CN104660304A - User side-based coaxial network link quality detection method - Google Patents

Abstract

The invention provides a user side-based coaxial network link quality detection method which comprises the following steps: initiating time domain reflection test at a coaxial access user side; receiving time domain reflection signals at the coaxial access user side; testing the coaxial cables of the coaxial network one by one from the coaxial access user side to a coaxial access head side according to the received time domain reflection signals of corresponding coaxial cables so as to judge whether faults occur; when testing that one coaxial cable does not have fault and judging that the coaxial cable is connected with a branch/distributor, analyzing the impedance matching condition of the branch/distributor and the connected coaxial cable according to the time domain reflection signal corresponding to the branch/distributor so as to determine the link quality. The method is initiated from user family side, so that the transmission quality of the coaxial cable and the branch/distributor in the coaxial network link can be rapidly checked, high convenience and correctness are provided, and the commercial additional values of the broadband and TV businesses are greatly increased at the same time.

Description

A kind of coaxial network link-quality detection method initiated based on user side

Technical field

The present invention relates to communication test technical field, particularly relate to a kind of method of testing of coaxial network link-quality.

Background technology

Along with Two-way Reconstruction in CATV Network and Chinese Next generation broadcasting network (Next Generation BroadcastingNetwork, that NGB) builds carries out, the transmission medium that coaxial network link is registered one's residence as cable network final stage, act as more and more important effect.The coaxial network of NGB not only carries One-to-All Broadcast television services, also by adopting ether data by co-axial cables transport (Ethernet over Coax, EOC) or C-DOCSIS broadband access technology carry two-way broadband business, therefore, higher requirement is proposed to the performance index and link-quality etc. of coaxial network.

Current network management system only manages the broadband access equipment that coaxial network is disposed, but lacks and monitor devices such as the coaxial cable in coaxial networking, branch/distributors.If break down in somewhere in coaxial network, often immediately can not be confirmed to be device fails or coaxial links breaks down, and, operation maintenance personnel is needed manually to locate to scene with professional test instrument, so not only increase equipment to install and O&M cost, and operating efficiency is not high, the time solving fault is long, thus have impact on the satisfaction of user.

The time-domain measurement technique of existing Time Domain Reflectometry test (TDR) is mainly used in measuring to assess line quality to single transmission medium (as twisted-pair feeder, coaxial cable), but lacks the coax network system link method of measurement to being made up of coaxial cable and branch/distributor.And existing EOC technology calculates each work frequency sub-band SNR value by EOC head end and terminal interoperability usually, carry out coaxial links quality evaluation, although this method energy assessing link quality, but cannot locate reliably link quality problems, such as cannot judge the problem of branch/distributor or coaxial cable or the reason of noise in coaxial links.

Summary of the invention

The shortcoming of prior art in view of the above, the object of the present invention is to provide a kind of coaxial network link-quality detection method initiated based on user side, cannot the problem of branch/distributor or coaxial cable signal transmission quality in detection and location coaxial links for solving prior art.

For achieving the above object and other relevant objects, the invention provides a kind of coaxial network link-quality detection method initiated based on user side, described coaxial network is connected between coaxial access head end and coaxial access user end, and described method comprises: initiate Time Domain Reflectometry test at described coaxial access user end; Otdr signal is received in described coaxial access user termination; According to the otdr signal of received corresponding coaxial cable, coaxial cable in described coaxial network is tested one by one to judge whether to break down from described coaxial access user end to coaxial access head end, and, in test to when wherein a coaxial cable does not break down and judges that described coaxial cable is connected with branch/distributor, analyze the impedance match situation of described branch/distributor and the tie point of the coaxial cable that is connected to determine link-quality according to the otdr signal of the described branch/distributor of correspondence.

Preferably, from described coaxial access user end, the waving map calculated signals formula of kth section coaxial cable initiating terminal is: wherein, the waving map calculated signals formula of the Time Domain Reflectometry test of the 1st section of coaxial cable initiating terminal from described coaxial access user end is: u _{in (0)}=∫ U _{in (0)}(f) × e ^{j2 π ft}df; Wherein, u _{in (0)}described coaxial cable waving map signal amplitude, U _{in (0)}f () is test signal amplitude, f is frequency test signal, and t is testing time point;

Wherein, according to the measuring range L between described coaxial access head end and coaxial access user end, selected test signal step frequency Δ f; Described Δ f meets wherein, v _coaxiallyfor the medium signal transmission speed of known described coaxial cable; According to presumptive test precision (Δ _precision) selected test signal cut-off frequency F _cut-off, satisfy condition:

Preferably, the otdr signal of described corresponding coaxial cable is that correspondence produced from impedance mismatch place each on described coaxial cable.

