WO2025177565A1 - Wireless communication system, link control device, link control method, and link control program - Google Patents

Abstract

In a wireless communication system according to one embodiment, one or more node stations that move relative to the ground surface and a plurality of base stations disposed on the ground perform wireless communication. The wireless communication system is characterized by comprising: a score calculation unit that calculates scores based on a parameter related to the communication quality of wireless communication links between all the node stations and all the base stations; and a control unit that controls the wireless communication links so as to maximize the number of wireless communication links connecting the base stations and the node stations, with the highest priority placed on maximizing the total sum of the scores calculated by the score calculation unit.

Description

Wireless communication system, link control device, link control method, and link control program

The present invention relates to a wireless communication system, a link control device, a link control method, and a link control program.

In recent years, mobile communication systems have evolved, making it possible to enjoy mobile services over most of the earth. Ultra-wide coverage is one of the requirements for the 5th generation (Beyond 5G) and 6th generation mobile communication systems, which are expected to be commercialized in the future.

Ultra-coverage refers to expanding the service area to locations where the cost of installing existing terrestrial base stations (base stations) is high or difficult, such as mountains, oceans, and the air. There is also a need to strengthen the nation's resilience against natural disasters, and there is a desire for the emergence of a communications system that is resistant to terrestrial disasters.

To meet these demands, hopes are being placed on non-terrestrial networks (NTNs) that use satellites, unmanned aerial vehicles, high-altitude platforms, drones, and other such devices. Among these, satellites that travel in orbits lower than geostationary orbit are attracting particular attention due to their excellent low-latency communications capabilities. In an NTN, traffic requested by each terminal is transmitted to terrestrial mobile networks via satellites and base stations.

In the NTN, the radio wave propagation environment for the wireless communication links that carry out communication between satellites and base stations fluctuates from moment to moment due to the movement of the satellites and rainfall. If a communication interruption occurs on a wireless communication link, another base station that is capable of communication is searched for and the wireless communication link is reconnected, or traffic is transferred via an inter-satellite communication link to another satellite that is capable of communicating with the base station.

For example, when switching a wireless communication link to another base station, a known prior art technique for selecting a base station to which the wireless communication link should be connected is one that uses maximum connection time or maximum reception strength as criteria (see, for example, Non-Patent Document 1).

If the maximum connection time is used as the criterion for selecting a base station to connect to for a wireless communication link, even lines with extremely low communication capacity (lines where the CINR: Carrier to Interference and Noise Ratio is close to the communication threshold) will be prioritized as a connection destination if the connection time is long.

On the other hand, if maximum reception strength is used as the criterion for selecting a base station to connect to for a wireless communication link, even a line with an extremely short communication time will be prioritized as a connection destination if its reception strength is strong.

E. Papapetrou, et al., "Satellite Handover Techniques for LEO Networks"

In the past, even if the line was connected, there were cases where the throughput did not meet the traffic requirements, or where throughput decreased due to frequent switching of wireless communication links.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a wireless communication system, link control device, link control method, and link control program that can suppress a decrease in throughput in a wireless communication system in which one or more node stations that move relative to the Earth's surface communicate wirelessly with multiple base stations located on the ground.

A wireless communication system according to one embodiment of the present invention is a wireless communication system in which one or more node stations that move relative to the Earth's surface communicate wirelessly with multiple base stations located on the ground. The system is characterized by having a score calculation unit that calculates scores based on parameters related to the communication quality of the wireless communication links between all of the node stations and all of the base stations, and a control unit that controls the wireless communication links so as to increase the number of wireless communication links connecting the base stations and the node stations, with the highest priority being given to maximizing the sum of the scores calculated by the score calculation unit.

Furthermore, a link control device according to one embodiment of the present invention is a link control device that controls wireless communication links between one or more node stations that move relative to the Earth's surface and multiple base stations located on the ground, and is characterized by having a score calculation unit that calculates scores based on parameters related to the communication quality of the wireless communication links between all of the node stations and all of the base stations, and a control unit that controls the wireless communication links so as to increase the number of wireless communication links connecting the base stations and the node stations, with the highest priority being given to maximizing the sum of the scores calculated by the score calculation unit.

