Communication management device, communication management method, and mobile communication system

Abstract

The present invention provides a communication management device that can set a bitrate according to the communication bandwidth even when the communication bandwidth between the mobile device and the ground equipment fluctuates, thereby reducing distortion of images transmitted from the mobile device. [Solution] A communication management device for determining the bitrate when transmitting images from a camera 11 mounted on a railway vehicle 10, comprising a video transmission central control unit 21 which includes a prediction unit that predicts the communication bandwidth based on information about the state of the railway vehicle 10, and a determination unit that determines the bitrate when transmitting images from the railway vehicle 10 as a bitrate setting value based on the predicted communication bandwidth.

Description

Technical Field

[0001] The present invention relates to a communication management device, a communication management method, and a mobile communication system. In particular, the present invention relates to a communication management device and the like that manage the bit rate when transmitting the video of a camera mounted on a mobile body.

Background Art

[0002] In recent years, attempts have been made to transmit images taken by a mobile body to a ground device, store them in the ground device, and use them for various purposes. Examples of such purposes include learning cognitive processing based on images, checking for troubles inside the mobile body, and confirming the situation when an abnormality occurs in the mobile body.

[0003] Patent Document 1 discloses an in-vehicle server that acquires video data from a video recording device that records video data of a camera mounted on a mobile body traveling on a track and transfers the video data to a center device installed outside the mobile body. When this in-vehicle server acquires video request information from the center device, it receives mobile body state information indicating the state of the mobile body and the operation plan of the mobile body from the mobile body. Further, the in-vehicle server calculates a transfer deadline for each video data corresponding to the video request information using the mobile body state information and the operation plan with respect to the video request information. Furthermore, the in-vehicle server controls to transfer the corresponding video data in order from the ones with a closer calculated transfer deadline. The transfer includes at least any one of the transfer from the video recording device to the in-vehicle server and the transfer from the in-vehicle server to the center device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, the communication bandwidth between the mobile device and the ground equipment fluctuates as the mobile device moves. Therefore, if the bitrate used to transfer images from the mobile device to the ground equipment exceeds the communication bandwidth, the image may become distorted. The present invention aims to provide a communication management device, etc., that can set a bitrate according to the communication bandwidth even when the communication bandwidth between a mobile device and a ground device fluctuates, thereby reducing distortion of images transmitted from the mobile device. [Means for solving the problem]

[0006] To solve the above problems, the present invention provides a communication management device for determining the bitrate when transmitting images from a camera mounted on a mobile device, comprising: a prediction unit that predicts the communication bandwidth based on information about the state of the mobile device; and a determination unit that determines the bitrate when transmitting images from the mobile device as a bitrate setting value based on the predicted communication bandwidth. In this case, even if the communication bandwidth between the mobile device and the ground device fluctuates, the bitrate can be set according to the communication bandwidth, and a communication management device can be provided that makes it less likely for images transmitted from the mobile device to be distorted.

[0007] Here, for example, the prediction unit predicts the communication bandwidth based on predetermined communication metrics according to the position of the mobile object. In this case, the communication bandwidth can be predicted more accurately based on past communication metrics. Furthermore, for example, if the prediction unit can acquire communication metrics from other mobile objects located at the destination, it will predict the communication bandwidth using the acquired communication metrics from those other mobile objects instead of predetermined communication metrics. In this case, the acquired communication metrics from those other mobile objects can be used to predict the most recent communication bandwidth. Furthermore, for example, if the moving object is a railway vehicle, the prediction unit predicts the communication bandwidth by adding at least one of the congestion rate of the next station, the occupancy rate of the railway vehicle, and the time of day. In this case, the communication bandwidth can be predicted according to the conditions of the railway line on which the railway vehicle is traveling. Furthermore, for example, the decision unit predicts the bitrate, and if the predicted bitrate exceeds the predicted bandwidth, it sets the bitrate to a value below the predicted bandwidth. In this case, the image transmitted from the moving object becomes even less prone to distortion. For example, if the predicted bitrate does not exceed the predicted bandwidth, the decision unit determines whether the predicted bitrate exceeds the current bitrate. If it does, it determines the bitrate setting value based on the predicted bandwidth or the predicted bitrate. In this case, a more appropriate bitrate setting value can be determined, making it less likely for images transmitted from a moving object to be distorted.

[0008] Furthermore, the present invention relates to a communication management method for determining the bitrate when transmitting images from a camera mounted on a mobile device. In this method, a processor executes a program stored in memory to predict the communication bandwidth based on information about the state of the mobile device, and then determines the bitrate when transmitting images from the mobile device as a bitrate setting value based on the predicted communication bandwidth. In this case, even if the communication bandwidth between the mobile device and the ground equipment fluctuates, the bitrate can be set according to the communication bandwidth, providing a communication management method that reduces the likelihood of image distortion when transmitting from the mobile device.

