Communication relay system, communication relay control program, and communication relay system control method

Abstract

To provide a communication relay system or the like capable of suppressing a failure assumed when an optical repeater system is not synchronized with TDD timing.SOLUTION: A communication relay system according to an embodiment includes a master unit device connected to a first communication device on an upstream side, and a slave unit device provided between the master unit device and a second communication device on a downstream side, and relays communication between the first communication device and the second communication device by a time division multiplexing system. The slave unit device includes a first amplifier that amplifies a downlink signal, a second amplifier that amplifies an uplink signal, a switch that selectively switches a communication path in the slave unit device between a downlink side and an uplink side, and a timing control unit that turns off the first amplifier, turns off the second amplifier, and switches the switch to the downlink side when a synchronization abnormality related to a time division multiplexing scheme is detected.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a communication relay system, a communication relay control program, and a communication relay system control method. [Background technology]

[0002] Conventionally, DAS (Distributed Antenna System) has been used as an indoor coverage measure for mobile communication network systems using mobile phones, smartphones, etc. DAS relays signals between mobile stations and base stations and consists of a master unit and multiple slave units located in a distributed manner. The master unit distributes the signal from one base station to multiple slave units, and each slave unit outputs the same downlink signal from its respective antenna, thereby creating an area as one cell.

[0003] In mobile communication network systems, there are cases where an optical repeater system and a radio base station are shared using an antenna duplexer. This case may also occur when multiple optical repeater systems share the same antenna. Conventionally, there has been a problem of interference from downlink signals in the uplink section. To address this issue, a technique has been proposed to avoid it when the optical repeater system and TDD timing are synchronized. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-71690 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, no clear avoidance techniques have been proposed for the problems that may occur when the optical repeater system and TDD timing are not synchronized.

[0006] The problem that the present disclosure aims to solve is to realize a communication relay system, a communication relay control program, and a communication relay system control method that can suppress malfunctions that are expected when the optical repeater system and TDD timing are not synchronized. [Means for solving the problem]

[0007] A communication relay system according to an embodiment includes a master device connected to a first upstream communication device and a slave device provided between the master device and a second downstream communication device, and relays communications between the first and second communication devices using a time division multiplexing system. The slave device includes a first amplifier for amplifying a downlink signal, a second amplifier for amplifying an uplink signal, a switch for selectively switching a communication path in the slave device between the downlink side and the uplink side, and a timing control unit for turning off the first amplifier, turning off the second amplifier, and switching the switch to the downlink side when a synchronization abnormality related to the time division multiplexing system is detected. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of a schematic configuration of a mobile communication network system according to an embodiment. [Figure 2] FIG. 2 is a diagram showing an example of a schematic configuration of an optical repeater system according to an embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of a schematic configuration of a parent device and a child device according to the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of timing for switching between uplink and downlink in the master device and the slave device. [Figure 5] FIG. 5 shows an example of slave amplifier switch switching control when TDD timing synchronization is not achieved. [Figure 6] FIG. 6 is a flowchart showing an example of the flow of operations performed by the optical repeater system according to the embodiment when TDD timing is asynchronous. [Figure 7] FIG. 7 is a flowchart showing an example of the flow of operations performed by an optical repeater system according to a modified example when TDD timing is asynchronous. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an information processing system, an information processing device, and an information processing method according to embodiments will be described with reference to the drawings. Note that parts with the same reference numerals perform similar operations, and redundant explanations will be omitted as appropriate. The following embodiments do not limit the disclosed technology. Furthermore, each embodiment can be combined as appropriate within the scope of not causing contradictions in the processing content.

[0010] Fig. 1 is a diagram showing an example of a schematic configuration of a mobile communication network system 10 according to an embodiment. As shown in Fig. 1, the mobile communication network system 10 includes an other connection carrier communication network 11, a mobile phone core network 12, a plurality of base station control devices 13, a plurality of (three in Fig. 1) radio base stations (BTS: Base Transceiver Stations) 14-1 to 14-3, an optical repeater system (communication relay system) 15, an antenna 16, and an antenna duplexer / distributor 17.

[0011] For the sake of concreteness, the optical repeater system 15, the antenna 16, and the antenna duplexer / distributor 17 are assumed to be located in a building BLD and an underground mall UG, which are a type of so-called blind zone.

[0012] The mobile phone core network 12 interconnects with the communication networks 11 of other connection carriers via an interconnecting gateway switch (not shown), and controls connections of mobile phone terminals belonging to the connection carriers.

