Transmission device, method, and program

Abstract

This transmission device is provided in a communication system that includes the transmission device, a plurality of relay nodes, and a reception device, and in which at least one of the transmission device, the plurality of relay nodes, and the reception device is a mobile node. The transmission device includes: a communication means capable of wirelessly connecting to a plurality of connection target relay nodes; a configuration means for configuring a first communication path including a first connection target relay node and extending from the transmission device to the reception device, and a second communication path including a second connection target relay node; and an allocation means for allocating each of a plurality of transmission signals to the first communication path or the second communication path.

Description

Transmission apparatus, method, and program

[0001] The present disclosure relates to a transmission apparatus, a method, and a program.

[0002] Technologies for selecting a communication path have been proposed (for example, Patent Document 1). In Patent Document 1, for example, one communication path that minimizes the number of handover occurrences is selected.

[0003] Japanese Unexamined Patent Publication No. 2002-141851

[0004] However, in the technology of Patent Document 1, since a single communication path is used for communication, there is a possibility that sufficient throughput cannot be obtained.

[0005] An object of the present disclosure is to provide a transmission apparatus, a method, and a program that can improve throughput. It should be noted that this object is merely one of a plurality of objects to be achieved by the plurality of embodiments disclosed in the present specification. Other objects or problems and novel features will become apparent from the description of the present specification and the accompanying drawings.

[0006] The transmission apparatus according to the present disclosure is the transmission apparatus in a communication system that includes the transmission apparatus, a plurality of relay nodes, and a reception apparatus, and at least one of the transmission apparatus, the plurality of relay nodes, and the reception apparatus is a movable mobile node, the transmission apparatus comprising: communication means capable of wirelessly connecting to a plurality of connection target relay nodes; setting means for setting a first communication path from the transmission apparatus to the reception apparatus that includes a first connection target relay node, and a second communication path from the transmission apparatus to the reception apparatus that includes a second connection target relay node; and distribution means for distributing each of a plurality of transmission signals to the first communication path or the second communication path.

[0007] The method relating to this disclosure is a method performed by a transmitting device in a communication system which includes a transmitting device, a plurality of relay nodes, and a receiving device, wherein at least one of the transmitting device, the plurality of relay nodes, and the receiving device is a mobile node, and includes setting up a first communication path from the transmitting device to the receiving device which includes a first connection target relay node, and a second communication path from the transmitting device to the receiving device which includes a second connection target relay node, and distributing each of a plurality of transmission signals to the first communication path or the second communication path.

[0008] The program relating to this disclosure causes the transmitting device in a communication system which includes a transmitting device, a plurality of relay nodes, and a receiving device, wherein at least one of the transmitting device, the plurality of relay nodes, and the receiving device is a mobile node, to execute a process that includes setting a first communication path from the transmitting device to the receiving device which includes a first relay node to be connected to, and a second communication path from the transmitting device to the receiving device which includes a second relay node to be connected to, and distributing each of a plurality of transmission signals to the first communication path or the second communication path.

[0009] This disclosure provides a transmission device, method, and program that can improve throughput.

[0010] This figure shows an example of the communication system of this disclosure. This block diagram shows an example of the transmitting device of this disclosure. This block diagram shows an example of the relay node of this disclosure. This block diagram shows an example of the receiving device of this disclosure. This flowchart shows an example of the processing operation of the transmitting device of this disclosure. This figure shows another example of the communication system of this disclosure. This block diagram shows another example of the transmitting device of this disclosure. This flowchart shows an example of the processing operation of the movement parameter estimation unit and the required time estimation unit. This flowchart shows an example of the processing operation of the distribution unit. This figure shows another example of the communication system of this disclosure. This figure shows another example of the communication system of this disclosure. This block diagram shows another example of the transmitting device of this disclosure. This flowchart shows another example of the processing operation of the transmitting device of this disclosure. This figure shows another example of the communication system of this disclosure. This block diagram shows another example of the transmitting device of this disclosure. This flowchart shows another example of the processing operation of the transmitting device of this disclosure. This figure shows another example of the communication system of this disclosure. This figure shows another example of the communication system of this disclosure. This figure shows another example of the communication system of this disclosure. This figure shows the trend of propagation delay time of the communication path in the communication system of this disclosure. This figure shows the trend of data transmission volume of the communication path in the communication system of this disclosure. This figure shows the trend of throughput and delay time on the receiving side in the communication system of this disclosure. This figure shows the changes in propagation delay time of the communication path in the comparative example communication system. This figure shows the changes in the amount of data transmitted along the communication path in the communication system of this disclosure. This figure shows the changes in throughput and delay time on the receiving side in the communication system of this disclosure. This figure shows an example of the configuration of the transmitting device.

[0011] The embodiments will be described below with reference to the drawings. In this disclosure, the drawings may be associated with one or more embodiments. Also, each element in the drawings may correspond to one or more embodiments. Furthermore, in the embodiments, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0012] <First Embodiment> <Overview of the Communication System> Figure 1 is a diagram showing an example of the communication system of the present disclosure. In Figure 1, the communication system 1 includes a transmitting device 10, relay nodes 20-11, 20-12, 20-21, 20-22, and a receiving device 30. In the following, when relay nodes 20-11, 20-12, 20-21, and 20-22 are not distinguished, each of the relay nodes 20-11, 20-12, 20-21, and 20-22, or relay nodes 20-11, 20-12, 20-21, and 20-22 collectively may be simply referred to as relay node 20. Although four relay nodes 20 are shown in Figure 1, the number included in the communication system 1 is not limited to four.

[0013] For example, at least one of the transmitting device 10, relay node 20, and receiving device 30 is a mobile node. For example, the transmitting device 10 and receiving device 30 may be communication devices located on the ground, and the relay node 20 may be a satellite. Alternatively, for example, the transmitting device 10 and relay node 20 may be satellites, and the receiving device 30 may be communication devices located on the ground. Alternatively, for example, the transmitting device 10 may be a satellite, and the relay node 20 and receiving device 30 may be communication devices located on the ground. In this case, the receiving device 30 may be a mobile terminal. In the following explanation, as an example, we will describe a configuration where the transmitting device 10 and receiving device 30 are communication devices located on the ground, and the relay node 20 is a satellite.

[0014] In Figure 1, relay nodes 20-11 and 20-21 are located within the communication space CS 10 of the transmitting device 10. Also in Figure 1, relay nodes 20-12 and 20-22 are located within the communication space CS 30 of the receiving device 30. That is, Figure 1 shows the state of communication system 1 in which the transmitting device 10 and relay node 20-11 can establish link L11. Also in Figure 1, the state of communication system 1 in which the transmitting device 10 and relay node 20-21 can establish link L21. From the perspective of the transmitting device 10, relay nodes 20-11 and 20-21 are the relay nodes to be connected. Also in Figure 1, the state of communication system 1 in which the receiving device 30 and relay node 20-12 can establish link L13. Also in Figure 1, the state of communication system 1 in which the receiving device 30 and relay node 20-22 can establish link L23. Furthermore, in Figure 1, relay nodes 20-11 and 20-12 are connected via link L12. Also, in Figure 1, relay nodes 20-21 and 20-22 are connected via link L22.

[0015] In Figure 1, a first communication path including relay nodes 20-11 and 20-21, and a second communication path including relay nodes 20-12 and 20-22 are established between the transmitting device 10 and the receiving device 30. As will be described later, both the first and second communication paths may be already established paths, or one of the first and second communication paths may be already established and the other may be established in the near future. In Figure 1, the first communication path includes links L11, L12, and L13, and the second communication path includes links L21, L22, and L23. Although Figure 1 shows a state in which two communication paths are established, this disclosure is not limited to this, and there may be three or more communication paths established. That is, the number of relay nodes 20 to be connected may be three or more.

