Dual 4G on Xiaomi: What it means and how to activate

Xiaomi and Redmi smartphones have long since ceased to be just callers, becoming powerful multimedia centers where the quality and stability of the Internet connection is critical. For many users, having two SIM cards has become the norm: one for personal calls, another for work contacts or a tariff with a large amount of traffic. However, for a long time, Android device owners have faced an annoying limitation: when using a mobile network on one SIM card, the second forced to switch to 2G or 3G mode, remaining inaccessible to high-speed Internet.

Dual 4G (or Dual VoLTE) has been the answer to the needs of the engineers, allowing both communication modules to work simultaneously on fourth-generation networks. This means that you can take calls to the second SIM card without interrupting the download of files or video stream on the first. On MIUI devices and the new HyperOS, this feature is often turned on by default, but depending on the region of the firmware or smartphone model, the settings can be hidden in the depth of the engineering menu or completely hidden from the user.

In this article, we will discuss in detail how this mode works, why it is important for comfortable use of a smartphone and what nuances should be considered when activating it. Understanding the principles of the radio module will help you not only to set up communication, but also to optimize the power consumption of the device.

The principle of operation of two SIM cards in LTE networks

To understand the technology, we need to look at the evolution of communication standards. In the 3G era, the network architecture allowed only one SIM card to maintain high-speed connection, while the second one deactivated its radio module or went into low-power standby mode. With the advent of LTE, this changed, but not immediately. Initially, VoLTE (Voice over LTE) was also supported for only one active card, which created a situation where the Internet on the second SIM card could temporarily disappear or the speed would drop to a minimum.

Dual 4G mode means that both SIM cards are permanently logged into the fourth generation network. The smartphone uses a complex time-frequency sharing system to maintain a connection to the operator's base stations for both numbers simultaneously, requiring a more productive modem and optimized operation of the Android operating system in conjunction with the manufacturer's shell.

⚠️ Note: Even if your phone supports Dual 4G, Downloads can only be transmitted through one selected SIM card. LTE exclusively for voice communication and SMS, Staying on standby for receiving calls.

It is important to note that the implementation of this function depends on the device’s processor. Qualcomm Snapdragon and MediaTek chipsets have different approaches to organizing radio channels. In some cases, especially on older models, activation of a second SIM card in 4G mode could lead to a decrease in overall speed due to the separation of antenna resources, but on modern models Xiaomi 13, Xiaomi 14 and the Redmi Note series, this problem is almost eliminated.

Advantages of Dual VoLTE Activation

Enabling dual SIM card simultaneous operation on 4G networks gives users a number of tangible benefits that improve the comfort of daily smartphone use, the main one being the continuity of communication. You will no longer miss an important work call on number two while watching a video or playing an online game via mobile Internet on the first.

In addition, voice quality is greatly improved by HD Voice technology, sound is cleaner, background noises are eliminated, and connection is established faster. For users who are often in the area of insecure reception, this can be a decisive factor, as LTE networks often cover the territory better than legacy 2G/3G networks.

Also worth mentioning is the switching speed. In older implementations, when a second SIM card is called in, the phone could lose the network on the first one for a few seconds while the frequency switching is going on. Dual 4G minimizes these delays by making the process invisible to the user. This is especially true for those who use the smartphone to navigate while on the way, since the card will not freeze at the time of the incoming call.

• 📶 Constant online: Both SIM cards are always available to receive calls and SMS switch-on 2G.
• 🗣️ High quality sound: The use of codecs HD Voice for both numbers at the same time.
• 🚀 Stable Internet: No connection breaks on the main SIM card when the second one is active.
• ⚡ Fast connection: Instant dialing and receiving a call thanks to pre-registration on the network LTE.

How to check and enable Dual 4G on Xiaomi

On most modern Xiaomi, Redmi and POCO smartphones released after 2019, Dual 4G is activated by default at the firmware level if it is supported by a carrier. However, in some cases, especially on global firmware versions (Global ROM) or Chinese versions (CN ROM), access to settings can be limited or hidden.

First, check the basic settings. Go to the Settings menu. → SIM-Maps and mobile networks. Here you should see the "Use" switch. 4G second SIM-phrasing like "Enable" (or similar phrasing like "Enable") 4G for second SIM"). If it's present and active, it means your phone is already working in the right mode. In newer versions of HyperOS, the interface may be slightly different, but the logic remains the same.

