Wireless communication system

Abstract

This disclosure relates to a wireless communication system. The wireless communication system provides a bandwidth-guaranteed service and a non-bandwidth-guaranteed service, and comprises a terminal, a core network that communicates with the terminal via a feeder link, and a communication control device that performs communication control in the feeder link. The communication control device is configured to perform: processing for calculating a maximum traffic quantity on the basis of information regarding occurring traffic quantities; processing for calculating the communication capacity of the feeder link on the basis of information regarding a modulation system which is currently applied; processing for calculating the ratio of the maximum traffic quantity relative to the communication capacity of the feeder link; recomputation processing for, if the ratio exceeds a specified threshold value, recomputing the transmission rate of traffic for the non-bandwidth-guaranteed service so that the ratio is reduced to the threshold value or below; and processing for notifying the core network of the recomputation result. The core network is configured to set the recomputation result as the new transmission rate of traffic for the non-bandwidth-guaranteed service.

Description

wireless communication system

[0001] The present disclosure relates to wireless communication systems.

[0002] With the recent development of mobile communication systems, mobile services can now be enjoyed over most of the earth. In particular, the fifth generation (5G) and sixth generation (6G) mobile communication systems are expected to be commercialized in the future.

[0003] One of the requirements for 5G and 6G mobile communication systems is ultra-coverage. Ultra-coverage means expanding the service area to areas where the cost of installing existing base stations is high or difficult, such as mountains, oceans, or airspace. There is also a need to strengthen the nation's resilience against natural disasters, and the emergence of a communication system that is resistant to terrestrial disasters is desirable.

[0004] Non-Terrestrial Networks (NTNs) are gaining attention as a way to achieve the above. NTNs are networks that use unmanned aerial vehicles (High Altitude Platform Stations: HAPS) that fly in the stratosphere or satellites. NTNs also offer non-guaranteed bandwidth services and guaranteed bandwidth services.

[0005] Athanasios D. Panagopoulos, Pantelis-Daniel M. Arapoglou, Panayotis G. Cottis, "Satellite communications at KU, KA, and V bands: Propagation impairments and mitigation techniques," IEEE Communications Surveys & Tutorials, Vol. 6, Issue 3, Third Quarter 2004.

[0006] However, the high-frequency radio waves that are widely used in NTN have the problem of being easily affected by rain. Non-Patent Document 1 discloses a wireless communication system that switches to a redundant network when it rains as a solution to this problem. However, this system has the problem of high costs required to build the system.

[0007] Another known solution is a wireless communication system that uses adaptive modulation control. However, when adaptive modulation control changes the modulation method to mitigate the effects of rainfall, the overall communication capacity of the service provided decreases. In other words, there is an issue in that the transmission speed required for bandwidth-guaranteed services cannot be guaranteed.

[0008] In order to solve the above-mentioned problems, the present disclosure aims to provide a wireless communication system that can guarantee the transmission speed required for bandwidth-guaranteed services without increasing the cost required to build the system.

[0009] An aspect of the present disclosure is a wireless communication system that provides bandwidth-guaranteed services and non-bandwidth-guaranteed services, comprising: a terminal; a core network that communicates with the terminal via a feeder link; and a communication control device that performs communication control in the feeder link, wherein the communication control device is configured to perform the following processes: calculate a maximum traffic volume based on information on the volume of traffic generated; calculate the communication capacity of the feeder link based on information on the modulation method being applied; calculate a ratio of the maximum traffic volume to the communication capacity of the feeder link; if the ratio is greater than a specific threshold, recalculate a transmission rate of traffic for non-guaranteed services so that the ratio is equal to or less than the threshold; and notify the core network of the recalculation result; and wherein the core network is configured to set the result of the recalculation as the transmission rate of traffic for the new non-guaranteed service.

[0010] According to aspects of the present disclosure, it is possible to guarantee the transmission speed required for a bandwidth guaranteed service without increasing the cost required for system construction.

[0011] 1 is a diagram illustrating an example configuration of a wireless communication system according to a first embodiment of the present disclosure. FIG. 2 is a block diagram illustrating an example configuration of an unmanned aerial vehicle according to a first embodiment of the present disclosure. FIG. 3 is a block diagram illustrating an example configuration of a communication control device according to a first embodiment of the present disclosure. FIG. 4 is a diagram illustrating an example hardware configuration of a communication control device according to a first embodiment of the present disclosure. FIG. 5 is a diagram illustrating a 5G protocol stack according to a first embodiment of the present disclosure. FIG. 6 is a flowchart illustrating processing performed by a communication control device according to a first embodiment of the present disclosure. FIG. 7 is a diagram illustrating an example configuration of a wireless communication system during rainfall according to a first embodiment of the present disclosure. FIG. 8 is a diagram illustrating a wireless communication system according to a first comparative example. FIG. 9 is a diagram illustrating a wireless communication system according to a second comparative example. FIG. 10 is a block diagram illustrating an example configuration of a wireless communication system according to a second embodiment of the present disclosure. FIG. 11 is a block diagram illustrating an example configuration of a communication control device according to a second embodiment of the present disclosure. FIG. 12 is a diagram illustrating an example configuration of a wireless communication system during rainfall according to a sixth embodiment of the present disclosure.

[0012] 1 is a diagram illustrating a configuration example of a wireless communication system according to a first embodiment of the present disclosure. The wireless communication system 100 is configured with an NTN. Here, the wireless communication system 100 provides 5G communication services by an NTN using an unmanned aerial vehicle 2.

[0013] The wireless communication system 100 includes an unmanned aerial vehicle 2. The unmanned aerial vehicle 2 flies in the stratosphere and irradiates a beam onto the ground, thereby forming a service area 4. In this case, the service area 4 is a 5G service area.

[0014] A terminal 6 is installed within the service area 4. The terminal 6 communicates with an application server and the like present in the core network 10 via the unmanned aerial vehicle 2 and a terrestrial base station 8. The terminal 6 is, for example, a UE (User Equipment). The core network 10 here is a 5G core network.

