Wireless communication system, wireless communication method, and communication path determination device

Abstract

A radio communication system according to an embodiment of the present invention performs a first calculation step of calculating positional information indicating the position of each of node stations and load information indicating the traffic load of each of the node stations and calculating, on the basis of the calculated positional information, a propagation time of a link from a transmission device to each of the node stations, a propagation time of each of inter node-station links, a buffering time for which each of the node stations needs to retain data before the link is established, and a propagation time of a link from each of the node stations to a reception device; performs a second calculation step of calculating a queuing time of each of the node stations on the basis of the calculated load information; calculates a total delay time in data transmission for each of routes from the transmission device to the reception device on the basis of the times calculated in the first calculation step and the times calculated in the second calculation step; and determines, as a communication route, a route the calculated total delay time of which is smallest.

Description

[Technical field]

[0001] The present invention relates to a wireless communication system, a wireless communication method, and a communication path determination device. [Background technology]

[0002] Known technologies for constructing mobile networks include those using geostationary satellites, medium earth orbit satellites (MEO: Medium Earth Orbit), low earth orbit satellites (LEO: Low Earth Orbit), high altitude pseudo satellites (HAPS: High Altitude Platform Station), airplanes, drones, etc.

[0003] For example, low-earth-orbit satellite networks are closer to the ground than geostationary satellites, resulting in smaller propagation delays and lower power costs for transmission and reception. Low-earth-orbit satellites can also calculate their position from their orbits.

[0004] However, even though low-earth orbit satellite networks cover the entire globe, due to uneven distribution of network users, traffic can sometimes be concentrated at satellite relay stations (hereinafter referred to as node stations) that cover specific regions.

[0005] For example, Non-Patent Document 1 discloses a traffic control method that performs load balancing using congestion prediction in order to suppress the occurrence of congestion due to bias in traffic distribution. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Daigo Kudo and 2 others, "Traffic Control Using Congestion Prediction in LEO Satellite IP Networks," IEICE Technical Report, Institute of Electronics, Information and Communication Engineers, May 2008, pp.19-24 Summary of the Invention [Problem to be solved by the invention]

[0007] For example, when a link between a ground station or a ground terminal station and a node station is cut off, the node station needs to temporarily hold (hereinafter, buffer) traffic until the next link is established.

[0008] However, in the past, traffic control did not take into account delays caused by buffering, which could result in a decrease in the throughput of the entire system. In other words, in low-earth-orbit satellite networks, it is sometimes necessary to implement control to improve throughput according to link and traffic conditions.

[0009] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a wireless communication system, a wireless communication method, and a communication path determination device that enable efficient wireless communication via moving node stations. [Means for solving the problem]

[0010] A wireless communication system according to one embodiment of the present invention is a wireless communication system in which data to be transmitted from a transmitting device to a receiving device is wirelessly transmitted over a communication path via a plurality of node stations, at least one of which moves. The wireless communication system is characterized by having an information calculation unit that calculates location information indicating the location of each of the node stations and load information indicating the load due to traffic of each of the node stations, a first calculation unit that calculates, based on the location information calculated by the information calculation unit, a propagation time of the link from the transmitting device to the node station, a propagation time of each of the links between the node stations, a buffering time in which each of the node stations should hold data until a link is established, and a propagation time of the link from the node station to the receiving device, based on the load information calculated by the information calculation unit, a second calculation unit that calculates a queuing time of each of the node stations based on the load information calculated by the information calculation unit, a delay time calculation unit that calculates a sum of delay times occurring in data transmission for each of the paths from the transmitting device to the receiving device based on each of the times calculated by the first calculation unit and each of the times calculated by the second calculation unit, and a determination unit that determines the path for which the sum of the delay times calculated by the delay time calculation unit is the smallest as the communication path.

