JPH0715509A - Method and device for testing subscriber line - Google Patents

Abstract

PURPOSE:To test economically each subscriber regardless of accommodation scale of number of subscribers accommodated to each of subscriber interfaces located remotely. CONSTITUTION:While a test signal is sent from a post-stage of a line concentration switch 81 to a 4-wire outgoing signal line of a subscriber circuit 501, the signal is echoed via a 2/4-wire conversion circuit of the circuit 501. When an echo signal to a 4-wire incoming signal line is received via the switch 81 and a state of the line 3 is discriminated based on the characteristic of a subscriber line 3 estimated from the echo signal and the test signal, a hardware for exclusive use is not required for each of subscriber interface devices 5 to test the state of the subscriber 1 stored in each of the devices 5 economically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric condition in which a subscriber line and a subscriber terminal connected to this subscriber line are placed, that is, some trouble occurs in the subscriber line. The present invention relates to a subscriber line test method and an apparatus therefor for economically detecting whether or not the subscriber interface is installed, especially when the subscriber is accommodated in each subscriber interface device installed remotely from the exchange. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a subscriber line test method and apparatus for economically testing the electrical condition of a subscriber housed in each apparatus from the exchange side.

[0002]

2. Description of the Related Art As shown in FIG. 5, a plurality of subscriber terminals to be accommodated in a (digital) exchange 8 have hitherto been used as part of the maintenance of an infrastructure of a communication network using optical fiber cables. A subscriber interface 1 including a plurality of subscriber circuits 501, each of which is installed at a remote location such as a user building via a subscriber line 3.
In addition to being temporarily housed in the switch device 5, it is further housed in a concentrator switch (concentrator) in the exchange 8 via an optical fiber cable 11 for time division multiplexing transmission. . Although not shown in the figure, each of the other subscriber interface devices has a similar structure to the optical fiber cable.
It is housed in the concentrator switch in the exchange 8 via the cable.

By the way, in the case where such a subscriber accommodation system is adopted, in order to test the subscriber line 3 and the subscriber terminal 1 connected to the subscriber line 3, the subscriber interface has hitherto been available. It is carried out in a state in which the two-line signal on the subscriber line 3 to be tested is selectively pulled into the dedicated test device 502 provided in the switch device 5 via the corresponding subscriber circuit 501. There is. 2 on subscriber line 3
When the line signal is pulled in, the dedicated test apparatus 502 is controlled by the test control apparatus (not shown) installed in or near the exchange 8 so that the subscriber line 3 and the subscriber terminal 1 are controlled. The test was carried out. Incidentally, as a technique related to such a test, NTT technical journal 1990.9.P39-41
(Development of a remote monitoring test device that promotes the introduction of the optical subscriber system), and Research Practical Report Vol. 31, No. 11 (198)
2) .P81-93 (maintenance test method for digital subscriber line exchanges).

[0004]

However, according to the above-mentioned subscriber line test method, the same applies to each subscriber accommodated in each subscriber interface device installed remotely from the exchange. Since it is necessary to test the contents, the dedicated test device provided in each subscriber interface device is configured regardless of the number of subscribers accommodated in the subscriber interface device. Have to be the same.
That is, if each of the subscriber interface devices accommodates a large-scale subscriber, and if the subscriber interface device accommodates a small-scale subscriber, the test cost per subscriber increases considerably. Inevitably, this makes the testing of subscriber lines impractical.

An object of the present invention is to perform a subscriber line test method capable of economically testing each subscriber line regardless of the number of subscribers accommodated in each remotely installed subscriber interface device. And that equipment.

[0006]

The above-mentioned object is basically to send a test signal from the concentrator switch side to the four-line down signal line of the corresponding subscriber circuit via the optical fiber cable, while the subscriber circuit is being transmitted. The echo signal to the 4-line upstream signal line echoed through the 2-line to 4-line conversion section of is received through the optical fiber cable and the concentrator switch, and the subscriber estimated from the echo signal and the test signal. This is achieved by determining the status of the subscriber line based on the line characteristics. The subscriber line test apparatus includes a test signal generating section for sending a test signal to the four-line down signal line of the corresponding subscriber circuit and two of the corresponding subscriber circuit as its constituent elements.
From the test signal receiving unit that receives the echo signal to the 4-line upstream signal line echoed through the line-to-line 4-line converting unit, the test signal from the test signal generating unit, and the echo signal from the test signal receiving unit. By providing a subscriber line characteristic estimation unit that estimates the characteristics of the subscriber line, and a subscriber line characteristic determination unit that determines the state of the subscriber line based on the estimation result from this subscriber line characteristic estimation unit. To be achieved.

