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

Technical Field

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

Background Art

[0002] In mobile communication such as railway communication, as the position of a communication device mounted on a moving object such as a train changes with the movement of the moving object, the radio quality and the communication quality fluctuate. Also, even when the position of the communication device does not change, the radio quality and the communication quality may fluctuate due to changes in the surrounding environment, the influence of communication of other communication devices, and the like. Therefore, the communication device appropriately measures the radio quality and the communication quality, and for example, when detecting a decrease in the communication quality, performs a process for recovering the communication quality.

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the technology described in Patent Document 1 does not take into account the effects of adding data for measuring communication quality to packets. Therefore, if communication quality is measured using the method described in Patent Document 1 while user data is being transferred, the bandwidth used by the communication line and the number of packets transferred will increase due to the transmission and reception of packets for measuring communication quality, which may increase the network load and affect the transfer of user data.

[0006] For example, measuring communication quality while the load on the communication equipment's packet forwarding process is high may result in user data being lost or delays increasing. Furthermore, adding communication quality measurement data to packets containing user data may exceed the data size limit for a single transfer, leading to data fragmentation (splitting the data into multiple packets) and potentially increasing network load.

[0007] This disclosure is made in view of the above, and aims to provide a communication device that can measure communication quality while minimizing the impact on user data transfer. [Means for solving the problem]

[0008] To solve the above-mentioned problems and achieve the objective, the communication device according to this disclosure includes a data transfer unit connected to a communication line and transferring application user data to the communication line, a communication quality measurement unit that measures the communication quality of the communication line, and a unit that, based on the size of the measurement data transmitted by the communication quality measurement unit when measuring the communication quality, the occurrence of user data, and the maximum transfer size of the communication line, the measurement data Which method should be used: sending the data attached to the user data, or sending the measurement data separately from the user data? It is characterized by comprising a measurement condition determination unit that determines the following: [Effects of the Invention]

[0009] The communication device described in this disclosure has the effect of enabling the measurement of communication quality while minimizing the impact on user data transfer. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram showing an example of application of the communication device according to Embodiment 1. [Figure 2] This diagram shows an overview of the operation of a system to which the communication device according to Embodiment 1 is applied. [Figure 3] This figure shows an example configuration of a communication system and communication device according to Embodiment 1. [Figure 4] This figure shows an example of the configuration of transmitted data along the path when the communication device according to Embodiment 1 transmits measurement data together with user data. [Figure 5] This figure shows an example of measurement information transmitted and received by the communication device according to Embodiment 1 for communication quality measurement. [Figure 6] This figure shows an example of the configuration of transmitted data when the communication device according to Embodiment 1 transmits user data independently. [Figure 7] This figure shows an example of the data structure when the communication device according to Embodiment 1 transmits measurement data independently. [Figure 8] A flowchart illustrating an example of the operation by which the communication device according to Embodiment 1 transmits measurement information. [Figure 9] This figure shows an example of measurement response information transmitted and received by the communication device according to Embodiment 1 for communication quality measurement. [Figure 10] A flowchart illustrating an example of the operation by which the communication device according to Embodiment 1 transmits measurement response information. [Figure 11] Sequence diagram showing an example of the overall operation (measurement request operation) of the communication system according to Embodiment 1. [Figure 12] Sequence diagram showing an example of the overall operation (measurement response operation) of the communication system according to Embodiment 1. [Figure 13] This figure shows an example of the hardware configuration of a communication device according to Embodiment 1. [Figure 14] This figure shows another example of the hardware configuration of the communication device according to Embodiment 1. [Figure 15] This figure shows an example of the minimum measurement time used in the determination process by the measurement condition determination unit according to Embodiment 2. [Figure 16] FIG. showing an example of the minimum measurement time used by the measurement condition determination unit according to Embodiment 3 in the determination process [Figure 17] FIG. showing an example of the minimum measurement time used by the measurement condition determination unit according to Embodiment 4 in the determination process [Figure 18] FIG. showing an example of the minimum measurement time used by the measurement condition determination unit according to Embodiment 5 in the determination process [Figure 19] FIG. showing an example of the minimum measurement time used by the measurement condition determination unit according to Embodiment 6 in the determination process

Embodiments for Carrying Out the Invention

[0011] Hereinafter, 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 based on the drawings.

[0012] Embodiment 1. FIG. 1 is a diagram showing an application example of the communication device according to Embodiment 1. The communication devices according to Embodiment 1 are, 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 corresponding to the fifth-generation mobile communication system (hereinafter referred to as the 5G (5th Generation) system). The communication device 1 is mounted on a moving body, the train 10. The communication device 2 is installed on the ground side, specifically, at a station, a communication equipment room, a command center, etc. 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 that is a base station of the 5G system. The 5G base station 4 is connected to a 5G control device 3 that forms the 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 in addition to the 5G control device 3, but their description is omitted in FIG. 1. In the following description, the communication device 1 may be referred to as an in-vehicle 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 train 10 moves, the relative positions of the 5G terminal 5 mounted on the train and the 5G base station 4 change. Consequently, the wireless quality between the 5G terminal 5 and the 5G base station 4 changes, and the communication quality between the onboard communication device and the ground communication device also changes. Therefore, as shown in Figure 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 onboard communication device and the ground communication device. These quality measurements may be performed in parallel with the transfer of user data between applications (labeled "apps" in Figure 2) that utilize communication devices 1 and 2. In this case, as mentioned above, communication quality measurements during user data transfer may affect user data transfer. Therefore, communication devices 1 and 2 perform communication quality measurements in a manner that takes into account the impact on user data transfer. Figure 2 is a diagram illustrating the operation overview of a system to which the communication device according to Embodiment 1 is applied.

