Communication device, communication quality measurement method, control circuit, and storage medium

Abstract

A communication device (1, 2) comprising: a data transfer unit (11, 21) that is connected to a communication line and transfers user data of an application to the communication line; a communication quality measurement unit (12, 22) that measures the communication quality of the communication line; and a measurement condition determination unit (13, 23) that determines a method for transmitting measurement data, which is transmitted when the communication quality measurement unit (12, 22) measures the communication quality, on the basis of the size of the measurement data, the occurrence status of the user data, and the maximum transfer size of the communication line.

Description

Communication device, communication quality measurement method, control circuit, and storage medium

[0001] The present disclosure relates to a communication device, a communication quality measurement method, a control circuit, and a storage medium that are applied to mobile communications.

[0002] In mobile communications, such as railway communications, when the position of a communication device that performs wireless communications changes as a train or the like equipped with the communication device moves, the wireless quality and communication quality fluctuate. Even if the position of the communication device does not change, the wireless quality and communication quality may fluctuate due to changes in the surrounding environment, the influence of communications from other communication devices, etc. Therefore, the communication device measures the wireless quality and communication quality as appropriate, and, for example, when it detects a deterioration in communication quality, it performs processing to restore the communication quality.

[0003] A communication device can measure communication quality such as transmission delay, throughput, packet loss rate, etc. by transmitting and receiving measurement packets with an opposing communication device. For example, Patent Document 1 discloses a wireless communication system that transmits and receives packets with timestamps added to the headers as communication quality measurement data, and measures packet transfer delay time, throughput, fluctuation, etc. based on the timestamps on the packet receiving side.

[0004] International Publication No. 2012 / 164675

[0005] However, the technology described in Patent Document 1 fails to take into consideration the impact of adding communication quality measurement data to packets. Therefore, if communication quality is measured using the method described in Patent Document 1 while user data is being transferred, the transmission and reception of packets for communication quality measurement increases the bandwidth used on the communication line and the number of transferred packets, which increases the network load and may affect the transfer of user data.

[0006] For example, if communication quality is measured when the load of packet forwarding processing of a communication device is high, there is a possibility that user data transfer will be lost or delays will increase. Furthermore, as a result of adding communication quality measurement data to a packet containing user data, the data size that can be transferred in one transfer unit may be exceeded, and the data may be divided into multiple packets for transfer (fragmentation), which may cause an increase in network load.

[0007] The present disclosure has been made in view of the above, and aims to provide a communication device that is capable of measuring communication quality while minimizing the impact on user data transfer.

[0008] In order to solve the above-mentioned problems and achieve the objectives, the communication device disclosed herein is characterized by comprising: a data transfer unit that is connected to a communication line and transfers user data of an application to the communication line; a communication quality measurement unit that measures the communication quality of the communication line; and a measurement condition determination unit that determines a method for transmitting the measurement data based on the size of the measurement data that the communication quality measurement unit transmits when measuring the communication quality, the generation status of the user data, and the maximum transfer size of the communication line.

[0009] The communication device according to the present disclosure has an effect of being able to measure communication quality while minimizing the impact on user data transfer.

[0010] FIG. 1 is a diagram showing an application example of a communication device according to a first embodiment. FIG. 2 is a diagram showing an outline of the operation of a system to which a communication device according to a first embodiment is applied. FIG. 3 is a diagram showing an example of the configuration of transmission data on a path when a communication device according to a first embodiment transmits measurement data together with user data. FIG. 4 is a diagram showing an example of measurement information transmitted and received by a communication device according to a first embodiment for measuring communication quality. FIG. 5 is a diagram showing an example of the configuration of transmission data when a communication device according to a first embodiment transmits user data alone. FIG. 6 is a diagram showing an example of the configuration of transmission data when a communication device according to a first embodiment transmits measurement data alone. FIG. 1 is a flowchart showing an example of an operation for transmitting measurement response information; FIG. 2 is a sequence diagram showing an example of an overall operation (measurement request operation) of the communication system according to the first embodiment; FIG. 3 is a sequence diagram showing an example of an overall operation (measurement response operation) of the communication system according to the first embodiment; FIG. 4 is a diagram showing an example of a hardware configuration of the communication device according to the first embodiment; FIG. 5 is a diagram showing another example of a hardware configuration of the communication device according to the first embodiment; FIG. 6 is a diagram showing an example of a minimum measurement time used in the determination process by the measurement condition determination unit according to the second embodiment; FIG. 7 is a diagram showing an example of a minimum measurement time used in the determination process by the measurement condition determination unit according to the third embodiment;

[0011] A communication device, a communication quality measurement method, a control circuit, and a storage medium according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0012] First Embodiment. FIG. 1 is a diagram illustrating an application example of a communication device according to a first embodiment. The communication device according to the first embodiment is, for example, communication devices 1 and 2 applied to a railway system as shown in FIG. 1. The communication devices 1 and 2 are, for example, communication devices compatible with a fifth-generation mobile communication system (hereinafter referred to as a 5G (5th Generation) system). The communication device 1 is mounted on a train 10, which is a moving object. The communication device 2 is installed on the ground side, specifically, in a station, a communication equipment room, a control center, or the like. The communication device 1 is connected to a 5G terminal 5 that transmits and receives wireless signals to and from a 5G base station 4, which is a base station of the 5G system. The 5G base station 4 is connected to a 5G control device 3 that forms a core network of the 5G system. The communication device 2 is connected to the 5G control device 3. Note that there are other network devices that form the core network of the 5G system besides the 5G control device 3, but these are not illustrated in FIG. 1. In the following description, the communication device 1 may be referred to as an on-board communication device, and the communication device 2 may be referred to as a ground communication device.

[0013] When the train 10 is located within the communication coverage area 200 of the 5G base station 4, the communication device 1 communicates with the communication device 2 via the 5G terminal 5, the 5G base station 4 and the 5G control device 3.

[0014] As the train 10 moves, the positional relationship between the 5G terminal 5 and the 5G base station 4 mounted on the train changes, which in turn changes the wireless quality between the 5G terminal 5 and the 5G base station 4, and also changes the communication quality between the on-board communication device and the trackside communication device. For this reason, as shown in FIG. 2 , wireless quality measurements are performed between the 5G terminal 5 and the 5G base station 4, and communication quality measurements are performed between the on-board communication device and the trackside communication device. These quality measurements may be performed in parallel with user data transfer between applications (denoted as "apps" in FIG. 2 ) that use the communication devices 1 and 2. In this case, as described above, communication quality measurements during user data transfer may affect the user data transfer. For this reason, the communication devices 1 and 2 perform communication quality measurements in a manner that takes into account the impact on user data transfer. Note that FIG. 2 is a diagram illustrating an overview of the operation of a system to which the communication device according to the first embodiment is applied.

[0015] 3 is a diagram illustrating an example of the configuration of a communication system 100 and communication devices 1 and 2 according to the first embodiment. The communication device 1 includes a data transfer unit 11, a communication quality measurement unit 12, a measurement condition determination unit 13, and a storage unit 14. The communication device 2 includes a data transfer unit 21, a communication quality measurement unit 22, a measurement condition determination unit 23, and a storage unit 24. Note that the 5G control device 3, 5G base station 4, and 5G terminal 5 illustrated in FIGS. 1 and 2 are omitted in FIG. 3 .

