Wireless communication method and centralized management device

Abstract

The purpose of this invention is to allocate a communication path with a large delay and low capacity to delay-tolerant data or narrowband data. The present disclosure is a wireless communication method that uses a non-terrestrial network having a plurality of aerial wireless stations connecting links to neighboring stations or ground base stations, the method comprising: selecting a communication path candidate for data to be transmitted; calculating a link cost value for each link included in the candidate by using a reference value coefficient corresponding to the frequency band or the tolerable delay time for the data; calculating a cost value for the candidate by adding up the link cost values; and determining, from among the candidates, a communication path that minimizes the cost value, and allocating the determined communication path to the data. The link cost value is corrected using the reference value coefficient so as to become smaller as the data becomes a narrower band or the tolerable delay time for the data becomes larger.

Description

Wireless communication method and centralized control device

[0001] The present disclosure relates to a wireless communication method and a centralized control device using a non-terrestrial network.

[0002] With the recent spread of 4G / 5G services, the demand for network communication bandwidth is increasing year by year. Furthermore, ultra-wide coverage is required for future B5G / 6G services. To expand the coverage area, B5G / 6G services are expected to use NTNs (Non-Terrestrial Networks). This will enable the expansion of service areas to locations where the construction of terrestrial base stations is expensive or difficult, such as mountainous, marine, or aerial locations. It will also enable the construction of communication systems that are resistant to terrestrial disasters.

[0003] Non-Patent Document 1 discloses a communication path control method that can distribute an appropriate amount of data to each layer in a two-layered satellite network.

[0004] "A Study on Efficient Routing Control in Hierarchical Satellite Networks" Institute of Electronics, Information and Communication Engineers, IEICE Technical Report, SAT2010-9 (2010-06).

[0005] In the above-described method, an optimal communication route is selected based on a cost value C calculated for each candidate communication route. However, in the conventional technology, the allowable delay time and frequency band of the data to be transmitted are not taken into consideration when calculating the cost value C. In the above-described method, a low-delay communication route is assigned to delay-tolerant data that starts communication first, and the same route cannot be assigned to delay-intolerant data that starts communication later, resulting in a problem in which the required quality for the delay-intolerant data cannot be met.

[0006] In order to solve the above-mentioned problems, a first object of the present disclosure is to provide a wireless communication method that can allocate a communication path with a large delay and low capacity to delay-tolerant data or narrowband data.

[0007] A second object of the present disclosure is to provide a centralized management device that can allocate a communication path with a large delay and low capacity to delay-tolerant data or narrowband data.

[0008] A first aspect of the present disclosure is a wireless communication method using a non-terrestrial network having a plurality of overhead radio stations that link with neighboring stations or terrestrial base stations, comprising: selecting candidate communication paths for the overhead radio stations for data to be transmitted; acquiring the frequency band or allowable delay time of the data; calculating a link cost value for each of the links included in the candidates using a reference value coefficient corresponding to the frequency band or the allowable delay time; calculating a cost value for the candidate by adding up the link cost values; determining a communication path from the candidates that minimizes the cost value, and allocating the determined communication path to the data; and it is preferable that the link cost value be corrected by the reference value coefficient so that the link cost value becomes smaller as the frequency band of the data becomes narrower or the allowable delay time of the data becomes longer.

[0009] A second aspect is a centralized management device used in wireless communications using a non-terrestrial network having a plurality of overhead radio stations that link with neighboring stations or terrestrial base stations, and is configured to perform the following processes: selecting candidate communication routes by the overhead radio stations for data to be transmitted; acquiring the frequency band or allowable delay time of the data; calculating a link cost value for each of the links included in the candidates using a reference value coefficient corresponding to the frequency band or the allowable delay time; calculating a cost value for the candidate by adding up the link cost values; and determining a communication route from the candidates that minimizes the cost value, and assigning the determined communication route to the data. It is preferable that the link cost value is corrected by the reference value coefficient so that the link cost value becomes smaller as the frequency band of the data becomes narrower or the allowable delay time of the data becomes longer.

[0010] According to aspects of the present disclosure, the link cost value C for delay-tolerant data is ｉ is the link cost value C for delay-intolerant data ｉ The link cost value C for narrowband data is corrected to be smaller than ｉ is the link cost value C for broadband data ｉ Therefore, a communication path with a large delay and low capacity can be assigned to delay-tolerant data or narrowband data.