[0016] <Example of Transmitting Device Configuration> Figure 2 is a block diagram showing an example of a transmitting device according to the present disclosure. In Figure 2, the transmitting device 10 includes a communication unit 11 and a control unit (control device) 12. The control unit 12 includes a setting unit 12A and a distribution unit 12B.

[0017] The communication unit 11 is configured to be able to wirelessly connect to multiple relay nodes 20 that are to be connected.

[0018] The configuration unit 12A sets up multiple communication paths that pass through each of the multiple relay nodes 20 to be connected. In the situation shown in Figure 1, the configuration unit 12A sets up a first communication path that includes relay nodes 20-11 and extends from the transmitting device 10 to the receiving device 30, and a second communication path that includes relay nodes 20-21 to be connected.

[0019] The distribution unit 12B distributes each of the multiple transmission signals (for example, multiple transmission packets) to either the first communication path or the second communication path. Since the transmission signals can be distributed to multiple communication paths set by the setting unit 12A in this way, throughput can be improved. The distribution unit 12B also adds information indicating the order of the transmission signals when distributing them. As a result, the receiving device 30 can rearrange the received signals based on this order information.

[0020] <Example of relay node configuration> Figure 3 is a block diagram showing an example of a relay node according to the present disclosure. In Figure 3, the relay node 20 has a communication interface unit 21 and a communication interface unit 22.

[0021] The communication interface unit 21 is a communication interface that communicates with communication devices located on the ground (i.e., the transmitting device 10 or the receiving device 30). For example, at relay nodes 20-11, the communication interface unit 21 receives the transmission signal sent from the transmitting device 10. Also, for example, at relay node 20-12, the communication interface unit 21 transmits the signal forwarded from relay node 20-11 to the receiving device 30.

[0022] The communication interface unit 22 is a communication interface that communicates with other relay stations 20. For example, at relay node 20-11, the communication interface unit 22 forwards the signal received by the communication interface unit 21 to relay node 20-12. Also, for example, at relay node 20-12, the communication interface unit 22 receives the signal forwarded from relay node 20-11. This received signal is forwarded to the receiving device 30 by the communication interface unit 21. If the communication path that includes relay node 20 includes other relay nodes 20 further down the line, the communication interface unit 22 transmits the signal received from the preceding relay node 20 to the other relay node 20 further down the line.

[0023] <Example of Receiving Device Configuration> Figure 4 is a block diagram showing an example of a receiving device according to the present disclosure. In Figure 4, the receiving device 30 has a communication unit 31 and a control unit (control device) 32. The control unit 32 has a receiving processing unit 32A.

[0024] The communication unit 31 is configured to be able to wirelessly connect to multiple target relay nodes 20. The communication unit 31 receives signals transmitted from each target relay node 20 and outputs the received signals to the receiving processing unit 32A. In the example in Figure 1, the communication unit 31 receives signals transmitted from relay nodes 20-12 and 20-22. That is, the communication unit 31 receives signals transmitted via the first communication path and signals transmitted via the second communication path.

[0025] The receiving processing unit 32A rearranges the multiple signals received from the communication unit 31 based on the information indicating the above order.

[0026] <Example of Communication System Operation> An example of the processing operation of the communication system 1 having the above configuration will be described. Here, in particular, an example of the processing operation of the transmitting device 10 will be described. Figure 5 is a flowchart showing an example of the processing operation of the transmitting device of this disclosure.

[0027] The setting unit 12A sets the first communication path and the second communication path (step S11).

[0028] The distribution unit 12B distributes each of the multiple transmission signals to either the first communication path or the second communication path (step S12).

[0029] As described above, according to the first embodiment, the setting unit 12A in the transmitting device 10 sets the first communication path and the second communication path. Then, the distribution unit 12B distributes each of the multiple transmission signals to either the first communication path or the second communication path.

[0030] This configuration of the transmitting device 10 allows for the simultaneous use of multiple communication paths, thereby improving throughput.

[0031] <Second Embodiment> <Overview of the Communication System> Figure 6 shows another example of the communication system of the present disclosure. In Figure 6, the communication system 2 includes a transmitting device 40, relay nodes 20-11, 20-12, 20-21, 20-22, and a receiving device 30. That is, the communication system 2 differs from the communication system 1 in that it includes a transmitting device 40 instead of a transmitting device 10. In particular, Figure 6 shows a case in which the transmitting device 40 and the receiving device 30 are communication devices located on the ground, and the relay nodes 20 are satellites. Here, the relay nodes 20 are described as mobile nodes that move. Multiple relay nodes 20 constitute a constellation. In Figure 6, the first communication path is shown as communication path CP1, and the second communication path is shown as communication path CP2.

[0032] <Example of Transmitting Device Configuration> Figure 7 is a block diagram showing another example of the transmitting device of this disclosure. In Figure 7, the transmitting device 40 has a communication unit 41 and a control unit (control device) 42. The control unit 42 has a movement parameter estimation unit 42A, a setting unit 42B, a required time estimation unit 42C, a distribution unit 42D, and a communication control unit 42E. The communication unit 41 has a transmission unit 41A and transmission buffers 41B1 and 41B2. The movement parameter estimation unit 42A has an estimation processing unit 42A1 and a holding unit 42A2.

[0033] The transmit buffer 41B1 corresponds to the communication path CP1. The transmit buffer 41B1 temporarily holds the transmit signals that have been allocated to the communication path CP1 by the distribution unit 42D.

[0034] The transmit buffer 41B2 corresponds to the communication path CP2. The transmit buffer 41B2 temporarily holds the transmit signals that have been allocated to the communication path CP2 by the distribution unit 42D.

[0035] The transmitting unit 41A transmits the transmission signal held in the transmission buffer 41B1 to the communication path CP1 (i.e., relay nodes 20-11) in accordance with the control of the communication control unit 42E. The transmitting unit 41A also transmits the transmission signal held in the transmission buffer 41B2 to the communication path CP2 (i.e., relay nodes 20-21) in accordance with the control of the communication control unit 42E.

[0036] The estimation processing unit 42A1 acquires information regarding the movement of the relay node 20 (for example, orbital information). The orbital information is, for example, a two-line orbital element set (TLE). The TLE includes data necessary to calculate the position of the relay node 20 at past points in time (orbital elements such as orbital inclination and right ascension of the ascending node, and the number of orbits).

[0037] The estimation processing unit 42A1 then estimates (calculates) the position posi and velocity vi of each relay node 20 at a past time Ti, based on the trajectory information. Time Ti, position posi, and velocity vi are the movement parameters of the relay node 20.

[0038] The storage unit 42A2 stores the time Ti, position posi, and speed vi in ​​association with each relay node 20 included in each communication path.

[0039] The setting unit 42B sets communication paths CP1 and CP2, similar to the setting unit 12A. Alternatively, the setting unit 42B may set the communication paths based on the location of each relay node 20 estimated by the estimation processing unit 42A1.

[0040] The time estimation unit 42C estimates (calculates) the time required for the transmission signal allocated to communication path CP1 to reach the receiving device 30 (hereinafter sometimes referred to as the "first time required"). The time estimation unit 42C also estimates the time required for the transmission signal allocated to communication path CP2 to reach the receiving device 30 (hereinafter sometimes referred to as the "second time required"). For example, if the relay node 20-11 connected to communication path CP1 and the relay node 20-21 connected to communication path CP2 are connected to the communication unit 41, the first time required and the second time required may each include the "transmission processing time" and the "propagation path time". The transmission processing time is the time required from when the transmission signal to be allocated is input to the transmission buffer 41B corresponding to the communication path until the communication unit 41 transmits the transmission signal to be allocated. Furthermore, the propagation path time is the time required from the time the transmission signal to be distributed is transmitted from the communication unit 41 until it is received by the receiving device 30.

