Owners of modern Xiaomi smartphones often face a dilemma when using two SIM-Maps: Which one to choose as the primary data carrier, and not only does the connection stability depend on the right choice, but it also affects the speed of page loading, the quality of streaming, and the operation of navigation applications. Many users mistakenly believe that the physical location of the card in the tray strictly dictates its priority, but in the ecosystem. MIUI HyperOS is much more flexible and technologically advanced.
In fact, the question of “which slot is better to insert a sim with the Internet xiaomi” is technically based, but it concerns frequency support rather than mechanical socket. Modern devices support Dual SIM Dual Standby technology, which allows both numbers to stay online at the same time. However, a full-fledged high-speed 4G or 5G channel in most scenarios only works on one active card at a particular time, unless a special channel aggregation mode is enabled.
Understanding the modem architecture in your Xiaomi will help you avoid situations where the Internet “disappears” during a voice call or speed drops to a minimum in the area of uncertain reception. In this article, we will discuss in detail the physical and software aspects of choosing a slot, and also explain how to programmatically manage priorities for maximum efficiency.
Don’t ignore this issue, as improper configuration can lead to increased battery consumption and heat of the device.The modem will constantly search for the network or switch between communication standards if the settings are not optimized for your terms of use.
Physical features of slots and support for communication standards
In modern Xiaomi smartphones, starting with the Redmi Note series and ending with the flagships Mi and Xiaomi, manufacturers are striving to unify slots. SIM-The cards are technically identical and support the same communication standards, including: 4G LTE and 5G. This means that from a physical point of view, you can insert an internet fare card into any free slot without losing functionality.
However, in older models or budget devices entry-level sometimes there is a division where the first slot is combined or prioritized for high-speed networks.In such cases, the second slot could be limited to the 2G/3G standard. To make sure that your device is capable, you need the specification of the specific model on the official website or in the Service application and feedback.
How to check for frequency support in the engineering menu
To check the modem's real mode, you can use a hidden menu. Dial ##4636## in the call app. Go to Phone Information. There you will see the current network type (for example, the current type of network, LTE) You can force the preferred network type to switch for each SIM-cards separately if the software restriction allows this.> It is important to consider the physical wear and tear of the contacts. If you change the SIM cards often, the contacts in one of the slots may become oxidized or weakened. ⚠️ Warning: Always turn off your smartphone before removing the tray. While many modern phones support hot replacement, on Xiaomi devices this can cause a software failure of the communication module that requires a reboot to restore registration in the network. Programmatic management of priorities in MIUI The main advantage of Xiaomi smartphones is the deep integration of network management into the shell MIUI (The system allows you to flexibly configure which one SIM-The map is used for mobile traffic, no matter what physical slot it is installed in, which makes the issue of physical location less critical, shifting the focus to software settings, and to manage priorities, you need to go to the settings menu. The path usually looks like this: Settings → SIM-And you'll see here a list of the cards installed, and the system allows you to assign one of them as the primary data transfer card, and this card will provide Internet connectivity for all the applications of the system. ☑️ Setting priorities SIM-Map Open settings SIM-Select a card for mobile Internet Enable mode 4G for the selected card Check the Internet in the browser: 0 / 4 It is worth noting the function of “Smart switching” SIM-If activated, the phone can automatically switch the mobile Internet to a second SIM card if the main signal disappears or the traffic packet runs out (provided that the operator supports this function and the corresponding profiles are configured). However, for stable operation, it is recommended to keep this feature off if you are not sure about the tariffs of both operators. SIM-This feature is called Network Acceleration or Channel Aggregation». When it's turned on, the phone uses the resources of both operators, which can significantly increase speed, but also lead to faster battery discharge. One of the most common problems is the situation when during an incoming or outgoing voice call on one of the cards. SIM-The map interrupts the Internet to another, and that's because the modem handles voice traffic, and if the call goes through the standard voice channels, it's the way the modem handles voice traffic (2G/3G), modem can temporarily switch the antenna to support this standard, interrupting the antenna. LTE-The solution to this problem is VoLTE (Voice over) technology. LTE). It allows you to transmit voice as a data stream through the network. 4G, On Xiaomi smartphones, VoLTE support depends not only on the device itself, but also on the operator. Make sure the service is connected to your operator and activated in the settings: → SIM-maps and mobile networks → Choose. SIM → Use VoLTE. If you use one card exclusively for calls and the other for the Internet, it makes sense to assign a card with Internet to the main data and a card for calls to the default voice. In this case, even if VoLTE is not supported, the interruption of the Internet will be minimal, since the main data session will remain on its map, and the voice channel will take up the second one. There is also a nuance with roaming. If you are in another country, the settings may work differently. In some cases, the system may attempt to register a second card on the roaming partner's network, resulting in unexpected costs.Always check your data settings before you travel. The effect of slot selection on speed 4G and 5G The question of speed often becomes the deciding factor when choosing a slot. 4G/5G, However, in practice, there are cases where one of the slots (usually the first) has priority in the modem request queue, especially when the system is booted or when it is out of flight mode. For users who are critically important to maximum speed (for example, for mobile gaming or for mobile gaming). 