Train radio system and relay device

Abstract

Relay devices 3a, 3b, 3c are connected in series by a leakage coaxial cable (LCX) 4. A relay device 3b included among the relay devices 3a, 3b, 3c has a structure that outputs a high-frequency signal to an LCX 4d that is present on the latter-stage side of the relay device 3b and an LCX 4b that is present on the front-stage side of the relay device 3b. The high-frequency signal is used in order to perform radio communication.

Description

Technical Field

[0001] The present disclosure relates to a train radio system and a relay device that use a high-frequency signal utilized for performing wireless communication.

Background Art

[0002] In an LCX (Leakage Coaxial Cable) - type train radio system using an LCX, there is a system that uses RoF (Radio on Fiber), which is a high-frequency optical transmission method. In the train radio system, a high-frequency signal, which is an optical signal output from a base station, is transmitted to a relay device by RoF.

[0003] The relay device converts a high-frequency signal, which is an optical signal, into a high-frequency signal, which is an electrical signal, and transmits the high-frequency signal to the LCX. The high-frequency signal is used as data. A mobile station provided on a train receives a signal as radio waves leaked from the LCX. Also, in the process of the mobile station on the train transmitting a signal to the base station, the signal is transmitted to the base station through a path opposite to the above path.

[0004] Patent Document 1 discloses a configuration of an LCX - type train radio system (hereinafter, also referred to as "related configuration A"). In related configuration A, a plurality of relay devices that perform wireless communication with a mobile station perform processing for communication between the mobile station and the base station. The base station is connected to each of the plurality of relay devices via an optical fiber transmission line using RoF. The optical fiber transmission line is a transmission line for performing one - heart bidirectional communication.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] A configuration for performing wireless communication using an LCX generally has a configuration in which a plurality of relay devices are connected in series by the LCX. In this configuration, each relay device outputs a high-frequency signal used for performing wireless communication only to the LCX on one side of the relay device. Therefore, in this configuration, when one of the plurality of relay devices fails, there is a problem that the quality of wireless communication deteriorates.

[0007] The present disclosure has been made to solve such problems, and an object thereof is to provide a train wireless system or the like capable of suppressing deterioration in the quality of wireless communication in a situation where a plurality of relay devices are connected in series by an LCX.

Means for Solving the Problems

[0008] In order to achieve the above object, a train wireless system according to an aspect of the present disclosure is a system for performing wireless communication with a mobile station provided on a train. The train wireless system includes a base station that Transmission via an optical fiber transmission line generates a high-frequency signal used for performing the wireless communication, and a plurality of relay devices connected in series by an LCX (Leakage Coaxial Cable) for transmitting the high-frequency signal. The LCX exists on each of the front-stage side and the rear-stage side of a specific relay device included in the plurality of relay devices, and the specific relay device has a configuration in which the high-frequency signal is output to the LCX existing on the rear-stage side of the specific relay device and the LCX existing on the front-stage side of the specific relay device.

Effects of the Invention

[0009] According to the present disclosure, a plurality of relay devices are connected in series by an LCX (Leakage Coaxial Cable). A specific relay device included in the plurality of relay devices is configured to output the high-frequency signal to the LCX existing on the subsequent stage side of the specific relay device and the LCX existing on the preceding stage side of the specific relay device. The high-frequency signal is a signal used for wireless communication.

[0010] Thereby, in a situation where a plurality of relay devices are connected in series by an LCX, it is possible to suppress deterioration in the quality of wireless communication.

[0011] The object, features, aspects, and advantages of the present disclosure will become clearer from the following detailed description and the accompanying drawings.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments will be described with reference to the drawings. In the following drawings, the same reference numerals are assigned to the same components. The names and functions of the components with the same reference numerals are the same. Therefore, detailed descriptions of some of the components with the same reference numerals may be omitted.

[0014] <Embodiment 1> (Configuration) FIG. 1 is a diagram showing the configuration of a train radio system 100 according to Embodiment 1. The train radio system 100 is an LCX-based train radio system. The train radio system 100 is a system that uses RoF. In FIG. 1, directions D1a and D1b are shown for easier understanding of the description.

[0015] Hereinafter, the path using RoF will also be referred to as the "RoF path 2" or the "RoF path". The RoF path 2 is an optical fiber transmission path for transmitting a high-frequency signal. The high-frequency signal is used as data. Specifically, the RoF path 2 is a path for transmitting a high-frequency signal converted into an optical signal by an optical fiber. In FIG. 1, the RoF path is denoted as "RoF". In the following figures as well, the RoF path is denoted as "RoF".

[0016] The train radio system 100 is a system in which the base station 20 performs wireless communication with the mobile station 5 provided in the train MV1 using LCX. The mobile station 5 moves along with the movement of the train MV1. The mobile station 5 is a device for controlling the train MV1. The mobile station 5 controls, for example, the transceivers in the train MV1.

[0017] As shown in FIG. 1, the train radio system 100 mainly includes a base station 20, a plurality of relay devices 3, a plurality of LCXs 4, a plurality of RoF paths 2, and a mobile station 5. In FIG. 1, as an example, three relay devices 3 are shown.

[0018] Note that the number of relay devices 3 included in the train radio system 100 is not limited to 3 and may be 4 or more. Also, in FIG. 1, as an example, eight LCX4s are shown. Note that the number of LCX4s included in the train radio system 100 is not limited to 8 and may be an integer different from 8 and also an integer of 2 or more.

[0019] The base station 20 is a device that controls a plurality of relay devices 3. The base station 20 outputs a high-frequency signal. Also, the high-frequency signal is a signal used for wireless communication using an LCX. The base station 20 performs, for example, transmission or reception of a high-frequency signal converted into an optical signal.

[0020] The base station 20 is connected to each of the plurality of relay devices 3 via the RoF path 2. The high-frequency signal, which is an optical signal, output by the base station 20 is transmitted to each of the plurality of relay devices 3 via the RoF path 2.

[0021] Each of the plurality of relay devices 3 is a device for transmitting a signal. The plurality of relay devices 3 are installed along the route of the train MV1. The plurality of relay devices 3 included in the train radio system 100 are connected in series by LCX4.

