<div dir="ltr"><div>Thanks Dan! I was wondering if there exists a modem manager version that works on openwrt/embedded systems ? I will start another thread on that to keep things seperate. </div>Rgds, Gopa. </div><div class="gmail_extra"> <div class="gmail_quote">On Wed, Sep 17, 2014 at 11:48 AM, Dan Williams <<a href="mailto:dcbw@redhat.com" target="_blank">dcbw@redhat.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On Wed, 2014-09-17 at 09:08 -0700, Gopakumar Choorakkot Edakkunni wrote: > Thanks again for the response Dan. > > >> If you are connected to LTE and run out of LTE coverage but EVDO is > available, the data connection will simply terminate, the modem will > eventually register on EVDO, and you will need to manually re-start the > data connection. > > From ModemManager code, I am assuming that reading the $NWQMISTATUS would > faithfully report such conditions ? Like if I keep polling for > $NWQMISTATUS, I would see status change from connected to not-connected > (whatever their equivalent values are) if this LTE-->EVDO change happens ? Right, the "novatel-lte" plugin in ModemManager polls $NWQMISTATUS every 5 seconds (because the modem doesn't report unsolicited $NWQMISTATUS I believe) and if it notices a disconnect it should indicate that to D-Bus clients by terminating the bearer. It's then up to the connection manager to apply some kind of policy and request a reconnection when the modem enters the REGISTERED state. But this plugin is only for the E362 PCI-E minicard device, not the 551L. ModemManager drives the 551L with QMI, and since QMI is more completely implemented than the $NWQMI AT commands, network disconnections are indicated immediately via QMI instead of 5 seconds (worst case) with $NWQMI. Dan <div class="HOEnZb"><div class="h5"> > Rgds, > Gopa. > > > On Wed, Sep 17, 2014 at 7:21 AM, Dan Williams <<a href="mailto:dcbw@redhat.com">dcbw@redhat.com</a>> wrote: > > > On Tue, 2014-09-16 at 12:39 -0700, Gopakumar Choorakkot Edakkunni wrote: > > > 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") > > > > Again, this is all if eHRPD is not available in the network, or somehow > > not enabled/supported in the modem. eHRPD is the protocol that allows > > roaming between 3GPP2 (CDMA/EVDO) and 3GPP (LTE) RANs. > > > > So, if eHRPD is not available/working: > > > > If you are connected to EVDO, and LTE becomes available, the modem will > > *not* hand the data connection from EVDO to LTE. You must terminate the > > data connection manually, wait for the modem to up-register to LTE, and > > then manually re-start the data connection. > > > > If you are connected to LTE and run out of LTE coverage but EVDO is > > available, the data connection will simply terminate, the modem will > > eventually register on EVDO, and you will need to manually re-start the > > data connection. > > > > Verizon had this hand-off issue for quite a while after deploying their > > LTE network in 2011, though they seem to have largely solved it by 2013. > > However, some of these initial launch devices (of which the USB551L is > > one) may not have firmware updates that fix all eHRPD issues, because > > they are long since out of production and unfortunately the > > manufacturers don't really care about old hardware. > > > > On the user side, a connection manager/modem manager would usually > > handle the reconnection without user interaction if that policy was > > desired. > > > > > 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. > > > > AFAIK yes, that's basically what happens in the firmware. It > > decapsulates the IP packets from the over-the-air protocol (PPP for > > CDMA/EVDO, SNDCP for GPRS, IP for LTE) and re-encapsulates them into > > ethernet packets for the wwan0 interface. > > > > Dan > > > > > Rgds, > > > Gopa. > > > > > > > > > On Tue, Sep 16, 2014 at 11:47 AM, Dan Williams <<a href="mailto:dcbw@redhat.com">dcbw@redhat.com</a>> 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 > > > > > > > > > > > _______________________________________________ > > > libqmi-devel mailing list > > > <a href="mailto:libqmi-devel@lists.freedesktop.org">libqmi-devel@lists.freedesktop.org</a> > > > <a href="http://lists.freedesktop.org/mailman/listinfo/libqmi-devel" target="_blank">http://lists.freedesktop.org/mailman/listinfo/libqmi-devel</a> > > > > > > > _______________________________________________ > libqmi-devel mailing list > <a href="mailto:libqmi-devel@lists.freedesktop.org">libqmi-devel@lists.freedesktop.org</a> > <a href="http://lists.freedesktop.org/mailman/listinfo/libqmi-devel" target="_blank">http://lists.freedesktop.org/mailman/listinfo/libqmi-devel</a> </div></div></blockquote></div> </div>