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If I run the command iw reg get in my system (Ubuntu 16.04.4 LTS, kernel 4.13, iw version 3.17), I get the following output:

country PT: DFS-ETSI
    (2402 - 2482 @ 40), (N/A, 20), (N/A)
    (5170 - 5250 @ 80), (N/A, 20), (N/A)
    (5250 - 5330 @ 80), (N/A, 20), (0 ms), DFS
    (5490 - 5710 @ 160), (N/A, 27), (0 ms), DFS
    (57000 - 66000 @ 2160), (N/A, 40), (N/A)

Questions:

  1. How should I interpret the above information? While I can guess what the first column refers to (I assume <channel-frequency-range> @ <channel-width>), I'm not sure about the other columns.
  2. Furthermore, how compatible should the above information be with the output of the iw phy or iw list command?

For example, in my system, I get the output shown below for the iw list command (I've only considered the part related with the 5.0 GHz band). Given the presence of 'N/A' for the 5170 - 5250 frequency range in the iw reg get command, shouldn't these frequencies show up as (disabled) in iw list's output? Is the distinction based on the channel width? But then again, why doesn't iw reg get include results for the 20 MHz channel width?

Band 2:
        Capabilities: 0x2fe
            HT20/HT40
            SM Power Save disabled
            RX Greenfield
            RX HT20 SGI
            RX HT40 SGI
            TX STBC
            RX STBC 2-streams
            Max AMSDU length: 3839 bytes
            No DSSS/CCK HT40
        Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
        Minimum RX AMPDU time spacing: 2 usec (0x04)
        HT TX/RX MCS rate indexes supported: 0-15, 32
        Bitrates (non-HT):
            * 6.0 Mbps
            * 9.0 Mbps
            * 12.0 Mbps
            * 18.0 Mbps
            * 24.0 Mbps
            * 36.0 Mbps
            * 48.0 Mbps
            * 54.0 Mbps
        Frequencies:
            * 5180 MHz [36] (20.0 dBm)
            * 5190 MHz [38] (20.0 dBm)
            * 5200 MHz [40] (20.0 dBm)
            * 5210 MHz [42] (20.0 dBm)
            * 5220 MHz [44] (20.0 dBm)
            * 5230 MHz [46] (20.0 dBm)
            * 5240 MHz [48] (20.0 dBm)
            * 5250 MHz [50] (disabled)
            * 5260 MHz [52] (20.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5270 MHz [54] (20.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5280 MHz [56] (20.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5290 MHz [58] (20.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5300 MHz [60] (20.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5310 MHz [62] (20.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5320 MHz [64] (20.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5500 MHz [100] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5510 MHz [102] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5520 MHz [104] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5530 MHz [106] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5540 MHz [108] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5550 MHz [110] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5560 MHz [112] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5570 MHz [114] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5580 MHz [116] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5590 MHz [118] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5600 MHz [120] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5610 MHz [122] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5620 MHz [124] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5630 MHz [126] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5640 MHz [128] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5650 MHz [130] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5660 MHz [132] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5670 MHz [134] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5680 MHz [136] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5690 MHz [138] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5700 MHz [140] (27.0 dBm) (radar detection)
              DFS state: usable (for 1693 sec)
              DFS CAC time: 60000 ms
            * 5745 MHz [149] (disabled)
            * 5755 MHz [151] (disabled)
            * 5765 MHz [153] (disabled)
            * 5775 MHz [155] (disabled)
            * 5785 MHz [157] (disabled)
            * 5795 MHz [159] (disabled)
            * 5805 MHz [161] (disabled)
            * 5825 MHz [165] (disabled)
            * 4920 MHz [184] (disabled)
            * 4940 MHz [188] (disabled)
            * 4960 MHz [192] (disabled)
            * 4980 MHz [196] (disabled)
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1 Answer 1

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10

Interesting question, and I didn't know the answer, so here is how I found out:

The source code for 3.17 shows where the data comes from. In particular,

  • The first group (5250 - 5330 @ 80) is the frequency range and maximum bandwidth for which this particular rule applies (so you don't need two rules for 40 MHz bandwidth and 20 MHz bandwidth)
  • The second group (N/A, 20) is the maximum antenna gain and the maximum EIRP (Effective Isotropic Radiated Power).
  • The third group (0 ms) is the DFS (Dynamic Frequency Selection) CAC (Channel Availability Check) Time. I don't know if a value of zero is special.
  • The fourth group DFS contains various flags; again, DFS is Dynamic Frequency Selection.

N/A doesn't mean "this should be disabled", it means "there is no regulation for this". Some countries would restrict the maximum antenna gain, some would restrict maximum EIRP, etc.

So the actual values shouldn't be over the regulatory limits, but any value is fine as long as it complies with the regulation.

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  • It makes sense! Thank you for taking the time to look through the source code by the way.
    – fortune_pickle
    Commented May 28, 2018 at 9:34
  • 1
    It didn't take much time, and it's really often the fastest way if you want to find out something.
    – dirkt
    Commented May 28, 2018 at 9:55

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