Wireless communication system

Abstract

We provide a wireless communication system that can offer appropriate services tailored to the communication partner while keeping implementation costs down. [Solution] The wireless communication system 1 comprises a fixed station and a mobile station. The fixed station comprises a wireless communication device 10a that performs wireless communication on a first channel and a wireless communication device 10b that performs wireless communication on a second channel. The mobile station comprises a wireless device 21 that performs wireless communication on a first channel and a wireless device 22 that performs wireless communication on a second channel. The beam directions of the wireless communication device 10a and the beam directions of the wireless communication device 10b are different from each other, and the beam directions of the wireless device 21 and the beam directions of the wireless device 22 are different from each other.

Description

Technical Field

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

Background Art

[0002] Conventionally, a technique for assisting the operation of a train formation by presenting an image of a home to the driver of the train formation is known. In this technique, a wireless communication system is used that transmits an image captured by a camera installed at the home to the train formation, receives the transmitted image, and outputs and displays it on a liquid crystal display device installed in the driver's cab of the train formation. For details of such a wireless communication system, see, for example, Patent Documents 1 and 2 below.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, due to train schedule disruptions or maintenance, the relationship between the track and the train formation entering the track often has to be changed. Therefore, in the above-described wireless communication system, it is preferable that the identification settings for communication (for example, the center frequency and SSID (Service Set Identifier) during wireless communication) are common settings for all train formations. Therefore, in the conventional wireless communication system, in order to provide an appropriate image to the train formation entering the home track, a detection system for detecting the train formation entering the home track is separately required, resulting in a problem of high introduction costs.

[0005] This invention has been made in view of the above circumstances, and aims to provide a wireless communication system that can provide appropriate services according to the communication partner while keeping implementation costs down. [Means for solving the problem]

[0006] To solve the above problems, a first aspect of the present invention provides a wireless communication system (1) comprising a fixed station and a mobile station, wherein the fixed station comprises a first wireless communication device (10a) that performs wireless communication on a first channel and a second wireless communication device (10b) that performs wireless communication on a second channel, and the mobile station comprises a first wireless device (21) that performs wireless communication on the first channel and a second wireless device (22) that performs wireless communication on the second channel, wherein the beam direction of the first wireless communication device and the beam direction of the second wireless communication device are different from each other, and the beam direction of the first wireless device and the beam direction of the second wireless device are different from each other.

[0007] A wireless communication system according to a first aspect of the present invention includes a fixed station comprising a first wireless communication device that performs wireless communication on a first channel and a second wireless communication device that performs wireless communication on a second channel, wherein the beam directions of the first wireless communication device and the beam directions of the second wireless communication device are different from each other. Furthermore, a mobile station comprises a first wireless device that performs wireless communication on a first channel and a second wireless device that performs wireless communication on a second channel, wherein the beam directions of the first wireless device and the beam directions of the second wireless device are different from each other. As a result, depending on the positional relationship of the mobile station with respect to the fixed station, the first wireless communication device and the first wireless device can communicate wirelessly, enabling the provision of a service suitable for the first wireless device, or the second wireless communication device and the second wireless device can communicate wirelessly, enabling the provision of a service suitable for the second wireless device. Therefore, it is possible to provide appropriate services according to the communication partner while keeping the introduction cost down.

[0008] Furthermore, in the wireless communication system according to the second aspect of the present invention, the first wireless device and the second wireless device are each capable of scanning the direction of a beam, and the scanning ranges of the beams in the first wireless device and the second wireless device are limited so that the directions of their beams are not the same.

[0009] Furthermore, in a third aspect of the present invention, the wireless communication system is a wireless communication system according to the second aspect of the present invention, wherein the beam scanning range of the first wireless device is limited to a range in which the direction of the beam is in a direction that facilitates wireless communication with the first wireless communication device, and the beam scanning range of the second wireless device is limited to a range in which the direction of the beam is in a direction that facilitates wireless communication with the second wireless communication device.

[0010] Furthermore, in a wireless communication system according to a fourth aspect of the present invention, in a wireless communication system according to a second or third aspect of the present invention, the first wireless communication device and the second wireless communication device are each capable of scanning the direction of the beam within a reference scanning range which is a predetermined scanning range.

[0011] Furthermore, in the wireless communication system according to the fifth aspect of the present invention, the first wireless communication device and the second wireless communication device limit the beam scanning range to a range narrower than the reference scanning range.

[0012] Furthermore, in the wireless communication system according to the sixth aspect of the present invention, in the wireless communication system according to the fourth or fifth aspect of the present invention, the first wireless communication device and the second wireless communication device terminate the control of scanning the direction of the beam when they determine that the beam of the other party with whom they are communicating has been affected by reflection.

