Base station control system, base station control method, base station control device and program

Abstract

The present invention provides a base station control system including first base stations the positions of which are not determined and a base station control device. The base station control device includes: a generation unit that, for multiple terminal combinations selected from multiple terminals connected to an existing second base station and corresponding to the number of the first base stations, generates multiple patterns of combinations of position candidates and transmission power candidates of the respective first base stations on the basis of the positions of the terminals corresponding to the terminal combinations; a calculation unit that calculates, for each pattern, the number of first terminals connected to the first base stations and the number of second terminals connected to the second base station on the basis of an assumption that the first base stations are placed in the positions corresponding to the pattern and the first base stations output transmission power corresponding to the pattern; and a selection unit that selects one of the multiple candidates on the basis of the number of the first terminals and the number of the second terminals. With this configuration, the base station control device reduces the imbalance in the number of terminals connected to each base station.

Description

[Technical field]

[0001] The present invention relates to a base station control system, a base station control method, a base station control device, and a program. [Background technology]

[0002] If wireless base stations are evenly distributed throughout an area to efficiently ensure area coverage, it is possible that communication quality in a particular area may decline due to terminal congestion, obstruction, etc. In response to this, technology is being considered to dynamically distribute mobile base stations in areas where communication quality has declined to improve communication quality (Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Takuto Arai, Daisuke Goto, Masashi Iwabuchi, Tatsuhiko Iwakuni, Kazuki Maruta, "Proposal of an Adaptive Mobile AP System to Improve Offload Efficiency," IEICE Technical Report, vol. 116, no. 46, RCS2016-43, pp. 107-112, May 2016. Summary of the Invention [Problem to be solved by the invention]

[0004] However, when dynamically deploying a mobile base station, if the received power from that mobile base station at each terminal becomes too high compared to other base stations, many terminals may autonomously connect to that mobile base station, resulting in excessive bias in terminal connections and a deterioration in communication quality.

[0005] Figure 1 is a diagram for explaining the problems with the conventional technology. Figure 1 explains an example in which two mobile base stations are installed in an environment with three existing base stations and 11 terminals. Figure 1 (1) shows the state before the mobile base stations are installed, and (2) shows the state after the mobile base stations are installed.

[0006] Before the mobile base station is deployed (1), there is one terminal connected to the existing base station on the far left, and five terminals are connected to each of the other two existing base stations. The dashed lines connecting each terminal to the existing base station indicate the connection relationship between the terminal and the existing base station. In this state, the two existing base stations are congested. Therefore, we aim to eliminate or alleviate the congestion by deploying one mobile base station for each of the two existing base stations.

[0007] In the conventional technology, the location of a mobile base station is calculated by clustering 10 terminals connected to one of two congested existing base stations. As a result, a mobile base station is installed, for example, as shown in (2). In (2), each cluster is shown by a curved frame line, and a mobile base station is installed at the center of gravity of each cluster.

[0008] In general wireless systems, when a terminal can receive signals from multiple base stations, it connects to the base station with the strongest reception power. Therefore, when mobile base stations are arranged as in (2), five terminals will connect to one mobile base station, and two terminals will connect to the other mobile base station. As a result, the congestion at the existing base station that was congested in (1) is eliminated, but congestion occurs at one of the mobile base stations. Thus, according to conventional technology, there is a possibility that excessive imbalance will occur in the number of terminals connected to each base station (existing base station or mobile base station).

[0009] The present invention has been made in consideration of the above-mentioned points, and has an object to reduce the imbalance in the number of terminals connected to each base station. [Means for solving the problem]

[0010] In order to solve the above problem, in a base station control system including a first base station whose location has not been determined and a base station control device, the base station control device selects the number of the first base station from among a plurality of terminals connected to an existing second base station. If we choose a number of terminals equal to Multiple ways The terminala generation unit that generates, for a combination, a pattern of a plurality of combinations of candidate locations and candidate transmission powers of the first base station based on a location of each terminal related to the combination; a calculation unit that calculates, for each pattern, the number of first terminals connected to the first base station and the number of second terminals connected to the second base station when the first base station is placed at a location related to the pattern and the first base station outputs the transmission power related to the pattern; and based on the number of the first terminals and the number of the second terminals, Multiple Number The above pattern One of the The above pattern and a selection unit for selecting Effect of the Invention

