Radio communication system and radio communication method

Abstract

A radio communication system is provided with a control apparatus and at least one base station apparatus. The control apparatus comprises: an acquisition unit that acquires first information indicating the distance from the at least one base station apparatus to a terminal apparatus, and second information relating to a direction perpendicular to the central axis direction of the at least one base station apparatus; and a determination unit that, on the basis of the first information and the second information acquired by the acquisition unit, determines whether the terminal apparatus is to communicate with the at least one base station apparatus.

Description

Wireless communication systems and wireless communication methods

[0001] The present invention relates to a wireless communication system and a wireless communication method.

[0002] When a wireless communication terminal device moves between multiple base station devices, it is necessary to switch connections to the optimal base station device and to switch base station devices quickly. In mobile communications, the wireless quality of multiple base station devices can be constantly monitored, allowing for the detection of the optimal base station device at all times. If the base station device to which the terminal device is currently connected is not the optimal base station device, it is possible to switch to the optimal base station device immediately. Furthermore, the optimal base station device to which the terminal device is connected can be determined even before the switch is made. Therefore, the terminal device can switch the base station device it is connected to in a short amount of time without spending time searching for nearby base station devices.

[0003] On the other hand, wireless communication that does not assume mobility, such as Wi-Fi (Local Area Network), does not assume the existence of multiple base station devices. Therefore, the terminal device only begins searching for a new base station device after the base station device to which it is connected has been disconnected. Consequently, the terminal device maintains its connection to a base station device until it disconnects from the currently connected base station device. This creates a problem where, even if there is another optimal base station device with better wireless quality, the terminal device maintains its connection to a base station device with degraded wireless quality. Furthermore, because the terminal device begins searching for a new base station device only after the connection has been disconnected, there is a problem in that switching processing takes time.

[0004] As a countermeasure, in the case of wireless communication using a high-frequency band, a method is known in which the positioning of a terminal device is performed by the communication radio wave itself, and based on the positioning, the terminal device switches the connection to an optimal base station device (Non-Patent Document 1). In the method described in Non-Patent Document 1, as a countermeasure against large radio wave propagation attenuation in the high-frequency band, a narrow-directional antenna beam is utilized to obtain system gain. Further, in the method described in Non-Patent Document 1, the azimuth estimation of the terminal device using a narrow-directional antenna beam (hereinafter referred to as the antenna beam) and the distance estimation of the terminal device using the broadband nature of the signal band are performed by utilizing the broadband nature of the signal band. Thereby, in the method described in Non-Patent Document 1, even with only one base station device, the position estimation of the terminal device can be performed with high accuracy. Therefore, it is possible to perform the positioning of the terminal device even in wireless communication where only one base station device such as a wireless LAN can be connected.

[0005] In the method described in Non-Patent Document 1, by performing the positioning of the terminal device using the communication radio wave, the switching of the base station device is performed with high accuracy at the boundary of the design zone of each base station device. As the design zone, there is a design based on the distance of each base station device. For example, the zone of each base station device is set within a certain distance, or the terminal device is connected to the base station device that is the closest in distance at the position of each terminal device. In this case, depending on the position of the terminal device measured, if the distance to the connected base station device is within a certain distance, the terminal device continues the connection with that base station device, and if it exceeds a certain distance range, the terminal device switches the connection to a base station device whose another distance falls within a certain range.

[0006] As a result, in the method described in Non-Patent Document 1, even if high-speed wireless transmission is still possible with the currently connected base station device, if the terminal location is in a position where high-speed wireless transmission is possible even when connected to an adjacent base station device, the system switches to the adjacent base station device in advance, before the wireless transmission speed slows down with the currently connected base station device. Thus, in the method described in Non-Patent Document 1, the base station device is switched while maintaining high-speed wireless transmission. Furthermore, in the method described in Non-Patent Document 1, the optimal base station device based on the design zone is specified based on the location of the terminal device, thus eliminating the time the terminal device spends searching for nearby base station devices and enabling a quick switch of base station devices. In this way, by taking advantage of the characteristics of high-frequency band wireless communication, even with just one base station device, the direction and distance of the terminal device are estimated using communication radio waves, the terminal location is estimated, and the system switches to the optimal base station device at the boundary of the design zone.

[0007] In base station equipment switching based on wireless quality, such as the normal reception level, the reception level fluctuates greatly due to fading phenomena such as reflection from the ground, and distance attenuation is small in a free-space environment, occurring at about 6 dB when the distance doubles. Therefore, wireless quality such as the reception level has low accuracy in identifying the location of terminal devices, making it difficult to perform high-precision base station switching at the boundary of design zones. On the other hand, the method described in Non-Patent Document 1 identifies the location of terminal devices with high precision.

[0008] Furthermore, in outdoor environments where GPS (Global Positioning System) can be used, it is possible to perform processing similar to the method described in Non-Patent Document 1 by obtaining the location of the terminal device using GPS. However, the method described in Non-Patent Document 1 makes it possible to identify the location of the terminal device even in indoor environments where GPS cannot be used, or in terminal devices that do not have GPS.

[0009] “Handover Experiment of 60-GHz-Band Wireless LAN in over 200-km / h High-Speed ​​Mobility Environment,” Tatsuhiko IWAKUNI, Daisei UCHIDA, Takuto ARAI, Shuki WAI, and Naoki KITA, IEICE TRANS. COMMUN. , VOL. E106-B, NO. 4 APRIL 2023

[0010] The method described in Non-Patent Document 1 positions the terminal device using azimuth estimation based on the antenna beam direction and distance estimation based on a broadband signal. However, the accuracy of azimuth estimation depends on the granularity of the antenna beam angle. If the granularity is coarse, it results in azimuth estimation errors, and if the distance is long, the positioning accuracy deteriorates in proportion to the distance. For example, if the direction of the base station's antenna beam can only be changed in 10-degree increments, the error can reach a maximum of 10 degrees. If the distance to the terminal device is 100m, a 10-degree azimuth error will result in a large error of 17m or more in the estimated position. Therefore, in the method described in Non-Patent Document 1, when the terminal device moves in the azimuth direction of the base station, the accuracy of identifying the terminal device's position deteriorates, making it difficult to switch base station devices with high accuracy at the boundaries of the design zone.

[0011] Furthermore, regarding the beam direction of the antenna beam, it is usually electronically aligned using an array antenna. However, the antenna directivity gain of an array antenna decreases as the beam direction approaches an obtuse angle, and the SNR (Signal-to-Noise Ratio) deteriorates. Therefore, when the beam direction emitted by the base station equipment is obtuse, the accuracy of the beam direction deteriorates compared to when the beam direction is acute. Consequently, even if the terminal equipment does not move in the azimuth direction, if the azimuth angle is obtuse, the accuracy of azimuth estimation deteriorates, the accuracy of positioning the terminal equipment by the base station equipment worsens, and it becomes difficult to switch base station equipment with high precision at the boundary of the design zone.

[0012] On the other hand, when zone design for each base station device is based on distance, that is, when the zone for each base station device is set to be within a certain distance range, or when the zone for a terminal device is set to be the base station device that is closest to the terminal device, the terminal device may move in the azimuthal direction relative to the base station device. In this case, the positioning accuracy deteriorates in proportion to the coarseness of the beam direction granularity and the distance. Furthermore, when the terminal device moves in the azimuthal direction, the probability that the terminal device will enter an obtuse angle range relative to the base station device where beam direction accuracy is likely to deteriorate also increases. If the terminal device enters that obtuse angle range, the accuracy of azimuthal estimation deteriorates further, and the accuracy of position estimation also deteriorates. In this case, when switching base station devices based on the terminal device's position, using conventional methods would result in a deterioration of the accuracy of terminal device position estimation, which in turn deteriorates the accuracy of base station device switching, making it difficult for the terminal device to switch to a connected base station device with high accuracy at the boundary of the design zone.

[0013] In other words, the method described in Non-Patent Document 1 had the problem that even if the terminal device was located at an obtuse angle to the beam emitted by the base station device, and the accuracy of the base station device's estimation of the terminal device's position was low, the base station device would still initiate communication with the terminal device, making it impossible to perform sophisticated switching control between the base station device and the terminal device based on the terminal device's position.

[0014] The present invention aims to provide a technology that enables highly sophisticated switching control between a terminal device and a base station device based on the terminal device's position, and that prevents a base station device from initiating communication with a terminal device when the terminal device is located at an obtuse angle to the beam emitted by the base station device.

[0015] One aspect of the present invention is a wireless communication system comprising a control device and at least one base station device, wherein the control device includes an acquisition unit that acquires first information indicating the distance from the at least one base station device to a terminal device and second information relating to a direction perpendicular to the central axis direction of the at least one base station device, and a determination unit that determines whether the terminal device communicates with the at least one base station device based on the first information and the second information acquired by the acquisition unit.

[0016] Another aspect of the present invention is a wireless communication method used in a wireless communication system comprising a control device and at least one base station device, wherein the method acquires first information indicating the distance from the at least one base station device to a terminal device and second information relating to a direction perpendicular to the central axis direction of the at least one base station device, and determines whether the terminal device communicates with the at least one base station device based on the acquired first information and second information.

[0017] According to the present invention, in order to enable highly sophisticated switching control between a terminal device and a base station device based on the position of the terminal device, it is possible to avoid the base station device initiating communication with the terminal device when the terminal device is located at an obtuse angle to the beam emitted by the base station device.

