Your browser does not support JavaScript!

Theory of communication. Part 1: The analysis of information

Theory of communication. Part 1: The analysis of information

For access to this article, please select a purchase option:

Buy article PDF
(plus tax if applicable)
Buy Knowledge Pack
10 articles for $120.00
(plus taxes if applicable)

IET members benefit from discounts to all IET publications and free access to E&T Magazine. If you are an IET member, log in to your account and the discounts will automatically be applied.

Learn more about IET membership 

Recommend Title Publication to library

You must fill out fields marked with: *

Librarian details
Your details
Why are you recommending this title?
Select reason:
Journal of the Institution of Electrical Engineers - Part III: Radio and Communication Engineering — Recommend this title to your library

Thank you

Your recommendation has been sent to your librarian.

Hitherto communication theory was based on two alternative methods of signal analysis. One is the description of the signal as a function of time; the other is Fourier analysis. Both are idealizations, as the first method operates with sharply defined instants of time, the second with infinite wave-trains of rigorously defined frequencies. But our everyday experiences—especially our auditory sensations—insist on a description in terms of both time and frequency. In the present paper this point of view is developed in quantitative language. Signals are represented in two dimensions, with time and frequency as co-ordinates. Such two-dimensional representations can be called “information diagrams,” as areas in them are proportional to the number of independent data which they can convey. This is a consequence of the fact that the frequency of a signal which is not of infinite duration can be defined only with a certain inaccuracy, which is inversely proportional to the duration, and vice versa. This “uncertainty relation” suggests a new method of description, intermediate between the two extremes of time analysis and spectral analysis. There are certain “elementary signals” which occupy the smallest possible area in the information diagram. They are harmonic oscillations modulated by a “probability pulse.” Each elementary signal can be considered as conveying exactly one datum, or one “quantum of information.” Any signal can be expanded in terms of these by a process which includes time analysis and Fourier analysis as extreme cases.These new methods of analysis, which involve some of the mathematical apparatus of quantum theory, are illustrated by application to some problems of transmission theory, such as direct generation of single sidebands, signals transmitted in minimum time through limited frequency channels, frequency modulation and time-division multiplex telephony.

Inspec keywords: telecommunication

Subjects: Information theory


    1. 1)
      • F.F. Roberts , J.C. Simmonds . The Physical Realizability of Electrical Networks having Prescribed Characteristics. Philosophical Magazine , 7
    2. 2)
      • P.C. Goldmark , P.S. Hendricks . Synthetic Reverberation. Proceedings of the Institute of Radio Engineers
    3. 3)
      • J.R. Carson . Notes on the Theory of Modulation. Proceedings of the Institute of Radio Engineers
    4. 4)
      • F.F. Roberts , J.C. Simmonds . Further Properties of Recurrent Exponential and Probability Wave forms. Philosophical Magazine , 7
    5. 5)
      • K. Küpfmüller . Transient Phenomena in Wave Filters. Elektrische Nachrichten-Technik
    6. 6)
      • J.R. Carson , T.C. Fry . Variable-frequency Electric Circuit Theory. Bell System Technical Journal
    7. 7)
      • G.A. Campbell , R.M. Foster . Fourier Integrals for Practical Applications. Bell Telephone System Monograph
    8. 8)
      • F. Lüschen . Modern Communication Systems. Journal I.E.E.
    9. 9)
      • H. Nyquist . Certain Factors affecting Telegraph Speed. Bell System Technical Journal
    10. 10)
      • H.A. Wheeler , A.V. Loughren . The Fine Structure of Television Images. Proceedings of the Institute of Radio Engineers
    11. 11)
      • G.W. Stewart . Problems Suggested by an Uncertainty Principle in Acoustics. Journal of the Acoustical Society of America
    12. 12)
      • F. Gray , J.W. Horton , R.C. Mathes . The Production and Utilization of Television Signals. Bell System Technical Journal
    13. 13)
      • R.V.L. Hartley . Transmission of Information. Bell System Technical Journal
    14. 14)
      • F.F. Roberts , J.C. Simmonds . Some Properties of a Special Type of Electrical Pulse. Philosophical Magazine , 7
    15. 15)
      • W.R. Bennett . Time-division Multiplex Systems. Bell System Technical Journal

Related content

This article has following corresponding article(s):
Theory of communication
This article has following corresponding article(s):
Theory of communication. Part 2: The analysis of hearing
This is a required field
Please enter a valid email address