[0013] Furthermore, in the wireless communication system according to the seventh aspect of the present invention, in the wireless communication system according to any of the fourth to sixth aspects of the present invention, the first wireless communication device and the second wireless communication device and the first wireless device and the second wireless device control the beam scanning direction so that the received power of the party communicating wirelessly is maximized.

[0014] Furthermore, in the eighth aspect of the present invention, the wireless communication system is a wireless communication system according to any one of the first to seventh aspects of the present invention, wherein the first wireless communication device and the second wireless communication device and the first wireless equipment and the second wireless equipment are equipped with a phased array antenna (11), and the direction of the beam is the direction in which the main lobe of the radiation pattern of the phased array antenna appears.

[0015] Furthermore, in the wireless communication system according to the ninth aspect of the present invention, in the wireless communication system according to the first to eighth aspects of the present invention, the first wireless communication device and the second wireless communication device provided at the fixed station and the first wireless device and the second wireless device provided at the mobile station start processing for wireless communication when the distance between the fixed station and the mobile station becomes less than or equal to a predetermined distance.

[0016] Furthermore, in the tenth aspect of the present invention, the wireless communication system is a wireless communication system according to any one of the first to ninth aspects of the present invention, wherein the fixed station is installed on a platform (HM), and the mobile station is installed on a train set (TR) entering the platform.

[0017] In addition, in the wireless communication system according to the 11th aspect of the present invention, in the wireless communication system according to the 10th aspect of the present invention, the first wireless communication device and the second wireless communication device provided in the fixed station provide a service for transmitting an image of the home corresponding to the track number of the home where the vehicle formation enters, with respect to the vehicle formation entering the home, and the first wireless device and the second wireless device provided in the mobile station receive the image transmitted from the first wireless communication device or the second wireless communication device and output and display it on the display device (40) installed in the vehicle formation.

Effect of the Invention

[0018] According to the present invention, there is an effect that an appropriate service corresponding to the communication partner can be provided while suppressing the introduction cost.

Brief Description of the Drawings

[0019] [Figure 1] It is a block diagram showing a wireless communication system according to the first embodiment of the present invention. [Figure 2] It is a block diagram showing a main part configuration of a wireless communication device in the first embodiment of the present invention. [Figure 3] It is a diagram showing an example of a beam formed in the first embodiment of the present invention. [Figure 4] It is a timing chart for explaining the operation of the wireless communication system according to the first embodiment of the present invention. [Figure 5] It is a diagram showing the relationship between the search range of the beam sector and the line connection range in the first embodiment of the present invention. [Figure 6] [[ID=**30**]]It is a diagram for explaining a wireless communication system according to the second embodiment of the present invention. [Figure 7] It is a timing chart for explaining the first operation of the wireless communication system according to the second embodiment of the present invention. [Figure 8] It is a diagram showing the relationship between the search range of the beam sector and the line connection range in the first operation example of the second embodiment of the present invention. [Figure 9] Note: There seems to be a small error in the original text where "本発明の第2実施形態による無線通信システムを説明するための図である。" has an incorrect line break. It should be a single line in a proper patent text format, and I've adjusted the translation accordingly. Also, the line numbering in the translation is maintained as per the original text's structure.A timing chart for explaining the second operation of the wireless communication system according to the second embodiment of the present invention. [Figure 10] A diagram showing the relationship between the search range of a beam sector and the line connection range in the second operation example of the second embodiment of the present invention.

Mode for Carrying Out the Invention

[0020] Hereinafter, a wireless communication system according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0021] 〔First Embodiment〕 FIG. 1 is a block diagram showing a wireless communication system according to the first embodiment of the present invention. The wireless communication system 1 of the present embodiment is applied to a monitoring system for monitoring a platform HM such as a station.

[0022] As shown in FIG. 1, the wireless communication system 1 of the present embodiment includes a plurality of wireless communication devices 10 (fixed stations), a plurality of wireless devices 21 (mobile stations, first wireless devices), a plurality of wireless devices 22 (mobile stations, second wireless devices), a plurality of image transmission systems 30, and a plurality of monitors 40 (display devices). The plurality of wireless communication devices 10 and the plurality of image transmission systems 30 are installed on the platform HM of the station, and the plurality of wireless devices 21, 22 and the monitors 40 are installed on a plurality of trains TR (vehicle formations), respectively.

[0023] 4] Such a wireless communication system 1 is a system capable of point-to-point (Point To Point) communication between any one of the wireless communication device 10a and the wireless devices 21a, 21b, and between any one of the wireless communication device 10b and the wireless devices 22a, 22b. Such a wireless communication system 1 performs wireless communication between any one of the wireless communication device 10a and the wireless devices 21a, 21b, and between any one of the wireless communication device 10b and the wireless devices 22a, 22b, and thereby provides a service for transmitting and displaying an image of the platform HM corresponding to the platform number of the platform HM where the train TR enters, to the incoming train TR.