[0022] The LCX4 is a cable for transmitting a signal. For example, the LCX4 is a cable for transmitting a high-frequency signal. The LCX4 is laid along the route of the train MV1. The LCX4 has no signal directionality. That is, the LCX4 can transmit a signal in either direction D1a or direction D1b.

[0023] When a high-frequency signal is transmitted through the LCX4, the high-frequency signal attenuates. The relay device 3 amplifies the attenuated high-frequency signal.

[0024] In train radio system 100, during the period when LCX4 transmits a high-frequency signal, radio communication is performed by radiating the radio waves leaked from the LCX4 to mobile station 5 provided in train MV1. LCX4 functions as an antenna for radiating the radio waves. That is, LCX4 constitutes a radio link for performing radio communication. Hereinafter, the quality of the radio link is also referred to as "radio link quality". The radio link quality is the quality of radio communication.

[0025] As described above, the high-frequency signal, which is an optical signal output by base station 20, is transmitted to each of a plurality of relay devices 3 via RoF path 2. With this configuration, in a situation where one of the plurality of relay devices 3 fails, even if the redundancy processing described later is not performed, the section where the radio link quality deteriorates can be limited to only the section corresponding to the failed relay device 3.

[0026] Hereinafter, among the plurality of relay devices 3 connected in series, the relay device 3 at the forefront is also referred to as the "foremost relay device". Also, hereinafter, among the plurality of relay devices 3 connected in series, the relay device 3 at the rearmost stage is also referred to as the "rearmost relay device". Further, hereinafter, among three or more relay devices 3 connected in series, the relay device 3 existing between the foremost relay device and the rearmost relay device is also referred to as the "middle relay device".

[0027] The rearmost relay device is connected to a terminal device (not shown) via LCX4. The terminal device performs terminal processing of the signal. The terminal processing is processing for preventing reflection of the signal. The terminal processing is, for example, processing for converting the signal into heat.

[0028] In the following, in a plurality of relay devices 3 connected in series, the situation where there is a middle-stage relay device is also referred to as the "middle-stage presence situation". The middle-stage presence situation is a situation where three or more relay devices 3 exist. In the following, in the middle-stage presence situation, the relay device 3 before the middle-stage relay device is also referred to as the "front-stage relay device". Also, in the following, in the middle-stage presence situation, the relay device 3 after the middle-stage relay device is also referred to as the "rear-stage relay device".

[0029] Also, in the following, in the middle-stage presence situation, the section between the middle-stage relay device and the front-stage relay device is also referred to as the "front-stage side of the middle-stage relay device". Also, in the following, in the middle-stage presence situation, the section between the middle-stage relay device and the rear-stage relay device is also referred to as the "rear-stage side of the middle-stage relay device".

[0030] In the middle-stage presence situation, an LCX 4 exists on each of the front-stage side of the middle-stage relay device and the rear-stage side of the middle-stage relay device. In the following, in the middle-stage presence situation, the LCX 4 existing on the rear-stage side of the middle-stage relay device which is the relay device 3 is also referred to as the "rear-stage side LCX". Also, in the following, in the middle-stage presence situation, the LCX 4 existing on the front-stage side of the middle-stage relay device which is the relay device 3 is also referred to as the "front-stage side LCX".

[0031] Also, in the following, the three relay devices 3 shown in the train radio system 100 of FIG. 1 are also referred to as relay device 3a, relay device 3b, and relay device 3c respectively. The situation where relay device 3a, relay device 3b, and relay device 3c exist is the aforementioned middle-stage presence situation.

[0032] In the middle-stage presence situation where relay device 3a, relay device 3b, and relay device 3c exist, relay device 3b is the middle-stage relay device. Also, in the middle-stage presence situation, relay device 3a is the relay device 3 before the middle-stage relay device. Also, in the middle-stage presence situation, relay device 3c is the relay device 3 after the middle-stage relay device.

[0033] In the following, the section existing between two relay devices 3 is also referred to as the "relay device section". The relay device section is, for example, the section existing between relay device 3a and relay device 3b. An LCX 4 is laid in the relay device section. That is, the LCX 4 exists in the relay device section.

[0034] Relay devices 3a, 3b, and 3c are connected in series by the LCX 4. Relay devices 3a and 3b are connected to each other by two LCX 4s. Also, relay devices 3b and 3c are connected to each other by two LCX 4s.

[0035] Note that the number of LCX 4s connecting relay device 3a and relay device 3b is not limited to 2, and may be 1 or 3 or more. Also, the number of LCX 4s connecting relay device 3b and relay device 3c is not limited to 2, and may be 1 or 3 or more.

[0036] Relay device 3b is included in relay devices 3a, 3b, and 3c connected in series by the LCX 4.

[0037] Hereinafter, for easier understanding, the explanation will be given using relay devices 3a, 3b, and 3c, which are three relay devices 3. In the following, the two LCX 4s connecting relay device 3a and relay device 3b are also referred to as LCX 4a and LCX 4b, respectively. Also, in the following, the two LCX 4s connecting relay device 3b and relay device 3c are also referred to as LCX 4c and LCX 4d, respectively.

[0038] LCX 4a and LCX 4c are used, for example, for data communication with trains on the up line. Also, LCX 4a and LCX 4c are laid, for example, along the line of trains on the up line. LCX 4b and LCX 4d are used, for example, for data communication with trains on the down line. Also, LCX 4b and LCX 4d are laid, for example, along the line of trains on the down line.

[0039] On the front stage side of the relay device 3b which is a middle stage relay device, there are LCXs 4a and 4b as the front stage side LCXs. Also, on the rear stage side of the relay device 3b which is a middle stage relay device, there are LCXs 4c and 4d as the rear stage side LCXs.

[0040] In the following, in FIG. 1, the three RoF paths 2 connected to the base station 20 are also referred to as RoF path 2a, RoF path 2b, and RoF path 2c, respectively. The RoF paths 2a, 2b, and 2c are connected to the relay devices 3a, 3b, and 3c, respectively. That is, the base station 20 is connected to the relay devices 3a, 3b, and 3c via the RoF paths 2a, 2b, and 2c.