Preferably, if from described coaxial access user end kth bar coaxial cable, there is j at the impedance mismatch place on described kth bar coaxial cable, and kth bar coaxial cable described in cutting is j+1 section, and wherein, the impedance of jth section is designated as z _k,j; A jth otdr signal that impedance mismatch place produces feeds back to the computing formula of described kth bar coaxial cable initiating terminal:

$u_{\mathrm{ref}(j,0)}^k=\begin{array}{c}{\∫}^{{\mathrm{\Γ}}_{j,j+1}^k}\×(1-{\left({\mathrm{\Γ}}_{\mathrm{1,2}}^k\right)}^2)\×...\×(1-{\left({\mathrm{\Γ}}_{j-1,j}^k\right)}^2)\×\\ U_{\mathrm{in}\left(0\right)}^k\left(f\right)\×e^{j2\mathrm{\πft}}{e}^{-2\mathrm{\α}}(l_{k,1}+...+l_{k,j})\end{array}\mathrm{df};$ Wherein, l _k,jfor described jth section coaxial cable length; for reflection coefficient, computing formula is:

${\mathrm{\Γ}}_{j,j+1}^k=\frac{z_{k,j+1}-z_{k,j}}{z_{k,j+1}+z_{k,j}}.$

Preferably, the waving map signal of described kth bar coaxial cable time delay computing formula is:

The output signal of described kth bar coaxial cable computing formula is:

$u_{\mathrm{out}}^k=\∫\begin{array}{c}(1-{\mathrm{\Γ}}_{\mathrm{1,2}}^k)\×...\×(1-{\mathrm{\Γ}}_{n-1,n}^k)\×\\ U_{\mathrm{in}\left(0\right)}^k\left(f\right)\×e^{j2\mathrm{\πft}}\×e^{-\mathrm{\α}\left(l_{k,1+...+l_{k,n}}\right)}\end{array}\mathrm{df}$

Preferably, according to received otdr signal, test coaxial cable in described coaxial network from described coaxial access user end one by one to coaxial access head end and, to judge whether to break down, comprising: set described fault and comprise open circuit, short circuit; Computing formula according to otdr signal under described otdr signal computing formula acquisition open circuit situation: computing formula according to otdr signal under described otdr signal computing formula acquisition short circuit condition: $u_{\mathrm{ref}\left(\mathrm{1,0}\right)}^1=\∫(-1)\×U_{\mathrm{in}\left(0\right)}^1\left(f\right)\×e^{j2\mathrm{\πft}}\×e^{-2\mathrm{\α}{l}_{\mathrm{1,1}}}\mathrm{df},$ Wherein, α is the attenuation coefficient of signal at co-axial cables transport; Under otdr signal that comparison receives and described open circuit situation, otdr signal under otdr signal, short circuit condition, judges fault when comparison is consistent.

Preferably, the described coaxial cable of described judgement is connected with branch/distributor, comprising: in preset time period, receive plural reflected signal continuously, and reflected signal fluctuates within the specific limits, then judge to be connected with branch/distributor.

Preferably, if a kth branch/distributor comprises 1 input from described coaxial access user end, n output, n is natural number; Described Time Domain Reflectometry test selects an output input test signal at described branch/distributor, and the waving map calculated signals formula of selected output is: the waving map calculated signals formula of described input is:

$u_{\mathrm{in}\left({\mathrm{\Δ}}_k\right)}^{D.k}=\∫(1-{\mathrm{\Γ}}_{\mathrm{OUT}}^{D.k})\×U_{\mathrm{in}\left(0\right)}^{D.k}\left(f\right)\×e^{j2\mathrm{\πft}}\mathrm{df};$ Wherein, described branch/distributor waving map signal amplitude, be test signal amplitude, Δ k is the transmission range of output to input; Reflection coefficient computing formula: ${\mathrm{\Γ}}_{\mathrm{OIT}}^{D.k}=\frac{z_{D.k}-z_{k,n}}{z_{D.k}+z_{k,n}}.$

Preferably, the otdr signal of corresponding described branch/distributor is corresponding described branch/distributor does not mate place with the tie point middle impedance of institute connecting coaxial cable.

