Patent ID: 12221142

MODES FOR CARRYING OUT INVENTION

Embodiment 1

Hereinafter, embodiments of the present disclosure will be described.

FIG.1shows a configuration of a wireless train control system. In each of the following figures, the same symbols indicate the same or equivalent parts. Ground wireless devices100to140are installed along a railway track. On-board wireless devices200and210that are each installed on a train continue to communicate with one of the ground wireless devices100to140depending on their locations on the railway track while moving along the railway track. A wireless control device300is installed, for example, in an equipment room and is connected to one of the ground wireless devices, to manage transmission destinations of information transmitted between the ground and a train. For example, in the case where the on-board wireless device200is connected to the ground wireless device100and moves toward the ground wireless device110in future (Direction A), the wireless control device300duplicates and transmits train control information to a plurality of ground wireless devices corresponding to the destinations of the train, the plurality of ground wireless devices being the ground wireless device110and the ground wireless device120. The wireless relay device400is connected to the ground wireless device100and the data is relayed between the wireless relay devices400to440, so that the wireless control device300and the ground wireless devices110to140can communicate with each other.

The information transmitted between the ground wireless device100and the on-board wireless device200may include general transmission information, not to mention the train control information. The train control information is information used for controlling train travel such as brake command information, and in addition, train travel position information, speed information, train travel permission location information, and speed limit information can be exemplified. General transmission information is information that is not included in the train control information, such as air conditioning temperature information, in-train display information, and surveillance camera image information.

FIG.2shows a functional configuration of the ground wireless device100. The ground wireless device100includes: a wireless communication unit (between ground and train)101; a wired connection unit102; a wireless control unit103which controls a wireless line; a wired control unit104which controls a wired line; and a wireless resource management unit105which manages wireless resources. The ground wireless devices110to140have the same functional configuration.

FIG.3shows a functional configuration of the on-board wireless device200. The on-board wireless device200includes: a wireless communication unit (between ground and train)201; a wireless control unit202which controls a wireless line; a wired connection unit203for connecting to other devices on the train; and a wired control unit204which controls a wired line.FIG.4shows a functional configuration of the wireless control device300. The wireless control device300includes: a wired connection unit301; a wired control unit302; an on-board wireless device management unit303which manages the communication state of the on-board wireless device; a destination wireless device determination unit304which determines ground wireless devices corresponding to the movement of the on-board wireless device; a communication path table; and a database unit305with a communication reservation table.

FIG.5shows a functional configuration of the wireless relay device400. The wireless relay device400includes: a first communication interface unit401which connects to the wireless control device or an upstream wireless relay device; a second communication interface unit402which connects to a ground wireless device; a third communication interface unit403which connects to a downstream wireless relay device; an information classification unit405which analyzes packets received from the first communication interface unit401, divides the combined packets, and classifies the divided packets based on the analysis result; and a message generation unit406which combines the packets held during a predetermined period of time and generates transmission packets for a device under the control of the wireless relay device400.

FIG.6shows a hardware configuration of the ground wireless device100. The ground wireless device100includes: a wireless antenna interface504which connects an antenna502in Direction A and an antenna503in Direction B by a divider501; a wired interface505; a memory506; a processor507; and a power supply circuit508. The memory506stores a program of the wireless communication unit (between ground and train)101, the wired connection unit102, the wireless control unit103, the wired control unit104, and the wireless resource management unit105; the processor507reads out the program from the memory506to execute the program. The information transmitted from the wireless communication unit (between ground and train)101and addressed to the on-board wireless device200is that transmitted in Direction A and Direction B via the wireless antenna interface504and the divider501, regardless of the location of the on-board wireless device200. Similarly, in the case of reception, the information received from Direction A and the information received from Direction B are mixed and inputted to the wireless communication unit (between ground and train)101. The information transmitted from the wireless relay device400to the ground wireless device100is received by the wired interface505. The ground wireless devices110to140also have the same hardware configuration as the ground wireless device100.

