Owners of Xiaomi and Redmi smartphones often notice a mysterious “HD” icon in the status bar next to the network indicator. This symbol appears during a conversation or in standby mode, raising questions from users who are used to the standard designations 3G or 4G. The appearance of this icon is not a system error or a sign of a virus, but indicates the activation of modern voice technology.
HD stands for High Definition, which literally means "high definition." In the mobile world, this refers to VoLTE (Voice over LTE) as a feature that allows voice traffic to be transmitted over fourth-generation networks, providing crystal clear sound and instantaneous subscriber connections.
Many users do not even suspect that their device supports this option until the operator connects the service or updates the network settings. Understanding the principle of VoLTE based on Qualcomm or MediaTek processors will help you not only remove unnecessary icons, but also significantly improve the quality of communication in the conditions of poor signal reception.
VoLTE technology and the principle of its operation on smartphones
Traditional voice calls on networks 2G and 3G They use circuit switching, where part of the spectrum is allocated exclusively to the voice. LTE The main emphasis was placed on high-speed Internet, and voice for a long time was transmitted through the fall of the network to the Internet. 3G (technology CSFB). VoLTE solves this problem by packing the voice into the IP-Packages and transferring it in parallel with Internet traffic.
When you see an HD icon on your Redmi Note or Xiaomi Mi screen, it means that the phone has established a connection to the carrier base station that supports batch voice, which allows you to talk and use the Internet simultaneously without switching between network modes.
The sound quality of HD Voice is far superior to standard audio, with a broadband audio codec that transmits frequencies between 50 Hz and 7000 Hz, whereas a regular call is limited to a narrow range, making speech more natural, removing metallic hues, and allowing for better word discernment in noisy environments.
- 📶 Instant connection: dialing the number for 1-2 seconds instead of the usual 5-10 horn-stop.
- 🗣️ Improved legibility: the interlocutor is heard more clearly, even if he is in a moving vehicle or on the street.
- 🌐 Simultaneous operation: the ability to play online games or download files during a conversation without losing speed 4G.
⚠️ Note: For the function to work, it is necessary that your operator’s tariff plan supports voice transmission through the service. LTE. In some regions, this service may be paid or require a separate connection through the operator’s application.
Why does the HD icon appear in the status bar?
The appearance of the HD icon in the status bar of the Xiaomi device signals that the phone has successfully registered in the IMS (IP Multimedia Subsystem) network. This is a software indicator that is controlled by the MIUI or HyperOS firmware and displays the current status of the service registration.
Sometimes users notice that the icon pops up and goes away, and this may be due to moving between coverage areas, and if you step out of LTE, the phone automatically switches to 3G or 2G to ensure continuity, and the HD icon goes missing.
It is also worth considering that some operators require the activation of services through the USSD-Without this operator-side activation, even a phone that supports technology will not display an icon and use high-definition mode.
It is important to distinguish between VoLTE and Wi-Fi Calling. Although both provide voice over IP, the HD icon is more often associated with LTE cellular networks. If you are in an area without cellular coverage but connected to Wi-Fi, a separate phone icon with the Wi-Fi symbol can be displayed.
Instructions for enabling and configuring VoLTE on Xiaomi
In most modern Xiaomi and Redmi models, the function is enabled by default if it is supported by the operator. SIM-cards or custom firmware, settings can be hidden or knocked down.
To check and activate, go to the settings menu. The path usually looks like this: → SIM-Select the SIM card you want and find the switch Use VoLTE. If the switch is active, the function works.
☑️ Testing of VoLTE Readiness
If you don't see the switch in the standard menu, it may be hidden in the engineering menu or it needs activation through codes. Try entering ##86583## in the dialer code. The message that appears should say "VoLTE carrier check was DISABLED", which means removing the software restriction.
