Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L43/00—Arrangements for monitoring or testing data switching networks
  • H04L43/50—Testing arrangements
• • 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
  • H04L1/24—Testing correct operation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/54—Store-and-forward switching systems 
  • H04L12/56—Packet switching systems
  • H04L12/5601—Transfer mode dependent, e.g. ATM
  • H04L2012/5628—Testing

Definitions

• the invention relates to a method for recovering test data transmitted from a transmitting end to a receiving end via a transmission link for digital data streams with a cell structure at the receiving end.
• a cross-correlation of the code word received in each case is carried out by evaluating the main maximum of the respective cross-correlation function in order to retrieve the test data.
• Such a method is used primarily in measurement technology for broadband ISDN transmission technology.
• a known method of this type is described in DE 40 12 850 AI.
• numbers of test cells introduced into the data stream are coded at the transmission end of the transmission link with a code word which, in an auto-correlated manner, gives a Dirac pulse; such a code word is, for example, an m-sequence or a code word from the code word stock of the Barker code.
• the code word is changed from test cell to test cell as part of the coding each shifted an equal distance. This means that further code words are formed by cyclically shifting the one code word.
• a receiver At the receiving end of the transmission link, a receiver is followed by a correlator which carries out a cross-correlation of the code word received in each case.
• the bit error rate is inferred from the height of the main maxima of the cross-correlation functions formed in this way, while the relative temporal position of the main maxima allows information about the test cell number, as a result of which the test data on the transmission side can be recovered. This is done very reliably in the known method, since it still works precisely even with a high bit error rate; With a 2 m sequence, for example as a code word, up to 7 bit errors can occur without impairing the reliability of the method.
• the invention has for its object to further develop the known method so that it enables a safe recovery of a larger number of test data available on the transmission side on the receiving side.
• Moving the code word adds additional binary code words and a binary zero word and the different test data to the different code words and the zero word 1 assigned and
• Identify the main maxima of the cross-correlation function and use codewords to retrieve the assigned test data or 10 - a checksum below a predefined further value identifies the transmitted null word and is used to retrieve a test date assigned to the null value.
• the main advantage of the method according to the invention is that by using the zero word (in this word all binary digits have a "0") the
• One word is added to the pool of available encryption words. If, for example, 5 20 of a 2 m sequence is used, the invention leads to a total of 32 encryption words. This makes it possible to code a total of 32 different test data to be transmitted (that is to say each varying over a length of 5 bits) and to securely re-transmit them on the reception side
• REPLACEMENTB - Identify the main maxima of the cross-correlation which are on the receiving side above a predetermined lower value and use codewords to retrieve the assigned test data, taking into account the signs of the main maxima, or
• a cross-sum lying below a predetermined further value identifies the transmitted null word and is used to retrieve a test date assigned to the null word, or
• a checksum above an additional predetermined value identifies a one-word and is used to retrieve a test date assigned to the one-word.
• main maxima of different types can also be acquired by shifting the value range of the cross-correlation functions by such a value that the values of the main maxima of different types are always in the positive range.
• test data transmitted from the transmitting side and recovered on the receiving side can be further processed in various ways in the method according to the invention.
• the method according to the invention not only enables the test data to be retrieved on the receiving side, but also, by evaluating the level of the main maxima of the cross-correlation functions of the code words, a statement about the number of bit errors; Such a statement is also possible with regard to the zero word or the one word, because the number of bit errors can be determined from the checksum.
• FIG. 1 shows a block diagram of an embodiment of an arrangement for carrying out the method according to the invention
• FIG. 2 shows a list of the encryption words
• FIG. 3 shows an embodiment of a coder of an arrangement for a further embodiment of the method according to the invention
• FIG. 4 shows an embodiment of the receiving side of the same arrangement shown to carry out this further embodiment of the method according to the invention.
