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Topic: Signal (information theory)

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  Signal (information theory) - Wikipedia, the free encyclopedia
In information theory, a signal is the sequence of states of a communications channel that encodes a message.
Information theory studies both continuous signals, commonly called analog signals; and discrete signals (Shannon 2005, 3), or quantized signals, of which the most common today are digital signals.
In information theory, the message is generated by a stochastic process, and the transmitted signal derives its statistical properties from the message.
en.wikipedia.org /wiki/Signal_(information_theory)   (810 words)

 Information theory - Wikipedia, the free encyclopedia
Information theory is the mathematical theory of data communication and storage, generally considered to have been founded in 1948 by Claude E. Shannon.
Information theory is a broad and deep mathematical theory, with equally broad and deep applications, chief among them coding theory.
This division of coding theory into compression and transmission is justified by the information transmission theorems, or source-channel separation theorems that justify the use of bits as the universal currency for information in many contexts.
en.wikipedia.org /wiki/Information_theory   (3686 words)

 information theory. The Columbia Encyclopedia, Sixth Edition. 2001-05
In information theory, the term information is used in a special sense; it is a measure of the freedom of choice with which a message is selected from the set of all possible messages.
Information is thus distinct from meaning, since it is entirely possible for a string of nonsense words and a meaningful sentence to be equivalent with respect to information content.
An important theorem of information theory states that if a source with a given entropy feeds information to a channel with a given capacity, and if the source entropy is less than the channel capacity, a code exists for which the frequency of errors may be reduced as low as desired.
www.bartleby.com /65/in/inform-th.html   (755 words)

 The Beginnings of ``Information Theory"
The hierarchical model of information may be applied to the description of any domain in which information appears, such as that used by Claude Shannon in the 1940s when he developed what is now referred to as ``information theory" to study communication systems.
The amount of information in the output of a process is related to the amount of information that is available about the input to the process combined with the information provided by the process itself.
The information that is input to the function has measurable information, in its capacity as being the output of some other process, about which it provides information, the amount being measurable in terms of this earlier process.
ils.unc.edu /~losee/b5/node7.html   (2065 words)

 Information theory founders
Information Theory was born in 1948 out of Claude Shannon's landmark paper, "A Mathematical Theory of Communication.
Estimates of the accuracy of a given transmission of information under known conditions of noise interference, for example, are probabilistic, as are the numerous approaches to encoding and decoding that have been developed to reduce uncertainty or error to minimal levels.
That is, information is a decrease in uncertainty.
it-science.net   (1070 words)

 [No title]
In information theory, one of the basic notions is that of the amount of information associated with a given situation.
The present note outlines a new approach to information theory which is aimed specifically at the analysis of certain communication problems in which there exist a number of information sources simultaneously in operation.
In particular, we derive information rates and obtain rate-distortion relationships for practical data-compression schemes, for the reproduction of the unordered sequence of Poisson event occurrences, for the reproduction of the sample functions of the Poisson counting process, and for the reproduction of the sequence of intervals between the event occurrences of a Poisson process.
www.eecs.berkeley.edu /~asarwate/Public/ITTrans.txt   (7147 words)

Although information is sometimes measured in characters, as when describing the length of an email message, or in digits (as in the length of a phone number), the convention in information theory is to measure information in bits.
The information content of a sequence is defined as the number of bits required to transmit that sequence using an optimal encoding.
Information theory provides us with a formula for determining the number of bits required in an optimal code even when we don't know the code.
www.cs.cmu.edu /~dst/Tutorials/Info-Theory   (2126 words)

 Information Theory   (Site not responding. Last check: 2007-10-21)
The IEEE Transactions on Information Theory is the main western journal devoted to information theory.
Concurrent with the growth of devices for transmitting and processing information, a unifying theory known as information theory was developed and became the subject of intensive research.
It is an example of a theory that was initiated primarily by one man, the U.S. electrical engineer, Claude E. Shannon, whose initial ideas appeared in the article "The Mathematical Theory of Communication" in the Bell System Technical Journal (1948).
www.dam.brown.edu /people/yiannis/info.html   (600 words)

Information theory is difficult for many people two understand at first glance because of its mathematical nature.
The source of the communication signal is the speaker's brain, the transmitter is his vocal system, the channel is air, the receiver is the listener's ear, and the destination is the listener's brain.
Information and the associated concepts decrease when the number of message choices decrease, or when a few or one message is far more probable than the others.
zimmer.csufresno.edu /~johnca/spch100/information.htm   (3108 words)