[0018] This is a schematic diagram of a wireless communication system according to the first embodiment of the present invention. This is a flowchart illustrating the processing performed by the control device according to the first embodiment of the present invention. This is a diagram illustrating the beam irradiation range of the first to fourth base station devices according to the first embodiment of the present invention. This is a diagram illustrating an example of a method for switching the communication destination of a terminal device according to the first embodiment of the present invention. This is a flowchart illustrating the processing performed by the control device according to a modified version of the first embodiment of the present invention. This is a diagram illustrating distance X and distance Y. This is a diagram illustrating the beam irradiation range of the first to fourth base station devices according to a modified version of the first embodiment of the present invention. This is a diagram illustrating an example of a method for switching the communication destination of a terminal device according to a modified version of the first embodiment of the present invention. This is a flowchart illustrating the processing performed by the control device according to the second embodiment of the present invention. This is a diagram illustrating the beam irradiation range of the first to fourth base station devices according to the second embodiment of the present invention. This is a diagram illustrating an example of a method for switching the communication destination of a terminal device according to the second embodiment of the present invention. This is a flowchart illustrating the processing performed by the control device according to a modified version of the second embodiment of the present invention. This is a diagram illustrating the beam irradiation range of the first to fourth base station devices according to a modified version of the second embodiment of the present invention. This is a diagram illustrating an example of a method for switching the communication destination of a terminal device according to a modified version of the second embodiment of the present invention.

[0019] Hereinafter, several embodiments of the present invention will be described with reference to the drawings. First, a first embodiment of the present invention will be described.

[0020] [First Embodiment] First, a first embodiment of the present invention will be described. Figure 1 is a schematic diagram of a wireless communication system 100 according to the first embodiment of the present invention. The wireless communication system 100 comprises a terminal device 10, a first base station device 20A, a second base station device 20B, a third base station device 20C, a fourth base station device 20D, and a control device 30.

[0021] The terminal device 10 is a portable device with wireless communication capabilities, such as a smartphone. The terminal device 10 comprises a control unit 11, a storage unit 12, and a communication unit 13. The control unit 11 is composed of a CPU (Central Processing Unit) and the like. The control unit 11 is connected to the storage unit 12 and the communication unit 13. The control unit 11 controls the storage unit 12 and the communication unit 13 that constitute the terminal device 10.

[0022] The storage unit 12 is composed of RAM (Random Access Memory) and the like. The storage unit 12 is connected to the control unit 11. The storage unit 12 stores data that terminal device 10 transmits to other terminal devices (not shown) and stores data that terminal device 10 receives from other terminal devices.

[0023] The communication unit 13 consists of a transmitting and receiving circuit and an antenna. The communication unit 13 is connected to the control unit 11. Based on the control of the control unit 11, the communication unit 13 reads data transmitted from terminal device 10 to other terminal devices (not shown) from the storage unit 12, performs transmission processing such as modulation and encoding, and transmits it from the antenna to the base station device (first base station device 20A in Figure 1). The communication unit 13 receives data transmitted from other terminal devices (not shown) to terminal device 10 with the antenna, performs reception processing such as decoding and demodulation, and outputs it to the control unit 11.

[0024] The first base station device 20A comprises a control unit 21, a storage unit 22, a communication unit 23, and a beam irradiation unit 24. The control unit 21 is composed of a CPU and the like. The control unit 21 is connected to the storage unit 22, the communication unit 23, and the beam irradiation unit 24. The control unit 21 controls the storage unit 22, the communication unit 23, and the beam irradiation unit 24 that constitute the first base station device 20A. The storage unit 22 is composed of a RAM and the like. The storage unit 22 is connected to the control unit 21. The storage unit 22 stores data that the first base station device 20A exchanges with terminal devices 10 and control devices 30.

[0025] The communication unit 23 consists of a transmitting and receiving circuit and an antenna. The communication unit 23 is connected to the control unit 21. Based on the control of the control unit 21, the communication unit 23 reads data to be transmitted to the terminal device 10 and the control device 30 from the storage unit 22, performs transmission processing such as modulation and encoding, and transmits it to the terminal device 10 and the control device 30 via the antenna. The communication unit 23 receives data transmitted from the terminal device 10 and the control device 30 to the first base station device 20A with the antenna, performs reception processing such as decoding and demodulation, and outputs it to the control unit 21.

[0026] The beam irradiation unit 24 irradiates a beam used by the first base station device 20A when searching for terminal devices 10 or communicating with terminal devices 10. The beam irradiation unit 24 is capable of irradiating a beam around the first base station device 20A, but here we will mainly describe the case in which the beam irradiation unit 24 irradiates a beam in a predetermined direction of the first base station device 20A (also referred to as the beam's central axis direction) at an acute irradiation angle (an angle greater than 0 degrees and less than 90 degrees).

[0027] In Figure 1, the base station equipment is shown as the first base station equipment 20A, the second base station equipment 20B, the third base station equipment 20C, and the fourth base station equipment 20D. However, since the configurations of the second base station equipment 20B, the third base station equipment 20C, and the fourth base station equipment 20D are the same as those of the first base station equipment 20A, the explanation of the configurations of the second base station equipment 20B, the third base station equipment 20C, and the fourth base station equipment 20D will be omitted.

[0028] Note that Figure 1 shows a case where there are four base station devices: the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D, but it is not limited to this. There can be any number of base station devices, as long as there are two or more.

[0029] The control device 30 comprises a control unit 31, a storage unit 32, and a communication unit 33. The control device 30 is a device that controls the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D. The control device 30 controls which of the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D the terminal device 10 connects to and communicates with.

[0030] The control unit 31 is composed of a CPU and the like. The control unit 31 is connected to the storage unit 32 and the communication unit 33. The control unit 31 controls the storage unit 32 and the communication unit 33 that constitute the control device 30. The control unit 31 includes an acquisition unit 311 and a calculation unit 312.

[0031] The acquisition unit 311 acquires the location information of the terminal device 10. The acquisition unit 311 also acquires the distance and angle of the terminal device 10 as seen from the first to fourth base station devices 20A, 20B, 20C, and 20D, respectively. Any method can be used to acquire the location of the terminal device 10, but for example, the location of the terminal device 10 may be acquired by GPS.

[0032] The determination unit 312 determines the base station device with which the terminal device 10 will communicate, based on the information acquired by the acquisition unit 311. The specific processing of the determination unit 312 will be described later with reference to the flowchart in Figure 2.

[0033] Figure 2 is a flowchart showing the process performed by the control device 30 according to the first embodiment of the present invention. First, the acquisition unit 311 of the control device 30 acquires location information indicating the location of the terminal device 10 (step S101). For example, since the first base station device 20A, which is communicating with the terminal device 10, knows the location of the terminal device 10, the acquisition unit 311 acquires the location information of the terminal device 10 from the first base station device 20A.

[0034] Next, the acquisition unit 311 of the control device 30 acquires the distance and angle of the terminal device 10 as seen from the base station device (for example, the first base station device 20A) to which the terminal device 10 is connected (step S102). For example, the acquisition unit 311 acquires the distance between the terminal device 10 and the first base station device 20A to which the terminal device 10 is connected. The storage unit 32 has in advance store location information indicating the locations where the first to fourth base station devices 20A, 20B, 20C, and 20D are installed. Therefore, the acquisition unit 311 acquires the distance between the terminal device 10 and the first base station device 20A based on the location information indicating the location where the first base station device 20A is installed and the location information of the terminal device acquired in step S101. The storage unit 32 also has in advance store central axis direction information indicating the direction of the central axis of the beams emitted by the first to fourth base station devices 20A, 20B, 20C, and 20D. The acquisition unit 311 acquires the angle of the terminal device 10 by determining the angle at which the terminal device 10 is located relative to the central axis of the beam emitted by the first base station device 20A.

[0035] Next, the determination unit 312 of the control device 30 determines whether the angle obtained in step S102 exceeds the angle threshold of the base station device (for example, the first base station device 20A) connected to the terminal device 10 (step S103). The angle threshold is set for all base station devices 20A, 20B, 20C, and 20D. The angle thresholds set for base station devices 20A, 20B, 20C, and 20D may be the same value or different values. The angle threshold is preferably set to an obtuse angle, for example, to 60 degrees.

[0036] If the angle obtained in step S102 exceeds the angle threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (YES in step S103), the determination unit 312 performs the processing in step S105, which will be described later. On the other hand, if the angle obtained in step S102 does not exceed the angle threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (NO in step S103), the determination unit 312 determines whether the distance obtained in step S102 exceeds the distance threshold of the base station device connected to the terminal device 10 (step S104). The distance threshold is set for all base station devices (here, the first to fourth base station devices 20A, 20B, 20C, 20D). The distance threshold set for all base station devices may be the same value or may be different values. The distance threshold is set, for example, to the distance from the location where the base station device is installed to the location where the beam of that base station device reaches.

[0037] If the distance obtained in step S102 does not exceed the distance threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (NO in step S104), the determination unit 312 performs the processing of step S110, which will be described later. On the other hand, if the distance obtained in step S102 exceeds the distance threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (YES in step S104), the acquisition unit 311 obtains the distance and angle of the terminal device 10 as seen from other base station devices (for example, the second to fourth base station devices 20B, 20C, 20D) (step S105).

[0038] Here, the acquisition unit 311 acquires the distance between the terminal device 10 and each of the other base station devices 20B, 20C, and 20D, other than the first base station device 20A to which the terminal device 10 is connected. Specifically, the acquisition unit 311 acquires the distance between the terminal device 10 and the second to fourth base station devices 20B, 20C, and 20D based on location information indicating the locations where the second to fourth base station devices 20B, 20C, and 20D are installed and the location information of the terminal device 10 acquired in step S105. In addition, for example, the acquisition unit 311 acquires the angle of the terminal device 10 by identifying the angle at which the terminal device 10 is located relative to the direction of the central axis of the beam emitted by each of the second to fourth base station devices 20B, 20C, and 20D.

[0039] Next, the determination unit 312 of the control device 30 determines whether or not there is a base station device in which the angle acquired in step S105 is within the angle threshold and the distance acquired in step S105 is within the distance threshold (step S106). If there is no base station device in which the angle acquired in step S105 is within the angle threshold and the distance acquired in step S105 is within the distance threshold (NO in step S106), the determination unit 312 performs the processing of step S110, which will be described later. On the other hand, if there is a base station device in which the angle acquired in step S105 is within the angle threshold and the distance acquired in step S105 is within the distance threshold (YES in step S106), the determination unit 312 determines whether or not there are multiple base station devices in which the angle acquired in step S105 is within the angle threshold and the distance acquired in step S105 is within the distance threshold (step S107).

