Relay control device

Abstract

The purpose of the present disclosure is to provide a relay control device capable of determining a movement position of a mobile relay station such that relay communication quality is improved. A relay control device according to the present disclosure controls a mobile relay station that relays wireless communication between first and second wireless stations. The relay control device executes: processing for acquiring position information of the first and second wireless stations; processing for selecting a plurality of positions as candidates for a movement position of the mobile relay station on the basis of the position information; processing for calculating, for the plurality of positions, a first communication quality between the first wireless station and the mobile relay station on the basis of the antenna pattern of the first wireless station; processing for calculating, for the plurality of positions, a second communication quality between the second wireless station and the mobile relay station on the basis of the antenna pattern of the second wireless station; processing for extracting, on the basis of calculation results for the plurality of positions, an area in which each of the first and second communication qualities satisfies a required value; processing for determining the movement position of the mobile relay station as a position within the area; and processing for moving the mobile relay station to the determined movement position.

Description

Relay control device

[0001] The present disclosure relates to a relay control device that controls the moving position of a mobile relay station.

[0002] Non-Patent Document 1 proposes optimizing the moving position when moving a mobile relay station in response to changes in the movement of a terminal or the shielding environment. In this case, the moving position is determined so as to suppress moving costs such as the moving distance and moving time.

[0003] Murayama, Nakahira, Takaya, Moriyama, "Method for calculating the optimal position of a mobile relay station considering moving costs," 2022 IEICE Society Conference on Communications, B-5-58, 2022.

[0004] However, in the above method, the antenna patterns of the radio stations at the relay source and the relay destination are not considered in the calculation of the moving position. Therefore, there is a problem that the mobile relay station cannot be moved to an area where the communication quality of the relay is good.

[0005] An object of the present disclosure is to provide a relay control device capable of determining the moving position of a mobile relay station so as to improve the communication quality of the relay in order to solve the above problems.

[0006] An aspect of the present disclosure is a relay control device that controls a mobile relay station that relays wireless communication between a first radio station and a second radio station, the process of obtaining the position information of the first radio station and the second radio station, and based on the position information, selecting a plurality of positions as candidates for the moving position of the mobile relay station, calculating the first communication quality between the first radio station and the mobile relay station for the plurality of positions based on the antenna pattern of the first radio station, and calculating the second communication quality between the second radio station and the mobile relay station for the plurality of positions based on the antenna pattern of the second radio station, extracting an area where each of the first communication quality and the second communication quality satisfies a required value based on the calculation results for the plurality of positions, and a determination process of determining the moving position of the mobile relay station to a position within the area, and a process of moving the mobile relay station to the determined moving position are preferably configured to be executed.

[0007] The relay control device of this disclosure extracts areas where the first communication quality between the first radio station and the mobile relay station, and the second communication quality between the second radio station and the mobile relay station, each meet the required values, based on the antenna patterns of the first radio station and the second radio station. Since the mobile relay station's position is determined from within these areas, the mobile relay station's position can be calculated to improve the relay communication quality.

[0008] This is a diagram illustrating control by the relay control device according to Embodiment 1. This is a diagram illustrating the method for determining the movement position considering the antenna pattern according to Embodiment 1. This is a block diagram showing an example configuration of the relay control device according to Embodiment 1. This is a diagram showing the hardware configuration of the relay control device according to Embodiment 1. This is a flowchart illustrating the processing performed by the CPU of the relay control device according to Embodiment 1. This is the line-of-sight rate P according to Embodiment 2. l This diagram outlines a method for determining the movement position, taking into consideration the following: Line of sight ratio P according to Embodiment 2. l This figure shows the method for calculating the forecast rate P according to Embodiment 2. l This diagram illustrates a method for determining the movement position, taking the following into consideration. This flowchart illustrates the process executed by the CPU of the relay control device according to Embodiment 2.

