Area design method, area design program, area design device, and construction method for wireless communication system

Abstract

Provided are: an area design method; an area design program, and an area design device capable of designing an efficient area, which satisfies target quality, in a wireless communication system; and a construction method for a wireless communication system. In the area design method, a generational change for updating a plurality of individuals of a group by using a genetic algorithm method is performed on the basis of evaluation using an objective function for each individual of the group. Each individual has genetic information indicating whether a wireless base station 4 is installed at each installation candidate point 13 identified by a location and a frequency channel in a target area. Subsequently, by selecting an individual from the group after a plurality of generational changes are performed, an area design pattern corresponding to the individual is obtained. The objective function is calculated on the basis of the wireless communication quality of a wireless terminal 2 in consideration of interference between frequency channels when the wireless base station 4 is installed at the location of the installation candidate point 13 and the frequency channel of the installation candidate point 13 is set in the wireless base station 4.

Description

Area design method for wireless communication systems, area design program, area design device, and construction method.

[0001] This disclosure relates to a method for designing an area of ​​a wireless communication system, an area design program, an area design device, and a method for constructing such a system.

[0002] There is a limit to the range of radio waves that can reach from a wireless base station. Furthermore, there is a limit to the number of wireless terminals that a single wireless base station can accommodate. Therefore, if the number of wireless base stations is insufficient, problems arise such as insufficient coverage area and insufficient capacity for wireless terminals. On the other hand, if the number of wireless base stations is excessive, it becomes inefficient due to increased costs for the base station equipment itself. For these reasons, when determining the placement of wireless base stations, it is necessary to place a sufficient number of wireless base stations in appropriate locations, and various base station placement design methods, such as those disclosed in Non-Patent Document 1, are being considered. Additionally, by appropriately designing the frequency channels used by each wireless base station after installation, the performance of the installed wireless base stations can be maximized. For this reason, various frequency channel design methods, such as those disclosed in Non-Patent Document 2, are being considered. Furthermore, methods such as those disclosed in Non-Patent Document 3 are being considered for evaluating throughput in frequency channel design.

[0003] Here, site design and frequency channel design can be reduced to combinatorial optimization problems, and various methods have been proposed for solving general combinatorial optimization problems. For example, the evolutionary algorithm shown in Non-Patent Document 4 is proposed as a population-based metaheuristic optimization algorithm inspired by evolutionary mechanisms such as reproduction, mutation, genetic modification, natural selection, and survival of the fittest.

[0004] Toshiro Nakahira, Daisuke Murayama, Satoshi Takaya, Kenichi Kawamura, Takayoshi Moriyama, "Multi-Wireless Area Design Method Based on Communication Capacity and Base Station Cost," IEICE Technical Review, IEICE General Conference, B-5-97, Mar. 2022. BAHS Abeysekera, M. Matsui, Y. Asai and M. Mizoguchi, "Network controlled frequency channel and bandwidth allocation scheme for IEEE 802.11a / n / ac wireless LANs: RATOP," 2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communication (PIMRC), Washington, DC, USA, 2014, pp. 1041-1045, doi: 10.1109 / PIMRC.2014.7136320.SC Liew, C. Kai, J. Leung and B. Wong, "Back-of-the-Envelope Computation of Throughput Distributions "in CSMA Wireless Networks," 2009 IEEE International Conference on Communications, Dresden, Germany, 2009, pp. 1-6, doi: 10.1109 / ICC.2009.5198774. Shota Yagami, Sho Kuwajima, "Evolutionary Algorithms," [online], April 2014, [Retrieved September 6, 2024], Internet <URL: http: / / mikilab.doshisha.ac.jp / dia / monthly / monthly2014 / mlm152 / syagami / syagami.pdf>

[0005] In area design for wireless communication systems, site placement design, as disclosed in Non-Patent Document 1, and frequency channel design, as disclosed in Non-Patent Document 2, are carried out sequentially as separate designs. In this case, for example, evaluation of the site placement design cannot be performed in light of the subsequent frequency channel design, and evaluation of the frequency channel design is performed on the site placement design that has already been determined. As a result, in area design for wireless communication systems, it may not be possible to efficiently obtain design results that meet the target quality, such as the required user throughput.

[0006] This disclosure relates to solving these problems. This disclosure provides an area design method, an area design program, and an area design device that enable efficient area design that meets target quality requirements in wireless communication systems, as well as a method for constructing a wireless communication system using the same.

