"Turn" 4G mobile phone call why will break network 4G Internet and call cannot coexist cause analysis

Source: Internet
Author: User

Compared with 2g/3g, 4G is the biggest feature is to provide a peak rate of more than 100Mbps, since the speed can be off 20M of fiber-optic fixed network, that used for voice calls is a piece of cake? Unfortunately, this is where the problem arises.

Because the current LTE network (4G) does not support voice services, so whether it is Td-lte (mobile 4G) or Fdd-lte (may be unicom/telecom 4G), the system will automatically disconnect the 4G signal when a call comes in, automatically fall back to the 2g/3g signal to complete the voice call, After the call, then back to the 4G network. In other words, the current 4G data service (4G Internet) cannot be performed concurrently with voice calls.

Thus, for example: When you are using the 4G network to see the news, suddenly want to call friends (or friends to call you), the phone needs to first switch the 4G network to 2g/3g mode, and this switch time in 2 seconds ~15 seconds (specific time depending on the mobile phone and operator side optimization). That is, in the period of time signal switching, your phone is not to be dialed out, and the other side is not to enter.

Therefore, some users make a phone call with 4G mobile phone when the switch off the line, when someone calls you will always prompt "Sorry, you dialed the user temporarily unable to connect" the tone. Fortunately, the above problems only occur occasionally, and not all 4G mobile phones will appear this phenomenon.

Why not all 4G mobile phones will appear this problem, 4G Internet can also be the first time to answer the phone, and even do not affect the network connection when the call? To answer this question, we need to understand the solutions of the three voice calls in the 4G era.

Three voice solutions in the 4G era

After entering the 4G era, three solutions were derived from the voice calling field, namely "CSFB" (Circuit switched Fallback), "Sglte" (simultaneousgsm and LTE), and "VoLTE" (voice Over LTE).

CSFB: One of the call networking

Any 4G internet encounters a phone call problem, the basic can determine the choice of CSFB program, on behalf of the mobile phone has oppo Find7 and Apple iphone 5S and so on. The CSFB solution's mobile phone only has a set of RF chips, either for networking, or for calls, both of which can only be one. The biggest drawback of the scheme is that 4G Internet can not be switched to 2g/3g network in time, resulting in a short period of time the phone can not be dialed out, can not come in, after the phone also need to wait a while to switch to 4G network to continue the Internet. Want to minimize the impact, can only look forward to mobile phone manufacturers system updates and operator network optimization upgrade. If you are worried about missing an important call, you may be able to alert your business by calling SMS.

Little Tips

are CSFB solutions, but the products of different operators will still have some differences. In the case of the iphone 5S, the mobile 4G version will automatically switch to the 2G network during the call (no Internet connection during the call), and the telecom 4G version will switch to the CDMA1X network (no internet connection during the call), but the Unicom version has the opportunity to switch to the 42MB/S 3G network during the call. Voice calls can also use a high-speed hspa+ network. For example, Huawei P7 Mobile version adopted the Sglte scheme, but the Unicom version is CSFB.

Different versions of the same model phone, RF-related chips may differ. For example, this figure is the iphone 5S two version of the RF chip area of the comparison chart

Sglte: Communication Network two not delay

Sglte (also known as "dual standby") The biggest feature of the mobile phone is the simultaneous built-in support for both LTE and GSM RF chips, can simultaneously achieve 2G calls and 4G networking. Representatives of such phones are Samsung Galaxy Note 3 n9008v and Lenovo Vibe Z2 Pro (K920), which appears to be a single card cell phone signal bar will appear both 4g/3g and 2G two line signal icon. Although the Sglte can simultaneously achieve the characteristics of Internet and call, but the two sets of radio frequency transmission system will also bring relatively higher power consumption, but also a fish and bear paw can not be combined with the Sequela bar.

VoLTE: Just think about it.

VoLTE should be the best-in-class 4G call solution, which is an end-to-end voice scheme built on a 4G network that brings lower access latency (waiting time after dialing), and a drop-off probability close to zero. Unfortunately, before the 4G network became ubiquitous, VoLTE was just the ideal "utopia".


In a word, the contradiction between 4G and voice calls exists, but it can be avoided. Just, different brands in the design of 4G mobile phones in the end will favor CSFB or Sglte, the final choice is not in the hands of consumers. Therefore, whether your 4G mobile phone in the internet when the smooth access to the phone, or the middle of the phone can be normal network, these are based on the premise of mobile phone hardware. If you do not have the restrictions of the operator, the individual or recommend the choice of communication between the two non-delayed sglte solution, the additional power consumption can be solved by the mobile, but missed important calls are difficult to compensate.


A person bill of lading double-pass problem, there are a few big V a bunch of double-pass useless theory! The Unicorn 650 single chip integrated CDMA baseband, telecom secondary card can double-pass the problem! And then let people set up call forwarding! Double pass is not money, open call transfer, once the phone used the call transfer is to money! And the opening of the call transfer or the leakage of the phone, call transfer, the person who calls you is generally heard on the phone call, and you do not know who is calling the phone, so you may have to open the phone call alert function, and call waiting function! MATE9 does not support capacity is telecom's side of the Internet while talking! is to open the mobile volte, but also only to solve the mobile single-card side of the internet while calling, dual-card case of the main card phone come in, vice-cards mobile, telecommunications, unicom are disconnected! And even if the one or two-line city, I see the mobile volte also did not do indoor signal how good! The volte implementation of telecommunications is relatively difficult, the earliest in the second half of 2017 can be used, it is estimated that MATE10 will be listed at that time! The United States its name said to solve the vice card unicom 3G, but the dual SIM status, the main card phone came in Vice card Unicom 3G is still disconnected! And there is no plug-in baseband, telecom deputy card will never have 3G signal! Some people say who can pick up two phone calls at the same time, the meaning of the double pass is the main cartoon words, the deputy card someone called in to know who called the phone! There are people who say that the business is busy to the phone while the internet! Very simple, a customer calls in, to see a mobile phone QQ or on the news! More exasperating is that there is harassment phone come in, and you good in chatting with people, broken! Or the harassment of spam phone interception, in the absence of the network will expire!

"Turn" 4G mobile phone call why will break network 4G Internet and call cannot coexist cause analysis

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