[0011] 1 is a diagram illustrating a configuration of a wireless communication system according to a first embodiment of the present disclosure. FIG. 2 is a diagram illustrating a method for selecting a communication path in a conventional wireless communication system. FIG. 3 is a diagram illustrating a method for selecting a communication path in a conventional wireless communication system. FIG. 4 is a diagram illustrating a method for calculating a communication path according to the first embodiment of the present disclosure. FIG. 5 is a diagram illustrating an effect of the wireless communication system according to the present disclosure. FIG. 6 is a diagram illustrating an effect of the wireless communication system according to the present disclosure. FIG. 7 is a block diagram illustrating an example configuration of a centralized management device according to the first embodiment of the present disclosure. FIG. 8 is a block diagram illustrating an example configuration of an overhead radio station according to the first embodiment of the present disclosure. FIG. 9 is a diagram illustrating a reference value coefficient calculated by the centralized management device according to the second embodiment of the present disclosure. FIG. 10 is a flowchart of processing executed by the centralized management device according to the second embodiment of the present disclosure. FIG. 11 is a diagram illustrating a configuration of a wireless communication system according to a third embodiment of the present disclosure. FIG. 12 is a diagram illustrating a reference value coefficient calculated by the centralized management device according to the third embodiment of the present disclosure. FIG. 13 is a diagram illustrating a frequency band determined by the centralized management device for each of the overhead radio stations included in the communication path according to the third embodiment of the present disclosure.

[0012] Embodiments of the present disclosure will be described with reference to the drawings. The same or corresponding components will be designated by the same reference numerals, and repeated description may be omitted.

[0013] 1 is a diagram showing the configuration of a wireless communication system 100 according to a first embodiment of the present disclosure. Here, a three-layer network is shown. The wireless communication system 100 includes a plurality of first-layer airborne radio stations 110, a plurality of second-layer airborne radio stations 120, and a plurality of third-layer airborne radio stations 130. Furthermore, the wireless communication system 100 includes a centralized management device 150 and one or more terrestrial base stations 140.

[0014] The first-tier airborne radio station 110 is a radio relay station (also called a node station) that moves in the sky, including outer space, or that moves in the sky, including outer space, but appears to be stationary relative to the ground. A known example of the first-tier airborne radio station 110 is the High Altitude Platform System (HAPS), which moves at an altitude of around 20 km.

[0015] Neighboring first-tier airborne radio stations 110 are connected to each other by intra-layer links 2 and perform wireless or optical signal communication. The first-tier airborne radio stations 110 connected by the intra-layer links 2 form a first airborne network 111.

[0016] The first-tier airborne radio station 110 receives data transmitted from the ground terminal station 180 via the inter-ground station link 1. The first-tier airborne radio station 110 relays the data via the first airborne network 111 to the first-tier airborne radio station 110 that has established the inter-network link 3.

[0017] The first tier radio station 110 that has established the inter-network link 3 transmits the received data to the second tier radio station 120 via the link.

[0018] Alternatively, the first-tier airborne radio station 110 relays the data to the first-tier airborne radio station 110 that has established the inter-base station link 5. The first-tier airborne radio station 110 that has established the inter-base station link 5 transmits the data received via the link to the terrestrial base station 140.

[0019] The second-tier overhead radio station 120 is a radio relay station that moves at a higher altitude than the first-tier overhead radio station 110. A known example of the second-tier overhead radio station 120 is a LEO (Low Earth Orbit) satellite located in a low Earth orbit at an altitude of 2000 km or less.

[0020] Neighboring second-layer airborne radio stations 120 are connected to each other by intra-layer links 4 and perform radio or optical signal communication. The second-layer airborne radio stations 120 connected by the intra-layer links 4 form a second airborne network 121.

[0021] Similarly, the second layer airborne radio station 120 receives data transmitted from the ground terminal station 180 via an inter-ground station link (not shown). It also receives data transmitted from the first layer airborne radio station 110 or the third layer airborne radio station 130 via inter-network links 3 and 8, respectively.

[0022] The second layer airborne radio station 120 relays the received data via the second airborne network 121 to a second layer airborne radio station 120 that can communicate with airborne radio stations in other layers, or to a second layer airborne radio station 120 that can communicate with a terrestrial base station 140.

