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[aprssig] Broken digis (Ohio to Oklahoma and everywhere inbetween)

Rick Green rtg at aapsc.com
Mon Jul 30 17:18:02 UTC 2007


On Mon, 30 Jul 2007, Robert Bruninga wrote:

>> OK, maybe I'm one... that needs educating.
>> I thought that the 'new paradigm' was just
>> [replacing RELAY,WIDE with WIDE2-2]...
>> No big deal.  It saves a few bytes of bandwidth.
>
> Actually, it cuts QRM from unneeded dupes by a factor of 2 to 5!
> That is the main advantage.  It changes the worst networks from
   You'll have to explain that to me.  How does changing the name of the 
digi reduce dupes?  What we need is better dup checking algorithms, not 
different digi naming convention.
   Aren't the fill-in digis necessary at the end of the path as well as the 
beginning?  In cluttered terrain like a city you need the fill-in to 
repeat all the packets from the highly-placed digi, so that the local 
users can see the situation in the whole area, not just their local 
canyon.
   All this talk about digi naming, special paths, etc., just seems to be 
another kluge...  Let's work on putting the intelligence in the network.
   I still think my proposal of putting a geographical filter in the digi 
software is the answer.  It's the digi owner who's in the position to know 
the local terrain and environment best, not the user (especially 
transients, and mobiles are the main reason for APRS, after all!).  So let 
the Digi owner program a filter for their own 'service area' (which may 
not be a circle, like the 'aloha' concept).  Coupled with an effective dup 
filter, simply digi any 'new' packet which originated in the service area, 
and ignore all others.
   Eventually, we could get fancy with the filtering, such as:
  1) treating certain neighboring digis as 'partners', and not digi'ing any 
packet which has been already digi'd by the partner.
  2) Insert a minimum 'hold time' on packets heard direct, so the we'll 
only digi any packets NOT picked up by one of the 'partners'.
  3) Defining the 'service area' as a group of prioritized areas, and 
coupling them to congestion criteria, so that in low-utilization times the 
service area can automatically expand, and in rush hours it'll 
automatically contract.

   Then the users have only two paths to encode:  Direct for IDs and local 
info, and Via APRS for beacons to the limits determined by the network 
sysops.

-- 
Rick Green, N8BJX

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
                                   -Benjamin Franklin





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