Because of the special network system environment and the lack of real name system in China, dual card dual standby mobile phones have become a feature of the domestic communication industry. What about the technical principle of dual card dual standby mobile phones? Why do many big brands of mobile phones rarely have dual card dual standby products? Two SIM cards can be inserted into the dual SIM phone at the same time, And it can be standby at the same time. The dual card dual standby in the market generally refers to the dual card dual standby in the same GSM network. Of course, there are also CDMA network It is only possible that the latter two products are very few. Maybe someone will ask, if I have a mobile card and a telecommunications card, if only the same network system is supported, how can I achieve dual card and dual standby? At this time, another technology based on dual card and dual standby was born, that is, dual mode and dual standby. As the name implies, this product can support standby requirements of two network systems.
Operator network environment:
The six major domestic operators refer to China Mobile, China Unicom, China Telecom, China Netcom, China Railcom and China Satcom. From the perspective of communication or ground network, these six operators are the largest and strongest. Of course, their focus is different from each other, and the network system they advocate is also different. Let's just talk about mobile network here. China Mobile mainly operates GSM network TD-SCDMA ； China Unicom mainly operates GSM, CDMA and WCDMA; China Telecom operates CDMA, PHS, CDMA1X and CDMA2000 networks.
Three cards and three waiting phones
Technical principle:
In terms of technical implementation, there are several dual card schemes. The old practice is to use two chipsets, that is, two sets of baseband chips, RF chips and memory systems are installed in the mobile phone, which is equivalent to two complete mobile phone mainboards being put together in the same mobile phone shell. This implementation method can support two SIM cards to work at the same time, and does not need to switch on or off again when switching, but the problem is that its cost is almost twice that of an ordinary mobile phone, and the power consumption is often twice that of a normal mobile phone. Many heavy dual card dual standby mobile phones in the market use this solution. The other is to add an Analog Switch on the traditional mobile phone chipset to manually switch the network. The latter is usually the implementation of "dual card single standby" mobile phones, but later some enterprises used it in dual standby mobile phones, but it is prone to problems such as incompatibility with various SIM cards and immature control software, and the drop rate is high during calls. Is there a way to realize dual card dual standby without using two chipsets at the same time, so as to save costs and reduce power consumption? At this time, double cards, double standby and single pass appeared, which is a popular practice nowadays. The principle is to use one control IC (chip) to switch between the two networks through software and automatically search the network. Because the switching time is very short, such as the frequency of one thousandth of a millisecond, consumers cannot feel that the network has switched, which is equivalent to the realization of simultaneous standby of two cards. If a phone is connected to another card when one card is talking, the software also sets a way to send a short message to inform the missed call. From the perspective of consumers, it will not miss any calls, which is similar to "double waiting".
Do we really need two SIM cards?
Why do many big brand mobile phones not have dual card dual standby mobile phones? In fact, the reason is very simple. Double card, double standby or exaggerated multi card, multi standby mobile phones are common products in many developing countries. The main reason is that the prices of telecom operators in these countries are chaotic, and many people want to take into account the advantages of the prices of various operators. Therefore, the demand for multi card, in the final analysis, is to save money, China has even exported three card and three waiting products to India. Another reason is that the number in developed countries is real name system, and there will be relevant laws and regulations, so it is a trouble to change the number in these countries, let alone use multiple mobile phone numbers. Japan has officially implemented the Law on the Prevention of Improper Use of Mobile Phones since April 1, 2006. According to the law, all mobile phone users, whether applying for a new number or transferring a number, must be confirmed by the owner with a valid certificate. Among them, minors must submit the guardian's consent form and the guardian's valid certificate in addition to the valid certificate when applying. If the applicant is a legal person, in addition to the legal person certification materials, it is also necessary to submit the valid certificates, incumbency certificates and the official seal of the legal person unit of the person who came to handle business. Otherwise, it is impossible for any individual or unit to apply for a mobile phone number from any operator. In addition, users should cooperate with judicial authorities according to laws and provide necessary information.