[0015] Figure 3 shows an example configuration of the communication system 100 and communication devices 1 and 2 according to Embodiment 1. 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. 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 in Figure 3, the 5G control device 3, 5G base station 4, and 5G terminal 5 described in Figures 1 and 2 are omitted.

[0016] Data transfer units 11 and 21 process the transfer of user data generated by the application. Communication quality measurement units 12 and 22 measure the communication quality for each of the n communication lines (where n is an integer greater than or equal to 1) through which communication device 1 and communication device 2 communicate. Measurement condition determination units 13 and 23 determine whether the defined measurement conditions are met for each communication line. Storage units 14 and 24 store the measurement conditions used during communication quality measurement and the measurement results of the communication quality.

[0017] Next, the operation by which communication devices 1 and 2 measure communication quality will be explained. Communication devices 1 and 2 send and receive measurement data for measuring communication quality, and determine the communication quality from the results of sending and receiving the measurement data. At this time, communication devices 1 and 2 change the method of sending the measurement data according to the status of user data generation, etc. Specifically, if no user data has been generated, i.e., if there is no user data to be transferred, communication devices 1 and 2 send the measurement data alone. If user data has been generated, they use either sending the measurement data together with the user data or sending the measurement data separately from the user data, depending on the size of the user data to be transferred and the measurement data.

[0018] Figure 4 is a diagram showing an example of the configuration of transmitted data along the path when communication devices 1 and 2 according to Embodiment 1 transmit measurement data together with user data. In Figure 4, the in-vehicle application is an application that sends and receives user data via an in-vehicle communication device corresponding to communication device 1 shown in Figures 1 to 3, and the ground application is an application that sends and receives user data via a ground communication device corresponding to communication device 2 shown in Figures 1 to 3.

[0019] For example, when an in-vehicle communication device transmits measurement information, which is measurement data, to a ground communication device, the in-vehicle communication device receives a data packet containing user data from an in-vehicle application, inserts the measurement information into this 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 in-vehicle communication device and forwards it to the 5G base station. When the 5G base station receives the data packet from the 5G terminal, it forwards it to the 5G control unit. When the 5G control unit receives the data packet from the 5G base station, it removes the 5G-AN layer information from the received data packet, adds GTP-U layer, UDP / IP layer, Layer 2 (L2), and Layer 1 (L1) information, and forwards it. The ground communication device receives a data packet with the same configuration as when the in-vehicle communication device forwarded it, extracts the measurement information from the received data packet, and forwards it to the ground application. The configuration of the transmitted data is similar when the ground communication device transmits measurement information to the in-vehicle communication device.

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

[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 the sequence number as an element of the 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 the measurement information. Dummy data for measurement may be included as an element of the measurement information. For example, if measurement information is transmitted separately from user data, dummy data for measurement may be included as an element of the measurement information. When measuring reception interval as communication quality, it is not necessary to transmit measurement information.

[0022] The maximum transfer size shown in Figure 4 is the maximum data size that can be transmitted in a single packet over the communication line between the on-board communication device and the ground communication device, i.e., the maximum data size 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 will split the data into two and send the two split data packets. Packet splitting occurs if the total size of user data and measurement information (shown as "User Data + Measurement Information Size") exceeds the maximum transfer size. The maximum transfer size should be pre-set for each communication line. Data transmission and reception in the configuration shown in Figure 4 is performed when the total size of user data and measurement information is less than or equal to the maximum transfer size.

[0023] Figures 6 and 7 show examples of the configuration of transmitted data on the path when communication devices 1 and 2 according to Embodiment 1 transmit measurement data separately from user data. Figure 6 shows an example of the configuration of transmitted data when communication devices 1 and 2 according to Embodiment 1 transmit user data alone, and Figure 7 shows an example of the configuration of transmitted data when communication devices 1 and 2 according to Embodiment 1 transmit measurement data alone.

[0024] As shown in Figure 6, when user data is transmitted independently, the transmitted data sent and received between the on-board communication device and the ground communication device has a configuration in which the measurement information has been removed from the transmitted data shown in Figure 4.

[0025] Furthermore, as shown in Figure 7, when measurement information is transmitted independently, the transmitted data sent and received between the on-board communication device and the ground communication device is configured such that the user data sent and received between the on-board application and the ground application is removed from the transmitted data shown in Figure 4.

[0026] Next, we will describe the operation of communication devices 1 and 2 according to Embodiment 1 in which they send and receive measurement data for communication quality measurement, specifically, the operation in which one communication device sends measurement information to the other communication device, and the other communication device sends back information corresponding to the measurement information (hereinafter referred to as measurement response information). Note that the operation when communication device 1 sends measurement information to communication device 2 and communication device 2 sends back measurement response information is the same as the operation when communication device 2 sends measurement information to communication device 1 and communication device 1 sends back measurement response information. For this reason, in this embodiment, as an example, we will describe the operation when communication device 1 sends measurement information and communication device 2 sends back measurement response information.

