JP2014060644A - Train communication system and train communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a train communication system capable of suppressing order reversal of data by reducing a switching frequency while selecting an optimum communication channel in communication between a train and the ground using a plurality of communication channels.SOLUTION: A train communication system comprises: an on-train system 1 mounted on a train; and a ground system 5 installed on the ground, where the on-train system 1 and ground system 5 are connected by a plurality of channels and perform communication by using any of the channels. The on-train system 1 comprises an on-train communication server 11 for controlling communication with the ground system 5; and the ground system 5 comprises a ground communication server 51 for controlling communication with the on-train system 1. The on-train communication server 11 and ground communication server 51 periodically collect communication information showing communication states of the plurality of channels, and determine whether to switch a channel used for communication or not on the basis of the collected communication information and lapse time from the last channel switching.

Description

  The present invention relates to a train communication system that performs communication between a train and the ground side.

  Conventionally, as a technique for communicating between the ground and a train using a wireless communication technique in a railway system, for example, in Patent Document 1 below, a plurality of communications with different communication methods capable of wireless communication between a ground base station and a mobile body Place the medium, receive the radio wave transmitted from each communication medium of either the ground base station or the mobile body with each other communication medium, monitor the radio wave condition, and select the communication medium with the good radio wave condition A technique for performing communication by switching communication media is disclosed.

JP 2005-159873 A

  However, according to the above-described conventional technique, the communication medium is switched to a communication medium with a good radio wave state during communication. However, since the radio wave state changes every moment depending on the moving speed and location, there is a possibility that the communication medium is frequently switched. . When switching communication media, data transmitted after switching may arrive earlier than data transmitted before switching due to differences in communication speed. The receiving side performs control so that the data is in the correct order. However, since the data that has arrived first is suspended until the data is in the correct order, the communication speed cannot be increased. Therefore, there is a problem that the communication situation does not always improve even if a communication medium with a good radio wave condition is selected when switching is frequently performed under the radio wave condition that changes depending on the speed of the train and the travel location. .

  The present invention has been made in view of the above, and in communication between the ground and a train using a plurality of communication lines having different communication methods, the switching frequency is reduced while selecting an optimal communication line, and the communication line The purpose of the present invention is to obtain a train communication system capable of suppressing the reversal of the data order due to the speed difference.

  In order to solve the above-described problems and achieve the object, the present invention includes an on-vehicle system mounted on a train and a ground system installed on the ground, and the on-vehicle system and the ground system include a plurality of lines. A train communication system that communicates using any of the lines, and the on-board system includes an on-board communication server that controls communication with the ground system, the ground system Includes a ground communication server that controls communication with the on-board system, and the on-board communication server and the ground communication server periodically collect communication information indicating communication states of the plurality of lines. It is characterized in that it is determined whether or not to switch the line used for communication based on the collected communication information and the elapsed time since the line was switched.

  According to the present invention, in communication between the ground and the train using a plurality of communication lines having different communication methods, the switching frequency is reduced while selecting the optimum communication line, and the data order is reversed due to the speed difference of the communication lines. It has the effect that it can suppress.

FIG. 1 is a diagram illustrating a configuration example of a train communication system according to the first embodiment. FIG. 2 is a diagram illustrating a configuration example of the on-board communication server and the ground communication server according to the first embodiment. FIG. 3 is a sequence diagram showing a communication method when transmitting data from the vehicle to the ground in the first embodiment. FIG. 4 is a flowchart showing optimum line selection processing in the on-board communication server and the ground control server in the first embodiment. FIG. 5 is a flowchart showing data transmission processing of the on-board communication server and the ground communication server in the first embodiment. FIG. 6 is a diagram illustrating a configuration example of a packet when data is transmitted. FIG. 7 is a flowchart showing data reception processing of on-vehicle communication server 11 and ground communication server 51 in the first embodiment. FIG. 8 is a sequence diagram showing a communication method when transmitting data from the ground to the vehicle in the first embodiment. FIG. 9 is a diagram illustrating a configuration example of the on-board communication server and the ground communication server according to the second embodiment. FIG. 10 is a sequence diagram illustrating a communication method when transmitting data from the ground to the vehicle in the second embodiment. FIG. 11 is a flowchart showing an optimum line selection process in the on-board communication server 11a and the ground control server 51a according to the second embodiment. FIG. 12 is a flowchart showing data transmission processing of the on-board communication server 11a and the ground communication server 51a in the second embodiment. FIG. 13 is a flowchart showing data reception processing of the on-board communication server 11a and the ground communication server 51a in the second embodiment.

