CONTROL METHOD, CONTROL DEVICE, AND WIRELESS COMMUNICATION SYSTEM

Abstract

According to this control method, in order to facilitate maintenance of a radio link when a user terminal has moved in a radio communication system including a movable base station, a control device that controls the movable base station, which is a radio base station mounted on a movable device, executes: an acquisition process of acquiring position information of the movable base station and a user terminal that performs radio communication with the movable base station; a first calculation process of calculating the distance between the movable base station and the user terminal; and a movement instructing process of instructing the movable base station to move such that the distance between the movable base station and the user terminal is equal to or less than a pre-set first distance.

Description

[Technical field]

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

[0002] A wireless network control technology has been proposed that dynamically forms a wireless communication area according to communication requirements, propagation environment, etc., using multiple mobile base stations, each of which has a wireless base station mounted on a mobile device (see, for example, non-patent document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Toshiro Nakahira, Motoharu Sasaki, Takatsune Moriyama, and Yasuji Takatori, "Dynamic optimization of wireless networks using mobile base stations in multi-radio proactive control technology (Cradio)," IEICE Technical Report, 2021 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, in mobile communications, base stations are generally fixed in place. However, in environments such as factories where there is severe shielding and user terminals and shields move, when a system using high frequency bands such as local 5G (5th Generation) is introduced, it may be difficult to establish or maintain a wireless link.

[0005] The technology disclosed in Non-Patent Document 1 makes it possible to optimize the placement of mobile base stations in response to changes in the wireless environment. However, it does not solve the problem of difficulty in maintaining a wireless link, for example, when a user terminal moves.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS The present invention has been made in view of the above problems, and facilitates maintaining a radio link when a user terminal moves in a wireless communication system including a mobile base station. [Means for solving the problem]

[0007] In order to solve the above problems, a control method according to an embodiment of the present invention includes a control device that controls a mobile base station having a radio base station mounted on a mobile device, and executes an acquisition process to acquire location information of the mobile base station and a user terminal that wirelessly communicates with the mobile base station, a first calculation process to calculate a distance between the mobile base station and the user terminal, and a movement instruction process to instruct the mobile base station to move so that the distance between the mobile base station and the user terminal is equal to or smaller than a first distance set in advance. The movement instruction process instructs the mobile base station to move when the user terminal is within a range in which the mobile base station can move following the user terminal. Effect of the Invention

[0008] SUMMARY OF THE PRESENT EMBODIMENTS Embodiments of the present invention facilitate maintaining radio links in wireless communication systems including mobile base stations when user terminals move. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of a system configuration of a wireless communication system according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram for explaining an overview of the process according to the present embodiment; [Diagram 3] FIG. 2 is a diagram for explaining an overview of the process according to the present embodiment. [Figure 4] FIG. 3 is a diagram for explaining an overview of the processing according to the present embodiment. [Diagram 5] FIG. 4 is a diagram for explaining an overview of the processing according to the present embodiment. [Figure 6] FIG. 2 is a diagram illustrating an example of a functional configuration of a wireless communication system according to the present embodiment. [Figure 7]4 is a flowchart showing an example of a process performed by the control device according to the first embodiment. [Figure 8] FIG. 4 is a diagram for explaining a first distance and a second distance according to the first embodiment. [Figure 9] FIG. 1 is a diagram for explaining an example of a method for selecting a travel destination candidate according to the first embodiment; [Figure 10] FIG. 2 is a diagram for explaining an example of a method for selecting travel destination candidates according to the first embodiment; [Figure 11] 10 is a flowchart showing an example of a process performed by a control device according to a second embodiment. [Figure 12] FIG. 11 is a diagram illustrating an image of processing in a wireless communication system according to a second embodiment. [Figure 13] FIG. 2 is a diagram illustrating an example of the hardware configuration of a control device, a mobile base station, and a user terminal according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention (the present embodiment) will be described with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0011] <System configuration> Fig. 1 is a diagram showing an example of the system configuration of a wireless communication system according to this embodiment. The wireless communication system 1 includes a plurality of mobile base stations 100-1, 100-2, 100-3, ... each of which has a wireless base station mounted on a mobile device, and a control device 10 which controls the plurality of mobile base stations 100-1, 100-2, 100-3, .... In the following description, "mobile base station 100" is used to refer to any mobile base station among the plurality of mobile base stations 100-1, 100-2, 100-3, ....