[0011] The imbalance in the number of terminals connected to each base station can be reduced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram for explaining a problem with the conventional technology. [Diagram 2] 1 is a diagram illustrating an example of a configuration of a communication system 1 according to an embodiment of the present invention. [Diagram 3] 2 is a diagram illustrating an example of a hardware configuration of a control station 10 according to the embodiment of the present invention. [Figure 4] 2 is a diagram illustrating an example of a functional configuration of a control station 10 according to the embodiment of the present invention. [Diagram 5] 10 is a flowchart illustrating an example of a processing procedure executed by the control station 10. [Figure 6] 2 is a diagram showing a specific example of a connection state of a terminal 50 to an existing base station 30. FIG. [Figure 7] FIG. 13 is a diagram showing an example of a candidate pattern. [Figure 8] 13 is a diagram showing an example of a calculation result of an evaluation value X of each candidate pattern. FIG. [Figure 9] FIG. 13 is a diagram showing an example of a calculation result of an evaluation value Yi of each candidate pattern. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 2 is a diagram showing an example of the configuration of a communication system in an embodiment of the present invention. As shown in Fig. 2, a communication system 1 includes one or more existing base stations 30, one or more mobile base stations 20, one or more relay base stations 40, a control station 10, etc. Note that a base station refers to a base station (access point) for wireless communication (for example, wireless LAN).

[0014] In this embodiment, the existing base station 30 is an already installed base station. In this embodiment, the existing base station 30 is not a target for movement, but the existing base station 30 may be movable.

[0015] The mobile base station 20 is a mobile base station, and in this embodiment, is a base station that is newly deployed (the deployment location has not been decided). For example, when communication is congested at an existing base station 30, the mobile base station 20 is dynamically deployed. The driving means for moving the mobile base station 20 is not limited to a specific one. For example, the driving means may be a vehicle or a drone. The mobile base station 20 may also be configured to move on rails that have been laid in advance.

[0016] The relay base station 40 is a base station that relays communication between the mobile base station 20 and the control station 10. The relay base station 40 is connected to the mobile base station 20 by wireless communication. Therefore, the mobile base station 20 is movable within a range where wireless communication with the relay base station 40 is possible.

[0017] In the following, when there is no need to distinguish between the existing base station 30 and the mobile base station 20, they are simply referred to as "base station." Although not shown in the figure, there are multiple terminals (hereinafter, terminals 50) that wirelessly connect to any of the base stations and communicate. Each terminal connects to any of the base stations through autonomous control. The autonomous control is, for example, a control in which a terminal connects to a base station with a relatively large reception power at the terminal.

[0018] The control station 10 is one or more computers that control the placement of the mobile base station 20 and the transmission power of the mobile base station 20. The control station 10 is connected to each existing base station 30 and each relay base station 40 via a network (whether wired or wireless). The control station 10 controls the placement of the mobile base station 20 and the transmission power of the mobile base station 20 based on information collected from each base station and terminal via the network.

[0019] Fig. 3 is a diagram showing an example of a hardware configuration of a control station 10 in an embodiment of the present invention. The control station 10 in Fig. 3 includes a drive device 100, an auxiliary storage device 102, a memory device 103, a CPU 104, and an interface device 105, which are all connected to each other via a bus B.

[0020] A program for implementing the processing in the control station 10 is provided by a recording medium 101 such as a CD-ROM. When the recording medium 101 storing the program is set in the drive device 100, the program is installed from the recording medium 101 to the auxiliary storage device 102 via the drive device 100. However, the program does not necessarily have to be installed from the recording medium 101, but may be downloaded from another computer via a network. The auxiliary storage device 102 stores the installed program as well as necessary files, data, and the like.

[0021] When an instruction to start a program is received, the memory device 103 reads out the program from the auxiliary storage device 102 and stores it. The CPU 104 executes functions related to the control station 10 in accordance with the program stored in the memory device 103. The interface device 105 is used as an interface for connecting to a network.

