WO2007112631A1

WO2007112631A1 - Method and device for testing degree of line longitudinal balance

Info

Publication number: WO2007112631A1
Application number: PCT/CN2007/000197
Authority: WO
Inventors: Hongya Wang
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2006-04-05
Filing date: 2007-01-18
Publication date: 2007-10-11
Also published as: CN1968309A; CN101322324B; CN101322324A; CN100454939C

Abstract

Method and device for testing degree of line longitudinal balance is to solve problem of long testing time in the prior art one and problem of non-line imbalance factor having great influence on testing result in the prior art two. The method includes the following steps: determining reliable common mode amplitude of each frequency point to be tested; grouping every frequency point into one group based on characteristic of line to be tested and said reliable common mode amplitude, and respectively computing degree of line longitudinal balance of each frequency point in every group. According to present invention, testing time is reduced, and real balance status of line is well and truly reflected.

Description

Method and device for testing longitudinal balance of circuit

The present invention relates to the field of telecommunications networks, and more particularly to a method and apparatus for testing the longitudinal balance of a line. Background technique

In the field of telecommunication services, operators provide broadband telecom services and narrowband telecommunication services to users through local telephone cables (usually twisted pairs), such as ADSL over POTS (ADSL over PODSL) and ADSL over ISDN (ISDN ESD). ), VDSL over POTS (VDSL over PODSL), VDSL over ISDN (ISDN extended VDSL) and other services, such applications have been quite common in China and abroad. (In this article, ADSL and VDSL are collectively referred to as xDSL)

As shown in Figure 1, the xDSL signal and the POTS/ISDN signal coexist in one user's external line. On the central office side, the splitter (SPL) in the interoffice broadband equipment (DSLAM) separates the wide and narrow services and sends them separately. The broadband service board (xDSL service board) and the narrowband service board (POTS/ISDN service board) are processed, and on the user side, the splitter in the interoffice broadband equipment sends the separated wide and narrowband services to the client. RTU and phone.

During the operation and maintenance of such services, if a user declares a fault, it is often necessary to measure the subscriber line parameters (eg, line voltage parameters, line resistance parameters, line capacitance parameters, line frequency response, line background noise, lines). Balance to the ground, etc.). Based on these parameter data, the quality and fault conditions of the line can be judged. '

During the maintenance of the system, the longitudinal balance is used to measure the longitudinal balance performance of the line, that is, the line-to-ground imbalance performance. The longitudinal balance of the line is an important indicator to measure the quality of the line when the line is used for high-speed data transmission. This is mainly because: the line-to-ground imbalance may cause a potential difference between the two lines of the pair, and then form between the two lines. The potential loop creates a loop current that causes additional interference. Due to the existence of the potential loop, an electromagnetic field is formed around the line, causing a large amount of external interference to be integrated into the line, affecting normal communication. At present, the national standard provides for the opening of ADSL. Service requirements: For the ADSL service, the longitudinal conversion loss is not less than 50 dB in the range of 26 kHz to 1104 kHz, and is allowed to be greater than 40 dB in special cases.

The longitudinal balance Bm-1 is defined as:

Bm-l=201g ( El/ Em ) ( dB )

The Em in the above formula is called the lateral voltage, as shown in Figure 2, that is, the potential difference between the line TIP and the RING line terminal, also called the differential mode amplitude. E1 is called vertical voltage, which is caused by the imbalance of TIP and RING lines to ground. E1 is equal to 1/2 of the left-to-ground potential difference of R1 and the sum of the left-to-ground potential difference of R2, also called common mode amplitude. Referring to Figure 2, the theoretical formula for longitudinal equilibrium is: 4 = 201. d In general, it is necessary to perform longitudinal balance test on each frequency point of the entire ADSL frequency band, including but not limited to the vertical balance of each tone frequency point. That is, the frequency at which the longitudinal balance needs to be measured includes, but is not limited to, the center frequency of each tone.