[0011] Moreover, a wireless communication method according to one embodiment of the present invention is a wireless communication method for wirelessly transmitting data to be transmitted from a transmitting device to a receiving device over a communication path via a plurality of node stations, at least one of which moves, the method comprising the steps of: an information calculation step of calculating location information indicating the location of each of the node stations and load information indicating the load due to traffic of each of the node stations; a first calculation step of calculating, based on the calculated location information, a propagation time of a link from the transmitting device to the node station, a propagation time of each of the links between the node stations, a buffering time in which each of the node stations should hold data until a link is established, and a propagation time of a link from the node station to the receiving device; a second calculation step of calculating, based on the calculated load information, a queuing time of each of the node stations; a delay time calculation step of calculating a sum of delay times occurring in data transmission for each of the paths from the transmitting device to the receiving device based on each of the times calculated in the first calculation step and each of the times calculated in the second calculation step; and a determination step of determining, as the communication path, a path for which the sum of the calculated delay times is smallest.

[0012] Moreover, a communication path determination device according to one embodiment of the present invention is a communication path determination device that determines a communication path for wirelessly transmitting data to be transmitted from a transmitting device to a receiving device via a plurality of node stations, at least one of which moves, and is characterized in having an information calculation unit that calculates location information indicating the location of each of the node stations and load information indicating the load due to traffic of each of the node stations, a first calculation unit that calculates, based on the location information calculated by the information calculation unit, a propagation time of the link from the transmitting device to the node station, a propagation time of each of the links between the node stations, a buffering time in which each of the node stations should hold data until a link is established, and a propagation time of the link from the node station to the receiving device, based on the load information calculated by the information calculation unit, a second calculation unit that calculates a queuing time of each of the node stations based on the load information calculated by the information calculation unit, a delay time calculation unit that calculates a sum of delay times occurring in data transmission for each of the paths from the transmitting device to the receiving device based on each of the times calculated by the first calculation unit and each of the times calculated by the second calculation unit, and a determination unit that determines, as the communication path, the path for which the sum of the delay times calculated by the delay time calculation unit is the smallest. Effect of the Invention

[0013] According to the present invention, it is possible to perform efficient wireless communication via a moving node station. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Diagram 2] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system as a comparative example. [Diagram 3] FIG. 10 is a diagram illustrating an example of an operation of a wireless communication system as a comparative example. [Figure 4] 1 is a diagram illustrating a configuration and a first operation of a wireless communication system according to an embodiment. [Diagram 5] FIG. 2 is a diagram illustrating an example of a configuration of a ground station according to an embodiment. [Figure 6]4 is a functional block diagram illustrating functions of a communication path calculation unit. FIG. [Figure 7] 1 is a diagram illustrating a configuration and a second operation of a wireless communication system according to an embodiment. [Figure 8] 11 is a flowchart illustrating a process performed by a communication path calculation unit when a wireless communication system according to an embodiment performs a second operation. [Figure 9] FIG. 11 is a diagram illustrating a configuration and a third operation of a wireless communication system according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] First, the background that led to the invention will be described in more detail. Fig. 1 is a diagram showing an example of the configuration of a wireless communication system 1. As shown in Fig. 1, the wireless communication system 1 is configured such that each terminal station (terrestrial terminal station) 10 is connected to a terrestrial station (satellite terrestrial station) 3 by using, for example, any of communication paths passing through a plurality of node stations 2.

[0016] The terminal station 10 and the ground station 3 each have a function as a transmitting device and a function as a receiving device, and perform two-way wireless communication. The terminal station 10 may perform wireless communication with another terminal station 10 using any of the communication paths passing through the multiple node stations 2. Each of the node stations 2 is a mobile relay station such as a low-earth orbit satellite (mobile satellite) or a geostationary satellite. Each wireless link in the wireless communication system 1 includes a communication line and a control line.

[0017] If the node station 2 is a low-orbit satellite, it moves in the sky at an altitude of, for example, 2000 km or less above the Earth's surface. If the node station 2 is a geostationary satellite, it moves in a geostationary orbit at an altitude of about 36000 km above the Earth's surface, revolving around the Earth with the same period as the Earth's rotation period.

