JP3873073B2 - Housing design evaluation method for broadband transmission equipment - Google Patents

Description

  The present invention relates to a housing design evaluation method for a broadband transmission device.

A plurality of communication lines are accommodated in the communication cable, but there are many cases where a plurality of transmission systems coexist in one communication cable. For example, there is a system using a CTC (train central control device) line as one of transmission systems in railway communication. Since this CTC line is an important line related to train operation, it is determined whether or not multiple transmission systems can coexist, taking into account the influence of other transmission systems accommodated in the same communication cable. Must-have. Such a coexistence determination determines whether or not coexistence is possible in an actual local environment (for example, see Non-Patent Document 1).
Kawamata: “Transmission test results of metallic high-speed digital transmission systems using railway communication lines”, IEICE Communication Research Materials, CMN-02-3, pp.13-18 (2002.1)

  However, in the verification work in such a local actual environment, there are restrictions on the distance between devices used for verification work, restrictions on the accommodation position in the communication cable, restrictions on the type of cable, etc. as conditions for coexistence. There are many problems such as the time and labor required for conducting the field test. Therefore, it is preferable if the verification work can be performed outside the actual local environment.

  Whether or not a plurality of transmission systems can coexist can be evaluated by transmission quality, but the transmission quality is generally determined by the reception level and noise level. When simulating the local environment, it is possible to simulate the attenuation of the communication cable (simulation of reception level) by setting parameters that can simulate the local reception level such as core wire diameter, insulator, transmission distance, etc. However, it is currently difficult to simulate noise (especially the near-end crosstalk noise, which is said to be the largest). In addition, the noise characteristics vary depending on the accommodation position in the communication cable of the communication line used by the transmission system to be determined. Also, a method for simulating the coexistence of three or more types of transmission systems has not been considered. Furthermore, a system that does not consider the frequency characteristics of crosstalk noise has been devised as a system that simulates coexistence. However, when this system is applied to an xDSL transmission system having a wide frequency band, the frequency characteristics must be fully considered. There must be. In addition, coexistence simulation by the cable accommodation position is not possible. Therefore, at this stage, it is necessary to carry out a number of field tests, and not only railway operators but also telecommunication operators are worried.

  On the other hand, the applicant of the present application, in Japanese Patent Application No. 2003-46383, simulates generation of key crosstalk noise by generating crosstalk using a cable of a certain length. Judgment method "was proposed. However, the crosstalk characteristics of cables vary greatly depending on the combination of the lines, and even if coexistence transmission tests are performed using any line, "variations" occur in the results of transmission quality, transmittable distance, etc. . For example, the crosstalk characteristics of one jumping quad also have a large “variation” depending on the combination of lines. Therefore, the reliability of the determination result of coexistence may be lowered. Therefore, there is a problem that it is desired to evaluate the accommodation design of a broadband transmission device such as xDSL more appropriately.

  Therefore, the present invention proposes a method for appropriately evaluating the accommodation design of the broadband transmission apparatus.

  The method for evaluating accommodation design of a broadband transmission apparatus according to the present invention considers the influence of a broadband transmission line newly scheduled to be accommodated on an existing transmission line in a communication cable accommodating a plurality of communication lines. This is to evaluate the accommodation design of the transmission device. Then, simulated transmission means capable of simulating the local reception level at which the communication cable is to be arranged (11: In this section, in order to facilitate understanding of the invention, as necessary, The reference numeral used in the "Best Mode of the" field is attached, but it is not meant to limit the scope of claims by this reference.) And has the same structure as a communication cable to simulate crosstalk noise. Using a simulated line (10) having a crosstalk simulation line (12) and capable of functioning as a broadband transmission line by connecting the broadband transmission device (5) to an arbitrary communication line in the crosstalk simulation line, The simulated line method is evaluated according to the following procedure.

The evaluation using the simulated line method is performed according to the following procedure.
(Procedure 1) The near-end crosstalk characteristic of the simulated line is measured in advance, and the data is stored.
(Procedure 2) After setting various parameters such as the transmission speed of the broadband transmission line to be newly accommodated, the transmission spectrum is measured and the data is stored.

