Correction device, correction method, and program

Abstract

This correction device mitigates errors in estimating the state of a radio wave arrival from a base station by being provided with: a reception power calculation unit configured to calculate, for each of a plurality of points, a reception power value from a candidate station location; a determination unit configured to determine, for each said point, whether or not it is necessary to correct the reception power value of that point on the basis of a comparison between the reception power value of that point and the reception power value of said point within a predetermined range from that point; and a correction unit configured to correct the reception power value determined to be necessary to be corrected, on the basis of the reception power value of said point within a predetermined range from the point pertaining to that reception power value.

Description

Correction device, correction method, and program

[0001] The present invention relates to a correction device, a correction method, and a program.

[0002] Because there are limits to the range of radio waves from a wireless base station and the number of terminals that one wireless base station can accommodate, if there are too few wireless base stations installed, the area coverage and terminal accommodation will be insufficient. On the other hand, if there are too many wireless base stations installed, the cost of the base station equipment itself, as well as installation and operation costs, will increase, resulting in inefficiency. Therefore, it is necessary to properly design wireless stations so that a sufficient number of wireless base stations are placed in appropriate locations.

[0003] To build a coverage area for a wireless communication system, base station placement design is performed to determine the base station placement (installation location and antenna direction). In the base station placement design, after selecting the base station placement, methods such as ray tracing are used to perform simulation evaluation of the coverage area (Non-Patent Document 1).

[0004] Furthermore, as a conventional technique for station placement design, for example, Non-Patent Document 2 proposes a method for combining a plurality of wireless systems to perform wireless station placement design based on communication quality and cost.

[0005] Tetsuro Imai, "Ray Tracing Method Using Genetic Algorithm for Radio Wave Propagation Estimation," NTT DoCoMo Technical Journal Vol. 15 No. 3 Toshiro Nakahira, Daisuke Murayama, Satoshi Takatani, Kenichi Kawamura, Takatsugu Moriyama, "Multi-Wireless Area Design Method Based on Communication Capacity and Base Station Cost," IEICE General Conference, B-5-97, Mar. 2022

[0006] In the ray tracing method, which evaluates the radio wave coverage of an area by emitting rays (light) from a base station, the ray tracing evaluation results may show that an area is actually covered by radio waves as a dead area, due to incompleteness of the ray illumination conditions and building data used. Therefore, when using information on radio wave coverage to design a station, errors in the information on radio wave coverage may reduce the accuracy of the radio station design results.

[0007] The present invention has been made in view of the above points, and has as its object to reduce estimation errors in the radio wave coverage status from a base station.

[0008] In order to solve the above problem, the correction device has a received power calculation unit configured to calculate a received power value from a candidate base station location for each of a plurality of points, a determination unit configured to determine, for each point, whether or not the received power value of the point needs to be corrected based on a comparison between the received power value of the point and the received power values ​​of points within a predetermined range from the point, and a correction unit configured to correct the received power value determined to need correction based on the received power values ​​of the points within a predetermined range from the point related to the received power value.

[0009] This can reduce the estimation error of the radio wave arrival status from the base station.

[0010] Fig. 1 is a diagram showing an example of a hardware configuration of a station placement design device 10 according to an embodiment of the present invention. Fig. 2 is a diagram showing an example of a functional configuration of the station placement design device 10 according to an embodiment of the present invention. Fig. 3 is a flowchart for explaining an example of a processing procedure executed by the station placement design device 10. Fig. 4 is a diagram for explaining a determination of whether or not correction of a received power value from a certain base station of a certain terminal is necessary. Fig. 5 is a diagram for explaining a method of correcting a received power value.

[0011] In this embodiment, a station location design device 10 is disclosed that performs a correction calculation on the input received power estimation result (correcting the received power value at a certain evaluation point using the median / average value of the surrounding received power values, etc.) to mitigate estimation errors in the radio wave arrival status from the base station.

