A SIM fails to register to the RAN if MT cannot speak 2G=GERAN?

Dear polite fellow forum inhabitants,

excuse my noob question. I work as a support techie / FAE in a company selling various industrial PC’s, Ethernet and fieldbus communication gadgets. I have fond memories of dial-up modems and episodic experience with WWAN modems over the last two decades. So much for my background.

The problem at hand is: I have a tablet PC with an M.2 WWAN modem. The original was a Sierra EM7455, which I considered replacing with a Quectel EM05 - except that the EM7455 is deep inside. And, I have a SIM card, supplied by the customer, who’s running a fleet of vehicles with on-board computers containing WWAN modems - obviously, my customer is not willing to switch his GSM operator just to get that pesky tablet to work. The “culprit operator” here is O2 CZ. Czech Republic is an EU member country - the trio of operators here are the ex-incumbent O2 (no longer owned by O2 international), T-Mobile and Vodafone. We have various RAN’s in bands 1/3/7/8/20/28. Curiously to me, as I have started debugging this particular case yesterday, I’ve noticed that apparently, no 3G networks are in sight anymore (WCDMA, UTRAN, whatever). All the transponders I can see are either 2G=GERAN or 4G=LTE=E-UTRA (I don’t have a 5G=NR modem in my claws yet). So much for the environment.

Now for the problem description: with either of those two modems (Sierra/Quectel), the O2 SIM at hand fails to achieve network registration. The SIM is present, AT+CPIN? says READY, but AT+CREG says either “searching for network” or “registration denied”.

ati3
Manufacturer: Sierra Wireless, Incorporated
Model: EM7455
Revision: SWI9X30C_02.33.03.00 r8209 CARMD-EV-FRMWR2 2019/08/28 20:59:30
MEID: 35982032939552
IMEI: 359820329395527
IMEI SV: 20
FSN: LF140650430310
+GCAP: +CGSM

OK
at+cpin?
+CPIN: READY

OK
at+creg?
+CREG: 0,3

OK
AT+COPS?
+COPS: 0

OK
AT!GSTATUS?
!GSTATUS:
Current Time:  1173             Temperature: 31
Reset Counter: 1                Mode:        ONLINE
System mode:   LTE              PS state:    Not attached
LTE band:      B20              LTE bw:      10 MHz
LTE Rx chan:   6300             LTE Tx chan: 4294967295
LTE CA state:  NOT ASSIGNED
EMM state:     Deregistered     Attach Needed
RRC state:     RRC Idle
IMS reg state: No Srv

PCC RxM RSSI:  -69              RSRP (dBm):  -94
PCC RxD RSSI:  -72              RSRP (dBm):  -96
Tx Power:      --               TAC:         05E7 (1511)
RSRQ (dB):     -6.8             Cell ID:     06440700 (105121536)
SINR (dB):      7.8

OK
AT!PCINFO?
State: Online
LPM voters - Temp:0, Volt:0, User:0, W_DISABLE:0, IMSWITCH:0, BIOS:0, LWM2M:0, OMADM:0, FOTA:0
LPM persistence - None

OK



C:\Users\User>netsh mbn sh int

There is 1 interface on the system:

    Name               : Cellular
    Description        : Sierra Wireless EM7455 Qualcommr SnapdragonT X7 LTE-A
    GUID               : {2AC33EB3-3DBD-45F6-A12E-A172CB760499}
    Physical Address   : 80:99:97:5e:40:5a
    State              : Not connected
    Device type        : This is a remote device
    Cellular class     : GSM
    Device Id          : 359820329395527
    Manufacturer       : Sierra Wireless, Incorporated
    Model              : Sierra Wireless EM7455 Qualcomm
    Firmware Version   : SWI9X30C_02.33.03.00
    Provider Name      : O2-CZ
    Roaming            : Not roaming
    Signal             : 0%
    RSSI / RSCP        : 0 (-113 dBm)


C:\Users\User>netsh mbn sh read int=*

Ready information for interface Cellular:
-------------------------------------
    State            : Ready to power up and register
    Emergency mode   : Off
    Subscriber Id    : 230021200115552
    SIM ICC Id       : 8942020322801035550
    Number of telephone numbers  : 0