Furthermore, a link control method according to one embodiment of the present invention is a link control method for controlling wireless communication links between one or more node stations that move relative to the Earth's surface and multiple base stations located on the ground, and is characterized by including a score calculation step for calculating scores based on parameters related to the communication quality of the wireless communication links between all of the node stations and all of the base stations, and a control step for controlling the wireless communication links so as to increase the number of wireless communication links connecting the base stations and the node stations, with the highest priority being given to maximizing the sum of the scores calculated in the score calculation step.

The present invention makes it possible to suppress a decrease in throughput in a wireless communication system in which one or more node stations that move relative to the Earth's surface communicate wirelessly with multiple base stations located on the ground.

1 is a diagram illustrating an example of the configuration of a wireless communication system according to an embodiment. 2 is a functional block diagram illustrating a configuration example of a link control device according to an embodiment. FIG. 1 is a diagram illustrating a wireless communication link (switching of wireless communication links) between one node station and multiple base stations. FIG. 10 is a diagram showing a reference table for presetting base stations to which connections are made for each time period. 1 is a graph illustrating link capacity. FIG. 1 is a diagram illustrating a first operation example of a wireless communication system. FIG. 10 is a diagram illustrating a second operation example of the wireless communication system. 1A is a diagram showing the operation results when selecting a base station with the highest score for a node station, and FIG. 1B is a diagram showing the operation results when selecting a base station by giving priority to a node station with a small number of connection destination candidates. FIG. 2 is a diagram illustrating an example of a hardware configuration of a link control device according to an embodiment. 1A is a diagram illustrating an overview of a wireless communication system of a comparative example in which a base station to which a wireless communication link is connected is selected based on a maximum connection time, and FIG. 1B is a diagram illustrating an overview of a wireless communication system of a comparative example in which a base station to which a wireless communication link is connected is selected based on a maximum reception strength.

Before explaining a wireless communication system according to one embodiment, the background to the invention will first be explained using Figure 10. Figure 10 is a diagram showing an overview of a wireless communication system of a comparative example. Figure 10(a) is a diagram showing an overview of a wireless communication system of a comparative example in which a base station to which a wireless communication link is connected is selected based on the maximum connection time. Figure 10(b) is a diagram showing an overview of a wireless communication system of a comparative example in which a base station to which a wireless communication link is connected is selected based on the maximum reception strength.

The wireless communication system of the comparative example is a wireless communication system in which wireless communication is conducted between multiple base stations 1a and 1b located on the ground and one or more node stations 2, such as satellites, that move relative to the Earth's surface.

As shown in Figure 10(a), when the wireless communication system of the comparative example selects a base station to connect to a wireless communication link based on the maximum connection time, even if base station 1b exists that can ensure communication at 1 Gbps, base station 1a, which has a connection time of 6 minutes, is selected.

On the other hand, as shown in Figure 10(b), when the wireless communication system of the comparative example selects a base station to connect to a wireless communication link based on the maximum reception strength, even if base station 1b with a maximum connection time of 5 minutes exists, base station 1a is selected because its reception strength is strong and it can ensure communication at 2 Gbps.

In other words, in both cases shown in Figures 10(a) and 10(b), selecting base station 1b as the destination base station for the wireless communication link would result in a larger communication capacity, but depending on the selection criteria, base station 1a may be selected. In this way, the wireless communication system of the comparative example may result in a decrease in the throughput of the entire system, depending on the base station selected.

Next, a wireless communication system according to one embodiment will be described. Figure 1 is a diagram showing an example configuration of a wireless communication system 10 according to one embodiment. As shown in Figure 1, the wireless communication system 10 according to one embodiment includes, for example, terminals 20-1 to 20-3, node stations 30-1 to 30-5, base stations 40-1 to 40-3, a link control device 50, and an external device 100. Note that when there is no need to specify one of multiple components, such as node stations 30-1 to 30-5, it will simply be abbreviated as node station 30, etc.

Node stations 30-1 to 30-5 are wireless communication node stations that move relative to the Earth's surface. More specifically, node stations 30 include all wireless communication node stations that move relative to the Earth's surface, such as low-earth orbit satellites (LEO satellites), medium-earth orbit satellites (MEO satellites), high-altitude platforms (HAPS), as well as drones, unmanned aerial vehicles (UAVs), aircraft, and automobiles.