4K-streaming, it is recommended to conduct a practical test. SIM-The card with the Internet in the first slot, measure the speed through the Speedtest service, then move to the second and repeat the measurement. 10-15% It's also important to consider Band support, which is the first slot on some processor models. 4G (Band 3, 7, 20 etc.). If your smartphone in a particular slot better catches the frequencies of your operator (which happens with the hardware features of the antenna group), then this slot will be preferred. td>Standard Slot 1 (Upper/Left) Slot 2 (Lower/Right) Support 5G Full (in most models) Full (depends on the model) Priority when loading High Average VoLTE stability Maximum Depends on firmware Roaming Work May require manual tuning. When using the mobile Internet modemor actively, Full (in most models) Full (depends on the power in the phone to reduces the power of the signal, which reduces the power of the first modem to maintain the power of the device, the power of the device, which reduces the power of the switch. ⚠️ Note: Do not use homemade adapters or cropped SIM-cards (micro-to-nano) without professional bezels.In Xiaomi smartphones with a thin body, this can lead to tray getting stuck or contacts damaged inside the slot, requiring expensive repairs. APN Often the problem of low speed lies not in the slot, but in the incorrect settings of the access point (APN). When installing a new SIM-Xiaomi cards usually automatically load settings, but sometimes this process is incorrect, especially for virtual operators or regional tariffs. To check or change the settings, go to Settings → SIM-maps and mobile networks → Choose. SIM → Access points (APN). Here you will see a list of profiles. Make sure you choose the right profile for your operator. If the internet is not available or it is slow, try to create a new access point manually by entering data from the operator’s official website. 💡Reset the settings. APN In the access point menu, click the menu button (three dots) and select Reset to default settings. This often solves connection problems after changing the tariff. For some operators, it is important to correctly specify the type of protocol APN. In the advanced settings of the access point parameter Type APN The default, supl or default,supl,dun must be included. The absence of the supl parameter can lead to problems with the work. GPS-b browsing when using mobile internet. If you use specific corporate rates or IoT SIMs, the automatic setup may not work. In this case, manual registration of parameters APN, Username and Password is a must-do step to activate a high-speed channel. Diagnostics of mobile Internet problems If you have determined which slot to insert a sim with the Internet Xiaomi, but the speed still does not meet the requirements, you need to conduct a diagnosis. The first step should always be to check the balance and traffic balance, and make sure that the device is on data transfer (slider in the notification curtain). The second step is to check the network mode. Make sure that the preferred network type is selected in the settings: 4G (LTE) or 5G. Sometimes after updating the firmware, the phone can be reset to mode «3G/2G», It also helps to have a short-term flight mode that forces the modem to re-register and find the nearest tower with the best signal. For advanced users, a useful tool will be the Cellular-Z application or the built-in network analyzer. They show the signal level in dBm. -70 before -90 dBm, if the signal is weaker -110 dBm, stable. 4G Don’t wait, and changing your phone or slot can help. 💡The most effective way to diagnose this is to compare speeds across different slots under the same conditions. 10-20 Mbps can be crucial for comfortable use. Remember that the speed is affected by the operator's tower load. In the evening, when the network load is maximum, the speed can drop regardless of the settings of your smartphone. 4G» through the engineering menu so that the phone does not try to go into overload 3G. Frequently asked questions (FAQ) Can I give away Wi-Fi with SIM-A card that is not selected for the Internet? By default, the Wi-Fi distribution (modem mode) uses the one that is used for the Internet. SIM-The card that is assigned to the primary data transfer, however, in some versions MIUI When you turn on the access point, the system can tell you which card to distribute the Internet from if both have traffic. SIM? This happens if VoLTE technology is not enabled or if the phone switched to the network during the call. 2G/3G. Make sure that VoLTE is activated in both settings. SIM-Does the security glass or cover affect the reception of the signal in different slots? Yes, metal cases or magnetic covers can shield the antennas. Because the antennas in the smartphone are arranged differently (often one at the top, the other at the bottom of the case), the case can more strongly jam the signal of one of the slots. How to reset all network settings on Xiaomi? Go to Settings → Connection and sharing → Resetting Wi-Fi, mobile networks and Bluetooth.This action will remove stored Wi-Fi passwords and Bluetooth settings, but often resolves issues with unstable internet.Whether all Xiaomi models support the two SIM-map 4G Most modern models (beginning with the 2018-2019 support the Dual regime 4G However, in very budget models or older devices, the second card can only work in mode. 2G/3G, When the first one is busy with voice calls or active internet.