  Hereinafter, embodiments of a train communication system according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a train communication system according to the present embodiment. The train communication system includes an on-vehicle system 1 and a ground system 5, and the two systems are connected as a plurality of wireless networks via networks 2, 3, and 4. In FIG. 1, as an example of a wireless network, a case in which WiMAX, LTE (Long Term Evolution), and wireless LAN (Local Area Network) are connected is shown. For convenience of explanation, FIG. 1 shows only one on-vehicle system 1, but this is not a limitation. The ground system 5 can be connected to a plurality of on-vehicle systems 1 mounted on different trains via networks 2, 3, and 4.

  The on-board communication server 11 and the ground communication server 51 are assigned IP addresses for communication. The ground communication server 51 is assigned a representative address A1, a WiMAX address A2, an LTE address A3, and a wireless LAN address A4. The on-board communication server 11 is assigned a representative address A5, WiMAX address A6, LTE address A7, and wireless LAN address A8. In communication between the on-board communication server 11 and the ground communication server 51, the on-board communication server 11 of the communication destination train and the ground side ground communication server 51 are specified using the representative address. The WiMAX address, LTE address, and wireless LAN address are used when communicating via each network after selecting an optimum line.

  The on-board system 1 is mounted on a train, executes applications on the on-board equipment 12 according to data received from the ground system 5 via a plurality of networks, and performs data acquisition and control from the on-board equipment 12. The ground system 5 is used when acquiring instructions and train data for a train on which the on-board system 1 is mounted.

  The configuration of the on-vehicle system 1 will be described. The on-board system 1 includes an on-board communication server 11, an on-board device 12, a SW 13, a WiMAX control device 14, an LTE control device 15, and a wireless LAN control device 16. The on-board communication server 11 selects an optimum line from the plurality of networks 2, 3, and 4 and controls communication with the ground system 5. The on-board device 12 executes the application according to the data received from the ground system 5. For example, it is possible to control the air conditioning, electric power, motor, etc. in the train as necessary according to the received data. The SW 13 is a communication device (switch) that connects the on-board communication server 11 to the WiMAX control device 14, the LTE control device 15, and the wireless LAN control device 16 and relays communication of the on-board communication server 11. The WiMAX control device 14, the LTE control device 15, and the wireless LAN control device 16 are devices for connecting the on-board system 1 to each network, and are connected to the on-board communication server 11 via the SW 13.

  The configuration of the ground system 5 will be described. The ground system 5 includes a ground communication server 51, a ground terminal 52, a SW 53, a router (WiMAX) 54, a router (LTE) 55, and a router (wireless LAN) 56. The ground communication server 51 communicates data received from the ground terminal 52 with the on-vehicle system 1 using an optimum line. The ground terminal 52 controls the air conditioning, electric power, motor, and the like of the train, and manages traveling information from the train. The SW 53 is a communication device that connects the ground communication server 51 and the routers 54, 55, and 56 and relays communication of the ground communication server 51. The routers 54, 55, and 56 are communication devices that connect the ground system 5 to each network.

  FIG. 2 is a diagram illustrating a configuration example of the on-board communication server 11 and the ground communication server 51 according to the present embodiment. Here, the on-board communication server 11 and the terrestrial communication server 51 have the same configuration, and transmit data received from the on-board equipment 12 and the terrestrial terminal 52 using an optimum line, respectively. The ground communication server 51 may communicate with a plurality of trains, and selects and communicates an optimum line for each train.

  In FIG. 2, the on-board communication server 11 and the ground communication server 51 include a network communication unit 60, a communication information collection unit 61, a switching determination unit 62, an optimum line switching unit 63, a header adding unit 64, and a header deletion. Unit 65, order control unit 66, and terminal communication unit 67.

  The network communication unit 60 transmits and receives data between the on-board communication server 11 and the ground communication server 51 via the network. The communication information collection unit 61 acquires communication information such as radio wave intensity and the number of transmission / reception data from the WiMAX control device 14, the LTE control device 15, the wireless LAN control device 16, or the routers 54, 55, and 56. The switching determination unit 62 selects an optimum line based on the communication information acquired by the communication information collection unit 61 and determines whether or not the line to be used is switched. The optimum line switching unit 63 refers to the determination result of the switching determination unit 62 and switches the line to be used. The header assigning unit 64 assigns a header to data (packet) transmitted between the on-board communication server 11 and the ground communication server 51, and sets an address used for communication. The header deletion unit 65 deletes the header added by the header addition unit 64 on the communication partner side from the received data (packet). When the order of data transmitted between the on-board communication server 11 and the ground communication server 51 is reversed, the order control unit 66 shapes the data into the correct order. The terminal communication unit 67 communicates with the on-board device 12 or the ground terminal 52.