[0040] If the angle obtained in step S105 is within the angle threshold and there are not multiple base station devices for which the distance obtained in step S105 is within the distance threshold (NO in step S107), that is, if there is only one base station device for which the angle obtained in step S105 is within the angle threshold and the distance obtained in step S105 is within the distance threshold, the decision unit 312 decides to connect the terminal device 10 to that one base station device (step S109). In this case, the decision unit 312 transmits a control signal to the base station device to which the terminal device 10 is connected (for example, the first base station device 20A) and to the one base station device determined in step S109 (for example, the second base station device 20B), thereby switching the connection of the terminal device 10 from the base station device to which the terminal device 10 is connected to to the one base station device determined in step S109. After that, the decision unit 312 performs the processing of step S110, which will be described later.

[0041] On the other hand, if there are multiple base station devices whose angles obtained in step S105 are within the angle threshold and whose distances obtained in step S105 are within the distance threshold (YES in step S107), the decision unit 312 decides to connect the terminal device 10 to the base station device with the shortest distance to the terminal device 10, based on the distance obtained in step S105 (step S108). In this case, the decision unit 312 transmits a control signal to the base station device to which the terminal device 10 is connected (for example, the first base station device 20A) and to the one base station device decided in step S108, thereby switching the connection of the terminal device 10 from the base station device to which the terminal device 10 is connected to to the one base station device decided in step S108.

[0042] Next, the determination unit 312 of the control device 30 determines whether a predetermined time (for example, 1 second) has elapsed since the start of the process in step S101 (step S110). If it is determined that the predetermined time has not elapsed (NO in step S110), the determination unit 312 performs the process in step S110 again. On the other hand, if it is determined that the predetermined time has elapsed (YES in step S110), the process in step S101 is performed.

[0043] FIG. 3 is a diagram for explaining the beam irradiation ranges of the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D according to the first embodiment of the present invention.

[0044] When the upward direction on the paper surface of FIG. 3 is defined as north and the rightward direction on the paper surface is defined as east, the first base station device 20A irradiates a beam whose central axis A11 of the beam is in the east direction and whose irradiation angle B11 of the beam is an acute angle. Thereby, when the terminal device 10 exists within the fan-shaped communication range C11, the first base station device 20A can communicate with the terminal device 10 using the beam irradiated by the first base station device 20A.

[0045] Further, the second base station device 20B irradiates a beam whose central axis A12 of the beam is in the north direction and whose irradiation angle B12 of the beam is an acute angle. Thereby, when the terminal device 10 exists within the fan-shaped communication range C12, the second base station device 20B can communicate with the terminal device 10 using the beam irradiated by the second base station device 20B.

[0046] Further, the third base station device 20C irradiates a beam whose central axis A13 of the beam is in the west direction and whose irradiation angle B13 of the beam is an acute angle. Thereby, when the terminal device 10 exists within the fan-shaped communication range C13, the third base station device 20C can communicate with the terminal device 10 using the beam irradiated by the third base station device 20C.

[0047] Further, the fourth base station device 20D irradiates a beam whose central axis A14 of the beam is in the south direction and whose irradiation angle B14 of the beam is an acute angle. Thereby, when the terminal device 10 exists within the fan-shaped communication range C14, the fourth base station device 20D can communicate with the terminal device 10 using the beam irradiated by the fourth base station device 20D.

[0048] In FIG. 3, a fan-shaped communication area C11 formed by the beam irradiated by the first base station device 20A, a fan-shaped communication area C12 formed by the beam irradiated by the second base station device 20B, a fan-shaped communication area C13 formed by the beam irradiated by the third base station device 20C, and a fan-shaped communication area C14 formed by the beam irradiated by the fourth base station device 20D form a rectangular communication range C15 within which the terminal device 10 can communicate with at least one of the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D.

[0049] In FIG. 3, the irradiation angles B11, B12, B13, and B14 may be the same or different. For example, for a base station device with a short radius of the fan-shaped communication areas C11, C12, C13, and C14, that is, a short zone distance, since the error influence of the azimuth estimation error on the position estimation is small, the irradiation angle may be increased. Also, for a base station device with a long zone distance, since the error influence of the azimuth estimation error on the position estimation is large, the irradiation angle may be decreased.

[0050] FIG. 4 is a diagram for explaining an example of a method for switching the communication destination of the terminal device 10 according to the first embodiment of the present invention. In FIG. 4, parts having the same configuration as in FIG. 3 are denoted by the same reference numerals, and their descriptions are omitted. FIG. 4 shows a case where passenger cars E111, E121, E131, and E141 are present inside or outside the communication range C15. A case where the terminal device 10 owned by the driver is placed in each of the passenger cars E111, E121, E131, and E141 will be described.

[0051] In Figure 4, at time t1, the terminal device 10 located in the passenger car E111, which was receiving beam D112 within the communication range C11 of the first base station device 20A, moves into the communication range C12 of the second base station device 20B at time t2 and receives beam D121. In the first embodiment of the present invention, when the terminal device 10 located in the passenger car E111 is within the distance threshold of the beam irradiated by the first base station device 20A, and is within the angle threshold of the beam irradiated by the first base station device 20A, that is, when the terminal device 10 is located within the communication range C11 of the first base station device 20A, the terminal device 10 communicates with the first base station device 20A. Subsequently, when the passenger car E111, which is within the communication range C11, moves into the passenger car E112, which is within the communication range C12, the terminal device 10 has moved out of the distance threshold of the beam irradiated by the first base station device 20A, and therefore terminates communication with the first base station device 20A. Then, the terminal device 10 located inside the passenger car E112 starts communication with a second base station device 20B, where the terminal device 10 is located within the distance threshold of the beam being emitted and within the angle threshold of the beam being emitted.

[0052] Furthermore, in Figure 4, at time t1, the terminal device 10 located in the passenger car E131, which was receiving beam D122 within the communication range C12 of the second base station device 20B, moves into the communication range C13 of the third base station device 20C at time t2 and receives beam D131. In the first embodiment of the present invention, when the terminal device 10 located in the passenger car E131 is located within the distance threshold of the beam irradiated by the second base station device 20B and within the angle threshold of the beam irradiated by the second base station device 20B, that is, when the terminal device 10 is located within the communication range C12 of the second base station device 20B, the terminal device 10 communicates with the second base station device 20B. Subsequently, when passenger car E131, which is within communication range C12, moves to passenger car E132, which is within communication range C13, the terminal device 10 has moved outside the distance threshold of the beam emitted by the second base station device 20B, and therefore terminates communication with the second base station device 20B. Then, the terminal device 10, which is located in passenger car E132, starts communication with the third base station device 20C, which is located within the distance threshold of the beam being emitted and within the angle threshold of the beam being emitted.

[0053] Furthermore, in Figure 4, at time t1, the terminal device 10 located in the passenger car E141, which was receiving beam D141 within the communication range C14 of the fourth base station device 20D, moves into the communication range C11 of the first base station device 20A at time t2 and receives beam D111. In the first embodiment of the present invention, when the terminal device 10 located in the passenger car E141 is located within the distance threshold of the beam irradiated by the fourth base station device 20D and within the angle threshold of the beam irradiated by the fourth base station device 20D, that is, when the terminal device 10 is located within the communication range C14 of the fourth base station device 20D, the terminal device 10 communicates with the fourth base station device 20D. Subsequently, if passenger car E141, which is within the communication range C14, moves to passenger car E142, which is within the communication range C11, the terminal device 10 will have moved outside the distance threshold of the beam emitted by the fourth base station device 20D, and will therefore terminate communication with the fourth base station device 20D. Then, the terminal device 10, which is located in passenger car E142, will begin communication with the first base station device 20A, which is located within the distance threshold of the beam being emitted and within the angle threshold of the beam being emitted.

[0054] In the first embodiment of the present invention, if the passenger car E121 is located outside the communication range C15, and one of the base station devices in the communication range C15 (in this case, the first base station device 20A) searches beyond the acute-angle beam irradiation range and detects the terminal device 10 located in the passenger car E121, the first base station device 20A may communicate with the terminal device 10 located in the passenger car E121 using beam D113.

[0055] A wireless communication system 100 according to a first embodiment of the present invention includes, for example, a control device 30 and at least one base station device (here, first to fourth base station devices 20A to 20D). The control device 30 includes an acquisition unit 311 that acquires first information indicating the distance from at least one base station device to the terminal device 10 and second information relating to a direction perpendicular to the central axis direction of at least one base station device (here, the angle of the terminal device 10 as seen from at least one base station device). The control device 30 also includes a determination unit 312 that determines whether the terminal device 10 should communicate with at least one base station device based on the first and second information acquired by the acquisition unit 311.

[0056] Furthermore, in the first embodiment, at least one base station device is provided, which is a plurality of first to fourth base station devices 20A, 20B, 20C, and 20D. The determination unit 312 then determines that the base station device with the shortest distance indicated by the first information is the base station device with which the terminal device 10 will communicate.

[0057] According to the wireless communication system 100 of the first embodiment of the present invention, when the terminal device 10 is located at an obtuse angle to the beam irradiated by the base station device (the first to fourth base station devices 20A to 20D), the base station device can avoid initiating communication with the terminal device 10 by assuming that the terminal device 10 is located outside the angular threshold of the beam irradiated by the base station device.