[0012] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a diagram showing an example of the hardware configuration of a station location design device 10 according to an embodiment of the present invention. The station location design device 10 in Fig. 1 includes a drive device 100, an auxiliary storage device 102, a memory device 103, a processor 104, and an interface device 105, all of which are interconnected via a bus B.

[0013] A program that realizes the processing in the station design device 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, etc.

[0014] When an instruction to start the program is received, the memory device 103 reads and stores the program from the auxiliary storage device 102. The processor 104 is a CPU or a GPU (Graphics Processing Unit), or a CPU and a GPU, and executes functions related to the station design device 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.

[0015] 2 is a diagram showing an example of the functional configuration of a station location design device 10 according to an embodiment of the present invention. In FIG. 2, the station location design device 10 includes an initial placement unit 11, a received power calculation unit 12, a determination unit 13, a correction unit 14, a conversion unit 15, a base station placement selection unit 16, and an output unit 17. Each of these units is implemented by a processor 104 executing one or more programs installed in the station location design device 10. The station location design device 10 also uses a data storage unit 121. The data storage unit 121 can be implemented using, for example, the auxiliary storage device 102 or a storage device connectable to the station location design device 10 via a network.

[0016] The following describes the processing procedure executed by the station placement design device 10. FIG.

[0017] In step S101, the initial placement unit 11 places multiple terminals and multiple base stations in an area (hereinafter referred to as the "target area") where the base stations are to be placed. At this time, the initial placement unit 11 places each base station in a provisional placement state and each terminal in an unaccommodated state. The placement positions of each base station and each terminal are stored in advance in the data storage unit 121. The base stations in the provisional placement state serve as candidates for the placement positions of the base stations. Furthermore, the terminals serve as points (evaluation points) for evaluating the reception status of radio waves from each base station. Therefore, the placement positions of the terminals in step S101 may differ from their actual placement positions.

[0018] Next, the received power calculation unit 12 calculates an estimate of the received power (hereinafter referred to as the "received power value") from each base station at each terminal (each location) based on the wireless communication method that each base station plans to use and the corresponding antenna pattern (S102). The calculation of the received power value can be performed using a known radio wave propagation estimation technique or the like. Parameters required for the calculation (e.g., wireless parameters of the base station, etc.) can be stored in advance in the data storage unit 121.

[0019] Next, for each terminal, the determination unit 13 determines whether correction is necessary for the received power value from each base station based on a comparison between the received power value of the terminal and the received power values ​​of terminals within a predetermined range from the terminal (S103).

[0020] FIG. 4 is a diagram illustrating a determination of whether a certain terminal needs to correct its received power value from a certain base station. In FIG. 4, each circle represents one terminal, and different backgrounds of the circles indicate different received power values. In FIG. 4, terminal t1 is the target of the determination of whether correction is necessary. In this case, the determination unit 13 determines whether correction is necessary for terminal t1's received power value from the base station based on a comparison between the received power value of terminal t1 and the values ​​of a group of terminals within radius R from terminal t1. Specifically, the determination unit 13 determines whether the difference between the received power value of terminal t1 and the average or median received power value of the group of terminals within radius R is equal to or greater than threshold P. If the difference between the received power value of terminal t1 is equal to or greater than threshold P, the determination unit 13 determines that correction is necessary for terminal t1's received power value from the base station. The determination unit 13 performs this process for all terminals and all base stations. Note that true values ​​are used as received power values. The radius R and the threshold value P are set in advance and stored in the data storage unit 121 .

[0021] Next, the correction unit 14 corrects the received power value determined to require correction based on the received power value from the base station associated with that received power value at terminals within a predetermined range from the terminal associated with that received power value (S104).

