Control device, control method, wireless communication system, and program

Abstract

To appropriately rescue communication at a radio base station.SOLUTION: A control device for determining rescue carriers that rescue communication in a specific area and their antenna tilt angles includes an area aggregation unit that aggregates multiple areas to generate a single aggregated area, a rescue carrier selection unit that selects multiple rescue carriers for the aggregated area, and a tilt angle determination unit that optimizes multiple antenna tilt angles for the multiple rescue carriers.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technique for relieving an area in which communication is unavailable due to a failure of a wireless base station in a mobile communication network. [Background technology]

[0002] When a wireless base station breaks down due to a natural disaster or other reason, communication disruptions occur in the area that the base station covered. Wireless communication requires high availability, so recovery is required within a short time, such as a few minutes.

[0003] In response to this, a technology is being considered to recover from a failure by changing the depression angle (tilt angle) of the beam (carrier) of a specific frequency band in the antenna of a base station located around the area where the failure occurred (failure area) to cover (relieve) the failed area (for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Masanao Iwamoto, Akito Suzuki, and Shigeaki Harada, "Antenna Tilt Angle Control Method for Rapid Recovery of Disturbed Areas," IEICE Society Conference, B-7-6, September 2020. [Non-patent document 2] J. Kennedy and R. Eberhart, "Particle swarm optimization," Proceedings of ICNN'95 - International Conference on Neural Networks, 1995, pp. 1942-1948 vol.4, doi: 10.1109 / ICNN.1995.488968. Summary of the Invention [Problem to be solved by the invention]

[0005] However, with conventional techniques for recovering a failed area, there are cases where the failed area caused by a wireless base station failure cannot be covered completely, the failed area cannot be quickly recovered, or even if the failed area is covered sufficiently, the communication quality may be reduced. In other words, the conventional techniques have the problem that the failed area caused by a wireless base station failure may not be properly recovered.

[0006] The present invention has been made in view of the above points, and has an object to provide a technique that enables appropriate relief of a failure area caused by a failure of a wireless base station. [Means for solving the problem]

[0007] According to the disclosed technology, there is provided a control device for determining a rescue carrier for rescuing communication in a specific area and its antenna tilt angle, the control device comprising: an area aggregation unit that aggregates a plurality of adjacent areas to generate a single aggregated area; a relief carrier selection unit that selects a plurality of relief carriers for the aggregation area; a tilt angle determination unit that simultaneously optimizes a plurality of antenna tilt angles for the plurality of rescue carriers; A control device is provided comprising: [Effects of the Invention]

[0008] The disclosed technology provides a technology that enables appropriate recovery of a failure area caused by a failure of a wireless base station. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a configuration diagram of a system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating the configuration of a radio base station control device. [Figure 3] 4 is a flowchart illustrating the operation of the radio base station control device. [Figure 4] FIG. 10 is a diagram showing dmax and dmin. [Figure 5] FIG. 1 shows two sectors. [Figure 6] FIG. 2 illustrates an example of a hardware configuration of the apparatus. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] (Definition of terms) First, the definitions of "antenna, carrier" and "area mesh" used in this specification will be explained.

[0012] (1) Antenna, carrier A base station consists of multiple antennas, each responsible for communication coverage in a specific direction.Antennas consist of multiple carriers, and each carrier in a given antenna is responsible for communication coverage in an area in a specific frequency band in the same direction.At this time, a tilt angle is set for each carrier, and different angles result in different coverage areas.

[0013] Since there are cases where only some of the antennas of a base station fail, this embodiment considers failures in antenna units rather than failures in base stations.

[0014] (2) Regional Grid The regional mesh is "an area divided into meshes of approximately the same size based on latitude and longitude" as defined by the Administrative Management Agency (currently the Ministry of Internal Affairs and Communications). In this embodiment, the area is considered in units of meshes.

[0015] There are multiple regional meshes depending on the granularity of the mesh, i.e., the size of the area per mesh. For example, there are half regional meshes (each side is approximately 500m long) and one-eighth regional meshes (each side is approximately 125m long).

