WO1989010661A1 - Procede a efficacite spectrale pour la communication d'un signal d'information - Google Patents

Procede a efficacite spectrale pour la communication d'un signal d'information Download PDF

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Publication number
WO1989010661A1
WO1989010661A1 PCT/US1989/001345 US8901345W WO8910661A1 WO 1989010661 A1 WO1989010661 A1 WO 1989010661A1 US 8901345 W US8901345 W US 8901345W WO 8910661 A1 WO8910661 A1 WO 8910661A1
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WO
WIPO (PCT)
Prior art keywords
samples
signal
channel
sample
digitally
Prior art date
Application number
PCT/US1989/001345
Other languages
English (en)
Inventor
Michael Dale Kotzin
Anthony Patrick Van Den Heuvel
Kenneth J. Crisler
Bradley Michael Hiben
Lawrence M. Mohl
Mark Richard Poulin
Original Assignee
Motorola, Inc.
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
Priority claimed from US07/187,685 external-priority patent/US4979188A/en
Application filed by Motorola, Inc. filed Critical Motorola, Inc.
Priority to KR1019890702478A priority Critical patent/KR920007093B1/ko
Publication of WO1989010661A1 publication Critical patent/WO1989010661A1/fr
Priority to FI896174A priority patent/FI896174A0/fi
Priority to DK666789A priority patent/DK666789A/da
Priority to NO89895318A priority patent/NO895318L/no

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/66—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission for reducing bandwidth of signals; for improving efficiency of transmission
    • H04B1/667—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission for reducing bandwidth of signals; for improving efficiency of transmission using a division in frequency subbands
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/02—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation
    • H04B14/04—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation using pulse code modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00—Secret communication
    • H04K1/02—Secret communication by adding a second signal to make the desired signal unintelligible