FIG.7shows a hardware configuration of the on-board wireless device200. The on-board wireless device200includes: an antenna601; a wireless antenna interface602; a wired interface603; a memory604; a processor605; and a power supply circuit606. The memory604stores a program of the wireless communication unit (between ground and train)201, the wireless control unit202, the wired connection unit203, and the wired control unit204; the processor605reads out the program from the memory604to execute the program. The on-board wireless device200communicates with the ground wireless device100via the wireless antenna interface602and the antenna601. The wired interface603is an interface to communication equipment on the train. The on-board wireless device210has the same hardware configuration as the on-board wireless device200.

FIG.8shows a hardware configuration of the wireless control device300. The wireless control device300includes: a wired interface701; a memory702; a processor703; and a power supply circuit704. The memory702stores a program of the wired connection unit301, the wired control unit302, the on-board wireless device management unit303, the destination wireless device determination unit304, and the data of the database unit305; the processor703reads out the program from the memory702to execute the program. The wireless control device300communicates with the wireless relay device400via the wired interface701.

FIG.9shows a hardware configuration of the wireless relay device400. The wireless relay device includes: a first communication interface801; a second communication interface802; a third communication interface803; a memory804; a processor805; and a power supply circuit806. The first communication interface801, the second communication interface802, and the third communication interface803correspond to the hardware of the first communication interface unit401, the second communication interface unit402, and the third communication interface unit403, respectively. The memory804stores a program of the information classification unit405and the message generation unit406; the processor805reads out the program from the memory804to execute the program.

FIG.10shows an example of the communication path table set in the database unit305of the wireless control device300.FIG.11shows an example of the communication reservation table set in the database unit305of the wireless control device300. Next, the operation of the wireless control device300for duplicating and transmitting the train control information will be described. In the wireless control device300shown inFIG.4, when an information generation unit (not shown) generates the train control information addressed to the on-board wireless devices200and210installed on the respective trains, the on-board wireless device management unit303refers to the communication path table set in the database unit305, and using an on-board wireless device ID of the destination train that is contained in the train control information, selects an ID of a ground wireless device that is currently connected to the train, from among the ground wireless devices100to140. According toFIG.10, the ground wireless device100is selected for the on-board wireless device200.

Also, the destination wireless device determination unit304refers to the communication reservation table set in the database unit305, and using the ID of the ground wireless device, selects a coverage area for which a wireless resource should be reserved for the train. According toFIG.11, the ground wireless devices110and120are selected for the ground wireless device100.

As a result, for the on-board wireless device200, the ground wireless devices100,110, and120are selected, and the data transfer messages (M200-100, M200-110, M200-120) for transmitting the train control information to each of them are transmitted from the wired connection unit301via the wired control unit302. Similarly, for the on-board wireless device210, the on-board wireless devices120,130, and140are selected, and the data transfer messages (M210-120, M210-130, M210-140) are transmitted to each of them.

Next, the operation of the wireless relay device400will be described referring toFIGS.12and13. In the case of receiving the data transfer message M200-100in the first communication interface unit401(5101), the wireless relay device400extracts the train control information contained in the message (S102) in the information classification unit405and determines whether the on-board wireless device200is connected to the ground wireless device100under the control of the wireless relay device400(S103). If the on-board wireless device200is connected under the control of the wireless relay device400(S103:YES), the information classification unit405divides the data transfer message M200-100, extracts the train control information from the data transfer message M200-100(S104) and classifies the extracted information as the control information to the ground wireless device100. The message generation unit406generates one message from the extracted information and starts the transfer of the generated message from the second communication interface unit402to the ground wireless device100(S105). Note that the train control information extracted in S104is first control information which requires immediacy and the message generation unit406generates one message from the first control information contained in one piece of the train control information.

In contrast, when the data transfer messages M200-110and M200-120are received, the information classification unit405of the wireless relay device400determines that the on-board wireless device200is not connected under the control of the wireless relay device400and that the received messages are advance transmission messages generated by referring to the communication reservation table (S106: YES), and then the information classification unit405divides the data transfer messages M200-110and M200-120, extracts the train control information from the data transfer messages M200-110and M200-120, and classifies the extracted train control information as the control information to be transmitted in advance to the ground wireless devices110and120. The advance transmission control information is not started to be transferred immediately but is held by the message generation unit406of the wireless relay device (S107). Note that the train control information extracted here is second control information which does not require immediacy.

