JP2015211406A - One-to-multiple multidrop metal wire communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a one-to-multiple multidrop metal wire communication system capable of improving efficiency in construction work.SOLUTION: A one-to-multiple multidrop metal wire communication system 100 includes a communication path construction control CPU 50 incorporating a relay optimization logic 20 including: a crosstalk property acquisition section 21 including a master/slave switching function 21a, a crosstalk test function 21b and a crosstalk amount determination function 21c for determining a difference of transmission and reception data amounts as a crosstalk amount; a cable property storage section 22; an S/N calculation section 23 for calculating an S/N; a throughput estimation section 24 for calculating a throughput value from the S/N; a relay point determination section 25 for determining a slave modem to which a relay function is set in accordance with throughput values and positions of all slave modems; and a relay function setting section 26 for setting the relay function.

Description

  The present invention relates to a one-to-many multi-drop type metal line communication system that automatically measures crosstalk characteristics of an aggregate cable and automatically constructs a communication path between parent and child modems.

  In the conventional one-to-many multi-drop type metal line high-speed communication system, when long-distance transmission is required such that direct communication between a parent modem and a remote child modem is not possible, other child modems existing in the middle are used. It is necessary to establish a parent-child communication path at both ends depending on the relay function to be set.

  When communication is performed using a single-core pair cable, the range of the child modem that can be relayed can be roughly estimated from the signal attenuation characteristics of the pair cable and the communication throughput requirement of the modem. By the way, in the case where a plurality of communication paths are accommodated using an aggregate cable, crosstalk between cables at the near end of the parent modem side occurs, making it difficult for signals to reach.

  Therefore, it is necessary to set the relay function to the child modem at a point nearer than the position of the relay point assumed in the case of a single core pair cable. The amount of signal crosstalk between cables varies greatly depending on the positional relationship of each pair cable in the aggregate cable. Therefore, in order to set an appropriate relay point, it is necessary to measure the amount of signal crosstalk in advance, and it takes time and cost.

  Therefore, as a conventional technique for measuring the signal crosstalk amount of the aggregate cable, a technique for measuring the signal crosstalk amount between arbitrary lines in the aggregate cable, grasping the communication state from the result, and determining the used line (for example, patent Document 1) and a technique for measuring the signal crosstalk amount from other lines and adjusting the signal level of the transmission apparatus (for example, Patent Document 2) have been proposed.

JP 2003-244034 A JP 2000-13283 A

  However, each technology is not a technology that estimates the position of the appropriate relay point between the parent modem and the child modem that are far away and automatically constructs the optimum communication path, but uses the measured results. Eventually, there was a problem that a person had to set a relay point.

  The present invention has been made to solve such a problem, and the relay modem function is automatically set to the child modem existing in the route after installing the device and the cable without performing the prior measurement and the network design. It is an object of the present invention to provide a one-to-many multi-drop type metal line communication system capable of improving the efficiency of communication network construction work.

The one-to-many multi-drop metal line communication system according to the present invention is
A plurality of pair cables to which a plurality of parent modems are connected are collectively housed in one end to form a collecting portion, and a plurality of child modems are sequentially connected to each pair cable branched from the collecting portion. In the one-to-many multi-drop metal line communication system,
One virtual parent modem among the plurality of parent modems and one parent modem among the other parent modems are set as virtual child modems as being connected by the same pair cable. A parent-child switching function for constructing a virtual parent-child relationship, a crosstalk test function for transmitting test data from the virtual parent modem to the virtual child modem, an amount of data transmitted by the virtual parent modem, and the virtual child modem A crosstalk characteristic acquisition unit having a crosstalk amount determination function for determining a difference in data amount received as a crosstalk amount;
A cable characteristic storage unit that stores data of signal attenuation with respect to the length of the pair cable based on the unique cable characteristics of the pair cable;
An SN ratio calculation unit that calculates an SN ratio of the pair cable for each distance from the crosstalk amount and the attenuation amount; a throughput estimation unit that calculates a throughput value for each distance from the SN ratio;
The relay function is set for any of the child modems among the child modems based on the throughput values calculated for each distance and the distances of all the child modems connected to the virtual parent modem from the virtual parent modem. A relay point determination unit for determining whether or not
A relay function setting unit for setting the relay function in the child modem;
Is provided with a communication path construction control CPU incorporating a relay optimization logic having

