Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1999-07-26
2001-04-03
Decady, Albert (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S702000
Reexamination Certificate
active
06212662
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for the transmission of data with transmission error checking. More in particular, the invention is related to a method for the transmission of data between a transmitting end and a receiving end of a transmission channel, involving the generation of supplementary data at the transmitting and the receiving end by a first and a second function respectively, and the comparison of the supplementary data generated by said functions in order to detect transmission errors. The invention further relates to devices for the application of such a method.
A method and devices of the above-mentioned kind are known in the prior art. In this connection, the transmission channel can be set up for transmission in space (bridging a distance) as well as for transmission in time (storage and display). Further, the second function can be implemented in such a manner that it is, for example, an inverse of the first function, so that the original data are reconstructed. This allows the original data, rather than the supplementary data, to be compared. Reference is made to European Patent Application 0,494,036 and U.S. Pat. No. 4,961,192.
Transmission errors may arise, for example, through electromagnetic radiation, inadequacies in a storage medium (transmission in time), and errors in switching and transmission equipment. Prior art methods provide for the checking of transmitted (user) data by the addition of supplementary data which, as redundant information, enable the detection of transmission errors to a certain degree. As an example of such supplementary data, so-called parity bits, which at the transmitting end can be added to binary data by a first function and, for example, represent the number of ones and zeroes, can be mentioned. At the receiving end it can be checked whether this number of ones and zeros, as represented by the parity bits, corresponds with the data received. If the parity bits do not correspond with the data received, a transmission error has apparently occurred and the data concerned could be transmitted again if necessary.
In prior art methods the problem arises that systematic errors are sometimes not detected. Systematic errors, that is to say, errors which repeat themselves, can arise inter alla through an error which repeats itself in the transmission channel (for example an interference signal with a certain frequency) or through an equipment error. For (binary) data it holds that there is always a probability that erroneous data are considered to be correct data because the supplementary data may be correct by coincidence (the supplementary data are always restricted in length and therefore a finite number of supplementary data can be distinguished). With systematic errors the case may therefore arise that an error once not recognized as such, is continually not detected.
International Patent Application WO87/03442 discloses a data encryption device comprising a CRC (Cyclic Redundancy Code) generator. A counter produces count bits related to the data. The CRC generator computes a CRC on the basis of the encrypted data to which the count bits are appended. Although the appending of count bits provides an improved protection against systematic errors, such errors can still not be excluded as the data proper are not altered.
The non-detection of a transmission error in the data can make itself felt in the rest of the data received. This is especially the case if, on the transmission path, the data is compressed or otherwise encoded. In the decoding process, not only the erroneous data, but in some cases all following data may become unusable, in particular if the statistics by means of which the compression and decompression take place are affected by the erroneous data.
The ITU-standard V.42 bis describes, for example, an adaptive compression scheme which, during the compression, records statistics of the data to be compressed. If systematic errors are not detected, the said statistics no longer correspond with the data, so that at the receiving end an incorrect decompression takes place. This may result in all decompressed data becoming unusable.
SUMMARY OF THE INVENTION
An object of the invention is to deal with the above-mentioned and other disadvantages of the prior art, and to provide a method which allows data to be checked for errors in a better way, and thus considerably increases the probability of transmission errors being detected. A further object of the invention is to provide a method which is particularly suitable for application to compressed data and which can be applied in a simple manner.
These and other objects are met in accordance with the invention by a method for the transmission of data between a transmitting end and a receiving end of a transmission channel while providing an error check, said method comprising the steps of: generating, at the transmitting end, supplementary data on the basis of original data by means of a first function, said first function varying said original data in time; transmitting both the original data and the supplementary data over a transmission path; regenerating, at the receiving end, supplementary data on the basis of the reprocessed transmitted data by means of a second function, said second function varying said original data in time; and checking the transmitted data by comparing the regenerated supplementary data with the transmitted supplementary data.
In this way it is achieved that the detection probability of systematic errors in particular increases considerably, since (erroneous) data are always varied in time, and are thus effectively checked by a different function each time. The probability that an error, once not recognized as such, is continually not detected, has hereby become minimal.
The invention is therefore based on the insight that an error which repeats itself, once not detected by a normal (fixed) checking function, will repeatedly go undetected. The invention is also based on the insight that a variable checking function can almost always prevent the non-detection of repetitive errors. A further aspect of the invention is based on the insight that the varying of the checking function can be advantageously based on the data to be checked, and that the varying of the data can be used to accomplish a varying, i.e. time-dependent checking function. A further insight which is of importance for the invention is that between the transmitter and receiving end a form of synchronization must exist, in other words that the relationship between user data and supplementary data must be maintained.
The said functions, that is to say the first and the second function, are used for the creation of supplementary data at the transmitting end (first function) and the creation also of supplementary data at the receiving end (second function), after which the supplementary data generated by the two functions are compared. In principle, the two functions should be identical or should provide identical results for identical data. In some cases the second function may not be identical to the first, but may, for example, be formed by its inverse. The second function may be of the kind which is referred to as parity check function.
A function can be varied as a whole, for example by continually applying another function from a group of functions. Preferably, however, a function comprises a first and a second part, of which only the second part is varied. In this case, the first part can consist of the function proper, which can be invariable, the second part being a value which is varied, preferably under influence of the data. The functions can thus, if the data are transmitted in a bit stream, be varied every n bits, where n ≧1. If the data are transmitted in data packets, the functions can be varied on the basis of one or more parameters of the data packets. As a matter of fact, the term “data packets” is here also taken to mean frames, containers and other data structures. The said parameters can comprise an index, t
Hekstra Andries Pieter
Herrera Van Der Nood José Manuel
Chase Shelly A
De'cady Albert
Koninklijke KPN N.V.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
LandOfFree
Method and devices for the transmission of data with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and devices for the transmission of data with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and devices for the transmission of data with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2476943