EP0044845A1 - Procede et dispositif pour la transmission protegee de signaux vocaux. - Google Patents

Procede et dispositif pour la transmission protegee de signaux vocaux.

Info

Publication number
EP0044845A1
EP0044845A1 EP19810900305 EP81900305A EP0044845A1 EP 0044845 A1 EP0044845 A1 EP 0044845A1 EP 19810900305 EP19810900305 EP 19810900305 EP 81900305 A EP81900305 A EP 81900305A EP 0044845 A1 EP0044845 A1 EP 0044845A1
Authority
EP
European Patent Office
Prior art keywords
transmitter
speech
transmission
transmitted
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP19810900305
Other languages
German (de)
English (en)
Other versions
EP0044845B1 (fr
Inventor
Peter Meier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Patelhold Patenverwertungs and Elektro-Holding AG
Original Assignee
Patelhold Patenverwertungs and Elektro-Holding AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Patelhold Patenverwertungs and Elektro-Holding AG filed Critical Patelhold Patenverwertungs and Elektro-Holding AG
Publication of EP0044845A1 publication Critical patent/EP0044845A1/fr
Application granted granted Critical
Publication of EP0044845B1 publication Critical patent/EP0044845B1/fr
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00—Secret communication

Definitions

  • the present invention is based on a method for the secure transmission of voice signals according to the preamble of claim 1 and a circuit arrangement according to the preamble of claim 4.
  • a method for concealing voice signals according to the preamble of claim 1 is known (DAS 25 23 828).
  • a speech signal limited in bandwidth to 3 kHz is pulse code modulated and divided into samples controlled by a time scrambler.
  • Image samples are obtained from the samples using an orthogonal matrix and their values are successively transmitted in sections from a transmitter to a receiver.
  • the transmission path has been assumed to be ideal in this method; In practice, only a very limited intelligibility can be achieved, because the system limits of a real transmission path (e.g. CCITT voice channel) are not sufficiently taken into account.
  • a real transmission path e.g. CCITT voice channel
  • the method mentioned in claim 1 proves to be particularly advantageous for transmission links with a CCITT voice channel (cf. CCITT, International Telecommunication Union, Geneva 1977, Vol. III Line Transmission, Vol. V Telephone Transmission Quality).
  • the information reduction according to claim 1 is based on the knowledge that the phase information of the speech signal is of little importance from the human ear, especially at frequencies above approximately 1 kHz.
  • the corresponding information reduction, adapted to human hearing, now allows the image samples obtained by the orthogonal transformation to be additionally transmitted via encryption despite the limited bandwidth, which on the one hand provides greater protection against unauthorized eavesdropping and on the other hand reduces the sensitivity to interference of the signals in the transmission path.
  • the method according to claim 2 can be implemented relatively easily with the means of modern electronics and has the advantages of high operational and interference immunity and good transmission quality.
  • the advantage of a method expanded in accordance with claim 3 lies in the additional security against eavesdropping achieved.
  • the circuit arrangement according to claim 4 gives the advantage of easy to monitor function groups.
  • the embodiment according to claim 7 results in additional protection against unauthorized unveiling.
  • Fig. 1 is a block diagram of a transmitter
  • FIG. 2 is a block diagram of a receiver in a system for secure voice transmission
  • FIG. 5 shows the Fourier spectrum of FIG. 4 according to its weighting
  • FIG. 7 shows the speech parameters FIG. 7 after their coding
  • 9 shows the transmitted modulated speech parameter signal (transmitter signal f '(t))
  • FIG. 16b shows the speech parameter signals FIG. 16a after modulation has taken place
  • 16c shows the effect of a bandpass filtering (of signal 16b) corresponding to a CCITT voice channel with a pass band of 300 to 3,000 Hz and
  • a transmitter according to FIG. 1 essentially has a speech parameterization unit A with a downstream data reduction stage B and a subsequent coding unit C.
  • a receiver corresponding to the transmitter, FIG. 2 is equipped with a return coding unit C, a parameter recovery unit B 'and a speech signal generator A'.
  • a speech signal S (t) is first supplied in a known manner to a bandpass filter with a pass band from 400 to 2,800 Hz. Finally, the speech signal is digitized in a conventional manner by a 12-bit analog / digital converter at a sampling frequency of 6.4 kHz.
  • a resulting speech section (English frame), consisting of 128 data points in a time interval of 20 msec. is shown as pulse code modulated signal s (t) in FIG. 3.
  • the discrete Fourier transformation stage 2 downstream of the digitization stage 1 the complex discrete spectrum of this speech section is obtained, so that a function A (f) according to FIG. 4 arises at one output.
  • the transmitted speech parameter signal f '(t) (transmitted transmitter signal) reaches the input of a demodulator 9, Fig. 2; it is demodulated here so that A (t) has a profile according to FIG. 10.
  • This signal is then fed to a sync chronization detector / decoder 10 and appears at its output in the decoded form A (t) according to FIG. 11.
  • the signal curve A (t) according to FIG. 12 is achieved in a downstream decoder 11 , which has the same parameter sequence as that of FIG. 6.
  • This signal is fed to a data converter 12, whereupon the reconstructed Fourier spectrum A (f) shown in FIG. 13 arises.
  • the inverse weighted Fourier spectrum is formed in accordance with FIG. 14.
  • This spectrum A (f) undergoes a reverse transformation in the downstream discrete Fourier re-transformation stage 14 and is subsequently converted into a reconstructed speech signal S in the section boundary adjuster 15 and digital / analog converter 16 (12-bit D / A converter with low-pass filter) connected in series '(t), Fig. 15 worked up.
  • FIG. 16 a representation A (t) of coded speech parameters over 5 image samples corresponding to an interval of 100 msec. further relationships can be recognized.
  • 16a shows the speech parameter signals with the ones symbolized by arrows s at intervals of 20 msec. synchronization information.
  • the same speech parameters have a time profile according to FIG. 16b after their modulation and a profile according to FIG. 16c after bandpass filtering with a passband of 300-3 * 000 Hz (which corresponds to a real transmission path).
  • a pseudo random number generator 17 is already provided in the exemplary embodiment, FIG. 1, which controls the number N of samples in the speech parameterization stage. Accordingly, the formation of Postab takes place cuts in the receiver, Fig. 2, by a synchronized pseudo-random generator (18).
  • FIG. 17a represents the original speech signal S (t)
  • FIG. 17b the reconstructed speech signal S '(t).