[0041] For example, the time estimation unit 42C acquires transmission time information included in the acknowledgment (ACK) transmitted from the receiving device 30 and received by the transmitting device 40. The time estimation unit 42C then calculates the round trip time (RTT) for each of the communication paths CP1 and CP2. However, the RTT calculated here is the route delay at a past point in time. If the length of the communication paths CP1 and CP2 fluctuates significantly over time, the RTT will be a different value from the route delay at the current time.

[0042] The time estimation unit 42C then estimates (calculates) the first and second required times based on the position posi and velocity vi of each relay node 20 included in the communication paths CP1 and CP2, which are held in the holding unit 42A2, at time τi, and the route delay (RTT) calculated for each of the communication paths CP1 and CP2.

[0043] Specifically, the required time estimating unit 42C estimates (calculates) the position of each relay node 20 included in the communication paths CP1 and CP2 at a transmission timing candidate. For example, the required time estimating unit 42C calculates the position of each relay node 20 included in the communication paths CP1 and CP2 at a transmission timing candidate based on the following formula (1). In formula (1), t is a transmission timing candidate (for example, the current time). Further, posi' is the position of the relay node 20 at the transmission timing candidate.

[0044] Next, the required time estimating unit 42C estimates (calculates) a propagation delay time for each link l included in each of the communication paths CP1 and CP2. For example, the required time estimating unit 42C calculates a propagation delay time at a transmission timing candidate by the following formula (2). Further, the required time estimating unit 42C calculates a propagation delay time at a past time point τi by the following formula (3). This calculation is performed for each of the communication paths CP1 and CP2. Note that the subscripts s and t represent any one of the transmitting device 40, the relay node 20, and the receiving device 30. Further, for the positions pos of the transmitting device 40 and the receiving device 30, which are communication devices located on the ground, preset values are used.

[0045] Next, the required time estimating unit 42C estimates (calculates) a propagation path required time at a transmission timing candidate by the following formula (4). This calculation is performed for each of the communication paths CP1 and CP2. In formula (4), the propagation path required time at a transmission timing candidate is obtained by correcting the calculation result (RTT) of the path delay at the past time point τi according to the variation of the propagation delay due to the passage of time. Note that the required time estimating unit 42C may calculate the propagation path required time for each of a plurality of transmission timing candidates.

[0046] Next, the required time estimating unit 42C estimates (calculates) a transmission processing required time at distribution timing by the following formula (5). This calculation is performed for each of the communication paths CP1 and CP2. In equation (5), qj is the size of the transmission signal (data packet) waiting to be transmitted. That is, qj is the size of the transmission signal (data packet) already held in the transmission buffer 41B. Also, Thrj is the transmission throughput.

[0047] Next, the time estimation unit 42C estimates (calculates) the time required at the distribution timing using the following formula (6). That is, the time estimation unit 42C calculates the time required at the distribution timing by adding the transmission processing time at the distribution timing and the propagation path time at the candidate transmission timing. This calculation is performed for each of the communication paths CP1 and CP2. In calculating the propagation time, delays due to data retransmission may be taken into account by calculating based not only on RTT but also on TCP information.

[0048] If the time estimation unit 42C has calculated the propagation path time for each of the multiple transmission timing candidates, the time required at the distribution timing may be calculated using the propagation path time at the transmission timing candidate closest to the scheduled transmission timing of the distribution target transmission signal.

[0049] The distribution unit 42D distributes each of the multiple transmission signals (for example, multiple transmission packets) to either the first or second communication path based on the first and second required times estimated by the required time estimation unit 42C. Similar to the distribution unit 12B, the distribution unit 42D adds information indicating the order of the transmission signals when distributing them.

[0050] The communication control unit 42E controls the transmission unit 41A to cause the transmission unit 41A to transmit a transmission signal.

[0051] <Example of Communication System Operation> An example of the processing operation of the communication system 2 having the above configuration will be described. Here, in particular, an example of the processing operation of the transmitting device 40 will be described. Figure 8 is a flowchart showing an example of the processing operation of the movement parameter estimation unit and the required time estimation unit. Figure 9 is a flowchart showing an example of the processing operation of the distribution unit.

[0052] In Figure 8, the movement parameter estimation unit 42A estimates the position posi and velocity vi of each relay node 20 at a past time point Ti based on the trajectory information (step S21).

[0053] The time estimation unit 42C estimates the propagation time for each communication path based on the position posi and velocity vi of each relay node 20 at past time Ti (step S22). For example, as described above, the time estimation unit 42C calculates the path delay (RTT: Round trip time) for each communication path. The time estimation unit 42C also calculates the propagation delay time for each link and calculates the propagation delay time for each communication path based on the calculated propagation delay time for each link. Then, the time estimation unit 42C calculates the propagation time by correcting the calculated path delay result (RTT) by the amount of variation in propagation delay due to the passage of time.

[0054] The time estimation unit 42C estimates the time required for transmission processing for each communication path (step S23).

[0055] The time estimation unit 42C estimates the required time based on the transmission processing time for each communication path (step S24). The processing flow in Figure 8 is executed repeatedly.

[0056] In Figure 9, the distribution unit 42D selects the communication path corresponding to the smaller of the first required time and the second required time for the transmission signal to be distributed as the distribution destination path (step S31).

[0057] The distribution unit 42D distributes the transmission signals to be distributed to the transmission buffers corresponding to the distribution destination paths (step S32).

[0058] As described above, according to the second embodiment, in the transmitting device 40, the movement parameter estimation unit 42A estimates the position and speed of the relay node (moving node) 20 based on information regarding the movement of the relay node (moving node). The required time estimation unit 42C estimates the first required time for communication path CP1 and the second required time for communication path CP2 based on the estimated position and speed of the moving node. The distribution unit 42D distributes the transmission signals to be distributed to either communication path CP1 or communication path CP2 based on the first and second required times.

[0059] The configuration of this transmitting device 40 allows for the estimation of the required time for each communication path based on the estimated position and speed of the mobile node. Therefore, even when the propagation delay of the communication path is changing, the accurate required time for each communication path at the distribution timing can be estimated. Furthermore, since the transmission signals to be distributed are allocated to either communication path CP1 or communication path CP2 based on the first and second required times, the time it takes for the transmission signals to reach the receiving device 30 can be equalized. This prevents the timing at which multiple transmission signals that are close in order arrive at the receiving device 30 from being dispersed, so that the receiving processing unit 32A can execute the sorting process of the received signals without delay. In other words, fluctuations in communication delay can be suppressed.

[0060] <Modification of the Second Embodiment> When communication path CP2 is newly established while communication path CP1 is already established, and TCP (Transmission Control Protocol) is applied to the communication unit 41, the communication control unit 42E may set the initial value of the congestion control window corresponding to communication path CP2 based on the product of the second required time and the predicted value of the communication bandwidth corresponding to communication path CP2. The communication control unit 42E may calculate the predicted value of the communication bandwidth [packet / s] by, for example, the following equation (7). This improves the reduction in the amount of data transmitted due to slow start and reduces the transmission waiting time in communication path CP2. As a result, it is possible to avoid the timing at which multiple transmission signals that are close in order arrive at the receiving device 30 being dispersed, so that the receiving processing unit 32A can execute the receiving signal sorting process without delay. Transmission signals may be distributed to communication path CP2 only up to the number of transmittable packets.

