Modern smartphones, including the popular Xiaomi Redmi Note 9, are equipped with a multitude of features that often remain hidden from the average user. One such feature is VoWiFi technology, which allows voice calls over a wireless network, bypassing cellular coverage limitations. This feature becomes critical in buildings with thick walls, basements, or remote areas where base station signals are virtually nonexistent but internet access is available.
Enabling this option on devices running MIUI may seem like a non-obvious task, as the settings menu often changes depending on the firmware version and region. Owners Redmi Note 9 Sometimes you encounter a situation where the switch is simply missing or not working properly. Understanding the technical nuances and following the correct sequence of actions will help you enjoy reliable, high-quality voice communication anywhere.
In this article, we'll cover every setup step in detail, from checking operator support to making extensive system changes via the engineering menu. You'll learn how to correctly interpret on-screen indicators and what to do if standard methods fail. The VoWiFi feature on Redmi Note 9 only works if your mobile operator officially supports this technology and has activated it on your SIM card.
Checking operator and tariff plan compatibility
Before delving into your smartphone's settings, make sure your mobile operator offers Voice over Wi-Fi. This technology requires network support, and even the most modern phone won't be able to use it without permission from your provider. In Russia and the CIS, major operators are gradually rolling out this feature, but it's not available on all plans or in all regions.
Users often forget that VoWiFi requires a phone number to be linked to a specific service region. If you're roaming or have changed your address without notifying your operator, the service may be blocked automatically. Check your account or contact technical support to confirm the service status for your specific number.
It's also important to remember that the SIM card must be relatively new. Older Mini-SIM cards or earlier versions of Micro-SIM may not support the necessary encryption and data transfer protocols for internet voice calls. In this case, you'll need to have the card replaced at a mobile phone store, which usually takes a few minutes.
⚠️ Attention: VoWiFi service terms are subject to change by the operator. Before setting up, make sure your plan's minutes or data allowance hasn't been exhausted, as calls consume data from the main package or a special minute pool.
Basic activation via the standard settings menu
On most devices Xiaomi Redmi Note 9 With the latest version of MIUI, the function switch is located in the standard mobile network settings section. The path to it may vary slightly depending on the operating system version. Android, but the interface logic remains the same. To get started, open the "Settings" app and find the section for SIM cards and mobile networks.
In the menu, select the active SIM card you plan to use for calls. Settings may vary for each card, so it's important to check the settings for both slots if you're using two numbers. Look for the option labeled "Wi-Fi Calling" and toggle the slider to on.
If the switch is found and enabled, but the handset icon with the Wi-Fi symbol doesn't appear in the status bar, try restarting the device. Sometimes the system needs time to register with the carrier's network via a new protocol. Make sure the wireless module is enabled and the phone is connected to a stable network.
☑️ Checking Basic Activation
In some cases, the system may request that you confirm your address for emergency services. This is a standard safety procedure, as the operator needs to know your geolocation when calling emergency services online. Enter your current address, even if you're at home, to avoid problems in a critical situation.
Hidden settings and the Xiaomi engineering menu
If the standard switch is missing, it doesn't always mean the phone doesn't support the technology. In the shell MIUI There's a hidden engineering menu that allows you to control the radio module's in-depth parameters. It's accessed through the standard "Phone" app by entering a special character combination.
Enter the code ##869434## or ##869434## (The code may vary depending on the regional firmware version.) If the code is correct, a notification will appear on the screen that says "Wi-Fi Calling carrier check was disabled" or a similar message confirming debug mode has been entered. After this, a previously hidden option may appear in the regular settings menu.
An alternative way to access hidden features is to use an app MIUI Hidden Settings or similar snails available in repositories. However, using third-party software carries risks, so it's best to stick with the system's built-in capabilities. Be careful when changing parameters in the engineering menu, as incorrect settings can lead to signal loss.
What to do if the code doesn't work?
If entering the code doesn't work, your firmware version may block access to the engineering menu for regular users. In this case, enter the code ##4636##, go to "About phone" and look for settings there, although the chance of success is lower.
It's worth noting that after a system update, hidden settings may be reset to factory defaults. If the feature stops working after the update, you'll have to repeat the activation process using codes. This is a security feature. Xiaomi, which aims to standardize user experience.
Comparison of VoLTE and VoWiFi technologies
Users often confuse the two advanced voice transmission technologies, as both are aimed at improving communication quality. Understanding the differences between VoLTE (Voice over LTE) and VoWiFi (Voice over Wi-Fi) will help you set up your smartphone correctly and save battery life. Below is a table showing the key differences.
| Characteristic | VoLTE (4G) | VoWiFi (Wi-Fi) |
|---|---|---|
| Basis of transmission | 4G/LTE cell towers | Wi-Fi router access points |
| Dependence on coverage | Cellular network signal required | All you need is internet |
| Sound quality | HD sound, high quality | Depends on the internet speed |
| Traffic consumption | Usually not charged | Usually not charged |
The main advantage of VoWiFi is the ability to stay connected in places where cellular coverage simply doesn't work. Office basements, thick-walled country houses, or remote summer cottages are all scenarios where this technology is indispensable. At the same time, VoLTE provides improved mobility when moving around the city.
