[fundamentals of wireless communication-14]: illustrated mobile communication technology and application development-2-the first generation mobile analog communication big brother

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Preface ：

The first generation mobile communication mainly adopts analog communication technology and frequency division multiple access (FDMA) technology .

Analog communication （analog communication ） Is to use the amplitude of the sine wave 、 A change in frequency or phase , Or use the amplitude of the pulse 、 Changes in width or position to simulate the original signal , For the purpose of communication , So it is called analog communication .

Analog communication It is a communication mode that transmits information by analog signal . Non electrical signal （ Such as sound 、 Light, etc ） Input to the converter （ Such as Transmitter 、 Photocells ）, Make it output continuous electrical signals , Make the frequency or amplitude of the electrical signal change with the input non electrical signal . The signal transmitted by ordinary telephone is analog signal . Telephone communication is the most commonly used analog communication . The analog communication system is mainly composed of user equipment 、 Terminal equipment and transmission equipment etc . Its working process is ： At the sending end , First, the user equipment converts the non electric signal sent by the user into Analog electrical signals , Then it is modulated into an analog electrical signal suitable for channel transmission by the terminal equipment , Then sent to channel transmission . At the receiving end , Demodulated by terminal equipment , Then the user equipment will restore the analog electrical signal to a non electrical signal , Send to user .

There are many different techniques for frequency division multiple access to achieve channel sharing . Divide the channel frequency band into several narrower disjoint frequency bands （ It is called subband ）, Each sub-band is allocated to a user （ It's called address ）. This technology is called “ FDMA ” technology . Frequency division multiplexing （FDM） It refers to the subchannel in which the carrier bandwidth is divided into a variety of different frequency bands , A technique in which each subchannel can transmit one channel of signals in parallel . Frequency division multiplexing technology , Multiple users can share a physical communication channel , This process is called frequency division multiple access multiplexing （FDMA）.FDMA Analog transmission is the least efficient network , This is mainly reflected in that the analog channel can only be used by one user at a time , The bandwidth is not fully utilized .

Due to the limitation of transmission bandwidth , Unable to conduct long-distance roaming of mobile communication , It can only be a regional mobile communication system .

The first generation mobile communication has many formats , Our country mainly adopts TACS.

The first generation mobile communication has many shortcomings , Such as limited capacity 、 There are too many systems 、 Not compatible with each other 、 Poor confidentiality 、 The quality of the call is not good 、 Unable to provide data services and automatic roaming .

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The first 2 Chapter Analog mobile communication technology