[0016] The coarser the regional mesh, the less calculation is required to calculate the coverage area, and the shorter the time required to estimate the coverage area. The granularity of the regional mesh can be predetermined, for example, by the operator of the radio base station control device 100 in this embodiment.

[0017] (About the assignment) Here, the conventional technology and its problems will be described in detail. In the following description, the contents disclosed in Non-Patent Document 1 are publicly known, but the contents of the explanation of the problems are not publicly known.

[0018] (1) Conventional Technology and its Issues 1 As an existing method, Non-Patent Document 1 discloses a method for covering a faulty area caused by a base station failure, etc. In this method, one carrier (relief carrier) is selected from the base stations surrounding the faulty area to provide relief, and the tilt angle of the carrier is changed so that the faulty area is covered.

[0019] This process is repeated until the affected area is fully covered or until all carriers of nearby base stations are in use. If multiple base stations fail at the same time, the affected areas associated with each failure are rescued in turn.

[0020] In this case, the rescue carrier must be selected from carriers other than those that have been used for rescue up until now. Therefore, with the technology disclosed in Non-Patent Document 1, particularly in cases where "simultaneous failures of multiple base stations occur in areas such as rural areas with few surrounding base stations (surrounding stations)," there is a high possibility that there will be a shortage of rescue carriers for the failed area to be rescued later, resulting in the occurrence of a failed area that cannot be covered.

[0021] (2) Conventional Technology and its Issues 2 As mentioned above, the technology disclosed in Non-Patent Document 1 repairs multiple failed areas in order for each failed area. Furthermore, for each failed area, a repair carrier is selected one by one, and the tilt angle is calculated.

[0022] Therefore, the time required for all control calculations increases according to the number of failed base stations, and it may not be possible to provide prompt relief for multiple failed areas.

[0023] (3) Conventional Technology and its Issues 3 As mentioned above, the technology disclosed in Non-Patent Document 1 selects a rescue carrier and calculates the tilt angle for each failed area. In addition, the purpose of this is to cover only the failed area, and overlap with the coverage area of an already selected rescue carrier is not taken into consideration.

[0024] Therefore, even if sufficient coverage is achieved, there is a possibility that radio wave interference will be significant and communication quality will be poor.

[0025] (Features (Key Points) of the Technology Relating to the Embodiments) In the technology according to the present embodiment, in order to solve the above-mentioned problems, a radio base station control device (described later) controls the tilt angles of neighboring base stations in order to cover a faulty area caused by a base station failure or the like. The technology according to the present embodiment can solve the above-mentioned problems by being provided with the following features (points) in particular. Note that the points described below are points in the technology according to the embodiment, and it is not essential for the invention to include all of the points.

[0026] <Point 1> When multiple base stations fail and the failure areas associated with each are adjacent to each other, they are treated as a single failure area, and the rescue carrier and tilt angle are calculated for this.

[0027] <Point 2> Relief carriers are prepared in advance for the faulty area, and their tilt angles are simultaneously optimized to adopt a combination of tilt angles that provides a high coverage rate.

[0028] <Point 3> In the simultaneous optimization of tilt angles, the objective function is not only the "coverage rate of the fault area," but also the "size of the coverage area of the relief carrier" is added as a penalty term.

[0029] (Effects of the Technology According to the Embodiments) The technology according to the present embodiment having the above-mentioned features provides the following effects.

[0030] <Effect 1> Point 1 can alleviate the problem of a lack of candidates for rescue carriers in the affected area, as described in Challenge 1. This can improve the coverage rate compared to existing methods when multiple base station failures occur in an area with few surrounding stations.

[0031] <Effect 2> Point 1 solves problem 2 by preventing the control calculation time from increasing in proportion to the number of failed base stations, making it possible to quickly provide relief even when there are a large number of failed base stations.

[0032] <Effect 3> Point 2 allows the tilt angles of multiple relief carriers to be optimized simultaneously, thereby improving the accuracy of coverage compared to the conventional method of changing the tilt angle for each relief carrier sequentially.