[0012] The mobile base station 100 is a wireless base station that performs predetermined wireless communication, such as 5G (5th Generation), LTE (Long Term Evolution), etc., with a user terminal 102 used by a user who uses the wireless communication system 1. The mobile base station 100 is communicably connected to the control device 10, and is configured to be movable within a predetermined range centered on a reference point in response to an instruction from the control device 10.

[0013] For example, the mobile base station 100-1 can perform wireless communication with the user terminal 102 within the coverage area 101-1 of the mobile base station 100-1 by moving within a predetermined range centered on a reference point. Similarly, the mobile base station 100-2 can perform wireless communication with the user terminal 102 within the coverage area 101-2, and the mobile base station 100-3 can perform wireless communication with the user terminal 102 within the coverage area 101-2.

[0014] The control device 10 is a device that controls multiple mobile base stations 100, or a system including multiple devices. The control device 10 acquires location information from the mobile base stations 100 and the user terminals 102, and moves the mobile base stations so that the distance between the mobile base stations 100 and the user terminals 102 is within a predetermined distance.

[0015] The user terminal 102 is a wireless station used by a user, and connects to the mobile base station 100 having the best communication quality among a plurality of mobile base stations 100-1, 100-2, 100-3, . . . by predetermined wireless communication.

[0016] (Processing Overview) 2 to 5 are diagrams for explaining an overview of the process according to this embodiment. The mobile base station 100 is preset with a distance (hereinafter referred to as a first distance D1) at which a predetermined communication quality can be obtained based on previously measured data or design values. This first distance D1 can be determined based on, for example, the following formula (1).

[0017]

number

[0018] As shown in Fig. 1, the user terminal 102 connected to the mobile base station 100-1 by wireless communication moves out of the range 201-1 of the first distance D1 from the mobile base station 100-1 as shown in Fig. 2 (step S1 in Fig. 2). In this case, the control device 10 instructs the mobile base station 100-1 to move so that the distance between the mobile base station 100-1 and the user terminal 102 becomes equal to or less than the first distance D1 (step S2 in Fig. 2). As a result, the mobile base station 100-1 moves to a point where the distance between the mobile base station 100-1 and the user terminal 102 becomes equal to or less than the first distance as shown in Fig. 3 (step S3 in Fig. 3).

[0019] In this way, the control device 10 moves the mobile base station 100-1 so that the distance between the mobile base station 100-1 and the user terminal 102 is within the first distance D1, thereby allowing the user terminal 102 to obtain good communication quality within the coverage area 101-1.

[0020] Also, assume that the user terminal 102 moves from the coverage area 101-1 of the mobile base station 100-1 to the coverage area 101-2 of the mobile base station 100-2 as shown in FIG. 4 (step S4 in FIG. 4). In this case, the control device 10 instructs the mobile base station 100-2 to move so that the distance between the other mobile base station 100-2 and the user terminal 102 is within a first distance (step S5 in FIG. 4). As a result, the mobile base station 100-2 moves to a point where the distance between the mobile base station 100-2 and the user terminal 102 is within the first distance as shown in FIG. 5 (step S6 in FIG. 5). When the user terminal 102 moves into the coverage area 101-3 of the mobile base station 100-3, the control device 10 performs the same process on the mobile base station 100-3.

[0021] In this way, the control device 10 moves the movable base station 100 to a location where the distance to the user terminal 102 is within the first distance, so that the distance between the movable base station 100 and the user terminal 102 is within the first distance. As a result, according to this embodiment, in the wireless communication system 1 including the movable base station 100, when the user terminal 102 moves, it becomes easy to maintain the wireless link.

