Technical Field
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The present invention relates to a communication control device and a communication control method for a railway communication system that controls a communication path for a railway.
Background Art
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In a railway communication system, train control is performed by transmitting control data and the like between devices, such as between a train and a ground control device, and between a ground central control device and a ground field device.
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For example, in a communication based train control (CBTC) system that performs train control using wireless communication, the train control is implemented by transmitting and receiving information required for the train control between a train and a ground control device. Further, data or signal information is transmitted and received between a ground central control device and a ground field device (for example, a signal device or a railroad switch) mainly through a dedicated wired communication line.
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Conventionally, for communication with a system involved in railway operation control, efforts have been made to ensure communication quality by using wired communication through a private wireless line or line dedicated for the communication system.
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Meanwhile, in order to reduce communication infrastructure and reduce equipment operating costs, there is a demand for the use of general-purpose, multi-purpose shared communication equipment and a public network line that can be shared among multiple communication equipment, without providing dedicated communication equipment for each equipment. Examples of a representative public network include public wired communication networks such as the Internet and cellular public wireless communication networks.
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While the use of shared communication equipment and a public network line is expected to reduce the costs of installing and operating equipment, the reliability of communication may be lower than in the case of building communication equipment using privately operated equipment.
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In order to ensure the reliability of communication while using a public network line, a method of simultaneously using multiple communication paths and making the communication paths redundant can be considered. As the method of making the communication paths redundant, a wide variety of combinations can be considered, which include a method of using multiple public network lines in parallel, and a method of effectively mixing a location where privately operated communication equipment is installed with a location where communication is performed only via a public network line.
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As the background art regarding making communication paths redundant in the railway communication field, for example, Patent Literature 1 discloses a technique for providing redundancy by providing multiple communication paths in a case where control information is transmitted and received via wireless communication between an on-vehicle control device installed in a train and a ground control device.
Citation List
Patent Literature
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Patent Literature 1:
Japanese Unexamined Patent Application Publication No. 2009-067357 Summary of Invention
Technical Problem
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In the technique disclosed in Patent Literature 1 described above, multiple communication paths are simultaneously used, but all paths made redundant are applied to communication without performing priority control or switching control of the communication paths. Therefore, it is expected that as the number of communication paths made redundant increases, a processing load in communication processing and the amount of communication increase.
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Therefore, the present invention makes it possible to ensure communication performance while reducing a communication processing load, and to reduce the amount of communication data by switching a communication path used for transmitting and receiving control data while making communication paths redundant. In this case, the present invention can be applied to any mode of communication path redundancy, such as redundancy by communication between a privately operated communication network and a public network, and redundancy of wired communication and wireless communication.
Solution to Problem
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In order to solve the above-described problems, one of representative communication control devices of the present invention is a communication control device for a railway communication system that performs data transmission between a plurality of devices via a plurality of communication paths including at least a wireless communication path, and includes a communication path monitoring unit that monitors whether each of the plurality of communication paths is usable, a communication path determining unit that determines a communication path to be used for the data transmission from among the plurality of communication paths, and a path management unit that manages each of the plurality of communication paths as any of a communication path in a used state, a communication path in a standby state, and a communication path in an unavailable state. The communication path determining unit determines a communication path to be used for the data transmission based on a result of the monitoring by the communication path monitoring unit, assigns each of the plurality of communication paths to any of a used state, a standby state, and an unavailable state, and registers the plurality of communication paths to the path management unit.
Advantageous Effects of Invention
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According to the present invention, by assigning only a communication path to be used for communication among communication paths made redundant to a used path pool, it is possible to eliminate the need to use, for communication, all communication paths made redundant (i.e., to eliminate the need to perform communication processing on all the communication paths made redundant simultaneously), thereby improving the reliability of communication while reducing a processing load related to data transmission processing.
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Issues, configurations, and effects other than the above will be apparent from the description of the following embodiments.
Brief Description of Drawings
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- Fig. 1 is a diagram illustrating an example of a communication configuration to which a railway communication system according to the present invention is applied.
- Fig. 2 is a diagram illustrating an example of a configuration of a ground wireless control unit and an on-vehicle wireless control unit in a railway communication system according to a first embodiment of the present invention.
- Fig. 3 is a diagram illustrating an example of a configuration of a ground wireless control unit and an on-vehicle wireless control unit in a railway communication system according to a second embodiment of the present invention.
- Fig. 4 is a diagram illustrating an example of an operation mode in a case where communication path determination control is performed by the configuration illustrated in Fig. 3.
