The appearance of a new icon in the status bar of a smartphone often raises questions among users, especially if it appears suddenly or after a system update. On Xiaomi Redmi 9 Pro devices, many owners notice the VoLTE symbol, which signals the transition to a higher quality voice call standard. This technology allows you to conduct conversations over a 4G LTE network, providing crystal clear sound and the ability to use mobile Internet simultaneously.
Unlike the old standards, where the phone switched to 3G or 2G mode when it was incoming, Voice over LTE retains a high-speed connection, which means you can talk on the phone and download files at the same time, the navigator will not stop working, and the audio quality will be comparable to instant messengers. Understanding the principles of this feature will help you better manage battery resources and communication quality.
In this article, we will discuss in detail what this icon means, why it can burn gray or flash, and also consider the step-by-step algorithm for activating a function if it does not work automatically. Redmi 9 Pro has all the necessary technical characteristics to support modern communication standards, but the setting often depends on the operator and regional features of the firmware.
VoLTE technology: the principle of operation and advantages
VoLTE stands for Voice over Long Term Evolution, and the technology is about delivering voice traffic as a data stream over a packet-based LTE network, bypassing traditional switching channels. In the past, 4G networks were built solely for data, and voice was used for second and third generation (2G/3G), and now Redmi 9 Pro can transmit your voice as normal Internet traffic, which dramatically changes the quality of the connection.
The main advantage is the speed of connection, when dialing through Voice over LTE, the call connects almost instantly, while older networks take time to switch frequencies, and the sound range during this transfer is much wider, making the interlocutor’s speech more natural and legible, removing the effect of the “metal” voice.
- 📶 High speed connection - the call comes for 1-2 seconds.
- 🎙️ HD-sound quality – wide frequency range of voice transmission.
- 🌐 Simultaneous work 4G — The internet doesn’t fall during a conversation.
- 🔋 Energy efficiency – the communication module operates in the same mode, does not jump between standards.
It is important to note that the technology needs support from your mobile operator to work properly. If the SIM card or tariff plan does not support this standard, the phone may display an icon, but the connection will occur using old protocols. Xiaomi owners often face a situation where the function is formally enabled but is not actually used due to restrictions on the service provider.
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Check the relevance of your operator’s APN settings, as incorrect settings can block VoLTE even if you have support for the tariff.
Why does the VoLTE icon burn gray or flash
Sometimes users notice that the VoLTE indicator on the Redmi 9 Pro screen turns gray or begins to disappear periodically, a condition that indicates that the smartphone software is ready to work in the new standard, but the current network conditions do not allow you to activate voice transmission over LTE. Most often the problem lies in network coverage or temporary failures at the operator's base station.
The gray color of the icon can also indicate that the phone is in the zone of insecure reception of the 4G signal. In such cases, the device automatically switches to 3G for stability, since Voice over LTE requires a stable signal of a certain power. If you are on the move, the constant change of cell towers can also cause a temporary shutdown of the function.
⚠️ Warning: If the icon is always on fire, even in the city center, check if the “Only” mode is activated. 4G» In the engineering menu, as this may block the possibility of returning to the 2G/3G for voice calls in the absence of LTE.
Another reason for the instability can be the use of two SIM cards. On many Xiaomi models, including the Redmi 9 Pro, the technology fully works on only one SIM card selected as the main one for data transfer. The second card at this point can work in 2G/3G standby mode, and the icon on it may not display or burn dull.
How to enable VoLTE on Xiaomi Redmi 9 Pro
Activation of the feature on modern Xiaomi smartphones usually occurs automatically when you install a compatible SIM card. However, if the icon does not appear, you need to check the settings manually. To do this, open the settings menu and go to the section responsible for the parameters of mobile networks. The path may vary slightly depending on the version of the MIUI shell.
You need to find a 4G connection. Often it's hidden in the network type selection sub-menu. Make sure you select "Preferred to be 4G (LTE)" mode. Without this condition, Voice over LTE activation is technically impossible, as the phone won't attempt to log into the fourth generation network for voice calls.
☑️ Checking the communication settings
If there is no standard switch on the menu, it may mean that the operator has not certified the feature for this model in your region, or the smartphone firmware does not contain the corresponding configuration files. In some cases, resetting network settings helps, which will return all parameters to factory values and force the operator to request the current configurations.
- 📱 Go to Settings. → SIM-maps and mobile networks.
- 🔍 Select an active SIM card from the list.
