The main features of digital communication networks are digitalization

In simple terms, a digital communication system refers to a communication system that uses digital signals to transmit messages. Composition: source-modulator-encoder-encryptor-channel-decryptor-decoder-demodulator-letter Main features of digital communication 1 Strong anti-interference ability, especially after the digital signal is regenerated through the relay, the noise accumulation can be eliminated; 2. The digital signal is coded by error control, which can improve the reliability of communication; 3. Because digital communication transmission generally adopts binary code, computers can be used to process digital signals, realize complex long-distance large-scale automatic control systems and automatic data processing systems, and realize computer-centered communication networks.

4 In digital communication, all kinds of messages (analog and discrete) can be transmitted as a unified digital signal. Digital signals can be used for monitoring signals, control signals and business signals of digital signal transmission in the system. The ISDN composed of digital transmission and digital switching technology automatically transforms, synthesizes, transmits, processes, stores and separates signals from different sources to achieve various integrated services.

5 Digital signals are easy to encrypt and process, so digital communication is highly confidential. The disadvantage of digital communication is that it takes up more bandwidth than analog signals, however, due to the advent of millimeter wave and fiber optic communications, bandwidth is no longer an issue.

(1) Strong anti-interference ability, and no noise accumulation.

2) The transmission error is controllable, which can be detected and corrected through channel coding technology, reducing the bit error rate and improving the transmission quality.

3) It is convenient to process, transform and store digital information with modern digital signal processing technology.

4) Easy to integrate, miniaturization and weight reduction of communication equipment.

5) Easy to encrypt and have good confidentiality.

1.The anti-interference ability is strong, and each relay station can shape the distorted received signal to eliminate the accumulation of waveform errors along the line.

2.Error control techniques such as error correction coding can be used, which greatly improves the anti-interference performance.

3.It can use digital encryption technology with high confidentiality, which greatly improves the confidentiality of the system.

4.It can transmit a variety of analog and digital input information in a comprehensive manner, and is easy to store and process.

5.It can be compressed by source coding to reduce redundancy and improve channel utilization.

6.Digital communication equipment is easier to design and manufacture, smaller in size, and lighter in weight than analog communication equipment.

7.In an analog modulation system, the input signal-to-noise ratio at the receiver only increases proportionally to the bandwidth. In a digital modulation system, the output signal-to-noise ratio increases exponentially with bandwidth.

Features: strong anti-interference ability, no noise interference. Easy to encrypt. Occupied bandwidth. The equipment is easy to integrate and miniaturize.

The special point of the digital signal is ().

a.It is continuous in time and amplitude.

b.It is discrete in terms of time and continuous in amplitude.

c.It is continuous in time and discrete in amplitude.

d.It is discontinuous in time and amplitude.

Correct Answer: It is discontinuous in time and amplitude.

Features of digital signals:

The characteristics of digital signals are strong anti-interference ability, easy to encrypt processing, easy to store, process and exchange, easy to integrate, miniaturized, easy to form an integrated digital network and an integrated service digital network, and occupy a wide channel frequency band.

1. Strong anti-interference ability, noiseless noise accumulation. In analog communication, in order to improve the signal-to-noise ratio, it is necessary to amplify the attenuated transmission signal in time during signal transmission, and the noise that is inevitably superimposed on the signal during the transmission process is also amplified at the same time. As the transmission distance increases, the noise accumulates more and more, resulting in a serious deterioration of the transmission quality.

2. Easy to encrypt. The security and confidentiality of information transmission are becoming more and more important, and the encryption of digital communication is much easier than that of analog communication.

3. Easy to store, process and exchange. The signal form of digital communication is consistent with the signal used by the computer, which is binary, so it is convenient to network with the computer, and it is also convenient to store, process and exchange the digital signal with the computer, which can make the management and maintenance of the communication network automatic and intelligent.

4. The equipment is easy to integrate and miniaturize. Digital communication uses time-division multiplexing, which does not require a bulky filter. Most of the circuitry in the device is digital and can be implemented with large-scale and ultra-large-scale integrated circuits, so it is small in size and low in power consumption.