Shulou(Shulou.com)06/01 Report--

A brief talk on the silly confusion of 1G, 2G, 3G, 4G.

Although I have studied the computer network in university, I always look at what the 1G gravity, 2G, 3G and 4G are constantly sprayed on the Internet, but I always feel scratchy and can't see its essential difference. I don't want to explain in detail the smelly and long key technologies among them. Let's talk about the differences between these different generations of network technologies in terms of concepts that we can understand.

Let's start with concepts and differences.

1G: there is nothing to say. It is estimated that it was only with the later 2 or 3G that I thought of calling the original 1G. 1G adopts FDMA (Analog and Frequency Division multiple access) technology, which can realize regional mobility services, which represents the first generation of analog mobile phones. Mobile phone, the call is locked at a certain frequency, and the phone can be eavesdropped by using an adjustable frequency radio. It is not compatible with each other because of its poor confidentiality, limited capacity, and can not provide data services and automatic roaming.

2G: the representative is GSM (Global System for Mobile Communication) Global Mobile Communication system, CDMA, which turns on digital communication. The biggest difference of GSM compared with before is that its signaling and voice channel are digital, call quality is stable, confidentiality is strong, spectrum efficiency is high, GPRS supporting MMS and WAP service on the Internet and other services.

2.5G:GPRS: general packet radio service is a new bearer service developed on the GSM system. It makes use of the legendary 2.5G of the unused TDMA channel in the GSM network.

GPRS adopts the same wireless modulation standard, frequency band, burst structure, frequency hopping rules and the same TDMA frame structure as GSM.

The most fundamental difference from GSM is that GSM is a circuit switching system, while GPRS is a packet switching system.

GPRS allows users to send and receive data in end-to-end packet mode without using the network resources of circuit switching mode, thus providing an efficient and low-cost wireless packet data service.

Compared with the GSM communication network, the technical features such as high resource utilization, high transmission rate (64-128Kbps), short access time, always on-line, supporting IP protocol and X.25 protocol, low cost, charging based on the amount of data in the communication.

3G: wireless cellular telephone communication protocol, three mainstream 3G standards: W-CDMA, CDMA2000 and TD-SCDMA. Focusing on the network speed, the main advantage of 3G technology is that it can greatly increase the system capacity, improve the communication quality and data transmission rate. In addition, by using the seamless roaming technology between different networks, the wireless communication system can be connected with Internet, and multimedia forms such as images, music and videos can be handled.

Due to the adoption of a modulation and multiple access communication mode based on spread frequency communication, its capacity is 10 times higher than that of analog technology and about 4 times higher than that of GSM network, and CDMA (Code Division multiple access) based on broadband technology makes video applications in mobile communications possible, thus making mobile phones move from narrow services such as making phone calls and sending short messages to broadband multimedia applications.

4G: including two TD-LTE,FDD-LTE systems, integrating 3G and WLAN, using OFDM (orthogonal Frequency Division multiple access) technology, 4G has changed the construction mode and operating cost of operators' networks from 2G to 3G. 4G no longer reserves wireless communication resources to run voice, but all resources are used to run data-- that is, all are used for the Internet; faster, up to uplink 20Mbps, downlink 100Mbps. The network channel is wider.

4G technology supports the downlink network bandwidth of 100Mbps~150Mbps, which means that 4G mobile phone users can experience the maximum downstream speed of 12.5MB/s~18.75MB/s. It is 35 times that of China Mobile 3G (TD-SCDMA) 2.8Mbps and 14 times that of China Unicom 3G (WCDMA) 7.2Mbps.

Is the measured network speed of 4G really that fast?

Measured map of April 2014

At present, operators are stepping up the deployment of 4G networks and shouting that 4G speed can reach 100Mbps every day, but those who have used 4G all know that the current speed of 4G is not as fast as advertised. According to the actual network test in 2014, the download rate of telecom can reach 43Mbps, mobile 38.18Mbps, while Unicom only has 25Mbps, which is related to Unicom's low 4G coverage. No matter how fast 4G is, if it is not covered, it will not be enjoyed.

At a time when the public is still debating whether to buy a 4G phone, change the card, and enjoy what 4G is going to do, the era of 4G + is coming again. The next article details what 4G will look like.

Do you want to change 4G cards for 4G phones? What's the difference between 4G card and 2G card?

In fact, in the 3G era, Telecom and China Unicom have replaced the SIM card, the telecom mobile phone card is called UIM, and the Unicom 3G mobile phone card is called USIM. They all mean the same thing, that is, the user identification card, which is a personal data card for digital mobile phone users around the world.

4G mobile phones need to use 4G SIM cards, also known as USIM cards.

If you have changed to a 4G phone, for mobile users, you need to change the original SIM card to USIM, not the number, you need to change the card to complete the upgrade. For Unicom 3G users, if they already have a USIM card, they can not change the number or change the card, but they need to go to the business hall to upgrade to 4G service in order to use 4G function.

For users, in addition to the difference in size and at their own expense, these cards are faster and larger than before.

So what is the specific difference between SIM and USIM?

SIM card (Subscriber Identity Module): the user identification card, which is the personal data card of the GSM mobile phone. Use this for 2G.

USIM is the abbreviation of Universal Subscriber Identity Module (Global user Identification Card). The Global subscriber identity Module (USIM), also known as upgrade SIM, appeared in 3G.

The upgrades to USIM are as follows:

1) two-way authentication, the network can not help authenticating users, users also have to authenticate to the network, which improves the security of the card.

2) the storage capacity has been greatly increased, and the card capacity and read speed are several times faster than before.

3) Mobile payment upgrade, there is a card called wallet USIM, this card supports NFC function, can carry finance, public transportation and other third-party applications. Many friends use this function to swipe their mobile phones on the bus instead of swiping their bus cards.

4) encryption technology upgrade. The chip part of the replaced USIM card has a larger area, on the one hand, due to the increase in storage capacity, such as from 64KB to 128KB, and on the other hand, due to the upgrade of encryption technology.

In the era of 2G functional phones, we also use SIM cards to store contact information, but in the 3G era, with the popularity of large-capacity smartphones, this information has long been stored in mobile phone memory, so the greater significance of replacing USIM cards lies in a higher level of encryption, that is, more secure and more difficult to crack.

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