[0024] The wireless communication system 1 performs wireless communication using high-frequency signals such as microwaves, quasi-millimeter waves, and millimeter waves. The wireless communication system 1 also performs wireless communication compliant with the wireless communication standard IEEE 802.11ad. The wireless communication device 10 corresponds to a base station device that manages connections, and corresponds to, for example, an AP (Access Point) or PCP (PBSS Control Point) as defined in the wireless communication standard IEEE 802.11. The multiple wireless devices 21 and 22 correspond to wireless terminals connected to the base station device, and correspond to, for example, an STA (Station) as defined in the wireless communication standard IEEE 802.11.

[0025] The platform HM shown in Figure 1 is an island platform with tracks on both sides. However, the platform HM is not limited to island platforms; it can be a single platform with tracks on only one side, a side platform with two single platforms facing each other, or any other type of platform. In the following, one track of the platform HM shown in Figure 1 will be referred to as "Track 1," and the other track of the platform HM will be referred to as "Track 2."

[0026] A wireless communication device 10a (first wireless communication device) and an image transmission system 30a are provided on the track 1 side of the platform HM, and a wireless communication device 10b (second wireless communication device) and an image transmission system 30b are provided on the track 2 side of the platform HM.

[0027] Wireless communication devices 10a and 10b perform wireless communication on different channels. That is, wireless communication device 10a performs wireless communication on the first channel, and wireless communication device 10b performs wireless communication on a second channel, which is different from the first channel. In addition, the direction of beam BM (BM1) of wireless communication device 10a and the direction of beam BM (BM2) of wireless communication device 10b are different.

[0028] In this embodiment, as shown in Figure 1, the angle of the beam BM radiated from the wireless communication device 10 toward the right in the drawing is set to 0°. An angle clockwise from this angle (0°) is considered positive, and an angle counterclockwise is considered negative. Therefore, the direction of beam BM1 of wireless communication device 10a is in the direction of a negative angle, and the direction of beam BM2 of wireless communication device 10b is in the direction of a positive angle. In other words, the direction of beam BM1 of wireless communication device 10a is set to point toward train TR1 entering track 1, and the direction of beam BM2 of wireless communication device 10b is set to point toward train TR2 entering track 2.

[0029] Furthermore, wireless communication devices 10a and 10b are capable of scanning the beam direction within a predetermined scanning range (reference scanning range). For example, wireless communication devices 10a and 10b can scan within the range of -45° to +45°. Note that this reference scanning range is merely an example, and the reference scanning ranges of wireless communication devices 10a and 10b can be set arbitrarily, and the reference scanning ranges of wireless communication devices 10a and 10b can be set individually. In addition, wireless communication devices 10a and 10b can also limit the beam scanning range to a range narrower than the reference scanning range.

[0030] Figure 2 is a block diagram showing the main components of a wireless communication device in a first embodiment of the present invention. Since wireless communication devices 10a and 10b have similar configurations, they will be described here as wireless communication device 10. As shown in Figure 2, wireless communication device 10 includes a phased array antenna 11 and a control unit 12, and provides a service, for example, transmitting an image of the platform headmark (HM) of a train TR entering the station to the train TR. The service provided by wireless communication device 10 is not limited to the above example and may include other services.

[0031] The phased array antenna 11 is an antenna equipped with multiple antenna elements (not shown) that can freely change its beam pattern (antenna directivity). In other words, the phased array antenna 11 is an antenna with beamforming capabilities. In the phased array antenna 11, the beamforming function is achieved by adjusting at least one of the intensity and phase of the signal supplied to the multiple antenna elements (transmitted signal) or the signal supplied from the multiple antenna elements (received signal).

[0032] In the phased array antenna 11, any beam pattern can be formed by adjusting the intensity and phase as described above. For example, the beam BM shown in Figure 2 is formed as the beam pattern of the phased array antenna 11. The direction of the formed beam BM is the direction in which the main lobe of the radiation pattern of the phased array antenna 11 appears.

[0033] Figure 3 shows an example of a beam formed in the first embodiment of the present invention. As described above, the direction of the beam BM formed by the phased array antenna 11 is the direction in which the main lobe of the radiation pattern of the phased array antenna 11 appears. The full width at half maximum of the beam BM is the angle of the beam BM at the point where the intensity of the beam BM decreases by 3 dB from the maximum value of the main lobe.