Preferably, analyze the impedance match situation of described branch/distributor and the tie point of the coaxial cable that is connected, refer to: if there is the impedance mismatch of the output of input waving map signal at a kth branch/distributor, then corresponding otdr signal computing formula is: $u_{\mathrm{ref}(\mathrm{out},0)}^{D.k}=\∫{\mathrm{\Γ}}_{\mathrm{OUT}}^{D.k}\×U_{\mathrm{in}\left(0\right)}^{D.k}\left(f\right)\×e^{j2\mathrm{\πft}}\mathrm{df};$ Wherein, reflection coefficient ${\mathrm{\Γ}}_{\mathrm{OUT}}^{D.k}=\frac{z_{D.k}-z_{k,n}}{z_{D.k}+z_{k,n}};$ If the impedance mismatch of other outputs, then corresponding otdr signal computing formula is:

$u_{\mathrm{ref}({\mathrm{\Δ}}_k,0)}^{D.k}={\∫\mathrm{\λ}}_{D.k}\×{\mathrm{\Γ}}_{\mathrm{IN}}^{D.k}\×(1-{\left({\mathrm{\Γ}}_{\mathrm{OUT}}^{D.k}\right)}^2)\×U_{\mathrm{in}\left(0\right)}^{D.k}\left(f\right)\×e^{j2\mathrm{\πft}}\mathrm{df}.$

Preferably, the waving map signal of a described kth branch/distributor time delay computing formula is:

Wherein, v _{branch distributor}for the signal velocity in known branches/distributor;

If the impedance mismatch of a kth branch/distributor input, then its reflected signal computing formula:

$u_{\mathrm{ref}\left({\mathrm{\Δ}}_k\right)}^{D.k}=\∫{\mathrm{\Γ}}_{\mathrm{IN}}^{D.k}\×(1-{\mathrm{\Γ}}_{\mathrm{OUT}}^{D.k})\×U_{\mathrm{in}\left(0\right)}^{D.k}\left(f\right)\×e^{j2\mathrm{\πft}}\mathrm{df}$

Wherein, reflection coefficient calculates formula:

Preferably, the input calculating branch/distributor in link and output end signal reflection loss is also comprised.

Preferably, described coaxial network is passive network.

As mentioned above, the coaxial network link-quality detection method initiated based on user side provided by the invention, described method is by initiating Time Domain Reflectometry test at coaxial access user end, otdr signal is received in described coaxial access user termination, according to the otdr signal of received corresponding coaxial cable, coaxial cable in described coaxial network is tested one by one to judge whether to break down from described coaxial access user end to coaxial access head end, and, in test to when wherein a coaxial cable does not break down and judges that described coaxial cable is connected with branch/distributor, the impedance match situation of described branch/distributor and the tie point of the coaxial cable that is connected is analyzed to determine link-quality according to the otdr signal of the described branch/distributor of correspondence, the method is initiated from subscriber household end, be convenient to the transmission quality investigating coaxial network link standard coaxial cable and branch/distributor fast, accurately convenient, greatly increase broadband simultaneously, television services business added value.

Accompanying drawing explanation

Fig. 1 is shown as the schematic flow sheet of an embodiment of the coaxial network link-quality detection method based on user side initiation of the present invention.

Fig. 2 is shown as coaxial network structural representation in the present invention.

Fig. 3 is shown as the coaxial cable otdr signal model schematic of the coaxial network link-quality detection method based on user side initiation of the present invention.

Fig. 4 is shown as the branch/distributor reflected signal model schematic of the coaxial network link-quality detection method based on user side initiation of the present invention.

Fig. 5 is shown as the another embodiment link structure schematic diagram of the coaxial network link-quality detection method based on user side initiation of the present invention

Element numbers explanation

S1 ~ S3 step

Embodiment

Below by way of specific instantiation, embodiments of the present invention are described, those skilled in the art the content disclosed by this specification can understand other advantages of the present invention and effect easily.The present invention can also be implemented or be applied by embodiments different in addition, and the every details in this specification also can based on different viewpoints and application, carries out various modification or change not deviating under spirit of the present invention.

