Many users of modern smartphones, when studying mobile network settings, are faced with an incomprehensible parameter that has a name LTE2. This option is often hidden in deep menus or becomes available only after activating developer mode, causing a lot of questions among owners of devices based on Android. Essentially, this term refers to the ability of a second SIM card to operate in high-speed 4G mode, which radically changes the experience of using two numbers on one device.
Previously, standard practice was to use one card in 4G/LTE mode for Internet and calls, while the second card was forced to switch to 2G or 3G only for receiving calls and SMS. This created inconvenience: if you were talking on the main SIM card, the Internet on the second one completely disappeared, and the data transfer speed on the backup line was extremely low. The advent of technology DSDS (Dual SIM Dual Standby) with support for two LTE channels solved this problem, allowing both cards to remain in high-speed standby mode.
In this material we will analyze in detail the technical features of this function, how to activate it on various firmware and hidden pitfalls that manufacturers are silent about. You will learn why your phone may not see this setting and how to correctly distribute roles between SIM cards for maximum efficiency.
The technical essence of the Dual SIM Dual LTE technology
The function LTE2 is not a marketing gimmick, but represents a serious hardware and software achievement in the field of smartphone radio modules. To implement the full operation of two SIM cards in a fourth-generation network, the device requires two independent transceivers or one advanced modem that can instantly switch between frequencies without breaking the connection. In older models Samsung, Xiaomi or Huawei the DSDS scheme was implemented, where only one data transmission channel was active.
When you activate the mode LTE2, the operating system Android instructs the modem to keep the second SIM card registered in the network 4G. This means that even if the first card is busy with a voice call via VoLTE, the second one remains available for incoming calls and fast Internet. However, it is worth understanding that it is still impossible to physically transmit data simultaneously over two 4G channels on most civilian smartphones due to limitations of the antenna system and power consumption.
⚠️ Attention: Activating the LTE2 mode on both cards at the same time can lead to a significant increase in power consumption and heating of the device case, since the modem is forced to constantly scan and hold two high-frequency signals.
The implementation of this technology directly depends on the version of the operator's base station and support for the standard VoLTE (Voice over LTE). Without voice over the Internet technology, the second SIM card will still be forced to switch to 3G or 2G mode to establish a connection when there is an incoming call, which will temporarily disconnect it from the high-speed Internet. Therefore, the presence of a checkmark LTE in the status bar does not always guarantee stable operation of two lines without switching.
If you travel frequently, check the roaming agreements of operators: not all foreign networks support the simultaneous operation of two SIMs in 4G mode, even if your phone can do it.
How to find and enable the LTE2 setting in the menu smartphone
By default, manufacturers often hide the ability to select the network type for the second SIM card to avoid confusion among users. To access advanced settings, you may need to go to the hidden engineering menu or activate developer mode. On devices with a chipset MediaTek access is often carried out through the service code, while on processors Qualcomm Snapdragon the settings can be hidden in the standard SIM card menu.
First, check the standard path: go to Settings → Connections → SIM card manager. Here, select the second SIM card and find the “Preferred network type” item. If there is an option 4G/3G/2G (auto) or just LTEin the list, then your phone already supports the second card in high-speed mode. If only 3G is available, you will need to use special codes.
Try entering the following service code in the “Phone” application: ##4636##. This will open the testing menu, where you need to select “Phone Information 2” (for the second SIM card). In the "Configure preferred network type" drop-down list, select the value containing LTE. Be careful: the wrong choice may temporarily disrupt communication.
☑️ Checking readiness to enable LTE2
It is important to note that after changing the settings in the engineering menu, the interface may not change visually, but the icon 4G should appear next to the icon of the second SIM card in the notification shade. If the icon does not appear, try switching airplane mode for 10 seconds to force re-registration on the network.
The impact of dual SIM mode on Internet speed and battery
Using the configuration LTE + LTE imposes certain restrictions on the channel capacity. Although both cards are registered to the 4G network, the physical radio can often only run at full speed with one of them at a time. When you actively download a file through the first SIM card, the second goes into standby mode with reduced resource consumption, but retains the ability to quickly switch.
Battery drain is a significant factor. Constantly searching for a signal and maintaining two high-speed connections requires more energy than the classic circuit 4G + 2G. Users note that in areas of poor reception, battery life may be reduced by 15-20%. This is due to the fact that the phone has to amplify the transmitter signal more often to maintain a stable connection on both channels.
| Operating mode | Internet speed (SIM 1) | Internet speed (SIM 2) | Impact on battery |
|---|---|---|---|
| 4G + 2G (Classic) | High (up to 100 Mbit/s) | Low (up to 0.3 Mbit/s) | Standard |
| 4G + 4G (LTE2) | High (up to 100 Mbit/s) | High (when switching) | Increased |
| Only 3G + 3G | Medium (up to 20 Mbit/s) | Average (up to 20 Mbit/s) | Moderate |
| 5G + 4G (New flagships) | Ultra-high | High | Critical high |
However, for many use cases, the speed benefit outweighs the energy cost. For example, if you use a second SIM card as a backup communication channel for instant messengers or navigation, the ability to instantly access the Internet through it without manually switching in the settings is critical.