[0041] Next, the configuration of the relay device 3 will be described. FIG. 2 is a block diagram showing the configuration of the relay device 3 according to Embodiment 1. In FIG. 2, the relay device 3 as the relay device 3b is shown.

[0042] As shown in FIG. 2, the relay device 3 mainly includes a power supply unit 6, a monitoring unit 7, two optical transmission units 8, two high-frequency units 9, and two amplification units 10.

[0043] The power supply unit 6 performs, for example, supply of direct current, monitoring of output current, protection of output, etc. The monitoring unit 7 performs, for example, monitoring of the state of the relay device 3. The state of the relay device 3 includes a normal state and an alarm state. Also, the monitoring unit 7 communicates with, for example, the monitoring unit of another relay device 3.

[0044] The optical transmission unit 8 performs, for example, the process of converting an optical signal into an electrical signal. Also, the optical transmission unit 8 performs, for example, signal synthesis, signal separation, etc. The high-frequency unit 9 performs, for example, demultiplexing of high-frequency signals, synthesis of high-frequency signals, etc. Also, the high-frequency unit 9 has a function of detecting the level of high-frequency signals.

[0045] The amplifier unit 10 amplifies, for example, a high-frequency signal. The amplifier unit 10 is configured to output a high-frequency signal to the LCX on the subsequent stage side of the relay device 3 including the amplifier unit 10 and the LCX on the preceding stage side of the relay device 3. Therefore, the relay device 3 including the amplifier unit 10 is configured to output a high-frequency signal to the LCX on the subsequent stage side of the relay device 3 and the LCX on the preceding stage side of the relay device 3.

[0046] The configurations of the relay devices 3a and 3c in FIG. 1 are the same as the configuration of the relay device 3b in FIG. 2. Therefore, the description of the configurations of the relay devices 3a and 3c is omitted.

[0047] Hereinafter, the power supply unit 6 included in the relay device 3b is also referred to as "power supply unit 6b". Hereinafter, the monitoring unit 7 included in the relay device 3b is also referred to as "monitoring unit 7b". Hereinafter, the two optical transmission units 8 included in the relay device 3b are also referred to as optical transmission unit 8c and optical transmission unit 8d, respectively.

[0048] Hereinafter, the two high-frequency units 9 included in the relay device 3b are also referred to as high-frequency unit 9c and high-frequency unit 9d, respectively. Hereinafter, the two amplifier units 10 included in the relay device 3b are also referred to as amplifier unit 10c and amplifier unit 10d, respectively.

[0049] The relay device 3b includes a power supply unit 6b, a monitoring unit 7b, optical transmission units 8c and 8d, high-frequency units 9c and 9d, and amplifier units 10c and 10d.

[0050] The optical transmission unit 8c, the high-frequency unit 9c, and the amplifier unit 10c are components corresponding to the LCXs 4b and 4d. The optical transmission unit 8d, the high-frequency unit 9d, and the amplifier unit 10d are components corresponding to the LCXs 4a and 4c.

[0051] FIG. 3 is a block diagram showing the configurations of the relay device 3a and the relay device 3b according to Embodiment 1. FIG. 3 shows a part of the configuration of the train radio system 100 in FIG. 1. In the following, the power supply unit 6 included in the relay device 3a is also referred to as "power supply unit 6a". Also, in the following, the monitoring unit 7 included in the relay device 3a is also referred to as "monitoring unit 7a".

[0052] Also, in the following, the two optical transmission units 8 included in the relay device 3a are also referred to as optical transmission unit 8a and optical transmission unit 8b, respectively. Also, in the following, the two high-frequency units 9 included in the relay device 3a are also referred to as high-frequency unit 9a and high-frequency unit 9b, respectively. Also, in the following, the two amplification units 10 included in the relay device 3a are also referred to as amplification unit 10a and amplification unit 10b, respectively.

[0053] The relay device 3a includes a power supply unit 6a, a monitoring unit 7a, optical transmission units 8a and 8b, high-frequency units 9a and 9b, and amplification units 10a and 10b.

[0054] Here, with reference to FIGS. 2 and 3, the processing performed by the relay device 3b, which is the middle-stage relay device (hereinafter also referred to as "relay processing N"), will be described. In the relay processing N, the high-frequency signal, which is an optical signal transmitted through the RoF path 2b, is converted into a high-frequency signal, which is an electrical signal, by the optical transmission unit 8c and the high-frequency unit 9c. The amplification unit 10c amplifies the converted high-frequency signal. The amplification unit 10c outputs the high-frequency signal to each of the LCX 4d as the rear-stage LCX and the LCX 4b as the front-stage LCX.

[0055] Also, in the relay processing N, the high-frequency signal, which is an optical signal transmitted through the RoF path 2b, is converted into a high-frequency signal, which is an electrical signal, by the optical transmission unit 8d and the high-frequency unit 9d. The amplification unit 10d amplifies the converted high-frequency signal. The amplification unit 10d outputs the high-frequency signal to each of the LCX 4c as the rear-stage LCX and the LCX 4a as the front-stage LCX.

[0056] Here, a comparative example to be compared with the present embodiment will be described. In the following, the train radio system according to the comparative example is also referred to as "train radio system J". The train radio system J is not shown. The configuration of the train radio system J is the same as the configuration of the train radio system 100 in FIG. 1. That is, the train radio system J includes relay devices 3a, 3b, and 3c as relay devices 3.

[0057] The configuration of the relay device 3 according to the comparative example is different from the configuration of the relay device 3 according to the first embodiment. That is, the configuration of the relay device 3 included in the train radio system J is different from the configuration of the relay device 3 included in the train radio system 100.

[0058] FIG. 7 is a block diagram showing the configuration of the relay device 3 according to the comparative example. In FIG. 7, the relay device 3b as the relay device 3 according to the comparative example is shown.

[0059] The relay device 3b in FIG. 7 is different from the relay device 3b in FIG. 2 in that two amplifying units 10c and 10d, which are the amplifying units 10, output the high-frequency signal only to the LCX on the subsequent stage side. The other configuration of the relay device 3b in FIG. 7 is the same as that of the relay device 3b in FIG. 2. The configuration of each of the relay devices 3a and 3c in the comparative example is also the same as the configuration of the relay device 3b in FIG. 7.

