On Feb 24, 2010, at 4:33 PM, rootki...@yahoo.it wrote: > On Wed, Feb 24, 2010 at 8:41 PM, Galen <gal...@zinkconsulting.com> 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. >> >> It is possible that MRC is 100% hardware based (DSP-level) and "invisible" >> to the hardware. Is that what you mean when you say, "I don't know about >> MRC" ? >> >> As for transmit beamforming, here's a great example of their clear-as-mud >> information: >> http://www.atheros.com/news/xspan.html >> >> Note how they say "The new 802.11n draft specification defines an array of >> technical elements that Atheros is uniquely qualified to deliver" and list >> many features which I know the hardware supports - then list two I'm not >> sure about, MRC and TxBF. >> >> They clearly state that MRC and TxBF were implemented in chipsets dating >> back to 2004. However, are they in their shipping 802.11n chipsets? It's not >> clear. But why would they drop important features like that from a >> next-generation chipset? They also have this new brand for their MIMO >> technology - "Signal Sustain" technology - which nicely obfuscates what's >> actually happening. >> >> -Galen >> > > Now they also have SST3: http://www.atheros.com/news/AR9300.html > > "Leveraging the Rich Array of 11n Features to Enhance Rate-over-Range > Atheros’ new implementation of 11n leverages a variety of range > enhancement options to ensure that the high throughput levels achieved > with the 3x3 MIMO configuration are maintained across the entire WLAN > link. > > Low Density Parity Check (LDPC) guards against packet loss at every > point on the link. > Maximum Likelihood Demodulation (MLD) optimizes MIMO demodulation to > boost signal strength at close range. > Transmit Beamforming (TxBF) focuses transmit signals to the receiver > to enhance the link rate at mid-range on the link continuum. > Maximal Ratio Combining (MRC) enables the receiver to optimally > combine the MIMO signal paths, aligning time and phase of the signal > receive to extend link reliability at longer range." > > It seems they don't claim such feature set in AR9200: > > http://www.atheros.com/news/AR9280_AR9281.html > http://www.atheros.com/pt/AR9285.htm > http://www.atheros.com/news/AR9220_AR9223.html > > so I'm a bit confused about this
I am aware of the AR9300 features / SST3. The AR9100 and AR9200 also contains SST. It is not always mentioned, but it is present in many different specifications I have seen for the AR9100 and AR9200 family of chipsets. I think there is some discussion still as to what SST is, however... -Galen _______________________________________________ ath9k-devel mailing list ath9k-devel@lists.ath9k.org https://lists.ath9k.org/mailman/listinfo/ath9k-devel