  According to the one-to-many multidrop type metal line communication system according to Embodiment 1 of the present invention, one parent modem among a plurality of parent modems is set as a virtual parent modem, and the other parent modems are temporarily set. Change the setting as a virtual child modem under the virtual parent modem, and send test data of a predetermined capacity from the virtual parent modem to one of the virtual child modems, By comparing the amount of data received by the slave modem, it is possible to measure the amount of signal crosstalk in the collective cable that occurs during actual communication.

  Accordingly, the signal attenuation amount generated as a single line and the signal crosstalk amount generated due to crosstalk are combined to calculate the SN ratio value of the pair cable for each distance on the communication path, and these SN ratio values are calculated. Therefore, it is possible to calculate an approximate value of the throughput for each distance from the group of child modems installed on the pair cable path, and to the child modem located farthest in the range that can satisfy the quality required for the communication system, The relay function of the signal from the parent modem can be set for other child modems located farther than the child modem.

It is sectional drawing and the side surface schematic diagram of the assembly | attachment metal cable which concerns on Embodiment 1 of this invention. It is a figure which shows the example of installation of the relay point in the communication by the single line as a comparative example, and the example of installation of the relay point in the communication by the multi-line using the collective cable of the present invention. 1 is a system configuration diagram of a one-to-many multi-drop metal line communication system according to a first embodiment of the present invention. It is a block diagram which shows the structure of the relay optimization logic of the communication path construction control CPU concerning Embodiment 1 of this invention. It is a figure which shows the transmission / reception relationship of each modem when measuring the signal crosstalk amount of a pair cable using the crosstalk characteristic acquisition part and parent modem which concern on Embodiment 1 of this invention. It is a graph showing the signal crosstalk amount between the pair cables which concern on Embodiment 1 of this invention. It is an assumption signal attenuation amount graph according to distance concerning Embodiment 1 of the present invention. 8 is a graph in which FIG. 6 and FIG. 7 are superimposed. It is the figure which represented the change of the SN ratio of the pair cable by the signal loss resulting from attenuation and crosstalk concerning Embodiment 1 of this invention for every distance. It is a principal part system block diagram of the one-to-many multidrop type | mold metal wire communication system which concerns on Embodiment 2 of this invention. It is a system configuration | structure figure of the one-to-many multidrop type | mold metal line communication system which concerns on Embodiment 3 of this invention. It is a system configuration | structure figure of the one-to-many multidrop type | mold metal line communication system which concerns on Embodiment 4 of this invention.

Embodiment 1 FIG.
Hereinafter, the one-to-many multi-drop metal line communication system according to the first embodiment of the present invention will be described with reference to the drawings.
FIG. 1A is a cross-sectional view of a collective metal cable 10 (hereinafter referred to as collective cable 10) used in the present embodiment.
FIG. 1B is a schematic diagram showing a mutual interference state of the metal pair cables P1 to PN (hereinafter referred to as pair cables P1 to PN) in the aggregate portion 11 of the aggregate cable 10.

  The aggregate cable 10 is composed of N pairs of cable pairs P1 to PN. The pair cables P <b> 1 to PN may be separately covered one by one or may be stored in a twisted state. Each number in the cross section of Fig.1 (a) is the number allocated to each pair cable P1-PN. As shown in FIG. 1B, each pair cable P1 to PN of the aggregate cable 10 has a characteristic that the degree of interference (interference amount) varies depending on the positional relationship in the aggregate section 11. .

