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Learn everything about Mobile Telephony!
The operation of mobile telephony in Greece, like in most countries of the world, is based on the GSM (Global System for Mobile Communications), which was created in 1987 under the Single European Telecommunications Policy. The European GSM system determines the frequency bands, which are at 900 and 1800 MHz, as well as the protocols for transmitting mobile telephony telecommunication signals.
With the evolution of technology and the increasing telecommunications needs, the mobile telephony companies currently also provide 3G mobile telephony services. These combine telecommunications and information technology and operate in the 2000 MHz frequency range. The mobile telephony services are based on the third generation UMTS (Universal Mobile Telecommunications System) telecommunications protocol. UMTS (Universal Mobile Telecommunications System).The structure and operation of the 3G networks is similar to that of the second-generation networks that have been operating in Greece since 1993.
The GSM is a transmission system for telecommunications signals that uses electromagnetic waves. Its operation is based on a sequence of antennae that are known as Base Stations. The arrangement of the Base Stations creates a series of cells, i.e. areas, where each one is covered by the range of a particular Base Station. Accordingly, tangent cells have a different transmission frequency, to prevent any interference and the transmission power levels are kept to a minimum so they don’t create interference with non adjacent cells using the same frequency.
A typical Base Station operates at a power capacity of around 60 Watts. Accordingly, the GSM is known as a cellular or a cellular system. The size of a cell is associated with the expected number of mobile telephone users in each region. Thus, in sparsely populated areas such as rural areas, the cells are larger in size with a diameter of up to 35 km. Conversely, in densely populated areas like cities, the cells are smaller with a diameter that can reach only 300 m.
When the number of mobile telephones that use a cell are greatly increased, the Base Station is then insufficient to serve all the users and we have phenomena of overloading. We then have the so-called subdivision of cells, i.e. they are divided into smaller cells and are generally covered by less powerful Base Stations. Consequently, the more Base Stations that are placed in a given area, the lower the operating power of each Station, and accordingly the transmission power of the mobile telephones that communicate with those stations closest to the user is smaller.
Every time we call or accept calls via a mobile telephone, the transmission of the telecommunications signals is carried out by using electromagnetic waves emitted from the Base Station and our mobile telephone. Both emit and receive electromagnetic waves. In order that mobile telephony to function we need fixed Base Stations and mobile telephones. This information uses electromagnetic waves emitted and received by mobile telephones and the fixed Base Stations as a “transportation medium”.
Suppose that we want to communicate over our mobile telephone with a friend on the road who also has a mobile telephone. As soon as we key in the phone number the mobile telephone automatically contacts the nearest Base Station. It accordingly uses the available frequencies, which are the transportation for the signal with our request to find a friend with whom we can talk. The electromagnetic energy emitted by every mobile telephone during a call reduces or increases depending on the signal strength, i.e. according to the distance of the mobile telephone from the nearest Base Station.
When the mobile telephone is far from the Base Station it does not have a good signal, it then transmits at its maximum power, which is 250 mW. But if there was a Base Station near the mobile telephone, the device would then operate at an average power of 62.5 mW, a value far below the maximum. Therefore, a dense network of mobile telephony stations ensures that the mobile telephones operate at minimal power and users receive less electromagnetic energy from their device.
The mobile telephony Base Station receives and transmits the signal with our request to search and identify our friend to the company’s telecommunications centre, on the network to which we are connected. The company’s telecommunications centre identifies the cell where our friend is situated and sends the signal to the Base Station nearest to him/her. From there again, by using the available frequencies, the signal is sent to the mobile telephone and so we can communicate with them.
It should therefore be strongly emphasized that the technical specifications and physical limitations of the GSM system worldwide, impose the installation of Base Stations within the urban structure, since this is where the majority of users are situated. Nowadays, there are no mobile telephony networks that operate or can operate and provide communication coverage when they are only installed outside inhabited areas.