Mobile Phones to become truly mobile. What was once exclusively a business tool, requiring a cumbersome separate battery unit, could be easily slipped into a pocket and used relatively cheaply, often completely replacing a traditional phone line. Mobile phone networks cover most urban areas of the world and continue to expand. With increased coverage and greatly reduced cost, the number of users increased more than ten-fold in the 1990s. In 2000 alone, around 400 million handsets were sold. It is estimated that by 2005, there will be more than 1 billion mobile phone subscribers worldwide.
In the early 1990s, there was a worldwide move to a digital standard for mobile phones. Digital compression techniques allow for a greater volume of information to be transmitted within the same frequency band, increasing the capacity of each cell. In Europe, GSM (global standard for mobile communications) operating on the 900 megahertz band, became the digital standard (although many countries, including the U.K., now have a separate 1800 megahertz band used by newer networks). In the U.S., mobile phone systems operate at 800 and 1900 megahertz on the PCS (personal communication system) standard. Although the systems are incompatible, both use a technique called time division multiple access (TDMA). This works by splitting the available transmission time on each channel into a number of time slots (typically eight), allowing more users to simultaneously use each channel.
Digital mobile telephony also allows for the reliable transmission of data. One development is the addition of WAP (wireless application protocol) facilities to handsets, which permits rudimentary Internet access. However, slow downloads and a paucity of available information have prevented WAP from being adopted as quickly as other less advanced features such as SMS (short message service) text-messaging, which has revolutionized the way many users interact with their phones. A third generation of mobile phone technology (the analog standard is the first and digital the second) promises to further change the way we use our handsets, offering multimedia and respectable Internet access, but this will involve the construction of new networks in the twentyfirst century.
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