Then, each node station 30 establishes a wireless communication link with a base station 40 located on the ground, realizing communication between the terminal 20 and the base station 40. Here, it is assumed that multiple node stations 30 and multiple base stations 40 perform one-to-one wireless communication. Furthermore, in the wireless communication system 10, traffic accommodated throughout the system is transmitted to the base station via available wireless communication links while utilizing communication links connecting the node stations 30. Therefore, the greater the number of wireless communication links between the node stations 30 and the base stations 40, the greater the throughput of the entire system.

The link control device 50 calculates a score that serves as a criterion for determining whether to switch wireless communication links, based on (e.g., all) parameters related to the communication quality of the wireless communication link. In other words, when the wireless communication system 10 needs to switch from the base station 40 currently connected to a wireless communication link to another base station 40 for some reason, it selects the base station 40 to switch to, for example, based on the score calculated by the link control device 50.

The wireless communication system 10 may use either distributed or centralized control for the calculation of scores and the selection of base stations 40 to connect to. In the case of a distributed control system, these controls are performed by each base station 40 or each node station 30. The link control device 50 may also control the wireless communication link via an external device 100, or may control the wireless communication link by directly controlling the base station 40.

FIG. 2 is a functional block diagram showing an example configuration of a link control device 50 according to one embodiment. As shown in FIG. 2, the link control device 50 includes, for example, a communication unit 52, a control unit 54, a score calculation unit 56, and a selection unit 58.

The communication unit 52 acquires external information such as time information from the external device 100 and outputs it to the control unit 54. The communication unit 52 also has the function of communicating with the base station 40.

The control unit 54 controls each component of the link control device 50. For example, the control unit 54 controls wireless communication links to increase the number of wireless communication links between the node stations 30 and the base station 40, with the highest priority being to maximize the total score calculated by the score calculation unit 56 (described below).

The score calculation unit 56 calculates scores based on (e.g., all) parameters related to the communication quality of the wireless communication links between all node stations 30 and all base stations 40, and outputs these to the selection unit 58. For example, parameters related to the communication quality of the wireless communication links include communication capacity and remaining communication time.

When the communication capacity and remaining communication time (link life) are used as parameters related to the communication quality of the wireless communication link, the score calculation unit 56 calculates the score using the following formula (1):

Here, the capacity of the wireless communication link is represented by C [GB], the link lifetime is represented by tl [s], the reference value of the link lifetime is represented by tr [s], and an arbitrary real number is represented by R.

The score serves as a criterion for selecting wireless communication links. Furthermore, the score is not simply calculated by multiplying the link capacity by the link lifespan, but is normalized by the reference value of the link lifespan and set as an arbitrary real number exponent. This prevents large differences in scores between wireless communication links with extremely short communication times compared to the reference value of the link lifespan. Furthermore, by selecting the real number R, it is possible to weight the link lifespan in relation to the score.

Here, we will use Figures 3 to 5 to explain in detail the link life reference value and link capacity. Figure 3 is a diagram that schematically shows switching of wireless communication links between one node station 30 and multiple base stations 40. Figure 4 is a diagram showing a lookup table that pre-determines the base station 40 to which the wireless communication link will connect, by time. Figure 5 is a graph that illustrates link capacity.

For example, when the node station 30 moves above the base station 40-2, the score calculation unit 56 uses the remaining connection time tr in the lookup table as the reference value for the link lifespan.

The capacity C [GB] of a wireless communication link is defined as the time change in the CINR of the wireless communication link, CINR(t), integrated over the range 0≦t≦tl, of the time change in the spectral efficiency that can be achieved with CINR(t) for 0≦t≦tl.

Note that the link lifespan and the change in CINR of the wireless communication link over time may be obtained using any method, and the change in frequency efficiency over time may be calculated using an appropriate method based on the change in CINR over time and an MCS table, etc.

The selection unit 58 selects a connection pair of a node station 30 and a base station 40 based on the score calculated by the score calculation unit 56.

Then, the control unit 54 controls the wireless communication links of the node station 30 and the base station 40 via the communication unit 52 based on the results selected by the selection unit 58.