  FIG. 2A is a diagram illustrating an installation example of relay points in communication using a single line Q as a comparative example. A plurality of child modems Qa to Qg are sequentially connected to the single line Q. A portion indicated by a solid line arrow S1 indicates a range in which communication from the parent modem A to the direct child modem can be performed without requiring relay, and a broken line arrow S2 indicates a range in which the signal is attenuated and needs to be relayed. . The limit point G1 that needs to be relayed can be easily determined from the cable characteristics and the like because no crosstalk occurs with other lines on a single line. Therefore, before operation of the communication system, the limit point G1 can be determined in advance, and in order for the parent modem A and the child modems Qd to Qg to communicate, it is only necessary to set the relay function to the child modem Qc.

FIG. 2B is a diagram showing an example of multi-line communication using the aggregate cable 10 according to the present invention.
The arrangement of the child modems P1a to P1g with respect to the parent modem M1 is the same as the arrangement of the child modems Qa to Qg with respect to the parent modem A in FIG. By the way, when trying to communicate from the parent modem M1 to any one of the child modems P1a to P1g using the pair cable P1 as described above, a set as shown in FIG. The occurrence of crosstalk between adjacent pair cables in the cable 10 becomes a problem.

  Therefore, as compared with the case of the single line Q shown in FIG. 2A, the child modem for setting the relay function needs to exist on the parent modem M1 side. In addition, since the signal crosstalk amount at this time varies depending on the arrangement of the pair cables P1 to PN in the aggregation unit 11 as described above, all the lines of the pair cables P1 to PN are stably without a repeater. The distance between the parent modem and the child modem that can be directly communicated will be different. Therefore, in this embodiment, the signal crosstalk amount to all other lines is measured for each of the pair cables P1 to PN constituting each line, and the relay function is automatically performed for the child modem at the optimum relay position. I am going to set it.

  FIG. 3 is a configuration diagram of a one-to-many multi-drop metal line communication system 100 (hereinafter referred to as communication system 100). A plurality of parent modems M1 to MN connected to the hub 3 are connected to a pair of pair cables P1 to PN via the terminal block 8, respectively, and each constitutes one line. In the pair cables P1 to PN constituting the aggregate cable 10, the fixed portions on the terminal block 8 side are collectively an aggregate portion 11 covered with a film, and the slave modem side is divided apart.

  A plurality of child modems are sequentially connected to the pair cables P1 to PN, one end of which is connected to the parent modems M1 to MN via the terminal block 8, at intervals as necessary. Some of the pair cables P1 to Pn are not used.

  Each of the pair cables P1 to PN is provided with a child modem (hereinafter referred to as a relay child modem) having a function as a repeater in addition to a function as a normal child modem. A child modem having “t” at the end of the code is a repeater modem. The position of the repeater modem from the terminal block 8 varies depending on the crosstalk characteristics of the respective pair cables P1 to PN. As shown in FIG. 3, the pair cable P3 that interferes with other pair cables and has a lot of crosstalk has a repeater modem P3at installed in the nearest place, but has little interference with other pair cables. The pair cable P2 has a repeater modem P2ct installed at a position farther from the repeater modems of the other pair cables.

Next, a method for determining the installation position of the repeater modem will be described.
FIG. 4 is a block diagram showing a configuration of the relay optimization logic 20 of the communication path construction control CPU 50.
First, an outline of each function will be described. The crosstalk characteristic acquisition unit 21 provides a function of calculating the amount of signal crosstalk leaked from each pair cable P1 to PN to another pair cable during communication. The cable characteristic storage unit 22 includes a frequency band specific to each pair cable stored in the aggregate cable 10 (meaning a plurality of frequencies at a predetermined frequency interval from the lower limit frequency to the upper limit frequency, the same applies hereinafter) and the transmission source At a distance of a predetermined distance in units of 1 km from (for example, up to 1 km, 2 km, 3 km ·· 9 km. D times the unit length (D is a natural number). The signal attenuation characteristics are preserved.

