Method for detecting deterioration of leaky coaxial cable and communication system

Abstract

To allow a deteriorated leaky coaxial cable to be identified from a communication device.SOLUTION: A communication system according to the present disclosure includes a transmission path, a leaky coaxial cable group provided on the transmission path and having a plurality of leaky coaxial cables with different frequency characteristics from each other and connected in series, a first communication device, and a second communication device that is connected to the first communication device by the transmission path and detects the presence or absence of deterioration in the leaky coaxial cables from the frequency characteristics of the leaky coaxial cable group.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to detecting impairments in leaky coaxial cables. [Background technology]

[0002] In the field of wireless communication, for example, a technique for monitoring train radio, a technique using a leaky coaxial cable (hereinafter sometimes abbreviated as "LCX") is known. For example, a technique for maintaining an LCX from a ground facility has been proposed.

[0003] Generally, an LCX has a section that transmits signals and a section that is used for suspension, and its cross section perpendicular to the direction of extension is gourd-shaped. Due to this cross-sectional shape and its light weight, the LCX experiences what is called dancing when exposed to crosswinds. Dancing can cause the LCX to deteriorate and break.

[0004] For example, in Patent Document 1, a central device, which is a higher-level device, monitors a terminal device, which is a lower-level device. The terminal device notifies the higher-level device of the interruption of the power supply state from the LCX, and thus the occurrence of a disconnection of the LCX between the base station and the terminal device is detected. In consideration of the effect on train radio, it is desirable to quickly restore the LCX when it is disconnected. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-153691 A Summary of the Invention [Problem to be solved by the invention]

[0006] Detecting the deterioration of the LCX itself or identifying the cause of the deterioration will contribute to preventing the disconnection of the LCX. In order to perform such detection or identification using an inspection car, the inspection car needs to be running. However, it is not easy to quickly check the deterioration over a long section of track, such as the entire track, by running the inspection car.

[0007] The present disclosure has an object to identify a deteriorated leaky coaxial cable from a communication device. [Means for solving the problem]

[0008] The method for detecting deterioration of a leaky coaxial cable according to the present disclosure includes a first step of determining the frequency characteristics of a leaky coaxial cable group having a plurality of leaky coaxial cables connected in series and having different frequency characteristics from each other, and a second step of detecting the presence or absence of deterioration in the leaky coaxial cables from the frequency characteristics of the leaky coaxial cable group determined in the first step.

[0009] The communication system according to the present disclosure includes a transmission path, a leaky coaxial cable group provided on the transmission path and having a plurality of leaky coaxial cables connected in series with different frequency characteristics, a first communication device, and a second communication device connected to the first communication device by the transmission path and detecting the presence or absence of deterioration in the leaky coaxial cables from the frequency characteristics of the leaky coaxial cable group. Effect of the Invention

[0010] According to the present disclosure, identification of a degraded leaky coaxial cable is performed from a communication device. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram illustrating a schematic configuration of a communication system. [Diagram 2] FIG. 2 is a block diagram illustrating generally components of a communication system in a communication zone. [Diagram 3]FIG. 13 is a block diagram that illustrates generally components of a communication system in another communication zone. [Figure 4] 1 is a block diagram illustrating a schematic configuration of a base station device in a first embodiment. [Diagram 5] 1 is a block diagram illustrating a schematic configuration of a relay device according to a first embodiment. [Figure 6] 2 is a block diagram illustrating a schematic configuration of a termination device according to the first embodiment. FIG. [Figure 7] FIG. 1 is a block diagram illustrating a schematic configuration of a leaky coaxial cable group. [Figure 8] 1 is a graph showing the dependence of attenuation on position in a leaky coaxial cable group when there is no degradation in the leaky coaxial cable group. [Figure 9] 11 is a graph showing the dependency of the attenuation of a leaky coaxial cable group on the position in the leaky coaxial cable group when the leaky coaxial cable is deteriorated. [Figure 10] 11 is a graph showing the dependence of the attenuation of a leaky coaxial cable group on the position in the leaky coaxial cable group when degradation is present in other leaky coaxial cables; [Figure 11] 10 is a graph showing the dependency of the attenuation of a leaky coaxial cable group on the position in the leaky coaxial cable group when deterioration is present in other leaky coaxial cables. [Figure 12] 4 is a flowchart illustrating a process of identifying a deteriorated portion in a group of leaky coaxial cables in the first embodiment. [Figure 13] 11 is a flowchart illustrating details of steps executed for each section. [Figure 14] FIG. 11 is a block diagram illustrating a schematic configuration of a base station device in a second embodiment. [Figure 15] FIG. 11 is a block diagram illustrating a schematic configuration of a relay device according to a second embodiment. [Figure 16] 1 is a schematic diagram illustrating a state in which one leaky coaxial cable group receives leaky radio waves leaking from another leaky coaxial cable group; [Figure 17]11 is a flowchart illustrating a process of identifying a deteriorated portion in a group of leaky coaxial cables in the second embodiment. [Figure 18] 11 is a flow chart illustrating details of the steps of identifying a leaky coaxial cable having a degraded portion by transmitting from the upper side to the lower side. [Figure 19] 11 is a flow chart illustrating details of the steps of identifying a leaky coaxial cable having a degraded portion by transmission from a low-side to a high-side; [Figure 20] FIG. 11 is a block diagram illustrating a schematic configuration of a termination device according to a second embodiment. [Figure 21] 13 is a flowchart illustrating a process of identifying a deteriorated portion in a group of leaky coaxial cables in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Outline of the communication system configuration> 1 is a block diagram illustrating a schematic configuration of a communication system 100. The communication system 100 includes a central device 10 and base station devices 201 and 202.

[0013] The base station device 201 can communicate with the central device 10. They are connected to each other, for example, using a local area network (hereinafter abbreviated as "LAN") 801. The base station device 201 exists in a communication zone 11. The central device 10 manages and controls communications in the communication zone 11 via the base station device 201.

[0014] The base station device 202 can communicate with the central unit 10. They are connected to each other using, for example, a LAN 802. The base station device 202 is present in a communication zone 12. The central unit 10 manages and controls communications in the communication zone 12 via the base station device 202.

[0015] 2 is a block diagram illustrating a schematic configuration of a communication system 100 in a communication zone 11. The communication system 100 includes one or more mobile station devices 6. The mobile station device 6 can move in either of the communication zones 11 and 12, and can also travel between the communication zones 11 and 12. For example, the mobile station device 6 is mounted on a railway vehicle. In the following, a case where the mobile station device 6 is present in the communication zone 11 is illustrated.

[0016] The communication system 100 includes a base station device 201, a termination device 401, one or more relay devices 301, transmission lines 500A and 500B as communication lines, two or more leaky coaxial cable groups 501A and 501B, and a monitoring line 901 in a communication zone 11.

[0017] All relay devices 301 are provided between base station device 201 and terminal device 401. Transmission paths 500A and 500B connect base station device 201, relay devices 301, and terminal device 401 in, for example, a daisy chain configuration.

[0018] Between the base station device 201 and the relay device 301, which are adjacent to each other, a leaky coaxial cable group 501A is provided in a transmission line 500A, and a leaky coaxial cable group 501B is provided in 500B. Between the base station device 201 and the relay device 301, wired communication is performed via the leaky coaxial cable groups 501A and 501B.

[0019] Between the repeater 301 and the terminal device 401, which are adjacent to each other, a leaky coaxial cable group 501A is provided in a transmission line 500A, and a leaky coaxial cable group 501B is provided in 500B. Between the repeater 301 and the terminal device 401, wired communication is performed via the leaky coaxial cable groups 501A and 501B.

[0020] When the communication system 100 includes a plurality of repeater devices 301 in the communication zone 11, a leaky coaxial cable group 501A is provided in a transmission line 500A between two adjacent repeater devices 301, and a leaky coaxial cable group 501B is provided in 500B. Wired communication is performed between the two adjacent repeater devices 301 via the leaky coaxial cable groups 501A and 501B.

[0021] In the communication zone 11, wireless communication is performed between the mobile station device 6 and the leaky coaxial cable group 501A, and between the mobile station device 6 and the leaky coaxial cable group 501B.

[0022] For example, when the mobile station device 6 moves in the direction from the base station device 201 to the termination device 401, the leaky coaxial cable group 501A is used for wired communication and wireless communication, and when the mobile station device 6 moves in the direction from the termination device 401 to the base station device 201, the leaky coaxial cable group 501B is used for wired communication and wireless communication.

[0023] The base station device 201 communicates with the terminal device 401 via the relay device 301 using the leaky coaxial cables 501A and 501B in the communication zone 11. The base station device 201 communicates with the mobile station device 6, for example, by wireless communication using signals leaking from the leaky coaxial cables 501A and 501B, transmitting and receiving voice and data.

[0024] The monitoring line 901 connects the base station device 201, the relay device 301, and the terminal device 401, for example, in a daisy chain form. The monitoring line 901 transmits a monitoring signal (hereinafter, "monitoring signal"), for example, from the relay device 301 and from the terminal device 401 via the relay device 301 to the base station device 201.

[0025] The base station device 201 uses a monitoring signal to monitor information indicating a fault in the communication zone 11. The central device 10 transmits and receives voice and data to and from the base station device 201 and the mobile station device 6 via the LAN 801, and collects information for monitoring the base station device 201, the relay device 301, the terminating device 401, and the mobile station device 6.

[0026] FIG. 3 is a block diagram that generally illustrates components of communication system 100 in communication zone 12.

[0027] The communication system 100 includes, in a communication zone 12, a base station device 202, a termination device 402, one or more repeaters 302A, 302B, transmission paths 500A, 500B, two or more leaky coaxial cable groups 502A, 502B, and a monitoring line 902.

[0028] All of the relay devices 302A are provided between the base station device 202 and the terminal device 401 (see FIG. 2) in the communication zone 11. All of the relay devices 302B are provided between the base station device 202 and the terminal device 402. Transmission paths 500A and 500B connect the terminal device 401, the relay device 302A, the base station device 202, the relay device 302B, and the terminal device 402, for example, in a daisy chain form.

[0029] A transmission line 500A connecting the base station device 202 and the terminal device 401 via the repeater device 302A, and a transmission line 500A connecting the base station device 202 and the terminal device 402 via the repeater device 302B are each provided with a leaky coaxial cable group 502A.

[0030] A transmission path 500B connecting the base station device 202 and the terminal device 401 via the repeater device 302A, and a transmission path 500B connecting the base station device 202 and the terminal device 402 via the repeater device 302B are each provided with a leaky coaxial cable group 502B.

[0031] Between the base station device 202 and the relay devices 302A and 302B, between the relay device 302A and the terminating device 401, and between the relay device 302B and the terminating device 402, wired communications are performed via leaky coaxial cable groups 501A and 501B.

[0032] In the communication zone 12, wireless communication is performed between the mobile station device 6 and the leaky coaxial cable group 502A, and between the mobile station device 6 and the leaky coaxial cable group 502B.

[0033] The base station device 202 performs wired communication using the leaky coaxial cable groups 502A and 502B to reach the terminal device 401 via the relay device 302A, and then to reach the terminal device 402 via the relay device 302B. The base station device 202 communicates with the mobile station device 6, for example, by wireless communication using signals leaking from the leaky coaxial cable groups 502A and 502B, and performs communication such as transmission and reception of voice and data.

[0034] For example, when the mobile station device 6 moves in the direction from the relay device 302A to the terminal device 402, the leaky coaxial cable group 502A is used for wired communication and wireless communication, and when the mobile station device 6 moves in the direction from the terminal device 402 to the relay device 302A, the leaky coaxial cable group 502B is used for wired communication and wireless communication.

[0035] The monitoring line 902 connects the base station device 202, the relay devices 302A and 302B, and the terminal devices 401 and 402 in, for example, a daisy chain configuration. The monitoring line 902 transmits monitoring signals from the terminal device 402 via, for example, the relay device 302B, and from the relay devices 302A and 302B to the base station device 202.

[0036] The base station device 202 uses a monitoring signal to monitor information indicating a fault in the communication zone 12. The central device 10 transmits and receives voice and data to and from the base station device 202 and the mobile station device 6 via the LAN 802, and collects information for monitoring the base station device 202, the relay devices 302A and 302B, the terminating device 402, and the mobile station device 6.

[0037] The base station devices 201 and 202, the relay devices 301, 302A, and 302B, the terminating devices 401 and 402, and the mobile station device 6 can all be considered to be communication devices that transmit and receive signals to and from one another.

[0038] The communication system 100 is realized, for example, as a train radio system. In this case, the mobile station device 6 is realized, for example, as a radio communication device mounted on a train. The transmission paths 500A and 500B, and therefore the leaky coaxial cable groups 501A, 501B, 502A, and 502B, are arranged, for example, along a railroad track on which the train on which the mobile station device 6 is mounted runs.

[0039] When the communication system 100 is realized as a train radio system, the base station devices 201 and 202, the relay devices 301, 302A, and 302B, and the terminal devices 401 and 402 are all provided, for example, in ground facilities. Alternatively, the base station devices 201 and 202, the relay devices 301, 302A, and 302B, and the terminal devices 401 and 402 can all be considered to be ground facilities.

