Communication refers to the communication between people or between people and nature through certain behaviors ormediumThe exchange and transmission of information, in a broad sense, means that the two or more parties that need information use any method or medium to transmit information from one party to the other accurately and safely without violating their own will[1]。
[communicate by letter; correspond];Use letters to reflect the situation.
Frequently communicate with friends
Citation explanation
1. Exchange messages.《Jin Shu·Biography of Wang Cheng: "Cheng said because he had gone down, 'How do you communicate with Du Tao?'" Tang Li Deyu《On behalf of Liu Mian and the Uighur Prime Minister》"Afraid that the Uighurs would communicate with the Tubo, they have ordered their troops to cut off the Sanhekou Road."
2. Inform.Volume V of "Surprise at the First Moment": "Then Pei Pushe's family chose the date of marriage and asked the matchmaker to come to Zhang Shangshu's home to communicate." The 18th chapter of "Nine Fates of Strange Grievance": "Who hasn't received great kindness from his nephew and father, who still communicates?" Today, it refers to the use of telecommunications equipment or letters to convey information and reflect the situation.The fifth and third chapter of Yangu's old man "Xu Niaohai Flower": "Hua Fu has announced again that please issue a secret telegram for secret communication." The third act of Cao Yu's Peking Man: "We can often communicate in the future."《People's Daily》1982. 12.5: "The freedom and privacy of correspondence of citizens of the People's Republic of China are protected by law."
3. Articles reporting news.Lu Xun's Collection of Southern Tunes and Northern Tunes: Another Discussion on the "Third Kind of People": "What I want to say now, but what must be pointed out in the correspondence." Xu Zhucheng's "Old News of the Sea" 16:“《The Dagong Daily》It has successively published rural survey correspondence, travel correspondence, travel sketch and battlefield correspondence presided over by Comrade Changjiang. "
Development status
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Benefiting from the country's attention to government and public security, as well as the increase in large-scale activities brought about by China's rapid economic development, China's private network communication market has maintained a rapid growth in recent years. In 2016, China's private network communication market size reached 16.2 billion yuan, and by 2020, the market size will grow to 34.4 billion yuan, with a growth rate of 13.9%.In 2021, the market size of China's private network communication industry will maintain a stable growth trend, with the market size of about 38.7 billion yuan.
The market of private network communication in China is relatively concentrated, and enterprises with advanced technology and brand and channel advantages occupy most of the market shares of the industry.Based on the data analysis of the sample enterprises, the total revenue of the sample enterprises will reach 26.274 billion yuan in 2020.In general, the performance of the sample enterprises varies greatly. Hytera maintains its leading position in the civil private network, with a revenue of 6.109 billion yuan in 2020;Hager Communications has maintained its leading position in the military private network, with a revenue of 5.122 billion yuan in 2020.The revenue of Jiaxun Feihong and Xinwei Technology is less than 1 billion yuan, far lower than that of Hytera and Hager Communications.[5]
natural science
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concept
Communication has different interpretations in different environments. After the emergence of radio wave transmission communication, communication is simply interpreted as the transmission of information, which refers to the transmission and exchange of information from one place to another, with the purpose of transmitting messages.However, in the process of human practice, with the development of social productive forces, communication has constantly improved the requirements for message transmission, making human civilization progress.Among all kinds of communication methods, the communication method that uses "electricity" to transmit messages is called telecommunications. This kind of communication has the characteristics of rapidity, accuracy, reliability, and is almost not limited by time, place, space, and distance, so it has been developed rapidly and widely used;Nowadays, due to the rapidity of radio waves, the physical communication (postal communication), which combines cultural exchanges with the continuous accumulation and progress of the real economy from the ancient human material exchange process, is understood by mankind as an obstacle to economic development.
In ancient times, human beingsPost station、Flying Pigeon Messenger, beacon fire alarm, symbols, body language, eyes, touch and other means of information transmission.
With the rapid development of modern science, various communication modes such as radio, fixed phone, mobile phone, Internet and even video phone have emerged.Communication technology has narrowed the distance between people, improved economic efficiency, and profoundly changed the way of life and social outlook of human beings[3]。
mode
E-MAIL
Ancient, mainly visual and sound transmissionthe Beacon Tower, drummingSemaphoreIn modern times, fast horse relay, carrier pigeon, postal communication, etc.In the past, for long-distance communication, it took several days at the fastest, while modern communication is often based on telecommunications, such as telegraph, telephone, express mail, short messageE-mail and others pay attention to instant communication. As a natural science, postal communication can better reflect the harmony and communication between man and nature. However, in the period of paying attention to economic interests, it often fails to pay attention to the relationship between man and nature, which makes postal communication unacceptable to instant communication.Federal CommunicationsThe French definition of communication includes telecommunications and radio and television.It should be noted that this communication law is not suitable for China.Since ancient times, China has focused on the humanistic and natural concept of "harmony between man and nature" and the pursuit of harmonious coexistence between people.
The definition of telecommunications in China's telecommunications regulations includes public telecommunications and radio and television.China《Postal law》Is not violating《Universal Postal Convention》In combination with China's national conditions.