[0058] In the first embodiment of the present invention, the terminal device 10 within the communication area C15 has an azimuth angle from the central axis of the beams irradiated by the first to fourth base station devices 20A to 20D that is within the irradiation angles B11, B12, B13, and B14. Therefore, when the first to fourth base station devices 20A to 20D perform positioning of the terminal device 10 using communication radio waves, it is possible to prevent deterioration of positioning accuracy due to obtuse azimuth angles, and to perform highly accurate positioning. As a result, it is possible to switch base station devices with high accuracy at the boundaries of communication areas C11, C12, C13, and C14. In addition, since the direction of movement of the terminal device 10 is mostly in the distance direction rather than the azimuth direction, the identification accuracy of the positioning results of the terminal device 10 is also increased. As a result, it is possible to switch base station devices with high accuracy at the boundaries of communication areas C11, C12, C13, and C14.

[0059] When positioning a terminal device 10 using communication radio waves from a single base station, direction estimation and distance estimation are performed. However, in light of the fact that direction estimation is less accurate than distance estimation, in the first embodiment of the present invention, in order to improve the positioning accuracy by distance estimation, the azimuth angle is made smaller (acute) as seen from the base station to which the terminal device 10 is connected, and the movement of the terminal device 10 is in the distance direction.

[0060] [Modifications of the First Embodiment] Next, modifications of the first embodiment of the present invention will be described. Note that if a modification of the first embodiment has the same parts as the first embodiment, the description will be omitted. For example, the wireless communication system according to the modification of the first embodiment has the same configuration as the wireless communication system according to the first embodiment, so its description will be omitted.

[0061] Figure 5 shows a modified example of the first embodiment of the present invention (201). For example, since the first base station device 20A, which is communicating with the terminal device 10, knows the location of the terminal device 10, the acquisition unit 311 acquires the location information of the terminal device 10 from the first base station device 20A.

[0062] Next, the acquisition unit 311 of the control device 30 acquires the distance X and distance Y of the terminal device 10 as seen from the base station device to which the terminal device 10 is connected (for example, the first base station device 20A) (step S202). For example, the acquisition unit 311 acquires the distance X and distance Y based on the position of the terminal device 10, the position of the base station device to which the terminal device 10 is connected, and the direction of the central axis of the beam emitted by that base station device.

[0063] Figure 6 is a diagram illustrating distances X and Y. Distance X is the length of the perpendicular line drawn from the position of the terminal device 10 mounted on the passenger car to the central axis of the beam emitted by the base station device 20 (any of the first to fourth base station devices 20A, 20B, 20C, and 20D). Distance Y is the length from the point where the perpendicular line drawn from the central axis of the beam emitted by the base station device 20 (any of the first to fourth base station devices 20A, 20B, 20C, and 20D) intersects with the central axis, to the position of the base station device 20.

[0064] The X threshold is set for all base station devices 20A, 20B, 20C, and 20D. The X threshold set for base station devices 20A, 20B, 20C, and 20D may be the same value or different values. The Y threshold is set for all base station devices 20A, 20B, 20C, and 20D. The Y threshold set for base station devices 20A, 20B, 20C, and 20D may be the same value or different values. For example, the X threshold and Y threshold are set based on the area that the beam irradiated by base station device 20 can reach.

[0065] Returning to the explanation of Figure 5, the determination unit 312 of the control device 30 determines whether the distance X obtained in step S202 exceeds the X threshold of the base station device (for example, the first base station device 20A) connected to the terminal device 10 (step S203).

[0066] If the distance X obtained in step S202 exceeds the X threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (YES in step S203), the determination unit 312 performs the processing in step S205, which will be described later. On the other hand, if the distance X obtained in step S202 does not exceed the X threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (NO in step S203), the determination unit 312 determines whether the distance Y obtained in step S202 exceeds the Y threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (step S204).

[0067] If the distance Y obtained in step S202 does not exceed the Y threshold of the base station device connected to the terminal device 10 (NO in step S204), the determination unit 312 performs the processing of step S210, which will be described later. On the other hand, if the distance Y obtained in step S202 exceeds the Y threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (YES in step S204), the acquisition unit 311 obtains the distance X and distance Y of the terminal device 10 as seen from other base station devices (for example, the second to fourth base station devices 20B, 20C, 20D) (step S205).

[0068] Here, the acquisition unit 311 acquires the distance X and distance Y of the terminal device 10 as seen from the second to fourth base station devices 20B, 20C, and 20D, based on the respective positions of the second to fourth base station devices 20B, 20C, and 20D (other than the first base station device 20A to which the terminal device 10 is connected), the central axis of the beams emitted by the second to fourth base station devices 20B, 20C, and 20D, and the position of the terminal device 10.

[0069] Next, the determination unit 312 of the control device 30 determines whether or not there is a base station device where the distance X acquired in step S205 is within the X threshold and the distance Y acquired in step S205 is within the Y threshold (step S206). If there is no base station device where the distance X acquired in step S205 is within the X threshold and the distance Y acquired in step S205 is within the Y threshold (NO in step S206), the determination unit 312 performs the processing of step S210, which will be described later. On the other hand, if there is a base station device where the distance X acquired in step S205 is within the X threshold and the distance Y acquired in step S205 is within the Y threshold (YES in step S206), the determination unit 312 determines whether or not there are multiple base station devices where the distance X acquired in step S205 is within the X threshold and the distance Y acquired in step S205 is within the Y threshold (step S207).

[0070] If the distance X obtained in step S205 is within the X threshold and there are not multiple base station devices where the distance Y obtained in step S205 is within the Y threshold (NO in step S207), that is, if there is only one base station device where the distance X obtained in step S205 is within the X threshold and the distance Y obtained in step S205 is within the Y threshold, the decision unit 312 decides to connect the terminal device 10 to that one base station device (step S209). In this case, the decision unit 312 transmits a control signal to the base station device to which the terminal device 10 is connected (for example, the first base station device 20A) and to the one base station device determined in step S209 (for example, the second base station device 20B), thereby switching the connection of the terminal device 10 from the base station device to which the terminal device 10 is connected to to the one base station device determined in step S209. After that, the decision unit 312 performs the processing of step S210, which will be described later.

[0071] On the other hand, if there are multiple base station devices where the distance X obtained in step S205 is within the X threshold and the distance Y obtained in step S205 is within the Y threshold (YES in step S207), the decision unit 312 decides to connect the terminal device 10 to the base station device with the smallest distance to the terminal device 10, as determined in step S205 (step S208). In this case, the decision unit 312 transmits a control signal to the base station device to which the terminal device 10 is connected (for example, the first base station device 20A) and to the one base station device determined in step S208, thereby switching the connection of the terminal device 10 from the base station device to which the terminal device 10 is connected to to the one base station device determined in step S208.

[0072] Next, the determination unit 312 of the control device 30 determines whether a predetermined time (for example, 1 second) has elapsed since the start of the process in step S201 (step S210). If it is determined that the predetermined time has not elapsed (NO in step S210), the determination unit 312 performs the process in step S210 again. On the other hand, if it is determined that the predetermined time has elapsed (YES in step S210), the process in step S201 is performed.

[0073] Figure 7 illustrates the beam irradiation ranges of the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D, which are modified versions of the first embodiment of the present invention.

[0074] Assuming that the top of Figure 7 is north and the right side of the paper is east, the direction of the central axis A21 of the beam emitted by the first base station device 20A is east. The first base station device 20A provides a rectangular communication range C21 with a width of 2 × d11 by adjusting the irradiation angle of the beam it emits. As a result, when the terminal device 10 is located within the rectangular communication range C21, the first base station device 20A can communicate with the terminal device 10 using the beam emitted by the first base station device 20A. For example, d11 is set as the X threshold of the first base station device 20A. Also, for example, the maximum distance that the beam emitted by the first base station device 20A reaches in the direction of the central axis is set as the Y threshold of the first base station device 20A.

[0075] Furthermore, the direction of the central axis A22 of the beam emitted by the second base station device 20B is north. The second base station device 20B provides a rectangular communication range C22 with a width of 2 × d12 by adjusting the irradiation angle of the emitted beam. As a result, when the terminal device 10 is located within the rectangular communication range C22, the second base station device 20B can communicate with the terminal device 10 using the beam emitted by the second base station device 20B. For example, d12 is set as the X threshold of the second base station device 20B. Also, for example, the maximum distance that the beam emitted by the second base station device 20B reaches in the direction of the central axis is set as the Y threshold of the second base station device 20B.

[0076] Furthermore, the direction of the central axis A23 of the beam emitted by the third base station device 20C is west. The third base station device 20C provides a rectangular communication range C23 with a width of 2 × d13 by adjusting the irradiation angle of the emitted beam. As a result, when the terminal device 10 is located within the rectangular communication range C23, the third base station device 20C can communicate with the terminal device 10 using the beam emitted by the third base station device 20C. For example, d13 is set as the X threshold of the third base station device 20C. Also, for example, the maximum distance that the beam emitted by the third base station device 20C can reach in the direction of the central axis is set as the Y threshold of the third base station device 20C.

[0077] Furthermore, the direction of the central axis A24 of the beam emitted by the fourth base station device 20D is south. The fourth base station device 20D provides a rectangular communication range C24 with a width of 2 × d14 by adjusting the irradiation angle of the emitted beam. As a result, when the terminal device 10 is located within the rectangular communication range C24, the fourth base station device 20D can communicate with the terminal device 10 using the beam emitted by the fourth base station device 20D. For example, d14 is set as the X threshold of the fourth base station device 20D. Also, for example, the maximum distance that the beam emitted by the fourth base station device 20D reaches in the direction of the central axis is set as the Y threshold of the fourth base station device 20D.

[0078] In Figure 7, a rectangular communication area C21 formed by the beam emitted by the first base station device 20A, a fan-shaped communication area C22 formed by the beam emitted by the second base station device 20B, a fan-shaped communication area C23 formed by the beam emitted by the third base station device 20C, and a fan-shaped communication area C24 formed by the beam emitted by the fourth base station device 20D forms a rectangular communication area C25 that allows the terminal device 10 to communicate with at least one of the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D.