[0023] The second-tier airborne radio station 120 that can communicate with the airborne radio station of another tier transmits the received data to the airborne radio station of the target tier via the inter-network links 3 and 8. The second-tier airborne radio station 120 that can communicate with the terrestrial base station 140 transmits the received data to the terrestrial base station 140 via the inter-base station link 11 (not shown).

[0024] The third-tier overhead radio station 130 is a radio relay station that moves at a higher altitude than the second-tier overhead radio station 120. A known example of the third-tier overhead radio station 130 is a GEO (Geostationary Orbit) satellite that moves in a geostationary orbit at an altitude of 36,000 km. The communication method of the third-tier overhead radio station 130 is the same as that of the first-tier overhead radio station 110 and the second-tier overhead radio station 120, so a description thereof will be omitted.

[0025] The first layer airborne radio station 110 is not limited to a HAPS, but may be a drone, an unmanned aerial vehicle, or an aircraft. The second layer airborne radio station 120 and the third layer airborne radio station 130 are also not limited to the above examples.

[0026] If necessary, the wireless communication system 100 may include a fourth layer airborne radio station, a fifth layer airborne radio station, and so on.

[0027] In this manner, in the wireless communication system 100 of the present disclosure, overhead radio stations at the same hierarchical level are connected to each other via intra-layer links 2, 4, and 9 to form an overhead network. Furthermore, one or more inter-network links 3 and 8 are formed between overhead radio stations at different hierarchical levels.

[0028] In the following description, when there is no need to distinguish between the first-tier airborne radio station 110, the second-tier airborne radio station 120, and the third-tier airborne radio station 130, they will simply be referred to as airborne radio station 160. Only when it is necessary to distinguish between them will the respective names be described.

[0029] Similarly, when the description is applicable to each of the links connected by the airborne radio station 160, such as the inter-ground station link 1, the intra-layer links 2, 4, and 9, the inter-network links 3 and 8, and the inter-base station links 5 and 11, and there is no need to distinguish between the types of links, they will simply be referred to as link 6. Only when it is necessary to distinguish between them will the names of each be written.

[0030] The terrestrial base station 140 receives data transmitted from the airborne radio station 160 via the inter-base station link 5, and transmits the packet data contained in the radio waves to a terrestrial core network 190 (not shown). In other words, the terrestrial base station 140 functions as a terrestrial gateway station.

[0031] The ground terminal station 180 is a wireless terminal such as a smartphone that performs wireless communication with the airborne radio station 160 via the inter-ground station link 1. The ground terminal station 180 transmits and receives data such as internet data to and from the airborne radio station 160.

[0032] The centralized control device 150 selects candidate communication paths for the overhead radio stations 160 and calculates a cost value C for each candidate. The cost value C is adjusted to give priority to communication paths with long delays based on delay-tolerance data 50 (not shown). Furthermore, the centralized control device 150 determines the communication path that minimizes the cost value C and assigns it to the data to be transmitted.

[0033] The centralized control device 150 is located at an absolute overhead radio station 170. The absolute overhead radio station 170 is an overhead radio station 160 that can establish a control link 7 (not shown) with all overhead radio stations except for itself. The absolute overhead radio station 170 and each of the overhead radio stations 160 except for the absolute overhead radio station 170 are connected by the control link 7. Via the control link 7, the centralized control device 150 aggregates information from each overhead radio station 160 and notifies each overhead radio station 160 of the information.

[0034] In this manner, in this embodiment, a communication path with a large delay is preferentially assigned to the delay tolerance data 50 .

[0035] In the above description, the data transmitted from the terrestrial terminal station 180 is transmitted to the terrestrial base station 140 via a relay from the overhead radio station 160. However, it is also possible to transmit the data transmitted from the terrestrial base station 140 to the terrestrial terminal station 180 via a relay from the overhead radio station 160.

[0036] Comparative Example Here, a communication path selection method in Non-Patent Document 1 will be described as a comparative example of the present disclosure.

[0037] In the prior art, communication path candidates are selected for data to be transmitted. Furthermore, a link cost value C is determined for each of the links 6 included in the candidates. ｉ The cost value C for the candidate is calculated by adding up the above values.

[0038]

[0039] n is the total number of links 6 included in the communication path. ｉis the sum of the reciprocal of the link capacity of the i-th link 6 and the delay time, and is expressed by the following (Equation 2).