[0009] Here, for example, the communication bandwidth is predicted based on predetermined communication metrics according to the location of the mobile object. In this case, the communication bandwidth can be predicted more accurately based on past communication metrics. Furthermore, if, for example, communication metrics of other mobile devices located at the destination can be obtained, the communication bandwidth is predicted using the obtained communication metrics of those other mobile devices instead of predetermined communication metrics. In this case, the communication bandwidth of the immediate vicinity can be predicted using the obtained communication metrics of those other mobile devices. Furthermore, for example, if the moving object is a railway vehicle, the communication bandwidth is predicted by adding at least one of the following: the congestion rate of the next station, the occupancy rate of the railway vehicle, and the time of day. In this case, the communication bandwidth can be predicted according to the conditions of the railway line on which the railway vehicle is traveling. Furthermore, for example, the bitrate is predicted, and if the predicted bitrate exceeds the predicted bandwidth, the bitrate setting is set to be below the predicted bandwidth. In this case, the image transmitted from the moving object becomes even less likely to be distorted. Furthermore, for example, if the predicted bitrate does not exceed the predicted bandwidth, the system determines whether the predicted bitrate exceeds the current bitrate. If it does, it determines the bitrate setting based on the predicted bandwidth or the predicted bitrate. In this case, a more appropriate bitrate setting can be determined, reducing the likelihood of image distortion when transmitting from a moving object.

[0010] Furthermore, the present invention provides a mobile communication system comprising: an on-board device disposed on a mobile body equipped with a camera and transmitting video captured by the camera; and a ground device that receives video transmitted from the on-board device, wherein the ground device comprises a prediction unit that predicts the communication bandwidth based on information about the state of the mobile body, and a determination unit that determines the bitrate to be used when transmitting images from the mobile body as a bitrate setting value based on the predicted communication bandwidth. In this case, even if the communication bandwidth between the mobile body and the ground device fluctuates, a bitrate can be set according to the communication bandwidth, and a communication management method can be provided that makes it less likely for images transmitted from the mobile body to be distorted.

[0011] Here, the on-board equipment adjusts the bitrate setting sent from the ground equipment based on the presence or absence of an event and the round-trip time. In this case, an even more appropriate bitrate setting can be determined. [Effects of the Invention]

[0012] According to the present invention, even if the communication bandwidth between a mobile device and a ground device fluctuates, it is possible to set a bitrate according to the communication bandwidth, and a communication management device that makes it less likely for images transmitted from a mobile device to be distorted can be provided. [Brief explanation of the drawing]

[0013] [Figure 1]It is a block diagram showing the overall configuration of the mobile communication system in this embodiment. [Figure 2] It is a diagram exemplifying a route map on which a railway vehicle travels and the train position. [Figure 3] It is a diagram showing a mobile metric table. [Figure 4] It is a diagram showing a communication metric table. [Figure 5] It is a diagram showing a video metric table. [Figure 6] It is a diagram showing a section-effective bandwidth table. [Figure 7] It is a flowchart explaining the operation of the video transfer central control unit of the center server. [Figure 8] It is a flowchart explaining the operation of the video transfer control unit of the on-vehicle server. [Figure 9] In S703 of FIG. 7, it is a flowchart explaining in detail the process in which the video transfer central control unit predicts the communication bandwidth.

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0015] <Explanation of the Overall Configuration of the Mobile Communication System 1> FIG. 1 is a block diagram showing the overall configuration of the mobile communication system 1 in this embodiment. The illustrated mobile communication system 1 includes a railway vehicle 10 which is an example of a mobile body, and a center server 20 which is an example of a ground device and a communication management device. The railway vehicle 10 further includes cameras 11a to 11d, video recording devices 12a to 12b, a train information management device 13, and on-vehicle servers 14a to 14b. Hereinafter, when not distinguishing each of the cameras 11a to 11d, they will simply be referred to as camera 11. Also, when not distinguishing each of the video recording devices 12a to 12b, they will simply be referred to as video recording device 12. Furthermore, when not distinguishing each of the on-vehicle servers 14a to 14b, they will simply be referred to as on-vehicle server 14.

[0016] Camera 11 photographs the outside or inside of the railway vehicle 10. Camera 11 is, for example, a front monitoring camera that photographs the front of the railway vehicle 10. In this case, for example, the front monitoring camera can detect obstacles on the track. The front monitoring camera may be a monocular camera, or may be a stereo camera with a plurality of cameras arranged at a predetermined distance apart. Also, camera 11 is, for example, a side vehicle camera attached to the side of the railway vehicle 10. In this case, for example, by projecting the photographed video onto a monitor or the like installed on the driver's cab, it is possible to confirm the boarding and alighting of passengers from the driver's seat. Furthermore, camera 11 is, for example, an in-vehicle camera that photographs the inside of the railway vehicle 10. Thereby, for example, it is possible to detect the situation inside the vehicle and abnormalities inside the vehicle. A plurality of cameras 11 may be provided in one formation of the railway vehicle 10. Also, the video photographed by camera 11 may be either a moving image or a still image.

[0017] The video recording device 12 is a device that is connected to the camera 11 and records the video data photographed by the camera 11. The video recording device 12 has a video data storage unit 121. The video data storage unit 121 is, for example, a storage such as a HDD (Hard Disk Drive) or SSD (Solid State Drive), and stores the video data.

[0018] The train information management device 13 manages data related to the operation and status of railway vehicles. The train information management device 13 has a mobile vehicle status storage unit 131. The mobile vehicle status storage unit 131 is a storage unit, similar to the video data storage unit 121, and stores, for example, the mileage indicating the location of the railway vehicle 10, the occupancy rate, and event information such as delays and malfunctions.

