Claude Shannon (April 30, 1916 - February 24, 2001)
He might well have been called The Playful Genius. Who else but a genius, a playful genius no less, would ride a unicycle down the hallowed halls of Bell Labs? Claude Shannon did - and he did it while practicing his juggling.
His first unicycle, but certainly not his last, was a gift from his wife Betty, who knew he loved gadgets. Within a few days he was riding around the block, and in a few weeks was doing so while juggling three balls. To make matters more interesting, he later assembled a unicycle with an eccentric wheel, so that the rider would move up and down as he pedaled forward.
Then there was the maze-solving mouse, Theseus. The maze consisted of 25 squares that could be arranged in a variety of ways. Theseus, the magnetic mouse, would move about this maze, and could always find its way to the destination. Furthermore, no matter where the mouse was placed, it would “remember” if it had been there before, and move directly in the appropriate direction. The “brain” that directed Theseus was a circuit of about 100 relays located beneath the maze, driving a pair of motors that moved an electromagnet. Today those 100 relays would be replaced by a single semiconductor chip, but there was no such thing as a chip back then in 1950.
Then there was the motorized pogo stick, and a three-ball juggling robot, and a chess-playing computer. And not to be missed was his Ultimate Machine. The Ultimate Machine was described by futurist Arthur C. Clarke as follows: “Nothing could be simpler. It is merely a small wooden casket, the size and shape of a cigar box, with a single switch on one face. When you throw the switch, there is an angry, purposeful buzzing. The lid slowly rises, and from beneath it emerges a hand. The hand reaches down, turns the switch off and retreats into the box. With the finality of a closing coffin, the lid snaps shut, the buzzing ceases and peace reigns once more…. There is something unspeakably sinister about a machine that does nothing – absolutely nothing – except switch itself off.”
So much for fun and games. What about the “genius” moniker? These devices and gadgets were certainly inventions, but they were not industry-shaking inventions. They, of themselves, did nothing to promote efficiency or sustainability in the telephone network. What then?
The first evidence of this genius, and his efforts to improve the efficiency of the network, was his work in the late 1930s. At the time he was a graduate student at MIT working for his professor, Vannevar Bush. Claude’s job was to tend the mechanical computing device that Bush was working on: the Differential Analyzer.
Associated with the Differential Analyzer was a logic circuit of some 100 relays. Shannon recognized that the design of this circuit had been more art than science. Also, he thought back to his undergraduate days at the University of Michigan when he had studied a mathematical science called Boolean algebra. It seemed to him that the 1’s and 0’s it used was little different from the On’s and Off’s of a relay. Might Boolean algebra be used in the design of relay circuits? This, he thought, might be a way not only of designing a circuit, but of designing it in the simplest manner possible.
Shannon pursued this line of thinking, and it became the subject of his masters thesis A Symbolic Analysis of Relay and Switching Circuits. Shannon’s has been called the most important master’s thesis of the 20th Century; it turned an art into a science.
The idea was immediately put to use in the design of telephone switching systems, and later, in the design of digital computers. Indeed, few inventions have so contributed to the sustainability and efficiency of the telephone network.
Important though his work on switching theory was, it is considered to be his second-most important contribution to the telecommunications industry. The most important output was his work on Information Theory.
This work, culminating in 1948 in a paper entitled A Mathematical Theory of Communications has been described as "The Magna Carta of the information age." In this work Shannon identified the three significant parts of a communications system: the sender, the transmission channel, and the receiver.
It is almost intuitive that the capacity (i.e., bandwidth) of a channel must be large enough to handle the rate of information produced at the source. And that the noise (thermal noise is inherent) on the channel must be kept as low as possible.
Furthermore, if redundancy can be removed from the message being transmitted, we will be holding to a minimum the required bandwidth of the sender. Exotic coding systems, of course, are one way of reducing this redundancy.
But how does one measure all this?
Shannon developed an equation: C = W log2 (P/N + 1) bits per second
In this equation W is the bandwidth (cycles per second = hertz), P is the received power, and N is the noise. The signal-to-noise ratio is P/N.
Shannon's theorem states that if one attempts to transmit information at a rate greater than C, only at best C bits per second will be received. On the other hand if the rate is less than or equal to C, then one may have as few errors as desired, so long as the channel is properly coded.
As a consequence of Shannon's theorem, we now have satellite communications, the Internet, and wireless communications. Once again his work improved the efficiency of the network.
How, then, might we be able to transmit more information over a channel? Clearly, it can be done with more sophisticated coding techniques, larger bandwidth, or less noise. All of these are being pursued in this 21st Century, because our present-day transmission systems are getting ever closer to what has been called the Shannon Limit.
To say that the field of Information Theory is intellectually stimulating would be a gross understatement. But the work done by Claude Shannon in the field is unquestionably among the most important ever done.
Claude Shannon died in 2001. Over the span of his life he received many awards and more than a dozen honorary degrees He was, truly, a telecommunications giant.
Bob Stoffels is a telecommunications consultant with more than 50 years of experience. He can be reached at 727.867.5378 or emailed at: firstname.lastname@example.org.