Due to noise and other non-line imbalance factors, the line test may actually be much larger than the differential mode amplitude due to line imbalance. Set the differential mode amplitude caused by line imbalance to V: 'the differential mode amplitude caused by non-line imbalance factors (such as noise)), then the vertical balance of the actual line is calculated as: A = 201og(" "^^. In the actual line, it can be approximated that the influence of the longitudinal sheep's balance is floating up and down within a fixed interval.

The hardware design currently used is to send a common mode signal and measure the differential mode signal. Referring to FIG. 3, the digital signal processing module DSP generates a modulation signal to D/A, and the D/A device is converted into a common mode analog signal and then sent to the actual differential line. Due to the existence of the line imbalance factor, the differential line actually The voltages are not equal, there is a potential difference, the differential signal is converted into a standard differential signal by a differential transformer, and then the sampled data is processed by the A/D device, and the DSP performs processing on the received sampled data by FFT (Fast Fourier Transform). The frequency domain differential amplitude of each corresponding frequency point is calculated, thereby realizing the calculation of the longitudinal balance degree.

Based on the above vertical balance test theory, and applying the above test hardware device, the current test line There are two options for the vertical balance of the road.

Existing scheme 1: Single-frequency point-by-one transmission method. Referring to FIG. 4, the following specific steps are included: XII, sending a common mode amplitude of a single frequency point to a differential line;

X12, monitoring signals on the differential line and recording the monitored data;

X13. Calculate the frequency domain differential amplitude of the single frequency point;

X14. Calculate a longitudinal balance of the single frequency point;

X15, judging whether all frequency points are sent, if not, return to step XII; if the sending is finished, proceed to step X16;

X16, draw and report the results.

Since the technology uses only one frequency point processing at a time, the energy of the frequency point to be measured can be set relatively large, has a high signal to noise ratio, and has strong anti-noise ability, so that the longitudinal balance of the test can be accurately reflected. The actual balance of the line. See the above formula for calculating the vertical balance of the actual line. This scheme can make the common mode amplitude! ^ large enough, the differential mode amplitude is similar to the differential mode amplitude caused by the line imbalance, that is, the influence on the line balance Small. However, due to the single-frequency point-by-one transmission method, the entire processing time is too long, and the "sensitivity" requirement of the test for time cannot be well satisfied.

Existing scheme 2: All transmission points to be tested are transmitted once. See Figure 5, which includes the following specific steps:

Χ 21. Generate a modulated wave common mode signal for all frequency points to be measured;

Χ 22. Sending the modulated signal to the line;

Χ 23. Monitor the signals on the differential lines and record the monitored data;

Χ24, calculating the frequency domain differential amplitude of each frequency point;

Χ25, calculating the longitudinal balance of each frequency point;

Χ26, draw and report the results.

The scheme has the advantage of fast calculation speed, but considering the actual bearing capacity of the hardware circuit, the sum of the energy of the modulated combined wave cannot exceed the actual bearing capacity of the hardware circuit, and the energy of each transmitting frequency needs to be reduced by multiple times, due to the influence of test line noise and the like. The existence of vertical balance factors The signal-to-noise ratio is relatively small, and the noise resistance of each frequency point signal is poor, which causes noise and the like to have a large influence on the longitudinal balance degree, so that the test result cannot truly reflect the actual balance of the line. See the above formula for calculating the vertical balance of the actual line. This scheme can make the common mode amplitude small enough. In the case of ideal line balance, the differential mode amplitude is approximately 1 „, that is, „pair balance most influential. Summary of the invention

The embodiment of the invention provides a method and a device for testing the longitudinal balance of a line, which are used to solve the problem of long test time in the prior art, and solve the problem that the non-line imbalance factor in the prior art 2 has a great influence on the test result. problem.

The method of the present invention includes: determining a reliable common mode amplitude of each frequency point to be tested; grouping each frequency point according to the measured line characteristic and the reliable common mode amplitude; and calculating each of the groups in units of The vertical balance of each frequency point in the group.

