellite Date Rates
David P. Reed
dpreed at reed.com
Fri Nov 26 13:01:13 PST 2004
Lloyd Wood wrote:
>On Fri, 26 Nov 2004, David P. Reed wrote:
>>This just triggered a thought on my part that might be worth following
>>up. Why not use erasure-coding (tornado code or digital fountain) as
>>the basis of recovery for lost packets on such long-delay links?
>because, when you have a backchannel for some form of ARQ strategy,
>the loss of link capacity simply isn't worth it, and simple FEC gives
>better link utilisation without adversely affecting path utilisation.
>Erasure codes are a massive performance hit, and lack the tuning to
>channel conditions of FEC.
"simply isn't worth it" is an attempt to "put down" my idea without one
instant of thinking. Do you have a hair up your ***? Do suggestions
from others challenge your manhood? Ignoring your utterly foul attitude
for the moment, erasure codes are not a massive performance hit on the
wire, since they use zero extraneous bits, and for that matter are not
terribly expensive to compute, compared, say, to the cost of the system
that tracks and manages the satellite.
>I see that XM satellite radio licensed erasure codes from Digital
>Fountain for satellite broadcast in November 2003.
>No backchannel there -- and that predates your specious claim below.
My claim, if you read it carefully, was for the use of erasure codes in
a novel hybrid ARQ scheme, not as a pure FEC scheme, and would be
distinct from the use licensed. I am fully aware that Digital Fountain
is a patent factory, just like Qualcomm. I don't begrudge them that,
but am very careful to establish dates on any possible novel ideas that
get close to their grabby little hands. If I happen to invent
something, I don't want someone else claiming it. And in my case, that
has happened several times. The most extreme case, which is beyond
dispute, is a patent filed by Data General that consists entirely of
paragraph-for-paragraph transcriptions of my S.M. thesis, which was in
the public domain. Unfortunately, the patent expired shortly after
they attempted to use it to extort money out of IBM and others, which is
what brought it to my attention, or I'd probably be a rich man.
Regarding your use of the word "specious", it may be that you were
trying to be nasty, but I'll presume the primary definition instead,
below, and thank you for the flattery.
From Webster's Revised Unabridged Dictionary:
\Spe"cious\, a. [L. speciosusgood-looking, beautiful, specious, fr.
species look, show, appearance; cf. F. sp['e]coeux. See Species
1. Presenting a pleasing appearance; pleasing in form or look; showy.
Some [serpents] specious and beautiful to the eye. --Bp. Richardson.
The rest, far greater part, Will deem in outward rites and
specious forms Religion satisfied. --Milton.
2. Apparently right; superficially fair, just, or correct, but not
so in reality; appearing well at first view; plausible; as, specious
reasoning; a specious argument.
Misled for a moment by the specious names of religion, liberty,
and property. --Macaulay.
In consequence of their greater command of specious expression.
Syn: Plausible; showy; ostensible; colorable; feasible. See
Plausible <http://dictionary.reference.com/search?q=plausible>. --
<http://dictionary.reference.com/search?q=spe%22xious%2Aly>, adv. --
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