[0061] <Third Embodiment> <Overview of the Communication System> Figures 10A and 10B show another example of the communication system of the present disclosure. In Figures 10A and 10B, the communication system 3 includes a transmitting device 50, relay nodes 20-11, 20-12, 20-21, 20-22, and a receiving device 30. That is, the communication system 3 differs from the communication system 2 in that it includes a transmitting device 50 instead of a transmitting device 40. In particular, Figures 10A and 10B show a case in which the transmitting device 50 and the receiving device 30 are communication devices located on the ground, and the relay nodes 20 are satellites. Here, the explanation assumes that the relay nodes 20 are mobile nodes that move. Multiple relay nodes 20 constitute a constellation. Figure 10A shows the state of the communication system 3 in which communication path CP1 has been established, but communication path CP2 has not yet been established. In other words, in Figure 10A, the transmitter 50 is connected to the relay node 20-11 because the relay node 20-11 is located within the connectable space of the transmitter 50. On the other hand, in Figure 10A, the transmitter 50 is not connected to the relay node 20-21 because the relay node 20-21 is located outside the connectable space of the transmitter 50.

[0062] Figure 10B shows the state of communication system 3 where both communication paths CP1 and CP2 are established. Specifically, Figure 10B shows the state of communication system 3 where relay nodes 20-21 have moved from the state in Figure 10A and entered the connectable space of the transmitter 50, and the transmitter 50 and relay nodes 20-21 are connected. Although relay node 20-11 has also moved from the state in Figure 10A, relay node 20-11 is located within the connectable space of the transmitter 50, and therefore maintains its connection with the transmitter 50.

[0063] <Example of Transmitter Configuration> Figure 11 is a block diagram showing another example of the transmitter according to this disclosure. In Figure 11, the transmitter 50 has a communication unit 41 and a control unit (control device) 51. The control unit 51 has a setting unit 51A, a scheduled timing estimation unit 51B, a required time estimation unit 51C, a communication control unit 51D, a movement parameter estimation unit 42A, and a distribution unit 42D.

[0064] The configuration unit 51A configures the communication path that goes through the relay node 20 to be connected. The configured communication path may include not only the communication path that includes the relay node 20 to be connected that the transmitting device 50 is currently connected to, but also the communication path that includes the relay node 20 to be connected that the transmitting device 50 will connect to in the near future.

[0065] For example, the setting unit 51A may also designate relay nodes 20 that satisfy the following equation (8), even if they are not currently connected to the transmitting device 50, as target relay nodes 20 for connection. The setting unit 51A may then configure a communication path that includes these target relay nodes 20. Here, distance() means calculating the distance between the transmitter 50 and the relay node 20. posi is the position of the relay node 20 calculated from the orbital information. posg is the position of the transmitter 50. distancereshold is a threshold, which is set based on, for example, the line-of-sight distance of the link between the transmitter 50 and the relay node 20.

[0066] Alternatively, the setting unit 51A may also designate relay nodes 20 that satisfy the following equation (9), even if they are not currently connected to the transmitting device 50, as target relay nodes 20. The setting unit 51A may then configure a communication path that includes these target relay nodes 20. Here, elevation() means calculating the elevation angle of the relay node 20 as seen from the transmitter 50. elevationthrehold is a threshold value, which is set based on the line of sight at the transmitter 50.

[0067] The scheduled timing estimation unit 51B estimates the scheduled connection timing of the communication path set by the setting unit 51A.

[0068] For example, the scheduled timing estimation unit 51B can calculate the scheduled connection timing of the communication path by calculating the following formula (10). posi' can be calculated using the above formula (1). ethrs is the threshold. That is, the planned connection timing can be calculated by working backward from the time when the elevation angle matches the threshold.

[0069] The time estimation unit 51C estimates the first required time, similar to the time estimation unit 42C, when the relay node 20-11 to be connected to the communication path CP1 is connected to the transmitting device 50, as shown in Figure 10A.

[0070] On the other hand, if the relay nodes 20-21 to be connected to the communication path CP2 are not connected to the transmitting device 50, as shown in Figure 10A, the time estimation unit 51C may calculate a second time by adding up, for example, the "connection time", "transmission processing time", and "propagation path time". Here, the connection time is the time from the current timing (distribution timing) to the planned connection timing when the communication unit 41 connects to the relay nodes 20-21 to be connected. Note that the connection time for a communication path that is currently connected is zero. The transmission processing time is the time required from the planned connection timing until the communication unit 41 transmits the transmission signal to be distributed. The propagation path time is the time required from when the transmission signal to be distributed is transmitted from the communication unit 41 until it is received by the receiving device 30. Note that the time estimation unit 51C may calculate the propagation delay time as the propagation path time, for example, as shown in the following equation (11), using equation (3).

[0071] The distribution unit 42D distributes each of the multiple transmission signals (for example, multiple transmission packets) to either communication path CP1 or communication path CP2 based on the first and second required times estimated by the required time estimation unit 51C. Therefore, even if a communication path is not connected, if the required time is shorter than that of a connected communication path, the transmission signal can be distributed to the unconnected communication path. This makes it possible to equalize the time it takes for the transmission signal to reach the receiving device 30.

[0072] The communication control unit 51D controls the transmission unit 41A to start transmitting the transmission signal held in the transmission buffer 41B2 to the communication path CP2 when the scheduled connection timing arrives.

[0073] <Example of Communication System Operation> Figure 12 is a flowchart showing another example of the processing operation of the transmitting device of this disclosure. In particular, Figure 12 shows an example of the processing operation of the movement parameter estimation unit, setting unit, scheduled timing estimation unit, and required time estimation unit.

[0074] The movement parameter estimation unit 42A estimates the position posi and velocity vi of each relay node 20 at a past time point Ti, based on the trajectory information, similar to step S21 (step S41).

[0075] The configuration unit 51A configures the communication path (step S42). Here, the communication path includes not only the communication path that includes the transmitting device 50 and the relay node 20 to be connected, but also the communication path that includes the relay node 20 to be connected to the transmitting device 50 in the near future.

[0076] The scheduled timing estimation unit 51B estimates the scheduled connection timing of the communication path set by the setting unit 51A (step S43).

[0077] The scheduled timing estimation unit 51B estimates the connection time required for each communication path (step S44). Note that the connection time required for a communication path that is currently connected is zero.

[0078] The time estimation unit 51C estimates the propagation path time for each communication path (step S45). For communication paths that are currently connected, the time estimation unit 51C can calculate the propagation path time using the above formula (4). For communication paths that are not currently connected, the time estimation unit 51C can calculate the propagation path time using the above formula (11).

[0079] The time estimation unit 51C estimates the time required for transmission processing for each communication path (step S46).

[0080] The time estimation unit 51C estimates the required time based on the connection time, transmission processing time, and transmission processing time for each communication path (step S47). The processing flow in Figure 12 is executed repeatedly.

[0081] As described above, according to the third embodiment, the scheduled timing estimation unit 51B in the transmitting device 50 estimates the scheduled connection timing of the communication path. The required time estimation unit 51C estimates the required time for each communication path by adding up the "connection required time," "transmission processing required time," and "propagation path required time." The distribution unit 42D distributes the transmission signals to be distributed to multiple communication paths based on the required time.