Refer to Fig. 1, the invention provides a kind of coaxial network link-quality detection method initiated based on user side, described coaxial network is connected between coaxial access head end and coaxial access user end, and described method comprises:

Step S1: initiate Time Domain Reflectometry test at described coaxial access user end;

Step S2: receive otdr signal in described coaxial access user termination;

Step S3: according to the otdr signal of received corresponding coaxial cable, coaxial cable in described coaxial network is tested one by one to judge whether to break down from described coaxial access user end to coaxial access head end, and, in test to when wherein a coaxial cable does not break down and judges that described coaxial cable is connected with branch/distributor (i.e. splitter or distributor), analyze the impedance match situation of described branch/distributor and the tie point of the coaxial cable that is connected to determine link-quality according to the otdr signal of the described branch/distributor of correspondence.

As shown in Figure 2, described coaxial network be passive can as the connected mode of Fig. 2, under regular situation, described network can be cable TV network, and cable TV signal is exactly deliver to coaxial access user end from coaxial access head end; And the present invention initiates Time Domain Reflectometry test at coaxial access user end, sense is contrary; In the present embodiment, described coaxial network is coax network, is Passive Coax network.Certainly also can be active network in other embodiments, is not restriction with the present embodiment.

It should be noted that, thought principle of the present invention is: when coaxial network link somewhere exists impedance mismatch, when coaxial user terminal transmits, corresponding signal will be reflected back, analyzed from upper joint, by analyzing the time delay of the strong and weak incoming signal relative to polarity and reflected signal of the signal be reflected back, just can position and analysis the place of impedance mismatch.Produce the reason of impedance mismatch, one side is the fluctuation of coaxial cable and the impedance of branch/distributor existing for manufacturing process itself, and being because their oxidations are impaired, loose contact produces on the one hand, is exactly that link existence is opened a way, the situation of short circuit in addition.Therefore, coaxial links analysis algorithm should be able to distinguish coaxial cable and branch's distribution impedance fluctuations phenomenon under normal circumstances, and there is the difference between failure condition.Following factor is considered: the normal impedance fluctuation that A. coaxial cable produces due to manufacturing process can be ignored when designing coaxial links analysis algorithm; The link circuit condition of coaxial cable considers emphatically the situation of its broken string, short circuit; B. branch/distributor is due to reasons such as its distinctive project organization, manufacturing process, can produce the phenomenon of impedance fluctuations within short especially time.There is situation and orientation in what can judge branch/distributor by this feature; C. because signal can produce decay in co-axial cables transport, reflected signal can produce decay through branch/distributor especially, therefore for the reflected signal through one or more branch/distributors, should take into full account the decay of its signal.

Therefore, since Time Domain Reflectometry test (TDR) will be done, so first signal Modling model is carried out to coaxial cable, branch/distributor.

As shown in Figure 3, the otdr signal model of display coaxial network kth bar coaxial cable, coaxial cable characteristic impedance conventional is at present generally definite value, but due to reasons such as manufacturing process, there is certain fluctuation, if fluctuation not quite can be thought a normal scope, if certain existing problems in coaxial cable, just create the problem of impedance mismatch, suppose that coaxial cable somewhere there occurs the problem of impedance mismatch, its distribution of impedance as shown in the figure.

Therefore preferred, from described coaxial access user end, the waving map calculated signals formula of kth section coaxial cable initiating terminal is: wherein, the waving map calculated signals formula of the Time Domain Reflectometry test of the 1st section of coaxial cable initiating terminal from described coaxial access user end is: u _{in (0)}=∫ U _{in (0)}(f) × e ^{j2 π ft}df; Wherein, u _{in (0)}described coaxial cable waving map signal amplitude, U _{in (0)}f () is test signal amplitude, f is frequency test signal, and t is testing time point;

Wherein, according to the measuring range L between described coaxial access head end and subscriber signal receiving terminal, selected test signal step frequency Δ f; Described Δ f meets wherein, v _coaxiallyfor the medium signal transmission speed of known described coaxial cable; According to presumptive test precision (Δ _precision) selected test signal cut-off frequency F _cut-off, satisfy condition:

Preferably, the otdr signal of described corresponding coaxial cable is that correspondence produced from impedance mismatch place each on described coaxial cable.

