Cellular Communication
In cellular communication networks the covered area is partitioned into multiple cells and each cell is serviced by its own low range transmitter. Each mobile telephone communicates with a transmitter within range and the information is forwarded within the cellular network towards the recipient. Cellular communication networks have the advantage that only a small distance to the stationary transmitters has to be bridged. Furthermore, transmitters which are far apart can use the same frequencies as illustrated the following figure:
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When a mobile user travels from one cell to another the communication link has to be reconfigured. As neighbouring cells use different frequencies, the mobile device switches its frequency to the new cell. This reconfiguration is called handover.
First generation mobile communication system were introduced in the eighties and were analog systems primarily developed for voice communication.
The Global System for Mobile Communication (GSM) differs significantly from its predecessors. Both signalling and speech channels are digital, which means that it is seen as a second generation mobile communication system. For GSM the frequency bands 890-915 MHz and 935-960 MHz have been allocated by ERC Decision (94)01. GSM allows bitrates of 9.6 kbps for data transfer.
Second generation cellular communication networks were built mainly for telephone calls and only had slow data transmission capabilities. Due to the rapid changes in technology, these factors do not meet the requirements of today's wireless revolution. Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system allowing much higher bitrates. UMTS is designed with both terrestrial and global satellite components. For terrestrial UMTS the frequency bands 1900-1980 MHz, 2010-2025 MHz and 2110-2170 MHz, and for satellite UMTS the frequency bands 1980-2010 MHz and 2170-2200 MHz have been allocated by ERC Decision (97)07. The bitrate is 144 kbps for full outdoor mobility applications in all environments, 384 kbps for limited-mobility outdoor applications in the micro and macro cellular environments (in urban and suburban areas), and 2048 Mbps for low-mobility outdoor applications, particularly in the pico and micro cellular environments (in indoor and urban areas).