  The S / N ratio calculation unit 23 calculates the signal crosstalk amount at the near end of the terminal block 8 on the parent modem side acquired by the crosstalk characteristic acquisition unit 21 and the signal attenuation prediction for each frequency band and each distance acquired from the cable characteristic storage unit 22. The value of the SN ratio for each frequency band and for each distance is acquired from the quantity. The throughput estimation unit 24 acquires the value of the SN ratio corresponding to the frequency band actually used from the SN ratio data for each frequency band and distance calculated by the SN ratio calculation unit 23, and the distance in the frequency band Calculate an approximate value for each throughput. The relay point determination unit 25 determines, for each of the pair cables P1 to PN, a child modem that is farthest from the parent modem among relay modems that can satisfy a throughput value that is requested in advance. The relay function setting unit 26 sets the relay function for the modem determined by the relay point determination unit 25 as the relay slave modem.

Next, each function of the relay optimization logic 20 will be described in detail.
FIG. 5 is a diagram showing a transmission / reception relationship between the parent modems M1 to MN when the signal crosstalk amount of the pair cable P1 is measured using the crosstalk characteristic acquisition unit 21 and the parent modem M1.
As shown in FIG. 5, the parent modems M1 to MN are connected to the communication path construction control CPU 50 via the hub 3. The crosstalk characteristic acquisition unit 21 of the relay optimization logic 20 changes the setting of each of the parent modems M1 to MN to change the individual pair cables of the pair cables P1 to PN in the above-described aggregate cable 10 at the time of communication. Provides a function to acquire the amount of signal crosstalk to the pair cable.

  First, the parent / child switching function 21a of the crosstalk characteristic acquisition unit 21 temporarily changes the settings of the parent modems M2 to MN other than the parent modem M1 as virtual child modems M2 to MN under the parent modem M1 (as virtual child modems). The set parent modems M1 to MN are referred to as virtual child modems M1 to MN in the following text (note that the same reference numerals are used since the devices are the same). Then, the crosstalk test function 21b of the crosstalk characteristic acquisition unit 21 transmits test data having a predetermined capacity to each of the virtual child modems M2 to MN to the parent modem M1 that is the virtual parent modem in a plurality of frequency bands. To do about.

  Originally, the virtual parent modem M1 and the virtual child modems M2 to MN are connected to different pair cables, so that actual communication is not performed between these modems. However, here, the virtual child modems M2 to MN form a virtual parent-child relationship as if they are connected to the virtual parent modem M1 via a pair cable, and test communication is tried in order.

  First, test data is transmitted to the virtual child modem M2 using the virtual parent modem M1. Then, the crosstalk amount determination function 21c of the crosstalk characteristic acquisition unit 21 measures the amount of data received by the virtual child modem M2. In this way, the same operation and measurement are repeated up to the virtual child modem MN.

  Next, the parent-child switching function 21a of the crosstalk characteristic acquisition unit 21 changes the setting of the virtual child modem M2 to the virtual parent modem M2, and sets the setting of the virtual parent modem M1 as the virtual child modem M1 under the virtual parent modem M2. Then, the settings of the other virtual child modems M3 to MN are changed to virtual child modems M3 to MN under the virtual parent modem M2. The above operation is repeated for all the virtual parent modems M1 to MN, and the data communication amount between all the pair cables is measured by the crosstalk amount determination function 21c. The reception amount of each communication data measured here is equal to the signal crosstalk amount to other pair cables generated when communicating with the child modem to which each parent modem M1 to MN is directly connected. become.

