WO1992012483A1 - Technique de reception de donnees - Google Patents

Technique de reception de donnees Download PDF

Info

Publication number
WO1992012483A1
WO1992012483A1 PCT/US1992/000222 US9200222W WO9212483A1 WO 1992012483 A1 WO1992012483 A1 WO 1992012483A1 US 9200222 W US9200222 W US 9200222W WO 9212483 A1 WO9212483 A1 WO 9212483A1
Authority
WO
WIPO (PCT)
Prior art keywords
data
received data
replacing
value
datapoints
Prior art date
Application number
PCT/US1992/000222
Other languages
English (en)
Inventor
Arie Heiman
Original Assignee
The Dsp Group, 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
Application filed by The Dsp Group, Inc. filed Critical The Dsp Group, Inc.
Publication of WO1992012483A1 publication Critical patent/WO1992012483A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/409—Edge or detail enhancement; Noise or error suppression
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/22—Arrangements for detecting or preventing errors in the information received using redundant apparatus to increase reliability
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/41—Bandwidth or redundancy reduction
    • H04N1/411—Bandwidth or redundancy reduction for the transmission or storage or reproduction of two-tone pictures, e.g. black and white pictures
    • H04N1/413—Systems or arrangements allowing the picture to be reproduced without loss or modification of picture-information
    • H04N1/419—Systems or arrangements allowing the picture to be reproduced without loss or modification of picture-information in which encoding of the length of a succession of picture-elements of the same value along a scanning line is the only encoding step

