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[aprssig] Mobile Digi (TEMPn-N)

Steve Noskowicz noskosteve at yahoo.com
Tue Jun 16 01:08:35 UTC 2009




--- Robert Bruninga wrote:

> Sorry to say, this wont work.  I tried it.
> 
> ... Everyone of them always respond to the FIRST packet.  
> Sure, they all wait DWAIT before
> transmitting, but the decision to digipeat was made
> -instantly- when the packet was received 

  At first I thought that the idea was that each would not transmit if it received a dupe during DWAIT.  However, they'll all wait for each other!   (randomizing may fix) 

It seems like a built-in paradox.  
In addition, If one digi does happen to prevail with some "ideal" algorithm, how do you know if the packet will get to a WIDE, unless the/a WIDE hears them all, then you only need any one of them anyway.

Looks like a solution that simply sparks lots of debate.  (:-)

73, Steve, K9DCI


> > -----Original Message-----
> > From: aprssig-bounces at tapr.org
> 
> > [mailto:aprssig-bounces at tapr.org]
> On Behalf Of Tom Hayward
> > Sent: Monday, June 15, 2009 1:53 PM
> > To: TAPR APRS Mailing List
> > Subject: Re: [aprssig] Mobile Digi (TEMPn-N)
> > 
> > >> -at a fill-in or mobile digi, wait for 5-10
> seconds to hear
> another
> > >>  digi to digipeat the packet, if it's not
> heard, then
> digipeat
> > >
> > > <sarcasm> Did Kenwood OpenSource their D7,
> D700, and D710 
> > control code so
> > > that we could actually do something like this?
> > 
> > Well, this one is possible. Set DWAIT on your mobile
> digi to
> 70 (0.7
> > seconds) or so. If the mobile doesn't hear the packet
> from
> another
> > digipeater within 0.7 seconds after the original
> transmission,
> it's
> > safe to say the packet needs some help along, from a
> mobile or
> fixed
> > digi. No need to wait a whole 5-10 seconds.
> > 
> > For this to work the conditions would have to be
> approaching
> perfect.
> > The mobile digi would have to be able to reliably
> decode the
> fixed
> > digi. And if the channel is congested, and the first
> packet
> was missed
> > due to QRM, digipeating it from another mobile will
> likely
> just add to
> > QRM.
> > 
> > There are times when mobile-digipeater and
> everyone-is-a-digipeater
> > can work, like during a search and rescue mission in
> the
> backcountry
> > where there is no existing infrastructure and you're
> attempting your
> > own mesh infrastructure by setting all the mobiles to
> digipeat. Most
> > of the time, a mobile digipeater is probably not
> helpful.
> > 
> > Tom KD7LXL
> > 
> > _______________________________________________
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> > aprssig at tapr.org
> > https://www.tapr.org/cgi-bin/mailman/listinfo/aprssig
> > 
> 
> 
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