FIG. 6 is a graph showing the amount of signal crosstalk during communication between the pair cables P1-P2 (meaning from P1 to P2, hereinafter the same), P1-P3, and P1-P4.
The horizontal axis represents the frequency band, and the vertical axis represents the signal crosstalk amount. The crosstalk amount determination function 21c passes the data between the pair cables P1 and P2 in which the maximum crosstalk amount at the frequency C used in actual communication is recorded, to the SN ratio calculation unit 23. The crosstalk from the pair cable P1 does not actually affect only a specific adjacent pair cable, but affects all the pair cables at the same time. Therefore, it is sufficient to adopt the leakage amount to the pair cable P2 in which the maximum value is recorded.

Next, the function of the cable characteristic storage unit 22 will be described.
FIG. 7 is a graph of assumed signal attenuation by distance.
In the present embodiment, the cable characteristic storage unit 22 includes the assumed signal attenuation amount from the transmission source to the 1 km unit and the maximum length of 9 km for the type of the pair cable in the aggregate cable 10 used by the communication system 100. Data recorded for each frequency band is stored. This data is an assumed value of signal attenuation when a pair cable is used as a single line. In FIG. 7, the horizontal axis represents the frequency band, the vertical axis represents the signal attenuation, and a graph of the assumed signal attenuation for each distance is shown.

Next, the function of the SN ratio (SNR) calculation unit 23 will be described.
FIG. 8 shows a graph of the signal crosstalk amount between the pair cables P1 and P2 in which the maximum crosstalk amount from the pair cable P1 to the pair cable P2 shown in FIG. 6 is recorded, and the assumed signal attenuation graph by distance of FIG. It is a graph displayed in an overlapping manner.
FIG. 9A shows changes in the SN ratio of the pair cable P1 due to signal loss due to attenuation inherent to the pair cable P1 and crosstalk, for each distance. The horizontal axis represents the frequency band, and the vertical axis represents the SN ratio. The S / N ratio calculation unit 23 is configured to obtain the signal attenuation based on the cable characteristics specific to the line type of the pair cable P1 acquired from the cable characteristic storage unit 22, and the pair cables P1 to P1 in the aggregation unit 11 acquired from the crosstalk characteristic acquisition unit 21. The SN ratio of the pair cable P1 for each distance is calculated for each frequency band by combining the signal crosstalk amount resulting from the PN arrangement.

  FIG. 9B is a calculation result of the expected transmission throughput value for each distance at the frequency C in FIG. The throughput estimation unit 24 of the relay optimization logic 20 calculates a throughput value that can be expected for each distance from the SN ratio value for each distance corresponding to the frequency C. Here, assuming that the minimum throughput value required for the communication system 100 is 2 Mbps or more, 6 Km in FIG. 9B is the limit distance that can be communicated between the parent and child modems.

  Next, as shown in FIG. 3, the relay point determination unit 25, for the pair cable P1, among the child modems existing within 6 km from the parent modem M1, the child modem P1bt farthest from the parent modem M1 (see FIG. 3) Is determined as a relay modem. The distance between the parent modem and the child modem is estimated by the transmission delay value of the communication between the parent and child modems.

  The relay function setting unit 26 sets the relay function via the parent modem M1 for the child modem P1bt determined by the relay point determination unit 25 as the relay child modem. Thereafter, the relay child modem P1bt receives the signal addressed to itself as a normal child modem, and does not accept the signal addressed to the child modems P1c and P1d under the parent modem M1 installed at a position farther than the own location. , Function as a repeater.

  According to the one-to-many multi-drop type metal line communication system 100 according to Embodiment 1 of the present invention, one parent modem connected to the terminal block 8 near end is a virtual parent modem, and other parent modems are Temporarily change the setting as a virtual child modem under the virtual parent modem, and send test data of a predetermined capacity from the virtual parent modem to each of the virtual child modems. By comparing the amount of data received by the modem, it is possible to measure the amount of signal crosstalk in the assembly portion 11 of the assembly cable 10 that occurs during actual communication.

