| 1,Purpose of ResearchIn recent ten years, communication of countryside developed very quickly under all levels of government and telecommunication department and telephone users increased equally 35% every year. Communication plays an important role in economic development of our country. But it can't be ignored there are 110 million villages in which telephone is can't be used meanwhile communication condition of western distinct and countryside is regard badly.To realize popular service of western distinct and countryside becomes more and more important now. Besides CDMA450, there are wire optical fiber, satellite communication, PHS, and SCDMA. Especially SCDMA technology of Datang, which is received by Information Industry Department, is recommended as the first choice to"Village to Village"Project. But advantage of CDMA450 is obviously, such as technology profile and low price, so that it attracts large superior producer and operation manager.2,Introduction of CDMA450 technologyCDMA450 works at 450MHz, and it is based on CDMA2000 technology. At first, CDMA450 is used to upgrade simulated NMT450 system to digital system which supports multi-media application in Eastern and northern Europe.CDMA450 has advantages, such as low frequency, large coverage, good penetrability, large volume and supporting wireless high speed packet, and another important advantage is large coverage leads to good investment cost even if user density is very low.CDMA450 is based on IS2000, and its protocol is divided into 3 levels, that is physical level, the second level ,which includes media access control and link access control, the high level. As for physical level, many forward and reverse... |
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