Chosing the right modem PLS8 vs BM818

UMTS on B3 is highly uncommon, and therefore rarely supported.

Also, 3G support shouldn’t be of any concern anyway, because there are not that many 3G networks left, more will be phased out when the Librem hits the market, and in 3 years at the latest, almost none will exist.

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Just for clarification: We are talking about the firmware of the modem, right? Isn’t it still a blob. Just one that is not loaded and executed on the main CPU but on the chip of the modem? If this is right I would not say that there are nor blobs included in the Librem 5. As the modem is separated from the main CPU etc. of the Librem 5 it may be safe anyway or at least safer compared to the conventional highly integrated architecture of common smartphones.

I don’t wan’t to spread any FUD. I would like to get a better understanding. So please explain.

In short: there’s zero proprietary code executed or even seen (copied) by the main CPU.

I think the definition of blob is a binary (e.g. a file) that is loaded into a device at runtime and executed there. Thus, I call it runtime-firmware (in contrast to fw that resides on the device)

And yes, both radios contain (resident) firmware, but have no access to the system. Remote code execution seems almost impossible. In any case that would be a bug in the (free) kernel driver - in contrast to all other modems that could read and write freely to RAM, without any way to prevent it.


Even resident firmware is of some concern. Whether the device has firmware loaded or firmware permanently resident, if that firmware is closed source then it is unable to be audited and hence it may be trusted but it is not verified. So the device itself retains a level of untrustworthiness. That’s just where the world is at right now - and it applies to every computer, not just the Librem 5.

As others have commented, being unable to update the firmware is a two-edged sword.

and that is good but it is as good as it gets right now.

For radios it may not matter so much because a) you are going to broadcast the traffic for anyone to receive, and - for the modem - b) it is going to be received by an untrusted party (the telco / the government). Ideally therefore you are running end-to-end encryption for the traffic over those radios.


ideally we would trust encryption to remain unencrypted by a third party only if the firmware residing on the lowest level was not compromised.

ah there was the “possibility” of brute-force-cracking a 2048 bit encryption but nowadays you really don’t use that unless you’re after the BIG fish. then there is quantum canon-blowing-encryption but that’s a mistery to me.

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Running end-to-end encryption means that you don’t have to trust the card that is implementing the transmission and/or the encryption.

However since the mobile phone network doesn’t have end-to-end encryption, the firmware on the mobile card is a consideration, just not one that will be solved in a hurry.

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the question is WHO is going to solve it because at the present moment the-spoon-is-in-the-corner. sure Purisms road-map looks good at first glance, for most people maybe even acceptable but experts know better right ?

Besides talking about bands and carrier compatibility, do we know anything about reception sensitivity and power usage of the modems?
In the light of this reddit post, this seems an issue that was not discussed here yet and I wonder if there is information available.

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Its also very hard to find information on such a comparison. In general I think both cards are based on Qualcomm chips (see here). On the FCC website you can find out which chip the Broadmobi card uses but unfortunately not for the Gemalto card. But even with knowing the exact modem IC its hard to find information since Qualcomm is not really open with that.

The Gemalto card offers LTE cat 3. The Broadmobi offers Cat4 (a later revision). Hence I would assume the modem IC Broadmobi uses is a slightly newer modem and maybe has a better reception (due to more development time on the later IC version). But thats a big assumption…

Maybe you find some additional information on the FCC website. At least the uplink (from the phone to the base station) part can be compared using the output power listed on the FCC site of boths cards PLS8-US BM818. I did not see any information on the sensitivity for the downlink.


Just to confirm…
I am seeing the following options:

Option 1 is Gemalto’s PLS8. Two variants are considered, PLS8-E and PLS8-US.
Option 2 is BroadMobi BM818. Also two variants are considered, BM818-E1 and BM818-A1.

Does this mean people will have the option to choose from 4 variants; PLS8-E, PLS8-US, BM818-E1 and BM818-A1? What are the finalized options, if this is not correct?

That’s the impression I’m getting.

Based on my understanding, that is correct. Two choices per region, with two region choices.

Birch Shipping Email Received


Sorry for reviving yet another modem thread, but since I read about the voLTE issue, I am at a loss, and this thread seems to be the best for my needs.

I thought I knew what modem would be best for use in Europe: the Broadmobi 818, because it supports a lot more frequencies than the Gemalto.

Now it turns out the lack of voLTE support in the Broadmobi 818 makes it a far less attractive option, to say the least: it (soon) might not work, or not even be admitted on the networks of the main network providers.

Of course I’m hoping I am wrong, and panicking (slightly) for nothing. But I can’t figure it out on my own, nor is my mind put to rest by other peoples speculations. I don’t mind being laughed at because I ordered a ‘weird’ phone and prepared to wait this long for it. I would mind being laughed at when it turns out, I can’t use it to make phone calls.

So, I would really appreciate to hear from Purism on this.

In the light of the voLTE issue, what modem should we pick?!
Will Purism send us a replacement modem - free of charge - if the L5 is or gets banned?

And, no, AweSIM is not a viable alternative. Even if it was available in Europe, I don’t want to swap my limited, 15 euro data plan for a 99 dollar one.

(Maybe it is not too late to switch to this Broadmobi modem: )


It may be too long. It is longer than the BM818.

It may be too thick. It is thicker than the BM818.

Maybe it fits. Maybe it doesn’t.

Indeed. All you are getting is speculation.

This itself may be speculation.

The suggestion to use the other broadmobi was sort of a joke.
The broadmobi not having voLTE is no speculation - read the specs…

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Based on the comments by @dos, I’m guessing that Purism is waiting on BroadMobi to add VoLTE support, which he indicates is a matter to configuration and international testing. If that is the case, then a firmware update can fix it, but of course only BroadMobi can provide that.

I would wait until Purism is ready to ship Evergreen and see what Purism says before making any decisions.

Another issue is whether you have a cellular provider that has a whitelist of allowed phones on its network. You might want to check the policies of your provider. In the US, this is a big problem. It isn’t where I live in South America.


I’m currently planning on going with the Gemalto PLS8-US and Tracfone service unless the situation changes. I’ll watch what amosbatto and kieran report too in the meantime. You guys are the best and most affordable tech support! Thank you

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Sure, if Purism can wait it out, I will too. But this sort of strikes me as an unexpected turn of events at a very inopportune time. And I am slightly worried Purism did not see it coming.
So, I was just looking for some peace of mind, really.

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As @amosbatto says, there is much more to the story than that.

All cellular modems available in the entire world are blackboxes. As customers, we are dependent on the modem manufacturer to deliver VoLTE support. We are also dependent on the carrier to offer VoLTE support and to release the needed information to use it.

Best case: It really is “preliminary” in the BM818 (i.e. the code is present) and just a small matter of “configuration and testing”. (Yeah, I’ve heard that one before …)

So presumably some countries and carriers will be officially supported by Broadmobi for VoLTE. Some it might work but not be officially supported. Some it might never work.

I would guess that getting the US carriers supported would be a priority for Broadmobi. However I don’t think you have said what country and carrier you are interested in.

For some countries and carriers VoLTE support might be buggy, but be improved over time.

I understand that you want peace of mind but it is going to be messier than that.

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i’m going to play it safe and get BOTH or more modems if i can and test … besides m2 is easy enough to swap if you’re not constantly on the move …