The device for testing the longitudinal balance of the line includes: a frequency generating module, configured to combine the frequency points to be transmitted to generate a modulated signal of the excitation signal source, and send the modulated signal to the line to be tested; and a longitudinal balance calculation module, configured to The modulated signal on the measured line calculates the longitudinal balance of each frequency point; the reliable amplitude determining module is used to determine the reliable common mode amplitude of each frequency point; the grouping module is used to determine the characteristics and reliability of the measured line The reliable common mode amplitude outputted by the amplitude determining module groups each frequency point and outputs it to the frequency generating module one by one in units of groups.

The embodiment of the method of the present invention no longer directly sends the common mode amplitude of the single frequency point to the differential line for testing, and does not generate the modulated wave common mode signal for all the frequency points to be measured, and sends the modulated signal to the line. Test on it.

The method embodiment of the present invention considers the noise interference of the actual line, and obtains the reliable common mode amplitude of each frequency point to be tested according to the noise difference mode amplitude of each frequency to be measured, and further according to the characteristics of the tested line and the described The reliable common mode amplitude groups each frequency point. Finally, the vertical balance of each frequency point in each group is calculated in units of groups.

Obviously, compared with the prior art 1, the method of the invention emits more than one frequency to be tested at a time, reducing The number of transmissions is saved, thereby saving test time; and according to the above grouping strategy, the effect of the prior art that accurately reflects the actual balance of the line is also inherited.

Compared to the prior art 2, the method of the invention emits several but not all frequency points to be tested at a time. According to the above grouping strategy, the energy of each frequency point is increased, but the line load can be satisfied, so that the effect of accurately reflecting the actual balance condition of the line can be achieved; and since the grouping strategy is adopted, the prior art second test is also inherited. Faster speed effect.

Embodiments of the present invention also provide an apparatus for testing the longitudinal balance of a line. DRAWINGS

Figure 1 is a schematic diagram of an existing xDSL service;

2 is a circuit schematic diagram of a conventional differential mode amplitude and a common mode amplitude;

3 is a schematic diagram of a hardware structure of an existing test longitudinal balance;

4 is a flow chart showing the steps of the conventional single-frequency point-by-one transmission method;

FIG. 5 is a flow chart showing the steps of all existing transmission methods of frequency points to be tested;

6 is a schematic diagram of a hardware structure for testing a longitudinal flat copper-degree according to an embodiment of the present invention;

Figure 7 is a flow chart showing the steps of an embodiment of the method of the present invention. detailed description

In order to ensure the test speed and the test quality when measuring the longitudinal balance of the line, the embodiment of the invention provides a device for testing the longitudinal balance of the line, which is applied to the ADSL line and can also be applied to other xDSL lines. Referring to FIG. 6, the method includes: a reliable amplitude determining module, a grouping module, a frequency generating module, and a longitudinal balance calculating module connected in sequence.

The reliable amplitude determining module is configured to calculate a noise difference mode amplitude of each frequency point in the tested line, and determine a reliable common mode amplitude of each frequency point.

The grouping module is configured to group each frequency point according to the measured common line amplitude of the measured line characteristic and the reliable amplitude determining module output, and output to the frequency generating mode one by one in units of groups The frequency generating module is configured to combine the frequency points to be transmitted to generate a modulated signal of the excitation signal source, and send the modulated signal to the line to be tested.

The longitudinal balance calculation module is configured to calculate a longitudinal balance degree of each corresponding frequency point according to a modulation signal on the measured line.

The above-described frequency generation module and longitudinal balance calculation module have the same functions as the existing vertical balance test device shown in Fig. 3.

An embodiment of the present invention provides a method for testing the longitudinal balance of a line. Referring to FIG. 7, the method example includes the following specific steps:

51. Determine the longitudinal flatness test result requirements, and determine the frequency points to be tested within the frequency range to be sought.