C:\Users\User>netsh mbn sh rad int=*

Radio state information for interface Cellular:
-------------------------------------
    Hardware radio state      : On
    Software radio state      : On


C:\Users\User>netsh mbn sh cap int=*

Device capability information for interface Cellular:
-------------------------------------------------------
    Device type                  : This is a remote device
    Cellular class               : GSM
    Voice class                  : No voice
    Sim class                    : SIM is removable
    Data class                   : UMTS, HSDPA, HSUPA, LTE
    GSM band class               : Unknown
    SMS capability               : PDU receive, PDU send
    Control capability           : Manual network selection is allowed
                                   USSD support available
    Device Id                    : 359820329395527
    Manufacturer                 : Sierra Wireless, Incorporated
    Model                        : Sierra Wireless EM7455 Qualcomm
    Firmware Information         : SWI9X30C_02.33.03.00
    Maximum activation contexts  : 8


C:\Users\User>netsh mbn sh vis int=*
Scanning for available networks. Device can take few minutes to complete this operation

Visible providers list for interface Cellular:
-----------------------------------------------
    Provider # 1
      Name           : O2 - CZ
      Id             : 23002
      state          : Home, Preferred, Visible, Registered
      data class     : UMTS, HSDPA, HSUPA, LTE
      cellular class : GSM
      rssi           : 99
      error rate     : 99

    Provider # 2
      Name           : T-Mobile CZ
      Id             : 23001
      state          : Forbidden, Visible
      data class     : UMTS, HSDPA, HSUPA, LTE
      cellular class : GSM
      rssi           : 99
      error rate     : 99

    Provider # 3
      Name           : Vodafone CZ
      Id             : 23003
      state          : Forbidden, Visible
      data class     : UMTS, HSDPA, HSUPA, LTE
      cellular class : GSM
      rssi           : 99
      error rate     : 99


# yet, the Windows MBN GUI systray applet reports "Cellular: no service".
# And:

at+creg?
+CREG: 0,2

OK

And, for comparison, here is a listing from the Quectel, providing a slightly different angle:

ati3
Quectel
EM05
Revision: EM05EFAR06A04M4G

OK
AT+CPIN?
+CPIN: READY

OK
at+creg?
+CREG: 0,2

OK
AT+QNWINFO
+QNWINFO: "FDD LTE","23002","LTE BAND 20",6300

OK
AT+QENG="servingcell"
+QENG: "servingcell","SEARCH"

OK
AT+QENG="neighbourcell"
+QENG: "neighbourcell intra","LTE",6300,235,-13,-83,-52,-20,41,255,20,8,62
+QENG: "neighbourcell intra","LTE",6300,432,-20,-92,-60,-20,31,255,20,8,62
+QENG: "neighbourcell inter","LTE",9260,335,-12,-80,-58,-20,39,0,20,255
+QENG: "neighbourcell inter","LTE",100,-,-,-,-,-,-,0,20,6

AT+QENG="servingcell"
+QENG: "servingcell","LIMSRV","LTE","FDD",230,02,64407B4,335,9260,28,3,3,5E7,-96,-10,-68,10,27

OK
AT+QENG="neighbourcell"
+QENG: "neighbourcell intra","LTE",6300,235,-16,-99,-65,-20,24,255,20,8,62
+QENG: "neighbourcell intra","LTE",6300,432,-15,-98,-72,-20,26,255,20,8,62
+QENG: "neighbourcell inter","LTE",100,-,-,-,-,-,-,0,20,6
+QENG: "neighbourcell inter","LTE",1379,-,-,-,-,-,-,0,20,5

at+qcops=7,1
+QCOPS: "4G","","56047","LTE BAND 3",1379,5e7,3A,-84,-115,-10
+QCOPS: "4G","","56047","LTE BAND 20",6300,5e7,1B0,-68,-100,-15
+QCOPS: "4G","","56047","LTE BAND 28",9260,5e7,14F,-63,-96,-16
+QCOPS: "4G","","56031","LTE BAND 1",473,3866,FC,-75,-102,-8
+QCOPS: "4G","","56031","LTE BAND 3",1579,3866,B4,-75,-111,-15
+QCOPS: "4G","","56031","LTE BAND 20",6200,3866,AE,-71,-99,-11
+QCOPS: "4G","","56063","LTE BAND 1",300,8dcc,CC,-75,-109,-14
+QCOPS: "4G","","56063","LTE BAND 3",1849,8dcc,2C,-69,-107,-18
+QCOPS: "4G","","56063","LTE BAND 20",6400,8dcc,84,-70,-100,-13

If I try a T-Mobile SIM, I do get registered to an LTE RAN, I can launch a PDP context etc. (Windows just get a breath of LTE connectivity, the bar-graph is all green, operator name gets displayed in the “cellular systray applet” and an IP address gets assigned etc.) Not with the O2 SIM.

