Movement control device and movement control method

Abstract

To improve a throughput by using a multiple beam at a maximum.SOLUTION: A movement control device is a movement control device that controls the movement of a movement base station which communicates with a user terminal by radio, and includes a memory, and a processor connected to the memory. The processor executes processing of: acquiring position information on the user terminal; counting the number of user terminals positioned in a direction of a beam formed by the movement base station for each movement destination candidate of the movement base station on the basis of the acquired position information; calculating, by using a count result, a beam multiplex number corresponding to the number of beams in which the user terminals positioned in the direction of the beam exist, for each movement destination candidate; and designating the movement destination candidate whose calculated beam multiplex number is the maximum, to the movement base station as a movement destination of the movement base station.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a mobile control device and a mobile control method. [Background technology]

[0002] In recent years, wireless communication using ultra-high frequency bands, such as millimeter wave communication, has attracted attention. While ultra-high frequency wireless communication enables large-capacity communication using a wide bandwidth, it also suffers from large losses due to propagation loss and shielding.

[0003] Therefore, studies are being conducted to realize high-quality communications by mounting base stations (or relay stations) on mobile objects such as automobiles or UAVs (Unmanned Aerial Vehicles) and moving them to appropriate locations that improve the propagation environment with user terminals. For example, when multiple user terminals communicate with a UAV base station using frequency division multiplexing, a method is being studied to determine the position of the UAV base station so that the sum of the transmission rates calculated from the SNR (Signal to Noise Ratio) is maximized. In addition, such UAV base stations may be equipped with a beam multiplexing function that simultaneously forms multiple beams pointing in different directions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-169829 [Patent Document 2] Japanese Patent Application Publication No. 2019-16904 [Patent Document 3] US Patent Application Publication No. 2019 / 0316910 [Non-patent literature]

[0005] [Non-Patent Document 1] Z Xiao et al. "Unmanned Aerial Vehicle Base Station (UAV-BS) Deployment With Millimeter-Wave Beamforming", IEEE Internet of Things Journal, Vol.7, No.2, pp. 1336-1349, February 2020 Summary of the Invention [Problem to be solved by the invention]

[0006] However, even if a UAV base station has a beam multiplexing function, there is a problem that beam multiplexing does not sufficiently improve throughput depending on the location of the user terminal. Specifically, when multiple user terminals are located in the direction of a single beam, these user terminals use this beam to perform wireless communication using time division or frequency division. Therefore, even if a UAV base station forms multiple beams using beam multiplexing, if there are user terminals only in the directions of some of the beams, the remaining beams will not be used and the wireless resources of some of the beams will be shared and used by the multiple user terminals.

[0007] As a result, compared to when all beams are used, the radio resources available to each user terminal are reduced, hindering improvement in throughput.

[0008] The disclosed technology has been made in consideration of the above points, and aims to provide a mobile control device and a mobile control method that can improve throughput by making maximum use of multiplexed beams. [Means for solving the problem]

[0009] In one aspect, the mobile control device disclosed in the present application is a mobile control device that controls the movement of a mobile base station that communicates wirelessly with a user terminal, and has a memory and a processor connected to the memory, wherein the processor acquires location information of the user terminal, and based on the acquired location information, counts the number of user terminals located in the direction of a beam formed by the mobile base station for each destination candidate of the mobile base station, and uses the counting result to calculate a beam multiplexing number for each destination candidate corresponding to the number of beams in which user terminals located in the beam direction are located, and executes a process of instructing the mobile base station to select the destination candidate with the largest calculated beam multiplexing number as the destination of the mobile base station. [Effects of the Invention]

[0010] According to one aspect of the mobile control device and the mobile control method disclosed in the present application, it is possible to obtain an effect that the throughput can be improved by making maximum use of the multiplexed beams. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a communication system. [Figure 2] FIG. 2 is a block diagram showing the configuration of the mobile control device according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing a specific example of beam information. [Figure 4] FIG. 4 is a diagram showing a specific example of destination candidates. [Figure 5] FIG. 5 is a diagram showing a specific example of the terminal count. [Figure 6] FIG. 6 is a diagram showing a specific example of calculation of the number of multiplexed beams. [Figure 7] FIG. 7 is a flowchart showing a movement control method according to the first embodiment. [Figure 8] FIG. 8 is a diagram showing a specific example of movement of a mobile base station. [Figure 9] FIG. 9 is a block diagram showing the configuration of a mobile control device according to the second embodiment. [Figure 10]FIG. 10 is a diagram showing a specific example of communication availability information. [Figure 11] FIG. 11 is a diagram showing a specific example of calculation of the number of multiplexed beams. [Figure 12] FIG. 12 is a flowchart showing a movement control method according to the second embodiment. [Figure 13] FIG. 13 is a block diagram showing the configuration of a mobile control device according to the third embodiment. [Figure 14] FIG. 14 is a diagram showing a specific example of the connected terminal information. [Figure 15] FIG. 15 is a diagram showing a specific example of the terminal count. [Figure 16] FIG. 16 is a diagram showing a specific example of calculation of the number of multiplexed beams. [Figure 17] FIG. 17 is a block diagram showing the configuration of a mobile control device according to the fourth embodiment. [Figure 18] FIG. 18 is a diagram showing a specific example of the beam table. [Figure 19] FIG. 19 is a flowchart showing a movement control method according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a mobile control device and a mobile control method disclosed in the present application will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments.