[0018] The node station 2 may also be another mobile relay station such as a medium earth orbit satellite, a high altitude pseudo satellite, or an airplane. Each connection (link) in the wireless communication system 1 may be realized by wireless communication using radio waves, or may be realized by other wireless communication such as optical communication.

[0019] Fig. 2 is a diagram showing an example of the configuration of a wireless communication system as a comparative example. As shown in Fig. 2, a terminal station 10 performs wireless communication with a ground station 3 via a plurality of node stations 2 (any of node stations 2-1 to 2-8). Here, the terminal station 10 is assumed to be a transmitting device and to transmit data to the ground station 3, which is a receiving device.

[0020] In the wireless communication system shown in FIG. 2, the terminal station 10 transmits data to the ground station 3 via a communication path that minimizes the total delay time T outlined in the following equation (1).

[0021] T=T L ×N L +T q ×N S +T E (1)

[0022] however, T L : Propagation time of the link between node station 2 and node station 2 T E : Propagation time of the link between the node station 2 and the terminal station 10 or the earth station 3 T q : Node 2 queuing time N L : The total number of links between node station 2 and node station 2 included in the route N S : Total number of nodes 2 included in the route

[0023] In the wireless communication system shown in Fig. 2, the shortest route is route A indicated by the thick dashed arrow. However, for example, if traffic is concentrated on node station 2-2 and node station 2-3, causing congestion, the wireless communication system will select route B as the communication route instead of the shortest route A based on the above formula (1). In this way, congestion can be avoided by selecting as the communication route a detour route that has the smallest total delay time T among routes that do not pass through node station 2-2 and node station 2-3, whose queuing times are equal to or greater than a threshold.

[0024] However, in an actual wireless communication system, when the service is first introduced or for cost reasons or other reasons, it is conceivable that the node stations 2 are not densely arranged and there is not even one node station 2 with which the earth station 3 or terminal station 10 can communicate.

[0025] For example, as shown in FIG. 3, if the link between node station 2-4 and earth station 3 is severed and communication becomes impossible, node station 2-4 needs to temporarily hold (buffer) traffic until communication with earth station 3 becomes possible, regardless of whether the communication path is the shortest path A or the detour path B.

[0026] In this case, the conventional technology is unable to perform control that takes into account the delay time due to buffering, and the throughput of the entire wireless communication system decreases.

[0027] Therefore, the wireless communication system according to the embodiment is configured to enable efficient wireless communication even when the link between the moving node station and the receiving device is cut off.

[0028] Next, a configuration example of a wireless communication system according to an embodiment will be described. In the wireless communication system according to the embodiment, the same components as those described above are denoted by the same reference numerals.

[0029] 4 is a diagram illustrating a configuration and a first operation of a wireless communication system 1 according to an embodiment. As shown in FIG. 4, in the wireless communication system 1, a terminal station 10 transmits data to a ground station 3a via a communication path using, for example, any two or more of node stations 2-1 to 2-7.

[0030] That is, the wireless communication system 1 wirelessly transmits data from the terminal station 10, which is a transmitting device, to the ground station 3a, which is a receiving device, via a communication path that passes through multiple node stations 2-1 to 2-7, at least one of which moves. The same applies when the ground station 3a is the transmitting device and the terminal station 10 is the receiving device. When there is no need to specify any one of the multiple configurations, such as the node stations 2-1 to 2-7, they will simply be abbreviated as node station 2.

[0031] Here, the node stations 2-1 to 2-6 are assumed to be low-earth orbit satellites. The node station 2-7 is assumed to be a geostationary satellite and an absolute node station that can always communicate with the ground station 3a. In the wireless communication system 1, the terminal station 10 transmits data to the ground station 3a via a communication path that minimizes the total delay time T outlined in the following formula (2).

