CN100454939C - A method and device for testing the longitudinal balance of a line - Google Patents

Abstract

The invention discloses a method and device for testing the longitudinal balance degree of a line, which is used to solve the problem of long test time in the prior art 1, and solve the problem in the prior art 2 that non-line imbalance factors have a great influence on the test result . The method of the present invention includes: A, determining the reliable common-mode amplitude of each frequency point to be tested; B, grouping each frequency point according to the characteristics of the tested line and the reliable common-mode amplitude; C, taking the group as a unit, The longitudinal balance of each frequency point in each group is calculated separately. The implementation of the invention not only shortens the test time, but also accurately reflects the actual balance status of the line.

Description

A kind of method of testing longitudinal balance degree of link and device

Technical field

The present invention relates to field of telecommunication networks, particularly relate to a kind of method and device of testing longitudinal balance degree of link.

Background technology

In the telecommunication service field, operator is by local cable (normally twisted-pair feeder), provide broad band telecommunication service and arrowband telecommunication service simultaneously to the user, professional as ADSL over POTS (plain old telephone increase ADSL), ADSL over ISDN (ISDN establishes ADSL newly), VDSL over POTS (plain old telephone increase VDSL), VDSL over ISDN (ISDN establishes VDSL newly) etc., it is quite general that such is applied in home and overseas.(ADSL, VDSL being referred to as xDSL herein)

As shown in Figure 1, xDSL signal and POTS/ISDN signal coexistence are in a user outline, in the local side side, separator (SPL) in the broadband access equipment (DSLAM) comes wide, narrow traffic differentiation, be sent to broadband services plate (xDSL business board) respectively and narrowband service board (POTS/ISDN business board) is handled, and distolateral the user, separator (SPL) then is sent to user side RTU and phone with isolated wide, narrow band service.

In the operation and maintenance process of this type of business, if there is the user to declare fault, then often need measure (as: line voltage distribution parameter, line resistance parameter, line capacitance parameter, line frequency response, circuit background noise, the line-to-ground degree of balance etc.) to the subscriber's line parameter.According to these supplemental characteristics, can judge the quality and the failure condition of circuit.

In the maintenance process of this system, longitudinal balance degree is used for weighing circuit longitudinal balance performance, i.e. the uneven performance of line-to-ground.The circuit longitudinal balance degree is an important indicator weighing line quality when circuit is used for high speed data transfer, this mainly be because: the line-to-line that it is right that the line-to-ground imbalance may cause line exists potential to ground poor, and then in line-to-line formation electromotive force loop, produce loop current, thereby cause extra interference.Because the existence in electromotive force loop can form electromagnetic field around circuit, cause a large amount of external interference to be coupled in the circuit, influences proper communication.At present, stipulated to open the requirement of ADSL business in the national standard: for the ADSL business, in the 26kHz-1104kHz scope, longitudinal conversion loss is not less than 50dB, allows greater than 40dB under special circumstances.

Longitudinal balance degree Bm-1 is defined as:

Bm-1＝20lg(E1/Em) (dB)

Em is called lateral voltage in the formula, and referring to shown in Figure 2, promptly the electrical potential difference between circuit TIP and RING line terminals also claims the differential mode amplitude.E1 is called longitudinal voliage, cause by TIP, the unbalanced to ground of RING line end, E1 equal R1 left end potential to ground difference and R2 left end potential to ground difference vector and 1/2, also claim the common mode amplitude.

Referring to shown in Figure 2, the computing formula of longitudinal balance degree is in theory: $L_b=20\log \left(\frac{V_d}{V_c}\right)$

Generally speaking, need carry out the longitudinal balance degree test to each frequency of ADSL whole frequency, need be including but not limited to the longitudinal balance degree of each tone frequency.The frequency that promptly needs to measure longitudinal balance degree includes but not limited to the center frequency point of each tone.