[0013] A plurality of base station control devices 13 are connected to the mobile phone core network 12 and manage and control the base stations.

[0014] The plurality of wireless base stations 14-1 to 14-3 are connected to each base station control device 13. In this embodiment, when the plurality of wireless base stations 14-1 to 14-3 are not to be distinguished from one another, they are simply referred to as "wireless base station 14." The plurality of wireless base stations 14-1 to 14-3 are an example of a first communication device.

[0015] The optical repeater system 15 transmits wireless signals over optical fiber lines to areas where mobile terminals cannot receive signals, enabling communication, and is also called a DAS (Distributed Antenna System). The optical repeater system 15 includes a master device that connects to the wireless base station 14, and multiple slave devices that transmit and receive wireless signals to and from the mobile terminals (details will be described later). The optical repeater system 15 is connected to the corresponding wireless base station 14-1 via an optical cable LC. The optical repeater system 15 is an example of a communication relay system.

[0016] The antenna duplexer / distributor 17 is connected to the optical repeater system 15 and the wireless base station 14-2, and shares the antenna 16 between the optical repeater system 15 and the wireless base station 14-2. The antenna duplexer / distributor 17 is an example of a second communication device.

[0017] Fig. 2 is a diagram showing an example of a schematic configuration of an optical repeater system according to an embodiment. As shown in Fig. 2, the optical repeater system 15 includes a master unit (MU) 21, hub units (HU) 22-1 and 22-2, and a plurality of remote units (RU) 24 and 24A. In the example shown in Fig. 2, the remote unit 24A shares an antenna 16 with the radio base station 14-2 via an antenna duplexer / distributor 17.

[0018] The master device 21 is connected to the wireless base station 14-1 via a coaxial cable to transmit and receive signals.

[0019] The hub device 22-1 is connected to the parent device 21 via an optical communication cable. The hub device 22-2 is connected to the hub device 22-1 via an optical communication cable.

[0020] In this embodiment, when there is no need to distinguish between the hub device 22-1 and the hub device 22-2, they are simply referred to as "hub device 22."

[0021] The multiple slave devices 24, 24A are connected to hub devices 22-1 and 22-2 via optical communication cables and are distributed around master device 21. The multiple slave devices 24, 24A are wirelessly connected to mobile communication terminal device 23 to transmit and receive signals. In Fig. 2, the slave devices 24, 24A are represented as RU.

[0022] The mobile communication terminal device 23 is a communication device such as a mobile phone, a smartphone, etc. The mobile communication terminal device 23 is an example of a second communication device.

[0023] 3 is a diagram showing an example of a schematic configuration of a parent device and a child device according to an embodiment, in which the hub device 22-1 is omitted for the sake of convenience.

[0024] As shown in FIG. 3, the parent device 21 includes a switch 31, a coupler 32, a TDD timing extraction and control unit 33, a TDD timing adjustment unit 34, an E / O conversion unit 35, an O / E conversion unit 36, a delay measurement unit 37, and a control unit 38.

[0025] The switch 31 has one end connected to the radio base station 14-1 and switches between the downlink communication channel DLC and the uplink communication channel ULC.

[0026] The coupler 32 splits the transmission signal of the downlink communication channel DLC into two systems.

[0027] The TDD timing extraction and control unit 33 receives the transmission signal of one of the branches branched by the coupler 32, extracts a TDD (Time Division Duplex) timing signal, controls the switching of the switch 31, and also controls the TDD timing adjustment.

[0028] Under the control of the TDD timing extraction and control unit 33, the TDD timing adjustment unit 34 generates and outputs a TDD timing adjustment signal for performing actual TDD timing adjustment for each of the slave devices 24, 24A.

[0029] The E / O converter 35 has one end connected to the downlink communication channel DLC, performs electrical / optical conversion, and outputs the signal from the other end to the slave devices 24 and 24A.

[0030] The O / E converter 36 has one end connected to the slave devices 24, 24A, performs optical / electrical conversion on the uplink signal input from the slave devices 24, 24A, and outputs it from the other end to the uplink communication channel ULC.

[0031] The delay measurement unit 37 outputs a delay measurement signal to the slave devices 24, 24A via the E / O conversion unit 35, and receives a delay measurement signal returned by the slave devices 24, 24A that received the delay measurement signal via the O / E conversion unit 36, and measures the delay time based on the transmission time and reception time of the delay measurement signal.

[0032] The control unit 38 is an electronic circuit that controls the entire parent device 21. The control unit 38 executes calculations based on data and software (programs) input from each device, etc., in the internal configuration of the parent device 21, and outputs calculation results and control signals to each device, etc.