[0007]

The test signal is sent from the rear stage of the concentrator switch to the four-line down signal line of the corresponding subscriber circuit through the optical fiber cable, while being reflected by the two-line to four-line conversion section of the subscriber circuit. The echo signal to the upstream signal line is received through the optical fiber cable and the concentrator switch, the characteristics of the subscriber line are estimated from the echo signal and the test signal, and the subscriber is based on the estimated characteristics. When the line condition is judged, a test dedicated to each subscriber interface device is used to test each subscriber accommodated in each subscriber interface device installed remotely from the exchange. No need to install any hardware for
Moreover, the state of each subscriber accommodated in each subscriber interface device can be economically tested only by transmitting and receiving a test signal at the latter stage of the concentrator switch. In other words, the presence / absence of a failure on the subscriber side can be detected only by transmitting and receiving signals from the four-line side of the subscriber line. Therefore,
When the subscriber line test device according to the present invention for transmitting and receiving a test signal is installed at the rear side of the concentrator switch, the subscriber terminal and the subscriber accommodated in each of the remotely installed subscriber interface devices. The test on the line is enabled by simply connecting the subscriber under test and the subscriber line test equipment by a switch. In general, a concentrator switch accommodates a large number of subscribers via respective subscriber interface devices, but the minimum required number of subscriber line test devices is installed at the rear stage of the concentrator switch according to the test traffic to these subscribers. If so, those subscribers can be tested very economically.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS. First, the subscriber line test method according to the present invention will be described. FIG. 1 shows its outline. As shown in the figure, the subscriber terminal 1 is connected to the subscriber line 3 via the terminal connection terminal 2, and the subscriber line 3 is also accommodated in the subscriber interface device 5 described above via the subscriber connection terminal 4. However, when the subscriber terminal 1 is accommodated, the subscriber terminal 1 is accommodated in the subscriber circuit 501 corresponding to the subscriber terminal 1. Similarly, the other subscriber terminals are also accommodated in the subscriber circuit corresponding to that subscriber terminal. On the other hand, the concentrator switch 81 provided in the exchange 8 can accommodate one or more subscriber interface devices, but any subscriber in any subscriber interface device can be used for the test. Whether the circuit is selectively connected to the subscriber line test device 9 depends on the concentrator switch 81.

That is, from the subscriber connection terminal 4 to the subscriber terminal 1
Assuming that a test is performed on the subscriber line 3 up to, the concentrator switch 81 is operated as desired prior to the test so that the subscriber line test device 9 and the device under test are operated via the concentrator switch 81. The 4-line up signal terminal 6 and the 4-line down signal terminal 7 of the subscriber circuit 501 are connected to each other. The test is performed by the subscriber line test device 9 for the first time in a state where the subscriber circuit 501 and the subscriber line test device 9 are connected. When the test is performed, a test signal is transmitted from the test signal transmitting / receiving unit 91, and this test signal is input to the subscriber circuit 501 via the concentrator switch 81 and the 4-line down signal terminal 7. There is. This test signal is echoed as a reverberant signal to the 4-line up signal terminal 6 through the 2-line / 4-line converter in the subscriber circuit 501. This reverberant signal is the concentrator switch 81.
By being received by the test signal transmitting / receiving unit 91 via the, the subscriber line test apparatus 9 can test the subscriber line 3 for the first time. In more detail,
In the subscriber line characteristic estimating unit 92, the test signal transmitting / receiving unit 91
The electrical total characteristics of the subscriber terminal 1 and the subscriber line 3 are estimated from the information on each of the transmission test signal and the reception echo signal. On the basis of this estimation result, the subscriber line characteristic judging section 93 detects whether or not there is a failure in the subscriber terminal 1 and the subscriber line 3, and outputs the result as a test result from the judgment result sending terminal 10 to the outside. Is. Therefore, for example, each time the subscriber circuit under test is updated, the test result is taken into the microprocessor as a subscriber circuit-compatible one, and is stored as information including the presence or absence of a fault and the fault type. By extracting and displaying the information corresponding to the subscriber circuits as needed, the test results for each subscriber circuit can be displayed as a list.