[0013] (Embodiment 1) Fig. 1 is a diagram showing an example of the configuration of a communication system according to embodiment 1. As shown in Fig. 1, the communication system has a mobile base station 200 connected to a mobile control device 100, and the mobile base station 200 and user terminal 300 perform wireless communication. At this time, the mobile base station 200 multiplexes multiple beams 210 and performs wireless communication using the beams 210 with user terminals 300 located in the directions of each beam 210.

[0014] The mobile control device 100 controls the movement of the mobile base station 200. The mobile control device 100 is, for example, wirelessly connected to the mobile base station 200, selects one destination from a plurality of predefined candidate destinations, and instructs the mobile base station 200 to move to the selected destination. At this time, the mobile control device 100 selects the destination so that the multiple beams 210 formed by the mobile base station 200 are utilized to the maximum extent. In other words, the mobile control device 100 selects the destination so that the number of beams 210 utilized by the user terminal 300 is maximized and the number of multiplexed beams is maximized. The configuration and operation of the mobile control device 100 will be described in detail later.

[0015] Mobile base station 200 is a base station mounted on, for example, a UAV. Mobile base station 200 moves according to instructions from mobile control device 100, and forms multiple beams 210 at each destination. The directions of the multiple beams 210 formed by mobile base station 200 are fixed in advance, and the positions of beams 210 change as mobile base station 200 moves. Mobile base station 200 performs wireless communication using beams 210 with user terminals 300 located in the direction of each beam 210.

[0016] The user terminal 300 is a terminal that performs wireless communication with the mobile base station 200. The user terminal 300 wirelessly communicates with the mobile base station 200 using a beam 210 that corresponds to the location of the user terminal 300, out of multiple beams 210 formed by the mobile base station 200. When other user terminals 300 also use the same beam 210, the user terminal 300 uses the radio resources of this beam 210 by frequency division or time division among the multiple user terminals 300. Furthermore, the user terminal 300 reports its own location information to the mobile control device 100 via the mobile base station 200.

[0017] 1, the communication system may include multiple mobile base stations 200 or may include a fixed base station that does not move. The user terminal 300 may then report location information to the mobile control device 100 via the fixed base station.

[0018] Fig. 2 is a block diagram showing the configuration of a mobile control device 100 according to embodiment 1. The mobile control device 100 shown in Fig. 2 includes a communication interface unit (hereinafter abbreviated as "communication IF unit") 110, a processor 120, and a memory 130.

[0019] The communication IF unit 110 is an interface capable of communicating with the mobile base station 200. The communication IF unit 110 communicates with the mobile base station 200, for example, wirelessly. The communication IF unit 110 may also communicate with a fixed base station (not shown), or may be connected to the mobile base station 200 and the fixed base station by wire.

[0020] The communication IF unit 110 receives location information of multiple user terminals 300 from the mobile base station 200 or a fixed base station. The communication IF unit 110 also transmits a movement instruction to the mobile base station 200 to instruct the mobile base station 200 on the movement destination.

[0021] The processor 120 includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), and controls the entire mobile control device 100. Specifically, the processor 120 includes a terminal location information acquisition unit 121, a beam information management unit 122, a destination candidate management unit 123, a terminal number counting unit 124, a beam multiplex number calculation unit 125, and a mobile control unit 126.

[0022] The terminal location information acquisition unit 121 acquires location information of the user terminal 300 received by the communication IF unit 110. The location information may be transmitted periodically by each user terminal 300, or may be transmitted by each user terminal 300 in response to a periodic request from the mobile control device 100. The terminal location information acquisition unit 121 not only acquires location information of the user terminal 300 that communicates wirelessly with the mobile base station 200, but may also acquire location information of the user terminal 300 that communicates wirelessly with other base stations.

[0023] Beam information management unit 122 manages information about beams 210 formed by mobile base station 200. Specifically, as shown in Fig. 3, beam information management unit 122 stores the directions covered by each beam 210 in association with a beam ID that identifies multiple beams 210 that mobile base station 200 can form. The beam information shown in Fig. 3 stores, for example, that beam 210 with beam ID "Beam #1" covers a range of -45° to -15° in the horizontal direction and a range of -15° to 15° in the vertical direction. Mobile base station 200 can multiplex and simultaneously form multiple beams 210 for which beam information is stored.

[0024] The destination candidate management unit 123 manages information on destination candidates for the mobile base station 200. Specifically, as shown in FIG. 4, for example, the destination candidate management unit 123 stores the coordinates of each destination candidate in association with a destination ID that identifies multiple destination candidates for the mobile base station 200. In the destination candidates shown in FIG. 4, for example, the destination candidate with a destination ID of "destination #1" is stored as being at coordinates (-10, 0, 0). The coordinates of the destination candidate may indicate an absolute position relative to a predetermined reference position, or may indicate a relative position relative to the current position of the mobile base station 200. The mobile base station 200 can move to the destination candidates managed by the destination candidate management unit 123.

[0025] When the terminal location information acquisition unit 121 acquires the location information of the user terminals 300, the terminal number counting unit 124 counts the number of user terminals 300 in the direction of each beam 210 for each candidate destination of the mobile base station 200. That is, the terminal number counting unit 124 calculates the positional relationship between the mobile base station 200 and each user terminal 300 for each candidate destination of the mobile base station 200, and identifies the direction of the beam 210 in which each user terminal 300 is located. The terminal number counting unit 124 then counts how many user terminals 300 are in the direction of each beam 210 for each candidate destination.

