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1. Introduction
As a computer major, you will often hear that XXX uses half-duplex, XXX uses full-duplex, what about serial communication, what about this communication protocol, but there is no such thing as this. Real mastery means a little understanding, so look up the information and record it.
Two, the concept
According to the user's call status and frequency usage method, mobile communication can be divided into three working modes: simplex, half-duplex and duplex. Simplex, half-duplex, and full-duplex are the three communication channels in telecommunication computer networks, and these communication channels can provide a way to convey information. The communication channel can be a physical transmission medium or a logical connection through a multiplexed medium. The physical transmission medium refers to materials that can propagate energy waves, such as wires in data communications. And the logical connection usually refers to a circuit switched connection or a packet mode virtual circuit connection, such as a wireless telecommunication channel. Thanks to the help of communication channels, information can be transmitted without obstacles. In the computer network, the duplex mode is mainly used. The local area network uses the half-duplex mode, and the metropolitan area network and the wide area network use the full-duplex mode.
1. Simplex
Simplex (Simplex Communication) mode of data transmission is one-way. Among the two communication parties, one is fixed as the sending end, and the other is fixed as the receiving end. Information can only be transmitted in one direction, using a transmission line. In layman's terms, you, as a hard worker, worked hard for a month, and sent the results of your work this month to your boss. After the boss receives your information, he will notify the finance company and send it to you. Salary: This process is one-way. There is no boss who reports to you as a worker. If you pay the boss, then what else do you do as a part-time job?
Simplex mode is generally used in situations where data is transmitted in only one direction. For example, the communication between the computer and the printer is a simplex mode, because only the computer transmits data to the printer, and there is no data transmission in the opposite direction. There are also some communication channels, such as simplex wireless transmission.
2. Half duplex
Half duplex (Half Duplex) data transmission means that data can be transmitted in both directions of a signal carrier, but cannot be transmitted at the same time. For example, using a technology with half-duplex transmission on a local area network, a workstation can send data online, and then immediately receive the data online. These data come from the direction the data was just transmitted. Like full-duplex transmission, half-duplex includes a bidirectional line (the line can transmit data in both directions). To give a simple example: it's like walking a single-plank bridge, one person alone, if I don't pass, you don't want to come over.
Half-duplex communication uses the same transmission line, which can both send and receive data, but cannot send and receive at the same time. Data transmission allows data to be transmitted in two directions, but at any time, only one of them can send data and the other can receive data. Therefore, half-duplex mode can use one data line or two data lines. It is actually a simplex communication that switches directions, just like a walkie-talkie (walkie-talkie). In half-duplex communication, an electronic switch for transmitting and receiving is required at each end, which determines the direction in which data is transmitted through the switch. Because of the switching, there will be a time delay. Information transmission efficiency is lower.
3. Full duplex
Full duplex (Full Duplex) is a term for communication transmission. Communication allows data to be transmitted in two directions at the same time, which is equivalent to a combination of two simplex communication methods in terms of capability. Full duplex refers to the simultaneous (instantaneous) bidirectional transmission of signals (A→B and B→A). Refers to A→B at the same time B→A, which is instantaneously synchronized.
Full-duplex data communication allows data to be transmitted in both directions at the same time. Therefore, full-duplex communication is a combination of two simplex communication methods. It requires that the sending device and the receiving device have independent receiving and sending capabilities, just like the telephone. same. In the full-duplex mode, each end has a transmitter and a receiver, and there are two transmission lines, which can be used in interactive applications and remote monitoring systems, and the information transmission efficiency is high.