[0022] FIG. 5 is a diagram illustrating a method for correcting a received power value. (1) in FIG. 5 shows a state in which it has been determined that the received power value of terminal t1 from a certain base station needs to be corrected. (2) in FIG. 5 shows a state in which the received power value of terminal t1 from the base station has been corrected. The correction unit 14 corrects the received power value of terminal t1 based on the received power values ​​of a group of terminals included within a radius R from terminal t1 from the base station. Specifically, the correction unit 14 sets the average or median of the received power values ​​of the group of terminals as the corrected received power value of terminal t1, or sets the average of the received power value of terminal t1 and the average or median as the corrected received power value of terminal t1. The correction unit 14 performs this process for the received power values ​​from all base stations for all terminals.

[0023] Next, the conversion unit 15 converts the received power value from each base station at each terminal into a wireless transmission rate according to the wireless communication method of each base station (S105), in order to obtain data that can be compared between different wireless communication methods.

[0024] In steps S106 to S112, the base station placement selection unit 16 uses a greedy algorithm to select a base station placement that maximizes the number of terminals that can be accommodated per base station cost. However, the base station placement may be selected using an algorithm other than steps S106 to S112.

[0025] In step S106, the base station allocation selection unit 16 determines whether all terminals have been accommodated by any base station, i.e., whether the status of all terminals has changed from an unaccommodated state to an accommodated state.

[0026] If there are any unaccommodated terminals remaining (No in S106), the base station allocation selection unit 16 determines whether there is a base station in a provisional allocation state that can accommodate one or more unaccommodated terminals (S107). A base station in a provisional allocation state that can accommodate one or more unaccommodated terminals is a base station that satisfies the following three conditions: (1) It is in a provisional allocation state. (2) Among the accommodation candidate terminals of the base station, there is one or more unaccommodated terminals. (3) The value obtained by dividing the wireless transmission rate of any terminal that satisfies (2) by (the number of accommodated terminals of the base station + 1) is equal to or greater than the threshold value α.

[0027] (2) The candidate terminals for accommodation by the base station are terminals whose received power value from the base station is equal to or greater than a threshold value.

[0028] The condition (3) corresponds to the condition in step S111 described later. The number of terminals that satisfies the condition (3) is the number of terminals that can be accommodated by the base station.

[0029] If a corresponding base station is found (Yes in S107), the base station placement selection unit 16 selects one base station from the base stations in the provisional placement state that can accommodate the largest number of terminals per base station cost, changes the selected base station to an installed state, and sets the number of connected terminals to that base station to 0 (S108). The base station cost refers to the cost required to install a base station and may differ for each base station. The base station cost may be an absolute value (amount), but may also be a relative value (e.g., ratio of amounts) as long as it is possible to compare base stations.

[0030] Next, the base station placement selection unit 16 determines whether or not the base station selected in step S108 (hereinafter referred to as the "target base station") has already accommodated all of the candidate terminals (S109). If all of the candidate terminals have already been accommodated (Yes in S109), the process returns to step S106.

[0031] If there is a terminal that is not yet accommodated among the accommodation candidate terminals (No in S109), the base station placement selection unit 16 selects one unaccommodated terminal from the accommodation candidate terminals of the target base station that has the highest wireless transmission rate based on the received power value from the target base station (or the received power value if the rate is the same) (S110). Hereinafter, the selected one terminal will be referred to as the "target terminal."

[0032] Next, the base station placement selection unit 16 determines whether the value obtained by dividing the wireless transmission rate of the target terminal by (the number of terminals accommodated by the target base station + 1) is equal to or greater than a preset threshold α (S111). If the value is less than the threshold α (No in S111), the target terminal is not accommodated in the target base station and the process returns to step S106.

[0033] If the value is equal to or greater than the threshold value α (Yes in S111), the base station placement selection unit 16 accommodates the target terminal in the target base station (changes the state of the target terminal from unaccommodated state to accommodated state), and adds 1 to the number of terminals connected to the target base station (S112). Then, the process returns to step S109.

[0034] That is, in steps S109 to S112, unaccommodated terminals are selected as targets for accommodation in the order of highest wireless transmission rate (or highest received power if the wireless transmission rate is the same) within the range where the result of dividing the wireless transmission rate by (the number of terminals accommodated by the target base station + 1) is equal to or greater than the threshold value α.