[0040] The communication system 100 may have communication zones other than the communication zones 11 and 12. In Figures 1 and 3, the illustration of communication zones other than the communication zones 11 and 12 to which the transmission paths 500A and 500B and the monitoring line 903 are connected is omitted. Similarly to the case in which the monitoring lines 901 and 902 are connected to the terminating device 401 illustrated in Figure 2, the case in which the monitoring lines 902 and 903 are connected to the terminating device 402 is illustrated in Figure 3.

[0041] In the following, in order to simply and clearly explain the technology according to the present disclosure, the technology will be mainly explained in the communication zone 11. Naturally, the technology according to the present disclosure is not limited to being realized within the communication zone 11, but can also be realized in the communication zone 12.

[0042] <Embodiment 1> <Outline of the configuration of base station device 201> Fig. 4 is a block diagram illustrating a schematic configuration of the base station device 201 in the embodiment 1. In Fig. 4, the central unit 10, the LAN 801, the monitoring line 901, the leaky coaxial cable groups 501A and 501B, and the transmission paths 500A and 500B are also illustrated.

[0043] The base station device 201 has a monitor control device 21, a splitter 22, a receiving detector 23, and a transmitter 24. The monitor control device 21 is connected to the central device 10 via a LAN 801, and performs communication between the base station device 201 and the central device 10. The monitor control device 21 is connected to the relay device 301 via a monitor line 901, and performs communication between the relay device 301 and the base station device 201.

[0044] The transmitter 24 is connected to the leaky coaxial cable group 501A in the transmission line 500A, and is connected to the leaky coaxial cable group 501B in the transmission line 500B. The transmitter 24 has a function of transmitting a signal for transmission (hereinafter referred to as a "transmission signal") to one or both of the leaky coaxial cable groups 501A and 501B. The receiving detector 23 is connected to the transmission lines 500A and 500B via the splitter 22.

[0045] The receiving detector 23 detects the signal strength (hereinafter tentatively referred to as "initial strength of the transmission signal") at the end of the leaky coaxial cables 501A, 501B on the central unit 10 side of the transmission signal demultiplexed into different frequency bands by the demultiplexer 22. The signal strength is transmitted to the monitoring control device 21 via the transmitter 24, for example, for each frequency component of the transmission signal. The monitoring control device 21 knows the initial strength of the transmission signal for each frequency component.

[0046] The base station device 202 has a similar configuration to the base station device 201. However, since relay devices 302A and 302B are connected to the base station device 202, a pair of leaky coaxial cables 502A is used instead of the leaky coaxial cables 501A, and a pair of leaky coaxial cables 502B is used instead of the leaky coaxial cables 501B in the configuration shown in Fig. 4. A LAN802 is used instead of the LAN801.

[0047] <Outline of the configuration of relay device 301> 5 is a block diagram illustrating a schematic configuration of a repeater 301 according to the embodiment 1. The repeater 301 includes a monitoring device 31, splitters 32u and 32d, receiving detectors 33u and 33d, and amplifiers 34u and 34d.

[0048] 5 also shows the monitoring line 901, the leaky coaxial cable groups 501A and 501B, and the transmission paths 500A and 500B. The monitoring line 901 closer to the base station device 201 than the monitoring device 31 is marked with the reference symbol "901u" in parentheses, and the monitoring line 901 closer to the termination device 401 than the monitoring device 31 is marked with the reference symbol "901d" in parentheses to distinguish between the two.

[0049] In the following, the side closer to the base station device 201 may be referred to as the "upper side," and the side closer to the terminal device 402 may be referred to as the "lower side."

[0050] The leaky coaxial cable group 501A on the upper side of the repeater device 301 is marked with the reference symbol "501Au" in parentheses, and the leaky coaxial cable group 501A on the lower side of the repeater device 301 is marked with the reference symbol "501Ad" in parentheses to distinguish between the two. The leaky coaxial cable group 501B on the upper side of the repeater device 301 is marked with the reference symbol "501Bu" in parentheses, and the leaky coaxial cable group 501B on the lower side of the repeater device 301 is marked with the reference symbol "501Bd" in parentheses to distinguish between the two.

[0051] The leaky coaxial cable group 501Au is connected to the leaky coaxial cable group 501Ad in the transmission line 500A in the repeater 301. The leaky coaxial cable group 501Bu is connected to the leaky coaxial cable group 501Bd in the transmission line 500B in the repeater 301.

[0052] The branching filter 32u is connected to the leaky coaxial cable group 501Au in the transmission line 500A in the repeater 301. The branching filter 32u is connected to the leaky coaxial cable group 501Bu in the transmission line 500B in the repeater 301.

[0053] The branching filter 32d is connected to the leaky coaxial cable group 501Ad in the transmission line 500A in the repeater 301. The branching filter 32d is connected to the leaky coaxial cable group 501Bd in the transmission line 500B in the repeater 301.

[0054] For example, the duplexer 32u is connected between the leaky coaxial cable groups 501Au and 501Ad on the upstream side of the duplexer 32d. For example, the duplexer 32u is connected between the leaky coaxial cable groups 501Bu and 501Bd on the upstream side of the duplexer 32d.

[0055] The receiving detector 33u is connected to the splitter 32u. The receiving detector 33u detects the signal strength at the lower end of the leaky coaxial cable group 501Au, 501Bu of the transmission signal split into different frequency bands by the splitter 32u. The signal strength is notified to the base station device 201 or further to the central device 10 via the monitoring device 31 for each frequency component. At this time, gain control may be performed.

[0056] 5 illustrates an example in which an amplifier 34u used for the gain control is provided in a repeater device 301. The monitoring device 31 is connected to a receiving detector 33u via the amplifier 34u.

[0057] The receiving detector 33d is connected to the splitter 32d. The receiving detector 33d detects the signal strength at the upstream end of the leaky coaxial cable group 501Ad, 501Bd of the transmission signal split into different frequency bands by the splitter 32d. The signal strength is notified to the base station device 201 or further to the central device 10 via the monitoring device 31 for each frequency component. At this time, gain control may be performed.

[0058] 5 illustrates an example in which an amplifier 34d used for the gain control is provided in a repeater 301. The monitoring device 31 is connected to a receiving detector 33d via the amplifier 34d.

[0059] In this manner, the signal strengths at the points where the leaky coaxial cables 501A are connected in the relay device 301 and at the points where the leaky coaxial cables 501B are connected are notified to the base station device 201 for each different frequency component.

[0060] The repeater devices 302A and 302B are configured in the same manner as the repeater device 301. For example, the repeater devices 302A and 302B can be described in the same manner as the repeater device 301 illustrated in Fig. 5 and described above, by replacing the monitoring line 901 with the monitoring line 902 and the leaky coaxial cable groups 501A and 501B with the leaky coaxial cable groups 502A and 502B, respectively.

[0061] <Outline of the configuration of the terminating device 401> Fig. 6 is a block diagram illustrating a schematic configuration of the termination device 401 in the embodiment 1. In Fig. 6, monitoring lines 901 and 902, leaky coaxial cable groups 501A, 501B, 502A, and 502B, and transmission lines 500A and 500B are also illustrated.

[0062] The leaky coaxial cable group 501A is connected to the leaky coaxial cable group 502A in a transmission line 500A in the termination device 401. The leaky coaxial cable group 501B is connected to the leaky coaxial cable group 502B in a transmission line 500B in the termination device 401.

[0063] The termination device 401 includes a monitoring device 41, splitters 421 and 422, and receiving detectors 431 and 432.

[0064] The demultiplexer 421 is connected to the leaky coaxial cable group 501A in the transmission line 500A in the termination device 401. The demultiplexer 421 is connected to the leaky coaxial cable group 501B in the transmission line 500B in the termination device 401.

[0065] The demultiplexer 422 is connected to the leaky coaxial cable group 502A in the transmission line 500A in the termination device 401. The demultiplexer 422 is connected to the leaky coaxial cable group 502B in the transmission line 500B in the termination device 401.

[0066] For example, the splitter 421 is connected between the leaky coaxial cables 501A and 502A on the communication zone 11 side of the splitter 422. For example, the splitter 421 is connected between the leaky coaxial cables 501B and 502B on the communication zone 11 side of the splitter 422.

[0067] The receiving detector 431 is connected to the splitter 421. The receiving detector 431 detects the signal strength at the ends of the leaky coaxial cables 501A and 501B on the communication zone 12 side of the transmission signals split into different frequency bands by the splitter 421. The signal strength is notified to the base station device 201 or further to the central device 10 via the monitoring device 41 and the monitoring line 901 for each frequency component. At this time, gain control may be performed.

[0068] 6 shows an example in which an amplifier 441 used for the gain control is provided in a termination device 401. The monitoring device 41 is connected to a receiving detector 431 via the amplifier 441.

[0069] The receiving detector 432 is connected to the splitter 422. The receiving detector 432 detects the signal strength at the ends of the leaky coaxial cables 502A and 502B on the communication zone 11 side of the transmission signals split into different frequency bands by the splitter 422. The signal strength is notified to the base station device 202 or further to the central device 10 via the monitoring device 41 and the monitoring line 902 for each frequency component. At this time, gain control may be performed.

[0070] 6 shows an example in which an amplifier 442 used for the gain control is provided in a terminal device 401. The monitoring device 41 is connected to a receiving detector 432 via the amplifier 442.

[0071] The signal strength at the point where the leaky coaxial cable groups 501A and 502A are connected in the termination device 401 is notified to the base station device 201 for each frequency component. The signal strength at the point where the leaky coaxial cable groups 501B and 502B are connected in the termination device 401 is notified to the base station device 202 via the relay device 302A for each frequency component. These signal strengths may be notified to the central device 10.

[0072] The termination device 402 is also configured in the same manner as, for example, the termination device 401. For example, in the explanation of the termination device 401 illustrated in Fig. 6 and described above, the configuration and function of the termination device 402 can be explained by replacing the monitoring lines 901 and 902 with the monitoring lines 902 and 903, the leaky coaxial cable groups 501A and 501B with the leaky coaxial cable groups 502A and 502B, and the leaky coaxial cable groups 502A and 502B with other leaky coaxial cable groups (not shown).

[0073] <Outline of the configuration of leaky coaxial cable groups 501A and 501B> Fig. 7 is a block diagram illustrating a schematic configuration of the leaky coaxial cable group 5. Fig. 7 also shows the distribution of coupling loss in the leaky coaxial cable group 5 and the amount of attenuation when a signal is transmitted from the upper side to the lower side. For example, the leaky coaxial cable group 5 is used for all of the leaky coaxial cable groups 501A, 501B, 502A, and 502B.

[0074] 7, the leaky coaxial cable group 5 has leaky coaxial cables 51, 52, and 53 connected in series. The leaky coaxial cable 51 is connected to the upstream side of the leaky coaxial cable 52, and the leaky coaxial cable 52 is connected to the upstream side of the leaky coaxial cable 53. For convenience of explanation, neither a connector that couples the leaky coaxial cables 51 and 52 nor a connector that couples the leaky coaxial cables 52 and 53 is taken into consideration.

[0075] Specifically, the leaky coaxial cable group 5 is provided between positions P01 and P30 (position P30 is lower than position P01). In the leaky coaxial cable group 5, the leaky coaxial cable 51 is provided between positions P01 and P12 (position P12 is lower than position P01), the leaky coaxial cable 52 is provided between positions P12 and P23 (position P23 is lower than position P12), and the leaky coaxial cable 53 is provided between positions P23 and P30 (position P30 is lower than position P23).

[0076] For example, when the leaky coaxial cable group 5 is adopted as the leaky coaxial cable group 501A provided between the base station device 201 and the repeater device 301 (see FIG. 2), the upper end of the leaky coaxial cable 51 is connected to the transmitter 24 and the splitter 22 of the base station device 201 (see FIG. 4), and the lower end of the leaky coaxial cable 53 is connected to the splitter 32u and the amplifier 34u of the repeater device 301 (see FIG. 5).

[0077] For example, when the leaky coaxial cable group 5 is adopted as a leaky coaxial cable group 501A provided between two relay devices 301 that are connected without passing through another relay device 301, the upper end of the leaky coaxial cable 51 is connected to the splitter 32d and amplifier 34d of the upper relay device 301, and the lower end of the leaky coaxial cable 53 is connected to the splitter 32u and amplifier 34u of the lower relay device 301 (see FIG. 5).

[0078] For example, when the leaky coaxial cable group 5 is adopted as a leaky coaxial cable group 501A provided between the repeater 301 and the terminal device 401, the lower end of the leaky coaxial cable 51 is connected to the splitter 32d and amplifier 34d of the repeater 301 (see FIG. 5), and the upper end of the leaky coaxial cable 53 is connected to the splitter 421 and amplifier 441 of the terminal device 401 (see FIG. 6).

[0079] For example, when the leaky coaxial cable group 5 is adopted as the leaky coaxial cable group 502A provided between the termination device 401 and the repeater device 302A, the upper end of the leaky coaxial cable 51 is connected to the splitter 422 and the amplifier 442 of the termination device 401 (see FIG. 6), and the lower end of the leaky coaxial cable 53 is connected to the repeater device 302A.

[0080] For example, slots are provided in each of the leaky coaxial cables 51, 52, and 53. The leaky coaxial cables 5 perform wireless communication with the mobile station device 6 by using radio waves (leaking radio waves) leaking from these slots. The leaky coaxial cables 51, 52, and 53 have different coupling losses due to differences in the shape, angle, and length of the slots.

