Classification of mobile communication systems ::::::::::::::::::::::::::::::::::::: Another emerging class of wireless networks are being used for short-range communication.Bluetooth, for example, replaces cables by enabling direct wireless information exchange between electronic devices (e.g. between cellular phones, Personal Digital Assistants(PDAs), computers and peripherals). These networks are also called Body Area Networks or Personal Area Networks. Unlike the mobile technologies mentioned above, they are not based on a fixed network infrastructure (e.g. base stations). The possibility of building up such networks in a spontaneous and fast way gave them the name ad hoc networks.WLAN technologies also include the capability for peer-to-peer ad hoc communication (in addition to the classical client-to-base station transmission modus). GSM and UMTS belong to the class of cellular networks that are used predominantly for public mass communication. These had an early success with analog systems such as the Advanced Mobile Phone System (AMPS) in America, the Nordic Mobile Telephone (NMT) in Scandinavia, or the C-Netz in Germany. Founded on the digital system GSM (with its variants for 900, 1800 and 1900 MHz), a market with millions of subscribers worldwide was generated, and it represents an important economic force. A strongly contributing factor to this rapid development of markets and technologies has been the deregulation of the telecommunication markets, which allowed the establishment of new network operators. Another competing or supplementary technology is satellite communication based on Low Earth Orbiting (LEO) or Medium Earth Orbiting (MEO) satellites, which also offer global, and in the long term even broadband, communication services. Trunked radio systems – in digital form with the European standard Trans European Trunked Radio (TETRA) – are used for business applications such as fleet control. They offer private services that are only accessible by closed user groups. In addition to bidirectional communication systems, there also exists a variety of unidirectional systems, where subscribers can only receive but not send data. With unidirectional message systems (paging systems) users may receive short text messages. A couple of years ago, paging systems were very popular, since they offered a cost-effective reachability with wide-area coverage. Today, the SMS in GSM has basically replaced the function of paging systems. Some billion SMS messages are being exchanged between mobile GSM users each month. Digital broadcast systems, such as Digital Audio Broadcast (DAB) and Digital Video Broadcast (DVB), are very interesting for wireless transmission of radio and television stations as well as for audio- and video-on-demand and broadband transmission of Internet pages. GSM and its enhancements (including UMTS air interfaces), however, will remain the technological base for mobile communication for many years, and will continue to open up new application areas.
Posted on: Wed, 20 Nov 2013 07:10:58 +0000
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