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* Exploring Past Discoveries That Led to Wireless * Exploring Present Applications for Wireless * Introduction to Wardriving * Introduction to Wardriving with Linux * Wardriving with Linux and Kismet
Exploring Past Discoveries That Led to Wireless
Wireless technology is the method of delivering data from one point to another without using physical wires, and includes radio, cellular, infrared, and satellite. A historic perspective will provide you with a general understanding of the substantial evolution that has taken place in this area. The common wireless networks of today originated from many evolutionary stages of wireless communications and telegraph and radio applications. Although some discoveries occurred in the early 1800s, much of the evolution of wireless communication began with the emergence of the electrical age and was affected by modern economics as much as by discoveries in physics.
Because the current demand of wireless technology is a direct outgrowth of traditional wired 10-Base-T Ethernet networks, we will also briefly cover the advent of the computer and the evolution of computer networks. Physical networks, and their limitations, significantly impacted wireless technology. This section presents some of the aspects of traditional computer networks and how they relate to wireless networks. Another significant impact to wireless is the invention of the cell phone. This section will briefly explain significant strides in the area of cellular communication.
Early writings show that people were aware of magnetism for several centuries before the middle 1600s; however, people did not become aware of the correlation between magnetism and electricity until the 1800s. In 1820, Hans Christian Oersted, a Danish physicist and philosopher working at that time as a professor at the University of Copenhagen, attached a wire to a battery during a lecture; coincidentally, he just happened to do this near a compass and he noticed that the compass needle swung around. This is how he discovered that there was a relationship between electricity and magnetism. Oersted continued to explore this relationship, influencing the works of contemporaries Michael Faraday and Joseph Henry.
Michael Faraday, an English scientific lecturer and scholar, was engrossed in magnets and magnetic effects. In 1831, Michael Faraday theorized that a changing magnetic field is necessary to induce a current in a nearby circuit. This theory is actually the definition of induction. To test his theory, he made a coil by wrapping a paper cylinder with wire. He connected the coil to a device called a galvanometer, and then moved a magnet back and forth inside the cylinder. When the magnet was moved, the galvanometer needle moved, indicating that a current was induced in the coil. This proved that you must have a moving magnetic field for electromagnetic induction to occur. During this experiment, Faraday had not only discovered induction but also had created the world's first electric generator. Faraday's initial findings still serve as the basis of modern electromagnetic technology.
Around the same time that Faraday worked with electromagnetism, an American professor named Joseph Henry became the first person to transmit a practical electrical signal. As a watchmaker, he constructed batteries and experimented with magnets. Henry was the first to wind insulated wires around an iron core to make electromagnets. Henry worked on a theory known as self-inductance, the inertial characteristic of an electric current. If a current is flowing, it is kept flowing by the property of self-inductance. Henry found that the property of self-inductance is affected by how the circuit is configured, especially by the coiling of wire. Part of his experimentation involved simple signaling.
It turns out that Henry had also derived many of the same conclusions that Faraday had. Though Faraday won the race to publish those findings, Henry still is remembered for actually finding a way to communicate with electromagnetic waves. Although Henry never developed his work on electrical signaling on his own, he did help a man by the name of Samuel Morse. In 1832, Morse read about Faraday's findings regarding inductance, which inspired him to develop his ideas about an emerging technology called the telegraph. Henry actually helped Morse construct a repeater that allowed telegraphy to span long distances, eventually making his Morse Code a worldwide language in which to communicate. Morse introduced the repeater technology with his 1838 patent for a Morse Code telegraph. Like so many great inventions, the telegraph revolutionized the communications world by replacing nearly every other means of communication—including services such as the Pony Express.
Samuel Morse spent a fair amount of time working on wireless technology, but he also chose to use mediums such as earth and water to pass signals. In 1842, he performed a spectacular demonstration for the public in which he attempted to pass electric current through a cable that was underwater. The ultimate result of the demonstration was wireless communication by conduction, although it was not what he first intended. Morse submerged a mile of insulated cable between Governor's Island and Castle Garden in New York to prove that a current could pass through wire laid in water. He transmitted a few characters successfully, but, much to his dismay, the communication suddenly halted—sailors on a ship between the islands, unseen to the spectators, raised their ship's anchor and accidentally pulled up the cable, and not knowing what it was for, proceeded to cut it. Morse faced considerable heckling from the spectators and immediately began modification to the experiment. He successfully retested his idea by transmitting a wireless signal between copper plates he placed in the Susquehanna River, spanning a distance of approximately one mile. In doing so, he became the first person to demonstrate wireless by conduction. Conduction is the flow of electricity charges through a substance (in this case, the water in the river) resulting from a difference in electric potential based on the substance.