[0019] The on-board server 14 is an example of an on-board device that is installed in a railway vehicle 10 equipped with a camera 11 and transmits video footage captured by the camera 11. The on-board server 14 is connected to a video recording device 12 and a train information management device 13, and processes the data sent from these devices and controls the transmission of this information to the central server 20. The on-board server 14 may be installed in each of the railway vehicles 10, or in each train set. The on-board server 14 includes a video processing unit 141, a video transfer control unit 142, a video transmission unit 143, and a metrics transmission unit 144. The on-board server 14 also includes a mobile status table 145, a communication status table 146, and a video status table 147. The video processing unit 141 processes the video data acquired from the video recording device 12. For example, the video processing unit 141 can change the resolution of the video data or combine multiple videos into one. The video transfer control unit 142 controls the acquisition of video data from the video recording device 12. The video transfer control unit 142 also controls the transfer of video to the central server 20. In this process, the video transfer control unit 142, for example, changes the output video bitrate when transmitting the acquired video data to the central server 20. The video transmission unit 143 transmits video data to the center server 20. Data transmission is performed wirelessly. A dedicated line may be used, but public communication networks such as LTE (Long Term Evolution) or 5G can also be used. The metrics transmission unit 144 transmits the data stored in the mobile status table 145, the communication status table 146, and the video status table 147 as metrics to the center server 20.

[0020] The mobile vehicle status table 145 is a table that stores data related to the operation and status of railway vehicles. The mobile vehicle status table 145 obtains this data from the train information management device 13. Specifically, the mobile vehicle status table 145 stores the mileage indicating the location of the railway vehicle 10, the occupancy rate, and event information such as delays and disruptions. The communication status table 146 is a table that stores data on the communication status between the railway vehicle 10 and the central server 20. The communication status data includes, for example, available bandwidth, packet loss rate, and round trip time. The video status table 147 is a table that stores data related to the status of the video. This data includes, for example, the camera ID, which is the ID of the camera 11 that acquires the video data; the input video bitrate, which is the bitrate of the video data acquired from camera 11; and the output video bitrate, which is the bitrate of the video data to be transmitted to the center server 20.

[0021] The mobile status table 145, the communication status table 146, and the video status table 147 are updated, for example, every second. However, the metrics transmission unit 144 transmits the data stored in these tables to the center server 20 as metrics, for example, once every minute, and the data for that minute is statistically processed (average, maximum, minimum, etc.).

[0022] The center server 20 receives video transmitted from the on-board server 14. The center server 20 comprises a video transmission central control unit 21, a video receiving unit 22, and a metrics receiving unit 23. The center server 20 also comprises a mobile metrics table 24, a communication metrics table 25, a video metrics table 26, a section-effective bandwidth table 27, a mobile status table 28, and a station status table 29.

[0023] The video transmission central control unit 21 controls the reception of video from the railway vehicle 10. The video transmission central control unit 21 also determines the output video bitrate when transmitting video data to the center server 20. This process will be described in more detail later. The video receiving unit 22 receives video data from the video transmitting unit 143 of the railway vehicle 10. The metrics receiver 23 receives metrics data from the metrics transmitter 144 of the railway vehicle 10. Specifically, it receives statistically processed data from the mobile status table 145, the communication status table 146, and the video status table 147.

[0024] The mobile device metrics table 24 is a table that stores data from the mobile device status table 145 that has been statistically processed from the metrics data received by the metrics receiving unit 23. The communication metrics table 25 is a table that stores the data from the communication status table 146 that has been statistically processed from the metrics data received by the metrics receiving unit 23. The video metrics table 26 is a table that stores the data from the video status table 147 that has been statistically processed from the metrics data received by the metrics receiving unit 23. The section-effective bandwidth table 27 is a table created based on past metrics for each section on which the railway vehicle 10 travels. The mobile metrics table 24, communication metrics table 25, video metrics table 26, and segment-effective bandwidth table 27 will be discussed in more detail later.

[0025] The mobile status table 28 is a table that stores data on the status of the railway vehicle 10. Here, data on train formation, mileage, and occupancy rate are stored. The station status table 29 is a table that stores data about the status of each station obtained from each station. Figure 1 shows that congestion rates are obtained from stations A and B, and the data for the station, platform, and congestion rate is stored.

[0026] Figure 2 is an example diagram illustrating the route map and train position on which the railway vehicle 10 travels. The illustrated route includes stations A through E, with the distances from each station being 0, 3, 5, 8, and 10 km, respectively, starting from station A. The section from station A to station C is underground, while the section from station C to station E is above ground. Figure 2 shows the case where trains X and Y, which are railway vehicles 10, are traveling on this line. Train X is traveling towards station B in the section between station A and station B, and train Y is traveling towards station D in the section between station D and station E. Note that the positions of trains X and Y shown are just examples, and their positions will of course change over time. Examples of the mobile metrics table 24, communication metrics table 25, video metrics table 26, and section-effective bandwidth table 27 for such routes and trains X and Y are shown below.

