With the popularity of 4G, telecom professional terms such as "five mode 13 frequency, seven mode 19 frequency" began to bombard consumers. In addition to judging whether your mobile phone card can be supported, now we need to consider whether your mobile phone can support the corresponding 4G band. If you want to buy parallel mobile phones, you should also consider the difference between domestic and foreign network frequency bands, as well as the decline of 3 and 4G signals.
Many people may have heard these words too much, so this article will popularize the commonly used network systems. I hope this article can help you understand the network support list in the mobile phone parameter table, judge whether the machine supports your mobile phone card, whether it can use the domestic 4G, and whether it has the potential to crack the network.
Network band allocation
But how do you know what network system your mobile phone card needs? This is another profound proposition of life. Here is a brief introduction to the network system. All stories should start from the characteristics of electromagnetic waves, from infrared, ultraviolet and visible light to wifi and mobile phone signals, all are electromagnetic waves Well, space is limited. Let's say something conclusive.
Like wifi, 2/3/4G networks of mobile phones have their own frequency ranges, that is Occupied frequency band. Due to limited frequency resources, In order to facilitate management, international and "relevant departments" For different devices, Artificial rigidity Different frequency ranges (i.e. frequency bands) are divided. For example, the commonly used GSM mobile phones occupy the 900/1800/1900 MHz frequency band, while telecommunications The 800MHz frequency band (CDMA1X) occupied by CDMA mobile phones.
The only rule to remember is the frequency of electromagnetic waves (MHz value) Higher The shorter the transmission range, the more difficult the signal coverage will be. This is also an important reason why people always say that the mobile phone signal of Telecom (800MHz) is always better than that of Mobile Unicom (900MHz).
The figure above shows the distribution of 4G spectrum
In the 4G era, the network is not only divided into FDD-LTE and TDD-LTE, but also the spectrum of each network is divided into quite a number of frequency bands. When I first saw the table above, I knelt down deeply.
The first column in the table is the artificial band label band2， Or B1 and B2 refer to the uplink and downlink frequency of that line. Among them, band1-28 is the FDD-LTE frequency band. Because FDD adopts independent frequency bands for uplink and downlink, their uplink and downlink frequency bands are different; Band33-44 is the frequency band of TDD-LTE. Since it is the shared frequency band of uplink and downlink, the left and right numbers are the same.
Frequency band conclusion
After roughly understanding the meaning of frequency band, it is actually enough to select mobile phones. When buying a machine, click the parameter specification page, and the manufacturer will indicate the network system supported by the machine, but what are they writing?
Network system supported by Samsung S6
Network system supported by Apple iPhone 6s
Network formats supported by Moto X Style
Relatively speaking, the motorcycle network format is more careful and simple. Unfortunately, not all manufacturers will do so. Moreover, the 2/3/4G system of the three major operators of China Mobile Unicom is almost different, and it is unclear for a while. Let's just look at the conclusion.
There are two kinds of 2G networks (Ensure that the mobile phone can talk, and the low-speed network):
Mobile Unicom is GSM (900/1800/1900 MHz)
Telecom CDMA 1X (800MHz, or band class 0, abbreviated as BC0), sometimes called CDMA800
There are three types of 3G networks:
Mobile 3G is TD-SCDMA, with poor speed and signal coverage. Note that it is very poor
Unicom 3G is WCDMA (1900/2100+1700/850MHz, that is, band 2, 4, 5), sometimes written as UMTS HSDPA。 It is the fastest 3G system, but the signal coverage in small cities is poor
Telecom 3G is CDMA EV-DO (1900/800MHz, namely band class 1, 10, abbreviated as BC0, BC10）， Medium speed but best signal
There are two types of 4G networks:
Mobile only has TD-LTE, covering band 38/39/40, and the current signal coverage is the best
The TD-LTE of China Unicom and China Telecom covers band 40/41, FDD-LTE mainly covers band 1/3, and band 7/17/20 has not been licensed. China Unicom's FDD coverage is much better than its TD network, but its coverage is worse than that of China Mobile, and it is still on the way to rural coverage.
Speaking of which, the previous question of "five mode thirteen frequency, seven mode nineteen frequency" can also be answered. "X-mode" refers to Network system domestic The three operators' 2/3/4G together have 7 network systems (2G has 2 types+3G has 3 types+4G has 2 types), while "X frequency" is the number of frequency bands in the network system (such as band 1/3/7 in 4G).
To simplify it, China Mobile is targeting TD-SCDMA, China Unicom is targeting WCDMA or UMTS, and China Telecom is targeting CDMA. And went to In the field of 4G, as long as we focus on the band 1/3 of FDD, TD's band 38/39/40/41 can run 4G in China.
If you find that your phone's parameter table does not support these bands, or only supports some bands, you should consider cracking.
Prerequisites for cracking/hardware premise
The demand for network cracking originated from the smuggled mobile phone users in the US/Japan/Europe/Hong Kong market. Although the price of smugglers is conscientious, many smugglers will encounter many network restrictions in China due to the difference in network frequency bands at home and abroad and the lack of configuration data from domestic operators.
The other part of the demand for cracking comes from the customized phones of domestic operators. Mobile phones/Unicom phones/Telecom phones are generally blocked from other operators' networks. Once the cards of other operators are replaced, even mobile phones may have to be replaced. Therefore, opening the network lock and 4G has become the beginning of many airplane users' struggle.
Qualcomm's MDM9615M baseband chip
Baseband+RF chip+software jointly determine what network system the mobile phone can support. Both baseband and RF chip are uncontrollable hardware, and the cracking method can only be based on software modification. Therefore, before embarking on/about to embark on the road of cracking, it is necessary to check whether the baseband and RF chips of the target machine support the target network system.
For example, the American S6 edge is divided into the ATT, Sprint and Verizon versions, the first two of which use Samsung's own Shannon baseband (Shannon 333). The latter uses Qualcomm's MDM9635M baseband, just like the original G9250 of the Bank of China, which supports all networks, so the latter itself has the hardware foundation to open the whole network.
The good news is that since Qualcomm Snapdragon 800, many Android phones with Qualcomm processors have a hardware foundation of three networks 4G, among which the more famous models are the V version HTC M8, Note 3 (900V), Nexus 5 (D820), Nexus 6, Moto X.
Of course, it is not ruled out that the manufacturer did not configure the radio frequency chip and antenna of all Netcom when it configured the baseband of all Netcom. Therefore, if conditions permit, it is necessary to find out the model of the radio frequency chip of the machine. For example, the HTC M8 and ATT versions of Samsung S5 use Snapdragon 801+Qualcomm's WTR1625L RF chip, while the older HTC DNA and Nexus 5 use Snapdragon 800 (MDM9615 baseband)+Qualcomm's wtr1605l RF chip, both of which are hardware capable of cracking 4G throughout the network.
The question of how to crack the network restrictions will be left in the next popular science article, please pay attention.