Modern smartphones, including Redmi Note 9, can automatically switch between these modes. If you leave Wi-Fi range during a call, the phone will attempt to transfer the call to an LTE network without losing the connection if the carrier supports the eSRVCC feature. However, this transition isn't always seamless and depends on network settings.
Network priority and connection type selection
In the mobile network settings Xiaomi There is often an option to select your preferred network type. For Wi-Fi calling to work correctly, it is important that the correct settings are selected in this menu. Go to Settings → SIM cards and mobile networks → Preferred network type.
It is recommended to select the "LTE Preference" or "5G/LTE/3G/2G (Auto)" mode. If the "3G/2G Only" mode is selected, the phone will not be able to use modern voice protocols, and the VoWiFi feature may not activate or work correctly. The system must be able to freely switch between communication standards.
There's also a priority setting for calls themselves. The "Wi-Fi Calling" menu may have a "Network Preference" option. Here, you can choose whether your phone prioritizes Wi-Fi when available or switches to the mobile network if the 4G signal is strong enough. To save data and battery life indoors, it's best to prioritize Wi-Fi.
- 📶 Prefer Wi-Fi: The phone will try to make all calls over the wireless network, even if there is a strong 4G connection.
- 📶 Prefer mobile network: Calls will be made via Wi-Fi only if there is no cellular signal.
- 📶 Never use: Completely disable the function, even if it is activated in the system.
Properly setting up priority is especially important for users with unlimited mobile data but limited home data, or vice versa. Selecting the optimal scenario will help avoid unexpected charges and ensure the best connection quality under specific operating conditions.
Diagnosing and troubleshooting
Even with proper configuration, situations may arise where the feature doesn't work. One symptom is a blinking Wi-Fi handset icon or its complete absence after being turned on. Often, the problem lies in an IP address conflict or in the router's DNS settings. Try forgetting the Wi-Fi network in your phone's settings and reconnecting using the password.
Another common cause is the use of VPN services or ad-blocking apps that modify network packets. VoWiFi protocols are sensitive to packet header modifications and may be blocked by the carrier for security reasons. To check, disable all VPN connections and try making a test call.
If all else fails, reset your network settings. This won't delete your personal files, photos, or contacts, but it will return all network settings (Wi-Fi, Bluetooth, and mobile data) to factory defaults. Here's how to reset: Settings → Connection and sharing → Reset Wi-Fi, mobile networks, and Bluetooth.
⚠️ Attention: After resetting your network settings, you'll need to re-enter passwords for all saved Wi-Fi networks and Bluetooth devices. Make sure you remember the passwords for important access points before performing this operation.
In rare cases, the problem may be related to a specific firmware version. MIUIIf you're using a global version on a Chinese device, or vice versa, some features may be disabled by software. In such cases, users often wait for official updates or resort to custom solutions, but this requires a high level of expertise.
Impact of power saving mode on communication
shell MIUI is known for its aggressive power optimization system. In "Power Saver" or "Ultra Power Saver" mode, the system may limit background communication module activity to extend battery life. This may result in the phone not registering on a VoWiFi network while the screen is off.
To avoid connection interruptions, add the Phone app and system services to the power saving exceptions list. Go to battery settings, find the list of apps, and set the background activity limit for system communication components to "No restrictions." This will allow the module to constantly maintain a connection to the carrier's server.
It's also worth checking your sleep mode settings. If your phone goes into deep sleep too quickly, it may lose Wi-Fi network registration for calls. Increase the sleep time or disable adaptive brightness and other features that may indirectly affect background radio operation.
Frequently Asked Questions (FAQ)
Will I be charged for minutes when talking over Wi-Fi?
In most cases, you'll be charged according to your primary plan, as if you were calling over a cellular network. Minutes are deducted from your package, not your data plan. However, if you're roaming internationally, the terms may vary, and a Wi-Fi call may be considered incoming or outgoing from your home network, which is beneficial. Always check with your carrier for details.
Why does the VoWiFi icon appear but calls don't go through?
This could indicate a problem with your internet connection (high ping or packet loss), blocked ports by your internet service provider, or a temporary outage on your carrier's end. Also, check if international calling is blocked if you're trying to make international calls even from home.
Can I use VoWiFi if my SIM card is blocked by my carrier?
No. To register with the VoWiFi network, your phone still needs to authenticate with the operator's network via the SIM card. If the SIM card is blocked, not activated, or the phone doesn't see the network (no operator icons), the feature won't work, even if Wi-Fi is available.
Does this feature work on two SIM cards at the same time?
Technically Redmi Note 9 Supports two active SIM cards, but voice calls are only made through one of them at a time. You can set up VoWiFi for both cards, but the feature will only be active for the one making the call or the one selected by default for voice calls.