- Raspberry Pi
- 3G/4G & LTE Base Shield
- LTE – GNSS Dual u.FL Antenna – 100mm
- LTE Full Band PCB Antenna – u.FL Plug – 100mm
- Right Angle Micro USB Cable
- Quectel EC25 Mini PCle 4G/LTE Module or Telit LE910C1 Mini PCle LTE CAT1 Module
Make sure the right antenna is connected to the right port. Attach LTE full band PCB antenna/LTE connector of the LTE-GNSS dual antenna to the main Antenna interface/diversity antenna interface & GPS Antenna portion goes to the GNSS antenna interface.
We have two options to reach the internet using mini PCle module with our Base Shield and Raspberry Pi.
- PPP (Point to Point Protocol)
- QMI (Qualcomm MSM Interface)
PPP vs QMI
PPP(Point-to-Point Protocol) is a data layer communication protocol that is established through the serial port of the modem. These Serial port communication could be either the UART(/dev/ttyS0) or the serial exposed to USB(/dev/ttyUSB3). This serial is also used for both modem commands (AT commands) and responses. This connection is established by dial-up (ATD*99#)
PPP is easy to establish, widely used protocol, and flexible with the devices. PPP may show a drop of the connection while using the AT command set for other functionality of modem.
The LTE radio protocol has native support of TCP/IP and IPv6, so there is no need to actually wrap TCP/IP into PPP over the radio interface. The PPP protocol is just used between the computer and the modem to make the connection look like a legacy dial-up modem-based network connection.
To get rid of the legacy cruft, newer ways to present USB-connected LTE modems like QMI and MBIM have been developed.
Quectel modules offer QMI(Qualcomm MSM Interface) which is established as a real network interface, such as ethernet(typically shows as wwan0). The QMI is also counted among the non-AT protocols which is communicated over /dev/cdc-wdm0 port.
In order to establish a connection, proper qmi/gobinet proxy should be installed, which again depends on the chipset of the module/modem and the kernel of linux, gets a bit complicated. The QMI offers more accessible and faster connection compared to the PPP protocol.
If you need to establish an internet connection for a short period of time and the date to be transferred is not high, you may stick to PPP.
Updated over 2 years ago