[0016] The data transfer units 11 and 21 transfer user data generated by the application. The communication quality measurement units 12 and 22 measure the communication quality for each of n communication lines (n is an integer equal to or greater than 1) over which communication device 1 and communication device 2 communicate. The measurement condition determination units 13 and 23 determine for each communication line whether the specified measurement conditions are met. The storage units 14 and 24 store the measurement conditions used when measuring communication quality and the measurement results of communication quality.

[0017] Next, the operation of communication devices 1 and 2 to measure communication quality will be described. Communication devices 1 and 2 transmit and receive measurement data for measuring communication quality and calculate communication quality from the results of transmitting and receiving the measurement data. At this time, communication devices 1 and 2 change the method of transmitting the measurement data depending on the user data generation status, etc. Specifically, when user data is not generated, i.e., when there is no user data to transfer, communication devices 1 and 2 transmit the measurement data alone. When user data is generated, communication devices 1 and 2 selectively transmit the measurement data together with the user data or transmit the measurement data separately from the user data depending on the size of the user data to be transferred and the measurement data.

[0018] 4 is a diagram showing an example of the configuration of transmission data on a route when communication devices 1 and 2 according to embodiment 1 transmit measurement data together with user data. In Fig. 4, the on-board application is an application that transmits and receives user data via an on-board communication device corresponding to communication device 1 shown in Figs. 1 to 3, and the ground application is an application that transmits and receives user data via a ground communication device corresponding to communication device 2 shown in Figs. 1 to 3.

[0019] For example, when an on-board communication device transmits measurement information, which is measurement data, to a trackside communication device, the on-board communication device receives a data packet containing user data from an on-board application, inserts the measurement information into the data packet, and forwards it to the 5G terminal. The 5G terminal adds PDU (Protocol Data Unit) layer information and 5G-AN (Access Network) layer information to the data packet received from the on-board communication device and forwards it to a 5G base station. The 5G base station receives a data packet from the 5G terminal and forwards it to a 5G control device. When the 5G control device receives a data packet from a 5G base station, it removes 5G-AN layer information from the received data packet, then adds GTP-U layer, UDP / IP layer, Layer 2 (L2), and Layer 1 (L1) information and forwards it. The trackside communication device receives a data packet with the same configuration as when it was forwarded by the on-board communication device, extracts measurement information from the received data packet, and forwards it to the trackside application. The configuration of the transmitted data when the trackside communication device transmits measurement information to the on-board communication device is also similar.

[0020] The measurement information transmitted and received between the on-board communication device and the wayside communication device varies depending on the type of communication quality to be measured (measurement content). An example of the measurement information is shown in Fig. 5. Fig. 5 is a diagram showing an example of the measurement information transmitted and received by the communication devices 1 and 2 according to the first embodiment for measuring communication quality.

[0021] As shown in Figure 5, when measuring packet loss, transmission delay, or jitter (transmission fluctuation) as communication quality, communication devices 1 and 2 use sequence numbers as elements of measurement information. When measuring throughput as communication quality, communication devices 1 and 2 use the transmission time and size of the measurement information as elements of measurement information. Measurement dummy data may be included in the elements of measurement information. For example, when measurement information is transmitted separately from user data, measurement dummy data may be included in the elements of measurement information. When measuring reception intervals as communication quality, measurement information does not need to be transmitted.

[0022] The maximum transfer size shown in Figure 4 is the maximum data size that can be transmitted in a single packet on the communication line between the on-board communication device and the wayside communication device, i.e., the maximum size of data that can be included in a packet. If the data size exceeds the maximum transfer size, packet splitting occurs. That is, the on-board communication device splits the data into two pieces and transmits the two pieces of data in two packets. Packet splitting occurs if the total size of the user data and measurement information (the "size of user data + measurement information" shown in the figure) is larger than the maximum transfer size. The maximum transfer size is set in advance for each communication line. Data transmission and reception in the configuration shown in Figure 4 is performed when the total size of the user data and measurement information is equal to or less than the maximum transfer size.

[0023] 6 and 7 are diagrams showing examples of the configuration of transmission data on a path when the communication devices 1 and 2 according to the first embodiment transmit measurement data separately from user data. Fig. 6 shows an example of the configuration of transmission data when the communication devices 1 and 2 according to the first embodiment transmit user data alone, and Fig. 7 shows an example of the configuration of transmission data when the communication devices 1 and 2 according to the first embodiment transmit measurement data alone.

[0024] As shown in Figure 6, when user data is transmitted alone, the transmission data exchanged between the on-board communication device and the wayside communication device has a structure in which the measurement information has been removed from the transmission data shown in Figure 4.

[0025] Also, as shown in Figure 7, when measurement information is transmitted alone, the transmission data transmitted and received between the on-board communication device and the wayside communication device has a configuration in which the user data transmitted and received between the on-board application and the wayside application is removed from the transmission data shown in Figure 4.

[0026] Next, the operation of communication devices 1 and 2 according to the first embodiment transmitting and receiving measurement data for measuring communication quality will be described. Specifically, the operation of one communication device transmitting measurement information to the other communication device and the other communication device returning information corresponding to the measurement information (hereinafter, this information will be referred to as measurement response information). Note that the operation when communication device 1 transmits measurement information to communication device 2 and communication device 2 returns measurement response information is the same as the operation when communication device 2 transmits measurement information to communication device 1 and communication device 1 returns measurement response information. Therefore, in this embodiment, as an example, the operation when communication device 1 transmits measurement information and communication device 2 returns measurement response information will be described.

[0027] FIG. 8 is a flowchart illustrating an example of an operation of the communication device 1 according to the first embodiment to transmit measurement information.

[0028] After starting operation, the communication device 1 first checks whether user data has been generated (step S11). That is, the communication device 1 checks whether there is user data generated by the above-described on-board application and held by the data transfer unit 11 to be transferred to the 5G terminal 5, in other words, whether the data transfer unit 11 holds user data waiting to be transferred to the communication line.

[0029] If user data is being generated (step S11: Yes), the communication device 1 checks whether a predetermined minimum measurement time has elapsed (step S12). This check is performed by the measurement condition determination unit 13. The minimum measurement time is the minimum value of the interval between transmissions of measurement information and is stored in the storage unit 14 as a measurement condition. The measurement condition determination unit 13 compares the time elapsed since the communication device 1 started operation or the time elapsed since the previous transmission of measurement information with the minimum measurement time. Note that the determination of whether the minimum measurement time has elapsed may be omitted between the time when the communication device 1 started operation and the first transmission of measurement information.

[0030] If the minimum measurement time has elapsed, i.e., if "minimum measurement time < elapsed time" is true (step S12: Yes), the measurement condition determination unit 13 checks whether the size condition is met (step S13). Specifically, the measurement condition determination unit 13 checks whether the total size of the generated user data and measurement information is equal to or less than the maximum transfer size described above. The maximum transfer size is stored in the storage unit 14 as a measurement condition. If the size condition is met (step S13: Yes), the measurement condition determination unit 13 notifies the communication quality measurement unit 12 that the size condition is met, and the communication quality measurement unit 12 generates measurement information and adds it to the user data (step S14). Next, the data transfer unit 11 transfers the user data with the measurement information added, i.e., a data packet including the measurement information and the user data, to the 5G terminal 5 (step S19). Note that the measurement information generated by the communication quality measurement unit 12 differs depending on the type of communication quality to be measured (measurement content), as described with reference to FIG. 5. The data packet transferred to the 5G terminal 5 reaches the communication device 2 via the 5G base station 4 and the 5G control device 3.