Because the existence of noise and other logicalnot circuit unbalanced factors causes circuit V _cTest in fact might be much larger than the differential mode amplitude that causes owing to the circuit imbalance.If the differential mode amplitude that the circuit imbalance causes is V ' _c, the differential mode amplitude that logicalnot circuit unbalanced factor (as noise etc.) causes is V _n, then the longitudinal balance degree computing formula of actual track is: $L_b=20\log \left(\frac{V_d}{V_c^{\′}+V_n}\right).$ In actual track, can be similar to and think V _nInfluence fluctuates in a fixed interval to longitudinal balance degree.

Usually the hardware designs that adopts is to send out common-mode signal, error of measurement mould signal at present.Referring to shown in Figure 3, digital signal processing module DSP produces modulation signal and gives D/A, the D/A device sends on the practical differential circuit after being converted to the common mode analog signal, because the existence of circuit unbalanced factor, the differential lines virtual voltage is unequal, there is electrical potential difference, this differential signal becomes the standard deviation sub-signal through differential transformers, behind A/D device transform sampling, sampled data is handled to DSP again, DSP carries out the frequency domain differential demodulation amplitude that FFT (fast fourier transform) handled and calculated each corresponding frequency to the sampled data that receives, thereby realizes the calculating of longitudinal balance degree.

Based on the above-mentioned longitudinal balance degree theory of testing, and use above-mentioned testing hardware device, testing longitudinal balance degree of link has two kinds of schemes at present.

Existing scheme one: single-frequency point sends method one by one.Referring to shown in Figure 4, comprise following concrete steps:

The common mode amplitude of X11, transmission 1 single-frequency point is to differential line;

The data that signal on X12, the monitoring differential line and record monitor;

X13, calculate this single-frequency point frequency domain differential demodulation amplitude;

X14, calculate the longitudinal balance degree of this single-frequency point;

X15, judge whether all frequencies send,, then return step X11 if do not send; If send execution in step X16;

X16, drafting and reported result.

This technology is owing to adopt the mode that once only sends a frequency processing, the energy of tested frequency can be provided with bigger, have higher signal to noise ratio, noise resisting ability is more intense, makes the longitudinal balance degree that tests out can accurately reflect the real balance situation of circuit substantially.Referring to the longitudinal balance degree computing formula of above-mentioned actual track, this scheme can make common mode amplitude V ^dEnough big, the differential mode amplitude is similar to the differential mode amplitude V ' that the circuit imbalance causes _c, promptly this moment V _nLess to the line balance influence.But shortcoming also is conspicuous: because the method that adopts single-frequency point to send one by one, the entire process overlong time, can not fine satisfied test to " sensitivity " requirement of time.

Existing scheme two: all frequencies to be measured once send method.Referring to shown in Figure 5, comprise following concrete steps:

X21, all frequencies to be measured are generated the modulating wave common-mode signal;

X22, this modulation signal is sent on the circuit;

The data that signal on X23, the monitoring differential line and record monitor;

X24, calculate each frequency frequency domain differential demodulation amplitude;

X25, calculate the longitudinal balance degree degree of each frequency;

X26, drafting and reported result.

This scheme has the fast advantage of computational speed, but shortcoming is very obvious: the ability to cope with the exigency of considering hardware circuit, the energy sum of combinations of modulation ripple can not surpass the ability to cope with the exigency of hardware circuit, each energy demand that sends frequency reduces at double, because measurement circuit noise etc. influences the existence of longitudinal balance degree factor, make the signal to noise ratio of each frequency less, each frequency signal anti-noise ability is relatively poor, cause noise etc. bigger, make test result can't reflect the real balance situation of circuit really result's influence of longitudinal balance degree.Referring to the longitudinal balance degree computing formula of above-mentioned actual track, this scheme can make common mode amplitude V ^dEnough little, under the more satisfactory situation of line balance, the differential mode amplitude is similar to V _n, promptly this moment V _nLine balance is had the greatest impact.

Summary of the invention

The invention provides a kind of method and device of testing longitudinal balance degree of link, in order to long problem of solution one testing time of prior art, and the logicalnot circuit unbalanced factor influences bigger problem to test result in the solution prior art two.