[0027] Figure 8 is a flowchart showing an example of the operation in which the communication device 1 according to Embodiment 1 transmits 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 in-vehicle application described above that the data transfer unit 11 is holding for transfer to the 5G terminal 5, or in other words, whether the data transfer unit 11 is holding user data that is waiting to be transferred to the communication line.

[0029] If user data has been generated (Step S11: Yes), the communication device 1 checks whether the 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 interval between transmissions of measurement information and is stored as a measurement condition in the storage unit 14. The measurement condition determination unit 13 compares the elapsed time since the communication device 1 started operating, or the elapsed time since the last 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 start of operation of the communication device 1 and the first transmission of measurement information.

[0030] If the minimum measurement time has elapsed, that is, 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 less than or equal to 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, that is, the data packet containing the measurement information and the user data, to the 5G terminal 5 (Step S19). 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 explained using Figure 5. Data packets transferred to the 5G terminal 5 reach 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, that is, if "minimum measurement time < elapsed time" does not hold true (step S12: No), the measurement condition determination unit 13 notifies the data transfer unit 11 to transfer the user data alone, and the data transfer unit 11 transfers the user data without measurement information attached, that is, a data packet containing only the user data, to the 5G terminal 5 (step S19).

[0032] Furthermore, if no user data has been generated (Step S11: No), the measurement condition determination unit 13 checks whether the predetermined maximum measurement time has elapsed (Step S15). The maximum measurement time is the maximum value of the measurement information transmission interval and is stored as a measurement condition in the storage unit 14. Note that the maximum measurement time is set to a value greater than the minimum measurement time mentioned above.

[0033] When the maximum measurement time has elapsed, that is, when "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, that is, to transmit the measurement information alone. 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 containing only the measurement information input from the communication quality measurement unit 12 to the 5G terminal 5 (step S19).

[0034] Furthermore, if the maximum measurement time has not elapsed, that is, if "maximum measurement time < elapsed time" does not hold true (step S15: No), the communication device 1 returns to step S11 and repeats the processing of steps S11 to S19 described above. Also, after transferring one or both of the user data and measurement information in step S19, the communication device 1 returns to step S11 and repeats the processing of steps S11 to S19 described above.

[0035] Furthermore, if the total size of user data and measurement information does not meet the above size conditions (step S13: No), the measurement condition determination unit 13 checks whether the maximum measurement time described above 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 to transmit the measurement information separately from the user data. The communication quality measurement unit 12 generates the 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 also 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 to transfer the user data alone, and the data transfer unit 11 transfers a data packet containing only the user data to the 5G terminal 5 (step S19). After the communication device 1 has performed only the transfer of user data in step S19, and after performing the transfer of user data and the transmission of measurement information separately, it returns to step S11 and repeats the processing of steps S11 to S19 described above.

[0036] When communication device 2 receives measurement information from communication device 1, it sends back information corresponding to the received measurement information as measurement response information. Similar to when communication device 1 transmits response information, communication device 2 sends back the measurement response information to communication device 1 either together with the user data or by itself, depending on the status of user data generation, the size of the user data being generated, and the size of the measurement response information to be sent back.

[0037] The measurement response information that communication device 2 sends back to communication device 1 varies depending on the type of communication quality being measured (measurement content). An example of measurement response information is shown in Figure 9. Figure 9 is a diagram showing an example of measurement response information that communication devices 1 and 2 according to Embodiment 1 transmit and receive for communication quality measurement.

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

[0039] Figure 10 is a flowchart showing an example of the operation in which the communication device 2 according to Embodiment 1 transmits 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 terrestrial application described above that the data transfer unit 21 is holding for transfer to the 5G control device 3, or in other words, whether the data transfer unit 21 is holding user data that is waiting to be transferred to the communication line.

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

[0042] If 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 measurement response information is less than or equal to 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 with the measurement response information added, that is, the data packet containing the measurement response information and the user data, to the 5G control device 3 (Step S30). 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 explained using Figure 9. Data packets transferred to the 5G control device 3 reach the communication device 1 via the 5G base station 4 and the 5G terminal 5.

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

[0044] Furthermore, if no user data has been generated (Step S21: No), the measurement condition determination unit 23 checks whether or not measurement information has been received (Step S25). If measurement information has been received (Step S25: Yes), the measurement condition determination unit 23 checks whether or not the predetermined maximum response transmission time has elapsed (Step S26). The maximum response transmission time is the maximum value of the 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 since receiving measurement information from the communication device 1 with the maximum response transmission time.

[0045] When the maximum response transmission time has elapsed, that is, when "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 containing 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 containing only measurement response information when the maximum response transmission time has elapsed, the frequency of adding and transferring measurement response information to user data can be increased. This reduces the number of times packets are sent and received solely for the purpose of communication quality measurement, and prevents an increase in network load.

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

[0047] Furthermore, if the total size of the user data and the measurement response information does not meet the above size conditions (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 to transmit the measurement response information separately from the user data. The communication quality measurement unit 22 generates the 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 also 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 to transfer the user data alone, and the data transfer unit 21 transfers a data packet containing only the user data to the 5G terminal 5 (step S30). After the communication device 1 has transferred only the user data in step S30, and after it has transferred the user data and transmitted the measurement response information separately, it returns to step S21 and repeats the processing of steps S21 to S30 described above.