[0040]

[0041] Here, R ｉ is the link capacity of the i-th link 6, B ｒ is the reference value of the link capacity, d ｉ is the delay time of the i-th link 6, B ｄ is the reference value of the delay time. ｒ and reference value B ｄ is common to all links 6 and can take any value.

[0042] In the conventional technology, a cost value C calculated by (Equation 1) and (Equation 2) is calculated for each candidate communication path. Since a communication path with a smaller cost value C has lower delay and larger capacity, in the conventional technology, the communication path with the smallest cost value C is assigned as the communication path for the data to be transmitted.

[0043] By the way, in the prior art, the reference value B ｒ and reference value B ｄ is set to be the same for all data, regardless of the allowable delay time of the data. Problems with the conventional technology that arise from this will be explained below with reference to FIGS.

[0044] 2 and 3 are diagrams showing a method for selecting a communication path in a conventional wireless communication system 200. The conventional wireless communication system 200 is assumed to be a two-layer system including a plurality of first-layer airborne radio stations 110 and a plurality of second-layer airborne radio stations 120.

[0045] 2, it is assumed that the first communication path 10, which has the smallest cost value C among multiple communication path candidates, is first assigned to the delay tolerance data 50. The delay of the first communication path 10 is, for example, 5 ms.

[0046] The delay tolerance data 50 is, for example, data of Class C (IP telephone: required quality is a delay of 400 ms or less) in the call quality standards established by the Ministry of Internal Affairs and Communications of Japan. Since the delay of the first communication path 10 is 5 ms, the conventional wireless communication system 200 satisfies the required quality for Class C data.

[0047] 3, the first communication path 10 is being used by delay-tolerant data 50 and has insufficient link capacity, so the second communication path 20, which has the second smallest cost value, is assigned to delay-intolerant data 60, which starts communication later. Because the second communication path 20 passes through a high-altitude second-tier airborne radio station 120, it is expected to experience a longer delay than the first communication path 10, which passes only through a first-tier airborne radio station 110. As an example, the delay of the second communication path 20 is about 250 ms.

[0048] The delay-intolerant data 60 is, for example, data of class A (analog telephone: required quality is a delay of 100 ms or less) in the speech quality standards established by the Ministry of Internal Affairs and Communications of Japan. Since the delay of the second communication path 20 is about 250 ms, this means that the conventional wireless communication system 200 cannot satisfy the required quality for class A data.

[0049] In this way, in the conventional wireless communication system 200, a communication path is determined based on the cost value C calculated without taking into consideration the allowable delay time of the data to be transmitted, which may result in a case where the required quality of the data cannot be met.

[0050] On the other hand, in the wireless communication system 100 of the present disclosure, the reference value B ｒ and reference value B ｄ is corrected in accordance with the allowable delay time of the data to be transmitted, and then the cost value C is calculated.

[0051] The calculation formulas for the cost value in this disclosure are shown in (Formula 3) and (Formula 4). α is the reference value B ｒ is the reference value coefficient for ｄ The other parameters are the same as those in the comparative example, so the explanation will be omitted.

[0052]

[0053]

[0054] In the present disclosure, the link cost value C for the delay tolerance data 50 in which delay is allowed is ｉ is set to the link cost value C of the delay-intolerant data 60, which is not allowed to have a delay. ｉ The reference value coefficients α and β in (Equation 4) are adjusted so that they are smaller than

[0055] 4 is a diagram illustrating a method for calculating a communication path according to the first embodiment of the present disclosure. As a specific example, it is assumed that the inter-network link 3 and the inter-base station link 11 are delay-prone, and the delay time is d ｉ = 250 ms. Furthermore, it is assumed that the intra-layer link 2 and the inter-base station link 5 have low delay, and the delay time is d ｉ = 5 ms. The link capacity is common to all links 6, and R ｉ = 1 Gbps. Furthermore, the reference value of the link capacity is set to B ｒ = 1 Gbps, the reference value of delay is B ｄ = 10 ms.

[0056] The link cost value C calculated by (Equation 4) for the delayed inter-network link 3 and inter-base station link 11 ｉ In the case of delay tolerant data 50 and delay intolerant data 60, the following is true: In the case of delay tolerant data 50, the reference value coefficients α=1 and β=100 are used, and C ｉ = 1.25 In the case of delay intolerance data 60, the reference value coefficients α = 1 and β = 1. ｉ =26

[0057] Link cost value C for delay tolerance data 50 ｉ is about 1 / 20 of that in the case of delay-intolerant data 60, and as a result, the i-th link 6 is more likely to be selected as a communication path for transmitting delay-tolerant data 50.

