[Xiaomi Mi A1 Themes, Apps, and Mods] findrome:
Before I begin, I'd like to thank:

phhh for assisting Sooti

[MENTION=4460995]sooti[/MENTION] for his work on Pixel Experience

[MENTION=4936496]joeyhuab[/MENTION] for his work on the modem

Mentor.37 for the GSM patch

And to many other XDA contributors who have addressed similar troubles on other devices.

I'm writing this in narrative, use of "I" in any of it's applications denotes my effort to utilize what I've learned.

I stood upon the shoulders of giants.

Disclaimer

If you pursue anything mentioned or alluded to here, you assume all risk.

Please don't ask me any how to's. All you need to help yourself is here and the search function works fine.

Depending on region or network or both, MiA1 stock had inherent network trouble. This is especially true if using a custom ROM. The phone never, from unboxing, successfully registered itself to the network, so I had to research and install all the appropriate APN settings for my MVNO. There are several, and all are needed.

The mobile network worked well on stock until around the December 2017 update. It was initially blamed on the update from 7.x.x to 8.0, calling it a bug. It was in the following February that I stumbled across a report that Germany identified the MiA1, specifically, as generating the greatest emmission of RF out of all current phones (link (1)).

It appears, and I assume, that in response to this government report, Xiaomi modified the firmware to reduce RF emmission to bring rhe device into compliance. Likely, the radio power was reduced.

I began searching for modems, ROMs, kernels, band availability, whatever work was being done in regard to the network problem up to and including all the hardware information that I could personally verify or felt comfortable building upon.

Hardware may complicate our issue, but it is not the cause or the solution. However, if an aftermarket plastic battery cover becomes available I will swap battery covers to observe the effect. I'm aware the metal battery cover is integrated into the atenna function.

What I've done, and what has worked;

I found a thread for the stock modem (link (2)) and I flashed the file, but the network dropped dead from area to area.

Later, I stumbled across a CDMA to GSM patch (link (3)). A script, developed several years ago that fully enabled the GSM function on phones sold originally for CDMA. Ours was initially capable of operating on both GSM and CDMA. I flashed it, and it helped greatly, but the network reset to 2g after every reboot.

I Flashed the modem on top of the patch, and found the OS became laggy and later I started getting an error "android has stopped".

I have long since flashed PE (link (4)). The June update included the GSM patch. I have flashed April modem over PE stock as a matter of preference.

The network issue has stabilized, with exception of indoors- which I still believe to be either a firmware or hardware issue, but likely both. Ultimately, indoors I have steady reception but it spends half of the time on 2g. I can call out nicely from indoors and with WiFi, that's all I need.

**Edit**

A significant volume of this is based on educated assumption, of which was inferred as opposed to verified by me- this contradicts my ethics as a mechanical technician- but I do as I'm able until I have learned coding, logcats, and commands successfully enough to hash out what I must in the name of accuracy. You must, and I encourage you to, do your own research. I will do my best to correct anything here as appropriate.