JP7750098B2 - Movement control device and movement control method - Google Patents

Description

The present invention relates to a mobility control device and a mobility control method.

In recent years, wireless communications using ultra-high frequency bands, such as millimeter wave communications, have been attracting attention. While ultra-high frequency wireless communications enable high-capacity communications using wide bandwidths, they also suffer from significant losses due to propagation loss and shielding.

Therefore, efforts are being made to achieve high-quality communications by mounting base stations (or relay stations) on mobile vehicles 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, methods are being considered for determining 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 beam multiplexing functionality, which simultaneously forms multiple beams pointing in different directions.

JP 2019-169829 A Japanese Patent Application Laid-Open No. 2019-16904 US Patent Application Publication No. 2019/0316910

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

However, even if a UAV base station has beam multiplexing capabilities, there is a problem in that beam multiplexing does not sufficiently improve throughput depending on the location of the user terminal. Specifically, if multiple user terminals are located in the direction of a single beam, these user terminals will use this beam to perform wireless communications 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 direction 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 multiple user terminals.

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

The disclosed technology was developed in light of these issues, and aims to provide a mobility control device and a mobility control method that can maximize the use of multiplexed beams to improve throughput.

In one aspect, the mobile control device disclosed in this application is a mobile control device that controls the movement of a mobile base station that wirelessly communicates with a user terminal, and has a memory and a processor connected to the memory. 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 the beam formed by the mobile base station for each destination candidate of the mobile base station. Using the counted results, the processor calculates, for each destination candidate, a beam multiplexing number corresponding to the number of beams in which user terminals located in the beam direction are present, and instructs the mobile base station to select the destination candidate with the largest calculated beam multiplexing number as the destination of the mobile base station.

One aspect of the mobility control device and mobility control method disclosed in this application has the effect of making maximum use of multiplexed beams to improve throughput.

FIG. 1 is a diagram illustrating an example of the configuration of a communication system. FIG. 2 is a block diagram showing the configuration of the mobile control device according to the first embodiment. FIG. 3 is a diagram showing a specific example of beam information. FIG. 4 is a diagram showing specific examples of destination candidates. FIG. 5 is a diagram showing a specific example of terminal counting. FIG. 6 is a diagram showing a specific example of calculation of the number of multiplexed beams. FIG. 7 is a flow diagram showing a movement control method according to the first embodiment. FIG. 8 is a diagram showing a specific example of movement of a mobile base station. FIG. 9 is a block diagram showing the configuration of a mobile control device according to the second embodiment. FIG. 10 is a diagram showing a specific example of communication availability information. FIG. 11 is a diagram showing a specific example of calculation of the number of multiplexed beams. FIG. 12 is a flow diagram showing a movement control method according to the second embodiment. FIG. 13 is a block diagram showing the configuration of a mobile control device according to the third embodiment. FIG. 14 is a diagram showing a specific example of the connection terminal information. FIG. 15 is a diagram showing a specific example of terminal counting. FIG. 16 is a diagram showing a specific example of calculation of the number of multiplexed beams. FIG. 17 is a block diagram showing the configuration of a mobile control device according to the fourth embodiment. FIG. 18 is a diagram showing a specific example of a beam table. FIG. 19 is a flow diagram showing a movement control method according to the fourth embodiment.

Embodiments of the mobility control device and mobility control method disclosed in this application will be described in detail below with reference to the drawings. Note that the present invention is not limited to these embodiments.

(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 with user terminals 300 located in the directions of each beam 210 using the beams 210.

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 used to the maximum extent possible. In other words, the mobile control device 100 selects the destination so that the number of beams 210 used by the user terminal 300 is maximized and the number of beam multiplexing is maximized. The configuration and operation of the mobile control device 100 will be described in detail later.

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

The user terminal 300 is a terminal that performs wireless communication with the mobile base station 200. The user terminal 300 communicates wirelessly with the mobile base station 200 using a beam 210 corresponding to the location of the user terminal, 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. In addition, the user terminal 300 reports its own location information to the mobile control device 100 via the mobile base station 200.