Preferably, if from described coaxial access user end kth bar coaxial cable, there is j at the impedance mismatch place on described kth bar coaxial cable, and kth bar coaxial cable described in cutting is j+1 section, and wherein, the impedance of jth section is designated as z _k,j; A jth otdr signal that impedance mismatch place produces feeds back to the computing formula of described kth bar coaxial cable initiating terminal:

$u_{\mathrm{ref}(j,0)}^k=\∫\begin{array}{c}{\mathrm{\Γ}}_{j,j+1}^k\×(1-{\left({\mathrm{\Γ}}_{\mathrm{1,2}}^k\right)}^2)\×...\×(1-{\left({\mathrm{\Γ}}_{j-1,j}^k\right)}^2)\×\\ U_{\mathrm{in}\left(0\right)}^k\left(f\right)\×e^{j2\mathrm{\πft}}\×e^{-2\mathrm{\α}(l_{k,1}+...+l_{k,j})}\end{array}\mathrm{df};$ Wherein, l _k,jfor described jth section coaxial cable length; for reflection coefficient, computing formula is:

${\mathrm{\Γ}}_{j,j+1}^k=\frac{z_{k,j+1}-z_{k,j}}{z_{k,j+1}+z_{k,j}}.$

Preferably, the waving map signal of described kth bar coaxial cable time delay computing formula is:

The output signal of described kth bar coaxial cable computing formula is:

$u_{\mathrm{out}}^k=\∫\begin{array}{c}(1-{\mathrm{\Γ}}_{\mathrm{1,2}}^k)\×...\×(1-{\mathrm{\Γ}}_{n-1,n}^k)\×\\ U_{\mathrm{in}\left(0\right)}^k\left(f\right)\×e^{j2\mathrm{\πft}}\×e^{-\mathrm{\α}\left(l_{k1,+...+l_{k,n}}\right)}\end{array}\mathrm{df}$

Preferably, according to received otdr signal, test coaxial cable in described coaxial network from described coaxial access user end one by one to coaxial access head end and, to judge whether to break down, comprising: set described fault and comprise open circuit, short circuit; Computing formula according to otdr signal under described otdr signal computing formula acquisition open circuit situation: computing formula according to otdr signal under described otdr signal computing formula acquisition short circuit condition: $u_{\mathrm{ref}\left(\mathrm{1,0}\right)}^1=f(-1)\×U_{\mathrm{in}\left(0\right)}^1\left(f\right)\×e^{j2\mathrm{\πft}}\×e^{-2\mathrm{\α}{l}_{\mathrm{1,1}}}\mathrm{df},$ Wherein, α is the attenuation coefficient of signal at co-axial cables transport; Otdr signal under otdr signal, short circuit condition under otdr signal that comparison receives and described open circuit situation, judges fault (open circuit or short circuit) when comparison is consistent.

One of main points of the present invention are to increase the transmission quality analysis to branch/distributor in link, therefore, following determining step can be done: the described coaxial cable of described judgement is connected with branch/distributor, comprise: in preset time period, receive plural reflected signal continuously, and reflected signal fluctuates within the specific limits, then judge to be connected with branch/distributor.

As shown in Figure 4, because need the transmission quality analysis to branch/distributor, therefore need give signal modeling equally: branch/distributor has 1 IN input port, 1 to multiple OUT delivery outlet.

Preferably, if a kth branch/distributor comprises 1 input from described user's receiving terminal, n output; Described Time Domain Reflectometry test selects an output input test signal at described branch/distributor, and the waving map calculated signals formula of selected output is: the waving map calculated signals formula of described input is:

$u_{\mathrm{in}\left({\mathrm{\Δ}}_k\right)}^{D.k}=\∫(1-{\mathrm{\Γ}}_{\mathrm{OUT}}^{D.k})\×U_{\mathrm{in}\left(0\right)}^{D.k}\left(f\right)\×e^{j2\mathrm{\πft}}\mathrm{df};$ Wherein, described branch/distributor waving map signal amplitude, test signal amplitude, for output is to the transmission range of input; Reflection coefficient computing formula: ${\mathrm{\Γ}}_{\mathrm{OUT}}^{D.k}=\frac{z_{D.k}-z_{k,n}}{z_{D.k}-z_{k,n}}.$

Preferably, the otdr signal of corresponding described branch/distributor is corresponding described branch/distributor does not mate place with the tie point middle impedance of institute connecting coaxial cable.