[0022] <Functional configuration> Next, the functional configuration of the wireless communication system 1 according to this embodiment will be described. Fig. 6 is a diagram showing an example of the functional configuration of the wireless communication system according to this embodiment. In Fig. 6, it is assumed that the mobile base stations 100-2 and 100-3 have the same functional configuration as the mobile base station 100-1.

[0023] (Functional configuration of the control device) The control device 10 has a computer configuration, and the computer executes a predetermined program to realize, for example, a communication unit 601, an acquisition unit 602, a first calculation unit 603, a second calculation unit 604, a movement instruction unit 605, an information management unit 606, and a storage unit 607. At least a part of the above functional configurations may be realized by hardware.

[0024] The communication unit 601 executes communication processing to communicate with the mobile base station 100. In addition, the communication unit 601 can communicate with the user terminal 102 directly or via the mobile base station 100, for example.

[0025] The acquisition unit 602 executes an acquisition process to acquire location information of the mobile base station 100 and the user terminal 102 that performs wireless communication with the mobile base station 100 via the communication unit 601 .

[0026] The first calculation unit 603 executes a first calculation process to calculate the distance between the mobile base station 100 and the user terminal 102. For example, the first calculation unit 603 calculates the distance between the mobile base station 100 and the user terminal 102 using the location information of the mobile base station 100 acquired by the acquisition unit 602 and the user terminal 102 that wirelessly communicates with the mobile base station 100.

[0027] The second calculation unit 604 executes a second calculation process to calculate the distance between the reference point, which is the reference of the moving range of the mobile base station 100, and the user terminal 102. For example, the control device 10 pre-stores base station information 608 including position information of the reference point of each mobile base station 100. The second calculation unit 604 calculates the distance between the reference point of the mobile base station 100 and the user terminal 102 using the position information of this reference point and the position information of the user terminal 102.

[0028] The movement instruction unit 605 executes a movement instruction process to instruct the mobile base station to move so that the distance between the mobile base station 100 and the user terminal 102 that communicates wirelessly with the mobile base station becomes less than a predetermined first distance D1.

[0029] The information management unit 606 stores and manages information such as the first distance D1, the second distance D2, and base station information 608 in the storage unit 607. The storage unit 607 stores various data, information, programs, and the like including information such as the first distance D1, the second distance D2, and base station information 608.

[0030] The functional configuration of the control device 10 shown in Fig. 6 is an example. For example, the function of the acquisition unit 602 may be included in the first calculation unit 603, and the first calculation unit 603 and the second calculation unit 604 may be a single calculation unit. The storage unit 607 may be realized by a storage server or the like external to the control device 10. Furthermore, each functional configuration of the control device 10 shown in Fig. 6 may be distributed and provided in a plurality of devices.

[0031] (Functional configuration of mobile base station) The mobile base station 100 has a computer configuration, and the computer executes a predetermined program to realize, for example, a communication unit 621, a communication control unit 622, a location information transmission unit 623, and a mobility control unit 624. At least a part of the above functional configurations may be realized by hardware.

[0032] The communication unit 621 executes a first communication process for communicating with the control device 10. The communication unit 621 also executes a second communication process for wirelessly communicating with the user terminal 102. Note that the first communication method by which the communication unit 621 communicates with the control device 10 and the second communication method by which the communication unit 621 communicates with the user terminal 102 may be the same communication method or different communication methods.

[0033] The communication control unit 622 controls the communication unit 621 to execute communication control processing (such as call control) for controlling wireless communication with the user terminal 102. The location information transmission unit 623 acquires location information indicating the location of the mobile base station 100, and executes location information transmission processing for transmitting the acquired location information to the control device 10. The mobility control unit 624 executes mobility control processing for controlling a movable device provided in the mobile base station 100 so as to move the mobile base station 100 to a location instructed by the control device 10.

[0034] (User terminal functional configuration) The user terminal 102 may have any functional configuration as long as it has a function of acquiring location information indicating the location of the user terminal 102 and transmitting the acquired location information to the control device 10. For example, the user terminal 102 transmits the location information of the user terminal 102 to the control device 10 via the mobile base station 100. <Processing flow> Next, the process flow of the control method according to this embodiment will be described by taking a number of examples as examples.

