Linux wireless regulatory domain information / 2014-02-26

I noticed in the logs of the weather station computer ritchie:

[770336.506717] cfg80211: Calling CRDA to update world regulatory domain
[770336.906545] cfg80211: World regulatory domain updated:
[770336.906567] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[770336.906585] cfg80211:   (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[770336.906602] cfg80211:   (2457000 KHz - 2482000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[770336.906619] cfg80211:   (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
[770336.906635] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[770336.906652] cfg80211:   (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)

But I'm in a specific country (the Netherlands) although the access-point is old enough to not transmit the regulatory domain information. I found out I can update the default in the client using:

root@ritchie:~# iw reg get
country 00: DFS-UNSET
        (2402 - 2472 @ 40), (3, 20)
        (2457 - 2482 @ 40), (3, 20), NO-IR
        (2474 - 2494 @ 20), (3, 20), NO-OFDM, NO-IR
        (5170 - 5250 @ 40), (3, 20), NO-IR
        (5735 - 5835 @ 40), (3, 20), NO-IR
root@ritchie:~# iw reg set NL
root@ritchie:~# iw reg get
country NL: DFS-UNSET
        (2402 - 2482 @ 40), (N/A, 20)
        (5170 - 5250 @ 40), (N/A, 20), NO-OUTDOOR
        (5250 - 5330 @ 40), (N/A, 20), NO-OUTDOOR, DFS
        (5490 - 5710 @ 40), (N/A, 27), DFS
        (57240 - 65880 @ 2160), (N/A, 40), NO-OUTDOOR

This changes maximum power, bandwidth and frequency ranges. And indeed in dmesg:

[770977.623611] cfg80211: Calling CRDA for country: NL
[770977.715887] cfg80211: Regulatory domain changed to country: NL
[770977.715909] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[770977.715926] cfg80211:   (2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[770977.715941] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[770977.715957] cfg80211:   (5250000 KHz - 5330000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[770977.715972] cfg80211:   (5490000 KHz - 5710000 KHz @ 40000 KHz), (N/A, 2700 mBm)
[770977.715988] cfg80211:   (57240000 KHz - 65880000 KHz @ 2160000 KHz), (N/A, 4000 mBm)

Now I wonder about the flags... NO-IR = no initiating radiation the device may not transmit on a frequency until it has received beacons on the frequency. DFS = Dynamic Frequency Selection which is mainly avoiding collision on the 5 GHz wireless band with weather radars.

More information about this subject at Regulatory - Linux Wireless.