[0015] The unmanned aerial vehicle 2 is also equipped with a signal relay function. Packets sent from the terminal 6 are transmitted to the data network 12 via the unmanned aerial vehicle 2, terrestrial base station 8, and core network 10. Conversely, packets sent from the data network 12 are transmitted to the terminal 6 via the core network 10, terrestrial base station 8, and unmanned aerial vehicle 2. Note that a service link 14 is provided between the terminal 6 and the unmanned aerial vehicle 2, and a feeder link 16 is provided between the unmanned aerial vehicle 2 and the terrestrial base station 8.

[0016] The wireless communication system 100 further includes a communication control device 9. The communication control device 9 controls communication in the feeder link 16 via the terrestrial base station 8. Details of the communication control will be described later.

[0017] 2 is a block diagram showing an example configuration of an unmanned aerial vehicle according to embodiment 1 of the present disclosure. Here, components that realize functions possessed by the unmanned aerial vehicle 2 of this embodiment, in addition to the flight function, power generation function, and power storage function inherent to the unmanned aerial vehicle 2, will be described.

[0018] The unmanned aerial vehicle 2 includes a base station unit 22. The base station unit 22 is a component that performs processing related to communication using the service link 14, and functions as a 5G base station in this case. The base station unit 22 performs processing to form a service area on the ground and processing to communicate with terminals 6 within the service area 4 via the service link 14.

[0019] The base station unit 22 transmits traffic destined for the core network 10 to the transmission unit 24. The transmission unit 24 is a component that performs processing related to communications using the feeder link 16. The transmission unit 24 converts the received traffic into a radio signal for the feeder link and transmits it to the terrestrial base station 8. The terrestrial base station 8 restores the transmitted signal to the original traffic and transmits it to the core network 10.

[0020] The core network 10 performs authentication of the terminal 6, management of location information and billing of the terminal 6, and gateway processing between data networks. The core network 10 also controls the transmission speed (bit rate) per terminal for each service (slice) by performing traffic transmission scheduling control. This transmission scheduling control is performed based on information about the transmission speed of traffic for non-bandwidth-guaranteed services. The transmission speed of traffic for non-bandwidth-guaranteed services is, for example, the maximum transmission speed per terminal for each service (UE-slice-Maximum Bit Rate: UE-slice-MBR). Note that the "maximum transmission speed" in this disclosure refers to the upper limit speed allowable for the corresponding communication.

[0021] Meanwhile, the terrestrial base station 8 converts traffic addressed to the terminal 6 transmitted from the core network 10 into a feeder link radio signal and transmits it to the unmanned aerial vehicle 2. The transmission unit 24 restores the transmitted signal to the original traffic and transmits it to the base station unit 22. The base station unit 22 transmits the transmitted traffic to the terminal 6.

[0022] The transmission unit 24 also controls the modulation method for wireless transmission in the feeder link 16 by adaptive modulation control. Adaptive modulation control is a technique for adaptively changing the modulation method depending on the received power, error rate, etc. In adaptive modulation control, the modulation method is changed when the received power decreases or the error rate increases. In this change, a modulation method with a small number of multi-levels is applied so that the required SNR (signal-to-noise power ratio) in communication is reduced. This change makes it possible to maintain communication. The terrestrial base station 8 performs similar control in conjunction with the transmission unit 24.

[0023] 3 is a block diagram showing a configuration example of a communication control device according to the first embodiment of the present disclosure. The communication control device 9 includes a traffic volume monitoring unit 92. The traffic volume monitoring unit 92 acquires information on the volume of traffic generated from the core network 10. Then, the traffic volume monitoring unit 92 calculates the maximum volume of traffic flowing in the feeder link 16 based on the acquired information.

[0024] The communication control device 9 also includes a communication capacity monitoring unit 94. The communication capacity monitoring unit 94 acquires information on the modulation method currently being applied from the terrestrial base station 8. Then, the communication capacity monitoring unit 94 calculates the communication capacity of the feeder link 16 based on the acquired information.

[0025] The communication control device 9 further includes a communication control unit 96. The communication control unit 96 calculates the transmission rate of the traffic of the non-bandwidth guaranteed service based on the maximum traffic volume flowing in the feeder link 16 and the communication capacity of the feeder link 16. The communication control device 9 then notifies the core network 10 of the calculation result.

[0026] 4 is a diagram illustrating an example of a hardware configuration of a communication control device according to the first embodiment of the present disclosure. Each function of the communication control device 9 may be partially or entirely configured by hardware such as a programmable logic device (PLD) or a field programmable gate array (FPGA), or may be configured as a program executed by a processor such as a CPU.

[0027] For example, the communication control device 9 can be realized using a computer and a program, and the program can be recorded on a storage medium or provided via a network.

[0028] 4, the communication control device 9 has an input unit 900, an output unit 901, a communication unit 902, a CPU 903, a memory 904, and an HDD 905 connected via a bus 906, and functions as a computer. The communication control device 9 is also capable of inputting and outputting data to and from a computer-readable storage medium 907.

[0029] The input unit 900 is, for example, a keyboard and a mouse, etc. The output unit 901 is, for example, a display device such as a display.

[0030] The communication unit 902 is, for example, a communication interface that communicates with a wireless device to be controlled.

[0031] The CPU 903 controls each component of the communication control device 9 and performs predetermined processing, etc. The memory 904 and HDD 905 store data, etc.

[0032] The storage medium 907 is capable of storing programs and the like that cause the communication control device 9 to execute the functions of the communication control device 9. Note that the architecture that configures the communication control device 9 is not limited to the example shown in FIG.

[0033] 5 is a diagram illustrating a 5G protocol stack according to the first embodiment of the present disclosure. The stack illustrates protocols used in transmissions between the terminal 6, the unmanned aerial vehicle 2, the terrestrial base station 8, and the core network 10.

[0034] The UDP / IP and GTP-U protocols are used for transmission between the unmanned aerial vehicle 2 and the core network 10. Meanwhile, in the lower layers, feeder link radio signals are used for transmission between the unmanned aerial vehicle 2, particularly the base station unit 22, and the terrestrial base station 8. Adaptive modulation control is used in the transmission of these feeder link radio signals. The adaptive modulation control patterns assumed in this embodiment are as shown in Table 1.

