(CELLular telePHONE) The first ubiquitous wireless telephone. Originally analog, all new cellular systems are digital, which has enabled the cellphone to turn into a smart phone that has access to the Internet. Digital cellphone systems are also offered in the PCS band, which is radio spectrum that was auctioned off by the U.S. government in the mid-1990s. Introduced in the mid 1980s, cellphone sales exploded worldwide in the 1990s.

Major Carriers

In the U.S., the major cellular carriers by total subscribers at the end of 2004, starting with the largest, are Cingular Wireless (formerly Cellular One and including AT&T Wireless), Verizon Wireless (formerly Bell Atlantic Mobile), Sprint Nextel (merger of Sprint and Nextel) and T-Mobile. The largest cellular company in the world is UK-based Vodaphone with 2003 revenues exceeding $60 billion. As of 2004, Vodaphone had a substantial ownership in Verizon Wireless.

Cell Technology

The concept behind a cellular system is that an area is divided into a number of slightly overlapping circular "cells." Each cell contains a base station, which is identifiable from its transmitting and receiving tower. The multiple cells combined with low power transmitters allow the same frequencies to be reused with different conversations in different cells within the same city or locale. The primary digital cellphone technologies are TDMA, CDMA and GSM.

The Cells

The cellular system uses multiple base stations to cover a geographic area. As the mobile phone user travels from cell to cell, the call is automatically "handed off" to the next station. The more cells, the more customers can be handled in the entire system overall, because the same frequencies can be reused within the cell.

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