Description of Embodiments
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Hereinafter, as embodiments of the present invention, first and second embodiments will be described with reference to the drawings. Note that the present invention is not limited by these embodiments. In the description of the drawings, the same portions are denoted by the same reference signs.
First Embodiment
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Fig. 1 is a diagram illustrating an example of a communication configuration to which a railway communication system according to the present invention is applied. The railway communication system performs communication between devices that transmit and receive control information to and from each other. Although Fig. 1 illustrates communication between a device installed on the ground and a device installed on a vehicle, the same applies to a case where the railway communication system performs communication between devices both installed on the ground or between devices both installed on a vehicle, and the railway communication system is not limited in form.
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Communication of control information is performed between a train 101 and ground equipment 108. The communication of the control information is, for example, communication of data of a plurality of applications represented by a train control application 104 and a voice call application 105.
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Application data of the ground equipment 108 is output to communication networks such as a (public) wireless network 110 and a (private operated) wireless network 111 via a ground wireless control unit 109. Similarly, application data of on-vehicle equipment 103 installed in the train 101 is output to the communication networks such as the (public) wireless network 110 and the (privately operated) wireless network 111 via an on-vehicle wireless control unit 102.
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In a case where communication is performed between devices both installed on the ground, the devices may be connected wirelessly or via a wire. However, in a case where communication is performed between the device installed on the ground and the device installed on the vehicle as illustrated in Fig. 1, wireless communication is generally used. Therefore, a wireless device 112 is provided to output, to the communication networks, data output by the on-vehicle wireless control unit 102.
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Fig. 2 is a diagram illustrating an example of a configuration of the ground wireless control unit and the on-vehicle wireless control unit in the railway communication system according to the first embodiment of the present invention. The ground wireless control unit and the on-vehicle wireless control unit are both communication control devices having the same configuration and the same operating mode.
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The ground wireless control unit or the on-vehicle wireless control unit 214 performs transmission output control to output, to a wired/wireless communication network 201, data received from a railway application (104 to 107) 215. As the wired/wireless communication network 201, for example, any number of multiple communication paths for a wired communication network 202 and wireless communication networks 1 to 4 (203 to 206) are prepared in advance.
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The purpose of preparing the multiple communication paths in this manner is to make the communication paths redundant and improve the quality of communication. Particularly, if a public wireless communication network is used for wireless communication, it is difficult for an entity (for example, a railway operator) that operates an applicable railway communication system to control the quality of communication in a communication path, and thus it is expected that the quality of communication may be lower than in a case where a privately operated communication network is installed, or that the quality may not be constant and may fluctuate depending on the situation. In order to reduce the effect of this, it is useful to provide means for preparing multiple communication paths in advance.
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The ground wireless control unit or the on-vehicle wireless control unit 214 includes a communication path monitoring unit 207, a communication path determining unit 213, a path management pool 209, and a packet transmission control unit 208. Further, the path management pool 209 functions as a path management unit and includes a used path pool 210 for managing a path used for communication of control data in the defined wired/wireless communication network 201, a standby path pool 211 for managing a path that is not used for communication of the control data at the current time but is usable as a communication path, and an unavailable path pool 212 for managing a path unavailable for communication of the control data at the current time.
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The communication path monitoring unit 207 monitors each of all defined communication paths and checks whether communication is possible, that is, whether each of the communication paths is usable. As a method of monitoring each of the communication paths, some methods are conceivable, which include a method of monitoring a communication carrier level for each of the communication paths, a method of transmitting a test packet (ping data or the like) for communication path monitoring to check liveness of each of the communication paths (whether each of the communication paths is available) and to check a response time including a delay time, a method of monitoring a communication quality (communication error rate or the like) in each of the communication paths for a past certain period of time, and a method of monitoring throughput available for communication in each of the paths. The communication path monitoring unit 207 performs monitoring by using at least one of these methods and notifies a result of monitoring each of the paths to the communication path determining unit 213.
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The communication path determining unit 213 assigns and registers each of the communication paths to any of the pools of the path management pool 209 based on the result of the monitoring by the communication path monitoring unit 207. As the determination method by the communication path determining unit 213, methods are conceivable, which include a method of determining a path to which a determination threshold is assigned based on the result of the monitoring by the communication path monitoring unit 207, and a method of performing determination based on the trend of monitoring results for a past certain period of time.