The results of the longitudinal balance test are scheduled to be: When the noise power spectral density is relatively large (such as -lOOdbm or -90dbm), the longitudinal balance of the line after the noise influence is more than 60db. Take the noise power spectral density as -90dbm as an example.

For ADSL lines, the frequency range to be sought is 0 to 2.2 MHz, and other lines are subject to the relevant protocol.

In general, it is necessary to perform longitudinal balance test on each frequency band of the entire ADSL frequency band, including but not limited to the vertical balance of each tone frequency point. That is, the frequency at which the longitudinal balance needs to be measured includes, but is not limited to, the center frequency of each tone. If only the center frequency of each tone is calculated, the frequency of the measurement and longitudinal balance is (43 \2.5i) Hz...... ( = 6,7,8... 511,512).

52. Calculate the noise difference mode amplitude of each frequency point in the tested line.

According to the noise power spectrum analysis, the noise power spectral density PSD of the random noise signal in the ADSL signal unit Tone unit bandwidth is:

₌ _L f ^w _od two ^{_{1 f ΨΛ 2 Α · ^ 1}} f ΨΛ 2 f s = 1 f 4 Kf

^Prom —summer ^{Pf f} ~ BW t Nf _s Z _f ⁷ ~BW t Nf _s Z _f N ~ BW N ² Z _f

Where is the frequency domain energy corresponding to the frequency to be sought, N is the FFT calculation point, 2, is the characteristic impedance corresponding to the frequency point on the transmission line, SPf is the width of the tone, and . is the sampling frequency. The " ² " in the above formula is defined as:

, int means rounding down. Where: Set: FFT points N=16K, 100 ohms, measured noise power spectral density maximum -90dbm (given in step SI).

That is lOlog) +30--90; then = ^10-12 . Set at the frequency f, the noise difference mode amplitude is J,, m=6, B |J:

In turn, it can be calculated: 1 V _f

(v), that is, the differential mode amplitude caused by noise is 2.68*10_ ⁴

(V).

S3. Determine the reliable common mode amplitude of each frequency point to be tested. According to the design requirement: =60 (given in step S1), it can be known that:

The amplitude of the frequency point f =) ^ * 10 ³ = 2.68 * 10 - ¹ (V) = 268 (MV).

According to the above formula, the amplitudes of other frequency points are calculated separately.

Considering the influence of noise on the longitudinal balance measurement of the line, if the line noise has a good longitudinal balance under -90dbm, the determined reliable common mode amplitude should not be less than the amplitude of any frequency. Assume that the reliable common mode amplitude is 300 MV (in actual processing, the reliable common mode amplitude required to transmit each frequency point is not necessarily equal, that is, the reliable common mode amplitude can be multiple, but as long as it is not less than either The amplitude of the frequency point can be).

S4. Group each frequency point.

Assume that the maximum voltage amplitude of the signal on the line at the same time determined by the hardware performance of the board cannot exceed 3V, and the reliable common mode amplitude obtained according to step S3 is 300MV.

The maximum number of transmission frequency points at the same time is 3V/300MV-10, that is, in this embodiment, the maximum number of transmission frequency points per group is 10. For the sake of brevity in this example, the number of frequency points per transmission is set to 10 (or may not be evenly grouped). 7 According to the formula = (4312.5z')i3⁄4...... = 6,7,8· - ·511,512), the number of frequency points to be measured is 512-6+1, combined with the set frequency of 10 frequency points. Then the number of sending groups is (512-6+1)/10 = 51 groups.

S5. Calculate the longitudinal balance of each frequency point in each group in units of groups.

According to the above calculation, the amplitude of the frequency to be measured is 300 MV, and each group sends 10 frequency points, which are sent a total of 51 times. Compared with the prior art 1, the number of transmissions is reduced from 507 to 51 times, which obviously saves the test time; compared with the prior art 2, the transmission amplitude of the frequency to be tested is increased to 300 MV, which can meet the test requirements.

