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[Ham-80211] High Speed AX.25 over half-duplex serial?

Guillaume Filion gfk at logidac.com
Sat Nov 12 14:45:41 UTC 2005


I just bought a pair of Aerocomm 900 MHz ConnexLink radios 
(http://www.aerocomm.com/Devices/link.htm) and I would like to pass 
TCP/IP traffic through them. These radios are designed to be used as a 
very long serial cable (they don't need any driver) and work at a speed 
of 78.6 Kbps.

To use them, I connected a USB-serial converter to a NSLU2 and connected 
that to the ConnexLink. I was able to do TCP/IP with PPP but found out 
that PPP requires a full-duplex link and that the radios are 
half-duplex. The ConnexLink has an option to emulate full-duplex, but it 
reduces the available bandwidth by 50%.

I heared that AX.25 is designed for half-duplex links, but I don't know 
anything about AX.25. I read the AX.25 HOWTO but I'm still confused 
about what driver I would need to use it on a serial link with no TNC.

So, I'm basically wondering if AX.25 is suitable for my setup, especially:
- Does it support compression?
- Can it handle speeds up to 300-400 Kbps?
- Could you give me an idea of the commands that I should use to set 
this up over a serial link?

Thanks and 73,

PS: For infos about the NSLU2, see
Guillaume Filion, ing. jr
Logidac Tech., Beaumont, Québec, Canada - http://logidac.com/
PGP Key and more: http://guillaume.filion.org/

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