JPH04365231A - Line quality measurement system - Google Patents

Abstract

PURPOSE:To exactly and accurately measure line quality like a change with the pasage of time at a transmission line as well by providing an adaptive equalizer as a demodulating means and detecting the state change of the adap tive equalizer. CONSTITUTION:A transmitting data generator 1 to generate random binary sequential data as transmitting data, a transmitter 2 to modulate the binary sequential data and to transmit them to a transmission line 10, and a reception part 3 to receive the modulated data propagated in the transmission line 10 and to measure the quality of the transmission line 10 based on the received data are provided. The reception part 3 is equipped with an adaptive equalizer 4 as the demodulating means and a measurement part 5 to measure the quality of the line by detecting the state change of the adaptive equalizer 4. The measurement part 5 calculates prescribed evaluation scale as the state value of the adaptive equalizer 4, calculates the condition of disturbance generated at the transmission line 10 based on the evaluation scale and measures this condition as the line quality.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line quality measurement system for measuring the quality of a transmission line.

0002

[Prior Art] Conventionally, to measure the quality of a transmission line,
A method using a network analyzer and a method measuring the bit error rate are known.

FIG. 13 is a block diagram of a system for measuring the quality of a transmission line using a network analyzer. In the system of FIG. 13, the network analyzer 50 is
A transmission data generation section 51 that generates data such as a chirp wave as transmission data, a transmission device 52 that transmits data from the transmission data generation section 51 to a transmission path 60, and a transmission path 60.
It has a receiving device 53 that receives the propagated data as received data, and a frequency analyzer 54 that analyzes the frequency of the received data using FFT, DFT, etc. It is possible to measure 60 characteristics (frequency characteristics, phase characteristics, group delay characteristics, etc.).

FIG. 14 is a block diagram of a system for measuring the quality of a transmission line by measuring the bit error rate. The system of FIG. 14 includes a transmission data generation section 71 that generates random binary sequence data such as a PN sequence signal as transmission data, and a transmission data generation section 71 that modulates the binary sequence data from the transmission data generation section 71 and sends it to a transmission path 80. transmitting device 72
, a receiving device 73 that receives the modulated data propagated through the transmission path 80, demodulates it, and converts it into binary data; It has a bit counter 74 that counts the number of error bits by comparing the number of error bits with the value data, and calculates the bit error rate by dividing the number of error bits counted by the bit counter 74 by the total number of transmitted bits. The line quality of the line 80 can be measured.

[0005]

[Problems to be Solved by the Invention] However, the system with the configuration shown in FIG. 13 using a network analyzer requires complicated frequency analysis (frequency conversion) processing, and this processing takes a considerable amount of time. When the line quality changes frequently over time, for example when a situation of sudden signal deterioration (so-called disturbance situation) occurs, it is difficult to accurately and accurately measure the time-varying line quality. could not.

In addition, in the system configured as shown in FIG. 14 for measuring the bit error rate, the bit error rate obtained by dividing the number of error bits counted by the bit counter 74 by the total number of transmitted bits is equal to the average number of error bits. Therefore, even based on this bit error rate, it is necessary to accurately and precisely measure time-varying line quality when disturbances occur, similar to a system using a network analyzer. I couldn't.

[0007] As described above, the conventional line quality measurement system has the drawback that it is not possible to accurately and accurately measure time-varying line quality when disturbance occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a line quality measurement system that can easily measure time-varying line quality of a transmission line accurately and with high precision.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an adaptive equalizer as a demodulating means for demodulating modulated data sent from a transmitting side via a transmission path, and The receiving side is characterized in that a measuring means for determining the state value of the device and measuring the line quality of the transmission line is provided on the receiving side.

[0010] A predetermined evaluation scale is obtained as the state value of the adaptive equalizer, and based on the evaluation scale, the state of disturbance occurring in the transmission path is determined, and this is measured as the line quality. It is a feature.