If there is no standard switch, it does not always mean that the phone does not support the technology. Often manufacturers hide this option for certain regions or operators. In this case, you can try to activate a hidden settings menu. To do this, open the Phone app and enter the code ##4636#. In the open menu, select Phone Information. Here you can find additional switches associated with the preferred network type, but be careful: changing the parameters in the engineering menu without understanding the consequences can lead to unstable communication.

⚠️ Note: Entering codes in the engineering menu (#4636###) should be done with caution. Do not change the values of parameters that are not sure, as this may disrupt the operation of the radio module.

It’s also worth considering that for Dual 4G to work, both SIM cards must be registered on networks that support VoLTE. If your carrier does not provide this service or it is not activated on the tariff, the phone will not physically be able to hold the second SIM card in 4G mode, resetting it to 3G or 2G to provide voice communication.

Compatibility of operators and tariff plans

The technical capability of a smartphone is only half the equation. The second, and equally important, part is the support of the technology from the telecom operator. In Russia and the CIS, large operators (MTS, MegaFon, Beeline, Tele2) have been actively implementing and supporting VoLTE for several years.

For example, some operators have VoLTE enabled automatically when a supported device is available, while others have to send it to the operator. USSD-request or change the settings in your personal account. Without an active service VoLTE on the operator side, the smartphone will not be able to register a SIM card in mode 4G for voice calls, and Dual 4G It will not work even if the phone is technically ready.

There is also a frequency compatibility issue. Operators use different frequency bands (Band 3, Band 7, Band 20, Band 38, etc.). Global versions of Xiaomi smartphones usually support the full spectrum of frequencies used in Europe and Asia. However, Chinese versions (CN) imported via parallel imports may not support some frequencies (for example, Band 20), which in rural areas can lead to the loss of 4G signal on one of the SIM cards.

The impact of Dual 4G on autonomy

One of the most common questions users have is: “Does the Dual 4G battery land faster?”. The answer is unequivocal: yes, two radio modules in active 4G mode consume more power than a mode where one SIM card is waiting for 2G. Constant search for a signal, sharing service data with two different base stations and maintaining two communication channels require the resources of a processor and a modem.

However, the difference in consumption on modern devices with energy-efficient Snapdragon chipsets 7 Snapdragon 8 When using a smartphone (screen is on, applications are running), the radio module contributes a smaller part to the overall power consumption compared to the brightness of the display and the operation of the processor. You may notice acceleration in standby mode (when the phone is in your pocket) around the 5-10% day-by-day.

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If you're in a very weak signal zone, the phone is constantly looking for a network that consumes a charge. In these situations, Dual 4G mode can drain the battery noticeably faster. Consider turning off the second SIM card or going into flight mode.

On the other hand, switching between 3G and 4G (if Dual 4G is turned off) is also energy-intensive.The phone spends a lot of energy re-adjusting the radio channel every time a call comes to a second SIM card.So in the long run, a stable Dual 4G connection may be even more energy efficient than the constant jumps between communication standards.

Possible problems and ways to solve them

Despite the technology, users may face a number of problems, most common being the absence of a VoLTE or 4G icon near the second SIM card, which can be caused by software failure and incompatibility of the SIM card. In some cases, older SIM cards released 5-7 years ago do not have a profile for working in new generation networks and require replacement in the carrier cabin.

Another problem is that the main SIM card is missing while you're talking to the second one, which indicates that Dual 4G is actually not working, and the phone is resetting one of the cards. The solution is often to update the firmware. Xiaomi engineers regularly release patches that improve compatibility with carriers in different countries.

If the settings are down, reset the network settings. Go to Settings → Connection and Sharing → Reset Wi-Fi, mobile networks and Bluetooth. Note that this action will remove saved passwords from Wi-Fi and associated Bluetooth devices, but return the communication settings to factory values, which often solves the problem of registration on the network.

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If Dual 4G stopped working after the system update, the first thing to do is check if your carrier's APN settings have reset, and often the software update overwrites these settings to standard ones that may not be suitable for your region.

In rare cases, the problem can be hardware. If the phone fell or was exposed to moisture, the antenna module could damage, in which case one of the SIM cards can see the network, but can not maintain a stable LTE connection, constantly switching to EDGE.

FAQ: Frequently Asked Questions