  Next, in the train communication system, a method for selecting an optimum line when transmitting and receiving data between the on-board equipment 12 of the on-board system 1 and the ground terminal 52 of the ground system 5 will be described as a train communication method. First, a method for selecting an optimum line when data is transmitted from the onboard equipment 12 of the onboard system 1 to the ground terminal 52 of the ground system 5 will be described. FIG. 3 is a sequence diagram showing a communication method when data is transmitted from the vehicle to the ground in the present embodiment. FIG. 4 is a flowchart showing the optimum line selection processing in the on-board communication server 11 and the ground control server 51 in the present embodiment.

  In the on-board communication server 11, the communication information collecting unit 61 periodically acquires communication information from the WiMAX control device 14, the LTE control device 15, and the wireless LAN control device 16 via the network communication unit 60 (steps S1 to S3). ).

  In the on-board communication server 11, the switching determination unit 62 uses the communication information acquired by the communication information collection unit 61, the communication speed is fast, the communication rate required by the application is met, data loss is small, Optimal line candidates are determined based on conditions such as low delay. Here, a case where a line having a high communication speed is selected as a condition will be described. From the collected communication information, the one having the fast communication speed is determined as the optimum line candidate, and the first communication speed is V1 = communication speed of the optimum line candidate and the second communication speed is V2 = the line used in the current communication. A communication speed is obtained (step S4). In the example of FIG. 3, since the communication speed of the collected communication time information is WiMAX 2 Mbps, LTE 1 Mbps, and wireless LAN 0 Mbps, WiMAX is set as the optimum line candidate.

  The switching determination unit 62, for example, immediately after the system is started, is not the same as the optimum line candidate and the line used (step S5: No), and the line (optimum line) to be used has not been determined (step S6: Yes). ), A determination is made to switch the WiMAX line as the optimum line, and the optimum line switching unit 63 performs control to switch the actual line to the WiMAX line. At this time, the switching determination unit 62 holds the switching time T1 = current time as the switching time to the WiMAX line (step S8). The switching determination unit 62 starts a timer (for example, 1 second) (step S9), and after the timeout, the communication information collection unit 61 repeats the process of acquiring communication information.

  In the on-board communication server 11, the communication information collecting unit 61 periodically acquires communication information from the WiMAX control device 14, the LTE control device 15, and the wireless LAN control device 16 via the network communication unit 60 (steps S1 to S3). ). In FIG. 3, since the communication information acquired for the second time is WiMAX 2 Mbps, LTE 2.1 Mbps, and wireless LAN 0 Mbps, the switching determination unit 62 sets LTE as the optimum line candidate and V1 = 2.1 Mbps. Also, since the line currently used for communication is WiMAX, V2 = 2 Mbps (step S4).

  The switching determination unit 62 compares the switching determination value D with V1−V2 = 0.1 Mbps because the optimal line candidate is not the same as the line being used (step S5: No) (step S6). The switching determination value D is set in advance as a specified value, for example, 0.5 Mbps. Since the switching determination unit 62 has V1-V2 smaller than the switching determination value D and the line to be used is not yet determined (step S6: No), the switching time at which the current time and the previous optimal line are switched next. A difference from T1 is obtained, and whether or not the difference exceeds the switching determination time T is calculated (step S7). The switching determination time T is set in advance as a specified value, for example, 10 seconds. Since the previous switch to the optimum line is one second ago, the current time -T1 is smaller than the switching determination time T (step S7: No), and the switching determination unit 62 starts a timer (for example, one second). (Step S9). After the timeout, the communication information collection unit 61 repeats the process of acquiring the communication information.

  In the on-board communication server 11, the communication information collecting unit 61 periodically acquires communication information from the WiMAX control device 14, the LTE control device 15, and the wireless LAN control device 16 via the network communication unit 60 (steps S1 to S3). ). In FIG. 3, the communication information collected after 10 seconds from the time of switching to the previous optimum line is WiMAX 2 Mbps, LTE 2.1 Mbps, and wireless LAN 0 Mbps. 2.1 Mbps. Further, since the currently communicating line is WiMAX, V2 = 2 Mbps (step S4).