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As a result of the determination by the communication path determining unit 213, a path determined to be unavailable for communication is assigned to the unavailable path pool 212, and a path determined to be available for communication is assigned to the used path pool 210 or the standby path pool 211. In this case, an assignment rule for determining whether a path is assigned to the used path pool 210 or the standby path pool 211 is defined in the communication path determining unit 213 in advance. For example, in a case where all paths available for communication are defined in advance to be assigned and registered to the used path pool 210, a path to be assigned to the standby path pool 211 is not present.
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The packet transmission control unit 208 controls transmission of data of the railway application (104 to 107) 215 to a communication path assigned and registered to the used path pool 210. Therefore, in a case where a large number of paths available for communication are present, all of the paths are assigned and registered to the used path pool 210, and the data of the railway application (104 to 107) 215 is transmitted to all of the communication paths. In this case, when the packet transmission control unit 208 transmits the data of the railway application (104 to 107) 215 to each of the communication paths, the packet transmission control unit 208 copies the contents of the same data and transmits the data to all of the communication paths.
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According to the above-described definition rule for the used path pool 210, the more paths available for communication, the more paths are used for transmission control, which increases the processing load of the transmission control. Further, even in a situation where a large number of communication paths are usable and the quality of communication can be ensured, all available communication paths are used, which will result in an increase in communication costs if the communication paths to be used are public communication networks for a pay-as-you-go billing system. Therefore, in a case where even if a path available for communication is present, and another path available for communication is present, it is possible to adopt a method of not using some communication paths for control data communication of the railway application (104 to 107) 215 by assigning and registering the communication paths to the standby path pool 211.
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For example, in a case where the communication path determining unit 213 determines that a plurality of communication paths are available for communication, a path to be preferentially registered to the used path pool and the priority order for registration to the used path pool are defined in advance. In a case where the maximum number of communication paths via which the packet transmission control unit 208 transmits data is determined as N paths (N is any value greater than or equal to 1), if the total number of paths determined available for communication by the communication path determining unit 213 is less than or equal to N paths, a path available for communication is registered to the used path pool. On the other hand, if the total number is greater than N paths, N number of communication paths are registered to the used path pool 210 in accordance with the predefined priority order, and other paths available for communication are registered to the standby path pool 211. Therefore, up to N paths can be simultaneously selected as transmission paths and subjected to transmission processing by the packet transmission control unit 208, and other transmission processing (load) does not occur.
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Although the paths assigned and registered to the standby path pool 211 are not used for transmission of the data of the railway application 215, the statuses of the paths can be recorded as paths usable for communication. When any of the paths assigned and registered to the used path pool 210 is not available for communication, a control method can be adopted in which a communication path registered to the standby path pool 211 immediately before that time is preferentially used next.
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A period of monitoring of a communication path by the communication path monitoring unit 207 and a period of determination of a communication path by the communication path determining unit 213 are not set, but as the periods are shortened, an optimal path available for communication at that time can be assigned and registered to the used path pool 210 at any time. The packet transmission control unit 208 can perform data transmission using a path available for communication immediately after registration.
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Fig. 2 illustrates an example in which in a case where a wireless communication network 2 (204) and a wireless communication network 3 (205) are assigned and registered to the used path pool 210, the packet transmission control unit 208 transmits the data of the railway application 215 to the two paths.
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Fig. 2 illustrates transmission of packets but does not illustrate reception. The packets can be received from paths other than paths through which the packets are transmitted. Further, path selection based on the used path pool 210 is for transmission paths and does not constrain reception paths.
Second Embodiment
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Fig. 3 is a diagram illustrating an example of a configuration of the ground wireless control unit and the on-vehicle wireless control unit in the railway communication system according to a second embodiment of the present invention. In the configuration, a path selection unit 216 is added to the configuration according to the first embodiment illustrated in Fig. 1.
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The communication path determining unit 213 assigns and registers each communication path to any of the pools (210 to 212) of the path management pool 209 based on information from the path selection unit 216 in addition to a result of path monitoring by the communication path monitoring unit 207.
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For example, in a case where a plurality of communication paths available for communication are present based on information from the communication path monitoring unit 207, it is possible to determine, based on information from the path selection unit 216, which path is preferentially registered to the used path pool 210.
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In addition, in a case where an instruction to always select a specific path is given from the path selection unit 216, the communication path determining unit 213 can preferentially assign and register the specific path to the used path pool 210 regardless of a result of monitoring by the communication path monitoring unit 207. An example of such a method is a method of fixing and setting a communication path by an operation of a commander or an engineer of a command center and notifying the set information to the path selection unit 216 to select the fixed and set communication path.