Through the combination of body, eyes, gestures, rocks, trees and other natural media to convey information.
2. Oral era
Standing upright makes people's demand for the way of information transmission increase, thus giving birth to language.
3. The era of writing
With the development of productive forces, people have a demand for information records, and words have come into being.
4. Printing era
In 1044, Bi Sheng invented movable type printing.
In 1450, German Gutenberg invented metal movable type printing.
In 1837, American Morse invented the telegraph.
In 1857, the transatlantic telegraph cable was completed.
In 1875, Bell invented the first telephone in history.
In 1895, Russian Popov and Italian Marconi successfully developedRadio receiver。
In 1895, the Lumiere brothers of France premiered their first film in Paris.
In 1912, the radio saved more than 700 lives in the sinking of the Titanic.
In 1920s, radio came out.
In 1920s, the British Baird successfully transmitted television pictures, and was known as the inventor of television.
When World War II broke out, the television industry was interrupted. The war highlighted the low cost of broadcasting and easy reception, and the audience increased again.
In 1962, the United States launched the first communication satellite, opening the era of television satellite transmission.
In 1969, the US military established ARPANET to prevent communication interruption when attacked.
In 1983, the US Department of Defense divided the Arpanet into military and civilian networks, and gradually expanded it into today's Internet.
In 1993, the United States announced the plan to build an information highway to integrate computer, telephone and television media.
In 1996, under the leadership of ITU (International Telecommunication Union), a consensus building blueprint for the communication system IMT-2000, namely the 3G third generation mobile communication system, was produced.
In 2009, the concept of Internet of Things emerged, and formed a turbulent wave at a growth rate far higher than that of mobile Internet.
In 2018, 5G standards will be collected, and any relevant manufacturer and standard organization can submit suggestions.In order to meet the requirements of 5G communication network for different connection characteristics, 5G network adopts many new wireless communication technologies, among which the most representative are beam forming, massive MIMO, and millimeter wave communication.[6]
classification
1. Classification by transmission medium
wire communication: It refers to the communication in the form of wire, cable, optical cable, waveguide, nano material, etc., whose characteristic is that the medium can be seen and touched (open line communication, cable communication, optical cable communication, optical fiber and optical cable communication).
wireless communication : refers to a form of communication in which the transmission medium cannot be seen or touched (such as electromagnetic waves)[2]。
(Microwave communication, short wave communication, mobile communication, satellite communication, scattering communication).
2. Classification according to the signal transmitted in the channel
analog signal: Any parameter of signal (such as amplitude, frequency, phase of continuous wave, amplitude, width, position of pulse wave, etc.) can take an infinite number of values and directly correspond to the message. Sometimes, analog signal is also called continuous signal.This continuity means that a certain parameter of the signal can change continuously.
digital signal: A parameter of a signal that can only take a finite number of values and often does not directly correspond to the message is also called a discrete signal[1]。
3. Classification by operating frequency band
long-wave communication.
Medium wave communication.
Short wave communication.
Microwave communication.
4. Classification by modulation mode
Baseband transmission: refers to the communication mode in which the signal is directly sent to the channel for transmission without modulation.
Band transmission: refers to the communication mode in which the signal is modulated and then sent to the channel for transmission, and the receiver has corresponding demodulation measures.
5. Classified according to the division of labor and data transmission direction of both communication parties.
For point-to-point communication, the communication modes can be divided into simplex communication, half duplex communication andFull duplex communicationThree.
Simplex communication refers to a communication mode in which messages can only be transmitted in one direction.There are many examples of simplex communication, such as broadcasting, remote control, wireless paging, etc.Here, signals (messages) are only transmitted from radio transmitter, remote controller and wireless paging center to radio, remote control object and BP machine.
The so-called half duplex communication means that both sides of the communication can send and receive messages, but cannot send and receive messages at the same time.Intercom, transceiver, etc. are all this communication mode.
The so-called full duplex communication refers to the working mode in which both sides of the communication 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 of full duplex communication must be a two-way channel.There are many examples of full duplex communication in life, such as ordinary phones, mobile phones, etc[4]。
form
communication system
All technical equipment and transmission media required for information transmission are collectively referred to as communication systems.
Source: the place where messages are generated. Its function is to convert various messages into original electrical signals, called message signals or baseband signals.Telephone, TV camera, telex, computer and other digital terminal equipment are the source of information.
Transmitting equipment: match the source with the channel, that is, transform the message signal generated by the source into an occasion suitable for moving in the channel. Modulation is the most common transformation method.Modulation is the most common conversion method for the occasions requiring spectrum shifting.For digital communication systems, transmission 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. In order to facilitate analysis, noise sources are abstractly added to the channel as the concentrated representation of various noises.
Receiving equipment: complete the inverse transformation of the transmitting equipment, that is, perform demodulation, decoding, decoding, etc.Its task is to correctly recover the corresponding original baseband signal from the received signal with interference.
Destination: the destination of information transmission, which is used to convert the restored original signal into corresponding information[2]。