  Since the optimum line candidate and the line being used are not the same (step S5: No), the switching determination unit 62 compares V1-V2 = 0.1 Mbps with the switching determination value D (step S6). Since the switching determination unit 62 has V1-V2 smaller than the switching determination value D and the line to be used is not yet determined (step S6: No), the switching time at which the current time and the previous optimal line are switched next. A difference from T1 is obtained, and whether or not the difference exceeds the switching determination time T is calculated (step S7). Since the switch to the optimum line last time was 10 seconds ago, and the current time -T1 is equal to or longer than the switching determination time T (step S7: Yes), the switching determination unit 62 determines to switch the LTE line as the optimal line. The optimum line switching unit 63 performs control to switch the actual line from the WiMAX line to the LTE line. At this time, the switching determination unit 62 holds the switching time T1 = current time as the switching time to the LTE line (step S8). The switching determination unit 62 starts a timer (for example, 1 second) (step S9), and after the timeout, the communication information collection unit 61 repeats the process of acquiring communication information.

  When the optimum line candidate is the same as the line currently used for communication (step S5: Yes), the switching determination unit 62 does not need to perform the switching determination, so the switching determination process is omitted and the timer is set. Start (step S9). The subsequent processing is the same as the processing described above.

  Next, the data transmission process of the on-board communication server 11 will be described. FIG. 5 is a flowchart showing data transmission processing of the on-board communication server 11 and the ground communication server 51 in the present embodiment. In the on-board communication server 11, the terminal communication unit 67 receives data addressed to the ground terminal 52 from the on-board device 12. The terminal communication unit 67 acquires the representative address A1 of the ground communication server 51 that is the destination (step S11), and acquires the representative address A5 of the on-board communication server 11 that is the transmission source (step S12).

  FIG. 6 is a diagram illustrating a configuration example of a packet when data is transmitted. The packet includes a new IP header 71 newly added as a feature of the present embodiment, a conventional IP header 72, a TCP header 73, and data 74. The terminal communication unit 67 sets the acquired representative address in the IP header 72 as the representative address A1 of the ground communication server 51 as the destination and the representative address A5 of the on-board communication server 11 as the transmission source.

  The optimum line switching unit 63 acquires information on the current optimum line from the switching determination unit 62 (step S13). If it is the initial stage of FIG. 3 as an optimum line, WiMAX is acquired. When the acquired line information is different, control to switch the line is performed.

  The header adding unit 64 adds a header to the packet to be transmitted (step S14). The header to be added is a new IP header 71 shown in FIG. In the new IP header 71, the WiMAX address A2 of the ground communication server 51 is set as the destination, and the WiMAX address A6 of the on-board communication server 11 is set as the transmission source.

  Then, the network communication unit 60 outputs the packet (data) to the WiMAX control device 14 (step S15).

  Next, data reception processing of the ground communication server 51 will be described. FIG. 7 is a flowchart showing data reception processing of the on-board communication server 11 and the ground communication server 51 in the present embodiment. In the ground communication server 51, the network communication unit 60 receives the packet transmitted from the on-board communication server 11, and the header deletion unit 65 deletes the new IP header 71 from the packet (step S21). When the packet order is reversed, the order control unit 66 controls the order by shaping (step S22). And the terminal communication part 67 transmits data to the ground terminal 52 (step S23).

  Next, a method for selecting an optimum line when data is transmitted from the ground terminal 52 of the ground system 5 to the onboard equipment 12 of the onboard system 1 will be described with reference to FIGS. FIG. 8 is a sequence diagram showing a communication method when data is transmitted from the ground to the vehicle in the present embodiment. In addition, the flowchart of the optimal line selection process in the ground control server 51, the transmission process, and the reception process in the vehicle communication server 11 is a flowchart when data is transmitted from the vehicle to the ground (see FIGS. 4, 5, and 7). It is the same.

  In the ground communication server 51, the communication information collection unit 61 periodically acquires communication information from the routers 54 to 56 connected to the WiMAX, LTE, and wireless LAN networks via the network communication unit 60 (steps S1 to S3). ).

  In the ground communication server 51, the switching determination unit 62 determines the optimum line candidate using the communication information acquired by the communication information collection unit 61. Here, as in the case of the on-board communication server 11, a case where a line having a high communication speed is selected as a condition will be described. From the collected communication information, the one having the fast communication speed is determined as the optimum line candidate, and V1 = communication speed of the optimum line candidate and V2 = the transmission speed of the line currently used in communication (step S4). In the example of FIG. 8, since the communication speed of the collected communication information is WiMAX 4 Mbps, LTE 2 Mbps, and wireless LAN 1 Mbps, WiMAX is set as the optimum line candidate.