 Information theory
In the information theory we are not dealing with classical physical notions such as mass, power, energy, but with a more intangible notion as form or structure.
He described himself as a behavioral scientist and his critical use of the information theory in his field work and in his many publications is outstanding, since he as a true scientist with a very broad, impartial view, investigated the natural communication between living organisms such as humans and mammals.
The theory of dis-continuity between categories and their elements is also called "the theory of logical types", which Bateson used as the fundament for his theory of communication.
home22.inet.tele.dk /hightower/information.htm   (5502 words)

 Science Show - 17/06/00: Information Theory & Whale Song
David Baron: Information theory is a field of mathematics that scientists use to analyse strings of data, whether carried by DNA or radio waves or telephone wires.
John Buck: Information theory can look at it - a signal with no real context to it - and tell you well what's the most amount of information that could be in the signal.
Suzuki says information theory can be used for breaking codes, and that's how he saw his task; akin to deciphering enemy messages in war time.
www.abc.net.au /rn/science/ss/stories/s140922.htm   (997 words)

 Gaussian Nodes » Information theory and practice
Information theory is a branch of mathematics that deals with transmission of information across communications channels.
One of the basic tools of information theory is the so-called entropy of a signal.
The information content of any positive integer is defined to be the smallest number of atoms required to build a computer that could output* the integer in question in a finite amount of time.
northcountrynumerics.com /blog/2006/02/21/information-theory-and-practice   (469 words)

 Information theory founders
This data, transformed into electrical signals that were proportional in intensity to the shades and tones of the image, were transmitted over phone lines and deposited onto a similarly spinning sheet of photographic negative film, which was then developed in a darkroom.
Erd calls the measuring of the signal "sampling." Good old Harry Nyquist also recommended that the number of samples per second for a good representation of the signal has to be twice as big as the number of Hertz of the fastest sine wave contained in the analog signal.
Signal Sampling Theory was an exercise in frustration for Nyquist, since it needed 30,000 samples a second to make it work, and no system at that time could measure, record, store and reread that much information that quickly.
it-science.net /nyquist.html   (2929 words)

 Communication Theory: A First Look
Shannon’s published theory was paired with an interpretive essay by Weaver that presented information theory as ‘‘exceedingly general in its scope, fundamental in the problems it treats, and of classic simplicity and power in the results it reaches."1 The essay suggested that whatever the communication problem, reducing information loss was the solution.
The received signal may be diminished by an ear that’s been overexposed to hard rock, and your friend is quite capable of altering the message as it moves from ear to brain.
Information theory did, however, foster modest advances in the study of the redundancy inherent in language, an issue of syntax.
www.afirstlook.com /archive/information.cfm?source=archther   (3037 words)

 Nyquist Shannon sampling theorem   (Site not responding. Last check: 2007-10-21)
The Nyquist-Shannon sampling theorem is the fundamental theorem in the field of information theory, in particular telecommunications.
The theorem states that: when sampling a signal (e.g., converting from an analog signal to digital), the sampling frequency must be greater than twice the bandwidth of the input signal in order to be able to reconstruct the original perfectly from the sampled version.
Equivalently, the entire spectrum of the bandlimited signal should be expressible in terms of the finitely many time-domain coefficients obtained from sampling the signal.
read-and-go.hopto.org /Information-theory/Nyquist-Shannon-sampling-theorem.html   (1094 words)

 Research-Information Theory
Information Theory began during World War II when two men, Norbert Weiner and Claude E. Shannon, were concerned with the need for communication and the technical problems that arose because of the war.
Therefore, it is important that the person receving the message must be able to distinguish the origianl message from the one that he or she has received, or the system has failed.
Information theory uses a logarithm to measure the amount of information being transmitted.
oak.cats.ohiou.edu /~th104196/ITResearch.htm   (897 words)

 Laurie Spiegel - An Information Theory Based Compositional Model
Put simply, information theory[1] is a mathematical theory of how to optimize a signal for communication in a noisy channel and of how communication degrades in such a medium.
In this case, we are using random noise in place of information to increase entropy, to counteract redundency.
Information about and examples of her work are available on the web at http://www2.factory.com/spiegel/.
retiary.org /ls/writings/info_theory_music.html   (1173 words)

 information theory on Encyclopedia.com
INFORMATION THEORY [information theory] or communication theory, mathematical theory formulated principally by the American scientist Claude E. Shannon to explain aspects and problems of information and communication.
Establishing the micro foundations of a macro theory: information, movers, and the competitive local market for public goods.
Surveying the use of theory in Library and Information Science research: a disciplinary perspective.
www.encyclopedia.com /html/i/inform-th.asp   (1349 words)

