Xiaomi smartphone owners often face the need to optimize communication quality, especially in dense urban areas or remote areas. Voice over LTE (VoLTE) has become the standard for modern communications, allowing voice calls to be transmitted over fourth-generation networks. On the Redmi Note 9, this feature is implemented hardwarely, but the software limitations of operators or firmware sometimes hide the possibility of using it.
Activating this mode not only provides crystal clear sound, but also allows you to use mobile Internet at high speed during a conversation. Without this technology, the phone often switches to 3G or even 2G mode when calling or out, which interrupts page loading. In this article, we will discuss in detail how to make your Redmi Note 9 work in HD Voice mode.
The principle of Voice over LTE technology
Voice over LTE is fundamentally changing the way we use voice, where in the old standards voice was transmitted over dedicated voice channels (CS), LTE networks use packet data (PS), which means that your voice is digitized and transmitted as a data stream, similar to the message in the messenger, but with the highest priority.
The main advantage for Xiaomi is the speed of the connection. dial and horns appear almost instantly, without delay.In addition, the AMR-WB (Adaptive Multi-Rate Wideband) codec used in this technology transmits frequencies in the range of up to 7000 Hz, whereas conventional cellular communication is limited to 3400 Hz. This makes the voice of the interlocutor more natural and legible.
⚠️ Note: The technology must be used to SIM-The map was replaced with a format USIM (usually issued by the operator when moving to 4G tariffs) and the tariff plan supported the transmission of voice through LTE.
It is important to understand that the Redmi Note 9 supports the two. SIM-map-mode 4G, But VoLTE can only be active on one of them at a time if the operator does not support Dual VoLTE technology. 3G.
Support check by the operator and the region
Before looking for hidden settings in a smartphone menu, make sure your mobile operator provides the service in your area: Major carriers such as MTS, Beeline, MegaFon and Tele2 are actively implementing this technology, but coverage can vary in different areas.
It is often the case that on the global version of MIUI firmware, the list of supported carriers is limited. If you do not see the VoLTE or HD icon in the status bar after inclusion, this may mean that your operator is not on the Xiaomi whitelist for your region, in which case manual activation through the engineering menu is required.
You can check the connection status by sending USSD-request or contact the operator's personal account, the service may be free, but require activation (APN) Your operator has no restrictions blocking the transmission IMS-traffic.
Standard activation via MIUI settings
In most cases, the standard shell interface is enough to enable the feature on the Redmi Note 9. The path to settings may vary slightly depending on the Android and MIUI version, but the logic remains the same.
Go to the Settings menu first. Find the section. SIM-Select the SIM card you want to activate the high-speed voice for. There must be a VoLTE switch. If you have one, just activate it.
- 📱 Make sure that the "Network Type" is selected preferably. 4G or LTE.
- 📶 Check if the indicator is on. 4G/LTE pre-call.
- 🔊 After activation, the icon HD VoLTE should appear near the signal level.
If the switch is missing or inactive (shaded), it means that the system has blocked it due to the absence of an operator profile in the phone’s database, and in this situation, you need to move to deeper methods of setting up through the engineering menu.
Activation through the Xiaomi Engineering Menu
The unsupported operators use a hidden engineering menu to force the feature to turn on. On the Redmi Note 9 with a Snapdragon processor, it is accessed via a standard dialer. Be careful when changing parameters, as this affects the operation of the radio module.
Dial the code ##86583##. If you did everything right, the message "VoLTE Carrier check was disabled" should appear on the screen. This means that the operator check is disabled, and the switch in the settings should become active. If the message "enabled" appears, then the check is already disabled or the code does not work (try to enter the code again).
☑️ Verification of VoLTE activation
After entering the code, return to Settings → SIM-Now you're going to have an active switchboard, if you don't have one, try rebooting the device. Sometimes you need to activate the mode further using code ##4636##, selecting "Phone Information" and turning on "VoLTE Provisioned".
⚠️ Warning: Do not change other options in the engineering menu unless you are sure of their purpose.Resetting the radio module settings can lead to temporary loss of the network.
Solving the problems with the disappearance of the VoLTE icon
Even after successful setup, Xiaomi users may notice that the VoLTE icon periodically disappears, often because the phone switches to a tower that does not support the technology, or an IMS session occurs.
Try clearing the Phone and System UI app data. Go to Settings → Applications → All apps. Find the Phone app, click Clear → Clear everything. Repeat the same for Settings. This won't delete your contacts, but resets the call settings.
| Problem. | Possible cause | Method of decision |
|---|---|---|
| The HD badge doesn't burn. | Operator does not support | Check fare and coverage |
| The internet falls when you call | VoLTE not activated | Enable through the engineering menu |
| I can't hear the interviewer. | Codec conflict | Rebooting or resetting network settings |
| No VoLTE menu | Firmware locking | Use the code ##86583## |
Another reason could be the use of a low-quality protective glass that overlies the proximity sensor or antenna, although on the Redmi Note 9, the antennas are located around the perimeter of the housing.
Why is VoLTE draining the battery?
Comparison of communication quality: VoLTE vs. 3G
To understand the real benefits of the technology, it's worth comparing it to classic calls: 3G networks (UMTS) have a narrow bandwidth of sound quality, which creates a "phone" voice effect, and when you switch to HD Voice, you'll notice no noise and a wider range.
Also, the important aspect is the simultaneous operation of data. In a 3G network, when an incoming call is made, the Internet connection often breaks or slows down greatly (EDGE). With VoLTE enabled on the Redmi Note 9, you can play online games, watch 4K videos or navigate around the map without interrupting the connection during a conversation.
- 🚀 Connection speed: 1-2 second-on 5-7 second-in-second 3G.
- 🎙️ Sound quality: Broadband (HD) narrow-band.
- 🌐 Internet during the call: Operating at full speed LTE.
⚠️ Note: When roaming abroad, VoLTE may not be available or charged as internet traffic, even if calls are free.
Frequently Asked Questions (FAQ)
Does the inclusion of VoLTE affect traffic consumption?
Can I turn on VoLTE on custom firmware?
Why does the VoLTE icon burn, but calls go through 3G?
Do I need to reflash my phone to run VoLTE?
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If after all the manipulations VoLTE did not work, try to extract SIM-I can use a map, wipe the contacts, and put them in another slot, and sometimes the problem is that the contacts of the card are oxidized.
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The VoLTE technology on the Xiaomi Redmi Note 9 significantly improves the quality of communication and allows you to use the Internet during a conversation, but requires the correct activation through hidden menus, unless the operator is determined automatically.