JP7662174B2 - Propagation prediction system, propagation prediction method, and propagation prediction program - Google Patents

Description

The present invention relates to a propagation prediction system, a propagation prediction method, and a propagation prediction program, and is particularly suitable for use in a propagation prediction system, a propagation prediction method, and a propagation prediction program for predicting propagation loss between base stations of two wireless communication systems that use the same frequency.

The frequency band used in wireless communication is limited, and with the spread of mobile terminals that perform wireless communication, there is a demand for methods to use frequency bands more efficiently. From this perspective, technology is being considered to allocate the same frequency band to multiple wireless communication systems.

Here, in order to prevent mutual interference, a control may be considered in which at least a part of a secondary wireless communication system with a lower priority that uses the same frequency is stopped during the time and area in which a primary wireless communication system with a higher priority performs wireless communication. This control may be performed by predicting the interference power to a primary base station included in the primary wireless communication system for each secondary base station included in the secondary wireless communication system. This interference power may be predicted based on the propagation loss between the primary base station and the secondary base station.

Examples of wireless communication systems with higher priority include wireless relay transmission systems for television broadcasting and wireless communication systems related to disaster prevention or defense. Examples of wireless communication systems with lower priority include wireless communication using mobile phones and smartphones, especially wireless communication using carrier aggregation that bundles together multiple frequency bands.

In relation to the above, Non-Patent Document 1 (ITU-R (Radiocommunication Sector of International Telecommunication Union), "Recommendation ITU-R P.2108-0 (06/2017) Prediction of clutter loss P Series Radiowave "Electromagnetic wave propagation", [Online], June 20, 2017, Internet <URL: https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.2108-0-201706-I!!PDF-E.pdf>) discloses a calculation method for modeling the electromagnetic wave propagation environment and approximately predicting the propagation loss due to clutter present in this propagation environment.

The standard model in Non-Patent Document 1 does not take into account the difference in altitude between the transmitting antenna, the receiving antenna, clutter, etc., and the error in the predicted propagation loss becomes large when clutter such as a building that is significantly taller than the antenna is present.

ITU-R (Radiocommunication Sector of International Telecommunication Union), "Recommendation ITU-R P.2108-0 (06/2017) Prediction of clutter loss P Series Radiowave propagation", [Online], June 20, 2017, Internet <URL: https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.2108-0-201706-I!!PDF-E.pdf>

The objective of this disclosure is to accurately predict propagation loss. Other issues and novel features will become apparent from the description of this specification and the accompanying drawings.

Below, the means for solving the problem are explained using the numbers used in (Mode for carrying out the invention). These numbers are added to clarify the correspondence between the description in (Claims) and (Mode for carrying out the invention). However, these numbers should not be used to interpret the technical scope of the invention described in (Claims).

According to one embodiment, the propagation prediction system (1) includes a calculation device (23) and an input/output device (22). The calculation device (23) estimates a propagation path between a primary base station (41) and a secondary base station (51) and predicts a propagation loss in the propagation path. The input/output device (22) outputs an output signal according to the propagation loss. The calculation device (23) selects, from among the clutters (63, 64, 65) located between the primary base station (41) and the secondary base station (51), a first dominant clutter (64) having the largest elevation angle (θ _clut ) when the apexes (631, 641, 651) of the clutters (63, 64, 65) are seen from the primary base station (41), and a second dominant clutter (64, 65) having the largest elevation angle (θ _clut ) when the apexes (631, 641, 651) of the clutters (63, 64, 65) are seen from the secondary base station (51). The calculation device (23) calculates components of the propagation loss caused by the first dominant clutter (64) and the second dominant clutter (64, 65) as clutter loss (A h ) based on the distance from the primary base station (41) to the first dominant clutter (64), the distance from the first dominant clutter (64) to the second dominant clutter (64, 65), the distance from the second dominant clutter (64, 65) to the secondary base station (51), and the respective altitudes of the primary base station (41), the first dominant clutter (64), the second dominant clutter (64, 65), and the secondary base station ( ₅₁ ). The calculation device predicts the propagation loss by approximating components of the propagation loss excluding the clutter loss (A _h ) to free space loss.

According to one embodiment, the propagation prediction method includes estimating a propagation path between a primary base station (41) and a secondary base station (51), predicting a propagation loss of the propagation path, and outputting (S05) an output signal (14) according to the propagation loss. Predicting the propagation loss includes selecting (S03) a first dominant clutter (64) having the largest elevation angle (θ clut ) when the clutter apex (631, 641, 651) is seen from the primary base station (41) from among the clutters (63, 64, 65) located between the primary base station (41) and the secondary base station (51), and selecting (S03) a second dominant clutter (64, 65) having the largest elevation angle (θ _clut ) when the clutter apex (631, 641, 651) is seen from the secondary base station (51) from among _{the clutters} (63, 64, 65) located between the primary base station (41) and the secondary base station (51). Predicting the propagation loss further includes calculating (S04) components of the propagation loss caused by the first dominant clutter (64) and the second dominant clutter (64, 65) as clutter loss (A h ) based on the distance from the primary base station (41) to the first dominant clutter (64), the distance from the first dominant clutter (64) to the second dominant clutter (64, 65), the distance from the second dominant clutter (64, 65) to the secondary base station (51), and the respective altitudes of the primary base station (41), the first dominant clutter ( ₆₄ ), the second dominant clutter (64, 65), and the secondary base station (51). Predicting the propagation loss further includes approximating components of the propagation loss excluding the clutter loss (A _h ) to a free space loss (S04).

According to one embodiment, the propagation prediction program is for causing a computer to realize a predetermined function, which includes estimating a propagation path between a primary base station (41) and a secondary base station (51), predicting a propagation loss of the propagation path, and outputting an output signal (14) according to the propagation loss (S04). Predicting the propagation loss includes selecting (S03) a first dominant clutter (64) having the largest elevation angle (θ clut ) when the clutter apex (631, 641, 651) is seen from the primary base station (41) from among the clutters (63, 64, 65) located between the primary base station (41) and the secondary base station (51), and selecting (S03) a second dominant clutter (64, 65) having the largest elevation angle (θ _clut ) when the clutter apex (631, 641, 651) is seen from the secondary base station (51) from among _{the clutters} (63, 64, 65) located between the primary base station (41) and the secondary base station (51). Predicting the propagation loss further includes calculating (S04) components of the propagation loss caused by the first dominant clutter (64) and the second dominant clutter (64, 65) as clutter loss (A h ) based on the distance from the primary base station (41) to the first dominant clutter (64), the distance from the first dominant clutter (64) to the second dominant clutter (64, 65), the distance from the second dominant clutter (64, 65) to the secondary base station (51), and the respective altitudes of the primary base station (41), the first dominant clutter ( ₆₄ ), the second dominant clutter (64, 65), and the secondary base station (51). Predicting the propagation loss further includes approximating components of the propagation loss excluding the clutter loss (A _h ) to a free space loss (S04).

According to the embodiment, it is possible to predict propagation loss with high accuracy.

FIG. 1 is a diagram showing an example of a configuration of a propagation prediction system according to an embodiment. FIG. 2A is a block circuit diagram showing an example of a configuration of a server according to an embodiment. FIG. 2B is a block circuit diagram showing an example of the configuration of the server shown in FIG. 2A from a functional point of view. FIG. 3 is a flowchart showing an example of a configuration of a propagation prediction method according to an embodiment. FIG. 4 is a diagram for explaining a method for selecting dominant clutter in one embodiment. FIG. 5 is a diagram for explaining parameters derived from the positional relationship between the antenna and the dominant clutter according to one embodiment. FIG. 6 is a diagram for explaining a case where the dominant clutter corresponding to two antennas is the same in one embodiment. FIG. 7 is a flowchart illustrating a variation of the propagation prediction method according to one embodiment. FIG. 8A is a flow chart illustrating another variation of a propagation prediction method according to one embodiment. FIG. 8B is a flow chart illustrating yet another variation of the propagation prediction method according to one embodiment. FIG. 8C is a flow chart illustrating a variation of the propagation prediction method according to one embodiment. FIG. 9 is a diagram for explaining parameters derived from the positional relationship between two antennas at different altitudes and dominant clutter in one embodiment.