[0026] Specifically, as shown in Fig. 5, for example, the terminal number counting unit 124 counts the number of user terminals 300 in the direction of each beam 210 managed by the beam information management unit 122 for each destination candidate managed by the destination candidate management unit 123. In the example shown in Fig. 5, for example, when the mobile base station 200 moves to "destination #1," it is found that there is one user terminal 300 in the direction of "beam #1," one user terminal 300 in the direction of "beam #2," and one user terminal 300 in the direction of "beam #3." Similarly, for example, when the mobile base station 200 moves to "destination #2," it is found that there are two user terminals 300 in the direction of "beam #1," no user terminal 300 in the direction of "beam #2," and one user terminal 300 in the direction of "beam #3."

[0027] The beam multiplexing number calculation unit 125 calculates the number of beams to be multiplexed for each destination candidate of the mobile base station 200 based on the counting result by the terminal number counting unit 124. That is, the beam multiplexing number calculation unit 125 calculates, for each destination candidate, the number of beams 210 for which there are user terminals 300 that can use the beams 210 as the number of beams to be multiplexed. Therefore, for each destination candidate, the beam multiplexing number calculation unit 125 calculates, as the number of beams 210 for which the number of user terminals 300 in the direction of the beams 210 is not zero.

[0028] Specifically, as shown in Fig. 6, for each destination candidate, the beam multiplexing number calculation unit 125 calculates the number of beams 210 for which the number of user terminals 300 that can use the beams 210 is not zero as the beam multiplexing number. In the example shown in Fig. 6, for example, at "destination #1," user terminals 300 are present in the directions of three beams 210, "beam #1," "beam #2," and "beam #3," so the beam multiplexing number is calculated to be 3. Also, for example, at "destination #2," user terminals 300 are present in the directions of two beams 210, "beam #1" and "beam #3," so the beam multiplexing number is calculated to be 2.

[0029] Then, the beam multiplexing number calculation unit 125 selects the destination candidate with the largest calculated beam multiplexing number as the destination of the mobile base station 200. In other words, the beam multiplexing number calculation unit 125 determines the destination candidate in which the multiple beams 210 formed by the mobile base station 200 are most frequently used. Therefore, in the example shown in Fig. 6, for example, the beam multiplexing number calculation unit 125 selects "destination #1" as the destination of the mobile base station 200 because the beam multiplexing number for "destination #1" is 3, which is the largest.

[0030] When the beam multiplex number calculation unit 125 determines the destination of the mobile base station 200, the movement control unit 126 generates a movement instruction to instruct the mobile base station 200 to move to this destination. The movement instruction includes information such as the coordinates of the destination. Then, the movement control unit 126 transmits the movement instruction to the mobile base station 200 via the communication IF unit 110.

[0031] The memory 130 includes, for example, a random access memory (RAM) or a read only memory (ROM), and stores information used in processing by the processor 120.

[0032] Next, a movement control method using the movement control device 100 configured as described above will be described with reference to the flow chart shown in FIG.

[0033] The user terminals 300 periodically report their own location information to the mobile control device 100, or in response to a request from the mobile control device 100. The location information of each user terminal 300 is received by the communication IF unit 110 of the mobile control device 100 via the mobile base station 200 or another fixed base station. The location information is then acquired by the terminal location information acquisition unit 121 (step S101). Once the location information of each user terminal 300 is acquired, this location information is notified to the terminal number counting unit 124, which then counts the number of terminals for each destination candidate. Therefore, the following process executed by the terminal number counting unit 124 is repeated for each destination candidate managed by the destination candidate management unit 123.

[0034] First, the relative position of each user terminal 300 when the mobile base station 200 moves to a candidate destination is calculated (step S102). Specifically, the difference between the coordinates of the candidate destination of the mobile base station 200 and the coordinates of the user terminal 300 is calculated as the relative position of each user terminal 300. Here, for example, the relative position of the ith user terminal 300 is calculated as (x i ,y i ,z i ) shall be expressed as

[0035] Then, the relative direction of the user terminal 300 with respect to the mobile base station 200 is calculated from the relative position of the user terminal 300 (step S103). Specifically, the horizontal and vertical angles of the user terminal 300 as seen from the mobile base station 200 that is a candidate destination are calculated as the relative direction. For example, the relative direction of the ith user terminal 300 can be calculated using the following equation:

number

[0036] In the above equation, θ i is the vertical angle of the i-th user terminal 300, and φ i is the horizontal angle of the i-th user terminal 300. In this way, the relative direction of the user terminal 300 can be calculated from the relative position of the user terminal 300 using inverse trigonometric functions.

[0037] Once the relative directions of the user terminals 300 are calculated, beams 210 that can be used by each user terminal 300 are identified (step S104). That is, the beam information managed by the beam information management unit 122 is referenced, and beams 210 that include the relative directions of each user terminal 300 are identified. Then, once the beams 210 for all user terminals 300 have been identified, the number of user terminals 300 for each beam 210 is tallied (step S105). That is, when the mobile base station 200 moves to a candidate destination, the number of user terminals 300 that use each beam 210 is counted.

[0038] The above counting of the user terminals 300 is repeatedly performed for each destination candidate by the terminal number counting unit 124. As a result, for example, as shown in FIG. 5, the number of user terminals 300 using each beam 210 for each destination candidate is obtained.