[0007] The area design method relating to this disclosure is an area design method that performs the following: a computer sets conditions for the area of ​​a wireless communication system to be designed, including the placement of one or more wireless terminals and the placement of one or more candidate installation points, each of which is identified by location and frequency channel; generates a population including multiple individuals such that each of the multiple individuals has genetic information in which an area design pattern is encoded by representing the installation or non-installation of a wireless base station at each of the one or more candidate installation points in a binary manner; performs generational changes to update the multiple individuals included in the population using a genetic algorithm method based on an evaluation using an objective function for each of the multiple individuals included in the population; and after performing the generational changes multiple times, obtains an area design pattern represented by the genetic information of individuals selected from the multiple individuals included in the population based on pre-set criteria. The objective function is calculated based on the area design pattern represented by the genetic information of the target individual, assuming that a wireless base station is installed at each of the candidate installation points designated for installation in the area design pattern, and that the frequency channel of the candidate installation point is set to that wireless base station, taking into account the wireless communication quality of the one or more wireless terminals considering interference between frequency channels.

[0008] The area design program relating to this disclosure is an area design program that causes a computer to perform the following: setting conditions for the area of ​​a wireless communication system to be designed, including the placement of one or more wireless terminals and the placement of one or more candidate installation points, each of which is identified by location and frequency channel; generating a population containing multiple individuals such that each of the multiple individuals has genetic information in which an area design pattern is encoded by representing, in a binary way, whether or not a wireless base station is installed at each of the one or more candidate installation points; performing generational changes to update the multiple individuals in the population using a genetic algorithm method based on an evaluation using an objective function for each of the multiple individuals in the population; and, after performing the generational changes multiple times, obtaining an area design pattern represented by the genetic information of individuals selected from the multiple individuals in the population based on pre-set criteria. The objective function is calculated based on the area design pattern represented by the genetic information of the target individual, assuming that a wireless base station is installed at each of the candidate installation points designated for installation in the area design pattern, and that the frequency channel of the candidate installation point is set to that wireless base station, taking into account the wireless communication quality of the one or more wireless terminals considering interference between frequency channels.

[0009] The area design device according to this disclosure includes: a setting unit that sets conditions for the area of ​​a wireless communication system to be designed, including the placement of one or more wireless terminals and the placement of one or more candidate installation points, each of which is specified by location and frequency channel; a generation unit that generates a population including multiple individuals such that each of the multiple individuals has genetic information in which an area design pattern is encoded by representing the installation or non-installation of a wireless base station at each of the one or more candidate installation points in a binary manner; an update unit that performs generational changes to update the multiple individuals included in the population using a genetic algorithm method based on an evaluation using an objective function for each of the multiple individuals included in the population; and a selection unit that, after performing the generational changes multiple times, obtains an area design pattern represented by the genetic information of individuals selected from the multiple individuals included in the population based on pre-set criteria. The objective function is calculated based on the area design pattern represented by the genetic information of the target individual, assuming that a wireless base station is installed at each of the candidate installation points designated for installation in the area design pattern, and that the frequency channel of the candidate installation point is set to that wireless base station, taking into account the wireless communication quality of the one or more wireless terminals considering interference between frequency channels.

[0010] The method for constructing a wireless communication system according to this disclosure includes: obtaining an area design pattern by having a computer execute the area design method described above; installing a wireless base station in the area to be designed at a location corresponding to one or more candidate installation points that have been designated as installation points in the obtained area design pattern; and setting the frequency channel used by the wireless base station installed in the area to be designed to the frequency channel corresponding to the candidate installation point that has been designated as installation points in the area design pattern.

[0011] According to the area design method, area design program, or area design device related to this disclosure, or the method for constructing a wireless communication system using the same, it becomes possible to efficiently meet target quality.

[0012] This is a configuration diagram of a wireless communication system according to Embodiment 1. This is a configuration diagram of an area design device according to Embodiment 1. This is a diagram illustrating an example of area design for a wireless communication system according to Embodiment 1. This is a block diagram showing an example of the functions of an area design device according to Embodiment 1. This is a diagram showing an example of the operation of an area design device according to Embodiment 1. This is a diagram showing an example of the operation of an area design device according to Embodiment 1. This is a diagram showing an example of the operation of an area design device according to Embodiment 1.

[0013] Embodiments of this disclosure will be described with reference to the attached drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are simplified or omitted as appropriate. This disclosure is not limited to the following embodiments, and any combination of embodiments, any modification of any component of each embodiment, or any omission of any component of each embodiment is permitted without departing from the spirit of this disclosure.

[0014] Embodiment 1. Figure 1 is a configuration diagram of the wireless communication system 1 according to Embodiment 1.

[0015] The wireless communication system 1 is a system that provides wireless communication functionality to one or more wireless terminals 2 in the applicable area. Each wireless terminal 2 is, for example, an information processing terminal device capable of wireless communication. Each wireless terminal 2 may be, for example, a general-purpose information processing device such as a tablet computer, smartphone, or smartwatch, or it may be a vehicle, robot, mobility device, or other device equipped with a wireless communication module. The wireless terminal 2 may be a device that moves around the target area, or it may be a device that is fixedly installed in the target area.

[0016] In the area where the wireless communication system 1 is applied, there is one or more shielding objects 3. In this example, there are multiple shielding objects 3 in the area. The shielding objects 3 are objects that block the wireless signals from the wireless communication system 1. The shielding objects 3 may be fixed objects such as buildings, or moving objects such as vehicles.

