[aprssig] Device Capabilities & proportional pathing

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Wed Nov 9 15:46:40 CST 2011

Actually, if you think about it, Proportional Pathing and SmartBeaconing 
are anathema to each other.  Consider their differing goals:

Proportional Pathing: Vary the "reach" of packets on a 1 / 2 / 4 scale 
as follows:

1 min - "local" no path
2 min - 1 hop path
3 min - no path
4 min - 2 hop path
5 min - no path
6 min - 1 hop
7 min - no hop
8 min - 2 hop

Rinse and repeat...

SmartBeaconing: Transmit a packet ONLY when it is a significant change 
or a (relatively) long time.

So, consider the following SB-triggered and PP-modified transmissions:

SB sees you turn (from a stop), PP sends it out local
SB sees you turn onto the highway, PP sends it out 1 hop
SB sees you turn onto the Interstate, PP sends it out local
You drive a (relatively) straight line, so SB goes onto a (fairly) long 
timer and PP sends it out 2 hops (finally, the world knows!)
The Interstate turns, SB transmits, and PP sends it out no hops
You drive straight again, so the long timer applies, PP sends it out 1 hop
Another long time, PP sends out local
You turn again, PP sends it out 2 hops
You complete the turn (a broad sweeping 90), PP sends it out local

So, which way does the world (the IGate is 2 hops away, and so are the 
remainder of the APRS-monitoring stations as you drive away from town) 
think you're going?

Yeah, with SmartBeaconing, every single packet is, by definition, 
important to your travel.  Proportional Pathing assumes that every 
packet is just as redundant as any other and simply varies the path 
accordingly.  It makes no sense (to me at least) to mix the two.

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

On 11/9/2011 4:22 PM, Tom Hayward wrote:
> On Wed, Nov 9, 2011 at 11:35, Bob Bruninga<bruninga at usna.edu>  wrote:
>> Curt,
>> Please add a row for Proportional Pathing on the Device chart (and client
>> chart if it is not there).  Add it adjacent to Smart Beaconing.
>> You can mark the Kenwood D72 and D710 as having it.  I think that the VX8's
>> also have it?
> Unfortunately, the D72 and D710 don't honor the Proportional Pathing
> setting when Smart Beaconing is enabled. Two features that improve
> efficiency of APRS bandwidth, but you can't use them both. I guess
> Kenwood doesn't want APRS to be too efficient.
> Tom KD7LXL
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