[0022] Fig. 4 is a diagram showing an example of a functional configuration of the control station 10 in the embodiment of the present invention. In Fig. 4, the control station 10 has a generation unit 11, a calculation unit 12, a selection unit 13, and an arrangement unit 14. Each of these units is realized by a process in which one or more programs installed in the control station 10 are executed by the CPU 104.

[0023] The following describes the process steps executed by the control station 10. FIG 5 is a flowchart for explaining an example of the process steps executed by the control station 10.

[0024] In step S101, the generation unit selects an existing base station 30 (hereinafter referred to as a "target existing base station 30") as a target for installation of the movable base station 20 (the load of which is reduced by the movable base station 20) based on the number of connected terminals of each of the multiple existing base stations 30. For example, some existing base stations 30 in which terminal connections are relatively congested (the number of connected terminals is relatively large) are selected as the target existing base station 30. In this case, the generation unit determines whether the terminal connections of each existing base station 30 are congested. For example, the generation unit determines that an existing base station 30 in which the number of connected terminals 50 (the number of connected terminals) is equal to or greater than a predetermined threshold is congested.

[0025] 6 is a diagram showing a specific example of a connection state of a terminal 50 to an existing base station 30. In this embodiment, it is assumed that three existing base stations 30 are installed, and two movable base stations 20 are additionally installed in a state in which eleven terminals 50 are connected to any of the existing base stations 30. In addition, in the figure, the dashed lines connecting the terminals 50 and the existing base stations 30 indicate the connection relationship between the terminals 50 and the existing base stations 30 (which existing base station 30 the terminal 50 is connected to). Therefore, in the example of FIG. 6, the number of connected terminals of the existing base station 30-1 is 1, the number of connected terminals of the existing base station 30-2 is 5, and the number of connected terminals of the existing base station 30-3 is 5.

[0026] 6, if the threshold for determining whether the existing base station 30 is congested is 5, two existing base stations 30, the existing base station 30-2 and the existing base station 30-3, are determined to be congested. Therefore, these two existing base stations 30 are selected as the target existing base stations 30.

[0027] Alternatively, as another determination method, it may be determined that a base station is congested if the number of connected terminals is included in the top α% of all existing base stations 30, and that a base station is not congested if the number is not included in the top α% of all existing base stations 30. α is a parameter, and for example, when α=50, the top 50% of existing base stations 30 are in a congested state.

[0028] Alternatively, as another determination method, an existing base station 30 in which the number of connected terminals exceeds the average number of connected terminals of all the existing base stations 30 may be determined to be in a congested state.

[0029] Next, the generating unit 11 generates candidates for the placement positions of each mobile base station 20 (hereinafter referred to as "placement candidates") for a plurality of combinations (all combinations) of terminals 50, the number of which is equal to the number of mobile base stations 20, from among the group of terminals 50 connected to any of the target existing base stations 30 (S102). For example, for each terminal 50 related to a certain combination, the vicinity of the terminal 50 is set as a placement candidate for one mobile base station 20. Therefore, for each combination of terminals 50, the number of which is equal to the number of mobile base stations 20 (for example, two), a combination of placement candidates for each mobile base station 20 (hereinafter referred to as "placement candidate sequence") is generated. Here, the vicinity of the terminal 50 refers to, for example, a position randomly selected within a predetermined distance range from the terminal 50. Alternatively, a position whose direction and distance from the terminal 50 are predetermined values ​​may be the vicinity of the terminal 50.

[0030] Next, the generation unit 11 generates pattern candidates (hereinafter referred to as "candidate patterns") relating to the placement and transmission power of the mobile base station 20 by combining multiple combinations of transmission power adjustment amounts for each mobile base station 20 with each placement candidate array (each combination of terminals 50) determined in step S102 (S103). The transmission power adjustment amount refers to the relative amount of power reduction from the maximum transmission power. For example, since the settable transmission power differs depending on the country, in this embodiment, it is a relative value based on the maximum value. However, the absolute value of the transmission power may be used instead of the transmission power adjustment amount.

