Re: [tracker2] Re: Packet collision avoidance.
- On Fri, Apr 20, 2012 at 3:44 PM, Bill Vodall <wa7nwp@...> wrote:
> ... assuming that the digipeater you hear repeating the packet coversAs stated, Viscous Digipeating should be limited to FIRST HOP only. ie
> everywhere your local digi covers so there are no areas not covered.
> It's always something...
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