[0035]

[0036] In conventional adaptive modulation control, the modulation method and the coding rate are often controlled, but in this embodiment, only the modulation method is controlled, and the coding rate is left unchanged.

[0037] 6 is a flowchart showing a process performed by the communication control device according to the first embodiment of the present disclosure. First, in step 100, the traffic volume monitoring unit 92 calculates the maximum traffic volume MTf flowing in the feeder link 16. MTf is calculated based on information regarding the traffic volume generated, which is acquired from the core network 10.

[0038] The information on the amount of traffic generated is, for example, the transmission rate of traffic for bandwidth-guaranteed services, the transmission rate of traffic for non-guaranteed services, and the number of terminals 6 receiving each service. The transmission rate of traffic for bandwidth-guaranteed services is, for example, the guaranteed transmission rate (GBR) for each service. The transmission rate of traffic for non-guaranteed services is, for example, the maximum transmission rate per terminal 6 for each service (UE-slice-MBR).

[0039] If the number of services is n, the transmission rate of traffic of service k is XBR(k), and the number of terminals receiving service k is Nu(k), MTf is expressed by Equation 1.

[0040]

[0041] Next, in step 102, the communication capacity monitor 94 calculates the communication capacity Cf of the feeder link 16. Cf is calculated based on information on the modulation method currently being applied, which is acquired from the terrestrial base station 8.

[0042] Next, in step 104, the communication control unit 96 calculates the ratio Rc of MTf to Cf. Rc is expressed by Equation 2.

[0043]

[0044] Next, in step 106, the communication control unit 96 determines whether Rc is greater than a specific threshold value Δ. If it is greater than Δ, the process proceeds to step 108. If it is not greater than Δ, the process ends.

[0045] Δ may be set based on at least one of the frequency with which the communication control device 9 performs processing, the increase or decrease in the number of terminals 6 connected per unit time, the amount of traffic fluctuation, or the service stability required for bandwidth-guaranteed services.

[0046] In step 108, communication control unit 96 recalculates XBR(k) so that Rc is equal to or less than a specific Δ, and notifies the result to core network 10. However, in this embodiment, the transmission rate of traffic of bandwidth-guaranteed services is not subject to recalculation, and only the transmission rate of traffic of non-bandwidth-guaranteed services is subject to recalculation.

[0047] Core network 10 sets the notified recalculation result as the transmission rate of traffic for the new non-bandwidth-guaranteed service. Core network 10 also transmits the notified recalculation result to base station unit 22. Base station unit 22 sets the notified recalculation result as the transmission rate of traffic for the new non-bandwidth-guaranteed service. From this point on, communication between core network 10 and base station unit 22 is controlled based on the transmission rate of traffic for the new non-bandwidth-guaranteed service.

[0048] It is assumed that the process shown in FIG. 6 is executed periodically in the wireless communication system 100.

[0049] An example of the operation of the wireless communication system 100 is shown below. Here, it is assumed that the communication control device 9 performs adaptive modulation control in the feeder link 16 using the set in Table 1. The maximum communication capacity of the feeder link 16 is 1000 Mbit / s when the modulation method of item number 4 is applied.

[0050] In addition, in the adaptive modulation control of this operation example, when the packet error rate observed over a certain period of time exceeds 0.1, the modulation method with the next lower item number (a smaller item number) is selected. Furthermore, in the adaptive modulation control of this operation example, when the packet error rate observed over a certain period of time falls below 0.1, the modulation method with the next higher item number (a larger item number) is selected. Δ is set to 0.9 (90%).

[0051] There are 70 terminals 6 in the 5G service area. The terminals 6 are connected to a data network and are performing communications. Of the 70 terminals, 20 are cameras for a bandwidth-guaranteed disaster monitoring service. The bandwidth required for the disaster monitoring service is 10 Mbit / s. The feeder link 16 uses the modulation method of item number 4, and the communication capacity Cf is 1000 Mbit / s.

[0052] The remaining 50 terminals are terminals for a web browsing service that is of the best-effort type, i.e., a non-bandwidth-guaranteed type. Unlike the disaster monitoring service, which is of the bandwidth-guaranteed type, the web browsing service does not determine the required bandwidth in advance.

[0053] First, the maximum transmission speed of the web browsing service is determined by the process shown in Fig. 6. This is because the maximum transmission speed of the web browsing service has not yet been determined in the initial stage.

[0054] The communication control device 9 calculates the MTf based on step 100. In this case, the information relating to the amount of traffic generated is the guaranteed transmission speed of the disaster monitoring service and the number of terminals 6 receiving the disaster monitoring service and the web browsing service.

[0055] Here, the guaranteed transmission rate of the disaster monitoring service is GBR_D, and the maximum transmission rate of the web browsing service is MBR_B. Since GBR_D is 10 Mbit / s, MTf is calculated using Equation 3.

[0056]

[0057] Next, the communication control device 9 calculates Cf based on step 102. Cf is calculated based on the modulation method of item number 4 used in the feeder link 16.

[0058] Next, the communication control device 9 calculates Rc in step 104. Rc is calculated using Equation 4.

[0059]

[0060] Here, MBR_B is set to the maximum value for which Δ≧Rc, and as a result, MBR_B is calculated to be 14 Mbit / s.

[0061] Next, the communication control device 9 determines whether Rc is greater than Δ based on step 106. Δ is 0.9 as described above. Here, in step 104, MBR_B is calculated so that Δ≧Rc. In other words, Rc is not greater than Δ, so the process ends.

[0062] The communication control device 9 sets the UE-slice-MBR for the web browsing service to 14 Mbit / s and notifies the core network 10. Based on the notification, the core network 10 sets the UE-slice-MBR for the web browsing service to 14 Mbit / s. Furthermore, the core network 10 transmits this notification to the base station unit 22 of the unmanned aerial vehicle 2. The base station unit 22 sets the UE-slice-MBR to 14 Mbit / s.

[0063] Thereafter, communication control based on the UE-slice MBR is performed between the core network 10 and the base station unit 22, and communication services are operated.

