On 2010-02-21 9:41 PM, Galen wrote: > Hello All, > > I have been testing out ath9k in a variety of situations. I have > observed it appears to have poorer handling in MIMO-intensive > environments than the binary drivers under Mac OS X and Windows. I > have two computers with identical radios (3x3:2 AR5008 Mini PCI-e) > and as similar of antenna configurations as possible. One computer > runs Windows XP + latest Atheros binary drivers and Linux 2.6.32 + > latest compat-wireless. (I have also tested some older versions with > similar results.) The other computer runs Mac OS X 10.6.2 which > contains the latest Atheros binary drivers. > > *** Further Testing *** I plan to create a triple-boot environment so > I can compare any OS combination on exactly the same hardware. > Absolute care will be used when rebooting as not to move anything. I > will run a standard series of network tests under Linux and OS X. (It > is a significantly larger headache to setup Cygwin to use the same > tools on Windows and I will only do so if OS X versus Linux testing > is inconclusive.) I will also have another system in monitor mode and > be recording the raw 802.11 frames for later review. > > I do not expect a significant change in behavior in my testing > environment, but I do expect more accurate and precise data, which > can hopefully help me identify the cause of the performance > differences. > > *** Discussion *** While I realize some of my examples are rather > extreme, they clearly demonstrate the huge disparity between ath9k > and proprietary drivers. I suspect that ath9k may have inferior MIMO > support code (MRC, beamforming, etc.) as compared to the proprietary > drivers. I believe that STBC is still not supported yet either. All of the currently available common Atheros hardware such as AR9280 and earlier chip generations do not have MRC, Beamforming and similar advanced features. 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.
While I haven't done any tests with it yet, I believe STBC could potentially make a difference in strong multipath environments, especially when dealing with lower signal strength. The signal strength issues might also be related to ANI, you should probably disable that in ath9k to make sure that it's not screwing up your test results. > Can anybody comment on this issue? Have you experienced it yourself? While I haven't done any extensive testing in that area, nor compared it against proprietary APs directly, your description of ath9k issues sounds somewhat similar to what I'm seeing with AR9280 hardware in my tests. > Does anybody have ideas on how this might be improved? I have been > considering ath9k for an embedded installation, but these multi-path > performance differences are pretty disturbing. Atheros has a > proprietary driver available with source for a very hefty license > fee, but I'd rather put energies into ath9k - the kind of licensing > fees they are working with can pay for a lot of developer time. I'm currently working on a new rate control algorithm for 11n, and I also intend to add STBC support to ath9k soon (it's only a few flags missing, nothing major). Maybe I should do STBC first, as it should be fairly straightforward. - Felix _______________________________________________ ath9k-devel mailing list ath9k-devel@lists.ath9k.org https://lists.ath9k.org/mailman/listinfo/ath9k-devel