[0032] T=T L ×N L +T q ×N S +T E +T b (2)

[0033] however, T L : Propagation time of the link between node station 2 and node station 2 T E : Propagation time of the link between the node station 2 and the terminal station 10 or the earth station 3a T q : Node 2 queuing time T b : Buffering time of node 2 N L : The total number of links between node station 2 and node station 2 included in the route N S: Total number of nodes 2 included in the route

[0034] The node stations 2-1 to 2-6 are capable of calculating their respective positions based on their respective orbit information. Here, the buffering time of the node station 2 is defined as the time required for a node station 2 that has lost communication with the terminal station 10 or the ground station 3a to move and become able to communicate again. If buffering is not required, the buffering time is zero.

[0035] The calculation of the communication path using the above formula (2) may be performed individually by any of the terminal station 10, the node station 2, or the ground station 3a. The wireless communication system 1 may be configured such that, for example, one communication path determination device (not shown) calculates the communication path using the above formula (2) and shares the calculation result with other devices.

[0036] Here, for example, the ground station 3a calculates the communication path using the above equation (2) (described in detail using Figures 4 and 5), and each device constituting the wireless communication system 1 shares the calculation results of the communication path to realize communication between the terminal station 10 and the ground station 3a.

[0037] For example, when a link is established between the node station 2-3 and the earth station 3a, no buffering is required in the node station 2. Therefore, the total delay time T is likely to be smallest in the route X1 that passes only through the node stations 2-1 to 2-3, which are low-earth orbit satellites.

[0038] On the other hand, if the link between the node station 2-3 and the earth station 3a is cut off and communication is not possible, there is no low-earth orbit satellite that can communicate with the earth station 3a. In this case, buffering is required for all routes that go through only low-earth orbit satellites. Therefore, the total delay time T is likely to be smallest on the route Y1 that goes through the node station 2-7, which is a geostationary satellite that does not require buffering.

[0039] In addition, although the link between the node station 2-3 and the ground station 3a is currently disconnected and communication is not possible, it may be expected that the link between the node station 2-3 and the ground station 3a will be established after a short time has passed due to the movement of the node station 2-3, etc. In this case, the total delay time T may be smaller for the path X1 that requires buffering than for the path Y1 that does not require buffering.

[0040] Next, a specific configuration example of the ground station 3a will be described. Fig. 5 is a diagram showing a configuration example of the ground station 3a according to an embodiment. The terminal station 10 and the like may also be configured as shown in Fig. 5.

[0041] As shown in FIG. 5, the ground station 3a includes, for example, an antenna 30, an RF (Radio Frequency) unit 32, a modem unit 34, a database (DB) 36, and a communication path calculation unit 4.

[0042] The antenna 30 transmits and receives signals such as network information (NW information) and data (traffic) by radio waves for performing wireless communication in the wireless communication system 1. The antenna 30 outputs the received signals to the RF unit 32, and transmits signals such as data input from the RF unit 32 by radio waves. The antenna 30 may be a single high-performance antenna, or may be configured with multiple antennas.

[0043] The RF unit 32 converts the signal input from the antenna 30 into a baseband signal and outputs it to the modem unit 34. The RF unit 32 also converts the signal input from the modem unit 34 into a radio frequency signal and outputs it to the antenna 30.

[0044] The modem unit 34 demodulates and processes the signal input from the RF unit 32, and outputs the result to a database 36. The modem unit 34 also processes and modulates information including the signal input from the communication path calculation unit 4 (the communication path calculation result), and outputs the result to the RF unit 32.

[0045] The database 36 stores the signal (information) input from the modem unit 34, and outputs a signal in response to an access from, for example, the communication path calculation unit 4. The database 36 may be placed on a network connected to the wireless communication system 1.

[0046] The signals (information) stored in the database 36 include various parameters necessary for calculating the above-mentioned sum T of delay times, data that is the main part of traffic, etc. For example, the various parameters stored in the database 36 include information exchanged by each device in the wireless communication system 1 to calculate location information indicating the location of each node station 2, and load information indicating the load caused by the traffic of each node station 2.