[0011] As an evaluation measure, a first measure consisting of the root mean square value of the error of the output of the adaptive equalizer and/or a difference value of the ratio of the center tap and the next tap of the tap coefficients of the adaptive equalizer is used. Based on the first and/or second scale, the type of disturbance, the number of occurrences of each type of disturbance, the length of the disturbance section, or the frequency distribution for each disturbance section length is determined as the line quality. It is characterized by being designed to measure.

[0012] Furthermore, the characteristics of the adaptive equalizer may be determined as the state value of the adaptive equalizer, and the line quality of the transmission path may be obtained based on the characteristics of the adaptive equalizer.

[0013] Furthermore, after determining the characteristics of the adaptive equalizer, by further determining the inverse characteristics of the characteristics of the adaptive equalizer,
The characteristics of the transmission path may also be determined.

When determining the characteristics of the adaptive equalizer as state values, the tap coefficients of the adaptive equalizer are Fourier transformed, and based on the Fourier transform results, the frequency characteristics of the adaptive equalizer,
The feature is that the phase characteristics and group delay characteristics are determined as state values.

[0015] Furthermore, the transmitting side is provided with transmitting data generating means for generating random binary series data, and transmitting means for modulating the binary series data from the transmitting data generating means and transmitting the modulated binary series data to the transmission path. It is characterized by

[0016] Instead of the above-mentioned transmission data generation means and transmission means, a facsimile machine may be used on the transmission side.

[0017]

[Operation] In the line quality measurement system configured as described above, the operation of the adaptive equalizer provided on the receiving side adaptively changes depending on the line status of the transmission path. The measurement method is
Obtain this state change of the adaptive equalizer as a state value,
Based on this, the line quality of the transmission path is measured.

[0018] Furthermore, using a facsimile machine on the sending side,
Sends modulated data from the facsimile machine to the transmission line,
By receiving this, the line quality of the transmission path can be measured.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of a line quality measurement system according to the present invention. The line quality measurement system of the first embodiment includes a transmission data generator 1 that generates random binary sequence data as transmission data, and a transmission line 10 that modulates the binary sequence data from the transmission data generator 1. A transmitting device 2 transmits data to the transmission path 10, receives modulated data propagated through the transmission path 10, and transmits the modulated data to the transmission path 1 based on the received data.
It has a receiving section 3 that measures the quality of 0.

By the way, in modems such as PSK and DPSK, an adaptive equalizer is used to equalize the transmission characteristics of the transmission line, and the operation of this adaptive equalizer is is known to change adaptively depending on the situation (for example, the situation where a disturbance occurs).

The inventor of the present application focused on the operation of such an adaptive equalizer, and since it can be seen that the change in the state of the adaptive equalizer reflects the line situation, the demodulation means on the receiving side We found that line quality can be measured by using an adaptive equalizer.

Based on this intention, the receiving section 3 of FIG.
is provided with an adaptive equalizer 4 as demodulation means, and a measuring section 5 that measures the quality of the line by detecting changes in the state of the adaptive equalizer 4.

FIG. 2 is a diagram showing an example of the configuration of the adaptive equalizer 4. The adaptive equalizer 4 in FIG.
IR (Acyclic type: Finite Impu Ise R
esponse) filter. That is, delay devices D1 to Dn that delay input data Xi by a predetermined time, and multipliers that multiply input data Xi and each delayed data from each delay device D1 to Dn by tap coefficients C0 to Cn, respectively. M0 to Mn
and an adder AD that adds the multiplication results from each of the multipliers M0 to Mn and outputs the addition result qi, and the tap coefficient Ci is updated each time according to the following equation.

[0024]

[Math. 1] Ci=Ci-r・e・CNJ[Xi]

002
5] Here, Xi is the data input to the adaptive equalizer 4, C
NJ[Xi] is the conjugate complex number of Xi, e is the phase error, and r is a coefficient for adjusting the convergence speed.