Preferably, analyze the impedance match situation of described branch/distributor and the tie point of the coaxial cable that is connected, refer to: if there is the impedance mismatch of the output of input waving map signal at a kth branch/distributor, then corresponding otdr signal computing formula is: wherein, reflection coefficient if the impedance mismatch of other outputs, then corresponding otdr signal computing formula is:

$u_{\mathrm{ref}({\mathrm{\Δ}}_k,0)}^{D.k}={\∫\mathrm{\λ}}_{D.k}\×{\mathrm{\Γ}}_{\mathrm{IN}}^{D.k}\×(1-{\left({\mathrm{\Γ}}_{\mathrm{OUT}}^{D.k}\right)}^2)\×U_{\mathrm{in}\left(0\right)}^{D.k}\left(f\right)\×e^{j2\mathrm{\πft}}\mathrm{dt}.$

Preferably, the waving map signal of a described kth branch/distributor time delay computing formula is:

Wherein, v _{branch distributor}for the signal velocity in known branches/distributor;

If the impedance mismatch of a kth branch/distributor input, then its reflected signal computing formula:

$u_{\mathrm{ref}\left({\mathrm{\Δ}}_k\right)}^{D.k}={\∫\mathrm{\Γ}}_{\mathrm{IN}}^{D.k}\×(1-{\mathrm{\Γ}}_{\mathrm{OUT}}^{D.k})\×U_{\mathrm{in}\left(0\right)}^{D.k}\left(f\right)\×e^{j2\mathrm{\πft}}\mathrm{dt}$

Wherein, reflection coefficient calculates formula:

Preferably, the input calculating branch/distributor in link and output end signal reflection loss is also comprised.

Preferably, described coaxial network is passive network.

Comprehensive above-mentioned principle, concrete testing procedure is as follows:

(1) by carrying out the input of TDR Test signal in fc-specific test FC frequency range: u _{in (0)}=∫ U _{in (0)}(f) × e ^{j2 π ft}df;

Wherein, according to access head end coaxial in coaxial network to be measured and the measuring range (L) coaxially accessed terminal, selected step frequency Δ f:

cut-off frequency F _cut-offaccording to measuring accuracy (Δ _precision) select to determine:

(2) reflected signal received is gathered, if signal is respectively uref (1,0), uref (2,0) ..., uref (k, 0) ..., uref (n, 0), they and input signal u _{in (0)}time delay be respectively: t _{ref (1,0)}, tref (2,0) ..., tref (k, 0) ... .tref (n, 0)

(3) analyze the link circuit condition of the 1st bar of coaxial cable, and differentiate whether there is branch/distributor:

(4) judge whether according to the otdr signal model of coaxial network coaxial cable the situation that there is open circuit and short circuit, the signal being reflected back test point under open circuit with short circuit condition is respectively:

$u_{\mathrm{ref}\left(\mathrm{1,0}\right)}^1={\∫U}_{\mathrm{in}\left(0\right)}^1\left(f\right)\×e^{j2\mathrm{\πft}}\×e^{-2{\mathrm{\αl}}_{\mathrm{1,1}}}\mathrm{dt}$

$u_{\mathrm{ref}\left(\mathrm{1,0}\right)}^1=\∫(-1)\×U_{\mathrm{in}\left(0\right)}^{\left(1\right)}\left(f\right)\×e^{j2\mathrm{\πft}}\×e^{-2{\mathrm{\αl}}_{\mathrm{1,1}}}\mathrm{df}$

Wherein, α is the attenuation coefficient of signal at co-axial cables transport.

In conjunction with these two formula, the reflected signal situation according to receiving judges.

(5) if the 1st bar of coaxial cable does not exist the problem of opening a way with short circuit, then judge its branch's distribution condition connected: if (be generally the extremely short time at described Preset Time, as 3ns ~ 5ns) in receive two or more reflected signal continuously, and reflected signal fluctuates within the specific limits, then judge that it is connected with branch/distributor; According to the model of coaxial network branch/distributor, in conjunction with the continuous signal received, analyze the situation of impedance fluctuations.

(6) according to the otdr signal model of coaxial cable and branch/distributor, in conjunction with the reflected signal obtained, analyze the impedance match situation of kth end coaxial cable and branch/distributor, to judge coaxial links quality, until analyze the whole piece link that namely last reflected signal has analyzed the user input connection initiating test.

