Diagnostic recommendations for 3G/4G connections

What to do if my 3G/4G USB modem is not able to connect to my Keenetic router (for mobile Internet connection)? What should I do if the 3G/4G USB modem often disconnects or works unstably?

1. Make sure that your USB modem is in the list of supported models.
We do not guarantee the correct operation of USB modems, which are not integrated into KeeneticOS.

Make sure that your router has the latest version of the KeeneticOS built-in operating system: 'Updating the router', and the USB modem has the original (or at least official) firmware version.

Use the supplied power adapter with the router.

2. Follow the steps below to diagnose a 3G/4G connection:

2.1 Try to disable the 'Ping Check' Internet availability mechanism.

2.2. Make sure that the USB modem is functioning correctly, that it is in the zone of reliable 3G/4G network reception (for example, on the window sill or near the window) and works stably in the same place when connected to a USB port of a computer or a laptop (PC). To get reliable results, work for a few hours this way. Such a check will allow you to find out whether the problem is observed only when working with the USB modem via the router or not. If you are also having poor connection quality when working through the PC, as well as through the router, there is probably a problem with the busy network of your service provider.
When comparing the work of the USB modem through the router and the PC, the USB modem mustn't change its location in space, the signal level, and, consequently, data transmission speed and connection stability may depend on it. For example, if the router is on the floor under a desktop and the PC is closer to a window, in this case, the comparison will be incorrect.

2.3. Make sure that the SIM card used in the modem is not blocked and that the SIM card does not request a PIN code (this can be done in the cell phone menu by temporarily installing the card from the modem, or using the modem utility by connecting the modem to a PC).

2.4 Connect your USB modem to the Keenetic router directly without using extension cables.
Do not use a USB cable that is longer than 2 meters, as voltage drop may occur in the cable, which may negatively affect the operation of the modem. A too-long cable will cause a significant voltage drop. The point is that the current at the output of a USB-port is strictly fixed (according to the standard USB 2.0, it is up to 500 mA, and in USB 3.0 - up to 900 mA). Due to the cable length, the voltage drop may occur, in this case, the router outputs 5V, and the lower value reaches the modem, and therefore, it cannot work correctly in this situation. That is why we do not recommend the use of extension cables longer than 2 meters.

NOTE: Important! In the latest Keenetic models, the voltage on the USB port was increased to 5.2 V, and the current on the USB 2.0 port is now supplied according to the standard in USB 3.0, and the smoothing capacitors are installed.

2.5. Connect the USB modem to your Keenetic using a high-quality (shielded) USB extension cable and move it away from the router to the area of reliable 3G/4G reception (closer to the window) to eliminate the influence of Wi-Fi transmitter and other electromagnetic interference. Do not use a USB cable that is longer than 2 meters, as the voltage drop may occur in the cable, which will negatively affect the operation of the modem.
As a rule, quality USB cables and extension cords have a wire section at least as thick as a standard Ethernet cable. Be guided by the following principle - 'the thicker the cable, the better', and pay attention to the characteristics of the cable or extension cord, which should indicate the presence of shielding for the wire and connector to reduce high-frequency interference.

2.6. Place the USB modem away from possible sources of high-frequency interference to improve the useful signal and reduce the noise. Interference from the other nearby devices may have a negative impact on the modem. For example, an external hard drive operating in accordance with the USB 3.0 standard may be a possible source of interference.

2.7. To perform full connection diagnostics, enable the debugging mode on the USB modem interface.
Please, refer to the instruction for details: 'How to enable a USB modem connection diagnostics'.

2.8. If possible, please check work with another USB modem in the same conditions. A low-quality 3G/4G modem may work incorrectly through the router, it can limit the speed or break the connection.

3. Please, refer to the article: 'LTE signal quality parameters' to find information about 4G/LTE signal quality parameters in Keenetic routers, and to know more about available options to improve the received signal level and connection quality.

4. For Huawei USB modems in Keenetic settings you can lock 2G (GSM) / 3G (UMTS) / 4G (LTE) network operation mode. You can find details in the article: 'Change of GSM/3G/LTE mode for Huawei USB modems'.

5. If the connection is still not working or is extremely unstable, please send the system file 'self-test.txt' from your Keenetic router to the Technical Support Service. It contains a system log file and other diagnostic information. You can read about how to save this file in the article: 'Saving the self-test system file'.
Also, together with the 'self-test.txt' file, please, tell us the exact model of your modem, or better make a photo of your USB modem with its name and send it to us. USB modems are often manufactured with different revision versions, and therefore, there may be specific features when using particular models.

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