[0060] Here, using FIG. 7, the process performed by the relay device 3b in the comparative example (hereinafter also referred to as "relay process J") will be described. In the relay process J, the high-frequency signal, which is an optical signal transmitted through the RoF path 2b, is converted into a high-frequency signal, which is an electrical signal, by the optical transmission unit 8c and the high-frequency unit 9c. The amplifying unit 10c amplifies the converted high-frequency signal and outputs the high-frequency signal to the LCX4d as the LCX on the subsequent stage side.

[0061] Also, in the relay process J, the high-frequency signal, which is an optical signal transmitted through the RoF path 2b, is converted into a high-frequency signal, which is an electrical signal, by the optical transmission unit 8d and the high-frequency unit 9d. The amplifying unit 10d amplifies the converted high-frequency signal and outputs the high-frequency signal to the LCX4c as the LCX on the subsequent stage side.

[0062] Also, in the relay process J, the high-frequency signal output from the relay device 3b reaches a relay device 3c (not shown) of the comparative example via the LCX4c or LCX4d as the subsequent-stage LCX. Thereafter, the high-frequency signal is received by one of the two high-frequency units 9 of the relay device 3c. The high-frequency unit 9 that has received the high-frequency signal performs termination processing of the high-frequency signal.

[0063] Here, assume that a failure occurs in the amplifier unit 10c of the relay device 3b of the comparative example before the relay process J is performed. Also assume that the failure is such that the amplifier unit 10c cannot output a high-frequency signal to the LCX4d.

[0064] In this case, in the relay process J, a high-frequency signal is not output to the LCX4d. That is, data transmission is not performed to the LCX4d. As a result, deterioration of the radio link quality occurs in the relay device section corresponding to the LCX4d.

[0065] By the way, the relay device 3c of the comparative example in a train radio system J (not shown) having the same configuration as that of FIG. 1 receives a high-frequency signal as data via the RoF path 2c. Therefore, for example, deterioration of the radio link quality does not occur in the relay device section corresponding to the LCX4 different from the LCX4d.

[0066] On the other hand, in the relay process N of the present embodiment, as described above, the amplifier unit 10c of the relay device 3b outputs a high-frequency signal to each of the LCX4d as the subsequent-stage LCX and the LCX4b as the preceding-stage LCX. Also, the amplifier unit 10d of the relay device 3b outputs a high-frequency signal to each of the LCX4c as the subsequent-stage LCX and the LCX4a as the preceding-stage LCX. That is, data transmission is made redundant for the LCX4a and 4b as the preceding-stage LCX.

[0067] Here, assume that a failure occurs in the amplifier unit 10c of the relay device 3b before the relay process N is performed. Also assume that the failure is such that the amplifier unit 10c cannot output a high-frequency signal to the LCX4d.

[0068] In this case, in the relay process N, the amplifier unit 10c does not output a high-frequency signal to the LCX4d. However, one of the two amplifier units 10 of the relay device 3c in FIG. 1 outputs a high-frequency signal to the LCX4d. Thereby, even if a failure occurs in the amplifier unit 10, it is possible to suppress the occurrence of deterioration in the radio line quality in the relay device section.

[0069] Hereinafter, a configuration in which the relay device 3 outputs a high-frequency signal to each of the front-stage LCX and the rear-stage LCX of the relay device 3 is also referred to as a "redundant configuration". Each relay device 3 in the train radio system 100 of the present embodiment has a redundant configuration.

[0070] Next, with reference to FIG. 3, the process using the redundant configuration of the relay device 3 (hereinafter also referred to as "relay control process") will be described in detail.

[0071] Hereinafter, the process of outputting a high-frequency signal as data to the rear-stage LCX and the front-stage LCX is also referred to as "redundancy process". The redundancy process is a process in which the amplifier unit 10 of each relay device 3 outputs a high-frequency signal to the rear-stage LCX and the front-stage LCX. In the relay control process of the present embodiment, the redundancy process is always performed.

[0072] Here, in order to make an example of the relay control process easier to understand, the relay control process performed under the following premise Pm1 will be described.

[0073] Under premise Pm1, signal transmission is performed between relay device 3a and relay device 3b. Also, under premise Pm1, a failure has occurred in the amplifier unit 10a of relay device 3a. The failure is such that the amplifier unit 10a cannot output the signal to LCX4b. That is, under premise Pm1, the amplifier unit 10a cannot output the high-frequency signal to LCX4b. Therefore, under premise Pm1, the high-frequency signal is not output from the amplifier unit 10a to LCX4b. The amplifier unit 10a can transmit the signal to the high-frequency unit 9a and receive the signal.

[0074] In the relay control process under premise Pm1, the amplifier unit 10c of relay device 3b outputs the high-frequency signal to LCX4d as the LCX on the subsequent stage side and LCX4b as the LCX on the preceding stage side. That is, the amplifier unit 10c of relay device 3b outputs the high-frequency signal to LCX4b as the LCX on the preceding stage side. Thereby, the high-frequency signal reaches relay device 3a via LCX4b. Thereafter, the high-frequency signal reaches the high-frequency unit 9a via the amplifier unit 10a. The high-frequency unit 9a performs termination processing of the high-frequency signal.

[0075] Thereby, in the relay control process under premise Pm1, the high-frequency signal is output from relay device 3b to LCX4b which cannot receive the high-frequency signal from relay device 3a due to the failure of the amplifier unit 10a. Therefore, it is possible to suppress the occurrence of deterioration of the radio link quality in all relay device sections. Also, in a state where the arrangement configuration of the plurality of relay devices 3 in the train radio system 100 is the same as the arrangement configuration of the plurality of relay devices 3 in the train radio system J, the reliability of data transmission can be improved.

[0076] (Summary) As described above, according to the present embodiment, the relay devices 3a, 3b, 3c are connected in series by LCX4. The relay device 3b included in the relay devices 3a, 3b, 3c has a configuration that outputs a high-frequency signal to LCX4d existing on the subsequent stage side of the relay device 3b and LCX4b existing on the preceding stage side of the relay device 3b. The high-frequency signal is a signal used for performing wireless communication.