  (Procedure 3) Investigate the line availability of the local laying cable to be placed, and based on the result of the investigation, grasp the geometric accommodation position of the existing transmission line as the interfered line and the broadband transmission line as the interfering line To do.

  (Procedure 4) For all the line combinations that satisfy the geometric accommodation position of Procedure 3, the pseudo crosstalk noise level is calculated using the data stored in Procedure 1 and Procedure 2, and the value is the largest. Or a line combination with a 1% risk factor.

(Procedure 5) Set the simulated transmission line length to the required transmission distance, conduct a coexistence transmission test with the line combination selected in Procedure 4, and measure the transmission quality of the existing transmission line during coexistence transmission.
(Procedure 6) Based on whether or not the required transmission quality is satisfied, it is determined whether or not a broadband transmission line to be newly accommodated can be accommodated.

According to such a method for evaluating the accommodation design of the broadband transmission apparatus, it is possible to appropriately evaluate the accommodation design of the broadband transmission apparatus in the following points.
・ Since the degree of impact can be determined in advance, the time limit is small. Moreover, since it is an evaluation method based on laboratory experiments, a more detailed evaluation can be performed than a method based on desktop calculation.

・ Near-end crosstalk noise can be simulated indoors, so coexistence can be determined in advance.
-It is easy to design accommodation because the cable accommodation position, number of accommodation transmission devices, transmission distance, transmission speed, etc. can be changed easily.

-Coexistence evaluation of three or more types of transmission systems is possible with a crosstalk simulation line. Even when such three or more types of coexistence simulations are performed, the system configuration is simple.
-Experiments can be performed by selecting and using circuits with poor line crosstalk characteristics, average circuits, etc., which cannot normally be implemented with locally installed cables.

  ・ Because the experiment can be performed using the line with the worst line crosstalk characteristics, it is possible to evaluate the safety side, and it is possible to evaluate the bandwidth guarantee type (not the best effort) which is a requirement of the communication quality in the railway communication.

  Further, as described in claim 2, it is determined whether or not an existing transmission line as an interfered line is used in a system that uses a voice band, and is not used in a system that uses a voice band (FIG. 4). The evaluation by the simulated line method may be performed only in the case of NO in S40). When not used in a system that uses a voice band, it is highly likely to be used in a system that uses a relatively wide frequency band. Conduct an evaluation by

  In this case (that is, when the existing transmission line that becomes the interfered line is not used in the system that uses the voice band), as shown in claim 3, the existing transmission that becomes the interfered line is further added. It is determined whether or not the frequency band to be used in the broadband transmission line as the interference line and the interference line overlaps (S80 in FIG. 4). It can be considered that it is possible (S90, S100). This is because coexistence is possible if the frequency bands to be used do not overlap.

  On the other hand, when an existing transmission line that is an interfered line is used in a system that uses a voice band, it is conceivable to make it as shown in claim 4. That is, it is further determined whether or not the frequency bands used in the existing transmission line serving as the interfered line and the wideband transmission line serving as the interference line overlap (S50). Evaluation is performed by a direct application method in which the degree of influence is evaluated by directly applying noise generated from a transmission line to an existing transmission line as an interfered line, and if they do not overlap, it is determined that they can be accommodated (S60, S70). It is possible.

For the evaluation by the direct application method, for example, a method as disclosed in Japanese Patent Application Laid-Open No. 2004-25951 can be used.
As a transmission system using the existing transmission line as the interfered line, for example, at least one of a CTC line, a direction line, a communication cut-off line, a remote control line, and a train radio line in railway communication is used. It is possible that the system was These transmission systems are highly important from the viewpoint of ensuring safety in railway communications, and there is also a high need for evaluation in consideration of the influence on the existing system when further accommodating a broadband transmission line.

Embodiments of the present invention will be described below with reference to the drawings.
[XDSL accommodation design method]
When installing an xDSL transmission line in an existing cable, other existing systems such as a telephone, FAX, PCM line, CTC (train central control unit) line, train radio line, existing xDSL line, etc., depending on the type and setting conditions of the xDSL modem (Hereinafter referred to as “existing system”).

  Therefore, before installing the xDSL transmission line, consider the mutual influence with the existing system, and in order not to affect the existing system, whether or not to install the xDSL transmission line and the setting conditions of the xDSL modem (transmission distance, transmission speed, line accommodation) It is necessary to carry out introduction evaluation of position, etc.).