[0009] Embodiments of this disclosure will be described with reference to the drawings. The same or corresponding components will be denoted by the same reference numerals, and repetition of the description may be omitted.

[0010] Embodiment 1 Figure 1 is a diagram illustrating the control by the relay control device 100 according to Embodiment 1. The relay control device 100 controls the movement of the mobile relay station 130. The mobile relay station 130 is a radio station that relays radio communication between the first radio station 110 and the second radio station 120, and moves to a position instructed by the relay control device 100. The mobile relay station 130 here is assumed to be, for example, a small unmanned aerial vehicle such as a drone, or an unmanned aerial vehicle (UAV), but any mobile radio station may be a ground station.

[0011] The first radio station 110 is assumed to be a small unmanned aerial vehicle or a mobile non-ground terminal such as an unmanned aerial vehicle, but it may also be a ground mobile station or fixed station. The second radio station 120 is assumed to be a ground fixed station or mobile station, but it may also be a non-ground radio station. If the second radio station 120 is a ground station, the relay control device 100 may be housed in the second radio station 120.

[0012] The relay control device 100 determines the mobile relay station 130's position after considering the antenna patterns of the first radio station 110 and the second radio station 120.

[0013] <Method for determining the mobile position considering the antenna pattern> Figure 2 is a diagram illustrating the method for determining the mobile position considering the antenna pattern according to Embodiment 1. For the relay control device 100, the antenna patterns of the first radio station 110 and the second radio station 120 are known as directivity functions. The relay control device 100 extracts an area 50 in which the first communication quality between the first radio station 110 and the mobile relay station 130, and the second communication quality between the second radio station 120 and the mobile relay station 130, satisfy the required values. Furthermore, the relay control device 100 performs a process (determination process) to determine the mobile position of the mobile relay station 130 from within the area 50.

[0014] The following section specifically explains how to determine the movement position considering the antenna pattern. Here, we will explain the case where the first and second communication quality levels are at the received level.

[0015] The coordinate system set for the first radio station 110 is defined as the terminal coordinate system (x',y',z'), and the x' direction (i.e., (x',y',z') = (1,0,0)) is defined as the direction of travel of the first radio station 110. The polar coordinate representation of the terminal coordinate system (x',y',z') is defined as the polar coordinate system (θ',φ'). In the polar coordinate system, the radial component is omitted.

[0016] In Figure 2, the directivity of the antenna of the first radio station 110 is shown to be maximized in the direction of travel of the first radio station 110, that is, in the terminal coordinate system (x',y',z')=(1,0,0) and in the polar coordinate system (θ',φ')=(90°,0°). However, the direction of antenna directivity is not limited.

[0017] Also, the coordinate system set on the ground is taken as the reference coordinate system (x, y, z). The coordinates of the position of the first radio station 110 represented in the reference coordinate system are (X A , Y A , Z A ). The position coordinates (X A , Y A , Z A ) are the position coordinates of the origin of the terminal coordinate system (x', y', z') as seen from the reference coordinate system. Similarly, the coordinates of the position of the second radio station 120 represented in the reference coordinate system are (X B , Y B , Z B ), and the coordinates of the position of the mobile relay station 130 are (X C , Y C , Z C ). Further, the polar coordinate representation of the reference coordinate system (x, y, z) is taken as the polar coordinate system (θ, φ). Note that the reference coordinate system (x, y, z) does not necessarily have to be set on the ground and may be set at a point in space.

[0018] Note that the directivity of the antenna of the second radio station 120 is set to be maximum, for example, in the direction of (θ, φ) = (θ B , φ B ) in the polar coordinate system in the reference coordinate system (x, y, z). However, the directivity direction of the antenna is not limited.

[0019] First, when the terminal coordinate system (x', y', z') is rotated by an angle α about the x-axis, an angle β about the y-axis, and an angle γ about the z-axis with respect to the reference coordinate system (x, y, z), the relationship between the two coordinate systems is represented by the following (Equation 1).

