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

[Jeromie Reeves]

Jim Thompson wrote:

>
>
> Benjamin Henrion wrote:
>
>> Hi,
>>
>> 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.

This is not possible with Atheros or any other software 802.11 radio 
that I know of.
The cause is that they just change the channel bandwidth from 22 mhz to 
44 mhz. This
can now be set to 5 and 10mhz but so far only with specific drivers. I 
would love to see
the come to windows.

>
>
>> 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 openbsd.)

Mikrotik made Nstream and Nstream2. This drasticly alters the HAL's. 
They have polling too.

>
>
>> 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 mistake.

That would not be good. Maybe a group could get together and obtain the 
atheros source and produce a project from it?

>
>
> Jim
> (*) 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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