VoLTE support progress

I have just got around to testing VoLTE on my Librem 5, so here are some more data points:

I used the AT commands indicated in the ‘VoLTE support’ bug report.

VoLTE worked perfectly with no further configuration on the Three network in the UK and also on the iD Mobile network (which is an MVNO using the Three network). This worked both for outgoing calls and incoming calls.

The only minor problem is that I don’t know how I would undo the modem configuration change if it had caused problems. I thought I could just make a note of the previous configuration value returned by querying the modem and then set it to that value again later. But actually, when enabling VoLTE, the new value was simply appended, leaving the original value in place in what became a list of two values. It’s not obvious how to remove it. Fortunately I don’t seem to need to change it back, but if I did need to I think I’d have to contact support.


Always a good thing to know if you are a tinkerer … :wink:

Maybe it’s not a permanent change i.e. just toggle the modem kill switch? Can you test that?


No, it is persistent and non-volatile. In fact, one of the steps for setting the new configuration, listed in the bug report, was to turn it off and on again! I’ve already power cycled the thing several times since.


updated that ticket: https://source.puri.sm/Librem5/OS-issues/-/issues/162#note_158176


Tried the instructions in the ticket. Works for the first call, but not after. All further calls require a reboot of the phone otherwise it just gets stuck at “Calling” but never rings.

Provider: T-Mobile (via Tracfone) (US)

Interestingly I put the IMEI number into the t-mobile site to check for compatibility, and it said my device was compatible. Which suggests to me that T-Mobile doesn’t block this.
Due to a reboot fixing it, it seems like some form of software, driver or firmware bug. I’ve applied for an account on the gitlab instance to report the bug. I’m happy to act as a guinea pig to try things out.

edit: switching the modem of and on again doesn’t fix it either.


This sounds like a problem I was having with T-Mobile’s weak 3G signal where I lived, combined with my Android’s lack of VoLTE capability. Calls appeared to be trying to connect (and dropping from 4G LTE to 3G), but then sometimes not ringing or connecting at all. I had to switch to an AT&T MVNO.

How’s the 3G in your area:

Zoom way down to street level.

I don’t have 3G at my house just 4G and 2G. However, I thought VOLTE is only 4G?
I only have this issue when VOLTE is enabled(currently running with it disabled unless there’s something to test).

The map shows nothing for my house, just some line of 4G down a road about 3 miles from my house

edit: only have this issue when VOLTE is enabled, not 4G

VoLTE is only 4G LTE (voice over 4G LTE).

Your phone must be dropping to 2G during calls, then. If you didn’t have the issue before, maybe T-Mobile has been adjusting some of their towers in your area lately. What does your status bar indicate for network speed when you’re making a call?

I’ve also noticed that sometimes I have to go into the L5’s settings and reselect/reset my saved network provider. Do you see “Tracfone” (or similar) on the main page of Mobile settings, or is it blank? If it’s blank, tap it and reset the provider.

P.S. I lost sight of the fact that you were testing VoLTE according to that ticket. Apologies. But my last comment about the network settings might still apply.

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I’m more confused now. It seems to work ok now all except one phone number(happened to be one of the ones I was testing). Which I can call on my landline fine, but not on my cell phone… It just sits there in “calling…” and eventually stops trying without any sound.

(VOLTE is on now)

Another oddity is I no longer hear ringing when I call someone from the L5. (Their phone rings, but I hear nothing until they pick up).
Though I am driving my wife nuts by continuously calling the landline to test :D.


Had to turn VOLTE off as I can’t seem to connect to certain numbers with it on. Not sure why. It just says calling for a bit then goes back to the calls address book.

Anyone having good luck with VoLTE with any carrier in the US?

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VoLTE support is still a work in progress, in our trials we had some cases of VoLTE working in the US. But we do not recommend users to try on their own, because since it is still a work in progress it can leave the modem in an unknown state.

Our devs have extra modems to cover such cases, not all end users have an extra modem at hand in case.

P.S; of course our recommendation is not a prohibition, one of the points of having a Librem 5 is user freedom.

But really beware of that. The current Work In Progress state VoLTE may trigger various consequences, including: a provider toggling a flag in its database that any further connection attempts to this particular device should be done via VoLTE - which is something we cannot control. Therefore it should be done ONLY by users who are ready to get their SIM and/or modem replaced.


To make it clearer: you can effectively brick your modem, because it’s not guaranteed that anyone will have any idea about how to bring it back to normal. So once you try VoLTE before it’s officially supported, you’re on your own. Take that into account.


Good to know, I won’t mess with that anymore then I guess.

Out of curiosity, is it the firmware or drivers for the modem that are at issue for getting volte working?

It’s firmware.

Damn, well then we’re waiting on modem manufacturer then… There isn’t by chance a ticket we can track/view on this?

Further to my previous post, and as a cautionary message to others, I have now found that VoLTE does not always work on iD Mobile. (I no longer have a Three SIM to test.)

It seems as though it might depend which cell tower I am connected to. At my home address, it works fine and is more reliable than 3G due to the poor 3G signal in my home. But, out and about, it seems to be slightly hit or miss whether the call will actually connect. Usually it does, but sometimes it does not.

Having today experienced issues making a call while out and about, I found it took a couple of attempts to make a test call go through after I returned home. I have also experienced the behaviour that others have reported, where there is silence and no ringing tone until the call is answered.

I might possibly be getting some missed incoming calls as well, although that’s hard to pin down, because I would have to be paying attention to witness whether the phone rang or not.

So, yes, I think the warnings above, from @joao.azevedo and @dcz are worth heeding. We who prematurely try VoLTE do not know what forces we are playing with.

I look forward to reliable VoLTE in the future. :slight_smile:


So I got an SMS yesterday from my carrier (an MVNO on top of AT&T network) saying that I would need to get a new phone in the future because VoLTE was not supported on my phone. It didn’t give a deadline, maybe it is the 2/2022 AT&T date I think I saw announced somewhere? Anyway, I am wondering if we can ever expect VoLTE to work reliably on the Librem 5, assuming even the carriers will allow us to use VoLTE on their networks?

As an alternative, what about mobile VOIP and a data-only SIM card? There are some mobile VOIP providers that supposedly support SMS/MMS. Some of these so-called cloud VOIP providers like phone.com and Zadarma look like an option to use with a SIP client like twinkle that someone mentioned on a VOIP thread. Using mobile VOIP may not be as convenient as just popping in a SIM card from your favorite carrier, but may have some advantages with desktop access to things as well. Of course Google Voice is an option (I have had that for a long time), but I am looking for a solution that is less likely to use information about everyone I call, know, etc.

If we can’t get VoLTE working reliably, without an alternative like mobile VOIP then after a while this won’t be usable as a phone. I know that some people say the Librem 5 is more like a Linux computer that is also a phone, but without a solution to calling and texting, it seems like it will end up being more like a Linux PDA.

I am not trying to dump on all the effort going into getting VoLTE working, I am more wondering about the mobile VOIP alternative.


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That might be an option, if you can find a carrier that will let you use a data-only SIM in the L5. The question is: To mobile carriers, does the L5 present as a telephone, an automobile modem, or a computing device?