Compatibility problems with telecom operators and VoLTE
Even if your smartphone technically supports LTE2, the success of the operation depends on the policy of the telecom operator. Not all mobile providers allow the registration of a subscriber's second SIM card in the 4G network at the same time as the first. Some operators deliberately block this feature at the network level to encourage the purchase of additional devices or more expensive plans.
The key element here is technology VoLTE. If your operator does not support voice transmission over the LTE network, then when there is an incoming call to the second SIM card, the phone will be forced to perform the procedure CSFB (Circuit Switched Fallback). This means temporarily rolling back the network from 4G to 3G or 2G for making a voice call. At this moment, the Internet on this card will be interrupted, which negates the advantages of the LTE2 mode.
⚠️ Attention: The terms of provision of VoLTE services and operation in Dual 4G mode can be changed unilaterally by the operator. Check the latest information about technology support in the personal account of your mobile operator.
It often happens that in the home region both cards work in 4G, and in roaming the second one automatically falls into 3G. This is due to the lack of appropriate agreements between operators in different countries. In such cases, forcing the mode LTE Only through the engineering menu can lead to a complete loss of connection, since the phone will no longer see 2G/3G networks for a backup connection.
What to do if the 4G icon does not appear on the second SIM card?
Try swapping the SIM card slots. On many smartphones, the first slot is a priority for working in 4G mode. Also check whether an outdated version of the firmware is installed, which may not have up-to-date operator profiles.
Implementation differences on MediaTek and Qualcomm processors
The architecture of the modem plays a decisive role in how exactly the function LTE2 will work on your device. Processor-based smartphones MediaTek historically have had more flexible settings through the engineering menu, allowing the user to manually select frequency ranges and operating modes for each slot separately. Commands like AT+... are entered through a special terminal or application of engineering modes.
Devices on Qualcomm Snapdragon often have a tighter link to the operator settings hardwired into the firmware. Here, turning on the second 4G line often occurs automatically if the phone detects network support, and there may be no hidden switches for the user at all. In some cases, activation requires editing system configuration files, which is not recommended without deep knowledge.
It is also worth mentioning the support for Carrier Aggregation. Advanced modems Snapdragon are capable of aggregating frequencies even when two SIM cards are working, providing a more stable signal. At the same time, budget solutions on MediaTek can disable aggregation on one of the cards when the second one is activated, which reduces the actual data download speed.
Having a processor with support for Dual 4G is only half the battle; the second half depends on the manufacturer's firmware and the settings of your mobile operator.
Alternative solutions and future communication standards
Technology LTE2 is a transitional stage towards more advanced communication standards. Already today, flagship smartphones are beginning to support the mode DSDA (Dual SIM Dual Active), which allows you to actually simultaneously talk on one SIM card and surf the Internet through another without any delays or switching. This is achieved by installing additional radio modules, which still remains the prerogative of expensive devices.
With the advent of fifth generation networks 5G the concept of a dual SIM card is being transformed even more. New standards NR (New Radio) imply even greater flexibility in resource allocation. However, until the 5G infrastructure becomes widespread, customization remains the most effective way to get the most out of current 4G networks for users with two active numbers. If your smartphone does not support this feature in hardware, the only option is to use external modems or manually switch between SIM cards. But for most modern devices released after 2018, the problem is solved programmatically through a software update or correct menu settings. LTE2 remains the most effective way to get the most out of current 4G networks for users with two active numbers.
If your smartphone does not support this function in hardware, the only option is to use external modems or switch between SIM cards manually. But for most modern devices released after 2018, the problem is solved programmatically through a software update or correct menu settings.
Does enabling LTE2 affect the quality of voice calls?
With the correct settings and support for VoLTE, the quality of calls does not suffer, and even improves through the use of a wideband audio codec. However, if the signal is poor, trying to hold 4G may result in the call being dropped, so in areas of poor reception it is better to allow switching to 3G.
Is it possible to play online games through a second SIM card in LTE2 mode?
Yes, it is possible. If you have configured the second SIM card as the main one for data transfer in the settings menu, games will run through it at high speed. Switching between cards for the Internet occurs instantly in modern Android shells.
Why did the LTE2 setting disappear after updating Android?
Manufacturers often change security policies and access to network settings in new versions of the OS. Hidden engineering menus can be blocked, and network settings can be tied exclusively to the operator’s profile. In this case, returning to the old version of the firmware or obtaining root access can restore access, but this carries risks.
Does LTE2 work if one of the SIM cards is an old model (not 4G)?
No. For Dual 4G mode to work, both SIM cards must be USIM standard and support fourth generation networks. If one of the cards is old (2G/3G), the phone will automatically switch it to the appropriate mode, ignoring the LTE2 settings for this slot.
Do I need to pay the operator to connect to the Dual 4G service?
In most cases, this function is provided free of charge and depends only on the technical capabilities of the network and your tariff plan. However, some operators may require connecting the VoLTE option, which is also usually free, but requires a statement in support.