[aprssig] Viscous digipeating

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Tue Mar 19 20:40:09 EDT 2013

Consider the purpose of APRS, especially RF APRS and Digipeaters.  Which 
of the following is it?  a) to get packets to an IGate or b) to get 
packets propagated for local RF reception?  IMHO, the purpose of a 
digipeater is both, but a) shouldn't trump b).

I have a personal issue with the concept of a digipeater not repeating a 
packet just because it heard some other digipeater repeating it.  
Unless, of course, the coverage of the viscous digipeater is fully 
covered by the other digipeater.  Otherwise, the viscous suppression may 
be depriving RF users that are covered by that digi from hearing packets 
just because another digipeater acted on them, possibly on the far side 
of the viscous digipeater.

As with all networks, you need to consider the topology and compare 
coverage areas before deciding not to act on any given packet under 
whatever conditions are being considered.

But, IMNSHO, the presence of a packet on the APRS-IS is not just cause 
for not repeating it on the local RF if the digipeater making that 
decision provides some unique patch of coverage area.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

On 3/19/2013 7:22 PM, Samúel Úlfr Þór Guðjónsson wrote:
> Oh yeah, and actually to be more accurate, it'd have to check APRS IS 
> and see if the packet *really* went from RF to IS.
> Maybe that's an idea? But that would require that digipeater to have 
> IGate functionality, or at least be able to listen to APRS IS. That 
> could perhaps, improve the QRM even more? And it wouldn't stop NOGATE 
> or RFONLY from digipeating again...
> I do however think that this problem can be improved, so to speak, 
> with tactical positions of digipeaters. So that every fillin would be 
> able to hear at least one high level digipeater (actually, why set up 
> a fillin if you can't reach a high level digipeater?) but wont be able 
> to throw the packet to too many high levels (decrease TX power perhaps 
> if necessary?)
> This may need some thinking, hi hi.
> 73 de TF2SUT - Samúel
> On 19 March 2013 21:13, Lynn W. Deffenbaugh (Mr) <ldeffenb at homeside.to 
> <mailto:ldeffenb at homeside.to>> wrote:
>     On 3/19/2013 4:01 PM, Samúel Úlfr Þór Guðjónsson wrote:
>         That way, the digipeater will only digipeat if no other digi
>         hears the packet, but does not add extra traffic to RF if the
>         packet is received by another digi. TX IGate would also be
>         good within that setup, with or without the digipeater functions.
>     Well, at least that's the hope of viscous digipeating.  It would
>     be more accurate to say:
>         A viscous digipeater will only digipeat a packet if it doesn't
>         decode another digipeat of the packet within the delay period.
>     It is completely based on receiving and decoding the remote
>     digipeater's packets as there is no way to truly know that "no
>     other digi" heard and/or digipeated the packet.
>     Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32
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