Definitions

  • the present invention relates to data reception techniques generally and to data reception techniques using inherent redundancy in received data for error recovery in particular.
  • the corrupt data is either no longer useful, such as is the case for corrupted bank account data, or is useful but with a significant decrease in the quality of the data, such as is the case for documents or images typically received by a facsimile machines.
  • error correction techniques redundant bits are added to the original data stream before transmission. If errors are introduced to the data, the error correction technique utilizes the redundant bits as well as the original data to correct the error. The quality of the correction depends on the type of error
  • the data is partitioned into packets to which are added redundant bits.
  • the redundant bit is used to detect if errors have been added to the data in the packet. If an error is detected, the packet is retransmitted.
  • Both the error detection and the error correction techniques require the addition of redundant bits to the data to be transmitted. Recovery from errors is either by retransmission of the data with the errors or through utilization of data in the added redundant bits. It will be appreciated that addition of the redundant bits adds to the amount of data to be transmitted.
  • a data reception system which utilizes modem information and redundant data which is inherent in the received dat to effect error recovery.
  • a data reception system including a modem for receiving transmitted data including inherent redundant data and for providing received data and information regarding the received data and error recovery apparatus operating on the received data for utilizing the inherent redundant data and the information regarding the received data to identify and to correct errors introduced into the received data.
  • the error recovery apparatus includes apparatus for identifying a plurality of suspected erroneous datapoints in the received data and apparatus for checking that the inherent redundant data is consistent with the received data wherein an inconsistent result indicates that a first value of at
  • the error recovery apparatus also includes apparatus for replacing the first value with a second possible value wherein the second possible value is different from the first value, apparatus for repeating the steps of checking and replacing with at least a portion of the suspected erroneous datapoints until either the received data is consistent with the inherent redundant data or no suspected erroneous datapoints remain and apparatus for returning the at least one suspected erroneous datapoint to the first value if the result of the step of checking is inconsistent.
  • the apparatus for replacing includes apparatus for replacing the plurality of suspected erroneous datapoints one at a time.
  • the apparatus for replacing includes apparatus for replacing the plurality of suspected erroneous datapoint more than one at a time.
  • the data reception system is characterized in that generally no retransmission of received data into which errors have been introduced is performed.
  • a facsimile system including the elements of the data reception system.
  • a data reception technique including the steps of receiving via modem means transmitted data including inherent redundant data and providing received data, providing from the modem means information regarding the received data and utilizing the inherent redundant data and the information regarding the received data to identify
  • the step of utilizing includes the steps of identifying a plurality of suspected erroneous datapoints in the received data, checking that the inherent redundant data is consistent with the received data wherein an inconsistent result indicates that a first value of at least one of the suspected erroneous datapoints is incorrect, replacing the first value with a second possible value wherein the second possible value is different from the first value, repeating the steps of checking and replacing with at least a portion of the suspected erroneous datapoints until either the received data is consistent with the inherent redundant data or no suspected erroneous datapoints remain and returning the at least one suspected erroneous datapoint to the first value if the result of the step of checking is inconsistent.
  • Fig. 1 is a block diagram illustration of a transmission and a data reception system constructed and operative in accordance with one embodiment of the present invention
  • Fig. 2 is a graphical illustration of an example four phase Quadrature Amplification Modulation (QAM) phasor coordinate system useful in understanding the operation of the system of Fig. 1; and
  • QAM Quadrature Amplification Modulation
  • Fig. 3 is a block diagram illustration of a transmission system and a data reception system constructed and operative in accordance with an alternative embodiment of the present invention.
  • Fig. 1 illustrates a transmission system 10 and a data reception system 12 constructed and operative in accordance with an embodiment of the present invention.
  • the transmission system 10 is operative for preparing and transmitting data to be transmitted and data reception system 12 is operative for receiving the transmitted data and for recovering most of the data into which errors have been introduced.
  • the transmission system 10 typically comprises a data format unit 14 for preparing data to be transmitted in a suitable format for transmission, such as by compressing the data, by packetizing it, and/or by adding End-Of-Line (EOL) , End-Of-Page (EOP) or End-Of- Block (EOB) or other such indications.
  • the transmission system 10 also comprises a transmitting modem 16 for collecting the data to be transmitted from the data format unit 14 and for transmitting the data to be transmitted.
  • a typical data format unit 14 typically implements within communication software a communication protocol, such as CCITT Recommendations T4 and T6 for facsimile machines.
  • An example transmitting modem 16 is one which performs QAM modulation and operates in accordance with one of CCITT Standards V22, V27, V29 or V32 however, any suitable modem can be utilized.
  • the reception system 12 typically comprises a receiving modem 18 for receiving the transmitted data, and an error recovery unit 22, working with information received from the receiving modem 18, for recovering data received in error.
  • the error recovery unit 22 typically includes a data deformat unit 20 for reversing the operation performed by the format unit 14 which typically implements the communication protocol implemented by data format unit 14.
  • a typical receiving modem 18 typically operates the same protocol as transmitting modem 16.
  • SUBSTITUTESHEET As is known in the art of QAM modulation, the receiving modem 18 receives phasors and de ines them by the symbols which they most closely match, where a symbol typically is at least one bit of data.
  • An example "closeness" measure is the Euclidian distance but any suitable measure can be used. This process is illustrated for a four phase QAM modem in Fig. 2, to which reference is now briefly made, where Yl is an example received phasor. V2 is the symbol which matches Yl and thus, is the symbol produced by receiving modem 18 when Yl is received.
  • Data deformat unit 20 takes the symbols produced by receiving modem 18 and reverses the process performed by data format unit 14. Thus, if unit 14 compressed the data, unit 20 uncompresses the data.
  • the received data comprise a plurality of datapoints some of which are inherently redundant.
  • Group 3 facsimile machines use data compression protocols, such as Modified Huffman coding, in accordance with the CCITT recommendation T4.
  • Modified Huffman coding In these protocols, at the end of each scanning line, an EOL indication or datapoint is sent. Additionally, at the end of each page an EOP indication or datapoint is sent.
  • EOL Error-tosimile art that if errors are introduced into compressed received data, one of the following phenomena will occur: a) illegal code words will be detected by the data deformat unit 20, where illegal code words are code words that the data compression protocol cannot produce; and b) the EOL will be inconsistent with the data.
  • Each received compressed line consists of N pixels. If errors are introduced into the received data, the probability is very low that the number of reconstructed pixels in the line will equal N.
  • error correction bits added to the data for the purpose of error correction.
  • error correction bits include information about the received data.
  • An example error correction protocol is the High level Data Link Control (HDLC) protocol which utilizes the Cyclic Redundancy Code (CRC) for error correction.
  • HDLC High level Data Link Control
  • the error recovery unit 22 utilizes the inherently redundant data point to check that the received data is consistent and thus, has no errors in it.
  • this process entails calculating the redundant data point and comparing the calculated value with the received value. If they match, then the received data is consistent. If not, then errors exist.
  • the process requires correlating at least two lines in the image. A low value for the correlation typically indicates that there might be errors in the transmitted image.
  • the consistency check is typically performed on a segment of data, such as a line in a facsimile transmission. If the consistency check fails, then all symbols received by receiving modem 18 with a low level of confidence will be tested. An example of such a symbol is the symbol produced from phasor Y2 of Fig. 2. Receiving modem 18 will typically define phasor Y2 by
  • Error recovery unit 22 typically requests from receiving modem 18 an alternative possible symbol for the symbol received with a low level of confidence where an alternative possible symbol is one which is close to the phasor, but not closest.
  • an alternative possible symbol is one which is close to the phasor, but not closest.
  • VI although further from Y2 than V2, is the next best, or "second best", symbol for phasor Y2. It is possible to request other available symbols; in the example of Fig. 2, these would be third best symbol V3 or fourth best symbol V4.
  • Error recovery unit 22 then repeats the consistency check. If there is consistency in the data, the system proceeds to the next segment of data. If the data is inconsistent, the process is repeated for the next symbol received with a low level of confidence.
  • the present invention performs error recovery as a post- transmission process and does not require changes in the transmission system 10.
  • the error recovery is generally performed without retransmission and without the need for insertion of error detection data. If, however, it is desired that such error detection be inserted, the present invention utilizes the inserted error detection data for error recovery, as shown in more detail hereinbelow.
  • FIG. 3 illustrates an alternative embodiment of the present invention utilizing error detection. Similar reference numerals are used to indicate similar elements.
  • a transmission system 70 is operative for preparing and transmitting data to be transmitted and a data reception system 72 is operative for receiving the transmitted data and for recovering most of the data into which errors have been
  • the transmission system 70 comprises an error detection data inserter 74 for inserting error detection bits, such as CRC parity bits, into the data to be transmitted and transmitting modem 16.
  • error detection data inserter 74 is one operating the HDLC protocol and is typically instantiated in communication software or in communication terminals.
  • the error detection data inserter 74 inserts error detection bits into the data to be transmitted, in accordance with an error detection algorithm, such as the CRC parity bit algorithm. Inserter 74 also formats the data into packets and possibly also compresses the packets. The resultant data is then sent to transmitting modem 16 which transmits the data to reception system 72.
  • an error detection algorithm such as the CRC parity bit algorithm. Inserter 74 also formats the data into packets and possibly also compresses the packets. The resultant data is then sent to transmitting modem 16 which transmits the data to reception system 72.
  • the reception system 72 comprises receiving modem 18 and an error recovery unit 78, working with information received from receiving modem 18, for recovering data received in error.
  • Error recovery unit 78 typically includes an error detection data extracter 76 for extracting the error detection bits inserted by inserter 74, for detecting errors and for reversing the format operation of inserter 74.
  • An example of inserter 74 is one which performs the HDLC protocol.
  • Receiving modem 18 receives the transmitted data and sends it to error recovery unit 78.
  • Error recovery unit 78 utilizes extracter 76 to extract the error detection bits and utilizes the extracted bits for error recovery in accordance with the method as described hereinabove, an example of which is illustrated in Fig. 3.
  • the consistency check consists of recalculating the error detection bits from the received data. For example, if CRC error detection is used, the CRC bit is recalculated for each consistency check.

