Many owners of smartphones Xiaomi, Redmi and Poco are faced with an unpleasant situation: at the time of incoming or outgoing call, the device automatically switches from fast to fast. 4G/LTE slow-moving 3G or 2G. As a result, access to the Internet either disappears completely or speed becomes unsuitable for navigating or messaging, which is especially critical if you work remotely or wait for an important notification in a conversation.
The main reason is the architecture of mobile networks and the lack of support for VoLTE (Voice over LTE) on the operator side or in the settings of the gadget itself. Without this technology, the phone has to break the high-speed connection to transmit voice over old channels. Fortunately, in most cases, the problem can be solved software by changing hidden parameters or choosing the right access point.
In this guide, we will look at all the methods available to keep your Internet connection active during a conversation, and we will touch on both the standard menu settings and the engineering codes that allow you to access advanced modem functions. It is important to understand that the success of the operation depends not only on the phone model, but also on your carrier’s tariff plan.
Why Xiaomi’s Internet is Lost When Talking
The fundamental problem is how data and voice are transmitted. Fourth-generation (LTE) networks were originally designed to transmit both voice and Internet over a single packet channel. However, in the early stages of 4G, carrier infrastructure was not ready for mass VoLTE, so for voice calls, the phone was forced to switch to second (2G) or third (3G) generation networks, a process called CSFB (Circuit Switched Fallback).
When you make a call, your Xiaomi receives a command from the base station to change frequency. If VoLTE technology is not activated, the phone falls into the phone. 3G, where voice and data channels often cannot work simultaneously SIM-map (especially in the standard) WCDMA without HSPA+). It's at this point that the badge 4G or+ shift 3G or E, and the web pages stop loading.
⚠️ Attention: Even if you are on 4G, The lack of VoLTE support from the carrier in your area will make it impossible for voice and internet to work simultaneously.
This is even worse if you use two. SIM-Most Xiaomi smartphones have a single radio module that can’t physically take a voice call on one SIM and transmit data through another at the time of a call unless the right priority is set up. VoLTE technology solves this problem by packing voice into internet packages, but it requires support from three sides: phone, SIM card and operator.
Verification and activation of VoLTE in the standard menu
The first and most obvious step is to check the basic settings. In modern versions of the MIUI shell and HyperOS, the VoLTE switch is often hidden or, conversely, enabled by default, but requires manual activation for specific SIM cards. You need to go to the settings menu to make sure the feature is available and active.
Go to the Settings section, then select SIM-You'll see a list of installed cards here. You'll click on the SIM card you call most often. You'll find the "Use VoLTE" option and activate it. If you don't, it's probably hidden by the system, and you'll need to use the methods described below.
- 📱 Make sure that preference is selected in the network type settings LTE, Not "Only." 3G".
- 🔄 After VoLTE is enabled, restart the device to apply changes to the network profile.
- 📶 Check the icon in the status bar: next to the network division, a VoLTE symbol should appear or HD.
If the switch is present but is inactive (gray), it is a signal that Xiaomi does not see support for the function from the operator in the current location or the SIM card is too old. USIM, work-related LTE-voice.
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If the VoLTE icon doesn’t appear after turning on, try removing the SIM card, erase the contacts with a pin and paste back, then restart the phone.
Activation of the hidden switch through the engineering menu
Often, the carrier supports the technology, the SIM card is new, but there is no slider on the Xiaomi menu to turn on. It's a software restriction that can be bypassed through the engineering menu, which allows you to force the display of the switch or activate the function itself at the modem level.
To enter the diagnostic menu, open the Phone app and dial the code ##86583##. In the pop-up window that appears, you will see the message VoLTE carrier check was DISABLED. This means that the operator check is disabled, and now the VoLTE switch should appear in the SIM card settings. If the message says ENABLED, then the check is on and you need to repeat the action.
☑️ Activation of VoLTE through code
There is an alternative way through a deeper engineering menu that runs on MediaTek processors and some Snapdragon. Dial ##4636#. From the menu that opens, select Phone Information. There may be a separate VoLTE Provisioned switch, which activates it to tell the network that your device is ready to work with voice over LTE.