The outline of the subscriber line test method and apparatus according to the present invention has been described above. Hereinafter, the present invention will be described more specifically and in detail, but before that, the echo signal according to the present invention will be briefly described. In general, the subscriber circuit can be modeled as an equivalent circuit shown in FIG. 4, 21 and 22 are terminal connection terminals, 31 and 32 are subscriber lines, 41 and 42 are subscriber connection terminals, 51 is a voltage amplifier of gain A, and 52 is a conversion coefficient g _m . A voltage-current converter, 53 and 57 are adders, 54 is a termination filter, 55 is a transmission filter, 56 is a reception filter, and 58 is an echo signal elimination filter. To explain its internal operation, the signal input through the 4-line downlink signal terminal 7 is received by the reception filter 5
6. The voltage-current converter 52 is applied to the voltage-current converter 52 via the adder 53. In the voltage-current converter 52, a current having a conversion coefficient g _m times the applied signal is applied between the subscriber connection terminals 41 and 42. By doing so, 2-line to 4-line conversion is performed. Also, due to the current, the subscriber connection terminal 4
A back electromotive force is generated between the first and the second terminals 42, and this back electromotive force is transmitted as a reverberation signal to the 4-line upstream signal terminal 6 via the voltage amplifier 51, the transmission filter 55, and the adder 57. .

Now, the present invention will be described in detail. The impedance when the subscriber terminal 1 side is viewed from the subscriber connection terminals 41 and 42 is Z, and the input signal to the 4-line down signal terminal 7 is Vs.
, The echo signal Ve to the 4-line up signal terminal 6
Is the following Equation 1 and H in the Equation 1
_BN and Zin are represented by Equations 2 and 3, respectively.

[0012]

[Equation 1]

[0013]

[Equation 2]

[0014]

[Equation 3]

However, G _X is a transmission filter characteristic, G _R is a reception filter characteristic, H _BN is an echo signal elimination filter characteristic, and H
_T is the terminal filter characteristic, and Zo is the ideal terminal characteristic.

In the following, for simplification of explanation, the filter characteristics G _X and G _{R in} each of the transmission filter 55 and the reception filter 56 are G _X = G _R = 1 regardless of the signal frequency. Assuming that the subscriber line test device 9
2 shows a specific configuration example of the test signal transmitting / receiving unit 91. In FIG. 2, 911 is an echo signal receiving terminal, 912 is a test signal transmitting terminal, and 913 is a test signal transmitting terminal.
Is an echo signal monitor, and 914 is a test signal source. Therefore, assuming that the test signal sent from the test signal sending source 914 is Vs and G _X = G _R = 1, the echo signal Ve received at the echo signal receiving terminal 916 becomes _{by X} = G _R = 1 condition is substituted, it will be expressed by equation 4 below.

[0017]

[Equation 4]

By substituting the condition of G _X = G _R = 1 in the equation 2, the echo signal elimination filter characteristic H _BN can be obtained as the following equation 5.

[0019]

[Equation 5]

Here, for further simplification of description,
Assuming that Zin = Zo = R (R is a pure resistance), the reception signal Vr (= echo signal Ve) at the echo signal monitor 913 can be obtained as Expression 6.

[0021]

[Equation 6]

Therefore, the subscriber line characteristic estimation unit 92 uses the test signal Vs and the received signal Vr from the test signal transmission / reception unit 91 as the following equations 7 and 8 to obtain the gain | G (S ) |, And phase ∠G (S) are detected, and further, based on the detection results, the subscriber line characteristic judging section 93 detects the presence / absence of a fault in the subscriber terminal and the subscriber line and the fault type. Tests are being conducted for each subscriber in such a way that

[0023]

[Equation 7]

[0024]

[Equation 8]

Incidentally, here, as the simplest example, assuming that the subscriber line is disconnected, the above-mentioned impedance Z takes the value shown in the following expression 9.

[0026]

[Equation 9]

Under this condition, the echo signal monitor 913
The received signal Vr obtained from Eq. (6) is obtained from Eqs.

[0028]

[Equation 10]

Therefore, the gain of the received signal Vr described above |
G (S) | and phase ∠G (S) are obtained by the mathematical expressions 11 and 12, respectively.