Definitions

  • This invention relates generally to the spectrally efficient transmission of information signals, and more specifically to the transmission of information signals that have been processed by information coders, and is more particularly directed toward the spectrally efficient transmission of information processed using sub-band coders.
  • Voice coders are known in the art. Regarding communication systems, the goal of any vo ⁇ coder is to encode a speech signal for transmission over a channel. Since communication channels are often quite limited in information carrying capacity (bandwidth), the amount of encoded information required for transmission is preferably minimized. Thus the vo-coding process usually entails compressing the information signal by discarding redundant spectral elements (or other unnecessary information), while retaining only that information that when transmitted to a receiver, allows necessary components to be regenerated (or inferred) thereby permitting the synthesis of a perceptually acceptable recreation of the original speech input. Those skilled in the art will appreciate that a speech signal contains a large amount of redundant or unnecessary information.
  • Speech production can be modeled as an excitation signal (e.g., sound impulses generated by the vocal cords), driving a filter (e.g., the vocal tract), which possesses a certain resonant structure.
  • the spoken sound changes with time since both the excitation signal and/or filter vary with time.
  • the excitation is noise ⁇ like for unvoiced sounds (e.g., consonants), and appears periodic for voice sounds (e.g., vowels).
  • voice sounds e.g., vowels
  • Predominantly, and especially for voiced sounds most of the essential speech energy is concentrated in only a few frequency sub-bands and these particular frequency bands containing the most energy generally vary slowly over time. It has been found that transmitting only the information contained about these spectral peaks is all that is normally required to provide a reasonable reconstruction of the input speech.
  • contemporary vo-coder designers advantageously exploit the advantages of digital signal processing, such as, for example, the operational repeatability of digital filters, the immunity of digital circuits to variations due to aging, and the natural invariance of digital circuits to temperature, humidity, vibration, and other adverse conditions.
  • contemporary methods for transmitting information from digital speech coders produces spectral inefficiencies, which can compromise the benefits achieved in removing the redundant speech information. For example, it is known that a high quality analog unprocessed speech signal occupies approximately 4 kHz of bandwidth. After digitization (via pulse code modulation (PCM)), the digital representation of this signal has a data rate of 64 kb/s, which occupies approximately 30 kHz of bandwidth (assuming the use of conventional binary channel modulation techniques).
  • PCM pulse code modulation
  • an information signal such as a voice signal
  • a sub-band encoder Digitally processed samples produced by the sub-band encoder are modulated onto a communication channel to create channel symbols having a magnitude of modulation proportional to a characteristic (preferably the sample magnitude) of a respective digitally processed sample.
  • This technique of channel modulation provides, during periods of high signal strength, a superior estimation of the digitally processed sample at a receiver. This facilitates receiver speech reconstruction thereby providing a higher quality speech signal.
  • the overall effect of the present invention provides robustness to noise corruption, while providing improved spectral efficiency.
  • encryption of the digitally processed samples is provided to ensure communication privacy.
  • Figure 3 is a block diagram of the vector coder of Figure 2;
  • Figure 4a is an illustration of the preferred sub- frame channel format of the present invention;
  • Figure 4b is an illustration of a voice sample and a corrupting noise signal
  • FIG. 5 is a block diagram of the radio frequency decoder of the present invention.
  • Figure 6 is a block diagram of the allocation decoder of Figure 5;
  • Figure 7 is a block diagram of the wireline encoder of the present invention
  • Figure 8 is a block diagram of the wireline decoder of the present invention
  • Figure 9 is a block diagram of a radio frequency transmitter and receiver employing the encoder of Figure 1 and the decoder of Figure 5;
  • Figure 10 is an illustration of the preferred inbound-to-repeater and outbound-to-mobile time- division-multiplex RF channel protocols;
  • FIG 11 b is a block diagram of a radio frequency receiver employing encryption according to the present invention.
  • FIGS 12a-d are illustrations of the preferred encryption technique of the present invention. Detailed Description of the Preferred Embodiment
  • the present invention operates to reduce the occupied transmission bandwidth of information signals such as, for example, voice, video, telemetry or similar signals that contain, or may be adapted to contain, redundant spectral or other unnecessary information.
  • the information signal is sampled, quantized, and digitally processed to produce digitally processed samples.
  • a communication channel is modulated using the digitally processed samples to create channel symbols having a magnitude of modulation proportional to a characteristic of a respective digitally processed sample.
  • the preferred transmitted signal comprises the channel symbols together with overhead data which maybe used to synchronize a receiver and transfer information regarding the proper reconstruction of the information signal.
  • the digitally processed samples may be normalized, companded or encrypted to provide a spectrally efficient communication system having superior signal quality during periods of high signal strength, and exhibiting robustness to noise corruption of the transmitted signal.
  • RF radio frequency
  • an information signal is sampled, quantized, and processed digitally to reduce the occupied bandwidth of the information signal thereby permitting up to four such processed signals (which may be encrypted) to be transmitted on a single 25 kHz land mobile communication channel.
  • a voice signal is sampled, quantized, digitally processed.
  • these digitally processed samples are utilized to create a multi-subcarrier signal which is centered in the available bandwidth of a standard (uncompensated) narrowband telephone channel to provide communications.
  • filter 104 occupies the band from DC to 250 Hz
  • filter 105 resides in the 250-500 Hz band
  • filter 119 which is situated in the 3750-4000 Hz band.
  • the present state of the art apportions an information signal into sixteen (16) bands.
  • several filters (104 and 116-119) need not be used if the information signal is a voice signal, since the amount of voice energy residing in the spectrum associated with these filters is small or unnecessary to the proper reproduction (synthesis) of a voice signal at a receiver.
  • another arrangement of the sixteen filters may be required depending upon the un-processed spectral characteristics of the information signal and the desired recovered signal quality.