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On the other hand, it is also possible to always keep a specific path to be unused based on information from the path selection unit 216, and to assign and register the specific path to the unavailable path pool 212 even if the specific path is available for communication.
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In addition, if a rule is defined in the communication path determining unit 213 to assign and register a specific communication path to any one of the three path pools by using, as a trigger, the time when a train is positioned at or passes a specific geographical location, paths can be assigned in accordance with position information.
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In this case, position information of the train is acquired as external setting information from the path selection unit 216. Examples of a method of acquiring the position information of the train include a method using position information of a GPS and a method using position information acquired from a transponder ground coil.
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Further, by comparing position information with a result of monitoring a communication path, it is possible to define determination of assignment and registration by the communication path determining unit 213.
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Fig. 4 is a diagram illustrating an example of the operation mode in a case where communication path determination control is performed by the configuration illustrated in Fig. 3. In Fig. 4, as paths for performing communication services in a section from a location 1 (408) to a location 8 (415) as the communication paths, satellite communication 406, a public communication network carrier A (405), and a public communication network carrier B (404) are present. In addition, a public communication network carrier C (403) for performing a communication service in a section from the location 1 (408) to the location 5 (412) and in a section from the location 5 (412) to a location present between the location 5 and the location 6 (413), a public communication network carrier D (402) for performing a communication service in a section from the location 4 (411) to the location 8 (415), and a privately operated communication network 401 defined as an area available for communication in a section from the location 6 (413) to the location 7 (414) are present.
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An upper diagram of Fig. 4 illustrates a path for performing the communication services provided in the section from the location 1 (408) to the location 8 (415). A lower diagram of Fig. 4 illustrates states of registration to each of the pools in the path management pool 209 in the section from the location 1 (408) to the location 8 (415).
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A case where the train 101 is located in each of sections from (1) to (7) when the train 101 travels from the location 1 (408) to the location 8 (415) will be described. In this example, the maximum number of paths that can be assigned and registered to a used path pool 310 is predefined to be three.
(1) Location 1 (408) to Location 2 (409)
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The communication path determining unit 213 determines, based on information from a result of monitoring by the communication path monitoring unit 207, that four paths, the public communication network carrier A (405), the public communication network carrier B (404), the public communication network carrier C (403), and the satellite communication (406), are available for communication.
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Since the maximum number of paths that can be assigned and registered to the used path pool 210 is three, the communication path determining unit 213 selects the paths that are assigned and registered to the used path pool 210 based on path priority selection information and traveling position information acquired from the path selection unit 216.
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In this example, the public communication network carrier A (405), the public communication network carrier B (404), and the public communication network carrier C (403) are assigned and registered to the used path pool 210 and used for control of transmission of the application data. In addition, the remaining satellite communication (406) is assigned and registered to the standby path pool 211. The privately operated communication network 401 is determined to be unavailable for communication as a result of monitoring the communication paths and is assigned and registered to the unavailable path pool 212.
(2) Location 2 (409) to Location 3 (410)
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It is assumed that, this section is a section (communication failure section) where a communication congestion or another failure occurs in the public communication network carrier C (403), causing a communication failure.
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The communication path monitoring unit 207 outputs, based on communication path monitoring, a monitoring result indicating that the communication congestion has occurred in the public communication network carrier C (403), causing the communication failure. The communication path determining unit 213 determines, based on information of the monitoring result, that the public communication network carrier C (403) is unavailable for communication, and assigns and registers the public communication network carrier C (403) to the unavailable path pool 212. Instead, the satellite communication 406 registered to the standby path pool 211 is assigned and registered to the used path pool 210. That is, in this section, communication is performed using the three paths of (the public communication network carrier A (405), the public communication network carrier B (404), and the satellite communication 406) including the satellite communication 406.
(3) Location 3 (410) to Location 4 (411)
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In this section, a communication congestion does not occur in the public communication network carrier C (403), and the communication path determining unit 213 determines, based on information of a result of monitoring by the communication path monitoring unit 207, that the public communication network carrier C (403) is available for communication. Therefore, as in a case where the train is located in the section (1) (from the location 1 (408) to the location 2 (409)) described above, the satellite communication 406 is assigned and registered to the standby path pool 211 based on path priority selection.
(4) Location 4 (411) to Location 5 (412)
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The communication path determining unit 213 determines, based on information of a result of monitoring by the communication path monitoring unit 207, that in addition to the public communication network carrier A (405), the public communication network carrier B (404), and the public communication network carrier C (403), the public communication network carrier D (402) is also available for communication.
