EP1668812A1 - Procede et dispositif de decodage de paquets de donnees codes transmis par l'intermediaire de reseaux de transmission de donnees orientes paquets et procede et dispositif de codage et decodage de paquets de donnees a transmettre par l'intermediaire de reseaux de transmission de donnees orientes paquets - Google Patents

Procede et dispositif de decodage de paquets de donnees codes transmis par l'intermediaire de reseaux de transmission de donnees orientes paquets et procede et dispositif de codage et decodage de paquets de donnees a transmettre par l'intermediaire de reseaux de transmission de donnees orientes paquets

Info

Publication number
EP1668812A1
EP1668812A1 EP04787236A EP04787236A EP1668812A1 EP 1668812 A1 EP1668812 A1 EP 1668812A1 EP 04787236 A EP04787236 A EP 04787236A EP 04787236 A EP04787236 A EP 04787236A EP 1668812 A1 EP1668812 A1 EP 1668812A1
Authority
EP
European Patent Office
Prior art keywords
data
data packets
error correction
decoding
carried out
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.)
Ceased
Application number
EP04787236A
Other languages
German (de)
English (en)
Inventor
Robert Kutka
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.)
Nokia Solutions and Networks GmbH and Co KG
Original Assignee
Siemens AG
Nokia Siemens Networks GmbH and Co KG
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 Siemens AG, Nokia Siemens Networks GmbH and Co KG filed Critical Siemens AG
Publication of EP1668812A1 publication Critical patent/EP1668812A1/fr
Ceased legal-status Critical Current

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Classifications

    • 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
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0045—Arrangements at the receiver end
    • H04L1/0047—Decoding adapted to other signal detection operation
    • H04L1/005—Iterative decoding, including iteration between signal detection and decoding operation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/29—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes combining two or more codes or code structures, e.g. product codes, generalised product codes, concatenated codes, inner and outer codes
    • H03M13/2906—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes combining two or more codes or code structures, e.g. product codes, generalised product codes, concatenated codes, inner and outer codes using block codes
    • H03M13/2909—Product codes
    • H03M13/2915—Product codes with an error detection code in one dimension
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/29—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes combining two or more codes or code structures, e.g. product codes, generalised product codes, concatenated codes, inner and outer codes
    • H03M13/2906—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes combining two or more codes or code structures, e.g. product codes, generalised product codes, concatenated codes, inner and outer codes using block codes
    • H03M13/2927—Decoding strategies
    • H03M13/293—Decoding strategies with erasure setting
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/29—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes combining two or more codes or code structures, e.g. product codes, generalised product codes, concatenated codes, inner and outer codes
    • H03M13/2948—Iterative decoding
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/35—Unequal or adaptive error protection, e.g. by providing a different level of protection according to significance of source information or by adapting the coding according to the change of transmission channel characteristics
    • H03M13/356—Unequal error protection [UEP]
    • 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
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0057—Block codes
    • 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
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0061—Error detection codes
    • 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
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0071—Use of interleaving
    • 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
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0072—Error control for data other than payload data, e.g. control data
    • 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
    • H04L2001/0098—Unequal error protection