[0031] On the other hand, if the minimum measurement time has not elapsed, i.e., if the "minimum measurement time < elapsed time" is not true (step S12: No), the measurement condition determination unit 13 notifies the data transfer unit 11 that the user data will be transferred alone, and the data transfer unit 11 transfers the user data without measurement information, i.e., a data packet containing only the user data, to the 5G terminal 5 (step S19).

[0032] If no user data is generated (step S11: No), the measurement condition determination unit 13 checks whether a predetermined maximum measurement time has elapsed (step S15). The maximum measurement time is the maximum value of the interval between transmissions of measurement information, and is stored as a measurement condition in the storage unit 14. The maximum measurement time is set to a value greater than the minimum measurement time described above.

[0033] If the maximum measurement time has elapsed, i.e., if "maximum measurement time < elapsed time" is true (step S15: Yes), the measurement condition determination unit 13 notifies the communication quality measurement unit 12 that the maximum measurement time has elapsed, i.e., that the measurement information will be transmitted alone, and the communication quality measurement unit 12 generates only the measurement information (step S16) and outputs it to the data transfer unit 11. The data transfer unit 11 transfers a data packet including only the measurement information input from the communication quality measurement unit 12 to the 5G terminal 5 (step S19).

[0034] If the maximum measurement time has not elapsed, i.e., if the condition "maximum measurement time < elapsed time" is not satisfied (step S15: No), the communication device 1 returns to step S11 and repeats the above-described processing of steps S11 to S19. After transferring either or both of the user data and the measurement information in step S19, the communication device 1 returns to step S11 and repeats the above-described processing of steps S11 to S19.

[0035] Furthermore, if the total size of the user data and the measurement information does not conform to the above size condition (step S13: No), the measurement condition determination unit 13 checks whether the above-mentioned maximum measurement time has elapsed (step S17). If the maximum measurement time has elapsed (step S17: Yes), the measurement condition determination unit 13 notifies the communication quality measurement unit 12 and the data transfer unit 11 that the measurement information will be transmitted separately from the user data. The communication quality measurement unit 12 generates measurement information (step S18) and outputs it to the data transfer unit 11. The data transfer unit 11 transmits a data packet containing only the measurement information input from the communication quality measurement unit 12 to the 5G terminal 5, and transfers a data packet containing only the user data to the 5G terminal 5 (step S19). On the other hand, if the maximum measurement time has not elapsed (step S17: No), the measurement condition determination unit 13 notifies the data transfer unit 11 that the user data will be transferred alone, and the data transfer unit 11 transfers the data packet containing only the user data to the 5G terminal 5 (step S19). After transferring only the user data in step S19, and after transferring the user data and transmitting the measurement information separately, the communication device 1 returns to step S11 and repeats the processes of steps S11 to S19 described above.

[0036] The communication device 2 that has received the measurement information from the communication device 1 returns information corresponding to the received measurement information as measurement response information. Similar to when the communication device 1 sends response information, the communication device 2 returns the measurement response information to the communication device 1 together with the user data or separately depending on the user data generation status, the size of the generated user data, and the size of the measurement response information to be returned.

[0037] The measurement response information returned by the communication device 2 to the communication device 1 varies depending on the type of communication quality to be measured (measurement content). An example of the measurement response information is shown in Fig. 9. Fig. 9 is a diagram illustrating an example of measurement response information transmitted and received by the communication devices 1 and 2 according to the first embodiment for measuring communication quality.

[0038] As shown in Figure 9, when measuring packet loss as communication quality, the communication device 2 returns a reception sequence number, which is the sequence number of a received packet, to the communication device 1 as measurement response information. When measuring transmission delay or jitter as communication quality, the communication device 2 returns the sequence number of the received packet and the processing time from receiving the measurement information to generating the measurement response information to the communication device 1 as measurement response information. When measuring throughput as communication quality, the communication device 2 returns the measurement result of the throughput to the communication device 1 as measurement response information. Furthermore, when measuring the reception interval of data packets as communication quality, the communication device 2 returns the measurement result of the reception interval to the communication device 1 as measurement response information. The communication device 2 measures the communication quality corresponding to each measurement content shown in Figure 9 using a known method. The communication quality is measured, for example, by the communication quality measurement unit 22.

[0039] FIG. 10 is a flowchart illustrating an example of an operation of the communication device 2 according to the first embodiment to transmit measurement response information.

[0040] After starting operation, the communication device 2 first checks whether user data has been generated (step S21). That is, the communication device 2 checks whether there is user data generated by the above-mentioned ground application and held by the data transfer unit 21 to be transferred to the 5G control device 3, in other words, whether the data transfer unit 21 holds user data waiting to be transferred to the communication line.

[0041] If user data is generated (step S21: Yes), the communication device 2 checks whether the above-mentioned measurement information has been received from the communication device 1 (step S22).

[0042] If the measurement information has been received (step S22: Yes), the measurement condition determination unit 23 checks whether the size condition is met (step S23). Specifically, the measurement condition determination unit 23 checks whether the total size of the generated user data and the measurement response information is equal to or less than the maximum transfer size described above. The maximum transfer size is stored in the storage unit 24 as a measurement condition. If the size condition is met (step S23: Yes), the measurement condition determination unit 23 notifies the communication quality measurement unit 22 that the size condition is met, and the communication quality measurement unit 22 generates measurement response information and adds it to the user data (step S24). Next, the data transfer unit 21 transfers the user data to which the measurement response information has been added, i.e., a data packet including the measurement response information and the user data, to the 5G control device 3 (step S30). Note that the measurement response information generated by the communication quality measurement unit 22 differs depending on the type of communication quality to be measured (measurement content), as described with reference to FIG. 9. The data packet transferred to the 5G control device 3 reaches the communication device 1 via the 5G base station 4 and the 5G terminal 5.

[0043] On the other hand, if the measurement information has not been received (step S22: No), the measurement condition determination unit 23 notifies the data transfer unit 21 that the user data will be transferred alone, and the data transfer unit 21 transfers the user data without the measurement response information, i.e., the data packet containing only the user data, to the 5G control device 3 (step S30).

[0044] If no user data has been generated (step S21: No), the measurement condition determination unit 23 checks whether measurement information has been received (step S25). If measurement information has been received (step S25: Yes), the measurement condition determination unit 23 checks whether a predetermined maximum response transmission time has elapsed (step S26). The maximum response transmission time is the maximum time from receiving measurement information to transmitting measurement response information, and is stored in the storage unit 24 as a measurement condition. The measurement condition determination unit 23 compares the elapsed time from receiving measurement information from the communication device 1 with the maximum response transmission time.

