The difference between digital communication and analog communications

Source: Internet
Author: User
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According to the different signal modes, communication can be divided into analog communication and digital communications. What is analog communication? For example, in telephone communication, the electrical signals that are transmitted on the user's line vary with the user's voice size. This changed electrical signal, whether in time or amplitude, is continuous, which is called analog signal. The mode of communication that transmits analog signals on the user line is called "Analog communication".

Digital signal is different from analog signal, it is a kind of discrete, Pulse has no combination form, it is the signal of load digital information. The Telegraph signal belongs to the digital signal. The most common digital signal now is a waveform with only two amplitudes (0 and 1), called a "binary signal". "Digital communication" refers to the use of digital signal as a carrier to transmit information, or digital signal to the carrier digital modulation after the transmission of the communication mode.

Compared with analog communication, digital communications has obvious advantages: first, the anti-interference ability is strong. Analog signal in the transmission process and superimposed noise is difficult to separate, noise will be transmitted with the signal, amplification, seriously affect the quality of communication. The information in the digital communication is included in the pulse, as long as the absolute value of the noise does not exceed a threshold, the receiving end can determine whether the pulse, to ensure the reliability of communication. The second is that long distance transmission can still guarantee the quality. Because digital communication is the use of regenerative relay, can eliminate noise, regenerated digital signal and the original digital signal, can continue to transmission, so that the quality of communication will not be affected by distance, high-quality long-distance communication. In addition, it also has to adapt to a variety of communications business requirements (such as telephone, telegram, image, data, etc.), easy to achieve a unified integrated Services digital network, easy to use large scale integrated circuit, easy to achieve encryption processing, easy to achieve the communication network Computer Management and so on.

To realize digital communication, the analog signal sent by the transmitter must be turned into digital signal, which is called "modulus transformation". The most basic method of analog signal digitalization is three processes, the first step is "sampling", that is, discrete processing of continuous analog signals, usually the sample values of analog signals are extracted at equal intervals. The second step is "quantization", which transforms the analog signal sample value to the nearest numeric value. The sample value after sampling is discrete in time, but still continuous in amplitude, and the quantization process is to transform the continuous sampling on the amplitude into discrete. The third step is "coding", which is to quantify the sample value signal with a set of binary digital code to represent the final completion of the simulation signal digitization. Digital signals are sent to the digital network for transmission. The receiving end is a reduction process that transforms the received digital signal into an analog signal, the "Data Touch Transformation", to reproduce the sound or image.

If the signal sent by the transmitter is a digital signal, then the digital signal can be transferred directly into the digital network without the analog-to-digital conversion process.

Because of the rapid increase of people's demand for all kinds of communication services, digital communication is developing rapidly in the direction of miniaturization, intellectualization and high speed, which will eventually replace the analog communications.

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