The inventive method comprises: A, according to the longitudinal balance degree test result require and test line in the noise differential mode amplitude of each frequency determine the reliable common mode amplitude of each frequency to be measured; B, the maximum amplitude, frequency points to be measured and the described reliable common mode amplitude that can bear according to test line are divided into groups to each frequency; C, according to order of packets, each frequency in a group to be measured is merged the modulation signal that generates exciting signal source; The modulation signal that obtains exciting signal source is sent on the measurement circuit; By to the signal sampling on the measurement circuit, and sampled data carried out fast fourier transform, obtain the frequency domain differential demodulation amplitude of each frequency correspondence in this group; Calculate the longitudinal balance degree of each frequency in this group according to the frequency domain differential demodulation amplitude of each frequency correspondence in this group.

Also comprise before the wherein said steps A:

-waiting to ask definite each frequency to be measured in the frequency range;

The noise differential mode amplitude of each frequency in the-calculating test line;

-determine the requirement of longitudinal balance degree test result.

Further described steps A comprises: A1, according to the noise differential mode amplitude of each frequency in the test line, and the longitudinal balance degree test result requires to determine the amplitude of each frequency to be measured; The reliable common mode amplitude of A2, described each frequency is not less than the amplitude of arbitrary frequency.

Further described step B comprises: B1, maximum amplitude and described reliable common mode amplitude that test line be can bear are divided by, and obtain the quantity of every group of frequency; B2, according to the quantity of frequency quantity to be measured and every group of frequency, calculate frequency group number.

Further described step C comprises: judge whether to also have the not group of test, if having, then return step C; Otherwise, report test result.

Frequency range described to be asked is 0 to 2.2MHz.

Described each frequency to be measured is determined by following formula:

f _i=4312.5iHz, i=6 wherein, 7,8...511,512.

Obtain the noise differential mode amplitude of each frequency in the described test line according to the spectrum density of noise power.

Described test line is a DSL xDSL circuit.

In order to support the inventive method, the device of a kind of testing longitudinal balance degree of link of the present invention comprises:

The frequency generation module is used for frequency to be sent is merged the modulation signal that generates exciting signal source, and sends on the test line;

The longitudinal balance degree computing module, be used for according to the modulation signal on the test line, by to the signal sampling on the measurement circuit, and sampled data carried out fast fourier transform, obtain the frequency domain differential demodulation amplitude of each frequency correspondence in this group, thereby calculate the longitudinal balance degree of each frequency in this group;

Reliable amplitude determination module, the reliable common mode amplitude that is used for calculating the noise differential mode amplitude of each frequency of test line and determines each frequency;

Grouping module is used for according to the reliable common mode amplitude of test line characteristic and the output of reliable amplitude determination module each frequency being divided into groups, and is unit with the group, outputs to described frequency generation module one by one.

Beneficial effect of the present invention is as follows: the no longer direct common mode amplitude with single-frequency point of the inventive method sends on the differential line one by one tests, also no longer all frequencies to be measured are generated the modulating wave common-mode signal, and this modulation signal sent on the circuit test.

The inventive method has been considered the noise jamming of actual track, and according to the noise differential mode amplitude of each frequency to be measured, obtain the reliable common mode amplitude of each frequency to be measured, and then each frequency is divided into groups according to test line characteristic and described reliable common mode amplitude.Be unit at last with the group, calculate the longitudinal balance degree of each frequency in each group respectively.

Obviously with respect to prior art one, the inventive method is once sent a more than frequency to be measured, has reduced the transmission number of times, thereby has saved the testing time; And, also inherited the effect that prior art one can accurately reflect the real balance situation of circuit according to above-mentioned grouping strategy.

With respect to prior art two, the inventive method is once sent several but not every frequency to be measured.According to above-mentioned grouping strategy, make the energy of each frequency increase, but can satisfy line load, so can reach the effect of the real balance situation of accurate reflection circuit; And owing to adopt grouping strategy, so also inherited prior art two test speeds effect faster.