In the same way, when the wireless relay device400receives the data transfer message M210-120, the information classification unit405determines that the message is addressed to the ground wireless device120currently connected to the on-board wireless device210that is not connected under the control of the wireless relay device400(S106: NO), and then divides the data transfer message M210-120to extract the train control information from the data transfer message M210-120, and classifies the extracted information as the control information to the ground wireless device120. The extracted information is combined by the message generation unit406, and the transfer from the third communication interface unit403to the wireless relay device410is started (S108). These processes are repeated until the unprocessed data transfer message does not remain. Note that the train control information extracted here is the first control information which requires immediacy and the message generation unit406generates one message from the first control information contained in one piece of the train control information.

When the wireless relay device400receives data transfer messages M210-130and M210-140, the information classification unit405determines that the on-board wireless device210is not connected under the control of the wireless relay device400(S103: NO) and that the received messages are the advance transmission message generated by referring to the communication reservation table (S106: YES), extracts the train control information from the data transfer messages M210-130and M210-140, and classifies the extracted information as the control information to be transferred in advance to the ground wireless devices130and140. The advance transmission message is not started to be transmitted immediately but is held by the message generation unit406of the wireless relay device (S107). Note that the train control information extracted here is the second control information which does not require immediacy.

Next, when the transmission timing between the wireless relay devices arrives in the wireless relay device400(S201), the message generation unit406determines whether the transmission timing agrees with the predetermined timing to release the held messages (S202). When it is the timing to release the held messages (S202: YES), the message generation unit406of the wireless relay device400combines the held data transfer messages M200-110, M200-120, M210-130, and M210-140and the messages which require immediacy into one data transfer message M400to transfer it from the third communication interface unit403to the next wireless relay device410(S204). When it is not the timing to release the held messages (S202: NO), the message generation unit406of the wireless relay device400generates a data transfer message from the messages which require immediacy and transfers it from the third communication interface unit403to the next wireless relay device410(S203). That is, when it is the timing to release the held messages, the message generation unit406generates one message from a plurality of pieces of the second control information contained in a plurality of pieces of the train control information, and the message is transmitted from the third communication interface unit403being a transmission unit. When it is not the timing to release the held messages, the message generation unit406generates one message from the first control information which requires immediacy contained in a piece of the train control information, and the message is transmitted from the third communication interface unit403being the transmission unit.

Next, the operation when the wireless relay device410receives the data transfer message M210-120will be described. When receiving the data transfer message M210-120from the first communication interface unit401, the wireless relay device410determines that the on-board wireless device210is not connected to the ground wireless device110under the control of the wireless relay device410in the information classification unit405and that the message is addressed to the ground wireless device120which is currently in communication, and starts the transfer of the message to the wireless relay device420using the third communication interface unit403.

When the wireless relay device410receives the data transfer message M400in which the data transfer messages M200-110, M200-120, M210-130, and M210-140are combined, the combined message is firstly divided in the information classification unit405. Next, the wireless relay device410determines whether they are addressed to the ground wireless device110under the control the wireless relay device410for each of the divided data transfer messages. When the data transfer message M200-110is determined to be addressed to the ground wireless device110, the wireless relay device410starts the transfer of the data transfer message M200-110to the ground wireless device110using the second communication interface unit402being the transmission unit. On the other hand, with respect to the data transfer messages M200-120, M210-130, and M210-140, the information classification unit405determines that the on-board wireless devices are not connected to the ground wireless device110under the control of the wireless relay device410and then determines that these data transfer messages are the advance transmission messages generated by referring to the communication reservation table. The advance transmission messages are not transferred immediately but held in the message generation unit406of the wireless relay device. When the next transmission timing between the wireless relay devices arrives, the message generation unit406combines the held data transfer messages into one data transfer message M410and transfers the combined message from the third communication interface unit403to the next wireless relay device420. That is, the information classification unit405extracts from the received message the train control information addressed to a ground wireless device connected to another wireless relay device, the message generation unit406generates one message from a plurality of pieces of the train control information extracted by the information classification unit405, and the second communication interface unit402being a transmission unit transmits the one generated message to the adjacent wireless relay device.

