Unit Five Technology Mobile Communications
? GSM is one of the leading mobile networks in the world with over 60% of the world cellular market. ? The development of GSM started in the early 1980s. ? It was the mainstay of the plans for Europe’s mobile communication infrastructure for the ['infr?'str?kt??] 1990s. 基础结构，基础设施
? Today, GSM and its DCS 1800 and PCS 1900 versions have spread far beyond Western Europe with networks installed across all continents. ? By 1986, it was clear that some of these analogue cellular networks would run out of capacity by the early 1990s.
DCS Digital Cellular System 数字蜂窝系统
PCS Personal Communications Service 个人通信业务
? As a result, a directive was issued for two blocks of frequencies in the 900MHz band, albeit 虽然，即使 somewhat smaller than recommended by the CEPT (Conference of European Posts &Telegraphs), to be reserved absolutely for a pan-European service to be opened in 1991.
? In the meantime, the GSM members were making excellent progress with the development of agreed standards. ? One major decision was to adopt a digital rather 而不是 than an analogue system. ? The digital system would offer improved spectrum efficiency, better quality transmission and new services with enhanced features including security. ['spektr?m]
? It would also permit the use of Very Large Scale Integration (VLSI) technology which would lead to smaller and cheaper mobiles, including hand held terminals. 手持式终端 ? Finally, a digital approach would complement the development of the Integrated Services Digital Network (ISDN) with which GSM would have to interface.
? GSM initially stood for Group Special Mobile. ? The CEPT formed the group to develop a PanEuropean cellular system to replace the many systems already in place in Europe that were all incompatible.
? The main features of GSM were to be International Roaming ability, good sound quality, small cheap handsets and ability to handle high volumes of users. ? GSM was taken over in 1989 by the ETSI (European Telecommunications Standards Institute) and they finalized the GSM standard in 1990. ETSI 欧洲电信标准协会
? GSM service started in 1991. ? It was also renamed this year to Global System for Mobile communications.
? GSM has been the backbone of the phenomenal success in mobile telecom over the last decade. ? Motorola delivered the industry’s first commercial Code Division Multiple Access (CDMA) network in 1995. ? Motorola CDMA solutions provide flexibility for voice and data services, the highest peak average data throughputs, and cost-effective migration.
CDMA Code Division