Equation 1 above shows that the error e of the output qi of the equalizer 4
This indicates that the tap coefficients C0 to Cn are updated so that the values become smaller, and as a result of this update, the transmission characteristics of the transmission path 10 are equalized. Therefore, the tap coefficients C0 to Cn that are updated each time are as follows:
This represents an impulse response that shows the inverse characteristics of the transmission line 10, and in principle, it is possible to measure the characteristics of the transmission line 10 by finding the inverse characteristic of this impulse response.

Based on the above knowledge, the measuring unit 5 calculates the evaluation scales E(k) and Ter(k) as the state values of the adaptive equalizer 4, for example, as follows, and calculates these evaluation scales E. (k) and Ter(k) to measure the line quality of the transmission path 10.

[0028]

[Math 2]

[0029]

[Math. 3] Ter(k)=Te(k)−Te(k−1)T
e(k)=Real(C1・CNJ[C0])

003
[0] Note that the evaluation scale E(k) calculated by Equation 2 is the short-time average value of the error e of the equalizer output qi, and this evaluation scale E(k) is calculated based on the momentary temporal value of the input data Xi. Since it changes following the fluctuation, the measurement unit 5 detects whether or not the transmission path 10 is in a disturbance occurrence situation by determining whether this is large or not. Also,
The evaluation scale Ter(k) calculated by Equation 3 is the difference value of the coefficient ratio between the coefficient C0 of the center tap of the equalizer 4 and the coefficient C1 of the next tap, and this reflects the physical quantity related to timing. It has become.

FIG. 3 is a diagram showing an example of the configuration of the measuring section 5.
This measurement unit 5 includes the above-mentioned evaluation scales E(k), Ter(
first and second evaluation scale calculation units 6 that calculate k) respectively;
, 7 and the evaluation scale E(k) calculated by the first evaluation scale calculation unit 6, a disturbance detection unit 8 detects the disturbance.
When receiving a signal from the disturbance detection section 8 indicating that the disturbance has been detected as an impulsive disturbance, an impulsive disturbance counting section 9 counts the number of occurrences of this signal, and a signal from the disturbance detection section 8 that indicates that the disturbance has been detected as an impulsive disturbance is sent to the When receiving a signal (disturbance interval signal) indicating that a burst type that lasts over a time interval (disturbance interval) is received, a disturbance interval counting unit 1 counts the number of occurrences of this signal, that is, the number of occurrences of the disturbance interval.
0, a disturbance section length counting section 11 that counts the section length of this disturbance when a burst disturbance is detected by the disturbance detection section 8, and section length frequency distribution creation section that creates an occurrence frequency distribution for each disturbance section length. The evaluation scales E(k) and Ter(
k) and a disturbance type determination unit 13 that determines the disturbance type using both of the above.

Specifically, as shown in FIG. 4, the disturbance section counting section 10 is configured to count the number of times a disturbance section appears within a predetermined period of time. That is, Figure 4
The disturbance section counting unit 10 counts the number of occurrences of a disturbance section signal indicating the existence of a disturbance section using a counter 14,
When a pulse signal is generated from the control circuit 16 at predetermined time intervals (for example, 1 minute), the latch circuit 15 latches and holds the counted value by the counting counter 14 in synchronization with this pulse signal, and uses this as a disturbance section within a predetermined time. It is designed to be output as the number of occurrences. Note that after the count value is output from the latch circuit 15, the count counter 14 is reset,
Similar counting is repeated.

Next, a method of measuring line quality when the measuring section 5 has the configuration shown in FIG. 3 will be explained. In FIG. 1, when random binary series data is generated from a transmission data generator 1, the binary series data is modulated by a transmitter 2 and sent to a transmission path 10. Receiving section 3
Then, the modulated data propagated through the transmission path 10 is received and inputted to the adaptive equalizer 4 as input data Xi. The state of the adaptive equalizer 4 also changes as the input data Xi changes over time. When the measurement unit 5 has a configuration as shown in FIG. The evaluation scale calculation units 6 and 7 perform calculations, respectively.