[0033] <Effect 4> Point 3 prevents each rescue carrier from unintentionally expanding its coverage area, reducing overlap in coverage areas between rescue carriers. This reduces radio interference between rescue carriers, as explained in Issue 3, more than with conventional methods, and is expected to improve communication quality.

[0034] (Overall system configuration) Fig. 1 shows an example of the overall configuration of a wireless communication system according to an embodiment of the present invention. As shown in Fig. 1, the system according to this embodiment has a configuration in which a plurality of wireless base stations 10 and a wireless base station control device 100 are connected to a network 200. The network 200 is, for example, a network that includes a mobile core network. Communication terminals exist under the control of each wireless base station, and each communication terminal communicates with the wireless base station wirelessly.

[0035] The configuration and operation of the radio base station controller 100 according to this embodiment will be described in detail below.

[0036] (Configuration example of radio base station controller 100) 2 shows a configuration diagram of a radio base station controller 100 according to an embodiment of the present invention. As shown in FIG. 2, the radio base station controller 100 includes an input receiving unit 110, a data processing unit 120, and a radio base station control unit .

[0037] 2, data processing unit 120 includes a rescue priority determination unit 121, a rescue carrier selection unit 122, a failure area aggregation unit 123, and a tilt angle determination unit 123. Radio base station control unit 130 includes a receiving unit 131 and a transmitting unit 132.

[0038] The radio base station controller 100 may be a single physical device, or may be a system consisting of multiple physical devices. For example, the "input reception unit 110 + data processing unit 120" may be a single device, and the radio base station controller 130 may be a single device. The "input reception unit 110 + data processing unit 120" or the "data processing unit 120" may be called a controller. The functions of each unit are outlined below.

[0039] <Radio base station control unit 130> The receiver 131 and transmitter 132 of the wireless base station controller 130 are each capable of communicating with a wireless base station, with the receiver 131 receiving information from the wireless base station and the transmitter 132 transmitting information to the wireless base station.

[0040] <Input Receiving Unit 110> The input receiving unit 110 receives from the wireless base station control unit 130 "information on each wireless base station," "information on a faulty antenna in a faulty station (faulty antenna)," and "important area information."

[0041] The "information about each wireless base station" includes, for example, the following information:

[0042] - Location (latitude, longitude), height, and direction of all carriers installed at wireless base stations Vertical and horizontal beam widths of each carrier beam Tilt angle set for each carrier Neighboring station information In this embodiment, a wireless base station that is located within a distance of n (km) from a certain wireless base station (a target wireless base station (for example, a faulty station)) and is not a faulty station is defined as an adjacent station of the target wireless base station.

[0043] "Information about a faulty antenna (faulty antenna) within a faulty station" includes, for example, the following information. Note that the "area" below is defined as a collection of regional meshes. Also, the "area covered by the faulty antenna" below is defined as the failure area.

[0044] - Whether there are any important facilities in the area covered by the failed antenna The area covered by the faulty antenna Number of active users communicating with the faulty antenna -Total traffic volume handled by the failed antenna The "important area information" is as follows:

[0045] - Important areas are regional meshes that include important facilities or collections of regional meshes that are designated in advance by the operator. Information is managed as important area information by embedding flag information indicating important areas in these meshes in advance.

[0046] <Failure Area Aggregation Unit 123> The failure area aggregation unit 123 receives information from the input receiving unit 110 and generates a failure area by aggregating adjacent failure areas into a single failure area. A single failure area into which multiple failure areas are aggregated may be called an aggregated failure area.

[0047] <Relief Priority Determination Unit 121> The repair priority determination unit 121 receives information from the input reception unit 110 and the failure area aggregation unit 121 and determines the repair priority of the failure area. The repair priority is defined based on the properties of the failure area. Repair is considered one by one, starting with the failure area with the highest repair priority.

[0048] <Relief Carrier Selection Unit 122> The rescue carrier selection unit 122 selects a rescue carrier from the base stations located in the vicinity of the failure area to be rescued.