[0035] [Example 1] Fig. 7 is a flowchart showing an example of the process of the control device according to the first embodiment. This process shows an example of the process executed by the control device 10 having the functional configuration described in Fig. 6, for example. It is assumed that at the start of the process shown in Fig. 7, the user terminal 102 is performing wireless communication with the mobile base station 1 of the movement source (for example, the mobile base station 100-1 in Fig. 1). It is also assumed that the user terminal 102 is moving toward the mobile base station 2 of the movement destination (for example, the mobile base station 100-2 in Fig. 1). Furthermore, it is assumed that the control device 10 repeatedly executes the process of Fig. 7 at predetermined time intervals (for example, every second).

[0036] In step S701, the acquisition unit 602 of the control device 10 acquires location information of the mobile base station 100 and the user terminal 102. For example, the acquisition unit 602 acquires location information transmitted by the user terminal 102 and the multiple mobile base stations 100-1, 100-2, 100-3, ... in Fig. 6.

[0037] In step S702, the first calculation unit 603 of the control device 10 uses the location information acquired in step S701 to calculate the distance X between the mobile base station 100 and the user terminal 102. Note that the distance X calculated by the first calculation unit 603 includes the distance X1 between the mobile base station 1 and the user terminal 102, and the distance X2 between the mobile base station 2 and the user terminal 102.

[0038] In step S703, the control device 10 judges whether the distance X1 calculated by the first calculation unit 603 is equal to or less than a preset first distance D1. If the distance X1 is equal to or less than the first distance D1, the control device 10 ends the process. On the other hand, if the distance X1 exceeds the first distance D1, the control device 10 shifts the process to step S704.

[0039] In step S704, the second calculation unit 604 of the control device 10 calculates the distance Y1 between the reference point 1 of the mobile base station 1 and the user terminal 102.

[0040] 8 is a diagram for explaining the first distance and the second distance according to the first embodiment. When the distance between the mobile base station 1 and the user terminal 102 is equal to or less than the first distance D1, the control device 10 determines that the communication quality is sufficiently good and does not instruct the mobile base station 1 to move. On the other hand, when the distance between the mobile base station 1 and the user terminal 102 exceeds the first distance D1, the control device 10 instructs the mobile base station 1 to move so that the distance between the mobile base station 1 and the user terminal 102 becomes equal to or less than the first distance D1.

[0041] However, in this embodiment, a second distance D2 that the mobile base station 1 can move from the reference point 1, which is the center of the moving range of the mobile base station 1, is set in advance. When the distance Y1 between the reference point 1 and the user terminal 102 is equal to or less than the second distance D2, the control device 10 instructs the mobile base station 1 to move so that the distance X1 between the mobile base station 1 and the user terminal 102 becomes equal to or less than the first distance D1. On the other hand, when the distance Y1 between the reference point 1 and the user terminal 102 exceeds the second distance D2, the control device 10 instructs the mobile base station 2 to move so that the distance X2 between another mobile base station 2 and the user terminal 102 becomes equal to or less than the first distance D1.

[0042] Returning now to Fig. 7, the description of the flowchart will be continued. In step S705 of Fig. 7, the control device 10 judges whether the distance Y1 calculated by the second calculation unit 604 is equal to or less than the second distance D2. If the distance Y1 is equal to or less than the second distance D2, the control device 10 shifts the process to step S706. On the other hand, if the distance Y1 exceeds the second distance D2, the control device 10 shifts the process to step S708.

[0043] When proceeding to step S706, the movement instruction unit 605 of the control device 10 selects, from among the movement candidate points of the mobile base station 1 whose distance to the user terminal 102 is less than the first distance D1, the movement candidate point that is the shortest distance from the user terminal 102 or the movement candidate point that is the shortest distance from the mobile base station 1.