The operation of the wireless relay device420when the data transfer message is received will be described. In the case where the wireless relay device420receives the data transfer message M210-120from the first communication interface unit, the wireless relay device420determines that the on-board wireless device210is connected to the ground wireless device120under the control of the wireless relay device420, extracts the train control information from the received data transfer message, and starts the transfer of the train control information to the ground wireless device120using the second communication interface unit402.

Further, when the wireless relay device420receives a data transfer message in which the data transfer messages M200-120, M210-130, and M210-140are combined, the wireless relay device420firstly divides the combined message. Next, the wireless relay device420determines whether they are addressed to the ground wireless device120under the control of the relay device420for each of the divided data transfer messages.

When the data transfer message M200-120is determined to be addressed to the ground wireless device120, the transfer of the data transfer message M200-120to the ground wireless device120from the second communication interface unit402is started. On the other hand, with respect to the data transfer messages M210-130and M210-140, the wireless relay device420determines that the on-board wireless device is not connected to the ground wireless device120under the control of the wireless relay device420and then determines that the data transfer messages are the advance transmission messages generated by referring to the communication reservation table. The advance transmission messages are not transferred immediately but held in the wireless relay device. When the next transmission timing between wireless relay devices arrives and it is the timing to release the held messages, the held data transfer messages are combined with the other held data transfer messages into one data transfer message M420and transferred from the third communication interface unit403to the next wireless relay device430.

Next, the operation when the wireless relay device430receives the data transfer message M420will be described. When receiving, in the first communication interface unit, the data transfer message M420in which the data transfer message M210-130and M210-140are combined, the wireless relay device430firstly divides the combined message. Next, for each of the divided data transfer messages, it is determined whether they are addressed to the ground wireless device130under the control of the wireless relay device430.

When it is determined that the data transfer message M210-130is addressed to the ground wireless device130, the transfer of the data transfer message M210-130to the ground wireless device130is started using the second communication interface unit402. On the other hand, with respect to the data transfer message M210-140, the wireless relay device430detects that the on-board wireless device is not connected to the ground wireless device130under the control of the wireless relay device430and then determines that the data transfer message M210-140is the advance transmission message generated by referring to the communication reservation table. The advance transmission message is not transferred immediately but held in the wireless relay device. When the next timing for transmission between wireless relay devices arrives and the held messages are allowed to be released, the held data transfer message is combined with the other held data transfer messages into one data transfer message M430and transferred from the third communication interface unit403to the next wireless relay device440.

Next, the operation when the wireless relay device440receives the data transfer message M430will be described. When receiving the data transfer message M430from the first communication interface unit, the wireless relay device440firstly divides the combined message. Next, when it is determined that the divided data transfer message M210-140is addressed to the ground wireless device140under the control of the wireless relay device430, the transfer of the data transfer message M210-140to the ground wireless device140is started from the second communication interface unit402.

Next, the flow of the train control information transmitted from the on-board wireless device200to the wireless control device300will be described. When receiving the train control information from the on-board wireless device200, the ground wireless device100transmits the received train control information to the wireless relay device400. The wireless relay device400starts the transfer of the received train control information as the data transfer message M200-300to the next wireless relay device410using the third communication interface unit403.

When receiving the data transfer message M200-300in the first communication interface unit401, the wireless relay device410determines that the received message is not addressed to the ground wireless device110under the control of the wireless relay device420and starts the transfer of the received message to the wireless relay device420. Subsequent transfer continues in the same way.

To summarize the above, the wireless relay device400starts, at the next transmission timing, the transfer of a data transfer message containing the train control information which the on-board wireless device200should transfer to the ground wireless device100currently in communication therewith. On the other hand, the data transfer messages as the advance transmission messages to be transferred in advance in preparation for the movement are not started to be transferred immediately, but, when the predetermined timing to release the held messages that is set by the wireless relay device400arrives, the plurality of data transfer messages held so far are combined into one data transfer message and then the transfer thereof is started.

As the result, the number of the data transfer messages transferred between the wireless relay devices400to440can be reduced.

The effects obtained in the present embodiment described above are as follows. Among the data transfer messages transferred between the wireless relay devices400to440, the number of the data transfer messages containing the train control information transmitted in advance can be reduced, which leads to the reduction of the number of packets transferred per second. This contributes to securing the transmission capacity for communicating other types of information between the wireless relay devices400to440, resulting in a large capacity for the ground-to-train wireless communication for the transmission of general transmission information and further an increase in the manageable number of trains.