[0017] The wireless communication system 1 comprises one or more wireless base stations 4. In this example, the wireless communication system 1 comprises a plurality of wireless base stations 4. Each wireless base station 4 is located in an area to which the wireless communication system 1 is applied. Each wireless base station 4 is equipped with the function of transmitting and receiving wireless signals of the wireless communication system 1. The wireless communication system 1 may comprise a plurality of wireless base stations 4 corresponding to different wireless communication schemes. Each wireless base station 4 is configured to communicate wirelessly or via wired connection with equipment inside or outside the wireless communication system 1. A frequency channel for wireless communication is set in the wireless base station 4. Multiple frequency channels for wireless communication may be set in the wireless base station 4 for a single wireless communication scheme. Each wireless base station 4 provides wireless communication functionality to a wireless terminal 2 by transmitting and receiving wireless signals to and from the wireless terminal 2.

[0018] The wireless communication system 1 is constructed by actually installing one or more wireless base stations 4 in locations determined in advance by area design within the target area. Here, the installation of wireless base stations 4 includes, for example, physically arranging the equipment of the wireless base stations 4 within the target area and setting the frequency channels that the wireless base stations 4 will use for wireless communication. In some cases, the construction of the wireless communication system 1 so that it can operate is expressed as manufacturing the wireless communication system 1. The area design of the wireless communication system 1 is performed, for example, using an area design device 5 not shown in Figure 1.

[0019] Figure 2 is a configuration diagram of the area design device 5 according to Embodiment 1.

[0020] The area design device 5 is, for example, a computer system consisting of one or more server devices, or a device including such a system. Here, a computer system consisting of one or more devices may be simply referred to as a computer. When the area design device 5 is composed of multiple server devices, these multiple server devices may be located in different locations. Some or all of the functions of the area design device 5 may be implemented, for example, by a virtual machine on a cloud service, or by processing or storage resources on a cloud service. The area design device 5 includes a communication unit 6, an external input / output unit 7, a processing unit 8, and a database 9.

[0021] The communication unit 6 communicates with the input / output device 10 located outside the area design device 5 via wired or wireless connection. The input / output device 10 receives information input from the operator and displays the input information and the information output from the area design device 5 on a display.

[0022] The external input / output unit 7 is an interface between the communication unit 6 and the processing unit 8, and the communication unit 6 inputs information received from the input / output device 10 to the processing unit 8. The external input / output unit 7 also outputs information obtained from calculation processing by the processing unit 8 to the communication unit 6 and transmits it to the input / output device 10 via the communication unit 6.

[0023] The processing unit 8 comprises a processor 11 and a memory 12. The processor 11 is typically a CPU. The memory 12 stores programs that can be executed by the processor 11. The processor 11 is, for example, a CPU, arithmetic unit, microprocessor, or microcomputer. The memory 12 is, for example, a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, and EEPROM, or a magnetic disk, flexible disk, optical disk, compact disk, minidisc, or DVD. The memory 12 stores, for example, programs as software or firmware. The area design device 5 then performs pre-set processing by having the processor 11 execute the programs stored in the memory 12, and realizes each function as a result of the cooperation between hardware and software. The program can be stored on a computer-readable storage medium. The program can also be provided via a communication network. The program may be a program package that includes multiple subprograms, modules, or libraries. The program is sometimes called a program product. Each function of the area design device 5 may be realized by a processing circuit. Alternatively, some or all of the functions of the area design device 5 may be implemented together in a processing circuit. The processing circuit may be implemented as, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, or an FPGA, or a combination thereof.

[0024] Database 9 stores information such as calculation conditions or calculation results in area design. Information such as calculation conditions stored in database 9 can be read from database 9 by the processing unit 8 during area design. Various types of information, such as calculation results in area design, can be written to database 9 by the processing unit 8. Various types of information in area design can be written to database 9 by the operator operating the input / output device 10. Information stored in database 9 can be read from database 9 by the operator operating the input / output device 10. Information read from database 9 can be displayed on the input / output device 10 or transmitted externally via a communication network.

[0025] Figure 3 is a diagram illustrating an example of area design for a wireless communication system 1 according to Embodiment 1.