The two modems that I’ve mentioned so far, have at least one aspect in common: they lack support for 2G GERAN. They support 3G and 4G only. Does that ring a bell maybe? Could it be that the O2 network requires a registration to a 2G transponder first, and only then allows the MT to switch to 4G ? Is this a feature of the network, or is this somehow encoded in the SIM and a local decision of the MT (modem) based on SIM contents?

I’ve also tried with two other modems:

  1. an old Sierra MC8092 is 2G/3G. Registers happily to 2G GERAN and runs that way. Does not report any 3G carriers in sight.
at+csq
+csq: 31,99

OK
AT+CPIN?
+CPIN: READY

OK
AT+CREG?
+CREG: 0,1

OK
AT+COPS?
+COPS: 0,0,"O2-CZ",0

OK
AT!GSTATUS?
!GSTATUS:
Current Time:  173              Temperature: 21
Bootup Time:   0                Mode:        ONLINE
System mode:   GSM              PS state:    Attached
GSM band:      GSM900
GSM channel:   122
GMM (PS) state:REGISTERED       NORMAL SERVICE
MM (CS) state: IDLE             NORMAL SERVICE
Serving Cell:  519 (GSM 1800   )
RX level (dBm):-47.8750         LAC:         05E7 (1511)
GPRS State:    GPRS STANDBY     Cell ID:     00009C9D (40093)
  1. the low-cost EC200T from Quectel. Capable of 2G/3G/4G, just lacking a WWAN driver in Windows. But the USB Serial interfaces do work, the modem reports 2G and 4G towers in sight and I can see that it quickly locks onto a 4G cell… well at least it says “CREG: 0,1” - in Windows I have no further clues.
ati
Quectel
EC200T
Revision: EC200TEUHAR05A01M16

OK
at+cpin?
+CPIN: READY

OK
at+creg?
+CREG: 0,1

OK
at+cgreg?
+CGREG: 0,1

OK
at+QCFG="band"
+QCFG: "band",0x93,0x1a0080800c5

OK
at+qnwinfo
+QNWINFO: "FDD LTE","23002","LTE BAND 3",1379

OK
at+qcfg="nwscanseq"
+QCFG: "nwscanseq",0

OK
AT+QENTAT+QENG="neighbourcell"
+CME ERROR: 50
AT+QENG="neighbourcell"
+QENG: "neighbourcell inter","LTE",44192,65535,-140,-20,-,-,0,2,2,7
+QENG: "neighbourcell inter","LTE",44892,65535,-140,-20,-,-,0,2,2,7
+QENG: "neighbourcell inter","LTE",45490,65535,-140,-20,-,-,0,2,2,7
+QENG: "neighbourcell inter","LTE",100,65535,-140,-20,-,-,0,4,20,6
+QENG: "neighbourcell inter","LTE",2850,65535,-140,-20,-,-,0,4,20,6
+QENG: "neighbourcell inter","LTE",1404,65535,-140,-20,-,-,0,4,20,5
+QENG: "neighbourcell inter","LTE",6300,65535,-140,-20,-,-,0,4,20,4
+QENG: "neighbourcell inter","LTE",9260,65535,-140,-20,-,-,0,4,20,4
+QENG: "neighbourcell inter","LTE",100,7,-121,-14,-,-,2,4,20,6
+QENG: "neighbourcell inter","LTE",6300,235,-92,-15,-,-,27,4,20,4
+QENG: "neighbourcell inter","LTE",9260,335,-81,-14,-,-,38,4,20,4
+QENG: "neighbourcell","GSM",68,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",519,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",122,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",115,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",111,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",101,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",93,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",89,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",87,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",86,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",83,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",75,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",69,0,0,0,0,0,255,0,0
+QENG: "neighbourcell","GSM",111,1,20,4,255,0,14,-63,687
+QENG: "neighbourcell","GSM",69,1,20,4,255,0,11,-72,531
+QENG: "neighbourcell","GSM",519,1,20,4,255,0,14,-74,507

OK
AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","LTE","FDD",230,02,644075A,58,1379,3,5,5,5E7,-93,-12,-78,11,30

What an amazing sensitivity, BTW. The longest list of towers that I’ve seen so far, here in my lab.