The following describes an embodiment of the propagation prediction system, propagation prediction method, and propagation prediction program according to the present invention with reference to the accompanying drawings.

(First embodiment)
A configuration example of a propagation prediction system 1 according to an embodiment will be described with reference to Fig. 1. The propagation prediction system 1 is connected to a primary wireless communication system 4 and a secondary wireless communication system 5. Hereinafter, a case where the primary wireless communication system 4 and the secondary wireless communication system 5 are external to the propagation prediction system 1 will be described, but this embodiment does not necessarily exclude a case where the primary wireless communication system 4 and the secondary wireless communication system 5 are included in the propagation prediction system 1.

In this embodiment, a case will be described in which the primary wireless communication system 4 is a transmission/reception system for an FPU (Field Pickup Unit: wireless relay transmission device). The FPU is used, for example, for transmitting material for broadcasting a marathon. The primary wireless communication system 4 includes a primary base station 41 and a primary mobile station 42. The primary base station 41 and the primary mobile station 42 perform wireless communication using a specific frequency band assigned to the primary wireless communication system 4.

In addition, in this embodiment, a case where the secondary wireless communication system 5 is a cellular system will be described. The cellular system is used for wireless communication, for example, for mobile phones, smartphones, etc. The secondary wireless communication system 5 includes secondary base stations 51A, 51B, 51C, 51D, and 51E, a secondary operation server 50 that controls the secondary base stations 51A, 51B, 51C, 51D, and 51E, and a secondary mobile station (not shown). Hereinafter, when the secondary base stations 51A, 51B, 51C, 51D, and 51E are not distinguished from each other, they may be simply referred to as secondary base stations 51. In the example of FIG. 1, the total number of secondary base stations 51 is 5, but this embodiment is not limited to this total number. Furthermore, this embodiment is not limited to the total number of secondary mobile stations. The secondary base stations 51 and the secondary mobile stations perform wireless communication using a predetermined frequency band assigned to the secondary wireless communication system 5.

Here, in this embodiment, a case will be described in which the secondary wireless communication system 5 uses a frequency band that may interfere with the frequency band of the primary wireless communication system 4. In other words, a case will be described in which a wireless signal emitted from the secondary base station 51 may reach the primary base station 41 as an interference wave 53. The primary wireless communication system 4 preferentially uses this frequency band over the secondary wireless communication system 5, and the secondary wireless communication system 5 uses the same frequency band within a range that does not interfere with the primary wireless communication system 4. This frequency band may be, for example, a frequency band used in 5G (fifth generation mobile communication system).

The propagation prediction system 1 performs control to suppress interference from the secondary wireless communication system 5 to the primary wireless communication system 4 by predicting the propagation loss between the primary wireless communication system 4 and the secondary wireless communication system 5. First, the propagation prediction system 1 acquires operation information from each of the primary wireless communication system 4 and the secondary wireless communication system 5. The primary operation information 44 of the primary wireless communication system 4 may be provided to the propagation prediction system 1 from the primary base station 41, or may be provided to the propagation prediction system 1 from a primary operation server (not shown). The secondary operation information 54 of the secondary wireless communication system 5 is provided to the propagation prediction system 1 from a secondary operation server 50 included in the secondary wireless communication system 5.

The propagation prediction system 1 predicts the propagation loss of each secondary base station 51 based on this operation information, and performs control to limit the operation of the secondary wireless communication system 5 so that the interference power from the secondary base station 51 to the primary base station 41 is equal to or less than a desired threshold. This threshold may be determined based on a protection rule for protecting the primary wireless communication system 4. This control may also be performed by the propagation prediction system 1 generating and outputting an output signal 14 according to the propagation loss of each secondary base station 51, and the secondary operation server 50 stopping or operating each of the secondary base stations 51 based on the output signal 14.

To calculate this interference power, the propagation prediction system 1 calculates the propagation loss between the primary wireless communication system 4 and the secondary wireless communication system 5. To calculate this propagation loss, the propagation prediction system 1 refers to three-dimensional map information of the area in which the primary wireless communication system 4 and the secondary wireless communication system 5 are located.

The three-dimensional map information includes position information indicating the horizontal position and altitude of clutter located between the primary wireless communication system 4 and the secondary wireless communication system 5. Clutter is a general term for objects other than terrain that exist on the Earth's surface, such as buildings and vegetation. The position information of the clutter may indicate the horizontal position and altitude of vertices at which diffraction of electromagnetic waves may occur in the clutter.

The three-dimensional map information further includes location information representing the horizontal position and altitude of the primary wireless communication system 4, particularly the primary base station 41, and location information representing the horizontal position and altitude of the secondary wireless communication system 5, particularly the secondary base station 51. The location information of the primary base station 41 may represent the horizontal position and altitude of an antenna provided in the primary base station 41. The location information of the secondary base station 51 may represent the horizontal position and altitude of an antenna provided in the secondary base station 51.

The propagation prediction system 1 may store in advance three-dimensional map information of the area in which the primary wireless communication system 4, the secondary wireless communication system 5, and the clutter are located, or may obtain the information from an external source as necessary.

When clutter is present that blocks the virtual straight line connecting the primary wireless communication system 4 and the secondary wireless communication system 5, propagation loss occurs due to the clutter. Such propagation loss is called clutter loss. In other words, the clutter loss of a certain clutter is the component of the propagation loss between the primary wireless communication system 4 and the secondary wireless communication system 5 that is due to that clutter.

With reference to the block circuit diagram of FIG. 2A, an example of the configuration of the propagation prediction system 1 according to one embodiment will be described. Each function of the propagation prediction system 1 may be realized using the configuration of the server 2. The server 2 includes a bus 21, an input/output device 22, a computing device 23, a storage device 24, and an external storage device 25. The input/output device 22 inputs and outputs information, signals, and the like between the server 2 and the external configuration. The computing device 23 can realize a predetermined function by reading and executing a program stored in the storage device 24. The storage device 24 stores programs, data, and the like that the computing device 23 reads to realize a predetermined function. The external storage device 25 can read programs, data, and the like from the recording medium 26, and can also write programs, data, and the like to the recording medium 26. The recording medium 26 may be non-transient. The input/output device 22, the computing device 23, the storage device 24, and the external storage device 25 can communicate with each other via the bus 21.

With reference to the block circuit diagram of FIG. 2B, an example configuration of the server 2 shown in FIG. 2A will be described from a functional point of view. The server 2 includes a communication unit 201, a clutter selection unit 202, a propagation loss calculation unit 203, and a control unit 204. The communication unit 201 and the control unit 204 are each functional units realized by the input/output device 22, the arithmetic unit 23, and the storage device 24 working together. The clutter selection unit 202 and the propagation loss calculation unit 203 are each functional units realized by the arithmetic unit 23 and the storage device 24 working together. The functions of the communication unit 201, the clutter selection unit 202, the propagation loss calculation unit 203, and the control unit 204 will be described later.

With reference to the flowchart in FIG. 3, an example of the configuration of a propagation prediction method according to one embodiment will be described. Note that describing an example of the configuration of a propagation prediction method according to this embodiment is to describe the operation of the propagation prediction system 1 according to this embodiment, and is also to describe an example of the configuration of a propagation prediction program according to this embodiment.

