Wireless update - 802.11n development

A few of us have been working towards 802.11n support in FreeBSD. Bernhard Schmidt and I were hoping to get 802.11n support up to scratch before 9.0-RELEASE but a combination of timing constraints and work constraints has hampered things somewhat.

But that said, we the net80211 support for 802.11n is in a lot better shape than it was in previous releases. Bernhard has been working out the kinks in the intel driver (if_iwn) and has 802.11n support mostly stable for those NICs. Someone else has been working on if_ral 802.11n support and has had quite a bit of success there. And I've been working on if_ath/ath_hal support.

(As a side-note, I've ordered some Marvell if_mwl compatible NICs to do some testing with.)

The 802.11n support in the FreeBSD atheros driver is already mostly usable for testing - 802.11n TX and RX works, but 802.11n TX aggregation doesn't work. So if you'd like to test it out in 9.0-RELEASE, you can do this:

* build a kernel with "options ATH_ENABLE_11N";
* ifconfig wlan0 -ampdutx
* associate as per normal to an 802.11n network.

Your download speeds will be good (as RX aggregation works) but as TX aggregation doesn't, you won't be getting full speed.

Now, as for the current work I'm doing. I've been porting over (and reimplementing in places) the 802.11n TX aggregation support, based on a combination of the atheros reference/carrier codebases and what's filtered through to the Linux ath9k driver.

In short - so far, so good. There's a lot to do, but basic TX aggregation is working in both station and hostap mode. My current test setup is:

• A routerstation pro with an AR9160 NIC, running locally built firmware (FreeBSD) in hostap mode;
• An EEEPC 701 retrofitted with an AR9280 NIC, running FreeBSD, as a station;
• My macbook pro (broadcom 802.11n) as a station.

So far it's performing well - 200mbit TX/RX UDP in 5ghz HT/40 2x2 stream mode; and 130-140mbit TX/RX TCP.

I'm currently doing the work in a FreeBSD user svn branch. The details are in the Wiki - http://wiki.freebsd.org/AdrianChadd/AtherosTxAgg . I currently have exactly one tester (AR5416 STA, AR9280 hostap) who is reporting excellent success. I'd obviously like a few more. :)

There's still a lot of work to be done before this can be merged into HEAD. I'm sorry to say it won't happen before 9.0-RELEASE as there are some upcoming net80211 changes which will be rather intrusive and a bit risky to throw into the release at this late stage. It may also be difficult to backport as some changes will break kernel ABI.

But don't let anyone tell you FreeBSD doesn't support 802.11n. 9.0-RELEASE may not have much support, but all the key pieces are there. Once the release has been cut, I'll do some chasing up to get the Intel, Marvell and Ralink 802.11n support updated. (If someone would like to take charge of the broadcom NIC drivers, please drop freebsd-wireless@ a line.)

The next 6 months will be very interesting in the FreeBSD 802.11 world. :)

Finally, none of this current work would've been possible without the support of the sponsor paying me to get FreeBSD's net80211 and ath support updated - Hobnob, Inc. They contacted me a few months ago to help work out kinks in the Atheros NIC they're using in FreeBSD and seem impressed enough by my work to sponsor general net80211/ath improvements which they'll likely roll into future products. So when you're using Atheros 802.11n hardware in FreeBSD and getting that nice 140-150mbit TCP throughput, please give them thanks. :)

And finally finally, Qualcomm Atheros and the Linux ath9k developers have been instrumental in this work. The documentation, reference code and general interactive discussions have allowed me to get all of this work done in such a short period of time. (Yes, I did say "Atheros", "Documentation" and "Source Code" there, in the context of open source. Honest.)