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)
  • Communication Control (AREA)

Abstract

L'invention concerne un système et une technique de réception de données. Le système comprend un modem (18) destiné à recevoir des données émises comprenant des données redondantes inhérentes et à fournir des données reçues et des informations concernant les données reçues, ainsi qu'un appareil de reprise (22) fonctionnant sur la base des données reçues pour utiliser les données redondantes inhérentes et les informations concernant les données reçues afin d'identifier et de corriger des erreurs introduites dans les données reçues. La technique présentée comprend les étapes suivantes: réception des données émises comprenant des données redondantes inhérentes, fourniture des données reçues et des informations concernant les données reçues, identification d'une pluralité de points de données suspectés d'être erronés dans les données reçues et vérification de la compatibilité des données redondantes inhérentes avec les données reçues. Le procédé consiste ensuite à remplacer la première valeur par une seconde valeur possible et à répéter les étapes de la vérification de la comptabilité et du remplacement des valeurs jusqu'à ce que les données reçues soient compatibles avec les données redondantes inhérentes.
PCT/US1992/000222 1991-01-08 1992-01-07 Technique de reception de donnees WO1992012483A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US63967391A 1991-01-08 1991-01-08
US639,673 1991-01-08

Publications (1)

Publication Number Publication Date
WO1992012483A1 true WO1992012483A1 (fr) 1992-07-23

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1992/000222 WO1992012483A1 (fr) 1991-01-08 1992-01-07 Technique de reception de donnees

Country Status (2)

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IL (1) IL100615A0 (fr)
WO (1) WO1992012483A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997011542A2 (fr) * 1995-09-22 1997-03-27 Siemens Aktiengesellschaft Procede et circuiterie pour le traitement de donnees utiles

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3656107A (en) * 1970-10-23 1972-04-11 Ibm Automatic double error detection and correction apparatus
US4163147A (en) * 1978-01-20 1979-07-31 Sperry Rand Corporation Double bit error correction using double bit complementing
US4319357A (en) * 1979-12-14 1982-03-09 International Business Machines Corp. Double error correction using single error correcting code
US4605921A (en) * 1983-06-20 1986-08-12 Riddle Herbert S Digital word-framing technique and system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3656107A (en) * 1970-10-23 1972-04-11 Ibm Automatic double error detection and correction apparatus
US4163147A (en) * 1978-01-20 1979-07-31 Sperry Rand Corporation Double bit error correction using double bit complementing
US4319357A (en) * 1979-12-14 1982-03-09 International Business Machines Corp. Double error correction using single error correcting code
US4605921A (en) * 1983-06-20 1986-08-12 Riddle Herbert S Digital word-framing technique and system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997011542A2 (fr) * 1995-09-22 1997-03-27 Siemens Aktiengesellschaft Procede et circuiterie pour le traitement de donnees utiles
WO1997011542A3 (fr) * 1995-09-22 1997-05-22 Siemens Ag Procede et circuiterie pour le traitement de donnees utiles

Also Published As

Publication number Publication date
IL100615A0 (en) 1992-09-06

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