[aprssig] OpenAPRS New Features Release

Bob Bruninga bruninga at usna.edu
Sun Sep 7 20:47:18 CDT 2008

> It may not make sense to use decay when you 
> can just beacon it anyways?

The point of decay has to do with data latency.   If somone posts an object right now, then that data is important right now.  You want it to go out right now.  And follow up with a retry almost immediately (say 1 minute), incase there was a collision.  Thus the Decay.  This lets you send a retry very soon, but eventually get down to the 10 minute standard APRS net cycle time for local info (on the internet, the entire APRS-IS is considered one local net).

Your Internet capability for posting Objects is presumed to be real-time, so when someone posts it, we want everyone to have a very high probably of getting it very soon, not having to wait a full net-cycle time for a refresh.  Thus the reason for the decay algorithm... (though on the APRS-IS, presumably, there are no collisions)...

> Do normal digipeaters that advertise their 
> objects or remote sites decay as well?

No, becuse they are not changing.  New data is supposed to be refreshed very quickly, and then decay.  The permanent objects in digipeaters are long term and are not changing, so 10 minutes after they are entered, they would already have decayed down to 10 minutes whre they will remain for ever (since they are local direct).  ANy object or station, or info that is transmitted more than 1 hop or direct, uses the 30 minute eventual net cycle time.


>   Greg
>   NV6G
>   OpenAPRS.Net
>   On Sun, Sep 7, 2008 at 1:09 PM, Bob Bruninga
>   <bruninga at usna.edu> wrote:
>     > I've recently added object creation...
>     > Of course object creation is APRS-IS only...
>     > ...check our blog at http://blog.oaprs.net/
>     Great work!  Comments:...
>     I think you need to implement the usual APRS
>     decaying algorithm for new objects.  Otherwise,
>     the only people that will see them are people who
>     were logged on at the instant of creation.
>     This will fail the most common application... That
>     is, see something happen, post an object, send out
>     a message to the world to "see this", but when
>     they log on, it is never seen again..
>     So I'd suggest a packet at creation, then maybe
>     2.5, 5 and then 10 minute refresh.  Then keep it
>     at 10 minutes for the next 12 hours.  Then
>     automatically cease transmitting it, or even
>     consider sending a kill..
>     Bob
>     WB4APR
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