[0049] <Tilt Angle Determination Unit 124> The tilt angle determination unit 124 determines a tilt angle for the relief carriers selected by the relief carrier selection unit 122 such that a high coverage rate for the faulty area is obtained and the overlap between the coverage areas of the relief carriers is reduced. The specific operation will be described later.

[0050] The tilt angle determination unit 124 transmits the determined tilt angle to the radio base station control unit 130, and changes the tilt angle of the rescue carrier in the radio base station.

[0051] (Operation of the radio base station controller 100) An example of the operation of the radio base station controller 100 having the above configuration will now be described in detail along the steps of the flowchart in FIG.

[0052] <s1> In S1, the input receiving unit 110 receives input of failure area information and important area information as information necessary for rescue from the radio base station control unit 130. The information received by the input receiving unit 110 is passed to the failure area summarizing unit 123 and the rescue priority determining unit 121.

[0053] <s2> In S2, the failure area aggregation unit 123 aggregates adjacent failure areas into one. That is, for each failure area, the failure area aggregation unit 123 aggregates adjacent areas into a single failure area. An upper limit may be set for the number of areas to be aggregated and the size of the areas.

[0054] At this time, the failure area consolidation unit 123 also adds up the number of active users who were communicating and the total amount of traffic being processed, and consolidates the information into one failure area.

[0055] <S3、S4> If there are multiple failed areas that have been subjected to the process of S2, the radio base station control device 100 recovers the failed areas one by one starting from the failed area with the highest recovery priority.

[0056] Therefore, in S3, the repair priority determination unit 121 checks whether there are any unrepaired failure areas, and if there are no unrepaired failure areas, the process ends. If there are any unrepaired failure areas, the process proceeds to S4, where the repair priority determination unit 121 determines the repair priority of each unrepaired failure area and selects one of the unrepaired failure areas with the highest repair priority.

[0057] The method by which the rescue priority determination unit 121 determines the rescue priority of each failed area is not limited to a specific method, but the rescue priority can be determined based on an index corresponding to the urgency of establishing communication, such as "presence or absence of important facilities in the failed area," "size of important areas within the failed area," "size of the failed area," "number of active users communicating with a failed antenna associated with the failed area," "total traffic volume processed by a failed antenna associated with the failed area," etc. The specific index may be determined appropriately by the system operator.

[0058] For example, when the rescue priority determination unit 121 determines the rescue priority based on the "number of active users communicating with the failed antenna," the rescue priority is set higher as the number of active users increases. Note that the rescue priority determination unit 121 may determine the rescue priority using one or more of the following: "presence or absence of important facilities in the failure area," "size of important areas within the failure area," "size of the failure area," "number of active users communicating with the failed antenna linked to the failure area," and "total traffic volume processed by the failed antenna linked to the failure area."

[0059] <s5> In S5, the relief carrier selection unit 122 selects a relief carrier for the damaged area to be relieved. Here, a plurality of carriers are selected from the base stations around the damaged area and used as relief carriers. Specifically, it is as follows.

[0060] The relief carrier selection unit 122 first calculates the centroid of the damaged area. Then, m base stations are selected in the order of proximity to this centroid, and one carrier with the lowest frequency band at each base station is selected from each base station, and these are used as relief carriers.

[0061] For example, assume that in the order of proximity to the centroid of the damaged area, there are base station 1, base station 2, and base station 3, and the relief carrier of base station 1 is carrier 1, the relief carrier of base station 2 is relief carrier 2, and the relief carrier of base station 3 is relief carrier 3. In this case, first, for relief carrier 1, S6 to S8 are executed. If the determination in S8 is No, then for relief carrier 1 and relief carrier 2, S6 to S8 are executed. If the determination in S8 is Yes, relief is executed at the tilt angles determined for each of relief carrier 1 and relief carrier 2. Note that such processing is an example. For example, S6 to S8 may be executed for a plurality of relief carriers from the beginning.

[0062] In this embodiment, based on the property that radio wave attenuation due to distance is less for lower frequency bands, carriers in lower frequency bands with a prospect of covering areas further away are preferentially selected as relief carriers. In addition, if the traffic load situation for each carrier can be obtained, the carrier with the lowest load may be selected as the relief carrier.