I’m still waiting for an EC25-E to arrive in a day or two (2G/3G/4G), which should allow me to probe the bands and carriers and practical Windows behavior a little further.

Ho hum.
As for the EM7455 - is there some way for me to debug the mystery further?
Increase verbosity, add some progress messages related to network registration (CREG), make the modem comment on SIM contents? I’ve also noticed the AT+CRSM command - would this possibly be any use to identify any “service configuration features” relevant to the observed misbehavior?

Actually the very first thing I tried was an upgrade to firmware 02.38.00.00_00_GENERIC_002.082_000 which did not solve the problem. So I retreated back to 02.33.03.00_00_GENERIC_002.072_001 which we consider previously tested and proven…

Any ideas are welcome.

Did you set correctly for APN in at+cgdcont?

Is your sim working fine for lte network?

Thanks for chiming in :slight_smile: You’re as swift as usual.

IMO, CGDCONT (definition of PDP context templates) is irrelevant if you don’t get past a basic CREG. BTW, yes I have tried filling in a CGDCONT entry, and no that didn’t help.
On a modem that can speak EDGE (the Sierra MC8092), Windows offered the connection profile (in the tray app) and were able to connect (on demand) even without CGDCONT being filled in - with that same SIM card.

If the SIM is working for the LTE network, that’s a question I have yet to answer. I’d have to rob some colleague of his telephone to test this, or, I’m actually waiting for a delivery of an EC25E by Quectel which is proven to work in 2G/3G/4G, and I’ll see how the SIM works in that. Just for comparison - mechanically that Quectel model is not fit for the application (a different form factor, and a Sierra EM7455 gets delivered as part of the package by the PC vendor). I could also try preventing the EC25E from using some bands or RAT’s - speculatively, by means of configuration, to see if that makes a difference. I’ll be back with a report how the EC25E fared in my torture chamber.

I remember for some network, if module cannot register LTE network if wrong APN is used, as but as you say, you have entered correct APN, then this part might not be relevant.

BTW, EM7455 does not support 2G network…
For registration status in LTE network, we should not use +CREG as it is for CS network, AT!GSTATUS should be used.

@jyijyi thanks again for sharing your wisdom.
I don’t have that EC25E in my hands yet, but I’ve tried taking a scan with a T-mobile SIM for comparison, still with the EM7455, and with the EM05. Neither of them speaks 2G. I’d hazard to say that AT+CREG reports as usual even in 4G. Also note that AT+CGDCONT is not filled in (I do know what APN name I should use for each operator) and the modems register to T-Mobile LTE just fine, even though there doesn’t appear to be any 3G tower in sight…

Sierra EM7455 on T-Mobile:

ati3
Manufacturer: Sierra Wireless, Incorporated
Model: EM7455
Revision: SWI9X30C_02.33.03.00 r8209 CARMD-EV-FRMWR2 2019/08/28 20:59:30
MEID: 35982032939552
IMEI: 359820329395527
IMEI SV: 20
FSN: LF140650430310
+GCAP: +CGSM


OK
at+cpin?
+CPIN: READY

OK
at+creg?
+CREG: 0,1

OK
AT+COPS?
+COPS: 0,0,"T-Mobile CZ",7

OK

AT!GSTATUS?
!GSTATUS:
Current Time:  99               Temperature: 25
Reset Counter: 1                Mode:        ONLINE
System mode:   LTE              PS state:    Attached
LTE band:      B3               LTE bw:      20 MHz
LTE Rx chan:   1579             LTE Tx chan: 19579
LTE CA state:  INACTIVE                 LTE Scell band:B20
LTE Scell bw:10 MHz             LTE Scell chan:6200
EMM state:     Registered       Normal Service
RRC state:     RRC Connected
IMS reg state: No Srv

