Mobile data connection troubleshooting

This is a quick guide to help in the debugging process of a router if encounters issues with mobile data connection.

Preparation

• First, to establish a data connection only through mobile module on RUT, you need connect to router via CLI/SSH (use SSH software such as Putty):

CLI/SSH username: root
CLI/SSH password: <your router’s password>

• Connect to mobile module of the router:

... 
root@Teltonika:~# ifdown ppp
root@Teltonika:~# /etc/init.d/gsmd stop
root@Teltonika:~# microcom /dev/modem_cmd
+QCSQ: "LTE",47,-75,166,-10
+QCSQ: "LTE",47,-75,161,-10
+CREG: 1,"008B","012CD17",7
...

• Most likely you will not see anything and that’s because screen echo might be disabled. ATE1 command will enable it so that you can see what you write. at+qcsq=0 and at+creg=0 command stops showing unnecessary output:

...
ATE1
OK
at+qcsq=0
OK
at+creg=0
OK
...

• Check communication (wait for the module to respond OK):

... 
AT
OK
...

Debugging process

• Query SIM card status:

• AT+CPIN? 5. If PIN is required, initialize modem with your PIN code: • AT+CPIN="xxxx" 6. Check SIM card status again (Reboot the module if it fails to identify SIM): • AT+CPIN? 7. Check GSM connection (OK means that the module has registered on CS domain service): • AT+CREG 8. Check PS Service (OK means that the module has registered in UMTS/LTE network) • AT+CGREG 9. Configure APN, user name, password and auth type by AT+QICSGP • AT+QICSGP=<contextID>[,<context_type>,<APN>[,<username>,<password>)[,<authentication>]]] <context type> The protocol type (1 – IPV4; 2 – IPv6). <context id> The range is 1-16. <authentication> The authentication methods (0 – NONE; 1 – PAP; 2 – CHAP; 3-PAP or CHAP). Example: AT+QICSGP=1,1,"APN_Name","","",1

10. Activate a PDP context: • AT+QIACT=<contextID>

11. Query IP Address of the PDP context: • AT+QIACT? (*Try and activate a PDP context a few times. If failed, then reboot the module). 12. Open connection: • AT+QIOPEN (*If failed – deactivate PDP context - use command AT+QIDEACT=<context ID> to deactivate PDP context.) 13. Use AT commands to ping a Remote Server • AT+QPING=1,"8.8.8.8"

• 1 –The context ID. The range is 1-16;
• 8.8.8.8 - The host address in string type. The format is a dotted decimal IP address.

Response: • If ping a remote server successfully, response: OK (means that the module works properly) • If there is any error, response: ERROR (means the problem is in the module)

Example fo the provided configuration: