Modern smartphones brand Xiaomi has long ceased to be just devices for calls, turning into powerful multimedia centers, where the stability of the Internet connection plays a critical role. 4G, The second one has to be content with the slow. 2G or 3G, This is a problem when waiting for important calls or SMS And it's to solve this dilemma that engineers have introduced Dual technology. 4G, Allows both communication modules to maintain high-speed mode at the same time.
Understanding this feature is essential for every dual-sim phone owner, as it directly affects communication quality and power consumption. In this article, we will discuss in detail how LTE is maintained simultaneously on two SIM cards, what are the limitations of the processor and operator, and provide step-by-step instructions for activating hidden settings.
You don't have to be a tech person to understand the nuances of your gadget's radios, but we structured the information so that you can quickly find the answer to why your device doesn't have a second SIM card catching 4G, and how to fix it without losing warranty.
What is Dual 4G Technology and How Does It Work?
Dual Technology 4G (or dual SIM Dual Standby 4G) This is the ability of the smartphone to support registration in networks of the fourth generation for both SIM-In the classic old phone models, when you were using the Internet on the first SIM card, the second card automatically switched to mode. 2G or 3G, This created a situation where the user could miss a notification from a messenger or bank if it came to a second number.
The principle of operation is based on the use of modern modems such as Qualcomm or MediaTek, which are able to process signals from two different frequency bands in parallel. When one SIM card is busy transmitting data (for example, you are watching a video on YouTube), the second is in standby mode on the LTE network, ready at any time to accept an incoming call or SMS without losing connection quality. However, it is important to understand that simultaneous active data transfer via both SIM cards at the same second is technically impossible on most consumer devices.
⚠️ Note: Even with Dual mode on 4G, The only time you're using active Internet traffic is one SIM card you've chosen. 4G only in the background.
This function depends on three key factors: the capabilities of the processor (SoC), the version of the MIUI or HyperOS operating system, and support from your mobile operator. If any of these components does not meet the requirements, the smartphone will force the second SIM card to 3G/2G mode for resource savings and system stability.
Technical details of the modem operation
Compatibility of Xiaomi processors and models
Not all of the Chinese giant’s smartphones are equally good at running two SIM cards at the same time in high-speed mode, and the chipset installed by the manufacturer is often the main limiting factor. Older or budget processors may not have enough RF channels to maintain two active CPUs. LTE-compound.
Devices based on Snapdragon 600, 700 and 800 series processors, as well as modern MediaTek Dimensity, usually fully support Dual 4G out of the box. However, in the budget segment, where entry-level Helio G chips or older Snapdragon 4xx chips are used, this feature may be software limited or absent.
| Xiaomi Series | Typical processor | Dual 4G support | Nuances of work |
|---|---|---|---|
| Redmi Note (10-13) | Snapdragon / Dimensity | Complete. | Including in settings is required |
| Xiaomi Mi / Digital Series | Flagship Snapdragon | Complete. | Works stably with VoLTE |
| POCO (M and X series) | MediaTek / Snapdragon | Depends on the model. | In the budget M-series may not be |
| Redmi A/C Series | Budget Helio | Partial/No | The second sim often in 3G/2G |
It is worth noting that even with a powerful processor, global versions of firmware (Global) ROM) Sometimes they have hidden limitations compared to the Chinese versions (CN ROM). This is due to the certification of equipment in different regions and the frequency bands used by telecom operators in Europe and Asia.
How to enable Dual 4G in MIUI and HyperOS settings
Activating the function doesn’t usually require complex manipulation, but the path to the desired switch may vary depending on the shell version. In most current versions of MIUI 12, 13, 14 and the new HyperOS, the setting is in the standard mobile menu. First, make sure that both SIM cards are inserted into the device and defined by the system.
Go to the Settings menu, then select a paragraph. SIM-In the list that opens, you will see two tabs for each SIM card, and you will need to enter the settings of each SIM card separately (usually a tab with the name of the operator or the user "SIM 1", "SIM Search for the item entitled “Use”. 4G" or "Preferred Network Type" where you need to select the mode 4G (recommended).