[0031] FIG. 7 is a diagram showing an example of a candidate pattern. As shown in FIG. 7, one candidate pattern includes a candidate pattern number, an arrangement candidate sequence, and a transmission power adjustment amount sequence. The candidate pattern number is an identification number of the candidate pattern. The arrangement candidate sequence is a combination of arrangement candidates for each mobile base station 20. In FIG. 7, the value of the arrangement candidate is indicated by the identification information (A to J) of the terminal 50. For example, the first A in the arrangement candidate sequence [A, B] for the candidate pattern number = 1 indicates that the arrangement candidate of one mobile base station 20 is near the terminal 50-A. The second B indicates that the arrangement candidate of the other mobile base station 20 is near the terminal 50-B. The transmission power adjustment amount sequence is a combination of transmission power adjustment amounts for each mobile base station 20. For example, the first 0 in the transmission power adjustment amount sequence [0, 0] for the candidate pattern number = 1 indicates the transmission power adjustment amount for one mobile base station 20, and the second 0 indicates the transmission power adjustment amount for the other mobile base station 20.

[0032] Next, the calculation unit 12 calculates evaluation parameters for each candidate pattern based on the position of each base station (the movable base station 20 and the existing base station 30) and the position of each terminal 50 (each terminal 50 connected to the target base station) (S104). In this embodiment, the evaluation parameters are (a) the number of terminals connected to the existing base station, (b) the number of terminals connected to the movable base station, and (c) terminals that cannot be connected to a base station.

[0033] (a) The number of connected terminals of an existing base station for a certain candidate pattern refers to the number of terminals 50 that will connect to a target existing base station 30 when each movable base station 20 is placed at the placement location indicated by the placement candidate sequence for that candidate pattern and each movable base station 20 outputs the transmission power indicated by the transmission power adjustment amount sequence for that candidate pattern.

[0034] The number of connected terminals of a mobile base station (b) for a certain candidate pattern refers to the number of terminals 50 connected to the mobile base station 20 when each mobile base station 20 is placed at the placement location indicated by the placement candidate sequence for that candidate pattern and each mobile base station 20 outputs the transmission power indicated by the transmission power adjustment amount sequence for that candidate pattern.

[0035] The (c) base station connection incapable terminal of a certain candidate pattern refers to a terminal 50 that is present in an area in which an existing base station 30 is located and that cannot connect to either the movable base station 20 or the target existing base station 30 when each movable base station 20 is located at the location indicated by the location candidate sequence related to that candidate pattern and each movable base station 20 outputs the transmission power indicated by the transmission power adjustment amount sequence related to that candidate pattern. The value of (c) is 0 when a terminal 50 corresponding to a base station connection incapable terminal exists, and is 1 when no terminal 50 corresponding to a base station connection incapable terminal exists.

[0036] Regarding (a) and (b), the calculation unit 12 calculates the received power at each terminal 50 from the target existing base station 30 and the movable base station 20 based on the distance between each terminal 50 and the target existing base station 30 and each movable base station 20, and the transmission power of each of the target existing base station 30 and the movable base station 20, and calculates the number of connected terminals for each base station when the terminal 50 is connected to the base station with the highest received power. At this time, the transmission power of the movable base station 20 may be a default value different from the transmission power of the target existing base station 30, or may be the same value as the transmission power of the target existing base station 30.

[0037] Regarding (c), the calculation unit 12 determines as a result whether or not there is a terminal 50 for which the maximum value of the received power calculated for each base station for each terminal 50 regarding (a) and (b) (the maximum value of the received power from the target existing base station 30 and the received power from the movable base station 20) is below a predetermined threshold value (required received power).

[0038] Next, the calculation unit 12 calculates an evaluation value X for each candidate pattern based on (a) to (c) (S105). Here, as an example, the product of (a), (b), and (c) ((a)×(b)×(c)) is calculated as the evaluation value X.