When the propagation prediction method according to this embodiment starts, step S01 is executed and three-dimensional map information is prepared in the storage device 24. As described above, this three-dimensional map information is for an area in which the primary wireless communication system 4 including the primary base station 41, the secondary wireless communication system 5 including the secondary base station 51, and the clutter of the primary base station 41 and the secondary base station 51 are located. The three-dimensional map information may be read in part or in whole from the outside by the communication unit 201 of the server 2 and stored in the storage device 24.

Following step S01, step S02 is executed, and the communication unit 201 of the server 2 acquires primary operation information 44 from the primary base station 41 or the primary operation server, and acquires secondary operation information 54 from the secondary operation server 50. The primary operation information 44 may include various information representing the horizontal position and altitude of the primary base station 41, the frequency band used by the primary wireless communication system 4, the strength of the wireless signal transmitted from the primary mobile station 42 and reaching the primary base station 41, the time period during which the primary wireless communication system 4 operates, and the like. Similarly, the secondary operation information 54 may include various information representing the horizontal position and altitude of the secondary base station 51, the frequency band used by the secondary wireless communication system 5, the strength of the wireless signal transmitted from the secondary base station 51, the time period during which each of the secondary base stations 51 operates, and the like. Note that the information representing the horizontal position and altitude of each of the primary base station 41 and the secondary base station 51 may be supplied from any one of the three-dimensional map information, the primary operation information 44, and the secondary operation information 54, or may be supplied in duplicate from multiple sources. Regarding duplicated operational information that is provided, server 2 may decide which operational information to adopt based on appropriate criteria, such as adopting the most recent operational information.

Following step S02, step S03 is executed, in which the clutter selection unit 202 of the server 2 selects, from among the clutter located between the primary base station 41 and the secondary base station 51, a dominant clutter that has a dominant effect on the propagation loss between the primary base station 41 and the secondary base station 51.

With reference to FIG. 4, an example of a method for selecting dominant clutter in one embodiment will be described. In the example of FIG. 4, three clutters 63, 64, and 65 exist between a first antenna 61 of the primary base station 41 and a second antenna 62 of the secondary base station 51. In the following description using the example of FIG. 4, it is assumed that the altitudes of the first antenna 61 and the second antenna 62 are the same, but the present embodiment is not limited to this example.

Each of the clutters 63, 64, 65 is arranged so as to have a portion that blocks the virtual straight path 612 connecting the first antenna 61 and the second antenna 62. In other words, each of the clutters 63, 64, 65 is arranged between the first antenna 61 and the second antenna 62, and has a portion whose altitude is higher than the altitude of the first antenna 61 and the second antenna 62. At least, a direct wave cannot propagate along this virtual straight path 612 between the first antenna 61 and the second antenna 62.

On the other hand, the electromagnetic waves emitted from the first antenna 61 may reach the second antenna 62 by being diffracted at the ends of the clutters 63, 64, and 65. Similarly, the electromagnetic waves emitted from the second antenna 62 may reach the first antenna 61 by being diffracted at the ends of the clutters 63, 64, and 65. However, propagation loss occurs due to diffraction.

In the clutter model according to this embodiment, the clutters 63, 64, and 65 have vertices 631, 641, and 651, respectively. The propagation loss may be calculated by taking into account all of the diffraction occurring at these vertices 631, 641, and 651, but the amount of calculation required for this may be relatively large. Therefore, in this embodiment, an approximation is performed in which a first dominant clutter, the influence of which is predominantly due to propagation loss to the first antenna 61, and a second dominant clutter, the influence of which is predominantly due to propagation loss to the second antenna 62, are selected from the clutters located between the first antenna 61 and the second antenna 62, and the propagation loss caused by the remaining clutters is ignored.

In the example of FIG. 4, clutter 64 is selected as the first dominant clutter corresponding to the first antenna 61. The selection criterion is that the clutter has the maximum elevation angle when the vertices 631, 641, and 651 of the clutters 63, 64, and 65 are viewed from the first antenna 61. Here, path 613, which is a straight line connecting the first antenna 61 and the vertex 631 of the clutter 63, is blocked by the clutter 64, and path 615, which is a straight line connecting the first antenna 61 and the vertex 651 of the clutter 65, is also blocked by the clutter 64. On the other hand, path 614, which is a straight line connecting the first antenna 61 and the vertex 641 of the clutter 64, is not blocked by the other clutters 63 and 65. Therefore, it is considered that the propagation loss of the electromagnetic waves transmitted and received by the first antenna 61 is greater when diffracted by the clutter 64 than when diffracted by the clutter 63 or 65.

Similarly, in the example of FIG. 4, clutter 65 is selected as the second dominant clutter corresponding to second antenna 62. The selection criterion is that the clutter has the maximum elevation angle when the vertices 631, 641, and 651 of clutters 63, 64, and 65 are viewed from second antenna 62. Here, path 623, which is a straight line connecting second antenna 62 and vertex 631 of clutter 63, is blocked by clutters 64 and 65, and path 624, which is a straight line connecting second antenna 62 and vertex 641 of clutter 64, is blocked by clutter 65. On the other hand, path 615, which is a straight line connecting second antenna 62 and vertex 651 of clutter 65, is not blocked by other clutters 63 and 64. Therefore, it is considered that the propagation loss of the electromagnetic waves transmitted and received by second antenna 62 is greater when diffracted by clutter 65 than when diffracted by clutter 63 or 64.

Another criterion for selecting the dominant clutter for a given antenna may be to select the clutter with the largest clearance factor for that antenna. Here, the clearance factor is a parameter related to the loss of electromagnetic waves propagating through obstacles.

In this embodiment, the propagation loss of the propagation path between the first antenna 61 and the second antenna 62, i.e., the propagation loss of the propagation path between the primary base station 41 and the secondary base station 51, except for the clutter loss caused by the first dominant clutter 64 and the second dominant clutter 65, is calculated and/or predicted by approximating the free space loss. In the example of FIG. 4, when calculating the propagation loss when the electromagnetic wave transmitted from the second antenna 62 passes through the path 625, the path 645, and the path 614 and is received by the first antenna 61, first, the propagation losses in the path 625, the path 645, and the path 614 are approximated to the propagation loss in the free space of the distance of the path 612. In other words, it is estimated that the propagation path between the first antenna 61 and the second antenna 62 is the free space of the distance of the path 612. Next, the propagation loss is approximately calculated by adding the clutter loss caused by the first dominant clutter 64 and the clutter loss caused by the second dominant clutter 65 to the free space loss for the distance of the path 612. As a modified example of the method for calculating the propagation loss through the paths 625, 645, and 614, the propagation loss through the paths 625, 645, and 614 may be the propagation loss in free space for the same distance. In this modified example, by selecting the first dominant clutter 64 corresponding to the first antenna 61 and the second dominant clutter 65 corresponding to the second antenna 62, it is estimated that the propagation path between the first antenna 61 and the second antenna 62 is a set of the paths 625, 645, and 614 that pass through the vertex 641 of the first dominant clutter 64 and the vertex 651 of the second dominant clutter 65.

In this way, in this embodiment, improvements are made to the clutter model defined in non-patent document 1 (ITU-R (Radiocommunication Sector of International Telecommunication Union), "Recommendation ITU-R P.2108-0 (06/2017) Prediction of clutter loss P Series Radiowave propagation", [Online], June 20, 2017, Internet <URL: https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.2108-0-201706-I!!PDF-E.pdf>). By doing this, the present embodiment allows propagation loss to be calculated and/or predicted with high accuracy.

When multiple secondary base stations 51 exist, the clutter selection unit 202 selects multiple second dominant clutters corresponding to each of the multiple secondary base stations 51.

