2014-02-26
Linux wireless regulatory domain information
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-OUTDOORThis 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.