[0034] The control unit 12 controls the beam direction of the phased array antenna 11 and performs the control to provide the services described above. Here, the control unit 12 controls the beam BM of the phased array antenna 11 so that the received power of the wireless device 21 or wireless device 22 performing wireless communication is maximized. The control unit 12 controls the beam BM of the phased array antenna 11 using a beam table (not shown) in which beam sectors and beam directions are associated. The beam sector is information that identifies the beam formed by the phased array antenna 11, and for example, an integer (number) in the range of 0 to 63 is stored. The beam direction is information that indicates the direction of the beam BM of the phased array antenna 11, and for example, any angle in the range of -45° to +45° is stored. Since there is a one-to-one correspondence between the beam sector and the beam direction, when the beam sector is identified, the beam direction is identified.

[0035] Furthermore, after controlling the direction of the beam BM of the phased array antenna 11, the control unit 12 performs the control to provide the services described above. Specifically, it performs the control to transmit the image obtained from the image transmission system 30 (the image of track 1 or track 2) to train TR. The control unit 12 of the wireless communication device 10a performs the control to transmit the image of track 1 obtained from the image transmission system 30a to train TR1. The control unit 12 of the wireless communication device 10b performs the control to transmit the image of track 2 obtained from the image transmission system 30b to train TR2.

[0036] The image transmission system 30 includes a camera group 31 and an image synthesis device 32. Images captured by the camera group 31 are synthesized by the image synthesis device 32 and transmitted to the wireless communication device 10. Image transmission system 30a transmits the synthesized image to the wireless communication device 10a, and image transmission system 30b transmits the synthesized image to the wireless communication device 10b. Although Figure 1 shows two image transmission systems 30a and 30b as multiple image transmission systems 30, the number of image transmission systems 30 is not limited to two. There may be three or more image transmission systems 30.

[0037] The image transmission system 30a comprises a camera group 31a and an image combining device 32a. The camera group 31a comprises multiple cameras connected by cable CB1. The multiple cameras of the camera group 31a are arranged along the platform HM (along the direction of train TR's entry) on the track 1 side of the platform HM. In other words, the multiple cameras of the camera group 31a are arranged to capture images from different positions on the track 1 side of the platform HM. The image combining device 32a combines (encodes) the images captured by the multiple cameras of the camera group 31a and transmitted by cable CB1. The image combining device 32a is connected to the wireless communication device 10a and outputs the combined image to the wireless communication device 10a.

[0038] The image transmission system 30b comprises a camera group 31b and an image combining device 32b. The camera group 31b comprises multiple cameras connected by cable CB2. The multiple cameras of camera group 31b are arranged along the platform HM (along the direction of train TR entry) on the track 2 side of platform HM. In other words, the multiple cameras of camera group 31b are arranged to capture images from different positions on the track 2 side of platform HM. The image combining device 32b combines (encodes) the images captured by the multiple cameras of camera group 31b and transmitted by cable CB2. The image combining device 32b is connected to the wireless communication device 10b and outputs the combined image to the wireless communication device 10b.

[0039] Wireless devices 21 and 22 are devices that communicate wirelessly with the wireless communication device 10. Wireless devices 21 and 22 communicate wirelessly on different channels. That is, wireless device 21 communicates wirelessly on the first channel, and wireless device 22 communicates wirelessly on a second channel which is different from the first channel. In addition, the beam directions of wireless device 21 and wireless device 22 are different from each other.

[0040] Wireless devices 21 and 22 are equipped with phased array antennas similar to the phased array antenna 11 of the wireless communication device 10, for example, and are capable of scanning the direction of their beams. However, the beam scanning ranges of wireless devices 21 and 22 are limited so that the beam directions of each device are not the same. For example, the beam scanning range of wireless device 21 is limited to a range in which the beam direction is suitable for wireless communication with wireless communication device 10a. Similarly, the beam scanning range of wireless device 22 is limited to a range in which the beam direction is suitable for wireless communication with wireless communication device 10b.

[0041] The monitor 40 is equipped with a display device such as a liquid crystal display device, and receives signals from the wireless device 21 or wireless device 22, decodes the output from the wireless device 21 or wireless device 22, and displays it. The monitor 40 is installed, for example, in the driver's cab of a train TR.

[0042] In the example shown in Figure 1, radio equipment 21a, radio equipment 22a, and monitor 40a are installed on train TR1 which enters track 1 of platform HM, and radio equipment 21b, radio equipment 22b, and monitor 40b are installed on train TR2 which enters track 2 of platform HM. Note that radio equipment 21, radio equipment 22, and monitor 40 may be installed on all train TRs that are scheduled to enter platform HM, for example.

[0043] Figure 4 is a timing chart illustrating the operation of a wireless communication system according to the first embodiment of the present invention. For the sake of simplicity, the explanation will use the example of train TR1 entering platform HM track 1 and train TR2 entering platform HM track 2 simultaneously.