[0064] Next, assume that the number of terminals using the web browsing service increases by 20 to 70. In this case, the process shown in FIG. 6 is executed again. Steps 100 and 102 are the same as those described above, so a description thereof will be omitted. The value of Rc recalculated based on step 104 becomes 1.18, as shown in Equation 5.

[0065]

[0066] Here, when the determination based on step 106 is made, Rc>Δ is found, and therefore recalculation based on step 108 is performed. That is, the maximum MBR_B that satisfies Δ≧Rc is calculated. In this case, MBR_B is calculated to be 10 Mbit / s.

[0067] Therefore, the communication control device 9 sets the maximum transmission speed per terminal 6 for the web browsing service to 10 Mbit / s and notifies the core network 10. Based on the notification, the core network 10 sets the UE-slice-MBR of the web browsing service to 10 Mbit / s. Furthermore, the core network 10 transmits this notification to the base station unit 22 of the unmanned aerial vehicle 2. The base station unit 22 sets the UE-slice-MBR to 10 Mbit / s.

[0068] Thereafter, communication control based on the UE-slice MBR is performed between the core network 10 and the base station unit 22, and communication services are operated.

[0069] 7 is a diagram illustrating an example of the configuration of a wireless communication system during rainfall according to the first embodiment of the present disclosure. The wireless communication system 100a differs from the wireless communication system 100 in that the feeder link 16a is affected by rainfall 18.

[0070] The received power of the feeder link 16a is reduced due to power attenuation caused by rainfall 18. As a result, the required SNR for the modulation method 32APSK cannot be achieved, and the error rate exceeds 0.1.

[0071] In this case, the process shown in Fig. 6 is also executed. As for step 100, the content is the same as that described above, and therefore the explanation will be omitted.

[0072] The communication control device 9 calculates Cf based on step 102. In this case, the adaptive modulation control applies modulation schemes with progressively lower item numbers, thereby selecting a modulation scheme with an error rate below 0.1. For example, if the error rate falls below 0.1 when QPSK, item number 1, is applied, the modulation scheme is changed from 32APSK to QPSK. In this case, the number of bits that can be transmitted per symbol changes from 5 bits to 2 bits, and Cf, which is the communication capacity of the feeder link 16, becomes 400 Mbit / s.

[0073] Next, the communication control device 9 calculates Rc in step 104. Rc is calculated using equation 6 and is 2.25.

[0074]

[0075] Next, the communication control device 9 determines whether Rc is greater than Δ in step 106. Δ is 0.9 as described above. Since Rc > Δ, the process proceeds to step 108, where the maximum MBR_B for which Δ ≥ Rc is calculated. As a result, MBR_B is calculated to be 2.28 Mbit / s.

[0076] Therefore, the communication control device 9 sets the UE-slice-MBR for the web browsing service to 2.28 Mbit / s and notifies the core network 10. Based on the notification, the core network 10 sets the UE-slice-MBR for the web browsing service to 2.28 Mbit / s. Furthermore, the core network 10 transmits this notification to the base station unit 22 of the unmanned aerial vehicle 2. The base station unit 22 sets the UE-slice-MBR to 2.28 Mbit / s.

[0077] As described above, by limiting the transmission speed of non-guaranteed services, the communication capacity of guaranteed services can be secured, i.e., the transmission speed required for guaranteed services can be guaranteed without increasing the cost required to build the system.

[0078] In this embodiment, the maximum transmission speed is set for each service based on the type of service, but this is not limited to this. For example, if a maximum or guaranteed transmission speed can be set for each terminal 6 in the communication system, the speed may be calculated and set for each terminal 6 based on the service information used by the terminal 6.

[0079] Furthermore, a maximum or guaranteed transmission rate may be set for each session established between terminals and the core network. In this case, control similar to that in this embodiment can be performed based on the service information of the session.

[0080] Although this embodiment assumes that there is only one non-bandwidth-guaranteed service, there may be multiple non-bandwidth-guaranteed services. In this case, similar processing can be performed by setting the maximum transmission speed for each non-bandwidth-guaranteed service, taking into account the priority of each service.

[0081] Furthermore, there may be cases where multiple bandwidth-guaranteed services exist, and simply resetting the maximum transmission rate of the non-guaranteed service does not bring Rc below Δ. In such cases, the priority of each bandwidth-guaranteed service is taken into consideration, and the guaranteed transmission rate of the bandwidth-guaranteed service with the lowest priority is recalculated and reset.

[0082] More specifically, communication control device 9 further performs a process of setting priorities for multiple bandwidth-guaranteed services. Furthermore, if Rc is not less than Δ, communication control device 9 recalculates the transmission rates of the traffic for the bandwidth-guaranteed services in addition to the transmission rates of the traffic for the non-bandwidth-guaranteed services, in ascending order of priority. This process ensures that the transmission rates required for the more important bandwidth-guaranteed services are guaranteed.

[0083] Additionally, although this embodiment assumes a wireless communication system using adaptive modulation control, this is not limiting. For example, similar processing may be performed by setting the transmission rate of each service in consideration of factors related to fluctuations in the communication capacity of the feeder link, such as the number of multiplexing in MIMO transmission.

[0084] Furthermore, in this embodiment, a decrease in the communication capacity of the feeder link due to rainfall is assumed, but this is not limited to this. For example, this control may be applied when the communication capacity fluctuates due to control of changing the frequency or bandwidth of the feeder link to avoid interference with the terrestrial network.

[0085] [Wireless Communication System According to Comparative Example] In order to describe in detail the problem solved by this embodiment, a comparative example will be described. Fig. 8 is a diagram showing a wireless communication system according to a first comparative example. The wireless communication system 500 is a wireless communication system configured with an NTN using HAPS. The wireless communication system 500 differs from the wireless communication system 100 in that it does not include a communication control device 9.

[0086] Terminals 6 receive mobile communication services and communicate with application servers and the like present on data network 12. At this time, traffic flows between terminals and between servers via service link 14 and feeder link 16. In particular, feeder link 16 transfers a large amount of traffic from the many terminals 6 receiving mobile communication services to data network 12, or from data network 12 to terminals 6. Therefore, feeder link 16 requires a high communication capacity.