[0026] In area design, for example, the area to which the wireless communication system 1 is applied is designated as the area to be designed, and site placement design, which determines the number and placement of wireless base stations 4 within the area, and frequency channel design, which determines the frequency channel to be used for wireless communication for each of the wireless base stations 4 to be placed, are performed together. The wireless base stations 4 are installed in part or all of one or more candidate installation points 13 located within the area. The candidate installation points 13 are set to locations where wireless base stations 4 can be placed, depending on the area. The candidate installation points 13 are identified, for example, by both their location within the area and their frequency channel. For the same location within the area, for example, candidate installation points 13 for wireless base stations 4 with a first frequency channel set and candidate installation points 13 for wireless base stations 4 with a second frequency channel set may be set separately. The first frequency channel and the second frequency channel are, for example, different frequency channels in the same wireless communication system. With respect to the candidate installation points 13 corresponding to the first frequency channel and the candidate installation points 13 corresponding to the first frequency channel that are set separately for the same location within the area, wireless base stations 4 may be installed at both. In this case, for example, both the first frequency channel and the second frequency channel may be set for a single wireless base station 4 installed at a location corresponding to one of these candidate installation points 13. Alternatively, for example, different wireless base stations 4 corresponding to the first frequency channel and the second frequency channel may be installed at the locations corresponding to these candidate installation points 13. In area design, for example, an area design pattern is determined that indicates which of the candidate installation points 13 within the area will have a wireless base station 4 installed and which will not.

[0027] In area design, for example, the communication quality when wireless base stations 4 are installed at some or all of the candidate installation points 13 is evaluated. The evaluation of communication quality is performed by simulation of a wireless communication system 1 virtually constructed on the area design device 5 for the area to be designed. At this time, one or more wireless terminals 2 are placed in the virtual area. One or more wireless terminals 2 may be placed on a grid within the area, randomly, based on previously observed placements, or by other methods.

[0028] Figure 4 is a block diagram showing an example of the functions of the area design device 5 according to Embodiment 1.

[0029] In this example, the area design device 5 performs area design for the wireless communication system 1 by solving a combinatorial optimization problem using a genetic algorithm. The area design device 5 comprises a setting unit 14, a generation unit 15, an update unit 16, and a selection unit 17 as functional units. The functions of each functional unit of the area design device 5 are realized, for example, as calculation processing in the processing unit 8.

[0030] The setting unit 14 is a part equipped with a function for setting area design conditions for the area to be designed. Setting the area design conditions includes setting the size of the virtual area on the area design device 5, the arrangement of shielding objects 3 within the area, and other calculation conditions. The virtual area on the area design device 5 is set, for example, based on a model of the actual area to be designed. Setting the area design conditions includes placing one or more wireless terminals 2 in the virtual area on the area design device 5. Setting the area design conditions also includes placing one or more candidate installation points 13 in the virtual area on the area design device 5. The setting unit 14 sets the area design conditions, for example, based on information input by the operator to the input / output device 10. The operator inputs, for example, the arrangement of one or more wireless terminals 2 and the arrangement of one or more candidate installation points 13 within the area to the area design device 5 via the input / output device 10.

[0031] The generation unit 15 is a part equipped with the function of generating a population containing multiple individuals as an initial population as a processing of a genetic algorithm. Each individual included in the population has genetic information that represents the area design pattern corresponding to it. The genetic information is information that encodes the area design pattern. In the genetic information of this example, the area design pattern is encoded by representing the installation or non-installation of a wireless base station 4 at each candidate installation point 13 with a binary value such as "1" or "0". For example, for numbered candidate installation points 13, the genetic information that encodes an area design pattern in which a wireless base station 4 is installed at the first candidate installation point 13, not installed at the second candidate installation point 13, and installed at the third candidate installation point 13 is represented as "101...". The generation unit 15 generates multiple individuals with random genetic information according to the area design conditions set by the setting unit 14, for example, and uses the population containing the generated multiple individuals as the initial population.

[0032] The update unit 16 is a part equipped with the function of performing generational change processing on a population that includes multiple individuals, such as the initial population generated by the generation unit 15. The generational change processing is a process of updating multiple individuals included in the population using the methods of a genetic algorithm. The generational change processing is performed based on an evaluation using a pre-set objective function for each individual included in the current generation population. The generational change processing includes processes such as elite preservation, tournament selection, uniform crossover, and mutation.

[0033] Elite preservation is a process that carries over individuals with good evaluation scores based on the objective function from the current generation to the next generation. Here, in optimization problems where the goal is to maximize the objective function, a higher evaluation score is considered better, while in optimization problems where the goal is to minimize the objective function, a lower evaluation score is considered better. In elite preservation, for example, one or more individuals are carried over to the next generation in order of their evaluation scores based on the objective function, in descending order of quality. As a result, the individual with the best evaluation score in each generation, i.e., the evaluation score of the optimal solution, is updated in a direction that improves.

[0034] Tournament selection is the process of selecting individuals with good evaluation scores based on the objective function from a randomly selected population of the current generation. Uniform crossover is the process of randomly swapping the binary elements of the genetic information of two individuals selected from the current generation population through tournament selection or similar methods, and passing them on to the next generation population. Mutation is the process of randomly transforming the genetic information of individuals selected from the current generation population or individuals that have undergone processes such as uniform crossover, for example, by bit inversion or bit string swapping, and passing them on to the next generation population. This diversifies the genetic information of the next generation population.