[0081] In the leaky coaxial cable group 5, the coupling loss on the lower side is smaller than the coupling loss on the upper side. Specifically, the coupling loss of leaky coaxial cable 52 is smaller than the coupling loss of leaky coaxial cable 51, and the coupling loss of leaky coaxial cable 53 is smaller than the coupling loss of leaky coaxial cable 52. The characteristic in which the coupling loss on the side farther from the signal source (here, the lower side) is smaller than the coupling loss on the side closer to the signal source (here, the upper side) is commonly called grading.

[0082] In the leaky coaxial cable group 5 with the characteristics selected in this way, the coupling loss is lower at a greater distance where the attenuation of the signal from the base station device 201 inside the leaky coaxial cable group 5 is greater. With such characteristics, wireless communication is performed with a transmission / reception strength equal to or greater than a desired value between the leaky coaxial cable groups 501A, 501B and the mobile station device 6, regardless of where the train carrying the mobile station device 6 is located in the communication zone 11 between the base station device 201, the relay device 301, and the termination device 401. The same advantage is also obtained in wireless communication in the communication zone 12.

[0083] The technology according to Embodiment 1 determines the presence or absence of deterioration in the leaky coaxial cable group 5, and identifies which of the leaky coaxial cables 51, 52, 53 has deterioration when there is deterioration in the leaky coaxial cable group 5. For example, in Embodiment 1, based on the attenuation amount in the leaky coaxial cable group 5, the presence or absence of deterioration and the identification of the location where deterioration occurs are performed.

[0084] FIG. 8 is a graph showing the dependence on the position in the leaky coaxial cable group 5 with the attenuation amount when there is no deterioration in the leaky coaxial cable group 5 taken as the "normal attenuation amount".

[0085] The broken lines G5a, G5b, G5c indicate the normal attenuation amounts of the frequency components of the transmission signal (hereinafter referred to as the "transmission signal") in the state of being transmitted in the leaky coaxial cable group 5. The broken lines G5a, G5b, G5c respectively correspond to the components of the frequencies Fa, Fb, Fc. For example, there is a relationship of Fa < Fb < Fc, and for example, Fa = 100 [MHz], Fb = 200 [MHz], Fc = 300 [MHz]. At the position P01, it is considered that there is no attenuation by the leaky coaxial cable group 5 regardless of the frequencies Fa, Fb, Fc. Therefore, the normal attenuation amounts at the position P01 of the broken lines G5a, G5b, G5c are shown to be the same.

[0086] In FIG. 8, an example is illustrated where the smaller the coupling loss, the larger the attenuation coefficient regardless of the frequency component of the transmission signal. For any of the broken lines G5a, G5b, G5c, the slope between their respective positions P12, P23 (that is, in the leaky coaxial cable 52) is larger than the slope between their respective positions P01, P12 (that is, in the leaky coaxial cable 51). For any of the broken lines G5a, G5b, G5c, the slope between their respective positions P23, P30 (that is, in the leaky coaxial cable 53) is larger than the slope between their respective positions P12, P23 (that is, in the leaky coaxial cable 52).

[0087] 8 illustrates a case where the higher the frequency of the frequency component of the transmission signal, the smaller the attenuation coefficient is, regardless of the coupling loss. Regardless of the position in the leaky coaxial cable group 5, the inclination of the folded line G5b is smaller than that of the folded line G5a, and the inclination of the folded line G5c is smaller than that of the folded line G5b.

[0088] In the following, the following characteristics are assumed: the increase in attenuation of the leaky coaxial cable 51 when it deteriorates is equal to or less than a specified value for each of the differences between the frequencies Fa, Fb, and Fc; the increase in attenuation of the leaky coaxial cable 52 when it deteriorates is greater than the specified value for each of the frequencies Fa and Fb, and the increase in attenuation of the leaky coaxial cable 53 when it deteriorates is greater than the specified value for each of the frequencies Fb and Fc. The specified value is set to be greater than the measurement accuracy of the attenuation.

[0089] Fig. 9 is a graph showing the attenuation of the leaky coaxial cable group 5 when the leaky coaxial cable 51 is deteriorated, designated as "attenuation when LCX51 is deteriorated," and showing its dependency on the position in the leaky coaxial cable group 5. An example is shown in which deterioration occurs at position P51 of the leaky coaxial cable 51. The deterioration occurs due to, for example, aging, dancing, or clogging of the slot. Fig. 9 shows an example in which the attenuation of the leaky coaxial cable 51 increases in a step-like manner at position P51.

[0090] The broken lines G51a, G51b, and G51c respectively show the attenuation amounts of the frequency components Fa, Fb, and Fc in the leaky coaxial cable group 5. As in Fig. 8, the broken lines G51a, G51b, and G51c show the same attenuation amount at the position P01.

[0091] The increase in attenuation at position P51 is also reflected in the attenuation below position P51. In Fig. 9, of the broken lines G5a, G5b, and G5c indicating the attenuation under normal conditions, the portion at position P30 and its vicinity are also shown by dashed lines. When the leaky coaxial cable 51 is deteriorated, the attenuation of the leaky coaxial cable group 5 is larger at position P30, more specifically at the lower end of the leaky coaxial cable group 5, by differences Δ51a, Δ51b, and Δ51c, compared to the attenuation under normal conditions.

[0092] The differences Δ51a, Δ51b, and Δ51c correspond to the components of frequencies Fa, Fb, and Fc, respectively. More specifically, for the component of frequency Fa of the transmission signal, the difference Δ51a is the attenuation amount by which the attenuation of the leaky coaxial cable group 5 increases when the leaky coaxial cable 51 is deteriorated at the lower end of the leaky coaxial cable group 5 compared to the normal attenuation amount when the leaky coaxial cable 51 is deteriorated at the lower end of the leaky coaxial cable group 5. For the component of frequency Fb of the transmission signal, the difference Δ51b is the attenuation amount by which the attenuation of the leaky coaxial cable group 5 increases when the leaky coaxial cable 51 is deteriorated at the lower end of the leaky coaxial cable group 5 compared to the normal attenuation amount when the leaky coaxial cable 51 is deteriorated at the lower end of the leaky coaxial cable group 5. For the component of frequency Fc of the transmission signal, the difference Δ51c is the attenuation amount by which the attenuation of the leaky coaxial cable group 5 increases when the leaky coaxial cable 51 is deteriorated at the lower end of the leaky coaxial cable group 5 compared to the normal attenuation amount when the leaky coaxial cable 51 is deteriorated at the lower end of the leaky coaxial cable group 5.

[0093] 9 shows a case where the step-like increase in attenuation at position P51 falls within a specified range regardless of the frequency of the transmission signal, and the differences Δ51a, Δ51b, and Δ51c also fall within the specified range, reflecting this tendency of increase. "Falling within a specified range" means that the values ​​being compared fall within a certain range, for example, the difference between the maximum and minimum values ​​of the differences Δ51a, Δ51b, and Δ51c is equal to or less than a preset threshold. The threshold is set to be greater than the measurement accuracy of the attenuation.

[0094] Fig. 10 is a graph showing the dependency of the attenuation of the leaky coaxial cable group 5 when the leaky coaxial cable 52 is deteriorated, which is defined as "attenuation when LCX52 is deteriorated", on the position in the leaky coaxial cable group 5. A case where deterioration occurs at position P52 of the leaky coaxial cable 52 is illustrated. Fig. 10 illustrates a case where the attenuation of the leaky coaxial cable 52 increases stepwise at position P52.

[0095] The broken lines G52a, G52b, and G52c respectively show the attenuation amounts of the frequency components Fa, Fb, and Fc in the leaky coaxial cable group 5. As in Fig. 8, the broken lines G52a, G52b, and G52c show the same attenuation amounts at the position P01.

[0096] The increase in attenuation at position P52 is also reflected in the attenuation below position P52. In Fig. 10, of the broken lines G5a, G5b, and G5c indicating the attenuation under normal conditions, the portion at position P30 and its vicinity are also shown by dashed lines. When the leaky coaxial cable 52 is deteriorated, the attenuation of the leaky coaxial cable group 5 is larger than the attenuation under normal conditions at position P30, more specifically, at the lower end of the leaky coaxial cable group 5, by differences Δ52a, Δ52b, and Δ52c.

[0097] The differences Δ52a, Δ52b, and Δ52c correspond to the components of frequencies Fa, Fb, and Fc, respectively. More specifically, for the component of frequency Fa of the transmission signal, the difference Δ52a is the attenuation amount by which the attenuation of the leaky coaxial cable group 5 increases when the leaky coaxial cable 52 is deteriorated at the lower end of the leaky coaxial cable group 5 compared to the normal attenuation amount when the leaky coaxial cable 52 is deteriorated at the lower end of the leaky coaxial cable group 5. For the component of frequency Fb of the transmission signal, the difference Δ52b is the attenuation amount by which the attenuation of the leaky coaxial cable group 5 increases when the leaky coaxial cable 52 is deteriorated at the lower end of the leaky coaxial cable group 5 compared to the normal attenuation amount when the leaky coaxial cable 52 is deteriorated at the lower end of the leaky coaxial cable group 5. For the component of frequency Fc of the transmission signal, the difference Δ52c is the attenuation amount by which the attenuation of the leaky coaxial cable group 5 increases when the leaky coaxial cable 52 is deteriorated at the lower end of the leaky coaxial cable group 5 compared to the normal attenuation amount when the leaky coaxial cable 52 is deteriorated at the lower end of the leaky coaxial cable group 5.

[0098] 10, the step-like increase in attenuation at position P52 is such that the difference between the component of frequency Fa and the component of frequency Fb of the transmission signal is equal to or smaller than a specified value, which is greater than the component of frequency Fc of the transmission signal by more than the specified value. Reflecting this difference, the difference between the differences Δ52a and Δ52b is equal to or smaller than a preset specified value, and the difference between the smaller of the differences Δ52a and Δ52b and the difference Δ52c is greater than the specified value. The specified value is set to be greater than the measurement accuracy of the attenuation.

[0099] Fig. 11 is a graph showing the attenuation of the leaky coaxial cable group 5 when the leaky coaxial cable 53 is deteriorated, which is designated as "attenuation when LCX53 is deteriorated", and showing its dependency on the position in the leaky coaxial cable group 5. The example shows a case where deterioration occurs at position P53 of the leaky coaxial cable 53. Fig. 11 shows a case where the attenuation of the leaky coaxial cable 53 increases stepwise at position P53.

[0100] The broken lines G53a, G53b, and G53c respectively show the attenuation amounts of the frequency components Fa, Fb, and Fc in the leaky coaxial cable group 5. As in Fig. 8, the broken lines G53a, G53b, and G53c show the same attenuation amounts at the position P01.

[0101] The increase in attenuation at position P53 is also reflected in the attenuation below position P53. In Fig. 11, the broken lines G5a, G5b, and G5c indicating the normal attenuation are also shown with dashed lines from position P53 to position P30. When the leaky coaxial cable 53 is deteriorated, the attenuation of the leaky coaxial cable group 5 is larger than the normal attenuation at position P30, more specifically, at the lower end of the leaky coaxial cable group 5, by differences Δ53a, Δ53b, and Δ53c.

[0102] The differences Δ53a, Δ53b, and Δ53c correspond to the components of frequencies Fa, Fb, and Fc, respectively. More specifically, for the component of frequency Fa of the transmission signal, the difference Δ53a is the attenuation amount by which the attenuation of the leaky coaxial cable group 5 increases when the leaky coaxial cable 53 is deteriorated at the lower end of the leaky coaxial cable group 5 compared to the normal attenuation amount when the leaky coaxial cable 53 is deteriorated at the lower end of the leaky coaxial cable group 5. For the component of frequency Fb of the transmission signal, the difference Δ53b is the attenuation amount by which the attenuation of the leaky coaxial cable group 5 increases when the leaky coaxial cable 53 is deteriorated at the lower end of the leaky coaxial cable group 5 compared to the normal attenuation amount when the leaky coaxial cable 53 is deteriorated at the lower end of the leaky coaxial cable group 5. For the component of frequency Fc of the transmission signal, the difference Δ53c is the attenuation amount by which the attenuation of the leaky coaxial cable group 5 increases when the leaky coaxial cable 53 is deteriorated at the lower end of the leaky coaxial cable group 5 compared to the normal attenuation amount when the leaky coaxial cable 53 is deteriorated at the lower end of the leaky coaxial cable group 5.

[0103] 11, the step-like increase in attenuation at position P53 is such that the difference between the frequency Fb component and the frequency Fc component of the transmission signal is equal to or less than a specified value, and the frequency Fa component of the transmission signal is greater than these components by more than the specified value. Reflecting this difference, the difference between the differences Δ53b and Δ53c is equal to or less than a preset specified value, and the difference between the larger of the differences Δ53b and Δ53c and the difference Δ53a is greater than the specified value. The specified value is set to be greater than the measurement accuracy of the attenuation.

[0104] In the first embodiment, when the attenuation at the lower end of the leaky coaxial cable group 5 is greater than the normal attenuation by more than a threshold value, it is determined at which position in the leaky coaxial cable group 5 deterioration occurs.

[0105] Fig. 12 is a flowchart illustrating a process of identifying a deteriorated portion in the leaky coaxial cable group 5 (labeled as "identification of deteriorated LCX" in Fig. 12) in the embodiment 1. Fig. 12 illustrates a case in which the process includes steps S11, S12, S13, S14, and S15, which are executed in this order.