[Determining prerequisites]
The preconditions for installing an xDSL transmission line in an existing cable are shown below.
(1) Types of xDSL modems Types of xDSL modems that can be used for railway communication lines include SDSL modems, HDSL modems, and ADSL modems.

(2) Type of cable The type of cable includes a layer type cable (composite optical fiber cable) and a unit type cable (communication cable (for general use)). In addition, since the layer type cable tends to move away from the circuit accommodation position, and the layer type cable tends to have better crosstalk characteristics than the unit type cable, the layer type cable can be selected when the layer type cable and the unit type cable can be selected. It is desirable to use

(3) Required transmission distance This is the distance between the xDSL modems used, and is mainly the cable laying distance.
(4) Required transmission rate Varies depending on the type of information to be transmitted and the system.

(5) Required transmission quality Varies depending on the degree to which transmission quality deterioration of information to be transmitted can be tolerated.
(6) Existing system accommodation status and frequency band It is necessary to know the type of existing system (telephone, FAX, CTC line, train radio line, other xDSL line, etc.) and frequency band.

(7) Cable vacant line status and accommodation position It is necessary to grasp the cable vacant line situation and the accommodation position of the existing system.
(8) Line noise Varies depending on the environmental conditions of the existing line and the train operation status.

[Simultaneous transmission test using simulated line method]
The coexistence transmission test by the simulated line method is performed when there is an existing system that mainly uses a frequency band other than the voice band in the existing cable and the frequency band of the xDSL modem overlaps with the existing system. An outline of the test configuration is shown in FIG. This configuration is installed in a place other than the site where an existing communication cable that is actually intended to be applied is present, such as a factory or laboratory.

  In this configuration, a pair of transmission devices of the existing system 1 and an M (one or more) pair of xDSLi (1 ≦ i ≦ M) modems 5 are arranged to face each other via a simulated line 10. The simulated line 10 includes a pseudo line unit 11 and a long cable unit 12, and the pseudo line unit 11 is arranged only between transmission devices of the existing system 1. On the other hand, the long cable portion 12 is disposed between the transmission devices of the existing system 1 and between the xDSLi modems 5. That is, the long cable unit 12 accommodates an interfered line between transmission apparatuses of the existing system 1 and an xDSLi line (becomes an interference line) between the xDSLi modems 5.

  The pseudo line section 11 corresponds to “simulated transmission means”, and is a line capable of simulating a local reception level where a communication cable scheduled to accommodate a plurality of transmission systems to be determined is to be arranged. Here, a so-called cable simulator capable of simulating various communication cables is used in order to provide versatility without limiting the transmission system to be determined. A communication cable usually has a transmission attenuation characteristic that attenuates a transmission signal passing through the communication cable. The degree of attenuation is determined depending on the type of communication cable, for example, core diameter (0.9 mm, 0.65 mm, 0.5 mm, 0.4 mm, 0.32 mm, etc.) or insulator type (polyethylene insulation, paper insulation, etc.) , And changes depending on conditions such as cable length (transmission distance) and also changes depending on the frequency of the transmission signal. Specifically, the cable transmission attenuation amount is substantially constant up to a certain frequency, but rapidly increases beyond this. That is, the cable transmission attenuation is not uniform and varies depending on the frequency of the transmission signal. The cable simulator can constitute a simulated line in consideration of the transmission attenuation characteristics of such a communication cable. Specifically, when a designated communication cable model number and cable length (transmission distance) are set, this is a known device that appropriately attenuates and outputs an input signal based on this setting.

  On the other hand, the long cable portion 12 corresponds to a “crosstalk simulation line”, and it is preferable to use a communication cable that is used when actually realizing a transmission system. However, since the long cable portion 12 is provided to simulate crosstalk noise, the same communication cable may not be used as long as such crosstalk noise can be simulated. The long cable portion 12 may have the same structure as the communication cable from the viewpoint of crosstalk simulation, but the length is not necessarily the same as that actually installed. This is because there is near-end crosstalk noise as the largest crosstalk noise, but this near-end crosstalk noise has almost no difference when the cable becomes a certain length. Therefore, for example, even if the length is actually several kilometers or more, a length of several meters to several hundred meters is sufficient for the long cable portion 12, and the drum is used for indoor measurement. A compact configuration can be obtained by winding.