[0045] If the maximum response transmission time has elapsed, i.e., if "maximum response transmission time < elapsed time" is true (step S26: Yes), the measurement condition determination unit 23 notifies the communication quality measurement unit 22 that the maximum response transmission time has elapsed, and the communication quality measurement unit 22 generates only measurement response information (step S27) and outputs it to the data transfer unit 21. The data transfer unit 21 transfers a data packet including only the measurement response information input from the communication quality measurement unit 22 to the 5G control device 3 (step S30). In this way, by configuring the system to transfer a data packet including only the measurement response information when the maximum response transmission time has elapsed, the frequency at which measurement response information is added to user data and transferred can be increased. This reduces the number of times packets are sent and received just for communication quality measurement, preventing an increase in network load.

[0046] If the measurement information has not been received (step S25: No) and the maximum response transmission time has not elapsed, i.e., if the condition "maximum response transmission time < elapsed time" is not met (step S26: No), the communication device 2 returns to step S21 and repeats the above-described processing of steps S21 to S30. After transferring either or both of the user data and the measurement response information in step S30, the communication device 2 returns to step S21 and repeats the above-described processing of steps S21 to S30.

[0047] Furthermore, if the total size of the user data and the measurement response information does not meet the above size condition (step S23: No), the measurement condition determination unit 23 checks whether the above-mentioned maximum response transmission time has elapsed (step S28). If the maximum response transmission time has elapsed (step S28: Yes), the measurement condition determination unit 23 notifies the communication quality measurement unit 22 and the data transfer unit 21 that the measurement response information will be transmitted separately from the user data. The communication quality measurement unit 22 generates measurement response information (step S29) and outputs it to the data transfer unit 21. The data transfer unit 21 transmits a data packet containing only the measurement response information input from the communication quality measurement unit 22 to the 5G terminal 5, and transfers a data packet containing only the user data to the 5G terminal 5 (step S30). On the other hand, if the maximum response transmission time has not elapsed (step S28: No), the measurement condition determination unit 23 notifies the data transfer unit 21 that the user data will be transferred alone, and the data transfer unit 21 transfers the data packet containing only the user data to the 5G terminal 5 (step S30). After the communication device 1 transfers only the user data in step S30, and after transferring the user data and transmitting the measurement response information separately, the communication device 1 returns to step S21 and repeats the processing of steps S21 to S30 described above.

[0048] 11 and 12 are sequence diagrams showing an example of the overall operation of the communication system 100 according to the first embodiment. The sequence diagram in Fig. 11 shows the first half of the overall operation, specifically, a measurement request operation for transmitting and receiving measurement information for measuring communication quality. In the example shown in Fig. 11 and 12, the on-board communication device transmits the above-mentioned measurement information, and the track-side communication device transmits the above-mentioned measurement response information.

[0049] Steps S50 to S61 in Fig. 11 show a measurement request operation in which the on-board communication device transmits measurement information to the wayside communication device. Steps S71 to S81 in Fig. 12 show a measurement response operation in which the wayside communication device transmits measurement response information to the on-board communication device.

[0050] [Measurement Request Operation] Suppose that user data is generated in the on-board application when a time Δt1 has elapsed since the on-board communication device last transmitted the measurement information (step S50). In this case, the on-board communication device selects a transmission method for the user data and the measurement information based on the relationship between the time Δt1 and the minimum measurement time, and the relationship between the size of the user data, the size of the measurement information, and the maximum transfer size.

[0051] Specifically, if (1) user data exists to be transferred and (1-1) time Δt1 > minimum measurement time, and (1-1-1) the size condition (total size of user data and measurement information ≦ maximum transfer size) is met, the on-board communication device generates measurement information (step S51), attaches it to the user data, and transmits it to the trackside communication device (step S52). The trackside communication device removes the measurement information attached to the received user data (step S53) and forwards the user data to the trackside application (step S59). On the other hand, if (1-1-2) the size condition is not met and (1-1-2-1) time Δt1 > maximum measurement time, the on-board communication device generates measurement information (step S54) and transmits the user data and measurement information separately to the trackside communication device (steps S55 and S56). The trackside communication device forwards the user data received in step S57 to the trackside application (step S59). Furthermore, if (1-1-2-2) the time Δt1 is not greater than the maximum measurement time, and if (1-2) the time Δt1 is not greater than the minimum measurement time, the on-board communication device transmits only the user data to the trackside communication device (steps S57 and S58). The trackside communication device transfers the user data received in steps S57 and S58 to the trackside application (step S59). Furthermore, if (2) there is no user data to transfer, and (2-1) the time Δt2 from the previous transmission of measurement information by the on-board communication device (step S50) to the present is greater than the maximum measurement time (Δt2 > maximum measurement time), the on-board communication device generates measurement information (step S60) and transmits only the measurement information to the trackside communication device (step S61).

[0052] 11 and 12, the operation of the wayside communication device when the previous measurement information is received from the on-board communication device in step S50 is omitted.

[0053] [Measurement Response Operation] Assume that user data is generated in the ground application when time Δt3 has elapsed since the ground communication device received the measurement information (step S52, S56, or S61). In this case, the ground communication device selects a transmission method for the user data and the measurement response information based on the relationship between time Δt3 and the maximum response transmission time, and the relationship between the size of the user data, the size of the measurement response information, and the maximum transfer size.

[0054] Specifically, if (3) user data to be transferred exists and (3-1) measurement information has been received, and (3-1-1) the size condition (the total size of the user data and the measurement response information ≦ the maximum transfer size) is met, the trackside communication device generates measurement response information (step S71), attaches it to the user data, and transmits it to the on-board communication device (step S72). The on-board communication device removes the measurement response information attached to the received user data (step S73) and forwards the user data to the on-board application (step S79). On the other hand, if (3-1-2) the size condition is not met, and (3-1-2-1) time Δt3 > the maximum response transmission time, the trackside communication device generates measurement response information (step S74) and transmits the user data and the measurement response information separately to the on-board communication device (steps S75 and S76). Furthermore, if (3-1-2-2) time Δt3 > the maximum response transmission time is not met, the trackside communication device transmits only the user data to the on-board communication device (step S77). The on-board communication device transfers the user data received in steps S75 and S77 to the on-board application (step S79).

[0055] Furthermore, (4) if there is no user data to transfer, and (4-1) if the measurement information has already been received, or (4-1-1) if the time Δt4 from the reception of the measurement information (step S52, S56 or S61) to the present is greater than the maximum response transmission time (Δt4 > maximum response transmission time), the trackside communication device generates measurement response information (step S80) and transmits only the measurement response information to the on-board communication device (step S81).

[0056] Although not shown in Figures 11 and 12, the communication quality measurement unit 22 of the wayside communication device that receives measurement information from the on-board communication device performs the following processing depending on the measurement content of the communication quality and generates measurement response information.

[0057] When the measurement content is "packet loss" shown in FIGS. 5 and 9, the communication quality measurement unit 22 holds the sequence number included in the received measurement information.

[0058] 5 and 9, the communication quality measurement unit 22 holds the sequence number included in the received measurement information and counts the processing time (Tb) from receiving the measurement information to generating the measurement response information.

[0059] 5 and 9, the communication quality measurement unit 22 calculates the throughput based on the reception time of the measurement information, the transmission time included in the received measurement information, and the size of the received measurement information, according to the following formula (1): Throughput = Size / (Reception time - Transmission time) (1)

[0060] When the measurement content is "throughput" shown in FIGS. 5 and 9, the communication quality measurement unit 22 calculates the reception interval of the measurement information based on the reception time of the measurement information.