PCC RxM RSSI:  -77              RSRP (dBm):  -113
PCC RxD RSSI:  -62              RSRP (dBm):  -99
SCC RxM RSSI:  -77              RSRP (dBm):  -99
SCC RxD RSSI:  -77              RSRP (dBm):  -96
Tx Power:      --               TAC:         3866 (14438)
RSRQ (dB):     -12.4            Cell ID:     06440715 (105121557)
SINR (dB):     17.0


OK
AT+CGDCONT?
+CGDCONT: 1,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0

OK
AT+CSQ
+CSQ: 22,99

OK

Quectel EM05 on T-Mobile:

ati3
Quectel
EM05
Revision: EM05EFAR06A04M4G

OK
at+cpin?
+CPIN: READY

OK
at+creg?
+CREG: 0,1

OK
at+cops?
+COPS: 0,0,"T-Mobile CZ T-Mobile CZ",7

OK
AT+QNWINFO
+QNWINFO: "FDD LTE","23001","LTE BAND 3",1579

OK
AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","LTE","FDD",230,01,6440715,180,1579,3,5,5,3866,-111,-10,-81,9,12

OK
AT+QENG="neighbourcell"
+QENG: "neighbourcell intra","LTE",473,252,-7,-88,-61,-20,35,7,6,4,42
+QENG: "neighbourcell inter","LTE",1579,180,-11,-90,-59,-20,0,0,8,6
+QENG: "neighbourcell inter","LTE",6200,-,-,-,-,-,-,0,8,5

OK
AT+QCOPS=7,1
+QCOPS: "4G","","56031","LTE BAND 1",473,3866,FC,-57,-89,-13
+QCOPS: "4G","","56031","LTE BAND 3",1579,3866,B4,-62,-90,-8
+QCOPS: "4G","","56031","LTE BAND 20",6200,3866,AE,-57,-84,-10
+QCOPS: "4G","","56063","LTE BAND 1",300,8dcc,84,-60,-91,-10
+QCOPS: "4G","","56063","LTE BAND 3",1849,8dcc,2C,-59,-97,-18
+QCOPS: "4G","","56063","LTE BAND 20",6400,8dcc,84,-62,-89,-10
+QCOPS: "4G","","56047","LTE BAND 3",1379,5e7,3A,-59,-96,-16
+QCOPS: "4G","","56047","LTE BAND 20",6300,5e7,EB,-55,-82,-9
+QCOPS: "4G","","56047","LTE BAND 28",9260,5e7,14F,-49,-77,-11

then it seems your O2 SIM has problem to register LTE network

Yes, I’m inclined to believe that this is something about the SIM card or the behavior of this particular operator’s network.

I’ve got the EC25E in my hands (2G/3G/4G) and with the culprit SIM by O2, I see the following behavior:
On start-up, the modem registers to the GSM network (GERAN).
I do get a +CREG: 0,1 and in Windows, the O2 CZ connection profile gets offered.
Only after I tell Windows to “connect”, the modem shifts to the LTE RAN. AT+CREG still says “registered”, and the “servingcell” attribute indicates LTE technology.
If I then tell Windows to “disconnect” from the profile, the modem remains registered to the LTE RAN.

at
OK
at+cpin?
+CPIN: READY

OK
at+creg?
+CREG: 0,1

OK
at+cops?
+COPS: 0

OK
AT+QENG="servingcell"
+QENG: "servingcell","SEARCH"

OK
AT+QENG="neighbourcell"
OK
AT+QENG="servingcell"
+QENG: "servingcell","SEARCH"

OK
AT+QENG="neighbourcell"
OK
AT+QCOPS=7,1

+QCOPS: "2G","O2 - CZ","23002","GSM 1800",519,5E7,9C9D,14,-63,43,1
+QCOPS: "2G","O2 - CZ","23002","GSM 900",69,5E7,9C9E,11,-63,43,1
+QCOPS: "2G","T-Mobile CZ","23001","GSM 900",26,3866,4EF7,37,-72,0,1
+QCOPS: "2G","T-Mobile CZ","23001","GSM 900",54,3866,5072,10,-72,0,1
+QCOPS: "2G","Vodafone CZ","23003","GSM 900",1006,8DCC,5E94,58,-59,0,1
+QCOPS: "4G","","56047","LTE BAND 3",1379,5e7,3A,-64,-93,-8
+QCOPS: "4G","","56047","LTE BAND 20",6300,5e7,EB,-53,-83,-12
+QCOPS: "4G","","56031","LTE BAND 20",6200,3866,AE,-54,-85,-13
+QCOPS: "4G","","56063","LTE BAND 3",1849,8dcc,2C,-60,-99,-18
+QCOPS: "4G","","56063","LTE BAND 20",6400,8dcc,84,-61,-90,-11

