Novatel 551L + qmi

[Gopakumar Choorakkot Edakkunni]

Hi Dan,

Thanks a lot for the response. So I guess my firmware is old, I will try
upgrading to see if it work with just QMI without needing any $NWQMICONNECT.

>> If eHRPD is not available on the network or is not enabled in the modem,
then you'll have to disconnect to move between 3G and 4G.

When you say "you'll have to disconnect", do you mean to say user
intervention is required - should the user click "reconnect" on the modem
manager etc.. ? Or will the modem firmware do that internally without any
user intervention required (yes, the user might see a connection getting
reset and re-established, but thats still better than user having to click
"reconnect")

Also when in 3G mode, eventually the packet encapsulation is ppp / slip I
guess - so does the firmware inside the modem initiate the ppp/slip when in
3G mode, because from linux side all we see is a wwan0 interface.

Rgds,
Gopa.


On Tue, Sep 16, 2014 at 11:47 AM, Dan Williams <dcbw at redhat.com> wrote:

> On Mon, 2014-09-15 at 19:29 -0700, Gopakumar Choorakkot Edakkunni wrote:
> > Hi,
> >
> > First of all I tried that modem on my Ubuntu 14.04 with the modemmanager
> > GUI, I ask the GUI to scan for networks and it fails all the time. But
> > thats ok - my real requirement was to get it running on my openwrt box.
> > Plugged it in, saw that the option1 driver takes control of ttyUSB[0-3]
> and
> > qmi_wwan creates a wwan0 interface. After that running a dhcp client over
> > wwan0 dint come back with any IP, so reading through the modemmanager
> code,
> > I found that we have to send an AT+$NWQMICONNECT over ttyUSB0. I did that
> > and presto!, wwan0 gets an IP (thanks modemmanager developers !).  A
> couple
> > of questions
>
> The device runs optimally with QMI, but does work with $NWQMICONNECT as
> a fallback.  However, QMI works much better after the firmware update to
> 1.41.
>
> $NWQMICONNECT likely just calls the QMI WDS data session functions
> anyway.  What you are probably missing is using qmicli or ModemManager
> to start the WDS data session with the QMI protocol, and *then* you can
> run DHCP on the network port.  You cannot just run DHCP without first
> starting the data session via QMI or $NWQMICONNECT.
>
> > 1. Does anyone know "internally" what is the modem doing on getting an
> > AT+$NWQMICONNECT ? Does it start a ppp session if the available band is
> > only 3G ? Once started in 3G and later a 4G-LTE connection is available,
> > will the modem internally drop the ppp session and switch the IP on
> 4G-LTE
> > (and vice versa) ?
>
> Handoff between 3G and 4G is kinda dicey with these first-gen
> Qualcomm-based Verizon devices (USB551L, Pantech UML290).  Part of the
> issue is eHRPD which is required for handoff between 3G and 4G.  If
> eHRPD is not available on the network or is not enabled in the modem,
> then you'll have to disconnect to move between 3G and 4G.
>
> > 2. Other than the AT+$NWQMICONNECT, do we need to send anything else to
> the
> > modem to make it work using all available bands based on availability
> (3G /
> > 4G) or do we have to specify anything to force the modem to work in
> "these
> > specific modes" ? I dint find anything like that in the modem manager
> code,
> > just thought of asking anyways.
>
> If you've left the technology preference, system selection preference,
> and band preferences alone, then the modem will automatically search for
> and connect to the best available technology (eg, LTE) and network.  But
> the device only supports one Verizon LTE band (eg, Band 13), so you're
> pretty limited on the LTE side.
>
> Dan
>
>
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