FR2702905A1 - Transmission system comprising a transmitter and a receiver. - Google Patents

Abstract

Transmission system comprising a transmitter (101) and a receiver (103), which are connected to each other by a transmission link (102), a device (A) making it possible to determine at least one measurement of the errors of code from the received data, an error pulse generator (1) to produce error pulses (a1) and a time pulse generator (2) to produce time pulses (a2), - the device (A) contains a first counter (1A) and a second counter (2A); - the state of the first counter (1A) can be incremented by the error pulses (a1) and the state of the second counter (A2) by the time pulses (a2); - the device (A) contains an evaluation circuit (4) which is provided to receive the states of the two counters (1A, 2A) and to derive therefrom a measurement of code errors when one of the two counters has reached a predetermined maximum value, and - the device (A) contains a logic circuit (3) which is provided to reset the counters to their starting state when one of the two counters has reached its predetermined maximum value.

Description

Transmission system comprising a transmitter and a receiver.

  The present invention relates to a transmission system comprising a transmitter and a receiver, which are connected to each other by a transmission link, a device for determining at least one measurement of the code errors from the received data, a error pulse generator for generating error pulses and a pulse generator for generating time pulses. In order to maintain the reliability of a telecommunication system as far as possible permanently, the transmission signal is checked, inter alia, in the case of important systems not only at the level of the intermediate generators but also at the level of the subscriber stations. to constantly check the presence of errors in the transmission code (see for this purpose, for example, document DE 37 26573 C 2 or EP 01 06 985 A 2) It follows in particular that the transmission code chosen is an automatic error detection code and that those skilled in the art knows enough circuits for detecting errors in such codes (see for this purpose, for example, DE 32 14 55 or DE 35 35 606 Such circuits may be designed such that they deliver an identified code error pulse. Since only these pulses are of interest in the explanations that follow, the associated circuitry will be called s "error pulse generators". By "pulse generator of time" is meant hereinafter any pulse generator for which the spacing between two pulses is known, which makes it possible to measure the length of time intervals. A particular case of such a time pulse generator would be, for example, a rhythm regenerator in

  an intermediate regenerator of one of the transmission systems mentioned above.

  As a measure of code errors, three magnitudes can be considered, namely the number of code errors, the code error rate and the number of code error blocks By number of code errors means the number of erroneous code elements with respect to the total number of code elements considered By code error rate means the number of erroneous code elements over a period comparable to the duration of the signal tested By number of code error blocks, here is meant the roughly quantized form of the number of code errors or the error rate

of code.

  It should also be added that the definitions given are valid for each code and also retain their meaning as long as the number

  erroneous code elements can be determined.

  For the user of a transmission network, the measurements of the code errors, which relate to the transmission code, are less interesting than the indications, which relate to the binary code in which his message was originally coded and in which its message will be redecoded after transmission The corresponding error measurements, which relate to the binary coded useful signal, will be called number of bit errors, bit error rate or number of bit error blocks As the network operator can not generally identify bit errors in the wanted signal, it must pass error measurements, which are obtained by measurement from the transmission code, to the corresponding measurements in binary code to be able to give its client information about the errors present in its signal To pass, for example, the code error rate (in the transmission signal) to the bit error rate (in the useful signal), uses empirically determined ratios Thus a small code error rate results in a proportional bit error rate, because each code error of the transmission signal causes a bit error in the wanted signal In the case of higher code error rates, there are deviations from this linear relationship. Deviations also depend on the transmission code used. In many cases, a code error in the signal of transmission results in several bit errors in the wanted signal By the ratio previously determined empirically of the bit error rate code error rate, the network operator can, after multiplication of the error rate of code measured in the transmission signal by a factor (depending on the code error rate), switch to the bit error rate and

  communicate to his client the desired information.

  To determine one of the above-mentioned code error measurements for the transmission signal, it is first necessary to determine the number of measured code errors in a predetermined measurement time. However, as the code errors are distributed statistically over time, in the case of a small number of errors, the measurement time should be very long for the conclusions drawn from

  measurement data can be obtained with sufficient statistical certainty.

  A rough calculation shows that the assignment of a measurement result to a number of error blocks with a scale of 1-2-5 of these numbers (see below for this purpose) requires the taking into account of 100 errors if this assignment is to be done with a statistical security of more than 95% When the number of code errors reaches, for example, 10-8 and the transmission bit rate reaches 2 Mbits per second, it is necessary to that the measuring time exceeds one hour for it

  there are about 100 errors in the measurement time.

  Similarly, in the case of slightly higher error rates and slightly less stringent conditions, the necessary measurement times easily reach the minutes range, which is again unacceptable for

  higher errors when consecutive reactions must be triggered.

  It is therefore an object of the invention to provide a transmission system having a device by means of which code error measurements can be performed in

  a significantly shorter time with better statistical security.

