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Re: [tracker2] Re: Packet collision avoidance.

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  • James Ewen
    ... As stated, Viscous Digipeating should be limited to FIRST HOP only. ie WIDE1-1 fill-in digipeaters that are there to assist low powered stations get INTO
    Message 1 of 9 , Apr 20, 2012
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      On Fri, Apr 20, 2012 at 3:44 PM, Bill Vodall <wa7nwp@...> wrote:

      > ... assuming that the digipeater you hear repeating the packet covers
      > everywhere your local digi covers so there are no areas not covered.
      > It's always something...

      As stated, Viscous Digipeating should be limited to FIRST HOP only. ie
      WIDE1-1 fill-in digipeaters that are there to assist low powered
      stations get INTO the digipeater network.

      There are some strange people in the PNW that espouse having EVERY
      APRS station being configured as a fill-in digipeater.

      In a situation where there are many APRS fanatics in a small area, and
      someone is running their 50 watt mobile with a path of WIDE1-1,WIDE2-1
      (because that's the suggested mobile path), you could end up with
      many, many fill-in digipeaters all making a cacophony of noise because
      EVERY home station is going to try and help that "low powered" 50 watt
      station get heard.

      If however those home stations were all configured with Viscous
      Digipeating, they would all hold off for a second or two. In that time
      most likely a main digipeater would have heard that 50 watt station,
      and digipeated the packet. All the home fill-in stations would then
      drop the packet, and not add to the din. If however a main digipeater
      did NOT act upon the packet, one of the home fill-in digipeaters would
      speak up, and the rest would then fall silent.

      Viscous digipeating on any hop other than the first hop would lead to
      issues where the packet would possibly not be propagated fully through
      the network. The concept works for hop requests that are only needed
      IF the packet isn't heard by a main digipeater.

      Because the APRS network is designed to cause packet collisions on
      purpose, it is possible that there may be some false positives where
      the viscous fill-in digipeater would not be able to decode the packet
      being handled by the main digipeaters, or by other fill-in digipeaters
      due to the same issue, or hidden transmitter issues. This still would
      not preclude the obvious advantage of using Viscous Digipeating to
      REDUCE the number of copies of a single packet being needlessly
      digipeated when it is KNOWN to have been propagated into the RF
      network.

      --
      James
      VE6SRV
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