[OLSR-users] atheros openbsd free hal and full duplex radio in 802.11a?

Jim Thompson (spam-protected)
Fri Nov 18 03:36:28 CET 2005

Benjamin Henrion wrote:

>I was confused about some rumors from a friend to have a full duplex
>radio in 802.11a.
>After some research, I found out that the atheros ar5xxx is a software
>radio, and that it uses 2 channels in 5ghz to have a 108MB/s mode.
>I think there were some discussions at WTH about having a modified
>version of the openbsd openhal to have a full duplex radio.
Full duplex radio (in the same channel) is a 100dB problem.

>The main problem right now with OLSR is the half duplex layer of the
>radio, where bandwidth is decreasing after 4 or 5 hops.
Can you solve this with two radios running in different bands? Part of 
this is also due to the CSMA/CA
nature of the MAC. Perhaps you and your friends could design a TDMA like 
MAC for use on top of
either the "openbsd" or "closed" HALs, and a method for syncronizing the 
clocks used in the MAC (note that I'm not talking 'ntp' here, much less 
the much-less stable (in terms of true time) implementation found in 

>Are there any plans to help the openbsd coders in that project?
Given that the "openbsd hal" is clearly (*) not 'reverse engineered', I 
advise against anyone in
the olsr community getting wrapped into potential contributary 
(copyright) infringement. Working on the code above the HAL is obviously 
fine, but working on the "openbsd hal" or shipping it could be a huge 

(*) I'm in a position to be able to see both the Atheros HAL source and 
(obviously) the "openBSD reverse-engineered" HAL.

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