[0020]

[0021] Note that the rotation angles α, β, γ of the terminal coordinate system (x', y', z') can be measured by mounting an attitude control sensor or the like on the first radio station 110.

[0022] Next, the direction (θ A , φ<mml:math xmlns:mml="http: / / www.w3.org / 1998 / Math / MathML"><mml:mi mathvariant="normal">0000019< / mml:mi>< / mml:math>), φ A , φ A ) and the distance r from the first radio station 110 at the position (X A , Y A , Z A ) represented in the reference coordinate system to the mobile relay station 130 as seen from the first radio station 110.A These are expressed by (Equation 2) and (Equation 3) below, respectively.

[0023]

[0024]

[0025] By substituting (Equation 1) and (Equation 3) into (Equation 2), the direction (θ) of the mobile relay station 130 as seen from the first radio station 110 can be determined. A ,φ A ) can be obtained by displaying it in the reference coordinate system (x, y, z).

[0026] The calculated (θ) A ,φ A ) is the directivity function G of the first radio station 110 A By substituting (θ',φ'), the antenna gain G of the first radio station 110 relative to the mobile relay station 130 can be obtained. A (θ A ,φ A )

[0027] Next, the reception level (hereinafter referred to as the first reception level) R when the mobile relay station 130 receives the radio signal from the first radio station 110. c (X C ,Y C ,Z C ) is calculated. The first received level is the antenna gain G of the first radio station 110. A (θ A ,φ A Using ), it can be expressed as follows (Equation 4).

[0028]

[0029] In (Equation 4), T A This is the transmission level (dBm) of the first radio station 110, L A This represents the propagation loss (dB) of the radio signal from the first radio station 110. The unit of the first received level is dBm, but is not limited to dBm.

[0030] From (Equation 4), the first reception level at the mobile relay station 130 is the antenna gain G of the first radio station 110. A (θ A ,φ A It depends on ).

[0031] Note that propagation loss L A L is the free-space loss. fA and forecast rate P l Loss L caused by R (P l Note that it can be expressed as the sum of ) by the following (Equation 5).

[0032]

[0033] Similarly, the antenna gain G of the second radio station 120 B By substituting (θ,φ), we will determine the reception level (hereinafter referred to as the second reception level) when the mobile relay station 130 receives the radio signal from the second radio station 120. The position (X) is expressed in the reference coordinate system (x,y,z). B ,Y B ,Z B The direction of the mobile relay station 130 as seen from the second radio station 120 (θ B ,φ B ) and distance r B This is expressed by the following equations (6) and (7).

[0034]

[0035]

[0036] By substituting (Equation 7) into (Equation 6), the direction of the mobile relay station 130 as seen from the second radio station 120 (θ B ,φ B ) can be obtained by displaying it in the reference coordinate system (x, y, z).

[0037] The calculated (θ) B ,φ B ) is the directivity function G of the second radio station 120 B By substituting (θ,φ), the antenna gain G of the second radio station 120 relative to the mobile relay station 130 can be obtained. B (θ B ,φ B )

[0038] Furthermore, the second reception level is expressed by the following equation (8).

[0039]

[0040] In (Equation 8), T BThis is the transmission level (dBm) of the second radio station 120, L B This represents the propagation loss (dB) of the radio signal from the second radio station 120. The unit of the second received level is dBm, but is not limited to dBm.

[0041] From (Equation 8), the second reception level at the mobile relay station 130 is equal to the antenna gain G of the second radio station 120. B (θ B ,φ B It depends on ).

[0042] Note that propagation loss L B L is the free-space loss. fB and forecast rate P l Loss L caused by R (P l The sum of ) is expressed as follows (Equation 9).

[0043]

[0044] The relay control device 100 extracts an area 50 in which the first reception level obtained by (Equation 4) and the second reception level obtained by (Equation 8) each satisfy the required values, and determines the mobile relay station 130's position within the area 50.