[0087] Therefore, the feeder link 16 increases the communication capacity by applying multilevel modulation such as 16QAM or 64QAM. Furthermore, the feeder link 16 ensures high communication capacity by using high frequency bands such as the Ka band. However, high frequency radio waves are subject to significant power attenuation due to rainfall. Therefore, there is a problem that the received power at the terrestrial base station 8 decreases in rainy weather.

[0088] To solve this problem, NTN often uses transmission power control, which compensates for temporary drops in received power by adjusting the transmission power. However, the amount of increase in transmission power depends on the performance of devices such as power amplifiers, so there is a problem that there is a limit to the transmission power that can be compensated.

[0089] 9 is a diagram showing a wireless communication system according to a second comparative example. The wireless communication system 600 has redundant terrestrial base stations and is configured as an NTN using HAPS. The wireless communication system 600 differs from the wireless communication system 500 in that it has a redundant network.

[0090] The wireless communication system 600 includes a redundant terrestrial base station 8b and a feeder link 16b. In the wireless communication system 600, the communication capacity of the normal feeder link 16a decreases due to the influence of rainfall 18 during rainy weather. In this case, the wireless communication system 600 switches from the normal feeder link 16a to the redundant feeder link 16b. The terrestrial base station 8 and the terrestrial base station 8b are installed far apart to prevent the feeder links from being simultaneously affected by weather. Therefore, this switching has the effect of improving communication capacity.

[0091] However, in order to prepare a redundant system, it is necessary to install an additional terrestrial base station 8b, which increases the cost required for building the system, and as a result, there is a problem that it is difficult to install a redundant system.

[0092] Another solution is a wireless communication system that uses adaptive modulation control. However, adaptive modulation control reduces communication capacity when a modulation scheme with a small number of modulation levels is used. In this case, the amount of traffic that can be transmitted and received between the NTN and the ground via the feeder link 16 decreases, which creates the problem of terminals 6 being unable to receive satisfactory service.

[0093] Furthermore, the services received by terminal 6 may include both bandwidth-guaranteed and non-guaranteed services. In this case, there is a problem that the traffic generated by the non-guaranteed service communication may make it impossible to meet the bandwidth required for the guaranteed bandwidth in the traffic transmission of the bandwidth-guaranteed service. This problem has a particularly large impact on the service quality of applications classified as URLLC (Ultra-Reliable and Low Latency Communications), which are part of the bandwidth-guaranteed service and require high reliability, such as disaster monitoring, autonomous driving, and driving assistance.

[0094] Furthermore, guaranteed bandwidth services include emergency communications and communications equipment maintenance. For terminals that require such services, which require prioritized communications, there is a problem that necessary communications cannot be performed. The present disclosure solves the problem associated with the comparative example described above.

[0095] 10 is a diagram illustrating a configuration example of a wireless communication system according to a second embodiment of the present disclosure. The configuration of the wireless communication system 200 is the same as that of the wireless communication system 100, except that the communication control device 9 is a communication control device 9a.

[0096] In the example according to the first embodiment, an example was shown in which the transmission rate is controlled for each service, whereas in the present embodiment, an example is shown in which the transmission rate is controlled for each type of terminal 6.

[0097] 11 is a block diagram showing a configuration example of a communication control device according to a second embodiment of the present disclosure. The communication control device 9a includes an information acquisition unit 98 in addition to the configuration of the communication control device 9. The information acquisition unit 98 acquires information about the terminal 6 from the core network 10. The information about the terminal 6 is, for example, the type of the terminal 6.

[0098] The communication control unit 96 calculates the transmission rate of the traffic of the non-bandwidth guaranteed service based on the type of terminal 6, the number of terminals 6 of each type, and the communication capacity of the feeder link 16. This transmission rate is, for example, the maximum transmission rate (UE-AMBR) for each terminal 6. Then, the communication control device 9a notifies the core network 10 of the calculated UE-AMBR.

[0099] The process performed by the communication control device 9a is shown in the flowchart of Fig. 6. First, in step 100, the traffic volume monitoring unit 92 calculates the maximum traffic volume MTf flowing in the feeder link 16. The maximum traffic volume MTf is calculated based on information regarding the traffic volume generated, which is acquired from the core network 10.

[0100] The information on the amount of traffic generated is, for example, the type of terminal 6, the number of terminals 6 of each type, the transmission rate of traffic for bandwidth-guaranteed services, and the transmission rate of traffic for non-bandwidth-guaranteed services. The information on the type of terminal 6 includes information on whether the type is classified as a bandwidth-guaranteed service or a non-bandwidth-guaranteed service. The transmission rate of traffic for bandwidth-guaranteed services is, for example, the guaranteed transmission rate for each type. The transmission rate of traffic for non-guaranteed services is, for example, the maximum transmission rate per terminal 6 for each type (UE-AMBR).

[0101] If the number of types of terminals 6 is n, the transmission rate of traffic of type m of terminals 6 is XBR(m), and the number of terminals of type m is Nu(m), the maximum traffic volume MTf is given by Equation 7.

[0102]

[0103] Next, in step 102, the communication capacity monitoring unit 94 calculates the communication capacity Cf of the feeder link 16. The communication capacity Cf is calculated based on information on the modulation method currently being applied, which is acquired from the terrestrial base station 8.

[0104] Next, in step 104, the communication control unit 96 calculates Rc, which is the ratio of MTf to Cf. Rc is expressed by Equation 2.

[0105] Next, in step 106, the communication control unit 96 determines whether Rc is greater than a specific Δ. If it is greater than Δ, the process proceeds to step 108. If it is not greater than Δ, the process ends.

[0106] In step 108, communication control unit 96 recalculates XBR(m) so that Rc is equal to or less than a specific Δ, and notifies the result to core network 10. However, in this embodiment, the transmission rate of traffic of bandwidth-guaranteed services is not subject to recalculation, and only the transmission rate of traffic of non-bandwidth-guaranteed services is subject to recalculation.