[0039] Then, the beam multiplexing number calculation unit 125 calculates the number of beams 210 for each destination candidate (step S106). That is, for each destination candidate of the mobile base station 200, the number of beams 210 for which the number of user terminals 300 using the beams 210 is not zero is calculated as the beam multiplexing number. Then, the beam multiplexing number calculation unit 125 selects the destination candidate with the largest number of beams 210 as the destination of the mobile base station 200 (step S107). That is, the destination candidate with the largest number of beams 210 used by the user terminals 300 is determined as the destination of the mobile base station 200.

[0040] Information about the determined movement destination is notified to the movement control unit 126, and the movement control unit 126 generates a movement instruction instructing the mobile base station 200 to move. Then, the movement instruction is transmitted from the movement control unit 126 to the mobile base station 200 via the communication IF unit 110 (step S108). As a result, the mobile base station 200 receives the movement instruction and moves to the instructed movement destination. At the movement destination of the mobile base station 200, the multiple beams 210 formed by the mobile base station 200 are utilized to the maximum by the user terminal 300. In other words, more user terminals 300 use different beams 210, and more radio resources are available for the user terminals 300 in each beam 210. In other words, the multiplexed beams can be utilized to the maximum extent possible to improve throughput.

[0041] Figure 8 is a diagram showing a specific example of movement of mobile base station 200. When mobile base station 200 is located at the position shown in Figure 8(a), two of the three beams 210 formed by mobile base station 200 are used by user terminals 300. That is, at the position shown in Figure 8(a), the number of multiplexed beams of mobile base station 200 is two. In this case, the number of user terminals 300 using the center beam 210 is zero, while the left beam 210 is used by two user terminals 300. Therefore, in the left beam 210, the two user terminals 300 use radio resources in a frequency-division or time-division manner.

[0042] Now, when mobile base station 200 moves to the position shown in Figure 8(b), all three beams 210 formed by mobile base station 200 are used by user terminal 300. That is, at the position of Figure 8(b), the number of multiplexed beams of mobile base station 200 is three. At this time, all beams 210 are used by one user terminal 300 each. Therefore, for each beam 210, user terminal 300 can occupy the radio resources of that beam 210. Therefore, compared to when mobile base station 200 is at the position of Figure 8(a), more radio resources are available for use by each user terminal 300, improving throughput.

[0043] In this way, by moving the mobile base station 200 so as to maximize the number of multiplexed beams, the user terminals 300 will use the beams 210 in a dispersed manner, thereby maximizing the radio resources available to each user terminal 300. This makes it possible to make maximum use of the multiplexed beams and improve throughput.

[0044] As described above, according to this embodiment, the number of user terminals located in the direction of each beam for each destination candidate of the mobile base station is tallied from the location information of the user terminals, and the number of multiplexed beams for each destination candidate is calculated. The destination candidate with the largest number of multiplexed beams is then determined as the destination of the mobile base station. This allows multiple user terminals to use the beams of the mobile base station in a distributed manner, maximizing the radio resources available to each user terminal. In other words, it is possible to make maximum use of the multiplexed beams and improve throughput.

[0045] (Embodiment 2) The feature of the second embodiment is that when a mobile base station moves, it reports to the mobile control device whether it can communicate with a user terminal, and when determining the destination of the mobile base station, it takes into account whether it can communicate with the user terminal at each candidate destination.

[0046] The configuration of the communication system according to the second embodiment is the same as that of the first embodiment (FIG. 1), and therefore a description thereof will be omitted.

[0047] Fig. 9 is a block diagram showing the configuration of a mobile control device 100 according to embodiment 2. In Fig. 9, the same components as those in Fig. 2 are denoted by the same reference numerals, and their description will be omitted. The mobile control device 100 shown in Fig. 9 has a communication feasibility management unit 141 and a beam multiplex number calculation unit 142 instead of the beam multiplex number calculation unit 125 of the mobile control device 100 shown in Fig. 2.

[0048] The communication feasibility management unit 141 acquires, from the communication IF unit 110, communication feasibility information indicating whether the mobile base station 200 was able to successfully communicate wirelessly with the user terminal 300 using the beam 210. The communication feasibility information acquired here is information that was transmitted from the mobile base station 200 after the mobile base station 200 moved and received by the communication IF unit 110.

[0049] When the mobile base station 200 moves in accordance with a movement instruction from the mobile control device 100, it forms multiple beams 210 and performs wireless communication with user terminals 300 located in the direction of each beam 210. At this time, for example, if there is an obstruction between the mobile base station 200 and the user terminal 300, wireless communication may not be performed normally. In such a case, the mobile base station 200 generates communication availability information reporting that wireless communication using this beam 210 is not being performed normally, and transmits this information to the mobile control device 100. For example, if there is even one user terminal 300 that cannot perform wireless communication normally among multiple user terminals 300 using one beam 210, the mobile base station 200 may transmit communication availability information indicating that wireless communication using this beam 210 is not possible.