 Information Theory
Information theory is often considered to have begun with work by Harry Nyquist.
In the first section of his paper, titled The Measurement of Information, he noted that "information is a very elastic term." In fact, Hartley never adequately defines this core concept.
Given a number of desired properties for an information measure, the Shannon and Hartley measures of information and only these measures have properties desirable in an information measure.
maththeory.info   (2098 words)

 information theory --  Encyclopædia Britannica
Most closely associated with the work of the American electrical engineer Claude Elwood Shannon in the mid-20th century, information theory is chiefly of interest to communication engineers, though some of the concepts have been adopted and used in such...
A scientific theory is a structure suggested by these laws and is devised to explain them in a scientifically rational manner.
Although control theory has deep connections with classical areas of mathematics, such as the calculus of variations and the theory of differential equations, it did not become a field in its own right until the late 1950s and early 1960s.
www.britannica.com /eb/article-9106012   (843 words)

 About Information Theory   (Site not responding. Last check: 2007-10-21)
This page is intended for the students at the Institut National des Télécoms who are studying Information Theory.
Before starting studying Information Theory, it has to be said that basic concepts in Probability are required.
The entropy of an information source is introduced and a proof of the noiseless coding theorem (theorem 9 page 16) is established.
www-citi.int-evry.fr /~uro/page-liens/information-theory.htm   (1297 words)

 Image and Video Quality Assessment Research at LIVE
Traditional perceptual image quality assessment approaches are based on measuring the errors (signal differences) between the distorted and the reference images, and attempt to quantify the errors in a way that simulates human visual error sensitivity features.
information is a statistical measure of information fidelity, and may only be loosely related with what humans regard as image information, it places fundamental limits on the amount of cognitive information that could be extracted from an image.
For example, in cases where the channel is distorting images severely, corresponding to low mutual information between the test and the reference, the ability of human viewers to obtain semantic information by discriminating and identifying objects in images is also hampered.
live.ece.utexas.edu /research/Quality/frqa.htm   (1157 words)

 Notes on Information Theory
The smallest unit of information in the digital worlds is a "bit" or byte.
Shannon and Weaver (the authors of Information Theory) redefined the meaning of "information": Information must not be confused with meaning!
Information is a measure of the predictability of the signal: If I meet you on the street, I can expect that we will say "Hi" to each other.
www.arts.ucsb.edu /faculty/legrady/classes/artst22/S02/S02_sections/infoTheory.html   (603 words)

 Information Theory Primer With an Appendix on Logarithms Postscript version: ftp://ftp.ncifcrf.gov/pub/delila/primer.ps ...
It means that we can convert the original signal into a string of 1's and 0's (binary digits), so that on the average there are 1.75 binary digits for every symbol in the original signal.
In the beginning of this primer we took information to be a decrease in uncertainty.
The amount of information that gets through is given by the decrease in uncertainty, equation (20).
www.lecb.ncifcrf.gov /~toms/paper/primer/latex   (1985 words)

 Postgraduate Course: Information Theory   (Site not responding. Last check: 2007-10-21)
The discipline of information theory was originally created to explain the behavior of communication systems [3].
Since then it has been recognized that information theory is also a theory as its own and it finds applications also in many other fields, the most notable being source coding and data compression.
What is more, information theory has also tight connection to statistics and statistical signal processing.
www.ee.oulu.fi /~juntti/it.html   (343 words)

 Chalmers: Information Theory   (Site not responding. Last check: 2007-10-21)
Research in information theory is concerned with general models and methods for the transfer of information.
Characteristics of speech signals and hearing are employed.
Models of signals as well as for perception are necessary tools.
www.chalmers.se /en/sections/research/research_profiles/signals_and_systems/information_theory   (258 words)

 From message alphabet to signal alphabet (from information theory) --  Britannica Student Encyclopedia
(TOE, or theory of everything), theory that attempts to unify theory of gravity and theories of other fundamental forces by interpreting subatomic phenomena as manifestations of vibrations of fundamental, one-dimensional strings; mathematics developed in 1960s; theory gained some support in 1980s; because of extremely small distances and high energies involved, the theory...
in mathematics and mechanics, theory that studies systems behaving unpredictably and randomly despite their seeming simplicity and fact that forces involved are supposedly governed by well-understood physical laws; applications of theory are diverse, including study of turbulent flow of fluids, irregularities in heartbeat, traffic jams, population dynamics, chemical...
Includes information on medical experiments, crematoria, escape attempts, the use of Zyklon B in the gas chambers, and the perpetrators and victims of the camp's atrocities.
www.britannica.com /ebi/article-214947   (793 words)

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