Data communication is the basic function of computer network.
"Data" in the computer system, whether it is text information, voice information, or graphics, image informationWebsite Design, they are converted into a unified 0,1 code sequence and stored on the storage medium of the system.Code sequence is data, which is the real information carrier.
Data communication is the exchange of information, which is a new way of communication produced by the combination of communication technology and computer technology.Specifically, it refers to the communication technology involved in the computer network, such as encoding technology, modulation technology, multiplexing technology, etc., in which the 0,1 digital data is transferred to the other end through transformation processing and communication media.
2. Data communication model
In the computer network, the data communication process can be roughly divided into five parts, as shown in Figure 2-1. (1) Source: the source station that generates data, that is, the source host.
(2) Host: the destination station receiving data, namely the destination host.
Digital data: data provided by the source or received by the destination, that is, 0, 1 sequence.
(3) Converter: responsible for transforming the digital data (including coding or modulation) sent by the source into some form of physical signal, and then sending it to the channel.
(4) Inverse converter: It is responsible for the inverse transformation (including demodulation or decoding) of physical signals on the channel into digital data and delivering it to the destination.
Physical signal: the carrier of digital data in the transmission process. It is the electromagnetic signal, optical signal, pulse signal or modulation signal that is transformed by the transmitter and processed to be suitable for transmission on the communication medium.
(5) Channel: refers to the channel for physical signal transmission, i.e. communication medium. The channel for analog signal transmission is analog channel;The channel for transmitting digital signals is digital channel.
Analog signal: the signal that changes continuously with time, as shown in Figure 2-2. Digital signal: signal strength keeps a constant value for a period of time, with discrete change characteristics.