[0077] This can suppress the deterioration of the quality of wireless communication in a situation where a plurality of relay devices are connected in series by an LCX.

[0078] Also, according to the present embodiment, in the relay control process, a redundancy process is always performed. The redundancy process is a process in which the amplifying unit 10 of each relay device 3 outputs a high-frequency signal to the LCX on the subsequent stage side and the LCX on the preceding stage side. Thereby, for example, even if a failure occurs in the amplifying unit 10 of one of the plurality of relay devices 3, the following problems can be suppressed from occurring.

[0079] The problem is, for example, a problem that data transmission is not performed in the relay device section. Also, the problem is, for example, a problem that radio waves are radiated only from one of the two LCXs in the relay device section.

[0080] Therefore, radio waves can always be emitted from both of the two LCXs in the relay device section. Therefore, a mobile station that receives radio waves in the relay device section can continuously obtain a diversity gain. Thereby, even in a situation where a failure occurs in the relay device, a situation with good quality of wireless communication can be continued. Therefore, an effect that the communication quality can be maintained in wireless communication is obtained.

[0081] Also, due to the redundancy process being performed, even if a failure occurs in one of the plurality of relay devices 3, wireless communication can always be performed with the mobile station in all relay device sections. Therefore, an effect that the reliability of the train radio system can be improved is obtained.

[0082] Incidentally, in the related configuration A described above, when one of the plurality of relay devices fails, the high-frequency signal that was supposed to be output from the failed relay device will not be output to the LCX. That is, the high-frequency signal will not be transmitted in the LCX that exists on the downstream side of the failed relay device. Therefore, there is a problem that a degradation section of the radio link quality will occur.

[0083] Therefore, the train radio system 100 of the present embodiment has a configuration for achieving the above effects. Therefore, the train radio system 100 of the present embodiment can solve the above problems.

[0084] As described above, in the relay control process of the present embodiment, the amplification unit 10 of the relay device 3 performs a redundancy process of constantly outputting a high-frequency signal as data to the downstream LCX and the upstream LCX. Therefore, in the LCX 4, there is a possibility that data interference occurs, that is, the signal traveling in the direction D1a and the signal traveling in the direction D1b interfere with each other.

[0085] Therefore, a filter for preventing the occurrence of data interference may be provided in the LCX 4. With this configuration, it is possible to prevent data interference from occurring in the LCX 4. As a result, data transmission can be constantly performed in all relay device sections without degrading the radio link quality. Therefore, it is possible to provide a train radio system capable of coping with a situation where a failure occurs in the relay device 3.

[0086] <Modification Example 1> In the following, the configuration of this modification example is also referred to as "Configuration Ctm1". Configuration Ctm1 is a configuration that performs a redundancy process only when a predetermined situation occurs. The predetermined situation is a situation where the radio link quality has deteriorated in the relay device section corresponding to the LCX 4. The predetermined situation occurs, for example, when at least one of the plurality of relay devices 3 fails. Configuration Ctm1 is applied to Embodiment 1. In the following, the configuration of Embodiment 1 to which Configuration Ctm1 is applied is also referred to as "Modified Configuration A".

[0087] Also, in the following, the process of transmitting the high-frequency signal as data only to the subsequent-stage LCX is also referred to as "non-redundancy processing". The non-redundancy processing is a process in which the amplification unit 10 of each relay device 3 transmits the high-frequency signal only to the subsequent-stage LCX.

[0088] Next, with reference to FIG. 3, the relay control process in the modified configuration A will be described. In the modified configuration A, each relay device 3 is set to perform non-redundancy processing as an initial state process.

[0089] As described above, in the middle-stage presence situation, the relay device 3 in the previous stage of the middle-stage relay device is also referred to as the "previous-stage relay device". The middle-stage relay device is, for example, the relay device 3b. Here, as shown in FIG. 1, among the relay devices 3a, 3b, and 3c connected in series, the relay device 3 in the previous stage of the middle-stage relay device 3b, which is the middle-stage relay device, is the relay device 3a. That is, the previous-stage relay device of the relay device 3b is the relay device 3a.

[0090] As described above, the high-frequency unit 9 included in the relay device 3 has a function of detecting the level of the high-frequency signal. Also, the high-frequency unit 9 included in the relay device 3 has a function of determining whether the previous-stage relay device of the relay device 3 is faulty based on the level of the high-frequency signal received from the previous-stage relay device of the relay device 3. When the level of the high-frequency signal is smaller than a predetermined threshold value, the high-frequency unit 9 determines that the previous-stage relay device is faulty. The predetermined threshold value is set to a value that can identify, for example, that the high-frequency signal has not been amplified.

[0091] Here, in order to make an example of the relay control process in the modified configuration A easier to understand, with reference to FIG. 3, the relay control process performed under the following premise Pm1a will be described.

[0092] In the premise Pm1a, signal transmission is performed between the relay device 3a and the relay device 3b. Also, in the premise Pm1a, each relay device 3 is set to perform non-redundancy processing as an initial state process.

[0093] Also, under premise Pm1a, a failure has occurred in the amplifier unit 10a of the relay device 3a. The failure is that the amplifier unit 10a cannot amplify high-frequency signals. Also, under premise Pm1a, the faulty amplifier unit 10a outputs a high-frequency signal that has not been amplified by the amplifier unit 10a.

[0094] Also, under premise Pm1a, the high-frequency signal output from the faulty amplifier unit 10a is transmitted to the high-frequency unit 9c of the relay device 3b via the LCX4b and the amplifier unit 10c of the relay device 3b. That is, under premise Pm1a, the relay device 3b receives a high-frequency signal from the relay device 3a, which is the relay device in the previous stage of the relay device 3b.

[0095] Also, under premise Pm1a, the level of the high-frequency signal output from the faulty amplifier unit 10a is smaller than a predetermined threshold value. The predetermined threshold value is set to a value that can identify that the high-frequency signal output from the amplifier unit 10a has not been amplified by the amplifier unit 10a.

