@dos @licho I would like someone who is well versed in the subject to chip in, because I see some mix up. I have some vague idea how radio communication works. With the v stress on *vague*.

Radio frequencies are managed by governments, according to some international conventions. Like: this range is for WiFi, that for ham radio, this for mobile phones, that for radio broadcasting, etc...

There might be different criteria defined for each use. Like, which conditions need to be fulfilled to use the frequency. Those conditions might be technical or legal.

For ham radio you need to have licence. And to get the licence, you need to have some knowledge. And you are legally allowed to build your own equipment, as long as it's compliant to the technical specification. Like, bandwidth during transmission, signal power etc.

For CB you usually do not need the b licence (YMMV, depending on the country), but you still need to follow technical requirements, similar to ham radio. You cannot just blast 1kW transmission around you.

Now we are getting to the point where I do not have a proper knowledge, and I'm guessing.

My guess is that - for WiFi or whatever successor of GSM - you don't need to use certified h/w, as long as it operates according to the specification.

The certification is to give you a paperwork, that someone has run a bunch of checks, and everything was OK. So, if something went wrong, you still need to fix things, but at least you've a confirmation, that the solution has passed the checks. What checks are - I do not know. Certainly, there are lab test runs of the equipment. But design review might happen as well.

Of course, you might add some feedback loop to your solution, to monitor the broadcast parameters, and shut the transmission off whenever it goes out of limit. But that means, the solution is more expensive (because of feedback loop), and less reliable (because of shutting off).

To make it clear. I do not know if just using uncertified h/w is punishable. But I know that transmitting signal not following the regulations for given band is. And here we are getting back to legal responsibility. For mass market devices the vendor is responsible in such cases. And if something goes wrong, you might expect a recall.

And if you make a design of your own solution, and I implement it, in case something goes wrong I doubt I can effectively use "an author told me it is OK" in my defence.

BTW, even if you use a certified chipset in your solution, you still might be at risk.

For example, for WiFi, the exact channels available, and signal power, vary between different regions of the world. That's why in the WiFi AP settings you might select the country or region. The h/w WiFi chipset can handle all the regions. But it needs to be told which region it operates in.

For WiFi the responsibility has been passed to the end user. For mobile telephony - if there are such differences - it needs to be handled properly depending where you are. And during the certification such switching is certainly checked.

Now I expect to be steamrolled by someone who has proper domain knowledge. Please do :)

@agturcz @licho I'm not an expert either, but I know for sure that bands for cellular networks are heavily regulated and the legal framework under which they are being used and certified is completely different than for ISM bands like Wi-Fi, which are sort of a special case here.

Also, depending on its design details, you may need to certify your whole product separately even if the module it uses is already certified.