Then, according to the grouping order, the respective frequency points in the group to be tested are combined to generate a modulation signal of the excitation signal source, and sent to the test line. For each set of frequency points sent to the line, the DSP samples the time domain information on the line, and calculates the frequency domain differential amplitude corresponding to each frequency point in the group by FFT or the like, and records it as J .

According to the formula, the longitudinal balance of each frequency point in the group can be calculated as:

After testing a set of frequency points, it is judged whether there are any untested groups. If yes, the next set of frequency points is combined to generate a modulated signal of the excitation signal source, and sent to the test line to complete the test; otherwise, the test result is reported.

It is apparent that those skilled in the art can make various modifications and variations to the invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of the inventions

Claims

Rights request

A method for testing a longitudinal balance of a line, comprising the steps of: determining a reliable common mode amplitude of each frequency point to be tested;

Each frequency point is grouped according to the measured line characteristics and the reliable common mode amplitude; and 'the longitudinal balance of each frequency point in each group is calculated separately in groups.

2. The method according to claim 1, wherein before determining the reliable common mode amplitude of each frequency point to be tested, the method further comprises:

- determining the respective frequency points to be tested within the frequency range to be sought;

- calculating the noise difference mode amplitude of each frequency point in the tested line;

- Determine the longitudinal balance test result requirements.

3. The method according to claim 2, wherein the determining the reliable common mode amplitude of each frequency point to be tested comprises the following substeps:

Determining the amplitude of each frequency point to be tested according to the noise difference mode amplitude of each frequency point in the tested line and the longitudinal balance test result requirement;

The common mode amplitude greater than the amplitude of any of the frequency points is used as the reliable common mode amplitude of the respective frequency points.

4. The method according to claim 2, wherein the grouping the respective frequency points according to the measured line characteristics and the reliable common mode amplitude comprises the following substeps:

Dividing the maximum amplitude that the circuit under test can with the reliable common mode amplitude to obtain the number of frequency points of each group;

Calculate the number of frequency groups based on the number of frequency points to be measured and the number of frequency points in each group.

5. The method according to claim 2, wherein the calculating the longitudinal balance of each frequency point in each group in units of groups comprises the following sub-steps:

Combining the respective frequency points in the group to be tested according to the grouping order to generate a modulation signal of the excitation signal source;

Transmitting a modulated signal from the excitation signal source to the test line; By sampling the signal on the test line and performing fast Fourier transform on the sampled data, the frequency domain differential amplitude corresponding to each frequency point in the group is obtained;

Calculating whether the longitudinal direction of each frequency point in the group is still untested according to the frequency domain differential amplitude corresponding to each frequency point in the group, and if so, according to the grouping order, each of the groups to be tested The frequency points are combined to generate a modulated signal of the excitation signal source, and the subsequent steps are performed; otherwise, the test result is reported.

6. The method according to claim 2, wherein the frequency to be sought ranges from 0 to 2·2.

7. The method according to claim 2, wherein each frequency point to be tested is determined by the following formula:

= (43 \2.5i)Hz · · ·· ·· (i = 6,7,8... 511,512)

8. The method according to claim 2, wherein the noise difference mode amplitude of each frequency point in the measured line is obtained according to a spectral density of the noise power.

The method according to any one of claims 1 to 8, wherein the line to be tested is a digital subscriber loop xDSL line.

10. A device for testing the longitudinal balance of a line, comprising:

a frequency generating module, configured to combine the frequency points to be sent to generate a modulated signal of the excitation signal source, and send the modulated signal to the line to be tested;

a longitudinal balance calculation module, configured to calculate a longitudinal balance degree of each corresponding frequency point according to a modulation signal on the tested line;

The device further includes:

a reliable amplitude determining module for determining a reliable common mode amplitude of each frequency point;

The grouping module is configured to group each frequency point according to the measured common line amplitude of the measured line characteristic and the reliable amplitude determining module output, and output to the frequency generating module one by one in units of groups.