As LTE-M usage is increasing, we started observing 0-data usage issues with IoT devices that transition from using 2G/3G access to LTE-M modems. This issue represents itself by attaching to LTE-M network successfully and even having successful PDP context activation but then failing to do any data exchange.

The reason for this issue is the necessity of modem specific AT commands to open the data communication channel that is different than 2G/3G models. These commands open a Network Interface to use the TCP/IP stack on the modem. The difference between the regular CGACT and these commands is that these commands open a Network Interface in addition to EPS bearer. CGACT only establishes EPS bearer (a.k.a PDP) but does not create a Network Interface. With LTE-M, we need CGACT to establish the bearer and then we need these commands to create network interface so that data communication becomes possible.

Below are examples of these modem specific commands. If you cannot find your specific modem in this list, please contact your device/modem manufacturer. We would appreciate if you could let us know the result also.

Telit LTE-M modems (e.g. ME310G1-W1)

AT#SGACT   // PDP context activation

Example:
AT#SGACT=1,1
#SGACT: 100.86.180.20

SIMCom LTE-M Modems (SIM7070/SIM7080 series, e.g. SIM7080G)

AT+CNCFG   //PDP Configure
AT+CNACT   //APP Network Active
AT+CAOPEN   //Open a TCP/UDP Connection

Also it will be a good practice to use the below command for ending a session after data communications is completed:
AT+CACLOSE   //Close a TCP/UDP Connection

Examples:
AT+CNCFG=0,1,"em"
AT+CNACT=0,1
AT+CAOPEN=0,0,"TCP","213.188.196.246",443
AT+CACLOSE=0

U-Blox LTE-M Modems (e.g. SARA-R422M8S)

AT+UHTTP   //Configure HTTP application profile parameters.

With "AT+UHTTP" the following parameters can be set:
• 0: HTTP server IP address
• 1: HTTP server name
• 2: username
• 3: password
• 4: authentication type
• 5: HTTP server port
• 6: HTTP Secure option (SSL encryption)
• 7: HTTP request timeout and TCP socket linger timer

Quectel LTE-M Modems (e.g. BG96)

AT+QICSGP   //Configure Parameters of a TCP/IP Context
AT+QIACT   //Activate a PDP Context
AT+QIDEACT   //Deactivate a PDP Context

However it was also observed that sometimes AT+CGACT worked better than AT+QIACT to activate a PDP context.

Thales / Gemalto LTE-M Modems

No information available yet

Mediatek LTE-M Modems

No information available yet

Qualcomm LTE-M Modems

No information available yet

Sierra Wireless LTE-M Modems

No information available yet

Meiglink LTE-M Modems

No information available yet