In either case, the clutter selection unit 202 stores information representing the selected dominant clutter in the storage device 24.

Referring again to the flowchart of FIG. 3, step S04 is executed following step S03, and the propagation loss calculation unit 203 of the server 2 calculates the propagation loss at a frequency included in the frequency band used by the secondary base station 51 in which interference with the primary base station 41 may occur. The first clutter loss, which is a component caused by the first dominant clutter, of the propagation loss between the primary base station 41 and the secondary base station 51 can be calculated based on the distance from the primary base station 41 to the first dominant clutter and the respective altitudes of the primary base station 41 and the first dominant clutter. Similarly, the second clutter loss, which is a component caused by the second dominant clutter, of the propagation loss between the primary base station 41 and the secondary base station 51 can be calculated based on the distance from the secondary base station 51 to the second dominant clutter and the respective altitudes of the secondary base station 51 and the second dominant clutter.

（１ａ）式において、「Ｊ（ν）」は回折による損失に関するパラメータであり、その単位はｄＢである。「ν」は支配的クラッタのクリアランス係数であり、その単位は無次元である。「６．０３」は近似された定数であり、近似の条件に応じて、例えば「６．０２」、「６．０４」、「６．００から６．０６までのいずれかの数値」などの、別の値に変更可能である。「ｈ」はアンテナの高度であり、その単位はｍ（メートル）である。「Ｒ」はこのアンテナに対応する支配的クラッタ６４の高度であり、その単位はｍである。 First, the clutter loss _Ah is defined by the following formula (1) in the standard model (suburban, city, trees, forest, dense city) of Non-Patent Document 1, and its unit is dB (decibels).

In formula (1a), "J(v)" is a parameter related to the loss due to diffraction, and its unit is dB. "v" is a clearance coefficient of the dominant clutter, and its unit is dimensionless. "6.03" is an approximated constant, and can be changed to another value, such as "6.02", "6.04", or "any number between 6.00 and 6.06", depending on the conditions of the approximation. "h" is the altitude of the antenna, and its unit is m (meters). "R" is the altitude of the dominant clutter 64 corresponding to this antenna, and its unit is m.

Referring to FIG. 5, the parameters derived from the positional relationship between the first antenna 61 and the dominant clutter 64 according to one embodiment will be described. The antenna altitude h and the dominant clutter altitude R shown in FIG. 5 are altitudes based on the same horizontal plane. These altitudes may be defined as height above sea level, or may be defined by adding the height above the ground to the height above sea level of the ground, but this embodiment is not limited to these examples. In either case, the calculation of clutter loss and/or propagation loss in this embodiment uses the difference between altitude h and altitude R, so the altitude of the reference horizontal plane may be arbitrary.

Equation (1a) is applied when the condition "h<R" is satisfied, i.e., when the dominant clutter blocks the imaginary straight line connecting the first antenna 61 and the second antenna 62. Equation (1b) is applied when the condition "h≧R" is satisfied, i.e., when electromagnetic waves can propagate directly along this imaginary straight line between the first antenna 61 and the second antenna 62. The method for calculating equation (1a) will be explained below.

The parameter J(ν) used in equation (1a) is defined as in equation (2) below.

（３）式において、「Ｋ_ｎｕ」は周波数に関するパラメータである。「ｈ_ｄｉｆ」は、図５に示すように、支配的クラッタ６４の高度Ｒと第１アンテナ６１の高度ｈの差であり、その単位はｍである。「θ_ｃｌｕｔ」は、図５に示すように、第１アンテナ６１から支配的クラッタ６４の頂点６４１を見た仰角であり、その単位はｄｅｇ（度）である。ここで、水平方向より上を見た場合の仰角の値は正であるが、水平方向より下を見た場合の俯角を値が負の仰角として扱ってもよい。 The clearance coefficient ν used in equation (2) is defined as in the following equation (3).

In formula (3), "K _nu " is a parameter related to frequency. "h _dif " is the difference between the altitude R of the dominant clutter 64 and the altitude h of the first antenna 61, as shown in Fig. 5, and is expressed in m. "θ _clut " is the elevation angle when the apex 641 of the dominant clutter 64 is viewed from the first antenna 61, as shown in Fig. 5, and is expressed in deg (degrees). Here, the elevation angle value when viewing above the horizontal direction is positive, but the depression angle when viewing below the horizontal direction may be treated as an elevation angle with a negative value.

（４）式において、「ｆ」は周波数であり、その単位はＧＨｚ（ギガヘルツ）である。 The parameter K _nu relating to frequency used in equation (3) is defined as in equation (4) below.

In equation (4), "f" is the frequency, and its unit is GHz (gigahertz).

The altitude difference h _dif used in equation (3) is defined as in the following equation (5).

（６）式において、「ｗ_ｓ」は、図５に示すように、第１アンテナ６１から支配的クラッタ６４の頂点６４１までの水平方向の距離であり、その単位はｍである。なお、距離ｗ_ｓは、非特許文献１の標準モデルで道路幅として定義されているパラメータに対応していてもよい。 The elevation angle θ _clut used in equation (3) is defined as in the following equation (6).

In formula (6), " _ws " is the horizontal distance from the first antenna 61 to the apex 641 of the dominant clutter 64, and its unit is meters, as shown in Fig. 5. The distance _ws may correspond to a parameter defined as the road width in the standard model of Non-Patent Document 1.

As described above, the clutter loss due to the dominant clutter 64 in the frequency band used can be calculated based on information on the position and altitude of each of the first antenna 61 and the dominant clutter 64, and the frequency values included in the frequency band used. The clutter loss can be calculated in a similar manner for the dominant clutter corresponding to the second antenna 62.

（７）式において、「Ｌ_０」は自由空間損失であり、その単位は無次元であるが、そのｌｏｇ（底が１０である対数）の１０倍を算出することで単位がｄＢの伝搬損失を算出できる。「ｄ」は自由空間としての伝搬経路で電磁波が伝搬する距離であり、その単位はｍである。「λ」は使用される周波数に対応する波長であり、その単位はｍである。 Next, the propagation path from the primary base station 41 to the secondary base station 51 is approximated to free space. Alternatively, in the case of a modified example in which this propagation path is divided by a dominant clutter 64 and a second dominant clutter 65, the propagation path from the primary base station 41 to the first dominant clutter 64, the propagation path from the first dominant clutter 64 to the second dominant clutter 65, and the propagation path from the second dominant clutter 65 to the secondary base station 51 are each approximated to free space. The propagation loss in each of these free spaces, i.e., the free space loss, is defined as in the following equation (7).

In formula (7), "L ₀ " is the free space loss, which is dimensionless, but the propagation loss in dB can be calculated by multiplying its log (logarithm with base 10) by 10. "d" is the distance that the electromagnetic wave propagates in the propagation path as free space, which is measured in m. "λ" is the wavelength corresponding to the frequency used, which is measured in m.

Next, by adding the clutter losses of the respective dominant clutters 64, 65 to the free space loss _L0 of each propagation path, the overall propagation loss from the primary base station 41 to the secondary base station 51 can be predicted.

Following step S04, step S05 is executed, in which the control unit 204 of the server 2 generates an output signal 14 according to the propagation loss calculated in step S04 and outputs it to the secondary operation server 50. Here, a propagation loss threshold may be set so that when the propagation loss is smaller than a predetermined threshold, the interference power from the secondary base station 51 to the primary base station 41 exceeds another predetermined threshold. The interference power can be calculated from the power of the radio signal transmitted from the secondary base station 51 and the propagation loss.

