What are the types of wireless transmission media, and what is the main purpose of each transmission

Wireless transmission media include radio signals, microwave signals, and satellite signals. In the field of computer networks, wireless communication media are mainly microwaves and satellites. Microwave communication refers to communication with microwave signals with frequencies ranging from 100MHz to 10GHz.

The features are: communication can only be carried out within the visual range;

The atmosphere has a great influence on the absorption and scattering of microwave signals.

Microwave communication is mainly used in the range of a few kilometers, which is not suitable for laying wired transmission media, and can only be used for point-to-point communication, and the rate is not high, generally several hundred kbps. Satellite communication refers to the communication method of using artificial satellites for transit: commercial communication satellites are generally launched in synchronous orbits 10,000 kilometers above the equator, and there are also small satellite communications in medium and low orbits, such as the Iridium system of Motorala.

The characteristics are: suitable for long-distance transmission, such as between countries and continents;

The transmission delay is large, generally about 500ms;

The cost is higher.

Wireless transmission media.

Electromagnetic waves can be used in free space to send and receive signals for communication, which is wireless transmission. The Earth's atmosphere provides the physical channel for most of the wireless transmission, which is often referred to as the wireless transmission medium. Wireless transmissions use a wide range of frequency bands, and several bands are now used for communication.

Ultraviolet light and higher wavelengths are not currently available for communication. Methods of wireless communication include radio waves, microwaves, and infrared.

Radio wave. Radio waves refer to electromagnetic waves in the radio frequency band that propagate in free space, including air and vacuum. Radio technology is the technology that transmits sound or other signals through radio waves.

The principle of radio technology is that a change in the intensity of the current in a conductor produces radio waves. Using this phenomenon, information can be loaded on top of radio waves by modulation. When the radio wave travels through space to the receiver, the change in the electromagnetic field caused by the radio wave will generate an electric current in the conductor.

The purpose of information transmission is achieved by extracting the information from the current change through demodulation.

Microwave. Microwave refers to electromagnetic waves with a frequency of 300MHz-300GHz, which is the abbreviation of a limited frequency band in radio waves, that is, electromagnetic waves with a wavelength between 1 meter (excluding 1 meter) and 1 millimeter, which is a general term for decimeter waves, centimeter waves, and millimeter waves. The frequency of microwaves is higher than that of ordinary radio waves, and it is also commonly referred to as "ultra-high frequency electromagnetic waves".

Infrared. Infrared is one of the many invisible rays of the sun's rays, discovered by the German scientist Hoxel in 1800, also known as infrared thermal radiation, he used a prism to break down the sunlight, placed a thermometer on the position of the color band of various colors, trying to measure the heating effect of various colors of light. It turned out that the thermometer on the outside of the red light warmed up the fastest.

Therefore, it is concluded that in the solar spectrum, there must be invisible light on the outside of the red light, which is infrared light. It can also be used as a medium for transmission.

The wavelength of infrared rays on the solar spectrum is greater than that of visible light, and the wavelength is. Infrared can be divided into three parts, namely near-infrared, with wavelengths between; mid-infrared, wavelengths between; Far infrared, wavelength between.

Infrared communication has two most prominent advantages:

1. It is not easy to be found and intercepted, and the confidentiality is strong;

2. It is almost free from electrical, celestial and man-made interference, and has strong anti-interference. In addition, the infrared communication machine is small in size, light in weight, simple in structure, and inexpensive. However, it must communicate within direct visual distance, and its propagation is affected by the weather.

In the case that you can't set up a wired line, and you are afraid of exposing yourself by using a radio, it is better to use infrared communication.

1. The wired transmission medium mainly includes twisted pair, coaxial cable and optical fiber.

2. Wireless transmission medium is divided into radio band, microwave, infrared, laser, etc.

Commonly used transmission media are divided into two categories: wired transmission media and wireless transmission media. Different transmission media have different characteristics, and their different characteristics have a great impact on the quality and speed of data communication in the network.