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[aprssig] APRS Meshing

Joe Della Barba joe at dellabarba.com
Thu Jan 5 09:45:56 UTC 2006


AFAIK there is no way to do what you suggest with COTS radios. The only 
APRS h/t I know of is the Kenwood TH-D7 and it is not a digi and there 
is no way to upgrade it. This brings up a question - Why has the 
commercial market abandoned APRS? For awhile I thought I was going to 
see an APRS h/t with a built in GPS and map screen, but now it looks 
like that will never happen.
73 de N3HGB


Richard W. Clement wrote:

> I am testing the viability of using APRS in a non-fixed station 
> environment - eg. no established digipeaters and no base stations.  
> The intention is to use a number of lightweight, portable radios such 
> as the TH-D7a to create an ad hoc mesh that is survivable even if some 
> radios fail.  I have worked with trying to create a mesh network - in 
> one case with nine radios using WIDE7-7 to ensure that as many radios 
> copied the signal as possible.  My reasoning for this was that if each 
> radio was almost in the fringe area of its neighbor radios and the 
> radios were in a line, for N radios it would take N-2 hops for an end 
> radio's data to traverse the network to the other side.  Obviously, 
> this creates many unneeded duplicate packets in less extreme 
> cases, and I am wrestling with ideas on how to solve that issue.  One 
> method I have come up with would be rather more software intensive:
>  
> 1. Remember your immediate neighbors.
> 2. For a given packet, choose a random wait time.  If you haven't 
> heard every neighbor digipeat the packet after a given wait time, 
> digipeat.
> 3. Maintain packet in memory for a fixed, user settable amount of time 
> to ensure that you do not digipeat it again.
>  
> I still see problems with the above protocol, although it would cut 
> down some on packets.
>  
> I have tried researching the spec to see if the meshing concept is 
> covered, but all I have seen so far assumes that there are fixed 
> stations and digipeaters.  Is there a part of the spec I have missed 
> that addresses this?  Has anyone else worked on a similar experiment?  
> Thanks for your help.
>  
> 73,
> Richard Clement (AE6QE)
>
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