  FIG. 2 simply shows a structural example of the long cable portion 12. The long cable portion 12 shown in FIG. 2 uses a composite optical fiber cable (30 pairs) in which the metal line is a layer type. Specifically, a plurality of quads are accommodated in one cable. The quad is a twist of two pairs of communication lines (copper wires), and there is no restriction on the use of the upstream transmission line and the downstream transmission line. In the example of FIG. 2, it is composed of 15 quads. For example, a quad with a quad number 5 is composed of a line No. 9 and a line No. 10. If necessary, it is desirable to apply white noise or the like to the interfered line.

The outline of the evaluation procedure is shown below.
(Procedure 1)
The near-end crosstalk characteristics of the long cable portion 12 constituting the simulated line 10 are measured in advance, and the data is stored. Once measured, there is no need to measure each time.

(Procedure 2)
After setting various parameters such as the transmission speed of the xDSL modem 5 to be newly accommodated, the transmission spectrum is measured using, for example, a spectrum analyzer and the data is stored. Once measured, there is no need to measure each time.

(Procedure 3)
Investigate the line availability of the local laying cable, and grasp the geometric accommodation positions of the interfered line and the xDSLi line (interfering line) based on the result of the investigation.

  Here, the “interfered line” means one line accommodated in the existing system 1 and means an affected line. Also, “xDSLi line (1 ≦ i ≦ M, M: maximum number of interfering lines)” means that there is a possibility that near-end crosstalk noise affects the interfered line in the newly accommodated xDSL modem 5. It means a line accommodated in a certain xDSLi modem 5. The xDSLi modem 5 includes an SDSL modem, an ADSL modem, an HDSL modem, and the like, and the user designates the modem type and the number of modems.

Here, a specific example of the “geometric accommodation position” will be described with reference to FIG. As shown in FIG. 2, there is an interfered line (existing system) in line No. 9, accommodating xDSL1 line in line No.10 (same quad) and xDSL2 line in line No.15 (2 flying quads). In this case, the geometric accommodation position at this time is "accommodating xDSL1 line in the same quad, and xDSL2 line in two-flight quad (number of interfering lines: M = 2)".
(Procedure 4)
In the simulated line 10 shown in FIG. 1, for all line combinations that satisfy the geometric accommodation position of (Procedure 3), pseudo crosstalk noise is calculated by the following equation using the data of (Procedure 1) and (Procedure 2). (Nsum) is calculated, and a line combination having the largest value or a line combination having a 1% risk rate is selected.

  Note that the geometric accommodation position in the case shown in FIG. 2 refers to a position in the case of “accommodating xDSL1 line in 2 quads and xDSL2 line in 2 flying quads”. In this case, the maximum number of line combinations is 112 (= 30 × 1 × 4-8) There exist.

  The pseudo crosstalk noise (Nsum) is calculated using the following equation.

Nsum: Sum of pseudo crosstalk noise power from the multiple interfering lines (M lines) to the interfered line [dBm]
M: Number of interfering lines P (i): Pseudo crosstalk noise power [W] from the xDSLi line to the interfered line (1 ≦ i ≦ M)
fL (i): Lower limit frequency [kHz] of the xDSLi modem 5 overlapping with the frequency band of the transmission device of the existing system 1 accommodated in the interfered line (1 ≦ i ≦ M)
fU (i): upper limit frequency [kHz] of the xDSLi modem 5 overlapping with the frequency band of the transmission apparatus of the existing system 1 accommodated in the interfered line (1 ≦ i ≦ M)
NEXT (i, f):… Near-end crosstalk attenuation [dB] at frequency f [kHz] from the xDSLi line to the interfered line
(In the laboratory experiment, f = 20 [kHz], 40 [kHz], 60 [kHz], ... ・ Use fU [kHz]),
BWS: Bandwidth of transmission power density of interfering modem 5 [kHz]
S (i, f): xDSLi modem 5 bandwidth at f [kHz] transmission power [dBm] at BWS,
(In the laboratory experiment, f = 20 [kHz], 40 [kHz], 60 [kHz], ... ・ Use fU [kHz]),
INTNEXT ... Near-end crosstalk attenuation measurement interval [kHz] (constant)
(Procedure 5)
The simulated line length is set to the required transmission distance (L1), and the coexistence transmission test is performed using the indoor simulated line with the line combination selected in step 4, and the transmission quality of the existing system (interfered line) during coexistence transmission ( Error rate).

