The current mobile communication systems use the
cellular
multiple access method, which is called space division multiple access.
In layman's terms, because the propagation distance of wireless signals is limited and we hope that our communication system can accommodate as many users as possible, we must think of many ways to make full use of existing resources and provide more user services. The resources used include signal frequency, signal type, and space.
Using signal frequencies to achieve multiple access is to use different frequencies to carry signals, so that we can provide services to different users at the same time. Just came up with a way to divide the ground space into small areas one by one, each area is called a cell, and the signals between the cell and the cell can try not to interfere with each other, so that the carriers of the same frequency can be spatially Used by different people.
The cellular network mainly consists of the following three parts: mobile station, base station subsystem, network subsystem. Mobile station is our network terminal equipment, such as mobile phones or some cellular industrial control equipment. The base station subsystem includes the mobile station (big iron tower) we see every day, wireless transceiver equipment, private network (usually optical fiber), countless digital equipment and so on. We can think of the base station subsystem as a translator between wireless and wired networks.
Common cellular network types are: GSM network (called pcs-1900 in some
countries
), CDMA network, 3G network, FDMA, TDMA, PDC, TACS, AMPS, etc.