[0048] Figures 11 and 12 are sequence diagrams showing an example of the overall operation of the communication system 100 according to Embodiment 1. The sequence diagram in Figure 11 shows the first half of the overall operation, specifically the measurement request operation in which measurement information is sent and received for communication quality measurement. In the example shown in Figures 11 and 12, the on-board communication device sends the above-mentioned measurement information, and the ground communication device sends the above-mentioned measurement response information.

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

[0050] [Measurement request operation] Assume that user data has been generated in the in-vehicle application after a time Δt1 has elapsed since the previous transmission of measurement information by the in-vehicle communication device (step S50). In this case, the in-vehicle communication device selects a method for transmitting user data and measurement information based on the relationship between 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, (1) if user data to be transferred exists and (1-1) time Δt1 > minimum measurement time, and (1-1-1) if 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 ground communication device (step S52). The ground communication device removes the measurement information attached to the received user data (step S53) and transfers the user data to the ground application (step S59). On the other hand, (1-1-2) if 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 ground communication device (steps S55, S56). The ground communication device transfers the user data received in step S57 to the ground application (step S59). Furthermore, (1-1-2-2) if time Δt1 > maximum measurement time is not true, and (1-2) if time Δt1 > minimum measurement time is not true, the on-board communication device transmits only user data to the ground communication device (steps S57, S58). The ground communication device transfers the user data received in steps S57, S58 to the ground application (step S59). Also, (2) if there is no user data to transfer, and (2-1) if 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 ground communication device (step S61).

[0052] Note that in Figures 11 and 12, the operation of the ground communication device when it receives the previous measurement information from the on-board communication device in step S50 is omitted from the description.

[0053] [Measurement response behavior] Assume that user data has been generated in the ground application after a time Δt3 has elapsed since the ground communication device received measurement information (steps S52, S56, or S61). In this case, the ground communication device selects a method for transmitting the user data and 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, (3) if user data to be transferred exists and (3-1) measurement information has been received, and (3-1-1) the size condition (total size of user data and measurement response information ≤ maximum transfer size) is met, the ground 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 transfers the user data to the on-board application (step S79). On the other hand, (3-1-2) if the size condition is not met, and (3-1-2-1) time Δt3 > maximum response transmission time, the ground communication device generates measurement response information (step S74) and transmits the user data and measurement response information separately to the on-board communication device (steps S75, S76). Furthermore, if (3-1-2-2) time Δt3 > maximum response transmission time, the ground communication device transmits only 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 be transferred, and (4-1) measurement information has already been received, if (4-1-1) the time Δt4 from the receipt of measurement information (step S52, S56, or S61) to the present is greater than the maximum response transmission time (Δt4 > maximum response transmission time), the ground 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 ground communication device, which receives measurement information from the on-board communication device, performs the following processing according to the content of the communication quality measurement and generates measurement response information.

[0057] If the measurement content is "packet loss" as shown in Figures 5 and 9, the communication quality measurement unit 22 stores the sequence number included in the received measurement information.

[0058] When the measurement content is "transmission delay" and "jitter" as shown in Figures 5 and 9, the communication quality measurement unit 22 stores the sequence number included in the received measurement information. The communication quality measurement unit 22 also counts the processing time (Tb) from the reception of the measurement information to the generation of the measurement response information.

[0059] If the measurement content is "throughput" as shown in Figures 5 and 9, the communication quality measurement unit 22 calculates the throughput according to the following formula (1) 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. Throughput = Size / (Receive time - Send time) ... (1)

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

[0061] Meanwhile, the communication quality measurement unit 12 of the on-board communication device, which receives measurement response information from the ground communication device, performs the following processing according to the content of the communication quality measurement and evaluates the communication quality.

[0062] If the measurement content is "packet loss" as shown in Figures 5 and 9, the communication quality measurement unit 12 checks the continuity of the sequence numbers included in the received measurement response information, calculates the packet loss rate from the number of lost packets, and records it in the storage unit 14 as a communication quality evaluation result.

[0063] When the measurement content is "transmission delay" as shown in Figures 5 and 9, 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 it receives 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, calculates the transmission delay (Ta-Tb) based on the times Ta and Tb, and records it in the storage unit 14 as a communication quality evaluation result.

[0064] When the measurement content is "jitter" as shown in Figures 5 and 9, 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 it receives 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 the transmission delay (Ta-Tb) based on the times Ta and Tb and records (stores) it in the storage unit 14. Then, the communication quality measurement unit 12 calculates the jitter based on the multiple transmission delays stored in the storage unit 14 and records it in the storage unit 14 as a communication quality evaluation result.

[0065] If the measurement content is "throughput" as shown in Figures 5 and 9, the communication quality measurement 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] If the measurement content is the "reception interval" shown in Figures 5 and 9, the communication quality measurement unit 12 records the reception 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 described is when the on-board communication device 1 transmits measurement information and the ground communication device 2, which receives the measurement information, returns measurement response information. However, the operation is similar when the ground communication device 2 transmits measurement information and the on-board communication device 1, which receives the measurement information, returns measurement response information. Furthermore, the communication quality measurement may be performed by both communication devices 1 and 2, or by only one of them. If only one of the communication devices 1 or 2 measures the communication quality, the communication device 1 or 2 that measured the communication quality may notify the other communication device of the measurement result as necessary.