Although not shown in Figure 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.

Figure 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 Figure 2 has a communication interface unit (hereinafter abbreviated as "communication IF unit") 110, a processor 120, and a memory 130.

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 via a wired connection.

The communication IF unit 110 receives location information for 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, instructing the mobile base station 200 on the movement destination.

The processor 120 includes, for example, a CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), or DSP (Digital Signal Processor), and provides overall control of the mobile control device 100. Specifically, the processor 120 includes a terminal position 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.

The terminal location information acquisition unit 121 acquires the 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 the location information of user terminals 300 that communicate wirelessly with the mobile base station 200, but may also acquire the location information of user terminals 300 that communicate wirelessly with other base stations.

The beam information management unit 122 manages information about the beams 210 formed by the mobile base station 200. Specifically, as shown in FIG. 3, for example, the beam information management unit 122 stores the direction covered by each beam 210, in association with a beam ID that identifies the multiple beams 210 that the mobile base station 200 can form. The beam information shown in FIG. 3 stores, for example, that the 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. The mobile base station 200 can multiplex and simultaneously form multiple beams 210 for which beam information is stored.

The candidate destination management unit 123 manages information on candidate destinations for the mobile base station 200. Specifically, as shown in FIG. 4, for example, the candidate destination management unit 123 stores the coordinates of each candidate destination in association with a destination ID that identifies multiple candidate destinations for the mobile base station 200. In the candidate destinations shown in FIG. 4, for example, the candidate destination with a destination ID of "Destination #1" is stored as being located at coordinates (-10, 0, 0). The coordinates of the candidate destination 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 a candidate destination managed by the candidate destination management unit 123.

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, for each candidate destination of the mobile base station 200, the terminal number counting unit 124 calculates the positional relationship between the mobile base station 200 and each user terminal 300, and identifies the direction of which beam 210 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.

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."

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

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.

The beam multiplexing number calculation unit 125 then 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 that most frequently uses the multiple beams 210 formed by the mobile base station 200. Therefore, in the example shown in Figure 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, the largest.

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

Memory 130 includes, for example, RAM (Random Access Memory) or ROM (Read Only Memory), and stores information used in processing by processor 120.

Next, the movement control method using the movement control device 100 configured as described above will be explained with reference to the flow chart shown in Figure 7.

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 has been 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.

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 i-th user terminal 300 is represented as ( _xi , _yi , _zi ).

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). 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 i-th user terminal 300 can be calculated using the following formula:

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.

Once the relative directions of the user terminals 300 have been calculated, the beams 210 available to each user terminal 300 are identified (step S104). That is, the beam information managed by the beam information management unit 122 is referenced, and the 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.

The above counting of user terminals 300 is repeatedly performed for each candidate destination by the terminal count unit 124. This allows the number of user terminals 300 using each beam 210 to be obtained for each candidate destination, as shown in Figure 5, for example.

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). 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.

The information about the determined destination is notified to the mobile control unit 126, which then generates a movement instruction instructing the mobile base station 200 to move. The movement instruction is then transmitted from the mobile 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. At the destination of the mobile base station 200, the multiple beams 210 formed by the mobile base station 200 are made maximum use of 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 terminal 300 in each beam 210. In other words, the multiplexed beams can be made maximum use of to improve throughput.

Figure 8 shows a specific example of the movement of a mobile base station 200. When the mobile base station 200 is located at the position shown in Figure 8(a), two of the three beams 210 formed by the mobile base station 200 are used by the user terminal 300. That is, at the position shown in Figure 8(a), the number of multiplexed beams of the 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.

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

In this way, by moving the mobile base station 200 so as to maximize the number of multiplexed beams, the user terminals 300 will be able to use the beams 210 in a dispersed manner, 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.

As described above, according to this embodiment, the number of user terminals located in the direction of each beam for each candidate destination of the mobile base station is tallied from the user terminal's location information, and the number of multiplexed beams for each candidate destination is calculated. The candidate destination 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, throughput can be improved by making maximum use of the multiplexed beams.