As shown in Figure 5, calculation specifications are carried out with a specific embodiment more below:

Carry out link-quality assessment to the coaxial network that distance range between coaxial access head end with coaxial access user end is 100 meters, certainty of measurement is 0.5 meter.For cable television system physical-foaming polythene insulation coaxial cable, it is to the propagation velocity v of signal _{coaxial ≈}0.66 × 3 × 10 ⁸=1.98 × 10 ⁸m/s, then select step frequency Δ f to be 950KHZ, select cut-off frequency F _{only carry}for 100MHZ, coaxial network is as shown in the figure initiated to carry out link-quality assessment test from terminal.

Amplitude is adopted to be that the incoming signal of 20mV sends test massage in the t0=0 moment:

By sampling analysis, the larger otdr signal obtained is as shown in the table:

Time point

Time (ns)

Otdr signal

t1	15ns	∫ 2.12×e j2πftdt
			t2	19ns	∫ (-1.81)×e j2πftdt
t3	110ns	∫ 8.12×e j2πftdf

By calculating, just can analyze and obtaining: the 1st article of coaxial length is 14.8m; Article 2, coaxial line length 9.39m; Open circuit is produced at the 2nd article of coaxial line end; Be connected with 2 branch/distributors between two sections of coaxial lines, circuit access diagram OUT end reflection loss be about-20.8dB.

In sum, the coaxial network link-quality detection method initiated based on user side provided by the invention, described method is by initiating Time Domain Reflectometry test at coaxial access user end, otdr signal is received in described coaxial access user termination, according to the otdr signal of received corresponding coaxial cable, coaxial cable in described coaxial network is tested one by one to judge whether to break down from described coaxial access user end to coaxial access head end, and, in test to when wherein a coaxial cable does not break down and judges that described coaxial cable is connected with branch/distributor, the impedance match situation of described branch/distributor and the tie point of the coaxial cable that is connected is analyzed to determine link-quality according to the otdr signal of the described branch/distributor of correspondence, the method is initiated from subscriber household end, be convenient to the transmission quality investigating coaxial network link standard coaxial cable and branch/distributor fast, accurately convenient, greatly increase broadband simultaneously, television services business added value.

Specifically, be exactly based on TDR measuring technique, detectable signal is initiated from the user side of coaxial network link, then receive reflected signal to analyze, according to based on the otdr signal model of coaxial links and coaxial links analysis algorithm, obtain the coaxial links quality from coaxial access user end to head end, comprise in assessment coaxial network link whether there is branch/distributor, branch/distributor reflection loss situation, and whether there are open circuit, open circuit etc.Owing to being initiatively initiate to carry out link-quality detection from user side, so apply when this method is highly suitable for EoC, C-DOCSIS user opening link: by the O&M engineer of operator when on-siteing install, the wired coaxial links quality between EoC, C-DOCSIS headend is arrived in quick inspection user family, to fix a breakdown hidden danger, improve user and take up rate.

Above-described embodiment is illustrative principle of the present invention and effect thereof only, but not for limiting the present invention.Any person skilled in the art scholar all without prejudice under spirit of the present invention and category, can modify above-described embodiment or changes.Therefore, such as have in art usually know the knowledgeable do not depart from complete under disclosed spirit and technological thought all equivalence modify or change, must be contained by claim of the present invention.

Claims (13)

1., based on the coaxial network link-quality detection method that user side is initiated, described coaxial network is connected between coaxial access head end and coaxial access user end, and it is characterized in that, described method comprises:

Time Domain Reflectometry test is initiated at described coaxial access user end;

Otdr signal is received in described coaxial access user termination;

According to the otdr signal of received corresponding coaxial cable, coaxial cable in described coaxial network is tested one by one to judge whether to break down from described coaxial access user end to coaxial access head end, and, in test to when wherein a coaxial cable does not break down and judges that described coaxial cable is connected with branch/distributor, analyze the impedance match situation of described branch/distributor and the tie point of the coaxial cable that is connected to determine link-quality according to the otdr signal of the described branch/distributor of correspondence.