Inventing the Radio
After the significant discoveries of induction and conduction, scientists began to test conduction with different mediums and apply electricity to machinery. The scholars and scientists of the day worked to apply these discoveries and explore the parameters of the properties. After the theory of conduction in water was proven, new theories were derived about conduction in the air. In 1887, a German named Heinrich Hertz became the first person to prove electricity travels in waves through the atmosphere. Hertz went on to show that electrical conductors reflect waves, whereas nonconductors simply let the waves pass through the medium. In addition, Hertz also proved that the velocity of light and radio waves are equal, as well as the fact that it is possible to detach electrical and magnetic waves from wires and radiate. Hertz served as inspiration to other researchers who scrambled to duplicate his results and further develop his findings. Inventors from all across the world easily validated Hertz's experiments, and the world prepared for a new era in radio, the wireless transmission of electromagnetic waves.
An Italian inventor called Guglielmo Marconi was particularly intrigued by Hertz's published results. Marconi was able to send wireless messages over a distance of ten miles with his patented radio equipment, and eventually across the English Channel. In late 1901, Marconi and his assistants built a wireless receiver in Newfoundland and intercepted the faint Morse code signaling of the letter "S" that had been sent across the Atlantic Ocean from a colleague in England. It was astounding proof that the wireless signal literally curved around the earth, past the horizon line—even Marconi could not explain how it happened, but he had successfully completed the world's first truly long-distance communication, and the communication world would never be the same.
Today we know that the sun's radiation forms a layer of ionized gas particles approximately one hundred miles above the earth's surface. This layer, the ionosphere, reflects radio waves back to the earth's surface, and the waves subsequently bounce back up to the ionosphere again. This process continues until the energy of the waves dissipates.
Another researcher by the name of Reginald Fessenden proceeded to further develop Marconi's achievements, and he became the first person to create a radio band wave of human speech. The importance of his results was felt worldwide, as radio was no longer limited to telegraph codes.
Mounting Radio-Telephones in Cars
In 1921, mobile radios began operating in the 2MHz range, which is just above the Amplitude Modulation (AM) frequency range of current radios. These mobile radios were generally used for law enforcement activities only. They were not integrated with the existing wireline phone systems that were much more common at that time—since the technology was still so new, the equipment was considered experimental and not practical for mass distribution. In fact, people originally did not consider mobile radio as a technology for the public sector. Instead, the technology was developed for police and emergency services personnel, who really served as the pioneers in mobile radio.
It was not until 1924 that the voice-based wireless telephone had the ability to be bi-directional, or two-way. Bell Laboratories invented this breakthrough telephone. Not only could people now receive messages wirelessly, they could also respond to the message immediately, greatly increasing convenience and efficiency. This improved system was still not connected to landline telephone systems, but the evolution of wireless communication had taken one more major step. One issue that still plagued this early mobile radio system was the sheer size of the radio; it took up an entire trunk. Add to the size restriction, the cost of the radio system that was almost as expensive as the vehicle.
In 1935, Edwin Howard Armstrong introduced Frequency Modulation (FM). This technology not only increased the overall transmission quality of wireless radio but also drastically reduced the size of the equipment. The timing could not have been any better. World War II had begun, and the military quickly embraced FM technology to provide two-way mobile radio communication. Due to the war, companies immediately sensed the urgency to develop the FM technology rapidly, and companies such as Motorola and AT&T immediately began designing considerably smaller equipment. Many of these new inventions became possible due to the invention of the circuit board, which changed the world of electronic equipment of all types.
Inventing Computers and Networks
Though the beginning of the computer age is widely discussed, computer discoveries can be attributed to a long line of inventors throughout the 1800s, beginning with the Englishman Charles Babbage, who in 1822 created the first calculator called the "Difference Engine." Then came Herman Hollerith, who in 1887 produced a punch card reader to tabulate the American census for 1890. Later developments led to the creation of different punch card technologies, binary representation, and the use of vacuum tubes.
The war effort in the 1940s produced the first decoding machine, the Colossus, used in England to break German codes. This machine was slow, taking about 3 to 5 seconds per calculation. The next significant breakthrough was the creation of the Electronic Numerical Integrator and Computer (ENIAC) by Americans John Presper Eckert and John W. Mauchley. The ENIAC was the first general-purpose computer that computed at speeds 1000 times greater than the Colossus. However, this machine was a behemoth, consuming over 160 Kilowatts of power–when it ran; it dimmed lights in an entire section of Philadelphia. The main reason these machines were so huge was the vacuum tube technology. The invention of the transistor in 1948 changed the computer's development and began shrinking the machinery. In the next thirty years, the computers got significantly faster and smaller.
Excerpted from Kismet Hacking by Brad 'RenderMan' Haines Michael J. Schearer Frank Thornton Copyright © 2008 by Elsevier, Inc.. Excerpted by permission of Syngress. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Posted January 16, 2012
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