6. Lab: Wi-Fi Channel Tool (wifichannel)

Bonus Lab, more of a warm up Lab

WLAN Pi comes with a small CLI tool called wifichannel

This tool began as a simple conversion utility, for switching between channel numbers and centre frequencies.

Requirements:

• WLAN Pi Go (powered and connected via USB-C)

• SSH capabilites to the WLAN Pi Go (10.42.0.1)

Channel maths

Query wifichannel with the command

wifichannel 7

The output gives you information about channel 7

Is 2.4 GHz channel 6 recommended?

wifichannel 6

Output

Is 6 GHz channel 17 a Preferred Scanning Channel (PSC)?

wifichannel 17

Output

What is the centre frequency of channel 60?

wifichannel 60

Output

What channel uses center frequency 6055 MHz?

wifichannel 6055

Output

List all channels

Display all 2.4 GHz channels:

wifichannel -2

Display all 5 GHz channels:

wifichannel -5

How would you display all 6 GHz channels?

Hint

This command will help you if you are ever in doubts:

wifichannel -h

Answer

Note the Lower 6 GHz and Upper 6 GHz channels.

In the FCC regulatory domain, we can use the entire band including the lower and upper 6 GHz channels.

In the ETSI and Ofcom regulatory domains, they can only use the Lower 6 GHz channels.

Filter output with Linux filters (grep)

You can filter the output of most command line utilities to make the output more efficient.

Example

How many channels in the 2.4 GHz band are 'recommended'?

First, run the command to display all 2.4 GHz channels:

wifichannel -2

You could count the lines manually, but there is no need. Computers can already do that, really fast.

Using a Linux utility called grep we can filter the output to only include lines that match an expression (a particular string or pattern):

wifichannel -2 | grep "Yes"

Be precise with your search terms (strings), capitalisation matters.

How many channels in the 2.4 GHz band are

Finally, we can simply count the number of lines returned by the command using word count, that command looks like this:

wifichannel -2 | grep "Yes" | wc -l

---

The wc command has nothing to do with restrooms 😉 It stands for "word count" and the "l" argument stands signifies lines.

Answer

Install wifichannel to your laptop

If you would like, you can install wifichannel on your laptop and use it even more often. Here are the instructions.