[Voyage-linux] Turbo mode

[Edwin Whitelaw]

Bob,

Tried this on my long distance link (18.5mi) with two XR5s on WRAPS and 
was able to get an association on one of the turbo channels.  However, 
it forced the acktimeout value to 22 (instead of the correct 225 for 
that distance or the default 25??) and, though associated, the 
throughput was as expected with a too short acktimeout set.  Attempts to 
reset the acktimeout were unsuccessful until going back to non-turbo mode.

With the CM9s on the short link, I can't even get a link up when 
choosing a turbo channel.  According to the Wiki, the rate *must* be set 
statically for this to work.  Tried every permutation/combination I can 
think of without success.  I believe I can get a 25+mbs  rate w/o the 
turbo but would love to have the X2 data rate for this backhaul link.

Edwin

bob wrote:
> Aloha Edwin,
>
> Your timing is impeccable, as I just turned up a new system with Alix, 
> Voyage 0.4.1, and wlm54ag.
>
> In the past, I've puzzled over the turbo mode, but never investigated 
> it to make it work.
>
> I've found that iwpriv ath0 get_turbo returns 1, even though I haven't 
> set it.
>
> Iwconfig shows Turbo mode on specific channels, and 11a on other 
> specific channels.  iwpriv ath0 turbo 1 does not appear to turn on 
> turbo on non turbo channels, and iwpriv ath0 turbo 0 does not appear 
> to turn off turbo mode.
>
> So, my guess is that turbo mode is being controlled by the eeprom and 
> channel selected.
>
> I don't know if turbo mode is really on or not, even though iwconfig 
> says it is, because the available rates are the same, turbo or not, 
> and I have not noted (and not explicitly checked) throughtput.
>
> I suspect that it is turbo mode, because it seems to require a 
> slightly better rx signal to associate.
>
> As a side note, I noted a couple of times, that a radio may not 
> associate when the distance is set too short.  This is not always the 
> case, because I usually set the dx after association and testing, but 
> on two separate occasions now, I have found that setting the dx out 
> beyond expected allowed for association.
>
> You might try setting the rate to auto to see if they associate at a 
> lower rate in turbo mode.
>
> Hope this helps.
> bob
>
> Edwin Whitelaw wrote:
>> I've been all over Google and the madwifi wiki, etc and have not 
>> found the magic incantation to invoke turbo mode with 
>> madwifi/Voyage.  The test setup at the moment is Voyage 0.4.1 on two 
>> shiny new ALIX boards.  Radios are CM9s, range is ~3.3mi (5280m).  
>> Running in 802.11a mode
>>
>> iwpriv ath0 turbo 1
>> iwconfig ath0 rate 54M
>>
>> Set Master end to one of the turbo channels and get no association.  
>> Any other channel links up right away.  I'm building an upgraded 
>> backhaul into my network and the additional bandwidth would be most 
>> helpful.
>>
>> If this doesn't work, is it a CM9 issue?  Madwifi?  Any other radios 
>> that will do turbo in this setup?
>>
>> TIA,
>>
>> Edwin
>>

-- 
<=+=+=+==+=+=+==+=+=+=+=+=+=+=+=>
Edwin Whitelaw, P.E.
New River Valley Unwired, LLC
2200 Lonesome Dove Dr
Christiansburg, VA 24073
540-239-0318