[0058] Here, for the low-delay link 6, the link cost value C ｉIt should be noted that the effect of adjusting the link cost value C in the low-delay intra-layer link 2 and the inter-base station link 5 is not large, and consideration is given to selecting the link cost value C in the low-delay intra-layer link 2 and the inter-base station link 5. ｉ In the case of delay tolerance data 50, the reference value coefficients α=1 and β=100 are set as follows: ｉ = 1.005 In the case of the delay intolerance data 60, the reference value coefficients α = 1 and β = 1. ｉ = 1.5

[0059] Here again, the link cost value C of the delay tolerance data 50 ｉ is smaller than the delay-intolerant data 60, but the ratio is small compared to the delay-prone link 6. Therefore, the low-delay link 6 is considered to be selected even in the delay-intolerant data 60.

[0060] The cost value for the delay-sensitive communication path 30 consisting of the inter-network link 3 and the inter-base station link 11 is calculated as follows using equation (3): In the case of delay-tolerant data 50, C=1.25+1.25=2.5 In the case of delay-intolerant data 60, C=26+26=52

[0061] On the other hand, the cost value for the low-delay communication path 40 consisting of two intra-layer links 2 and an inter-base station link 5 is calculated as follows using (Equation 3): In the case of delay-tolerant data 50, C = 1.005 + 1.005 + 1.005 = 3.015 In the case of delay-intolerant data 60, C = 1.5 + 1.5 + 1.5 = 4.5

[0062] In the case of delay-tolerant data 50, the cost value C of the delay-prone communication path 30 is the smallest. Therefore, the delay-prone communication path 30 can be assigned to the data. On the other hand, in the case of delay-intolerant data 60, the cost value C of the low-delay communication path 40 is the smallest. Therefore, the low-delay communication path 30 can be assigned to the data.

[0063] 5 and 6 are diagrams illustrating the effects of the wireless communication system 100 of the present disclosure. In Fig. 5, the second communication path 20 described above is assigned to the data based on the cost value C for delay tolerant data 50. Since the delay of the second communication path 20 is 250 ms, the required quality is met even when the delay tolerant data 50 is data of the above-mentioned class C (required quality is a delay of 400 ms or less).

[0064] 6, for delay-intolerant data 60, which started communication after delay-tolerant data 50, a cost value C for delay-intolerant data 60 is calculated, and as a result, the first communication path 10 is assigned. Since the delay of the first communication path 10 is 5 ms, the required quality is met even when the delay-intolerant data 60 is data of the above-mentioned Class A (required quality is a delay of 100 ms or less). This is an effect that cannot be obtained with the prior art.

[0065] 7 is a block diagram showing a configuration example of the centralized management device 150 according to the first embodiment of the present disclosure. The communication circuit 151 transmits the communication quality and the above-mentioned link capacity R ｉ , delay time d ｉ and so on via the control link 7. Furthermore, the communication circuit 151 receives information on the delay tolerance of data from the airborne radio station 160 that has received data from the terrestrial base station 140 or the terrestrial terminal station 180.

[0066] The coefficient calculation circuit 153 calculates the reference value coefficients α and β to be used in the case of delay-tolerant data 50 and delay-intolerant data 60 based on the information notified from the communication circuit 151, and notifies the route control circuit 152 of the calculation results. Note that if changes that may affect the communication quality of each link 6 are recognized, such as changes in weather, fluctuations in traffic volume, or movement of the airborne radio station 160 or the ground terminal station 180, the coefficient calculation circuit 153 may recalculate the reference value coefficients α and β. In this way, dynamic priority control becomes possible by using the reference value coefficients α and β according to the communication quality.

[0067] The route control circuit 152 selects candidate communication routes and calculates a cost value C for each candidate using reference coefficients α and β according to the delay tolerance of the data to be transmitted. Furthermore, the route control circuit 152 determines the communication route that minimizes the cost value C from among the candidates and notifies the overhead radio stations 160 included in the determined communication route of the information about the communication route. This allows the overhead radio stations 160 that receive the notification to start communication according to the designated communication route.

