LTE CAT-M chip and LTE chip recommendation

What do you mean by infrastructure? LTE radios for base stations?

Yes, EU and USA are replacing their 4G and 5G China infrastructure with allies` chips step by step.

So if you are in this business, you must be aware of this trend.

Avoid Hwawei, Quectel, SimCom, etc.

So you're trying to roll out an LTE network?!

Why don't you actually state your use-case properly, so that people don't have to second-guess?

I want to build a sub-1GHz Wi-SUN network so there must be a border router responsible for internet access.  If the user location does not have ethernet etc, LTE is needed.

You mean a gateway... a border router is something completely different. 

I'm only mentioning it in case you've not been searching using the correct search term and not realized, ready-made gateways exist which are secure, some are ruggedized, and it's pretty unlikely you'll be able to assemble some Linux box, with your LTE chip, write and test your secure code, for less; they don't cost much ready-made.

I see.

So I have to search an internet gateway rather than assemble my own gateway.

No. Maybe you wish to re-read what I wrote?

But, now you choose to interpret it in that manner rather than simply thanking someone for pointing you toward the correct term so that you don't waste your effort googling for the wrong information: Since you didn't know the correct terminology, will you be able to develop it? Do you know what goes on inside a gateway in terms of software functionality?

No. Maybe you wish to re-read what I wrote?

But, now you choose to interpret it in that manner rather than simply thanking someone for pointing you toward the correct term so that you don't waste your effort googling for the wrong information: Since you didn't know the correct terminology, will you be able to develop it? Do you know what goes on inside a gateway in terms of software functionality?

I can build an internet gateway with a Wi-SUN FAN server on a Raspberry Pi 4.  There are also Quectel chips which work on RPi 4.  I do not like this combination.  They are not tough and not secure. 

Other ready-made internet gateways cannot be customised.  

Could you recommend any industrial grade programmable internet gateway with LTE-M? 

I wouldn't call this industrial, but I've been using Mikrotik KNOT series products for Ethernet-to-LTE-M connectivity and they seem to work fine.

- Gough