The output signal 14 output by the control unit 204 may be a control signal for the secondary operation server 50 to stop the secondary base station 51 whose interference power to the primary base station 41 exceeds a predetermined protection standard. In other words, the secondary operation server 50 may stop the secondary base station 51 whose interference power to the primary base station 41 exceeds a predetermined protection standard in response to the output signal 14.

When step S05 is completed, the flowchart in Figure 3 ends.

With reference to FIG. 6, another example of a method for selecting a dominant clutter in one embodiment will be described. The example in FIG. 6 is the example in FIG. 4 with the following changes. That is, the altitude of clutter 65 is lowered. As a result, the second dominant clutter corresponding to the second antenna 62 is clutter 64 in the example in FIG. 6, whereas in the example in FIG. 4, it is clutter 65. On the other hand, the first dominant clutter corresponding to the first antenna 61 is clutter 64 in FIG. 6, just as in the case in FIG. 4. That is, in the example in FIG. 6, the first dominant clutter and the second dominant clutter are the same clutter 64.

The calculation of the propagation loss of the dominant clutter in step S04 of the flowchart in FIG. 3 may be performed in a different manner depending on whether the first dominant clutter 64 and the second dominant clutter 65 are different clutters as illustrated in FIG. 4 or whether the first dominant clutter 64 and the second dominant clutter 65 are the same dominant clutter 64 as illustrated in FIG. 6. Such a modified example will be described with reference to the flowchart in FIG. 7.

When the flowchart in FIG. 7 starts, step S11 is executed, and the propagation loss calculation unit 203 determines whether the first dominant clutter and the second dominant clutter are the same clutter. To make this determination, the propagation loss calculation unit 203 may read the result of the selection of the dominant clutter that the clutter selection unit 202 has stored in the storage device 24.

In step S11, if it is determined that the first dominant clutter 64 and the second dominant clutter 65 are different clutters from each other (No), as illustrated in FIG. 4, step S11 is followed by step S12. In step S12, the propagation loss calculation unit 203 calculates the overall propagation loss between the first antenna 61 of the primary base station 41 and the second antenna 62 of the secondary base station 51 as follows:

That is, the first clutter loss and the second clutter loss caused by the diffraction occurring in the first dominant clutter 64 and the second dominant clutter 65 are calculated using equations (1a) to (7), respectively, as described above.

When step S12 is completed, the flowchart in FIG. 7 ends and processing proceeds to step S05 in the flowchart in FIG. 3.

In step S11 of the flowchart in FIG. 7, if it is determined that the first dominant clutter 64 and the second dominant clutter 64 are the same dominant clutter 64 (Yes), as illustrated in FIG. 6, step S11 is followed by step S13. In step S13, the propagation loss calculation unit 203 calculates the overall propagation loss between the first antenna 61 of the primary base station 41 and the second antenna 62 of the secondary base station 51 as follows:

That is, the clutter loss of the same dominant clutter 64 is calculated based on the shorter of the first distance from the primary base station 41 to the dominant clutter 64 and the second distance from the secondary base station 51 to the dominant clutter 64.

Next, the propagation path from the primary base station 41 to the first dominant clutter 64 and the propagation path from the first dominant clutter 64 to the second antenna 62 are each approximated to free space. The free space loss in each of these free spaces is defined as in equation (7) above.

Next, by adding the clutter loss of the first dominant clutter 64 to the free space loss L ₀ of each propagation path, the overall propagation loss from the primary base station 41 to the secondary base station 51 can be predicted.

When step S13 is completed, the flowchart in FIG. 7 ends and processing proceeds to step S05 in the flowchart in FIG. 3.

In this way, depending on whether or not the process of the flowchart in FIG. 7 is performed, when the dominant clutter corresponding to the first antenna 61 and the second antenna 62 is the same clutter, it is possible to select whether the clutter loss caused by this dominant clutter is taken into account once or twice in the overall propagation loss between the first antenna 61 and the second antenna 62. This selection may be made according to the shape of the apex of the dominant clutter. As an example, if the dominant clutter is a rectangular building or the like, and there is a sufficiently long distance between the apex facing the first antenna 61 and the apex facing the second antenna 62, the accuracy of predicting the propagation loss may be higher if the process of the flowchart in FIG. 7 is not performed. On the other hand, if the distance between the apex facing the first antenna 61 and the apex facing the second antenna 62 is sufficiently short, the accuracy of predicting the propagation loss may be higher if the process of the flowchart in FIG. 7 is performed.

With reference to the flowchart in FIG. 8A, another modified example of the propagation prediction method according to one embodiment will be described. In this modified example, when calculating the clutter loss due to the dominant clutter in step S04 of the flowchart in FIG. 3 or step S12 or step S13 of the flowchart in FIG. 7, the altitude of the dominant clutter is replaced with another lower altitude if a predetermined condition is satisfied. In this way, it is possible to simulate propagation due to diffraction on the side of the dominant clutter, which is not taken into account in the standard model of Non-Patent Document 1.

When the flowchart in FIG. 8A starts, step S21 is executed, and the propagation loss calculation unit 203 determines whether the height of the dominant clutter is equal to or greater than a threshold value. To make this determination, the propagation loss calculation unit 203 may read out the selection result of the dominant clutter that the clutter selection unit 202 stored in the storage device 24 in step S03 of the flowchart in FIG. 3. The propagation loss calculation unit 203 may also read out the height of the dominant clutter that is stored in a database (not shown) or in the storage device 24.

If the result of the judgment in step S21 is that the altitude of the dominant clutter selected in step S03 is equal to or greater than a predetermined threshold (Yes), step S22 is executed following step S21. In step S22, the propagation loss calculation unit 203 replaces the altitude of this dominant clutter with this threshold. When step S22 is completed, the flowchart in FIG. 8A ends, and the process returns to step S04 in the flowchart in FIG. 3 or step S12 or step S13 in the flowchart in FIG. 7, and the propagation loss calculation unit 203 calculates the clutter loss and the propagation loss using the replaced altitude as the altitude of the dominant clutter.

If the result of the judgment in step S21 is that the altitude of the dominant clutter selected in step S03 is less than the predetermined threshold (No), the flowchart in FIG. 8A ends, and the process returns to step S04 in the flowchart in FIG. 3 or step S12 or step S13 in the flowchart in FIG. 7, and the propagation loss calculation unit 203 calculates the clutter loss and propagation loss using the unreplaced altitude as the altitude of the dominant clutter.

In this way, by using an appropriate altitude threshold as the altitude threshold of the dominant clutter when performing the process shown in the flowchart of Figure 8A, in addition to propagation via diffraction at the apex of the dominant clutter, it is possible to simulate propagation due to diffraction at the side of the dominant clutter, which is not taken into account in the standard model of Non-Patent Document 1. This process requires a relatively small amount of calculations as a method for calculating propagation loss due to diffraction at the side of the dominant clutter, and further leads to accurate prediction of propagation loss.

With reference to the flowchart in FIG. 8B, a further modified example of the propagation prediction method according to one embodiment will be described. In this modified example, as in the case of FIG. 8A, when calculating the clutter loss due to the dominant clutter in step S04 of the flowchart in FIG. 3 or step S12 or step S13 of the flowchart in FIG. 7, the altitude of the dominant clutter is replaced with another lower altitude if a predetermined condition is satisfied. In this way, it is possible to simulate propagation due to diffraction on the side of the dominant clutter, which is not taken into account in the standard model of Non-Patent Document 1.

When the flowchart of FIG. 8B starts, step S31 is executed, and the propagation loss calculation unit 203 determines whether the altitude difference between the dominant clutter and the corresponding base station is equal to or greater than a threshold. To make this determination, the propagation loss calculation unit 203 may read out the selection result of the dominant clutter that the clutter selection unit 202 stored in the storage device 24 in step S03 of the flowchart of FIG. 3. The propagation loss calculation unit 203 may also read out the respective altitudes of the primary base station 41, the secondary base station 51, and the dominant clutter that are stored in a database or the storage device 24.

