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一、前言十多年来,世界各国先后开始了移动通信网的研究和开发。在日本、美国和西欧,150MHz频段、450MHz频段或800MHz频段的移动通信网相继问世。在国内,近年来也加紧了400MHz频段的自动电话网的研制,并正对800MHz频段通信网的可实现性进行着有益的探讨。在一些工业发达的国家和地区,这类通信网已应用于公共汽车、航海、救灾、矿山、军事等场合,其应用范围正日益扩大。在国内,随着技术的不断发展,这种通信网也将获得越来越多的应用。
I. Foreword For more than a decade, all countries in the world have started the research and development of mobile communication networks. In Japan, the United States and Western Europe, the 150MHz band, 450MHz band or 800MHz band mobile communication networks have been introduced. In China, in recent years, the development of the automatic telephone network in the 400 MHz frequency band has also been stepped up, and the feasibility of the communication network in the 800 MHz frequency band is being discussed. In some industrialized countries and regions, such communication networks have been applied to the bus, marine navigation, disaster relief, mining, military and other occasions, and their applications are being expanded. In China, with the continuous development of technology, this kind of communication network will also get more and more applications.