[0047] The communication path calculation unit 4 uses information stored in the database 36 to calculate the sum T of delay times of multiple paths from a transmitting device, such as the terminal station 10, to a receiving device, such as the ground station 3a. Then, the communication path calculation unit 4 determines an optimal communication path from the multiple calculated paths as described below, and outputs a signal and data indicating the determined communication path to the modem unit 34.

[0048] The communication path calculation unit 4 is not limited to being provided in the ground station 3a, and may be provided in the terminal station 10, the node station 2, or may be configured by a plurality of devices. The communication path calculation unit 4 may be configured as a single communication path determination device installed on a network connected to the wireless communication system 1. The ground station 3a may be the communication path determination device.

[0049] Next, a specific example of the functions of the communication path calculation unit 4 will be described. Fig. 6 is a functional block diagram illustrating the functions of the communication path calculation unit 4. As shown in Fig. 6, the communication path calculation unit 4 has, for example, an information calculation unit 40, a first calculation unit 41, a second calculation unit 42, a delay time calculation unit 43, a determination unit 44, and a decision unit 45.

[0050] The information calculation unit 40 reads out various parameters stored in the database 36, calculates location information indicating the location of each node station 2, and outputs the calculated location information to the first calculation unit 41. The information calculation unit 40 also reads out various parameters and data stored in the database 36, calculates load information indicating the load due to traffic of each node station 2, and outputs the calculated load information to the second calculation unit 42.

[0051] The first calculation unit 41 calculates the propagation time of the link from the terminal station 10 to the node station 2, the propagation time of each link between the node stations 2, the buffering time that each node station 2 should hold data for until the link is established, and the propagation time of the link from the node station 2 to the ground station 3a, based on the position information calculated by the information calculation unit 40. Then, the first calculation unit 41 outputs each of the calculated results (time) to the delay time calculation unit 43.

[0052] The second calculation unit 42 calculates the queuing time of each node station 2 based on the load information calculated by the information calculation unit 40, and outputs each of the calculated results (time) to the delay time calculation unit 43.

[0053] The delay time calculation unit 43 calculates the sum T (see formula (2) above) of delay times occurring in data transmission for each path from the terminal station 10 to the ground station 3a based on the times calculated by the first calculation unit 41 and the times calculated by the second calculation unit 42. Then, the delay time calculation unit 43 outputs each of the calculated sums T of delay times to the determination unit 45.

[0054] The determination unit 44 reads various parameters and data stored in the database 36 and determines the priority of the traffic. Then, the determination unit 44 outputs the determined priority of the traffic and the data to the determination unit 45. Note that the determination unit 44 outputs the data to the determination unit 45 as it is when the traffic has no priority.

[0055] The determination unit 45 determines the route that minimizes the sum T of the delay times calculated by the delay time calculation unit 43 as the communication route from the terminal station 10 to the ground station 3a, and outputs information indicating the determined communication route together with the data to the modem unit 34.

[0056] For traffic determined by the determination unit 44 to have high priority, the determination unit 45 determines the route that minimizes the sum T of delay times calculated by the delay time calculation unit 43 as the communication route.

[0057] In addition, for traffic that the judgment unit 44 judges to have low priority, if the sum T of delay times calculated by the delay time calculation unit 43 is less than a predetermined threshold, the decision unit 45 determines the route that has the smallest sum T of delay times calculated by the delay time calculation unit 43 as the communication route.

[0058] Furthermore, when the sum T of delay times calculated by the delay time calculation unit 43 for traffic determined by the determination unit 44 to have low priority is equal to or greater than a predetermined threshold, the determination unit 45 determines the route with the maximum sum T of delay times calculated by the delay time calculation unit 43 as the communication route. After that, when the sum T of delay times calculated by the delay time calculation unit 43 becomes less than the predetermined threshold, the determination unit 45 determines and switches to the route with the minimum sum T of delay times calculated by the delay time calculation unit 43 as the communication route.