[0096] In the relay control process under premise Pm1a, the high-frequency signal output from the faulty amplifier unit 10a included in the relay device 3a is transmitted to the high-frequency unit 9c of the relay device 3b via the LCX4b and the amplifier unit 10c of the relay device 3b.

[0097] The high-frequency unit 9c included in the relay device 3b determines whether the previous-stage relay device is faulty based on the level of the high-frequency signal received from the relay device 3a, which is the previous-stage relay device of the relay device 3b.

[0098] Under premise Pm1a, the level of the high-frequency signal received by the high-frequency unit 9c is smaller than a predetermined threshold value. Therefore, the high-frequency unit 9c determines that the amplifier unit 10a of the relay device 3a, which is the previous-stage relay device, is faulty. That is, the high-frequency unit 9c determines that the relay device 3a, which is the previous-stage relay device, is faulty.

[0099] When it is determined that the relay device 3a, which is the front-stage relay device, has failed, the high-frequency unit 9c gives instruction A to the amplification unit 10c. The instruction A is an instruction for switching the processing performed by the relay device 3b from non-redundant processing to redundant processing.

[0100] The amplification unit 10c of the relay device 3b performs redundant processing according to instruction A. Specifically, the amplification unit 10c of the relay device 3b outputs the high-frequency signal to the LCX 4d as the rear-stage LCX and the LCX 4b as the front-stage LCX.

[0101] Thus, in the relay control process in premise Pm1a, when it is determined that the relay device 3a, which is the front-stage relay device, has failed, the amplification unit 10c outputs the high-frequency signal to the LCX 4d as the rear-stage LCX and the LCX 4b as the front-stage LCX.

[0102] (Summary) As described above, according to this modification example, among the plurality of relay devices 3, redundant processing is performed only when the radio link quality deteriorates due to the failure of at least one relay device 3. Thereby, the power consumption of each relay device 3 can be reduced. In addition, the occurrence frequency of the aforementioned data interference can be reduced. Therefore, the effects of improving the radio link quality and improving the reliability of the transmitted data can be obtained.

[0103] <Embodiment 2> (Configuration) The train radio system according to Embodiment 2 is the train radio system 100 in FIG. 1. FIG. 4 is a block diagram showing the configuration of the relay device 3 according to Embodiment 2. In FIG. 4, the relay device 3 as the relay device 3b included in the train radio system 100 is shown.

[0104] The configuration of the relay device 3 in Embodiment 2 is the same as the configuration of the relay device 3 in Embodiment 1. In the relay device 3 of Embodiment 2, each of the two amplification units 10 includes two amplification units 11. That is, the relay device 3 in Embodiment 2 includes four amplification units 11.

[0105] In this embodiment, four amplifying units 11 are used to output high-frequency signals as data to four LCX4s connected to the relay device 3. Also, for the four LCX4s connected to the relay device 3, four amplifying units 11 individually output high-frequency signals as data. In this embodiment, similar to Embodiment 1, data transmission redundancy is performed for LCX4a and LCX4b as the front-stage LCXs. Hereinafter, the configuration of this embodiment will be described in detail.

[0106] First, the configuration of the relay device 3b as the relay device 3 in this embodiment will be described. On the front-stage side of the relay device 3b, there are LCX4a and LCX4b as the front-stage LCXs. Also, on the rear-stage side of the relay device 3b, there are LCX4c and LCX4d as the rear-stage LCXs. The relay device 3b includes an amplifying unit 10c and an amplifying unit 10d as two amplifying units 10.

[0107] The amplifying unit 10c is a component corresponding to LCX4b and LCX4d. The amplifying unit 10d is a component corresponding to LCX4a and LCX4c.

[0108] Hereinafter, the two amplifying units 11 included in the amplifying unit 10c of the relay device 3b are also referred to as an amplifying unit 11a and an amplifying unit 11b, respectively. Also, hereinafter, the two amplifying units 11 included in the amplifying unit 10d of the relay device 3b are also referred to as an amplifying unit 11c and an amplifying unit 11d, respectively.

[0109] In this embodiment, the four amplifying units 11 are each associated with LCX4a, 4b, 4c, and 4d. Each amplifying unit 11 outputs a high-frequency signal as data to the LCX4 associated with that amplifying unit 11. That is, each amplifying unit 11 outputs a high-frequency signal as data to a different LCX4.

[0110] Specifically, the amplification unit 11a is associated with LCX4b. The amplification unit 11a outputs a high-frequency signal to LCX4b. Also, the amplification unit 11b is associated with LCX4d. The amplification unit 11b outputs a high-frequency signal to LCX4d. Also, the amplification unit 11c is associated with LCX4a. The amplification unit 11c outputs a high-frequency signal to LCX4a. Also, the amplification unit 11d is associated with LCX4c. The amplification unit 11d outputs a high-frequency signal to LCX4c.

[0111] FIG. 5 is a block diagram showing the configurations of the relay devices 3a and 3b according to Embodiment 2. The relay device 3a includes an amplification unit 10a and an amplification unit 10b as two amplification units 10.

[0112] Hereinafter, the two amplification units 11 included in the amplification unit 10a of the relay device 3a are also referred to as an amplification unit 11e and an amplification unit 11f, respectively. Also, hereinafter, the two amplification units 11 included in the amplification unit 10b of the relay device 3b are also referred to as an amplification unit 11g and an amplification unit 11h, respectively.

[0113] In the present embodiment, similar to Embodiment 1, relay control processing is performed. In the relay control processing of the present embodiment, redundancy processing is always performed. The redundancy processing is a process in which the amplification unit 10 of each relay device 3 outputs a high-frequency signal to the LCX on the subsequent stage side and the LCX on the preceding stage side. Specifically, the redundancy processing is a process in which the two amplification units 11 included in the amplification unit 10 of each relay device 3 output a high-frequency signal to the LCX on the subsequent stage side and the LCX on the preceding stage side, respectively.

[0114] Here, in order to make an example of the relay control processing of the present embodiment easier to understand, the relay control processing performed under the following premise Pm2 will be described.