2. the coaxial network link-quality detection method initiated based on user side according to claim 1, it is characterized in that, from described coaxial access user end, the waving map calculated signals formula of kth section coaxial cable initiating terminal is:

Wherein, the waving map calculated signals formula of the Time Domain Reflectometry test of the 1st section of coaxial cable initiating terminal from described coaxial access user end is: u _{in (0)}=∫ U _{in (0)}(f) × e ^{j2 π ft}df; Wherein, u _{in (0)}described coaxial cable waving map signal amplitude, U _{in (0)}f () is test signal amplitude, f is frequency test signal, and t is testing time point;

Wherein, according to the measuring range L between described coaxial access head end and coaxial access user end, selected test signal step frequency Δ f; Described Δ f meets wherein, v _coaxiallyfor the medium signal transmission speed of known described coaxial cable; According to presumptive test precision (Δ _precision) selected test signal cut-off frequency F _cut-off, satisfy condition:

3. the coaxial network link-quality detection method initiated based on user side according to claim 2, is characterized in that, the otdr signal of described corresponding coaxial cable, is that correspondence produced from impedance mismatch place each on described coaxial cable.

4. the coaxial network link-quality detection method initiated based on user side according to claim 3, it is characterized in that, if kth bar coaxial cable from described coaxial access user end, impedance mismatch place on described kth bar coaxial cable has j, and kth bar coaxial cable described in cutting is j+1 section, wherein, the impedance of jth section is designated as z _k,j;

A jth otdr signal that impedance mismatch place produces feeds back to the computing formula of described kth bar coaxial cable initiating terminal:

Wherein, l _k,jfor described jth section coaxial cable length; for reflection coefficient, computing formula is:

。

5. the coaxial network link-quality detection method initiated based on user side according to claim 3, is characterized in that, the waving map signal of described kth bar coaxial cable time delay computing formula is:

The output signal of described kth bar coaxial cable computing formula is:

。

6. the coaxial network link-quality detection method initiated based on user side according to claim 3, it is characterized in that, according to received otdr signal, test coaxial cable in described coaxial network from described coaxial access user end one by one to coaxial access head end, to judge whether to break down, to comprise:

Set described fault and comprise open circuit, short circuit;

Computing formula according to otdr signal under described otdr signal computing formula acquisition open circuit situation:

Computing formula according to otdr signal under described otdr signal computing formula acquisition short circuit condition: wherein, α is the attenuation coefficient of signal at co-axial cables transport;

Under otdr signal that comparison receives and described open circuit situation, otdr signal under otdr signal, short circuit condition, judges fault when comparison is consistent.

7. the coaxial network link-quality detection method initiated based on user side according to claim 1, it is characterized in that, the described coaxial cable of described judgement is connected with branch/distributor, comprising:

In preset time period, receive plural reflected signal continuously, and reflected signal fluctuates within the specific limits, then judge to be connected with branch/distributor.

8. the coaxial network link-quality detection method initiated based on user side according to claim 1 or 7, is characterized in that, if a kth branch/distributor comprises 1 input from described user's receiving terminal, and n output, n is natural number; The test of described Time Domain Reflectometry selects an output input test signal at described branch/distributor, selected output time

Domain test calculated signals formula is: the waving map calculated signals formula of described input is:

Wherein, described branch/distributor waving map signal amplitude, test signal amplitude, Δ _kfor output is to the transmission range of input; Reflection coefficient computing formula:

9. the coaxial network link-quality detection method initiated based on user side according to claim 8, it is characterized in that, the otdr signal of corresponding described branch/distributor is corresponding described branch/distributor does not mate place with the tie point middle impedance of institute connecting coaxial cable.

10. the coaxial network link-quality detection method initiated based on user side according to claim 9, is characterized in that, analyze described branch/distributor and the impedance match situation of the tie point of the coaxial cable that is connected, refer to:

If there is the impedance mismatch of the output of input waving map signal at a kth branch/distributor, then corresponding otdr signal computing formula is:

Wherein, reflection coefficient

If the impedance mismatch of other outputs, then corresponding otdr signal computing formula is:

The 11. coaxial network link-quality detection methods initiated based on user side according to claim 10, is characterized in that, the waving map signal of a described kth branch/distributor time delay computing formula is:

V _{branch/distributor}for the signal velocity in known branches/distributor;

If the impedance mismatch of a kth branch/distributor input, then its reflected signal computing formula:

Wherein, reflection coefficient calculates formula:

。

The 12. coaxial network link-quality detection methods initiated based on user side according to claim 8, is characterized in that, also comprise the input and output end signal reflection loss that calculate branch/distributor in link.

The 13. coaxial network link-quality detection methods initiated based on user side according to claim 1, it is characterized in that, described coaxial network is passive network.