[0045] The requested values ​​should preferably be set individually for the first and second reception levels, but they may also be set as a combined value for the first and second reception levels. Alternatively, the requested values ​​may be set using other methods.

[0046] Furthermore, in determining the relocation position, the relocation position may be the position within area 50 where the sum of the first reception level and the second reception level is highest. Alternatively, the relocation position may be the position within area 50 where either the first reception level or the second reception level is highest, or it may be determined by other methods.

[0047] In the above explanation, the first and second communication quality were described as being based on the received level. However, the first and second communication quality are not limited to the received level; they may also be propagation loss, received power strength such as RSSI and RSRQ, noise indicators such as RSRP and SINR, or other indicators. Furthermore, the first and second communication quality may be based on different indicators.

[0048] Figure 3 is a block diagram showing an example configuration of the relay control device 100 according to Embodiment 1. The communication device 38 acquires the position coordinates of the first radio station 110, the second radio station 120, and the mobile relay station 130, and notifies the mobile position determination circuit 32 of the received position coordinates. The mobile position determination circuit 32 determines the mobile position of the mobile relay station 130 using the method described above, based on the notified position coordinates and the antenna patterns of the first radio station 110 and the second radio station 120 stored in the storage device 36.

[0049] Specifically, the mobile position determination circuit 32 first selects multiple locations as candidate mobile positions for the mobile relay station 130 based on the position information of the first radio station 110 and the second radio station 120. Furthermore, the mobile position determination circuit 32 sets each of the selected locations as a virtual mobile position for the mobile relay station 130. In addition, the mobile position determination circuit 32 calculates a first communication quality between the first radio station 110 and the mobile relay station 130 for multiple locations based on the antenna pattern of the first radio station 110. Furthermore, the mobile position determination circuit 32 calculates a second communication quality between the second radio station 120 and the mobile relay station 130 for multiple locations based on the antenna pattern of the second radio station 120.

[0050] Furthermore, the mobile position determination circuit 32 extracts an area 50 from the calculation results for multiple locations in which both the first and second communication quality meet the required values. The mobile position determination circuit 32 then determines the location within area 50 as the mobile position of the mobile relay station 130. Finally, the mobile position determination circuit 32 notifies the communication device 38 of the information of the determined mobile position.

[0051] The communication device 38 notifies the mobile relay station 130 of its moving location, causing the mobile relay station 130 to move to that location. The storage device 36 stores the antenna patterns of the first radio station 110 and the second radio station 120 as directional functions. The location information storage device 37 stores the location information of the first radio station 110, the second radio station 120, and the mobile relay station 130.

[0052] Figure 4 shows the hardware configuration of the relay control device 100 according to Embodiment 1. The processing performed by the relay control device 100 may be executed by a program using a computer equipped with a CPU and memory, in which a program for determining the movement position is stored in the memory. Alternatively, it may be executed by a program using an integrated circuit such as an FPGA (Field Programmable Gate Array). The program for determining the movement position may be provided by recording it on a storage medium, or it may be provided via a network.

[0053] The relay control device 100 has an input unit 40, an output unit 41, a communication unit 42, a CPU (Central Processing Unit, also called a processor) 43, a memory 44, and an HDD (Hard Disk Drive) 45 connected via a bus 46, and functions as a computer. The relay control device 100 is also configured to input and output data to and from a storage medium 47 that can be read by a computer.

[0054] The input unit 40 is, for example, a keyboard and mouse. The output unit 41 is, for example, a display device such as a display.

[0055] The communication unit 42 is, for example, the aforementioned communication device 38 that communicates with the mobile relay station 130.

[0056] Memory 44 refers to volatile or non-volatile semiconductor memory such as RAM, ROM, and flash memory, or magnetic disks, flexible disks, optical disks, and DVDs.