  The error rate can be measured, for example, by determining whether the digital signal output from the interfered line is correct and measuring the BER (bit error rate). In general, measurement is performed using a pseudo-random signal sequence called a pseudo-random signal combined with a pulse pattern generator. However, an error determination may be performed by inputting an arbitrary pattern. Note that BER is an example of a code error rate, and is a ratio of the number of erroneously received bits to all received bits, as shown in the following equation.

Code error rate = number of errors within measurement time / (transmission rate (b / s) x measurement time)
Note that an error rate in units of frames, which are a collection of bits (lumps), can be used, for example, since it only needs to be an indicator of the degree of quality degradation. For example, even when analog data is transmitted, the code error rate can still be measured and evaluated by using a modem or the like.

(Procedure 6)
It is confirmed whether or not the required transmission quality is satisfied, and whether or not the new xDSL modem 5 can be accommodated is determined in consideration of the margin.

[Coexistence transmission test by direct application method]
The coexistence transmission test by the direct application method is performed when there is an existing system 1 that mainly uses a voice band in an existing cable and the frequency band of the xDSL modem 5 overlaps with the voice band. An outline of the test configuration is shown in FIG. This configuration is similar to the configuration in the case of the above-described simulated line system (see FIG. 1), but a place other than the site where the existing communication cable for which the transmission system is actually applied is present, such as a factory or laboratory It is installed at.

  In this configuration, a pair of transmission devices of the existing system 51 and a pair of xDSL modems 55 are arranged to face each other. A pseudo line 61 and a waveform synthesizer 62 are arranged between the transmission devices of the existing system 1. On the other hand, a waveform demultiplexer 63 is disposed between the xDSL modems 55, and the waveform demultiplexed by the waveform demultiplexer 63 is sent to a waveform synthesizer 62 via a matching transformer 64 and a variable attenuator 65. Is configured to input. As a result, noise generated by the xDSL line between the xDSLi modems 55 is directly applied to the interfered line between the transmission apparatuses of the existing system 1.

  The pseudo line 61 corresponds to “simulated transmission means”, and is a line capable of simulating a local reception level where a communication cable scheduled to accommodate a plurality of transmission systems to be determined is to be arranged. Specifically, the configuration may be the same as that of the pseudo line section 11 illustrated in FIG.

The outline of the evaluation procedure is shown below.
(Procedure 1)
The xDSL modem 55 is set to the requested transmission rate and the requested transmission output.

(Procedure 2)
The set length of the pseudo line 61 is set to the required transmission distance.
(Procedure 3)
Noise generated from the xDSL modem 55 is directly applied to the interfered line in the existing system 51 through the waveform demultiplexer 63, the matching transformer 64, the variable attenuator 65, and the waveform synthesizer 62, and a coexistence transmission test is performed.

(Procedure 4)
The margin (γ) is determined in consideration of the margin.
(Procedure 5)
The variable attenuator 65 is adjusted so as not to affect the existing system 1, and the allowable noise level (α) at that time is measured.

(Procedure 6)
The crosstalk noise level (β) from the xDSL modem 55 is measured using the existing cable or the same type of cable as the existing cable. The crosstalk noise level (β) uses a value of a line combination that is assumed to be the maximum value. For example, the maximum value of the crosstalk noise level measured so far, or the crosstalk noise level measured with the maximum value line combination selected in (Procedure 4) in the above-described “simultaneous transmission system coexistence transmission test” may be used. It is done.

(Procedure 7)
Whether or not the xDSL modem 55 can be accommodated is determined by checking whether or not “noise level difference (α−β)> margin (γ)”.

[Introduction evaluation procedure]
The introduction evaluation procedure will be described with reference to the flowcharts of FIGS.
As the flow of the introduction evaluation procedure, first, the preconditions are determined based on the investigation of the existing line and the use of the xDSL transmission line, then the conditions are classified according to the presence of the existing system and the frequency band of the existing system. Introductory evaluation is performed by conducting a coexistence transmission test using an application method or a simulated line method. It is the worker who actually makes each determination in the following description.