[0044] Fig. 9 is a diagram (1) for explaining an example of a method for selecting a movement candidate point according to the first embodiment. The mobile base station 100-1 according to the first embodiment has a plurality of movement candidate points 901, for example, as shown in Fig. 9. Also, as shown in Fig. 9, when the user terminal 102 moves beyond the first distance D1, the movement instruction unit 605 of the control device 10 selects one movement candidate point from the movement candidate points 901a and 901b whose distance to the user terminal 102 is equal to or less than the first distance D1.

[0045] As an example, the movement instruction unit 605 selects the movement candidate point 901a, 901b, which is the shortest distance from the user terminal 102. Preferably, when there are multiple movement candidate points (e.g., movement candidate points 901a, 901b) which are the shortest distance from the user terminal 102, the movement instruction unit 605 selects the movement candidate point 901a, which is the shortest distance from the mobile base station 100-1. As another example, the movement instruction unit 605 may select the movement candidate point 901a, which is the shortest distance from the mobile base station 1001-1, from the beginning, of the movement candidate points 901a, 901b.

[0046] Here, the explanation of the flowchart will be continued by returning to Fig. 7. In step S707 in Fig. 7, the movement instruction unit 605 instructs the mobile base station 1 to move to the movement candidate point selected in step S706.

[0047] On the other hand, when proceeding from step S705 to step S708, the movement instruction unit 605 selects, from among the movement candidate points of the movable base station 2 whose distance to the user terminal 102 is less than the first distance D1, the movement candidate point that is the shortest distance from the user terminal 102 or the movement distance from the movable base station 2.

[0048] Fig. 10 is a diagram (1) for explaining an example of a method for selecting a movement candidate point according to the first embodiment. Another mobile base station 100-2 according to the first embodiment also has a plurality of movement candidate points 901 as shown in Fig. 10. In addition, when the user terminal 102 moves beyond the second distance D2, the movement instruction unit 605 selects one movement candidate point from the plurality of movement candidate points 901c, 901d of the mobile base station 100-2.

[0049] As an example, the movement instruction unit 605 selects the movement candidate point 901c, 901d, which is the shortest distance from the user terminal 102. Preferably, when there are multiple movement candidate points (e.g., movement candidate points 901c, 901d) which are the shortest distance from the user terminal 102, the movement instruction unit 605 selects the movement candidate point 901c, which is the shortest distance from the mobile base station 100-2. As another example, the movement instruction unit 605 may select the movement candidate point 901c, which is the shortest distance from the mobile base station 1001-1, from the beginning, from the movement candidate points 901c, 901d.

[0050] In step S709 of FIG. 7, the movement instruction unit 605 instructs the mobile base station 2 to move to the movement candidate point selected in step S708.

[0051] By repeatedly executing the process of FIG. 7, the control device 10 can control the multiple mobile base stations 100 so that the distance between the mobile base station 100 and the user terminal 102 is equal to or shorter than the first distance D1.

[0052] [Example 2] In the first embodiment, the mobile base station 100 has a plurality of candidate moving points, but this is only an example. For example, the mobile base station 100 may be freely movable along a predetermined route such as a passage or a track.

[0053] Fig. 11 is a flowchart showing an example of the process of the control device according to the second embodiment. This process shows another example of the process executed by the control device 10 having the functional configuration described in Fig. 6. Among the processes shown in Fig. 11, the processes of steps S701 to S704 are similar to the processes of the control device according to the first embodiment described in Fig. 7, and therefore will not be described here.

[0054] In step S1101, the control device 10 determines whether the distance Y1 calculated by the second calculation unit 604 is equal to or less than the second distance D2. If the distance Y1 is equal to or less than the second distance D2, the control device 10 shifts the process to step S1102. On the other hand, if the distance Y1 exceeds the second distance D2, the control device 10 shifts the process to step S1104.

[0055] When shifting to step S1102, the movement instruction unit 605 of the control device 10 determines the movement point of the movable base station 1 where the distance to the user terminal 102 is equal to or less than the first distance D1. For example, when the movable base station 1 can freely move on a predetermined path, the movement instruction unit 605 may determine, as the movement point of the movable base station 1, a point on the predetermined path where the distance to the user terminal 102 is the shortest (or within a predetermined distance). Alternatively, the movement instruction unit 605 may determine, as the movement point of the movable base station 1, a point where the movement distance of the movable base station 1 is the shortest among the points where the distance to the user terminal 102 is equal to or less than a preset third distance D3 (D3 < D1). Further, the movement instruction unit 605 may select the movement point of the movable base station 1 by the same method as in the first embodiment.