[0044] The wireless communication devices 10a and 10b transmit beacons by broadcast at regular time intervals (step S11). The beacons transmitted from wireless communication device 10a and the beacons transmitted from wireless communication device 10b are transmitted on different channels. When train TR1 enters platform HM track 1 and train TR2 enters platform HM track 2, the beacon transmitted from wireless communication device 10a is received by wireless device 21a installed on train TR1, and the beacon transmitted from wireless communication device 10b is received by wireless device 22b installed on train TR2.

[0045] When wireless devices 21a and 22b receive a beacon, they verify the SSID and other information, and then send an association request to the wireless communication device 10a (step S12). The association request sent from wireless device 21a and the association request sent from wireless device 22b are transmitted on different channels.

[0046] When wireless communication device 10a receives an association request transmitted from wireless device 21a, it sends an ACK (ACKnowledgement) to wireless device 21a. Similarly, when wireless communication device 10b receives an association request transmitted from wireless device 22b, it sends an ACK (ACKnowledgement) to wireless device 21b (step S13). As a result, an association is established between wireless communication device 10a and wireless device 21a, and between wireless communication device 10b and wireless device 22b.

[0047] Once the association is established, a process to fix the beam sector is performed in each of the wireless devices 21a and 22b (step S14). For example, a process is performed to fix the beam sector so that the beam direction of wireless devices 21a and 22b faces the direction shown in Figure 1. Then, the wireless communication device 10a searches for the transmit beam sector of wireless device 21a, and the wireless communication device 10b searches for the transmit beam sector of wireless device 22b (step S15).

[0048] Figure 5 shows the relationship between the beam sector search range and the line connection range in the first embodiment of the present invention. The beam sector search range is, literally, the range in which the wireless communication devices 10a and 10b search for beam sectors. In contrast, the line connection range is the range of beam sectors that the wireless communication devices 10a and 10b can adopt (select) from the searched beam sectors. As shown in Figure 5, in this embodiment, the beam sector search range and the line connection range are equal. For example, the beam sector search range and line connection range of the wireless communication devices 10a and 10b are in the range of θa = -45° to θb = +45°.

[0049] Once the search for the transmit beam sector is complete, the optimal transmit and receive beam sector is searched between the wireless communication device 10a and the wireless device 21a, and the optimal transmit and receive beam sector is searched between the wireless communication device 10b and the wireless device 22b (step S16). Specifically, the receiving side is set to beamforming mode, and a process is performed to search for the optimal beam sector (beam direction) for both transmit and receive.

[0050] The optimal beam sector is the beam sector in which the received power is maximized on the wireless devices 21a and 22b. Specifically, this is the state in which the transmission and reception beam directions (the direction in which the main lobe appears) of the wireless communication device 10a and wireless device 21a are directly facing each other, and the transmission and reception beam directions (the direction in which the main lobe appears) of the wireless communication device 10b and wireless device 22b are directly facing each other. When the optimal transmission and reception beam sector is found, for example, as shown in Figure 1, beam BM1 is directed towards wireless device 21a installed on train TR1, and beam BM2 is directed towards wireless device 22b installed on train TR2.

[0051] Furthermore, the position of wireless device 21a changes according to the movement of train TR1, and the position of wireless device 22b changes according to the movement of train TR2. Therefore, the search for the optimal transmit / receive beam sector continues at least until trains TR1 and TR2 stop.

[0052] Once the optimal transmit / receive beam sector is found, the wireless communication device 10a converts the image output from the image transmission system 30a (image of line 1) into a data frame and transmits it to the wireless device 21a located in the direction of beam BM1. The wireless communication device 10b also converts the image output from the image transmission system 30b (image of line 2) into a data frame and transmits it to the wireless device 22b located in the direction of beam BM2 (step S17).

[0053] When wireless device 21a receives a data frame transmitted from wireless communication device 10a, it sends an ACK, and when wireless device 22b receives a data frame transmitted from wireless communication device 10b, it sends an ACK (step S18). Then, wireless device 21a outputs the received image data to monitor 40a, and wireless device 22b outputs the received image data to monitor 40b. As a result, images captured by the camera group 31a of the image transmission system 30a are displayed on monitor 40a installed on train TR1, and images captured by the camera group 31b of the image transmission system 30b are displayed on monitor 40b installed on train TR2.

[0054] As described above, in this embodiment, a wireless communication device 10a that performs wireless communication on the first channel and a wireless communication device 10b that performs wireless communication on the second channel are installed on the platform HM, and the beam directions of the wireless communication devices 10a and 10b are set to be different from each other. In addition, a wireless device 21 that performs wireless communication on the first channel and a wireless device 22 that performs wireless communication on the second channel are installed on the trains TR1 and TR2, respectively, and the beam directions of the wireless devices 21 and 22 are set to be different from each other in each of the trains TR1 and TR2.

