文档介绍：Cellular network
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Top of a cellular radio tower
A cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area. This enables a large number of portable transceivers (., mobile phones, pagers, etc.) to communicate with each other and with fixed transceivers and telephones anywhere in the network, via base stations, even if some of the transceivers are moving through more than one cell during transmission.
Cellular networks offer a number of advantages over alternative solutions:
increased capacity
reduced power use
larger coverage area
reduced interference from other signals
An example of a simple non-telephone cellular system is an old taxi driver's radio system where the taxi company has several transmitters based around a city that can communicate directly with each taxi.
Contents
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1 The concept
2 Cell signal encoding
3 Frequency reuse
4 Directional antennas
5 Broadcast messages and paging
6 Movement from cell to cell and handover
7 Example of a cellular network: the mobile phone network
 Structure of the mobile phone cellular network
 Cellular handover in mobile phone networks
 Cellular frequency choice in mobile phone networks
 Coverage comparison of different frequencies
8 See also
9 References
[edit]The concept
Example of frequency reuse factor or pattern 1/4
In a cellular radio system, a land area to be supplied with radio service is divided into regular shaped cells, which can be hexagonal, square, circular or some other irregular shapes, although hexagonal cells are conventional. Each of these cells is assigned multiple frequencies (f1 - f6) which have corresponding radio base stations. The group of frequencies can be reused in other cells, provided that the same frequenci