[ath9k-devel] Ath9k MIMO Performance versus Proprietary Drivers

[Luis R. Rodriguez <lrodriguez@atheros.com>]

On Wed, Feb 24, 2010 at 11:41:46AM -0800, Galen wrote:
> 
> On Feb 24, 2010, at 11:33 AM, Felix Fietkau wrote:
> 
> > On 2010-02-24 8:22 PM, Galen wrote:
> >> This is an addendum to my earlier reply.
> >> 
> >> On Feb 22, 2010, at 1:09 PM, Felix Fietkau wrote:
> >>>>> Except for STBC, ath9k seems to have pretty much the same hardware
> >>>>> features as Atheros' other drivers. There may be some workarounds for
> >>>>> various hw issues missing, I have not extensively reviewed that yet.
> >>>> I would be interested in knowing more about these. LDPC? Others?
> >>>> There appear good software implementations of LDPC out there:
> >>>> http://planete-bcast.inrialpes.fr/article.php3?id_article=7
> >>> I'm pretty sure the current hardware also doesn't do LDPC yet.
> >> 
> >> I have looked over data presented on the Atheros website and as best as I can tell, the AR5008 (and other newer chipsets, I assume) support:
> >> 
> >> - STBC (space-time block coding) for TX and RX
> >> - MRC (maximal ratio combining) via zero forcing algorithm 
> >> - TxBF (transmit beam forming) 
> >> 
> >> From what you're saying, my understanding is that MRC and and TxBF
> >> are both functioning with ath9k, with STBC being the primary
> >> remaining feature. Is this correct?
> > TxBF isn't supported by the currently available hardware, so ath9k
> > doesn't make use of it either. I don't know about MRC, but I don't see a
> > difference between ath9k and other Atheros drivers in that area.
> > So yes, of those options, only STBC is missing.
> 
> Atheros' data is not very clear in all cases. However, their statements
> lead one to believe that transmit beamforming is supported, as is MRC. 

MRC is supported on all 11n chipsets, but not for cck rates.
TX beamforming is only supported on the shiny new AR93xx
chipsets. TX beamforming seems to have been supported on
some old legacy chipset but there is no code to support it
and I wouldn't bother trying.

  Luis