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Wireless Networks: An Overview

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In this first in a series of articles on wireless networks, network expert Bill Stallings provides an overview of the subject.
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Wireless Comes of Age

Guglielmo Marconi invented the wireless telegraph in 1896. In 1901, he sent telegraphic signals across the Atlantic Ocean from Cornwall to St. John's Newfoundland, a distance of 1,800 miles. His invention allowed two parties to communicate by sending each other alphanumeric characters encoded in an analog signal. Over the last century, advances in wireless technologies have led to the radio, the television, the mobile telephone, and communications satellites. All types of information can now be sent to almost every corner of the world.

Recently, a great deal of attention has been focused on satellite communications, wireless networking, and cellular technology. Communications satellites were first launched in the 1960s. Those first satellites could only handle 240 voice circuits. Today's satellites carry about one-third of the voice traffic and all of the television signals between countries. Modern satellites typically introduce a quarter-second propagation delay to the signals they handle. Newer satellites in lower orbits, with less inherent signal delay, will soon be deployed to provide data services such as Internet access.

Wireless networking is allowing businesses to develop WANs, MANs, and LANs without a cable plant. The IEEE has developed 802.11 as a standard for wireless LANs. The Bluetooth industry consortium is also working to provide a seamless wireless networking technology.

The cellular or mobile telephone is the modern equivalent of Marconi's wireless telegraph, offering two-party, two-way communication. The first-generation wireless phones used analog technology. These devices were heavy and coverage was patchy, but they successfully demonstrated the inherent convenience of mobile communications. The current generation of wireless devices are built using digital technology instead of analog. Digital networks can carry much more traffic and provide better reception and security than analog networks. In addition, digital technology has made possible value-added services such as caller identification. The next-generation wireless device will also be digital and will connect to the Internet using new frequency ranges at higher information rates.

The impact of wireless communications has been and will continue to be profound. Very few inventions have been able to "shrink" the world in such a manner. The standards that define how wireless communication devices interact are quickly converging and soon will allow the creation of a global wireless network that will deliver a wide variety of services.

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