  Accordingly, the signal attenuation amount generated as a single line and the signal crosstalk amount generated due to crosstalk are combined to calculate the SN ratio value of the pair cable for each distance on the communication path, and these SN ratio values are calculated. Since the approximate value of the throughput for each distance can be calculated from the child modem group at the farthest position in the range that can satisfy the quality required for the communication system among the child modem groups installed on the path of each pair cable, The relay function of the signal from the parent modem can be set for other child modems farther than the child modem.

  In addition, since the relay child modem can be set only by the existing communication system 100, even if the position of the child modem is changed in the middle, or the extension or removal of the child modem occurs, it is easy. , The repeater modem can be reconfigured.

  In addition, crosstalk from the aggregate cable fluctuates just by moving the aggregate cable. In preparation for such a case, the crosstalk state may be periodically measured and the repeater modem may be reconfigured.

  In the present embodiment, the test data is repeatedly transmitted for a plurality of frequencies, and the data is collected. However, the data may be limited to only the frequency band to be used.

Embodiment 2. FIG.
Hereinafter, the second embodiment of the present invention will be described with reference to the drawings, with respect to differences from the first embodiment.
FIG. 10A is a system configuration diagram of a main part of the parent modems 2M1 to 2MN of the one-to-many multidrop type metal line communication system 200 (hereinafter referred to as the communication system 200). Although equivalent to FIG. 3 of the first embodiment, the configuration on the right side of the terminal block 8 is the same and is omitted.
FIG. 10B is a diagram showing the configuration of the parent modems 2M1 to 2MN.

  In the first embodiment, the relay optimization logic 20 is arranged in the external communication path construction control CPU 50, whereas in the present embodiment, each parent modem 2M1-2MN is provided separately from the communication unit MT. Each includes a communication path construction control CPU 250. The difference between the communication path construction control CPU 50 of the first embodiment and the communication path construction control CPU 250 incorporated in the parent modems 2M1 to 2MN is that the parent modems 2M1 to 2MN have a representative function and have one representative authority. A modem (a representatively set parent modem) functions as the external communication path construction control CPU 50 of the first embodiment. Since the hardware configuration of all the parent modems is the same, the representative setting can be changed to any parent modem.

  According to the one-to-many multi-drop type metal line communication system 200 according to the second embodiment of the present invention, the communication path construction control CPU 250 is built in each of the parent modems 2M1 to 2MN. The communication system 200 can be easily installed. Moreover, since the representative function can be set for any parent modem, the maintenance and inspection of the communication system is facilitated.

Embodiment 3 FIG.
Hereinafter, the third embodiment of the present invention will be described with reference to the drawings, with respect to differences from the first embodiment.
FIG. 11 is a system configuration diagram of a one-to-many multi-drop metal line communication system 300 (hereinafter referred to as communication system 300). This corresponds to FIG. 3 of the first embodiment.

  In the first embodiment, the relay optimization logic 20 is arranged in the external communication path construction control CPU 50, whereas in the present embodiment, the maintenance terminal 350 is connected to the hub 3 as the communication path construction control CPU. And use it. Other configurations are the same as those of the first embodiment.

  According to the one-to-many multidrop type metal line communication system 300 according to the third embodiment of the present invention, a general-purpose maintenance terminal 350 is used instead of the communication path construction control CPU. This saves labor and facilitates the installation of the communication system 300 and reduces the equipment cost and installation cost.

Embodiment 4 FIG.
Hereinafter, the fourth embodiment of the present invention will be described with reference to the drawings, with respect to the differences from the first embodiment.
1 is a system configuration diagram of a one-to-many multi-drop metal line communication system 400 (hereinafter referred to as a communication system 400). This corresponds to FIG. 3 of the first embodiment.

  In the first embodiment, the relay optimization logic 20 is arranged in the external communication path construction control CPU 50, whereas in this embodiment, the network monitoring device 450 is used as the communication path construction control CPU. Other configurations are the same as those of the first embodiment.