[0106] The following describes an example of a process for identifying deterioration in the leaky coaxial cable group 501A. This process is also applied to identifying deterioration in the leaky coaxial cable group 501B. For this reason, the notations "leaky coaxial cable group 501A (501B)" and "transmission path 500A (500B)" are used in Fig. 12 for the sake of convenience. Note that although the technology in the communication zone 11 is described in this embodiment, the same technology can be realized in the communication zone 12 as described above.

[0107] In step S11, the superimposed signal M0 is transmitted from the base station device 201 to the leaky coaxial cable group 501A. Here, the "superimposed signal" is a transmission signal having a plurality of frequency components, for example, all of the components of frequencies Fa, Fb, and Fc. When the superimposed signal M0 is transmitted, the initial strength of the transmission signal for each frequency component of the superimposed signal M0 is known by the monitor and control device 21 as described above.

[0108] In step S11, specifically, referring to FIG. 4, the central device 10 instructs the monitor and control device 21 of the base station device 201 to transmit the superimposed signal M0 by the transmitter 24 via the LAN 801. Based on the instruction, the transmitter 24 transmits the superimposed signal M0 to the transmission path 500A. The superimposed signal M0 is transmitted while being attenuated through the leaky coaxial cable group 501A (see FIG. 1 and FIG. 4) provided between the base station device 201 and the adjacent repeater device 301 (see FIG. 1). Similarly, the superimposed signal M0 is transmitted while being attenuated between the adjacent repeaters 301. Similarly, the superimposed signal M0 is transmitted while being attenuated between the adjacent repeaters 301 and the termination device 401.

[0109] In step S12, the signal strength of the transmission line 500A at the repeater 301 and the signal strength of the transmission line 500A at the terminator 401 are measured.

[0110] For example, referring to FIG. 5, the signal strength of the superimposed signal M0 transmitted through the leaky coaxial cable group 501Au, in other words at the lower end of the leaky coaxial cable group 501Au, is detected for each frequency component. Specifically, the superimposed signal M0 at the end is demultiplexed by the demultiplexer 32u to obtain a transmission signal for each frequency band. For example, the superimposed signal M0 is demultiplexed into components of frequencies Fa, Fb, and Fc as transmission signals. The signal strength of the transmission signal for each frequency component is detected by the receiving detector 33u. This detection can be said to be a measurement of the signal strength at the lower end of the leaky coaxial cable group 501Au, or a measurement of the signal strength at the upper end of the transmission path 500A in the repeater 301. These signal strengths are transmitted to the monitoring line 901u via the monitoring device 31.

[0111] After the signal strength is detected by the receiving detector 33u, the amplifier 34u amplifies the superimposed signal M0 in the transmission line 500A in the repeater 301. After the amplification, the signal strength of the superimposed signal M0 at the upper end of the leaky coaxial cable group 501Ad is detected for each frequency band. Specifically, the superimposed signal M0 at the end is demultiplexed by the demultiplexer 32d to obtain a transmission signal for each frequency band. For example, the superimposed signal M0 is demultiplexed into transmission signals that are components of frequencies Fa, Fb, and Fc. The signal strength of the transmission signal is detected for each frequency component by the receiving detector 33d. This detection can be said to be a measurement of the signal strength at the upper end of the leaky coaxial cable group 501Ad, or a measurement of the signal strength at the lower end of the transmission line 500A in the repeater 301. These signal strengths are transmitted to the monitoring line 901u via the monitoring device 31.

[0112] For example, referring to Fig. 6, the signal strength of the superimposed signal M0 at the end on the lower side of the leaky coaxial cable group 501A is detected for each frequency band. Specifically, the superimposed signal M0 at this end is demultiplexed by the demultiplexer 421 to obtain a transmission signal for each frequency band. For example, the superimposed signal M0 is demultiplexed into transmission signals that are components of frequencies Fa, Fb, and Fc. The signal strength of the transmission signal for each frequency component is detected by the receiving detector 431. This detection can be said to be a measurement of the signal strength at the end on the lower side of the leaky coaxial cable group 501A, or a measurement of the signal strength on the upper side of the transmission path 500A in the termination device 401. These signal strengths are transmitted to the monitoring line 901 via the monitoring device 41.

[0113] After the signal strength is detected by the receiving detector 431, the superimposed signal M0 in the transmission line 500A in the termination device 401 is amplified by the amplifier 441. After this amplification, the signal strength of the superimposed signal M0 at the upper end of the leaky coaxial cable group 502A is detected for each frequency band. Specifically, the superimposed signal M0 at this end is split by the splitter 422 to obtain a transmission signal for each frequency component.

[0114] For example, the superimposed signal M0 is branched into transmission signals having the respective frequency components Fa, Fb, and Fc. The signal strength of the transmission signal for each frequency component is detected by the receiving detector 432. This detection can be said to be a measurement of the signal strength at the upstream end of the leaky coaxial cable group 502A, or a measurement of the signal strength at the downstream end of the transmission path 500A in the termination device 401. These signal strengths are transmitted to the monitoring line 902 via the monitoring device 41.

[0115] The monitoring line 901u connected to the lower relay device 301 of the adjacent relay device 301 functions as a monitoring line 901d connected to the upper relay device 301 of the adjacent relay device 301. The strength of the received signal measured in the relay device 301 and the termination device 401 is transmitted to the monitoring device 31.

[0116] A monitor line 901u connected to a relay device 301 adjacent to the base station device 201 functions as a monitor line 901 connected to the base station device 201. The initial strength of the transmission signal is transmitted to the monitor device 31 from the monitor control device 21 in the base station device 201 via the monitor line 901.

[0117] In step S13, the attenuation amount for each section and each frequency band is calculated based on the signal strength. Here, a "section" refers to any of the sections between adjacent base station device 201 and relay device 301, between adjacent relay devices 301, and between adjacent relay devices 301 and terminal device 401.

[0118] The amount of attenuation in the section between the adjacent base station device 201 and relay device 301 is specifically obtained as the amount of attenuation of the signal strength measured by the receiving detector 33u in the relay device 301, as viewed from the initial strength of the transmitted signal (which is known as described above). The amount of attenuation is obtained, for example, in the monitoring device 31 of the relay device 301 or in the monitoring and controlling device 21 of the base station device 201.

[0119] Specifically, the amount of attenuation in the section between adjacent repeaters 301 is obtained as the amount of attenuation of the signal strength measured by the receiving detector 33u of the lower repeater 301, as viewed from the signal strength measured by the receiving detector 33d of the upper repeater 301. The amount of attenuation is obtained, for example, in the monitoring device 31 of the lower repeater 301 or in the monitoring device 31 of the upper repeater 301.

[0120] The amount of attenuation in the section between adjacent repeater 301 and termination device 401 is specifically obtained as the amount of attenuation of the signal strength measured by reception detector 431 in termination device 401, as viewed from the signal strength measured by reception detector 33d of repeater 301. The amount of attenuation is obtained, for example, in monitoring device 31 of downstream repeater 301 or in monitoring device 41 of termination device 401.

[0121] The attenuation in these sections is assumed to be the attenuation in the leaky coaxial cable group 501A provided in each section. As described in step S12, the signal strength of the received signal is obtained for each frequency band, and the initial strength of the transmitted signal is also notified to the monitor and control device 21 for each frequency band. The attenuation in these sections is obtained for each frequency band in each section.

[0122] Any of the amounts of attenuation in these sections may be determined in the monitor control device 21 using the signal strength transmitted to the monitor control device 21 via the monitor line 901 .

[0123] The signal strength transmitted to the monitor line 901 and the amount of attenuation transmitted to the monitor line 901 are examples of the monitor signal mentioned above.

[0124] The attenuation of the leaky coaxial cable group 502A installed in the section between the adjacent terminal device 402 and repeater device 302A is obtained as the amount of attenuation from the signal strength at the upstream end of the transmission path 500A in the repeater device 302A, as viewed from the signal strength measured by the receiving detector 432 in the terminal device 401. For example, these signal strengths are all transmitted to the base station device 202 via the monitoring line 902, and the attenuation is obtained in the base station device 202.

[0125] The amount of attenuation obtained by executing step S13 corresponds to the amount of attenuation at position P30 shown in FIGS.

[0126] In step S14, the amounts of attenuation for each frequency band are compared for each section to determine whether or not there is deterioration in each of the leaky coaxial cables 51, 52, and 53 that make up the leaky coaxial cable group 501A.

[0127] The attenuation of each of the leaky coaxial cables 51, 52, and 53 when no deterioration occurs (corresponding to the attenuation at position P30 shown in FIG. 8) is known from their specifications (for example, standard attenuation) and the lengths to which they are laid. The characteristics of the leaky coaxial cables 51, 52, and 53 when deteriorated can be understood by, for example, applying an environmental load to each of them to create a deteriorated state and conducting a test to measure the attenuation for each frequency band in the deteriorated state. The characteristics of the leaky coaxial cables 51, 52, and 53 when deteriorated may be obtained from the manufacturers of the leaky coaxial cables 51, 52, and 53.

[0128] Fig. 13 is a flowchart illustrating the details of step S14 executed for each section. Fig. 13 illustrates a case where step S14 includes steps S141 to S148.

[0129] In executing step S14, first, step S141 is executed. In step S141, differences Δ5a, Δ5b, and Δ5c are calculated for each frequency component of the superimposed signal M0 in the same section.

[0130] The normal attenuation of the transmission signal as the component of frequency Fa differs from the attenuation calculated in step S13 by a difference Δ5a. The normal attenuation of the transmission signal as the component of frequency Fb differs from the attenuation calculated in step S13 by a difference Δ5b. The normal attenuation of the transmission signal as the component of frequency Fc differs from the attenuation calculated in step S13 by a difference Δ5c. When there is no degradation in any of the leaky coaxial cables 51, 52, and 53, and therefore when there is no degradation in the leaky coaxial cable group 501A, the differences Δ5a, Δ5b, and Δ5c from the normal attenuation are small.

[0131] The flowchart in Fig. 13 will be described below with reference to the cases illustrated in Fig. 8 to Fig. 11. After step S141 is executed, the values ​​of the differences Δ5a, Δ5b, and Δ5c are examined in step S142. Specifically, for example, a positive threshold ε5 is set, and it is determined whether any of the differences Δ5a, Δ5b, and Δ5c is equal to or less than the threshold ε5 (Δ5a, Δ5b, Δ5c ≦ ε5).

[0132] When the leaky coaxial cable group 501 is not deteriorated, the difference between the attenuation at the lower end of the leaky coaxial cable group 5 and the normal attenuation is small for all of the frequency components Fa, Fb, and Fc. If the determination result of step S141 is positive, step S145 is executed. In step S145, it is determined that the leaky coaxial cable group 501 in the section of interest is not deteriorated.

[0133] If the determination result of step S141 is negative, step S143 is executed. When the leaky coaxial cable 51 is deteriorated, referring to Fig. 9, the differences Δ5a, Δ5b, Δ5c correspond to the differences Δ51a, Δ51b, Δ51c illustrated in Fig. 9, respectively. At this time, the differences Δ5a, Δ5b, Δ5c between their maximum and minimum values ​​are equal to or smaller than a preset specified value. The specified value is set to be greater than the measurement accuracy of the attenuation amount.

[0134] Since all of the differences Δ5a, Δ5b, and Δ5c are non-negative values, a positive threshold ε5a (where ε5<ε5a) is used in step S143, and it is determined whether all of the differences Δ5a, Δ5b, and Δ5c are equal to or less than the threshold ε5a (Δ5a, Δ5b, Δ5c≦ε5a). If the determination result is positive, the values ​​that the differences Δ5a, Δ5b, and Δ5c can take are equal to or greater than 0 and equal to or less than ε5a, so the difference between the maximum and minimum values ​​of the differences Δ5a, Δ5b, and Δ5c is equal to or less than the threshold ε5a. For example, the threshold ε5a is set to twice the minimum value of the differences Δ5a, Δ5b, and Δ5c.

[0135] When the determination result in step S143 is positive, step S148 is executed. In step S148, it is determined that the leaky coaxial cable 51 in the leaky coaxial cable group 501 in the section of interest is deteriorated.

[0136] When the determination result in step S143 is negative, it is assumed that deterioration exists in either the leaky coaxial cable 52 or 53 in the leaky coaxial cable group 501. The differences Δ5a, Δ5b, and Δ5c correspond to the differences Δ52a, Δ52b, and Δ52c in Fig. 10 illustrating the case where deterioration occurs in the leaky coaxial cable 52, or correspond to the differences Δ53a, Δ53b, and Δ53c in Fig. 11 illustrating the case where deterioration occurs in the leaky coaxial cable 53.

[0137] When the determination result in step S143 is negative, step S144 is executed. With reference to Fig. 10 and Fig. 11, in step S144, it is determined whether the difference Δ5b is greater than the difference Δ5c by exceeding a positive threshold ε5b (Δ5b>Δ5c+ε5b). When the determination result is positive, it corresponds to the example in Fig. 10, and when the determination result is negative, it corresponds to the example in Fig. 11. For example, the threshold ε5b is set to twice the difference Δ5c.

[0138] When the determination result in step S144 is positive, step S146 is executed. In step S146, it is determined that the leaky coaxial cable 52 in the leaky coaxial cable group 501 in the section of interest is deteriorated.

