Cellular network or mobile network (Cellular network) is a mobile communication hardware architecture, which divides the service of mobile phone into small hexagonal sub-areas, and each cell has a base station, which forms a structure similar to "cellular". Therefore, this mobile communication method is called a cellular mobile communication method. Cellular networks can be divided into analog cellular networks and digital cellular networks, which are mainly distinguished from the way information is transmitted.
The reason why cellular networks are widely used is the result of a mathematical conclusion that the planes are covered by a circle of the same radius, when the center of the circle is at the center of each regular hexagon of the regular hexagonal grid, that is, when the center of the circle is in the square of the regular triangle. The number of circles used is the least. Although the use of a minimum number of nodes can cover the largest area of ​​the graph, even if the node is required to be solved on a grid with a translational characteristic like a lattice, in the communication, a circle is used to express the practical requirements. It is usually reasonable, so a positive triangle mesh or a simple hexagonal grid is the best choice for saving equipment construction costs. The network thus formed is covered and shaped very much like a cell, so it is called a cellular network.
The cellular network consists of the following three parts: mobile station, base station subsystem, and network subsystem. A mobile station is our network terminal device, such as a mobile phone or some cellular industrial control device. The base station subsystem includes mobile base stations (large towers), wireless transceivers, private networks (generally optical fibers), countless digital devices, and the like that we commonly see on a daily basis. We can think of the base station subsystem as a converter between the wireless network and the wired network.
Cellular network typeCommon types of cellular networks are: GSM networks (some countries called pcs-1900), CDMA networks, 3G networks, FDMA, TDMA, PDC, TACS, AMPS, etc.
The so-called cellular mobile phone refers to dividing the mobile phone service area into a plurality of cells adjacent to each other, and each cell establishes a network structure of a base station. Since each cell has a regular hexagon and is adjacent to each other, the shape is similar to a honeycomb as a whole, so it is called a "cellular" network. A large- and medium-capacity mobile phone system that covers a whole service area with a plurality of cellular cells is called a cellular mobile phone system, or a cellular mobile phone for short.
The biggest benefit of cellular mobile phones is that the frequencies can be reused. As you may know, when we use a mobile phone to communicate, everyone has to occupy a channel, that is, the system has to take out a channel for you to use. There are more people talking at the same time, and a limited channel may not be enough, so communication congestion will occur. With the cellular structure, the same set of frequencies can be used repeatedly in several cells separated by a certain distance, thereby achieving the purpose of saving frequency resources.
For example, we divide a city into 72 cells, and each 12 cells form a cluster. Let them use 300 channels together. Then, we can divide 300 channels into 12 channel groups, each group has 25 channels, the first cell group of the first cell group uses the first group channel, and the first cell group of the second cell group uses the second group. Channel, and so on. With proper scheduling, channel groups of the same numbered cells of different cell groups can be reused. Although the radio frequencies used by these cell base stations are the same, since they are far apart from each other and the range of electric waves is limited, they do not cause interference with each other. In this way, a set of frequencies can be reused 6 times. The original 300 channels can only be used for 300 users to talk at the same time. Now, 1800 users can simultaneously talk at the same time.
The cellular mobile telephone system is mainly composed of a mobile station (a car phone, a mobile phone, etc.), a wireless base station, and a mobile telephone switching center. Each cell base station is connected to a mobile telephone switching center to form a cellular mobile telephone network. The mobile phone network is also connected to the public telephone network in the city and the domestic and international long-distance telephone network, so that the mobile phone user can not only communicate with the mobile phone users in the network, but also can communicate with a wider range of mobile users and fixed users. .
Since Bell Labs invented the concept of honeycomb in the 1970s,
Cellular technology is the foundation of mobile communications. Sometimes, everyone calls mobile communication cellular communication.
Several important parts of the cellular concept are the basis for the development of mobile communications.
1. Frequency reuse. Limited frequency resources can be reused within a certain range.
2. Cell division. When the capacity is insufficient, the range of the cell can be reduced, and more cells can be divided to further improve the frequency utilization efficiency.
Cellular limitationsThe concept of cellular solves the problem of limited frequency resources in mobile communications, which directly led to the development of mobile communications after the 1980s. But the concept of cellular is also limited. The main problem now is that the cell cannot be split indefinitely, which leads to the capacity of the system cannot be further improved, which hinders the further development of mobile communication.
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