If the standard switch is not enough, in some regions and firmware versions there is a hidden engineering menu or an additional switch. 4G second SIM-If you don't have one visually, you can activate it through a hidden developer menu or engineering code, but that requires caution.
☑️ Pre-insertion check
After making changes, the phone can briefly reboot the communication module, which will manifest itself in the loss of the signal for a few seconds, which is normal behavior of the system when re-registered in a new type of network.
Engineering menu and hidden activation codes
When the standard interface offers no choice or the function is not working correctly, users often turn to the Android engineering menu, a powerful diagnostic tool that allows you to control the parameters of the radio module at a deep level. To enter the engineering menu on Xiaomi smartphones, the code # #4636## is most often used.
From the menu that opens, select Phone Information. There may be several tabs corresponding to the SIM cards (Phone Information 1, Phone Information 2). You need to find the drop-down list "Set Preferred Network Type." To activate Dual 4G for both SIM cards, you need to select a mode containing LTE (for example, LTE Only or LTE/TD-SCDMA/WCDMA). However, setting the LTE Only mode may cause you to stop accepting normal voice calls if your carrier does not support VoLTE.
Code for entry: ##4636##
Path: Phone Information -> Set Preferred Network Type -> Select LTE...⚠️ Warning: Changing the settings in the engineering menu can lead to a complete loss of communication. Do not change the settings unless you are sure of their value, and remember that the mode "LTE Only" block incoming calls without VoLTE.
There is also code ##86583##, which forcibly includes the display of the hidden VoLTE switch in normal settings if it was hidden by the operator or firmware. Once you enter the code, you should see the message "VoLTE carrier check was disabled", which means permission to use the feature.
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If the code doesn’t work, you may have a global firmware with a stripped-down functionality, which can help to change the region in settings (for example, India or China), where the VoLTE certification requirements differ.
The impact of Dual 4G on battery and device heating
Using two SIM cards in constant search and retention mode of 4G signal inevitably affects the autonomy of the device. The radio module consumes significantly more energy when working with fourth-generation networks compared to 2G/3G, especially in areas of uncertain reception. When the phone loses the LTE signal, it begins to send requests to the base station more often, which leads to increased charge consumption.
In addition, the simultaneous operation of two radio channels can cause additional heating of the smartphone body, especially in the upper part, where the antennas are located. In the summer or when using heavy applications (navigator, games) in conjunction with active Dual 4G, the device can reset the brightness of the screen or reduce the performance of the processor for thermal protection.
However, modern Xiaomi algorithms have learned to effectively manage power consumption, so if the second SIM card does not have active traffic, the system puts it into deep sleep mode, minimizing the effect on the battery, the real consumption is noticeable mainly when switching between towers or when you actively use the Internet on both SIM cards in turn.
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Power saving mode can automatically limit the background activity of the second SIM card, which sometimes leads to its temporary switch to 3G to save charge.
Problems with operators and VoLTE
A key condition for the stable operation of Dual 4G is the support of VoLTE (Voice over LTE) technology by your mobile operator. Without this technology, when an incoming or outgoing call is made, the phone must fallback to a 3G or 2G network to transmit voice, at which point the Internet on the SIM card through which the call is being made is interrupted, and the second SIM card may temporarily lose registration in the 4G network.
In Russia and CIS countries, most major operators (MTS, Beeline, MegaFon, Tele2) already support VoLTE, but the service often needs to be activated on the subscriber or tariff plan side. If you see an HD or VoLTE icon in the status bar next to the network indicator, then the technology is working correctly.
A common problem is when one SIM card works in the 4G, The second one is constantly jumping between 3G and 4G. This may indicate a frequency band conflict or incompatibility of operator profiles, in which case it is recommended to manually select the network type in the settings or contact the operator for a profile update. SIM-map.
⚠️ Note: When using two SIM cards from different operators in Dual mode 4G, Make sure that neither of them blocks the other operator’s equipment (branded tariffs issue).