[0061] On the other hand, the communication quality measurement unit 12 of the on-board communication device that has received the measurement response information from the trackside communication device performs the following processing according to the measurement content of the communication quality to evaluate the communication quality.

[0062] When the measurement content is “packet loss” as shown in FIG. 5 and FIG. 9, the communication quality measurement unit 12 checks the continuity of the sequence numbers included in the received measurement response information to calculate the packet loss rate from the number of packet losses, and records the result in the memory unit 14 as the communication quality evaluation result.

[0063] 5 and 9, when the measurement content is "transmission delay," the communication quality measurement unit 12 measures the time (Ta) from transmitting the corresponding measurement information to receiving the measurement response information. The communication quality measurement unit 12 also acquires the processing time (Tb) from receiving the measurement information to generating the measurement response information, which is included in the received measurement response information, calculates the transmission delay (Ta - Tb) based on the times Ta and Tb, and records the calculated transmission delay in the storage unit 14 as the communication quality evaluation result.

[0064] 5 and 9, when the measurement content is "jitter," the communication quality measurement unit 12 measures the time (Ta) from the transmission of the corresponding measurement information to the reception of the measurement response information when receiving the measurement response information. The communication quality measurement unit 12 also acquires the processing time (Tb) from the reception of the measurement information to the generation of the measurement response information, which is included in the received measurement response information, and calculates a transmission delay (Ta-Tb) based on the times Ta and Tb, and records (accumulates) this in the storage unit 14. The communication quality measurement unit 12 then calculates jitter based on the multiple transmission delays accumulated in the storage unit 14, and records this in the storage unit 14 as a communication quality evaluation result.

[0065] When the measurement content is "throughput" shown in FIGS. 5 and 9, the communication quality measuring unit 12 records the throughput measurement result included in the received measurement response information in the storage unit 14 as the communication quality evaluation result.

[0066] When the measurement content is "receive interval" shown in FIGS. 5 and 9, the communication quality measuring unit 12 records the receive interval measurement result included in the received measurement response information in the storage unit 14 as the communication quality evaluation result.

[0067] In this embodiment, the operation has been described in which on-board communication device 1 transmits measurement information and wayside communication device 2, which receives the measurement information, returns measurement response information. However, the operation is similar when wayside communication device 2 transmits measurement information and on-board communication device 1, which receives the measurement information, returns measurement response information. Furthermore, communication quality may be measured by both communication devices 1 and 2, or by only one of them. When only one of communication devices 1 and 2 measures communication quality, communication device 1 or 2 that measured the communication quality may notify the opposing communication device of the measurement result as necessary.

[0068] Next, a description will be given of the hardware configuration of the communication devices 1 and 2. Fig. 13 is a diagram illustrating an example of the hardware configuration of the communication devices 1 and 2 according to the first embodiment. Since the hardware configurations of the communication devices 1 and 2 are similar, the following description will be given using the communication device 1 as an example.

[0069] The communication device 1 includes a memory 91 , a processor 92 , a power supply circuit 93 , an application interface 95 , and a communication interface 94 .

[0070] The memory 91 is, for example, a non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable read-only memory (EPROM), or an electrically programmable programmable read-only memory (EEPROM). The processor 92 is, for example, a central processing unit (CPU), a processing unit, an arithmetic unit, a microprocessor, a microcomputer, or a digital signal processor (DSP). The power supply circuit 93 is an electronic circuit that generates power for the processor 92. The power supply circuit 93 may also supply power to components of the communication device 1 other than the processor 92.

[0071] The communication interface 94 is a circuit that is connected to the 5G terminal 5 and performs communication processing with the communication device 2 via the 5G terminal 5. The application interface 95 is a circuit that exchanges user data with an on-board application.

[0072] 3 is realized by a communication interface 94 and an application interface 95. The storage unit 14 shown in FIG.

[0073] The communication quality measurement unit 12 and the measurement condition determination unit 13 shown in FIG. 3 are realized by a processor 92 executing a program for operating these units. The functions of the communication quality measurement unit 12 and the measurement condition determination unit 13 are written as a program and stored in a memory 91. The processor 92 realizes the functions of the communication quality measurement unit 12 and the measurement condition determination unit 13 by reading and executing the program stored in the memory 91. This program can also be said to cause a computer to execute the procedures or methods of the communication quality measurement unit 12 and the measurement condition determination unit 13. The memory 91 is also used as a temporary memory when the processor 92 executes various processes. The program for operating the communication quality measurement unit 12 and the measurement condition determination unit 13 stored in the memory 91 may be provided to a user of the communication device 1 in a form written on a storage medium such as a CD (Compact Disc)-ROM or a DVD (Digital Versatile Disc)-ROM, or may be provided via a communication network.

[0074] Figure 13 shows the hardware configuration when communication devices 1 and 2 are realized using general-purpose memory 91 and processor 92, but it is also possible to realize communication devices 1 and 2 using dedicated processing circuits instead of memory 91 and processor 92.

[0075] FIG. 14 is a diagram illustrating another example of the hardware configuration of the communication devices 1 and 2 according to the first embodiment. In the hardware illustrated in FIG. 14, the memory 91 and the processor 92 illustrated in FIG. 13 are replaced with a dedicated processing circuit 96. The processing circuit 96 is a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit that combines these. For example, when the communication device 1 is realized using the hardware illustrated in FIG. 14, the communication quality measurement unit 12 and the measurement condition determination unit 13 are realized using the processing circuit 96. The same applies when the communication device 2 is realized using the hardware illustrated in FIG. 14.

[0076] Note that some of the functions of the communication quality measurement unit 12 and the measurement condition determination unit 13 of the communication device 1 may be realized by a dedicated processing circuit equivalent to the processing circuit 96 shown in Fig. 14, and the remaining functions may be realized by a general-purpose memory and processor equivalent to the memory 91 and processor 92 shown in Fig. 13. The same applies to the communication device 2.

[0077] As described above, when the communication devices 1 and 2 according to the present embodiment transmit measurement data (measurement information, measurement response information) to a peer communication device for communication quality measurement, they determine a transmission method based on the occurrence status of user data to be transmitted to the peer communication device, the size of the measurement data, and the size of the generated user data. For example, when transmitting measurement information, if the minimum measurement time indicating the minimum value of the measurement information transmission interval has elapsed at the time the user data is generated and the sum of the size of the user data and the size of the measurement information is equal to or less than the maximum transfer size set for the communication line being used, the communication devices 1 and 2 transmit the measurement information attached to the user data. If the sum of the size of the user data and the size of the measurement information is greater than the maximum transfer size, the communication devices 1 and 2 transmit the measurement information separately from the user data. According to the communication devices 1 and 2 according to the present embodiment, it is possible to transmit and receive measurement data and measure communication quality while minimizing the impact on user data transmission.

[0078] Second Embodiment Next, a communication device according to a second embodiment will be described. The configuration of the communication device according to the second embodiment is the same as that of the first embodiment (see FIG. 3), but part of the operation of the measurement condition determination unit differs from that of the first embodiment. Therefore, in this embodiment, the description of the parts common to the first embodiment will be omitted, and only the operation of the measurement condition determination units 13 and 23 that perform operations different from those of the first embodiment will be described. As in the first embodiment, an example will be described in which the on-board communication device 1 generates measurement information and transmits it to the on-board communication device 2.

