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[aprssig] APRS Message workarounds

Robert Bruninga bruninga at usna.edu
Thu Jan 17 20:30:48 UTC 2008


> I understand the math, what I wonder about is 
> the accuracy of the actual value you are using 
> for the probability of a successful message 
> transmission.
> 
> Was P measured, is there some model that has 
> been shown to relate to typical APRS networks, 
> or was it obtained by aerial extraction? 

Every digi is different, every location is different, every site
is different every hop is different.  Chose P to best represent
what you personally experience in your situation, using the
intended path, intended digis, and send some messages.

In fact, you should be able to measure P by using Uiview.  Since
it uses the simplistic fixed rates, and no ACK enhancements,
then set the message rate to 1 minute, pick someone 2 hops away
and send them 10 message lines.

Time how many transmissions it takes before each line is
delivered.  Average those values.  Take the 4th root, and that
should give you P.  But that P is only good from your station A
location to that station B location using digipeaters X and Y.

Actually, that would be a great test.  But comparing any such
tests are completely apples and oranges unless they are between
the SAME stations.

It sure would be  nice to have two stations that BOTH have both
Uiview and  one of these (APRSdos, XASTIR, or APRS+SA).  Then
doing the same test and seeing the result.

Bob, WB4APR


> 
> -Jason
> kg4wsv 
> 





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