[0079] In Figure 7, distances d11, d12, d13, and d14 may be the same value or different values. For example, distances d11, d12, d13, and d14 may be flexibly changed according to the desired shape of the communication area C25.

[0080] Figure 8 illustrates an example of a method for switching the communication destination of a terminal device 10 according to a modification of the first embodiment of the present invention. In Figure 8, parts that have the same configuration as in Figure 7 are denoted by the same reference numerals, and their descriptions are omitted. Figure 8 shows the case where passenger cars E211, E221, E231, and E241 exist either within or outside the communication range C25. The case in which a terminal device 10 owned by the driver is placed inside each of the passenger cars E211, E221, E231, and E241 will be described.

[0081] In Figure 8, at time t1, the terminal device 10 located in the passenger car E211, which was receiving beam D212 within the communication range C21 of the first base station device 20A, moves into the communication range C22 of the second base station device 20B at time t2 and receives beam D222. In a modified version of the first embodiment of the present invention, when the terminal device 10 located in the passenger car E211 is located within the X threshold of the beam irradiated by the first base station device 20A and within the Y threshold of the beam irradiated by the first base station device 20A, that is, when the terminal device 10 is located within the communication range C21 of the first base station device 20A, the terminal device 10 communicates with the first base station device 20A. Subsequently, when passenger car E211, which is within communication range C21, moves to passenger car E212, which is within communication range C22, the terminal device 10 has moved outside the distance threshold of the beam emitted by the first base station device 20A, and therefore terminates communication with the first base station device 20A. Then, the terminal device 10, which is located in passenger car E212, starts communication with the second base station device 20B, which is located within the X threshold of the beam being emitted and also within the Y threshold of the beam being emitted.

[0082] Furthermore, in Figure 8, at time t1, the terminal device 10 located in the passenger car E231, which was receiving beam D221 within the communication range C22 of the second base station device 20B, moves into the communication range C23 of the third base station device 20C at time t2 and receives beam D231. In a modified version of the first embodiment of the present invention, when the terminal device 10 located in the passenger car E231 is located within the X threshold of the beam irradiated by the second base station device 20B and within the Y threshold of the beam irradiated by the second base station device 20B, that is, when the terminal device 10 is located within the communication range C22 of the second base station device 20B, the terminal device 10 communicates with the second base station device 20B. Subsequently, if passenger car E231, which is within communication range C22, moves to passenger car E232, which is within communication range C23, the terminal device 10 will terminate communication with the second base station device 20B because it has moved outside the distance threshold of the beam emitted by the second base station device 20B. Then, the terminal device 10, which is located in passenger car E232, will begin communication with the third base station device 20C, which is located within the X threshold of the emitted beam and also within the Y threshold of the emitted beam.

[0083] Furthermore, in Figure 8, at time t1, the terminal device 10 located in the passenger car E241, which was receiving beam D241 within the communication range C24 of the fourth base station device 20D, moves into the communication range C21 of the first base station device 20A at time t2 and receives beam D211. In a modified version of the first embodiment of the present invention, when the terminal device 10 located in the passenger car E241 is located within the X threshold of the beam irradiated by the fourth base station device 20D, and is located within the Y threshold of the beam irradiated by the fourth base station device 20D, that is, when the terminal device 10 is located within the communication range C24 of the fourth base station device 20D, the terminal device 10 communicates with the fourth base station device 20D. Subsequently, if passenger car E241, which is within communication range C24, moves to passenger car E242, which is within communication range C21, the terminal device 10 will have moved outside the distance threshold of the beam emitted by the fourth base station device 20D, and will therefore terminate communication with the fourth base station device 20D. Then, the terminal device 10, which is located in passenger car E242, will begin communication with the first base station device 20A, which is located within the X threshold of the beam being emitted and also within the Y threshold of the beam being emitted.

[0084] In a modified version of the first embodiment of the present invention, if the passenger car E221 is located outside the communication range C25, and one of the base station devices in the communication range C25 (in this case, the first base station device 20A) searches beyond the acute-angle beam irradiation range and detects the terminal device 10 located in the passenger car E221, the first base station device 20A communicates with the terminal device 10 located in the passenger car E221 using beam D213.

[0085] In a modified version of the first embodiment, the acquisition unit 311 of the control device 30 acquires first information indicating the distance from at least one base station device to the terminal device 10 (here, distance Y, which is the length from the point where a perpendicular line drawn from the central axis of the beam emitted by the base station device intersects with the central axis, to the position of the base station device), and second information relating to a direction perpendicular to the central axis direction of the base station device (here, distance X, which is the length of the perpendicular line from the terminal device 10 to the central axis of the base station device).

[0086] In the first embodiment, the first to fourth base station devices 20A to 20D provided a fan-shaped communication range C11 to C14, and the wireless communication system 100 as a whole provided a rectangular communication range C15. On the other hand, in a modified version of the first embodiment, the first to fourth base station devices 20A to 20D provide a rectangular communication range C21 to C24 by adjusting the beam irradiation angle, and the wireless communication system 100 as a whole provides a rectangular communication range C25. In the modified version of the first embodiment, the proportion of the communication range C25 covered by the rectangular communication ranges C21 to C24 is higher than the proportion of the communication range C15 covered by the fan-shaped communication ranges C11 to C14 in the first embodiment. Therefore, the wireless communication system 100 according to the modified version of the first embodiment (Figure 8) allows the terminal device 10 to communicate with the first to fourth base station devices 20A to 20D more reliably than the wireless communication system 100 according to the first embodiment (Figure 4).

[0087] In a modified version of the first embodiment, the azimuth angle from the base station is larger when the terminal device 10 is close to the base station than when it is farther away, but it is still possible to keep the azimuth angle within a certain range. Furthermore, since the direction of movement of the terminal device 10 can be made mostly in the distance direction rather than the azimuth direction, as in the first embodiment, the identification accuracy of the positioning result of the terminal device 10 is also improved. As a result, it becomes possible to switch base station devices with high precision at the boundary of the communication range C21 to C24.

[0088] [Second Embodiment] Next, a second embodiment of the present invention will be described. Note that the description of parts of the second embodiment that are the same as those of the first embodiment will be omitted. The configuration of the terminal device 10, the first to fourth base station devices 20A to 20D, and the control device 30 constituting the wireless communication system 100 according to the second embodiment is the same as the configuration of the terminal device 10, the first to fourth base station devices 20A to 20D, and the control device 30 constituting the wireless communication system 100 according to the first embodiment (Figure 1), so their descriptions will be omitted.

[0089] Figure 9 is a flowchart showing the processing performed by the control device 30 according to the second embodiment of the present invention. First, the acquisition unit 311 of the control device 30 acquires location information indicating the location of the terminal device 10 (step S301). For example, since the first base station device 20A, which is communicating with the terminal device 10, knows the location of the terminal device 10, the acquisition unit 311 acquires the location information of the terminal device 10 from the first base station device 20A.

[0090] Next, the acquisition unit 311 of the control device 30 acquires the distance and angle of the terminal device 10 as seen from the base station device (for example, the first base station device 20A) to which the terminal device 10 is connected (step S302). For example, the acquisition unit 311 acquires the distance between the terminal device 10 and the first base station device 20A to which the terminal device 10 is connected. The storage unit 32 has in advance store location information indicating the locations where the first to fourth base station devices 20A, 20B, 20C, and 20D are installed. Therefore, the acquisition unit 311 acquires the distance between the terminal device 10 and the first base station device 20A based on the location information indicating the location where the first base station device 20A is installed and the location information of the terminal device acquired in step S301. The storage unit 32 also has in advance central axis direction information indicating the direction of the central axis of the beams emitted by the first to fourth base station devices 20A, 20B, 20C, and 20D. The acquisition unit 311 acquires the angle of the terminal device 10 by determining the angle at which the terminal device 10 is located relative to the central axis of the beam emitted by the first base station device 20A.

[0091] Next, the determination unit 312 of the control device 30 determines whether the angle acquired in step S302 exceeds the irradiation range of the beam irradiated by the base station device (for example, the first base station device 20A) connected to the terminal device 10 (step S303). The irradiation range indicates the range in which the base station device can irradiate with a beam. All base station devices 20A, 20B, 20C, and 20D have an irradiation range. The irradiation ranges of the base station devices 20A, 20B, 20C, and 20D may be the same or different. The irradiation range is preferably obtuse, for example, 60 degrees.

[0092] If the angle obtained in step S302 exceeds the irradiation range of the beam emitted by the base station device connected to the terminal device 10 (for example, the first base station device 20A) (YES in step S303), the determination unit 312 performs the processing in step S305, which will be described later. On the other hand, if the angle obtained in step S302 does not exceed the irradiation range of the beam emitted by the base station device connected to the terminal device 10 (for example, the first base station device 20A) (NO in step S303), the determination unit 312 determines whether the distance obtained in step S302 exceeds the distance threshold of the base station device connected to the terminal device 10 (step S304). The distance threshold is set for all base station devices (here, the first to fourth base station devices 20A, 20B, 20C, 20D). The distance threshold set for all base station devices may be the same value or may be different values. The distance threshold is set, for example, to the distance from the location where the base station device is installed to the location where the beam of that base station device reaches.

[0093] If the distance obtained in step S302 does not exceed the distance threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (NO in step S304), the determination unit 312 performs the processing of step S310, which will be described later. On the other hand, if the distance obtained in step S302 exceeds the distance threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (YES in step S304), the acquisition unit 311 obtains the distance and angle of the terminal device 10 as seen from other base station devices (for example, the second to fourth base station devices 20B, 20C, 20D) (step S305).