If the result of the judgment in step S31 is that the altitude difference between the dominant clutter selected in step S03 and the corresponding base station is equal to or greater than a predetermined threshold (Yes), step S31 is followed by step S32. In step S32, the propagation loss calculation unit 203 replaces the altitude of this dominant clutter with a value that makes this altitude difference equal to the threshold. When step S32 is completed, the flowchart in FIG. 8B ends, and the process returns to step S04 in the flowchart in FIG. 3 or step S12 or step S13 in the flowchart in FIG. 7, and the propagation loss calculation unit 203 calculates the clutter loss and the propagation loss using the replaced altitude as the altitude of the dominant clutter.

If the result of the judgment in step S31 is that the altitude of the dominant clutter selected in step S03 is less than the predetermined threshold (No), the flowchart in FIG. 8B ends, and the process returns to step S04 in the flowchart in FIG. 3 or step S12 or step S13 in the flowchart in FIG. 7, and the propagation loss calculation unit 203 calculates the clutter loss and propagation loss using the unreplaced altitude as the altitude of the dominant clutter.

In this way, when performing the process shown in the flowchart of Figure 8B, as in the case of Figure 8A, by using an appropriate altitude threshold as the altitude threshold of the dominant clutter, it is possible to simulate propagation via diffraction at the apex of the dominant clutter, as well as propagation due to diffraction at the side of the dominant clutter, which is not taken into account in the standard model of Non-Patent Document 1. This process requires a relatively small amount of calculations as a method for calculating propagation loss due to diffraction at the side of the dominant clutter, and further leads to accurate prediction of propagation loss.

In the modified example described with reference to Figures 8A and 8B, if the altitude of the dominant clutter is replaced with another lower altitude to calculate the clutter loss, a similar replacement is also performed when selecting the dominant clutter as a preliminary step. This will be described with reference to Figure 8C.

In this modified example, when step S03 of the flowchart in FIG. 3 is executed, the flowchart in FIG. 8C is started. First, in step S41, the clutter selection unit 202 refers to map information, lists information on clutter that exists between the primary base station 41 and the secondary base station 51, and initializes the order in which the clutter is processed. The order in which the clutter is processed may be, for example, in order of proximity to the primary base station. In addition, an argument representing the order is initialized to zero, and an argument representing the total number of clutters listed is stored.

In step S42, the clutter selection unit 202 reads the next clutter information from the listed clutter information. At this time, the argument indicating the order in which the clutter is processed is incremented. In step S43, it is determined whether the value obtained by subtracting the reference altitude from the altitude of the clutter whose information has been read is greater than a predetermined threshold value. Here, if the first antenna 61 of the primary base station 41 and the second antenna 62 of the secondary base station 51 have the same altitude, the reference altitude is equal to this altitude.

When the first antenna 61 and the second antenna 62 have different altitudes, the altitude is the altitude of the point closest to the clutter apex that is included in the imaginary line connecting the first antenna 61 and the second antenna 62. In other words, the value obtained by subtracting the reference altitude from the clutter altitude is equal to the vertical length from the clutter apex to the imaginary line. When the first antenna 61 and the second antenna 62 have different altitudes, the clutter altitude is similarly replaced when calculating the clutter loss due to the dominant clutter. Details of this will be described later as another embodiment.

In either case, if the result of the determination is that the value obtained by subtracting the reference altitude from the altitude of the clutter whose information has been read is greater than the predetermined threshold (Yes), the altitude of the clutter is replaced with another lower altitude in step S44, and the process proceeds to step S45. Conversely, if the value obtained by subtracting the reference altitude from the altitude of the clutter whose information has been read is not greater than the predetermined threshold (No), step S44 is not executed and the process proceeds to step S45.

In step S45, it is determined whether information on all clutters has been read. In other words, it is determined whether the argument representing the order in which the clutters are processed has reached the argument representing the total number of clutters listed. If the result of the determination is that information on all clutters has been read (Yes), processing proceeds to step S46. Conversely, if there is still clutter for which information has not been read (No), processing returns to step S42.

In step S46, the clutter selection unit 202 extracts the dominant clutter. This operation is the same as step S03 in the flowchart of FIG. 3. When step S46 is completed, the flowchart of FIG. 8C ends, and the process proceeds to step S04 in the flowchart of FIG. 3.

In this modified example, by performing the above process, it is possible to achieve consistency between the process of extracting dominant clutter and the process of calculating clutter loss resulting from dominant clutter by replacing the clutter altitude in the same way.

Second Embodiment
In the above-mentioned first embodiment, a case has been described in which the altitudes of the first antenna 61 and the second antenna 62 are the same as each other, as exemplified in Fig. 4 and Fig. 6. This configuration conforms to the standard model of Non-Patent Document 1. In the second embodiment, a method of predicting propagation loss taking into account the altitude difference between the first antenna 61 and the second antenna 62 will be described.

With reference to Fig. 9, a parameter derived from the positional relationship between two antennas 61, 62 at different altitudes and a dominant clutter 66 in one embodiment will be described. In the example of Fig. 9, the altitude _heb of the first antenna 61 is higher than the altitude _Re of the clutter 66 on which the influence of propagation loss on the first antenna 61 is dominant, and the altitude _Re of the dominant clutter 66 is higher than the altitude _het of the second antenna 62. Here, each of these altitudes _heb , _het , and _Re is an altitude based on the same horizontal plane. This reference may be sea level or height from the ground surface, as in the case of Fig. 5, but the present embodiment is not limited to these examples.

When the altitude _heb of the first antenna 61 and the altitude _het of the second antenna 62 are different, the imaginary straight line connecting the first antenna 61 and the second antenna 62 is not horizontal. Even if the altitude _Re of the dominant clutter 66 is lower than the altitude _heb of the first antenna 61, depending on the position of the dominant clutter 66, the path 612 of this imaginary straight line may be blocked as illustrated in Fig. 9. Even in this case, the electromagnetic wave radiated from the second antenna 62 may reach the first antenna 61 via the path 616 connecting the first antenna 61 and the apex 661 of the dominant clutter and the path 626 connecting the apex 661 and the second antenna 62. In this embodiment, the formula used for calculating the propagation loss in the first embodiment is corrected as follows, so that the propagation loss can be calculated even when the altitude _heb of the first antenna 61 and the altitude _het of the second antenna 62 are different.

（８）式において、「Ｋ_ｎｕ」は、（４）式で定義された周波数に関するパラメータである。「ｈ’_ｄｉｆ」は、上述した（５）式の高度差ｈ_ｄｉｆを補正した長さである。「θ’_ｃｌｕｔ」は、上述した（６）式の仰角θ_ｃｌｕｔを補正した角度である。 The definition of the clearance coefficient v is corrected from equation (3) used in the first embodiment to equation (8) below.

In equation (8), "K _nu " is a parameter related to frequency defined in equation (4). "h' _dif " is a length obtained by correcting the altitude difference h _dif in equation (5) above. "θ' _clut " is an angle obtained by correcting the elevation angle θ _clut in equation (6) above.

（９）式において、「Ｒ_ｅ」は支配的クラッタ６６の高度であり、その単位はｍである。「ｈ_ｅｔ」は第２アンテナ６２の高度であり、その単位はｍである。「ｈ_ｅｂ」は第１アンテナ６１の高度であり、その単位はｍである。「ｗ_ｓ」は第１アンテナ６１から支配的クラッタ６６までの水平方向の距離であり、その単位はｍである。「ｄ」は第１アンテナ６１から第２アンテナ６２までの水平方向の距離であり、その単位はｍである。「θ_ｔｒ」は水平方向と、第１アンテナ６１と第２アンテナ６２を結ぶ仮想的な直線のパス６１２との間の角度であり、その単位はｄｅｇ（度）である。 The length _h'dif in equation (8) is the vertical length from the vertex 661 of the dominant clutter 66 to the imaginary line connecting the first antenna 61 and the second antenna 62, as shown in Fig. 9, and its unit is m. The definition of the length _h'dif is obtained by correcting the definition of _hdif in equation (5) used in the first embodiment as shown in the following equation (9).