[0055] As a result, when the positional relationship between the wireless communication device 10a installed on the platform HM and the trains TR1 and TR2 is such that the beams of the wireless communication device 10a and the wireless device 21 are directly facing each other, the wireless communication device 10a and the wireless device 21 become able to communicate, and images captured by the camera group 31a of the image transmission system 30a are transmitted from the wireless communication device 10a to the wireless device 21. Furthermore, when the positional relationship between the wireless communication device 10b installed on the platform HM and the trains TR1 and TR2 is such that the beams of the wireless communication device 10b and the wireless device 22 are directly facing each other, the wireless communication device 10b and the wireless device 22 become able to communicate, and images captured by the camera group 31b of the image transmission system 30b are transmitted from the wireless communication device 10b to the wireless device 22.

[0056] Thus, in this embodiment, without providing a separate detection system to detect trains entering the platform of the platform HM, an image of the platform of the platform HM that the train TR is entering can be displayed on the monitor 40 installed on the train TR entering the platform of the platform HM. Therefore, it is possible to provide appropriate services according to the communication partner while keeping the introduction cost down.

[0057] [Second Embodiment] Figure 6 is a diagram illustrating a wireless communication system according to a second embodiment of the present invention. The wireless communication system of this embodiment has substantially the same configuration as the wireless communication system 1 shown in Figure 1, but addresses unintended wireless connections (interference) caused by beam reflections generated by structures X surrounding the wireless communication system.

[0058] If no structure X is present around the wireless communication system, the beam of the wireless device 21b installed on the train TR2 entering track 2 is directed in the opposite direction to the platform HM, so the wireless communication device 10a and the wireless device 21b cannot be connected wirelessly. However, as shown in Figure 6, if structure X is present around the wireless communication system, the beam of the wireless communication device 10a is reflected by structure X, which can create a situation where the wireless communication device 10a and the wireless device 21b can be connected wirelessly. This embodiment addresses this situation.

[0059] Figure 7 is a timing chart illustrating the first operation of a wireless communication system according to a second embodiment of the present invention. For the sake of simplicity, the explanation will use as an example the case shown in Figure 6, where a structure X exists on the second track side of platform HM, and train TR1 enters platform HM on track 1, followed slightly later by train TR2 entering platform HM on track 2. In Figure 6, steps similar to those shown in Figure 4 are denoted by the same reference numerals.

[0060] The wireless communication devices 10a and 10b broadcast beacons on different channels at regular time intervals (step S11). When train TR1 enters platform HM, the beacon transmitted from wireless communication device 10a is received by wireless device 21a installed on train TR1. Upon receiving the beacon, wireless device 21a checks the SSID and other information and then sends an association request to wireless communication device 10a (step S12).

[0061] When the wireless communication device 10a receives an association request transmitted from the wireless device 21a, it sends an ACK to the wireless device 21a (step S13). This establishes an association between the wireless communication device 10a and the wireless device 21a.

[0062] Once the association is established, the wireless device 21a performs a process to fix the beam sector (step S14). For example, the beam sector is fixed so that the direction of the beam of the wireless device 21a points in the direction shown in Figure 1. The wireless communication device 10a also performs a process to limit the beam sector search range and the line connection range (step S21). Then, the wireless communication device 10a searches for the transmit beam sector of the wireless device 21a within the beam sector search range that has been limited (step S15).

[0063] Figure 8 shows the relationship between the beam sector search range and the line connection range in the first operation example of the second embodiment of the present invention. As shown in Figure 8, in this operation example, the beam sector search range and line connection range are limited to a narrower range than the initial range (reference scanning range) by the process in step S21. For example, if the initial beam sector search range and line connection range of the wireless communication device 10a were in the range of θa = -45° to θb = +45°, they will be limited to the range of θa = -45° to θc = 0°. By imposing such a restriction, it is possible to prevent the situation described using Figure 6 (a situation in which the beam of the wireless communication device 10a is reflected by structure X, and the wireless communication device 10a and wireless equipment 21b are connected in a wireless communication manner).

[0064] Once the search for the transmit beam sector is complete, the optimal transmit and receive beam sector is searched between the wireless communication device 10a and the wireless device 21a (step S16). When the optimal transmit and receive beam sector is found, the wireless communication device 10a converts the image output from the image transmission system 30a (the image of line 1) into a data frame and transmits it to the wireless device 21a located in the direction of beam BM1 (step S17).