[0139] When the result of the determination in step S144 is negative, step S147 is executed, in which it is determined that the leaky coaxial cable 53 in the leaky coaxial cable group 501 in the section of interest is deteriorated.

[0140] Any one of steps S145, S146, S147, and S148 is executed, step S14 is completed, and step S15 is executed.

[0141] 12, in step S15, information indicating a leaky coaxial cable having a deteriorated portion (abbreviated as "deteriorated LCX" in the figure) is transmitted from the base station device 201 to the central unit 10. Specifically, the monitor control device 21 executing step S14 transmits the information to the central unit 10 via the LAN 801. The user recognizes the leaky coaxial cable having a deteriorated portion, for example, by using a function that the central unit 10 normally has.

[0142] The deteriorated portion of the leaky coaxial cable group 501B can be identified in the same manner as the leaky coaxial cable group 501A.

[0143] The content of step S14 is not limited to the example shown in Fig. 13. For example, the standard attenuation of the leaky coaxial cable 51 at frequency Fa may be smaller than the standard attenuation at frequency Fb. For example, the standard attenuation of the leaky coaxial cable 51 at frequency Fa may be larger than the standard attenuation of the leaky coaxial cable 52 at frequency Fa. In these cases, the content of step S14 can be explained by appropriately replacing the differences Δ5a, Δ5b, and Δ5c shown in Fig. 13.

[0144] When the frequency characteristics of the leaky coaxial cables 51, 52 are equal, it may be possible to imagine a case where it is impossible to distinguish between deterioration in the leaky coaxial cable 51 and deterioration in the leaky coaxial cable 52. However, even in this case, if the frequency characteristics of the leaky coaxial cables 51, 52 differ from the frequency characteristics of the leaky coaxial cable 53, it is possible to determine whether deterioration has occurred in at least one of the leaky coaxial cables 51, 52.

[0145] The number of leaky coaxial cables included in each of the leaky coaxial cable groups 5 may be four or more. Performing attenuation measurements in the number of types of frequency bands equal to or more than the number of leaky coaxial cables contributes to identifying the location of the leaky coaxial cable where degradation is occurring.

[0146] The first embodiment is roughly divided into a first step exemplified by steps S11, S12, and S13 and a second step exemplified by step S14 with reference to Fig. 12. In the first step, the frequency characteristics of the leaky coaxial cable group 5 having the leaky coaxial cables 51, 52, and 53 connected in series with different frequency characteristics are obtained. In the above example, the frequency characteristics are the attenuation amounts for different frequencies at the position P30, and are specifically exemplified by the attenuation amounts at the position P30 of the folded lines G5a, G5b, and G5c (see Fig. 8), or the attenuation amounts at the position P30 of the folded lines G51a, G51b, and G51c (see Fig. 9), or the attenuation amounts at the position P30 of the folded lines G52a, G52b, and G52c (see Fig. 10), or the attenuation amounts at the position P30 of the folded lines G53a, G53b, and G53c (see Fig. 11).

[0147] In the second step, the presence or absence of deterioration in the leaky coaxial cables 51, 52, and 53 is detected from the frequency characteristics of the leaky coaxial cables 5 obtained in the first step.

[0148] In this manner, the frequency characteristics of the leaky coaxial cables 5 are obtained, and the presence or absence of deterioration in the leaky coaxial cables 51, 52, and 53 is detected from the frequency characteristics. Therefore, which of the leaky coaxial cables 51, 52, and 53 has deteriorated can be identified using a communication device.

[0149] Defects in each of the leaky coaxial cables 51, 52, and 53 are reflected in the frequency characteristics of the leaky coaxial cable group 5. As illustrated in step S13, a superimposed signal M0 is transmitted to the leaky coaxial cable group 5, and the attenuation in the leaky coaxial cable group 5 is found for each of the frequency components Fa, Fb, and Fc. As illustrated in step S14, the attenuation for each frequency band (i.e., each frequency component) is compared. In this way, in the first embodiment, the presence or absence of deterioration in the leaky coaxial cables 51, 52, and 53 is detected based on the attenuation, which contributes to identifying the deterioration using a communication device.

[0150] For example, as illustrated in step S141 (see FIG. 13), differences Δ5a, Δ5b, Δ5c between the attenuation of the leaky coaxial cable group 5 in the absence of degradation (see FIG. 8) and the attenuation of the leaky coaxial cable group 5 calculated in step S13 (see FIG. 9 to FIG. 11) are calculated for each frequency component. Then, as illustrated in steps S142 to S148, the differences Δ5a, Δ5b, Δ5c for the components of frequencies Fa, Fb, Fc are compared with each other. Defects in each of the leaky coaxial cables 51, 52, 53 are reflected as the differences Δ5a, Δ5b, Δ5c in the attenuation of the leaky coaxial cable group 5 depending on the frequency. Therefore, such comparison contributes to detection of the presence or absence of degradation in the leaky coaxial cables 51, 52, 53.

[0151] 1 to 3, the first embodiment is exemplified as a communication system 100 including a first communication device and a second communication device. Here, for example, the first communication device and the second communication device are base station device 201 and relay device 301, respectively, or adjacent upper relay device 301 and lower relay device 301, respectively, or relay device 301 and terminating device 401, respectively.

[0152] Hereinafter, communication system 100 will be exemplified from the viewpoint that the first communication device and the second communication device are base station device 201 and relay device 301, respectively. With reference to Fig. 1 to Fig. 5, communication system 100 includes transmission line 500A, a leaky coaxial cable group 501A, base station device 201 and relay device 301, and leaky coaxial cable group 501A is provided in transmission line 500A. It can also be said that communication system 100 includes transmission line 500B, a leaky coaxial cable group 501B, base station device 201 and relay device 301, and leaky coaxial cable group 501B is provided in transmission line 500B.

[0153] 7, leaky coaxial cable groups 501A and 501B employ, for example, a leaky coaxial cable group 5. The leaky coaxial cable group 5 has a plurality of leaky coaxial cables 51, 52, and 53 having different frequency characteristics and connected in series.

[0154] The relay device 301 is connected to the base station device 201 via a transmission line 500A, and detects the presence or absence of deterioration in the leaky coaxial cables 51, 52, and 53 from the frequency characteristics of the leaky coaxial cable group 5. In this manner, it is possible to identify, by using the base station device 201 and the relay device 301, which of the leaky coaxial cables 51, 52, and 53 has deteriorated.

[0155] The base station device 201 includes a transmitter 24. The transmitter 24 transmits a superimposed signal M0 including a plurality of frequency components to the leaky coaxial cables 5 at a specified intensity, specifically, at the initial intensity of the transmission signal.

[0156] The repeater 301 has a splitter 32u. The splitter 32u splits the superimposed signal M0 transmitted through the leaky coaxial cable group 5. The repeater 301 has a receiving detector 33u. The receiving detector 33u detects the signal strength of the transmission signal obtained by splitting the superimposed signal M0. From the above-mentioned specified strength and the signal strength, the attenuation amount in the leaky coaxial cable group 5 is calculated for each frequency component, and the attenuation amounts are compared. In the communication system 100, the presence or absence of deterioration in the leaky coaxial cables 51, 52, and 53 is detected based on the attenuation amount, which contributes to identifying the deterioration using the base station device 201 and the repeater 301.

[0157] <Embodiment 2> In the technology of the second embodiment, the presence or absence of deterioration in the leaky coaxial cable group 501B and the location of the deterioration are identified based on the coupling loss when the leaky coaxial cable group 501B receives leaky radio waves from the leaky coaxial cable group 501A.

[0158] <Outline of the configuration of base station device 201> Fig. 14 is a block diagram illustrating a schematic configuration of a base station device 201 in embodiment 2. For example, the configuration of the base station device 201 in embodiment 1 (see Fig. 4) is adopted as the configuration of the base station device 201 in embodiment 2. Fig. 14 also shows various signals used in embodiment 2.

[0159] Based on a command from the central unit 10 via the LAN 801, the monitoring and control device 21 outputs a signal (hereinafter referred to as a "control signal") T1 to the transmitter 24 to control the transmission of a transmission signal. For example, a user operates the central unit 10 to transmit the command to the monitoring and control device 21. Alternatively, the monitoring and control device 21 is operated by the user to output the control signal T1. Based on the control signal T1, the transmitter 24 transmits a transmission signal to the transmission path 500B, or does not transmit to the transmission path 500B. It does not matter whether the control signal T1 causes the transmission signal to be transmitted to the transmission path 500A or stops it. For example, the control signal T1 stops transmission to the transmission path 500A.

[0160] The monitor and control device 21 outputs control signals T2 and T3 (described later) to a monitor line 901 based on a command from the central device 10 via the LAN 801 or in response to a user's operation on the monitor and control device 21.

[0161] The transmission signal M3 is used to identify deterioration in the second embodiment, and is transmitted from the transmitter 24 to the transmission line 500A. A transmission signal M7, which will be described later, is attenuated while propagating through the leaky coaxial cable group 501A, and is input as a transmission signal M8 to the splitter 22. A transmission signal M10 is obtained from the leaky coaxial cable group 501B that has received a leakage signal M9, which will be described later, and is input to the splitter 22.

[0162] <Outline of the configuration of relay device 301> Fig. 15 is a block diagram illustrating a schematic configuration of the repeater device 301 in the embodiment 2. In Fig. 15, the monitoring line 901, the leaky coaxial cables 501Au, 501Bu, 501Ad, and 501Bd, and the transmission lines 500A and 500B are also illustrated.

[0163] Relay device 301 in the second embodiment differs from relay device 301 in the first embodiment (see FIG. 5) in that amplifiers 34u and 34d are each provided with a transmission circuit 35. The configuration other than transmission circuit 35 and the interrelationships between the components are the same as those in the first embodiment.

[0164] The monitoring device 31 obtains control signals T2 and T3 from the monitoring line 901 and outputs them to the transmission circuit 35 included in the amplifier 34u. The transmission circuit 35 transmits a transmission signal to the transmission path 500B based on the control signal T2, or does not transmit to the transmission path 500B. It does not matter whether the control signal T2 causes the transmission signal to be transmitted to the transmission path 500A or stops it. For example, the transmission to the transmission path 500A is stopped by the control signal T2.

[0165] The control signal T3 causes the transmission circuit 35 to transmit the transmission signal M7 to the transmission line 500A at various intensities.

[0166] The transmission signal M6 is obtained from the leaky coaxial cable group 501Bu that receives the leaky signal M5 described later. The transmission signal M4 is obtained from the leaky coaxial cable group 501A as described later. The transmission signals M4 and M6 are input to the splitter 32u.

[0167] <Transmission and reception of leaked radio waves> Fig. 16 is a schematic diagram illustrating a state in which the leaky coaxial cable group 501B receives leaky radio waves leaking from the leaky coaxial cable group 501A. Fig. 16 illustrates leaky coaxial cable groups 501A and 501B provided in transmission paths 500A and 500B connecting the base station device 201 illustrated in Fig. 14 and the repeater device 301 illustrated in Fig. 15. The leaky coaxial cable groups 501A and 501B illustrated in Fig. 15 are provided upstream of the repeater device 301, and therefore are represented as "501A (501Au)" and "501B (501Bu)" in the figure, respectively.

[0168] The leaky coaxial cable group 501A has leaky coaxial cables 51A, 52A, and 53A connected in series, which are connected in line from the upper side to the lower side in this order. The leaky coaxial cable group 501B has leaky coaxial cables 51B, 52B, and 53B connected in series, which are connected in line from the upper side to the lower side in this order. For convenience of explanation, the connector that couples the leaky coaxial cables 51A and 52A together, the connector that couples the leaky coaxial cables 52A and 53A together, the connector that couples the leaky coaxial cables 51B and 52B together, and the leaky coaxial cables 52B and 53B are all excluded from consideration.

[0169] The frequency dependence of the coupling loss of each of the leaky coaxial cables 51B, 52B, and 53B is different from one another. The following frequency dependence is exemplified: the coupling loss of the leaky coaxial cable 51B at frequency Fa is larger than the coupling loss of each of the leaky coaxial cables 52B and 53B at frequency Fa; the coupling loss of the leaky coaxial cable 52B at frequency Fb is larger than the coupling loss of each of the leaky coaxial cables 51B and 53B at frequency Fb; and the coupling loss of the leaky coaxial cable 53B at frequency Fc is larger than the coupling loss of each of the leaky coaxial cables 51B and 52B at frequency Fc.

[0170] A transmission signal M3 transmitted from the transmitter 24 is input to the upstream side of the leaky coaxial cable group 501A. The transmission signal M3 is attenuated while propagating through the leaky coaxial cable group 501A, and is output as a transmission signal M4 from the downstream side of the leaky coaxial cable group 501A.

[0171] A transmission signal M7 transmitted from the transmission circuit 35 is input to the lower side of the leaky coaxial cable group 501A. The transmission signal M7 is attenuated while propagating through the leaky coaxial cable group 501A, and is output as a transmission signal M8 from the upper side of the leaky coaxial cable group 501A.

[0172] Both of the leaky signals M5 and M9 are received by the leaky coaxial cable group 501B as leaky radio waves leaking from the leaky coaxial cable group 501A. The leaky signal M5 leaks when the transmission signal M3 is transmitted through the leaky coaxial cable group 501A. The leaky signal M9 leaks when the transmission signal M7 is transmitted through the leaky coaxial cable group 501A.