[0030]

[Equation 11]

[0031]

[Equation 12]

As a simplest example, assuming that the subscriber line is short-circuited, the impedance Z described above will take the value shown by the following expression 13.

[0033]

[Equation 13]

Under this condition, the echo signal monitor 913
The received signal Vr obtained from Eq. (6) is obtained from Eqs.

[0035]

[Equation 14]

Therefore, the gain of the received signal Vr described above |
G (S) | and phase ∠G (S) are obtained by the mathematical expressions 15 and 16, respectively.

[0037]

[Equation 15]

[0038]

[Equation 16]

As described above, the typical failure, that is, the disconnection of the subscriber line and its short circuit, is caused by the subscriber line characteristic judging section 9
In No. 3, it can be detected by examining the gain and phase characteristics of the received signal Vr. Similarly, as for the characteristic deterioration in the subscriber terminal and the subscriber line, the gain and the phase characteristic of the reception signal Vr at the normal time are measured in advance, and this and the gain of the reception signal Vr measured during the test are measured. It can be detected by comparing the phase characteristics with the phase characteristics.

Next, the internal structure of another example of the subscriber test apparatus according to the present invention will be described with reference to FIG. 91 in FIG.
Reference numerals 5 and 917 denote adders, 916 denotes a filter having an _HBN characteristic, 918 denotes a pseudo echo signal generation filter having a variable filter coefficient, and 921 denotes a pseudo echo signal generation filter coefficient identification unit. Now, again, for simplification of description, the subscriber circuit is modeled as shown in FIG.
The impedance of the subscriber terminal seen from the subscriber connection terminals 41 and 42 is Z, and the filter characteristics in each of the transmission filter 55 and the reception filter 56 are G _X = regardless of the signal frequency.
If G _R = 1 and the test signal Vs is transmitted from the test signal transmission source 914, the reverberation signal Ve received through the reverberation signal receiving terminal 916 is represented by the above-mentioned mathematical expression 1. . Furthermore, again, Zin = Zo = R
If (R is a pure resistance), the output V ₁ from the adder 915 is obtained as the following Expression 17.

[0041]

[Equation 17]

In the present example, the filter characteristic H _z in the pseudo echo signal generation filter 916 is obtained by adding V ₁ to the adder 917.
It is set to be automatically updated so that it is completely canceled. This is a pseudo echo signal generation filter 916.
If the output and the output V ₁ and the E an error signal resulting from subtracting in the adder 917 from, the echo replica generator filter coefficient identification unit 921, as shown as a formula 18, close to zero error signal E This is because the filter coefficient in the pseudo echo signal generation filter 916 is successively estimated in the direction, and the filter coefficient in the pseudo echo signal generation filter 916 is sequentially changed based on the estimation result.

[0043]

[Equation 18]

Here, the condition in which the expression 18 is satisfied is called the identification state, but the filter coefficient in the pseudo echo signal generation filter 916 in the identification state is obtained as a function of the characteristics of the subscriber terminal and the subscriber line. It will be done. Therefore, the subscriber line characteristic judging section 93 can detect the presence / absence of a fault in the subscriber terminal and the subscriber line and the fault type based on the filter coefficient in the identified state.

Finally, considering the effect of the present invention, for example, the number of subscribers accommodated in each of the remotely installed subscriber interface devices is 10, and the test traffic is 100 subscribers. Operator line test equipment 1
Assuming that a number of units is required, the conventional method requires one subscriber line test device for each subscriber interface device, that is, ten subscriber line test devices. It suffices to install only one subscriber line test device at the rear stage of the switch side concentrator switch accommodating 100 subscribers. That is, according to the present invention, the subscriber line can be tested extremely economically as compared with the conventional method.

[0046]

As described above, according to the first to third aspects, the subscriber line is accommodated regardless of the accommodation scale of the number of subscribers accommodated in each of the remotely installed subscriber interface devices. A subscriber line test method capable of economically testing each is provided, and in the case of claim 4, a subscriber line test device for carrying out the subscriber line test method is obtained.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an outline of a subscriber line test method according to the present invention.

FIG. 2 is a diagram showing an internal configuration of an example of a subscriber test apparatus configuration according to the present invention.

FIG. 3 is a diagram showing an internal configuration of another example of the subscriber test apparatus configuration according to the present invention.

FIG. 4 is a diagram showing an equivalent circuit of a subscriber circuit.