[0115] Under premise Pm2, signal transmission is performed between relay device 3a and relay device 3b. Also, under premise Pm2, a failure has occurred in amplifier section 11f included in amplifier section 10a of relay device 3a. The failure is that amplifier section 11f cannot output a signal to LCX4b. That is, under premise Pm2, amplifier section 11f cannot output a high-frequency signal to LCX4b. Therefore, under premise Pm2, the high-frequency signal is not output from amplifier section 11f to LCX4b. Amplifier section 11f can transmit a signal to high-frequency section 9a and receive a signal.

[0116] In the relay control process under premise Pm2, amplifier section 11b included in amplifier section 10c of relay device 3b outputs a high-frequency signal to LCX4d as the LCX on the subsequent stage side. That is, amplifier section 11b is the first amplifier section for outputting a high-frequency signal to the LCX on the subsequent stage side.

[0117] Also, amplifier section 11a included in amplifier section 10c of relay device 3b outputs a high-frequency signal to LCX4b as the LCX on the preceding stage side. That is, amplifier section 11a is the second amplifier section for outputting a high-frequency signal to the LCX on the preceding stage side. As a result, the high-frequency signal output by amplifier section 11a reaches relay device 3a via LCX4b. Thereafter, the high-frequency signal reaches high-frequency section 9a via amplifier section 11f. High-frequency section 9a performs termination processing of the high-frequency signal.

[0118] As a result, in the relay control process under premise Pm2, a high-frequency signal is output from relay device 3b to LCX4b where relay device 3a cannot receive the high-frequency signal due to the failure of amplifier section 11f. Therefore, it is possible to suppress the occurrence of deterioration in radio line quality in all relay device sections. Therefore, the reliability of data transmission can be improved.

[0119] (Summary) As described above, according to this embodiment, in the relay control process, redundancy processing is always performed. The redundancy processing of this embodiment is a process in which two amplifying units 11 included in the amplifying unit 10 of each relay device 3 output high-frequency signals to the rear-stage LCX and the front-stage LCX, respectively. Thereby, for example, even if a failure occurs in the amplifying unit 11 of one relay device 3 among a plurality of relay devices 3, it is possible to suppress the occurrence of deterioration of the radio line quality in all relay device sections. Therefore, the reliability of data transmission can be improved.

[0120] Also, according to this embodiment, each amplifying unit 11 outputs a high-frequency signal as data to different LCXs 4. Therefore, the level of the high-frequency signal to be transmitted can be set for each LCX4. That is, the level of the high-frequency signal to be transmitted can be set individually. Therefore, fine adjustment for performing wireless communication becomes possible.

[0121] Also, in this embodiment, similar to Embodiment 1, a filter for preventing the occurrence of data interference may be provided in the LCX4. With this configuration, it is possible to prevent data interference from occurring in the LCX4. Thereby, data transmission can be always performed in all relay device sections without degrading the radio line quality. Therefore, it is possible to provide a train radio system capable of coping with a situation where a failure has occurred in the relay device 3.

[0122] <Modification Example of Embodiment 2> The configuration Ctm1 of the above-described Modification Example 1 may be applied to Embodiment 2. As described above, the configuration Ctm1 is a configuration that performs redundancy processing only when a predetermined situation occurs. The predetermined situation is a situation where the radio line quality has deteriorated in the relay device section corresponding to the LCX4. The predetermined situation occurs, for example, when at least one of the plurality of relay devices 3 has failed. Hereinafter, the configuration of Embodiment 2 to which the configuration Ctm1 is applied is also referred to as "modified configuration B".

[0123] Next, with reference to FIGS. 1 and 5, the relay control process in the modified configuration B will be described. In the modified configuration B, each relay device 3 is set to perform the above-described non-redundancy process as an initial state process.

[0124] As described above, in the middle stage presence situation, the relay device 3 in the previous stage of the middle stage relay device is also referred to as the "previous stage relay device". The middle stage relay device is, for example, the relay device 3b. Here, as shown in FIG. 1, among the relay devices 3a, 3b, and 3c connected in series, the relay device 3 in the previous stage of the middle stage relay device 3b, which is the middle stage relay device, is the relay device 3a. That is, the previous stage relay device of the relay device 3b is the relay device 3a.

[0125] As described above, the high-frequency unit 9 included in the relay device 3 has a function of determining whether the previous stage relay device has failed based on the level of the high-frequency signal received from the previous stage relay device of the relay device 3. When the level of the high-frequency signal is smaller than a predetermined threshold value, the high-frequency unit 9 determines that the previous stage relay device has failed.

[0126] Here, in order to make an example of the relay control process in the modified configuration B easier to understand, with reference to FIG. 5, the relay control process performed under the following premise Pm2a will be described.

[0127] In the premise Pm2a, signal transmission is performed between the relay device 3a and the relay device 3b. Also, in the premise Pm2a, each relay device 3 is set to perform a non-redundancy process as an initial state process.

[0128] Also, in the premise Pm2a, a failure has occurred in the amplifier unit 11f included in the amplifier unit 10a of the relay device 3a. The failure is a failure in which the amplifier unit 11f included in the amplifier unit 10a cannot amplify the high-frequency signal. Also, in the premise Pm2a, the failed amplifier unit 11f outputs a high-frequency signal that has not been amplified by the amplifier unit 11f.

[0129] Also, in premise Pm2a, the high-frequency signal output from the failed amplifier unit 11f is transmitted to the high-frequency unit 9c of the relay device 3b via the LCX4b and the amplifier unit 11a of the relay device 3b. That is, in premise Pm2a, the relay device 3b receives a high-frequency signal from the relay device 3a in the previous stage of the relay device 3b. Also, in premise Pm2a, the level of the high-frequency signal output from the failed amplifier unit 11f is smaller than a predetermined threshold value.

[0130] In the relay control process in premise Pm2a, the high-frequency signal output from the failed amplifier unit 11f included in the relay device 3a is transmitted to the high-frequency unit 9c of the relay device 3b via the LCX4b and the amplifier unit 11a of the relay device 3b.