[0035] The update unit 16 performs elite preservation and then repeatedly performs processes such as tournament selection, uniform crossover, and mutation until the required number of individuals are included in the next generation population, thereby forming the next generation population. The update unit 16 may also perform generational changes using other genetic algorithms, such as roulette selection, ranking selection, two-point crossover, or other processes. The update unit 16 then repeatedly performs generational changes on the updated population. For example, the update unit 16 performs generational changes for a predetermined number of generations.

[0036] The selection unit 17 is a part equipped with the function of selecting one of several individuals included in the latest generation of the population after multiple generations have been performed on the population. The selection unit 17 selects one individual from the population based on, for example, a predetermined criterion. The selection unit 17 selects, for example, the individual with the best evaluation value according to the objective function from among the individuals included in the latest generation of the population. The selection unit 17 obtains an area design pattern represented by the genetic information of the selected individual as the result of area design.

[0037] The operator obtains and refers to the area design results obtained by the selection unit 17 from the area design device 5 via the input / output device 10.

[0038] Next, the objective function used in the area design device 5 will be described. The objective function is a function that returns an evaluation value for each individual having genetic information. The objective function is calculated using the wireless communication quality of the wireless terminal 2 when the wireless base station 4 is installed at the installation candidate point 13 based on the area design pattern represented by the genetic information of the target individual. The objective function is also calculated using a penalty corresponding to the number of installed wireless base stations 4 in the area design pattern. The objective function is represented by, for example, the following formula (1).

[0039]

[0040] Here, the first term of formula (1) represents the wireless communication quality, and the second term represents the penalty corresponding to the number of installed wireless base stations 4. The coefficient α and the coefficient μ are positive weights that determine the strength of the influence of the wireless communication quality and the penalty on the evaluation value of the objective function. The subscript j, which is an element of the set J, corresponds to each wireless terminal 2. The number of elements |J| of the set J is the number of wireless terminals 2 arranged in the area to be designed in the condition setting of the setting unit 14. The subscript n, which is an element of the set N, corresponds to each area design pattern. The number of elements of the set N is the total number of possible area design patterns for one or more installation candidate points 13 arranged in the area to be designed in the condition setting of the setting unit 14. The degree of goal achievement z ｊ，ｎ is a value indicating whether the throughput of the j-th wireless terminal 2 achieves the target value in the area design pattern n. The degree of goal achievement z ｊ，ｎ is represented by, for example, the following formula (2).

[0041]

[0042] The throughput p ｊ，ｎ represents the estimated value of the throughput of the j-th wireless terminal 2 in the area design pattern n. The target throughput p ｔ１ is the target value of the throughput of the wireless signal from the wireless base station 4 at each wireless terminal 2. The target throughput p ｔ１ is set, for example, so that wireless communication at the wireless terminal 2 can be performed with sufficient quality.

[0043] The throughput pｊ，ｎ is calculated as follows, for example. In the area design pattern n, the reception intensity of the radio signal transmitted from each radio base station 4 at each radio terminal 2 is calculated. Also, the reception intensity of the radio signal between each radio base station 4 in the area design pattern n is calculated. Here, the reception intensity of the radio signal is calculated, for example, based on the signal intensity of the radio signal transmitted by the radio base station 4, the distance between the radio base station 4 and the radio terminal 2 or another radio base station 4, and the presence or absence of the shielding object 3 between them. The reception intensity of the radio signal may be calculated considering, for example, the reflection of the radio signal between the radio base station 4 and the radio terminal 2 or another radio base station 4. Based on the reception intensity of the radio signal at each radio terminal 2, the radio base station 4 to which the radio terminal 2 connects is determined, and the radio transmission rate between the radio terminal 2 and the radio base station 4 is calculated. Also, based on the reception intensity of the radio signal between the radio base stations 4 and the frequency channel set in the radio base station 4, the amount of time resource or the ratio of the time resource available at each radio base station 4 is calculated. Based on the radio transmission rate and the amount of time resource calculated in this way, an estimated value of the throughput at each radio terminal 2 is calculated. In the calculation of the throughput, for example, the BoE method disclosed in Non-Patent Document 3 or other methods can be used. The throughput may be calculated, for example, based on the signal-to-interference power ratio at each radio terminal 2.

[0044] The degree of goal achievement z for the j-th radio terminal 2 ｊ，ｎ The value of ｊ，ｎ is 1 if the throughput p ｔ１ achieves the target throughput p

[0045] Here, in area design pattern n, each wireless base station 4 placed in the area to be designed is part of the group K ｎ It can be treated as an element of set K. ｎ Number of elements | K ｎ | represents the number of wireless base stations 4 to be placed in the area under design in area design pattern n. Penalty P is, for example, the number of wireless base stations 4 to be installed when following area design pattern n |K ｎ Using |, it can be expressed by the following equation (3).

