移動(dòng)通信技術(shù)發(fā)展趨勢(shì)-免費(fèi)閱讀
【正文】 s capacity, in 1997 presented the 1800MHz system, the GSM 900/1800 dualfrequency network popularized rapidly. in 2002 will invest mercial third generation system IMT2000 to locate in the 2GHz frequency band. The network tends the fusion, moves toward the unification The technical development, market demand39。s line. The user first time can any place wireless receive which is in them and dials telephones. The second generation of system has introduced the digital radio technology, it provides the higher network capacity, improved the voice quality and the secrecy, and has introduced the seamless international roaming for the user. Today world market second generation of digital wireless standard, including GSM, MMPS, PDC (Japan digital cellular system) and IS95 CDMA and so on, still for narrow band system. The third generation moves the system, namely IMT2000, is one kind of genuine wide band multimedia systems, it can provide the high grade wide band synthesis service and realize the global seamless cover. after 2000, the narrow band mobile phone service demand still will be very big, but along with Internet and so on high speed data correspondence and the multimedia correspondence demand39。s demand, global open agreement wireless application protocol (WAP) arises at the historic moment. WAP was transmits the Internet information content as well as the valueadded service to the mobile termination has provided one kind of open general standard, has realized IP and the GSM network bridge joint, was one provides accelerates the market for the manufacturer to grow, to avoid the network cleft grafting, protecting the standard which the operator invested, WAP guaranteed that any handset could work with WAP the patible GSM. （2）data rate development The GSM bearer service provides the GSM data rate is highest can only achieve (HSCSD) technology will realize the 57kbit/s data rate, to requested the continual bit rate and the transmission latency small application is ideal, like videoconference, , longdistance turning on enterprise39。s target market will be the sales personnels or scene engineer such user group. Sends the goal from these in the application to accumulate the wireless data the first experience, and profits. In the past39。s significance is at The reason that the mobile service the development swift and violent was mainly it has satisfied the people in any time. Any place carries on the correspondence with any individual the desire. The mobile munication realizes in the future the ideal persontoperson munication service way that must be taken. In the information support technology, the market petition and under the demand bined action, the mobile munication technology39。在第二代網(wǎng)絡(luò)中,GSM系統(tǒng)的開(kāi)始使用頻段為900MHz,IS95 CDMA系統(tǒng)為800MHz。智能網(wǎng)及其智能業(yè)務(wù)是構(gòu)成未來(lái)個(gè)人通信的基本條件。 第二代系統(tǒng)引入了數(shù)字無(wú)線(xiàn)電技術(shù),它提供更高的網(wǎng)絡(luò)容量,改善了話(huà)音質(zhì)量和保密性,并為用戶(hù)引入了無(wú)縫的國(guó)際漫游。對(duì)于運(yùn)動(dòng)中的用戶(hù)還有隨時(shí)隨地的各種信箱和娛樂(lè)服務(wù)。 對(duì)隨時(shí)隨地話(huà)音通信的追求使早期移動(dòng)通信走向成功。國(guó)際上1998年引入的高速電路交換數(shù)據(jù)(HSCSD)技術(shù)將實(shí)現(xiàn)57kbit/s的數(shù)據(jù)速率,對(duì)要求連續(xù)比特率和傳輸時(shí)延小的應(yīng)用是理想的,如會(huì)議電視、電子郵件、遠(yuǎn)程接入企業(yè)的局域網(wǎng)和無(wú)線(xiàn)圖像。從這些先發(fā)
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