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[aprssig] Lets Fix New-N now!

J T w0jrt at yahoo.com
Thu Oct 20 22:38:24 UTC 2005


Keith,

Could the problem be too much RF saturating your
network?  I looked at some of the data from findu.com
for stations in your area and saw some things that can
cause major network degredation, such as fixed
stations (home stations, Igates, and digis) sending
their positions with paths such as
RELAY,WIDE1-1,WIDE3-3 and RELAY,WIDE,WIDE1-1,WIDE2-2. 
Since they are fixed they normally don't need to use
RELAY (obsolete) or WIDE1-1 to reach a digi.  And
since the obsolete RELAY or the new WIDE1-1 is only
used (typically only by mobiles) for help in reaching
a wide digi, there is no reason for a digi to use
those in its path since, by definition, any packet it
sends came directly from the wide coverage digi.

Also, some of the fixed stations seem to be
transmitting with those paths at very high rates --
every minute or so.  This, combined with the the fixed
stations transmitting with RELAY and WIDE1-1 in the
path will quickly saturate the network (since every
home fill-in station will retransmit the packets)
making it very difficult for mobile stations to get
into the system.

Looking at the last 24 hours of data on findu.com from
your AG4AC-1 mobile, it appears that when you DO get
to an I-gate it typically only takes 0, 1, or 2 hops,
not the six that are specified in your path.  This is
an indication that the problem is due to RF network
congestion, probably caused by an abundance of
stations (fixed and mobile) using excessing non-dupe
checking paths with high beacon rates.

It's a catch-22.  When network performance is bad,
often the initial reaction is to bump up transmission
rates and use longer paths, which in turn causes even
worse network performance.  The solution is for all
APRS users (home stations, weather stations, I-gates,
digis, mobiles) to work together on it.  It's simple
in theory, but often difficult to get the cooperation
of everyone involved.

To show just how far your packets are going, your
AG4AC-9 digi sending its position with a 5-hop path
shows up (via RF) on my home station near Kansas City.

I feel fortunate that here in the Kansas City area
most  users and nearly all (if not all) digi operators
have switched to the new paradigm, and that even with
our relatively high concentration of users the network
performance is very reliable.  I can use a 2-hop path
for my 5 Watt bicycle station and routinely get
excellent coverage.  In fact, I could probably switch
to a 1-hop path and still get picked up by an I-gate
just as often.

-Jerome
W0JRT




	
		
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