[0063] Regarding the base stations from which the relief carriers are selected, it may be limited to the adjacent stations of the failed antenna in the damaged area. In this case, if the number l of adjacent stations is l < m, relief carriers are selected from all adjacent stations.

[0064] <s6> In S6, the tilt angle determination unit 124 estimates the radio wave propagation range for each combination of the relief carrier and tilt angle. These radio wave propagation range estimates can be calculated independently for each combination, allowing for parallel calculations. This makes it possible to speed up the calculations in S6.

[0065] The relief carrier has a settable range of tilt angles. In this embodiment, the tilt angle is changed within the settable range in granularity of a predetermined angle unit, such as 0.5° or 1.0°. The tilt angles prepared for each predetermined angle unit within the settable range are called "each tilt angle." Then, the radio wave propagation range is estimated independently for all combinations of each relief carrier and each tilt angle.

[0066] For example, if the settable range of the tilt angle of a certain relief carrier is 1° to 15° and the specified angle unit is 1°, the radio wave propagation range of that relief carrier is estimated for each of the 15 tilt angles {1°, 2°, ... 14°, 15°} using the method described below.

[0067] Generally, the precise radio wave propagation range is calculated in three dimensions: latitude, longitude, and altitude. However, to achieve rapid relief, it is necessary to estimate the radio wave propagation range in a shorter time. Therefore, in this embodiment, only the area covered by radio waves at 1.5 m above ground is considered as the radio wave propagation range. Note that, in this example, assuming a communication terminal held by a user, 1.5 m above ground is used as an example, but any height other than 1.5 m may be used.

[0068] This reduces the accuracy of the estimation results because the radio wave propagation range is not estimated in three dimensions, but it is expected that performance will improve in terms of calculation speed.

[0069] Moreover, tilt angle determination section 124 according to this embodiment calculates the radio wave propagation range using geometric approximation using a sector shape.

[0070] To accurately calculate the radio wave propagation range, it is common to estimate the electric field strength for each point and use the estimated results. However, as mentioned above, in order to prioritize speedy relief, it is necessary to estimate the radio wave propagation range in a shorter time. Therefore, in this embodiment, taking into account the property that "radio wave propagation loss increases with distance," it is assumed that radio waves reach an equal distance over the entire range of the beam width, and under this assumption, the radio wave propagation range is calculated using a geometric approximation using a sector shape. The specific calculation method is as follows.

[0071] Here, the position of the relief carrier is (latitude lat, longitude lon), the height of the carrier is h, and the central direction of the carrier is az center The tilt angle of the carrier is x, and the vertical and horizontal beam widths (°) of the carrier's beam are α and β, respectively. The height h of the carrier is the height from 1.5 m above the ground.

[0072] Also, for the setting range of tilt angle x, the minimum value is x min , the maximum value is x max Let's say.

[0073] At this time, the range of the carrier beam angle in the vertical direction is [v min ,v max ]. v min ,v max are calculated using the following formulas:

[0074] v min =max{x-α / 2,x min }, v max =min{x+α / 2,x max } The radius of the two sectors used to approximate the radio wave propagation range is d. min , d max Then, they can be calculated using the following formulas:

[0075] d min =h / tan(v max ), d max =h / tan(v min ) The d obtained from the above formula min , d max This is illustrated in Figure 4.

[0076] The starting azimuth of the two sectors mentioned above is az. start , the terminal azimuth is az end Then, these can be calculated by the following formula:

[0077] az start =az center +β / 2, az end =az center -β / 2 As mentioned above, the starting and ending azimuth angles of the two sectors are the same. However, az start , a-z end The domain of 0≦az start ,az end <360°. From the above formula, az start , a-z end If the calculated value is outside the domain of definition, the remainder modulo 360 is used.

[0078] Center is point (lat,lon), radius is d min , the central angle is az start -az end So, az start From az end Let the sector A be the sector facing the direction of . Similarly, the center is the point (lat,lon) and the radius is d max , the central angle is az start -az end So, az start From az end Let the sector facing in the direction of be sector B.

