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The mobile phone (also called a mobile, wireless, cellular phone, cell phone, or hand phone(hp)) is a short-range, portable electronic device used for mobile voice or data communication over a network of specialized base stations known as cell sites. In addition to the standard voice function of a telephone, current mobile phones may support many additional services, and accessories, such as SMS for text messaging, email, packet switching for access to the Internet,java gaming, bluetooth, infared, camera with video recorder and MMS for sending and receiving photos and video.
Most current mobile phones connect to a cellular network of base stations (cell sites), which is in turn interconnected to the public switched telephone network (PSTN) (the exception is satellite phones). Since the mid-2000s, an increasing number of cellphones can connect to the Internet, a portion of which can be navigated using cellphones.
Millions of people in the United States and around the world use cellular phones. They are such great gadgets -- with a cell phone, you can talk to anyone on the planet from just about anywhere! These days, cell phones provide an incredible array of functions, and new ones are being added at a breakneck pace. Depending on the cell-phone model, you can:
Store contact information, make task or to-do lists, keep track of appointments and set reminders, use the built-in calculator for simple math, send or receive e-mail, get information (news, entertainment, stock quotes) from the Internet, play games, watch TV, send text messages and integrate other devices such as PDAs, MP3 players and GPS receivers. Mobile phones send and receive radio signals with any number of cell site base stations fitted with microwave antennas.
These sites are usually mounted on a tower, pole or building, located throughout populated areas, then connected to a cabled communication network and switching system. The phones have a low-power transceiver that transmits voice and data to the nearest cell sites, normally not more than 8 to 13 km (approximately 5 to 8 miles) away.
When the mobile phone or data device is turned on, it registers with the mobile telephone exchange, or switch, with its unique identifiers, and will then be alerted by the mobile switch when there is an incoming telephone call. The handset constantly listens for the strongest signal being received from the surrounding base stations.
As the user moves around the network, the mobile device will "handoff" to various cell sites during calls, or while waiting (idle) between calls it will reselect cell sites. Cell sites have relatively low-power (often only one or two watts) radio transmitters which broadcast their presence and relay communications between the mobile handsets and the switch.
The switch in turn connects the call to another subscriber of the same wireless service provider or to the public telephone network, which includes the networks of other wireless carriers. Many of these sites are camouflaged to blend with existing environments, particularly in scenic areas.
The dialogue between the handset and the cell site is a stream of digital data that includes digitized audio (except for the first generation analog networks). The technology that achieves this depends on the system which the mobile phone operator has adopted.
The technologies are grouped by generation. The first-generation systems started in 1979 with Japan, are all analog and include AMPS and NMT. Second-generation systems, started in 1991 in Finland, are all digital and include GSM, CDMA and TDMA. Reference: http://en.wikipedia.org/wiki/Cellphones
Source: http://www.ArticlePros.com/author.php?Steve Smith
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