[0033] Furthermore, the control unit 38 executes a TDD synchronization abnormality detection process to detect whether a synchronization abnormality related to the TDD system has occurred. Specifically, the control unit 38 detects whether a downlink / uplink switching signal is not received from the radio base station 14-1 for a predetermined period of time or more (for example, a total of 5 ms, consisting of a downlink period of 1.3 ms and an uplink period of 3.7 ms). If the control unit 38 detects a situation in which a downlink / uplink switching signal is not received for a predetermined period of time or more, the control unit 38 determines that a TDD synchronization abnormality has occurred and outputs a signal to the slave device 24 notifying the slave device 24 of the TDD synchronization abnormality.

[0034] It should be noted that, for example, the TDD timing extraction and control section 33, the TDD timing adjustment section 34, the TDD synchronization abnormality detection function of the control section 38, and the like of the parent device 21 may be realized in part or in whole as software.

[0035] As shown in FIG. 3, the slave device 24 includes an O / E conversion unit 41, an amplifier 42, a switch 43, a low noise amplifier (LNA) 44, an E / O conversion unit 45, a TDD timing control unit 46, and a control unit 47.

[0036] The O / E converter 41 performs optical / electrical conversion on the downlink signal input from the parent device 21 side and outputs the converted signal.

[0037] The O / E converter 41 performs optical / electrical conversion on the downlink signal input from the parent device 21 side and outputs the converted signal.

[0038] The amplifier 42 amplifies and outputs the downlink signal, which is the output signal of the O / E conversion unit 41. The amplifier 42 is an example of a first amplifier.

[0039] The switch 43 has one end connected to the antenna 25 and switches the communication path between downlink reception and uplink transmission. That is, the switch 43 is a switch that selectively switches the communication path in the slave device 24 between the downlink side and the uplink side.

[0040] The low-noise amplifier 44 amplifies, with low noise, the uplink signal input via the antenna 25 and the switch 43. The low-noise amplifier 44 is an example of a second amplifier.

[0041] The E / O conversion unit 45 performs electrical / optical conversion on the output signal of the low noise amplifier 44 and outputs it.

[0042] The TDD timing control unit 46 controls the switch 43 , the amplifier 42 and the low-noise amplifier 44 based on a TDD timing adjustment signal from the TDD timing adjustment unit of the base unit 21 .

[0043] Furthermore, the TDD timing control unit 46 receives a signal notifying the control unit 47 of a TDD synchronization abnormality. When the TDD timing control unit 46 receives the signal notifying the TDD synchronization abnormality, it controls to switch the amplifier 42 to the uplink side (OFF control). When a synchronization abnormality related to the time division multiplexing method is detected, the TDD timing control unit 46 controls to switch the low noise amplifier 44 to the downlink side (OFF control). When a synchronization abnormality related to the time division multiplexing method is detected, the TDD timing control unit 46 switches the switch 43 to the downlink side. The TDD timing control unit 46 is an example of a timing control unit.

[0044] The control unit 47 is an electronic circuit that controls the entire slave device 24. The control unit 47 executes calculations based on data and software (programs) input from each device, etc., in the internal configuration of the slave device 24, and outputs calculation results and control signals to each device, etc.

[0045] Furthermore, the control unit 47 receives a signal notifying the TDD synchronization abnormality from the control unit 38 of the master device 21. The control unit 47 outputs the signal notifying the TDD synchronization abnormality to the TDD timing control unit 46.

[0046] When the slave device 24 is configured as the slave device 24 A, the switch 43 is connected to the antenna 16 via the antenna duplexer / distributor 17 instead of the antenna 25 .

[0047] Also, for example, the TDD timing control section 46 of the slave device 24 can be realized in part or in whole as software.

[0048] (Amplifier and switch control) Next, the amplifier / switch switching control executed by the slave device 24 of the optical repeater system 15 according to the embodiment will be described with reference to Fig. 4 to Fig. 7. This amplifier / switch switching control distinguishes between the amplifier / switch switching control in the slave device 24 when TDD synchronization is established in the master device 21 and when it is not.

[0049] First, amplifier and switch changeover control in the optical repeater system 15 when TDD timing synchronization is achieved will be described.

[0050] 4 is a diagram showing an example of switching control between uplink (UL) and downlink (DL) of the wireless base station 14, the parent device 21, and the child device 24 in the optical repeater system 15 according to the embodiment. In the parent device 21, as shown as "SW switching timing" in FIG. 4, switching control of the switch 31 is repeatedly executed between the uplink side and the downlink side according to a predetermined cycle.