[0027] <Explanation of the data structure of data used in mobile communication system 1> Figure 3 shows the mobile metrics table 24. The mobile metrics table 24 consists of the following items: train composition, distance traveled, occupancy rate, route, and date and time. The "Formation" field is, for example, an identifier for railway vehicle 10, and in this case, indicates data for train X or train Y. The "Kilometers" field indicates the location of train X or train Y. Here, it indicates the location of train X or train Y as the distance from station A. The "Occupancy Rate" field is the occupancy rate of train X or train Y. The "Section" field indicates which stations the train is traveling between. The "Date and Time" field is the date and time the above data was acquired.

[0028] For example, the first column of the mobile metrics table 24 indicates that, at 10:00 AM on September 27, 2024, train X is running on this line as a train formation, and train X is at a distance of 0 kilometers. It also indicates that train X has an occupancy rate of 60% and is between stations A and B.

[0029] Figure 4 shows the communication metrics table 25. The communication metrics table 25 consists of the following items: configuration, available bandwidth [MBPS], packet loss rate [%], round trip time [s], segment, and date and time. The configuration, section, and date / time are the same as in Figure 3. The available bandwidth [MBPS], packet loss rate [%], and round-trip time [s] represent the communication status between the railway vehicle 10 and the central server 20.

[0030] For example, the first column of communication metrics table 25 indicates that, on the date and time of 2024 / 09 / 27 10:00, the available bandwidth (available communication bandwidth) [MBPS], packet loss rate [%], and round trip time [s] for train X are 12.5, 0.00, and 0.10, respectively, and that train X is between station A and station B.

[0031] Figure 5 shows the video metrics table 26. The video metrics table 26 consists of the following items: train formation, car number, camera ID, camera type, input video bitrate, output video bitrate, and time. The train configuration is the same as in Figures 3 and 4. The car number indicates which car of the train 10 shown in the configuration has the camera 11 installed. The camera ID is the ID assigned to each camera 11. The camera type is the subject of the camera 11's photography, and here it indicates that it photographs the front or interior of train X,Y. The input video bitrate is the bitrate of the video data input from each camera 11 to the onboard server 14. The output video bitrate is the bitrate for each camera 11 when the onboard server 14 outputs video data to the central server 20. The time is the time when the above data was acquired.

[0032] For example, the first column of the mobile metrics table 24 shows that, on the date and time of 2024 / 09 / 27 10:00, camera 11, which is located in car 1 of train X, has camera ID and camera type 101, and is facing forward, has an input video bitrate of 10.0kbps and an output video bitrate of 3.2kbps, respectively. The communication bandwidth between a mobile device and ground equipment fluctuates as the mobile device moves. Factors that reduce the available bandwidth include, for example, locations with obstacles between the mobile device and the base station, such as elevated highways; locations without nearby base stations, such as areas with few houses; locations with many people accessing the base station, such as train stations; areas with high packet loss rates or round-trip times; and underground sections. In this embodiment, a section-effective bandwidth table 27 is created based on past metrics to represent the available bandwidth for each predetermined section, and the reduction in available bandwidth is predicted in advance.

[0033] Figure 6 shows the interval-effective bandwidth table 27. The section-effective bandwidth table 27 consists of entries for station and time period. A station indicates a section of track, and here it is defined as the section between two adjacent stations. Time zones are expressed in two ways here: morning and noon. For example, the first column of the section-effective bandwidth table 27 shows that the historical available bandwidth for the section between station A and station B was 15.53 kbps during the morning hours and 35.03 kbps during the evening hours. The section-effective bandwidth table 27 is updated periodically by statistically processing the metrics.

[0034] <Explanation of the operation of mobile communication system 1> Figure 7 is a flowchart illustrating the operation of the video transfer central control unit 21 of the center server 20. Here, the video transmission central control unit 21 repeats the processing of S701 to S708 for the number of moving railway vehicles 10. First, the video transmission central control unit 21 acquires the status of the moving railway vehicle 10 (S701). This data is stored, for example, in the mobile vehicle metrics table 24, the communication metrics table 25, and the video metrics table 26. Next, the video transmission central control unit 21 acquires the status of the next station (S702). This is, for example, station congestion data stored in the station status table 29.

[0035] Furthermore, the video transmission central control unit 21 predicts the communication bandwidth (S703). The predicted communication bandwidth may hereafter be referred to as the "predicted bandwidth." The method for predicting the communication bandwidth will be described later in Figure 9. The video transmission central control unit 21 then determines whether or not video from the railway vehicle 10 is being transmitted (S704). As a result, if the data is not being transferred (No in S704), the video transfer central control unit 21 terminates the series of processes. Conversely, if data is being transferred (Yes in S704), the video transfer central control unit 21 predicts the bitrate when outputting video data from the onboard server 14 (S705). This is a prediction of the total bitrate of the output video from the cameras 11 installed in the railway vehicle 10.