[0094] Here, the acquisition unit 311 acquires the distance between the terminal device 10 and each of the other base station devices 20B, 20C, and 20D, other than the first base station device 20A to which the terminal device 10 is connected. Specifically, the acquisition unit 311 acquires the distance between the terminal device 10 and the second to fourth base station devices 20B, 20C, and 20D based on location information indicating the locations where the second to fourth base station devices 20B, 20C, and 20D are installed and the location information of the terminal device 10 acquired in step S305. In addition, for example, the acquisition unit 311 acquires the angle of the terminal device 10 by identifying the angle at which the terminal device 10 is located relative to the direction of the central axis of the beam emitted by each of the second to fourth base station devices 20B, 20C, and 20D.

[0095] Next, the determination unit 312 of the control device 30 determines whether or not there is a base station device whose angle acquired in step S305 is within the illumination range and whose distance acquired in step S305 is within the distance threshold (step S306). If there is no base station device whose angle acquired in step S305 is within the angle threshold and whose distance acquired in step S305 is within the distance threshold (NO in step S306), the determination unit 312 performs the processing of step S310, which will be described later. On the other hand, if there is a base station device whose angle acquired in step S305 is within the illumination range and whose distance acquired in step S305 is within the distance threshold (YES in step S306), the determination unit 312 determines whether or not there are multiple base station devices whose angle acquired in step S305 is within the illumination range and whose distance acquired in step S305 is within the distance threshold (step S307).

[0096] If the angle acquired in step S305 is within the illumination range and there are not multiple base station devices for which the distance acquired in step S305 is within the distance threshold (NO in step S307), that is, if there is only one base station device for which the angle acquired in step S305 is within the illumination range and the distance acquired in step S305 is within the distance threshold, the decision unit 312 decides to connect the terminal device 10 to that one base station device (step S309). In this case, the decision unit 312 transmits a control signal to the base station device to which the terminal device 10 is connected (for example, the first base station device 20A) and to the one base station device determined in step S309 (for example, the second base station device 20B), thereby switching the connection of the terminal device 10 from the base station device to which the terminal device 10 is connected to to the one base station device determined in step S309. After that, the decision unit 312 performs the processing of step S310, which will be described later.

[0097] On the other hand, if there are multiple base station devices whose angle obtained in step S305 is within the illumination range and whose distance obtained in step S305 is within the distance threshold (YES in step S307), the decision unit 312 decides to connect the terminal device 10 to the base station device with the smallest distance to the terminal device 10, based on the distance obtained in step S305 (step S308). In this case, the decision unit 312 transmits a control signal to the base station device to which the terminal device 10 is connected (for example, the first base station device 20A) and to the one base station device decided in step S308, thereby switching the connection of the terminal device 10 from the base station device to which the terminal device 10 is connected to to the one base station device decided in step S308.

[0098] Next, the determination unit 312 of the control device 30 determines whether a predetermined time (for example, 1 second) has elapsed since the start of the process in step S301 (step S310). If it is determined that the predetermined time has not elapsed (NO in step S310), the determination unit 312 performs the process in step S310 again. On the other hand, if it is determined that the predetermined time has elapsed (YES in step S310), the process in step S301 is performed.

[0099] Figure 10 is a diagram illustrating the beam irradiation range of the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D according to the second embodiment of the present invention.

[0100] Assuming that the top of Figure 10 is north and the right side of the paper is east, the first base station device 20A emits a beam whose central axis is east and whose irradiation angle B31 is acute. As a result, when the terminal device 10 is located within the fan-shaped communication range C31, the first base station device 20A can communicate with the terminal device 10 using the beams emitted by the first base station device 20A (for example, D311, D312, D313, D314, D315).

[0101] In the first embodiment, the beam was sometimes directed outside the beam irradiation angle of the first base station device 20A (for example, beam D113 in Figure 4), but in the second embodiment, beam B316 is not directed outside the beam irradiation angle of the first base station device 20A.

[0102] Furthermore, the second base station device 20B emits a beam whose central axis is oriented north and whose irradiation angle B32 is acute. As a result, when the terminal device 10 is located within the fan-shaped communication range C22, the second base station device 20B can communicate with the terminal device 10 using the beam emitted by the second base station device 20B.

[0103] Furthermore, the third base station device 20C emits a beam whose central axis is west and whose irradiation angle B33 is acute. As a result, when the terminal device 10 is located within the fan-shaped communication range C13, the third base station device 20C can communicate with the terminal device 10 using the beam emitted by the third base station device 20C.

[0104] Furthermore, the fourth base station device 20D emits a beam whose central axis is oriented south and whose irradiation angle B34 is acute. As a result, when the terminal device 10 is located within the fan-shaped communication range C34, the fourth base station device 20D can communicate with the terminal device 10 using the beam emitted by the fourth base station device 20D.

[0105] In Figure 10, a rectangular communication area C35 is formed by a fan-shaped communication area C31 formed by the beam emitted by the first base station device 20A, a fan-shaped communication area C32 formed by the beam emitted by the second base station device 20B, a fan-shaped communication area C33 formed by the beam emitted by the third base station device 20C, and a fan-shaped communication area C34 formed by the beam emitted by the fourth base station device 20D, allowing the terminal device 10 to communicate with at least one of the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D.

[0106] In Figure 10, the illumination angles B31, B32, B33, and B34 may be the same or different. For example, a base station device with a short radius of the fan-shaped communication area C31, C32, C33, and C34, i.e., a short zone distance, may have a larger illumination angle because the impact of azimuth estimation errors on position estimation is small. Conversely, a base station device with a long zone distance may have a smaller illumination angle because the impact of azimuth estimation errors on position estimation is large.

[0107] Figure 11 illustrates an example of a method for switching the communication destination of a terminal device 10 according to a second embodiment of the present invention. In Figure 11, parts having the same configuration as in Figure 10 are denoted by the same reference numerals, and their descriptions are omitted. Figure 11 shows the case where passenger cars E311, E321, E331, and E341 exist either within or outside the communication range C35. The case in which a terminal device 10 owned by the driver is placed inside each of the passenger cars E311, E321, E331, and E341 will be described.

[0108] In Figure 11, at time t1, the terminal device 10 located in passenger car E311, which was receiving beam D318 within the communication range C31 of the first base station device 20A, moves into the communication range C32 of the second base station device 20B at time t2 and receives beam D321. In the second embodiment of the present invention, when the terminal device 10 located in passenger car E311 is within the distance threshold of the beam irradiated by the first base station device 20A, and is located within the irradiation range of the beam irradiated by the first base station device 20A, that is, when the terminal device 10 is located within the communication range C31 of the first base station device 20A, the terminal device 10 communicates with the first base station device 20A. Subsequently, when passenger car E311, which is in the communication range C31, moves to passenger car E312, which is in the communication range C32, the terminal device 10 has moved out of the distance threshold of the beam irradiated by the first base station device 20A, and therefore terminates communication with the first base station device 20A. Then, the terminal device 10 located inside the passenger car E312 starts communication with a second base station device 20B, which is located within the distance threshold of the beam being emitted and within the irradiation range of the beam being emitted.

[0109] Furthermore, in Figure 11, at time t1, the terminal device 10 located in the passenger car E331, which was receiving beam D322 within the communication range C32 of the second base station device 20B, moves into the communication range C33 of the third base station device 20C at time t2 and receives beam D331. In the second embodiment of the present invention, when the terminal device 10 located in the passenger car E331 is within the distance threshold of the beam irradiated by the third base station device 20B and within the irradiation range of the beam irradiated by the second base station device 20B, that is, when the terminal device 10 is located within the communication range C32 of the second base station device 20B, the terminal device 10 communicates with the second base station device 20B. Subsequently, if passenger car E331, which is within communication range C32, moves to passenger car E332, which is within communication range C33, the terminal device 10 will have moved outside the distance threshold of the beam emitted by the second base station device 20B, and will therefore terminate communication with the second base station device 20B. Then, the terminal device 10, which is located in passenger car E332, will begin communication with the third base station device 20C, which is located within the distance threshold of the beam being emitted and within the beam's illumination range.

[0110] Furthermore, in Figure 11, at time t1, the terminal device 10 located in the passenger car E341, which was receiving beam D341 within the communication range C34 of the fourth base station device 20D, moves into the communication range C41 of the first base station device 20A at time t2 and receives beam D317. In the second embodiment of the present invention, when the terminal device 10 located in the passenger car E341 is within the distance threshold of the beam irradiated by the fourth base station device 20D, and is located within the irradiation range of the beam irradiated by the fourth base station device 20D, that is, when the terminal device 10 is located within the communication range C34 of the fourth base station device 20D, the terminal device 10 communicates with the fourth base station device 20D. Subsequently, if passenger car E341, which is within the communication range C34, moves to passenger car E342, which is also within the communication range C34, the terminal device 10 will have moved outside the distance threshold of the beam emitted by the fourth base station device 20D, and will therefore terminate communication with the fourth base station device 20D. Then, the terminal device 10, which is located in passenger car E342, will begin communication with the first base station device 20A, which is located within the distance threshold of the beam being emitted and within the beam's illumination range.

[0111] In the second embodiment of the present invention, if the passenger car E321 is located outside the communication range C35, one of the base station devices providing the communication range C35 (in this case, the first base station device 20A) will not perform a search beyond the acute-angle beam irradiation range C31. In other words, the first base station device 20A will not irradiate the terminal device 10 located inside the passenger car E321, which is outside the communication range C35, with the beam D310, and will not communicate with the terminal device 10 inside the passenger car E321.

[0112] A wireless communication system 100 according to a second embodiment of the present invention includes, for example, a control device 30 and at least one base station device (here, first to fourth base station devices 20A to 20D). The control device 30 includes an acquisition unit 311 that acquires first information indicating the distance from at least one base station device to the terminal device 10 and second information relating to a direction perpendicular to the central axis direction of at least one base station device (here, the beam irradiation range of at least one base station device). The control device 30 also includes a determination unit 312 that determines whether the terminal device 10 should communicate with at least one base station device based on the first and second information acquired by the acquisition unit 311.