[0051] Furthermore, as shown as "signal timing" in FIG. 4, the master device 21 outputs a downlink signal (DL signal) to the slave device 24 at a predetermined cycle in conjunction with the "SW switching timing."

[0052] On the other hand, in the slave device 24, as shown as "SW switching timing" in FIG. 4, switching control of the switch 43 is repeatedly executed between the uplink side and the downlink side in accordance with a predetermined cycle.

[0053] Furthermore, in the slave device 24, as shown as "signal timing" in FIG. 4, a downlink signal (DL signal) is input from the master device 21 at a predetermined cycle in conjunction with the "SW switching timing."

[0054] 4, a repeater system DL delay occurs between the parent device 21 and the child device 24. This is due to a transmission delay due to the optical fiber in the optical repeater system 15. For example, as shown in FIG. 2, the optical repeater system 15 and the antenna duplexer / distributor 17 are provided between the wireless base station 14-1 and the antenna 16. In addition, only the antenna duplexer / distributor 17 is provided in the wireless base station 14-2. Therefore, when focusing on the downlink signal, a signal delay due to the optical repeater system (repeater system DL delay) occurs in the wireless base station 14-1 compared to the wireless base station 14-2.

[0055] For example, in the slave devices 24 and 24A on the side of the wireless base station 14-1 shown in Fig. 2, in addition to receiving a downlink signal from the master device 21 via optical fiber, they may also receive a downlink signal from the upper wireless base station 14-2 without passing through the master device 21 or optical fiber. In such cases, the downlink signal transmitted via optical fiber is affected by the DL delay of the repeater system, which occurs due to the distance between the master device and the slave devices. Therefore, during the uplink period, the slave devices 24 and 24A may not be able to operate normally if they receive a downlink signal that is affected by transmission delay and has a higher signal level than the uplink signal.

[0056] In the optical repeater system 15 according to this embodiment, the delay measurement unit 37 of the master device 21 measures the delay time between the master device 21 and each slave device 24, 24A using a delay measurement signal. Then, the TDD timing control unit 46 of the slave devices 24, 24A controls the SW switching timing of the switch 43 based on the delay time measured by the delay measurement unit 37 so as not to receive a downlink signal from the radio base station 14-2 during the time period when the slave devices 24, 24A are transmitting an uplink signal.

[0057] Next, amplifier and switch switching control when TDD timing synchronization is not achieved in the optical repeater system 15 according to the embodiment will be described.

[0058] 5 is a diagram showing an example of slave amplifier switch switching control when TDD timing synchronization is not achieved. As shown in FIG. 5, in master device 21, switching control of switch 31 is repeatedly executed between the uplink (UL) side and the downlink (DL) side according to a predetermined cycle. In addition, master device 21 outputs a downlink signal (DL signal) to slave device 24 at a predetermined cycle in conjunction with the "SW switching timing."

[0059] Meanwhile, in the slave device 24, as shown as "SW switching control 2," the TDD timing control unit 46 switches the amplifier 42 (denoted as "PA" in FIG. 5) to the uplink side and controls it to be off. The TDD timing control unit 46 also switches the switch 43 to the downlink side without being associated with (independent from) the switching control of the amplifier 42. The low-noise amplifier 44 also switches to the downlink side and controls it to be off.

[0060] The above-mentioned "SW switching control 2" is different from "SW switching control 1" shown in FIG. 4, that is, normal control in which the amplifier 42, the switch 43, and the low-noise amplifier 44 are all switched to the uplink side (or the downlink side).

[0061] This is to prevent signals (especially downlink signals, which have a higher level than uplink signals) from entering the circuit system that processes uplink signals when TDD timing synchronization is not achieved, thereby preventing equipment failure and alarms.

[0062] When TDD timing synchronization is achieved, the amplifier / switch switching control executed by the slave device 24 is changed from "SW switching control 2" to "SW switching control 1."

[0063] Next, an operation performed by the optical repeater system 15 according to the embodiment when the TDD timing is asynchronous will be described.

[0064] 6 is a flowchart showing an example of the flow of operations performed by the optical repeater system 15 according to the embodiment when the TDD timing is asynchronous. The operations shown in FIG. 6 are repeatedly performed at predetermined timings.

[0065] As shown in FIG. 6, the control unit 38 of the master device 21 executes a TDD synchronization abnormality detection process to detect whether there is an abnormality in the TDD timing with the wireless base station 14-1 (step S1A).