[0068] Next, the hardware configuration of communication devices 1 and 2 will be described. Figure 13 is a diagram showing an example of the hardware configuration of communication devices 1 and 2 according to Embodiment 1. Since the hardware configuration of communication devices 1 and 2 are the same, the following explanation will use the case of communication device 1 as an example.

[0069] The communication device 1 consists of 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 RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), or EEPROM (Electrically EPROM). The processor 92 is, for example, a CPU (Central Processing Unit), processing unit, arithmetic unit, microprocessor, microcomputer, or DSP (Digital Signal Processor). The power supply circuit 93 is an electronic circuit that generates the power to drive the processor 92. The power supply circuit 93 may also supply power to each part of the communication device 1 other than the processor 92.

[0071] The communication interface 94 is a circuit connected to the 5G terminal 5 and performs communication processing between the communication device 2 and the 5G terminal 5. The application interface 95 is a circuit that handles the exchange of user data between the in-vehicle application and the application.

[0072] The data transfer unit 11 of the communication device 1 shown in Figure 3 is implemented by a communication interface 94 and an application interface 95. The storage unit 14 shown in Figure 3 is implemented by a memory 91.

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

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

[0075] Figure 14 shows another example of the hardware configuration of communication devices 1 and 2 according to Embodiment 1. The hardware shown in Figure 14 replaces the memory 91 and processor 92 shown in Figure 13 with a dedicated processing circuit 96. The processing circuit 96 can be a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. For example, when implementing communication device 1 with the hardware shown in Figure 14, the communication quality measurement unit 12 and the measurement condition determination unit 13 are implemented by the processing circuit 96. The same applies when implementing communication device 2 with the hardware shown in Figure 14.

[0076] Furthermore, 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 implemented by a dedicated processing circuit corresponding to the processing circuit 96 shown in Figure 14, and the remainder may be implemented by a general-purpose memory and processor corresponding to the memory 91 and processor 92 shown in Figure 13. The same applies to the communication device 2.

[0077] As described above, when the communication devices 1 and 2 of this embodiment transmit measurement data (measurement information, measurement response information) to a counterpart communication device for communication quality measurement, they determine the transmission method based on the generation status of user data to be transmitted to the counterpart 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, which indicates the minimum value of the transmission interval for measurement information, has elapsed at the time user data is generated, and the sum of the size of the user data and the size of the measurement information is less than or equal to 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 of this embodiment, it is possible to transmit and receive measurement data while minimizing the impact on user data transfer and to measure communication quality.

[0078] Embodiment 2. Next, a communication device according to Embodiment 2 will be described. The configuration of the communication device according to Embodiment 2 is the same as that of Embodiment 1 (see Figure 3), but some of the operation of the measurement condition determination unit differs from that of Embodiment 1. For this reason, in this embodiment, the parts common to Embodiment 1 will be omitted from the explanation, and the operation of the measurement condition determination units 13 and 23, which operate differently from those in Embodiment 1, will be explained. As with Embodiment 1, an example will be described in which the on-board communication device 1 generates measurement information and transmits it to the ground communication device 2.

[0079] The measurement condition determination unit 13 of the communication device 1 according to Embodiment 2 allows the minimum measurement time used to determine whether or not the minimum measurement time has elapsed in step S12 shown in Figure 8 to be set to a different value for each communication quality measurement item. That is, the measurement condition determination unit 13 according to Embodiment 2 uses the minimum measurement time corresponding to the communication quality measurement item from among a plurality of minimum measurement times prepared in advance to perform the determination process of whether or not the minimum measurement time has elapsed.

[0080] Figure 15 shows examples of several pre-prepared minimum measurement times. Figure 15 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 Embodiment 2.

[0081] In the example shown in Figure 15, the minimum measurement time used by the measurement condition determination unit 13 when measuring packet loss is T1, the minimum measurement time used by the measurement condition determination unit 13 when measuring transmission delay is T2, the minimum measurement time used by the measurement condition determination unit 13 when measuring jitter is T3, and the minimum measurement time used by the measurement condition determination 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] In the second embodiment, the measurement condition determination unit 13 may further use the maximum measurement time used to determine whether the maximum measurement time has elapsed in step S15 shown in Figure 8 as a value for each communication quality measurement item.

[0083] This allows the communication device 1 to transmit measurement information at different timings depending on the type of communication quality measurement. In other words, the communication device 1 can transmit measurement information at the appropriate timing for each type of communication quality measurement.

[0084] The following is an example of how to set the minimum and maximum measurement times when the minimum and maximum measurement times differ depending on the type of communication quality measurement.

[0085] For example, if you want to measure packet loss frequently, set both the minimum and maximum measurement times for packet loss to small values.

[0086] Additionally, if you want to make the intervals for measuring jitter as equal as possible, set the minimum measurement time to a large value and the maximum measurement time to a small value (however, the minimum measurement time must be less than the maximum measurement time).

[0087] Furthermore, if you want to reduce the frequency of transmission speed measurements to suppress the increase in network load, set both the minimum and maximum measurement times for transmission speed measurements to large values.

[0088] The measurement condition determination unit 13 may set both the minimum and maximum measurement times used for the determination process to different values ​​for each communication quality measurement, or it may set only the minimum measurement time to a different value for each communication quality measurement.