[0079] The measurement condition determining unit 13 of the communication device 1 according to the second embodiment can set the minimum measurement time used when determining whether the minimum measurement time has elapsed in step S12 shown in Fig. 8 to a different value for each measurement content of communication quality. That is, the measurement condition determining unit 13 according to the second embodiment performs the process of determining whether the minimum measurement time has elapsed by using the minimum measurement time corresponding to the measurement content of communication quality from among a plurality of minimum measurement times prepared in advance.

[0080] An example of a plurality of minimum measurement times prepared in advance is shown in Fig. 15. Fig. 15 is a diagram showing an example of minimum measurement times used in the determination process by the measurement condition determination unit 13 according to the second embodiment.

[0081] 15, the minimum measurement time used by the measurement condition determining unit 13 when measuring packet loss is T1, the minimum measurement time used by the measurement condition determining unit 13 when measuring transmission delay is T2, the minimum measurement time used by the measurement condition determining unit 13 when measuring jitter is T3, and the minimum measurement time used by the measurement condition determining unit 13 when measuring transmission speed is T4. Note that two or more of T1 to T4 may be set to the same value.

[0082] The measurement condition determination unit 13 according to the second embodiment may further set the maximum measurement time used when determining whether the maximum measurement time has elapsed in step S15 shown in FIG. 8 as a value for each measurement content of communication quality.

[0083] This allows the communication device 1 to transmit the measurement information at different timings for each measurement content of communication quality. That is, the communication device 1 can transmit the measurement information at appropriate timings for each measurement content of communication quality.

[0084] The following shows an example of how to set the minimum and maximum measurement times when the minimum and maximum measurement times are set to different values ​​for each communication quality measurement item.

[0085] For example, if packet loss is to be measured frequently, the minimum and maximum measurement times for measuring packet loss are both set to small values.

[0086] Furthermore, if it is desired to make the intervals at which jitter is measured as equal as possible, the minimum measurement time for measuring jitter is set to a large value and the maximum measurement time is set to a small value (provided that the minimum measurement time is smaller than the maximum measurement time).

[0087] Furthermore, if it is desired to reduce the frequency of measuring the transmission speed in order to prevent an increase in the network load, both the minimum and maximum measurement times for measuring the transmission speed are set to large values.

[0088] In addition, both the minimum measurement time and the maximum measurement time used by the measurement condition determination unit 13 for the determination process may be set to different values ​​for each measurement content of communication quality, or only the minimum measurement time may be set to a different value for each measurement content of communication quality.

[0089] As described above, the communication devices 1 and 2 according to the present embodiment are capable of setting at least the minimum measurement time, which is used when determining whether the minimum measurement time has elapsed in step S12 shown in Fig. 8, and the maximum measurement time, which is used when determining whether the maximum measurement time has elapsed in step S15 shown in Fig. 8, for each measurement content of communication quality. The communication devices 1 and 2 according to the present embodiment are capable of transmitting measurement information at appropriate timing for each measurement content of communication quality, and therefore can achieve more accurate communication quality measurement than the first embodiment.

[0090] Third Embodiment Next, a communication device according to a third embodiment will be described. The configuration of the communication device according to the third embodiment is the same as that of the first embodiment (see FIG. 3), but part of the operation of the measurement condition determination unit differs from that of the first embodiment. Therefore, in this embodiment, a description of the parts common to the first embodiment will be omitted, and only the operation of the measurement condition determination units 13 and 23 that operate differently from that of the first embodiment will be described. As in the first and second embodiments, an example will be described in which the on-board communication device 1 generates measurement information and transmits it to the on-board communication device 2.

[0091] The measurement condition determining unit 13 of the communication device 1 according to the third embodiment can set a different value for each communication line as the minimum measurement time used when determining whether or not the minimum measurement time has elapsed in step S12 shown in Fig. 8. That is, the measurement condition determining unit 13 according to the third embodiment performs the process of determining whether or not the minimum measurement time has elapsed by using, from among a plurality of minimum measurement times prepared in advance, the minimum measurement time corresponding to the communication line whose communication quality is to be measured.

[0092] An example of a plurality of minimum measurement times prepared in advance is shown in Fig. 16. Fig. 16 is a diagram showing an example of the minimum measurement time used in the determination process by the measurement condition determination unit 13 according to the third embodiment. Fig. 16 shows an example in which there are two communication lines between the communication device 1 and the communication device 2.

[0093] 16, the minimum measurement time used by the measurement condition determination unit 13 when measuring the communication quality of communication line #1 is T1, and the minimum measurement time used when measuring the communication quality of communication line #2 is T2. Note that T1 and T2 may be set to the same value.

[0094] The measurement condition determining unit 13 according to the third embodiment may further set the maximum measurement time used when determining whether the maximum measurement time has elapsed in step S15 shown in FIG. 8 as a value for each communication line.

[0095] This allows the communication device 1 to transmit measurement information at different times for each communication line. That is, the communication device 1 can measure the communication quality by transmitting measurement information at an appropriate time for each communication line. Therefore, the frequency of measuring communication quality can be changed for each communication line, and for example, measurement can be performed more frequently for communication lines with unstable communication quality and less frequently for communication lines with stable communication quality.

[0096] An example of how to set the minimum and maximum measurement times when the minimum and maximum measurement times are set to different values ​​for each communication line is shown below.

[0097] For example, if communication line #1 shown in Figure 16 is a local 5G line and communication line #2 is a public 5G line, for the local 5G line (communication line #1), which does not incur communication charges, the minimum measurement time and maximum measurement time are both set to small values ​​so that the measurement information is transmitted more frequently.On the other hand, for the public 5G line (communication line #2), which incurs communication charges, the minimum measurement time and maximum measurement time are both set to large values ​​so that the measurement information is transmitted less frequently, thereby minimizing increases in communication charges.

[0098] In addition, both the minimum measurement time and the maximum measurement time used by the measurement condition determination unit 13 for the determination process may be set to different values ​​for each communication line, or only the minimum measurement time may be set to a different value for each communication line.

[0099] As described above, the communication devices 1 and 2 according to the present embodiment are capable of setting at least the minimum measurement time, which is used when determining whether the minimum measurement time has elapsed in step S12 shown in Fig. 8 , and the maximum measurement time, which is used when determining whether the maximum measurement time has elapsed in step S15 shown in Fig. 8 , for each communication line. The communication devices 1 and 2 according to the present embodiment are capable of transmitting measurement information at different frequencies for each communication line, thereby achieving more accurate communication quality measurement than in embodiment 1. Furthermore, the measurement information can be transmitted at a frequency that takes into account the communication charges for each communication line incurred when measuring communication quality.

[0100] Fourth Embodiment Next, a communication device according to a fourth embodiment will be described. The configuration of the communication device according to the fourth embodiment is the same as that of the first embodiment (see FIG. 3), but part of the operation of the measurement condition determination unit differs from that of the first embodiment. Therefore, in this embodiment, the description of the parts common to the first embodiment will be omitted, and only the operation of the measurement condition determination units 13 and 23 that perform operations different from those of the first embodiment will be described. As in the first to third embodiments, an example will be described in which the on-board communication device 1 generates measurement information and transmits it to the on-board communication device 2.