[0082] With the configuration of this transmitting device 50, even if a communication path is not connected, if the required time is shorter than that of a connected communication path, the transmission signal can be allocated to the unconnected communication path. This makes it possible to equalize the time it takes for the transmission signal to reach the receiving device 30. As a result, it is possible to avoid the timing of multiple transmission signals arriving at the receiving device 30 being dispersed, so that the receiving processing unit 32A can execute the sorting process of the received signals without delay. In other words, fluctuations in communication delay can be suppressed.

[0083] <Fourth Embodiment> <Overview of the Communication System> Figures 13A and 13B show another example of the communication system of the present disclosure. In Figures 13A and 13B, the communication system 4 includes a transmitting device 60, relay nodes 20-11, 20-12, 20-21, 20-22, and a receiving device 30. That is, the communication system 4 differs from the communication system 2 in that it includes a transmitting device 60 instead of a transmitting device 40. In particular, Figures 13A and 13B show a case in which the transmitting device 60 and the receiving device 30 are communication devices located on the ground, and the relay nodes 20 are satellites. Here, the explanation assumes that the relay nodes 20 are mobile nodes that move. Multiple relay nodes 20 constitute a constellation. Figure 13A shows the state of the communication system 4 in which both communication path CP1 and communication path CP2 have been established. In other words, in Figure 13A, the transmitting device 60 is connected to relay nodes 20-11 and 20-21 because these relay nodes are located within the connectable space of the transmitting device 50.

[0084] Figure 13B shows the state of communication system 4 where communication path CP1 is disconnected, while communication path CP2 is established. In other words, Figure 13B shows the state of communication system 3 where relay node 20-11 has moved from the state in Figure 13A to outside the connectable space of the transmitter 50, and the connection between the transmitter 50 and relay node 20-11 has been disconnected. Relay node 20-21 has also moved from the state in Figure 13A, but since relay node 20-21 is located within the connectable space of the transmitter 60, the connection with the transmitter 60 is maintained.

[0085] <Example of Transmitter Configuration> Figure 14 is a block diagram showing another example of the transmitter according to this disclosure. In Figure 14, the transmitter 60 has a communication unit 41 and a control unit (control device) 61. The control unit 61 has a setting unit 61A, a scheduled timing estimation unit 61B, a distribution unit 61C, a movement parameter estimation unit 42A, a required time estimation unit 51C, and a communication control unit 51D.

[0086] The configuration unit 61A, like the configuration unit 51A, configures communication paths that pass through the relay nodes 20 to be connected. The configured communication paths may include not only communication paths that include the relay nodes 20 to be connected that the transmitting device 60 is currently connected to, but also communication paths that include relay nodes 20 to be connected that the transmitting device 60 will connect to in the near future.

[0087] Furthermore, the setting unit 61A may exclude a communication path if the distance between the relay node 20 to be connected to the communication path and the transmitting device 50 becomes greater than distancethrehold. Alternatively, the setting unit 61A may exclude a communication path if the elevation angle of the relay node 20 to be connected to the communication path as seen from the transmitting device 50 becomes less than elevationthrehold.

[0088] The scheduled timing estimation unit 61B, like the scheduled timing estimation unit 51B, estimates the scheduled connection timing of the communication path (i.e., the candidate destination path) set by the setting unit 51A. The scheduled timing estimation unit 61B also estimates the scheduled disconnection timing of each communication path. The scheduled disconnection timing can be calculated, for example, using the above formula (10).

[0089] Similar to the distribution unit 42D, the distribution unit 61C distributes each of the multiple transmission signals (for example, multiple transmission packets) to either communication path CP1 or communication path CP2 based on the first and second required times estimated by the required time estimation unit 51C. Therefore, even if a communication path is not connected, if the required time is shorter than that of a connected communication path, the transmission signal can be distributed to the unconnected communication path. This makes it possible to equalize the time it takes for the transmission signal to reach the receiving device 30.

[0090] Furthermore, the distribution unit 61C may exclude a communication path from the list of candidate destination paths at a "predetermined time" before the scheduled disconnection timing of the connected communication path. This "predetermined time" may, for example, be the length of time it takes for an acknowledgment (ACK) to be returned when TCP is applied, that is, twice the propagation path duration calculated by equation (4). This prevents packet loss and the resulting retransmission, and has the effect of reducing jitter. Also, if the TCP connection is disconnected at the time the communication path is disconnected, this "predetermined time" may be four times the propagation path duration calculated by equation (4).

[0091] <Example of Communication System Operation> Figure 15 is a flowchart showing another example of the processing operation of the transmitting device of this disclosure. In particular, Figure 15 shows an example of the processing operation in which the distribution unit excludes a communication path from the candidate destination path.

[0092] The distribution unit 61C obtains the planned disconnection timing for each current distribution destination route candidate from the planned timing estimation unit 61B (step S51).

[0093] The distribution unit 61C selects one communication path from among the current candidate destination paths (step S52).

[0094] The distribution unit 61C determines whether the selected communication path satisfies the exclusion conditions (step S53). The exclusion conditions are, for example, that the current timing (distribution timing) is before the scheduled disconnection timing of the selected communication path and within a "predetermined time" from this scheduled disconnection timing. If the selected communication path does not satisfy the exclusion conditions (step S53NO), the processing steps proceed to step S55.

[0095] If the selected communication path meets the exclusion conditions (step S53 YES), the distribution unit 61C excludes that communication path from the list of candidate destination paths (step S54).

[0096] The distribution unit 61C determines whether it has selected all of the current candidate communication routes (step S55). If there are still communication routes that have not been selected (step S55 NO), the distribution unit 61C selects one of the remaining communication routes (step S52). If all communication routes have been selected (step S55 YES), the processing flow in Figure 15 ends. This processing flow in Figure 15 is executed repeatedly.

[0097] As described above, according to the fourth embodiment, the scheduled timing estimation unit 61B in the transmitting device 60 estimates the scheduled disconnection timing for each communication path. The distribution unit 61C excludes the communication path from the distribution destination path candidates at a timing "determined time" before the scheduled disconnection timing of the communication path.

[0098] This configuration of the transmitting device 60 prevents the distribution of transmission signals to the communication path before the communication path is actually disconnected, thereby preventing packet loss and the resulting retransmission of data. This allows for stabilization of throughput and latency.

[0099] <Fifth Embodiment> The fifth embodiment relates to handover between communication paths. The technologies described in the third and fourth embodiments can be applied to handover between communication paths. The basic configuration of the transmitting device in the fifth embodiment is the same as that of the transmitting device 60 in the fourth embodiment, so it will be described with reference to Figure 14.

[0100] Figures 16A, 16B, and 16C show another example of the communication system of this disclosure. In Figures 16A, 16B, and 16C, the communication system 4 includes a transmitting device 60, relay nodes 20-11, 20-12, 20-21, and 20-22, and a receiving device 30. Figures 16A, 16B, and 16C show a case where the transmitting device 60 and the receiving device 30 are ground-based communication devices, and the relay nodes 20 are satellites. Here, the relay nodes 20 are mobile nodes that move. Multiple relay nodes 20 constitute a constellation. Figure 16A shows the state of the communication system 4 where communication path CP1 has been established, but communication path CP2 has not yet been established. That is, Figure 16A shows the state of the communication system 4 before handover (before time T1). Time T1 corresponds to the planned connection timing described above.

[0101] Figure 16B shows the state of communication system 4 when both communication paths CP1 and CP2 are established. In other words, Figure 16B shows the state of communication system 4 during handover (from time T1 to time T3). Time T3 corresponds to the scheduled disconnection timing mentioned above.

[0102] Figure 16C shows the state of communication system 4 where communication path CP1 is disconnected, while communication path CP2 is established. In other words, Figure 16C shows the state of communication system 4 after the handover is completed.