FIG. 5 is a diagram showing a specific example of the change over time of the evaluation scale E(k) calculated by the measuring section 5 according to Equation 1. As mentioned above, the evaluation scale E(k) is the short-term average value of the error e of the equalizer output qi, so there are few changes in characteristics such as the situation of the transmission line 10, and there are no sudden changes in the input data Xi. When there is no input data Xi, the operation of the adaptive equalizer 4 is based on the input data Xi.
Therefore, the error e is small, and the evaluation scale E(k) is also small. On the other hand, when an impulsive or burst signal deterioration situation, a so-called disturbance situation occurs in the transmission line 10, the characteristics of the transmission line 10 change rapidly over time, and the input data Xi changes rapidly. Sometimes, the operation of the adaptive equalizer 4 cannot follow this, and therefore the error e becomes large and the evaluation measure E(k) becomes a large value equal to or larger than the predetermined threshold TH. In other words, since it can be considered that the fluctuation in the value of the evaluation scale E(k) indicates the line quality, the measurement unit 5 compares the value of the evaluation scale E(k) obtained by calculation with the threshold value TH. death,
When this threshold is exceeded, it is assumed that a disturbance is occurring and the line quality can be measured.

Specifically, when the calculation result of the evaluation scale E(k) as shown in FIG. Compare with TH. As a result of this comparison, the symbols A, B, C, and D are shown in FIG.
, E, when the evaluation scale E(k) impulsively exceeds the threshold TH, the disturbance detecting section 8 determines that an impulsive disturbance has occurred at this point, and the sign F As shown, when the evaluation scale E(k) exceeds the threshold value TH in a continuous interval, it is determined that a burst disturbance has occurred in this time interval. In addition,
In FIG. 5, sections other than the points A, B, C, D, and E and the section F are determined as steady state sections.

The impulsive disturbance counting section 9 of the measuring section 5 counts the number of occurrences of the impulsive disturbance detected by the disturbance detecting section 8 within a predetermined time, and the disturbance section counting section 10 of the measuring section 5 counts the number of occurrences of the impulsive disturbance detected by the disturbance detecting section 8. The number of times a section where a burst disturbance appears to be occurring within a predetermined period of time, that is, the number of times a disturbance section appears is counted. In this way, by counting the number of occurrences of impulsive disturbances and the number of occurrences of disturbance sections, it becomes clear how many times impulse and burst disturbances have actually occurred, and based on these counting results, Line quality can be expressed quantitatively.

Further, the disturbance section length counting section 11 of the measuring section 5 counts the length of the disturbance section when a burst disturbance appears to be occurring, and calculates the length of the disturbance section, and calculates the length of the disturbance section.
In step 2, the degree of occurrence (occurrence frequency distribution) for each interval length is created.

FIG. 6 is a diagram showing an example of the frequency distribution for each section length, and FIG. 6 shows the occurrence frequency distribution for each disturbance section length as well as the occurrence frequency distribution for each steady section length. The measurement unit 5 calculates not only the number of disturbance occurrences but also the frequency distribution for each section length as shown in FIG. 6, so that, for example, the frequency of occurrence of a disturbance section whose section length is "8" is "7"
, and the frequency of occurrence of a steady interval with an interval length of “8” is “
6'', and from this it is possible to clearly analyze the state of the disturbance section and the state of the steady section in the line, making it possible to understand the line quality in more detail.

Further, the disturbance type determining unit 13 of the measuring unit 5 refers to both the evaluation scales E(k) and Ter(k), and determines whether the type of disturbance is simply impulse type or burst type. Instead, it is determined in more detail. Figure 7(a), (
b) is a diagram showing the temporal changes in the evaluation scales E(k) and Ter(k) when a momentary interruption is added for only 1 second to the data input to the receiving unit 3; FIGS. 8(a) and 8(b) Figures 9(a) and 9(b) show the temporal changes in the evaluation scales E(k) and Ter(k) when amplitude fluctuation noise is added to the data input to the receiver 3 for only 1 second, respectively. Figures 10(a) and 10(b) are diagrams showing the temporal changes in the evaluation scales E(k) and Ter(k) when amplitude and phase fluctuation noise is added to the data input to the receiver 3 for only 1 second. 3 is a diagram showing temporal changes in evaluation scales E(k) and Ter(k) when randomly generated impulsive noise is added to data input to the receiving unit 3 for only one second. FIG.