⚠️ Warning: Be careful in the engineering menu. Don't change the values of parameters you're not sure about, especially those associated with radio frequencies (RF), Not to disrupt the antenna module.
After you've manipulated the codes, make sure you reboot. Sometimes the system doesn't apply changes on the fly. If after the reboot, the HD icon appears but the Internet still shuts down, the problem may lie in the settings of the APN access points, which we'll discuss later.
Configure APN access points for stable connection
Proper APN configuration is a critical step that is often ignored. Even with VoLTE enabled, if the access point profile does not specify the correct protocol type, the phone will break-session when it switches to voice call mode.
Go to the Settings path → SIM-maps and mobile networks → select a SIM card → Access points (APN). Click on the current active point (usually signed by the operator name, such as the Internet or mts). APN (APN Type. By default, it can simply say default,supl.
To properly work VoLTE and save the Internet, you need to add dun and xcap to this line. The final row should look something like this: default,supl,dun,xcap. The dun (Dial-Up Networking) option allows you to use the connection for other applications, and xcap is necessary for the operation of additional VoLTE services.
What if the APN type field is not edited?
Also note the APN protocol setting: Make sure that you choose IPv4/IPv6. Using only IPv4 in some regions can cause connection instability when switching between towers during a call. After making changes, save your profile and restart your smartphone.
Comparison of network modes and their impact on communication
Understanding the differences between network modes will help you choose the optimal balance between voice quality and Internet speed. Xiaomi’s settings often suggest choosing the preferred network type. Let’s take a look at how each affects the behavior of the phone during a call.
Regime. LTE Preferred (preferred) LTE) Makes the phone hold on to you. 4G It's the best choice for people who care about the Internet. 4G weak, voice quality can suffer, and the battery runs out faster due to constant search for a signal. 3G Preferred guarantees a stable voice, but dooms you to a slow internet that will likely shut down when you call.
| Network mode | Internet when calling | Voice quality | Battery consumption |
|---|---|---|---|
| LTE/4G (with VoLTE) | It's working (High speed) | HD (Excellent) | Medium. |
| LTE / 4G (without VoLTE) | Shutdown / 3G | Standard. | High (network search) |
| 3G / WCDMA | Partially (depends on HSPA) | Good. | Low. |
| 2G / GSM | No (EDGE only) | Low. | Minimum |
For most Xiaomi users, the optimal choice is the mode Preferably LTE in conjunction with activated VoLTE. If you are in the zone of uncertain reception, the phone itself will switch to 3G for saving, but with a stable 4G signal, it will take advantage of its advantages.
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Without activated VoLTE, 4G Only mode can make outbound calls impossible, as older 2G/3G networks will be blocked.
Problems with two-sim smartphones Xiaomi
Owners of models with two SIM-The way that the cards are dealing with the nuances of the modem is that Xiaomi phones often have a circuit where one SIM card is running in mode. 4G/3G/2G, And the second one is in 2G (for receiving calls and SMS), either of them can work in 4G, But the data is only going through one, and when you call on the first SIM, the second one may temporarily lose registration on the network.
To minimize problems, set the data priority. SIM-maps and mobile networks find the default for data transfer and select the SIM card on which you have the best tariff and coverage 4G. Also check the call settings through SIM. If you want the internet to work at all times, make sure that calls are made via the same SIM card that is set up to transfer data, or that VoLTE is enabled on both SIMs.
- 📞 When you call through SIM 1, the Internet will work through SIM 1 (if there is a VoLTE).
- 📉 If VoLTE is not available, the Internet can "lie down" on both SIMs at the time of switching to the Internet. 3G.
- ⚙️ Enable the “Allow Data Transfers During Call” feature in the advanced settings if such option is available in your version MIUI.
It is worth noting that on some global versions of Xiaomi firmware for certain regions (for example, Russia, India), operators are added to the white list, and VoLTE works out of the box. On Chinese versions (CN ROM) or flashed devices, the list of operators can be reduced, which requires manual editing of configuration files or the use of third-party activator applications.
⚠️ Note: Using third-party applications to activate VoLTE on global firmware can cause the radio module to run unstable.Use only proven methods through the engineering menu.