  First, the test preconditions are grasped and arranged (S10). Specifically, xDSL modem type, cable type, required transmission distance, required transmission speed, required transmission quality, accommodation status of existing system, line accommodation location (including grasping of available line status), characteristics of existing system, line Noise, transmission output, etc.

And it is judged whether the existing system is accommodated (S20). If the existing system is not accommodated (S20: NO), it is determined that there is no influence (that is, accommodation is possible) (S30), and the evaluation is terminated.
On the other hand, when the existing system is accommodated (S20: YES), it transfers to S40.

  In S40, it is determined whether the existing system is using a voice band. If the voice band is used (S40: YES), it is determined whether the xDSL band overlaps (S50). If the existing system and the xDSL band overlap (50: YES), the direct application method is used. It is determined that the evaluation based on the indoor simulation test is appropriate (S60). In this case, the process proceeds to S110 in FIG. On the other hand, if the existing system and the xDSL bandwidth do not overlap (50: NO), it is determined that there is no influence (that is, accommodation is possible) (S70), and the evaluation is terminated.

  If the voice band is not used (S40: NO), it is determined whether the xDSL band overlaps (S80). If the existing system and the xDSL band overlap (80: NO), the simulation is performed. It is determined that the evaluation based on the indoor simulation test using the line system is appropriate (S90). In this case, the process proceeds to S230 in FIG. On the other hand, if the existing system and the xDSL bandwidth do not overlap (80: NO), it is determined that there is no influence (that is, accommodation is possible) (S100), and the evaluation is terminated.

  In S110, when it is determined that the evaluation by the indoor simulation test by the direct application method is appropriate in S60 described above, the margin γ is determined. Then, an allowable noise level α by the direct application method is obtained (S120).

  Next, the crosstalk noise level β from the xDSL line is measured with the same type of cable as the local laying cable (S130). With regard to this “same type of cable laid on site”, using indoor drum cable, etc., the line combination that maximizes the pseudo crosstalk noise level calculated from the frequency band of the interfering modem, or the applicable cable of the site laid cable Adopt accommodation lines.

  Then, it is determined whether α−β> γ is satisfied (S140). If α−β> γ (S140: YES), it is determined that there is no influence by direct application (S150), and then it is determined whether the existing system uses other than the voice band (S160).

  If the existing system uses other than the voice band (S160: YES), the process proceeds to the evaluation by the indoor simulation test using the simulated line method. This is a process starting from S230. On the other hand, if the existing system does not use a band other than the voice band (S160: NO), it is determined that there is no influence (that is, it can be accommodated) (S180), and the introduction evaluation ends.

  If α−β> γ is not satisfied, that is, if α−β ≦ γ (S140: NO), it is determined whether the coexistence transmission condition can be changed (S190). The coexistence transmission conditions include a transmission speed, a transmission distance, a transmission output, an accommodation position, and the like.

If the coexistence transmission condition can be changed (S190: YES), the coexistence transmission condition is changed (S200), and the process returns to S110.
On the other hand, if the coexistence transmission condition cannot be changed (S190: NO), it is determined whether or not the test precondition can be changed (S210). If the test precondition can be changed (S210: YES). Return to S10. On the other hand, if the test precondition cannot be changed (S210: NO), it is determined that there is an influence (that is, accommodation is impossible) (S220), and the evaluation is terminated.

  In S90 of FIG. 6 which shifts to the case where it is determined in S90 of FIG. 4 that the evaluation by the indoor simulation test by the simulated line method is appropriate, the combination of the accommodated lines in the simulated line is selected. Specifically, the pseudo crosstalk noise level (sum of crosstalk noise power at each frequency) from the interfering line to the interfered line is calculated, and the combination of the line (maximum value line) with the largest value or its value Select a combination of lines (1% risk factor lines) that have a population average of approximately 99%.