Definitions

  • the invention relates to a method and a device for decoding coded data packets transmitted by means of packet-oriented data transmission networks, and a method and a device for coding and decoding data packets to be transmitted via packet-oriented data transmission networks.
  • the so-called packet-oriented data transmission is often used.
  • the data to be sent in the network are divided into small units, so-called packets.
  • these packages also contain information in order to convey them correctly to the corresponding recipient. If a large file is now to be sent via a packet-oriented network, it must first be divided into small packets in order to then be reassembled by the recipient.
  • Precautions must therefore be taken to prevent a signal from being corrupted, ie the occurrence of errors. defective data packets, to make them as unlikely as possible and to detect errors that have occurred with the highest possible probability and to be able to initiate corrective measures if necessary. This can only be done by including the sender and receiver and requires appropriate protective measures. However, these protective measures, which are generally referred to as error protection, require expensive transmission capacities.
  • the first and most important problem in the context of error protection is the problem of the reliable detection of errors. Appropriate measures to correct the error that has already occurred can only be taken if errors are identified with a high probability. A detection of transmission errors is only possible if the transmission errors
  • Data has some redundancy, i.e. if additional information is also transmitted which is "superfluous" information in the sense of data transmission, but which provides information as to whether the message has been falsified, i.e. by means of which a faulty transmission can be recognized.
  • a well known method of providing such redundancy in the transmission of data is to provide a so-called parity bit, which is used to secure ASCII or EBCDIC characters. In principle, it is not possible to detect errors without redundancy.
  • parity bits Each character to be transmitted is provided with a check bit which indicates the parity, i.e. indicates the number of 0 or 1 bits.
  • a so-called longitudinal parity can also be checked in addition to the cross.
  • n m + k bits are transmitted over the line. It can be shown mathematically that the parity bits do not offer high protection, i.e. that the security with which errors that occur are also recognized in the
  • Comparison z u other method is relatively low.
  • Methods which provide improved error detection are, for example, the so-called cyclical redundancy check (CRC), which essentially correspond to a division by a polynomial with residual value formation.
  • CRC cyclical redundancy check
  • the advantage of forward correction is that it can also be carried out on simplex channels and that time-consuming retransmission of data packets is avoided. For this, it has the disadvantage that transmission always has to be carried out with a high level of redundancy and not just a repetition in the event of an error.
  • the invention is based on the problem of increasing the transmission security in packet-oriented networks without the need for an increased transmission capacity due to additional correction bytes or correction bits.
  • the coded data packets are subjected to an error detection. Furthermore, an error correction is carried out for the data packets identified as defective, and the data elements of the data packets identified as incorrectly transmitted, which are recognized as being correctly transmitted, are used for error correction.
  • a device for decoding coded data packets transmitted by means of packet-oriented data transmission networks with a plurality of data elements has a decoder, which is set up in such a way that it subjects the coded data packets to an error detection, for which data packets identified as faulty carry out an error correction and for correcting the errors as correctly transmitted data elements of the data packets recognized as incorrect are used.
  • a plurality of data elements are encoded before transmission by means of an encoder to form data packets, which 200303865
  • the coded data packets are subjected to an error detection with a plurality of data elements; an error correction is carried out for the data packets identified as defective, the data elements of the data packets recognized as incorrect being recognized as being correct being used for the error correction.
  • a device for encoding, transmitting and decoding data packets to be transmitted via packet-oriented data transmission networks has an encoder and a decoder.
  • the encoder is set up in such a way that it encodes a plurality of data elements before transmission to data packets.
  • the decoder is set up in such a way that it subjects the coded data packets with a plurality of data elements to error detection, performs an error correction for the data packets identified as defective, and uses the data elements of the data packets recognized as defective to be corrected for error correction.