In order to support the inventive method, the present invention also provides a kind of device of testing longitudinal balance degree of link.

Description of drawings

Fig. 1 is the professional schematic diagram of xDSL;

Fig. 2 is the circuit theory diagrams of differential mode amplitude, common mode amplitude;

Fig. 3 is the hardware configuration schematic diagram of existing test longitudinal balance degree;

Fig. 4 sends the flow chart of steps of method one by one for existing single-frequency point;

Fig. 5 once sends the flow chart of steps of method for existing all frequencies to be measured;

Fig. 6 tests the hardware configuration schematic diagram of longitudinal balance degree for the present invention;

Fig. 7 is the inventive method flow chart of steps.

Embodiment

For when the longitudinal balance degree of measurement circuitry, can both guarantee test speed, guarantee test mass again, the invention provides a kind of device of testing longitudinal balance degree of link, be applied to adsl line, also can be applicable to other xDSL circuit.Referring to shown in Figure 6, it comprises: reliable amplitude determination module, grouping module, frequency generation module and the longitudinal balance degree computing module of Xiang Lianing successively.

Described reliable amplitude determination module is used for calculating the noise differential mode amplitude of each frequency of test line, and determines the reliable common mode amplitude of each frequency.

Described grouping module is used for according to the reliable common mode amplitude of test line characteristic and the output of reliable amplitude determination module each frequency being divided into groups, and is unit with the group, outputs to described frequency generation module one by one.

Described frequency generation module is used for frequency to be sent is merged the modulation signal that generates exciting signal source, and sends on the test line.

Described longitudinal balance degree computing module is used for according to the modulation signal on the test line, calculates the longitudinal balance degree of each corresponding frequency.

The function that said frequencies generation module and longitudinal balance degree computing module are had is identical with the function of existing longitudinal balance degree testing apparatus shown in Figure 3.

Use said apparatus, the invention provides a kind of method of testing longitudinal balance degree of link, referring to shown in Figure 7, the method example comprises following concrete steps:

S1, determine the requirement of longitudinal balance degree test result, and determine each frequency to be measured in the frequency range waiting to ask.

The longitudinal balance degree test result requires to be predefined for: noise power spectral density bigger (as-100dbm or-90dbm) time, the circuit longitudinal balance degree of testing after the noise effect is more than 60db.With noise power spectral density for-90dbm is an example.

For adsl line, frequency range to be asked is 0 to 2.2MHz, and other circuit is decided according to related protocol.

Generally speaking, need carry out the longitudinal balance degree test to each frequency of ADSL whole frequency, need be including but not limited to the longitudinal balance degree of each tone frequency.The frequency that promptly needs to measure longitudinal balance degree includes but not limited to the center frequency point of each tone.If only calculate the center frequency point of each tone, then need to measure, the frequency of longitudinal balance degree is f _i=(4312.5i) Hz ... (i=6,7,8 ... 511,512).

The noise differential mode amplitude of each frequency in S2, the calculating test line.

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

${\mathrm{\ρ}}_{\mathrm{Tone}}=\frac{1}{\mathrm{BW}}{\∫}_0^{\mathrm{BW}}{\mathrm{\ρ}}_f{d}_f\≅\frac{1}{\mathrm{BW}}\underset{k=1}{\overset{m}{\mathrm{\Σ}}}\frac{4{\left|V_k\right|}^2}{{\mathrm{Nf}}_s{Z}_f}\mathrm{\Δf}=\frac{1}{\mathrm{BW}}\underset{k=1}{\overset{m}{\mathrm{\Σ}}}\frac{4{\left|V_k\right|}^2}{{\mathrm{Nf}}_s{Z}_f}\frac{f_s}{N}=\frac{1}{\mathrm{BW}}\underset{k=1}{\overset{m}{\mathrm{\Σ}}}\frac{4{\left|V_k\right|}^2}{N^2{Z}_f}$

V wherein _kFor waiting that asking the pairing frequency domain energy of frequency, N is that Z is counted in FFT calculating _fBy being asked the impedance of frequency characteristic of correspondence on the transmission line, BW is the width of tone, f _sBe sample frequency.

