How do I determine if my librem 5 is compatible with phone carrier

Here are the requirements from my phone carrier: “The Compatibility criteria for GSM LTE Sim card is that the device must be unlocked, It must have Band 4 (1700/2100 MHz) and Band 12 (700 MHz) along with HD Voice/VoLTE feature.”

How do I determine whether my Librem 5 meets that criteria?

Frequencies and available modems (the -A1 is for N. America, the -E1 is for Europe, and the -T1 is for Down Under+Asia):

VoLTE is still a work-in-progress.

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See VoLTE support progress for more information.

(@amarok has beaten me to posting everything I was just about to post, except for this part!)


Sorry 'bout that! :rofl:
I thought you had abandoned.

(P.S. I have no life.)

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I was slow. Don’t worry about it!

Hmmm… Please be patient with me.

I don’t know how to read that table you referred me to.

Here is what the carrier told me: “The Compatibility criteria for GSM LTE Sim card is that the device must be unlocked, It must have Band 4 (1700/2100 MHz) and Band 12 (700 MHz) along with HD Voice/VoLTE feature.”

But, when I look at that table you referred me to, under the GSM section - I assume that’s the section I should be looking at??? - those frequencies don’t even appear at all. So, I’m confused. Is the carrier (US Mobile) telling me that they require phones to operate on frequencies that literally do not even exist? That doesn’t make sense to me, so I’m obviously not correctly understanding what the carrier is telling me and/or how to read that table.

In this screen-grab from the table, you want to look at the LTE bands: “LTE-FDD” in the table. “B4” and “B12” represent “Band 4” and “Band 12” (with the associated frequencies), which you can see by the checkmark are both included in the N. America modem (1st column to the right of the listed bands). Of the two bands only B4 is included with the Asia/Aus/NZ modem (3rd column), and neither band is included in the Europe modem (2nd column). (Some LTE bands are not used in some parts of the world.)

The phone company rep used the phrase “GSM LTE,” but I imagine they meant:
1: The phone must be of the GSM (able to work on most of the world’s networks) type, not CDMA (which is on its way out and only used in a couple of countries, historically), and
2. The GSM phone must work on Band 4 and Band 12, and
3. Must be able to carry phone calls over 4G/LTE (“VoLTE”).

[EDIT: Apparently US Mobile offers service on Verizon (which they call “Super LTE” and on T-mobile, which they refer to as “GSM LTE” so disregard my 1st point above.]

Ok, I see, thanks.

Yes, I was looking under the GSM section, nothing would have told me to look in the FDD section. (Don’t know what that means anyway.)

But mainly I was thinking I had to match the frequency numerals exactly as written to me by the carrier, now I understand that is not the case.

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BTW, the reason the GSM (2G) section, and especially the HSPA+/WCDMA (3G) section of that table are less important now is because 3G is disappearing in some countries, and 2G also to a lesser extent.

Soon the U.S. carriers will no longer use 3G. AT&T has also already retired its 2G network.

Thanks again.

So… The carrier I was in touch with “requires” VOLTE ability, which my Librem 5 currently lacks. Two questions:

  1. Other than Purism’s own plan, are there carriers in the USA that work fine with the Librem 5? Asking just in case you know where I can find this, I understand if you don’t.

  2. If I am interested in a data only plan, then the fact that my Librem 5 doesn’t currently support volte should not be a problem with the carrier I was talking to - Is my logic valid?

  1. Purism’s AweSIM will no doubt be subject to the same VoLTE requirement, as their plan, like all MVNOs, works on the network of one or more of the major carriers. All U.S. networks, and all the MVNOs/resellers that use those carriers’ networks, are affected.

It might turn out that the L5 (its modem, actually, which is removable/replaceable) will fly under the radar with the carriers, as this modem is normally used in automotive applications. I believe a couple of people in the forum have mentioned activating with no carrier gripes. You can test by checking the modem’s IMEI (see the modem settings) on, say, T-mobile’s compatibility checker.

Note that just because you get a SIM approved doesn’t mean that your calls will work 100%. As 3G continues to be shut down in various locales, a phone (modem) that relies on 3G for calls will not be able to find 3G anymore. There may be some 2G left as a fallback, but maybe not ubiquitous.

  1. A data-only SIM may also get approved, again, for the reason I mentioned above: it probably looks like automotive usage, or maybe even a computing device (which it is!) to the carrier.

If the U.S. carrier won’t issue a data-only SIM (because they frown on using those in phones, due to the lost revenue and lack of 911 availability), then an international travel SIM would probably work, as long as it doesn’t require some Android/iOS app. The trick is finding one with reasonable data rates, but it’s possible.

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Short answer, as I see this (and as you already guess), would be: no. Long answer is here: “You can activate any un-activated starter pack to it, but once a SIM is activated to a phone, it’s not eligible for data plans.

Therefore, please stay within known usage patterns, as already advised here:

Info within my above post link provided while US Mobile −> T-Mobile and while further below, same chapter as linked, you’ll find (under Settings and info) following APN for LTE devices: And as “a starter kit costs $10” (for 30 days) perhaps it is worth of trying if such SIM card package might suit your needs, if/when about to use it on Librem 5.

Too bad the chart doesn’t have a print button. (Auto format print gets four pages worth, mostly blank lines.)

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For people’s tests with different cellular carriers, see the community wiki:


I copied the table into a spreadsheet. You should be able to do the same. (I had to realign a couple of items, so please check for accuracy.)



Mouse right click: Take Screenshot.

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That works for me on the images we posted here, using “Copy Image” from my right-click context menu, but it’s not available on Purism’s original modem chart. (FYI)
With Linux Mint and Pale Moon browser, anyway. May be different in other systems.

(Although I could have used the “Take Screenshot” application in Linux Mint, and selected the area to grab. It’s a large, awkward area, though.)

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The U.S. carrier successes from that chart may change as the 3G networks continue shutting down. At least for calls over 3G. Just something to be aware of.