What is communication?

Communication refers to the exchange and transmission of information between people or between people and nature through some behavior or medium. In a broad sense, it refers to the use of information by two or more parties who need information without violating their respective wishes. Any method, any medium, to accurately and securely transmit information from one party to another.

Communication has different interpretations in different environments. After the emergence of radio wave transmission communication, communication (Communication) was simply interpreted as the transmission of information, which refers to the The purpose of transmitting and exchanging information from one place to another is to transmit messages.

However, communication is in the process of human practice. With the development of social productivity, the requirements for transmitting messages continue to increase, which makes human civilization continue to progress.

Among various communication methods, the communication method that uses "electricity" to transmit messages is called telecommunications. This kind of communication has the characteristics of rapid, accurate, reliable, and is almost independent of time. , location, space, and distance constraints, it has developed rapidly and been widely used; Physical communication (postal communication) is understood by humans as an obstacle to economic development.

In ancient times, humans transmitted information through inns, flying pigeons delivering messages, beacon fire alarms, symbols, body language, eyes, and touch.

With the rapid development of modern scientific level, various communication methods such as radio, landline phone, mobile phone, Internet and even video phone have appeared one after another. Communication technology has shortened the distance between people, improved economic efficiency, and profoundly changed human life style and social outlook.

Classification

1. Classification by transmission medium

Wired communication: refers to communication in the form of transmission media such as wires, cables, optical cables, waveguides, nanomaterials, etc. It is characterized by the fact that the medium can be seen and touched (open wire communication, cable communications, optical cable communications, optical fiber cable communications).

Wireless communication: refers to a form of communication in which the transmission medium is invisible and intangible (such as electromagnetic waves) [2] .

(Microwave communication, shortwave communication, mobile communication, satellite communication, scattering communication).

2. Classification according to the signal transmitted in the channel

Analog signal: A certain parameter of the signal (such as the amplitude, frequency, phase of the continuous wave, the amplitude, width, position of the pulse wave, etc.) can take an infinite number of values. And directly corresponding to the message, analog signals are sometimes called continuous signals. This continuity means that a certain parameter of the signal can change continuously.

Digital signal: If a certain parameter of the signal can only take on a limited number of values ​​and often does not directly correspond to the message, it is also called a discrete signal [1].

3. Classification by working frequency band

Long wave communication.

Medium wave communication.

Short wave communication.

Microwave communication.

4． Classification by modulation method

Baseband transmission: refers to a communication method in which the signal is directly sent to the channel for transmission

without being modulated.

Frequency band transmission: refers to a communication method in which the signal is modulated and then sent to the channel for transmission, and the receiving end

has corresponding demodulation measures.

5. Classified according to the division of labor between the communication parties and the direction of data transmission.

For point-to-point communication, according to the direction of message transmission, communication methods can be divided into three types: simplex communication, half-duplex communication and full-duplex communication.

The so-called simplex communication refers to a communication method in which messages can only be transmitted in one direction. There are many examples of simplex communication, such as broadcast, remote control, wireless paging, etc. Here, the signal (message) is only transmitted from the broadcast transmitter, remote control and wireless paging center to the radio, remote control object and BP machine respectively.

The so-called half-duplex communication method refers to a working method in which both communicating parties can send and receive messages, but cannot receive and send messages at the same time. Walkie-talkies, transceivers, etc. are all such communication methods.

The so-called full-duplex communication refers to a working method in which both communicating parties can transmit messages in both directions at the same time. In this way, both parties can send and receive messages at the same time. Obviously, the channel for full-duplex communication must be a two-way channel. There are many examples of full-duplex communication in life, such as ordinary telephones, mobile phones, etc.

Composition

The collective collection of all technical equipment and transmission media required to achieve information transmission is called a communication system.

Source: The place where the message is generated. Its function is to convert various messages into original electrical signals, which are called message signals or baseband signals. Various digital terminal equipment such as telephones, television cameras, telex machines, and computers are sources of information.

Sending equipment: Match the source and channel, that is, convert the message signal generated by the source into an occasion suitable for moving in the channel. Modulation is the most common conversion method. Modulation is the most common conversion method when spectrum shifting is required. For digital communication systems, sending equipment is often divided into source coding and channel coding.

Channel: The physical medium for transmitting signals.

Noise source: It is inherent in various devices and channels in the communication system. For the convenience of analysis, the noise source is regarded as a concentrated expression of noise everywhere and is abstractly added to the channel.

Receiving device: Complete the inverse transformation of the sending device, that is, demodulation, decoding, decoding, etc. Its task is to correctly recover the corresponding original baseband signal from the received signal with interference.

Information sink: The destination point of transmitted information. Its function is to convert the restored original signal into the corresponding information.

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