  • the selected filters are coupled to an allocation selector (120) via decimators (121 -136).
  • filters (105-1 15) are routed to the allocation selector (120) via decimators (122-132).
  • the allocation selector (120) investigates a predetermined portion (preferably fifteen samples corresponding to 30 ms of speech) of each of the decimated filter outputs to identify a predetermined subset of the filters that have significant energy content.
  • a predetermined portion preferably fifteen samples corresponding to 30 ms of speech
  • four filters are selected for transmission.
  • the remaining seven non-selected filter bands are investigated to determine an energy value associated with the amount of energy residing in the non-selected bands.
  • the allocation selector (120) forms a mask vector (149), which comprises a digital code identifying the four selected filters so that the receiver may properly synthesize the information signal.
  • the four selected filters each have fifteen samples routed to normalizers (138, 140, 142, and 144), which scale the fifteen samples of each selected filter to reside within some maximum amplitude range.
  • each of the normalizers (138, 140, 142 and 144) operate by increasing the amplitude of the samples in 6 dB steps, until it is determined that the next 6 dB increase would exceed a predetermined threshold.
  • This amplification (normalization) factor for each of the four selected filters is routed (139, 141 , 143 and 145) to the normalization selector (148).
  • the normalization selector (148) operates to select the lowest normalization factor provided by the normalizers (138, 140, 142 and 144) to scale (normalize) the energy values of the seven non-selected filters.
  • the normalizers (150-162) uniformly scale each energy value provided by the allocation selector (120) in accordance with the lowest normalization factor.
  • the preferred selection of the lowest normalization factor protects against clipping at the transmitter.
  • any noise or other adverse phenomenon that corrupts the energy sample will be attenuated by this normalization factor to reduce the impact.
  • the normalized energy values are not compared to a threshold because the effect of an energy value exceeding the threshold value is generally not detrimental to the recovered speech quality. The reason for this is that the energy values in the non-selected filters are ordinarily quite low (compared to the four selected filters) which, of course, is the reason the non- selected filters were not selected by the allocation selector (120).
  • a vector coder (244), which operates to provide the four bit binary mask vector (149) that identifies the four selected filters.
  • the mask vector (149) is coupled (246- 252) to a cross-point matrix (254), which routes the four selected filters (identified by the mask vector) to four corresponding output ports (256-262). Signals representing each of the energy values of the seven non- selected filters (as opposed to the actual filter samples) are routed to other output ports (264-276). In this way, only sample outputs from four filters (albeit normalized) and energy values (also normalized) representing the energy in the non-selected filters are modulated onto a communication channel for transmission.
  • each normalization step is 6 dB, 54 dB (9 x 6) of dynamic range is provided. Other arrangements, however, may be used.
  • the normalization value for the first selected filter has two ternary signals (406), which is followed by a pair of ternary signals for the filters SF2 (408), SF3 (410), and finally, SF4 (412).
  • the normalized energy values (414) of the non-selected filters are each transmitted as a single symbol (recall that the normalization constant for these energy values need not be transmitted since the receiver will select the lowest of the transmitted normalization values of the selected filters).
  • fifteen samples from each of the four selected filters (which may be normalized) are transmitted.
  • the binary mask bits, the ternary normalization factors, the symbols for the energy values, and the filter samples comprise the 80 symbol sub- frame format of the present invention.
  • the radio frequency voice decoder embodiment (500) is shown in block diagram form.
  • the general purpose of the decoder (500) is to reverse the coding process provided by the encoder (100). Accordingly, the received symbols comprising the sub-frame information (see Figure 4a for the preferred sub-frame format) are sampled, quantized, and the binary sample representations are coupled to the input (502) of the decoder (500) for synthesis of the information (voice) signal.
  • Each of the energy samples from the output ports (638-647) are coupled to normalizers (648-658) to control the amplitude of random noise supplied by noise generators (659-669).
  • This arrangement provides a scaled noise signal proportional to the magnitude of the energy of non-selected filters. Forcing scaled noise signals through the non-selected filters approximates the noise-like unvoiced sounds (i.e., consonants), which provides a fuller and more recognizable synthesized voice signal.
  • the noise sources (659-669) may be separate noise sources for each of the eleven filters, or they may be a single noise source routed to all of the normalizers (648-658), or random noise may be generated by a suitable software algorithm.
  • Such a weighting factor may be generated, for example, in relation to the received signal strength at the moment of receiving the particular sub-frame.
  • a history of the received energy symbols and normalization factors may be maintained, and should a marked departure from the established history appear, the decoder (500) may disregard the deviation in favor of the historical values (either singularly or averaged over several of the previous values).
  • the history table approach afforded by the present invention is viable mainly because each sub-frame represents 30 ms of speech.
  • the preferred physical arrangement for the wire line encoder (700) and decoder (800) comprises a digital signal processor (DSP) such as, for example, the Motorola DSP 56000.
  • DSP digital signal processor
  • the "history table" compensation arrangement which disregards marked deviations from previously received levels of particular information, may be used to enhance the proper reception of the received wireline signal.
  • a preferred TDM slot comprises eight sub-frames of Figure 4a. Each frame comprises four slots. Accordingly, four voice messages may simultaneously reside on a single RF land mobile communication channel having conventional 25 kHz channel spacings. Thus, three other TDM slots follow the illustrated single slot in Figure 10.
  • the sample masked voice and energy samples are routed (1116) to a modulus adder (1120), which recovers the original sample (denoted x) by subtracting the mask vector (denoted r) (1122) from the encrypted vector (denoted s).
  • the encryption generator (1124) is substantially similar to the encryption generator (1114) providing identical mask vectors (r) to be added and subtracted to the sample vectors.
  • the decrypted overhead and sample portions are provided to the decoder (500), which digitally processes the samples to reconstruct the voice signal.

