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 > _______________________________________________ > ath9k-devel mailing list > ath9k-devel@lists.ath9k.org > https://lists.ath9k.org/mailman/listinfo/ath9k-devel >
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 _______________________________________________ ath9k-devel mailing list ath9k-devel@lists.ath9k.org https://lists.ath9k.org/mailman/listinfo/ath9k-devel