[0173] It can be said that the leakage signal M5 is transmitted from the leaky coaxial cable group 501A and received by the leaky coaxial cable group 501B when the leaky coaxial cable group 501A receives the transmission signal M3, transmits it, and outputs the transmission signal M4. It can be said that the leakage signal M9 is transmitted from the leaky coaxial cable group 501A and received by the leaky coaxial cable group 501B when the leaky coaxial cable group 501A receives the transmission signal M7, transmits it, and outputs the transmission signal M8.

[0174] <Identifying the deteriorated area> In the following, a case where it is assumed that there is no deterioration in the leaky coaxial cable group 501A will be described first. When it is unclear whether there is deterioration in the leaky coaxial cable group 501A, it will be described later that, for example, the technique disclosed in the first embodiment is used in combination.

[0175] Fig. 17 is a flowchart illustrating a process of identifying a deteriorated portion in the leaky coaxial cable group 5 (labeled as "identification of deteriorated LCX" in Fig. 17) in the embodiment 2. Fig. 17 illustrates a case in which the process includes steps S21, S22, and S23 that are executed in this order.

[0176] However, in this process, the order of steps S21 and S22 may be reversed, or only one of steps S21 and S22 may be executed. Specifically, the process may include steps S22, S21, and S23 executed in this order, or steps S21 and S23 executed in this order, or steps S22 and S23 executed in this order.

[0177] In step S21, a leaky coaxial cable having a deteriorated portion (abbreviated as "deteriorated LCX" in the figure) is identified by transmission from the upper side to the lower side. In step S22, a leaky coaxial cable having a deteriorated portion is identified by transmission from the lower side to the upper side.

[0178] In step S23, information indicating the identified leaky coaxial cable is transmitted from the base station device 201, more specifically, from the monitor and control device 21 to the central unit 10. The user recognizes the leaky coaxial cable having a deteriorated portion, for example, by using a function that the central unit 10 normally has.

[0179] Fig. 18 is a flowchart illustrating the details of step S21. Fig. 19 is a flowchart illustrating the details of step S22. With reference to Figs. 18 and 19, a description will be given of an example of a section between adjacent base station device 201 and relay device 301 as a section in which degradation is identified.

[0180] <Transmission from upper side to lower side> 18 shows an example in which step S21 includes steps S211 to S219. Steps S213 to S217 are repeatedly executed a number of times as described below.

[0181] When step S21 is executed, steps S211 and S212 are executed. The order in which steps S211 and S212 are executed does not matter.

[0182] In step S211, the monitor control device 21 stops the transmission of the transmission signal to the transmission line 500B by the transmitter 24. Specifically, the monitor control device 21 transmits to the transmitter 24 a control signal T1 having contents instructing the transmitter 24 to stop transmitting the transmission signal.

[0183] In step S212, the monitoring control device 21 stops the transmission of the transmission signal from the transmission circuit 35 in the amplifier 34u to the transmission path 500B via the monitoring line 901u. Specifically, a control signal T2 instructing the stop is transmitted from the monitoring control device 21 to the transmission circuit 35 in the amplifier 34u via the monitoring device 31. The monitoring device 31 that has received the control signal T2 may transmit a signal to the transmission circuit 35 to stop the transmission of the transmission signal instead of the control signal T2.

[0184] By executing steps S211 and S212, a transmission signal reflecting the leaking radio waves from the leaky coaxial cable group 501A is transmitted to the leaky coaxial cable group 501B. When only the transmission signal M3 is input to the leaky coaxial cable group 501A and the transmission signal M4 is output, the transmission signal M6 reflects only the leakage signal M5.

[0185] After steps S211 and S212 are executed, steps S213 to S217 are executed N times (N is a positive integer). Here, "N times" means that a series of steps S213 to S217 are executed N times. The positive integer N is set to the number of types of leaky coaxial cables included in one leaky coaxial cable group 501B, which is the number of leaky coaxial cables 51, 52, and 53, 3 in this case.

[0186] In step S213, the monitor control device 21 causes the transmitter 24 to transmit a transmission signal M3 to the transmission path 500A. Specifically, the monitor control device 21 transmits to the transmitter 24 a control signal T1 whose contents cause the transmitter 24 to transmit the transmission signal M3 to the transmission path 500A.

[0187] The frequency of the transmission signal M3 transmitted in step S213 is, for example, frequency Fa in the first round of execution of steps S213 to S217, frequency Fb in the second round, and frequency Fc in the third round. In this manner, steps S213 to S217 are repeatedly executed with the frequency of the transmission signal M3 being changed.

[0188] The initial strength of the transmission signal M3 when it is transmitted in step S213 is small, and for example, a strength that is used for normal wireless communication between the mobile station device 6 and the leaky coaxial cable group 501A is adopted.

[0189] When the transmission signal M3 is transmitted in step S213, the initial strength of the transmission signal M3 is increased while maintaining its frequency until the signal strength of the transmission signal M6 exceeds a specified value. In step S214, the signal strength of the transmission signal M6 from the transmission line 500B in the repeater 301 is measured. This measurement is performed by the receiving detector 33u on the transmission signal M6 input to the receiving detector 33u via the splitter 32u. The specified value is set to be greater than the measurement accuracy of the signal strength.

[0190] After step S214 is executed, step S215 is executed. In step S215, it is determined whether the signal strength of the transmission signal M6 exceeds the specified value. Specifically, the signal strength of the transmission signal M6 measured by the receiving detector 33u is transmitted to the monitoring device 31, and the monitoring device 31 compares the signal strength with the specified value.

[0191] When the determination result is negative, that is, when the measured signal strength of the transmission signal M6 does not exceed the specified value, step S216 is executed. In step S216, the transmission level of the transmission signal M3 is increased. Specifically, for example, a control signal T4 is transmitted from the monitoring device 31 to the monitoring control device 21 via the monitoring line 901. Upon receiving the control signal T4, the monitoring control device 21 controls the transmitter 24 to increase the initial strength of the transmission signal M3 by a specified increment.

[0192] After step S216 is executed, steps S214 and S215 are executed again repeatedly. When the initial strength of the transmission signal M3 increases, the signal strength of the leakage signal M5 also increases, and thus the transmission signal M6 also increases. When the determination result of step S215 is positive, that is, when the measured signal strength of the transmission signal M6 exceeds the specified value, step S217 is executed.

[0193] In step S217, the overall receiving sensitivity of the leaky coaxial cable group 501B, the splitter 32u, and the receiving detector 33u is obtained. In step S214, the leaky coaxial cable group 501B receives the leaky signal M5 as an antenna, and the signal strength is obtained. The receiving sensitivity obtained in step S217 can be said to be the receiving sensitivity with the leaky coaxial cable group 501B as an antenna (hereinafter simply referred to as "receiving sensitivity"). Specifically, the receiving sensitivity is obtained by comparing the specified value that was the judgment criterion in step S215 with the initial strength of the transmission signal M3 immediately before step S217 is executed.

[0194] The specified value is, for example, stored in the monitor control device 21, or transmitted from the monitor device 31 to the monitor control device 21. The monitor control device 21 increases the initial strength of the transmission signal M3 when controlling the transmitter 24, and knows the initial strength immediately before step S217 is executed. The receiving sensitivity is obtained in the monitor control device 21.

[0195] Steps S213 to S217 are repeatedly executed by varying the frequency of the transmission signal M3, and the receiving sensitivity is obtained for each different frequency band. Every time step S217 is executed, step S218 is executed. In step S218, it is determined whether steps S213 to S217 have been repeatedly executed N times by varying the frequency of the transmission signal M3. In FIG. 18, the determination in step S218 is simplified as "N times?" for simplicity. If the determination result is negative, step S213 is executed again.

[0196] After steps S213 to S217 are executed for all of the frequency bands set for the transmission signal M3, for example, all of the frequencies Fa, Fb, and Fc, the result of the determination in step S218 becomes positive, and step S219 is executed. In step S219, a deteriorated leaky coaxial cable is found from the frequency dependency of the receiving sensitivity.

[0197] Specifically, for example, in step S219, it is determined whether the receiving sensitivity of a certain frequency band is smaller than the receiving sensitivity of other frequency bands by a specified value. The influence of the splitter 32u and the receiving detector 33u on the receiving sensitivity is independent of the influence of the antenna receiving sensitivity of the leaky coaxial cable group 501B on the receiving sensitivity. Obtaining the receiving sensitivity corresponds to indirectly obtaining the antenna receiving sensitivity of the leaky coaxial cable group 501B.

[0198] If there is no degradation in any of the leaky coaxial cables 51B, 52B, and 53B, the antenna receiving sensitivity does not depend on the frequency of the transmission signal M3, and the receiving sensitivity does not depend on the frequency of the transmission signal M3 and falls within a specified range. If the receiving sensitivity of any frequency band is lower than the receiving sensitivity of other frequency bands by more than the specified value, the leaky coaxial cable in which degradation has occurred is identified based on that frequency band. The specified value is set to be larger than the measurement accuracy of the receiving sensitivity.

[0199] In the above example, if the receiving sensitivity at 100 MHz is smaller than the receiving sensitivity at 200 MHz and the receiving sensitivity at 300 MHz by more than the specified value, it is determined that the leaky coaxial cable 51B is degraded, because the degradation leads to a degradation in the coupling loss of the leaky coaxial cable 51B, and in turn to a degradation in the performance of the leaky coaxial cable group 501B as an antenna receiving sensitivity.

[0200] Similarly, if the receiving sensitivity at 200 MHz is smaller than the specified value relative to both the receiving sensitivity at 100 MHz and the receiving sensitivity at 300 MHz, it is determined that the leaky coaxial cable 52B has deteriorated. Similarly, if the receiving sensitivity at 300 MHz is smaller than the specified value relative to both the receiving sensitivity at 100 MHz and the receiving sensitivity at 200 MHz, it is determined that the leaky coaxial cable 53B has deteriorated. The specified value is set to be larger than the measurement accuracy of the receiving sensitivity.

[0201] If the receiving sensitivity of any frequency band is not smaller than the receiving sensitivity of the other frequency bands by more than the specified value, the maximum and minimum values ​​of the receiving sensitivity for each frequency band are within the specified range. When the maximum and minimum values ​​of the receiving sensitivity for each frequency band are within the specified range, it is determined that there is no degradation in any of the leaky coaxial cables 51B, 52B, and 53B, that is, there is no degradation in the leaky coaxial cable group 501B.

[0202] <Transmission from lower to upper> 19 shows an example in which step S22 includes steps S221 to S229. Steps S223 to S227 are repeatedly executed a number of times as described later.

[0203] In the execution of step S22, steps S221 and S222 are executed. The order in which steps S221 and S222 are executed does not matter. The content executed in step S221 is the same as the content executed in step S211. The content executed in step S222 is the same as the content executed in step S212.

[0204] By executing steps S221 and S222, a transmission signal reflecting the leaking radio waves from the leaky coaxial cable group 501A is transmitted to the leaky coaxial cable group 501B. When only the transmission signal M7 is input to the leaky coaxial cable group 501A and the transmission signal M8 is output, the transmission signal M10 reflects only the leakage signal M9.

[0205] After steps S221 and S222 are executed, steps S223 to S227 are executed N times. Here, "N times" means that a series of steps S223 to S227 are executed N times. In the above example, the positive integer N is set to 3, which is the number of the leaky coaxial cables 51, 52, and 53.

[0206] In step S223, the monitoring control device 21 causes the transmission circuit 35 in the amplifier 34u to transmit the transmission signal M7 to the transmission line 500A. Specifically, the monitoring control device 21 instructs the transmission circuit 35 in the amplifier 34u to transmit the transmission signal M7 to the transmission line 500A via the monitoring line 901u. More specifically, the monitoring control device 21 transmits a control signal T3 instructing the transmission to the transmission circuit 35 in the amplifier 34u via the monitoring device 31. The monitoring device 31 that has received the control signal T3 may transmit a signal to the transmission circuit 35 to transmit the transmission signal M7, instead of the control signal T3.

[0207] The frequency of the transmission signal M7 transmitted in step S223 is, for example, frequency Fa in the first round of execution of steps S223 to S227, frequency Fb in the second round, and frequency Fc in the third round. In this manner, steps S223 to S227 are repeatedly executed with the frequency of the transmission signal M3 being changed.

[0208] The initial strength of the transmission signal M7 when it is transmitted in step S223 is small, and for example, a strength that is used for normal wireless communication between the mobile station device 6 and the leaky coaxial cable group 501A is adopted.

[0209] When the transmission signal M7 is transmitted in step S223, the initial strength of the transmission signal M7 is increased while maintaining its frequency until the signal strength of the transmission signal M10 exceeds a specified value. In step S224, the signal strength of the transmission signal M10 from the transmission path 500B is measured in the base station device 201. The measurement is performed by the reception detector 23 on the transmission signal M10 input to the reception detector 23 via the branching filter 22.

[0210] After step S224 is executed, step S225 is executed. In step S225, it is determined whether the signal strength of the transmission signal M10 exceeds a specified value. Specifically, the signal strength of the transmission signal M10 measured by the receiving detector 23 is transmitted to the monitor and control device 21, and the monitor and control device 21 compares the signal strength with a specified value.

[0211] If the result of the determination is negative, i.e., if the measured signal strength of the transmission signal M10 does not exceed the specified value, step S226 is executed. In step S226, the transmission level of the transmission signal M7 is increased. Specifically, for example, the monitor and control device 21 uses the control signal T3 to control the transmission circuit 35 so as to increase the initial strength of the transmission signal M7 by a specified increment.

