[ath9k-devel] 802.11n PCI-E 300Mbps with AP mode?

[Mihai Moldovan <ionic@ionic.de>]

* On 15.07.2011 04:35 AM, Grant wrote:
> Hmmm, so if I get a US EEPROM and travel to another country, I may
> need to patch ath5k to connect to a particular AP?

Nope, this stuff doesn't apply to client cards only, however AP mode is
severely restricted by regulatory rules.

If you get an US flashed card, everything will be fine, as all
legitimate channels in the US will be open. If you go to Japan with this
card, all non-legitimate channels there are disabled. Also, Japan allows
using WLAN on channels 12 and 13, whilst the US do not. As you've got an
US branded card, you won't get the additional channels unlocked.

Now, if Japan HAD disallowed channel 9 for instance and the US had not,
channel 8 would be locked in Japan, but not in the US. Of course, that's
not the case, just some gedankenexperiment.

That's what I mean. Channel restrictions do stack, but you won't get
channels unlocked if your base flashed information do forbid them already.

Ok, that's one part of the problem.

The other one is that many retailers sell cards with a world regdomain
flashed. This world regdomain is very restrictive, as it basically aims
to support the LARGEST subset of allowed channels common to all
countries in the world.
As such, you won't be able to run an AP on the 5GHz band (802.11a), as
many frequencies are marked as "no beaconing" (no AP mode), DFS (radar
scanning and frequency switching, iff some military radar unit wants to
use this specific frequency etc.) and the rest as both.

So for using the card as an AP on 5GHz and given the card has the world
regdomain flashed, you'd have to patch the kernel driver to either
unlock all channels (yeah, that's bad...) or force a specific regdomain,
preferably of your own country, i.e. US, which is more permissive than
the world regdom.

This being said, the 2.4GHz band (802.11b/g) is a deal less restrictive.
Keep in mind though, that there are only 2 non-overlapping channels with
HT40 (802.11n) - channel 3 and channel 11. AFAIK any world reg domains
allows AP mode on those channels, so you should be golden.

See also: http://linuxwireless.org/en/users/Drivers/ath?highlight=%28crda%29

Hope that helps and wasn't too confusing.

Best regards,


Mihai



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