  • the method for decoding according to the invention is based on the fact that even in the case of a defective data packet, only a small number of data elements, which can be data bytes or data bits, for example, of the defective data packet are defective, whereas the majority of data elements are also correctly transmitted in incorrectly transmitted data packets.
  • Using a simple algorithm it is possible to evaluate the correct data elements of a faulty data packet.
  • By evaluating and using the correct data elements of an incorrectly transmitted data packet it is possible to increase the error protection without increasing the number of correction elements transmitted, ie redundancy bytes or redundancy bits.
  • the "method can defective packets and forward error protection ;, in both error correction scenarios, ie return requirement are used. In the process of requesting defective packets, the number of newly requested packets can be reduced using the method according to the invention. In the process of forward error correction, the number of correctable data packets can be increased using the method according to the invention.
  • the error detection is preferably carried out in a unit of a communication transport layer.
  • the error correction can be carried out in a unit of a session layer or a presentation layer or a processing layer.
  • the layers here are to be understood as computer network layers which are based on layers in a transmission reference, e.g. the OSI reference model or the TCP / IP reference model.
  • a lower layer than the transport layer corresponds, for example, to the physical layer, the security layer or the network layer in the OSI reference model or in the TCP / IP reference model.
  • a layer higher than the transport layer is the session layer, the presentation layer and the processing layer in the OSI reference model and the processing layer in the TCP / IP reference model.
  • the data elements can be data bytes or data bits.
  • the decoder particularly preferably writes the data elements of each data packet in columns into a matrix and reads them line by line from the matrix for decoding.
  • the decoder can write the data elements of each data packet line by line into a matrix and read them out column by column for decoding. This clearly means that the entire matrix is tilted, i.e. the columns and rows are interchanged.
  • packet errors are converted into data element errors, which can subsequently be corrected more easily.
  • data element errors are understood to mean, for example, byte errors or bit errors.
  • the error correction of individual data packets is carried out if redundancy by means of redundancy elements is not sufficient to carry out an erasure correction of the individual data packets.
  • the erasure correction is carried out first before an error correction according to the invention is carried out. This leads to improved error protection and correction of the fetals.
  • the number of redundancy elements can differ per row or per column.
  • an additional deletion correction can be carried out.
  • additional error corrections and erasure corrections are preferably carried out recursively.
  • the method for decoding is particularly preferably combined with a soft decoding method.
  • the error correction capability of the method is additionally increased. Especially when selecting the potentially erroneous data elements to be corrected, those data elements that have the lowest reliability or, in other words, the highest probability of being erroneous can be selected first. This enables a gain of 1 dB to 3 dB to be achieved in the transmission [1].
  • the encoder writes the data elements to be transmitted line by line into a matrix and reads them column by column from the matrix for transmission as data packets
  • the decoder writes the data elements of each data packet column by column to a matrix and reads them line by line from the matrix for decoding out
  • the encoder can write the data elements to be transmitted in columns in a matrix and read them line by line from the matrix for transmission as data packets
  • the decoder can write the data elements of each data packet line by line in a matrix and read them out in columns for decoding.
  • the encoder writes and reads the data to be transmitted in a different order in a matrix, i.e. either writing row by row and reading column by column or vice versa
  • packet errors are converted into data element errors, which can subsequently be corrected more easily.
  • the decoder does this in exactly the opposite order, i.e. if the encoder writes line by line into the matrix and reads from the matrix column by column, the decoder writes column by column to the matrix and reads line by line and vice versa.
  • the encoder preferably provides a different number of redundancy elements per line or per column.
  • redundancy elements are understood to mean, for example, redundancy bytes or redundancy bits, depending on whether data bytes or data bits are assumed.
  • the redundancy elements are preferably provided per line when the encoder writes line by line into the matrix, whereas the redundancy elements are preferably provided per column when the encoder writes column by column into the matrix.