[0050] The communication availability management unit 141 manages the communication availability status for each destination candidate managed by the destination candidate management unit 123. Specifically, as shown in FIG. 10, the communication availability management unit 141 stores, for each destination candidate, the availability of wireless communication using the beam 210 in association with the beam ID of the beam 210 that the mobile base station 200 can form. The communication availability information shown in FIG. 10 indicates that, for example, for a destination candidate with a destination ID of "destination #1," wireless communication using "beam #1," "beam #2," and "beam #3" is possible. Furthermore, this communication availability information indicates, for example, for a destination candidate with a destination ID of "destination #2," wireless communication using "beam #1" and "beam #2" is possible, but wireless communication using "beam #3" is not possible.

[0051] The beam multiplexing number calculation unit 142 calculates the number of beams to be multiplexed for each destination candidate of the mobile base station 200 based on the counting result by the terminal number counting unit 124 and the communication availability information. That is, the beam multiplexing number calculation unit 142 calculates, as the number of beams to be multiplexed, the number of beams 210 for which there are user terminals 300 that can use the beams 210 and for which wireless communication is possible, for each destination candidate. Therefore, the beam multiplexing number calculation unit 142 calculates, as the number of beams to be multiplexed, the number of beams 210 for which the number of user terminals 300 in the direction of the beams 210 is not zero and for which wireless communication is indicated to be possible by the communication availability information, for each destination candidate.

[0052] Specifically, as shown in Fig. 11, for each destination candidate, the beam multiplexing number calculation unit 142 calculates the number of beams 210 for which the number of user terminals 300 that can use beams 210 is not 0 and for which wireless communication is possible as the beam multiplexing number. In the example shown in Fig. 11, for example, at "destination #1," user terminals 300 are present in the directions of three beams 210, "beam #1," "beam #2," and "beam #3," and wireless communication is possible with all of the beams 210, so the beam multiplexing number is calculated to be 3. Also, for example, at "destination #2," user terminals 300 are present in the directions of two beams 210, "beam #1" and "beam #3," but "beam #3" is excluded because wireless communication is not possible with it, and the beam multiplexing number is calculated to be 1.

[0053] Then, the beam multiplexing number calculation unit 142 selects the destination candidate with the largest calculated beam multiplexing number as the destination of the mobile base station 200. In other words, the beam multiplexing number calculation unit 142 determines the destination candidate in which the multiple beams 210 formed by the mobile base station 200 are most frequently used. Therefore, in the example shown in Fig. 11, for example, the beam multiplexing number calculation unit 142 selects "destination #1" as the destination of the mobile base station 200 because the beam multiplexing number for "destination #1" is 3, which is the largest.

[0054] Next, a movement control method by the movement control device 100 configured as described above will be described with reference to the flow chart shown in Fig. 12. In Fig. 12, the same parts as in Fig. 7 are given the same reference numerals, and detailed description thereof will be omitted.

[0055] When the terminal location information acquisition unit 121 acquires location information from the user terminal 300 (step S101), the terminal number tallying unit 124 tallies the number of terminals for each destination candidate.

[0056] That is, first, the relative position of each user terminal 300 when the mobile base station 200 moves to a candidate destination is calculated (step S102). Then, from the relative position of the user terminal 300, the relative direction of the user terminal 300 with respect to the mobile base station 200 is calculated (step S103). Once the relative direction of the user terminal 300 has been calculated, the beams 210 available to each user terminal 300 are identified (step S104). Then, once the beams 210 for all user terminals 300 have been identified, the number of user terminals 300 for each beam 210 is tallied (step S105).

[0057] The above counting of the user terminals 300 is repeatedly performed by the terminal number counting unit 124 for each candidate destination.

[0058] Then, the beam multiplexing number calculation unit 142 calculates the number of beams multiplexed for each destination candidate (step S201). That is, for each destination candidate of the mobile base station 200, the number of user terminals 300 using beams 210 is not zero, and the number of beams 210 that can be wirelessly communicated is calculated as the beam multiplexing number. Then, the beam multiplexing number calculation unit 142 selects the destination candidate with the largest number of beams multiplexed as the destination of the mobile base station 200 (step S107).

[0059] Information about the determined movement destination is notified to the movement control unit 126, and the movement control unit 126 generates a movement instruction instructing the mobile base station 200 to move. Then, the movement instruction is transmitted from the movement control unit 126 to the mobile base station 200 via the communication IF unit 110 (step S108). As a result, the mobile base station 200 receives the movement instruction and moves to the instructed movement destination. Once the mobile base station 200 moves to the movement destination, it forms multiple beams 210 and performs wireless communication with the user terminal 300 located in the direction of each beam 210. Then, the mobile base station 200 generates communication availability information for each beam 210 indicating whether normal wireless communication with the user terminal 300 is possible or not, and transmits the communication availability information to the mobile control device 100.

[0060] The communication availability information is received by the communication IF unit 110 of the mobile control device 100 and acquired by the communication availability management unit 141. Then, the communication availability information regarding the destination to which the mobile base station 200 has moved is updated by the communication availability management unit 141 (step S202). That is, for beams 210 for which wireless communication was possible at the destination of the mobile base station 200, the fact that wireless communication is possible is stored, and for beams 210 for which wireless communication was not possible is stored that wireless communication is not possible. As a result, when the next destination of the mobile base station 200 is determined, the number of multiplexed beams can be calculated using the latest communication availability information.

[0061] As described above, according to this embodiment, the number of multiplexed beams that a user terminal can use for wireless communication is calculated using communication availability information for each beam at the destination of the mobile base station. Then, the destination candidate with the largest number of multiplexed beams is determined as the destination of the mobile base station. This allows multiple user terminals to use the beams of the mobile base station in a distributed manner, maximizing the radio resources available to each user terminal. In other words, it is possible to make maximum use of the multiplexed beams and improve throughput.