In equation (9), "R _e " is the altitude of the dominant clutter 66, and its unit is m. "h _et " is the altitude of the second antenna 62, and its unit is m. "h _eb " is the altitude of the first antenna 61, and its unit is m. "w _s " is the horizontal distance from the first antenna 61 to the dominant clutter 66, and its unit is m. "d" is the horizontal distance from the first antenna 61 to the second antenna 62, and its unit is m. "θ _tr " is the angle between the horizontal direction and the imaginary straight line path 612 connecting the first antenna 61 and the second antenna 62, and its unit is deg (degrees).

The angle θ _tr in equation (9) is defined as in equation (10) below.

ここで、角度θ’_ｃｌｕｔは、第１アンテナ６１と第２アンテナ６２を結ぶ仮想的な直線のパス６１２を基準とした場合の、第１アンテナ６１から支配的クラッタ６６の頂点６６１を見た仰角と見做すことができる。 The angle _θ'clut in equation (8) is the angle between an imaginary straight path 612 connecting the first antenna 61 and the second antenna 62 and an imaginary straight path 616 connecting the first antenna 61 and a vertex 661 of the dominant clutter 66, and is expressed in degrees, as shown in Fig. 9. The definition of the angle _θ'clut is obtained by correcting the definition of the elevation angle _θclut according to equation (6) used in the first embodiment, as shown in the following equation (11).

Here, the angle θ′ _clut can be regarded as an elevation angle of the apex 661 of the dominant clutter 66 as seen from the first antenna 61, with respect to a virtual straight line path 612 connecting the first antenna 61 and the second antenna 62.

As a result of the above correction, the application condition of formula (1) is also corrected to the following formula (12).

By correcting each definition as described above, according to this embodiment, the propagation loss can be calculated with high accuracy, as in the first embodiment, even between the primary base station 41 and the secondary base station 51, where the altitudes of the antennas 61 and 62 are different.

Third Embodiment
In this embodiment, as a modification of the first and second embodiments, the following changes are made. That is, when the propagation loss between the primary base station 41 and the secondary base station 51 includes a first clutter loss, which is a component caused by a first dominant clutter, and a second clutter loss, which is a component caused by a second dominant clutter, the propagation loss is calculated by considering only one of the first clutter loss and the second clutter loss. At this time, the other of the first clutter loss and the second clutter loss, which was not considered in the propagation loss calculation, is replaced with a free space loss when the propagation loss is calculated. The free space loss is defined as in the above-mentioned formula (7).

In this embodiment, the smaller of the first clutter loss and the second clutter loss is considered, and the larger loss is replaced with the free space loss to calculate the propagation loss.

In a modified version of this embodiment, on the other hand, the larger of the first clutter loss and the second clutter loss is considered, and the smaller loss is replaced with the free space loss to calculate the propagation loss.

In this embodiment, by performing the calculations as described above, it is possible to accurately predict the propagation loss, particularly when setting a margin for the signal output when the primary wireless communication system 4 and the secondary wireless communication system 5 share a frequency.

The invention made by the inventor has been specifically described above based on the embodiment, but it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention. Furthermore, the features described in the above embodiment can be freely combined as long as they are not technically inconsistent.

As a modification of each of the above-mentioned embodiments, the clutter loss may be calculated using three-dimensional map information that is divided into a plurality of regions and in which altitude information is registered for each region. For example, mesh-shaped three-dimensional map information divided horizontally at a predetermined unit length may be used. The altitude information registered in these regions is the representative altitude of each region, and may be, for example, the average altitude within the region. The selection of the dominant clutter and the calculation of the clutter loss caused by the dominant clutter may be performed assuming that clutter of the representative altitude exists at the representative position of each region, for example, at the geometric center position. That is, the region in which the elevation angle of the representative altitude of the region as seen from the antenna is the maximum may be selected as the dominant region, and the component of the propagation loss caused by the dominant region may be calculated based on the distance from the antenna to the representative position of the dominant region, the height of the antenna, and the representative altitude. In addition, the area in which the primary base station 41 and the secondary base station 51 are located may be divided horizontally into a plurality of meshes at a predetermined unit length, and the average value of the altitude of the clutter included in each mesh may be treated as the altitude of each mesh. In this case, in step S03 of the flowchart in FIG. 3, the altitude of the clutter located between the primary base station 41 and the secondary base station 51 can be replaced with the altitude of the mesh located between the primary base station 41 and the secondary base station 51, and the dominant mesh can be selected instead of the dominant clutter. Also, in step S04 of the flowchart in FIG. 3, the altitude of the dominant clutter can be replaced with the altitude of the dominant mesh, and the clutter loss and propagation loss can be calculated.

Although a clutter model having an apex at the top position has been described, the present disclosure is not limited to this, and the clutter may be a rectangular parallelepiped structure, for example a building. In this case, the geometric center of the structure may be used as the position of the clutter, or the position of the wall surface closer to the antenna may be used. Furthermore, a model may be adopted in which the apex of the clutter is located directly above the position of the clutter and has the height of the clutter.

As a variation of step S05 in the flowchart of FIG. 3, the control unit 204 may generate and output an output signal 14 for displaying the propagation loss calculated in step S04 on an arbitrary display device. A user of the propagation prediction system 1 may control the secondary base station 51 via the secondary operation server 50 according to the propagation loss displayed on this display device.

REFERENCE SIGNS LIST 1 Propagation prediction system 14 Output signal 2 Server 21 Bus 22 Input/output device 23 Arithmetic unit 24 Storage device 25 External storage device 26 Recording medium 201 Communication unit 202 Clutter selection unit 203 Propagation loss calculation unit 204 Control unit 4 Primary wireless communication system 41 Primary base station 42 Primary mobile station 44 Primary operation information 5 Secondary wireless communication system 50 Secondary operation server 51, 51A to 51E Secondary base station 53 Interference wave 54 Secondary operation information 61, 62 Antennas 612 to 616, 623 to 626, 645 Paths 63, 64, 65, 66 Clutter 631, 641, 651, 661 Vertex

Claims (12)