[0056] In step S1103, the movement instruction unit 605 instructs the movable base station 1 to move to the movement candidate point determined in step S1102.

[0057] On the other hand, when shifting from step S1101 to step S1104, the movement instruction unit 605 searches for another movable base station 100 different from the movable base station 1 that can move to a position where the distance X to the user terminal 102 is equal to or less than the first distance D1. For example, the control device 10 stores in advance, in the base station information 608 or the like, the range within which each movable base station 100 can move. Further, the movement instruction unit 605 searches for another movable base station 100 that can move to a position where the distance X to the user terminal 102 is equal to or less than the first distance D1, using the range within which each movable base station 100 can move and the position information of the user terminal 102.

[0058] In step S1105, the movement instruction unit 605 determines whether there is a movable base station 100 that satisfies the condition of step S1104. If there is a movable base station 100 that satisfies the above condition, the movement instruction unit 605 causes the process to shift to step S1106. On the other hand, if there is no movable base station 100 that satisfies the above condition, the movement instruction unit 605 ends the process.

[0059] In step S1106, the movement instruction unit 605 selects one movable base station Z that satisfies the above condition, and determines a movement point of the movable base station Z whose distance to the user terminal 102 is equal to or shorter than the first distance. Note that the method of determining the movement point of the movable base station Z may be the same as that in step S1102.

[0060] Fig. 12 is a diagram showing an image of the processing of the wireless communication system according to the embodiment 2. By the processing of the above steps S1104 and S1105, as shown in Fig. 12, even if the user terminal 102 moves to, for example, the coverage area 101-Z of the mobile base station 100-Z instead of the coverage area 101-2 of the mobile base station 100-2, the mobile base station 100-Z can be controlled so that the distance between the mobile base station 100-Z and the user terminal 102 is equal to or shorter than the first distance D1.

[0061] In addition, if the destination of the user terminal 102 has coverage areas covered by multiple mobile base stations 100, the movement instruction unit 605 may, for example, select one mobile base station 100 that is closer to the user terminal 102, or may randomly select one mobile base station 100.

[0062] In step S1107 of FIG. 11, the movement instruction unit 605 instructs the mobile base station Z to move to the movement candidate point determined in step S1106.

[0063] By repeatedly executing the process of FIG. 11, the control device 10 can control the multiple mobile base stations 100 so that the distance between the mobile base station 100 and the user terminal 102 is equal to or shorter than the first distance D1.

[0064] <Hardware configuration example> Fig. 13 is a diagram showing an example of the hardware configuration of the control device, the mobile base station, and the user terminal according to this embodiment. The control device 10, the mobile base station 100, and the user terminal 102 each have, for example, the configuration of a computer 1300 as shown in Fig. 13. The mobile base station 100 has a configuration in which a radio base station having the configuration of the computer 1300 is mounted on a mobile device that moves according to the control from the computer 1300.

[0065] In the example of FIG. 13, a computer 1300 includes a processor 1301, a memory 1302, a storage device 1303, a communication device 1304, an input device 1305, an output device 1306, a bus B, and the like.

[0066] The processor 1301 is, for example, an arithmetic device such as a CPU (Central Processing Unit) that realizes various functions by executing a predetermined program. The memory 1302 is a storage medium readable by the computer 1300, and includes, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), etc. The storage device 1303 is a computer-readable storage medium, and may include, for example, a HDD (Hard Disk Drive), an SSD (Solid State Drive), various optical disks, and magneto-optical disks, etc.

[0067] The communication device 1304 includes one or more hardware (communication devices) for communicating with other devices via a wireless or wired network. The input device 1305 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that receives input from the outside. The output device 1306 is an output device (e.g., a display, a speaker, an LED lamp, etc.) that outputs to the outside. The input device 1305 and the output device 1306 may be integrated into one (e.g., an input / output device such as a touch panel display).