[0062] (Embodiment 3) A feature of the third embodiment is that when determining the destination of a mobile base station, the interference to user terminals connected to other base stations is taken into consideration.

[0063] The configuration of the communication system according to the third embodiment is the same as that of the first embodiment (FIG. 1), and therefore a description thereof will be omitted.

[0064] Fig. 13 is a block diagram showing the configuration of a mobile control device 100 according to embodiment 3. In Fig. 13, the same components as those in Fig. 2 are denoted by the same reference numerals, and their description will be omitted. The mobile control device 100 shown in Fig. 13 has a connected terminal management unit 151, a terminal number counting unit 152, and a beam multiplex number calculation unit 153, instead of the terminal number counting unit 124 and the beam multiplex number calculation unit 125 of the mobile control device 100 shown in Fig. 2.

[0065] The connected terminal management unit 151 acquires connected terminal information indicating user terminals (hereinafter referred to as "connected terminals") connected to each of a plurality of base stations including the mobile base station 200 from the communication IF unit 110. The connected terminal information acquired here is transmitted from a plurality of base stations including the mobile base station 200 and received by the communication IF unit 110. The connected terminal information includes, for example, identification information that identifies the connected terminal of each base station.

[0066] Then, the connected terminal management unit 151 manages connected terminals for each base station. Specifically, the connected terminal management unit 151 stores identification information of connected terminals in association with base station IDs that identify base stations, for example, as shown in Fig. 14. The connected terminal information shown in Fig. 14 indicates, for example, that user terminals currently in wireless communication with a base station having a base station ID of "BS#1" are "UE#1," "UE#2," and "UE#3," and that a user terminal currently in wireless communication with a base station having a base station ID of "BS#2" is "UE#4."

[0067] The terminal number counting unit 152 counts the number of user terminals by distinguishing between user terminals 300 connected to the mobile base station 200 and user terminals that are not connected to the mobile base station 200 but are connected to other base stations (hereinafter referred to as "unconnected terminals"). That is, the terminal number counting unit 152 counts the number of connected terminals and unconnected terminals in the direction of each beam 210 for each candidate destination of the mobile base station 200.

[0068] Specifically, as shown in Fig. 15, for example, the terminal number counting unit 152 counts the number of connected terminals and unconnected terminals in the direction of each beam 210 for each destination candidate. In the example shown in Fig. 15, when the mobile base station 200 moves to "destination #1," it is found that there is one connected terminal in each of the directions of "beam #1," "beam #2," and "beam #3," and no unconnected terminals in any direction. Similarly, when the mobile base station 200 moves to "destination #2," it is found that there are connected terminals in the directions of "beam #1" and "beam #3," and also an unconnected terminal in the direction of "beam #3."

[0069] The beam multiplexing number calculation unit 153 calculates the number of beams multiplexed for each destination candidate of the mobile base station 200 based on the counting result by the terminal number counting unit 152. That is, the beam multiplexing number calculation unit 153 calculates the number of beams 210 for each destination candidate, in which there are connected terminals that can use the beams 210, as the beam multiplexing number. At this time, the beam multiplexing number calculation unit 153 counts the number of beams 210 by multiplying the beams 210 for which there are unconnected terminals by a predetermined coefficient less than 1. That is, the beam multiplexing number calculation unit 153 adds a value less than 1 to the beam multiplexing number for beams 210 for which there are unconnected terminals, even if there are connected terminals that can use the beams 210.

[0070] Specifically, as shown in FIG. 16, for example, for each destination candidate, the beam multiplexing number calculation unit 153 counts a beam 210 for which the number of connected terminals that can use the beam 210 is not zero and the number of unconnected terminals located in the direction of the beam 210 is zero as 1 beam. Also, a beam 210 for which the number of connected terminals that can use the beam 210 is not zero and the number of unconnected terminals located in the direction of the beam 210 is not zero is counted as, for example, 0.5 beams. Then, the beam multiplexing number calculation unit 153 sets the number of beams counted for each destination candidate as the number of multiplexed beams. In the example shown in FIG. 16, for example, at "destination #1," connected terminals exist in the directions of three beams 210, "beam #1," "beam #2," and "beam #3," and no unconnected terminals exist in the directions of any of the beams 210, so the number of multiplexed beams is calculated to be 3. Also, for example, at "Destination #2," there are connected terminals in the directions of two beams 210, "Beam #1" and "Beam #3," and there is also a non-connected terminal in the direction of "Beam #3," so "Beam #1" is counted as 1 beam and "Beam #3" is counted as 0.5 beams, resulting in a calculated beam multiplexing number of 1.5.

[0071] Then, the beam multiplexing number calculation unit 153 selects the destination candidate with the largest calculated beam multiplexing number as the destination of the mobile base station 200. In other words, the beam multiplexing number calculation unit 153 determines the destination candidate in which the multiple beams 210 formed by the mobile base station 200 are most frequently used. Therefore, in the example shown in Fig. 16, for example, the beam multiplexing number calculation unit 153 selects "destination #1" as the destination of the mobile base station 200 because the beam multiplexing number for "destination #1" is 3, which is the largest.