[0059] In addition, when the link between the node station 2 that last transmitted data to the ground station 3a and the ground station 3a is severed, the determination unit 45 determines a communication path such that a link is established by giving priority to the node station that last transmitted data to the ground station 3a (e.g., node station 2-3) to one of the node stations 2 (e.g., node station 2-7, which is a geostationary satellite) that resides in a location where the link with the ground station 3a can be maintained.

[0060] 7 is a diagram illustrating a configuration and a second operation of the wireless communication system 1 according to an embodiment. When the link between the node station 2-3 and the earth station 3a is cut off and communication is not possible, the sum T of delay times in the route Y2 via the node station 2-7, which is a geostationary satellite, is minimized.

[0061] In this case, the communication path calculation unit 4 (see Figs. 5 and 6) determines the communication path for the high-priority traffic from the terminal station 10 to the ground station 3a to be the path Y2. In other words, the wireless communication system 1 determines the communication path for the high-priority traffic to be the path with the smallest total delay time T among the paths with established links.

[0062] Furthermore, for low-priority traffic, if the sum T of delay times on the path Y2 is less than a threshold, the communication path calculation unit 4 determines the communication path to be the path Y2.

[0063] Furthermore, if the sum T of delay times of the path Y2 for low-priority traffic is equal to or greater than a threshold, the communication path calculation unit 4 determines the communication path to be the path X2. At this time, the node station 2-3 performs data buffering. In other words, the wireless communication system 1 distributes the load of the node station 2 on the communication path that transmits the high-priority traffic.

[0064] Thereafter, if the total delay time T of the path Y2 becomes less than the threshold due to the movement of the node station 2 or the like, the communication path calculation unit 4 determines and switches the communication path to the path Y2. The node station 2-3 transmits the buffered traffic to the node station 2-7 via the path Z2, and transmits it to the ground station 3a via the node station 2-7.

[0065] In other words, the wireless communication system 1 ensures communication by avoiding congestion for high-priority traffic, and maintains communication as much as possible for low-priority traffic, thereby improving the throughput of the entire system.

[0066] FIG. 8 is a flowchart illustrating a process performed by the communication path calculation unit 4 (FIGS. 5 and 6) when the wireless communication system 1 according to an embodiment performs the second operation shown in FIG.

[0067] In step 100 (S100), the delay time calculation unit 43 calculates the sum T (see formula (2) above) of delay times occurring in data transmission for each path from the terminal station 10 to the earth station 3a.

[0068] In step 102 (S102), the determination unit 44 determines whether the traffic requires priority processing. If the traffic does not require priority processing (S102: No), the determination unit 44 proceeds to processing of S108, and if the traffic requires priority processing (S102: Yes), the determination unit 44 proceeds to processing of S104.

[0069] In step 104 (S104), the determination unit 44 determines whether the traffic priority is low or not. If the determination unit 44 determines that the traffic priority is not low (high) (S104: No), the process proceeds to S108, and if the determination unit 44 determines that the traffic priority is low (S104: Yes), the process proceeds to S106.

[0070] In step 106 (S106), the decision unit 45 determines whether the minimum value of the sum T of delay times is equal to or greater than a predetermined threshold, and if it is not equal to or greater than the threshold (S106: No), proceeds to processing of S108, and if it is equal to or greater than the threshold (S106: Yes), proceeds to processing of S110.

[0071] In step 108 (S108), the determination unit 45 determines the route with the smallest sum T of delay times as the communication route.

[0072] In step 110 (S110), the determination unit 45 determines the route with the maximum sum T of delay times as the communication route.

[0073] 9 is a diagram illustrating a configuration and a third operation of the wireless communication system 1 according to an embodiment. Here, it is assumed that the node station 2-7, which is a geostationary satellite, can select only one node station 2 (a mobile satellite) to establish a link.

