LTE to 3G handoff in low service areas

[dejanh]

I have the A1901 model of the iPhone X which uses the Intel modem. This is my first Apple device that uses the Intel modem instead of the Qualcomm. This also happens to be the most problematic device when it comes to cell network connection that I have ever had from Apple, and in fact the most problematic that I have ever owned period. Before you go all "what's this guy talking about" hear me out and note that I am just trying to gather more information so that I can get Apple to assist in addressing the issue for me and anyone else that may be affected by this. I have now been working with Apple on this issue for about a week, quite intensively, and I am exhausting information that I can provide.

Both devices exhibit the same issue. They take an unusually long time to connect to LTE whenever they are in a less-than-perfect LTE coverage area, and when they are locked onto LTE and the signal quality degrades, they have difficulty down-switching to 3G in order to maintain a stable connection. In fact, more often that not, in a low LTE service area instead of going to 3G, the device will try to maintain LTE even if it does not work causing data to basically stop working. The only way to alleviate this issue is to manually turn off LTE and switch to 3G, then re-enable LTE once the signal recovers. As you can imagine, this is highly undesirable as it requires a tremendous amount of manual maintenance. This is even worse when VoLTE is used because with VoLTE the device would not even attempt to connect to 3G for outgoing calls, so even outgoing calling is blocked in this case.

This is not a carrier or SIM issue. It is an iPhone X issue, full stop. It does not occur with the iPhone 8 Plus, or an iPhone 6s Plus that I have. It also does not occur with the BlackBerry KeyOne Black Edition, the Samsung Galaxy S8+, or Essential PH-1. All of those devices were tested for the same type of issue and only the iPhone X exhibits this problem. I have also tried iOS 11.1.2, 11.2 beta 3, and 11.2 beta 4, all seemingly with the same problem.

Last but not least, under normal usage somebody would may not even really be aware that their device is having a problem. The reason why is because the device never actually drops the LTE signal to fall back to 3G, it just hangs on to it beyond - what seems to be - operational range. Using the service menu I have noted LTE still wanting to stay connected when the signal dips below operational values. Here is a chart that illustrates what is acceptable signal range very well...

https://forms.na1.netsuite.com/app/...icle=understanding-lte-signal-strength-values



On this device I am regularly seeing RSRQ < -20dB and SINR below 5dB.

I realize that this may have been a crazy read, and if you got to the end, congrats. Now, please see if you can take your A1901 (check by going to Settings > General > About and then tapping on the value next to Model heading) from a functional LTE service area to a bad LTE service area, like a basement, where there is enough signal to still get LTE but not enough to use it comfortably, and see if you can still use data, and see if the phone falls back to 3G successfully. Also, if you can take note of your RSRP at that time it would be great. You can see the RSRP by typing in *3001#12345#* into the dialier, calling it, and then navigating to Serving Cell Meas (measurements related to the tower you're currently connected to).

Thanks all and please post your findings below! I am going to try to do some measurements tomorrow in the area where I can reproduce the problem at will and see what is the device returning.

 

[dejanh]

Apple is now logging my device to feed information back to engineering. They appear to be taking the problem seriously and there is some preliminary thought that it really might be the Intel modem in combination with the modem firmware that is causing these issues.

 

[zenjen]

I’ve experienced dropped calls. Only had the phone a week and I recall at least four occasions recently. I work from home and spend a good deal of time on conference calls. Never had the issue before now. Today, I was on a call, all was well, then all of a sudden, I’m connected but I can’t hear anyone and no one can hear me. It will stay connected for a minute or so, then drop. Has happened that way each of the times I remember. Not sure how to troubleshoot this further.

 

[dejanh]

I’ve experienced dropped calls. Only had the phone a week and I recall at least four occasions recently. I work from home and spend a good deal of time on conference calls. Never had the issue before now. Today, I was on a call, all was well, then all of a sudden, I’m connected but I can’t hear anyone and no one can hear me. It will stay connected for a minute or so, then drop. Has happened that way each of the times I remember. Not sure how to troubleshoot this further.

What model is your device?

 

[zenjen]

A1901 TMO is my carrier

 

[dejanh]

A1901 TMO is my carrier

Thanks. I sent all of my logs to Apple engineering tonight. All 1.7GB of them. I mentioned your situation as well and they logged it as another example of connection problems on A1901 devices. Let's see how it develops from here. I probably won't get an update until Saturday (that's what Apple committed to).

 

[zenjen]

Where are the logs?

 

[dejanh]

Where are the logs?

You have to get in touch with Apple first for them to start a support case. Senior advisory group (senior support) can provide you with a profile that gets installed to your device that starts the logging. Once the logging is complete, the files get submitted to Apple engineering via a special portal, associated to your case. You cannot get these yourself and they would also be pretty meaningless. Since I am technically inclined I finished all of the core troubleshooting before I even got in touch with Apple so I moved through the process with them pretty quickly to get to engineering. If you are not of the same mindset it will take a bit of time and testing before they will deploy a profile and pull the logs for analysis.

 

[zenjen]

I was only a week with my X. I changed from the A1901 GSM version to the A1865 version yesterday. Will see how that goes.

 

[Keith Molloy]

This is a known issue with the Intel chip apparently..Not sure if its just happening to some phones however or all phones with the Intel chip. The A1901 is the only model available here so i would be fuming if it's having such issues given its enormous price tag here. A phone this expensive should not have the problems alot of people are reporting it to have.

 

[dejanh]

I was only a week with my X. I changed from the A1901 GSM version to the A1865 version yesterday. Will see how that goes.

Please let us know here whether you experienced any improvement.

This is a known issue with the Intel chip apparently..Not sure if its just happening to some phones however or all phones with the Intel chip. The A1901 is the only model available here so i would be fuming if it's having such issues given its enormous price tag here. A phone this expensive should not have the problems alot of people are reporting it to have.

Very true and also why this is so frustrating. I actually like a lot of things about my X, but the instability of the cellular data connection is a huge problem. They should not have cheaped out with the Intel modem but since they are engaged in a highschool feud with Qualcomm we get stuck with an inferior product. I received an update that the engineers are investigating the logs from my device. Meanwhile I switched to the 11.2 beta 4 as it offers at least marginal improvement over 11.1.2 when it comes to cellular stability, at least in my case.