[0068] The bus B is commonly connected to the above components and transmits, for example, address signals, data signals, and various control signals, etc. The processor 1301 is not limited to a CPU, and may be, for example, a DSP (Digital Signal Processor), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array), etc.

[0069] (supplement) The control device 10 and the mobile base station 100 in this embodiment may be realized not only by a dedicated device but also by a general-purpose computer. In this case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to realize the function. Note that the "computer system" here includes hardware such as an OS and peripheral devices.

[0070] Additionally, the term "computer-readable recording medium" includes various storage devices such as portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as hard disks built into computer systems. Furthermore, the term "computer-readable recording medium" may also include devices that dynamically hold a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and devices that hold a program for a certain period of time, such as volatile memory within a computer system that serves as a server or client in such cases.

[0071] Furthermore, the above program may be for realizing part of the functions described above, or may be capable of realizing the functions described above in combination with a program already recorded in a computer system, or may be realized using hardware such as a PLD (Programmable Logic Device) or an FPGA (Field Programmable Gate Array).

[0072] <Effects of the embodiment> According to this embodiment, when the user terminal 102 moves in the wireless communication system 1 including the mobile base station 100, the wireless link can be easily maintained, for example, as described with reference to FIGS.

[0073] For example, the control device 10 can move the mobile base station 100-1 to follow the user terminal 102 moving in the coverage area 101-1 of the mobile base station 100-1, as described in Figures 2 and 3. Also, the control device 10 can move the mobile base station 100-2 to follow the user terminal 102 that has moved to the coverage area 101-2 of another adjacent or nearby mobile base station 100-2, as described in Figures 4 and 5. This makes it possible to maintain the required communication quality and prevent communication interruptions even if the user terminal 102 moves.

[0074] <Summary of the embodiment> This specification discloses at least the following wireless communication methods and wireless communication systems. (Section 1) A control device for controlling a mobile base station, An acquisition process for acquiring location information of the mobile base station and a user terminal that wirelessly communicates with the mobile base station; a first calculation process for calculating a distance between the mobile base station and the user terminal; a movement instruction process for instructing the mobile base station to move so that the distance between the mobile base station and the user terminal becomes equal to or shorter than a first distance set in advance; A control method for performing the above. (Section 2) The mobile base station has a plurality of candidate moving points to which the mobile base station can be moved, The control method described in paragraph 1, wherein the movement instruction process instructs the mobile base station to move to a movement candidate point that is the shortest distance from the user terminal, or a movement candidate point that is the shortest distance from the mobile base station, among the movement candidate points whose distance to the user terminal is less than the first distance. (Section 3) The control method according to claim 1 or 2, wherein the movement instruction process instructs the user terminal to move when the mobile base station is within a range in which the mobile base station can move following the user terminal. (Section 4) The acquisition process acquires location information of other mobile base stations adjacent to or close to the mobile base station, The control method described in any one of claims 1 to 3, wherein the movement instruction process, when the user terminal moves outside a range in which the mobile base station can move following the user terminal, instructs the other mobile base station to move so that the distance between the other mobile base station and the user terminal is less than or equal to the first distance. (Section 5) The control method described in paragraph 4, wherein the movement instruction process instructs other mobile base stations, among the other mobile base stations, that are capable of moving to a position where the distance between the other mobile base station and the user terminal is less than or equal to the first distance, to move. (Section 6) The control device, When the distance between the mobile base station and the user terminal exceeds the first distance, a second calculation process is executed to calculate the distance between the user terminal and a reference point that is a reference of a range in which the mobile base station can move; The control method according to claim 4 or 5, wherein the movement instruction process instructs the other mobile base station to move when the distance between the reference point and the user terminal exceeds a second distance set in advance. (Section 7) A control device for controlling a mobile base station, An acquisition unit configured to acquire location information of the mobile base station and a user terminal that wirelessly communicates with the mobile base station; a first calculation unit configured to calculate a distance between the mobile base station and the user terminal; a movement instruction unit configured to instruct the mobile base station to move so that a distance between the mobile base station and the user terminal becomes equal to or shorter than a first distance that is set in advance; A control device having the above configuration. (Section 8) A communication system including a mobile base station having a radio base station mounted on a mobile device, and a control device for controlling the mobile base station, The control device includes: An acquisition unit configured to acquire location information of the mobile base station and a user terminal that wirelessly communicates with the mobile base station; a first calculation unit configured to calculate a distance between the mobile base station and the user terminal; a movement instruction unit configured to instruct the mobile base station to move so that a distance between the mobile base station and the user terminal becomes equal to or shorter than a first distance that is set in advance; having A wireless communication system, wherein the mobile base station has a mobility control unit configured to move the mobile base station to a location instructed by the control device.