[0103] Figure 17A shows the trend of propagation delay time in the communication path in the communication system of this disclosure. Figure 17B shows the trend of data transmission volume in the communication path in the communication system of this disclosure. Figure 17C shows the trend of throughput and delay time on the receiving side in the communication system of this disclosure.

[0104] Figure 18A shows the trend of propagation delay time of the communication path in the comparative example's communication system. Figure 18B shows the trend of data transmission volume of the communication path in the comparative example's communication system. Figure 18C shows the trend of receiving throughput and delay time in the comparative example's communication system. Unlike the communication system of this disclosure, the comparative example's communication system is based on the premise that the amount of data to be distributed and transmitted is determined according to the past history of path delay. Also, unlike the communication system of this disclosure, the comparative example's communication system is based on the premise that slow start is applied. Unlike the communication system of this disclosure, the comparative example's communication system is based on the premise that the process of excluding the communication path from the distribution destination path candidates is not performed at a "predetermined time" before the scheduled timing of the disconnection of the communication path.

[0105] In Figure 17A, the solid line G11 represents the time change in the path delay of communication path CP1 in communication system 4. The dashed line G12 represents the time change in the path delay of communication path CP2 in communication system 4. In Figure 18A, the solid line G21 represents the time change in the path delay of communication path CP1 in the comparative example's communication system. The dashed line G22 represents the time change in the path delay of communication path CP2 in the comparative example's communication system. Assuming that communication system 4 and the comparative example's communication system have the same communication paths CP1 and CP2, the solid line G11 coincides with the solid line G21, and the dashed line G12 coincides with the dashed line G22.

[0106] In Figure 18B, the solid line G23 represents the data transmission rate of communication path CP1, and the dashed line G24 represents the data transmission rate of communication path CP2. This transmission rate reflects the data distribution rate. In communication path CP1, the transmission rate gradually decreases as the delay time increases until time T3. Next, at time T1, communication path CP2 is connected. In the comparative example communication system, the data distribution rate and transmission rate are determined according to the past history of path delay. Therefore, there is a delay in increasing the transmission rate, at least for the time required to measure the path delay. As a result, the transmission rate of communication path CP2 gradually increases from time T2, which is later than time T1. After this, communication paths CP1 and CP2 are connected to the transmitting device. Then, at time T3, communication path CP1 is disconnected. As a result, the transmission rate drops instantaneously, and packet loss occurs.

[0107] In Figure 17B, the solid line G13 represents the data transmission volume of communication path CP1, and the dashed line G14 represents the data transmission volume of communication path CP2. In the transmission device 60 of the communication system 4, the setting unit 61A sets communication path CP2 as a communication path even before it connects to the transmission device 60. Furthermore, when TCP (Transmission Control Protocol) is applied to the communication unit 41, the communication control unit 51D sets the initial value of the congestion control window corresponding to communication path CP2 based on the product of the second required time and the predicted value of the communication bandwidth corresponding to communication path CP2. This makes it possible to achieve a data transmission volume corresponding to the path delay immediately after connection at the connection time T1 of communication path CP2. In addition, the distribution unit 61C excludes communication path CP1 from the distribution destination path candidates at a "determined time" before the scheduled disconnection timing of communication path CP1. As a result, the solid line G13 gradually decreases from before time T3.

[0108] In Figure 18C, the solid line G25 represents the receiving throughput. This receiving throughput roughly matches the sum of the data transmission volumes of the two communication paths. However, the solid line G25 is shifted to the right by the amount of path delay compared to the sum of the data transmission volumes of the two communication paths. Furthermore, the solid line G25 shows significant fluctuations after time T3, when communication path CP1 is disconnected. First, immediately after time T4, when the data transmitted at time T3 arrives at the receiving side, the throughput drops significantly due to data retransmission caused by packet loss. Data transmission through communication path CP2 continues. However, because it takes time to retransmit the lost data and to align the data, the throughput drops significantly for a short period after time T4. After that, the throughput recovers and becomes the throughput corresponding to the path delay time of communication path CP2. Also, the dashed line G26, which represents the delay time as seen from the receiving side at this time, increases significantly due to the time required for data retransmission and alignment.

[0109] On the other hand, the transmitting device 60 of the communication system 4 calculates the path delay at the time of data distribution by referring to the trajectory information of the relay node 20, and calculates the required time. Therefore, the amount of data to be distributed to each communication path is determined in accordance with the delay time of the path at the time of data distribution. As a result, especially at the connection time T1 of communication path CP2, it is possible to achieve a data transmission amount corresponding to the path delay immediately after connection. In addition, the disconnection time of the communication path can be predicted based on the trajectory information. Therefore, the transmission amount can be reduced in advance at the time T3 when communication path CP1 is disconnected, and packet loss can be prevented. In Figure 17C, the solid line G15 represents the progress of the receiving side throughput. The dashed line G16 represents the progress of the receiving side delay time. In the communication system 4, it is possible to distribute data according to the accurate path state at the time of data distribution processing, so that excessive distribution relative to the transmission amount does not occur and packet loss when the path is disconnected can be prevented. As a result, it is possible to prevent increases in throughput and delay time due to data retransmission and alignment.

[0110] <Other Embodiments> Figure 19 shows an example of the configuration of a transmitting device. In Figure 19, the transmitting device 100 includes a processor 101, a memory 102, and a communication circuit 103. The processor 101 may be, for example, a microprocessor, an MPU (Micro Processing Unit), or a CPU (Central Processing Unit). The processor 101 may include multiple processors. The memory 102 is composed of a combination of volatile memory and non-volatile memory. The memory 102 may include storage located away from the processor 101. In this case, the processor 101 may access the memory 102 via an I (Input) / O (Output) interface, which is not shown.

[0111] The transmitting devices 10, 40, 50, and 60 of the first to fifth embodiments may each have the configuration shown in Figure 19. The control units 12, 32, 42, 51, and 61 of the transmitting devices 10, 40, 50, and 60 of the first to fifth embodiments may be implemented by the processor 101 reading and executing a program stored in the memory 102. In other words, the transmitting devices 10, 40, 50, and 60 of the first to fifth embodiments can be implemented in software. The program can be stored using various types of non-transitory computer-readable media and supplied to the transmitting devices 10, 40, 50, and 60. Examples of non-transitory computer-readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives) and magneto-optical recording media (e.g., magneto-optical disks). Furthermore, examples of non-transitory computer-readable media include CD-ROMs (Read Only Memory), CD-Rs, and CD-R / Ws. Furthermore, examples of non-transitory computer-readable media include semiconductor memory. Semiconductor memory includes, for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, and RAM (Random Access Memory). The program may also be supplied to the transmitters 10, 40, 50, and 60 by various types of transient computer-readable medium. Examples of transient computer-readable medium include electrical signals, optical signals, and electromagnetic waves. The transient computer-readable medium can supply the program to the transmitters 10, 40, 50, and 60 via wired communication channels such as electric wires and optical fibers, or via wireless communication channels.

[0112] Alternatively, the control units 12, 32, 42, 51, and 61 of the transmitting devices 10, 40, 50, and 60 in the first to fifth embodiments may each be implemented with dedicated hardware.

[0113] Although the present invention has been described above with reference to embodiments, the present invention is not limited thereto. Various modifications to the structure and details of the present invention can be made within the scope of the invention as can be understood by those skilled in the art. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0114] Each drawing is merely illustrative to illustrate one or more embodiments. Each drawing may be associated with one or more other embodiments, rather than being associated with only one specific embodiment. As those skilled in the art will understand, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings, for example, to create embodiments not explicitly shown or described. Not all features or steps shown in any one drawing to illustrate an exemplary embodiment are necessarily required, and some features or steps may be omitted. The order of steps described in any of the drawings may be changed as appropriate.

