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前言专用移动通信,在我国已有了广泛的应用(例如铁路、汽车、轮船等)。但是,由于其工作采用单频道固定方式,因此通信容量小、呼损率高,在一定程度上限制了它的作用的发挥。为了充分发挥专用移动通信的作用,只有采用多频道共用方式。多频道共用方式有多种,但就其构成而言,可分为呼叫频道方式、循环定位方式和循环不定位方式。本文根据专用移动通信的特点,采用循环不定位方式。它具有系统构成简单、不增加频偏、无交换设备、接续时间短、频道利用率高、无呼叫冲突和呼叫冲突概率小等一系列优点,是专用移动通信多频道共用的一种比较完善的方式。
Preface Dedicated mobile communications, has been widely used in our country (such as railways, cars, ships, etc.). However, due to its work using a single channel fixed mode, so the communication capacity is small, call loss rate is high, to a certain extent, limited its role. In order to give full play to the role of private mobile communications, only the use of multi-channel sharing. There are many ways to share multiple channels, but in terms of its composition, it can be divided into calling channel mode, circular positioning mode and cyclic non-positioning mode. This article based on the characteristics of private mobile communications, the use of circular non-positioning method. It has the advantages of simple system structure, no increase of frequency offset, no switching equipment, short connection time, high channel utilization rate, no call collision and small call collision probability, which is a kind of relatively perfect multi-channel shared use of dedicated mobile communication the way.