[0072] In this embodiment, the number of multiplexed beams is calculated by counting beams 210 in which unconnected terminals exist as a number of beams less than 1, and therefore the number of multiplexed beams tends to be small for destination candidates in which beams 210 that may interfere with unconnected terminals are formed. Therefore, destination candidates that may interfere with user terminals connected to other base stations are less likely to be selected as destinations for mobile base station 200. This makes it possible to suppress interference with user terminals connected to other base stations.

[0073] As described above, according to this embodiment, the number of user terminals for each beam in destination candidates is tallied based on connected terminal information indicating connected terminals for each base station, distinguishing between connected terminals and non-connected terminals of the mobile base station, and the number of beams multiplexed for each destination candidate is calculated. The destination candidate with the largest number of beams multiplexed is then determined as the destination of the mobile base station. This allows multiple user terminals to use the beams of the mobile base station in a distributed manner, maximizing the radio resources available to each user terminal. In other words, it is possible to make maximum use of multiplexed beams and improve throughput. It is also possible to suppress interference caused to non-connected terminals by the movement of the mobile base station.

[0074] (Fourth embodiment) The fourth embodiment is characterized in that the location information of user terminals is converted into a preset grid index, thereby reducing the amount of calculation required to count the number of user terminals.

[0075] The configuration of the communication system according to the fourth embodiment is the same as that of the first embodiment (FIG. 1), and therefore a description thereof will be omitted. In the fourth embodiment, for example, a lattice-shaped grid is set in advance in the area where the user terminal 300 is located, and each grid is assigned a unique index. Note that, in the following description, the area where the user terminal 300 is located is described as being partitioned into a lattice-shaped grid, but the shape of the partitioned area does not necessarily have to be a lattice-shaped grid. In other words, it is sufficient that the area where the user terminal 300 is located is divided into partitioned areas of any shape, and each partitioned area is assigned a unique index.

[0076] Fig. 17 is a block diagram showing the configuration of a mobile control device 100 according to embodiment 4. In Fig. 17, the same parts as in Fig. 2 are given the same reference numerals, and their description will be omitted. The mobile control device 100 shown in Fig. 17 has an index conversion unit 161, a beam table holding unit 162, and a terminal number counting unit 163 instead of the beam information management unit 122 and the terminal number counting unit 124 of the mobile control device 100 shown in Fig. 2.

[0077] The index conversion unit 161 converts the location information of the user terminal 300 acquired by the terminal location information acquisition unit 121 into a grid index. That is, the index conversion unit 161 identifies a grid including the coordinates indicated by the location information of the user terminal 300, and acquires the index of the identified grid. Then, the index conversion unit 161 notifies the terminal number counting unit 163 of the index corresponding to the location information of each user terminal 300.

[0078] The beam table storage unit 162 stores a beam table that stores beams corresponding to indexes for each destination candidate of the mobile base station 200. Specifically, the beam table storage unit 162 stores a beam table that stores beams for each destination candidate in association with grid indexes, as shown in FIG. 18, for example. In the beam table shown in FIG. 18, for example, in a destination candidate with a destination ID of "destination #1," "beam #1" corresponds to index "A-1," and "beam #2" corresponds to index "A-2." Furthermore, for example, in a destination candidate with a destination ID of "destination #2," "beam #1" corresponds to both indexes "A-1" and "A-2."

[0079] Since the candidate destinations of the mobile base station 200 and the grids to which indices are assigned are determined in advance, it is possible to create a beam table such as that shown in FIG. 18 based on the positional relationship between the candidate destinations and the grids.

[0080] When the index is notified from the index conversion unit 161, the terminal number counting unit 163 refers to the beam table and counts the number of user terminals 300 in the direction of each beam 210 for each candidate destination of the mobile base station 200. That is, the terminal number counting unit 163 identifies the beam corresponding to the notified index for each candidate destination of the mobile base station 200 and counts the number of indexes notified for each beam. Because the notified index indicates the location information of the user terminal 300, the terminal number counting unit 163 can count the number of user terminals 300 in the direction of each beam 210 without calculating the relative position, relative direction, etc. of the user terminal 300.

[0081] Next, a movement control method by the movement control device 100 configured as described above will be described with reference to the flow chart shown in Fig. 19. In Fig. 19, the same parts as in Fig. 7 are given the same reference numerals, and detailed description thereof will be omitted.

[0082] When the terminal location information acquisition unit 121 acquires location information from the user terminal 300 (step S101), the index conversion unit 161 converts the location information into a grid index (step S301). That is, a grid including the coordinates indicated by the location information is identified, and an index of the identified grid is acquired. The index corresponding to the location information of each user terminal 300 is notified to the terminal number counting unit 163, and the terminal number counting unit 163 counts up the number of terminals for each destination candidate.

[0083] That is, the beam table held by the beam table holding unit 162 is referenced, and the beam 210 corresponding to each index is identified (step S302). Then, once the beams 210 corresponding to all the indexes have been identified, the number of indexes for each beam 210 is tallied (step S105). Because the indexes correspond to the position information of the user terminals 300, the number of user terminals 300 can be tallied by tallying the number of indexes for each beam 210. Furthermore, in this talliation, there is no need to calculate the relative positions and relative directions of the user terminals 300, and therefore the amount of calculation can be reduced.

[0084] The above counting of the user terminals 300 is repeatedly performed by the terminal number counting unit 163 for each candidate destination.

