Hi All,

I am a newbie and am trying to change the operating frequency of WiFi card. I am using RB433AH and the WiFi card uses ath5k drivers. I want to change the channel 1 center frequency to 2382 MHz instead of 2412 MHz. I searched a little and found that it is possible (http://www.qsl.net/kb9mwr/projects/wireless/modify.html).

I am using attitude_adjustment 12.09. I tried seacrhing for the drivers that are resposible for the frequency and saw the frequency dependency only in hostapd, compat-wireless and iw3.6. The channel frequency is set in each of these drivers using

freq = 2407 + chan * 5;

I changed the value 2407 to 2377 (in iw3.6/util.c, compat-wireless-2014-01-23.1/include/linux/ieee80211.h and compat-wireless-2014-01-23.1/net/wireless/util.c) so that my channel 1 center frequency becomes 2382 MHz. I also set the value  caps->cap_range.range_2ghz_min = 2312 (which was 2412 by default) in compat-wireless-2014-01-23.1/drivers/net/wireless/ath/ath5k/caps.c

Now coming to the problem: The channel frequencies do get changed.
I added a printk(KERN_DEBUG "ieee80211_frequency_to_channel: freq = %d", freq) in the iw3.6/util.c

I set the channel to 1 in the /etc/config/wireless file.
When I enable wireless and restart the network, I get the following

ieee80211_frequency_to_channel: freq = 2382
ieee80211_frequency_to_channel: freq = 2387
ieee80211_frequency_to_channel: freq = 2392
ieee80211_frequency_to_channel: freq = 2397
ieee80211_frequency_to_channel: freq = 2402
ieee80211_frequency_to_channel: freq = 2407
ieee80211_frequency_to_channel: freq = 2412
ieee80211_frequency_to_channel: freq = 2417
ieee80211_frequency_to_channel: freq = 2422
ieee80211_frequency_to_channel: freq = 2427
ieee80211_frequency_to_channel: freq = 2432
ieee80211_frequency_to_channel: freq = 2437
ieee80211_frequency_to_channel: freq = 2442

However, now, if I check the list of frquencies, I get

iwlist frequency

wlan0     7 channels in total; available frequencies :
          Channel 07 : 2.412 GHz
          Channel 08 : 2.417 GHz
          Channel 09 : 2.422 GHz
          Channel 10 : 2.427 GHz
          Channel 11 : 2.432 GHz
          Channel 12 : 2.437 GHz
          Channel 13 : 2.442 GHz

Also, channel 1 by default sets to channel 7 (2412 MHz).

I tried this for a few other frequencies, and what's happening is when I set the channel to 1, the channel is set to the one which has frequency more than 2412 MHz. Channel 2 translates to channel 8, channel 3 to channel 9 and so on.

What am I missing? I tried searching for conditions in the driver to check if it prevents from changing the frequency but did not get any. Wherever the driver checked a condition such as freq >=2412, I replaced it with freq >=2312. Are there more files where I need to make changes?

Again, I am rather new to studying and modifying the drivers; so pardon me if I have made any obvious errors. Any help is sincerely appreciated.

Thanks,
Gaurang

regulatory problem?

what does

iw reg get

reports?

I haven't explored into the regulatory part.

This is the result i get for iw reg get

root@OpenWrt:/# iw reg get
country US:
        (2402 - 2472 @ 40), (3, 27)
        (5170 - 5250 @ 80), (3, 17)
        (5250 - 5330 @ 80), (3, 24), DFS
        (5490 - 5600 @ 80), (3, 24), DFS
        (5650 - 5710 @ 40), (3, 24), DFS
        (5735 - 5835 @ 80), (3, 30)
        (57240 - 63720 @ 2160), (N/A, 40)

Though, I dont know what to interpret.

Issue resolved.

I created a new regulatory domain with parameters : (2302000 KHz - 2402000 KHz @ 0 KHz), (300 mBi, 2000 mBm)

However, that alone is not sufficient. The reg domain was first set to US and then to the one I created. So, it is necessary to change the parameters of US to that as above. Once that is done, issue is resolved.

Thanks!
Gaurang