[0065] When the wireless device 21a receives a data frame transmitted from the wireless communication device 10a, it sends an ACK (step S18). Then, the wireless device 21a outputs the received image data to the monitor 40a. As a result, the images captured by the camera group 31a of the image transmission system 30a are displayed on the monitor 40a installed on the train TR1.

[0066] Figure 9 is a timing chart for illustrating the second operation of a wireless communication system according to a second embodiment of the present invention. Here, as with the first operation example, the explanation will be given using the case where, as shown in Figure 6, structure X exists on the second track side of platform HM, and train TR1 enters platform HM on track 1, followed slightly later by train TR2 entering platform HM on track 2. In Figure 9, the same reference numerals are used for steps similar to those shown in Figure 4.

[0067] The wireless communication devices 10a and 10b broadcast beacons on different channels at regular time intervals (step S11). When train TR1 enters platform HM, the beacon transmitted from wireless communication device 10a is received by the wireless device 21a installed on train TR1. Upon receiving the beacon, the wireless device 21a determines whether or not it has received a trigger signal indicating that it has approached wireless communication device 10a (step S31). This process is performed to ensure that the association is established only after train TR1 has approached wireless communication device 10a sufficiently.

[0068] In other words, interference may occur if the platform HM is curved or if the train TR1 is far away from the wireless communication device 10a. For this reason, the process of establishing an association is performed only after receiving a trigger signal indicating that the train TR1 is approaching the wireless communication device 10a. Here, the trigger signal may be, for example, distance information to the stopping position, speed information from the train TR1 during stopping (decelerating), or a signal output in response to the GPS (Global Positioning System) signal.

[0069] When the wireless device 21a determines that it has received a trigger signal, it checks the SSID and other information and then sends an association request to the wireless communication device 10a (step S12). In other words, the process for performing wireless communication starts after the distance between the fixed station and the mobile station falls below a predetermined distance. When the wireless communication device 10a receives the association request sent from the wireless device 21a, it sends an ACK to the wireless device 21a (step S13). This establishes an association between the wireless communication device 10a and the wireless device 21a. Once the association is established, both the wireless communication device 10a and the wireless device 21a perform a process to search for each other's transmit beam sectors (step S32).

[0070] Figure 10 shows the relationship between the beam sector search range and the line connection range in a second operation example of a second embodiment of the present invention. As shown in Figure 10, in this operation example, the line connection range is set to be narrower than the search range. For example, if the beam sector search range of the wireless communication device 10a is in the range of θa = -45° to θb = +45°, then the line connection range is θa = -45° to θc = 0°.

[0071] Here, if the wireless communication device 10a selects a beam sector that is not conceivable from the direction of the train TR1, it is considered an unintended wireless connection (interference) caused by beam reflection. In such a case, the wireless communication device 10a performs a process to disconnect the established association (step S33). That is, it terminates the control to scan the direction of the beam. Similarly, if the wireless device 21a or wireless device 21b selects a beam sector that is not conceivable from the direction of the train TR1, the wireless device 21a or wireless device 21b may perform a process to disconnect the established association (step S34). Note that the selection of a beam sector that is not conceivable from the direction of the train TR1 is, for example, when a beam sector in the range of θc to θb shown in Figure 10 is selected.

[0072] If steps S33 and S34 are not performed, the wireless communication device 10a and the wireless device 21a search for the optimal transmit / receive beam sector (step S16). Once the optimal transmit / receive beam sector is found, the wireless communication device 10a converts the image output from the image transmission system 30a (the image of line 1) into a data frame and transmits it to the wireless device 21a located in the direction of beam BM1 (step S17).

[0073] When the wireless device 21a receives a data frame transmitted from the wireless communication device 10a, it sends an ACK (step S18). Then, the wireless device 21a outputs the received image data to the monitor 40a. As a result, the images captured by the camera group 31a of the image transmission system 30a are displayed on the monitor 40a installed on the train TR1.

[0074] As described above, in this embodiment as well, similar to the first embodiment, a wireless communication device 10a that performs wireless communication on the first channel and a wireless communication device 10b that performs wireless communication on the second channel are installed on the platform HM, and the beam directions of the wireless communication devices 10a and 10b are set to be different from each other. In addition, a wireless device 21 that performs wireless communication on the first channel and a wireless device 22 that performs wireless communication on the second channel are installed on the trains TR1 and TR2, respectively, and the beam directions of the wireless devices 21 and 22 are set to be different from each other in each of the trains TR1 and TR2.