[0089] As described above, the communication devices 1 and 2 according to this embodiment allow at least the minimum measurement time, which is used when determining whether the minimum measurement time has elapsed in step S12 shown in Figure 8, and the maximum measurement time, which is used when determining whether the maximum measurement time has elapsed in step S15 shown in Figure 8, to be set for each communication quality measurement item. Since the communication devices 1 and 2 according to this embodiment can transmit measurement information at an appropriate timing for each communication quality measurement item, they can achieve more accurate communication quality measurement compared to Embodiment 1.

[0090] Embodiment 3. Next, a communication device according to Embodiment 3 will be described. The configuration of the communication device according to Embodiment 3 is the same as that of Embodiment 1 (see Figure 3), but some of the operation of the measurement condition determination unit differs from that of Embodiment 1. For this reason, in this embodiment, the parts common to Embodiment 1 will be omitted from the explanation, and the operation of the measurement condition determination units 13 and 23, which operate differently from those in Embodiment 1, will be explained. As with Embodiments 1 and 2, an example will be described in which the on-board communication device 1 generates measurement information and transmits it to the ground communication device 2.

[0091] The measurement condition determination unit 13 of the communication device 1 according to Embodiment 3 allows the minimum measurement time used to determine whether or not the minimum measurement time has elapsed in step S12 shown in Figure 8 to be set to a different value for each communication line. That is, the measurement condition determination unit 13 according to Embodiment 3 uses the minimum measurement time corresponding to the communication line whose communication quality is to be measured from among a plurality of minimum measurement times prepared in advance to perform the determination process of whether or not the minimum measurement time has elapsed.

[0092] Figure 16 shows examples of several pre-prepared minimum measurement times. Figure 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 Embodiment 3. Figure 16 shows an example where there are two communication lines between communication device 1 and communication device 2.

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

[0094] In the third embodiment, the measurement condition determination unit 13 may further use a value for each communication line as the maximum measurement time used to determine whether or not the maximum measurement time has elapsed in step S15 shown in Figure 8.

[0095] This allows the communication device 1 to transmit measurement information at different timings for each communication line. In other words, the communication device 1 can measure communication quality by transmitting measurement information at appropriate timings for each communication line. Therefore, the frequency of communication quality measurement can be changed for each communication line. For example, it is possible to measure communication lines with unstable communication quality at a high frequency and reduce the measurement frequency for communication lines with stable communication quality.

[0096] The following is an example of how to set the minimum and maximum measurement times when the minimum and maximum measurement times differ for each communication line.

[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, then for the local 5G line (communication line #1), where no communication charges are incurred, both the minimum and maximum measurement times are set to small values ​​to increase the frequency of sending measurement information. On the other hand, for the public 5G line (communication line #2), where communication charges are incurred, both the minimum and maximum measurement times are set to large values ​​to decrease the frequency of sending measurement information and minimize the increase in communication charges.

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

[0099] As described above, the communication devices 1 and 2 according to this embodiment allow at least the minimum measurement time, which is used when determining whether the minimum measurement time has elapsed in step S12 shown in Figure 8, and the maximum measurement time, which is used when determining whether the maximum measurement time has elapsed in step S15 shown in Figure 8, to be set for each communication line. Since the communication devices 1 and 2 according to this embodiment can transmit measurement information at different frequencies for each communication line, they can achieve more accurate communication quality measurement compared to Embodiment 1. In addition, it is possible to transmit measurement information at a frequency that takes into account the communication charges for each communication line incurred during communication quality measurement.

[0100] Embodiment 4. Next, a communication device according to Embodiment 4 will be described. The configuration of the communication device according to Embodiment 4 is the same as that of Embodiment 1 (see Figure 3), but some of the operation of the measurement condition determination unit differs from that of Embodiment 1. For this reason, in this embodiment, the parts common to Embodiment 1 will be omitted from the explanation, and the operation of the measurement condition determination units 13 and 23, which operate differently from those in Embodiment 1, will be explained. As with Embodiments 1 to 3, an example will be described in which the on-board communication device 1 generates measurement information and transmits it to the ground communication device 2.

[0101] The measurement condition determination unit 13 of the communication device 1 according to Embodiment 4 allows the minimum measurement time used to determine whether or not the minimum measurement time has elapsed in step S12 shown in Figure 8 to be set to a different value for each application type. That is, the measurement condition determination unit 13 according to Embodiment 4 uses the minimum measurement time corresponding to the application that creates the user data to be transferred, from among a plurality of minimum measurement times prepared in advance, to perform the determination process of whether or not the minimum measurement time has elapsed.

[0102] Figure 17 shows examples of several pre-prepared minimum measurement times. Figure 17 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 Embodiment 4. Figure 17 shows an example where there are two types of applications that create user data to be transferred between communication device 1 and communication device 2.

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

[0104] In the measurement condition determination unit 13 according to Embodiment 4, the maximum measurement time used when determining whether or not the maximum measurement time has elapsed in step S15 shown in Figure 8 may be a value for each application type.