  • redundancy elements make it possible for the decoder to correct incorrectly transmitted data elements of a data packet. This leads to an increase in transmission security.
  • the redundancy elements are added to the end of each line and can also be added to the end A check information is added to each column, by means of which each column can be examined for errors in the receiver.
  • the redundancy elements are added to the end of each column and, in addition, one is added to the end of each row
  • the number of redundancy elements can be defined individually for each row or column. This makes it possible to achieve uniform or non-uniform error protection.
  • the invention can be seen in the fact that when data is transmitted in packet-oriented networks, the transmission security is increased and the susceptibility to errors is reduced by using a new method for error correction.
  • data packets identified as faulty are not discarded, but instead are forwarded to an FEC decoder (forward error correction decoder, forward error correction decoder).
  • FEC decoder forward error correction decoder
  • data packets with the correct IP header checksum but incorrect UDP checksum are passed on to the FEC decoder, which is implemented, for example, in the Network Adaptation Layer (NAL).
  • NAL Network Adaptation Layer
  • the FEC decoder evaluates the correct bytes of a data packet identified as defective by means of an algorithm described in more detail in the detailed description of an exemplary embodiment.
  • the method according to the invention can be used for a scenario with an available return channel.
  • the use of the method according to the invention results in a lower number of data packets requested again, since some of the data packets identified as incorrect can be corrected.
  • the method according to the invention can also be used for a scenario without an available return channel, for example in the case of television broadcasts. The number of errors is reduced by the method for error correction according to the invention.
  • a preferred implementation of the error correction method according to the invention is that for each row of data bytes three different types of methods for correcting errors in succession in a block interleaver, i.e. a decoder.
  • the conventional erasure correction is used as a first step. However, this can only be used as long as the number of defective bytes in a packet does not exceed the erasure correction capability of the code, ie the transmitted data packets. If the number of defective bytes exceeds the erasure correction capability, but is less than the error correction capability of the code, the method according to the invention is used for error correction.
  • the number of potentially defective bytes is reduced to the maximum number that can be erased by erasure by selecting a subset from the potentially faulty bytes.
  • the erasure correction is then carried out and then the resulting bytes are verified by means of checksums. If the checksums indicate that the erasure correction has not corrected the errors within the data packet, a different subset is selected from the potentially faulty bytes and then the erasure correction is carried out again with subsequent verification of the checksums.
  • the selection of different subsets of potentially faulty bytes can be carried out until all the information contained in the redundancy of the code has been used to correct as many faulty bytes as possible.
  • a so-called Reed-Solomon decoder which uses a so-called Reed-Solomon code, can be used for the erasure correction and the error correction according to the invention.
  • the Reed-Solomon code is an error correction procedure that is used in mobile communication with CDPD, in wired communication with ADSL and ATM, but also in data storage on CDs and DVDs.
  • the Reed-Solomon code is a method with forward error correction (FEC) that enables the correction of incorrectly transmitted data blocks.
  • the FEC data are attached to the useful data in a code location in a data block and transmitted together with them.
  • the code word consists of the user data and a number of Reed-Solomon test bytes as well as one or more DMT symbols.
  • the mathematical Spelling is similar to that of the CRC method, whereby a previously formed Reed-Solomon check digit is used for the polynomial division.
  • bit-wise decoding i.e. Error correction
  • the method for error correction can be accelerated in a simple manner.
  • the elaborate part i.e. the computationally expensive part is the erasure correction with a reduced number of bytes.
  • This part can be accelerated by not selecting all combinations of subsets from potentially defective bytes, but rather canceling the selection of changed subsets after a predetermined period of time. This limits the time used for erasure correction and speeds up the error correction process. However, this also limits the ability to correct.
  • FIG. 1 shows a schematic matrix for explaining an exemplary embodiment of the invention, in which matrix an encoder can write data packets to be transmitted;