[0066] The control unit 38 of the master device 21 determines whether or not a TDD synchronization abnormality exists using the result of the TDD synchronization abnormality detection process (step S2A). If the control unit 38 of the master device 21 determines that a TDD synchronization abnormality exists (Yes in step S2A), it outputs a signal notifying the control unit 47 of the slave device of the TDD synchronization abnormality. The control unit 47 of the slave device outputs a signal notifying the TDD synchronization abnormality to the TDD timing control unit 46.

[0067] In response to the signal notifying of the TDD synchronization abnormality received from the parent device 21, the TDD timing control unit 46 of the child device 24 executes (continues) amplifier / switch switching control in accordance with "SW switching control 2" shown in Figure 5 (step S3A).

[0068] On the other hand, if control unit 38 of parent device 21 determines that there is no TDD synchronization abnormality (No in step S2A), it does not output a signal notifying control unit 47 of the child device of the TDD synchronization abnormality. TDD timing control unit 46 of child device 24 executes (continues) amplifier / switch switching control in accordance with "SW switching control 1" shown in Fig. 5 (step S4A).

[0069] As described above, the optical repeater system 15 according to the embodiment includes the base station 21 and the slave device 24, and relays communications between a first communication device and the second communication device using time division multiplexing. The base station 21 is connected to the upstream wireless base station 14, which serves as a first communication device. The slave device 24 is provided between the base station 21 and the downstream antenna duplexer / distributor 17 and the mobile communication terminal 23, which serve as second communication devices. The slave device 24 includes an amplifier 42, a switch 43, a low-noise amplifier 44, and a TDD timing control unit 46. When a synchronization abnormality related to the time division multiplexing is detected, the TDD timing control unit 46 turns off the amplifier 42 that amplifies the downlink signal, turns off the low-noise amplifier 44 that amplifies the uplink signal, and switches the switch 43, which selectively switches the communication path in the slave device 24 between the downlink side and the uplink side, to the downlink side.

[0070] Therefore, according to the optical repeater system 15 of the embodiment, when a synchronization abnormality related to the time division multiplexing system is detected, it is possible to suppress the intrusion of signals in the uplink direction in the slave device 24. For example, it is possible to suppress interference of downlink signals from the other wireless base station 14-2 that shares an antenna via the antenna duplexer / distributor 17 shown in FIG. 1 to the slave device 24. As a result, it is possible to suppress damage to the device due to excessive uplink (UL) input.

[0071] (Variation 1) In the above embodiment, the parent device 21 detects an abnormality in the TDD timing, and outputs a notification of the abnormality from the parent device 21 to the child device 24. However, it is also possible for the child device 24 to detect an abnormality in the TDD timing and perform similar control using the abnormality detection as a trigger.

[0072] Specifically, the control unit 47 of the slave device 24 detects whether or not a downlink / uplink switching signal is received from the master device 21 for a predetermined period of time (for example, a total of 5 ms, consisting of a downlink period of 1.3 ms and an uplink period of 3.7 ms) or longer. If the control unit 47 detects a situation in which a downlink / uplink switching signal is not received for a predetermined period of time or longer, the control unit 47 determines that a TDD synchronization abnormality has occurred, and outputs a signal notifying the TDD synchronization abnormality to the TDD timing control unit 46.

[0073] The TDD timing control unit 46 executes the above-described amplifier switch changeover control in response to the signal notifying the TDD synchronization abnormality.

[0074] (Variation 2) If the specifications of the slave device 24 are such that there is no possibility of the device being damaged by excessive uplink (UL) input, whether or not to perform the switching control of the amplifier switch according to the embodiment can be selected arbitrarily by settings.

[0075] Similarly, if the specifications of the slave device 24 do not allow for damage to the device due to excessive uplink (UL) input, when a synchronization abnormality related to the time division multiplexing method is detected in at least one of the master device 21 and the slave device 24, the slave device 24 may be configured to mask all alarm outputs related to excessive uplink (UL) input.

[0076] 7 is a flowchart showing an example of the flow of operations performed by the optical repeater system 15 according to the modified example when the TDD timing is asynchronous. The operations shown in FIG. 7 are repeatedly performed at predetermined timings.

[0077] As shown in FIG. 7, the master device 21 or slave device 24 executes a TDD synchronization abnormality detection process to detect whether there is an abnormality in the TDD timing with the wireless base station 14-1 (step S1B).