Note that the present embodiment describes a configuration in which the first communication interface unit401functions as a reception unit; the second communication interface unit402functions as the transmission unit; and the third communication interface unit403functions as the transmission unit.

As described above, the wireless relay device400according to Embodiment 1 includes: the reception unit (the first communication interface unit401) to receive train control information; the information classification unit405to classify the train control information into first control information requiring immediacy and second control information not requiring immediacy; the message generation unit406to generate one message from the first control information contained in a piece of the train control information and to generate one message from a plurality of pieces of the second control information contained in a plurality of pieces of the train control information; and the transmission unit (the second communication interface unit402and the third communication interface unit403) to transmit the message generated by the message generation unit406. With this configuration, it is possible to reduce the number of the data transfer messages for the train control information which does not require immediacy while the instantaneous communication for the train control information which requires immediacy is maintained. Note that reduction of the number of messages leads to less frequent message transmission, which makes it easier to secure the wireless capacity. Therefore, the reduction of the number of message transmissions is important for securing the wireless capacity, not to mention the reduction of the amount of information to be transmitted.

Further, in the wireless relay device400according to Embodiment 1, the message generation unit is characterized in that a plurality of pieces of the second control information are held until the predetermined timing arrives and then combined to generate one message from the a plurality of pieces of the second control information. With this configuration, the second control information until the predetermined timing arrives can be combined into one message, so that the number of transmissions of the data transfer messages which does not require immediacy can be reduced.

Also, in the wireless relay device400according to Embodiment 1, the first control information is the control information addressed to a first ground wireless device which is installed along the railway track and with which an on-board wireless device mounted on a train is currently communicating; the second control information is the control information addressed to a second ground wireless device which is installed along the railway track and with which the on-board wireless device is to be in communication when the train moves; and the transmission unit (the second communication interface unit402and the third communication interface unit403) transmits a message generated from the first control information to the first ground wireless device and a message generated from the second control information to a wireless relay device connected to the second ground wireless device. With this configuration, the control information addressed to the first ground wireless device installed along the railway track and currently in communication with the on-board wireless device mounted on the train can be transmitted immediately; and the control information addressed to the second ground wireless device which is installed along the railway track and which is to be in communication with the on-board wireless device when the train moves can be transmitted efficiently with a small number of messages.

Also, the wireless relay device400according to Embodiment 1 includes: the reception unit (the first communication interface unit401) to receive a first message in which a plurality of pieces of train control information are combined; the information classification unit405to extract from the first message, the train control information addressed to a ground wireless device connected to another wireless relay device; the message generation unit406to generate one second message from a plurality of pieces of the train control information extracted by the information classification unit405; and the transmission unit (the second communication interface unit402and the third communication interface unit403) to transmit the one second message generated by the message generation unit406to an adjacent wireless relay device. With this configuration, the second message which needs to be transmitted to an adjacent wireless relay device is extracted from the received first message and can be transmitted, so that the wireless resources for the communication between the wireless relay devices can be efficiently used.

Also, in the wireless relay device400according to Embodiment 1, the information classification unit405extracts, from the received first message, the train control information addressed to the ground wireless device connected to the wireless relay device; the message generation unit406generates a single third message from the train control information addressed to the ground wireless device connected to the wireless relay device; and the transmission unit (the second communication interface unit402and the third communication interface unit403) transmits the generated third message to the ground wireless device connected to the wireless relay device. With this configuration, the third message needed for the wireless relay device is extracted from the received first message and only the message needed for the ground wireless device connected to the wireless relay device can be transmitted, so that the communication between the wireless relay device and the ground wireless device can be performed efficiently.