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

Abstract

Selon l'invention, un signal d'information est échantillonné, quantifié et traité numériquement par un codeur d'information (100). Des échantillons traités numériquement (1104, 1106) produits par le codeur (100) sont modulés sur un canal de communication pour créer des symboles ayant une intensité de modulation proportionnelle à une caractéristique d'un échantillon respectif traité numériquement. L'invention décrit un mode de réalisation de transmission haute-fréquence (HF) ainsi qu'un mode de réalisation par conducteur électrique. Enfin, la présente invention concerne un chiffrement (1101) pour assurer la confidentialité des communications.
PCT/US1989/001345 1988-04-29 1989-04-03 Procede a efficacite spectrale pour la communication d'un signal d'information WO1989010661A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
KR1019890702478A KR920007093B1 (ko) 1988-04-29 1989-04-03 정보 신호 전송 방법
FI896174A FI896174A0 (fi) 1988-04-29 1989-12-21 Spektriskt effektivt foerfarande foer foermedlande av den informationssignal.
DK666789A DK666789A (da) 1988-04-29 1989-12-27 Fremgangsmaade til transmission af et informationssignal
NO89895318A NO895318L (no) 1988-04-29 1989-12-29 Framgangsmaate for overfoering av informasjonssignal.

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US18776688A 1988-04-29 1988-04-29
US07/187,685 US4979188A (en) 1988-04-29 1988-04-29 Spectrally efficient method for communicating an information signal
US187,685 1988-04-29
US187,766 1988-04-29

Publications (1)

Publication Number Publication Date
WO1989010661A1 true WO1989010661A1 (fr) 1989-11-02

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PCT/US1989/001345 WO1989010661A1 (fr) 1988-04-29 1989-04-03 Procede a efficacite spectrale pour la communication d'un signal d'information

Country Status (7)

Country Link
EP (1) EP0377687A4 (fr)
JP (1) JPH03500118A (fr)
KR (1) KR920007093B1 (fr)
CN (1) CN1038003A (fr)
FI (1) FI896174A0 (fr)
IL (1) IL89672A (fr)
WO (1) WO1989010661A1 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0508581A2 (fr) * 1991-03-12 1992-10-14 AT&T Corp. Compression de siganux utilisant un modèle perceptif
EP0565947A1 (fr) * 1992-04-13 1993-10-20 NOKIA TECHNOLOGY GmbH Méthode pour inclusion d'information digitale dans un signal audio avant decoder le canal
EP0648031A2 (fr) * 1993-10-12 1995-04-12 Matsushita Electric Industrial Co., Ltd. Système de brouillage audio pour le brouillage et le débrouillage de signaux audio
EP0653846A1 (fr) * 1993-05-31 1995-05-17 Sony Corporation Appareil et procede de codage ou decodage de signaux, et support d'enregistrement
EP0663739A1 (fr) * 1993-06-30 1995-07-19 Sony Corporation Dispositif de codage de signaux numeriques, son dispositif de decodage, et son support d'enregistrement
EP0692880A1 (fr) * 1993-11-04 1996-01-17 Sony Corporation Codeur de signaux, decodeur de signaux, support d'enregistrement et procede de codage de signaux
EP0693829A1 (fr) * 1994-02-05 1996-01-24 Sony Corporation Procede et dispositif de codage de l'information et procede et dispositif de decodage de l'information
EP0713295A1 (fr) * 1994-04-01 1996-05-22 Sony Corporation Methode et dispositif de codage et de decodage d'informations, methode de transmission d'informations et support d'enregistrement de l'information

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US4216354A (en) * 1977-12-23 1980-08-05 International Business Machines Corporation Process for compressing data relative to voice signals and device applying said process
US4455649A (en) * 1982-01-15 1984-06-19 International Business Machines Corporation Method and apparatus for efficient statistical multiplexing of voice and data signals
US4697265A (en) * 1984-06-01 1987-09-29 Fujitsu Limited Error monitor circuit