[0101] The measurement condition determining unit 13 of the communication device 1 according to the fourth embodiment can set a different value for each application type as the minimum measurement time used when determining whether or not the minimum measurement time has elapsed in step S12 shown in Fig. 8. That is, the measurement condition determining unit 13 according to the fourth embodiment performs a process of determining whether or not the minimum measurement time has elapsed by using, from among a plurality of minimum measurement times prepared in advance, the minimum measurement time corresponding to the application that creates the user data to be transferred.

[0102] An example of a plurality of minimum measurement times prepared in advance is shown in Fig. 17. Fig. 17 is a diagram showing an example of the minimum measurement times used in the determination process by the measurement condition determination unit 13 according to the fourth embodiment. Fig. 17 shows an example in which there are two types of applications that create user data to be transferred between the communication device 1 and the communication device 2.

[0103] 17, the minimum measurement time used by the measurement condition determination unit 13 when measuring the communication quality of a communication line that transfers user data of application #1 is T1, and the minimum measurement time used when measuring the communication quality of a communication line that transfers user data of application #2 is T2. Note that T1 and T2 may be set to the same value.

[0104] The measurement condition determining unit 13 according to the fourth embodiment may further set the maximum measurement time used when determining whether the maximum measurement time has elapsed in step S15 shown in FIG. 8 as a value for each application type.

[0105] This allows the communication device 1 to transmit measurement information at different timings for each application type. That is, the communication device 1 can measure communication quality by transmitting measurement information at appropriate timings for each application type. Therefore, the frequency of communication quality measurement can be changed for each application type. For example, it is possible to perform communication quality measurement more frequently for a communication line transferring an application that requires real-time performance, and to reduce the frequency of communication quality measurement for a communication line transferring an application that does not require real-time performance.

[0106] An example of a method for setting the minimum and maximum measurement times when the minimum and maximum measurement times are set to different values ​​for each application type is shown below.

[0107] 17, for example, if application #1 is a voice call and application #2 is a log transmission, for the voice call (application #1) that requires real-time performance, the minimum and maximum measurement times are both set to small values, so that the measurement information is transmitted more frequently.On the other hand, for the log transmission (application #2) that does not require real-time performance, the minimum and maximum measurement times are both set to large values, so that the measurement information is transmitted less frequently.

[0108] In addition, both the minimum measurement time and the maximum measurement time used by the measurement condition determination unit 13 for the determination process may be set to different values ​​for each application type, or only the minimum measurement time may be set to a different value for each application type.

[0109] As described above, the communication devices 1 and 2 according to the present embodiment are capable of setting at least the minimum measurement time for each application type, out of the minimum measurement time used to determine whether the minimum measurement time has elapsed in step S12 shown in Fig. 8 and the maximum measurement time used to determine whether the maximum measurement time has elapsed in step S15 shown in Fig. 8. The communication devices 1 and 2 according to the present embodiment are capable of transmitting measurement information at different frequencies for each application type, thereby achieving more accurate communication quality measurement than the first embodiment.

[0110] Fifth embodiment. Next, a communication device according to a fifth embodiment will be described. The configuration of the communication device according to the fifth embodiment is the same as that of the first embodiment (see FIG. 3), but part of the operation of the measurement condition determination unit differs from that of the first embodiment. Therefore, in this embodiment, the description of the parts common to the first embodiment will be omitted, and only the operation of the measurement condition determination units 13 and 23 that perform operations different from those of the first embodiment will be described. As in the first to fourth embodiments, an example will be described in which the on-board communication device 1 generates measurement information and transmits it to the on-board communication device 2.

[0111] The measurement condition determining unit 13 of the communication device 1 according to the fifth embodiment can set the minimum measurement time used when determining whether the minimum measurement time has elapsed in step S12 shown in Fig. 8 to a different value for each transmission protocol used. That is, the measurement condition determining unit 13 according to the fifth embodiment performs the process of determining whether the minimum measurement time has elapsed by using, from among a plurality of minimum measurement times prepared in advance, the minimum measurement time corresponding to the transmission protocol used in transferring user data.

[0112] An example of a plurality of minimum measurement times prepared in advance is shown in Fig. 18. Fig. 18 is a diagram showing an example of the minimum measurement times used in the determination process by the measurement condition determination unit 13 according to the fifth embodiment. Fig. 18 shows an example in which three types of transmission protocols are used in the user data transfer between the communication device 1 and the communication device 2.

[0113] 18, the minimum measurement time used by the measurement condition determining unit 13 when the transmission protocol is TCP (Transmission Control Protocol) is T1, the minimum measurement time used by the measurement condition determining unit 13 when the transmission protocol is UDP (User Datagram Protocol) is T2, and the minimum measurement time used by the measurement condition determining unit 13 when the transmission protocol is ICMP (Internet Control Message Protocol) is T3. Note that two or more of T1 to T3 may be set to the same value.

[0114] The measurement condition determination unit 13 according to the fifth embodiment may further set the maximum measurement time used when determining whether the maximum measurement time has elapsed in step S15 shown in FIG. 8 to a value that is different for each transmission protocol used.

[0115] This allows the communication device 1 to transmit measurement information at different timings for each transmission protocol used. That is, the communication device 1 can measure communication quality by transmitting measurement information at appropriate timings for each transmission protocol. Therefore, the frequency of communication quality measurement can be changed for each transmission protocol. For example, it is possible to perform communication quality measurement more frequently for a transmission protocol used for transferring user data that requires real-time performance, and to reduce the frequency of communication quality measurement for a transmission protocol used for transferring user data that does not require real-time performance.

[0116] An example of how to set the minimum and maximum measurement times when the minimum and maximum measurement times are set to different values ​​for each transmission protocol is shown below.

[0117] For example, if the three transmission protocols used are TCP, UDP, and ICMP as shown in Figure 18, ICMP is often used for status monitoring and has a high affinity with communication quality measurement, so the minimum and maximum measurement times are both set to small values ​​to increase the frequency of measurement information transmission. UDP does not have a session state and has the second highest affinity with communication quality measurement after ICMP, so the minimum and maximum measurement times are set to values ​​between those of ICMP and TCP. TCP has a session state and has a lower affinity with communication quality measurement than ICMP and UDP, so the minimum and maximum measurement times are set to larger values ​​than ICMP and UDP.

[0118] Both the minimum measurement time and the maximum measurement time used by the measurement condition determination unit 13 for the determination process may be set to different values ​​for each transmission protocol, or only the minimum measurement time may be set to a different value for each transmission protocol.

[0119] As described above, the communication devices 1 and 2 according to the present embodiment are capable of setting at least the minimum measurement time, which is used when determining whether the minimum measurement time has elapsed in step S12 shown in Fig. 8, and the maximum measurement time, which is used when determining whether the maximum measurement time has elapsed in step S15 shown in Fig. 8, for each transmission protocol. The communication devices 1 and 2 according to the present embodiment are capable of transmitting measurement information at different frequencies for each transmission protocol, and therefore can achieve more accurate communication quality measurement than the first embodiment.

[0120] Sixth embodiment. Next, a communication device according to a sixth embodiment will be described. The configuration of the communication device according to the sixth embodiment is the same as that of the first embodiment (see FIG. 3), but part of the operation of the measurement condition determination unit differs from that of the first embodiment. Therefore, in this embodiment, the description of the parts common to the first embodiment will be omitted, and only the operation of the measurement condition determination units 13 and 23 that operate differently from that of the first embodiment will be described. As with the first to fifth embodiments, an example will be described in which the on-board communication device 1 generates measurement information and transmits it to the on-board communication device 2.

