Basic network architecture
- Core network + base station (signal transmitter)
- Mobile phone (signal receiving end)
a brief introdction
The transmission of any information requires a medium, and cellular mobile communication, that is, the wireless transmission medium of'x
G'is a wireless electromagnetic wave. The electromagnetic wave was verified by the German Hertz in 1887, so the frequency unit of the electromagnetic wave is Hz, and the electromagnetic wave can be unimpeded. The ground penetrates the wall, but it will be blocked by large and thin metal sheets. Therefore, the general interior decoration has metal, which will affect the signal of the mobile phone.
The propagation speed of electromagnetic waves is as fast as the speed of light, 3*10^8m/s, equator A circle of 40076000m, divided by the speed of light, is approximately equal to 0.1336s, which means that the equator is run in 1336ms, but light travels in a straight line, so this theory does not exist.>__>QAQ...
Electromagnetic waves include radio waves, infrared rays, visible light, and ultraviolet rays. X-rays, g-rays are all the
original wireless communication technologies of electromagnetic waves : The radio
was invented by the Italian Marconi (x Tesla) in 1895. The two of them filed a lawsuit. The judge finally determined that the
radio was invented by Tesla. The technical principle of communication:
the change of the current strength in the conductor will generate radio waves, and the information will be added to the radio waves through modulation. When the radio waves propagate through space and reach the receiving end, the changes in the electromagnetic field caused by the radio waves will generate currents in the conductors. , Extracting information through demodulation
The invention of radio technology has been 126 years ago. Nowadays, according to the division of wavelength and frequency, radio has been used in various fields, such as broadcasting, television, telephone, satellite communication, Bluetooth, radio frequency identification, Navigation, radar, heating (microwave oven), etc. The
current application of normalizing is undoubtedly
the coverage of WiFi and Internet of Things technology WiFi coverage (about 90m), which means that if your home is 100m, the neighbors of the neighbors will not be able to find your home. network
WLAN is a wireless local area network alliance
WiFi is a trademark of the alliance. It can be understood as a brand and a technical standard
. The Internet of Things is widely used, such as smart homes. It uses the long-wavelength ultra-long wave (the lowest frequency) in the radio wave, 3-30kHz , To transmit information, currently the most widely used is the NB-IOT module device, which is used for LAN communication of smart home devices. When the device is alarmed, it is transmitted to the mobile phone through the gateway device to realize remote monitoring of the home condition.
The bandwidth of NB-IOT Is it 180kHz, the uplink rate is 16.9Kbps, the downlink rate is 26Kbps, and the power consumption is very low. In
cellular mobile communications, where is the cell?
That is, a circle with the same radius covers the plane, and when the center of the circle is at the exact center of the surrounding hexagons, the number of circles used is the smallest. Therefore, the coverage of the base stations is distributed in a hexagonal shape, and there is a base station in the center of each hexagon. Since the formed network is covered together and shaped like a honeycomb, it is called a cellular network.