  • FIG. 2 shows a schematic frequency distribution from a simulation, which indicates the frequency distribution of byte errors per packet length;
  • FIG. 3 shows a histogram in which frequency distributions of incorrect bytes per packet are entered;
  • FIG. 4 histograms in which the frequency distribution of faulty bytes per packet is entered for four different transmission conditions
  • FIG. 5 shows how many additional lines of data bytes can be corrected if an error correction method according to the invention is used
  • FIG. 6 shows a schematic representation of a simplified layer reference model with an explanation of the inventive idea
  • Figure 7 is a schematic representation of a message transmission system.
  • Introductory is a schematic with reference to FIG. 7
  • Communication system i.e. a system for transmitting data, explained, which has an encoder and a decoder and on which the inventive method for coding and decoding can be carried out.
  • source information 702 is supplied from a source 701, for example a computer, a video camera, a landline telephone or cell phone (not shown), a source encoder 703. From this, the source encoder 703 generates a data stream 704 which has a large number of useful data bits or useful data bytes.
  • Source coding is generally understood to be a coding in which the data to be transmitted are compressed, ie. redundant redundancy in the data to be transferred is eliminated.
  • the generated data stream 704 is fed to an encoder 705, also referred to as a channel encoder, coded by it, and the encoded data stream 706 is fed to a modulator 707, in which the encoded data stream 706 is modulated onto a carrier signal of a predeterminable frequency and is transmitted as a modulated signal 708 a physical channel 709, for example via a radio link or via a telephone line, to a receiver having a demodulator 710.
  • encoding or channel encoding is to be understood as a method or a method with which a data stream is encoded by adding redundancy data, also referred to in the application as redundancy elements, so that from source 701 to a sink 718 the can be transmitted with as few errors as possible.
  • redundancy is thus added to the actual user data in a controlled manner on the transmission side, so that errors which occur during transmission via: physical channel 709 can be detected and corrected on the reception side.
  • the operation of the encoder will be described in more detail below.
  • the modulated signal 708 is subject to interference 711 in the physical channel 709, as a result of which a disturbed modulated signal 712 is generated which is fed to the demodulator 710.
  • the demodulator 710 generates a demodulated data stream 713, which is fed to a decoder 714, also called a channel decoder.
  • the decoder 714 generates from the demodulated data stream 713 a decoded data stream 715 which is fed to a source decoder 716.
  • the source decoder 716 generates a result data stream 717 from the decoded data stream, which is fed to a sink. 6, a layer reference model 600, in the case shown a TCP / IP reference model, is shown schematically.
  • IP Internet Protocol
  • UDP User Datagram Protocol
  • Transport protocol 605 (RTP) is used.
  • 6 shows a fifth layer 606, which represents the application layer, which is the seventh layer in the OSI reference model.
  • the various applications or applications can be executed within the application layer 606, for example the application H.323.
  • the inventive idea is also outlined.
  • the arrow in Fig. 6 indicates that IP packets (data packets) with correct IP header checksum but with incorrect ÜDP checksum are transmitted to the layer of the "Network Adaptation Layer (NAL)", i.e. the fifth layer (application layer), even if the ÜDP checksum indicates that the relevant IP packet is faulty.
  • NAL Network Adaptation Layer
  • the error correction method according to the invention is then carried out layer by layer, which will be described in more detail below.
  • FIG. 1 illustrates a schematic matrix 100 in which an encoder can write data packets.
  • the matrix 100 shown consists of eleven rows 101, 102, 103, 104, 105, 106, 107, 108, 109, 110 and 111 and 20 columns 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130 and 131.
  • An encoder or interleaver writes the data bytes to be transmitted into this matrix. Here he writes the data bytes line by line into the matrix. At the end of each line, the encoder has the option of inserting redundancy elements, ie redundancy bytes.
  • the different number of redundancy bytes per line means that the individual lines have different redundancies and are therefore provided with different error protection. In this way, important data bytes can be reconstructed better, more accurately and more easily in the event of a faulty transmission than less important data bytes which are entered in one of the last lines in the example and which have a lower number of redundancy bytes. Uneven error protection is thus implemented.
