2. ORGANIZATION OF A CELLULAR MOBILE COMMUNICATION NETWORK GSM. 2.1. General provisions.

The main task of any communication system, as is known, is the transfer of various types of information (for example: voice, facsimile, computer data) to any place in real time (or at a time point required by the subscriber).
This task in telephone communication systems (before the advent of mobile communication systems) was solved by using cable lines of communication as transmission channels and automatic telephone exchanges (PBX) as switching systems.

In the data of stationary telephone networks the subscriber is rigidly tied via a wired subscriber line to the PBX. Any movement of the subscriber in space over considerable distances leads to the fact that he remains without communication. Developed and implemented subscriber terminals with radio extensions provide communication only up to a distance of hundreds of meters from a fixed telephone set. This lack of a fixed telephone network is eliminated by replacing the cable subscriber line with a wireless radio channel in mobile communication networks.

Thus, the main distinctive feature of cellular mobile communication networks from a fixed telephone network is the use of radio channels for mobile subscribers traveling long distances, while maintaining a two-way (duplex) mode of operation over the radio channel as from a mobile subscriber to the recipient of information or to another mobile subscriber), and from the recipient of information to the mobile subscriber.

It should be noted that the cellular mobile communication system in the general case is a complex and flexible radio engineering system that allows a wide variety of configuration options and a set of functions performed. Such a system provides voice and other types of information (in particular, facsimile messages and computer data), and duplex telephone communication, multi-party telephone communication (called conference calling), voice mail, etc. can be implemented.

In this mobile system, when organizing a normal two-way telephone conversation, starting with a call, possible modes of automatic dialing, call waiting, call forwarding, etc. are provided.