7(a), (b) to FIG. 10(a), (
As can be seen by comparing b), when a momentary interruption occurs as a disturbance, the change in the evaluation scale E(k) is larger than when other noises occur (see Fig. 7(a)),
There is little change in the evaluation scale Ter(k) (see FIG. 7(b)). Furthermore, when amplitude fluctuation noise occurs as a disturbance, the evaluation scale E(k), Ter
Both changes in (k) are small (see FIGS. 8(a) and (b)). Furthermore, when amplitude phase fluctuation noise occurs as a disturbance, changes in both evaluation scales E(k) and Ter(k) become large (see FIGS. 9(a) and 9(b)). Furthermore, when impulsive noise occurs as a disturbance, the change in the evaluation scale E(k) is not much different from when amplitude fluctuation noise occurs (see FIG. 10(a)), but the evaluation scale Ter(k)
It is characterized by a large change in (see FIG. 10(b)).

In this way, the evaluation scale E is determined for each type of disturbance.
(k) and Ter(k) change in different ways, the disturbance type discriminator 13 uses evaluation scales E(k) and Ter(k)
), it is possible to estimate the types of disturbance in more detail (four types in the above example).

As described above, by providing the adaptive equalizer 4 in the receiving section 3 and configuring the measuring section 5 of the receiving section 3 as shown in FIG. It is also possible to quantitatively, accurately and precisely measure time-varying qualities such as the type of disturbance, the section length of the disturbance, and the frequency distribution for each disturbance section length in a simple manner.

Note that in the configuration of FIG. 3, the measuring section 5 is
It is not necessary to have all of the impulsive disturbance counting section 9, the disturbance section counting section 10, the disturbance section length counting section 11, the section length frequency distribution creation section 12, and the disturbance type discriminating section 13; They may be selected and used as appropriate.

Furthermore, the measuring section 5 may have a configuration other than that shown in FIG. 3. FIG. 11 is a diagram showing another configuration example of the measurement unit 5. In the configuration shown in FIG. an arithmetic unit 22 that performs absolute value, argument, and differential operations on the Fourier transform result C(ω) of the coefficient Ci to determine the characteristics of the adaptive equalizer 4; and an adaptive equalizer determined by the arithmetic unit 22. An inverse characteristic calculating section 23 is provided which determines the characteristics of the transmission line 10 by finding the inverse characteristic of the characteristic of No. 4.

In the configuration shown in FIG. 11, the measuring section 5 discretely Fourier transforms the tap coefficient Ci of the adaptive equalizer 4 using the Fourier transformer 21 as shown in the following equation.

[0046]

[Math 4]

After obtaining the discrete Fourier transform result C(ω) of the tap coefficient in this way, the calculation unit 22 calculates its absolute value |C(ω)|, argument arg[C(ω)] , and the differential value of argument arg[C(ω)] -d[arg[C
(ω)]]/dω is obtained as the state value of the adaptive equalizer 4. Here, the Fourier transform result C(ω) of the tap coefficient Ci
The above absolute values, argument angles, and differential values respectively indicate the frequency characteristics, phase characteristics, and group delay characteristics of the adaptive equalizer 4. Therefore, as a result of the above calculation in the calculation section 22, each of the adaptive equalizer Characteristics can be obtained, and based on these characteristics, it is possible to judge the quality of the line.

