SU1594708A1 - Method of monitoring the state of data transmission channel - Google Patents

Abstract

The invention relates to telecommunications and provides improved control accuracy. On transmission, the information blocks are encoded with the M-cascade code, and they are decoded in reception in stages, completing the decoding either when an error is detected or at the end of the M-th stage. In the monitoring interval for each stage, the number of blocks with detected errors is calculated, by which the probabilities of an undetected error are determined for each of the stages from first to (M-K), and the probability of an undetected error is predicted for each of stages (M-K +1) th on M th. 1 il.

Description

The invention relates to telecommunications and can be used in data transmission systems to estimate the quality of a data transmission channel in terms of probability, an undetected error, and the selection of the required error correcting coding parameters.

The purpose of the invention is to improve the accuracy of control.

The drawing shows a structural electrical circuit of the device for implementing the proposed method.

The device for monitoring the state of the data transmission channel contains II-IM decoders, a counter 2, the number of received blocks, a 31-Zm counter of the number of blocks detected. errors, block 4 comparisons, block 5 controls, registers b1-6 m, calculator 7 probabilities and block 8 registration and display.

The essence of the proposed method is that the probability of finding

The error bars in each subsequent stage of decoding a concatenated code is actually the value by which the probability of undetected errors is reduced with respect to the previous stage of decoding. For the i-ro stage of decoding, the following relationship can be written:

i

PBO - 2 POOJ j i

.i

 POOJ + RNOR 1, (1)

Se j: VI o

00

i

where is rooj r

Pooi pc

D /

POOJ + PHOE.T PHO,

BOR - probability of correct (without distortion) transmission of the block;

ROO is the probability of detecting errors during decoding, PHO is the probability of block occurrence with undetected errors.

On this basis, the probability of an undetected error after the decoding stage can be represented as a sum of the probabilities of detected errors in the following really possible subsequent stages of decoding:

 POOI + PHOE. (2)

j i4 - S

Taking into account the rapidly decreasing nature of the distribution, as well as the requirement of control accuracy, the terms with a higher order of smallness can be discarded and an approximate estimate of the probability of an undetected error can be obtained:

 + ,,

PHO, foo, j. (3)

where K is the number of decoding stages that must be considered to ensure the required accuracy and depth of control.

Predicting Рно as a function of the number of control symbols of the code - г at the point гь1 + А Г can be carried out by linear approximation of the distribution on a logarithmic scale:

Rno (g) RNOY + (In Prioi-i Dg

- In PHOI where PHOi-1 and

. one

- d g; determined according to hOi-2

with expression (3),

Another variant of predicting the likelihood of an undetected error is also possible, based on introducing the coefficient y — reducing the likelihood of an undetected error per bit (the increment symbol of the code.

For the (i-1) -ro stage decoding

/ Rnoe

  fc

.7 then the probability of an undetected error at the point p of HN1 + Ar will be determined by the expression

Rno (g)) -1

Ag

 RNO | -1

1PH01-2

The device for monitoring the state of the data channel works as follows

in a way.

On the Start signal, the control unit 5 generates a signal by which

The counter 2 is the number of received blocks and all the counters are 3 the number of blocks with detected errors for the corresponding stages of decoding. Simultaneously in block 5 of the control, the initial sample size is set according to the number of received blocks, and the code of this number comparison, Next, a monitoring cycle begins, during which the code combinations go to the 0 input of the decoders 1, followed by the reception signal of the code combination. At the same time, these signals are fed to the summing input of the counter 2 for counting the received blocks. The code combination is decoded by the first stage decoder 1, and if errors are detected during the decoding, the further decoding is stopped and the error detection signal is summed with 0 by the first counter 3 of the number of errors detected. If the decoder 1 of the first stage did not detect errors, then the codeword is transmitted to the decoder 1 of the second stage, and so on. before detecting errors at one of 25 stages of decoding, or until complete de-. encoding by all decoders 1 without detecting errors.

during the monitoring cycle, counters 3 accumulate data on the number of code combinations with errors detected at the corresponding decoding stages. Comparison unit 4 compares the contents of counter 2 with the number of received blocks with the initial sample size code, 35 coming from control unit 5, and when matched, generates a signal that rewrites the contents of counters 3 into the corresponding registers 6 for temporary storage. The same signal starts 40 calculator 7, which, in accordance with the working program, checks the sufficiency of the sample — the codes of the number of blocks with detected errors for the corresponding decoding stages are compared with the minimum acceptable values and values. For this, calculator 7 uses the data stored in registers 6. If the sample size is insufficient, calculator 7 increases the sample size by 50 the number of received blocks and enters the new sample value into control block 5. The monitoring cycle continues until the next match signal appears at the output of comparison unit 4. When accumulating a sufficiently accurate sampling, the calculator 7 according to the working program successively for each stage of decoding calculates the estimate

PHOI 0 1 MK) and PHOI forecast for

flown decoding steps (

MK + 1M), e also the PHOI prediction for possible subsequent decoding steps.

The results of the calculations are given out in block 8 of registration and display of the state of the data transmission channel.

After the completion of the calculations, the calculator 7 enters into the control unit 5 the code of the initial sample size by the number of accepted blocks. the control unit 5 forms a signal for the initial installation of counters 2 and 3, and a new control cycle begins.

Claims (1)

Invention Formula A method for monitoring the state of a data transmission channel, including generating information blocks on transmission, coding them with an M-cascade code that detects errors, transmitting a sequence of code blocks on a discrete communication channel, decoding them at the reception and determining the reliability of transmission using blocks of information with detected errors, characterized in that, in order to increase the control accuracy, on receiving a decoder Each code block is carried out in stages and is completed either by error detection at the next stage or after the M-th stage. For each control cycle, for each stage, the number of code combinations with detected errors is calculated, which determine the probability of undetected error for each of the stages one through (M-K) -th, and predict the likelihood of an undetected error for each of stages (M-K + 1) -th through M-th according to the formula PHOI Pnom + (1n PHOI-I 1. -In Rno about ; Ages where i is the decoding stage number: RNO is the probability of an undetected error; Dg -r-- - relative increase in the number of l P-1 code control characters at the i-th stage of coding. Vh. inf. I