[0107] Core network 10 sets the notified recalculation result as the transmission rate of traffic for the new non-bandwidth-guaranteed service. Core network 10 also transmits the notified recalculation result to base station unit 22. Base station unit 22 sets the notified recalculation result as the transmission rate of traffic for the new non-bandwidth-guaranteed service. From this point on, communication between core network 10 and base station unit 22 is controlled based on the transmission rate of traffic for the new non-bandwidth-guaranteed service.

[0108] It is assumed that the process shown here is executed periodically in the wireless communication system 200.

[0109] An example of the operation of the wireless communication system 200 is shown below. Here, it is assumed that the communication control device 9a performs adaptive modulation control in the feeder link 16 using the set in Table 1. The maximum communication capacity of the feeder link 16 is 1000 Mbit / s when the modulation method of item number 4 is applied.

[0110] In addition, in the adaptive modulation control of this operation example, when the packet error rate observed over a certain period of time exceeds 0.1, the modulation method with the next lower item number is selected. Furthermore, in the adaptive modulation control of this operation example, when the packet error rate observed over a certain period of time falls below 0.1, the modulation method with the next higher item number is selected. Δ is set to 0.9 (90%).

[0111] Table 2 shows the Access Identity used as the type of terminal 6. There are several types of Access Identity defined by 3GPP (3rd Generation Partnership Project), but here we will assume the three types in Table 2. Note that 3GPP is a registered trademark. Terminals 6 with Access Identity values ​​of 0 and 1 are assumed to be for non-guaranteed bandwidth services. On the other hand, terminals 6 with Access Identity value 2 are assumed to be for guaranteed bandwidth services, and their required bandwidth is 20 Mbit / s.

[0112]

[0113] There are 40 terminals 6 in the 5G service area. The terminals 6 are connected to a data network and are performing communication. Of the 40 terminals 6, 10 have an Access Identity of 0. Of the remaining 30 terminals 6, 10 have an Access Identity of 1. The remaining 20 terminals 6 have an Access Identity of 2. The feeder link 16 uses the modulation method of item number 4, and has a communication capacity Cf = 1000 Mbit / s.

[0114] First, the maximum transmission rate of the terminal 6 whose Access Identity is 0 or 1 is determined based on the process shown in Fig. 6. This is because the maximum transmission rate is not yet determined at the initial stage.

[0115] The communication control device 9a calculates MTf based on step 110. In this case, the information relating to the amount of traffic generated corresponds to the type of terminal 6, the number of terminals 6 of each type, and the guaranteed transmission rate or UE-AMBR of each type.

[0116] First, the communication control device 9a acquires the Access Identity information of each terminal 6. Then, by aggregating the Access Identity information, it is determined that there are 10 terminals 6 whose Access Identity is 0, 10 terminals 6 whose Access Identity is 1, and 20 terminals 6 whose Access Identity is 2. Next, the communication control device 9a acquires the guaranteed transmission rate or UE-AMBR for each type from the core network 10, and calculates the MTf based on them.

[0117] Here, the guaranteed transmission rate of terminal 6 whose Access Identity is 2 is GBR_2, and the maximum transmission rate of terminal 6 whose Access Identity is 0 or 1 is MBR_01. Since GBR_2 is 20 Mbit / s, MTf is calculated using Equation 8.

[0118]

[0119] Next, the communication control device 9 calculates Cf based on step 102. Cf is calculated based on the modulation method of item number 4 used in the feeder link 16.

[0120] Next, the communication control device 9 calculates Rc in step 104. Rc is calculated using Equation 9.

[0121]

[0122] Here, MBR_01 is set to the maximum value for which Δ≧Rc, and as a result, MBR_01 is calculated to be 25 Mbit / s.

[0123] Next, the communication control device 9 determines whether Rc is greater than Δ based on step 106. Δ is 0.9 as described above. Here, in step 104, MBR_01 is calculated so that Δ≧Rc. In other words, Rc is not greater than Δ, so the process ends.

[0124] The communication control device 9 sets the UE-AMBR of terminals 6 whose Access Identities are 0 and 1 to 25 Mbit / s and notifies the core network 10. Based on the notification, the core network 10 sets the UE-AMBR of terminals 6 whose Access Identities are 0 and 1 to 25 Mbit / s. Furthermore, the core network 10 transmits this notification to the base station unit 22 of the unmanned air vehicle 2. The base station unit 22 sets the UE-AMBR of terminals 6 whose Access Identities are 0 and 1 to 25 Mbit / s.

[0125] Thereafter, communication control based on UE-AMBR is performed between the core network 10 and the base station unit 22, and communication services are operated.

[0126] 12 is a diagram illustrating a configuration example of a wireless communication system during rainfall according to the second embodiment of the present disclosure. The wireless communication system 200a differs from the wireless communication system 200 in that the feeder link 16a is affected by rainfall 18.

[0127] The received power of the feeder link 16a is reduced due to power attenuation caused by rainfall 18. As a result, the required SNR for the modulation method 32APSK cannot be achieved, and the error rate exceeds 0.1.

[0128] In this case, the process is also performed based on the process shown in Fig. 6. As for step 100, the content is the same as that described above, and therefore the explanation will be omitted.

[0129] The communication control device 9 calculates Cf based on step 102. In this case, the adaptive modulation control applies modulation schemes with progressively lower item numbers, thereby selecting a modulation scheme with an error rate below 0.1. For example, if the error rate falls below 0.1 when 8PSK, item number 2, is applied, the modulation scheme is changed from 32APSK to 8PSK. In this case, the number of bits that can be transmitted per symbol changes from 5 bits to 3 bits, and Cf, which is the communication capacity of the feeder link 16, becomes 600 Mbit / s.

[0130] Next, the communication control device 9 calculates Rc in step 104. Rc is calculated using equation 10 and is approximately 1.17.

[0131]

[0132] Next, the communication control device 9 determines whether Rc is greater than Δ in step 106. Δ is 0.9 as described above. Since Rc > Δ, the process proceeds to step 108, where the maximum MBR_01 that satisfies Δ ≥ Rc is calculated. MBR_01 is calculated using equation 11, which is 7 Mbit / s.