OK
AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","GSM",230,02,5E7,9C9D,14,519,0,-61,255,255,0,45,45,1,-,-,-,-,-,-,-,-,-,"-"

OK
AT+QENG="neighbourcell"
OK

### Here, I have told Windows to "connect" to the O2 CZ wireless connection profile

AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","LTE","FDD",230,02,6440700,235,6300,20,3,3,5E7,-83,-13,-52,1,40

OK
AT+QENG="neighbourcell"
+QENG: "neighbourcell intra","LTE",6300,235,-14,-83,-51,-20,40,4,20,8,62
+QENG: "neighbourcell inter","LTE",100,7,-8,-116,-98,-20,7,0,20,6
+QENG: "neighbourcell inter","LTE",1379,0,0,0,0,-20,0,0,20,5
+QENG: "neighbourcell","GSM",68,1,20,4,255,0,0,-1531,9
+QENG: "neighbourcell","GSM",519,1,20,4,255,0,14,-1069,35
+QENG: "neighbourcell","GSM",122,1,20,4,255,0,0,-1560,7
+QENG: "neighbourcell","GSM",115,1,20,4,255,0,0,-1388,14
+QENG: "neighbourcell","GSM",111,1,20,4,255,0,0,-1302,24
+QENG: "neighbourcell","GSM",101,1,20,4,255,0,0,-1674,-1
+QENG: "neighbourcell","GSM",93,1,20,4,255,0,0,-1391,18
+QENG: "neighbourcell","GSM",89,1,20,4,255,0,0,-1589,4

OK
at+CSQ
+CSQ: 29,99

OK
AT+COPS
OK
AT+COPS?
+COPS: 0,0,"O2 - CZ O2-CZ",7

OK

### Here, I have told Windows to "disconnect" the wireless connection profile

A/
+COPS: 0,0,"O2 - CZ O2-CZ",7

OK
AT+QENG="servingcell"
+QENG: "servingcell","NOCONN","LTE","FDD",230,02,644075A,58,1379,3,5,5,5E7,-93,-14,-57,9,31

OK

I was wondering, if perhaps the first successful logon has changed something. But, not the case. After I move the SIM back to a modem that’s not capable of 2G, just 3G+4G (and 3G is absent in the Ether), I’m left with +CREG: 0,2 and the modem never registers to the network.

What if you limit the EC25E to lte only?

@jyijyi good point, thank you.

I did proceed in that direction, eventually - but, inbetween, I’d noticed that my LTE session was not very stable. The EC25E kept losing the carrier and kept reconnecting or even searching for network. So I took a closer look and I’ve noticed that without manual intervention, the modem gets instructed by the network to attach to some “urban high band”, with free data capacity but poor signal coverage. I went “oh crap, not this topic again, has it all been about this old game of hide and seek?” I myself have covered this years ago, at that time mostly on the 3G RAT. Perhaps I’ve been on the wrong track all the time, over the past few days?

It took me a few moments to limit the selection of bands = allow only band 20 @ 800 MHz, which has the strongest signal by far. That’s using the AT+QCFG=“band” command. After that, my LTE service became reliable again. That was with 2G still enabled.

Next, I went on to disable 2G, and to leave only 4G=LTE enabled. Done that using the AT+QCFG=“nwscanmode” command. I entered the command, and restarted the EC25E for a good measure. After the reset, I verified that my settings stuck, yes they did, and indeed, the familiar misbehavior was back = no service, no WWAN connection profile advertised by the Windows systray applet. Identical behavior to the EM7455 / EM05.

So: my hypothesis still holds water. The one that with O2, 2G is needed to get the modem registred to the network. Modems without 2G capability cannot register to 4G.