The development of GSM

In the mid-1980s, when the analog cellular mobile communication system on the market just when the world's developed countries in the development of second-generation mobile communication systems. One of the most representative and more mature standard of a pan-European GSM, the United States ADC (D-AMPS) and Japan JDC (now renamed the PDC), and other digital mobile communication system. These figures are in the system, GSM development of the most eye-catching. 1991 GSM system in Europe, the official launch, the network opened.
GSM family are GSM900, DCS1800 and PCS1900 three parts, between the main difference is that the work of the band's differences.
The emergence of cellular mobile communications can be described as a mobile communications revolution. Their frequency reuse greatly increased the frequency of utilization and increase system capacity, the intelligent network to achieve a cross-district transfer and roaming capabilities, expanded customer service area, but there are four of these simulated shortcomings of the system: no system Public interface; difficult to carry business data; spectrum utilization of low-capacity can not meet demand; security poor, vulnerable to eavesdropping and easy to do "fake machine." Especially in Europe there is no system of public interface with each other can not roam on a lot of inconvenience to customers.
GSM digital mobile communication systems from Europe. As early as 1982, Europe has several analog cellular mobile operators in the system, such as the Nordic countries of the NMT (Nordic Mobile Telephone) and the United Kingdom of TACS (all-access communication system), other Western European countries to provide mobile service. At that time, these systems is the system can not be used abroad. In order to facilitate the reunification of Europe-wide use of mobile phones, the need for a public system, in 1982, the Nordic countries to the CEPT (Europe Chief of the General Assembly of Posts and Telecommunications) submitted a proposal that calls for the 900MHz band of public norms of the European telecommunications business. At the General Assembly on the establishment of a European Telecommunications Standards Institute (ETSI) Technical Committee under the "mobile particular group (Group Special Mobile)", referred to as "GSM", to formulate standards and proposals.
Since our establishment in 1992 in Jiaxing and the opening of the first demonstration of GSM system, and in September 1993 officially open the business, all over the country's mobile communications system used in most of the GSM system, making GSM system to become China's most mature and market share The largest was a kind of digital cellular systems. As of November 2002, Chinese mobile phone users 200,000,000, 2001 at the end of the additional 55,092,000.
GSM system has several important features: good ability to copy security, network capacity, resource-rich mobile phone number, the call clear, strong stability are less vulnerable to interference, and sensitive information, talk less dead, low-power mobile phones.
At present, China's two main GSM system for the GSM 900 and GSM1800, due to the different frequencies, so the application of the phone are not the same. But the most fundamental is the dual-band mobile phone, the two are free to switch between frequency bands. European countries are widely used by the GSM900 and GSM1800 system, in addition to the other joined the GSM1900, for the tri-band mobile phone handset. With the mobile phone market in China's further development, is now also have a tri-band phone can be in the GSM900 \ GSM1800 \ GSM1900 band of the three free to switch cell phone, a cell phone really can be enjoyed throughout the world.
Early look at, GSM900 the development of an earlier time, the use of more GSM1800 On the other hand the development of late. Physical properties, the former lower-frequency spectrum, longer wavelength, low penetration, but the transmission distance, and cell phone transmitting power stronger, more power and therefore a shorter waiting time; and the latter's high frequency , A shorter wavelength, the penetrating power of good, but to send a short distance, the transmission power of mobile phones smaller, stand-by time is correspondingly longer.
Emergency call system, GSM is the voice of a specific business function. Even in the GSM mobile phone to set the limit has not expired and insert SIM cards (SIM), as long as the GSM network coverage in the region, only the press of a button the user can be pre-determined number of special (such as 110, 119,120 and so on) sent to the appropriate units (police, fire brigade, first aid centers, etc.). This simplified approach is to dial in an emergency moment too late to carry out complex operations and specially designed.