近年来,蜂窝式无线移动电话的发展迅速,已经使移动电话用于公众成为现实。蜂窝式移动电话是把移动电话的服务地区分成许多小区。如图1所示,通常是7个小区或12个小区为一群,使无线频道能隔开一定距离重复使用,解决了无线电话的有限频率范围和众多用户打电话的矛盾。每个小区设有一个基地台,用户通过基地台和移动电话交换中心与市内电话接通。当移动用户从某个小区进入另一小区时, In recent years, the rapid development of cellular wireless mobile phones has made mobile telephones available to the public a reality. Cellular phones divide the service area of ​​a mobile phone into many cells. As shown in FIG. 1, a group of seven cells or twelve cells are usually used, so that the radio channels can be repeatedly used at a certain distance, thereby solving the conflict between the limited frequency range of a radio telephone and the number of users calling. Each district has a base station, the user through the base station and mobile switching centers and local calls connected. When a mobile user enters another cell from one cell,