WWAN Module Research Note

Some technical details of wireless wide area network (WWAN) modules—User Identity Module (UIM), Mini PCI Express, M.2, Access Point Name (APN), AT command set, Qualcomm MSM Interface (QMI), etc.

System Interfaces

User Identity Module (UIM)

Called SIM (subscriber identity module) for the most cases. The SIM circuit is part of the function of a Universal Integrated Circuit Card (UICC) physical smart card.

USB dongle modems usually have built-in SIM slots, on the other hand, WWAN expansion cards access UIM through M.2 or Mini PCI Express connectors. Both M.2 and Mini PCI Express specifications have defined a set of interfaces provided—which includes UIM—through the connector.


The M.2 connector has different keying notches that denote various purposes and capabilities of M.2 hosts and modules, preventing plugging of M.2 modules into feature-incompatible host connectors. You’ll need socket 2 (mechanical key B) in support of WWAN solutions.

  • M.2 – Wikipedia
  • PCI Express M.2 Specification
    • Socket 2 Pinout Diagram (Mechanical Key B)

Mini PCI Express


Application Interfaces

Most WWAN modules use USB interface on M.2 or Mini PCI Express connector to communicate with hosts, some act as a composite USB device to provide multiple application interfaces.

AT Command Interface

Qualcomm MSM Interface (QMI)

International Mobile Subscriber Identity (IMSI)

Read IMSI from SIM

AT command
qmicli --device=/dev/cdc-wdm0 --device-open-proxy --uim-read-transparent=0x3F00,0x7FFF,0x6F07

Mobile Country Code (MCC) and Mobile Network Code (MNC)

Access Point Name (APN)


Since SIM cards do not contain APN configuration details, it might be a good idea to have an up-to-date APN database for setting up either your WWAN module Wireless Data Service (WDS) or mobile phone data service.

Frequency Bands


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