[0079] Tilt angle determination unit 124 determines sector A and sector B using the above calculations, and determines the area included in sector B that is not included in sector A as the estimated result of the radio wave propagation range. Sector A and sector B are illustrated in Figure 5. Figure 5 shows the two sectors as viewed from above.

[0080] The tilt angle determination unit 124 performs the above calculation for each relief carrier and each tilt angle to estimate the radio wave propagation range.

[0081] <s7> In S7, tilt angle determination unit 124 calculates the tilt angles of the relief carriers. Specifically, for each relief carrier selected in S5, tilt angle determination unit 124 calculates a combination of tilt angles that covers the failure area and reduces the overlap of area coverage between relief carriers.

[0082] Here, an objective function is defined using the tilt angle of each rescue carrier as input, and the combination of tilt angles that yields the best objective function value is adopted as the calculation result. The objective function is defined by combining the "coverage rate of the faulty area," "coverage rate of the important area (if an important area exists)," and "coverage area size of the rescue carrier." The faulty area coverage rate, important area coverage rate, and rescue carrier coverage area size are calculated using the estimated radio wave propagation range corresponding to each carrier and tilt angle calculated in S6.

[0083] However, as a constraint, an upper limit is set on the number of meshes in the regional area (described later) for each carrier's coverage area, and the tilt angle is calculated within a range that does not exceed this limit.

[0084] In the following, we will explain how to calculate the fault area coverage rate, important area coverage rate, and coverage area size of the relief carrier, and then explain how to calculate the tilt angle combinations.

[0085] <How to calculate the coverage rate of the affected area> First, a method for calculating the failure area coverage rate will be described.

[0086] Here, the radio wave propagation range calculated in S6 is defined as the coverage area. Also, the area originally covered by the relief carrier is defined as the foot area. The foot area may be acquired as base station information, or the tilt angle determination unit 124 may estimate the foot area using the radio wave propagation range estimation method described above. The combined area of the failure area and the foot area is defined as the relief target failure area.

[0087] The tilt angle determination unit 124 compares the coverage area with the fault area to be repaired, calculates the proportion of the fault area to be repaired that is included in the coverage area, and sets this as the fault area coverage rate. The coverage rate is calculated using the number of meshes in the regional mesh.

[0088] If an area of the cover area that is also included in the repair target repair area is defined as a repairable repair area, when using the regional mesh as described above, the tilt angle determination unit 124 calculates the repair area cover rate using the following formula.

[0089] (Failure area coverage rate) = (Number of meshes in the repairable failure area) / (Number of meshes in the repairable failure area) <Calculation method for key area coverage rate> Next, a method for calculating the important area coverage rate will be described.

[0090] If an important area exists within an obstruction area, the area that includes the important area and the area under the ball's feet is defined as the important area requiring relief.

[0091] The tilt angle determination unit 124 compares the cover area with the important area to be repaired, calculates the proportion of the important area to be repaired that is included in the cover area, and sets this as the important area coverage rate.

[0092] That is, if an area of the cover area that is also included in the important area to be repaired is defined as an important repairable area, tilt angle determination section 124 calculates the important area cover rate using the following formula.

[0093] (Coverage rate of important areas) = (Number of meshes in salvageable important areas) / (Number of meshes in salvageable important areas) <Calculation method for the coverage area size of the relief carrier> Next, a method for calculating the cover area size of a relief carrier will be described. As shown below, the tilt angle determination unit 124 calculates the cover area size of each carrier as the ratio of the number of meshes in the calculated cover area to the upper limit of the number of meshes in the cover area.

[0094] (Carrier coverage area size) = ((Number of meshes in the coverage area)) / ((Maximum number of meshes in the coverage area)) The tilt angle determination unit 124 calculates this value for each rescue carrier, and uses the average value (coverage area size of rescue carrier) as the penalty term of the objective function. This prevents each rescue carrier from unnecessarily expanding its coverage area in order to improve the coverage rate, and makes it possible to suppress overlapping of the coverage areas between rescue carriers.