[0212] After step S226 is executed, steps S224 and S225 are executed again repeatedly. When the initial strength of the transmission signal M7 increases, the signal strength of the leakage signal M9 also increases, and thus the transmission signal M10 also increases. When the determination result of step S225 is positive, that is, when the measured signal strength of the transmission signal M10 exceeds the specified value, step S227 is executed.

[0213] In step S227, the receiving sensitivity is calculated as a whole of the leaky coaxial cable group 501B, the splitter 22, and the receiving detector 23. Specifically, the receiving sensitivity is calculated by comparing the specified value that was the judgment criterion in step S225 with the initial strength of the transmission signal M7 immediately before step S227 is executed. It can be said that the receiving sensitivity is also the receiving sensitivity with the leaky coaxial cable group 501B as an antenna.

[0214] The specified value used as the criterion in step S225 is stored, for example, in the monitor control device 21. The specified value used as the criterion in step S225 may be equal to or different from the specified value used as the criterion in step S215.

[0215] The monitor and control device 21 controls the transmission circuit 35 by, for example, the control signal T3 to increase the initial strength of the transmission signal M10, and knows the initial strength immediately before step S227 is executed.

[0216] Steps S223 to S227 are repeatedly executed by varying the frequency of the transmission signal M7, and the receiving sensitivity is obtained for each different frequency band. Every time step S227 is executed, step S228 is executed. In step S228, it is determined whether steps S223 to S227 have been repeatedly executed N times by varying the frequency of the transmission signal M7. In FIG. 19, the determination of step S228 is simplified as "N times?" for simplicity. If the determination result is negative, step S223 is executed again.

[0217] After steps S223 to S227 are executed for all of the frequency bands set for the transmission signal M7, for example, all of the frequencies Fa, Fb, and Fc, the result of the determination in step S228 becomes positive, and step S229 is executed. Step S229 is executed. In step S229, similarly to step S219, the frequency dependency of the receiving sensitivity is obtained, and a degraded leaky coaxial cable is found from the receiving sensitivity, or it is determined that no degradation has occurred in the leaky coaxial cable group 501B.

[0218] 18 and 19, the section in which degradation is identified is illustrated as being between adjacent base station device 201 and relay device 301. However, the section may be between adjacent relay device 301 and terminating device 401.

[0219] Fig. 20 is a block diagram illustrating a schematic configuration of the termination device 401 in the embodiment 2. In Fig. 20, monitoring lines 901 and 902, leaky coaxial cable groups 501A, 501B, 502A, and 502B, and transmission lines 500A and 500B are also illustrated.

[0220] Termination device 401 in the second embodiment differs from termination device 401 in the first embodiment (see FIG. 6) in that transmission circuits 45 are provided in amplifiers 441 and 442. The configuration other than transmission circuit 45 and the interrelationships between the components are the same as those in the first embodiment.

[0221] The termination device 401 receives the transmission signals M4 and M6 to the transmission paths 500A and 500B, respectively, in the same manner as the repeater device 301. The monitoring device 41 receives the control signals T2 and T3 in the same manner as the monitoring device 31.

[0222] The transmitting circuit 45 transmits a transmission signal to the transmission line 500B based on the control signal T2, or does not transmit to the transmission line 500B. The transmitting circuit 45 outputs a transmission signal M7 to the transmission line 500A, and further to the leaky coaxial cable group 501A, based on the control signal T3. The monitoring device 41 outputs a control signal T4 to the monitoring line 901, similar to the monitoring device 31.

[0223] By using the termination device 401 configured in this manner and appropriately modifying the flowcharts shown in Figures 18 and 19, deterioration in the leaky coaxial cable group 501B can be identified in the section between the adjacent relay device 301 and the termination device 401, similar to the section between the adjacent base station device 201 and the relay device 301.

[0224] <Modification of the second embodiment> The deteriorated portion of the leaky coaxial cable group 501A can be identified in the same manner as the leaky coaxial cable group 501B.

[0225] Since the deterioration in the leaky coaxial cable group 501B is detected by a similar method in both steps S21 and S22, either one may be omitted. Performing both steps S21 and S22 contributes to increasing the reliability of the deterioration detection. For example, the central device 10 judges that the reliability of the deterioration identification is higher when the deterioration location identified in step S21 and the deterioration location identified in step S22 match than when they do not match. Alternatively, both may be adopted as the basis for the user's judgment.

[0226] The leakage signals M5 and M9 are generated when the transmission signals M3 and M7 are transmitted through the leaky coaxial cable group 501A, and the strength of each signal depends on the frequency characteristics of the leaky coaxial cable group 501A. The transmission signals M6 and M10 are based on the leakage signals M5 and M9 received by the leaky coaxial cable group 501B, and the strength of each signal depends on the frequency characteristics of the leaky coaxial cable group 501B. From this perspective, the fact that the characteristics of the leaky coaxial cable groups 501A and 501B are consistent contributes to improving the reliability of identifying the location of deterioration.

[0227] When deterioration also occurs in the leaky coaxial cable group 501A, there may be cases where the deteriorated portion of the leaky coaxial cable group 501B cannot be correctly identified. For example, regardless of whether deterioration occurs in either of the leaky coaxial cables 51A and 51B, the receiving sensitivity at frequency Fa is smaller than the receiving sensitivity at each of frequencies Fb and Fc. In a section where deterioration is determined to exist in the second embodiment, identifying the deterioration using the technique exemplified in the first embodiment contributes to identifying in which of the leaky coaxial cable groups 501A and 501B the deterioration occurs.

[0228] In steps S21 and S22, the transmission of the transmission signal to the transmission path 500B is stopped, in step S21, the transmission signal M3 is transmitted to the transmission path 500A, and in step S22, the transmission signal M7 is transmitted to the transmission path 500A. In view of this situation, in principle, when the second embodiment is executed, wireless communication is not performed between the leaky coaxial cable groups 501A and 501B and the mobile station device 6.

[0229] However, when the frequency band used for the wireless communication is set apart from the frequencies of the transmission signals M3 and M7 employed in the second embodiment, that is, the frequencies Fa, Fb, and Fc in the above example, the wireless communication can be performed in parallel with the second embodiment. This is because the duplexer 32u is used in step S214 and the duplexer 22 is used in step S224, and the influence of the wireless communication on the calculation of the reception sensitivity is small. Specifically, for example, when steps S213 to S216 are performed for the frequency Fa, the wireless communication can be performed using the frequencies Fb and Fc.

[0230] The second embodiment is roughly divided into a first process exemplified by steps S213 to S218 and S223 to S228, and a second process exemplified by steps S219 and S229 (see FIGS. 18 and 19).

[0231] In the first step, the frequency characteristics of the leaky coaxial cable group 501B having the leaky coaxial cables 51B, 52B, and 53B connected in series with different frequency characteristics are obtained. In the above example, the frequency characteristics are the frequency dependence of the receiving sensitivity when the leaky coaxial cable group 501B is used as an antenna.

[0232] In the second step, the presence or absence of deterioration in the leaky coaxial cables 51B, 52B, and 53B is detected from the frequency characteristics of the leaky coaxial cable group 5 obtained in the first step. In this manner, in the second embodiment as in the first embodiment, which of the leaky coaxial cables 51B, 52B, and 53B has deteriorated is identified using a communication device.

[0233] Defects in each of the leaky coaxial cables 51B, 52B, and 53B are reflected in the receiving sensitivity of the leaky coaxial cable group 501B as an antenna. The transmission signal M3 is transmitted to the leaky coaxial cable group 501B at different frequencies as illustrated in steps S213 to S218, and the transmission signal M7 is transmitted to the leaky coaxial cable group 501B at different frequencies as illustrated in steps S223 to S228, and the receiving sensitivity of the leaky coaxial cable group 501B, the splitter 32u, and the receiving detector 33u as a whole is obtained. The receiving sensitivity reflects the deterioration of the leaky coaxial cable group 501B. The deterioration is identified from the frequency dependency of the receiving sensitivity as illustrated in steps S219 and S229. In this way, in the second embodiment, the presence or absence of deterioration in the leaky coaxial cables 51B, 52B, and 53B is detected based on the receiving sensitivity, which contributes to identifying the deterioration using a communication device.

[0234] In the second embodiment, the leaky signal M5 (or the leaky signal M9, or both the leaky signals M5 and M9) as a leaky radio wave from the leaky coaxial cable group 501A is received by the leaky coaxial cable group 501B (see FIG. 16). The receiving sensitivity is obtained by receiving the leaky radio wave from the leaky coaxial cable group 501A. Thus, in the second embodiment, there is no need to use the mobile station device 6, let alone run the inspection vehicle.

[0235] 1 to 3, the second embodiment is exemplified as a communication system 100 including a first communication device and a second communication device. Here, for example, the first communication device and the second communication device are base station device 201 and relay device 301, respectively, or adjacent upper relay device 301 and lower relay device 301, respectively, or relay device 301 and terminating device 401, respectively.

[0236] Hereinafter, the communication system 100 will be illustrated from the viewpoint that the first communication device and the second communication device are the base station device 201 and the relay device 301, respectively. With reference to Fig. 14 and Fig. 15, the communication system 100 includes a transmission line 500A, a leaky coaxial cable group 501A, the base station device 201 and the relay device 301, and the leaky coaxial cable group 501A is provided in the transmission line 500A. The communication system 100 includes a transmission line 500B, a leaky coaxial cable group 501B, the base station device 201 and the relay device 301, and the leaky coaxial cable group 501B is provided in the transmission line 500B.

[0237] 16, a leaky coaxial cable group 501B has a plurality of leaky coaxial cables 51B, 52B, and 53B having different frequency characteristics and connected in series.

[0238] The repeater 301 is connected to the base station device 201 via a transmission line 500B, and detects the presence or absence of deterioration in the leaky coaxial cables 51B, 52B, and 53B from the frequency characteristics of the leaky coaxial cable group 501B. In this manner, it is possible to identify, by using the base station device 201 and the repeater 301, which of the leaky coaxial cables 51B, 52B, and 53B has deteriorated.

[0239] In the second embodiment, the presence or absence of the deterioration in the leaky coaxial cables 51B, 52B, and 53B is detected based on the frequency dependency of the receiving sensitivity when the leaky coaxial cable group 501B is used as an antenna. In this way, in the second embodiment, the presence or absence of the deterioration in the leaky coaxial cables 51B, 52B, and 53B is detected based on the receiving sensitivity, which contributes to identifying the deterioration using the base station device 201 and the relay device 301.

[0240] In the second embodiment, the communication system 100 includes a transmission path 500A connecting the base station device 201 and the relay device 301, and a leaky coaxial cable group 501A provided on the transmission path 500A. A leaky signal M5 (or a leaky signal M9, or both of the leaky signals M5 and M9) as a leaky radio wave from the leaky coaxial cable group 501A is received by the leaky coaxial cable group 501B, and the reception sensitivity is obtained by receiving this leaky radio wave. It does not matter which of the leaky coaxial cables 51A, 52A, and 53A of the leaky coaxial cable group 501A the leaky radio wave leaks from, and the second embodiment is realized as long as the leaky radio wave leaks from any of them. Thus, in the second embodiment, it is not necessary to use the mobile station device 6, let alone run the inspection vehicle.

[0241] <Embodiment 3> By using wireless communication with the mobile station device 6 instead of leaky radio waves, the presence or absence of deterioration in the leaky coaxial cable group 501A does not affect the identification of deterioration in the leaky coaxial cable group 501B.

[0242] Fig. 21 is a flowchart illustrating a process of identifying a deteriorated portion in the leaky coaxial cable group 5 (labeled as "identification of deteriorated LCX" in Fig. 21) in the embodiment 3. Fig. 21 illustrates a case in which the process includes steps S31, S32, S33, S34, S35, and S36 executed in this order.

[0243] At the beginning of this process, steps S31 and S32 are executed. The order in which steps S31 and S32 are executed does not matter. The content executed in step S31 is the same as the content executed in step S211. The content executed in step S32 is the same as the content executed in step S212.

[0244] After steps S31 and S32 are executed, step S33 is executed. In step S33, the monitor control device 21 controls the mobile station device 6 to transmit a signal 60 as radio waves. This control is performed, for example, using the leaky coaxial cable group 501A. The mobile station device 6 can be said to be the source of the signal 60. For example, the signal 60 is a superimposed signal.

[0245] After step S33 is executed, in step S34, the receiving sensitivity is calculated as a whole for the leaky coaxial cable group 501B, the branching filter 22, and the receiving detector 23. This is realized by using the signal 60 instead of the leakage signals M5 and M9 in the second embodiment.

[0246] When the signal 60 is not a superimposed signal, steps S33 and S34 are repeatedly executed with the frequency of the signal 60 changed, similarly to steps S213 to S217 (see FIG. 18) and steps S223 to S227 (see FIG. 19) in the second embodiment.

[0247] Step S34 is executed, or steps S33 and S34 are executed repeatedly multiple times with different frequencies, and then step S35 is executed. In step S35, like step S219 (see FIG. 18) and step S229 (see FIG. 19) in the second embodiment, deteriorated leaky coaxial cables are found from the frequency dependency of the receiving sensitivity.