Furthermore, in the inverse characteristic calculation section 23, the calculation section 2
The inverse characteristic of the characteristic of the adaptive equalizer 4 obtained in step 2 is obtained. The characteristic of the adaptive equalizer 4 obtained by the calculation unit 22 represents an impulse response showing the inverse characteristic of the transmission line 10, so by finding the inverse characteristic of the characteristic of the adaptive equalizer 4, It becomes possible to obtain the characteristics of Note that when determining the line quality only from the characteristics obtained by the calculation unit 22, it is not necessarily necessary to provide the inverse characteristic calculation unit 23, but by providing the inverse characteristic calculation unit 23, the characteristics of the transmission line can be further improved. It becomes possible to judge easily.

In this way, by providing the adaptive equalizer 4 in the receiving section 3 and configuring the measuring section 5 of the receiving section 3 as shown in FIG. road properties can be measured in a simple manner.

Note that the measuring section 5 can have only one of the configurations shown in FIGS. 3 and 11, or can have a configuration that combines both of these configurations.

Further, in the above embodiment, the transmission data generator 1 and the transmission device 2 are provided on the transmission side, but a facsimile device may be used instead of these. FIG. 12 is a diagram showing a configuration example of a line quality measurement system using a facsimile device 30 on the transmitting side. Normally, a facsimile machine binarizes image information, MH encodes it, scrambles it, modulates it with DPSK, and sends it out to the transmission path. Corresponding to the transmission data generator 1 in FIG. 1, the function of performing DPSK modulation and sending out to a transmission path corresponds to the transmitter 2 in FIG. Therefore, even when a facsimile machine is used on the transmitting side as shown in FIG. 12, it is possible to measure the line quality of the transmission path 10 in the same manner as the system shown in FIG.

As described above, in this embodiment, the receiving section 3 is provided with the adaptive equalizer 4, and by utilizing the characteristics of the adaptive equalizer 4, the characteristics of the transmission line and the disturbance situation (the type of disturbance,
occurrence frequency, etc.) can be measured accurately and accurately in a simple manner. Furthermore, in the past, it was necessary to install the same measuring device on the transmitting and receiving sides of the transmission line, as shown in FIGS. do not have. Furthermore, in the present invention, as shown in FIG. 12, a normal facsimile machine can be used on the transmitting side, so line quality can be measured with a simple configuration.

[0053]

[Effects of the Invention] As explained above, according to the present invention,
The modulated data sent from the transmitting side via the transmission path is demodulated by the adaptive equalizer, and at this time, the state value of the adaptive equalizer is determined to measure the line quality of the transmission path. Time-varying line quality of a transmission path can also be measured accurately and accurately in a simple manner.

[0054] If a predetermined evaluation scale is obtained as the state value of the adaptive equalizer, the state of disturbance occurring in the transmission path is determined based on the evaluation scale, and this is measured as the line quality, it is possible to prevent disturbance from occurring. It is possible to accurately and accurately measure time-varying line quality when

[0055] As an evaluation measure, a first measure consists of the root mean square value of the error of the output of the adaptive equalizer and/or a difference value of the ratio of the center tap and the next tap of the tap coefficients of the adaptive equalizer. A second measure is obtained, and based on the first and/or second measure, the type of disturbance, the number of occurrences of various disturbances, the length of the disturbance section, or the frequency distribution for each disturbance section length is measured as the line quality. By doing so, time-varying line quality can be measured quantitatively.

In addition, time-varying line quality can be easily adjusted by determining the characteristics of the adaptive equalizer as the state value of the adaptive equalizer and obtaining the line quality of the transmission path based on the characteristics of the adaptive equalizer. can be measured accurately and precisely.

[0057] If the characteristics of the transmission path are determined by determining the characteristics of the adaptive equalizer and then determining the inverse characteristics of the characteristics of the adaptive equalizer, time-varying line quality can be more easily determined. can be measured accurately and precisely.

Furthermore, by using a facsimile machine on the transmitting side, time-varying line quality can be measured with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of a line quality measurement system according to the present invention.

FIG. 2 is a diagram showing a configuration example of an adaptive equalizer.

FIG. 3 is a diagram showing an example of the configuration of a measuring section.

FIG. 4 is a diagram showing a configuration example of a disturbance section counting section.

