Xiaomi’s current MIUI or HyperOS smartphones offer a wide range of opportunities to optimize communications, especially in unstable cellular coverage. VoWiFi (Voice over Wi-Fi) technology allows voice calls and SMS over a wireless network using an Internet channel instead of a base station radio. For MTS subscribers, this solution is a real salvation in buildings with thick walls, basements or country houses, where the GSM signal level often drops to zero.
The main advantage of the method is not only the stability of the connection, but also its cost-effectiveness: the operator MTS charges such conversations as ordinary minutes from your package, and if the minutes are unlimited, then the call is actually free. Unlike popular messengers, you don't need a special software or a smartphone of a particular brand; you call a regular phone number. The sound quality often exceeds the standard one. HD-Connection with high resolution codecs.
In this guide, we will discuss in detail how to activate this feature on Xiaomi devices, what settings you need to check in the operator’s personal account and what to do if the desired option does not appear on the menu. You will learn about the technical nuances of the technology, how to diagnose problems and secrets that will help ensure crystal clear communication even in the most difficult conditions of reception of a signal.
The principle of VoWiFi technology and its advantages
VoWiFi technology is the transmission of voice traffic through IP protocols, similar to how video calls work, but with integration into the standard phone book and dialer. When you activate this feature, the Xiaomi smartphone creates a secure tunnel to the gateway of the operator MTS. If at the time of dialing the cellular network is unavailable or its signal is weaker than the Wi-Fi signal, the system automatically redirects the call over the Internet. This happens unnoticed to the user if the VoLTE and Wi-Fi Calling function is configured.
The key difference from apps like WhatsApp or Telegram is transparency: you use a standard call interface, call history and contacts; the interviewer sees your number, not a random ID or account; and MTS gives priority to voice traffic, which minimizes the delays and cliffs that often occur when home networks congestion in the evening.
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Use a 5GHz network for calls if the router is in the same room – this will provide minimal latency and better sound quality compared to the congested 2.4GHz band.
It's important to understand that this feature requires support from three components: your smartphone, your SIM card, and your data plan. VoWiFi on MTS is free for all rates, including archive rates, and traffic is consumed from minute packets, not the Internet. This means that even if you don't have megabytes on your account, but you have minutes, you can make calls over Wi-Fi.
- 📶 Stable communication in the zones of the "dead signal" of the cellular network.
- 💰 Savings in roaming (depending on the tariff conditions).
- 🔋 Reducing smartphone power consumption compared to constant network search GSM.
Verification of compatibility of the device and SIM card MTS
Before you start settings, you need to make sure that your equipment and tariff fully meet the operator’s requirements. Not all Xiaomi models have certified firmware for working with VoWiFi on Russian carriers’ networks. Global versions (Global ROM) usually support this feature out of the box, while Chinese versions (CN ROM) may require additional manipulation or region change.
SIM card also plays an important role, if you use a SIM card issued by a more advanced MTS. 5-7 Older cards may not support the necessary authentication protocols for the purpose of IP-Replacing a SIM card in the operator’s salons or through the My MTS app is free and takes a few minutes, but this is a critical step for activating modern communication services.
The service can be checked through a personal account or USSD-Make sure that the number is free of blocking services and that the Internet Assistant or similar services that redirect calls are disabled, and it is also worth checking whether the VoLTE service is activated, since often the inclusion of one function automatically activates the other in the bundle.
⚠️ Note: If you use a dual-sim phone, set up a priority Wi-Fi SIM card in the appropriate menu to avoid a situation where the call is going through a mobile network with a poor signal, ignoring Wi-Fi.
Step-by-step instructions for activating VoWiFi on Xiaomi
The process of enabling the feature on Xiaomi smartphones is quite linear, but the location of menu items may vary slightly depending on the version of the MIUI shell or HyperOS. First of all, make sure that the Wi-Fi module is on and the smartphone is connected to the network. Then go to the main settings of the device.
Find the section that handles SIM cards and mobile networks, and in newer versions of firmware, it's often called the "SIM card" section. SIM-Select the MTS SIM card you want to activate calls for. From the menu you open, look for Wi-Fi or Wi-Fi Calling. Switch the slider to active position. If the system requests confirmation or emergency address input (E911), For Russia, this field can be left empty or enter any format, since the service of emergency calls via Wi-Fi in Russia is not yet fully functioning.