[0074] For example, in the case of communication from a terminal station 10 to a ground station 3a, if the link between the node station 2-3 and the ground station 3a is cut, the wireless communication system 1 switches the communication path to a path that passes through the node station 2-7, since there is no node station 2 that can communicate with the ground station 3a.

[0075] Traffic received by the node station 2-3 after the link between the node station 2-3 and the earth station 3a is cut is transmitted using the switched communication path.

[0076] At this time, if the node station 2-7 establishes a link with the node station 2-1 located away from the node station 2-3 that had been communicating with the earth station 3a until immediately before, the communication path becomes the path X3.

[0077] On the other hand, when the node station 2-7 establishes a link to the node station 2-3 that was communicating with the earth station 3a until immediately before, the communication path becomes the path Y3, which has one hop for connecting the node station 2-3 to the earth station 3a.

[0078] On the other hand, the number of hops for the path X3 to connect from the node station 2-3 to the earth station 3a is 3. In other words, the total delay time T of the path Y3 is smaller than that of the path X3.

[0079] In this way, the wireless communication system 1 improves the throughput of the entire system by having the node station 2-7 establish a link with priority over the node station 2-3 that was communicating with the earth station 3a until immediately before.

[0080] For example, due to frequency resources, cost, and other reasons, the node station 2-7 (absolute node station) may not be able to establish links with all of the node stations 2. In such a case, the determination unit 45 (FIG. 6) determines a communication route for the node station 2-7 to establish a link by giving priority to the node station 2-3 that was communicating with the earth station 3a until immediately before.

[0081] As described above, the wireless communication system 1 determines a communication route based on the buffering time for which each node station 2 should hold data until a link is established, thereby enabling efficient wireless communication via a moving node station 2.

[0082] Each function of the ground station 3a (or the node station 2, etc.) may be configured in part or in whole by hardware such as a PLD (Programmable Logic Device) or an FPGA (Field Programmable Gate Array), or may be configured as a program executed by a processor such as a CPU.

[0083] For example, the ground station 3a according to the present invention can be realized using a computer and a program, and the program can be recorded on a storage medium or provided via a network. [Explanation of symbols]

[0084] REFERENCE SIGNS LIST 1 wireless communication system, 2, 2-1 to 2-8 node stations, 3, 3a ground stations, 4 communication path calculation section, 10 terminal station, 30 antenna, 32 RF section, 34 modem section, 36 database, 40 information calculation section, 41 first calculation section, 42 second calculation section, 43 delay time calculation section, 44 judgment section, 45 decision section

Claims

1. In a wireless communication system, data to be transmitted from a transmitting device to a receiving device is wirelessly transmitted over a communication path passing through a plurality of node stations, at least one of which moves, an information calculation unit that calculates location information indicating a location of each of the node stations and load information indicating a load due to traffic of each of the node stations; a first calculation unit that calculates, based on the location information calculated by the information calculation unit, a propagation time of a link from the transmitting device to the node station, a propagation time of each of the links between the node stations, a buffering time during which each of the node stations should hold data until a link is established, and a propagation time of a link from the node station to the receiving device; a second calculation unit that calculates a queuing time for each of the node stations based on the load information calculated by the information calculation unit; a delay time calculation unit that calculates a sum of delay times occurring in data transmission for each path from the transmitting device to the receiving device based on each of the times calculated by the first calculation unit and each of the times calculated by the second calculation unit; a determination unit that determines, as the communication route, a route that minimizes the sum of the delay times calculated by the delay time calculation unit; A wireless communication system comprising:

2. A traffic priority determination section and The determination unit is For traffic determined by the determination unit to have a high priority, a route for which the sum of delay times calculated by the delay time calculation unit is smallest is determined as the communication route, and for traffic determined by the determination unit to have a low priority, if the sum of delay times calculated by the delay time calculation unit is less than a predetermined threshold, a route for which the sum of delay times calculated by the delay time calculation unit is smallest is determined as the communication route, and if the sum of delay times calculated by the delay time calculation unit is equal to or greater than a predetermined threshold, a route for which the sum of delay times calculated by the delay time calculation unit is largest is determined as the communication route.

