JPS63181540A - Line quality supervisory system - Google Patents

Abstract

PURPOSE:To accurately supervise line quality even at a decision point where a bit error rate BER is large and to reduce the time necessary for decision even at the decision point where the BER is small by using a small number of checked results at the decision point where the BER is large and using a large number of checked results at the decision point where the BER is small so as to detect the deterioration of the line quality. CONSTITUTION:The number of data bits for inserting a parity bit is set in order not to saturate the parity checks of data D12 at the decision point having the larger BER and a first threshold is set in the output frequency of a parity disagreement signal E1 at the decision point. By setting them, a decision circuit 7 decides that the line quality deteriorates in case of getting worse than the threshold at the decision point having the larger BER and outputs a line quality deterioration alarm A1. A second threshold is set in the sum of output frequencies of the parity disagreement signals E1 and E2 at the decision point having the smaller BER. By setting it, the decision circuit 7 decides that the line quality deteriorates if it gets worse than the threshold at the decision point having the smaller BER and outputs the line quality deterioration alarm A2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a line quality monitoring system, and particularly to a line quality monitoring system for digital transmission lines.

[Conventional technology]

In a communication system that has a protection line, it is necessary to monitor line quality in order to detect deterioration in line quality of the working line and switch to the protection line.

In transmission lines, such as microwave communication lines, where the line quality deteriorates mainly due to fading, it is necessary to switch over to the protection line as soon as possible before fading progresses and the working line is disconnected. It is important to detect line quality deterioration in time.

The line quality of digital transmission lines is affected by bit errors (bit errors).
error rate; BER), but direct measurement of Bgi takes a long time, so if the detection time of line quality deterioration is an issue, an odd-even test (
Recall quality is often monitored using a parity check (hereinafter referred to as a parity check).

When BEf is small enough that the probability of two or more bit errors occurring in the data bits used to create one parity bit is negligible, bit error detection by parity check (hereinafter referred to as parity mismatch) is difficult. Since the probability of occurrence and BER are proportional, line quality can be monitored by monitoring the probability of occurrence of parity mismatch.

However, in a state where the BER is so large that the probability of two or more bit errors occurring cannot be ignored, bit errors cannot necessarily be detected by the parity check, and the probability of occurrence of parity mismatch is no longer proportional to the BER. In other words, the parity check begins to saturate, making it no longer possible to accurately monitor line quality using the parity check.

Given a parity bit repetition period (hereinafter referred to as parity interval), if we reduce the number of data bits used to create parity bits within this parity interval, the parity check will begin to saturate with a larger BER. , line quality can be monitored over a wider HER range. Conversely, if the number of data and bits is increased, the probability of occurrence of parity mismatch increases under the same BER condition, and the detection time for line quality deterioration becomes shorter.

Therefore, BE)l at the decision point of line quality deterioration
Given a parity interval and a parity interval, there is an optimal value for the number of data bits used to create parity bits within this parity interval.

Incidentally, there are cases where deterioration in line quality must be detected at two decision points with different BEDs. As an example, a line switching device in a digital microwave communication system performs synchronous switching without bit errors while line quality deterioration is relatively small (for example, in the state of Bl = lQ-5). If this synchronous switching is not possible and the line quality deteriorates further (for example, to HER=10-2), system switching is performed using a coaxial switch.

[Problem that the invention seeks to solve]

However, conventional line quality monitoring methods use one type of parity pit, and adjust the number of data bits used to create this parity pit so that line quality can be accurately monitored even at the judgment point where BEI-L is larger. Since it is set,
There is a drawback that the determination time at the determination point where the Hg temperature is smaller is longer.

An object of the present invention is to provide a line quality monitoring system that can accurately monitor line quality even at a decision point where the BER is larger, and in which the judgment time is short even at a decision point where the BER is smaller.

[Means for solving problems]

The line quality monitoring system of the present invention creates odd-even check bits for at least two of a plurality of data bit groups each consisting of different data bits of data to be transmitted at the sending end of a transmission line, and inserts the odd-even check bits into the data. at the receiving end of the transmission line,
Performing an odd-even check on each IL of the odd-even check bits;
The apparatus is constructed to include an odd-even test means for outputting the respective test results, and a determination means for outputting at least two line quality deterioration reports based on the different numbers of the test results.

〔Example〕

The present invention will be described in detail below with reference to drawings showing embodiments.

FIG. 1 is a block diagram showing an embodiment of the line quality monitoring method of the present invention.

The embodiment shown in FIG. 1 is an embodiment of a digital microwave communication line that transmits data D11 t D21 using a four-phase phase modulation method, in which data 11 r D21 is input and data D12 and l'22 are output. parity bit insertion circuits 1 and 2, a transmitting device 3 of the front leg end station at the transmitting end which inputs data DI2+D2M, and data D12゜D.
The receiving device 4 of the receiving end wireless terminal station outputs the parity mismatch signal E1. parity check circuits 5 and 6 outputting a parity signal E, and a parity mismatch signal E.