[0046]

[0047] Thus, the evaluation value of the objective function expressed by equation (1) is obtained by subtracting from the first term, which represents the wireless communication quality in area design pattern n, a value obtained by multiplying the penalty P corresponding to the number of wireless base stations 4 by a coefficient μ. For this reason, the area design of the wireless communication system 1 becomes a problem of maximizing the objective function expressed by the following equation (4), under the conditions of equations (2) and (3).

[0048]

[0049] Furthermore, the penalty P in the objective function does not have to be simply the number of wireless base stations 4 installed. For example, considering the equipment costs of the wireless base stations 4 themselves, which differ depending on the type of wireless base station 4 to be installed at the candidate installation point 13, the penalty may be the number of wireless base stations 4 installed weighted according to the equipment cost, or the total value of the equipment costs.

[0050] Next, we will explain an example of the operation of the area design device 5 using Figures 5 to 7. Figures 5 to 7 are flowcharts illustrating an example of the operation of the area design device 5 according to Embodiment 1.

[0051] Figure 5 shows an example of the overall processing in the area design device 5 during area design.

[0052] In step S1, the setting unit 14 places the wireless terminal 2 and candidate installation points 13 in the area to be designed, based on information input by the operator to the input / output device 10, as a condition setting for area design. After that, the area design device 5 proceeds to step S2.

[0053] In step S2, the setting unit 14 calculates the received power at each wireless terminal 2 for the wireless signals transmitted by each wireless base station 4, based on the arrangement of wireless terminals 2 and candidate installation points 13 in the area to be designed, as well as the arrangement of shielding objects 3. After that, the area design device 5 proceeds to step S3.

[0054] In step S3, the setting unit 14 calculates the received power of the radio signals transmitted by other radio base stations 4 at each radio terminal 2, based on the arrangement of candidate installation points 13 and the arrangement of shielding objects 3 in the area to be designed. The setting unit 14 may perform the processes in steps S2 and S3 in parallel, or they may be performed in any order. After that, the area design device 5 proceeds to step S4.

[0055] In step S4, the area design device 5 searches for an area design pattern that optimizes the objective function using a genetic algorithm. In this example, the area design device 5 searches for an area design pattern that maximizes the objective function. After storing the searched area design pattern as a design result in a database 9 or the like, the processing of the area design device 5 is completed.

[0056] Figure 6 shows an example of the processing performed by the area design device 5 when searching for area design patterns using a genetic algorithm.

[0057] In step S41, the generation unit 15 generates, for example, multiple individuals with random genetic information. The generation unit 15 generates a population including these multiple individuals as the initial population. After that, the area design device 5 proceeds to step S42.

[0058] In step S42, the update unit 16 calculates an evaluation value using the objective function for each individual included in the group. After that, the area design device 5 proceeds to step S43.

[0059] In step S43, the update unit 16 performs generational change processing using the calculated evaluation values. In this example, as part of the generational change processing, the update unit 16 performs elite preservation processing, which involves passing on individuals with good evaluation values ​​based on the objective function to the next generation. The update unit 16 also performs processing to pass on individuals that have undergone tournament selection, uniform crossover, and mutation in sequence to the next generation as part of the generational change processing. After the required number of individuals are included in the next generation's population through the generational change processing, the area design device 5 proceeds to step S44.

[0060] In step S44, the update unit 16 determines whether the current group's generation count has reached a predetermined end generation count. If the end generation count has not been reached, the area design device 5 proceeds to step S42. On the other hand, if the end generation count has been reached, the area design device 5 proceeds to step S45.

[0061] In step S45, the selection unit 17 calculates an evaluation value using the objective function for each individual included in the latest generation of the population. The selection unit 17 selects the individual with the best evaluation value using the objective function from among the multiple individuals included in the population. In this example, the selection unit 17 selects the individual with the largest evaluation value using the objective function. The selection unit 17 obtains an area design pattern represented by the genetic information of the selected individual as the result of area design. After that, the processing of the area design device 5 for searching for the area design pattern is completed.

[0062] Figure 7 shows an example of the processing performed by the area design device 5 when calculating the evaluation value of the objective function.

[0063] In step S401, the area design device 5 determines which wireless base station 4 each wireless terminal 2 will connect to, based on the received strength of the radio signal from the wireless base station 4 at each wireless terminal 2. The area design device 5 may, for example, determine which wireless terminal 2 will connect to which wireless base station 4 transmits the radio signal that receives the strongest received strength at the wireless terminal 2, or it may determine which wireless base station 4 each wireless terminal 2 will connect to by other means. The area design device 5 calculates the radio transmission rate between the wireless terminal 2 and the wireless base station 4. After that, the processing of the area design device 5 proceeds to step S402.

[0064] In step S402, the area design device 5 calculates the amount of time resources or the percentage of time resources available at each radio base station 4 based on the received strength of the radio signals between the radio base stations 4 and the frequency channels set for each radio base station 4. The area design device 5 may perform steps S401 and S402 in parallel, or in any order. After that, the area design device 5 proceeds to step S403.

