Mobile phone coverage is distributed by networks consisting of multiple contiguous cells, each of which is served by a separate transmitter with fixed locations, called base station. Each cell covers a certain area and all the cells together provide radio coverage of a much wider geographical area. This makes it possible to operate simultaneously a plurality of mobile transceivers (e. G., mobile phones, pagers, among others), irrespective of whether they are stationary or moving from one cell to another.
Before the introduction of mobile phone networks there were mobile radiotelephone systems – for example, in cars. The radio telephone system, however, had only one central antenna tower in every city and a limited number (perhaps 25) of channels for use by each tower.
This means that the phone in a car needed a powerful transmitter so that it can link on a radio distance of 40 or 50 miles. This also means that it was also difficult for many people to simultaneously use the radio, as there were insufficient channels.
Mobile networks offer a number of advantages over other alternatives: increased capacity (service to many users simultaneously), low power consumption (for both individual devices and the base station), wider coverage and low interference. A simple example of a mobile network is a radio system for drivers of old taxis which were supported by multiple transceivers, each managed by a single operator.
In order to realize the mobile network, all base stations contribute directly to the radio signal that is divided into cells. The shape of the cells may be hexagon, a square, round or otherwise, the most common being the hexagon. Of each of these cells identify several operating frequencies (f1 – f6) of corresponding base stations. Same group of frequencies can be reused in other cells, provided that they are sufficiently remote, otherwise they create signal interference, which is undesirable.
Although initially towers with two-way radios were the center of a cell and emitted in all directions, it is possible for the network map to be redrawn. Each tower has three antennas oriented in three different directions, spaced 120 degrees from each other (total 360 degrees), and can transmit and receive at three different frequencies for the three cells. This provides at least three channels (three towers that operate it) for each cell.
The main feature of a network is the reuse of frequencies in different cells, in order to increase the coverage and capacity. For this purpose, each base station distinguishes the signal produced by its own transceiver from other signals received from neighboring base stations. There are two standardized solutions to this problem: frequency division multiplexing access (FDMA) and code division multiplexing access (CDMA). FDMA operates using different frequencies for each neighboring cell. By adjusting the frequency to a selected individual cell it can avoid signals from other cells.
Each cell network has some sort of radiative mechanism. It can be used directly for the submission of information to multiple mobile devices. Their most important task entails adjusting communication channels between the mobile transceiver and the base station. This is called paging. Details of the process of paging vary from network to network, but its foundation is the fact that the area where the phone is located is known.