[0036] Then, the video transmission central control unit 21 determines whether the predicted bitrate (predicted bitrate in the diagram) > predicted bandwidth (S706). As a result, if the predicted bitrate > predicted bandwidth (Yes in S706), the video transmission central control unit 21 sets the total output video bitrate of the cameras 11 installed on the railway vehicle 10 to predicted bandwidth minus margin (a value obtained by subtracting a predetermined margin from the predicted bandwidth) (S707). The total output video bitrate may hereafter be referred to as the "bitrate setting value". In this case, the video transmission central control unit 21 can also predict the bitrate and, if the predicted bitrate exceeds the predicted bandwidth, set the bitrate to a value below the predicted bandwidth. This makes the image transmitted from the railway vehicle 10 less prone to distortion. Furthermore, the video transmission central control unit 21 transmits the bitrate setting value to the on-board server 14 (S708).

[0037] On the other hand, if, in S706, the predicted bitrate is not greater than the predicted bandwidth (predicted bitrate ≤ predicted bandwidth) (Yes in S706), the video transmission central control unit 21 determines whether the predicted bitrate is greater than the current bitrate setting (S709). As a result, if the predicted bitrate > current bitrate setting (Yes in S709), the video transmission central control unit 21 sets the bitrate setting to the larger of either the predicted bandwidth minus the margin, or the predicted bitrate (S710). The process then proceeds to S708. In this case, the video transmission central control unit 21 can also be said to determine whether the predicted bitrate exceeds the current bitrate if the predicted bitrate does not exceed the predicted bandwidth, and if it does, it determines the bitrate setting value based on the predicted bandwidth or the predicted bitrate. This makes it possible to determine a more appropriate bitrate setting value, and the image transmitted from the railway vehicle 10 is less likely to be distorted.

[0038] Conversely, if the predicted bitrate is not greater than the current bitrate setting (predicted bitrate ≤ current bitrate setting) (No in S709), the video transfer central control unit 21 terminates the series of processes. In this case, the current bitrate setting remains the bitrate setting, and no change is made to the bitrate setting.

[0039] According to the above explanation, the video transmission central control unit 21 functions as a prediction unit that predicts the communication bandwidth based on information about the state of the moving object (in this case, the railway vehicle 10) (processing in S703). The video transmission central control unit 21 also functions as a determination unit that determines the bitrate to be used when transmitting images from the moving object as a bitrate setting value based on the predicted communication bandwidth (processing in S705 to S707, S709 to S710).

[0040] The bitrate setting is the sum of the bitrates of the output video from each camera 11 transmitted from the railway vehicle 10. The onboard server 14 uses this bitrate setting as a basis to perform metric-based adaptive bitrate control.

[0041] In the video metrics table 26 in Figure 5, at 10:07 on 2024 / 09 / 27, the output video bitrate of train Y is 1.2kbps, indicating low available bandwidth. Consequently, it is expected that the available bandwidth will be low when train X travels the same section from 10:09 to 10:10 on 2024 / 09 / 27, and therefore, the output video bitrate of train X was reduced from 1.1kbps to 0.0kbps at this time. In other words, it indicates that transmission from camera 11 with camera ID 101 was canceled. This is because the predicted bitrate > predicted bandwidth (Yes in S706), and as a result of the transmission control unit 21 setting the bitrate setting value to predicted bandwidth - margin in S707, the bitrate setting value of camera 11 with camera ID 101 became 0.0kbps.

[0042] Similarly, the video metrics table 26 in Figure 5 shows that at 10:09 on 2024 / 09 / 27, the output video bitrate of camera 11 of camera ID 102 on train X was reduced from 2.1kbps to 1.3kbps. This is because the predicted bitrate > predicted bandwidth (Yes in S706), and in S707, the transmission control unit 21 set the bitrate setting to predicted bandwidth - margin, resulting in the bitrate setting of camera 11 of camera ID 102 being reduced to 1.3kbps. However, since the predicted bitrate still > predicted bandwidth, the output video bitrate was further slightly reduced at 10:10, from 1.3kbps to 1.2kbps.

[0043] Figure 8 is a flowchart illustrating the operation of the video transfer control unit 142 of the onboard server 14. First, the video transfer control unit 142 determines whether or not the bitrate setting has been updated by the central server 20 (S801). As a result, if the bitrate setting is updated from the center server 20 (Yes in S801), the video transfer control unit 142 updates the base bitrate (S802). In contrast, if the bitrate setting value has not been updated from the center server 20 in S801 (No in S801), and after S802, the process proceeds to S803.

[0044] The video transmission control unit 142 determines whether there are any important data transmissions other than video transmissions scheduled within the next certain period of time (S803). Important data transmissions scheduled include, for example, cases where the on-board server 14 plans to send trace data within a certain period of time if an "event" occurs in the mobile state. As a result, if there is a scheduled transmission of important data (Yes in S803), the video transfer control unit 142 reduces the base bitrate by a certain amount (S804). Note that this reduction in the base bitrate is temporary, and the bitrate setting value instructed by the center server 20 is retained. In contrast, if there are no important data transmissions scheduled in S803 (No in S803), and after S804, the process proceeds to S805.

[0045] The video transmission control unit 142 acquires the communication status (S805). The communication status is, for example, the contents of the communication status table 146. Next, the video transmission control unit 142 determines whether the round-trip time exceeds the standard (S806). As a result, if the round-trip time exceeds the standard (Yes in S806), the video transmission control unit 142 slightly reduces the output video bitrate for each camera 11 or stops transmitting the video (S807). Then, the video transfer control unit 142 sends the bitrate setting value to the video transmission unit 143 (S808).