[0068] 8 is a block diagram showing an example configuration of an overhead radio station 160 according to the first embodiment of the present disclosure. Note that while the case of a first-layer overhead radio station 110 will be described here, the same applies to the overhead radio stations 160 in other layers. The intra-layer communication circuit 161 connects an intra-layer link 2 with a nearby first-layer overhead radio station 110 and communicates with it. The base station communication circuit 162 connects an inter-base station link 5 with a terrestrial base station 140 and communicates with it. The ground station communication circuit 163 connects an inter-ground station link 1 with a terrestrial terminal station 180 and communicates with it. The inter-network communication circuit 166 connects an inter-network link 3 with a nearby overhead radio station 160 in another layer and communicates with it.

[0069] The management circuit 165 identifies the QoS implemented in the wireless frame of data received from the terrestrial base station 140 or the terrestrial terminal station 180 and determines whether the data is delay-intolerant data 60, which does not allow delay, or delay-tolerant data 50, which does allow delay. For example, when communication complies with the IEEE 802.1Q standard, the QoS is identified by referencing the CoS value in the CoS (Class of Service) field in the VLAN (Virtual Local Area Network) tag. There are eight levels of CoS, and for example, when the CoS value is less than a predetermined threshold, it is considered delay-intolerant data 60, and when it is equal to or greater than the threshold, it is considered delay-tolerant data 50. The threshold is determined to be appropriate depending on the usage environment of the wireless communication system 100. The QoS may be IP precedence or DSCP (Differential Services Code Point) included in the IP header of an Ethernet (registered trademark) frame.

[0070] The management circuit 165 provides the result of the determination of the delay tolerance of the data to the centralized management device 150 via the control link 7. The management circuit 165 also determines the link capacity R of the link 6 established by the own station. ｉ , delay time d ｉ The management circuit 165 provides the centralized control device 150 with information such as the quality of communication and the like. Furthermore, when the centralized control device 150 notifies the management circuit 165 that it has been selected as the communication path for data to be transmitted, the management circuit 165 relays the data along the specified communication path. If the relay method is regenerative relay, the overhead radio station 160 reads information about the source radio station from the IP header included in the radio frame when receiving data, and checks whether the data was transmitted along the communication path. If it is determined that the data was transmitted along the communication path, the overhead radio station 160 transmits the data to the target radio station.

[0071] The processing performed by the centralized control device 150 and the overhead radio station 160 may be executed by a communication program using a computer equipped with a CPU and memory and storing the program in the memory. Alternatively, the processing may be executed by a communication program using an integrated circuit such as an FPGA (Field Programmable Gate Array). The communication program may be provided by being recorded on a storage medium or via a network. This point is common to all of the following embodiments.

[0072] As described above, according to this embodiment, the link cost value C ｉ is the link cost value C for the delay intolerant data 60 ｉ Reference value B ｒ and reference value B ｄ This allows a communication path with a large delay to be assigned to the delay tolerance data 50.

[0073] <Variation 1> In the above description, the centralized control device 150 is always located at the overhead radio station 170. However, the centralized control device 150 may also be located on the ground. By passing through the inter-base station link 5, the intra-layer links 2, 4, 9, the inter-network links 3, 8, etc., it becomes possible for the terrestrial centralized control device 150 to perform the above-mentioned control on the overhead radio station 160. This makes it possible to obtain the same effect as described above. Note that this point is common to all the embodiments.

[0074] <Modification 2> The wireless communication system 100 does not necessarily have to have a hierarchical structure. The above-mentioned effect can be obtained as long as there are two or more overhead radio stations 160 that can relay from the terrestrial terminal station 180 to the terrestrial base station 140, and the two or more overhead radio stations 160 may be in the same or different hierarchical layers.

[0075] Second Embodiment In this embodiment, the reference value coefficients α and β are set more precisely in accordance with the QoS of data to be transmitted than in the first embodiment. The following describes changes from the first embodiment.

[0076] FIG. 9 is a diagram showing the reference value coefficients calculated by the centralized management device 150 according to the second embodiment of the present disclosure. Here, the case where the QoS is DSCP is described. The DSCP has multiple stages of allowable data delay time settings. The centralized management device 150 calculates the reference value coefficients α and β so as to preferentially allocate communication paths with long delays to data with the highest delay tolerance (here, DSCP = 1). Furthermore, the centralized management device 150 stores the reference value coefficients α and β set according to each DSCP stage as a table as shown in the figure, and calculates the cost value C for each candidate communication path based on the table. The DSCP values ​​are merely examples.

