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[fundamentals of wireless communication-15]: illustrated mobile communication technology and application development-3-overview of digital communication 2G GSM, CDMA, 3G wdcma/cdma200/td-scdma, 4G LTE

2022-07-01 01:44:00 【Silicon based workshop of slow fire rock sugar】

Catalog

Preface ：

The first 3 Chapter Origin of digital mobile communication 2G

The first 4 Chapter Broadband digital mobile communication 3G-5G edit

The first 5 Chapter Mobile Internet edit

The first 6 Chapter 5G summary

Preface ：

analog signal It means that the value of amplitude is continuous （ The amplitude can be represented by an infinite number of values ）. An image in which a continuous analog signal changes continuously in time （ TV 、 Fax ） Signals, etc , Time discrete analog signal is a kind of Sampling The signal ,

digital signal The value of amplitude is discrete , amplitude Indicates being limited to a limited number of values . Binary code is a kind of digital signal . Binary code is less affected by noise . It's easy to have digital circuits for processing , So it has been widely used .

A communication mode in which messages are transmitted in digital form or carrier signals are modulated in digital form and then transmitted . Conventional telephone and television belong to analog communication . Telephone and TV analog signals are digitized , Then the digital signal is modulated and transmitted , It is called digital telephone and digital television . Data communication between computers , Because the signal itself is in digital form , It belongs to digital communication . Multi channel communication using time division or code division in satellite communication also belongs to digital communication .

Cellular mobile digital communication refers to the use of cellular wireless networking , The terminal and network equipment are connected through wireless channel , Thus, users can communicate with each other in activities . Its main feature is the mobility of the terminal , It also has the functions of handover and automatic roaming across the local network . Cellular mobile communication service refers to the voice provided by the cellular mobile communication network composed of base station subsystem and mobile switching subsystem 、 data 、 Video and image services .

Cellular system is probably the most important communication medium in today's society . Adopt digital communication technology , It can improve the communication reliability and communication quality of the system in the mobile environment . Channel adaptive equalization 、 Application of diversity and spread spectrum technology , It can make the system have the ability to resist multipath fading and multipath expansion . As mentioned above , The effect of digitalization is very obvious . Digital cellular mobile communication follows the basic concept of analog cellular mobile communication , It inherits the basic structure of cellular system and the basic functions of network management and control . however , Digital cellular mobile communication needs to solve some problems brought by digitalization , let me put it another way , Is to pay a certain price .