  The switching determination unit 62, for example, immediately after the system is started, is not the same as the optimum line candidate and the line used (step S5: No), and the line (optimum line) to be used has not been determined (step S6: Yes). ), A determination is made to switch the WiMAX line as the optimum line, and the optimum line switching unit 63 performs control to switch the actual line to the WiMAX line. At this time, the switching determination unit 62 holds the switching time T1 = current time as the switching time to the WiMAX line (step S8). The switching determination unit 62 starts a timer (for example, 1 second) (step S9), and after the timeout, the communication information collection unit 61 repeats the process of acquiring communication information.

  In the ground communication server 51, the communication information collection unit 61 periodically acquires communication information from the routers 54 to 56 via the network communication unit 60 (steps S1 to S3). In FIG. 8, since the communication information acquired for the second time is WiMAX 2 Mbps, LTE 4 Mbps, and wireless LAN 1 Mbps, the switching determination unit 62 sets LTE as the optimum line candidate and V1 = 4 Mbps. Also, since the line currently used for communication is WiMAX, V2 = 2 Mbps (step S4).

  The switching determination unit 62 compares the switching determination value D with V1−V2 = 2 Mbps because the optimum line candidate and the line being used are not the same (step S5: No) (step S6). The switching determination value D is set in advance as a specified value, for example, 0.5 Mbps. The switching determination unit 62 determines that the LTE line is switched as the optimum line because V1−V2 is larger than the switching determination value D (step S6: Yes), and the optimum line switching unit 63 switches the actual line from the WiMAX line. Control to switch to the LTE line is performed. At this time, the switching determination unit 62 holds the switching time T1 = current time as the switching time to the LTE line (step S8). The switching determination unit 62 starts a timer (for example, 1 second) (step S9), and after the timeout, the communication information collection unit 61 repeats the process of acquiring communication information.

  Similar to the on-board communication server 11, when the optimum line candidate is the same as the line currently used for communication (step S5: Yes), the switching determination unit 62 does not need to perform the switching determination. Is started and a timer is started (step S9). The subsequent processing is the same as the processing described above.

  Next, data transmission processing of the ground communication server 51 will be described with reference to FIG. In the ground communication server 51, the terminal communication unit 67 receives data addressed to the on-vehicle equipment 12 from the ground terminal 52. The terminal communication unit 67 acquires the representative address A5 of the on-board communication server 11 that is the destination (step S11), and acquires the representative address A1 of the ground communication server 51 that is the transmission source (step S12). The terminal communication unit 67 sets the acquired representative address in the IP header 72 as a representative address A5 of the on-board communication server 11 as a destination and a representative address A1 of the ground communication server 51 as a transmission source.

  The optimum line switching unit 63 acquires information on the current optimum line from the switching determination unit 62 (step S13). If the optimum line is after line switching in FIG. 8, LTE is acquired. When the acquired line information is different, control to switch the line is performed.

The header adding unit 64 adds a header to the packet to be transmitted (step S14). The header to be added is a new IP header 71 shown in FIG. In the new IP header 71, the LTE address A7 of the on-board communication server 11 is set as a destination, and the LTE address A3 of the ground communication server 51 is set as a transmission source.

  Then, the network communication unit 60 transmits the packet (data) via the router 55 (step S15).

  Next, data reception processing of the on-board communication server 11 will be described with reference to FIG. In the on-board communication server 11, the network communication unit 60 receives the packet transmitted from the ground communication server 51, and the header deletion unit 65 deletes the new IP header 71 from the packet (step S21). When the packet order is reversed, the order control unit 66 controls the order by shaping (step S22). And the terminal communication part 67 transmits data to the onboard equipment 12 (step S23).

  As described above, according to the present embodiment, the on-board system 1 and the ground system 5 collect the communication information of the communication network, and use the optimum line candidate determined from the collected communication information for the current communication. The line to be used is switched based on the difference from the communication speed of the existing line and the elapsed time since the previous switching. This prevents frequent switching of the line to be used even when the communication speed changes in a short period of time due to the radio field strength, and reduces the communication speed due to the reverse of the packet order when switching the line. Can be reduced.