[0075] As a result, when the positional relationship between the wireless communication device 10a installed on the platform HM and the trains TR1 and TR2 is such that the beams of the wireless communication device 10a and the wireless device 21 are directly facing each other, the wireless communication device 10a and the wireless device 21 become able to communicate, and images captured by the camera group 31a of the image transmission system 30a are transmitted from the wireless communication device 10a to the wireless device 21. Furthermore, when the positional relationship between the wireless communication device 10b installed on the platform HM and the trains TR1 and TR2 is such that the beams of the wireless communication device 10b and the wireless device 22 are directly facing each other, the wireless communication device 10b and the wireless device 22 become able to communicate, and images captured by the camera group 31b of the image transmission system 30b are transmitted from the wireless communication device 10b to the wireless device 22.

[0076] Thus, in this embodiment, without providing a separate detection system to detect trains entering the platform of the platform HM, an image of the platform of the platform HM that the train TR is entering can be displayed on the monitor 40 installed on the train TR entering the platform of the platform HM. Therefore, it is possible to provide appropriate services according to the communication partner while keeping the introduction cost down.

[0077] Furthermore, in this embodiment, as shown in Figure 8, the search range and the line connection range are limited, or as shown in Figure 10, only the line connection range is limited. This prevents unintended wireless connections (interference) caused by beam reflections generated by structures X surrounding the wireless communication system.

[0078] Although a wireless communication system according to an embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be freely modified within the scope of the present invention. For example, the service provided in the above embodiment was to display an image of the platform HM track to which the trains TR1 and TR2 that enter the platform HM track were entering on monitors 40 installed on the trains TR1 and TR2 that enter the platform HM track. However, conversely, the service may also be to display an image of the trains TR1 and TR2 that enter the platform HM track (for example, an image inside the train TR) on monitors installed for each platform HM track. [Explanation of symbols]

[0079] 1... Wireless communication system, 10, 10a, 10b... Wireless communication device, 11... Phased array antenna, 21, 21a, 21b... Wireless equipment, 22, 22a, 22b... Wireless equipment, 40... Monitor, HM... Home, TR... Train

Claims

1. A wireless communication system comprising a fixed station and a mobile station, The aforementioned fixed station is A first wireless communication device that performs wireless communication on the first channel, A second wireless communication device that performs wireless communication on the second channel, Equipped with, The aforementioned mobile station is A first wireless device that performs wireless communication on the first channel, A second wireless device that performs wireless communication on the second channel, Equipped with, The beam direction of the first wireless communication device and the beam direction of the second wireless communication device are different from each other. The beam direction of the first wireless device and the beam direction of the second wireless device are different from each other. Wireless communication system.

2. The first wireless device and the second wireless device are capable of scanning the direction of the beam, The beam scanning ranges in the first wireless device and the second wireless device are limited so that the direction of their beams is not the same. The wireless communication system according to claim 1.

3. The beam scanning range in the first wireless device is limited to a range in which the direction of the beam is in a direction that facilitates wireless communication with the first wireless communication device. The beam scanning range in the second wireless device is limited to a range in which the direction of the beam is in a direction that facilitates wireless communication with the second wireless communication device. The wireless communication system according to claim 2.

4. The wireless communication system according to claim 2, wherein the first wireless communication device and the second wireless communication device are each capable of scanning the direction of a beam within a reference scanning range which is a predetermined scanning range.

5. The wireless communication system according to claim 4, wherein the first wireless communication device and the second wireless communication device limit the beam scanning range to a range narrower than the reference scanning range.

6. The wireless communication system according to claim 4, wherein the first wireless communication device and the second wireless communication device terminate the control of scanning the direction of the beam when they determine that the beam of the other party with whom they are communicating has been affected by reflection.

7. The wireless communication system according to claim 4, wherein the first wireless communication device and the second wireless communication device and the first wireless device and the second wireless device control the beam scanning direction so that the received power of the wireless communication partner is maximized.

8. The first wireless communication device and the second wireless communication device, and the first wireless device and the second wireless device are equipped with a phased array antenna. The beam direction is the direction in which the main lobe of the radiation pattern of the phased array antenna appears. A wireless communication system according to any one of claims 1 to 7.

9. The wireless communication system according to claim 1, wherein the first wireless communication device and the second wireless communication device provided at the fixed station and the first wireless device and the second wireless device provided at the mobile station start processing for wireless communication when the distance between the fixed station and the mobile station becomes less than or equal to a predetermined distance.

10. The aforementioned fixed station is installed at home, The aforementioned mobile station is installed in the train set entering the aforementioned platform. The wireless communication system according to claim 1.

11. The first wireless communication device and the second wireless communication device installed at the fixed station provide a service to transmit an image of the platform corresponding to the platform number of the train set entering the platform. The first radio equipment and the second radio equipment installed in the mobile station receive the image transmitted from the first radio communication device or the second radio communication device and output it to a display device installed in the train set for display. The wireless communication system according to claim 10.

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