2. The wireless communication system according to claim 1,

3. The determination unit is When a link between the node station which last transmitted data to the receiving device and the receiving device is cut off, the communication path is determined so that a link is established by giving priority to the node station which last transmitted data to the receiving device and any of the node stations which reside in a place where a link with the receiving device can be continuously maintained.

3. The wireless communication system according to claim 1 or 2.

4. A wireless communication method for wirelessly transmitting data from a transmitting device to a receiving device over a communication path passing through a plurality of node stations, at least one of which moves, comprising: an information calculation step of calculating location information indicating a location of each of the node stations and load information indicating a load due to traffic of each of the node stations; a first calculation step of calculating, based on the calculated location information, a propagation time of a link from the transmitting device to the node station, a propagation time of each of the links between the node stations, a buffering time for each of the node stations to hold data until a link is established, and a propagation time of a link from the node station to the receiving device; a second calculation step of calculating a queuing time for each of the nodes based on the calculated load information; a delay time calculation step of calculating a sum of delay times occurring in data transmission for each path from the transmitting device to the receiving device based on each of the times calculated in the first calculation step and each of the times calculated in the second calculation step; a determination step of determining a route that minimizes the sum of the calculated delay times as the communication route; 13. A wireless communication method comprising:

5. A process for determining the priority of traffic Further comprising: In the determining step, For traffic determined to have a high priority in the determination step, a route with a minimum sum of calculated delay times is determined as the communication route, and for traffic determined to have a low priority in the determination step, if the sum of calculated delay times is less than a predetermined threshold, a route with a minimum sum of calculated delay times is determined as the communication route, and if the sum of calculated delay times is equal to or greater than a predetermined threshold, a route with a maximum sum of calculated delay times is determined as the communication route.

5. The wireless communication method according to claim 4,

6. A communication path determination device determines a communication path for wirelessly transmitting data to be transmitted from a transmitting device to a receiving device via a plurality of node stations, at least one of which moves, an information calculation unit that calculates location information indicating a location of each of the node stations and load information indicating a load due to traffic of each of the node stations; a first calculation unit that calculates, based on the location information calculated by the information calculation unit, a propagation time of a link from the transmitting device to the node station, a propagation time of each of the links between the node stations, a buffering time during which each of the node stations should hold data until a link is established, and a propagation time of a link from the node station to the receiving device; a second calculation unit that calculates a queuing time for each of the node stations based on the load information calculated by the information calculation unit; a delay time calculation unit that calculates a sum of delay times occurring in data transmission for each path from the transmitting device to the receiving device based on each of the times calculated by the first calculation unit and each of the times calculated by the second calculation unit; a determination unit that determines, as the communication route, a route that minimizes the sum of the delay times calculated by the delay time calculation unit; A communication path determination device comprising:

7. A traffic priority determination section and The determination unit is For traffic determined by the determination unit to have a high priority, a route for which the sum of delay times calculated by the delay time calculation unit is smallest is determined as the communication route, and for traffic determined by the determination unit to have a low priority, if the sum of delay times calculated by the delay time calculation unit is less than a predetermined threshold, a route for which the sum of delay times calculated by the delay time calculation unit is smallest is determined as the communication route, and if the sum of delay times calculated by the delay time calculation unit is equal to or greater than a predetermined threshold, a route for which the sum of delay times calculated by the delay time calculation unit is largest is determined as the communication route.

7. The communication path determining device according to claim 6,

8. The determination unit is When a link between the node station which last transmitted data to the receiving device and the receiving device is cut off, the communication path is determined so that a link is established by giving priority to the node station which last transmitted data to the receiving device and any of the node stations which reside in a place where a link with the receiving device can be continuously maintained.

8. The communication path determination device according to claim 6 or 7,

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