Embodiment 2. FIG.
In the first embodiment, the optimum line candidate determined from the collected communication information is compared with the information on the currently used line to prevent frequent switching of the line to be used. In this embodiment, the transmitted packet is prevented from arriving with the order reversed on the receiving side. A different part from Embodiment 1 is demonstrated.

  Although the configuration of the train communication system of the present embodiment is the same as that of the first embodiment (see FIG. 1), the on-board system 1, the on-board communication server 11, the ground system 5, and the ground communication server 51 are respectively The upper system 1a, the on-board communication server 11a, the ground system 5a, and the ground communication server 51a are used.

  FIG. 9 is a diagram illustrating a configuration example of the on-board communication server 11a and the ground communication server 51a according to the present embodiment. The on-vehicle communication server 11a and the ground communication server 51a include a network communication unit 60, a communication information collection unit 61, a switching determination unit 62, an optimum line switching unit 63, a header assignment unit 64, a header deletion unit 65, An order control unit 66a, a terminal communication unit 67, a non-Ack data transmission unit 68, and a non-Ack data holding unit 69 are provided. The non-Ack data transmission unit 68 performs control to retransmit data that has not received Ack at the time of line switching. The non-Ack data holding unit 69 performs control to hold and delete the transmitted data.

  Subsequently, in the train communication system, a method for selecting an optimum line when transmitting and receiving data between the ground terminal 52 of the ground system 5a and the on-board equipment 12 of the on-board system 1a will be described as a train communication method. Here, a method for selecting an optimum line when data is transmitted from the ground terminal 52 of the ground system 5a to the on-board equipment 12 of the on-board system 1a will be described. FIG. 10 is a sequence diagram showing a communication method when data is transmitted from the ground to the vehicle in the present embodiment. FIG. 11 is a flowchart showing the optimum line selection processing in the on-board communication server 11a and the ground control server 51a in the present embodiment.

  In the ground communication server 51a, the communication information collection unit 61 periodically acquires communication information from the routers 54 to 56 connected to the WiMAX, LTE, and wireless LAN networks via the network communication unit 60 (steps S1 to S3). ).

  In the ground communication server 51a, the switching determination unit 62 uses the communication information acquired by the communication information collection unit 61 to determine the optimum line candidate. Here, as in the first embodiment, a case where a line having a high communication speed is selected as a condition will be described. From the collected communication information, the one with the fast communication speed is determined as the optimum line candidate, and V1 = communication speed of the optimum line candidate and V2 = communication speed of the line currently used in communication (step S4). In the example of FIG. 10, since the communication speed of the collected communication time information is WiMAX 4 Mbps, LTE 2 Mbps, and wireless LAN 1 Mbps, WiMAX is set as the optimum line candidate.

  The switching determination unit 62, for example, immediately after the system is started, is not the same as the optimum line candidate and the line used (step S5: No), and the line (optimum line) to be used has not been determined (step S6: Yes). ), A determination is made to switch the WiMAX line as the optimum line, and the optimum line switching unit 63 performs control to switch the actual line to the WiMAX line. At this time, the switching determination unit 62 holds the switching time T1 = current time as the switching time to the WiMAX line (step S8).

  Here, the non-Ack data transmission unit 68 performs control to transmit the data held in the non-Ack data holding unit 69 to the on-board device 12 side of the on-board system 1a using the switched line ( Step S10). Note that the processing in step S10 is omitted immediately after the system is started up or when there is no stored data.

  The switching determination unit 62 starts a timer (for example, 1 second) (step S9), and after the timeout, the communication information collection unit 61 repeats the process of acquiring communication information.

  In the on-board communication server 11a, the communication information collection unit 61 periodically acquires communication information from the routers 54 to 56 via the network communication unit 60 (steps S1 to S3). In FIG. 10, since the communication information acquired for the second time is WiMAX 2 Mbps, LTE 4 Mbps, and wireless LAN 1 Mbps, the switching determination unit 62 sets LTE as the optimum line candidate and V1 = 4 Mbps. Further, since the currently communicating line is WiMAX, V2 = 2 Mbps (step S4).

  The switching determination unit 62 compares the switching determination value D with V1−V2 = 2 Mbps because the optimum line candidate and the line being used are not the same (step S5: No) (step S6). The switching determination value D is set in advance as a specified value, for example, 0.5 Mbps. The switching determination unit 62 determines that the LTE line is switched as the optimum line because V1−V2 is larger than the switching determination value D (step S6: Yes), and the optimum line switching unit 63 switches the actual line from the WiMAX line. Control to switch to the LTE line is performed. At this time, the switching determination unit 62 holds the switching time T1 = current time as the switching time to the LTE line (step S8).

