4G -> 5G WTF

NB: The least expensive (T-Mobile) 5G entry with enough features (Android 11, Snapdragon 480 vs. Snapdragon 805 and Android 7 in my 2015 Droid2), is probably the Nord N200 5G. ~$200, or about $140 (including tax) refurbished.

Links: EBay.com :: New in box older phones :: T-Mobile

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5G is definitely here and governments are rejoicing (all digital! AI packet inspection!). But as part of this rollout, providers began shutting down 3G networks. This meant the new fallback for voice calls became digital 4G, no more analog 3G. Also, different providers use different frequencies.

1. VoLTE functions (15:54) Telecom Tutorial info, 2018. Pre-5G video provides history of 2G, 3G, 4G and thorough description of VoLTE services including important note that the provider may not enable VoLTE on all handsets. 11:00 particularly applied to me.
2. VoLTE functions turn/on off (6:52) Make Knowledge Free, 2021. Thorough description of ways to enable VoLTE, assuming provider, handset, SIM, and handset firmware are provisioned to do so.

part 1 - 4G begins to malfunction

I have a reliable 4G phone. In March, a T-Mobile store checked the device and said, "it will work after the July 5G rollout". In August however, 4G data was reliable, but the phone dropped voice calls. Obviously, the phone was attempting to switch voice traffic to analog 3G, which no longer existed.

1st diagnostic

I checked several screens, but will only repeat the most relevant one below

analysis

1. 4G data is not a problem in this phone. The 4G icon is illuminated in the upper right, and there had been no interruptions to texts or internet.
2. my device is probably white-listed by T-Mobile, just as the store clerk said.
3. Hardware is provisioned for VoLTE or the greyed out "VoLTE provisioned" switch would not be present

Given 1-3, the disfunction must either be the device's firmware, or the device's SIM card. If it's the SIM, T-Mobile can send me a VoLTE provisioned SIM. If it's firmware... I'm out of luck and will have to purchase a new device. The phone (though reliable) is an unlocked former Verizon phone with Verizon firmware. Verizon firmware is impossible to update through T-Mobile.

2nd diagnostic - t-mobile

I recorded the IMEI of the phone but, as we can see from the screenshot above, SIM numbers were not provided to the user in Android 7. I physically pulled the SIM to record the ICCID number. With the ICCID and IMEI, I opened a laptop, went to the T-Mobile website and intiated a text chat with a tech. He took the numbers and determined the problem was likely SIM provisioning. He orded a new SIM overnighted to me. It arrived 2 days later.

3rd diagnostic - SIM install

After installing the new SIM (see below), there's a 2 hour delay for T-Mobile to fully detect and provision it.

I waited 3 hours and resarted the phone twice, however the VoLTE option was still greyed-out as previously. Verified also that voice calls were dropping. SIM was no solution. Failure.

2nd analysis

The remaining unverified problem was firmware. We can see from the phone info that both baseband and system firmware are Verizon. If I'd had unlimited patience, I might have written Verizon to see if they had a more recent version that was VoLTE enabled -- there was nothing on their website which looked like a solution.

conclusion

Appears I need to purchase a 5G phone; the Verizon firmware limitation cannot apparently be remedied. Lesson: if buying a cheap unlocked phone, it's smart to purchase a device which was previously used on my current provider's network. Accordingly, I found a 5G OnePlus Nord 200 on Ebay for $130, unlocked from T-Mobile.

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part 2 - related notes

Home: SIM installation (T-Mobile)

Home installation relies partly on one's online T-Mobile account. The old SIM needs to be operating to log-in (2FA) to that account, and a person must complete the SIM swap before the online account times-out. There's no way to 2FA back into the online account without the new SIM being registered. Here's what I needed:

• paper; copy down the new SIM number from the package
• a tool to quickly pop the SIM from the phone
• laptop to get on the T-Mobile website

1. login to T-Mobile. T-Mobile sends a 2FA text to my phone
2. Go to Account->Lines and Devices ->Change SIM.
3. Work fast before you're logged out.
   • turn-off the phone
   • pop-out old SIM and put in new SIM
   • power-on the phone (all kinds of error messages will appear -- disregard them)
4. enter the new SIM number in the box for it on website (laptop) and then "continue"
5. completion message appears
   
6. After about 20 minutes of the phone being inoperable, a text from T-Mobile arrived asking for new SIM verification.
7. re-establish accounts in phone. Most accounts (google play, voice, phone) are tied to a SIM card, not to a phone, so all of these accounts logged out and needed to be re-established.

Vendor: possible store visit

SIM config can only be done by the provider, so if the phone is still not properly registering in the network, take it to the provider. More about it here. Also the phone probably has to be registered for IMS, unlike 3G. And if a person has a perfectly configured 4G phone, the provider might also be banning that device model from the 5G network. With so many variables, it's good to be patient with oneself if a person eventually must visit the vendor shop.

VoLTE functions (23:15) Telecom Tutorial info, 2018. Pre-5G video provides in-depth PowerPoint of how 4G VoLTE connects from User Equipment(UE) with voice in an IP Multimedia System (IMS). Covers congested network scenarios also.