[0085] Then, the beam multiplexing number calculation unit 125 calculates the number of beams multiplexed for each destination candidate (step S106). That is, for each destination candidate of the mobile base station 200, the number of beams 210 for which the number of user terminals 300 using the beams 210 is not zero is calculated as the beam multiplexing number. Then, the beam multiplexing number calculation unit 125 selects the destination candidate with the largest number of beams multiplexed as the destination of the mobile base station 200 (step S107).

[0086] Information about the determined destination is notified to the mobility control unit 126, which then generates a movement instruction to instruct the mobile base station 200 to move. The movement instruction is then transmitted from the mobility control unit 126 to the mobile base station 200 via the communication IF unit 110 (step S108). As a result, the mobile base station 200 receives the movement instruction and moves to the instructed destination. Once the mobile base station 200 moves to the destination, it forms multiple beams 210 and performs wireless communication with the user terminal 300 located in the direction of each beam 210.

[0087] As described above, according to this embodiment, the position information of user terminals is converted into grid indices, and the number of user terminals for each beam is tallied by referring to a beam table that stores the correspondence between the indexes and beams. This eliminates the need to calculate the relative positions and directions of user terminals, and reduces the amount of calculation required to calculate the number of multiplexed beams.

[0088] In the above embodiments, the destination candidate with the largest number of multiplexed beams is determined as the destination of mobile base station 200, but there may be cases where the number of multiplexed beams is the largest among multiple destination candidates. In such cases, for each of the destination candidates with the largest number of multiplexed beams, the transmission rate for each user terminal 300 may be calculated from the SNR in the user terminal 300, and the destination candidate with the largest total transmission rate may be determined as the destination of mobile base station 200.

[0089] Furthermore, in the above-described embodiments, the mobile control device 100 and the mobile base station 200 are provided as separate entities, but the mobile control device 100 and the mobile base station 200 may be integrated together. That is, for example, if a mobile base station is equipped with the processor 120 of the mobile control device 100 according to the above-described embodiments, the mobile base station will be able to determine its own destination. Furthermore, the mobile control device 100 may be integrated with a base station other than the mobile base station 200. For example, if location information of the user terminal 300 is collected by a stationary base station that does not move, this base station may be equipped with the processor 120 of the mobile control device 100 according to the above-described embodiments. [Explanation of symbols]

[0090] 110 Communication IF section 120 processors 121 Terminal location information acquisition unit 122 Beam Information Management Department 123 Destination candidate management department 124, 152, 163 Terminal Counting Department 125, 142, 153 Beam multiplexing calculation unit 126 Movement control unit 130 memory 141 Communication Availability Management Department 151 Connection terminal management unit 161 Index conversion section 162 Beam table holder

Claims

1. A mobile control device that controls movement of a mobile base station that wirelessly communicates with a user terminal, Memory and a processor coupled to the memory; The processor: Acquire location information of the user terminal; Based on the acquired location information, for each candidate destination of the mobile base station, count the number of user terminals located in a direction of a beam formed by the mobile base station; Using the counting results, a beam multiplexing number corresponding to the number of beams in which user terminals located in the beam direction are present is calculated for each destination candidate; The mobile base station is instructed to select the destination candidate with the largest calculated number of multiplexed beams as the destination of the mobile base station. A mobile control device that executes processing.

2. The aggregation process includes: By referring to beam information indicating the coverage direction of the beam that can be formed by the mobile base station, the number of user terminals located in the beam direction is counted.

2. The movement control device according to claim 1.

3. The calculation process includes: The number of beams in which the number of user terminals located in the beam direction is one or more is calculated as the beam multiplexing number.

2. The movement control device according to claim 1.

4. The processor: further performing a process of managing communication availability information indicating whether the mobile base station has successfully performed wireless communication with the user terminal at the destination; The calculation process includes: Using the counting result and the communication availability information, the number of beam multiplexings is calculated, which corresponds to the number of beams in which user terminals located in the beam direction exist and with which wireless communication has been successfully performed with the user terminals.

2. The movement control device according to claim 1.

5. The managing process includes: After moving to the destination, a report is obtained from the mobile base station regarding wireless communication with the user terminal located in the direction of each beam, and the communication availability information is updated in accordance with the report.

5. The movement control device according to claim 4.

6. The processor: further performing a process of managing connected terminal information indicating user terminals connected to each of a plurality of base stations including the mobile base station; The calculation process includes: Using the counting result and the connected terminal information, the number of beams is counted depending on whether or not a user terminal located in the direction of the beam is a user terminal connected to the mobile base station, thereby calculating the number of multiplexed beams.

2. The movement control device according to claim 1.

7. The processor: further performing a process of converting the location information of the user terminal into an index of a partition area corresponding to the location information; The aggregation process includes: A beam table showing the correspondence between indexes and beams is referenced to identify the beam corresponding to the converted index, thereby counting the number of user terminals located in the direction of the beam.

2. The movement control device according to claim 1.

8. A mobility control method for controlling the movement of a mobile base station that wirelessly communicates with a user terminal, comprising: Acquire location information of the user terminal; Based on the acquired location information, for each candidate destination of the mobile base station, count the number of user terminals located in a direction of a beam formed by the mobile base station; Using the counting results, a beam multiplexing number corresponding to the number of beams in which user terminals located in the beam direction are present is calculated for each destination candidate; The mobile base station is instructed to select the destination candidate with the largest calculated number of multiplexed beams as the destination of the mobile base station. A movement control method comprising the steps of:

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