How to check the mobile 4g ??frequency band?

How to query the mobile 4G frequency band:

Method 1: Log in to the official website of China Mobile: /index/gd/i, search for your mobile phone model in the search bar of the official website, and check the following Parameters, here is an introduction to the 4G frequency bands supported by the mobile phone.

Method 2: Send SMS code *#*#7378423#*#* to 10086 via mobile phone to check. ?

The frequency bands obtained by China Mobile operators are: 1880-1900 MHz, 2320-2370 MHz, 2575-2635 MHz; (bands: 39 bands: 40 bands: 41).

Introduction to frequency band:

Overview:

Frequency band is a word related to communication and sound physics.

In the field of vocal music, the frequency band refers to the sound frequency. The human ear’s perception of sound frequency is from the lowest 20Hz to the highest 20KHz, while the frequency range of human speech is concentrated between 80Hz~12kHz. Time, sounds in different frequency bands have different feelings for people.

In the field of communications, the frequency band refers to the frequency range of electromagnetic waves. The unit is Hz. According to the frequency, it can be divided into:

Very low frequency (VLF) 3 kHz~30 kHz, corresponding to the wavelength of electromagnetic waves is very long wave 100 km~10 km.

Low frequency (LF) is 30 kHz ~300 kHz, and the corresponding electromagnetic wave wavelength is long wave 10 km ~ 1 km.

Medium frequency (MF) is 300 kHz ~ 3000 kHz, and the corresponding electromagnetic wave wavelength is medium wave 1000 m ~ 100 m.

High frequency (HF) 3 MHz ~ 30 MHz, corresponding to the wavelength of electromagnetic waves is short wave 100 m ~ 10 m.

Very high frequency (VHF) 30 MHz~300 MHz, corresponding to the wavelength of electromagnetic waves 10 m~1 m.

Ultra high frequency (UHF) 300 MHz ~ 3000 MHz, the corresponding electromagnetic wave wavelength is decimeter wave 100cm ~ 10 cm.

Super high frequency (SHF) 3 GHz~30 GHz, corresponding to the wavelength of electromagnetic waves is centimeter wave 10 cm~1 cm.

Extremely high frequency (EHF) 30 GHz ~ 300 GHz, corresponding to the wavelength of electromagnetic waves is millimeter wave 10 mm ~ 1 mm.

To the high frequency of 300 GHz ~ 3000 GHz, the corresponding electromagnetic wave wavelength is 1 mm ~ 0.1 mm.

Division of communication:

Various communication systems also have a selective and rational allocation problem for the frequency bands used in the channel, so as to rationally utilize and save spectrum resources as much as possible to meet the needs of effective and rational use. Requirements for reliable transmission.

For wired channels, it is important to choose different transmission media and channel frequency reuse of broadband media. Generally, the frequency band is determined based on the channel service requirements and considering the performance characteristics of the aforementioned wired channels (constant parameters) required by them, such as loss, delay and phase shift characteristics, as well as the lowest and highest cutoff frequencies, etc.

Undersea communication is suitable for extremely low frequency bands and has good transmission performance; any baseband signal transmission uses all low-frequency bands with the baseband signal bandwidth as the cut-off frequency. Low-frequency transmission of analog voice only uses 300~3400Hz or Premium sound (music) from 50Hz to 15kHz bandwidth.

The more complicated issue is that various wireless communications must select and appropriately allocate working frequency bands based on the propagation characteristics of space electromagnetic waves. ITU-R has formulated specific rules for spectrum allocation, and various departments in various countries scientifically and strictly control the use of frequency points.

There are generally three ways in which electromagnetic waves are transmitted from transmission to reception: first, those that propagate on the ground are called "ground waves"; second, those that propagate in a straight line between two points in space are called "space waves"; The third is propagation by single-hop or multi-hop reflection from the ionosphere above the earth to the ground, which is called "sky wave".

Ground waves propagating along the earth's surface will be attenuated by bad conductors such as the ground due to the induced current generated by jumping electromagnetic waves along the ground. The higher the frequency, the greater the skin effect and the greater the loss. Therefore, ground waves are suitable for medium and long waves and medium waves (ie, hundreds of kilohertz to several megahertz), such as civilian broadcasting from 535kHz to 1605kHz frequency band (one program every 10kHz).

Shortwave (high-frequency band) of several megahertz to tens of megahertz is suitable for sky wave propagation. The distance between transmitting and receiving is much larger than that of ground wave, and can reach hundreds to thousands of kilometers, which depends on the incident angle of the antenna. As mentioned above, the ionosphere will absorb and attenuate the reflected electromagnetic waves. The greater the ionization concentration, the greater the loss. This fluctuation and attenuation of electromagnetic waves caused by random changes in the ionosphere is the fading phenomenon.

If the wavelength is shorter, that is, a higher frequency band, such as hundreds of megahertz to several gigahertz (109MHz) or more, it enters the microwave band. Electromagnetic waves in this frequency band are rarely absorbed by the ionosphere and are no longer reflected back to the ground. For example, in satellite communications, electromagnetic waves can penetrate the ionosphere and propagate to satellites. This kind of space wave propagation is similar to light. Not only does it propagate in a straight line, but electromagnetic waves also have diffraction (diffraction) effects and can bypass some local obstacles. For example, microwave relay propagates in a straight line between points on the ground. In addition to being affected by the ground environment (swamps, mountains, forests, etc.), it is inconvenient to erect antennas too high, so the relay (relay) section is only 40 to 50 kilometers long. Often called "line-of-sight" communication.

Wireless communications require that the length of the transmitting and receiving antennas match the wavelength λ and the size of the antenna is 1/4·λ. Therefore, it is impossible for civilian broadcasting station antennas that use omnidirectional antennas to stably erect more than 100 meters. The GSM mobile phone antenna using the 900MHz frequency band can be as short as a few centimeters long, which is very convenient for mobile phones to be miniaturized and carried.

All wireless communications are propagated through free space. In order to use frequency bands rationally and prevent various communications in various regions from interfering with each other, ITU scientifically allocates frequency bands suitable for various communication systems, and the frequencies of each band and their wavelengths The corresponding values ??and their names are promulgated by the International Telecommunications Union Wireless Commission (ITU-R). Countries, regions, and cities have corresponding radio management committees responsible for the reasonable coordination of wireless frequencies in their own countries and regions.