Source
r/tmobile•
touchmeicutyou

Question about LTE calling

Question

So I've been using phones like Samsung galaxies and Iphones before and this issue has never happened. Recently switched to a Sony Xperia Z5 and I can't seem to call anymore. People who attempt to call me would get dropped to voicemai. It would take me 2-3 tries to call people because the phone is trying to drop the 4g signal, which takes like 30 secs, hence why it takes me 2-3 tries to call. The only way to fix this is to turn to GSM only mode in my network settings. Can someone explain why this happens? The other phones I've had in the past drops the 4g signal very fast so calls went through seamlessly. I called a Tmobile tech rep and they said it has to do with the Z5 not supporting certain LTE bands in Tmobile.

Posted Sep 24, 2017, 8:46 PM UTC · edited

210
4ndr0med4Recovering Sprint Victim•

Does it support VoLTE? That might be why.

I've been doing some research on the Z5 and it looks like some models do, and some don't. Interestingly enough, the Z5 supports B2, B4, and B12 (which are the most important you need)

2
touchmeicutyouOP•

I have the e6653 and from my research it seems that the phone is volte capable, but sony never went through certification for volte through tmobile. i guess that;s why.

1
4ndr0med4Recovering Sprint Victim•

Keep in mind some areas are switching B2 HSPA+ off for LTE, which means that it might be even harder for you to get a call with only B4 HSPA+ and 2G.

1
_mully_•

Yeah, I have this issue. Switched to t-mobile last year with an iphone from verizon and it worked fine for calls and everything, more or less, but I think they replaced the band 2/4/etc. support in my area in favor of band 12 and now I have loads of deadzones, including my house (fortunately the 5s is approved for wifi calling on tmobile, otherwise phone calls from my house would be basically impossible). I am really interested in the Sony phones, or other unlocked phones perhaps, but am quite worried I'll pay all that money to have just as crummy a functioning phone as my 5s. And, I have noticed that some unlocked phones seem to support wifi calling and some dont on tmobile, so if I were to switch to one that didnt and didnt have band 12/volte, it would be a for sure down grade to the point were i might not be able to make calls altogether nearly anywhere (from a four year old phone, wut?).

1
sgteqSpectrum Gateway•

What is the model number of your Z5? I see E6603 and E6653 do not support AWS UMTS. T-Mobile recently shutdown PCS UMTS in many cities so if the phone does not support AWS UMTS it may have troubles placing and receiving calls. It appears some phones spend too much time trying to find PCS UMTS instead of quickly falling back to GSM. When you force GSM it won't search for PCS UMTS so it works better.

Here is the list of affected cities but cities prior to August have been removed from the list so the full list is actually bigger. More here and here.

2
touchmeicutyouOP•

I have the e6653 and im in nyc

1
sgteqSpectrum Gateway•

Yeah, NYC doesn't have PCS UMTS anymore. Only B2, B4, B12 LTE, AWS UMTS and thin 1900 MHz GSM. Your options:

2
touchmeicutyouOP•

thank you!

1
andynaijaMetroPCS Customer•

Just curious, is there AWS UMTS still around? Because I thought T-Mobile originally moved UMTS to PCS to make room for current AWS LTE that we have now.

1
sgteqSpectrum Gateway•

Yes, all cities in my original comments have AWS UMTS. They keep AWS UMTS instead of PCS if AWS-1 spectrum holdings are greater than 20 MHz (example: Atlanta, GA -- AWS UMTS, 20x20 B4 LTE, 20x20 B2 LTE and 5x5 B12 LTE) or if the maximum contiguous spectrum block is in PCS (example: Denver, CO -- 15x15 B2 LTE, 10x10 and 5x5 B4 LTE, 5x5 B12 LTE and AWS UMTS). Otherwise they keep PCS UMTS.

1