[Replicant] Question regarding a freedom respecting modem

Denis 'GNUtoo' Carikli GNUtoo at cyberdimension.org
Thu Apr 8 17:19:41 UTC 2021

On Sat, 3 Apr 2021 17:20:49 +0000 (UTC)
m d <mdreplicantmd at yahoo.com> wrote:

> Hi,
> Had a lightbulb moment earlier today on this matter. Is it possible
> that there isn't a freedom respecting modem available so far because
> this might enable users to change their IMEI? Best
Having a freedom respecting modem would be very complicated because
even when it runs fully free software, the network still know where
each individual users are. That's part of the protocol.

Regardless, there are modems that can be operated with fully free
software, see the OsomcomBB project for more details[1].

Note that there is some big limitations in the way it's implemented: the
modems (or feature phones) only run the lower layers of the GSM
protocol, and they require a GNU/Linux computer to run the upper
layers. So you need an additional computer (or SOC) that is always on.

On an Openmoko that limits the battery life a lot and with feature
phones that's very inconvenient as you need a laptop connected to the

It is also possible to run osmocomBB with FPGAs but I don't know if it
works fine with only free software.

Additionally there are also devices that have modems that only run
nonfree software where people can change their IMEI. GerdaOS is a
distribution that enables to do that for instance. We'd also like to
enable it on phones supported by Replicant to be able to reconstruct
the modem data partition but we're not there yet.

The issue with free software on modems is the same than with many other
hardware related projects: we lack documentation and people to work on
that. Things that make the modems power efficient (like the DSPs) are
usually well guarded.

In addition, regulations don't make that easy for hardware
manufacturers to get involved as device manufacturers need to ship
devices with certified modems and the firmware is part of the
certification[2], and each new modified firmware would need to be
re-certified to be shipped. So I fear that the cost of certification
and re-certification is probably high here.


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