  • the sixth data packet which is formed by the sixth column 117, the ninth data packet which is formed by the ninth column 120, the tenth data packet which is formed by the tenth column 121, the eleventh data packet which is formed by the eleventh column 122 and the 14th data packet which is formed by the 14th column 125 is formed, transmitted incorrectly and thus each have at least one faulty byte.
  • the faulty data packets ie the columns, are identified in FIG. 1.
  • the individual faulty bytes within the faulty data packets are also marked with a cross in FIG. 1.
  • a faulty data packet represents only a single data byte within each line.
  • the FEC decoder (t - l) / 2 bytes can be corrected.
  • the algorithm is based on the data elements of an interleaver block, i.e. a matrix as shown in Fig. 1, used several times. The application continues until no further correction of data errors is possible, i.e. normally until all redundancy in the data is used for error correction.
  • the algorithm has a line loop, i.e. a command sequence which is processed for all lines of the interleaver block.
  • Each line is first examined for potentially defective bytes, i.e. an error detection is carried out. A decision is also made as to whether the total number of potentially defective bytes exceeds the erasure correction capability.
  • error decoding ie the decoding according to the invention or error correction according to the invention.
  • the checksums are used to check whether the error correction for the line just corrected was correct. This checks whether the CRC is correct, ie whether there are potentially defective bytes in the line.
  • the line is corrected.
  • the CRC checks are carried out again, i.e. the line is checked for potentially defective bytes and the columns of the interleaver block, which deliver a correct CRC check, are marked as correct.
  • the system then jumps back into the line loop and processes the next line of the interleaver block, i.e. it jumps back to b).
  • erasure decoding is carried out with a reduced number of bytes. This clearly means that the erasures, i.e. the deletion of potentially faulty bytes is arbitrarily reduced to the maximum number that can be corrected. That Randomly selected potentially erroneous bytes are deleted until only as many bytes remain as can be corrected using erasure decoding, whereby the corresponding number depends on the redundancy that is available in the line. It is then decoded and all CRC checksums checked again.
  • Loop over interleaver block e.g. a matrix as shown in FIG. 1:
  • the pseudo code makes it easy to see how the algorithm for correcting transmission errors according to an embodiment of the invention is implemented.
  • the algorithm shown for the reconstruction of incorrectly transmitted data packets is based on the correct bytes of the respective incorrect data packets. It should also be noted that it is also possible to swap columns and rows in the algorithm. This is necessary if the interleaver writes the data bytes into the matrix in columns and reads them out line by line for transmission.
  • FIGS. 2 to 5 which were obtained using simulations, describe how an error correction method according to the invention affects the transmission quality, ie the number of errors present after the error correction.
  • the simulations were based on a packet length of 20 bytes.
  • Fig. 2 the results of a simulation are shown schematically, which indicates the frequency distribution of byte errors per packet length.
  • the frequency with which a certain number of byte errors / packet length occurs is plotted. It can be seen that 0.05 byte errors / packet length, i.e. an error rate of one wrong byte per 20 byte packet length, approximately in 5V »of all cases occurs.
  • the frequency of occurrence of a certain ratio of byte error / packet length increases up to the ratio of 0.25 byte error / packet length, where it reaches a frequency of about 2.6%. After that, the frequency of the occurrence of a certain ratio of byte error / packet length drops to the ratio of 0.45 byte error / packet length, where it reaches a frequency of about 3%.
  • the simulation shown in Fig. 2 was used for the case of a mobile radio transmission, e.g. Cell phone calls, and shows that, on average, about 11% of the data packets contain faulty data bytes, i.e. that only every ninth data packet is transmitted incorrectly.
  • the 11% result from the sum of all frequencies shown in FIG. 2.
  • the maximum frequency is at a ratio of byte error / packet length of 0.25, i.e. one bad byte every four bytes of packet length, which means that every fourth byte is bad.
  • the frequency is only around 2.6%. It is thus easy to see that most data packets are transmitted without errors and that the majority of the bytes in the faulty data packets are transmitted correctly.
  • FIG. 3 shows a histogram in which the frequency distribution of defective bytes per packet is entered.
  • the absolute number of bad bytes on the X axis is arbitrary, since the number of bad bytes depends on the packet length used.
  • the frequency distribution for faulty bytes is entered, which could not be corrected despite the correction of errors.