[0065] In step S403, the area design device 5 calculates an estimated throughput for each wireless terminal 2 based on the wireless transmission rate and the amount of time resources. After that, the processing of the area design device 5 proceeds to step S404.

[0066] In step S404, the area design device 5 calculates the degree of target achievement by comparing the estimated throughput of each wireless terminal 2 with the target throughput. After that, the processing of the area design device 5 proceeds to step S405.

[0067] In step S405, the area design device 5 calculates an evaluation value of the objective function for the area design pattern based on the degree of target achievement of each wireless terminal 2 and the number of wireless base stations 4 installed. After that, the processing of the area design device 5 for calculating the evaluation value of the objective function is completed.

[0068] As described above, the area design method according to Embodiment 1 is performed by an area design device 5, which is a computer. The area design method includes setting conditions for the area to be designed. The condition setting includes the placement of one or more wireless terminals 2 and the placement of one or more candidate installation points 13. Each candidate installation point 13 is identified by its location and frequency channel. The area design method includes generating a population containing multiple individuals as an initial population. Each individual in the population has genetic information in which the area design pattern is encoded by representing the installation or non-installation of a wireless base station 4 at each candidate installation point 13 in binary. The area design method includes performing generational changes to update multiple individuals in the population using a genetic algorithm based on an evaluation using an objective function for each individual in the population. After performing generational changes multiple times, the area design method includes obtaining an area design pattern represented by the genetic information of individuals selected from multiple individuals in the population based on predetermined criteria. The objective function is calculated based on the wireless communication quality of each wireless terminal 2, taking into account interference between frequency channels, when a wireless base station 4 is installed at each of the candidate installation points 13 designated by the area design pattern represented by the genetic information of the target individual, and the frequency channel of the candidate installation point 13 is set to the wireless base station 4.

[0069] This configuration allows site placement design and frequency channel design to be performed together as a single combinatorial optimization problem, thus enabling efficient area design of the wireless communication system 1 that meets the target quality. However, in area design methods that use a site placement design method in which one wireless base station 4 is selected and placed for each of the candidate installation points 13 using a local search such as a greedy method, while the solution to the site placement design can be obtained with a small amount of computation even if there are many candidate installation points 13, the solution has the problem of being prone to falling into a local optimum. Also, if the optimization problem is attempted to be solved by exhaustive search for the candidate installation points 13, the amount of computation becomes enormous as the number of candidate installation points 13 increases, making the calculation difficult. Furthermore, site placement design, which determines the location of the wireless base station 4 and the wireless communication method, has a significant impact on the equipment cost of the wireless base station 4 and the types of services that the wireless communication system 1 can provide. On the other hand, although frequency channel design has a higher degree of freedom, such as the number of frequency channels, than site placement design, the target of adjustment is interference between frequency channels, so the impact on the cost of the wireless communication system 1 and the services provided is relatively smaller than that of site placement design. Therefore, in area design, site placement design and frequency channel design were carried out sequentially as separate designs. If site placement design and frequency channel design are attempted to be carried out together, the space for searching for the optimal solution becomes larger, increasing the likelihood of falling into a local optimum in local search and increasing the computational cost in exhaustive search. In contrast, the area design method according to Embodiment 1 makes it easier to obtain a global optimal solution than in the case of local search due to the diversity of genetic information in the genetic algorithm. Furthermore, even when the number of candidate installation points 13, i.e., the product of the candidate locations for installing the wireless base station 4 and the number of frequency channels that can be set for the wireless base station 4, is large, the increase in computational cost is suppressed compared to the case of exhaustive search. As a result, even when site placement design and frequency channel design are carried out together for efficient area design, the possibility of falling into a local optimum is suppressed and calculations can be performed efficiently.Furthermore, the wireless communication system 1 is constructed by actually installing wireless base stations 4 in locations defined by the area design pattern obtained by the area design device 5, etc., within the target area, and by setting the frequency channels defined by the area design pattern to the wireless base stations 4. This makes it possible to obtain a wireless communication system 1 that satisfies wireless communication quality considering interference between frequency channels more efficiently.

[0070] Furthermore, the candidate installation points 13 may be identified not only by their location and frequency channel within the area, but also by the wireless communication method of the wireless base station 4 to be installed. For the same location within the area, for example, candidate installation points 13 for a wireless base station 4 using a first wireless communication method and candidate installation points 13 for a wireless base station 4 using a second wireless communication method may be set separately. The first wireless communication method is, for example, a wireless communication method using radio signals in the 5.2 GHz band. The second wireless communication method is, for example, a wireless communication method using radio signals in the 28 GHz band. In addition, for each wireless communication method, further candidate installation points 13 may be set according to the number of configurable frequency channels. Furthermore, the candidate installation points 13 may be identified not only by their location and frequency channel within the area, but also by the type or direction of the antenna of the wireless base station 4. For the same location within the area, for example, candidate locations 13 for installing a wireless base station 4 with its antenna pointed in a first direction and candidate locations 13 for installing a wireless base station 4 with its antenna pointed in a second direction may be set separately.