- ⚙️ Find the switch to Use VoLTE and turn it on.
- 🔄 If no point, enter the code ##86583## to unlock hidden settings (does not work on all firmware).
Configure through the engineering menu and codes
For advanced users who are confident in the support of the technology by their operator, but can not find the switch in the interface, there is access to the engineering menu. This is a hidden part of the Android system that allows you to manage low-level modem parameters. On the Redmi 9 Pro, it can be accessed through a standard dialer.
Enter the code ##4636## in the Phone app. The Check menu will open, where you select Phone Information. Here you can find the item "Enable VoLTE Provisioned." Checking the box against this option forcibly tells the network that your device is ready to work with voice over LTE.
Sequence of action:
1. Open the Phone app.
2.Type ##4636##
3. Select "Phone Information 1" (for the first SIM).
4. Find the "VoLTE Provisioned" switch.
5. Activate it (if switched off).Be careful when changing the settings in the engineering menu. Incorrect configuration can cause the phone to stop seeing the network at all or only work in 2G mode. If after the changes, network signals disappear, just restart the device or reset the network settings in the regular menu.
What if the code doesn't work?
Table: Comparison of voice transmission standards
To better understand the difference between technologies, let’s take a look at a comparison table that will help us understand why the transition to VoLTE is an important step for the owners of modern smartphones like the Xiaomi Redmi 9 Pro.
| Parameter | 2G / 3G (CS) | VoLTE (4G LTE) | VoWiFi |
|---|---|---|---|
| Sound quality | Low/Mediocre | High (HD) | High (HD) |
| Connection speed | 5-10 seconds | 1-2 seconds | 1-2 seconds |
| The Internet | Only 2G/3G | 4G LTE (high speed) | Wi-Fi |
| Battery consumption | High (mode switching) | Low (stable mode) | Depends on Wi-Fi. |
As you can see from the table, the advantage of Voice over LTE is obvious not only in audio quality, but also in power consumption. The smartphone does not need to constantly “jump” between communication standards, which positively affects the battery life of the Redmi 9 Pro. VoWiFi mode, in turn, is a great addition to areas of poor cellular reception, but requires Wi-Fi.
Possible problems and ways to solve them
Despite the technology, users can experience various failures. Most often the problem is that there is a VoLTE icon, but calls still reset the network in 3G. This can be caused by an outdated version of the basic operator data on the SIM card, in which case it is recommended to remove the SIM card, wipe the contacts and paste back, waiting for full registration on the network.
Another common situation is a conflict of software settings after the MIUI update. New versions of shells can reset user preferences or change the logic of the communication modules. If the function stopped working after the update, try resetting the network settings. This action will not delete your personal data, photos or contacts, but will return Bluetooth, Wi-Fi and mobile settings to their original state.
⚠️ Note: Before resetting your network settings, make sure you remember the Wi-Fi passwords as they will be deleted from your device’s memory.
It’s also worth checking whether power saving mode is on for specific applications or system services.Aggressive battery saving on Xiaomi sometimes limits background activity of communication services, which can prevent you from correctly registering on the Voice over LTE network.Add phone and SIM card services to the power saving mode exceptions.
- 🔋 Check the energy saving mode - turn off the "Ultra" mode.
- 📡 Make sure that the network type setting selects “Preferred” LTE».
- 🔄 Perform a reset of network settings: Settings → Connection and sharing → Reset Wi-Fi, mobile networks and Bluetooth.
- 📞 Contact the operator to check the activation of the service on the tariff.
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In most cases, the problem is solved by simply restarting the device or re-registering the network, so don’t rush to do a full phone reset.
The effect of VoLTE on battery consumption and speed
There is a myth that 4G is a fast-burning device, but if you're in a strong reception zone, using Voice over LTE on the Redmi 9 Pro even saves you a lot of power. The phone doesn't waste energy on constantly searching and switching between 2G, 3G and 4G towers. The communication module is stable, which is a more energy-efficient scenario.
Network response speed also plays a role in the overall sense of smartphone performance. Because the voice channel does not take up resources to switch, background applications such as navigation or mail continue to work at full speed, which is especially important for those who use a smartphone for work on the road or taxis, where simultaneous communication and access to data are critical.
If the 4G signal is very weak, the phone will constantly amplify the signal, which can indeed lead to increased heating and charge consumption, in such situations, it is wiser to temporarily switch to 3G only or 2G/3G mode to save battery power, sacrificing Internet speed.