[0057] The CPU 43 controls each component of the relay control device 100 and performs processes such as determining the movement position. The memory 44 and HDD 45 are storage devices 36 that store, for example, a program for determining the movement position, and data on the antenna patterns of the first radio station 110 and the second radio station 120. The memory 44 and HDD 45 are also location information storage devices 37 that store location information of the first radio station 110, the second radio station 120, and the mobile relay station 130.

[0058] The storage medium 47 is capable of storing programs for determining movement positions, etc., that enable the relay control device 100 to execute its functions. The storage medium 47 is a USB (Universal Serial Bus) memory, a CD-ROM (Compact Disc Read Only Memory), etc.

[0059] Note that the architecture of the relay control device 100 is not limited to the example shown in the figure.

[0060] Figure 5 is a flowchart illustrating the processing performed by the CPU 43 of the relay control device 100 according to Embodiment 1. The CPU 43 reads the movement position determination program stored in the memory 44 or HDD 45 and executes the following processing.

[0061] First, the position coordinates of the first radio station 110, the second radio station 120, and the mobile relay station 130 are obtained (step S01). Furthermore, based on the obtained position information, multiple positions are selected as candidates for the mobile position of the mobile relay station 130 (step S02). Furthermore, based on the antenna pattern of the first radio station 110, the first communication quality between the first radio station 110 and the mobile relay station 130 is calculated for multiple positions (step S03). Furthermore, based on the antenna pattern of the second radio station 120, the second communication quality between the second radio station 120 and the mobile relay station 130 is calculated for multiple positions (step S04).

[0062] Furthermore, from the calculation results for multiple locations, an area 50 is extracted in which both the first and second communication quality meet the required values ​​(step S05). Then, the location within area 50 is determined as the mobile relay station 130's relocation location (step S06). Finally, the mobile relay station 130 is moved to the determined relocation location by notifying it of this location (step S07).

[0063] As described above, the relay control device 100 of this disclosure extracts an area 50 in which the first communication quality between the first radio station 110 and the mobile relay station 130, and the second communication quality between the second radio station 120 and the mobile relay station 130, each satisfy the required values, based on the antenna patterns of the first radio station 110 and the second radio station 120. Since the mobile position of the mobile relay station 130 is determined from within the area 50, the mobile position of the mobile relay station 130 can be determined in such a way that the relay communication quality is improved.

[0064] By having the mobile relay station 130 relay wireless communication at a moving position determined by the relay control device 100 of this disclosure, stabilization and long-range communication between the first radio station 110 and the second radio station 120 can be achieved. Furthermore, for example, when sequentially switching between multiple mobile relay stations 130 in response to the movement of the first radio station 110, the number of switches can be reduced. This prevents communication interruptions associated with switching, and as a result, communication capacity can be improved.

[0065] The relay control device 100, having the effects described above, can be applied to a system in which a ground-based controller flies an inspection drone to inspect equipment such as wind power generation devices. In Japan, Level 4 autonomous control of drones was legalized in December 2022, making it possible to fly drones even beyond the operator's line of sight. In that case, the distance between the ground-based controller and the inspection drone will be several kilometers, making it difficult for the controller to communicate directly with the inspection drone. By introducing a mobile relay station 130 controlled by the relay control device 100 of this disclosure, it is possible to stabilize and extend the range of wireless communication between the ground-based controller and the inspection drone.

[0066] In Embodiment 2 and subsequent embodiments, the changes from Embodiment 1 will be described.

[0067] The relay control device 100 of this embodiment has a line-of-sight ratio P during relay. l By taking this into consideration, the mobile relay station 130's relocation position is determined from within the area 50 described in Embodiment 1.

[0068] <Method for determining the movement position considering the line of sight rate> Figure 6 shows the line of sight rate P according to Embodiment 2.l This diagram outlines a method for determining the movement position, taking the following factors into consideration. The relay control device 100 divides area 50 into multiple sections. The method of dividing the sections is not limited, but for example, it may be divided into predetermined sizes.