FIG. 5 is a diagram showing changes over time in the evaluation scale E(k).

FIG. 6 is a diagram showing an example of frequency distribution for each section length.

7A and 7B are diagrams showing temporal changes in evaluation scales E(k) and Ter(k), respectively, when a momentary interruption is added for 1 second; FIG.

FIGS. 8(a) and 8(b) are diagrams showing temporal changes in evaluation scales E(k) and Ter(k), respectively, when amplitude fluctuation noise is added for 1 second.

9A and 9B are diagrams showing temporal changes in evaluation scales E(k) and Ter(k), respectively, when amplitude phase fluctuation noise is added for 1 second; FIG.

FIGS. 10(a) and 10(b) are diagrams showing temporal changes in evaluation scales E(k) and Ter(k), respectively, when impulsive noise is added for 1 second.

FIG. 11 is a diagram showing another example of the configuration of the measurement section.

FIG. 12 is a diagram showing a configuration example of a line quality measurement system using a facsimile on the transmitting side.

FIG. 13 is a configuration diagram of a conventional line quality measurement system that measures the quality of a transmission line using a network analyzer.

FIG. 14 is a configuration diagram of a conventional line quality measurement system that measures the quality of a transmission line by determining the bit error rate.

[Explanation of symbols]

1 Transmission data generator 2 Transmitting device 3 Receiving unit 4 Adaptive equalizer 5 Measuring unit 6 First evaluation scale calculation unit 7 Second evaluation scale calculation unit 8 Disturbance detection unit 9 Impulse disturbance counting unit 10 Disturbance section counting unit 11 Disturbance section length counting section 12 Section length frequency distribution creation section 13 Disturbance type discriminating section 14 Counter 15 Latch circuit 16 Control circuit 21 Fourier transformer 22 Computing section 23 Inverse characteristic computing section 30 Facsimile machine

Claims (8)

[Claims] 1. An adaptive equalizer as a demodulating means for demodulating modulated data sent from a transmitting side via a transmission line, and a state value of the adaptive equalizer is determined to measure the line quality of the transmission line. What is claimed is: 1. A line quality measurement system, characterized in that a measurement means for measuring line quality is provided on a receiving side. 2. The measuring means obtains a predetermined evaluation scale as a state value of the adaptive equalizer, determines the state of disturbance occurring in the transmission path based on the evaluation scale, and measures this as line quality. 2. The line quality measurement system according to claim 1, wherein: 3. The evaluation measure includes a first measure consisting of the root mean square value of the error of the output of the adaptive equalizer and/or a ratio of the center tap and the next tap of the tap coefficients of the adaptive equalizer. A second measure consisting of difference values is determined,
Based on the first and/or second scale, the type of disturbance, the number of occurrences of each type of disturbance, the length of the disturbance section, or the frequency distribution for each disturbance section length is measured as the line quality. 3. The line quality measurement system according to claim 2. 4. The measuring means obtains a characteristic of the adaptive equalizer as a state value of the adaptive equalizer, and obtains the line quality of the transmission line based on the characteristic of the adaptive equalizer. 3. The line quality measurement system according to claim 2. 5. The measuring means is characterized in that the characteristics of the transmission path are determined by determining the characteristics of the adaptive equalizer and further determining the inverse characteristics of the characteristics of the adaptive equalizer. The line quality measurement system according to claim 2. 6. The measuring means performs Fourier transform on the tap coefficients of the adaptive equalizer, and based on the Fourier transform result,
6. The line quality measurement system according to claim 4, wherein the frequency characteristics, phase characteristics, and group delay characteristics of the adaptive equalizer are determined as state values. 7. In the line quality measurement system according to claim 1, the transmission side includes transmission data generation means for generating random binary sequence data, and a transmission data generation means for modulating the binary sequence data from the transmission data generation means. 1. A line quality measurement system comprising: a transmission means for sending data to a transmission path. 8. The line quality measurement system according to claim 1, wherein a facsimile machine is used on the transmitting side.