A calculation device that estimates a propagation path between a primary base station and a secondary base station and predicts a propagation loss in the propagation path;
an input/output device that outputs an output signal according to the propagation loss;
The computing device includes:
selecting, from among the clutters located between the primary base station and the secondary base station, a first dominant clutter having a maximum elevation angle when the clutter apex is viewed from the primary base station, and a second dominant clutter having a maximum elevation angle when the clutter apex is viewed from the secondary base station;
calculating, as a clutter loss, a component of the propagation loss caused by the first dominant clutter and the second dominant clutter based on a distance from the primary base station to the first dominant clutter, a distance from the first dominant clutter to the second dominant clutter, a distance from the second dominant clutter to the secondary base station, and respective altitudes of the primary base station, the first dominant clutter, the second dominant clutter, and the secondary base station;
predicting the propagation loss by approximating a component of the propagation loss excluding the clutter loss to a free space loss;
The input/output device outputs the output signal for deactivating the secondary base station when the propagation loss is lower than a predetermined threshold.
Propagation prediction system. 2. The propagation prediction system according to claim 1 ,
The computing device includes:
calculating a first clutter loss attributable to the first dominant clutter among the clutter losses based on a first distance from the primary base station to the first dominant clutter and the altitudes of the primary base station and the first dominant clutter;
A propagation prediction system that calculates a second clutter loss attributable to the second dominant clutter among the clutter losses based on a second distance from the secondary base station to the second dominant clutter and the altitudes of the secondary base station and the second dominant clutter. 3. The propagation prediction system according to claim 2 ,
a propagation prediction system for predicting the propagation loss by replacing a larger component of the clutter loss, between the first clutter loss and the second clutter loss, which are components of the clutter loss, with a free space loss. 3. The propagation prediction system according to claim 2 ,
a propagation prediction system for predicting the propagation loss by replacing a smaller component of the clutter loss, between the first clutter loss and the second clutter loss, which are components of the clutter loss, with a free space loss. 2. The propagation prediction system according to claim 1 ,
When the first dominant clutter and the second dominant clutter are the same clutter, the calculation device
a first distance from the primary base station to the same clutter and a second distance from the secondary base station to the same clutter, the shorter of these;
an altitude of a base station among the primary base station and the secondary base station, the base station having a shorter distance to the same clutter than the primary base station and the secondary base station;
the height of the same clutter;
and calculating the clutter loss based on the propagation prediction system. The propagation prediction system according to any one of claims 1 to 5 ,
The computing device includes:
when selecting the first dominant clutter and the second dominant clutter, selecting from the clutters located between the primary base station and the secondary base station, the first dominant clutter having a maximum elevation angle when a peak of the clutter is seen from the primary base station and the second dominant clutter having a maximum elevation angle when a peak of the clutter is seen from the secondary base station when the altitude of the clutter is equal to or greater than a predetermined altitude threshold is replaced with the altitude threshold,
When a first altitude of the first dominant clutter is equal to or greater than the altitude threshold, the first altitude is replaced with the altitude threshold to calculate the clutter loss;
When a second altitude of the second dominant clutter is equal to or greater than the altitude threshold, the second altitude is replaced with the altitude threshold to calculate the clutter loss. The propagation prediction system according to any one of claims 1 to 5 ,
The computing device includes:
when selecting the first dominant clutter, for each of the clutters located between the primary base station and the secondary base station, when an altitude difference between the clutter and the primary base station is equal to or greater than a predetermined altitude difference threshold, selecting from the clutter the first dominant clutter which has a maximum elevation angle when a vertex of the clutter is viewed from the primary base station when the altitude of the clutter is replaced with a value that makes the altitude difference equal to the altitude difference threshold;
When a first altitude difference between the first dominant clutter and the primary base station is equal to or greater than the altitude difference threshold, replace the altitude of the first dominant clutter with a value that makes the first altitude difference equal to the altitude difference threshold to calculate the clutter loss;
when selecting the second dominant clutter, for each of the clutters located between the primary base station and the secondary base station, when an altitude difference between the clutter and the secondary base station is equal to or greater than a predetermined altitude difference threshold, selecting from the clutter the second dominant clutter which has a maximum elevation angle when a peak of the clutter is seen from the secondary base station when the altitude of the clutter is replaced with a value that makes the altitude difference equal to the altitude difference threshold;
a propagation prediction system that calculates the clutter loss by replacing the altitude of the second dominant clutter with a value that makes the second altitude difference equal to the altitude difference threshold when a second altitude difference between the second dominant clutter and the secondary base station is equal to or greater than the altitude difference threshold. The propagation prediction system according to any one of claims 1 to 5 ,
The computing device includes:
when selecting the first dominant clutter and the second dominant clutter, when a vertical length from an apex of the clutter to a virtual straight line connecting the primary base station and the secondary base station is equal to or greater than a predetermined length threshold for each of the clutters located between the primary base station and the secondary base station, selecting from the clutters the first dominant clutter for which the elevation angle when the apex of the clutter is seen from the primary base station and the second dominant clutter for which the elevation angle when the apex of the clutter is seen from the secondary base station is maximum when the altitude of the clutter is replaced with an altitude at which the length becomes the length threshold,
when a first length in a vertical direction from a first vertex of the first dominant clutter to the virtual straight line is equal to or greater than a predetermined length threshold, replacing an altitude of the first dominant clutter with an altitude at which the first length becomes the length threshold, thereby calculating the clutter loss;
and when a second length in a vertical direction from a second vertex of the second dominant clutter to the virtual straight line is equal to or greater than the length threshold, calculates the clutter loss by replacing an altitude of the second dominant clutter with an altitude at which the second length becomes the length threshold. The propagation prediction system according to any one of claims 1 to 8 ,
The computing device includes:
an area in which the first dominant clutter and the second dominant clutter are located is divided into a plurality of regions, and map information is referred to in which a representative position and a representative altitude of the representative position are registered for each of the plurality of regions;
a propagation prediction system which selects, from among areas blocking a virtual straight line connecting the primary base station and the secondary base station, a first dominant area in which the elevation angle when looking from the primary base station to a virtual apex at a representative altitude of a representative position of the area is maximum as the first dominant clutter, and a second dominant area in which the elevation angle when looking from the secondary base station to a virtual apex at a representative altitude of the representative position of the area is maximum as the second dominant clutter. The propagation prediction system according to any one of claims 1 to 8 ,
The calculation device predicts the propagation loss further based on first operation information including information representing a position, altitude, and frequency band used by the primary base station, and second operation information including information representing a position, altitude, and frequency band used by the secondary base station. Estimating a propagation path between a primary base station and a secondary base station and predicting a propagation loss in the propagation path;
outputting an output signal according to the propagation loss;
Predicting the propagation loss comprises:
selecting a first dominant clutter having a maximum elevation angle when a vertex of the clutter is seen from the primary base station, from among the clutters disposed between the primary base station and the secondary base station;
selecting, from among the clutters disposed between the primary base station and the secondary base station, a second dominant clutter having a maximum elevation angle when the apex of the clutter is seen from the secondary base station;
calculating, as a clutter loss, a component of the propagation loss caused by the first dominant clutter and the second dominant clutter based on a distance from the primary base station to the first dominant clutter, a distance from the first dominant clutter to the second dominant clutter, a distance from the second dominant clutter to the secondary base station, and respective altitudes of the primary base station, the first dominant clutter, the second dominant clutter, and the secondary base station;
and approximating a component of the propagation loss excluding the clutter loss to a free space loss;
The outputting step includes:
outputting the output signal for deactivating the secondary base station when the path loss is lower than a predetermined threshold.
Includes
Propagation prediction methods. A propagation prediction program for causing a computer to realize a predetermined function,
The predetermined function is
Assuming a propagation path between a primary base station and a secondary base station, and predicting a propagation loss in the propagation path;
outputting an output signal according to the propagation loss;
Predicting the propagation loss comprises:
selecting a first dominant clutter having a maximum elevation angle when a vertex of the clutter is seen from the primary base station, from among the clutters disposed between the primary base station and the secondary base station;
selecting, from among the clutters disposed between the primary base station and the secondary base station, a second dominant clutter having a maximum elevation angle when the apex of the clutter is seen from the secondary base station;
calculating, as a clutter loss, a component of the propagation loss caused by the first dominant clutter and the second dominant clutter based on a distance from the primary base station to the first dominant clutter, a distance from the first dominant clutter to the second dominant clutter, a distance from the second dominant clutter to the secondary base station, and respective altitudes of the primary base station, the first dominant clutter, the second dominant clutter, and the secondary base station;
and predicting the propagation loss by approximating a component of the propagation loss excluding the clutter loss to a free space loss ;
The outputting step includes:
outputting the output signal for deactivating the secondary base station when the path loss is lower than a predetermined threshold.
Includes
Propagation prediction program.

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