EMBODIMENT 2

In Embodiment 1, the train control information is transmitted to the ground wireless device100by the wireless control device300without additional information. As a matter of fact, however, the information transmitted from the wireless control device300sometimes includes, in addition to the train control information: wireless control information for controlling the wireless link between the ground wireless device100and the on-board wireless device200; ground control information for controlling the transmission between the wireless control device300and the ground wireless devices100to140; and identification information for identifying a ground wireless device to be a relay destination (for example, internet protocol (IP) header and user datagram protocol (UDP) header). In the present embodiment, the message transmitted from the wireless control device300to the ground wireless devices100to140is defined as a train control message including these described above, and a method of further improving the transfer efficiency of the data transfer message transferred between the wireless relay devices by focusing on the data structure of the train control information received by the wireless relay device400from the wireless control device300will be described.

In addition to the figures used in the description of Embodiment 1,FIG.14is referred as the figure necessary for the description of the present embodiment.FIG.14shows the packet structure of the train control message. The train control message includes: the train control information; the wireless control information for controlling the wireless link between the ground wireless device and the on-board wireless device; the ground control information for controlling the transmission between the wireless control device and the ground wireless devices; and the identification information for identifying the ground wireless device to be the relay destination (for example, IP header and UDP header).

Even when the wireless control device300duplicates the train control information for each of the destination ground wireless devices, the wireless control information, the ground control information, and the ground wireless device identification information may sometimes have to be different for each of the destination ground wireless devices. Therefore, in the present embodiment, these pieces of information are classified into an area that is uniquely determined in accordance with the ground wireless devices, an area that is partially different, and an area that is common regardless of the destination and the transmission path, and redundant information is deleted to further reduce the size of the data transfer message after combining a plurality of messages, or to combine more messages.

As in Embodiment 1, the operation of the wireless relay device400to transmit the data transfer messages will be described referring toFIG.15. In the description of the present embodiment, the difference from Embodiment 1 will be mainly described. When the predetermined transmission timing between the wireless relay devices arrives (S301), the wireless relay device400combines the data transfer messages M200-110, M200-120, M210-130, and M210-140that have been held (S302). At this time, the ground wireless device identification information uniquely determined in accordance with the ground wireless devices100to140is deleted. With respect to the ground control information different only in part in accordance with the ground wireless devices100to140, only the different information is left and the uniquely determined information is deleted (S303). With respect to the common information regardless of the ground wireless devices, only one piece of information is left in the combined data transfer message and the redundant information is deleted (S304). Note that the information to be deleted here is held commonly by all the wireless relay devices in advance. Accordingly, the information after the deletion is constructed as the data transfer message M400B, and the transfer is started to the wireless relay device410(S305).

Next, the operation of the wireless relay device410at the time of receiving the data transfer message M400B will be described. When receiving the data transfer message M400B into which the data transfer messages M200-110. M200-120, M210-130, and M210-140are combined, the wireless relay device410first restores and divides the data transfer message M400B. The information deleted at the time of combining is restored on the basis of the information held in common.

Since the subsequent processing is the same as that in Embodiment 1, the description thereof is omitted. The transmission performed by the wireless relay device410and the operations of the wireless relay device420and the subsequent wireless relay devices are the same as the operations performed by the wireless relay device400at the time of combining the messages and performed by the wireless relay device410at the time of receiving the combined message and thus the description thereof is omitted.

The effects obtained in the present embodiment described above are the same as those described in Embodiment 1.

As described above, the message generation unit406in the wireless relay device400according to Embodiment 2 is characterized in that it deletes the control information that is uniquely determined according to the ground wireless devices designated by the addresses that are contained in the second control information when generating one message from a plurality of pieces of the second control information. With this configuration, the amount of data of the messages to be transferred can be reduced, which leads to efficient utilization of wireless resources used between the wireless relay devices400to440.

Also, the message generation unit406in the wireless relay device400according to Embodiment 2 is characterized in that it deletes the common control information that is independent of the ground wireless devices designated by the addresses that are contained in a plurality of pieces of the second control information when generating one message from a plurality of pieces of the second control information. With this configuration, the amount of data of the messages to be transferred can be reduced, which leads to efficient utilization of wireless resources used between the wireless relay devices400to440.

Also, the information classification unit405in the wireless relay device410according to Embodiment 2 is characterized in that it restores the control information which can be uniquely determined according to the destination ground wireless devices when extracting the train control information addressed to the ground wireless devices connected to the other wireless relay devices. With this configuration, the control information deleted in the wireless relay device400can be restored by the wireless relay device410without losing the necessary control information, which leads to efficient utilization of the wireless resources used between the wireless relay devices400to440.