[0039] Fig. 8 is a diagram showing an example of the calculation result of the evaluation value X of each candidate pattern. Fig. 8 shows an example of the values ​​(a) to (c) and an example of the evaluation value X for each candidate pattern. Note that, among the two values ​​[x, y] in (a), x is a value for one of the two existing base stations 30, and y is a value for the other of the two existing base stations 30. Similarly, among the two values ​​[x, y] in (b), x is a value for one of the two mobile base stations 20, and y is a value for the other of the two mobile base stations 20.

[0040] Next, the selection unit 13 judges whether there are multiple candidate patterns with the maximum evaluation value X (S106). If there is one candidate pattern with the maximum evaluation value X (N in S106), the selection unit 13 selects the candidate pattern (S107) and proceeds to step S115. Note that the candidate pattern with the maximum evaluation value X is a candidate pattern with a small bias in the number of connected terminals between base stations and with no terminals that cannot connect to a base station, and can identify an arrangement position and transmission power adjustment amount with a small bias in terminal connections for the mobile base station 20.

[0041] On the other hand, if there are multiple candidate patterns with the maximum evaluation value X (Y in S106), the selection unit 13 calculates (d) the minimum value of the received power of the terminal connected to the existing base station and (e) the minimum value of the received power of the terminal connected to the movable base station for each candidate pattern with the maximum evaluation value X, and sets the i-th smallest value of (d) and (e) as the evaluation value Yi (S108). Note that (d) the minimum value of the received power of the terminal connected to the existing base station refers to the minimum value of the power of the signal received from the existing base station 30 at each existing base station connected terminal. (e) the minimum value of the received power of the terminal connected to the movable base station refers to the minimum value of the power of the signal received from the movable base station 20 at each mobile base station connected terminal. Note that the received power at the terminal 50 from each base station can be calculated based on the distance between each base station and the terminal 50, the transmission power of each base station, etc.

[0042] Fig. 9 is a diagram showing an example of the calculation result of the evaluation value Yi of each candidate pattern. Fig. 9 further shows, for multiple candidate patterns with the maximum evaluation value X, (d) the maximum distance between the existing base station connected terminal and the existing base station, (e) the maximum distance between the movable base station connected terminal and the movable base station, and the evaluation value Yi (evaluation value Y1, evaluation value Y2). The evaluation value Y1 is the larger of (d) and (e). The evaluation value Y2 is the smaller of (d) and (e).

[0043] Next, the selection unit 13 assigns 1 to the variable i (S109). Next, the selection unit 13 determines whether or not there are multiple candidate patterns with the smallest evaluation value Yi (S110). If there is one candidate pattern with the smallest evaluation value Yi (N in S110), the selection unit 13 selects that candidate pattern (S111) and proceeds to step S115.

[0044] On the other hand, if there are multiple candidate patterns with the smallest evaluation value Yi (Y in S110), the selection unit 13 selects the candidate pattern with the smallest evaluation value Yi (Y in S110) when the value of the variable i is i max It is determined whether or not the value matches the value (S112). max is the total number of target existing base stations 30 and mobile base stations 20 (here, 4). maxIf it does not match (N in S112), the selection unit 13 adds 1 to i (S113) and repeats step S110 and subsequent steps.

[0045] i is i max 9 (Y in S112), the selection unit 13 selects the candidate pattern which is first in the sorting order in Fig. 9 (has the smallest candidate pattern number) among the candidate patterns with the smallest evaluation value Yi (S114), and proceeds to step S115. By steps S108 and onwards, it is possible to select a candidate pattern with a larger minimum received power at the terminal 50. According to the example in Fig. 9, the candidate pattern with candidate pattern number 45 is selected.

[0046] In step S115, the allocation unit 14 controls the allocation of the mobile base station 20 to the allocation position indicated by the allocation position sequence related to the candidate pattern selected in step S107, S111 or S114.

[0047] Next, the setting unit 15 sets the transmission power adjustment amount in the transmission power adjustment amount sequence of the selected candidate pattern to each mobile base station 20 (S116).

[0048] As described above, according to this embodiment, it is possible to reduce the imbalance in the number of terminals connected to each base station, which is expected to improve communication quality.

[0049] If the base station can set different transmission powers for the beacon signal and the data signal, the transmission power may be reduced only for the beacon signal without reducing the signal transmission power for the data signal.