[0248] After step S35 is executed, step S36 is executed. In step S36, the same process as step S23 (see FIG. 17) in the second embodiment is executed. Specifically, information indicating the identified leaky coaxial cable is transmitted from the base station device 201, more specifically, from the monitor and control device 21 to the central unit 10. The user recognizes the leaky coaxial cable having a deteriorated portion, for example, by using a function that the central unit 10 normally has.

[0249] Since there is no need to move the mobile station device 6, it does not matter whether the train carrying the mobile station device 6 is running or not. This is because the execution of steps S31 to S is not hindered even if the train is stopped on the track.

[0250] Running a train equipped with the mobile station device 6 contributes to identifying deterioration of the leaky coaxial cable group in different sections, and therefore in different communication zones.

[0251] The third embodiment is roughly divided into a first process exemplified by steps S31 to S34 and a second process exemplified by step S35 (FIG. 21).

[0252] In the first step, the frequency characteristics of the leaky coaxial cable group 501B having the leaky coaxial cables 51B, 52B, and 53B connected in series with different frequency characteristics are obtained. In the above example, the frequency characteristics are the frequency dependence of the receiving sensitivity when the leaky coaxial cable group 501B is used as an antenna.

[0253] In the second step, the presence or absence of deterioration in the leaky coaxial cables 51B, 52B, and 53B is detected from the frequency characteristics of the leaky coaxial cable group 5 obtained in the first step. In this manner, similar to the second embodiment, in the third embodiment, which of the leaky coaxial cables 51B, 52B, and 53B has deteriorated is identified using a communication device.

[0254] Defects in each of the leaky coaxial cables 51B, 52B, and 53B are reflected in the receiving sensitivity of the leaky coaxial cable group 501B as an antenna. As illustrated in step S33, a signal 60 is transmitted to the leaky coaxial cable group 501B as, for example, a superimposed signal. The signal 60 is transmitted from a transmission source, for example, a mobile station device 6. The receiving sensitivity of the leaky coaxial cable group 501B, the splitter 32u, and the receiving detector 33u as a whole is obtained by receiving the signal 60. The receiving sensitivity reflects the deterioration of the leaky coaxial cable group 501B. As illustrated in step S35, the deterioration is identified from the frequency dependency of the receiving sensitivity. In this way, in the third embodiment, the presence or absence of deterioration in the leaky coaxial cables 51B, 52B, and 53B is detected based on the receiving sensitivity, which contributes to identifying the deterioration using a communication device.

[0255] 1 to 3, the third embodiment is exemplified as a communication system 100 including a first communication device and a second communication device. Here, for example, the first communication device and the second communication device are base station device 201 and relay device 301, respectively, or adjacent upper relay device 301 and lower relay device 301, respectively, or relay device 301 and terminating device 401, respectively.

[0256] Hereinafter, the communication system 100 will be illustrated from the viewpoint that the first communication device and the second communication device are the base station device 201 and the relay device 301, respectively. With reference to Fig. 14 and Fig. 15, the communication system 100 includes a transmission line 500B, a group of leaky coaxial cables 501B, the base station device 201 and the relay device 301, and the group of leaky coaxial cables 501B is provided in the transmission line 500B. Alternatively, it can be said that the communication system 100 includes a transmission line 500A, a group of leaky coaxial cables 501A, the base station device 201 and the relay device 301, and the group of leaky coaxial cables 501A is provided in the transmission line 500A.

[0257] As in the second embodiment, in the third embodiment, the presence or absence of deterioration in the leaky coaxial cables 51B, 52B, and 53B is detected from the frequency characteristics of the leaky coaxial cable group 501B, and which of the leaky coaxial cables 51B, 52B, and 53B has deteriorated is identified using the base station device 201 and the relay device 301.

[0258] As in the second embodiment, in the third embodiment, the presence or absence of the deterioration in the leaky coaxial cables 51B, 52B, and 53B is detected from the frequency dependence of the receiving sensitivity when the leaky coaxial cable group 501B is used as an antenna, which contributes to identifying the deterioration using the base station device 201 and the relay device 301.

[0259] The overall receiving sensitivity of the leaky coaxial cable group 501B, the splitter 32u, and the receiving detector 33u is obtained by receiving the signal 60. The receiving sensitivity reflects the deterioration of the leaky coaxial cable group 501B. In this way, the presence or absence of deterioration in the leaky coaxial cables 51B, 52B, and 53B is detected based on the receiving sensitivity, which contributes to identifying the deterioration using the base station device 201 and the relay device 301.

[0260] In any of the first, second and third embodiments, the presence or absence of deterioration of the leaky coaxial cable group, or further the location of the deterioration, is identified by the communication device. When the communication system 100 is realized as a train radio system, the deterioration is identified by the ground equipment. Identification of the deterioration does not require the running of an inspection car, and the identification can be performed quickly regardless of the time of day or section. For example, the identification can be easily performed outside the operating hours of the train. For example, the identification can be easily performed even in a situation where the inspection car cannot run, such as immediately after a disaster.

[0261] It should be noted that the embodiments can be freely combined, and each embodiment can be modified or omitted as appropriate.

[0262] Various aspects of the present disclosure are summarized below as appendices.

[0263] (Appendix 1) A first step of determining frequency characteristics of a leaky coaxial cable group having a plurality of leaky coaxial cables connected in series and having different frequency characteristics from each other; a second step of detecting the presence or absence of deterioration in the leaky coaxial cable based on the frequency characteristics of the leaky coaxial cable group obtained in the first step; A method for detecting deterioration of a leaky coaxial cable, comprising:

[0264] (Appendix 2) In the first step, a signal including a plurality of frequency components is transmitted through the leaky coaxial cable group, and an attenuation amount in the leaky coaxial cable group is obtained for each of the frequency components; 2. The method for detecting deterioration of a leaky coaxial cable according to claim 1, wherein in the second step, the amounts of attenuation for the respective frequency components are compared to detect the presence or absence of deterioration in the leaky coaxial cable.

[0265] (Appendix 3) In the second step, calculating a difference between an attenuation amount of the leaky coaxial cable group in a case where there is no deterioration and the attenuation amount of the leaky coaxial cable group calculated in the first step for each of the frequency components; The method for detecting deterioration of a leaky coaxial cable according to claim 2, further comprising: comparing the differences for each of the frequency components to detect the presence or absence of deterioration in the leaky coaxial cable.

[0266] (Appendix 4) In the first step, a receiving sensitivity of the leaky coaxial cable group as an antenna is obtained for each of a plurality of frequencies; 2. The method for detecting deterioration of a leaky coaxial cable according to claim 1, wherein in the second step, the presence or absence of the deterioration in the leaky coaxial cable is detected from the frequency dependency of the receiving sensitivity.

[0267] (Appendix 5) 5. The method for detecting deterioration of a leaky coaxial cable according to claim 4, wherein in the first step, the receiving sensitivity is obtained by receiving leakage radio waves from a group of other leaky coaxial cables.

[0268] (Appendix 6) 5. The method for detecting deterioration of a leaky coaxial cable according to claim 4, wherein in the first step, the receiving sensitivity is obtained by receiving a radio wave from a transmission source.

[0269] (Appendix 7) A transmission path; a leaky coaxial cable group provided on the transmission line and including a plurality of leaky coaxial cables connected in series and having different frequency characteristics; A first communication device; a second communication device connected to the first communication device by the transmission line, and configured to detect the presence or absence of deterioration in the leaky coaxial cable based on the frequency characteristics of the leaky coaxial cable group; A communication system comprising:

[0270] (Appendix 8) The first communication device is A transmitter that transmits a signal containing multiple frequency components at a specified intensity to the leaky coaxial cables. having The second communication device is a splitter for splitting the signals transmitted through the leaky coaxial cable group; a receiving detector for detecting the signal strength of the demultiplexed signal; having The communication system according to claim 7, wherein an amount of attenuation in the group of leaky coaxial cables is calculated for each frequency component from the specified strength and the signal strength, and the amounts of attenuation are compared to detect the presence or absence of deterioration in the group of leaky coaxial cables.

[0271] (Appendix 9) The communication system of claim 8, wherein the presence or absence of the degradation in the leaky coaxial cables is detected by comparing the difference between the attenuation in the leaky coaxial cables and the attenuation of the leaky coaxial cables in a case where there is no degradation, for each of the frequency components.

[0272] (Appendix 10) 8. The communication system according to claim 7, wherein the presence or absence of the deterioration in the leaky coaxial cables is detected from frequency dependence of reception sensitivity when the leaky coaxial cables are used as antennas.

[0273] (Appendix 11) a second transmission path connecting the first communication device and the second communication device; a leaky coaxial cable provided in the second transmission line; Further comprising: 11. The communication system according to claim 10, wherein the receiving sensitivity is obtained by receiving a leaky radio wave from the leaky coaxial cable provided in the second transmission line.

[0274] (Appendix 12) The communication system of claim 10, wherein the receiving sensitivity is obtained by receiving radio waves from a transmission source. [Explanation of symbols]

[0275] 5,501,501A,501Au,501Ad,501B,501Bu,501Bd,502A,502B leaky coaxial cable group,22,32d,32u,421,422 splitter,23,33d,33u,431,432 receiver detector,24 transmitter,51,51A,51B,52,52A,52B,53,53A,53B leaky coaxial cable,60 signal,100 communication system,201,202 base station equipment,301,302A,302B repeater,401,402 termination equipment,500A,500B transmission line,Fa,Fb,Fc frequency,M0 superimposed signal,M3,M4,M6~M8,M10 Transmitted signal, M5, M9 leakage signal, P01, P12, P23, P30, P51, P52, P53 position, S11~S15, S21~S23, S31~S36, S141~S148, S211~S219, S221~S229 steps, Δ5a, Δ5b, Δ5c, Δ51a, Δ51b, Δ51c, Δ52a, Δ52b, Δ52c, Δ53a, Δ53b, Δ53c differences.

Claims

1. A first step of determining a frequency characteristic of a leaky coaxial cable group having a plurality of leaky coaxial cables connected in series and having different frequency characteristics from each other; a second step of detecting the presence or absence of deterioration in the leaky coaxial cable based on the frequency characteristics of the leaky coaxial cable group obtained in the first step; A method for detecting deterioration of a leaky coaxial cable, comprising:

2. In the first step, a signal including a plurality of frequency components is transmitted through the leaky coaxial cable group, and an amount of attenuation in the leaky coaxial cable group is obtained for each of the frequency components; 2. The method for detecting deterioration of a leaky coaxial cable according to claim 1, wherein in the second step, the amounts of attenuation for the respective frequency components are compared to detect the presence or absence of the deterioration in the leaky coaxial cable.

3. In the second step, calculating a difference between an attenuation amount of the leaky coaxial cable group in a case where there is no deterioration and the attenuation amount of the leaky coaxial cable group calculated in the first step for each of the frequency components; 3. The method for detecting deterioration of a leaky coaxial cable according to claim 2, further comprising the step of comparing the differences for each of the frequency components to detect the presence or absence of the deterioration in the leaky coaxial cable.

4. In the first step, a receiving sensitivity of the leaky coaxial cable group as an antenna is obtained for each of a plurality of frequencies; 2. The method for detecting deterioration of a leaky coaxial cable according to claim 1, wherein in the second step, the presence or absence of the deterioration in the leaky coaxial cable is detected from the frequency dependency of the receiving sensitivity.

5. 5. The method for detecting deterioration of a leaky coaxial cable according to claim 4, wherein in the first step, the receiving sensitivity is obtained by receiving leaked radio waves from a group of other leaky coaxial cables.

6. 5. The method for detecting deterioration of a leaky coaxial cable according to claim 4, wherein in the first step, the receiving sensitivity is obtained by receiving a radio wave from a transmission source.

7. A transmission path; a leaky coaxial cable group provided on the transmission line and including a plurality of leaky coaxial cables connected in series and having different frequency characteristics; A first communication device; a second communication device connected to the first communication device by the transmission line, and configured to detect the presence or absence of deterioration in the leaky coaxial cable based on the frequency characteristics of the leaky coaxial cable group; A communication system comprising:

8. The first communication device is A transmitter that transmits a signal containing multiple frequency components at a specified intensity to the leaky coaxial cables. having The second communication device is a splitter for splitting the signals transmitted through the leaky coaxial cable group; a receiving detector for detecting the signal strength of the demultiplexed signal; having 8. The communication system according to claim 7, wherein an amount of attenuation in the group of leaky coaxial cables is calculated for each frequency component from the specified strength and the signal strength, and the amounts of attenuation are compared to detect the presence or absence of the deterioration in the group of leaky coaxial cables.

9. 9. The communication system according to claim 8, wherein the presence or absence of the deterioration in the leaky coaxial cable is detected by comparing the difference between the attenuation in the leaky coaxial cable group and the attenuation in the leaky coaxial cable group when there is no deterioration, for each of the frequency components.

10. 8. The communication system according to claim 7, wherein the presence or absence of the deterioration in the leaky coaxial cables is detected from frequency dependency of reception sensitivity when the leaky coaxial cables are used as an antenna.

11. a second transmission path connecting the first communication device and the second communication device; a leaky coaxial cable provided in the second transmission line; Further comprising:

11. The communication system according to claim 10, wherein the receiving sensitivity is obtained by receiving a leaky radio wave from the leaky coaxial cable provided in the second transmission line.

12. The communication system according to claim 10 , wherein the reception sensitivity is obtained by receiving a radio wave from a transmission source.

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