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第三代移动通信系统的发展及市场展望（下）□亓放３第三代系统的布设及反向兼容性反向兼容性很类似于ＧＳＭ／ＤＣＳ１８００双频段的概念，即第二、三代系统网络之间具有通话切换和自动漫游等功能，通过用户使用双模手机，使得运营商在第二代网络的基础上逐步建设和发展...
Third-generation mobile communication system development and market outlook (below) □ 亓 release 3 third generation system layout and reverse compatibility Reverse compatibility is very similar to the GSM / DCS1800 dual-band concept, the second and third generation systems The network has functions such as call switching and automatic roaming, and the user can gradually build and develop on the basis of the second generation network by using the dual-mode mobile phone.