☑️ Activation checklist
After turning on the status bar, next to the Wi-Fi indicator, a special phone icon with the Wi-Fi symbol or the words VoWiFi should appear. This signals that the smartphone is ready to route voice calls over the wireless network. If the icon does not appear immediately, try restarting the device or temporarily turning on flight mode, and then turn it off.
| Parameter | Meaning/Action | Status |
|---|---|---|
| Operator. | MTS | Supported |
| Technology | VoWiFi / Wi-Fi Calling | Activation required |
| Tariffing | Under fare conditions (minutes) | Free (from packages) |
| SIM Region | Any region of the Russian Federation | Works all over the country. |
Set up network preferences and operating modes
It's important to set your network preferences right for the technology to work. SIM-Select the preferred network type. It is recommended to set the mode Preferred LTE or 5G (This will ensure quick switching between Wi-Fi and the cellular network when leaving the coverage area of the wireless router without breaking.
Special attention should be paid to the energy saving settings. Xiaomi's aggressive energy saving algorithms can turn off background Wi-Fi processes to save charge, which will lead to the loss of the VoWiFi icon. Go to the Battery section and find settings for system services or the Phone application. Set up Unlimited mode.
Secret codes for diagnosis
There is also the option of setting network priority for calls. Some firmware versions have the option of: Prefer Wi-Fi or Prefer a mobile network. Choose the first option to make sure that with home Internet, the call will go through it, ensuring the best quality and savings of battery life, which is spent on finding a cell tower.
- 🔋 Turn off Super-Energy Saving mode when using VoWiFi.
- 📡 Make sure that the router settings do not block ports for SIP-protocol.
- 🔄 Regularly update the operator profile through settings SIM-map.
Solving Connection Problems and Errors
Despite the ease of setting up, users may encounter situations where the feature is not activated. One of the most common reasons is the lack of support from the IMS (IP Multimedia Subsystem) at the firmware level. If the menu does not contain the option "Calls over Wi-Fi", try changing the region of the device. Go to Settings → Advanced Settings → Region and select India or Indonesia. In these regions, VoWiFi is introduced long ago and often unlocked systemically.
The other problem is conflict. IP-addresses or settings DNS. Try in the settings of Wi-Fi on your smartphone to prescribe static DNS-servers such as those from Google (8.8.8.8) or Cloudflare (1.1.1.1) can help establish a more stable connection to MTS gateways if the home ISP has trouble routing.
⚠️ Note: When you change region, some system applications may change and advertising in standard programs will appear. After activating VoWiFi, the region can be returned back, but the function may stop working until the next reboot or reset network settings.
If a VoWiFi icon appears but calls don't pass, check the date and time on the device. Time mismatch may violate the encryption protocols needed to establish a secure connection with the operator, and it's also worth checking if the phone has a third-party antivirus or firewall that blocks network connections of system applications.
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Changing the region to India or Indonesia is the most effective way to unlock hidden VoWiFi menus on Xiaomi’s global firmware if the standard method doesn’t work.
Features of use in roaming and abroad
For travelers, MTS’s VoWiFi technology offers unique opportunities. While abroad, you can stay within the reach of the Russian network by connecting to your local Wi-Fi at a hotel or cafe. Incoming calls to your Russian number will be free, since you technically do not use a foreign operator’s network, but only a data channel.
Outbound calls are also charged according to your home fare, not the draconian international roaming rates, but it is important to check with the operator before traveling the terms of service in a particular country, as in some countries (e.g. UAE, India) VoIP and VoWiFi services may be blocked or restricted by law.
When using this feature overseas, it is strongly recommended to enable flight mode and then only activate Wi-Fi.This ensures that the phone does not accidentally register with the local cellular network, which can lead to a charge for incoming SMS or background data exchange if the Wi-Fi suddenly disappears.
- 🌍 Calls to Russian numbers from abroad via Wi-Fi are charged as home phone numbers.
- 📵 In flight mode with Wi-Fi enabled, the risk of accidental roaming is excluded.
- ⚠️ In some countries, the service may be blocked at the provider level.