Also, the information classification unit405in the wireless relay device410according to Embodiment 2 is characterized in that it restores the control information which can be uniquely determined according to the destination ground wireless device when extracting the train control information addressed to the ground wireless device connected to the wireless relay device. With this configuration, the control information deleted in the wireless relay device400can be restored by the wireless relay device410without losing the necessary control information, which leads to efficient utilization of the wireless resources available between the wireless relay devices400to440.

EMBODIMENT 3

In the present embodiment, a method of determining a hold time of the wireless relay device will be described. In Embodiment 1 and Embodiment 2, the hold time for messages to be combined and transferred is determined in advance for each of the wireless relay devices. Therefore, there is a possibility that the transfer delay increases as the number of times of relaying until reaching the destination ground wireless device increases. In the present embodiment, the hold time for the messages in the wireless relay devices is changed for each of the destination wireless relay devices.

In addition to the figures used in the description of Embodiment 1,FIG.16is referred as the figure necessary for the description of the present embodiment.FIG.16shows a transmission timing setting table set for the wireless relay device400. As in Embodiment 1, an operation of the wireless relay device400to transmit the data transfer messages will be described. In the present embodiment, the difference from Embodiment 1 will be mainly described.

When receiving the data transfer messages M210-130and M210-140from the first communication interface unit401, the wireless relay device400determines that the on-board wireless device210is not connected under the control of the wireless relay device400and that these messages are advance transmission messages generated by referring to the communication reservation table. The advance transmission messages are not transferred immediately but held in the wireless relay device. Note that train control information contained in the held messages is the second control information which does not require immediacy.

When the timing for transmission between the wireless relay devices arrives, the wireless relay device400refers toFIG.16and extracts destination wireless relay devices for which the transfer of the messages should be started at the current transmission timing (time slot). In the time slot0, the data addressed to the wireless relay devices410to440is transferred. In the time slot2and the time slot4, the data transfer messages addressed to the wireless relay device440and the wireless relay device430that is the second farthest relay device are transmitted. In the time slot3, the data transfer messages addressed to the wireless relay device440and the wireless relay device420are transmitted.

As described above, the transmission opportunity for each wireless relay device in one transmission period is given once for the wireless relay device410, twice for the wireless relay device420, three times for the wireless relay device430, and four times for the wireless relay device440, and more transmission opportunities are set for wireless relay devices addressed farther from the wireless relay device400. In addition to the effects described in Embodiment 1, the effects obtained in the present embodiment described above is such that the transmission delay increased by the number of transfers can be suppressed by increasing the number of transfers to distant destinations.

The configurations shown in Embodiment 1 to Embodiment 3 are examples of the implementation of the present disclosure. The present disclosure can be combined with other known techniques, and a part of the configuration can be omitted or changed without departing from the gist of the present disclosure.

As described above, the wireless relay device400according to Embodiment 3 is characterized in that the time period for which the second control information not requiring immediacy is held differs depending on the number of times the second control information is to be wirelessly relayed. With this configuration, the number of the transfers to the distant destination wireless relay devices is increased, so that the transmission delay that increases with the number of transfers can be suppressed.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

100,110,120,130,140: ground wireless device,101: wireless communication unit (between ground and train),102: the wired connection unit,200,210: on-board wireless device,201: wireless communication unit (between ground and train),202: wireless control unit,203: wired connection unit,204: wired control unit,205: wireless resource management unit,300: wireless control device,301: wired connection unit,302: wired control unit,303: on-board wireless device management unit,304: destination wireless device determination unit,305: database unit305,400: wireless relay device,401: first communication interface unit,402: second communication interface unit,403: third communication interface unit,404: packet analysis unit,405: information classification unit,406: message generation unit,501: divider,502: antenna,503: antenna,504: wireless antenna interface,505: wired interface,506: memory,507: processor,508: power supply circuit,601: antenna,602: wireless antenna interface,603: wired interface,604: memory,605: processor,606: power supply circuit,701: wired interface,702: memory,703: processor,704: power supply circuit,801: first communication interface,802: second communication interface,803: third communication interface,804: memory,805: processor,806: power supply circuit