Next, the transmission quality under coexistence transmission conditions is measured (S240). The coexistence transmission conditions include a transmission speed, a transmission distance, a transmission output, an accommodation position, and the like.
Then, it is determined whether or not the measured transmission quality is better than the required transmission quality (S250). If the measured transmission quality is better than the required transmission quality (S250: YES), it is determined that there is no influence (that is, accommodation is possible) (S260). ), The introduction evaluation ends. On the other hand, when the measured transmission quality is not better than the required transmission quality (S250: NO), it is determined whether or not the coexistence transmission conditions can be changed (S270).

If the coexistence transmission condition can be changed (S270: YES), the coexistence transmission condition is changed (S280), and the process returns to S230.
On the other hand, if the coexistence transmission condition cannot be changed (S270: NO), it is determined whether or not the test precondition can be changed (S290). If the test precondition can be changed (S290: YES). Return to S10. On the other hand, when the test precondition cannot be changed (S290: NO), it is determined that there is an influence (that is, accommodation is impossible) (S300), and the evaluation is terminated.

According to the xDSL accommodation design evaluation method described above, it is possible to appropriately evaluate the xDSL accommodation design in the following points.
(A) It can be performed using a line simulating it at a place other than the site where the existing communication cable that actually uses the transmission system to be evaluated is installed. That is, since the degree of influence can be determined in advance, the time limit is small. Moreover, since it is an evaluation method based on laboratory experiments, a more detailed evaluation can be performed than a method based on desktop calculation. Moreover, since near-end crosstalk noise can be simulated indoors by evaluation using a simulated line system, whether coexistence can be determined in advance.

  (B) In the configuration used for the evaluation by the simulated line system (see FIG. 1), the pseudo-line portion 11 and the long cable portion 12 can be used with a relatively short appropriate length. This xDSL accommodation design evaluation can be sufficiently performed in a limited space.

(C) Since the cable accommodation position, the number of accommodation transmission devices, the transmission distance, the transmission speed, and the like can be easily changed, the accommodation design is easy.
(D) The coexistence evaluation of three or more types of transmission systems can be performed by the long cable section 12, and the system configuration is simple even when such three or more types of coexistence simulations are performed.

(E) It is possible to conduct experiments by selecting and using a line with poor line crosstalk characteristics, an average line, etc., which cannot normally be carried out with locally installed cables.
(F) Since the experiment can be performed using the line having the worst line crosstalk characteristic, it is possible to perform a safety evaluation and to evaluate a bandwidth guarantee type (not a best effort) that is a requirement of communication quality in railroad communication. .

  (G) If there is an existing system that mainly uses a frequency band other than the voice band in the existing cable, and the frequency band of the xDSL modem overlaps with the existing system, an evaluation using the simulated line method will be carried out. If there is an existing system using the frequency band of the voice band and the frequency band of the xDSL modem overlaps with the existing system, the evaluation by the direct application method is performed. Therefore, appropriate evaluation can be performed according to the frequency band used by the existing system.

As mentioned above, although several embodiment of this invention was described, this invention is not limited to the said embodiment, It is possible to implement in various aspects.
For example, in the above embodiment, the description has been made on the assumption that the steps relating to the determination are performed by humans in the flowcharts shown in FIGS. 4 to 6, but naturally, the determination may be made automatically by the computer system. Good. Further, the change of the coexistence transmission condition in S280 of FIG. 6 may be automatically changed by the computer system.

  The basic transmission system to be evaluated for xDSL accommodation design is, for example, a system using at least one of a CTC line, a direction line, a communication cut-off line, a remote control line, and a train radio line in railway communication. Conceivable. These transmission systems are highly important from the viewpoint of ensuring safety in railway communications, and are highly evaluated.

  Also, xDSL is a typical example of a broadband transmission device, but transmission devices other than xDSL can be applied as long as they use a metal line as a transmission medium and use a wide band and consequently a high frequency. It is. For example, any device using a frequency of about several tens [kHz] or more is applicable. Therefore, even those that do not comply with the xDSL standard are applicable.

  Non-railway applications include general communications (Internet via ADSL, etc.), power company substation remote control equipment lines (similar to railways), gas company remote shut-off equipment lines (such as during earthquakes) It can be applied to gas shut-off in case of abnormality).