[0115] Some or all of the above embodiments may also be described as follows, but are not limited to the following: (Note 1) A transmitting device in a communication system which includes a transmitting device, a plurality of relay nodes, and a receiving device, wherein at least one of the transmitting device, the plurality of relay nodes, and the receiving device is a mobile node, comprising: communication means capable of wirelessly connecting to a plurality of target relay nodes; setting means for setting a first communication path from the transmitting device to the receiving device which includes a first target relay node, and a second communication path from the transmitting device to the receiving device which includes a second target relay node; and distribution means for distributing each of a plurality of transmission signals to the first communication path or the second communication path. (Note 2) The transmitting device according to Note 1, comprising: a first estimation means for estimating the position and speed of the mobile node based on information relating to the movement of the mobile node; and a second estimation means for estimating a first required time for a transmission signal allocated to the first communication path to reach the receiving device, and a second required time for a transmission signal allocated to the second communication path to reach the receiving device, based on the estimated position and speed of the mobile node, wherein the allocation means allocates each of the plurality of transmission signals to the first communication path or the second communication path based on the first required time and the second required time. (Note 3) When the first target relay node and the second target relay node are connected to the communication means, the first required time and the second required time each include the transmission processing time from when the transmission signal to be distributed is input to the transmission buffer corresponding to the communication path until the communication means transmits the transmission signal to be distributed, and the propagation path time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device, as described in Note 2.(Note 4) The transmitting device according to Note 2, further comprising a third estimation means for estimating the planned connection timing of the second communication path when the second relay node to be connected is not connected to the communication means, wherein when the second relay node to be connected is not connected to the communication means, the second required time includes the connection required time from the current timing to the planned connection timing when the communication means connects to the second relay node to be connected, the transmission processing required time from the planned connection timing until the communication means transmits the transmission signal to be distributed, and the propagation path required time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device. (Note 5) The transmitting device according to Note 4, further comprising a communication control means for setting the initial value of the congestion control window corresponding to the second communication path based on the product of the second required time and the communication bandwidth corresponding to the second communication path when TCP (Transmission Control Protocol) is applied to the communication means. (Note 6) The transmitting device according to Note 1 or 2, further comprising a fourth estimation means for estimating the scheduled timing for disconnection of the first communication path, wherein the distribution means excludes the first communication path from the distribution path candidates at a predetermined time before the scheduled timing for disconnection. (Note 7) The transmitting device according to Note 2, wherein, if the mobile node is a satellite, the information relating to the movement of the mobile node is the orbital information of the satellite. (Note 8) A method performed by the transmitting device in a communication system comprising a transmitting device, a plurality of relay nodes, and a receiving device, wherein at least one of the transmitting device, the plurality of relay nodes, and the receiving device is a mobile node, comprising: setting a first communication path from the transmitting device to the receiving device and including a first connection target relay node; and setting a second communication path from the transmitting device to the receiving device and including a second connection target relay node; and distributing each of a plurality of transmission signals to the first communication path or the second communication path.(Note 9) The method according to Note 8, comprising: estimating the position and speed of the mobile node based on information relating to the movement of the mobile node; and estimating, based on the estimated position and speed of the mobile node, a first time required for a transmission signal allocated to the first communication path to reach the receiving device, and a second time required for a transmission signal allocated to the second communication path to reach the receiving device, wherein the allocation includes allocating each of the plurality of transmission signals to the first communication path or the second communication path based on the first time and the second time. (Note 10) The method according to Note 9, wherein when the first target relay node and the second target relay node are connected to the communication means of the transmitting device, the first required time and the second required time each include the transmission processing time from when the transmission signal to be distributed is input to the transmission buffer corresponding to the communication path until the communication means transmits the transmission signal to be distributed, and the propagation path time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device. (Note 11) The method according to Note 9, comprising estimating the planned connection timing of the second communication path when the second relay node to be connected is not connected to the communication means of the transmitting device, wherein when the second relay node to be connected is not connected to the communication means, the second required time includes the connection required time from the current timing to the planned connection timing when the communication means connects to the second relay node to be connected, the transmission processing required time from the planned connection timing until the communication means transmits the transmission signal to be distributed, and the propagation path required time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device. (Note 12) The method according to Note 11, comprising setting the initial value of the congestion control window corresponding to the second communication path based on the product of the second required time and the communication bandwidth corresponding to the second communication path when TCP (Transmission Control Protocol) is applied to the communication means.(Note 13) The method according to Note 8 or 9, comprising estimating the scheduled timing for disconnection of the first communication path, wherein the distribution includes excluding the first communication path from the distribution path candidates at a predetermined time before the scheduled timing for disconnection. (Note 14) The method according to Note 9, wherein, if the mobile node is a satellite, the information relating to the movement of the mobile node is the orbital information of the satellite. (Note 15) A program that causes the transmitting device in a communication system comprising a transmitting device, a plurality of relay nodes, and a receiving device, wherein at least one of the transmitting device, the plurality of relay nodes, and the receiving device is a mobile node, to execute a process that includes setting a first communication path from the transmitting device to the receiving device and including a first connection target relay node, and a second communication path from the transmitting device to the receiving device and including a second connection target relay node, and distributing each of a plurality of transmission signals to the first communication path or the second communication path. (Note 16) The program described in Note 15, wherein the process includes: estimating the position and speed of the mobile node based on information relating to the movement of the mobile node; estimating a first time required for a transmission signal distributed to the first communication path to reach the receiving device, and a second time required for a transmission signal distributed to the second communication path to reach the receiving device, based on the estimated position and speed of the mobile node, and the distribution includes distributing each of the plurality of transmission signals to the first communication path or the second communication path based on the first time and the second time required. (Note 17) When the first target relay node and the second target relay node are connected to the communication means of the transmitting device, the first required time and the second required time each include the transmission processing time from when the transmission signal to be distributed is input to the transmission buffer corresponding to the communication path until the communication means transmits the transmission signal to be distributed, and the propagation path time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device, as described in Note 16.(Note 18) The program as described in Note 16, wherein the process includes estimating the planned connection timing of the second communication path when the second target relay node is not connected to the communication means of the transmitting device, and when the second target relay node is not connected to the communication means, the second required time includes the connection time from the current timing to the planned connection timing when the communication means connects to the second target relay node, the transmission processing time from the planned connection timing until the communication means transmits the distribution target transmission signal, and the propagation path time from when the distribution target transmission signal is transmitted from the communication means until it is received by the receiving device. (Note 19) The program as described in Note 18, wherein the process includes setting the initial value of the congestion control window corresponding to the second communication path based on the product of the second required time and the communication bandwidth corresponding to the second communication path when TCP (Transmission Control Protocol) is applied to the communication means. (Note 20) The program according to Note 15 or 16, wherein the process includes estimating the scheduled timing for disconnection of the first communication path, and the distribution includes excluding the first communication path from the distribution path candidates at a predetermined time before the scheduled timing for disconnection. (Note 21) The program according to Note 16, wherein if the mobile node is a satellite, the information relating to the movement of the mobile node is the orbital information of the satellite.

[0116] This application claims priority based on Japanese Patent Application No. 2025-045475, filed on 19 March 2025, and incorporates all of its disclosures herein.