[0069] The relay control device 100 calculates the centroid point for each of the divided sections and sets the centroid point as the virtual moving position of the mobile relay station 130. Furthermore, the relay control device 100 calculates the first Fresnel zone 10 between the first radio station 110 and the mobile relay station 130 for each centroid point.

[0070] The relay control device 100 of this embodiment stores information such as the location and size of the obstructing objects 60 within the area where the first radio station 110 and the second radio station 120 are located in the storage device 36. For each centroid point, the relay control device 100 calculates the line-of-sight ratio (hereinafter referred to as the first line-of-sight ratio) P between the first radio station 110 and the mobile relay station 130 based on the information of the first Fresnel zone 10 and the obstructing objects 60 located within the first Fresnel zone 10. l Calculate.

[0071] Furthermore, the relay control device 100 calculates the third communication quality between the first radio station 110 and the mobile relay station 130 for each centroid point. The third communication quality is, for example, the antenna gain G of the first radio station 110 relative to the mobile relay station 130. A (θ A ,φ A ) is the reception level of the radio signal from the mobile relay station 130 at the first radio station 110, but is not limited to this. The third communication quality may be, for example, propagation loss, noise index, or other index.

[0072] Similarly, the relay control device 100 calculates the first Fresnel zone 20 between the second radio station 120 and the mobile relay station 130 for each centroid point. Furthermore, for each centroid point, the relay control device 100 calculates the line-of-sight ratio (hereinafter referred to as the second line-of-sight ratio) P between the second radio station 120 and the mobile relay station 130 based on the information of the first Fresnel zone 20 and the obstructions 60 present in the first Fresnel zone 20. l Calculate.

[0073] Furthermore, the relay control device 100 calculates the fourth communication quality between the second radio station 120 and the mobile relay station 130 for each centroid point. The fourth communication quality is, for example, the antenna gain G of the second radio station 120 relative to the mobile relay station 130. B (θ B ,φ B ) is the reception level of the radio signal from the mobile relay station 130 at the second radio station 120, but is not limited to this. The fourth communication quality may be, for example, propagation loss, noise index, or other index. Furthermore, the fourth communication quality may be an index different from the third communication quality.

[0074] The relay control device 100 determines the centroid point to be the mobile relay station 130's moving position based on the first line-of-sight rate, second line-of-sight rate, third communication quality, and fourth communication quality calculated for each centroid point.

[0075] Figure 7 shows the line of sight P according to Embodiment 2. l This diagram shows the calculation method. For the sake of explanation, the mobile relay station 130 is referred to as the transmitting station 131, and the first radio station 110 or the second radio station 120 is referred to as the receiving station 111.

[0076] The distance from transmitting station 131 is d. １ When there is an obstruction 60 at a distance d2 from the receiving station 111, the first Fresnel radius r of the radio waves from the transmitting station 131 is expressed as follows, where λ is the wavelength of the radio waves.

[0077]

[0078] Generally, the forecast rate P l There is no unique formula for calculating this. However, in this disclosure, as an example, the ratio of the area obtained by subtracting the blocking area s, which is the cross-sectional area of ​​the shielding 60 itself, from the cross-sectional area of ​​the first Fresnel zone at the location of the shielding 60 to the cross-sectional area of ​​the first Fresnel zone is the line-of-sight P. l Let's assume that in this case, the forecast rate P l This is expressed in the following (Equation 11).

[0079]

[0080] The barrier area s can be calculated as s = h × w, for example, if the height of the barrier 60 is h and its width is w. However, the method for calculating the barrier area s is not limited to this.