Next, a first operation example of the wireless communication system 10 according to one embodiment will be described. Figure 6 is a diagram showing the first operation example of the wireless communication system 10. Note that while the wireless communication system of the comparative example used for reference performs the process of S100, the wireless communication system 10 according to one embodiment performs the processes of S200 and S202 in that order.

In step 100 (S100), the wireless communication system of the comparative example selects a base station 40 to which the node station 30 will connect based on the maximum connection time or maximum reception strength of the wireless communication link.

In response to this, in step 200 (S200), the wireless communication system 10 calculates a score based on (e.g., all) parameters related to the communication quality of the wireless communication link, and in step 202 (S202), selects a base station 40 to which the node station 30 will connect based on the score.

Next, a second operation example of the wireless communication system 10 according to one embodiment will be described using Figures 7 and 8. Figures 7 and 8 are diagrams showing the second operation example of the wireless communication system 10. Figure 8(a) is a diagram showing the operation results when selecting a base station 40 with the highest score for a node station 30. Figure 8(b) is a diagram showing the operation results when selecting a base station 40 by giving priority to node stations 30 with a small number of connection destination candidates.

In the comparative example wireless communication system, processing is performed in the order of S400, S402, S404, S406, and S408.

In the second operation example of the wireless communication system 10, the link control device 50 sets the number of attempts i = 0 in step 400 (S400). Here, the number of base stations 40 is N.

In step 402 (S402), the link control device 50 determines whether there is a pair (connection candidate pair) of a node station 30 and a base station 40 whose score is greater than or equal to the threshold and is the highest, excluding node stations 30 and base stations 40 that are already connected. If a connection candidate pair exists (S402: Yes), the link control device 50 proceeds to processing of S500; if a connection candidate pair does not exist (S402: No), the link control device 50 terminates processing.

In step 500 (S500), the link control device 50 determines whether or not there is a connection candidate pair that does not overlap with the base station 40. If such a connection candidate pair exists (S500: Yes), the process proceeds to S404. If such a connection candidate pair does not exist (S500: No), the process proceeds to S502.

In step 404 (S404), the link control device 50 determines the connection of the candidate connection pair.

In step 502 (S502), the link control device 50 extracts a group of nodes that are paired with the overlapping base station 40.

In step 504 (S504), the link control device 50 extracts from the node group the node station 30 (priority node) with the smallest number of base stations 40 with which it can communicate.

In step 506 (S506), the link control device 50 determines whether there is one priority node. If there is one (S506: Yes), the process proceeds to S508. If there is not one (S506: No), the process proceeds to S510.

In step 508 (S508), the link control device 50 determines the connection of the connection candidate pair including the priority node.

In step 510 (S510), the link control device 50 determines the connection of the pair with the highest score among the connection candidate pairs that include the priority node.

In step 512 (S512), the link control device 50 determines whether there are any other overlapping base stations 40 in the connection candidate pair. If there are no other overlapping base stations 40 (S512: Yes), the link control device 50 proceeds to processing of S406, and if there are other overlapping base stations 40 (S512: No), the link control device 50 returns to processing of S502.

In step 406 (S406), the link control device 50 increments the number of attempts i (i = i + 1).

In step 408 (S408), the link control device 50 determines whether i = N. If i = N (S408: Yes), the process ends. If i = N is not true (S408: No), the process returns to S402.

For example, as shown in Figure 8(a), if the base station 40 with the highest score is selected for the node station 30, the wireless communication links will be the two combinations marked with circles. In this case, base station 40-3 is not connected to any of the node stations 30, and the number of wireless communication links will be limited to two.

On the other hand, as shown in Figure 8(b), if a node station 30 with few connection candidates is preferentially connected to a base station 40, the wireless communication links will be the three combinations marked with circles. In this case, all base stations 40 are connected to the node station 30, and the number of wireless communication links increases to three.

However, if the total score of the wireless communication links is smaller when a node station 30 with fewer connection candidates is preferentially connected to a base station 40 than when the node station 30 is connected to the base station 40 with the highest score, the link control device 50 will connect to the base station 40 with the highest score for the node station 30, even if there are fewer wireless communication links.

In this way, the wireless communication system 10 prioritizes connecting node stations 30 with fewer connection candidates to the base station 40, making it possible to utilize wireless communication links between as many node stations 30 and base stations 40 as possible. This also enables the wireless communication system 10 to prevent a decrease in throughput and a decrease in the communication capacity of the entire system.