  • To obtain the data points of the upper curve 340 a correction of the transmission errors has been carried out in accordance with the prior art, in which the correct bytes of the faulty data packets not be used to correct the errors.
  • an error correction has been carried out in accordance with the method according to the invention, in which the correct bytes of the incorrect data packets are used for the error correction.
  • the histogram clearly shows that the error correction method according to the invention results in a significantly reduced number of incorrect bytes per data packet than the method according to the prior art.
  • Curve 341 is clearly shifted to the left, which means that a larger number of initial errors can be corrected if the error correction method according to the invention is used.
  • FIG. 4 shows four histograms ad, in which, as in FIG. 3, frequency distributions of defective bytes per packet are entered.
  • the absolute number of incorrect bytes on the X axis is again arbitrary, since the number of incorrect bytes depends on the packet length used.
  • the frequency distribution for faulty bytes is entered, which could not be corrected despite the correction of errors.
  • 4a and 4b transmission conditions are selected which correspond to transmission within a building, ie if, for example, a cell phone is operated within a building.
  • a correction of the transmission errors according to the prior art has been carried out, in which the correct bytes of the incorrect data packets are not used for the correction of the errors.
  • Figs. 4c and 4d correspond to a transmission situation within a vehicle, i.e. if, for example, a cell phone is operated inside a vehicle.
  • the upper curves 444 and 446 correspond to a correction of the transmission errors according to the prior art, in which the correct bytes of the incorrect data packets are not used for the correction of the errors.
  • an error correction was carried out in accordance with the method according to the invention, in which the correct bytes of the incorrect data packets are used for the error correction.
  • FIG. 5 shows how many additional lines of data bytes can be corrected if an error correction method according to the invention is used. More precisely, it shows how many consecutive correct ones Lines within an interleaver block, i. H . of a block as schematically shown as a matrix in Fig. 1, can be expected if an error correction method according to the invention is used.
  • the probability of a certain number of consecutive error-free lines can be easily calculated as follows:
  • n is the number of consecutive error-free lines
  • p is the probability of error of a single line
  • P (n) is the probability of n consecutive error-free lines.
  • the probabilities shown in FIG. 5 are based on the results shown in FIG. 3.
  • the lower curve 550 in FIG. 5 shows the probability of the occurrence of consecutive error-free lines. If the error correction method according to the invention is used without providing redundancy bytes, approximately three additional error-free lines which follow one another are expected. The number of three results from the probability value of 50%, i.e. there is more than 50% improvement by three additional consecutive error-free lines. It can thus be seen that by means of the error correction method according to the invention, which uses the correct bytes of error-containing data packets, by also using the error-containing data packets for error correction, the error correction can be improved. This achieves greater error protection and greater transmission security.
  • the upper curve 551 in FIG. 3 shows how the probabilities for successive error-free lines change. hold if one error per line can be corrected by using redundancy bytes. In this case, about 20 consecutive error-free lines are expected. The number of 20 in turn results from the probability value of 50%, ie more than 50% results in 20 successive error-free lines.
  • the error correction method according to the invention leads to a strong improvement in the correction capability and thus an improvement in error protection and an improvement in the transmission reliability.
  • the method for decoding according to the invention is based on the fact that even in the case of a defective data packet, only a small number of data elements, which can be data bytes or data bits, for example, of the defective data packet are faulty, whereas the predominant number "of data elements" is also in faulty data packets Using a simple algorithm, it is possible to evaluate the correct data elements of an incorrect data packet. By evaluating and using the correct data elements of an incorrectly transmitted data packet, it is possible to increase error protection without the number of correction elements transmitted, ie redundancy bytes or redundancy bits
  • the method according to the invention can be used in both error correction scenarios, ie reordering defective packets and forward error protection.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Probability & Statistics with Applications (AREA)
  • Theoretical Computer Science (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)

