Unable to set my channel with hostapd

Luciano Coelho coelho at ti.com
Mon Apr 29 05:01:56 EDT 2013


Hi Francisco,

On Mon, 2013-04-29 at 10:27 +0200, Francisco Cuesta wrote:
> Hello,  thanks for replying,
> 
> I'm using ath9k driver in openwrt with hostapd v2.0-devel.
> 
> iw reg get
>     (2412 - 2472 @ 40), (3, 27)
>     (5170 - 5250 @ 40), (N/A, 31)
>     (5250 - 5330 @ 40), (N/A, 31), DFS
>     (5490 - 5600 @ 40), (N/A, 31), DFS
>     (5650 - 5710 @ 40), (N/A, 31), DFS

Here you can see that the channel you want to use is not allowed by the
regulatory code.  It seems that you're using "00" as the country
(world).  From the regulatory database [1], you can see that channel 196
(4980 MHz) is only allowed in Japan (regulatory country "JP").


> iw list
> 
> Frequencies:
>             * 5180 MHz [36] (17.0 dBm)
>             * 5200 MHz [40] (21.0 dBm)
>             * 5220 MHz [44] (17.0 dBm)
>             * 5240 MHz [48] (17.0 dBm)
>             * 5260 MHz [52] (17.0 dBm) (radar detection)
>             * 5280 MHz [56] (17.0 dBm) (radar detection)
>             * 5300 MHz [60] (17.0 dBm) (radar detection)
>             * 5320 MHz [64] (17.0 dBm) (radar detection)
>             * 5500 MHz [100] (17.0 dBm) (radar detection)
>             * 5520 MHz [104] (21.0 dBm) (radar detection)
>             * 5540 MHz [108] (21.0 dBm) (radar detection)
>             * 5560 MHz [112] (21.0 dBm) (radar detection)
>             * 5580 MHz [116] (21.0 dBm) (radar detection)
>             * 5600 MHz [120] (disabled)
>             * 5620 MHz [124] (disabled)
>             * 5640 MHz [128] (disabled)
>             * 5660 MHz [132] (17.0 dBm) (radar detection)
>             * 5680 MHz [136] (17.0 dBm) (radar detection)
>             * 5700 MHz [140] (17.0 dBm) (radar detection)
>             * 5745 MHz [149] (21.0 dBm)
>             * 5765 MHz [153] (21.0 dBm)
>             * 5785 MHz [157] (21.0 dBm)
>             * 5805 MHz [161] (21.0 dBm)
>             * 5825 MHz [165] (20.0 dBm)
>             * 4915 MHz [183] (21.0 dBm)
>             * 4920 MHz [184] (21.0 dBm)
>             * 4925 MHz [185] (21.0 dBm)
>             * 4930 MHz [186] (21.0 dBm)
>             * 4935 MHz [187] (21.0 dBm)
>             * 4940 MHz [188] (21.0 dBm)
>             * 4945 MHz [189] (21.0 dBm)
>             * 4960 MHz [192] (21.0 dBm)
>             * 4980 MHz [196] (21.0 dBm)

This shows that the driver supports 4980, but it won't be able to use it
if the regulatory doesn't allow it.


> But, could you explain me the reason behing I get this error, I mean,
> what does it mean, for instance  problem with the interface, the
> channel isn't supported by the driver ..., I would like to understand
> it, not just resolve it.

This is because the radio regulations in the country you're choosing
("world" is a set of frequencies that is valid in *every* country)
doesn't allow WiFi operation on the channel you want to use.  You can
only legally use channel 196 in Japan.  So, if you are in Japan, you can
do this:

iw reg set JP

And hostapd should work on that channel.  If you're not in Japan, doing
this is not legal, so you should better choose a different channel
instead. ;)


-- 
Luca.



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