Telecommunication is the process of transmitting or receiving information over a distance by any electrical or electromagnetic medium in a variety of forms such as radio, telegraphy, television
, telephony, data communication and computer networking. In nowadays, communication equipment is indispensable to our daily life. By means of telephone networks, communication across great distances becomes possible and people around the world are pulled closer to each other than ever before. The telephone system has been greatly enhanced and become a widely accepted communication apparatus in households and offices since its invention. Home telephones have recently been provided with an increasing number of functions. While voice communication through the telephone becomes part of our daily lives, the widely used computer has created another format of communication over the Internet, namely data communication. One of them is electronic mail, or email. Computer networks allow a number of users to share data and resources, such as data storage systems
, file servers, switches
, and other peripherals. The telecommunication industry expands very fast, and the wireless telecommunication industry is growing especially rapidly. The utilization of cellular phones
(mobile phones) is becoming increasingly popular in today's wireless environment. Cellular communication networks are rapidly becoming a primary infrastructure for enabling communication in today's society. Consumers place more reliance on mobile phones than ever. Mobile phones enables a user to keep contact with others at any place and at any time. Mobile communication service systems may be classified into synchronous mobile communication systems and asynchronous mobile communication systems. Mobile or portable cellular phones are typically arranged to communicate via a radio link to a base station of a network. Alternatively, a mobile telephone may communicate directly with a satellite. Mobile telecommunications systems consist of a plurality of mobile units (e.g. cell phones) in communication with one or more base stations. Signals transmitted by the mobile units are received by a base station and typically relayed to a mobile switching center. Wireless portable telecommunication terminals transmit microwavelength signals. In mobile communication systems, the data transmission capacity available at the radio interface is divided among a plurality of users by a multiple access principle. The most common multiple access principles include time division multiple access (TDMA), code division multiple access (CDMA), and frequency division multiple access (FDMA). Satellite communications refers to communications via an orbiting communications satellite. Mobile telecommunication technology has transitioned from the narrow band second-generation phase to the wide band third-generation phase to increase capacity. The satellite carries communications equipment that relays signals to and from ground stations while the satellite orbits high above earthbound relay stations. Communication satellite services generally fall into one of two broad categories: fixed point-to-point, and point-to-multipoint or broadcast. A typical satellite communication system includes a hub earth station, a geostationary satellite, and a plurality of terminal earth stations. Increasingly, cellular radio communications technology is being built into other devices. These include portable laptop computers
and personal digital assistants
. These devices can then also send data or voice over cellular communications networks. The increasing applications of broadband systems provide many benefits, including greater bandwidth, more efficient use of bandwidth, and the ability to integrate voice, data, and video communications. In addition, local area networks (LANs) and metropolitan area networks (MANs) provide increased efficiency and speed for communicating between devices of the same or different types.