(Embodiment 2)
The feature of embodiment 2 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.

The configuration of the communication system in embodiment 2 is the same as that in embodiment 1 (Figure 1), so its description will be omitted.

Figure 9 is a block diagram showing the configuration of a mobile control device 100 according to embodiment 2. In Figure 9, the same components as those in Figure 2 are denoted by the same reference numerals, and their description will be omitted. The mobile control device 100 shown in Figure 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 Figure 2.

The communication feasibility management unit 141 acquires communication feasibility information from the communication IF unit 110, which indicates 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 transmitted from the mobile base station 200 after the mobile base station 200 has moved, and is received by the communication IF unit 110.

When the mobile base station 200 moves in accordance with movement instructions 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 properly. 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 properly, and transmits this information to the mobile control device 100. For example, if there is even one user terminal 300 that is unable to perform wireless communication properly among multiple user terminals 300 using one beam 210, the mobile base station 200 may transmit communication availability information indicating that wireless communication is not possible with this beam 210.

The communication availability management unit 141 then 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 the availability of wireless communication using beam 210 for each destination candidate, in association with the beam ID of beam 210 that can be formed by the mobile base station 200. 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.

The beam multiplexing number calculation unit 142 calculates the number of beams multiplexed for each destination candidate of the mobile base station 200 based on the counting results by the terminal number counting unit 124 and the communication availability information. That is, the beam multiplexing number calculation unit 142 calculates 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, as the beam multiplexing number for each destination candidate. Therefore, the beam multiplexing number calculation unit 142 calculates the number of beams 210 for which there is a non-zero number of user terminals 300 in the direction of the beams 210 and for which wireless communication is indicated to be possible by the communication availability information, as the beam multiplexing number for each destination candidate.

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 zero 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.

The beam multiplexing number calculation unit 142 then 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 that most frequently uses the multiple beams 210 formed by the mobile base station 200. Therefore, in the example shown in Figure 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, the largest.

Next, a movement control method using the movement control device 100 configured as described above will be explained with reference to the flow diagram shown in Figure 12. In Figure 12, the same parts as in Figure 7 are designated by the same reference numerals, and detailed explanations thereof will be omitted.

When location information from the user terminal 300 is acquired by the terminal location information acquisition unit 121 (step S101), the terminal number counting unit 124 counts the number of terminals for each destination candidate.

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).

The above counting of user terminals 300 is repeatedly performed by the terminal counting unit 124 for each potential destination.

Then, the beam multiplexing number calculation unit 142 calculates the beam multiplexing number 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 used for wireless communication is calculated as the beam multiplexing number. Then, the beam multiplexing number calculation unit 142 selects the destination candidate with the largest beam multiplexing number as the destination of the mobile base station 200 (step S107).

The information about the determined destination is notified to the mobile control unit 126, which generates a movement instruction instructing the mobile base station 200 to move. The movement instruction is then transmitted from the mobile control unit 126 to the mobile base station 200 via the communication IF unit 110 (step S108). The mobile base station 200 then receives the movement instruction and moves to the specified destination. Once the mobile base station 200 moves to the destination, it forms multiple beams 210 and performs wireless communication with user terminals 300 located in the direction of each beam 210. The mobile base station 200 then generates communication availability information for each beam 210 indicating whether normal wireless communication with the user terminal 300 is possible, and transmits this information to the mobile control device 100.

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. The communication availability information for the destination to which the mobile base station 200 has moved is then 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, it is stored that wireless communication is possible, and for beams 210 for which wireless communication was not possible, it 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.

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. 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 wireless resources available to each user terminal. In other words, throughput can be improved by making maximum use of the multiplexed beams.

(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.

The configuration of the communication system in embodiment 3 is the same as that in embodiment 1 (Figure 1), so its description will be omitted.

