1G realizes analog voice communication; 2G realizes the digitalization of voice communication; 3G realizes multimedia communication such as pictures other than voice; 4G has realized local high-speed Internet access. In a word, the appearance of 1G~4G is devoted to more convenient and quick communication between people, but the birth of 5G subverts all this, greatly reduces the limitations and realizes the interconnection of everything at any time and place.
Communication technology can be divided into wired communication and wireless communication from the transmission mode. Although the speed of wired communication is very high, it has always been a huge bottleneck for mobile communication to spread in the air. At present, the theoretical rate of mainstream 4G LTE is only 150Mbps, which is far from wired communication. So now the most important thing in the research and development of 5G network is to break through the bottleneck of wireless communication.
In fact, wireless communication uses electromagnetic waves to communicate, and the functional characteristics of electromagnetic waves are determined by their frequencies. Electromagnetic waves with different frequencies have different properties and characteristics, so they have different uses. For example, high-frequency gamma rays are very lethal and can be used to treat tumors. In addition, there will be interference between radio waves of different frequencies. In order to avoid this kind of interference and conflict between radio waves, we have divided radio waves and allocated different uses.
The mobile phones we use are mainly medium frequency to ultra-high frequency. For example, "CDMA800" often refers to CDMA with a working frequency band of 800MHz, and "GSM900" refers to GSM with a working frequency band of 900MHz.
From 1G to 4G, the frequency of radio waves used is getting higher and higher, and the higher the frequency, the richer the frequency resources that can be used, thus the higher the transmission rate. If frequency resources are compared to carriages, the higher the frequency, the more carriages there are, and the more information can be loaded under the same resources. Some people may ask, since high frequency is so powerful, why don't we use it? Actually, it's not useless, it's really unbearable.
Another notable feature of electromagnetic waves is that the higher the frequency, the shorter the wavelength, and the closer it is to straight line propagation, and the relative diffraction and wall-penetrating ability will become worse, so the higher the frequency, the greater the loss during propagation. Because of this, if high frequency is widely used in mobile communication, the transmission distance needs to be greatly shortened. So in the same range, 5G needs more base stations, but the increase of base stations means the increase of cost. It is precisely because of this that the three major operators are struggling to pursue low frequency bands. After all, consider the cost.