  Here, the non-Ack data transmission unit 68 transmits the data held in the non-Ack data holding unit 69 to the on-board equipment 12 side of the on-board system 1a using the switched line (LTE line). Control is performed (step S10). In other words, the non-Ack data transmitting unit 68 confirms the non-Ack data holding unit 69, and thus the data that has not received Ack from the on-board communication server 11a as the communication destination among the data transmitted through the WiMAX line. The unacknowledged data is transmitted on the switched line (LTE line). At this time, the header assigning unit 64 newly assigns the address of the line (LTE line) after the replacement to the new IP header 71 and performs transmission from the network communication unit 60.

  The switching determination unit 62 starts a timer (for example, 1 second) (step S9), and after the timeout, the communication information collection unit 61 repeats the process of acquiring communication information.

  As in the first embodiment, when the optimum line candidate is the same as the line currently used for communication (step S5: Yes), the switching determination unit 62 does not need to perform the switching determination. The timer is started by omitting it (step S9). The subsequent processing is the same as the processing described above.

  Next, the data transmission process of the ground communication server 51a will be described. FIG. 12 is a flowchart showing data transmission processing of the on-board communication server 11a and the ground communication server 51a in the present embodiment. In the ground communication server 51 a, the terminal communication unit 67 receives data addressed to the on-vehicle equipment 12 from the ground terminal 52. The terminal communication unit 67 acquires the representative address A5 of the on-board communication server 11a that is the destination (step S11), and acquires the representative address A1 of the ground communication server 51a that is the transmission source (step S12). The terminal communication unit 67 sets the acquired representative address in the IP header 72 as the representative address A5 of the on-board communication server 11a as the destination and the representative address A1 of the ground communication server 51a as the transmission source.

  The optimum line switching unit 63 acquires information on the current optimum line from the switching determination unit 62 (step S13). If the optimum line is after line switching in FIG. 10, LTE is acquired. When the acquired line information is different, control to switch the line is performed.

The header adding unit 64 adds a header to the packet to be transmitted (step S14). The header to be added is a new IP header 71 shown in FIG. In the new IP header 71, the LTE address A7 of the on-board communication server 11a is set as the destination, and the LTE address A3 of the ground communication server 51a is set as the transmission source.

  Then, the network communication unit 60 transmits the packet (data) via the router 55 (step S15), and further holds the data transmitted in step S15 in the non-Ack data holding unit 69 in the present embodiment ( Step S16).

  Next, the data reception process of the on-board communication server 11a will be described. FIG. 13 is a flowchart showing data reception processing of the on-board communication server 11a and the ground communication server 51a in the present embodiment. In the on-board communication server 11a, the network communication unit 60 receives the packet transmitted from the ground communication server 51, and the header deletion unit 65 deletes the new IP header 71 from the packet (step S21).

  The order control unit 66a checks whether or not the received packet is Ack (step S24). When the received packet is not Ack, that is, data (step S24: No), the order control unit 66a controls the order by shaping when the order of the packets is reversed (step S22). And the terminal communication part 67 transmits data to the onboard equipment 12 (step S23), and also in this Embodiment, performs control which transmits Ack corresponding to the said data addressed to the ground communication server 51a (step S23). S25). The process of transmitting Ack is the same as the case of transmitting data from terminal communication unit 67 in FIG. 12 except that transmission data is held.

  In the on-board communication server 11a, when the received packet is Ack (step S24: Yes), the order control unit 66a selects the data corresponding to the received Ack among the data held in the non-Ack data holding unit 69. Delete (step S26).

  In this embodiment, the order control unit 66a performs control to confirm whether or not the received packet is an Ack, and to delete the data held in the non-Ack data holding unit 69, but this is an example. However, the present invention is not limited to this. For example, another configuration for controlling whether or not the received packet is Ack and deleting the data held in the non-Ack data holding unit 69 may be newly provided.

  In the present embodiment, the case where data is transmitted from the ground terminal 52 of the ground system 5a to the on-board equipment 12 of the on-board system 1a is described as an example, and the on-board system is the same as in the first embodiment. The case where data is transmitted from the on-board equipment 12 of 1a to the ground terminal 52 of the ground system 5a can be described as a similar process.