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

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

The connected terminal management unit 151 then 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, as shown in FIG. 14, for example. The connected terminal information shown in FIG. 14 indicates that, for example, the user terminals currently in wireless communication with a base station with base station ID "BS#1" are "UE#1," "UE#2," and "UE#3," and the user terminal currently in wireless communication with a base station with base station ID "BS#2" is "UE#4."

The terminal number counting unit 152 counts the number of user terminals, 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 "non-connected terminals"). That is, the terminal number counting unit 152 counts the number of connected terminals and non-connected terminals in the direction of each beam 210 for each candidate destination of the mobile base station 200.

Specifically, 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, as shown in FIG. 15, for example. 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."

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 results 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, which is the number of beams 210 for 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 by a predetermined coefficient less than 1 for beams 210 for which there are unconnected terminals. 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.

Specifically, as shown in FIG. 16, for each destination candidate, the beam multiplexing number calculation unit 153 counts as one beam 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. 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. The beam multiplexing number calculation unit 153 then determines the number of beams counted for each destination candidate as the beam multiplexing number. In the example shown in FIG. 16, for example, at "destination #1," there are connected terminals in the directions of three beams 210, "beam #1," "beam #2," and "beam #3," and no unconnected terminals are located in the directions of any of the beams 210, so the beam multiplexing number is calculated to be three. 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." Therefore, "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.

The beam multiplexing number calculation unit 153 then 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 that most frequently uses the multiple beams 210 formed by the mobile base station 200. Therefore, in the example shown in Figure 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, the largest.

In this embodiment, the beam multiplexing number is calculated by counting beams 210 in which non-connected terminals exist as a beam number less than 1. Therefore, for destination candidates in which beams 210 that may cause interference to non-connected terminals are formed, the beam multiplexing number tends to be small. For this reason, destination candidates that may cause interference to user terminals connected to other base stations are less likely to be selected as destinations for the mobile base station 200. This makes it possible to suppress interference with user terminals connected to other base stations.

As described above, according to this embodiment, the number of user terminals for each beam at destination candidates is tallied based on connected terminal information indicating connected terminals for each base station, distinguishing between connected and unconnected 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 unconnected terminals by the movement of the mobile base station.

(Fourth embodiment)
A feature of the fourth embodiment is that the location information of the user terminals is converted into a preset grid index, thereby reducing the amount of calculation required to count the number of user terminals.

The configuration of the communication system according to embodiment 4 is the same as that of embodiment 1 (Figure 1), and therefore a description thereof will be omitted. In embodiment 4, a grid, for example, in a lattice pattern is set in advance in the area in which the user terminal 300 is located, and each grid is assigned a unique index. Note that, in the following description, the area in which the user terminal 300 is located is described as being divided into a lattice pattern, but the shape of the divided area does not necessarily have to be a lattice pattern. In other words, it is sufficient if the area in which the user terminal 300 is located is divided into divided areas of any shape, and each divided area is assigned a unique index.

Figure 17 is a block diagram showing the configuration of a mobile control device 100 according to embodiment 4. In Figure 17, the same components as those in Figure 2 are assigned the same reference numerals, and their description will be omitted. The mobile control device 100 shown in Figure 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 terminal number counting unit 124 of the mobile control device 100 shown in Figure 2.

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 that includes the coordinates indicated by the location information of the user terminal 300, and acquires the index of the identified grid. The index conversion unit 161 then notifies the terminal number counting unit 163 of the index corresponding to the location information of each user terminal 300.

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, for a destination candidate with a destination ID of "destination #1," index "A-1" corresponds to "beam #1," and index "A-2" corresponds to "beam #2." Furthermore, for example, for a destination candidate with a destination ID of "destination #2," both indexes "A-1" and "A-2" correspond to "beam #1."

The candidate destinations of the mobile base station 200 and the grids to which indexes are assigned are determined in advance, so it is possible to create a beam table like the one shown in Figure 18 based on the positional relationship between the candidate destinations and the grids.

When the index is notified by 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, for each candidate destination of the mobile base station 200, the terminal number counting unit 163 identifies the beam corresponding to the notified index 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 having to calculate the relative position and relative direction of the user terminal 300, etc.

