[OpenWrt-Devel] [OpenWrt] 2.4Ghz limited to 50mW in DFS-ETSI

[Gerald Matzka]

Well, it looks like the txpower of your wdnr3800 is limited to 17dBm because of the hardware reg-domain settings. 

Kind regards,

... sent from my iPhone

> Am 29.07.2015 um 10:43 schrieb Nicola von Thadden <nico at vthadden.de>:
> 
> Hi,
> 
> I have this strange behaviour down below, for which I also opened a
> ticket because I think this should not be like that ;)
> 
> Does anyone have an idea where the problem could originate from and how
> to fix it?
> 
> Thanks
> Nico
> 
>> On 07/29/2015 12:37 AM, OpenWrt wrote:
>> #20222: 2.4Ghz limited to 50mW in DFS-ETSI
>> ----------------------+----------------------------------
>> Reporter:  nicoduck  |      Owner:  developers
>>     Type:  defect    |     Status:  new
>> Priority:  normal    |  Milestone:  Chaos Calmer (trunk)
>> Component:  kernel    |    Version:  Trunk
>> Keywords:  wndr3800  |
>> ----------------------+----------------------------------
>> I have got a Netgear WNDR 3800 running with openwrt since quite a while.
>> I now upgraded to the latest version (trunk) and wanted to use WLAN within
>> the regulations here in Germany but also wanted to max out the output
>> power (within the regulations).
>> Switching the country to Germany limits the maximum output power to 17dBm,
>> although it does show as being limited on 20dBm:
>> root at OpenWrt:/# iwinfo wlan0 txpower
>>    0 dBm (   1 mW)
>>    1 dBm (   1 mW)
>>    2 dBm (   1 mW)
>>    3 dBm (   1 mW)
>>    4 dBm (   2 mW)
>>    5 dBm (   3 mW)
>>    6 dBm (   3 mW)
>>    7 dBm (   5 mW)
>>    8 dBm (   6 mW)
>>    9 dBm (   7 mW)
>>   10 dBm (  10 mW)
>>   11 dBm (  12 mW)
>>   12 dBm (  15 mW)
>>   13 dBm (  19 mW)
>>   14 dBm (  25 mW)
>>   15 dBm (  31 mW)
>>   16 dBm (  39 mW)
>> * 17 dBm (  50 mW)
>>   18 dBm (  63 mW)
>>   19 dBm (  79 mW)
>>   20 dBm ( 100 mW)
>> 
>> What I did: reset the device, flash it with various builts from trunk and
>> try to figure out what was going on.
>> I now modified my regdb and was able to isolate the source of the problem:
>> country DE: DFS-ETSI
>>         # entries 279004 and 280006
>>         (2400 - 2483.5 @ 40), (100 mW)
>>         # entry 303005
>>         (5150 - 5250 @ 80), (200 mW), NO-OUTDOOR, AUTO-BW
>>         # entries 304002 and 305002
>>         (5250 - 5350 @ 80), (100 mW), NO-OUTDOOR, DFS, AUTO-BW
>>         # entries 308002, 309001 and 310003
>>         (5470 - 5725 @ 160), (500 mW), DFS
>>         # 60 gHz band channels 1-4, ref: Etsi En 302 567
>>         (57000 - 66000 @ 2160), (40)
>> Thas does not work and has the mentioned behaviour, 2.4Ghz is limited at
>> 17dBm. It also does not depend on which values are set in the regulatory
>> database for the 2.4Ghz channels, anything over 17dBm will be limited to
>> 17dBm.
>> running "iw phy phy0 set txpower fixed 2000" gives no error but does not
>> change it to 20dBm. Changing the value to anything below 17dBm works
>> though.
>> 
>> country DE: DFS-FCC
>>         # entries 279004 and 280006
>>         (2400 - 2483.5 @ 40), (100 mW)
>>         # entry 303005
>>         (5150 - 5250 @ 80), (200 mW), NO-OUTDOOR, AUTO-BW
>>         # entries 304002 and 305002
>>         (5250 - 5350 @ 80), (100 mW), NO-OUTDOOR, DFS, AUTO-BW
>>         # entries 308002, 309001 and 310003
>>         (5470 - 5725 @ 160), (500 mW), DFS
>>         # 60 gHz band channels 1-4, ref: Etsi En 302 567
>>         (57000 - 66000 @ 2160), (40)
>> 
>> Thad does work. The only change to the entry above is "DFS-FCC" instead of
>> "DFS-ETSI". I can now select any powerlevel between 1 and 20dBm and it is
>> also reported as being used:
>> root at OpenWrt:/# iwinfo wlan0 txpower
>>    0 dBm (   1 mW)
>>    1 dBm (   1 mW)
>>    2 dBm (   1 mW)
>>    3 dBm (   1 mW)
>>    4 dBm (   2 mW)
>>    5 dBm (   3 mW)
>>    6 dBm (   3 mW)
>>    7 dBm (   5 mW)
>>    8 dBm (   6 mW)
>>    9 dBm (   7 mW)
>>   10 dBm (  10 mW)
>>   11 dBm (  12 mW)
>>   12 dBm (  15 mW)
>>   13 dBm (  19 mW)
>>   14 dBm (  25 mW)
>>   15 dBm (  31 mW)
>>   16 dBm (  39 mW)
>>   17 dBm (  50 mW)
>>   18 dBm (  63 mW)
>>   19 dBm (  79 mW)
>> * 20 dBm ( 100 mW)
>> 
>> 
>> I have no idea why but there seems to be a bug in the code parsing the DFS
>> regulations, limiting 2.4Ghz to lot lower values than allowed. Changing it
>> to DFS-FCC works for using the applicaple output power but does not seem
>> to be in compliance which German law.
>> 
>> Do you have an idea where the problem could be? I'm happy to try out more
>> builds and future versions.
>> 
>> Also (kind of off-topic): Do you know why 5Ghz channels 36-48 are forced
>> to be 17dBm only on the WNDR3800? I found two possible explanations:
>> either because of the factory calibration (is it possible to get them in a
>> human readable form somehow? The hexdump is not really readable and I have
>> not been able to find the code which pases them) or because these channels
>> are considered as "edge-channels" and someone thought it would be safe to
>> limit the power, to not disturb any other systems running on even lower
>> channels. The latter explanation is kind of weird because it would make no
>> sense to limit these 4 channels but no other ones. I find it especially
>> strange because that is typically the job of regulatory authorities, to
>> define those power levels.
>> 
>> --
>> Ticket URL: <https://dev.openwrt.org/ticket/20222>
>> OpenWrt <http://openwrt.org>
>> Opensource Wireless Router Technology
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