[0133]

[0134] Therefore, the communication control device 9 sets the UE-AMBR of the terminals 6 whose Access Identities are 0 and 1 to 7 Mbit / s and notifies the core network 10. Based on the notification, the core network 10 sets the UE-AMBR of the terminals 6 whose Access Identities are 0 and 1 to 7 Mbit / s. Furthermore, the core network 10 transmits this notification to the base station unit 22 of the unmanned air vehicle 2. The base station unit 22 sets the UE-AMBR of the terminals 6 whose Access Identities are 0 and 1 to 7 Mbit / s.

[0135] As described above, by limiting the transmission speed of non-guaranteed services, the communication capacity of guaranteed services can be secured, i.e., the transmission speed required for guaranteed services can be guaranteed without increasing the cost required to build the system.

[0136] Third Embodiment In the second embodiment, an example was shown in which the transmission rate was controlled for each type of terminal 6. On the other hand, in this embodiment, an example is shown in which the transmission rate is controlled based on the subscriber information of the terminal 6.

[0137] The subscriber information is, for example, the plan to which the subscriber subscribes or the billing status. In this case, the information about the terminal 6 acquired by the information acquisition unit 98 includes the subscriber information.

[0138] For example, a terminal 6 subscribed to a low-cost plan is subject to non-guaranteed bandwidth service, while a terminal 6 of a user subscribed to a high-cost plan is subject to guaranteed bandwidth service. This classification allows for the same control as in the second embodiment.

[0139] More specifically, communication control device 9 further performs processing to classify terminals 6 based on subscriber information. This classification is performed so that terminals 6 of users subscribed to low-cost plans are eligible for non-guaranteed bandwidth service, and terminals 6 of users subscribed to high-cost plans are eligible for guaranteed bandwidth service. This processing allows terminals 6 of users subscribed to high-cost plans to be given priority in being guaranteed the transmission speed required for the guaranteed bandwidth service.

[0140] As described above, according to this embodiment, it is possible to guarantee the transmission speed required for a bandwidth-guaranteed service without increasing the cost required for system construction. In addition, it is possible to guarantee the transmission speed of a service provided to a specific user on a priority basis.

[0141] In the first and second embodiments, the magnitude of Rc and Δ were compared in the processing performed by the communication control device. In this embodiment, when a change in the number of connected terminals is predicted or detected during processing by the communication control device, processing is performed to reduce the value of Δ during processing by the communication control device 9 or 9a, thereby mitigating the impact of a sudden decrease in communication capacity.

[0142] Δ is set when a buffer with a certain communication capacity is provided. The buffer is excess communication capacity. For example, in the wireless communication system according to the present disclosure, the transmission speed of traffic of non-guaranteed bandwidth services is periodically controlled. However, during this process, a change in the number of connected terminals may be predicted or detected. For example, a terminal 6 that is a target of the guaranteed bandwidth service may be newly connected to the wireless communication system.

[0143] Even in this case, terminal 6, which is a target of the bandwidth-guaranteed service, can communicate at the guaranteed transmission rate by using the communication capacity that the wireless communication system has as a buffer. In other words, even if the number of connections to terminal 6 fluctuates significantly during the processing of Figure 6, the impact of the increase in the number of connections to terminal 6 can be mitigated by reducing Δ and increasing the communication capacity buffer.

[0144] Furthermore, if the communication environment suddenly changes during processing, the communication capacity of the feeder link 16 or 16a may suddenly decrease, which will result in a decrease in the transmission speed of the terminal 6 that is the target of the bandwidth-guaranteed service.

[0145] Even in this case, terminal 6, which is the target of the bandwidth-guaranteed service, can communicate at the guaranteed transmission rate by using the communication capacity it has as a buffer. In other words, by reducing Δ and increasing the communication capacity buffer, the impact of a sudden decrease in communication capacity can be mitigated. As a result, the transmission rate required for the bandwidth-guaranteed service can be guaranteed.

[0146] In this embodiment, Δ is reduced when a change in the number of connected terminals is predicted or detected. For example, the transition of the communication capacity available in the wireless communication system may be recorded in advance, and Δ may be reduced at a timing when it is statistically predicted that the communication capacity will be insufficient. Alternatively, the communication capacity available in the wireless communication system may be periodically acquired, and Δ may be reduced at a timing when it is detected that the acquired communication capacity has become smaller than a specific threshold.

[0147] As described above, this embodiment can guarantee the transmission speed required for a bandwidth-guaranteed service without increasing the cost required for system construction, and can also mitigate the impact of a sudden drop in communication capacity.

[0148] In the first and second embodiments, information about the feeder link 16 or 16a is acquired in the process performed by the communication control device. In this embodiment, an example is shown in which the communication capacity of the feeder link 16 or 16a is a predicted value.

[0149] In this case, the communication capacity monitoring unit 94 stores the causes of past fluctuations in communication capacity and the magnitude of the fluctuations in communication capacity associated with those causes. The causes of fluctuations in communication capacity include, for example, weather fluctuations, fluctuations in the trajectory of the unmanned aerial vehicle 2, and events such as the occurrence of traffic in the vicinity. The communication capacity monitoring unit 94 predicts fluctuations in communication capacity based on the causes described above and notifies the communication control unit 96. Based on the notified communication capacity, the communication control unit 96 performs the processing shown in FIG. 6 to predict the required transmission speed of the traffic for the non-bandwidth-guaranteed service.

[0150] As an example, an example of predicting fluctuations in communication capacity due to weather fluctuations is shown below. Table 3 shows an example of fluctuations in communication capacity due to precipitation. This table shows fluctuations in communication capacity of the feeder link 16a due to precipitation based on past statistics. Furthermore, the communication capacity monitoring unit 94 can obtain information related to weather forecasts from weather forecast sites.