[0095] <How to calculate the tilt angle> Next, a method for calculating the tilt angle will be described. First, an objective function is defined as follows:

[0096] (Objective function) = α (important area coverage rate) + β (faulty area coverage rate) - γ (coverage area size of rescue carrier).

[0097] α, β, and γ are parameters that weight each item and are set in advance. For example, if the priorities for rescue are "maximizing the coverage rate of important areas," "maximizing the coverage rate of faulty areas (excluding important areas)," and "minimizing overlap of covered areas," then the order of α>β>γ (e.g., α=10, β=5, γ=1) may be used.

[0098] Next, tilt angle determination unit 124 maximizes the objective function using particle swarm optimization (Non-Patent Document 2). Particle swarm optimization is a metaheuristic method for obtaining an approximate solution to a combinatorial optimization problem. It prepares multiple solution candidates for the optimization problem, called particles, and updates each particle while sharing the objective function values between the particles. Note that using particle swarm optimization to maximize the objective function is just one example.

[0099] Here, the combination of all the relief carrier tilt angles corresponds to one particle. The i-th particle is x i Let x i The tilt angle of the jth relief carrier in ij (1 <j<m)とすると、x i =[θ i1 ,θ i2 ,...,θ im ].

[0100] In particle swarm optimization, each particle x i is updated according to the following formula:

[0101] Particle update equation: x i (t+1)=x i (t)+v i (t+1) The update formula for particle update velocity is: v i (t+1)=wv i (t+1)+c1r1(x i p (t)-x i (t))+c2r2(x g (t)-x i (t)) However, the meaning of each symbol (variable, etc.) is as follows:

[0102] x i (t): Particles at update count t v i (t): Particle velocity at update time t x i p (t): The best solution for particle i up to update count t x g (t): The best solution for all particles up to update count t w and c1c2 are coefficients, and r is a random number.

[0103] The update ends when the objective function value stops increasing or when the preset number of updates is reached. The particle with the largest objective function value among all particles obtained through the updates up to this point is adopted as the solution.

[0104] In addition to the above processing, if the coverage of the important area is given top priority, the particle with the largest coverage rate of the important area among the obtained particles may be used.

[0105] In the above example, an objective function is used whose optimization objective is to maximize the objective function value, but this is just an example. An objective function whose optimization objective is to minimize the objective function value may also be used.

[0106] <S8、S9> In S8, tilt angle determination unit 124 determines whether the calculation result satisfies the condition for ending the rescue, thereby determining whether the rescue should be ended.

[0107] The condition for ending rescue is, for example, "Through the control of the rescue station and tilt angle up to now, the important area coverage rate of the faulty area is P% or more and the faulty area coverage rate is Q% or more" or "(Number of rescue carriers) = (Number of adjacent stations l)".

[0108] Note that (number of rescue carriers)=(number of adjacent stations l) corresponds to a determination that the number of rescue carriers cannot be increased any further.

[0109] If the termination condition of S8 is met, the recovery of the faulty area currently being recovered is terminated, and the process proceeds to S9, where information on "each recovery carrier and tilt angle" is transmitted to the wireless base station control unit 130. Then the process returns to S3.

[0110] If the condition is not met in S8, the number of relief carriers is increased by one, and the process returns to S5, where the tilt angles of all relief carriers are recalculated.

[0111] (Example of hardware configuration) The radio base station control device (or control device) in this embodiment can be realized by, for example, making a computer execute a program describing the processing contents described in this embodiment. Note that this "computer" may be a physical machine or a virtual machine on the cloud. When a virtual machine is used, the "hardware" described here is virtual hardware.

[0112] The above program can be recorded on a computer-readable recording medium (such as a portable memory) and stored or distributed. The above program can also be provided via a network such as the Internet or email.

[0113] Fig. 6 is a diagram showing an example of the hardware configuration of the computer. The computer in Fig. 6 includes a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, and the like, all of which are interconnected via a bus BS.

[0114] A program for realizing processing on the computer is provided by a recording medium 1001 such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 to the auxiliary storage device 1002 via the drive device 1000. However, the program does not necessarily have to be installed from the recording medium 1001, but may be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program as well as necessary files, data, etc.