Furthermore, each function possessed by the external device 100, terminal 20, node station 30, base station 40, and link control device 50 may be configured in part or in whole by hardware such as a PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array), or may be configured as a program executed by a processor such as a CPU.

For example, the terminal 20, node station 30, base station 40, and link control device 50 can be implemented using a computer and a program, and the program can be recorded on a storage medium or provided via a network.

FIG. 9 is a diagram showing an example of the hardware configuration of a link control device 50 according to one embodiment. As shown in FIG. 9, for example, the link control device 50 has an input unit 500, an output unit 510, a communication unit 520, a CPU 530, a memory 540, and an HDD 550 connected via a bus 560, and has the functionality of a computer. The link control device 50 is also capable of inputting and outputting data to and from a computer-readable storage medium 570.

The input unit 500 is, for example, a keyboard and mouse. The output unit 510 is, for example, a display device. The communication unit 520 is, for example, a wireless network interface.

The CPU 530 controls each component of the link control device 50 and performs predetermined processing. The memory 540 and HDD 550 are storage units that store data, etc.

The storage medium 570 is capable of storing programs and the like that cause the link control device 50 to execute its functions. Note that the architecture that makes up the link control device 50 is not limited to the example shown in FIG. 8. Furthermore, other components that make up the wireless communication system 10, such as the node stations 30 and base stations 40, may also have the same hardware configuration as the link control device 50.

Although embodiments of the present invention have been described above with reference to the drawings, it is clear that the above-described embodiments are merely examples of the present invention and that the present invention is not limited to the above-described embodiments. Therefore, additions, omissions, substitutions, and other modifications of components may be made without departing from the technical spirit and scope of the present invention.

The functions performed by the components described herein may be implemented in circuitry or processing circuitry, including general purpose processors, application specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), CPUs (Central Processing Units), conventional circuits, and/or combinations thereof, programmed to perform the described functions.

A processor includes transistors and other circuits and is considered a circuitry or processing circuitry. A processor may also be a programmed processor, which executes programs stored in memory.

In this specification, a circuit, unit, or means refers to hardware that is programmed to realize or executes the described functions. The hardware may be any hardware disclosed in this specification or any hardware known to be programmed to realize or execute the described functions.

If the hardware is a processor, which is considered to be a type of circuitry, the circuitry, means, or unit is the combination of the hardware and the software used to configure the hardware and/or processor.

10: Wireless communication system, 20-1 to 20-3: Terminals, 30-1 to 30-5: Node stations, 40-1 to 40-3: Base stations, 50: Link control device, 52: Communication unit, 54: Control unit, 56: Score calculation unit, 58: Selection unit, 100: External device, 500: Input unit, 510: Output unit, 520: Communication unit, 530: CPU, 540: Memory, 550: HDD, 560: Bus, 570: Storage medium

Claims (4)

In a wireless communication system in which one or more node stations that move relative to the earth's surface communicate with a plurality of base stations located on the ground,
a score calculation unit that calculates scores based on parameters related to communication quality of wireless communication links between all of the node stations and all of the base stations;
a control unit that controls wireless communication links so as to increase the number of wireless communication links connecting the base station and the node station, while giving top priority to maximizing the total score calculated by the score calculation unit. A link control device for controlling links between one or more node stations that move relative to the Earth's surface and a plurality of base stations disposed on the ground,
a score calculation unit that calculates scores based on parameters related to communication quality of wireless communication links between all of the node stations and all of the base stations;
a control unit that controls wireless communication links so as to increase the number of wireless communication links connecting the base station and the node station, with the highest priority being given to maximizing the total score calculated by the score calculation unit. A link control method for controlling links between one or more node stations that move relative to the Earth's surface and a plurality of base stations located on the ground, comprising:
a score calculation step of calculating scores based on parameters relating to communication quality of wireless communication links between all of the node stations and all of the base stations;
a control step of controlling wireless communication links so as to increase the number of wireless communication links connecting the base station and the node station, with the highest priority being given to maximizing the total score calculated in the score calculation step. A link control program for causing a computer to function as each part of the link control device described in claim 2.