What is digital communication and analog communication
According to the different signal modes, communication can be divided into analog communication and digital communication. What is analog communication? For example, in telephone communication, the electric signal transmitted on the subscriber line changes with the change of the user's voice. This changing electrical signal is continuous in time or in amplitude, and this signal is called an analog signal. According to different signal modes for transmitting analog signals on subscriber lines, communication can be divided into analog communication and digital communication. What is analog communication? For example, in telephone communication, the electric signal transmitted on the subscriber line changes with the change of the user's voice. This changing electrical signal is continuous in time or in amplitude, and this signal is called an analog signal. The communication method of transmitting analog signals on the subscriber line is called 'analog communication'. Digital signal is different from analog signal. It is a discrete, pulsed combination form, and it is a signal that carries digital information. Telegraph signals are digital signals. The most common digital signal is a waveform with only two amplitude values u200bu200b(represented by 0 and 1), which is called a 'binary signal'. 'Digital communication' refers to a communication method that uses a digital signal as a carrier to transmit information, or uses a digital signal to digitally modulate the carrier wave before transmission. Compared with analog communication, digital communication has obvious advantages: first, it has strong anti-interference ability. The analog signal is difficult to separate from the superimposed noise in the transmission process, and the noise will be transmitted and amplified along with the signal, which will seriously affect the communication quality. The information in digital communication is included in the presence or absence of pulses. As long as the absolute value of the noise does not exceed a certain threshold, the receiving end can determine the presence or absence of pulses to ensure the reliability of communication. Secondly, long-distance transmission can still guarantee quality. Because digital communication adopts the regenerative relay method, which can eliminate noise, the regenerated digital signal is the same as the original digital signal and can be continuously transmitted, so that the communication quality is not affected by the distance, and high-quality long-distance communication can be carried out. In addition, it also has a computer that adapts to various communication service requirements (such as telephone, telegraph, image, data, etc.), facilitates the realization of a unified integrated service digital network, facilitates the use of large-scale integrated circuits, facilitates encryption processing, and facilitates the realization of communication networks. Management and other advantages. To realize digital communication, the analog signal sent by the transmitter must be turned into a digital signal. This process is called 'analog-to-digital conversion'. The most basic method of analog signal digitization has three processes. The first step is 'samplingThe second step is 'quantizationBecause the sample values u200bu200bafter sampling are discrete in time, they are still continuous in amplitude. The quantization process is to change the continuous sampling in amplitude to discrete. The third step is 'encodingThe digital signal is sent to the digital network for transmission. The receiving end is a restoration process, which converts the received digital signal into an analog signal, that is, 'data touch conversion If the signal sent by the sender is originally a digital signal, there is no need to perform the analog-to-digital conversion process, and the digital signal can directly enter the digital network for transmission. Due to the rapid increase in people's demand for various communication services, digital communication is developing rapidly in the direction of miniaturization, intelligence, high-speed and large-capacity, and will eventually replace analog communication.
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