The determination circuit 7 inputs E2 and outputs line quality deterioration alarms A, , A, and the like.

The parity bit insertion circuit 1 blocks the data Dll to the length of the parity interval, sequentially counts the parity of the data bits in a predetermined time slot in each block to create a parity pictogram, and inserts the parity bits into each block. It is inserted at the end and output as data I)tz. Note that in order to create a time slot for inserting a parity bit, it is necessary to convert the speed of data [) 11.

Parity bit insertion circuit 2 also inserts data D21 in the same way.
A parity bit is generated from the data I), inserted into the data I), and output as data D22.

The data D12 r D22 is converted into a four-phase phase modulated wave by the transmitting device 3 and sent to the wireless section, and the four-phase phase modulated wave transmitted in the wireless section is demodulated by the receiving device 4 and becomes data D, □, I again. ) zt.

The parity check circuit 5 sequentially counts the data bits used to create the parity bit among the data bits of the data D12 outputted by the receiving device 4, and whenever the count result does not match the parity bit in the data D12. , outputs one pulse as a parity mismatch signal E1.

Similarly, the parity check circuit 6 also checks the data Dzz'.
fr-parity is checked, and each time a parity mismatch is detected, one pulse is output as a parity mismatch signal E2.

The output frequency of the parity mismatch signals El and E2 is
12. D22 is completely proportional to the probability of occurrence of a consistency mismatch.

The determination circuit 7 outputs a line quality deterioration alarm A when the input frequency of the parity mismatch signal E1 becomes greater than a first threshold value, and outputs a parity mismatch signal Et.

When the sum of the input frequencies of E2 becomes larger than the second threshold, a line quality deterioration alarm A2 is output.

The number of data bits that make up parity bits is set so that the parity check of data I)tz is not saturated at the decision point where BER, is larger, and the parity mismatch signal E! at this decision point is set. Set a first threshold for the output frequency of . With these settings, the determination circuit 7 determines whether the line quality is BE
When the line quality has deteriorated below the threshold value at the judgment point where R is larger, this is determined and a line quality deterioration alarm A1 is output.

The second threshold is set to the sum of the output annoyances of the parity mismatch signals E, . With this setting, the determination circuit 7 determines that when the line quality deteriorates below the threshold value at the determination point with the smaller BER, it outputs a line quality deterioration alarm A2. Parity mismatch signal E1. The sum of the output frequencies of E! is the parity mismatch signal E! Alternatively, since the output frequency of the parity mismatch signal E! is twice as high as that of the single output frequency, the time required to generate the line quality deterioration alarm A2 is the same as that of the parity mismatch signal E! , E, can be made shorter than using only one of them.

An embodiment of the present invention in a digital microwave communication line using a four-phase phase modulation method has been described above.

In a digital microwave communication line using a 16-value orthogonal amplitude conversion system, transmitted data is arranged in four columns.

In this case, a parity check is performed separately for each column to obtain four harness mismatch signals, one of which is used to make a decision at a decision point with a large BER, and two are used to make a decision on a decision point with a large BER.
ER makes a judgment at an intermediate judgment point, and uses all four to make a BEI (.

It is also possible to make a decision at a decision point where the value is small.

Even when the data to be transmitted is one column, the data bits within the parity interval are divided into two groups, and a parity check is performed for each group to detect two parity mismatches as in the embodiment shown in FIG. I can get a signal.

〔Effect of the invention〕

As explained in detail above, the line quality monitoring method of the present invention divides the data bits of data to be transmitted into multiple data bit groups, performs a parity check on each data bit group, and checks multiple check results. At decision points where BEI is large, decimal check results are used, and at decision points where BEI is small, a large number of check results are used to detect line quality deterioration. This has the effect that it can be monitored and the time required for determination iJ1 can be shortened even at a determination point with a small BER.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the line quality monitoring system of the present invention. 1, 2... Parity pit insertion circuit, 3...
... Transmitting device, 4... Receiving device, 5, 6...
...Parity check circuit, 7...Judgment circuit. Agent Patent Attorney Susumu Uchihara Bora Manjime ″″

Claims (1)

[Claims] At the sending end of a transmission line, an odd-even check bit is created for at least two of a plurality of data bit groups each composed of different data bits of the data to be transmitted, and the odd-even check bit is inserted into the data. insertion means; an odd-even test means for performing an odd-even test on each of the odd-even test bits at a receiving end of the transmission line and outputting each test result; and at least two line quality tests based on different numbers of the test results. A line quality monitoring method comprising: a determination means for outputting a deterioration alarm; and a line quality monitoring method.