FIG. 5 is a diagram for explaining a subscriber line test method according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Subscriber terminal, 3 ... Subscriber line, 5 ... Subscriber interface device, 8 ... Exchanger, 81 ... Concentrator switch, 9 ... Subscriber line test device, 91 ... Test signal transmitting / receiving unit, 92 ... Subscriber line characteristic estimation Section, 93 ... Subscriber line characteristic judging section

Claims (4)

[Claims] 1. When each of the remotely installed subscriber interface devices, each of which houses a plurality of subscriber circuits, is housed in a concentrator switch installed on the exchange side through an optical fiber cable for time division multiplexing transmission. In addition, the electrical state in which the subscriber line and the subscriber terminal connected to the subscriber line are placed via the corresponding subscriber circuits accommodated in each of the subscriber interface devices, the concentrator switch A subscriber line test method for testing from the latter stage side, in which a test signal is sent from the concentrator switch side to the four down signal lines of the corresponding subscriber circuit via an optical fiber cable, while the The echo signal to the 4-line upstream signal line echoed through the line-to-line 4-line converter is received via the optical fiber cable and the concentrator switch, and the echo signal estimated from the echo signal and the test signal is added. A subscriber line test method that determines the state of the subscriber line based on the characteristics of the incoming line. 2. A remote-installed subscriber interface device, which houses a plurality of subscriber circuits, is housed in a concentrator switch installed on the exchange side via an optical fiber cable for time division multiplexing transmission. In addition, the electrical state in which the subscriber line and the subscriber terminal connected to the subscriber line are placed via the corresponding subscriber circuits accommodated in each of the subscriber interface devices, the concentrator switch A subscriber line test method for testing from the latter stage side, in which a test signal is sent from the concentrator switch side to the four down signal lines of the corresponding subscriber circuit via an optical fiber cable, while the The echo signal to the 4-line upstream signal line echoed through the 4-line 4-line converter is received via the optical fiber cable and the concentrating switch, and the signal level between the echo signal and the test signal is changed. A subscriber line test method that allows the state of the subscriber line to be judged based on the characteristics of the subscriber line estimated from the relationship between the phase and the phase. 3. When the remote-installed subscriber interface devices each containing a plurality of subscriber circuits are housed in a concentrator switch installed on the exchange side via an optical fiber cable for time division multiplexing transmission. In addition, the electrical state in which the subscriber line and the subscriber terminal connected to the subscriber line are placed via the corresponding subscriber circuits accommodated in each of the subscriber interface devices, the concentrator switch A subscriber line test method for testing from the latter stage side, in which a test signal is sent from the concentrator switch side to the four down signal lines of the corresponding subscriber circuit via an optical fiber cable, while the When the echo signal to the 4-line ascending signal line echoed through the line-to-line 4-line converter is received through the optical fiber cable and the concentrator switch, the echo signal is accompanied by the test signal. The output of the echo signal elimination filter and the output of the pseudo echo signal generation filter, which are input to, are sequentially subtracted, and the filter coefficients of the pseudo echo signal generation filter are sequentially updated and set so that the subtraction result approaches 0 as much as possible. The status of the subscriber line is determined based on the characteristics of the subscriber line estimated from the filter coefficient of the pseudo echo signal generation filter when the subtraction result approaches 0 without limit. Subscriber line test method. 4. A remote-installed subscriber interface device, which houses a plurality of subscriber circuits, is housed in a concentrator switch installed on the exchange side through an optical fiber cable for time division multiplexing transmission. In addition, the electrical state in which the subscriber line and the subscriber terminal connected to the subscriber line are placed via the corresponding subscriber circuits accommodated in each of the subscriber interface devices, the concentrator switch A subscriber line test device for testing from the latter stage side, comprising a test signal generator for transmitting a test signal to a 4-line down signal line of a corresponding subscriber circuit and a 2-line to 4-line converting unit of the corresponding subscriber circuit. The characteristics of the subscriber line are determined from the test signal receiving unit that receives the echo signal to the 4-line upstream signal line that is echoed via the test signal receiving unit and the test signal from the test signal generating unit and the echo signal from the test signal receiving unit. Extrapolation A subscriber line test apparatus comprising an incoming line characteristic estimation unit and a subscriber line characteristic determination unit that determines the state of the subscriber line based on the estimation result from the subscriber line characteristic estimation unit.