For models with Qualcomm processors, sometimes it helps to enter the code ##4636##. In the testing menu that opens, select Phone Information and find "VoLTE provisioned." Make sure the switch is on. Once you reboot, the HD icon should appear.
| Model Xiaomi/Redmi | Location of settings | Features |
|---|---|---|
| Redmi Note 8/9/10 | Settings → SIM-map | An unlock code is often required. |
| Xiaomi Mi 11/12/13 | Settings → Mobile network | Built-in by default |
| Poco F3/F4/F5 | Settings → SIM-map | Depends on the MIUI version. |
| Redmi 9/10/11 | Settings → SIM-map | A patch may be required. |
⚠️ Attention: When using two SIM-VoLTE mode can work simultaneously on only one of them or require the activation of the "Dual" mode. SIM 4G», Increases battery consumption.
The Impact of HD Calls on Battery Charge and Internet Speed
There's a myth that running in HD quickly puts the battery down. In fact, VoLTE is more energy efficient than constantly switching between 4G and 3G during a call. The phone doesn't need to waste energy finding a different standard network and rebuilding the radio module.
However, if the signal LTE weak, the phone has to increase the transmitter power to maintain a stable IP-In these conditions, the icon HD It can indirectly indicate increased energy consumption. In areas of uncertain reception, it is better to switch to "Only" mode. 3G» via the engineering menu ##4636##.
As for internet speed, VoLTE has little or no effect on ping or download speed in the background. Channels are logically separated, and voice traffic takes priority, but doesn't block other data. You can safely watch 4K video while you're talking.
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If you notice that the battery drains faster after the HD icon appears, try updating the firmware to the latest version of MIUI. Optimizing the modem often fixes similar problems.
It is worth noting that on older Xiaomi models with low RAM, real-time processing of voice packets could create a small load on the processor. On modern devices of the Redmi Note series and Xiaomi flagships, this factor is completely excluded.
Problem Solving: There is an icon, but calls don’t work
There are situations when the HD icon is on, but when you try to call the connection is broken or the voice is not transmitted, most often the problem lies in the incompatibility of the frequencies of the operator and the phone or incorrect settings of the APN access point.
The first thing you need to do is check the access point settings. Go to Settings. → SIM-maps and mobile networks → Yours. SIM → Access points (APN). Make sure that your operator’s access point is selected, and APN the default,supl,mms or similar value recommended by the operator.
The second step is resetting your network settings, which won't delete your personal data, but will return your network settings to factory settings. To do this, go to Settings → Connection and Sharing → Reset Wi-Fi, mobile networks and Bluetooth.
- 🔄 Restart the device after the change SIM-cards so that the phone is re-registered on the network IMS.
- 📱 Make sure you're on SIM-mapping PIN-code that can block automatic registration of services.
- 🏢 Check if your carrier has blocked the VoLTE service for corporate rates.
Hidden codes for diagnosis
If nothing helps, your phone may not be certified to work with the operator's VoLTE in your region, in which case the HD icon may be displayed incorrectly, but the connection will be reset. Contact the carrier's support for your model's compatibility.
Comparison of Communication Quality: VoLTE vs. Common Calls
The difference between a normal call and a call in HD is particularly noticeable when talking in noisy places or when a bad signal is bad. A regular call compresses the audio to a minimum to fit it into a narrow channel, making the voices sound deaf and indistinct.
VoLTE technology uses codecs AMR-WB (Adaptive Multi-Rate Wideband, which transmit sound in a format close to the FM-This allows you to hear the breathing of the interlocutor, intonation and rustling of clothes, which makes the conversation more lively and emotional.
In addition, the connection time is reduced by 3-4 times, in conventional networks, the phone must fall from 4G to 3G, set a voice channel and then start tone-up, and in HD mode this stage is skipped, since the channel is ready for data transfer.
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The main advantage of HD calls is not only sound quality, but also connection stability, and the probability of resetting a call when switching between towers in VoLTE mode is much lower.
For business conversations or important conversations, having an HD icon is a guarantee that you will hear all the details, but it is worth remembering that the interlocutor must also have support for this technology, otherwise the call will be translated into a normal format.