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

Keith Allen ag4ac at netscape.com
Sat Feb 12 09:46:36 UTC 2005


Bob, as far as I know, my KAM won't support widen-n.  I've been running 
as a relay on my alias for a while now.  comments?


Robert Bruninga wrote:

>>>>steve at dimse.com 2/11/05 1:27:37 PM >>>
>>>>        
>>>>
>>I understand all that, but as far as I can see, it only 
>>applies to paths of order 3 and above, like 
>>WIDE,WIDE,WIDE and WIDE3-3.  How can a path 
>>with only two digis bounce back and forth?
>>    
>>
>
>
>Yes, if the original packet hit one and only one
>initial digi.  But in many areas, most home stations
>hit 2 or more digis, and each of those strings will
>separately propogate through all digis as if they
>were totally different packets..
>
>Same goes for RELAY,WIDE.   In most cases,
>those packets can almost always hit multple
>initial RELAY's (since every digi also supports
>RELAY).
>
>And its even worse for RELAY,WIDEn-N because
>now with the near perfect propogation of WIDEn-N
>we have a perfect way of flooding all of the diferent
>initial RELAY copies!  Talk about shooting ourselves
>in the foot.
>
>ANd I was part of the problem.  I wanted the initial
>RELAY to force an identificaiton of the initial
>digi, (and to help with the black holes) not realizing
>how much duplication this was causing...
>
>  
>
>>Mobile transmits... If the same original packet was also heard 
>>by digi B directly, then both will transmit it, and if the timing 
>>works out, both will hear the other digipeat and repeat
>>it
>>    
>>
>
>Thus generating 4 copies of the original..
>
>  
>
>>regardless of whether the path is WIDE,WIDE or WIDE2-2...
>>    
>>
>
>Ah, there's the catch.  Both will only digi it once and ignore
>the second copy it sees.  Hence, a factor of *two*
>reduction in total channel QRM...
>
>and as you note, this initial mulitplication further 
>blows up if the original packet was 3 hops and even
>worse if it hit 3 digis...
>
>Bob
>
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>  
>




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