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)

Abstract

Le procede et le dispositif correspondant pour la transmission protegee de signaux vocaux sur un canal de transmission analogique a bande limitee (par exemple un canal vocal CCITT), protegent contre l'ecoute clandestine. En exploitant l'information de la parole percue par l'ouie humaine, le signal vocal a transmettre est numerise et soumis a une reduction de l'information (A (f)) correspondante basee sur la transformation de Fourier. Ceci permet de realiser la protection necessaire de l'information dans le codage subsequent, relativement aux distorsions de la transmission, et la modulation adaptee de maniere optimale au comportement de la transmission. La forme numerique existante avant ce codage se laisse facilement chiffrer de facon telle que le signal analogique transmis soit totalement incomprehensible et ne puisse pas etre reconstitue meme avec les methodes modernes d'analyse, tandis que pour les ecouteurs autorises subsiste une bonne intelligibilite. Ce procede offre la possibilite d'obtenir, par des moyens modernes de la technique numerique de traitement des signaux, une solution optimale pour la transmission analogique sure de la parole.
EP19810900305 1980-02-01 1981-01-30 Procede et dispositif pour la transmission protegee de signaux vocaux Expired EP0044845B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH817/80 1980-02-01
CH81780A CH649181A5 (de) 1980-02-01 1980-02-01 Verfahren und schaltungsanordnung zur gesicherten uebertragung von sprachsignalen.

Publications (2)

Publication Number Publication Date
EP0044845A1 true EP0044845A1 (fr) 1982-02-03
EP0044845B1 EP0044845B1 (fr) 1984-07-11

Family

ID=4195882

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19810900305 Expired EP0044845B1 (fr) 1980-02-01 1981-01-30 Procede et dispositif pour la transmission protegee de signaux vocaux

Country Status (5)

Country Link
EP (1) EP0044845B1 (fr)
JP (1) JPS57500089A (fr)
CH (1) CH649181A5 (fr)
DE (1) DE3164634D1 (fr)
WO (1) WO1981002234A1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4393276A (en) * 1981-03-19 1983-07-12 Bell Telephone Laboratories, Incorporated Fourier masking analog signal secure communication system
DE3506912A1 (de) * 1985-02-27 1986-08-28 Telefunken Fernseh Und Rundfunk Gmbh, 3000 Hannover Verfahren zur uebertragung eines audiosignals
EP0313029A1 (fr) * 1987-10-21 1989-04-26 Siemens Aktiengesellschaft Österreich Dispositif de transmission brouillée de signaux analogiques
GB8914880D0 (en) * 1989-06-29 1989-08-23 Indep Broadcasting Authority Video scrambling in the frequency domain
WO1991013464A1 (fr) * 1990-02-26 1991-09-05 Cray Research, Inc. Support intermediaire a capacitance reduite

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3944745A (en) * 1945-05-10 1976-03-16 Bell Telephone Laboratories, Incorporated Secret signaling system with means for preventing key disclosure
US4179586A (en) * 1972-08-02 1979-12-18 The United States Of America As Represented By The Secretary Of The Army System of encoded speech transmission and reception
US4064363A (en) * 1974-07-25 1977-12-20 Northrop Corporation Vocoder systems providing wave form analysis and synthesis using fourier transform representative signals
DE2523828C2 (de) * 1975-05-30 1982-08-12 TE KA DE Felten & Guilleaume Fernmeldeanlagen GmbH, 8500 Nürnberg Verfahren zur Verschleierung von Sprachsignalen mit Hilfe orthogonaler Matrizen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8102234A1 *

Also Published As

Publication number Publication date
WO1981002234A1 (fr) 1981-08-06
DE3164634D1 (en) 1984-08-16
JPS57500089A (fr) 1982-01-14
EP0044845B1 (fr) 1984-07-11
CH649181A5 (de) 1985-04-30

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