[0151]

[0152] An example of operation will be shown below. First, the communication capacity monitoring unit 94 predicts that the amount of precipitation for the next hour will be 10 mm based on information obtained from a weather forecasting site. Next, the communication capacity monitoring unit 94 predicts that the communication capacity of the feeder link 16a will be 600 Mbit / s based on Table 3. The communication capacity monitoring unit 94 then notifies the communication control unit 96 of the predicted communication capacity. Based on the notified communication capacity, the communication control unit 96 performs the processing shown in FIG. 6 to predict the required transmission speed of the traffic for the non-bandwidth-guaranteed service.

[0153] As described above, this embodiment can guarantee the transmission speed required for bandwidth-guaranteed services without increasing the cost required for system construction. In addition, it can quickly respond to fluctuations in the communication capacity of the feeder link due to events.

[0154] 13 is a diagram showing an example of the configuration of a wireless communication system according to a sixth embodiment of the present disclosure. In the first to fifth embodiments, the feeder link between the unmanned aerial vehicle 2 and the terrestrial base station 8 is the target. On the other hand, in this embodiment, a configuration is shown in which the target is any route between the unmanned aerial vehicle 2 and the core network 10.

[0155] In addition to the configuration of the wireless communication system 100, the wireless communication system 300 also includes an unmanned aerial vehicle 2-2, a satellite 3, and terrestrial base stations 8-2 to 8-4. The unmanned aerial vehicle 2-2 has the same functions as the unmanned aerial vehicle 2, and the terrestrial base stations 8-2 to 8-4 have the same functions as the terrestrial base station 8.

[0156] A change in the route between the unmanned aerial vehicle 2 and the core network 10 may result in a decrease in the communication capacity of the feeder link. For example, in the wireless communication system 300, the unmanned aerial vehicle 2 can connect to multiple terrestrial base stations. Therefore, a route via terrestrial base station 8-2 can be selected in addition to the route via terrestrial base station 8. Furthermore, because the unmanned aerial vehicle 2 and the unmanned aerial vehicle 2-2 are linked, a route via the unmanned aerial vehicle 2-2 and the terrestrial base station 8-3 can be selected. Furthermore, because the unmanned aerial vehicle 2 and the satellite 3 are linked, a route via the satellite 3 and the terrestrial base station 8-4 can be selected. The communication capacity of each route depends on the link bandwidth that is the bottleneck on each route.

[0157] For example, depending on the location where the unmanned aerial vehicle 2 flies, it may not be able to connect to the terrestrial base station 8. In that case, if control is performed to select another route, the transmission capacity between the unmanned aerial vehicle 2 and the core network 10 will change. Therefore, by applying the processing according to the present disclosure, it is possible to guarantee the transmission speed required for bandwidth-guaranteed services.

[0158] As described above, according to this embodiment, the transmission speed required for the bandwidth-guaranteed service can be guaranteed without increasing the cost required for system construction. In addition, the route that allows the above-mentioned guarantee can be expanded to any route between the unmanned aerial vehicle 2 and the core network 10.

[0159] 6 Terminal 9 Communication control device 9a Communication control device 10 Core network 16 Feeder link 16a Feeder link 16b Feeder link 100 Wireless communication system 100a Wireless communication system 200 Wireless communication system 200a Wireless communication system 300 Wireless communication system 500 Wireless communication system 600 Wireless communication system

Claims

1. A wireless communication system providing bandwidth-guaranteed services and non-bandwidth-guaranteed services, comprising: a terminal; a core network that communicates with the terminal via a feeder link; and a communication control device that controls communication in the feeder link, wherein the communication control device is configured to perform the following processes: calculate a maximum traffic volume based on information on generated traffic volume; calculate the communication capacity of the feeder link based on information on the modulation method being applied; calculate a ratio of the maximum traffic volume to the communication capacity of the feeder link; if the ratio is greater than a specific threshold, recalculate the transmission rate of the traffic of the non-bandwidth-guaranteed service so that the ratio is equal to or less than the threshold; and notify the core network of the recalculation result; and the core network is configured to set the result of the recalculation as the transmission rate of the traffic of the new non-bandwidth-guaranteed service.

2. A wireless communication system according to claim 1, wherein the information relating to the amount of traffic generated includes information on the transmission rate of traffic for bandwidth-guaranteed services, the transmission rate of traffic for non-bandwidth-guaranteed services, and the number of terminals receiving each service, wherein the transmission rate of traffic for bandwidth-guaranteed services is the guaranteed transmission rate for each service, and wherein the transmission rate of traffic for non-bandwidth-guaranteed services is the maximum transmission rate per terminal for each service.

3. A wireless communication system according to claim 1, wherein the information relating to the amount of traffic generated includes the transmission rate of traffic for bandwidth-guaranteed services, the transmission rate of traffic for non-guaranteed services, the type of terminal, and the number of terminals for each type, the transmission rate of traffic for bandwidth-guaranteed services being the guaranteed transmission rate for each type, and the transmission rate of traffic for non-guaranteed services being the maximum transmission rate per terminal for each type.

4. The wireless communication system according to claim 1, wherein the information relating to the amount of traffic generated includes subscriber information of the terminal, and the communication control device is further configured to perform processing to classify terminals into those eligible for non-guaranteed bandwidth service and those eligible for guaranteed bandwidth service based on the subscriber information.

5. The wireless communication system according to claim 1, wherein processing is performed to reduce the specific threshold value when a change in the number of connected terminals is predicted or detected during processing by the communication control device.

6. The wireless communication system according to claim 1, wherein the communication capacity of the feeder link is a value predicted based on causes of past fluctuations in communication capacity.

7. The wireless communication system according to claim 1, wherein there are a plurality of the bandwidth-guaranteed services, and the communication control device is further configured to perform a process of setting priorities for the plurality of the bandwidth-guaranteed services, and the recalculation process further includes a process of, when the ratio is greater than a specific threshold, recalculating the transmission rates of the traffic of the plurality of the bandwidth-guaranteed services in order of decreasing priority so that the ratio becomes equal to or less than the threshold.

8. The wireless communication system according to claim 1, wherein the specific threshold is set based on at least one of the frequency with which the communication control device performs processing, the increase or decrease in the number of terminals connected per unit time, the amount of traffic fluctuation, or the service stability required for bandwidth-guaranteed services.

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