Next, a movement control method using the movement control device 100 configured as described above will be explained with reference to the flow diagram shown in Figure 19. In Figure 19, the same parts as in Figure 7 are designated by the same reference numerals, and detailed explanations thereof will be omitted.

When location information from a user terminal 300 is acquired by the terminal location information acquisition unit 121 (step S101), the index conversion unit 161 converts the location information into a grid index (step S301). That is, a grid containing the coordinates indicated by the location information is identified, and the 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, which then counts the number of terminals for each destination candidate.

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 terminal 300, the number of user terminals 300 can be tallied by tallying the number of indexes for each beam 210. Furthermore, this talliation does not require calculation of the relative position and relative direction of the user terminal 300, thereby reducing the amount of calculation required.

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

Then, the beam multiplexing number calculation unit 125 calculates the number of beam multiplexing numbers 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 beam multiplexing numbers as the destination of the mobile base station 200 (step S107).

The information about the determined destination is notified to the mobile 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 mobile 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 has moved to the destination, it forms multiple beams 210 and performs wireless communication with user terminals 300 located in the direction of each beam 210.

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

In the above embodiments, the destination candidate with the largest number of beam multiplexings is determined as the destination of the mobile base station 200. However, there may be cases where the number of beam multiplexings is the largest for multiple destination candidates. In such cases, for each destination candidate with the largest number of beam multiplexings, the transmission rate for each user terminal 300 may be calculated, for example, from the SNR of the user terminal 300, and the destination candidate with the largest total transmission rate may be determined as the destination of the mobile base station 200.

In addition, in the above 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 also be integrated. That is, for example, if a mobile base station is equipped with the processor 120 of the mobile control device 100 according to each of the above-mentioned embodiments, the mobile base station will be able to determine its own destination. Furthermore, the mobile control device 100 may also be integrated with a base station other than the mobile base station 200. For example, if the 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 each of the above-mentioned embodiments.

110 Communication IF unit 120 Processor 121 Terminal position information acquisition unit 122 Beam information management unit 123 Movement destination candidate management unit 124, 152, 163 Terminal number counting unit 125, 142, 153 Beam multiplex number calculation unit 126 Movement control unit 130 Memory 141 Communication feasibility management unit 151 Connected terminal management unit 161 Index conversion unit 162 Beam table storage unit

Claims (8)

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;
A mobile control device characterized by executing a process of instructing the mobile base station to select the destination candidate with the largest calculated number of multiplexed beams as the destination of the mobile base station. The aggregation process includes:
The mobile control device according to claim 1, wherein the mobile control device counts the number of user terminals located in the direction of the beam by referring to beam information indicating the direction of coverage of the beam that the mobile base station can form. The calculation process includes:
The mobile control device according to claim 1, wherein the number of beams in which the number of user terminals located in the direction of the beams is one or more is calculated as the number of multiplexed beams. 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:
A mobile control device as described in claim 1, characterized in that, using the aggregation results and the communication availability information, the beam multiplexing number is calculated, which corresponds to the number of beams in which user terminals located in the direction of the beams exist and to the number of beams in which wireless communication with the user terminals has been successfully performed. The managing process includes:
The mobile control device according to claim 4, characterized in that after the mobile base station has moved to a destination, a report is obtained from the mobile base station regarding wireless communication with a user terminal located in the direction of each beam, and the communication availability information is updated in accordance with the report. 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:
The mobile control device according to claim 1, characterized in that the number of beams multiplexed is calculated by using the aggregation result and the connected terminal information to count the number of beams depending on whether a user terminal located in the direction of the beam is a user terminal connected to the mobile base station. 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:
The mobile control device according to claim 1, characterized in that the number of user terminals located in the direction of the beam is tallied by referring to a beam table showing the correspondence between indexes and beams and identifying the beam corresponding to the converted index. 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;
A mobility control method comprising a process of instructing the mobile base station to select the destination candidate with the largest calculated number of multiplexed beams as the destination of the mobile base station.