[0117] 1 Communication system 2 Communication system 3 Communication system 4 Communication system 10 Transmitting device 11 Communication unit 12 Control unit (control device) 12A Setting unit 12B Distribution unit 20 Relay node (mobile node) 21 Communication interface unit 22 Communication interface unit 30 Receiving device 31 Communication unit 32 Control unit (control device) 32A Receiving processing unit 40 Transmitting device 41 Communication unit 41A Transmitting unit 41B Transmitting buffer 42 Control unit (control device) 42A Movement parameter estimation unit 42A1 Estimation processing unit 42A2 Holding unit 42B Setting unit 42C Required time estimation unit 42D Distribution unit 42E Communication control unit 50 Transmitting device 51 Control unit (control device) 51A Setting unit 51B Scheduled timing estimation unit 51C Required time estimation unit 51D Communication control unit 60 Transmitter 61 Control unit (control device) 61A Setting unit 61B Scheduled timing estimation unit 61C Distribution unit

Claims

A communication system comprising a transmitting device, a plurality of relay nodes, and a receiving device, wherein at least one of the transmitting device, the plurality of relay nodes, and the receiving device is a mobile node, A communication means capable of wirelessly connecting to multiple relay nodes, Setting means for setting a first communication path from the transmitting device to the receiving device that includes a first relay node to be connected, and a second communication path from the transmitting device to the receiving device that includes a second relay node to be connected, Distribution means for distributing each of the multiple transmission signals to the first communication path or the second communication path, A transmitting device equipped with the following. 　 A first estimation means for estimating the position and velocity of the moving node based on information regarding the movement of the moving node, A second estimation means for estimating, based on the estimated position and speed of the mobile node, a first time required for the transmission signal distributed to the first communication path to reach the receiving device, and a second time required for the transmission signal distributed to the second communication path to reach the receiving device, It is equipped with, The distribution means distributes each of the plurality of transmission signals to the first communication path or the second communication path based on the first required time and the second required time. The transmitting device according to claim 1. 　 When the first target relay node and the second target relay node are connected to the communication means, the first required time and the second required time each include the transmission processing time from when the transmission signal to be distributed is input to the transmission buffer corresponding to the communication path until the communication means transmits the transmission signal to be distributed, and the propagation path time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device. The transmitting device according to claim 2. 　 The system includes a third estimation means for estimating the planned connection timing of the second communication path when the second target relay node is not connected to the communication means, If the second relay node to be connected is not connected to the communication means, the second required time includes the connection time from the current timing to the scheduled connection timing when the communication means connects to the second relay node to be connected, the transmission processing time from the scheduled connection timing until the communication means transmits the transmission signal to be distributed, and the propagation path time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device. The transmitting device according to claim 2. 　 When TCP (Transmission Control Protocol) is applied to the communication means, the system includes a communication control means that sets the initial value of the congestion control window corresponding to the second communication path based on the product of the second required time and the communication bandwidth corresponding to the second communication path. The transmitting device according to claim 4. 　 The system comprises a fourth estimation means for estimating the planned timing of disconnection of the first communication path, The distribution means excludes the first communication path from the distribution path candidates at a predetermined time before the scheduled disconnection timing. The transmitting device according to claim 1 or 2. 　 If the mobile node is a satellite, the information relating to the movement of the mobile node is the orbital information of the satellite. The transmitting device according to claim 2. 　 A method performed by a transmitting device in a communication system which includes a transmitting device, a plurality of relay nodes, and a receiving device, wherein at least one of the transmitting device, the plurality of relay nodes, and the receiving device is a mobile node, Setting up a first communication path that includes a first relay node to be connected and extends from the transmitting device to the receiving device, and a second communication path that includes a second relay node to be connected and extends from the transmitting device to the receiving device, Distributing each of the multiple transmission signals to the first communication path or the second communication path, A method that includes this. 　 Based on information regarding the movement of the aforementioned mobile node, the position and velocity of the mobile node are estimated. Based on the estimated position and speed of the mobile node, the first time required for the transmission signal distributed to the first communication path to reach the receiving device, and the second time required for the transmission signal distributed to the second communication path to reach the receiving device are estimated. Includes, The aforementioned distribution includes distributing each of the plurality of transmission signals to the first communication path or the second communication path based on the first required time and the second required time. The method according to claim 8. 　 When the first target relay node and the second target relay node are connected to the communication means of the transmitting device, the first required time and the second required time each include the transmission processing time from when the transmission signal to be distributed is input to the transmission buffer corresponding to the communication path until the communication means transmits the transmission signal to be distributed, and the propagation path time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device. The method according to claim 9. 　 This includes estimating the planned connection timing of the second communication path when the second relay node to be connected is not connected to the communication means of the transmitting device, If the second relay node to be connected is not connected to the communication means, the second required time includes the connection time from the current timing to the scheduled connection timing when the communication means connects to the second relay node to be connected, the transmission processing time from the scheduled connection timing until the communication means transmits the transmission signal to be distributed, and the propagation path time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device. The method according to claim 9. 　 When TCP (Transmission Control Protocol) is applied to the communication means, the initial value of the congestion control window corresponding to the second communication path is set based on the product of the second required time and the communication bandwidth corresponding to the second communication path. The method according to claim 11. This includes estimating the planned timing for disconnection of the first communication path, The aforementioned distribution includes excluding the first communication path from the distribution path candidates at a predetermined time before the scheduled disconnection timing. The method according to claim 8 or 9. 　 If the mobile node is a satellite, the information relating to the movement of the mobile node is the orbital information of the satellite. The method according to claim 9. 　 In a communication system that includes a transmitting device, a plurality of relay nodes, and a receiving device, wherein at least one of the transmitting device, the plurality of relay nodes, and the receiving device is a mobile node, the transmitting device Setting up a first communication path that includes a first relay node to be connected and extends from the transmitting device to the receiving device, and a second communication path that includes a second relay node to be connected and extends from the transmitting device to the receiving device, Distributing each of the multiple transmission signals to the first communication path or the second communication path, A program that performs a process that includes this. 　 The aforementioned process is, Based on information regarding the movement of the aforementioned mobile node, the position and velocity of the mobile node are estimated. Based on the estimated position and speed of the mobile node, the first time required for the transmission signal distributed to the first communication path to reach the receiving device, and the second time required for the transmission signal distributed to the second communication path to reach the receiving device are estimated. Includes, The aforementioned distribution includes distributing each of the plurality of transmission signals to the first communication path or the second communication path based on the first required time and the second required time. The program according to claim 15. 　 When the first target relay node and the second target relay node are connected to the communication means of the transmitting device, the first required time and the second required time each include the transmission processing time from when the transmission signal to be distributed is input to the transmission buffer corresponding to the communication path until the communication means transmits the transmission signal to be distributed, and the propagation path time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device. L as described in claim 16. 　 The process includes estimating the planned connection timing of the second communication path when the second relay node to be connected is not connected to the communication means of the transmitting device. If the second relay node to be connected is not connected to the communication means, the second required time includes the connection time from the current timing to the scheduled connection timing when the communication means connects to the second relay node to be connected, the transmission processing time from the scheduled connection timing until the communication means transmits the transmission signal to be distributed, and the propagation path time from when the transmission signal to be distributed is transmitted from the communication means until it is received by the receiving device. L as described in claim 16. 　 The process includes, when TCP (Transmission Control Protocol) is applied to the communication means, setting the initial value of the congestion control window corresponding to the second communication path based on the product of the second required time and the communication bandwidth corresponding to the second communication path. The program according to claim 18. 　 The process includes estimating the planned timing for disconnecting the first communication path. The aforementioned distribution includes excluding the first communication path from the distribution path candidates at a predetermined time before the scheduled disconnection timing. The program according to claim 15 or 16.

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