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[aprssig] APRS W,W and W,W,W example

Robert Bruninga bruninga at usna.edu
Fri Feb 11 14:51:51 UTC 2005


How bad are W,W and W,W,W paths?

If you still don't believe how much better WIDEn-N is than 
W,W then look at these figures:  While visiting Houston, 
TX on 11 Feb, I monitored from my motel room and got 
these statistics:

Evening:  (8:30 PM not many mobiles)
   47% of users used WIDE2-2,33,44,55 but used only 7% of channel
   42% of users used W,W or W,W,W or W,W,W,W and used 89% of channel

Morning:  (more mobiles)
   71% of users used WIDE2-2,33,44,55 used only 20% of channel
   30% of users used W,W or W,W,W or W,W,W,W and used 76% of channel

Lessons:

1)  In the evening with more home stations, the stations 
using W,W type paths take up more than TEN TIMES the 
channel capacity that a similar number of users using 
WIDEn-N paths! (including some 5-5's)

2)  In the morning with more mobiles and more stations 
using WIDEn-N, still 3/4ths of the channel is consumed 
by less than 1/3rd of the users still running W,W type paths.

The lessons are loud and clear.  Its time to abandon 
W,W (and R,W) type paths because their generation of 
3 to 5 times the number of dupes compared to WIDEn-N is  
far worse than any benefit by an occassional RELAY,WIDE 
boost from a home station.  

If a home station is absolutely needed in an area, it should 
be converted to a WIDEn-N digi.  Since WIDEn-N uses 
a perfect dupe-elimination algorithm, it is better to activate
WIDEn-N at such a home-station fill-in digi than to continue 
to encourage mobiles to use RELAY,WIDE paths.  That
is now obsolete and we must move on.

This data was obtained using the APRSTEST.EXE program 
on TNC capture files of raw packets.  It also shows the 
distribution of WIDEn-N In Houston Texas was:

 31% used 2-2, 
 46% used 3-3 
 23% used 5-5.  

These longer hops do not seem to be a problem at all in 
South Texas.   But if these 5-5 packets are getting into
Dallas also, then they are part of the problem there.

I'd like to hear how many hops it would actually take to 
get from outside of HOuston to Dallas area (in the absence 
of QRM)

Remember The New n-N Paradigm fully supports the
use of WIDEn-N everywhere.  The Paradigm evolved.
Forget the LINKn-N idea.  That was before we found
out how to use KPC-3's to TRAP large N's.  Now that
we can trap large N's in every existing digi, we have 
gone back to WIDEn-N is the answer everyhere and
now W,W and R,W is the bigger part of the QRM
problem...  That is the New n-N Paradigm.

see http://www.ew.usna.edu/~bruninga/aprs/fix14439.html

ANd also we learned how to make the old WIDE only
and TRACE only digis still be usable under this new
Paradigm without replacing the TNC (though replacement
is preferred in the long run)...

Lets do it.

de WB4APR, Bob





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