[0081] Figure 8 shows the line of sight P according to Embodiment 2. l This diagram illustrates the method for determining the movement position, taking the following into consideration. An enlarged view of area 50 is shown here. At points A, B, C, and D, which are the centroid points, the line-of-sight rate, the third communication quality, and the fourth communication quality are assumed to be as follows. The line-of-sight rate here is the average value based on the first line-of-sight rate and the second line-of-sight rate. Furthermore, the third communication quality is assumed to be the reception level at the first radio station 110 (hereinafter referred to as the third reception level), and the fourth communication quality is assumed to be the reception level at the second radio station 120 (hereinafter referred to as the fourth reception level). Point A: Line of sight = 90%, 3rd reception level = -60dBi, 4th reception level = -70dBi Point B: Line of sight = 80%, 3rd reception level = -80dBi, 4th reception level = -90dBi Point C: Line of sight = 80%, 3rd reception level = -60dBi, 4th reception level = -70dBi Point D: Line of sight = 98%, 3rd reception level = -40dBi, 4th reception level = -50dBi

[0082] The relay control device 100 extracts a centroid point where at least one of the third reception level and the fourth reception level satisfies the required value, and determines the centroid point with the highest line-of-sight ratio from among the extracted centroid points as the move position. In the example shown in the figure, the move position is determined to be point D.

[0083] However, the relocation position may be determined by other means. For example, the relocation position may be determined by considering only the line-of-sight ratio of each centroid and selecting the centroid with the highest line-of-sight ratio, or by extracting centroids that satisfy the required line-of-sight ratio and selecting the centroid with the highest sum of the third reception level and the fourth reception level from among the extracted centroids as the relocation position. In this case, the multiple sections obtained by dividing area 50 may be reclassified according to multiple predetermined line-of-sight ratio thresholds.

[0084] Alternatively, the relay control device 100 may set a route for moving the mobile relay station 130 to the determined moving position and control the mobile relay station 130 to move along that route. In this case, the relay control device 100 determines the route such that the fluctuation in the communication speed at the first radio station 110, i.e., the fluctuation in the third reception level, is minimized. This ensures that the reception level at the first radio station 110 remains stable even when the mobile relay station 130 is moving. The same applies if the first radio station 110 is replaced with the second radio station 120, and the third reception level is replaced with the fourth reception level.

[0085] Furthermore, the relay control device 100 may control the attitude of the mobile relay station 130 by taking into consideration the antenna pattern of the mobile relay station 130. In this case, the relay control device 100 controls the attitude of the mobile relay station 130 at the determined mobile position so that the sum of the third reception level and the fourth reception level is maximized, or the variation between the third reception level and the fourth reception level is minimized. It is assumed that the antenna pattern of the mobile relay station 130 is omnidirectional in the horizontal direction and directional in the elevation direction, but the direction of direction is not limited.

[0086] In the above explanation, the relay control device 100 calculates the center of gravity for each of the multiple sections and uses the center of gravity as the virtual moving position of the mobile relay station 130. However, it is not always necessary to calculate the center of gravity, and any position within each section may be used as the virtual moving position of the mobile relay station 130.

[0087] Figure 9 is a flowchart illustrating the process executed by the CPU 43 of the relay control device 100 according to Embodiment 2. The process described in this flowchart is the process executed in step S06 of Embodiment 1.

[0088] First, area 50 is divided into multiple sections (step S11). Furthermore, each of the multiple sections is designated as a virtual mobile position for the mobile relay station 130 (step S12).

[0089] Further, for each of the plurality of sections, the first Fresnel zone 10 between the first radio station 110 and the mobile relay station 130 is calculated (step S13). Further, a first line-of-sight rate is calculated for the plurality of sections based on the first Fresnel zone 10 and information on the obstacles 60 existing in the first Fresnel zone 10 (step S14). Further, for each of the plurality of sections, the third communication quality between the first radio station 110 and the mobile relay station 130 is calculated (step S15).

[0090] Further, for each of the plurality of sections, the first Fresnel zone 20 between the second radio station 120 and the mobile relay station 130 is calculated (step S16). Further, a second line-of-sight rate is calculated for the plurality of sections based on the first Fresnel zone 20 and information on the obstacles 60 existing in the first Fresnel zone 20 (step S17). Further, for each of the plurality of sections, the fourth communication quality between the second radio station 120 and the mobile relay station 130 is calculated (step S18).