[0078] The master device 21 or the slave device 24 determines whether or not a TDD synchronization abnormality exists based on the result of the TDD synchronization abnormality detection process (step S2B). If it is determined that a TDD synchronization abnormality exists (Yes in step S2B), the control unit 47 of the slave device outputs a signal notifying the TDD synchronization abnormality to the TDD timing control unit 46.

[0079] In response to the received signal notifying of the TDD synchronization abnormality, the TDD timing control unit 46 of the slave device 24 executes (continues) uplink (UL) excessive input power alarm masking processing (step S3B).

[0080] On the other hand, if it is determined that there is no TDD synchronization abnormality (No in step S2B), the TDD timing control unit 46 of the slave device cancels (or does not execute) the uplink (UL) excessive input alarm masking process without receiving a signal notifying of the TDD synchronization abnormality (step S4B).

[0081] For example, if the optical repeater system 15 is a system that issues an alarm when an abnormality is detected, and the specifications of the slave device 24 are such that there is no possibility of device damage due to excessive uplink (UL) input, it is possible to prevent unnecessary alarms from being issued.

[0082] The information processing described in each of the above embodiments can also be realized by a program executable by a computer. That is, it is possible to store a program that realizes the transmission method described in each of the above embodiments in a memory, read the program from the memory using a processing circuit of a computer, and configure the transmission system or transmission method described in each of the above embodiments by using software and hardware resources in cooperation with each other.

[0083] Although several embodiments (and variations) of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and variations thereof are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0084] 10 Mobile communication network systems 11. Communication networks of other connection carriers 12 Mobile Phone Core Network 13 Base Station Control Device 14-1~14-3 Wireless base station 15 Optical Repeater System 16 Antenna 17 Antenna sharing / distributor 21 Base unit 22 Hub device 23 Mobile communication terminal device 24, 24A handset device 25 Antenna 31 Switch 32 Coupler 33 TDD timing extraction and control section 34 TDD timing adjustment unit 35 E / O conversion section 36 O / E conversion section 37 Delay measurement unit 38 Control Unit 41 O / E conversion section 42 Amplifier 43 Switch 44 Low-Noise Amplifier 45 E / O conversion section 46 TDD timing control section

Claims

1. A communication relay system comprising a master device connected to a first communication device on an upstream side, and a slave device provided between the master device and a second communication device on a downstream side, and relaying communication between the first communication device and the second communication device by a time division multiplexing method, The slave device is a first amplifier for amplifying a downlink signal; a second amplifier for amplifying the uplink signal; a switch that selectively switches a communication path in the slave device between a downlink side and an uplink side; a timing control unit that turns off the first amplifier, turns off the second amplifier, and switches the switch to a downlink side when a synchronization abnormality related to the time division multiplexing method is detected. Communications relay system.

2. the master device includes a first detector for detecting the synchronization abnormality, the timing control unit turns off the first amplifier, turns off the second amplifier, and switches the switch to a downlink side in response to a notification signal regarding the synchronization abnormality from the first detection unit. The communication relay system according to claim 1 .

3. the slave device includes a second detection unit that detects the synchronization abnormality, the timing control unit turns off the first amplifier, turns off the second amplifier, and switches the switch to a downlink side in response to a notification signal regarding the synchronization abnormality from the second detection unit. The communication relay system according to claim 1 .

4. When the synchronization abnormality is detected, the timing control unit suppresses output of an alarm regarding an excessive input of a downlink signal. The communication relay system according to any one of claims 1 to 3.

5. A program used in a communication relay system that includes a master device connected to a first communication device on an upstream side and a slave device provided between the master device and a second communication device on a downstream side, and that relays communication between the first communication device and the second communication device by a time division multiplexing method, On the computer, When a synchronization abnormality related to the time division multiplexing method is detected, the slave device turning off a first amplifier that amplifies a downlink signal; turning off a second amplifier that amplifies the uplink signal; switching a switch for selectively switching a communication path between a downlink side and an uplink side in the slave device to the downlink side; A communication relay control program that realizes this.

6. A control method for a communication relay system comprising a master device connected to a first communication device on an upstream side and a slave device provided between the master device and a second communication device on a downstream side, the control method relaying communication between the first communication device and the second communication device by a time division multiplexing method, comprising: When a synchronization abnormality related to the time division multiplexing method is detected, the slave device turning off a first amplifier that amplifies a downlink signal; turning off a second amplifier that amplifies the uplink signal; switching a switch for selectively switching a communication path between a downlink side and an uplink side in the slave device to the downlink side; A communication relay system control method comprising:

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