Hi. I'm part of a student team delevoping ax.25 for a cubesat. I want to ask you if you advice to you this protocol or not, because I read on (http://groups.google.com/group/rec.radio.amateur.digital.misc/browse_thread/...) that nowaday IP is used instead of ax.25. Do you have some advice?
We are developing ax.25 based on this document (http://www.nj7p.org/AX25.2.2-Jul%2098-3.pdf) but we have found that some information are missing... Do you have some others document?
Thanks you for any info! Greetings
Davide
Hello Davide
that nowaday IP is used instead of ax.25.
Well in the AMPRNet standard, IP sits on top of AX.25 rather than instead of AX.25.
You need to ask yourself whether your particular application needs the added complexity of IP at all. Academically, I am sure it would be nice to be able to route the traffic, but do you _need_ to do that?
For AX.25 in space use, ask yourself whether you need connected frames at all, or could you just deal with UI frames? That would simplify further your implementation.
One problem with connected protocols under the marginal conditions of an amateur link in space (ie, consider fading!) means that the channel can become clogged with retry frames and re-establishing connection. Depending on your application, a UI frame model can circumvent this to some extent, allowing you to implement your own protocol on top of AX.25 UI frames.
73, Howard G6LVB
At 12:35 PM +0200 9/26/06, Davide Vosti wrote:
I'm part of a student team delevoping ax.25 for a cubesat. I want to ask you if you advice to you this protocol or not,
AX.25 is still current, but before going too far into implementation you will want to consider the needs of your application. Connected mode in AX.25 doesn't scale very well for multiple user access to spacecraft, but it's reasonably appropriate for a single station uploading critical data.
Depending on what you're trying to do in your CubeSat, you might want to consider using the PACSAT Protocol Suite, which builds on AX.25. See http://www.amsat.org/amsat/sats/nk6k/msatpro.html for protocol documentation. There are several groundstation implementations available. This has been the standard for amateur store-and-forward digital satellites since AO-16 in 1990.
If your needs are more modest, you may be able to simply ignore most of AX.25 and use only AX.25 UI frames as datagrams. The APRS standard may or may not be relevant to your application.
Regardless of what you implement on top of AX.25, I would call your attention to the FX.25 protocol extension for FEC that was proposed by Jim McGuire KB3MPL of the StenSat group. It's still just a proposal, but it seems to have promise. http://eludium.stensat.org/mcguire/FX-25_01_06.pdf
We are developing ax.25 based on this document (http://www.nj7p.org/AX25.2.2-Jul%2098-3.pdf) but we have found that some information are missing... Do you have some others document?
That looks like the document, though I'm not sure of the status of the 2006 changes. I would assume that http://www.tapr.org/pub_ax25.html is the authoritative source for AX.25.
There's a TAPR mailing list for AX.25 discussions. That would probably be the best place to ask technical questions about AX.25 issues. https://lists.tapr.org/cgi-bin/mailman/listinfo/ax25-layer2
73 -Paul kb5mu@amsat.org
participants (3)
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Davide Vosti -
Howard Long -
Paul Williamson