Abstract

L'invention concerne un procédé de décodage de paquets de données codés transmis par l'intermédiaire de réseaux de transmission de données orientés paquets, au cours duquel des paquets de données issus d'une pluralité d'éléments de données sont soumis à une détection d'erreur. Une correction d'erreur est par ailleurs réalisée sur les paquets de données défectueux identifiés, et cette correction d'erreur fait intervenir les éléments de données transmis correctement des paquets de données défectueux identifiés.
EP04787236A 2003-09-30 2004-09-28 Procede et dispositif de decodage de paquets de donnees codes transmis par l'intermediaire de reseaux de transmission de donnees orientes paquets et procede et dispositif de codage et decodage de paquets de donnees a transmettre par l'intermediaire de reseaux de transmission de donnees orientes paquets Ceased EP1668812A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2003145438 DE10345438B4 (de) 2003-09-30 2003-09-30 Verfahren und Vorrichtung zum Dekodieren von mittels paketorientierten Datenübertragungsnetzen übertragenen kodierten Datenpaketen und Verfahren und Vorrichtung zum Kodieren und Dekodieren von über paketorientierte Datenübertragungsnetze zu übertragende Datenpaketen
PCT/EP2004/052340 WO2005034413A1 (fr) 2003-09-30 2004-09-28 Procede et dispositif de decodage de paquets de donnees codes transmis par l'intermediaire de reseaux de transmission de donnees orientes paquets et procede et dispositif de codage et decodage de paquets de donnees a transmettre par l'intermediaire de reseaux de transmission de donnees orientes paquets

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EP1668812A1 true EP1668812A1 (fr) 2006-06-14

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EP04787236A Ceased EP1668812A1 (fr) 2003-09-30 2004-09-28 Procede et dispositif de decodage de paquets de donnees codes transmis par l'intermediaire de reseaux de transmission de donnees orientes paquets et procede et dispositif de codage et decodage de paquets de donnees a transmettre par l'intermediaire de reseaux de transmission de donnees orientes paquets

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EP (1) EP1668812A1 (fr)
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US7447980B2 (en) * 2005-10-17 2008-11-04 Newport Media, Inc. Error detection and correction in data transmission packets
US8917673B2 (en) 2006-07-14 2014-12-23 Qualcomm Incorporation Configurable downlink and uplink channels for improving transmission of data by switching duplex nominal frequency spacing according to conditions
FR2953345B1 (fr) * 2009-12-01 2015-12-11 Canon Kk Procede de determination d'une copie a decoder et d'un vecteur d'effacements associe, produit programme d'ordinateur, moyen de stockage et dispositif recepteur correspondants.

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DE4027496A1 (de) * 1990-08-30 1992-03-12 Deutsche Forsch Luft Raumfahrt Spreizverfahren zur uebertragung codierter, digitaler nachrichten
JP3190853B2 (ja) * 1997-05-23 2001-07-23 エヌイーシーマイクロシステム株式会社 誤り訂正処理方法及びその装置
WO1999030462A2 (fr) * 1997-12-12 1999-06-17 3Com Corporation Systeme de correction aval des erreurs pour media en temps reel a base de paquets
US6367047B1 (en) * 1998-10-20 2002-04-02 Ecrix Multi-level error detection and correction technique for data storage recording device
FI110831B (fi) * 1999-12-31 2003-03-31 Nokia Corp Menetelmä tiedonsiirron tehostamiseksi ja tiedonsiirtoprotokolla
DE10034977A1 (de) * 2000-07-13 2002-01-24 Ihp Gmbh Verfahren und Vorrichtungssystem zur Datenübertragung
FI112995B (fi) * 2001-01-16 2004-02-13 Nokia Corp Virheellisen datan käsittely pakettivälitteistä tiedonsiirtoa tarjoavassa tietoliikennejärjestelmässä
JP2003069535A (ja) * 2001-06-15 2003-03-07 Mitsubishi Electric Corp 誤り訂正多重化装置、誤り訂正多重分離装置、これらを用いた光伝送システムおよび誤り訂正多重化伝送方法

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WO2005034413A1 (fr) 2005-04-14
DE10345438A1 (de) 2005-05-12

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