Differentiate between Cat-M and NB-IoT

[Aleksander Morgado]

Hey Fredrik

> I'm working with a modem that supports GSM, LTE Cat-M, and NB-IoT. Ideally, I
> could both query and, more importantly, set which of these access technologies
> are allowed in the modem through ModemManager's API.
>
> As far as I understand, ModemManager understands the concepts of (1) modes,
> (2) capabilities, and (3) access technologies. From looking at the defined enums,
> (3) is more granular than (2) which is more granular than (1), but all relate to
> "access technology" in some way. (3) is the only one that differentiates between
> Cat-M and NB-IoT, but the D-Bus API only exposes "set" methods for (1) and (2).
>
> The modem itself treats GSM, Cat-M, and NB-IoT at the same abstraction level:
> "Selecting Radio Access Technology" from the AT command manual, so there is a
> slight disconnect between MM and the modem itself wrt. access technology.
>
> I'm open to submitting a patch that adds the functionality I want, but I don't
> know where to start attacking this problem. Perhaps MMModemCapability should
> split the concept of LTE into Cat-M, Cat-1 and NB-IoT? To me, many of these
> terms are ambiguous, so please note that I'm coming from a position of relative
> ignorance.
>

Yes, all that is not very well managed right now in MM. We recently
added some enum updates in MMModemAccessTechnology
(https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/commit/664610819e45943d8619de8c090b5e58ff916c51)
but not much more.

Could you let us know which modem you're using and which commands (AT
commands I assume) can be used to query whether Cat-M, Cat-1 and/or
NB-IoT are supported, and how to change them?

-- 
Aleksander