[0077] 10 is a flowchart of processing executed by the centralized management device 150 according to the second embodiment of the present disclosure. First, it is determined whether or not it is necessary to change the current values ​​of the reference value coefficients α and β based on the communication quality of each link 6 (step S01). If it is deemed necessary, the current values ​​of the reference value coefficients α and β are updated, and the process proceeds to step S03 (step S02). On the other hand, if it is deemed necessary, the reference value coefficients α and β are not changed.

[0078] Furthermore, the cost value C for each of the candidate communication paths is calculated using the reference coefficients α and β according to the QoS of the data to be transmitted (step S03). Note that the QoS information of the data to be transmitted is notified to the centralized control device 150 by the overhead radio station 160 that received the data.

[0079] Furthermore, the communication route that minimizes the cost value C is selected from among the candidates and assigned to the data to be transmitted (step S04).

[0080] By using the reference value coefficients α and β set according to the QoS level as in this embodiment, more detailed priority control is possible compared to the first embodiment.

[0081] Embodiment 3 In this embodiment, reference value coefficients α and β set according to S-NSSAI (Single Network Slice Selection Assistance Information), which is an identifier of a slice in network slicing technology of 5G (fifth generation mobile communication system), are used. Note that, hereinafter, changes from embodiment 1 will be described.

[0082] 11 is a diagram illustrating a configuration of a wireless communication system 100 according to a third embodiment of the present disclosure. Here, the NTN is shown to have two layers. In this embodiment, a centralized control device 150 is located on the ground.

[0083] Prior to transmitting or receiving data, the ground terminal station 180 notifies the core network 190 of its desired S-NSSAI. The core network 190 forms slices, which are virtually divided network layers, based on the S-NSSAI requested by the ground terminal station 180. This enables the ground terminal station 180 to transmit and receive data in slices to which frequency bands and the like are appropriately assigned according to applications and services. Furthermore, the core network 190 notifies the ground terminal station 180 of information on the assigned frequency bands. In the figure, frequency bands A to B are assigned to the ground terminal station 180.

[0084] The centralized control device 150 acquires information about the S-NSSAI transmitted by the terrestrial terminal station 180 via the core network 190. The centralized control device 150 also reads information about the frequency band in the slice that the terrestrial terminal station 180 uses to transmit and receive data from the S-NSSAI. The centralized control device 150 selects candidates for communication paths via the airborne radio station 160 and calculates a cost value C for each candidate using reference value coefficients α and β according to the frequency band of the data to be transmitted. The centralized control device 150 then determines the communication path that minimizes the cost value C from among the candidates.

[0085] In addition, assuming that the relay method at the overhead radio stations 160 is non-regenerative relay, the centralized control device 150 determines the reception frequency band and transmission frequency band when relaying data for each of the overhead radio stations 160 included in the determined communication path. The centralized control device 150 notifies each of the overhead radio stations 160 included in the determined communication path of information about the reception frequency band and transmission frequency band when relaying data, along with information about the communication path. In non-regenerative relay, it is known that it is difficult to identify the source wireless relay station from the IP header. By assigning a unique reception frequency band and transmission frequency band to each of the overhead radio stations 160 included in the communication path as disclosed herein, it becomes possible for the receiving overhead radio station 160 to identify that the data was transmitted according to the determined communication path.

[0086] In the figure, the first-tier overhead radio station 110-1 receives data in frequency bands A to B from the terrestrial terminal station 180, converts the frequency band to B to C according to the determined frequency band, and then relays the data to the first-tier overhead radio station 110-2.

[0087] 12 is a diagram illustrating the reference value coefficients calculated by the centralized management device 150 according to the third embodiment of the present disclosure. Here, S-NSSAI=0 indicates a wider bandwidth slice, and S-NSSAI=1 indicates a narrower bandwidth slice. The reference value coefficients α and β are calculated so as to preferentially allocate low-capacity communication paths to narrowband (S-NSSAI=1) data. The centralized management device 150 stores the calculation results as a table as shown in the figure.

[0088] FIG. 13 is a diagram showing frequency bands determined by the centralized control device 150 for each of the overhead radio stations 160 included in the communication path according to the third embodiment of the present disclosure.

