PDP settings for LTE only network

[Reinhard Speyerer]

On Wed, Jun 15, 2022 at 09:12:22PM +0200, Aleksander Morgado wrote:

> > > > Is there a similar command or NM setting to set the modem UE Usage Setting to data-centric mode?
> > > > Equivalent to: AT+QNVFW="/nv/item_files/modem/mmode/ue_usage_setting",01
> > > >
> > > > That command came from a Quectel document for AT&T 3G Sunset Guide.
> > > >
> > >
> > > mmcli has --3gpp-set-eps-ue-mode-operation=ps2 for that, but it will
> > > only work if the modem supports +CEMODE; not all modems I've found
> > > support it. And even so, I'm not sure if the CEMODE command would be
> > > fully equivalent to that change in the settings with QNVFW, maybe ask
> > > Quectel about that?
> >
> > Hi Aleksander,
> >
> > on all Qualcomm firmwares I have seen so far AT+CEMODE only supports
> > reading the setting but not changing it.
> 
> Could be the case; when I implemented it I was using an Intel-based
> TOBY-L4, which did support both reading and setting.
> 
> > The TS 27.007 command
> > corresponding to the above AT+QNVFW command seems to be AT+CEUS
> > which typically isn't implemented at all.
> >
> > However NASSetSystemSelectionPref TLV 0x21 which is already part
> > of the original Gobi API usually seems to work quite well.
> >
> 
> Oh, thanks for the hint!
> 
> So that would be
> qmi_message_nas_set_system_selection_preference_input_set_usage_preference()
> with QMI_NAS_USAGE_PREFERENCE_DATA_CENTRIC.
> 
> https://gitlab.freedesktop.org/mobile-broadband/libqmi/-/blob/main/data/qmi-service-nas.json#L1530
> 
> I think we could update ModemManager to support that.
> 
> Looks like AT+CEUS and the QMI variant are a subset of what AT+CEMODE
> allows, right? Or am I missing something?

Hi Aleksander,

you would have to combine TLV 0x21 with TLV 0x18 ("Service Domain Preference")
for switching between PS mode and CS/PS mode. However for QMI this TLV applies
to all RATs and therefore the result might differ from AT+CEMODE which
according to TS 27.007 only applies to EPS.

Regards,
Reinhard