[0091] Further, based on the first line-of-sight rate, the second line-of-sight rate, the third communication quality, and the fourth communication quality, the moving position of the mobile relay station 130 is determined from among the plurality of sections (step S19).

[0092] As described above, the relay control device 100 of the present embodiment determines the moving position of the mobile relay station 130 from within the area 50 by considering the line-of-sight rate P l at the time of relay. Thereby, the communication quality can be further improved as compared with the first embodiment.

[0093] In the above description, it has been stated that the relay control device 100 calculates both the first line-of-sight rate and the second line-of-sight rate and determines the moving position of the mobile relay station 130 based on both. However, the moving position does not necessarily have to be determined based on both the first line-of-sight rate and the second line-of-sight rate, and it may be determined based on at least one of them. For example, it may be known that the line of sight between the first radio station 110 and the mobile relay station 130 is good. In such a case, only the second line-of-sight rate may be calculated, and the moving position of the mobile relay station 130 may be determined based on the second line-of-sight rate.

[0094] This disclosure is not limited to the embodiments described above, and various modifications can be made during implementation without departing from its essence. Furthermore, each embodiment and its modifications may be combined as appropriate, and in that case, the combined effects can be obtained.

[0095] 10: First Fresnel Zone 20: First Fresnel Zone 32: Movement Position Determination Circuit 36: Memory Device 37: Position Information Memory Device 38: Communication Device 40: Input Unit 41: Output Unit 42: Communication Unit 43: CPU 44: Memory 45: HDD 46: Bus 47: Storage Medium 50: Area 60: Obstruction 100: Relay Control Device 110: First Radio Station 111: Receiving Station 120: Second Radio Station 130: Mobile Relay Station 131: Transmitting Station

Claims

1. A relay control device for controlling a mobile relay station that relays wireless communication between a first radio station and a second radio station, the relay control device being configured to perform: a process of acquiring location information of the first radio station and the second radio station; a process of selecting a plurality of locations as candidates for the mobile relay station's relocation based on the location information; a process of calculating a first communication quality between the first radio station and the mobile relay station for the plurality of locations based on the antenna pattern of the first radio station; a process of calculating a second communication quality between the second radio station and the mobile relay station for the plurality of locations based on the antenna pattern of the second radio station; a process of extracting an area where the first communication quality and the second communication quality each satisfy a required value based on the calculation results for the plurality of locations; a determination process of determining the mobile relay station's relocation to a location within the area; and a process of moving the mobile relay station to the determined relocation.

2. The relay control device according to claim 1, wherein the process for calculating the first communication quality is to calculate the antenna gain of the first radio station with respect to the mobile relay station based on the antenna pattern of the first radio station, and determine the first communication quality based on the calculated antenna gain, and the process for calculating the second communication quality is to calculate the antenna gain of the second radio station with respect to the mobile relay station based on the antenna pattern of the second radio station, and determine the second communication quality based on the calculated antenna gain.

3. The relay control device according to claim 2, wherein the first communication quality and the second communication quality are the reception levels at the mobile relay station.

4. The relay control device according to any one of claims 1 to 3, wherein the determination process comprises: a process of dividing the area into a plurality of sections; a process of making each of the plurality of sections a virtual moving position of the mobile relay station; a process of calculating a first Fresnel zone between at least one of the first radio station and the second radio station and the mobile relay station for each of the plurality of sections; a process of calculating a line-of-sight ratio between at least one of the first radio station and the second radio station and the mobile relay station for the plurality of sections based on the first Fresnel zone and information on obstacles present in the first Fresnel zone; and a process of determining the moving position of the mobile relay station from among the plurality of sections based on the line-of-sight ratio.

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