What is GSM? What is GSM?

GSM Full name is: Global System for Mobile Communications, the Chinese language for mobile communication systems, commonly known as the "global", is a originated in Europe, the mobile communication technology standards, is the second generation of mobile communication technology, The goal is to make it possible for a mobile phone network to be used globally across the globe, allowing users to use a single handset. The introduction of this technical standard in China in the early 1990s has been the use of cellular analog mobile technology, the first generation of GSM technology (December 31, 2001 our country closed the analog mobile network). At present, China Mobile and Unicom each have a GSM network, the world's largest mobile communications network. GSM system includes several frequency bands, such as GSM 900:900mhz, Gsm1800:1800mhz and Gsm-1900:1900mhz.

1.GSM use of intuitive features:

GSM system has several important features: good anti-theft ability, large network capacity, cell phone number rich resources, clear calls, stability is not easy to be disturbed, information sensitive, less dead, mobile phone power consumption low.

2.GSM Technical Features:

1. Spectrum efficiency. The system has high spectral efficiency because of its efficient modulator, channel coding, interleaving, equalization and Speech coding technology.

2. Capacity. Due to the increased bandwidth per channel transmission, so as to reduce the same frequency multiplexing to 9dB, so the same frequency multiplexing mode of GSM system can be reduced to 4/12 or 3/9 or even smaller (analog system is 7/21), plus the introduction of half rate voice coding and automatic traffic assignment to reduce the number of handoff The capacity efficiency of GSM system (channel number per cell) per MHz is 3~5 times higher than TACs system.

3. Voice quality. In view of the characteristics of the digital transmission technology and the definition of the air interface and voice coding in the GSM specification, the voice quality is always at the same level and independent of the wireless transmission quality when the threshold value is above.

4. Open Interface. The Open interface provided by the GSM standard is not limited to the air interface, but also to the press network directly and between the equipment entities in the network, such as a interface and Abis interface.

5. Safety. Through the use of authentication, encryption and Tmsi numbers, the purpose of security is achieved. Authentication is used to authenticate the user's right to access the network. The encryption is used for the air interface and is determined by the SIM card and the network AUC key. Tmsi is a temporary identification number assigned by a business network to a user to prevent anyone from leaking out of its geographic location.

6. Interconnection with ISDN, PSTN, etc. Interconnection with other networks usually utilizes existing interfaces, such as IsUp or Tup.

7. Roaming on the basis of SIM card. Roaming is an important feature of mobile communication, which indicates that users can automatically enter another network from one network. GSM systems can provide global roaming, and of course require certain protocols between network operators, such as billing.