  This object is achieved by a transmission system whose device for determining at least one code error measurement contains an error pulse generator and a time pulse generator and which is characterized in that the device contains a first counter and a second counter; the state of the first counter can be incremented by the error pulses and the state of the second counter by the time pulses; the device contains an evaluation circuit which is arranged to receive the states of both counters and derive a measurement of code errors when one of the two counters has reached a predetermined maximum value, and the device contains a logic circuit which is planned to return the two meters to their original state when one of the two meters has reached its value

predetermined maximum.

  In the case of high code error rates, the invention has the advantage that, in order to determine a measurement of code errors, it is no longer necessary to wait until the measurement time has elapsed. On the contrary, it is already possible to have a reliable result when the counter, which counts the error pulses, has reached its predetermined maximum value Thus, fast reactions, for example in the case of error rates

  of code that increase sharply, are possible.

  Advantageous developments of the invention reside in the fact that: the device contains a first register and a second register for temporarily storing the states of the first and second counter, and the evaluation circuit contains a ring memory which is provided to receive the state of the first counter when the second counter has reached its maximum value before the first counter and the length of the annular memory depends on

  numbers stored in this memory.

  The invention will now be explained in more detail with reference to the drawing appended hereto, in which: FIG. 1 is a transmission system and a receiver according to the invention, and FIG. 2 is a device according to the invention for determine a measure

code errors.

  The transmission system of FIG. 1 transmits digital data from a transmitter 101 to a receiver 103 via a transmission link 102. The data is transmitted in an automatic error detection code. error pulses 1 in the receiver 103 produces an error pulse ai whenever an error has been identified in the received signal Regardless of this, a time pulse generator 2 produces time pulses at 2 that is, pulses whose time spacing is known and which result, for example, in fractions of a second. The error pulses α1 and the time pulses a 2 are conveyed to a device A which

  determines at least one measure of code errors from these input data.

  Fig 2 shows the device A of Fig 1 in detail The same

  components and the same signals bear the same references in both figures.

  The error pulse generator 1 transmits its pulses via the line ai to the counting input of a first counter 1A, which is subsequently qualified as an error counter. The data outputs of this counter are connected to a counter. first register 1 B via multiple lines cl The same applies to the time pulse generator 2, the line a 2, a second counter 2 A (time counter), the multiple lines c 2 and a second register 2 B. The maximum value of the error counter l A, which counts the error pulses, is 128 When the error counter l A reaches its maximum value, it delivers, via a line b1, a transmission pulse which is routed to an entrance

  an OR gate 3 The maximum value of the time counter 2 A is also 128.

  In the same way, when this counter reaches its maximum value, it delivers a transmission pulse via a line b 2 which is connected to a second input of

the OR gate 3.

  The pulses counted by the time counter 2 A are equidistant and have the same spacing of 3 ms When the time counter 2 A starts to

  zero, it reaches its maximum value in 384 ms.

  When the error counter l A reaches its maximum value before

  2 A time counter, 128 error pulses or errors are logged.

  The transmission pulse of the error counter l A leads to obtaining a pulse at the output of the OR gate 3, which is routed again via control lines a 3 to the validation inputs of the registers 1 B and 2 B and the zeroing inputs of the counters l A and 2 A It causes, on the one hand, the transmission of the states of the counters in the associated registers 1 B and 2 B and the resetting of the counters l A and In addition, an evaluation circuit 4 (microcomputer) is informed via an interrupt input that new values are in the registers 1 B and 2 B and must

  be called for processing via lines dl and d 2.

  The same reactions are triggered when the time counter 2 A reaches its maximum value earlier than the error counter Ai or at the same time

than him.

  In the first case, the evaluation circuit 4 determines the probabilities of the state Z1 of the error counter l A (with Z1 = 128) and of the product K x Z2. In this case, Z2 is the state of the time counter 2 A which has been taken up in register 2 B and K is a factor dependent on Z1 and Z2 The quotient, for a value of K determined in an appropriate manner, is an estimated value for the number of errors of bits with high statistical security, as already mentioned above The factor K is itself still a product of the spacing between two time pulses (in this case 3 ms), the bit rate of the signal binary (decoded) and of a magnitude that reproduces the empirical relationship between the rate of code errors in the

  transmission signal and the bit error rate in the decoded binary signal.

  Whenever the time counter 2 A reaches its maximum value for the first time, the contents of the register 1 B, thus a registered state of the error counter 1A, are transcribed in an annular memory of the microprocessor 4, whose length is controlled by a management program The current length L of the ring memory, and therefore the number of its memory locations, makes it possible to recognize the frequency with which at least the time counter A 2 has reached the first its maximum value in a sequence uninterrupted, the management program adds the contents of the locations of the annular memory (sum of errors) and enlarges it of a memory location, with each new transmission of a count state Zl, until the sum of errors exceeds for the

  first time 128 or that a maximum number of memory locations are reached.

  In the example, this maximum number is 1023 When this maximum number of 1023 is reached, the oldest contents respectively are overwritten When the error sum is greater than 128, the memory locations with the content each time the most are annulled consecutively and thus the ring memory is shortened until, for the first time the sum of errors is smaller than 128 if we cancel another memory location This location of

  memory is no longer canceled.