• the exemplary embodiment shown in FIG. 1 contains an encryption generator 1 on the input side, which consists, for example, of an addressable memory.
• the resulting cross-correlation functions which look essentially as it is shown in the aforementioned DE 40 12 850 AI, are examined in a module 9 for the position of the main maxima.
• the relative temporal position of the main maximum of the respective cross-correlation function contains the information about the respectively transmitted test date, so that the transmitted test date can be obtained from the determined relative temporal position of the respective main maximum via a further memory (not shown) on the receiving side 6; in this way, however, only 31 different test data can be recovered on the receiving side.
• the zero word is recognized in block 10 and is done in such a way that a checksum is formed here. If the checksum is below a predefined value, for example in a 2 m sequence below the value 8, then this is an indication that the coded data transmitted is the null word. Accordingly, the associated test date can be retrieved in the course of the decoding by means of the memory (not shown) (block 11 in FIG. 1).
• the crossword is examined; their level is a direct measure of the number of bit errors.
• the method according to the invention is not tied to the use of a 2 m sequence (with its cyclical shifts), but can also be carried out with other m sequences. It is also possible to use the Barker code, the Gordon, Mills and Welch sequence or the Gold code.
• FIG. 3 shows another exemplary embodiment of an encryption word generator on the transmission side of a transmission path, not shown here, in the event that test data that vary over a length of 6 bits are to be encoded, that is to say a 6-bit data word D (x). exhibit.
• the generator here has a feedback shift register 20 with several stages 21 to 24 and
• a further exclusive OR gate 27 is arranged downstream of the shift register 20 in that it is connected with an input 28 directly to the output of the exclusive OR gate 26 and via one Changeover contact 29 in its position a can be connected to the output of stage 24.
• the one input 28 is acted upon by the signals of the lower five digits d-, d, - of the data word D (x).
• the further input 30 of the further exclusive OR gate 27 is acted upon by the signal of the uppermost (sixth) position of the data word D (x).
• the sixth position controls the inversion, so that, in deviation from the method according to FIGS. 1 and 2, 64 different encryption words are used here for assuming if a 2 m sequence is assumed as an example.
• data C (x) coded with the data words D (x) occurs in accordance with the test data to be transmitted, which - for example in addition to a 2 m sequence as the "basic code word" - 30 binary code words obtained cyclically, 31 further code words formed by inverting them, which may contain the zero word and the one word.
• coded data C (x) are transmitted via a transmission path (not shown) and reach the receiving end, the configuration of which is shown in FIG. 4.
• a cross-sum formation of the transmitted, coded data C (x) is carried out in a block 40.
• This checksum is in turn examined in a subordinate block 42 to determine whether it is less than 8. If this is the case, then the transmitted test date is detected as a null word. If the checksum is greater than 23, it is a binary one-word (all binary digits have a "1").
• inverse code words in this example result in negative main maxima of the cross-correlation functions; this allows the "normal" code words to be distinguished from the inverse code words when decoding.
• the amount of the main maxima is used here to distinguish the other code words from the zero or one word; amounts above a predetermined lower value
• the 25 m sequence as the basic code word is 16.
• test data D (x) to be transmitted can be recovered on the receiving side in block 43.
• reception side according to FIG. 4 is constructed as shown in FIG. 1.
• the bit errors are determined in a corresponding manner.
• the codes listed above can also be used here.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Detection And Prevention Of Errors In Transmission (AREA)
• Error Detection And Correction (AREA)
• Mobile Radio Communication Systems (AREA)

Applications Claiming Priority (3)

Publications (1)

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Family Applications (1)

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Family Cites Families (4)

• 1992
  • 1992-01-31 DE DE4203298A patent/DE4203298C1/de not_active Expired - Fee Related
• 1993
  • 1993-01-22 CA CA002129224A patent/CA2129224A1/en not_active Abandoned
  • 1993-01-22 AU AU33439/93A patent/AU3343993A/en not_active Abandoned
  • 1993-01-22 EP EP93902055A patent/EP0624295A1/de not_active Ceased
  • 1993-01-22 WO PCT/DE1993/000066 patent/WO1993015575A1/de not_active Ceased
• 1994
  • 1994-07-27 NO NO942802A patent/NO942802L/no unknown

Non-Patent Citations (1)

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