VoLTE support progress

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.


1 Like

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?

Some people reported that VoLTE works for them, so it’s definitely possible, depending on the carrier:

1 Like

Unfortunately it looks like AT&T has implemented a VoLTE whitelist where even if a phone supports VoLTE, it must be certified with AT&T in order to be provisioned for it.

You can find the whitelist here: https://www.att.com/idpassets/images/support/wireless/Service-Capabilities-Unlocked-Devices-ATT-Network.pdf What they call “HD Voice” is VoLTE

Verizon also has a VoLTE whitelist, but theirs isn’t public. Since the Purism team has indicated they’re not interested in certifying with any carriers due to privacy-related issues, it seems both of these networks will not be able to use VoLTE on the Librem 5, even when the devs implement it successfully.

So you can expect that when VoLTE is fully working on the Librem 5, The T-Mobile network will be your only option in the USA.


And I would imagine the T-Mobile network will do the same at some point.

Would the white list affect smaller carrier’s that piggyback off of the major carrier’s networks, such as Puretalk or AweSIM?

Yes, for sure.

Yes, it does apply. Non-whitelisted phones on MVNOs using AT&T’s network currently fallback to their 3G network for all calls. Come February 2022 the AT&T 3G network is decommissioned and all non-whitelisted phones will stop working altogether.

1 Like

I have tried the instructions listed here on TracFone (MVNO on top of AT&T). I get OK from the commands need to enable VOLTE. The “AT+BMRAT” command shows:


before a call, and shows:


during an outgoing call to a VOIP number. A call to my Librem5 from the VOIP number shows the same thing. Both showed 4G on the Librem 5 display. However, when I call from the Librem5 to an AT&T cell, the display changes immediately to 3G. So it seemed to switch to 3G when I called an AT&T number.

Anyway, I don’t know if the commands I was using worked correctly or not, but I was getting OK status back from the commands.

From what was discussed above, it seems like Purism would have to convince the carriers to whitelist the phone or we will be SOL.

It is not looking good. In lieu of this, the other possibilities I see are using either a data SIM and a VOIP number or some type of hotspot device (providing WiFi) and a VOIP number. Although more and more VOIP providers are providing SMS support (in addition to voice), some services which use SMS text for verficiation check to see if a given number is classed as mobile rather than landline (apparently VOIP are often classified as landline) and will not send the verification text to a VOIP (i.e. landline) number.
For example, as you can see here Azure doesn’t allow VOIP numbers for verification:

A Voice-over-IP (VoiP) phone number can’t be used for the phone verification process

The are other services (including some banks) that check the number and don’t allow verification with numbers not classified as mobile.

BTW, I mentioned a data-only SIM card before and someone suggested that it might not be allowed in the Librem5 by the carrier. I don’t expect most to care what it is used in, as it is typically for tablets etc. anyway. However, there are cars that have SIM card slots (for creating an internal WifI hotspot), so there must be carriers that allow you to by data-only SIMs for those. Since the Librem5 modem is essentially an automobile modem, I suspect that it would be possible to buy data-only SIMs for it.

So if we get to the point that we can’t make calls (and/or send/receive texts like other mobile phones), is the Librem5 still a mobile phone?

That’s disappointing. Out of curiosity, what is the privacy related issue to having a phone certified with a carrier? Does it call for a change in software/firmware that the grants the carrier access?

1 Like

Purism’s CTO Nicole Faerber posted this 2 years ago about carrier approvals being invasive.

Dunno if things have changed since then.


This is the sort of :poop: that makes me lose my noodle.
Not my area, but is there any possibility of being able spoof ATT/Verizon as to the identity of one’s L5, given that we can (hypothetically) do what we want on it? That is, what technology is used by the whitelist, and can it be corrupted?


Just one more or less minor addition to that - we (as in Purism) currently have no plans to get additional carrier approvals. Getting carrier approvals is a PITA and in most cases bound to very high restrictions on the device and a very expensive qualification process.

I don’t think this represents current policy at Purism. Since that time, Purism announced its AweSIM program, which makes Purism an MVNO of both the T-Mobile and AT&T networks. That means that Purism will have to eventually get the L5 on the whitelists for those two companies, so it will have to get the BM818’s VoLTE to be certified to work on their networks.


That’s encouraging info. Thx again Amos!

Would the modem then fallback to 2G/GSM?

1 Like

Yes, that is how it works. If 4G isn’t available, then it falls back to 3G, and if 3G isn’t available then it falls back to 2G. Most people are able to get 4G data, but because they don’t have VoLTE, they can only make phone calls with 3G or 2G.

I think the way the US carriers have implemented VoLTE with whitelists is ridiculous, and frankly the US government needs to step in and properly regulate the industry to stop carriers from excluding phone models that support VoLTE. The US mobile industry has all kinds of anti-consumer practices that a functioning government shouldn’t allow, but lobbying power and legalized bribery in the political system allow this to happen.


I have bad news. L5 doesn’t work like that.
Vodafone here decommissioned his 3G network, so only 4G and 2G are available. If I set the network mode to “2G 3G 4G (preferred)”, that’s the default setting, I cannot get incoming calls, sometimes it also fails to make calls. In order to be able to use the L5 like a phone I have to set the network mode to 2G only … and, of course, data connection becomes a pain in the neck.
I guess the phone is taking too long to switch from 4G to 2G when receiving a call so it goes to voicemail everytime. If it is set to 2G only it rings perfectly.
I’m in contact with Purism support in order to try and fix the issue, but it doesn’t look easy.