[0046] On the other hand, if the round-trip time does not exceed the standard in S806 (No in S806), the video transfer control unit 142 determines whether the sum of the current output video bitrates is less than the base bitrate (S809). As a result, if the sum of the current output video bitrates is less than the bitrate setting value (Yes in S809), the bitrate is slightly increased for each camera 11, or video transmission is resumed (S810). The process then proceeds to S808. Conversely, if the sum of the current output video bitrates is not less than the base bitrate (the sum of the current output video bitrates is greater than or equal to the base bitrate) (No in S809), proceed to S807. The video transfer control unit 142 performs the above processing periodically. Alternatively, as part of the processing in S803-S804 and S806-S807, the video transfer control unit 142 adjusts the bitrate setting value sent from the center server 20 based on the presence or absence of an event and the round-trip time.

[0047] The communication metrics table 25 in Figure 4 shows that at 10:09 on 2024 / 09 / 27, the available bandwidth [MBPS] of train X deteriorated from 3.2 to 1.2, and consequently, the round-trip time [s] increased from 0.80 to 2.80. In other words, if the communication bandwidth is insufficient, the round-trip time will be a large value. This corresponds to the case of Yes in S806 in Figure 8. As a result, in S807, the bitrate is slightly reduced / transmission is stopped for each camera 11, which corresponds to the fact that, in the video metrics table 26 in Figure 5, at the same time, transmission from camera 11 with camera ID 101 of train X was stopped, and the output video bitrate of camera 11 with camera ID 102 was reduced from 2.1kbps to 1.3kbps.

[0048] Furthermore, the video metrics table 26 in Figure 5 indicates that at 10:06 on 2024 / 09 / 27, an emergency call was received from inside train X, and recording began on camera 11 with camera ID 102. Accordingly, the video bitrate of camera 11 with camera ID 101 was reduced from 3.2kbps to 1.1kbps at 10:06. This corresponds to the case where there is a scheduled transmission of important data as shown in Figure 8 (Yes in S803), and the video transfer control unit 142 reduces the output video bitrate by a certain amount in S804.

[0049] Figure 9 is a flowchart that provides a detailed explanation of the process by which the video transmission central control unit 21 predicts the communication bandwidth in S703 of Figure 7. First, the video transmission central control unit 21 determines whether or not there are recent communication metrics for the destination section (S901). If recent communication metrics for the destination section can be obtained, for example, it is when there is another train in the destination section (for example, when train Y is traveling ahead of train X in Figure 2) and communication metrics can be obtained from it. Then, if there are recent communication metrics (Yes in S901), the video transmission central control unit 21 obtains the effective bandwidth of the destination section from the recent communication metrics (S902). Furthermore, the video transmission central control unit 21 corrects the effective bandwidth by taking into account the occupancy rate and congestion rate (S903). Then, the video transmission central control unit 21 uses the corrected effective bandwidth as the predicted bandwidth.

[0050] Conversely, if there are no recent communication metrics (No in S901), the video transmission central control unit 21 obtains the effective bandwidth of the destination section from the section-effective bandwidth table 27 (S904). In this case, the video transmission central control unit 21 can also be said to predict the communication bandwidth based on predetermined communication metrics (in this case, the section-effective bandwidth table 27) according to the position of the moving object, which is the railway vehicle 10. This makes it possible to predict the communication bandwidth more accurately based on past communication metrics. Furthermore, if the video transmission central control unit 21 can acquire communication metrics from another mobile object located at the destination (for example, train Y in Figure 2) (in this case, when the answer is Yes in S901), it can predict the communication bandwidth using the acquired communication metrics from the other mobile object instead of the predetermined communication metrics (in this case, the process in S902). This makes it possible to predict the immediate communication bandwidth using the acquired communication metrics from the other mobile object. Furthermore, the video transmission central control unit 21 predicts the communication bandwidth by adding at least one of the following: the congestion rate of the next station, the occupancy rate of the railway vehicle 10, and the time of day (in this case, the morning and midday time slots in the section-effective bandwidth table 27). This makes it possible to predict the communication bandwidth according to the conditions of the route on which the railway vehicle 10 is traveling.

[0051] <Explanation of effects> Railway dispatchers and depot assistants previously relied on telephone calls to ascertain the situation at the location of a railway vehicle. In recent years, the number of onboard cameras has increased, and the use of video, as well as a combination of video and telephone, is becoming more efficient in assessing the situation. For such video applications, it is desirable to have video distortion and minimal delay. Wireless communication is often used for transmitting video from moving objects such as railway vehicles. However, wireless communication bandwidth is affected by factors such as location, time of day, and the number and operational status of other terminals within the base station's area. In particular, bandwidth is very poor under highways and outside residential areas, and if the effective bandwidth falls below the bitrate of the output video, the video at the destination will be distorted. The following methods could be considered as countermeasures, but each has its drawbacks and is unsuitable for the intended purpose. For example, using a buffer for video transmission introduces a delay in video transmission due to the buffer. Furthermore, reducing the video output bitrate to match the lowest possible communication bandwidth will result in lower image quality at the destination. Furthermore, the method of reducing the video output bitrate using Network Access Control (NAC) results in video distortion until this instruction is received. Furthermore, methods that enhance communication reliability, such as using multiple lines or sending packets multiple times, increase the cost of communication. According to this embodiment, by predicting the communication bandwidth in advance and determining the video bitrate setting, it is possible to transmit video with an appropriate bitrate setting in advance. This means that even if the communication bandwidth between the mobile device and the ground equipment fluctuates, the bitrate can be set according to the communication bandwidth, making it less likely for the transmitted image to be distorted. Furthermore, this method does not require increasing the amount of communication equipment, and video can be transmitted to remote locations with low latency. In this embodiment, the method is particularly effective when the mobile device travels along a fixed route, such as a railway vehicle 10. That is, the communication bandwidth can be predicted by referring to past communication bandwidth data for each section, such as the section-effective bandwidth table 27. Also, if communication metrics of other mobile devices located at the destination (for example, train Y in Figure 2) can be obtained, the most recent communication bandwidth can be predicted. In other words, the accuracy of communication bandwidth prediction can be increased.