[0131] The high-frequency unit 9c included in the relay device 3b determines whether the previous-stage relay device is faulty based on the level of the high-frequency signal received from the relay device 3a, which is the previous-stage relay device of the relay device 3b.

[0132] In premise Pm2a, the level of the high-frequency signal received by the high-frequency unit 9c is smaller than a predetermined threshold value. Therefore, the high-frequency unit 9c determines that the amplifier unit 11f of the relay device 3a, which is the previous-stage relay device, is faulty. That is, the high-frequency unit 9c determines that the relay device 3a, which is the previous-stage relay device, is faulty.

[0133] When it is determined that the relay device 3a, which is the previous-stage relay device, is faulty, the high-frequency unit 9c gives instruction A to the amplifier units 11a and 11b included in the amplifier unit 10c. The instruction A is an instruction for the relay device 3b to switch the process from non-redundant processing to redundant processing.

[0134] The amplifier units 11a and 11b included in the amplifier unit 10c of the relay device 3b perform redundant processing according to instruction A. Specifically, the amplifier unit 11b included in the amplifier unit 10c of the relay device 3b outputs the high-frequency signal to the LCX4d as the LCX on the subsequent stage side. That is, the amplifier unit 11b is the first amplifier unit for outputting the high-frequency signal to the LCX on the subsequent stage side.

[0135] Further, an amplifier unit 11a included in the amplifier unit 10c of the relay device 3b outputs a high-frequency signal to the LCX 4b as the front-stage LCX. That is, the amplifier unit 11a is a second amplifier unit for outputting a high-frequency signal to the front-stage LCX.

[0136] Accordingly, in the relay control process in the premise Pm2a, when it is determined that the relay device 3a, which is the front-stage relay device, has failed, the amplifier unit 10c including the amplifier units 11a and 11b outputs a high-frequency signal to the LCX 4d as the rear-stage LCX and the LCX 4b as the front-stage LCX.

[0137] (Summary) As described above, according to the modified configuration B, the redundancy process is performed only when the radio link quality deteriorates due to the failure of at least one of the plurality of relay devices 3. For example, the process performed by the relay device 3b is switched from a non-redundant process to a redundant process. Thereby, the same effects as those of the aforementioned modified example 1 can be obtained. For example, the effects of improving the radio link quality and improving the reliability of the transmission data can be obtained.

[0138] (Functional block diagram) FIG. 6 is a block diagram showing a characteristic functional configuration of the train radio system 100. That is, FIG. 6 is a block diagram showing the main functions related to the present disclosure among the functions of the train radio system 100.

[0139] The train radio system 100 is a system for performing wireless communication with the mobile station 5 provided in the train MV1. The train radio system 100 includes a base station B1 and relay devices B2a, B2b, and B2c.

[0140] The base station B1 outputs a high-frequency signal used for performing wireless communication. The base station B1 corresponds to the base station 20.

[0141] The relay devices B2a, B2b, and B2c are connected in series by an LCX (Leakage Coaxial Cable) 4 for transmitting high-frequency signals. The relay devices B2a, B2b, and B2c respectively correspond to the relay devices 3a, 3b, and 3c.

[0142] On each of the front stage side and the rear stage side of the relay device B2b included in the relay devices B2a, B2b, and B2c, there is an LCX 4. The relay device B2b is configured to output a high-frequency signal to the LCX 4 existing on the rear stage side of the relay device B2b and the LCX 4 existing on the front stage side of the relay device B2b.

[0143] (Other modifications) Note that it is possible to freely combine each embodiment and modification, or to appropriately modify and omit each embodiment and modification.

[0144] For example, the train radio system 100 is not limited to a system using RoF. The train radio system 100 may be configured as a system that does not use RoF. In such a configuration, the base station 20 is connected to, for example, only the relay device 3a.

[0145] Also, for example, the relay device 3 does not have to include all the components shown in the figure. That is, the relay device 3 may include only the minimum number of components that can achieve the effects of the present disclosure.

[0146] Although the present disclosure has been described in detail, the above description is illustrative and not restrictive in all aspects. An infinite number of modifications that are not illustrated can be considered.

Explanation of reference numerals

[0147] Relay devices 3, 3a, 3b, 3c, B2a, B2b, B2c, LCXs 4, 4a, 4b, 4c, 4d, mobile stations 5, high-frequency sections 9, 9a, 9b, 9c, 9d, amplifying sections 10, 10a, 10b, 10c, 10d, 11, 11a, 11b, 11c, 11d, 11e, 11f, 11g, 11h, base stations 20, B1, train radio system 100, train MV1.

Claims

1. A train radio system for performing wireless communication with a mobile station provided on a train, comprising: a base station that transmits a high-frequency signal used for performing the wireless communication via an optical fiber transmission line; a plurality of relay devices connected in series by an LCX (Leakage Coaxial Cable) for transmitting the high-frequency signal; the LCX exists on each of the front-stage side and the rear-stage side of a specific relay device included in the plurality of relay devices; the specific relay device is configured to output the high-frequency signal to the LCX existing on the rear-stage side of the specific relay device and the LCX existing on the front-stage side of the specific relay device; A train radio system.

2. A relay device included in a plurality of relay devices connected in series by an LCX (Leakage Coaxial Cable) for transmitting a high-frequency signal used for performing wireless communication, wherein: the LCX exists on each of the front-stage side and the rear-stage side of the relay device; the relay device includes: an amplification unit configured to output the high-frequency signal transmitted from the base station via the optical fiber transmission line to a rear-stage side LCX which is the LCX existing on the rear-stage side of the relay device and a front-stage side LCX which is the LCX existing on the front-stage side of the relay device; A relay device.

3. The relay device further includes: a high-frequency unit configured to determine whether a front-stage relay device which is a relay device in the front stage of the relay device is faulty; when it is determined that the front-stage relay device is faulty, the amplification unit outputs the high-frequency signal to the rear-stage side LCX and the front-stage side LCX; The relay device according to Claim 2.

4. The amplification unit includes: a first amplification unit for outputting the high-frequency signal to the rear-stage side LCX; and a second amplification unit for outputting the high-frequency signal to the front-stage side LCX; The relay device according to Claim 2 or 3.

Images