[0113] According to the wireless communication system 100 of the second embodiment of the present invention, when the terminal device 10 is located at an obtuse angle to the beam emitted by the base station device (the first to fourth base station devices 20A to 20D), the base station device can avoid initiating communication with the terminal device 10 by assuming that the terminal device 10 is located outside the irradiation range of the beam emitted by the base station device.

[0114] In the second embodiment of the present invention, the angle range of the beam sweep is within the irradiation angles B31, B32, B33, and B34 of the fan-shaped communication areas C31 to C34 that form the communication area C35. Therefore, when the terminal device 10 connects to the base station device, the azimuth angle from the base station device is within the irradiation range, which is the irradiation angles B31, B32, B33, and B34. Thus, as in the first embodiment, when positioning of the terminal device 10 is performed using communication radio waves, deterioration of positioning accuracy due to the azimuth angle becoming obtuse can be prevented, and high-precision positioning can be achieved. Therefore, it is possible to switch base station devices with high precision at the boundary of communication areas C31 to C34. In addition, since the direction of movement of the terminal device 10 can be almost entirely in the distance direction rather than the azimuth direction, the identification accuracy of the positioning result of the terminal device 10 is also improved. Therefore, it is possible to switch base station devices with high precision at the boundary of communication areas C31 to C34. Furthermore, unlike the first embodiment, if the terminal device 10 is in an azimuth direction greater than the irradiation angles B31, B32, B33, and B34, the terminal device 10 does not connect to the base station device. Therefore, it is possible to avoid situations such as the azimuth angle becoming obtuse or the direction of movement of the terminal device 10 being in the azimuth direction, as in the first embodiment. Consequently, no matter where the terminal device 10 is located, it can be connected to one of the first to fourth base station devices 20A to 20D within the communication area C35, and it is possible to switch base station devices with high precision at the boundary of the communication areas C31 to C34.

[0115] [Modifications of the Second Embodiment] Next, modifications of the second embodiment of the present invention will be described. Note that descriptions of parts of the modifications of the second embodiment that are the same as those of the second embodiment will be omitted. Also, the wireless communication system according to the modification of the second embodiment has the same configuration as the wireless communication system according to the first embodiment, so its description will be omitted. In the second embodiment, a case was described in which the first to fourth base station devices 20A to 20D provide a fan-shaped communication range C31 to C34 by irradiating a beam, and the wireless communication system 100 as a whole provides a rectangular communication range C35. However, the system may also provide a communication range as shown in the modification of the second embodiment.

[0116] Figure 12 is a flowchart showing the processing performed by a control device 30 according to a modification of the second embodiment of the present invention. First, the acquisition unit 311 of the control device 30 acquires location information indicating the location of the terminal device 10 (step S401). For example, since the first base station device 20A, which is communicating with the terminal device 10, knows the location of the terminal device 10, the acquisition unit 311 acquires the location information of the terminal device 10 from the first base station device 20A.

[0117] Next, the acquisition unit 311 of the control device 30 acquires the distance X and distance Y of the terminal device 10 as seen from the base station device (for example, the first base station device 20A) to which the terminal device 10 is connected (step S402). For example, the acquisition unit 311 acquires the distance X and distance Y based on the position of the terminal device 10, the position of the base station device to which the terminal device 10 is connected, and the direction of the central axis of the beam emitted by the base station device. Note that the distance X and distance Y in the modified example of the second embodiment are the same as the distance X and distance Y described in the modified example of the first embodiment (see Figure 6).

[0118] The determination unit 312 of the control device 30 determines whether the distance X obtained in step S202 exceeds the "Y threshold × tan (irradiation range)" for the base station device (for example, the first base station device 20A) connected to the terminal device 10 (step S403). The Y threshold and irradiation range are determined for each base station device and may be the same or different for multiple base station devices. The Y threshold is the same as that described in the modified example of the first embodiment, and the irradiation range is the same as that described in the second embodiment.

[0119] If the distance X obtained in step S402 exceeds "Y threshold × tan (irradiation range)" (YES in step S403), the determination unit 312 performs the processing in step S405, which will be described later. On the other hand, if the distance X obtained in step S402 does not exceed "Y threshold × tan (irradiation range)" (NO in step S403), the determination unit 312 determines whether the distance Y obtained in step S202 exceeds the Y threshold of the base station device (for example, the first base station device 20A) connected to the terminal device 10 (step S404).

[0120] If the distance Y obtained in step S402 does not exceed the Y threshold of the base station device connected to the terminal device 10 (NO in step S404), the determination unit 312 performs the processing of step S410, which will be described later. On the other hand, if the distance Y obtained in step S402 exceeds the Y threshold of the base station device connected to the terminal device 10 (for example, the first base station device 20A) (YES in step S404), the acquisition unit 311 obtains the distance X and distance Y of the terminal device 10 as seen from other base station devices (for example, the second to fourth base station devices 20B, 20C, 20D) (step S405).

[0121] Here, the acquisition unit 311 acquires the distance X and distance Y of the terminal device 10 as seen from the second to fourth base station devices 20B, 20C, and 20D, based on the respective positions of the second to fourth base station devices 20B, 20C, and 20D (other than the first base station device 20A to which the terminal device 10 is connected), the central axis of the beams emitted by the second to fourth base station devices 20B, 20C, and 20D, and the position of the terminal device 10.

[0122] Next, the determination unit 312 of the control device 30 determines whether or not there is a base station device in which the distance X acquired in step S405 is within "Y threshold × tan (irradiation range)" and the distance Y acquired in step S405 is within the Y threshold (step S406). If there is no base station device in which the distance X acquired in step S405 is within "Y threshold × tan (irradiation range)" and the distance Y acquired in step S405 is within the Y threshold (NO in step S406), the determination unit 312 performs the processing of step S410, which will be described later. On the other hand, if there is a base station device in which the distance X acquired in step S405 is within "Y threshold × tan (irradiation range)" and the distance Y acquired in step S405 is within the Y threshold (YES in step S406), the determination unit 312 determines whether or not there are multiple base station devices in which the distance X acquired in step S405 is within "Y threshold × tan (irradiation range)" and the distance Y acquired in step S405 is within the Y threshold (step S407).

[0123] If the distance X obtained in step S405 is within "Y threshold × tan (irradiation range)" and there are not multiple base station devices for which the distance Y obtained in step S405 is within the Y threshold (NO in step S407), that is, if there is only one base station device for which the distance X obtained in step S405 is within "Y threshold × tan (irradiation range)" and the distance Y obtained in step S405 is within the Y threshold, the decision unit 312 decides to connect the terminal device 10 to that one base station device (step S409). In this case, the decision unit 312 transmits a control signal to the base station device to which the terminal device 10 is connected (for example, the first base station device 20A) and to the one base station device determined in step S409 (for example, the second base station device 20B), thereby switching the connection of the terminal device 10 from the base station device to which the terminal device 10 is connected to to the one base station device determined in step S409. After that, the decision unit 312 performs the processing of step S410, which will be described later.

[0124] On the other hand, if the distance X acquired in step S405 is within "Y threshold × tan (irradiation range)" and there are multiple base station devices whose distance Y acquired in step S405 is within the Y threshold (YES in step S407), the decision unit 312 decides to connect the terminal device 10 to the base station device with the smallest distance to the terminal device 10, based on the distance acquired in step S405 (step S408). In this case, the decision unit 312 transmits a control signal to the base station device to which the terminal device 10 is connected (for example, the first base station device 20A) and to the one base station device decided in step S408, thereby switching the connection of the terminal device 10 from the base station device to which the terminal device 10 is connected to to the one base station device decided in step S408.

[0125] Next, the determination unit 312 of the control device 30 determines whether a predetermined time (for example, 1 second) has elapsed since the start of the process in step S401 (step S410). If it is determined that the predetermined time has not elapsed (NO in step S410), the determination unit 312 performs the process in step S410 again. On the other hand, if it is determined that the predetermined time has elapsed (YES in step S410), the process in step S401 is performed.

[0126] Figure 13 is a diagram illustrating the beam irradiation ranges of the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D, according to a modification of the second embodiment of the present invention.

[0127] Assuming that the top of Figure 13 is north and the right side of the paper is east, the direction of the central axis A41 of the beam emitted by the first base station device 20A is east. The first base station device 20A provides a rectangular communication range C41 with a width of 2 × d21 by adjusting the irradiation angle of the beam it emits. As a result, when the terminal device 10 is located within the rectangular communication range C41, the first base station device 20A can communicate with the terminal device 10 using the beam emitted by the first base station device 20A. For example, d21 is set as "Y threshold × tan (irradiation range)" for the first base station device 20A. Alternatively, for example, the maximum distance that the beam emitted by the first base station device 20A reaches in the direction of the central axis is set as the Y threshold of the first base station device 20A.

[0128] Furthermore, the direction of the central axis A42 of the beam emitted by the second base station device 20B is north. The second base station device 20B provides a rectangular communication range C42 with a width of 2 × d22 by adjusting the irradiation angle of the emitted beam. As a result, when the terminal device 10 is located within the rectangular communication range C42, the second base station device 20B can communicate with the terminal device 10 using the beam emitted by the second base station device 20B. For example, d22 is set as "Y threshold × tan (irradiation range)" for the second base station device 20B. Also, for example, the maximum distance that the beam emitted by the second base station device 20B reaches in the direction of the central axis is set as the Y threshold of the second base station device 20B.

[0129] Furthermore, the direction of the central axis A43 of the beam emitted by the third base station device 20C is west. The third base station device 20C provides a rectangular communication range C43 with a width of 2 × d23 by adjusting the irradiation angle of the emitted beam. As a result, when the terminal device 10 is located within the rectangular communication range C43, the third base station device 20C can communicate with the terminal device 10 using the beam emitted by the third base station device 20C. For example, d23 is set as a value relating to the third base station device 20C. Also, for example, the maximum distance that the beam emitted by the third base station device 20C can reach in the direction of the central axis is set as the Y threshold of the third base station device 20C.