[0052] <Explanation of Communication Management Device Method> The processing performed by the Video Transfer Central Control Unit 21 is realized through the cooperation of software and hardware resources. Specifically, a processor such as a CPU provided in the Video Transfer Central Control Unit 21 loads programs that realize each function of the Video Transfer Central Control Unit 21 into main memory and executes them, thereby realizing each of these functions. Therefore, the processing performed by the video transmission central control unit 21 described above can be understood as a communication management method that determines the bitrate when transmitting images from a camera 11 mounted on a mobile vehicle, the railway vehicle 10. This method involves a processor executing a program stored in memory to predict the communication bandwidth based on information about the state of the railway vehicle 10, and then determining the bitrate when transmitting images from the railway vehicle 10 as the bitrate setting value based on the predicted communication bandwidth. This makes it possible to set a bitrate according to the communication bandwidth even if the communication bandwidth between the mobile vehicle and the ground equipment fluctuates, thus providing a communication management method that reduces the likelihood of image distortion when transmitting from the mobile vehicle.

[0053] The embodiment described above will include at least the following technical matters. <Technical matters 1> A communication management device for determining the bitrate when transmitting images from a camera mounted on a mobile body, comprising: a prediction unit that predicts the communication bandwidth based on information about the state of the mobile body; and a determination unit that determines the bitrate when transmitting images from the mobile body as a bitrate setting value based on the predicted communication bandwidth. <Technical matters 2> The communication management device described in Technical Item 1 above, wherein the prediction unit predicts the communication bandwidth based on predetermined communication metrics according to the position of the mobile body as the state of the mobile body. <Technical matters 3> In the communication management device described in Technical Item 2 above, if the prediction unit can acquire communication metrics of other mobile bodies located at the destination, it predicts the communication bandwidth using the acquired communication metrics of other mobile bodies instead of the predetermined communication metrics. <Technical matters 4> A communication management device as described in Technical Item 2 or Technical Item 3 above, wherein the mobile body is a railway vehicle, and the prediction unit predicts the communication bandwidth by adding at least one of the congestion rate of the next station, the occupancy rate of the railway vehicle, and the time of day. <Technical matters 5> A communication management device as described in any one of the above technical items 1 to 4, wherein the determination unit predicts the bitrate, and if the predicted bitrate exceeds the predicted bandwidth, the bitrate setting value is determined to be less than or equal to the predicted bandwidth. <Technical matters 6> In the communication management device described in technical item 5 above, the determination unit determines whether the predicted bitrate exceeds the current bitrate if the predicted bitrate does not exceed the predicted bandwidth, and if it does, determines the bitrate setting value based on the predicted bandwidth or the predicted bitrate.

[0054] <Technical matter 7> A communication management method for determining the bitrate when transmitting images from a camera mounted on a mobile device, wherein a processor executes a program stored in memory to predict the communication bandwidth based on information about the state of the mobile device, and determines the bitrate when transmitting images from the mobile device as a bitrate setting value based on the predicted communication bandwidth.

[0055] <Technical matters 8> The communication management method described in Technical Item 7 above predicts the communication bandwidth based on predetermined communication metrics according to the position of the mobile object, as a state of the mobile object. <Technical matter 9> In the communication management method described in technical item 8 above, if communication metrics of other mobile bodies located at the destination can be obtained, the communication bandwidth is predicted using the obtained communication metrics of other mobile bodies instead of the predetermined communication metrics. <Technical matters 10> A communication management method as described in Technical Item 7 or Technical Item 8 above, wherein the mobile entity is a railway vehicle, and the communication bandwidth is predicted by adding at least one of the congestion rate of the next station, the occupancy rate of the railway vehicle, and the time of day. <Technical matters 11> A communication management method as described in any one of the above technical items 10 to 13, wherein the bitrate is predicted, and if the predicted bitrate exceeds the predicted bandwidth, the bitrate setting value is set to be less than or equal to the predicted bandwidth. <Technical matter 12> The communication management method described in technical item 11 above is characterized in that, if the predicted bitrate does not exceed the predicted bandwidth, it is determined whether the predicted bitrate exceeds the current bitrate, and if it does, the bitrate setting value is determined based on the predicted bandwidth or the predicted bitrate. <Technical matter 13> A mobile communication system comprising: an on-board device disposed on a mobile body equipped with a camera and transmitting video footage captured by the camera; and a ground device that receives video footage transmitted from the on-board device, wherein the ground device comprises a prediction unit that predicts a communication bandwidth based on information about the state of the mobile body, and a determination unit that determines the bitrate to be used when transmitting images from the mobile body as a bitrate setting value based on the predicted communication bandwidth. <Technical matter 14> The mobile communication system described in technical item 13 above, wherein the on-board device adjusts the bitrate setting value sent from the ground device based on the presence or absence of an event and the round trip time.