  A calculation program now determines the number of bit errors desired after each measurement interval. This determination is made in such a way that the number of errors then indicated for a measurement interval that is too short is

  greater than the actual number of errors.

  As long as the length L of the annular memory is smaller than 64, the sum of errors is divided, in the calculation program, by the number of memory locations of the annular memory. The quotient is the desired result for the factor The safety margin will be added for the reasons given above. When the effective length L of the annular memory is greater than 64, the desired result is, at the factor K, the quotient 128 / L. If, for the effective length L, the sum of the errors measured is less than 128, the total measurement time will still be too short, so that the calculation program will indicate a number of bit errors which will be too large compared to the Measurement value The number of bit errors obtained is, however, approaching

  asymptotic of the real number as the measurement time increases.

7 2702905

  In both cases, the number of bit errors obtained is compared with the decision values of a quantization characteristic which is arranged in a table. A number of bit errors is assigned a number of error blocks determined when the first number is in a predetermined range which also contains the number of error blocks The limits of the intervals surrounding the numbers of error blocks are the decision values mentioned as numbers of error blocks, we can use the numbers 1 * 10-8, 2 * 1 18, 5 * 10-8, 1 * 10-7, 2 * 10-7, * 107 ,, 1 * 10-3 In the table, hysteresis can also be count the number of previous error blocks in the assignment of a new

number of error blocks.

REVBDICA 1 NS:

  1 transmission system comprising a transmitter (101) and a receiver (103), which are connected to each other by a transmission link (102), a device (A) for determining at least one measurement of the errors of code from the received data, an error pulse generator (1) for generating error pulses (ai) and a time pulse generator (2) for generating time pulses (a 2) characterized in that: the device (A) contains a first counter (1A) and a second counter (2A); the state of the first counter (I A) can be incremented by the error pulses (ai) and the state of the second counter (A 2) by the time pulses (a 2); the device (A) contains an evaluation circuit (4) which is arranged to receive the states of the two counters (1 A, 2 A) and to derive a measurement of code errors when one of the two counters has reached a predetermined maximum value, and the device (A) contains a logic circuit (3) which is provided to reset the meters to their initial state when one of the two meters has reached its

predetermined maximum value.

  2 transmission system according to claim 1, characterized in that the device (A) contains a first register (l B) and a second register (2 B) to put

  temporarily stores the states of the first and second counter.

  Transmission system according to Claim 1 or 2, characterized in that the evaluation circuit (4) contains an annular memory which is arranged to receive the state of the first counter (1 A) when the second counter (2 A) has reached its maximum value before the first counter (LA) and that the length of the memory

  annular depends on the numbers stored in this memory.

  Receiver (103) for digital data having a device (A) for determining at least one measurement of code errors from the received data, an error pulse generator (1) for generating error pulses ( ai) and a time pulse generator (2) for generating time pulses (a 2), characterized in that: the device (A) contains a first counter (1 A) and a second counter (2 A) ; the state of the first counter (1 A) can be incremented by the error pulses (ai) and the state of the second counter (2 A) by the time pulses (a 2); the device (A) contains an evaluation circuit (4) which is arranged to receive the states of the two counters and derive a measurement of code errors when one of the two counters has reached a predetermined maximum value, and the device (A) contains a logic circuit (3) which is provided to reset the meters to their initial state when one of the two meters has reached its

predetermined maximum value.

  Receiver according to claim 4, characterized in that the device contains a first register (l B) and a second register (2 B) for storing

  temporarily the states of the first and second counter.

  Receiver according to Claim 4 or 5, characterized in that the evaluation circuit (4) contains an annular memory which is arranged to receive the state of the first counter (1 A) when the second counter (2 A) has reached its maximum value before the first counter and that the length of the ring memory depends on the

  numbers stored in this memory.

  Apparatus (A) for determining at least one measurement of code errors including an error pulse generator (1) for generating error pulses (ai) and a time pulse generator (2) to produce time pulses (a 2), characterized in that: the device (A) contains a first counter (1 A) and a second counter (2 A); the state of the first counter (1 A) can be incremented by the error pulses (ai) and the state of the second counter (2 A) by the time pulses (a 2); the device (A) contains an evaluation circuit which is arranged to receive the states of the two counters and to take a measurement of code errors when one of the two counters has reached a predetermined maximum value, and the device (A ) contains a logic circuit which is intended to return the two meters to their initial state when one of the two meters has reached its

predetermined maximum value.

2702905

  8 Device according to claim 7, characterized in that the device contains a first register (l B) and a second register (2 B) to temporarily store the states of the first and second counter. Device according to claim 7 or 8, characterized in that the evaluation circuit contains an annular memory which is arranged to receive the state of the first counter when the second counter has reached its maximum value before the first counter.

  first counter, and that the length of the annular memory depends on the numbers stored in this memory.