Yes, they do.

It's a little different than it used to be though. Historically, the carriers require their magic signal bar algorithms/network type display by contract if you wanted to sell phones in their stores.

Now, less phones target each carrier specifically than used to, but ...

Some of them also used to require display of various network types in various situations (IE you were required to display 4G in circumstances where it was on their "4g network", regardless of whether you were using a 4g protocol)

You can't trust any of this when it comes to mobile networks, they control the domain and have to play by their rules.

Example? I used to work at a company that made femtocells, basically small 3g base stations. All 2 way radios are a co-operative medium, i.e. shouting 'fire' in a crowded room raises the noise floor for everybody so they all need to shout.

We had hundreds of handsets for testing so knew when a particular model/brand/firmware version wasn't working to spec. We'd shoot an email to the manufacturer to get it sorted. Most were fine, but the one that never responded? A certain fruit related company.

Orange!

Probably the fruit company with the most models of phone (Nearly all white label Huawei models, but still!)

Nope. A manufacturer not a mobile network, apologies if it wasn't clear.

Sounds like the green grocer sketch. "My Blackberry is not working"

https://www.youtube.com/watch?v=kAG39jKi0lI

> Yes, they do.

I don't think my operator even knows what kind of phone I have, let alone any access to any software on it. How could they be controlling it? Is it something actually in the SIM?

Baseband cpu. Your phone has 2 separate cpus, and you dont have any access to the 2nd one. Your provider does.

That's one of the reasons why the makers of the Librem 5 phone decided to use an internal USB bus which isolates the baseband from the SoC:

> To isolate the cellular modem from the SoC, we will be placing the modem on the (remarkably fast) USB bus and have the phone interact with the cellular modem through USB instead of on the main RAM bus. This will separate the cellular modem on its own bus without seeing any other data.

(https://puri.sm/posts/librem5-2018-09-hardware-report/)

These processors don't use a shared memory bus. It's just marketing dribble.

How do they get code onto that processor? From the SIM?

Over the network these days. Have you ever gotten a message on your phone similar to “carrier settings updated” especially after switching a device from one network to another? That’s what it means.

The operator knows your phone's IMEI which allows to determine the brand/model.

Doesn't Android or CarbonOS just get its signal strength information from the Qualcomm baseband OS? It's a second OS always running on your phone that you can't do much about.

The baseband OS could be lying about signal strength to your phone OS.

Android/etc allow carriers to customize the signal bar thresholds, etc.

So even if the baseband didn't lie (which is one mechanism), the carriers can control the thresholds used on their network.

Google's android does, and there are specific services in the OS for that, such as vz* sprint* tm* and carrier config/services. There are also a bunch of Qualcomm services running that to various things.

So my question was - I don't have any of that stuff on my phone, with a custom rooted rom, and those services disabled/removed. Simple test now - if I set my phone to 2G, it connects to 2G with full bars, and says 2G. If I set it to LTE, it says LTE and displays 1 bar. Also, every time I reboot the phone, it pop us "carrier config failed."

This makes me believe this likely applies to phones bought from a carrier and not re-flashed. The fact is, if you for some reason buy a phone from a carrier, you are buying into their ecosystem, and for people like that - most people, this 5G icon is what they want, because to them it means faster than the 4G icon on that phone, so I don't see an issue here.

Even if you buy the phone from a third party, there are a bunch of custom configs for every carrier in the world in the android source code.

They're mostly mundane things like 'should we believe the language specified in the sim card' or 'what max MTU should be used on this network', but there are also more sensitive things like 'what types of tethering to allow' or 'should we allow the user to manually select which network to connect to while roaming.

> That's interesting if true. Does the operator have that much control over the phone though?

For most customers, the operator literally sold them the phone. If you're using your own device, not provided by the operator, then it's not relevant to you.

I wouldn’t be so sure, the baseband firmware can be remotely updated by the carrier.

In addition, most carriers have settings inside AOSP itself. I remember when I had an International Galaxy S7, I'd see 4G if I connected to a carrier that used that branding for LTE (like AT&T) and LTE for others (like T-Mobile).