[0056] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations. Furthermore, each of the above configurations, functions, processing units, and processing means may be implemented in hardware, either partially or entirely, by designing them as integrated circuits, for example. Alternatively, each of the above configurations and functions may be implemented in software by having the processor interpret and execute programs that implement each function. Information such as programs, tables, and files that implement each function can be stored in memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD. Furthermore, the control lines and information lines shown are those deemed necessary for explanatory purposes, and not all control lines and information lines are necessarily shown in the actual product. In reality, it is safe to assume that almost all components are interconnected. [Explanation of Symbols]

[0057] 1...Mobile communication system, 10...Railway vehicle, 11,11a~11d...Camera, 12,12a~12b...Video recording device, 13...Train information management device, 14,14a~14b...On-board server, 20...Center server, 21...Central video transmission control unit, 22...Video receiving unit, 23...Metrics receiving unit, 24...Mobile metrics table, 25...Communication metrics table, 26...Video metrics table, 27...Section-effective bandwidth table, 28...Mobile status table, 29...Station status table, 141...Video processing unit, 142...Video transmission control unit, 143...Video transmission unit, 144...Metrics transmission unit, X,Y...Train

Claims

1. A communication management device that determines the bitrate when transmitting images from a camera mounted on a mobile device, A prediction unit predicts the communication bandwidth based on information about the state of the aforementioned mobile object, A determination unit determines the bitrate when transmitting images from the mobile device as a bitrate setting value, based on the predicted communication bandwidth, A communication management device equipped with the following features.

2. The communication management device according to claim 1, wherein the prediction unit predicts the communication bandwidth based on predetermined communication metrics according to the position of the moving body as the state of the moving body.

3. The communication management device according to claim 2, wherein if the prediction unit can acquire communication metrics of other mobile bodies located at the destination, it predicts the communication bandwidth using the acquired communication metrics of other mobile bodies instead of the predetermined communication metrics.

4. The aforementioned moving object is a railway vehicle, The communication management device according to claim 2, wherein the prediction unit predicts the communication bandwidth by adding at least one of the congestion rate of the next station, the occupancy rate of the railway vehicle, and the time of day.

5. The communication management device according to claim 1, wherein the determination unit predicts the bitrate, and if the predicted bitrate exceeds the predicted bandwidth, it determines the bitrate setting value to be less than or equal to the predicted bandwidth.

6. The communication management device according to claim 5, wherein the determination unit determines whether the predicted bitrate exceeds the current bitrate if the predicted bitrate does not exceed the predicted bandwidth, and if it does exceed the current bitrate, determines the bitrate setting value based on the predicted bandwidth or the predicted bitrate.

7. A communication management method for determining the bitrate when transmitting images from a camera mounted on a mobile device, The processor executes the program stored in memory, Based on the information regarding the status of the aforementioned mobile object, the communication bandwidth is predicted. Based on the predicted communication bandwidth, the bitrate used when transmitting images from the mobile device is determined as the bitrate setting value. Communication management methods.

8. The communication management method according to claim 7, wherein the communication bandwidth is predicted based on predetermined communication metrics according to the position of the mobile body as the state of the mobile body.

9. The communication management method according to claim 8, wherein if communication metrics of other mobile bodies located at the destination can be obtained, the communication bandwidth is predicted using the communication metrics of other mobile bodies obtained instead of the predetermined communication metrics.

10. The aforementioned moving object is a railway vehicle, The communication management method according to claim 8, which predicts the communication bandwidth by adding at least one of the congestion rate of the next station, the occupancy rate of the railway vehicle, and the time of day.

11. The communication management method according to claim 7, which predicts the bitrate and, if the predicted bitrate exceeds the predicted bandwidth, sets the bitrate setting value to be less than or equal to the predicted bandwidth.

12. The communication management method according to claim 11, wherein if the predicted bitrate does not exceed the predicted bandwidth, it is determined whether the predicted bitrate exceeds the current bitrate, and if it does, the bitrate setting value is determined based on the predicted bandwidth or the predicted bitrate.

13. A mobile communication system comprising: an on-board device mounted on a mobile body equipped with a camera, which transmits video captured by the camera; and a ground device that receives video transmitted from the on-board device, The aforementioned ground equipment is A prediction unit predicts the communication bandwidth based on information about the state of the aforementioned mobile object, A determination unit determines the bitrate when transmitting images from the mobile device as a bitrate setting value, based on the predicted communication bandwidth, A mobile communication system equipped with [a specific feature / feature].

14. The mobile communication system according to claim 13, wherein the on-board device adjusts the bitrate setting value sent from the ground device based on the presence or absence of an event and the round trip time.

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