[0089] As described above, according to this embodiment, the link cost value C for narrowband data is ｉ is the link cost value C for broadband data ｉ Reference value B ｒ and reference value B ｄ This allows low-capacity communication paths to be allocated to narrowband data.

[0090] The present disclosure is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the present disclosure. Furthermore, the embodiments may be implemented in appropriate combinations, and in such cases, the combined effects can be obtained.

[0091] 1 Ground station-to-ground station link, 2 Intra-layer link, 3 Inter-network link, 4 Intra-layer link, 5 Inter-base station link, 6 Link, 7 Control link, 8 Inter-network link, 9 Intra-layer link, 10 First communication path, 11 Inter-base station link, 20 Second communication path, 30 Communication path, 40 Communication path, 50 Delay tolerant data, 60 Delay intolerant data, 100 Wireless communication system, 110 First layer airborne radio station, 111 First airborne network, 120 Second layer airborne radio station, 121 Second airborne network, 130 Third layer airborne radio station, 140 Terrestrial base station, 150 Centralized control device, 151 Communication circuit, 152 Route control circuit, 153 Coefficient calculation circuit, 160 Airborne radio station, 161 Intra-layer communication circuit, 162 Base station communication circuit, 163 Ground station communication circuit, 165 Management circuit, 166 Inter-network communication circuit, 170 absolute airborne radio station, 180 ground terminal station, 190 core network, 200 conventional radio communication system

Claims

1. A wireless communication method using a non-terrestrial network having multiple airborne radio stations that link with neighboring stations or terrestrial base stations, comprising: selecting candidate communication routes for the airborne radio stations for data to be transmitted; acquiring the frequency band or allowable delay time of the data; calculating a link cost value for each of the links included in the candidates using a reference value coefficient corresponding to the frequency band or the allowable delay time; calculating a cost value for the candidate by adding up the link cost values; determining a communication route from the candidates that minimizes the cost value, and allocating the determined communication route to the data; wherein the link cost value is corrected by the reference value coefficient so that it becomes smaller the narrower the frequency band of the data or the longer the allowable delay time of the data.

2. The link cost value is R ｉ , delay time d ｉ The reference value of the link capacity shared by the links is B ｒ , the reference value of the delay time is B ｄ and the reference value B ｒ The reference value coefficient for α is ｄ The wireless communication method according to claim 1 , wherein the reference value coefficient for is β and is expressed by the following equation:

3. The wireless communication method according to claim 1 or 2, further comprising updating the reference value coefficient in accordance with the communication quality of the link.

4. A wireless communication method according to any one of claims 1 to 3, wherein the allowable delay time is acquired from a QoS included in a wireless frame of the data.

5. A wireless communication method according to any one of claims 1 to 4, wherein the frequency band of the data is a frequency band in a slice within a core network used by a terrestrial terminal station for transmitting and receiving the data, and the frequency band is acquired by an S-NSSAI notified from the terrestrial terminal station.

6. A wireless communication method according to any one of claims 1 to 5, further comprising: assigning a reception frequency band and a transmission frequency band for each of the overhead radio stations included in the determined communication route to be used when relaying the data, so that the reception frequency band and transmission frequency band are unique to each of the overhead radio stations; and converting the frequency band so that each of the overhead radio stations included in the determined communication route has the reception frequency band and transmission frequency band assigned to it, and then relaying the data along the communication route.

7. A centralized control device used in wireless communications using a non-terrestrial network having multiple airborne radio stations that link with neighboring stations or terrestrial base stations, configured to perform the following processes: selecting candidate communication routes for the airborne radio stations for data to be transmitted; acquiring the frequency band or allowable delay time of the data; calculating a link cost value for each of the links included in the candidates using a reference value coefficient corresponding to the frequency band or the allowable delay time; calculating a cost value for the candidates by adding up the link cost values; and determining a communication route from the candidates that minimizes the cost value and assigning the determined communication route to the data, wherein the link cost value is corrected by the reference value coefficient so that it becomes smaller the narrower the frequency band of the data or the longer the allowable delay time of the data.

8. The link cost value is R ｉ , delay time d ｉ The reference value of the link capacity shared by the links is B ｒ , the reference value of the delay time is B ｄ and the reference value B ｒ The reference value coefficient for α is ｄ The centralized control device according to claim 7 , wherein the reference value coefficient for is β and the reference value is expressed by the following equation:

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