M in the following formula is defined as:

$\left\{\begin{array}{c}m=\mathrm{int}\left(\frac{\mathrm{BW}}{\mathrm{\Δf}}\right)=\mathrm{int}\left(\frac{\mathrm{BW}}{f_s}N\right)\\ \mathrm{BW}=4.3125\mathrm{KHz}\end{array}\right.$ , int represents to round downwards.

Wherein: establish FFT points N=16K, Z _f=100 ohm, actual measurement noise power spectral density maximum-90dbm (given in step S1).

Be 10log (ρ _Tone)+30=-90; ρ then _Tone=10 ^-12

Being located at frequency f place noise differential mode amplitude is V _f, m=6, then:

${\mathrm{\ρ}}_{\mathrm{Tone}}=\frac{1}{\mathrm{BW}}\underset{k=1}{\overset{m}{\mathrm{\Σ}}}\frac{4{\left|V_k\right|}^2}{N^2{Z}_f}=\frac{1}{\mathrm{BW}}\frac{{\left|V_f\right|}^2*6}{Z_f}={10}^{-12}$

And then can calculate: | V _f|=2.68*10 ^-4(V), promptly the differential mode amplitude that causes of noise is 2.68*10 ^-4(V).

S3, determine the reliable common mode amplitude of each frequency to be measured.

According to designing requirement: order $L_b=20\log \left(\frac{V_d}{V_f}\right)=60$ (given in step S1), as can be known:

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

According to above-mentioned formula, calculate the amplitude of other frequency more respectively.

The present invention considers the influence that noise is measured the circuit longitudinal balance degree, if will make circuit noise under the situation of-90dbm, circuit has good longitudinal balance degree, and then the reliable common mode amplitude of Que Dinging should be less than the amplitude of arbitrary frequency.Suppose that reliable common mode amplitude is 300MV (in actual treatment, sends the needed reliable common mode amplitude of each frequency and not necessarily equate, that is to say that reliable common mode amplitude can satisfy the amplitude that is not less than arbitrary frequency but need only for a plurality of).

S4, each frequency is divided into groups.

The maximum voltage amplitude of supposing signal on the synchronization circuit of single plate hardware performance decision can not surpass 3V, and according to the reliable common mode amplitude that step S3 tries to achieve be 300MV as can be known:

The maximum transmission of synchronization frequency number is 3V/300MV=10, and promptly every group of transmission frequency points mostly is 10 most.Succinct for this example, setting each frequency points that sends is 10 (also can unequal dividing into groups).

According to formula f _i=(4312.5i) Hz ... (i=6,7,8 ... 511,512) frequency points to be measured as can be known is 512-6+1, and in conjunction with 10 frequencies of each transmission of setting, then transmission group number is (512-6+1)/10=51 group.

S5, be unit, calculate the longitudinal balance degree of each frequency in each group respectively with the group.

By aforementioned calculation as can be known, it is 300MV that frequency to be measured sends amplitude, and every group sends 10 frequencies, send altogether 51 times.With respect to prior art one, send number of times and be kept to 51 times from 507 times, obviously saved the testing time; With respect to prior art two, the transmission amplitude of frequency to be measured is increased to 300MV, can satisfy test request.

Afterwards, according to order of packets, each frequency in a group to be measured is merged the modulation signal that generates exciting signal source, and send on the measurement circuit.For the every group of frequency that sends to circuit, DSP samples to the time-domain information on the circuit, and calculates the frequency domain differential demodulation amplitude of each frequency correspondence in this group by methods such as FFT, is designated as V _Cf

Can calculate in this group each frequency according to formula gets longitudinal balance degree and is: $L_b=20\log \left(\frac{V_d}{V_f}\right)=20\log \left(\frac{300\mathrm{MV}}{V_{\mathrm{cf}}}\right)$

After testing one group of frequency, judge whether to also have the not group of test,, next group frequency is merged the modulation signal that generates exciting signal source, and send to and finish test on the measurement circuit if having; Otherwise, report test result.