[0050] In addition, the placement options for the mobile base station 20 may be limited in advance, taking into consideration the communication area of ​​the backhaul line that accommodates the mobile base station 20.

[0051] Furthermore, if the height of the mobile base station 20 can be adjusted, multiple placement options for the mobile base station 20 in the height direction may also be prepared.

[0052] Furthermore, when the mobile base station 20 can change the beam transmission direction (such as the direction of analog beamforming or the selection of antenna patterns for digital beamforming), the candidate patterns may be further differentiated depending on when the beam transmission direction is switched.

[0053] Furthermore, this embodiment may be applied not only to the mobile base station 20 but also to the placement of fixed base stations. For example, this embodiment may be applied to determining the placement position and transmission power of a newly established fixed base station.

[0054] In this embodiment, the mobile base station 20 is an example of a first base station, the existing base station 30 is an example of a second base station, and the control station 10 is an example of a base station control device.

[0055] Although the embodiment of the present invention has been described in detail above, the present invention is not limited to such specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0056] 1. Communication Systems 10 Control Station 11 Generation part 12 Calculation section 13 Selection section 14 Placement section 15 Setting section 20 Mobile base station 30 Existing base stations 40 Relay base station 50 terminals 100 Drive device 101 Recording media 102 Auxiliary storage 103 Memory device 104 CPU 105 Interface device B Bus

Claims

1. A base station control system including a first base station whose location has not been determined and a base station control device, The base station control device, a generation unit that generates a pattern of a plurality of combinations of terminal locations and transmission power candidates of the first base station based on a position of each terminal related to a plurality of combinations of terminals when a number of terminals equal to the number of the first base stations is selected from a plurality of terminals connected to an existing second base station; a calculation unit that calculates, for each of the patterns, the number of first terminals connected to the first base station and the number of second terminals connected to the second base station when the first base station is placed at a placement position related to the pattern and the first base station outputs a transmission power related to the pattern; a selection unit that selects one of the plurality of patterns based on the number of the first terminals and the number of the second terminals; A base station control system comprising:

2. The second base station is one of a plurality of existing base stations to which a relatively large number of terminals are connected.

2. The base station control system according to claim 1.

3. the calculation unit calculates, for each of the patterns, the number of third terminals that cannot connect to either the first base station or the second base station; The selection unit selects the pattern based on the number of the first terminals, the number of the second terminals, and the number of the third terminals.

3. The base station control system according to claim 1, wherein:

4. When one of the patterns cannot be selected, the selection unit further selects the pattern based on a reception power of the first terminal from the first base station and a reception power of the second terminal from the second base station, which are specified for each of the patterns.

4. The base station control system according to claim 1, wherein the base station control system further comprises:

5. a base station control device that controls a first base station whose location has not been decided, a generation step of generating a pattern of a plurality of combinations of terminals, the number of which is equal to the number of the first base stations, based on a position of each terminal in each combination, for a plurality of combinations of terminals when the number of terminals is equal to the number of the first base stations, from among a plurality of terminals connected to an existing second base station; a calculation step of calculating, for each of the patterns, the number of first terminals connected to the first base station and the number of second terminals connected to the second base station, when the first base station is placed at a placement position related to the pattern and the first base station outputs a transmission power related to the pattern; a selection step of selecting one of the plurality of patterns based on the number of the first terminals and the number of the second terminals; A base station control method comprising the steps of:

6. A base station control device that controls a first base station whose location has not been determined, a generation unit that generates a pattern of a plurality of combinations of terminal locations and transmission power candidates of the first base station based on a position of each terminal related to a plurality of combinations of terminals when a number of terminals equal to the number of the first base stations is selected from a plurality of terminals connected to an existing second base station; a calculation unit that calculates, for each of the patterns, the number of first terminals connected to the first base station and the number of second terminals connected to the second base station when the first base station is placed at a placement position related to the pattern and the first base station outputs a transmission power related to the pattern; a selection unit that selects one of the plurality of patterns based on the number of the first terminals and the number of the second terminals; A base station control device comprising:

7. 7. A program for causing a computer to function as the base station control device according to claim 6.

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