  As described above, in the present embodiment, when the ground communication server 51a (or on-vehicle communication server 11a) switches the line to be used, it transmits data that has not been confirmed to be received from the communication destination. did. As a result, it is possible to prevent the packet order from changing even when the line is switched to a line with a high communication speed.

  In the first and second embodiments, the case where communication is performed between the train side and the ground has been described. However, the object to be moved is not limited to the train, and for example, a communication system with an aircraft, a ship, a bus, or the like. Applicable.

  As described above, the train communication system according to the present invention is useful for a communication system in which one side that performs communication moves, and is particularly suitable for communication with a train.

  1,1a On-board system, 2,3,4 network, 5,5a Ground system, 11,11a On-board communication server, 12 On-board equipment, 13 SW, 14 WiMAX control device, 15 LTE control device, 16 Wireless LAN control Equipment, 51, 51a ground communication server, 52 ground terminal, 53 SW, 54, 55, 56 router, 60 network communication section, 61 communication information collection section, 62 switching determination section, 63 optimum line switching section, 64 header assignment section, 65 Header deletion unit, 66, 66a Order control unit, 67 Terminal communication unit, 68 UnAck data transmission unit, 69 UnAck data holding unit.

Claims (8)

A train communication system comprising an on-board system mounted on a train and a ground system installed on the ground, wherein the on-board system and the ground system are connected by a plurality of lines and communicate using any of the lines Because
An on-board communication server for controlling communication between the on-board system and the ground system;
With
A ground communication server for controlling communication between the ground system and the on-board system;
With
The on-board communication server and the ground communication server are:
Periodically collecting communication information indicating the communication state of the plurality of lines, and determining whether to switch the line used for communication based on the collected communication information and the elapsed time since switching the line;
A train communication system. The on-board communication server and the ground communication server are:
The first communication speed of the line with the fastest communication speed in the collected communication information is compared with the second communication speed of the line currently used for communication, and the first communication speed is the second communication speed. When the difference between the first communication speed and the second communication speed is less than a predetermined switching determination value that is faster than the speed, the switching time that has elapsed since the previous line was switched If it is more than the determination time, determine to switch to the first communication speed line,
The train communication system according to claim 1. The on-board communication server and the ground communication server are:
The first communication speed of the line with the fastest communication speed in the collected communication information is compared with the second communication speed of the line currently used for communication, and the first communication speed is the second communication speed. Faster than the speed, and when the difference between the first communication speed and the second communication speed is greater than a predetermined switching determination value, determine to switch to the line of the first communication speed,
The train communication system according to claim 1 or 2. The on-board communication server and the ground communication server are:
When transmission data is held and the line to be used is switched, among the transmission data, transmission data that has not received a reception response from the communication partner is transmitted on the switched line.
The train communication system according to claim 1, 2, or 3. A train communication system comprising an on-board system mounted on a train and a ground system installed on the ground, wherein the on-board system and the ground system are connected by a plurality of lines and communicate using any of the lines Train communication method in
When the on-board system includes an on-board communication server that controls communication with the ground system, and the ground system includes a ground communication server that controls communication with the on-board system.
A communication information collecting step in which the on-board communication server and the ground communication server periodically collect communication information indicating a communication state of the plurality of lines;
A switching determination step for determining whether to switch the line used for communication based on the communication information collected by the on-board communication server and the ground communication server and the elapsed time since the line was switched;
A train communication method comprising: In the switching determination step,
The on-board communication server and the ground communication server compare the first communication speed of the line with the fastest communication speed in the collected communication information with the second communication speed of the line currently used for communication, When the first communication speed is faster than the second communication speed and the difference between the first communication speed and the second communication speed is equal to or less than a predetermined switching determination value, the line used last time is When the elapsed time after switching is greater than or equal to the switching determination time defined in advance, it is determined to switch to the first communication speed line,
The train communication method according to claim 5. In the switching determination step,
The on-board communication server and the ground communication server compare the first communication speed of the line with the fastest communication speed in the collected communication information with the second communication speed of the line currently used for communication, When the first communication speed is faster than the second communication speed and the difference between the first communication speed and the second communication speed is larger than a predetermined switching determination value, the first communication speed Judgment to switch to speed line,
The train communication method according to claim 5 or 6, wherein When the on-board communication server and the ground communication server hold transmission data and switch the line to be used, after switching the transmission data that has not received a reception response from the communication partner among the transmission data Step for resending data to be sent on
The train communication method according to claim 5, 6 or 7, characterized by comprising:

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