[0105] This allows the communication device 1 to transmit measurement information at different timings depending on the application type. In other words, the communication device 1 can transmit measurement information at an appropriate timing for each application type to measure communication quality. Therefore, the frequency of communication quality measurement can be changed for each application type. For example, communication lines that transfer applications requiring real-time performance can have their communication quality measured frequently, while communication lines that transfer applications that do not require real-time performance can have their communication quality measured less frequently.

[0106] The following is an example of how to set the minimum and maximum measurement times when they differ for each application type.

[0107] For example, if application #1 in Figure 17 is used for voice calls and application #2 for log transmission, then for voice calls (application #1), which require real-time performance, both the minimum and maximum measurement times should be set to small values ​​to increase the frequency of sending measurement information. On the other hand, for log transmission (application #2), which does not require real-time performance, both the minimum and maximum measurement times should be set to large values ​​to decrease the frequency of sending measurement information.

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

[0109] As described above, the communication devices 1 and 2 according to this embodiment allow at least the minimum measurement time, which is used to determine whether the minimum measurement time has elapsed in step S12 shown in Figure 8, and the maximum measurement time, which is used to determine whether the maximum measurement time has elapsed in step S15 shown in Figure 8, to be set for each application type. Since the communication devices 1 and 2 according to this embodiment can transmit measurement information at different frequencies for each application type, they can achieve more accurate communication quality measurement compared to Embodiment 1.

[0110] Embodiment 5. Next, a communication device according to Embodiment 5 will be described. The configuration of the communication device according to Embodiment 5 is the same as that of Embodiment 1 (see Figure 3), but some of the operation of the measurement condition determination unit differs from that of Embodiment 1. For this reason, in this embodiment, the parts common to Embodiment 1 will be omitted from the explanation, and the operation of the measurement condition determination units 13 and 23, which operate differently from those in Embodiment 1, will be explained. As with Embodiments 1 to 4, an example will be described in which the on-board communication device 1 generates measurement information and transmits it to the ground communication device 2.

[0111] The measurement condition determination unit 13 of the communication device 1 according to Embodiment 5 allows the minimum measurement time used to determine whether the minimum measurement time has elapsed in step S12 shown in Figure 8 to be set to a different value for each transmission protocol used. That is, the measurement condition determination unit 13 according to Embodiment 5 uses the minimum measurement time corresponding to the transmission protocol used for transferring user data from among a plurality of minimum measurement times prepared in advance to perform the determination process of whether the minimum measurement time has elapsed.

[0112] Figure 18 shows examples of several pre-prepared minimum measurement times. Figure 18 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 Embodiment 5. Figure 18 shows an example where there are three types of transmission protocols used for user data transfer between communication device 1 and communication device 2.

[0113] In the example shown in Figure 18, the minimum measurement time used by the measurement condition determination unit 13 when the transmission protocol is TCP (Transmission Control Protocol) is T1, the minimum measurement time used by the measurement condition determination unit 13 when the transmission protocol is UDP (User Datagram Protocol) is T2, and the minimum measurement time used by the measurement condition determination 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] In the 5th embodiment, the measurement condition determination unit 13 may further use a value for each transmission protocol used when determining whether the maximum measurement time has elapsed in step S15 shown in Figure 8.

[0115] This allows the communication device 1 to transmit measurement information at different timings depending on the transmission protocol used. In other words, the communication device 1 can measure communication quality by transmitting measurement information at an appropriate timing 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 measurements at a high frequency for transmission protocols used for transferring user data that requires real-time performance, and reduce the frequency of communication quality measurements for transmission protocols used for transferring user data that does not require real-time performance.

[0116] The following is an example of how to set the minimum and maximum measurement times when they differ for each transmission protocol.

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

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

[0119] As described above, the communication devices 1 and 2 according to this embodiment allow at least the minimum measurement time, which is used when determining whether the minimum measurement time has elapsed in step S12 shown in Figure 8, and the maximum measurement time, which is used when determining whether the maximum measurement time has elapsed in step S15 shown in Figure 8, to be set for each transmission protocol. Since the communication devices 1 and 2 according to this embodiment can transmit measurement information at different frequencies for each transmission protocol, they can achieve more accurate communication quality measurement compared to Embodiment 1.

[0120] Embodiment 6. Next, a communication device according to Embodiment 6 will be described. The configuration of the communication device according to Embodiment 6 is the same as that of Embodiment 1 (see Figure 3), but some of the operation of the measurement condition determination unit differs from that of Embodiment 1. For this reason, in this embodiment, the parts common to Embodiment 1 will be omitted from the explanation, and the operation of the measurement condition determination units 13 and 23, which operate differently from those in Embodiment 1, will be explained. As with Embodiments 1 to 5, an example will be described in which the on-board communication device 1 generates measurement information and transmits it to the ground communication device 2.

[0121] The measurement condition determination unit 13 of the communication device 1 according to Embodiment 6 allows the minimum measurement time used to determine whether or not the minimum measurement time has elapsed in step S12 shown in Figure 8 to be changed according to the communication quality measurement result. That is, the measurement condition determination unit 13 according to Embodiment 6 uses the minimum measurement time corresponding to past communication quality measurement results from among a plurality of minimum measurement times prepared in advance to perform the determination process of whether or not the minimum measurement time has elapsed.

[0122] Figure 19 shows examples of several pre-prepared minimum measurement times. Figure 19 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 Embodiment 6.