[0130] Furthermore, the direction of the central axis A44 of the beam emitted by the fourth base station device 20D is south. The fourth base station device 20D provides a rectangular communication range C44 with a width of 2 × d24 by adjusting the irradiation angle of the emitted beam. As a result, when the terminal device 10 is located within the rectangular communication range C44, the fourth base station device 20D can communicate with the terminal device 10 using the beam emitted by the fourth base station device 20D. For example, d24 is set as "Y threshold × tan (irradiation range)" for the fourth base station device 20D. Also, for example, the maximum distance that the beam emitted by the fourth base station device 20D reaches in the direction of the central axis is set as the Y threshold of the fourth base station device 20D.

[0131] In Figure 13, a rectangular communication area C41 formed by the beam emitted by the first base station device 20A, a fan-shaped communication area C42 formed by the beam emitted by the second base station device 20B, a fan-shaped communication area C43 formed by the beam emitted by the third base station device 20C, and a fan-shaped communication area C44 formed by the beam emitted by the fourth base station device 20D forms a rectangular communication area C45 that allows the terminal device 10 to communicate with at least one of the first base station device 20A, the second base station device 20B, the third base station device 20C, and the fourth base station device 20D.

[0132] In Figure 13, distances d21, d22, d23, and d24 may be the same value or different values. For example, distances d21, d22, d23, and d24 may be flexibly changed according to the desired shape of the communication area C25.

[0133] Figure 14 illustrates an example of a method for switching the communication destination of a terminal device 10 according to a modification of the second embodiment of the present invention. In Figure 14, parts that have the same configuration as in Figure 13 are denoted by the same reference numerals, and their descriptions are omitted. Figure 14 shows the case where passenger cars E411, E421, E431, and E441 exist either within or outside the communication range C45. The case in which a terminal device 10 owned by the driver is placed inside each of the passenger cars E411, E421, E431, and E441 will be described.

[0134] In Figure 14, at time t1, the terminal device 10 located in the passenger car E411, which was receiving beam D413 within the communication range C41 of the first base station device 20A, moves into the communication range C42 of the second base station device 20B at time t2 and receives beam D421. In a modified version of the second embodiment, when the terminal device 10 located in the passenger car E411 is located within the "Y threshold × tan (irradiation range)" of the first base station device 20A, and is located within the Y threshold of the beam irradiated by the first base station device 20A, that is, when the terminal device 10 is located within the communication range C41 of the first base station device 20A, the terminal device 10 communicates with the first base station device 20A. Subsequently, when passenger car E411, which is within communication range C41, moves to passenger car E412, which is within communication range C42, the terminal device 10 has moved outside the distance threshold of the beam emitted by the first base station device 20A, and therefore terminates communication with the first base station device 20A. Then, the terminal device 10, which is located in passenger car E412, starts communication with the second base station device 20B, which is located within "Y threshold × tan (irradiation range)" and within the Y threshold of the beam being emitted.

[0135] Furthermore, in Figure 14, at time t1, the terminal device 10 located in the passenger car E431, which was receiving beam D421 within the communication range C42 of the second base station device 20B, moves into the communication range C43 of the third base station device 20C at time t2 and receives beam D431. In a modified version of the second embodiment of the present invention, when the terminal device 10 located in the passenger car E431 is located within the "Y threshold × tan (irradiation range)" of the second base station device 20B, and is located within the Y threshold of the beam irradiated by the second base station device 20B, that is, when the terminal device 10 is located within the communication range C42 of the second base station device 20B, the terminal device 10 communicates with the second base station device 20B. Subsequently, if passenger car E431, which is within communication range C42, moves to passenger car E432, which is within communication range C43, the terminal device 10 will have moved outside the distance threshold of the beam emitted by the second base station device 20B, and will therefore terminate communication with the second base station device 20B. Then, the terminal device 10, which is located in passenger car E432, will begin communication with the third base station device 20C, which is located within "Y threshold × tan (irradiation range)" and within the Y threshold of the beam being emitted.

[0136] Furthermore, in Figure 14, at time t1, the terminal device 10 located in the passenger car E441, which was receiving beam D441 within the communication range C44 of the fourth base station device 20D, moves into the communication range C41 of the first base station device 20A at time t2 and receives beam D412. In a modified example of the second embodiment of the present invention, when the terminal device 10 located in the passenger car E441 is located within the "Y threshold × tan (irradiation range)" of the fourth base station device 20D, and is located within the Y threshold of the beam irradiated by the fourth base station device 20D, that is, when the terminal device 10 is located within the communication range C44 of the fourth base station device 20D, the terminal device 10 communicates with the fourth base station device 20D. Subsequently, if passenger car E441, which is within communication range C44, moves to passenger car E442, which is within communication range C41, the terminal device 10 will have moved outside the distance threshold of the beam emitted by the fourth base station device 20D, and will therefore terminate communication with the fourth base station device 20D. Then, the terminal device 10, which is located in passenger car E442, will begin communication with the first base station device 20A, which is located within "Y threshold × tan (irradiation range)" and within the Y threshold of the beam being emitted.

[0137] In a modified version of the second embodiment of the present invention, if the passenger car E421 is located outside the communication range C45, and one of the base station devices in the communication range C45 (in this case, the first base station device 20A) searches beyond the acute-angle beam irradiation range and detects the terminal device 10 located in the passenger car E421, the first base station device 20A will not irradiate the beam D415 and will not communicate with the terminal device 10 located in the passenger car E421.

[0138] In a modified version of the second embodiment, the acquisition unit 311 of the control device 30 acquires first information indicating the distance from at least one base station device to the terminal device 10 (here, distance Y, which is the length from the point where a perpendicular line drawn from the central axis of the beam irradiated by the base station device intersects with the central axis, to the position of the base station device), and second information relating to a direction perpendicular to the central axis direction of the base station device (here, "Y threshold × tan (irradiation range)").

[0139] In the second embodiment, the first to fourth base station devices 20A to 20D provided a fan-shaped communication range C31 to C34, and the wireless communication system 100 as a whole provided a rectangular communication range C35. On the other hand, in a modified version of the second embodiment, the first to fourth base station devices 20A to 20D provide a rectangular communication range C41 to C44 by adjusting the beam irradiation angle, and the wireless communication system 100 as a whole provides a rectangular communication range C45. In the modified version of the second embodiment, the proportion of the communication range C45 covered by the rectangular communication range C41 to C44 is higher than the proportion of the communication range C35 covered by the fan-shaped communication range C31 to C34 in the second embodiment. Therefore, the wireless communication system 100 according to the modified version of the second embodiment (Figure 14) allows the terminal device 10 to communicate with the first to fourth base station devices 20A to 20D more reliably than the wireless communication system 100 according to the second embodiment (Figure 11).

[0140] In the first and second embodiments, the case in which the first to fourth base station devices 20A to 20D provide a fan-shaped communication range was described (see Figures 3 and 10). Furthermore, in the modified versions of the first and second embodiments, the case in which the first to fourth base station devices 20A to 20D provide a rectangular communication range was described (see Figures 7 and 13). However, the invention is not limited to these, and the first to fourth base station devices 20A to 20D may use a combination of a fan-shaped communication range and a rectangular communication range.

[0141] Furthermore, the functions of at least some of the parts of the apparatus in the first and second embodiments described above, and their modified versions, may be implemented by a computer. In that case, the functions may be implemented by recording a program for implementing these functions on a computer-readable recording medium, loading the program recorded on this recording medium into a computer system, and executing it. Here, "computer system" includes hardware such as an OS (Operating System) and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), CD-ROMs, and storage devices such as hard disks built into a computer system. In addition, "computer-readable recording medium" may also include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period of time, such as volatile memory inside a computer system that acts as a server or client in such cases. Furthermore, the above program may be for the purpose of realizing some of the functions described above, or it may be able to realize the above functions in combination with a program already recorded in the computer system, or it may be realized using a programmable logic device such as an FPGA.

[0142] Although several embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention.

[0143] The present invention aims to enable highly sophisticated switching control between a terminal device and a base station device based on the location of the terminal device. It can be applied to wireless communication systems and wireless communication methods where it is necessary to avoid a base station device initiating communication with a terminal device when the terminal device is located at an obtuse angle to the beam emitted by the base station device.

[0144] 10...Terminal device, 11...Control unit, 12...Storage unit, 13...Communication unit, 20A...First base station device, 20B...Second base station device, 20C...Third base station device, 20D...Fourth base station device, 21...Control unit, 22...Storage unit, 23...Communication unit, 24...Beam irradiation unit, 30...Control device, 31...Control unit, 32...Storage unit, 33...Communication unit, 100...Wireless communication system, 311...Acquisition unit, 312...Decision unit

Claims

1. A wireless communication system comprising a control device and at least one base station device, wherein the control device includes: an acquisition unit that acquires first information indicating the distance from the at least one base station device to a terminal device and second information relating to a direction perpendicular to the central axis direction of the at least one base station device; and a determination unit that determines whether the terminal device communicates with the at least one base station device based on the first information and the second information acquired by the acquisition unit.

2. The wireless communication system according to claim 1, wherein the acquisition unit uses as second information any of the following: the angle of the terminal device as seen from the at least one base station device, the length of the perpendicular from the terminal device to the central axis of the at least one base station device, or the beam irradiation range of the at least one base station device.

3. If the at least one base station device is a plurality of base station devices, the determination unit determines that the base station device with the shortest distance indicated by the first information is the base station device with which the terminal device communicates, according to claim 1.

4. A wireless communication method used in a wireless communication system comprising a control device and at least one base station device, wherein the method acquires first information indicating the distance from the at least one base station device to a terminal device and second information relating to a direction perpendicular to the central axis direction of the at least one base station device, and determines whether the terminal device communicates with the at least one base station device based on the acquired first information and second information.

Images