high short timing 怎么翻译

high short timing 怎么翻译
high short timing 怎么翻译

high short timing 怎么翻译
he rapid development of mobile communication is mainly is the satisfied people at any time, any place to communicate with any personal desire. Mobile communication is to realize the ideal of personal communications services. In information technology support, market competition and demand of mobile communication technology, the development is rapid, show the following several big trends: network business group, digital and network technology, network technology, broadband, higher frequencies, intelligent, more effective use of network tend to fusion frequency. This paper briefly introduced the first mobile communication technology under the history, a detailed analysis of the third generation mobile communication system, the key technology and the future development direction of mobile communication.
A, the mobile communication technology development history
Mobile communications, depend on the radio frequency is a valuable resource, but the spectrum resources are limited, with the rapid development of mobile communication, mobile users increase sharply, limited resources are infinite use, and sharp contradiction to solve this contradiction, is the mobile communication technology development, Namely the mobile communication technology development process is the constant use of the spectrum, business ability efficient stronger technical process.
1 the first generation of simulation mobile phones
Through the use of telephone exchange technology and cellular wireless technology in the late 1970s, born of the first generation simulation mobile phones. The first generation of wireless network technology of accomplishment is removed the telephone connection to the Internet user, users first to receive and wireless mobile state call. There are three main types of standard, they are either analog cellular system AMPS, North America and mobile phone system NMT TACS communications systems, access.
2 the second generation mobile communication system
Introducing digital wireless technology composed of digital cellular mobile communication system, and provide more network capacity, improve the quality and privacy, and voice for users to provide seamless international roaming. The second generation of the world market, including the GSM digital wireless standards, D - AMPS. PDC (Japan) and digital cellular systems, which IS 95CDMA - IS still narrowband systems. The existing mobile communication network mainly second-generation GSM, CDMA and GSM, CDMA, using GPRS IS 95B technology, data provided - the ability of kbit taller/s, global system for mobile communications (GSM) using enhanced data rate (EDGE) technology, the rate of 384kbit/s. The second generation mobile communication system in global 133 countries use, about 2.5 million subscribers in 2003, is expected to total could reach 4-5 billion.
(the third generation (3G) mobile communication system,
Namely IMT - 2000, is a real broadband mobile multimedia communication system, it can provide high quality service, and broadband multimedia integrated world, realize seamless coverage of global roaming. The third generation of technical data transmission rate can be as high as 2Mbit/s, its capacity is the second generation technology of 2-5 times, thus to third generation mobile communication technology evolution is the inevitable trend, the user is the ideal way to communication. So that the 20th century is the century, and telephone communications in the 21st century is the century of intelligent multimedia communication.
Second, third generation mobile communication system, the key technology
(1) efficient channel plait decoding technology
Spread spectrum technology in overcoming multipath fading, to provide high quality transmission channel has very good effect. But the existence of very low frequency spectrum efficiency faults. Therefore 3G systems must adopt channel coding technology to improve quality of communication. Now, to overcome the decline of technology is mainly adopts the effect to channel coding and error before interweave technology. Coding and intertwined are greatly depends on the features and business channel requirements. Not only for business channel, and channel coding using different control technology and intertwined. But for the same channel of different business also adopts different coding and intertwined technology.
(2) multi-access technologies
The multi-access technologies 3G systems including CDMA system DeZhiMa and various multi-access agreement on both sides of the study. Because of 3G systems using code division multiple access (cdma) technology, the choice of spread spectrum code becomes very important. 95 - IS adopted in the system function as Walsh 64-bit spread code, prior to the performance of the channel can be guaranteed but reverse channel performance IS unsitisfatory, now, people change of orthogonal code (spread-spectrum factor OVSF) on 7 extensive research, hoping to thoroughly solve the generation methods, usable and reuse; etc. For CDMA/PRMA multi-access agreement also paid great attention is regarded as the traditional group reservation multiple access (PRMA) system of early.