Hi!
I’m not a software or hardware engineer in any shape or form, I’m just a regular guy who loves technology more than anything. One thing that has gotten into my brain (quite obsessively) is the question if anyone can make a 2G phone work on a 4G network?
I’ve looked for electronic engineers on fiverr and some of them say that they can do it but it would cost a ridiculous amount of money that I don’t have and wouldn’t pay for unless I was rich.
My question is if anyone knows about anyone in the world who has solved this problem?
In short, no. They are entirely different systems. You could maybe build a box which provided a 2G network (base station and core) and then had a 4G cellular modem it used to attach to a live operator network. However this would just be like a sort of “wireless PABX”, with two different SIMs. So the 2G device would have it’s own internal number, but external called parties would see the 4G number and inbound calls would be connected to the 2G “extension”.
However, this is a complicated setup and you would need a 2G wireless spectrum licence, which you could arrange in the UK, Netherlands and maybe some other places, but certainly not the US.
Hi Andrew and thank you for your answer. I don’t mind bringing a second unit with me if it’s pocketable. I do live in Sweden and my provider gives me a 4G data card for free with 40gb of surf every month.
A quick google suggests that Sweden has mobile private network (MPN) spectrum available in 3.7 GHz and 26 GHz bands, both of which are for 5G use and cannot be used with 2G networks, which operate on completely different frequency bands.
Spectrum is usually licensed at a fixed location and it’s typical to have to provide not just GPS coordinates, but things like antenna height also. This is because cellular spectrum access, unlike WiFi, is carefully coordinated in an attempt to optimise use and eliminate the possibility of interference. What you’re describing is, unfortunately, a mobile jammer.
I’ll have to rethink this and I think that the best solution is to swap out the internals for a Linux based system that has 4G connectivity
You should bear in mind that 4G and 5G moved away from directly integrating a dedicated voice function, to using a system layered on top called IMS, which is a slightly unwieldy combination of SIP and IPsec. Handsets typically implement an IMS client via the application processor, which runs Android or iOS etc., and I’m not sure there are any practical open source implementations.
Fortunately there are some cellular modem modules which integrate an IMS client, but this is the exception rather than the rule. For example, Quectel EC25, which achieves this by seemingly running a cut down version of Android (+IMS client) directly on the module, which then has audio I/O connections, along with data. The PinePhone used this module, so that the phone could notionally run Linux, while still being able to support voice and SMS (there are other ways to support SMS, but IMS is typically used for this also).