It is explanatory drawing which shows the outline | summary of the coexistence transmission test structure by a simulated line system. It is explanatory drawing which shows the specific example of the geometric accommodation position when xDSL1 line | wire is accommodated in the same quad and xDSL2 line | wire is accommodated in 2 flying quads. It is explanatory drawing which shows the outline | summary of the coexistence transmission test structure by a direct application system. It is a flowchart which shows a part of introduction evaluation procedure of xDSL modem. It is a flowchart which shows a part of introduction evaluation procedure of xDSL modem. It is a flowchart which shows a part of introduction evaluation procedure of xDSL modem.

Explanation of symbols

1 ... Existing system 5 ... xDSLi modem (xDSL modem)
DESCRIPTION OF SYMBOLS 10 ... Simulated line 11 ... Pseudo line part 12 ... Long cable part 51 ... Existing system 55 ... xDSL modem 61 ... Pseudo line 62 ... Waveform synthesizer 63 ... Wave form demultiplexer 64 ... Matching transformer 65 ... Variable attenuator

Claims (5)

A method for evaluating accommodation design of a broadband transmission device in consideration of the influence of a broadband transmission line to be newly accommodated on an existing transmission line in a communication cable accommodating a plurality of communication lines. ,
Simulated transmission means capable of simulating the local reception level where the communication cable is to be arranged, and a crosstalk simulation line for simulating crosstalk noise having the same structure as the communication cable, The simulation line system is evaluated by the following procedure using a simulated line that can function as a broadband transmission line by connecting a broadband transmission device to any communication line in the crosstalk simulated line. A housing design evaluation method for a broadband transmission device.
(Procedure 1) The near-end crosstalk characteristic of the simulated line is measured in advance, and the data is stored.
(Procedure 2) After setting various parameters such as the transmission speed of the broadband transmission line to be newly accommodated, the transmission spectrum is measured and the data is stored.
(Procedure 3) Investigate the line availability of the local laying cable to be placed, and based on the result of the investigation, grasp the geometric accommodation position of the existing transmission line as the interfered line and the broadband transmission line as the interfering line To do.
(Procedure 4) For all the line combinations that satisfy the geometric accommodation position of Procedure 3, the pseudo crosstalk noise level is calculated using the data stored in Procedure 1 and Procedure 2, and the value is the largest. Or a line combination with a 1% risk factor.
(Procedure 5) Set the simulated transmission line length to the required transmission distance, conduct a coexistence transmission test with the line combination selected in Procedure 4, and measure the transmission quality of the existing transmission line during coexistence transmission.
(Procedure 6) Based on whether or not the required transmission quality is satisfied, it is determined whether or not a broadband transmission line to be newly accommodated can be accommodated. In the accommodation design evaluation method of the broadband transmission device according to claim 1,
It is determined whether or not the existing transmission line as the interfered line is used in a system that uses a voice band, and the evaluation by the simulated line method is performed only when it is not used in a system that uses a voice band. A method for evaluating accommodation design of a wideband transmission device. In the accommodation design evaluation method of the broadband transmission device according to claim 2,
When the existing transmission line serving as the interfered line is not used in a system using a voice band, the frequency used in the existing transmission line serving as the interfered line and the wideband transmission line serving as the interfering line A method for evaluating the accommodation design of a broadband transmission apparatus, wherein it is determined whether or not the bandwidths overlap, and the evaluation based on the simulated line method is performed only when the bandwidths overlap, and when the bandwidths do not overlap, it is determined that they can be accommodated. In the accommodation design evaluation method of the broadband transmission device according to claim 2 or 3,
When the existing transmission line serving as the interfered line is used in a system using a voice band, the frequency band used in the existing transmission line serving as the interfered line and the wideband transmission line serving as the interfering line In the case of overlapping, the noise generated from the wideband transmission line serving as the interference line is directly applied to the existing transmission line serving as the interfered line, and the degree of influence is directly evaluated. A method for evaluating the accommodation design of a broadband transmission device, characterized in that an evaluation is performed by an application method, and if it does not overlap, it is determined that the accommodation is possible. In the accommodation design evaluation method of the broadband transmission device according to any one of claims 1 to 4,
The transmission system using the existing transmission line as the interfered line is a system using at least one of a CTC line, a direction line, a communication cut-off line, a remote control line, and a train radio line in railway communication. A method for evaluating the accommodation design of a broadband transmission device.