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However, the selection priority of the public communication network carrier D (402) is defined in advance as being lower than that of the public communication network carrier C (403) until the train passes through the location 5 (412). Therefore, based on position information from the path selection unit 216, the communication path determining unit 213 preferentially assigns and registers the public communication network carrier C (403) to the used path pool.
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In this case, the public communication network carrier D (402) newly determined to be available for communication is assigned and registered to the standby path pool 211, but the public communication network carrier D (402) is kept on hot standby while being grasped as being available for communication, and can be smoothly switched to a used path after the train passes through the location 5 (412).
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In this example, after the train passes through the location 5 (412), the public communication network carrier D (402) is defined to be selected with higher priority than the public communication network carrier C (403). Therefore, a used path is switched to the public communication network carrier D (402) after the train passes through the location 5 (412). In this case, if the public communication network carrier D (402) is in a hot standby state, it is possible to switch the path from the public communication network carrier C (403) to the public communication network carrier D (402) after the certainty of maintaining communication is grasped.
(5) Location 5 (412) to Location 6 (413)
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As described above, the communication path determining unit 213 assigns and registers the public communication network carrier D (402) to the used path pool 210. Since a service area of the public communication network carrier C (403) is in the section from the location 5 (412) to the location present between the location 5 (412) and the location 6 (413), the communication path determining unit 213 determines assignment and registration of the public communication network carrier D (402) to the used path pool 210 based on position information acquired from the path selection unit 216 before traveling from the service section.
(6) Location 6 (413) to Location 7 (414)
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In this section, in addition to the public communication networks (402 to 405), the privately operated communication network 401 is installed. Since the privately operated communication network 401 is expected to have a more stable communication quality and a more stable communication level than those of the public communication networks (402 to 405), the privately operated communication network 401 is registered in advance to the communication path determining unit 213 or an instruction to force the path selection unit 216 to select the privately operated communication network 401 is set such that the privately operated communication network 401 is preferentially assigned and registered to the used path pool 210.
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The communication path determining unit 213 assigns and registers the privately operated communication network 401 to the used path pool 210 based on information of those definitions and instruction information or position information from the path selection unit 216. Instead, the public communication network carrier B (404) is assigned and registered to the standby path pool 211 based on a definition for preferentially selecting a path.
(7) Location 7 (414) to Location 8 (415)
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As in the section (1) (from the location 1 (408) to the location 2 (409)) described above, the communication path determining unit 213 assigns and registers the satellite communication 406 to the standby path pool 211.
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As described above, the communication path determining unit 213 determines a communication path to be assigned and registered to the used path pool 210, based on an external condition such as a position and the definition information, and thus is capable of selecting an optimal communication path while the maximum number of communication paths that can be simultaneously used is three.
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Although the first embodiment and the second embodiment are described above as the embodiments of the present invention, the present invention is not limited to the first embodiment and the second embodiment described above, and can be modified in various ways within the gist of the present invention.
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Further, the configurations, functions, and processing units described above may be partially or entirely implemented in hardware, for example, by designing them as an integrated circuit. In addition, each of the configurations, functions, and the like described above may be implemented in software by a processor interpreting and executing a program that implements each of the functions. In this case, information such as a program for implementing each of the functions can be stored in a storage device such as a memory or a hard disk, or in a storage medium such as an IC card, an SD card, or a
DVD.
List of Reference Signs
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101: train, 102: on-vehicle wireless control unit, 103: on-vehicle equipment, 104: train control application, 105: voice call application, 106: information content distribution application, 107: video transmission application, 108: ground equipment, 109: ground wireless control unit, 110: wireless network (public), 111: wireless network (private operated), 112: wireless device, 201: wired/wireless communication network, 202: wired communication network, 203: wireless communication network 1, 204: wireless communication network 2, 205: wireless communication network 3, 206: wireless communication network 4, 207: communication path monitoring unit, 208: packet transmission control unit, 209: path management pool, 210: used path pool, 211: standby path pool, 212: unavailable path pool, 213: communication path determining unit, 214: ground wireless control unit or the on-vehicle wireless control unit, 215: railway application, 216: path selection unit, 401: privately operated communication network, 402: public communication network carrier D, 403: public communication network carrier C, 404: public communication network carrier B, 405: public communication network carrier A, 406: satellite communication, 408: location 1, 409: location 2, 410: location 3, 411: location 4, 412: location 5, 413: location 6, 414: location 7, 415: location 8