[0121] The measurement condition determining unit 13 of the communication device 1 according to the sixth embodiment is capable of changing the minimum measurement time used when determining whether the minimum measurement time has elapsed in step S12 shown in Fig. 8, depending on the measurement result of communication quality. That is, the measurement condition determining unit 13 according to the sixth embodiment performs the process of determining whether the minimum measurement time has elapsed by using, from among a plurality of minimum measurement times prepared in advance, the minimum measurement time corresponding to the past communication quality measurement result.

[0122] An example of a plurality of minimum measurement times prepared in advance is shown in Fig. 19. Fig. 19 is a diagram showing an example of minimum measurement times used in the determination process by the measurement condition determination unit 13 according to the sixth embodiment.

[0123] In the example shown in Figure 19, the minimum measurement time used by the measurement condition determination unit 13 when the change amount A of communication quality calculated from past communication quality measurement results is less than threshold value #1 is T1, and the minimum measurement time used by the measurement condition determination unit 13 when the change amount A is greater than threshold value #1 and less than threshold value #2 is T2.

[0124] The measurement condition determination unit 13 according to the sixth embodiment may further be configured to be able to change the maximum measurement time used when determining whether the maximum measurement time has elapsed in step S15 shown in FIG. 8 in accordance with the measurement results of the communication quality.

[0125] This allows the communication device 1 to change the timing of transmitting the measurement information according to the measurement result of the communication quality. That is, the communication device 1 can measure the communication quality by transmitting the measurement information at a timing according to the amount of change in the communication quality. Therefore, for example, it is possible to perform an operation such as measuring the communication quality more frequently when the amount of change in the communication quality is large, and reducing the frequency of measuring the communication quality when the amount of change in the communication quality is small.

[0126] An example of a method for changing the minimum measurement time and the maximum measurement time according to the measurement results of communication quality is shown below.

[0127] For example, if the difference between the latest communication quality measurement result and the most recent communication quality measurement result is small, it is assumed that communication is stable, so the minimum measurement time and the maximum measurement time are both set to large values, and the frequency of transmission of measurement information is reduced.Also, if the difference between the latest communication quality measurement result and the most recent communication quality measurement result is large, it is assumed that communication is unstable, so the minimum measurement time and the maximum measurement time are both set to small values, and the frequency of transmission of measurement information is reduced.

[0128] In addition, both the minimum measurement time and the maximum measurement time used by the measurement condition determination unit 13 for the determination process may be changed depending on the measurement results of communication quality, or only the minimum measurement time may be changed depending on the measurement results of communication quality.

[0129] As described above, the communication devices 1 and 2 according to the present embodiment are capable of changing at least the minimum measurement time, which is used when determining whether the minimum measurement time has elapsed in step S12 shown in Fig. 8, and the maximum measurement time, which is used when determining whether the maximum measurement time has elapsed in step S15 shown in Fig. 8, in accordance with the measurement result of communication quality. The communication devices 1 and 2 according to the present embodiment are capable of transmitting measurement information at a frequency according to the communication quality, and therefore can achieve more accurate communication quality measurement than the first embodiment.

[0130] In each embodiment, an example in which the communication devices 1 and 2 are applied to a railway system has been described, but the application is not limited to railway systems. Also, in each embodiment, 5G has been described as an example, but the application is not limited to 5G, and the communication devices may be applied to similar mobile communication systems such as LTE (Long Term Evolution) and Wi-Fi (registered trademark).

[0131] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other, or part of the configuration may be omitted or modified without departing from the spirit of the invention. For example, two or more of the methods for setting the minimum measurement time and the maximum measurement time described in embodiments 2 to 6 may be combined to set only the minimum measurement time, or both the minimum measurement time and the maximum measurement time.

[0132] 1, 2 Communication device, 3 5G control device, 4 5G base station, 5 5G terminal, 10 Train, 11, 21 Data transfer unit, 12, 22 Communication quality measurement unit, 13, 23 Measurement condition determination unit, 14, 24 Storage unit, 100 Communication system.

Claims

1. A communication device comprising: a data transfer unit connected to a communication line and transferring user data of an application to the communication line; a communication quality measurement unit that measures the communication quality of the communication line; and a measurement condition determination unit that determines a method for transmitting the measurement data based on the size of the measurement data transmitted by the communication quality measurement unit when measuring the communication quality, the occurrence status of the user data, and the maximum transfer size of the communication line.

2. The communication device according to claim 1, wherein the maximum transfer size is the maximum size of data that can be transmitted in a single packet over the communication line.

3. The communication device according to claim 1 or 2, characterized in that, when there is forwarding user data, which is user data to be forwarded by the data forwarding unit to the communication line, and the elapsed time since the measurement data to be transmitted was last transmitted is greater than the minimum value of the transmission interval of the measurement data to be transmitted, if the sum of the size of the measurement data to be transmitted and the size of the forwarding user data is less than or equal to the maximum transfer size, selects a method of transmitting the measurement data to be transmitted attached to the forwarding user data, and if the sum is not less than or equal to the maximum transfer size, selects a method of transmitting the measurement data to be transmitted separately from the forwarding user data.

4. The communication device according to claim 3, wherein the minimum value can be set to a different value for each measurement content of communication quality by the communication quality measurement unit.

5. The communication device according to claim 3, wherein, when there are a plurality of communication lines, the minimum value can be set to a different value for each of the communication lines.

6. The communication device according to claim 3, wherein, when there are a plurality of applications, the minimum value can be set to a different value for each of the applications.

7. The communication device according to claim 3, wherein the minimum value can be set to a different value for each transmission protocol used in transmitting the user data.

8. The communication device according to claim 3, wherein the setting of the minimum value can be changed according to the result of measurement of communication quality by the communication quality measurement unit.

9. A communication device according to any one of claims 3 to 7, characterized in that, when the forwarding user data does not exist, the measurement condition determination unit determines to transmit the measurement data to be transmitted alone when the elapsed time reaches the maximum value of the transmission interval of the measurement data to be transmitted.

10. A communication quality measurement method executed by a communication device connected to a communication line and transferring user data of an application to the communication line, comprising: a first step of measuring the communication quality of the communication line; and a second step of determining a method of transmitting the measurement data based on the size of the measurement data to be transmitted when measuring the communication quality in the first step, the generation status of the user data, and the maximum transfer size of the communication line.

11. A control circuit constituting a communication device connected to a communication line and transferring user data of an application to said communication line, characterized in that the control circuit executes: a first step of measuring the communication quality of said communication line; and a second step of determining a method of transmitting said measurement data based on the size of the measurement data to be transmitted when measuring said communication quality in said first step, the generation status of said user data, and the maximum transfer size of said communication line.

12. A storage medium storing a program executed by a control circuit constituting a communication device that is connected to a communication line and transfers user data of an application to said communication line, wherein said program causes said control circuit to execute a first step of measuring the communication quality of said communication line, and a second step of determining a method of transmitting said measurement data based on the size of the measurement data to be transmitted when measuring said communication quality in said first step, the occurrence status of said user data, and the maximum transfer size of said communication line.

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