That's actually pretty amazing, and luckily the modules support VoLTE.

BMW modules only supported 3G (they were older though).

There isn't really such a thing as a module that only supports 3G...

Anything could support the minimum needed to connect to an LTE network with the right software update, but modem chipset makers don't make any money rewriting old firmware for old chipsets, so they refuse to rewrite the firmware to support lte.

I did not know this.

Now knowing this, could we (theoretically) update the firmware of an iPhone 3G so it works on a 4G network?

Yes. But beware that doing so is probably multiple man-years worth of effort.

Probably not. In general, this sort of thing is buried in the often unchangeable microcode of an RF ASIC. (Which makes sense, after all, the vendor is selling an RF modem for a specific band/modulation capability - they don't expect it to change, certainly not after they've built/configured it.)

If that's the case (as is common), then there is really nothing to update, short of scraping off that chip or module and replacing the hardware.

Chipset makers, probably correct but there aren't that many companies that make them. Depends on the analogue front end if they support the new frequencies.

I know the 3rd party module makers do tailor their modules to regions and the 'world wide' models can be quite pricey. On the region specific versions they don't include some of the hardware to physically operate on frequencies they don't specify. Sounds crazy, but a few cents here or there is worth running multiple SKU's.

There are probably other issues such as radio compliance and patents that also prevent an upgrade.

The VoLTE upgrade isn't so surprising. For a long time we had 3G/4G modules however the mobile networks didn't support VoLTE so everything would fall back to 3G. Once everyone got their act together, a quick firmware upgrade and VoLTE worked perfectly without adjusting the hardware.

Mine is a 2014, guess I narrowly dodged that bullet. Thanks for posting this.

Thanks for the link. I've got a Legacy that's had a 'weak' battery for a while now and it seems like it may coincide with this 3g sunsetting..