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

[0124] The measurement condition determination unit 13 according to Embodiment 6 may further allow the maximum measurement time used to determine whether or not the maximum measurement time has elapsed in step S15 shown in Figure 8 to be changed according to the measurement results of the communication quality.

[0125] This allows the communication device 1 to change the timing of transmitting measurement information according to the measurement results of the communication quality. In other words, the communication device 1 can measure the communication quality by transmitting measurement information at a timing corresponding to the amount of change in communication quality. Therefore, for example, it becomes possible to perform communication quality measurements frequently when the amount of change in communication quality is large, and reduce the frequency of communication quality measurements when the amount of change in communication quality is small.

[0126] The following is an example of how to change the minimum and maximum measurement times according to the communication quality measurement results.

[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 presumed that the communication is stable, so both the minimum and maximum measurement times are set to large values, and the frequency of sending measurement information is reduced. Conversely, if the difference between the latest communication quality measurement result and the most recent communication quality measurement result is large, it is presumed that the communication is unstable, so both the minimum and maximum measurement times are set to small values, and the frequency of sending measurement information is increased.

[0128] The measurement condition determination unit 13 may change both the minimum and maximum measurement times used in the determination process according to the communication quality measurement results, or it may change only the minimum measurement time according to the communication quality measurement results.

[0129] As described above, the communication devices 1 and 2 according to this embodiment can change at least the minimum measurement time, which is used when determining whether the minimum measurement time has elapsed in step S12 shown in Figure 8, and the maximum measurement time, which is used when determining whether the maximum measurement time has elapsed in step S15 shown in Figure 8, according to the results of the communication quality measurement. Since the communication devices 1 and 2 according to this embodiment can transmit measurement information at a frequency corresponding to the communication quality, they can achieve more accurate communication quality measurement compared to Embodiment 1.

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

[0131] The configurations shown in the above embodiments are examples only, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention. For example, two or more methods for setting the minimum and maximum measurement times described in Embodiments 2 to 6 may be combined to set only the minimum measurement time, or both the minimum and maximum measurement times. [Explanation of Symbols]

[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 data transfer unit connected to a communication line and transferring user data of an application to the communication line, A communication quality measurement unit for measuring the communication quality of the aforementioned communication line, A measurement condition determination unit determines, 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, whether to use a method of attaching the measurement data to the user data and transmitting it, or a method of transmitting the measurement data separately from the user data. A communication device characterized by comprising:

2. The maximum transfer size is defined as the maximum size of data that can be transmitted in a single packet on the aforementioned communication line. The communication device according to feature 1.

3. The measurement condition determination unit is, If there is user data to be transferred by the data transfer unit to the communication line, and the elapsed time since the last transmission of the measurement data to be transmitted is greater than the minimum transmission interval of the measurement data to be transmitted, then if the sum of the size of the measurement data to be transmitted and the size of the user data to be transmitted is less than or equal to the maximum transfer size, the unit selects to send the measurement data to be transmitted attached to the user data; otherwise, the unit selects to send the measurement data to be transmitted separately from the user data. A communication device according to claim 1 or 2.

4. The minimum value can be set to a different value for each type of communication quality measurement performed by the communication quality measurement unit. The communication device according to feature 3.

5. If there are multiple communication lines, The minimum value can be set to a different value for each communication line. The communication device according to feature 3.

6. If there are multiple applications, The minimum value can be set to a different value for each application. The communication device according to feature 3.

7. The minimum value can be set to a different value for each transmission protocol used to transmit the user data. The communication device according to feature 3.

8. The minimum value can be changed according to the communication quality measurement results from the communication quality measurement unit. The communication device according to feature 3.

9. The measurement condition determination unit is, If the aforementioned user data does not exist, and the elapsed time reaches the maximum transmission interval for the measurement data to be transmitted, it is decided to transmit the measurement data to be transmitted alone. The communication device according to feature 3.

10. A method for measuring communication quality performed by a communication device that is connected to a communication line and transfers user data of an application to the communication line, A first step is to measure the communication quality of the aforementioned communication line, A second step involves determining, based on the size of the measurement data to be transmitted when measuring the communication quality in the first step, the occurrence status of the user data, and the maximum transfer size of the communication line, whether to use a method of attaching the measurement data to the user data and transmitting it, or a method of transmitting the measurement data separately from the user data. A method for measuring communication quality, characterized by including the following:

11. A control circuit comprising a communication device connected to a communication line and transferring user data of an application to the communication line, A first step is to measure the communication quality of the aforementioned communication line, A second step involves determining, based on the size of the measurement data to be transmitted when measuring the communication quality in the first step, the occurrence status of the user data, and the maximum transfer size of the communication line, whether to use a method of attaching the measurement data to the user data and transmitting it, or a method of transmitting the measurement data separately from the user data. A control circuit characterized by performing the following actions.

12. A storage medium for storing a program executed by a control circuit that constitutes a communication device connected to a communication line and which transfers user data of an application to the communication line, The aforementioned program, A first step is to measure the communication quality of the aforementioned communication line, A second step involves determining, based on the size of the measurement data to be transmitted when measuring the communication quality in the first step, the occurrence status of the user data, and the maximum transfer size of the communication line, whether to use a method of attaching the measurement data to the user data and transmitting it, or a method of transmitting the measurement data separately from the user data. A storage medium characterized by causing the control circuit to execute the above.

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