[0035] In the process of repeating step S106 and subsequent steps, if the state of all terminals has become an accommodated state (Yes in S106), or if there is no base station in a provisionally arranged state that can accommodate one or more unaccommodated terminals (No in S107), the output unit 17 outputs the set of base stations in an installed state at that time (i.e., base station arrangement) as the result of station placement design (S113), and the processing procedure in FIG. 3 ends.

[0036] Although the above describes an example in which the value of radius R is set in advance, the determination unit 13 and the correction unit 14 may internally and automatically calculate the value according to the distribution of terminals. In this case, different values ​​may be used depending on the location within the area or for each terminal. For example, radius R may be set to be relatively small for areas with a relatively high density of terminals or for terminals located in such areas, and may be set to be relatively large for areas with a relatively low density of terminals or for terminals located in such areas.

[0037] In addition, although the example described above is such that the radius R when determining whether or not correction is necessary (S103) is the same as the radius R when correcting the received power value of the terminal (S104), the former R and the latter R may be different.

[0038] Furthermore, if the number of terminals or the proportion of terminals determined to require correction of the received power value in step S103 is equal to or greater than a certain level, there is a possibility that there is a problem with the estimation accuracy of the received power value. Therefore, in such a case, the output unit 17 may output a message to notify the user of this possibility.

[0039] As described above, according to this embodiment, when the difference between the received power value of a certain point (terminal) and the received power values ​​of the surrounding points is large, the received power value of the certain point can be corrected based on the received power values ​​of the surrounding points. As a result, it is possible to reduce the estimation error of the radio wave coverage status from the base station. As a result, it is possible to expect an improvement in the accuracy of the radio station design results.

[0040] In this embodiment, the station design device 10 is an example of a correction device.

[0041] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0042] REFERENCE SIGNS LIST 10 Station placement design device 11 Initial placement unit 12 Received power calculation unit 13 Determination unit 14 Correction unit 15 Conversion unit 16 Base station placement selection unit 17 Output unit 100 Drive device 101 Recording medium 102 Auxiliary storage device 103 Memory device 104 Processor 105 Interface device 121 Data storage unit B Bus

Claims

1. A correction device, comprising: a received power calculation unit configured to calculate a received power value from candidate positions of a base station for each of a plurality of locations; a determination unit configured to determine, for each of the locations, whether correction of the received power value of the location is necessary based on a comparison between the received power value of the location and the received power values of the locations within a predetermined range from the location; and a correction unit configured to correct the received power value determined to be in need of correction based on the received power values of the locations within a predetermined range from the location to which the received power value pertains.

2. The correction device according to claim 1, wherein the determination unit is configured to determine, for each of the locations, whether correction of the received power value of the location is necessary based on a comparison between the received power value of the location and an average value or a median value of the received power values of the locations within a predetermined range from the location, and the correction unit is configured to correct the received power value determined to be in need of correction based on the average value or the median value of the received power values of the locations within a predetermined range from the location to which the received power value pertains.

3. A correction method, characterized in that a computer executes: a received power calculation procedure for calculating a received power value from candidate positions of a base station for each of a plurality of locations; a determination procedure for determining, for each of the locations, whether correction of the received power value of the location is necessary based on a comparison between the received power value of the location and the received power values of the locations within a predetermined range from the location; and a correction procedure for correcting the received power value determined to be in need of correction based on the received power values of the locations within a predetermined range from the location to which the received power value pertains.

4. A program, characterized in that it causes a computer to execute: a received power calculation procedure for calculating a received power value from candidate positions of a base station for each of a plurality of locations; a determination procedure for determining, for each of the locations, whether correction of the received power value of the location is necessary based on a comparison between the received power value of the location and the received power values of the locations within a predetermined range from the location; and a correction procedure for correcting the received power value determined to be in need of correction based on the received power values of the locations within a predetermined range from the location to which the received power value pertains.

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