Family Cites Families (1)

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DE3506912A1 (de) * 1985-02-27 1986-08-28 Telefunken Fernseh Und Rundfunk Gmbh, 3000 Hannover Verfahren zur uebertragung eines audiosignals

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
US4216354A (en) * 1977-12-23 1980-08-05 International Business Machines Corporation Process for compressing data relative to voice signals and device applying said process
US4455649A (en) * 1982-01-15 1984-06-19 International Business Machines Corporation Method and apparatus for efficient statistical multiplexing of voice and data signals
US4697265A (en) * 1984-06-01 1987-09-29 Fujitsu Limited Error monitor circuit

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP0377687A4 *

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0508581B1 (fr) * 1991-03-12 1997-05-28 AT&T Corp. Compression de signaux utilisant un modèle perceptif
EP0508581A2 (fr) * 1991-03-12 1992-10-14 AT&T Corp. Compression de siganux utilisant un modèle perceptif
EP0565947A1 (fr) * 1992-04-13 1993-10-20 NOKIA TECHNOLOGY GmbH Méthode pour inclusion d'information digitale dans un signal audio avant decoder le canal
EP0653846A4 (fr) * 1993-05-31 1998-10-21 Sony Corp Appareil et procede de codage ou decodage de signaux, et support d'enregistrement.
EP0653846A1 (fr) * 1993-05-31 1995-05-17 Sony Corporation Appareil et procede de codage ou decodage de signaux, et support d'enregistrement
EP0663739A4 (fr) * 1993-06-30 1998-09-09 Sony Corp Dispositif de codage de signaux numeriques, son dispositif de decodage, et son support d'enregistrement.
EP1083674A3 (fr) * 1993-06-30 2001-04-11 Sony Corporation Dispositif de codage de signaux numeriques, son dispositif de décodage, et son support d'enregistrement
EP1083674A2 (fr) * 1993-06-30 2001-03-14 Sony Corporation Dispositif de codage de signaux numeriques, son dispositif de décodage, et son support d'enregistrement
EP0663739A1 (fr) * 1993-06-30 1995-07-19 Sony Corporation Dispositif de codage de signaux numeriques, son dispositif de decodage, et son support d'enregistrement
EP0648031A3 (fr) * 1993-10-12 1999-04-28 Matsushita Electric Industrial Co., Ltd. Système de brouillage audio pour le brouillage et le débrouillage de signaux audio
EP0648031A2 (fr) * 1993-10-12 1995-04-12 Matsushita Electric Industrial Co., Ltd. Système de brouillage audio pour le brouillage et le débrouillage de signaux audio
EP0692880A4 (fr) * 1993-11-04 1998-09-30 Sony Corp Codeur de signaux, decodeur de signaux, support d'enregistrement et procede de codage de signaux
EP0692880A1 (fr) * 1993-11-04 1996-01-17 Sony Corporation Codeur de signaux, decodeur de signaux, support d'enregistrement et procede de codage de signaux
EP0693829A4 (fr) * 1994-02-05 1998-08-26 Sony Corp Procede et dispositif de codage de l'information et procede et dispositif de decodage de l'information
EP0693829A1 (fr) * 1994-02-05 1996-01-24 Sony Corporation Procede et dispositif de codage de l'information et procede et dispositif de decodage de l'information
EP0713295A1 (fr) * 1994-04-01 1996-05-22 Sony Corporation Methode et dispositif de codage et de decodage d'informations, methode de transmission d'informations et support d'enregistrement de l'information
EP0713295A4 (fr) * 1994-04-01 2002-04-17 Sony Corp Methode et dispositif de codage et de decodage d'informations, methode de transmission d'informations et support d'enregistrement de l'information

Also Published As

Publication number Publication date
IL89672A (en) 1994-04-12
IL89672A0 (en) 1989-09-28
CN1038003A (zh) 1989-12-13
FI896174A0 (fi) 1989-12-21
KR900701082A (ko) 1990-08-17
KR920007093B1 (ko) 1992-08-24
EP0377687A4 (en) 1991-09-11
EP0377687A1 (fr) 1990-07-18
JPH03500118A (ja) 1991-01-10

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