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Pi 3 Wireless (WLAN / 802.11) not associating? - solution

shabaz

There's an odd bug in the March release that caught me out for a few hours.

Looks like only WLAN channels 1-11 are scanned by the Pi. In the UK (and most of the world), channels 12 and 13 are allowed.

If your AP happens to be using one of these channels then although your Pi will see the SSID, it will not associate.

The clue comes from typing the following command which dumps out wireless related events (press Ctrl-C to quit it afterwards):

iw event

When it displays 'scan finished' there will be a set of numbers. If there are 11 numbers on the list (and not 13), then this is the

symptom of the issue.

 

Others have hit this, and some solutions are listed here: wifi - How to enable Wi-Fi channel 12 on Raspberry Pi 3? - Raspberry Pi Stack Exchange

However I didn't try these.

My workaround was to modify my AP to avoid selecting channels 12 and 13 for now.

So, if you hit the problem where you can see the SSID, but cannot connect, and you're based in EMEA or Japan,  then you may have hit this issue.

  • 2.4 GHz Wi-Fi Channel Numbers

    Wi-Fi equipment in the U.S. and North America features 11 channels on the 2.4 GHzband:

    • channel 1 operates at a center frequency of 2.412 GHz
    • channel 11 operates at 2.462 GHz
    • other channels operate at frequencies in between, evenly spaced at 5 MHz (0.005 GHz) intervals.
    • Wi-Fi gear in Europe and other parts of the world also supports channels 12 and 13 running at the next higher frequency levels 2.467 and 2.472, respectively.

    A few additional restrictions and allowances apply in certain countries. For example, 2.4 GHz Wi-Fi technically supports 14 channels, although channel 14 is only available for old 802.11b equipment in Japan.

    Because each 2.4 GHz Wi-Fi channel requires a signaling band roughly 22 MHz wide, radio frequencies of neighboring channels numbers significantly overlap each other.

    So someone mentioned Channel 14 and I found where that one was used.

    Clem