FAQ – Answers to questions about 4G-eSIM -NBIoT

Here are some frequently asked questions about 4G, NB-IoT,…

1. Faults related to communication and power supply
   • Send Command AT but don’t get a response
     • The UART connection between the MCU (or USB-UART) must be cross-legged (TX_MCU–> RX_4G and RX_MCU–> TX_4G)
     • Check the power supply for correct and sufficient power supply
       • Depending on the module model, the power supply is 3.7-4.2V or 5-16V and must have a sufficient power of 8W (2A). See the power supply here: 4G module summary
     • Check for LEDs that flicker quickly (200ms ON/200ms OFF) or are fully lit (long lights up without turning off). If the power is not enough, the light will light up for 1-2s and then turn off for 3-5 seconds, the UART log will see ATREADY: 1 continuously
     • Can use apdapter on 2A or lithium battery,
     • Do not use AA or AAA batteries as there will not be enough current
     • When supplying power, the pins should be soldered to the module and the power supply circuit. Do not use breadboard to plug in the power supply bus, as the device uses a high peak current, so it will experience voltage drops and unstable operation (or reset)

• Check if the ending character “\r” is already there. On Hercules is $0A. (0x0A)
• Use the AT Command Test tool, to test the command with the module (the AT Command Test tool has a built-in \r character).
• Check the baudrate of the MCU or USB-UART (Computer) should be 115200. Do not use the baudrate 9600 as SIM800L
• LED Status (Connection Indicator LED)
  • LED Bright: The sim has not been attached or is connected to the network, in this case you can check the AT+CPIN command to see if the SIM is READY. You check if the sim attached to the tray is upside down, or if the antenna is properly attached. The sim bevel direction is turned inward (push-push sim tray).
  • LED Off: Unpowered
  • Rapid Flashing LED (200ms ON/200ms OFF): Network connected

2. Does 4G support calling and SMS?

• 4G technology supports SMS and VoLTE (Some modules will not support VoLTE, and some carriers do not support IoT devices).
• Apps to call:
  • You need to choose a module that supports VoLTE to use it
  • Both the 2 SIMs and the device (calling and listening) must support and register for VoLTE.
  • VoLTE Subscription:
    • Viettel: HDCALL to 191
    • Vina: HD CALL to 888
    • Mobi: DK VOLTE to 999 (Not yet supported, updated 05/2024)
    • Vietnammobile: ON to 345 (Not yet supported, updated 05/2024)
• When the SMS fails to be sent or the call fails, check the command AT+CSQ. CSQ > 25 will hear calls well, < 25 will hear weak calls. < 20 is almost very weak.
• Unable to call: you check if the module you purchased supports VoLTE. If available, you can register for 2-way VoLTE before calling.

1. How is LTE Cat 1 different from LTE Cat 4?
   • LTE Cat 1 supports downlink/uplink speeds of 10Mbps/5Mbps, while LTE Cat 4 supports downlink/uplink speeds of 150Mbps/50Mbps.
   • LTE Cat 1 is suitable for IoT applications, journey monitoring, usb dongle, audio streaming, VoIP, video streaming (HD)…
   • LTE Cat 4 is suitable for applications that need large bandwidth, streaming (Full HD, 4K), video uploading,…
2. Which application is NB-IoT vs LTE-M vs LTE Cat 4 suitable for?
   • NB-IoT is suitable for location-fixed applications (because the connectivity to other BTS stations is low), applications that require battery power is required (water meters,…) Not for applications that need to be on the go, such as journey monitoring. At the same time, the data rate is low, SMS, VoLTE is not supported. Normally, it supports MQTT(S), TCP/IP…
   • LTE-M: Almost similar to NB-IoT, but not deployed in Vietnam
   • LTE Cat 1: Suitable for fixed or mobile applications that require frequent connectivity (IoT gateways, journey monitoring), SMS, VoLTE or other 4G-based connections such as: HTTP(S), MQTT(S), VoIP, (S)FTP,…
3. Is AT Command of current 4G modules compatible with 2G modules such as SIM800 and SIM900?
   • Basic commands such as SIM check, signal signal,… will be relatively similar to 2G modules. However, some commands will change. When programming the 4G module, it is necessary to refer to the AT Command document.
   • AT Command Documents
4. How is an eSIMdifferent from a regular SIM?
   • The features of an eSIM are equivalent to a regular SIM. The current eSIM linhkienthuduc supports single profile (1 operator is active and has been loaded with profiles before selling).
   • To use eSIM, you first need to register an IoT eSIM contract with the carrier (Need to register a corporate legal entity, individuals cannot use eSIM). After that, the device will read the IMEI of the eSIM and send it to the carrier for setup.
5. Is the antenna includedwith the purchase of the 4G module?
   • For the pin module, linhkienthuduc has attached 1 antenna sticker to test and catch waves well. This antenna is an isotropic antenna (about 3dBi)
6. What does an extension antennado?
   • An extension antenna has the effect of bringing the antenna to an unshielded area, such as a metal enclosure or wall,…
   • In addition, the extension antenna also has the effect of amplifying the transceiver signal, by changing the radio pattern, e.g. 6dBi, 8dBi (dBi units). However, when installing, the direction must be corrected.
   • Extension antennas usually use SMA connectors, while 4G modules often use IPEX (IPEX1) connectors, so an IPEX to SMA converter is needed
7. If you only use 4G data (TCP/IP, HTTP(S), MQTT(S), (S)FTP) and/or SMS, which 4G module is optimal to use:
   • The 4G SIMCOM A7680C module TDM2309 the same pin replacement for the 2G SIM800 SIM800L Already out, integrated sim tray and power capacitor, fully compatible with the SIM800L
   • 4G SIMCOM module has come out with TDM-4G-V2-NV No-Volte Pin, integrated power circuit down to 3.8V (power supply from 5V-16V), sim tray.
8. If you have a call (via VoLTE) + 4G/SMS (optional), which module should you use?
   • SIMCOM A7680C 4G Module Replaces SIM800 SIM800L with VOLTE Pin Out, integrated sim tray and power capacitor, fully pin compatible with SIM800L
   • 4G SIMCOM Module Pin Output TDM-4G-V2-NV with Volte Pin Output, integrated power circuit down to 3.8V (power supply from 5V-16V), sim tray.
9. If GPS is needed, which module is suitable:
   • EG800K built-in 3.8V down power circuit (power supply from 5V-16V), sim tray and ipex for GPS antenna.
   • EG800Z Already pinned, built-in 3.8V down power circuit (power supply from 5V-16V), sim tray and ipex for GPS antenna. LTE Cat 4 support
10. Does the GPS antennacome with a module?
    • The shop does not include a GPS antenna for the 4G output module. You can refer here