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[aprssig] Q: Vicious digipeater

Steve Noskowicz noskosteve at yahoo.com
Fri Oct 23 22:04:15 UTC 2009


 
Would someone try explaining this concept again? 
  It was done a couple of weeks ago, but I didn't understand the reasoning.
 
 

-- 73, Steve, K9DCI
http://k9dci.home.comcast.net/

--- On Fri, 10/23/09, Robert Bruninga <bruninga at usna.edu> wrote:


From: Robert Bruninga <bruninga at usna.edu>
Subject: Re: [aprssig] Improving Messaging and dytnamic Object management
To: "'Jason KG4WSV'" <kg4wsv at gmail.com>, "'TAPR APRS Mailing List'" <aprssig at tapr.org>
Date: Friday, October 23, 2009, 11:50 AM


> This comment raises a question:  
> Why is such aggressive transmitting
> (8s/16s/30s/60s = average 30s interval) 
> desirable for objects, but aggressive 
> smart beaconing for mobiles is anathema?  

Good observation.  Not an anathema at all during an event.  That
is where Smart beaconing is PERFECT...  And that is also an
ideal place where the Decay algorithm has the same advantage for
objects.

1) The original APRS Decay algorithm is required for any
meaningful use of objects at an event.  This is so that when
anything is moved by an operator, everyone gets the information
very quickly due to the initial 8, 16, and 30  second retries...
but the older objects he moved or situated several minutes ago
are at longer periods to keep the overall load down.

2) Under the decay method, anything older than about 10 minutes
(from the last human intervention) will have decayed down to the
fixed rate of 10 minutes (for a local object (direct)) or to 30
minute rate for objects going via 2 hops...

TO be truely useful at any event or situtation, APRS is supposed
to maintain the ENTIRE tactical picture, not just those few
vehicles with GPS trackers.  This means tha APRS operators are
supposed to be INPUT OPERATORS, manually inputting and updating
the position of everything of singificance at an event so that
EVERYONE sees the same refreshed tactical situation on their
VIRTUAL APRS map displays.  Observers should see everything of
importance, not just the APRS toys.

This can result in dozens or more objects that often change
positions frequently.  The Decay algorithm assures that newly
moved objects get to everyone's screen FAST and RELIABLY
(initial high rate retries) but then once so delivered, they
decay to a lower rate to reduce the overall load on the channel,
while still assuring that newcomers or other stations still
eventually get the full picture no matter when they tune in.

*** Smart beaconing does this very well for the event too, by
only transmitting when NEW information is availble (A change in
direction or speed), and not transmitting when things are not
changing...  Smart Beaconing is ideal for this application.  My
only issue with Smart Beaconing has ever been the result of its
dependency on human nature settings that can sometimes be
inappropriate during 364 day routine operation at the expense of
others.  TO change the parameters between this special event,
and or routine operations requires human attention to detail
which has potential for human error or inadvertant settings with
consequencies for everyon else on the channel until corrected..

Hope that helps
Bob, WB4APR



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