CELL PHONE

CELL PHONE:
Telephony system that does not require a fixed link, for example via telephone cable for transmission and reception. Use the radio airwaves by as conventional radio, so the terminal will emit and receive the signals with an antenna to and from the nearest repeater (mobile phone masts) or satellite. The first mobile phone emissions can be traced back to the use of radio transmitters installed in vehicles, military or institutional use; as referred to by the first use by police in Detroit in 1921. The radios themselves were introduced in 1946 in the United States; the following year, the Bell Telephone developed cell technology based on modern systems of mobile phone itself. However, no developments were civilians until 1956, when a car terminal, 40 kg, which was fed by the vehicle battery was installed in Sweden. Japan's first cellular mobile telephone system in 1979 was launched; He was followed by the United Kingdom in 1983
Operating System
The mobile cellular system based on transmission areas, cells, covering areas between 1.5 and 5 km, within which there are one or more repeater stations, which work with a certain frequency, which must be different surrounding cells. The mobile phone sends the signal that is received by the station and sent through the network to the recipient; as the user moves, the recipient cell is also switched, by varying the frequency of the Hertzian wave transmission supports. According systems, it sends the signal or data packet sequentially, either as such or compressed and encrypted.
Digital systems
Currently, most cellular telephone systems employ digital systems have replaced analog first generation (1G); these systems were introduced in Spain in 1990 (MoviLine telephone company). The first European digital system (GSM Global System for Mobile Communication), commonly known as second-generation cellular system (2G) began to implement in 1992, and in 1995 operated for the first time in Spain; with it launched the transmission system short text messages, SMS (Short Messaging Service), and access to Internet through WAP (Wireless Application Protocol). And in 2000 in Europe and 2002 in the United States, they began trading gifted with GPRS (General Packet Radio Service, General packet radio service through information) systems; It is known as 2.5G telephony system, an intermediate technology between systems of second and third generation. Among the new features is the possibility of receiving and sending continuous data sets using the IP (Internet Protocol), which substantially improves navigation through the network and to overcome the limit of 160 characters in SMS, while to send and receive images and multimedia elements.
(3G) third generation systems, exploited commercially in Japan since 2001 by NTT DoCoMo, have suffered repeated postponements by technological and logistical problems worldwide, which has substantially slowed the market. In Europe and parts of Asia it has been chosen in 2000 by the UMTS (Universal Mobile Communication Service, universal mobile communications), and the United States and parts of Asia and America, the so-called CDMA-2000 system; both are part of the IMT-2000 standard of the International Telecommunications Union (ITU) in Geneva, Switzerland. 3G systems are mainly based on two standards, the CDMA-2000 (Code Division Multiple Access 2000) and W-CDMA (W-CDMA) and other owners of certain operators, such as NTT DoCoMo of that before being incompatible each other and differing in the maximum speed of data transmission. CDMA systems are easier to implement and provide up to three times greater transmission capacity; in the transmitter the data is converted to digital format and compressed, the receiver further to receive and decode data packets, does error checking and reconverted to wave format, if, for voice transmissions.
Messaging and multimedia
With the advent of digital systems (telephone second generation 2G), the terminals have the ability to send and receive short text messages (SMS), which operate much like email messages in Internet, although specifying as a destination terminal number and not a user ID. With the advent of 2.5G and 3G systems have been implemented EMS (Enhanced Messaging Service) and MMS (Multimedia Message Service) services, which offer improvements over basic SMS text service; thus allowed unlimited text size, including pictures, animations and melodies and, in the case of MMS, enable sending and receiving all kinds of multimedia elements, including videos. To use EMS and MMS required, respectively, of mobile terminals or other GPRS and UMTS 3G.
The integration of mobile phones with mobile computing has come in two different ways: with the connectivity of mobile phones with PDA using wireless technologies such as infrared or Bluetooth, and physical integration of both devices into a single device, such as is the case of other PocketPC Phone Edition running under Linux or Palm

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