[0071] Furthermore, the penalty in the objective function may be calculated according to the number of frequency channels set for wireless base stations 4 installed in the same location in the area design pattern. For example, if multiple frequency channels are set for a single wireless base station 4 installed in the same location, the penalty may be calculated for multiple installation candidate points 13 corresponding to these frequency channels, with the number of wireless base stations 4 installed or the equipment cost being equivalent to one unit. In addition, if more frequency channels than the number that can be set for a single wireless base station 4 are set in the area design pattern, an additional penalty may be added to the number of wireless base stations 4 installed or the equipment cost. For example, an additional penalty may be added to the objective function for an area design pattern in which three or more frequency channels are set for a wireless base station 4 that can only be set for up to two channels.

[0072] The area design method, area design program, area design device, and construction method relating to this disclosure are applicable to wireless communication systems.

[0073] 1. Wireless communication system, 2. Wireless terminal, 3. Shielding device, 4. Wireless base station, 5. Area design device, 6. Communication unit, 7. External input / output unit, 8. Processing unit, 9. Database, 10. Input / output device, 11. Processor, 12. Memory, 13. Installation candidate points, 14. Setting unit, 15. Generation unit, 16. Update unit, 17. Selection unit

Claims

1. An area design method comprising: a computer setting conditions for an area of ​​a wireless communication system to be designed, including the placement of one or more wireless terminals and one or more candidate installation points, each identified by location and frequency channel; generating a population containing multiple individuals such that each of the multiple individuals has genetic information encoding an area design pattern, where each of the multiple individuals represents, in a binary way, whether to install or not install a wireless base station at each of the one or more candidate installation points; performing generational changes to update the multiple individuals in the population using a genetic algorithm based on an evaluation using an objective function for each of the multiple individuals in the population; and, after performing the generational changes multiple times, obtaining an area design pattern represented by the genetic information of individuals selected from the multiple individuals in the population based on pre-set criteria. The objective function is calculated based on the wireless communication quality of one or more wireless terminals, taking into account interference between frequency channels, when, for an area design pattern represented by the genetic information of the target individual, a wireless base station is installed at each of the installation candidate points designated as installation locations in the area design pattern, and the frequency channels of the installation candidate points are set to those wireless base stations.

2. An area design program that causes a computer to perform the following: setting conditions for the area of ​​the wireless communication system to be designed, including the placement of one or more wireless terminals and the placement of one or more candidate installation points, each identified by location and frequency channel; generating a population containing multiple individuals such that each of the multiple individuals has genetic information that encodes an area design pattern by representing, in a binary way, whether or not to install a wireless base station at each of the one or more candidate installation points; performing generational changes to update the multiple individuals in the population using a genetic algorithm method based on an evaluation using an objective function for each of the multiple individuals in the population; and, after performing the generational changes multiple times, obtaining an area design pattern represented by the genetic information of individuals selected from the multiple individuals in the population based on pre-set criteria. The objective function is calculated based on the area design pattern represented by the genetic information of the target individual, using an area design program that considers interference between frequency channels, where a wireless base station is installed at each of the candidate installation points designated as installation points in the area design pattern, and the frequency channel of the candidate installation point is set to that wireless base station.

3. A setting unit that sets conditions for the area of ​​the wireless communication system to be designed, including the placement of one or more wireless terminals and the placement of one or more candidate installation points, each of which is specified by location and frequency channel; a generation unit that generates a population including multiple individuals such that each of the multiple individuals has genetic information that encodes an area design pattern by representing the installation or non-installation of a wireless base station at each of the one or more candidate installation points in a binary manner; an update unit that performs generational changes to update the multiple individuals included in the population using a genetic algorithm method based on an evaluation using an objective function for each of the multiple individuals included in the population; and a selection unit that, after performing the generational changes multiple times, obtains an area design pattern represented by the genetic information of individuals selected from the multiple individuals included in the population based on pre-set criteria. Area design device, wherein the objective function is calculated based on the area design pattern represented by the genetic information of the target individual, and a wireless base station is installed at each of the installation candidate points designated as installation points in the area design pattern, and the frequency channel of the installation candidate point is set to the wireless base station, taking into account the wireless communication quality of one or more wireless terminals considering interference between frequency channels.

4. A method for constructing a wireless communication system, comprising: having a computer execute the area design method described in claim 1 to obtain an area design pattern; installing wireless base stations in the area to be designed at locations corresponding to the installation candidate points designated as installation locations in the obtained area design pattern from among the one or more installation candidate points; and setting the frequency channels used by the wireless base stations installed in the area to be designed to the frequency channels corresponding to the installation candidate points designated as installation locations in the area design pattern.

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