  According to the one-to-many multi-drop type metal line communication system 400 according to the fourth embodiment of the present invention, the network monitoring device 450 is used instead of the communication path construction control CPU. Therefore, the installation of the communication system 400 becomes easy, and maintenance inspection after operation can be remotely operated, so that maintenance costs can be reduced. Further, since the network monitoring device 450 can be shared with other communication systems, the maintenance cost can be further reduced.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

100, 200, 300, 400 One-to-many multi-drop metal line communication system,
3 hub, 8 terminal block, A, M1-MN parent modem, C frequency,
Q Single line, 10 aggregate metal cable, 11 aggregate section, 20 relay optimization logic,
21 crosstalk characteristic acquisition unit, 21a parent-child switching function, 21b crosstalk test function,
21c Crosstalk amount determination function, 22 cable characteristic storage unit, 23 SN ratio calculation unit,
24 throughput estimation unit, 25 relay point determination unit, 26 relay function setting unit,
G1 limit point, M1-MN virtual parent modem, M1-MN virtual child modem,
MT communication part, P1-PN metal pair cable, P1 each pair cable,
P1 Each metal pair cable, P1a to P1d, P2a to P2d, etc.
P1bt, P2ct, P3at relay modem, S1 solid line arrow,
S2 dashed arrow, 350 maintenance terminal, 450 network monitoring device,
50, 250 Communication path construction control CPU.

Claims (8)

A plurality of pair cables to which a plurality of parent modems are connected are collectively housed in one end to form a collecting portion, and a plurality of child modems are sequentially connected to each pair cable branched from the collecting portion. In the one-to-many multi-drop metal line communication system,
One virtual parent modem among the plurality of parent modems and one parent modem among the other parent modems are set as virtual child modems as being connected by the same pair cable. A parent-child switching function for constructing a virtual parent-child relationship, a crosstalk test function for transmitting test data from the virtual parent modem to the virtual child modem, an amount of data transmitted by the virtual parent modem, and the virtual child modem A crosstalk characteristic acquisition unit having a crosstalk amount determination function for determining a difference in data amount received as a crosstalk amount;
A cable characteristic storage unit that stores data of signal attenuation with respect to the length of the pair cable based on the unique cable characteristics of the pair cable;
An SN ratio calculation unit that calculates an SN ratio of the pair cable for each distance from the crosstalk amount and the attenuation amount; a throughput estimation unit that calculates a throughput value for each distance from the SN ratio;
The relay function is set for any of the child modems among the child modems based on the throughput values calculated for each distance and the distances of all the child modems connected to the virtual parent modem from the virtual parent modem. A relay point determination unit for determining whether or not
A relay function setting unit for setting the relay function in the child modem;
A one-to-many multi-drop type metal line communication system including a communication path construction control CPU incorporating a relay optimization logic including: The crosstalk test function performs the test data for all the parent modems for one parent modem, and sets the maximum crosstalk amount to the crosstalk amount of the pair cable to which the parent modem is connected. The one-to-many multi-drop type metal line communication system according to claim 1 to be determined. 3. The one-to-many multi-drop metal line communication system according to claim 1, wherein the communication path construction control CPU applies the relay optimization logic to all the parent modems. The one-to-many multidrop type metal line communication system according to any one of claims 1 to 3, wherein the crosstalk test function transmits the test data for a plurality of frequencies. The one-to-many multi-drop type metal line communication system according to any one of claims 1 to 4, wherein the communication path construction control CPU periodically executes the relay optimization logic. The communication path construction control CPU is built in each parent modem, and one parent modem among the parent modems has a right to apply the relay optimization logic to all other parent modems. The one-to-many multi-drop type metal line communication system according to claim 1, comprising: The one-to-many multi-drop metal line communication system according to any one of claims 1 to 5, wherein the communication path construction control CPU is a maintenance terminal connected to each parent modem via a hub. 6. The one-to-many multi-drop metal line communication system according to claim 1, wherein the communication path construction control CPU is a network monitoring device connected to each parent modem via a hub. .

Images