[0115] The memory device 1003 reads and stores the program from the auxiliary storage device 1002 when an instruction to start the program is received. The CPU 1004 implements functions related to the radio base station controller 100 (controller) in accordance with the program stored in the memory device 1003. The interface device 1005 is used as an interface for connecting to a network. The display device 1006 displays a GUI (Graphical User Interface) or the like according to the program. The input device 1007 is composed of a keyboard, mouse, buttons, a touch panel, or the like, and is used to input various operation instructions. The output device 1008 outputs the results of calculations.

[0116] (Addendum) This specification describes at least the control device, wireless communication system, and program described in the following sections. (Section 1) A control device that determines a relief carrier and its antenna tilt angle for relieving communication in a specific area, an area aggregation unit that aggregates a plurality of adjacent areas to generate a single aggregated area; a relief carrier selection unit that selects a plurality of relief carriers for the aggregation area; a tilt angle determination unit that simultaneously optimizes a plurality of antenna tilt angles for the plurality of rescue carriers; A control device comprising: (Section 2) The rescue carrier selection unit selects, as a rescue carrier, a carrier with the lowest frequency in each base station selected in order from closest to the center of gravity of the aggregation area. 2. The control device according to claim 1. (Section 3) The tilt angle determination unit performs the optimization using an objective function that includes a coverage area size of a relief carrier as a penalty term. 3. The control device according to claim 1 or 2. (Section 4) The tilt angle determination unit performs the optimization using the objective function including an area coverage rate for the aggregation area, an important area coverage rate for an important area in the aggregation area, and a coverage area size of the relief carrier. 4. The control device according to claim 3. (Section 5) The control device according to any one of claims 1 to 4, and a radio base station that communicates using a rescue carrier and an antenna tilt angle determined by the control device. A wireless communication system comprising: (Section 6) A program for causing a computer to function as each part of the control device described in any one of paragraphs 1 to 4.

[0117] Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0118] 10. Radio base station 100 Radio base station control device 110 Input reception unit 120 Data Processing Unit 121 Relief Priority Determination Division 122 Relief Carrier Selection Department 123 Fault Area Consolidation Unit 124 Tilt angle determination unit 130 Radio base station control unit 131 Receiving unit 132 Transmitter 1000 Drive Device 1001 Recording media 1002 Auxiliary storage device 1003 Memory device 1004 CPU 1005 Interface device 1006 Display device 1007 Input Device 1008 Output Device

Claims

1. A control device that determines a relief carrier and its antenna tilt angle for relieving communication in a specific area, an area aggregation unit that aggregates a plurality of areas to generate a single aggregated area; a relief carrier selection unit that selects a plurality of relief carriers for the aggregation area; a tilt angle determination unit that optimizes a plurality of antenna tilt angles for the plurality of rescue carriers; A control device comprising:

2. The rescue carrier selection unit selects, as a rescue carrier, a carrier with the lowest frequency in each base station selected in order from closest to the center of gravity of the aggregation area. The control device according to claim 1 .

3. The tilt angle determination unit performs the optimization using an objective function that includes a coverage area size of a relief carrier as a penalty term. The control device according to claim 1 or 2.

4. The tilt angle determination unit performs the optimization using the objective function including an area coverage rate for the aggregation area, an important area coverage rate for an important area in the aggregation area, and a coverage area size of the relief carrier. The control device according to claim 3 .

5. The control device according to any one of claims 1 to 4, and a radio base station that performs communication using a rescue carrier and an antenna tilt angle determined by the control device. A wireless communication system comprising:

6. A control method executed by a control device that determines a rescue carrier and its antenna tilt angle for rescuing communication in a specific area, comprising: an area aggregation step of aggregating a plurality of areas to generate a single aggregated area; a rescue carrier selection step of selecting a plurality of rescue carriers for the aggregation area; a tilt angle determination step of optimizing a plurality of antenna tilt angles for the plurality of rescue carriers; A control method comprising:

7. A program for causing a computer to function as each unit in the control device according to any one of claims 1 to 4.

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