[0075] Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0076] 1. Wireless communication systems 10 Control device 100, 100-1, 100-2, 100-3 Mobile base station 102 User terminal 602 Acquisition Department 603 First Calculation Section 604 Second Calculation Section 605 Movement instruction section 623 Location information transmission unit 624 Movement control section

Claims

1. A control device for controlling a mobile base station, An acquisition process for acquiring location information of the mobile base station and a user terminal that wirelessly communicates with the mobile base station; a first calculation process for calculating a distance between the mobile base station and the user terminal; a movement instruction process for instructing the mobile base station to move so that the distance between the mobile base station and the user terminal becomes equal to or shorter than a first distance set in advance; Run The movement instruction process is a control method in which the user terminal instructs the mobile base station to move when the mobile base station is within a range in which the mobile base station can move while following the user terminal.

2. The mobile base station has a plurality of candidate moving points to which the mobile base station can be moved, 2. The control method according to claim 1, wherein the movement instruction process instructs the mobile base station to move to a movement candidate point that is the shortest distance from the user terminal, or a movement candidate point that is the shortest distance from the mobile base station, among the movement candidate points whose distance to the user terminal is less than the first distance.

3. The acquisition process acquires location information of other mobile base stations adjacent to or close to the mobile base station, The control method according to claim 1 or 2, wherein the movement instruction process, when the user terminal moves outside a range in which the mobile base station can move following the user terminal, instructs the other mobile base station to move so that the distance between the other mobile base station and the user terminal becomes equal to or less than the first distance.

4. The control method according to claim 3 , wherein the movement instruction process instructs, among the other mobile base stations, another mobile base station that is capable of moving to a position where the distance between the other mobile base station and the user terminal is equal to or less than the first distance, to move.

5. The control device, When the distance between the mobile base station and the user terminal exceeds the first distance, a second calculation process is executed to calculate a distance between the user terminal and a reference point that is a reference of a range in which the mobile base station can move; 5. The control method according to claim 3, wherein the movement instruction process instructs the other mobile base station to move when a distance between the reference point and the user terminal exceeds a preset second distance.

6. A control device for controlling a mobile base station, An acquisition unit configured to acquire location information of the mobile base station and a user terminal that wirelessly communicates with the mobile base station; a first calculation unit configured to calculate a distance between the mobile base station and the user terminal; a movement instruction unit configured to instruct the mobile base station to move so that a distance between the mobile base station and the user terminal becomes equal to or shorter than a first distance set in advance; having The movement instruction unit instructs the mobile base station to move when the user terminal is within a range in which the mobile base station can move while following the user terminal.

7. A communication system including a mobile base station having a radio base station mounted on a mobile device, and a control device for controlling the mobile base station, The control device includes: An acquisition unit configured to acquire location information of the mobile base station and a user terminal that wirelessly communicates with the mobile base station; a first calculation unit configured to calculate a distance between the mobile base station and the user terminal; a movement instruction unit configured to instruct the mobile base station to move so that a distance between the mobile base station and the user terminal becomes equal to or shorter than a first distance set in advance; having The movement instruction unit instructs the mobile base station to move when the user terminal is within a range in which the mobile base station can move while following the user terminal, A wireless communication system, wherein the mobile base station has a mobility control unit configured to move the mobile base station to a location instructed by the control device.

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