The inventive method is being passed through formula f _i=(4312.5i) Hz ... (i=6,7,8 ... 511,512) behind the frequency to be measured of Que Dinging, also can test the longitudinal balance degree of the frequency that is associated with described definite frequency to be measured earlier, utilize interpolation algorithm to calculate the longitudinal balance degree value of described definite frequency to be measured again.

Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.

Claims (10)

1, a kind of method of testing longitudinal balance degree of link is characterized in that, comprises the following steps:

A, according to the longitudinal balance degree test result require and test line in the noise differential mode amplitude of each frequency determine the reliable common mode amplitude of each frequency to be measured;

B, the maximum amplitude, frequency points to be measured and the described reliable common mode amplitude that can bear according to test line are divided into groups to each frequency;

C, according to order of packets, each frequency in a group to be measured is merged the modulation signal that generates exciting signal source; The modulation signal that obtains exciting signal source is sent on the measurement circuit; By to the signal sampling on the measurement circuit, and sampled data carried out fast fourier transform, obtain the frequency domain differential demodulation amplitude of each frequency correspondence in this group; Calculate the longitudinal balance degree of each frequency in this group according to the frequency domain differential demodulation amplitude of each frequency correspondence in this group.

2, the method for claim 1 is characterized in that, also comprises before the described steps A:

-waiting to ask definite each frequency to be measured in the frequency range;

The noise differential mode amplitude of each frequency in the-calculating test line;

-determine the requirement of longitudinal balance degree test result.

3, method as claimed in claim 2 is characterized in that, described steps A comprises:

A1, according to the noise differential mode amplitude of each frequency in the test line, and the longitudinal balance degree test result requires to determine the amplitude of each frequency to be measured;

The reliable common mode amplitude of A2, described each frequency is not less than the amplitude of arbitrary frequency.

4, method as claimed in claim 2 is characterized in that, described step B comprises:

B1, maximum amplitude and described reliable common mode amplitude that test line be can bear are divided by, and obtain the quantity of every group of frequency;

B2, according to the quantity of frequency quantity to be measured and every group of frequency, calculate frequency group number.

5, method as claimed in claim 2 is characterized in that, described step C also comprises:

Judge whether to also have the not group of test,, then return step C if having; Otherwise, report test result.

6, method as claimed in claim 2 is characterized in that, frequency range described to be asked is 0 to 2.2MHz.

7, method as claimed in claim 2 is characterized in that, described each frequency to be measured is determined by following formula:

f _i=4312.5iHz, i=6 wherein, 7,8...511,512.

8, method as claimed in claim 2 is characterized in that, obtains the noise differential mode amplitude of each frequency in the described test line according to the spectrum density of noise power.

As each described method of claim 1 to 8, it is characterized in that 9, described test line is a DSL xDSL circuit.

10, a kind of device of testing longitudinal balance degree of link comprises:

The frequency generation module is used for frequency to be sent is merged the modulation signal that generates exciting signal source, and sends on the test line;

The longitudinal balance degree computing module, be used for according to the modulation signal on the test line, by to the signal sampling on the measurement circuit, and sampled data carried out fast fourier transform, obtain the frequency domain differential demodulation amplitude of each frequency correspondence in this group, thereby calculate the longitudinal balance degree of each frequency in this group;

It is characterized in that described device also comprises:

Reliable amplitude determination module, the reliable common mode amplitude that is used for calculating the noise differential mode amplitude of each frequency of test line and determines each frequency;

Grouping module is used for according to the reliable common mode amplitude of test line characteristic and the output of reliable amplitude determination module each frequency being divided into groups, and is unit with the group, outputs to described frequency generation module one by one.

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