Communication system, AP device, STA device, control method, and program

Abstract

To reduce the occurrence of communication interruptions in wireless communication. [Solution] The AP device 11 is movable and includes a first wired interface connected to the mobile body 41 by wired communication, and a first wireless interface having the function of maintaining a state in which a wireless communication link is established with at least two of the plurality of STA devices 21, etc. Each of the plurality of STA devices 21, etc. includes a second wired interface connected to the communication partner of the mobile body 41 by wired communication, and a second wireless interface that establishes a wireless communication link with the AP device 11, and the plurality of STA devices 21, etc. are arranged so that any position within the area in which the AP device 11 is movable is within the communication range of the second wireless interface provided by two or more of the plurality of STA devices 21, etc.

Description

Technical Field

[0001] The present invention relates to a communication system, an AP device, a STA device, a control method, and a program.

Background Art

[0002] [[ID=1,2,3,4,5,6,7,8,9,10,11]]There is wireless communication using an AP (Access Point) device and a STA (Station) device. In a conventional wireless communication system, for example, a movable STA device communicates while maintaining a wireless communication connection with any one of a plurality of fixedly installed AP devices.

[0003] Thus, in a wireless communication system, a STA device can maintain a wireless communication connection with an AP device within the wireless communication range of a plurality of AP devices.

[0004] Patent Document 1 describes that a wireless terminal included in a moving body performs wireless communication while performing connection switching (so-called roaming) using a wireless relay station as an access point.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a wireless communication system, when a STA device switches its connection from one AP device to another AP device, a time period (also referred to as a communication interruption time) during which the STA device cannot communicate temporarily occurs. When the communication interruption time occurs, deterioration in the communication quality between the STA device and the AP device (more specifically, disappearance or delay of communication frames) may occur.

[0007] The present invention aims to provide a communication system that reduces the occurrence of communication interruptions in wireless communication. [Means for solving the problem]

[0008] The following describes examples of inventions that can be obtained from the disclosures in this specification, and explains the effects and other benefits that can be obtained from such inventions.

[0009] (1) A communication system comprising one AP device and a plurality of STA devices, wherein the one AP device is movable together with a mobile body within a predetermined area and comprises a first wired interface connected to the mobile body by wired communication, a first wireless interface having the function of maintaining a state in which a wireless communication link is established with at least two of the plurality of STA devices, and a first transfer unit that transfers frames between the first wired interface and the first wireless interface, and each of the plurality of STA devices comprises a second wired interface connected to the mobile body's communication partner by wired communication, a second wireless interface that establishes a wireless communication link with the one AP device, and a second transfer unit that transfers frames between the second wired interface and the second wireless interface, and the plurality of STA devices are arranged in a position where any position within the area is within the communication range of the second wireless interface provided by two or more of the plurality of STA devices.

[0010] According to the above embodiment, the communication system allows one AP device to be connected wirelessly to at least two STA devices. Therefore, even if the wireless communication connection between one of the two STA devices and one AP device is disconnected, the wireless communication connection between the other STA device and one AP device can be maintained. Thus, the communication system can reduce the occurrence of communication interruption time in wireless communication, even if the wireless communication connection between one of the two STA devices and one AP device is disconnected. In this way, the communication system reduces the occurrence of communication interruption time in wireless communication.

[0011] In this invention, the term "AP device" refers to any communication device that has the function of maintaining a state in which a wireless communication link is established simultaneously with multiple STA devices, and is not necessarily limited to a device that has all the functions of an AP in infrastructure mode compliant with the IEEE 802.11 standard.

[0012] (2) The communication system according to (1), wherein the plurality of STA devices are fixedly arranged so that any position within the area is within the communication range of the second wireless interface provided by the two or more STA devices, and the first wireless interface establishes the wireless communication link with the second wireless interface that enters the communication range of the first wireless interface when the one AP device moves, and disconnects the wireless communication link established with the second wireless interface that deviates from the communication range of the first wireless interface when the one AP device moves.

[0013] According to the above embodiment, the wireless communication system allows one AP device to sequentially establish wireless communication links with newly enabled STA devices from among a plurality of fixedly configured STA devices, and to sequentially disconnect wireless communication links established with STA devices that have become inoperable. As a result, one AP device can maintain wireless communication with at least one of the plurality of STA devices. This reduces the occurrence of communication interruptions in wireless communication.

[0014] (3) The communication system according to (1) or (2), wherein the one AP device further comprises a first control unit that generates designation information for one of the plurality of STA devices which the second transfer unit will transfer the frame from the second wired interface to the second wireless interface, and transmits the generated designation information to the plurality of STA devices.

[0015] According to the above embodiment, in a communication system, one AP device can designate one STA device (also called a designated STA device) from among multiple STA devices to wirelessly transfer frames to another AP device. This makes it possible to suppress the transfer of frames by two or more STA devices, which can contribute to reducing the amount of communication. As a result, the communication system contributes to reducing communication while reducing the occurrence of communication interruptions in wireless communication.

[0016] (4) The communication system according to (3), wherein the first control unit controls the first transfer unit to transfer the first frame received by the first wired interface from the mobile body to the first wireless interface, the first wireless interface transmits the first frame to only one of the plurality of STA devices, each of the plurality of STA devices further comprises a second control unit that receives the designated information transmitted by the one AP device, and the second control unit of each of the plurality of STA devices controls the second transfer unit of the STA device to transfer the second frame received by the second wired interface to the second wireless interface only if the STA device is the one designated by the designated information received from the one AP device, and the second wireless interface of only one of the plurality of STA devices transmits the second frame to the one AP device.

[0017] According to the above embodiment, in the communication system, one AP device forwards a first frame received from a mobile device and destined for a server to only one of several STA devices, and only the designated STA device forwards a second frame received from the server and destined for a mobile device to the one AP device. As a result, the communication system can forward both the first and second frames more reliably. This allows the communication system to reduce the occurrence of communication interruptions in wireless communication while ensuring more reliable frame forwarding.

[0018] (5) The communication system according to (3), wherein the first control unit transmits a beacon signal containing the specified information to the plurality of STA devices.

[0019] According to the above embodiment, in a communication system, one AP device can more easily transmit specified information to multiple STA devices by using a beacon signal commonly used in general wireless communication to transmit the specified information. Furthermore, multiple STA devices can more easily receive the specified information by using a beacon signal commonly used in general wireless communication to receive the specified information. As a result, the communication system can more easily reduce the occurrence of communication interruptions in wireless communication.

[0020] (6) The communication system according to (3), wherein the first control unit generates the designation information which designates, among the plurality of STA devices, the STA device from which the first wireless interface receives a higher received signal strength of radio waves as the first STA device, with higher priority.

[0021] According to the above embodiment, in a communication system, one AP device can more easily determine a designated STA device using the received signal strength of radio waves received from each of multiple STA devices. Determining a designated STA device using the received signal strength of radio waves can contribute to more appropriate wireless communication (e.g., low-latency wireless communication or low-loss wireless communication) between one AP device and a designated STA device. As a result, the communication system contributes to more appropriate wireless communication while reducing the occurrence of communication interruptions in wireless communication.

[0022] (7) The communication system according to (3), wherein the first control unit generates the designation information that designates, among the plurality of STA devices, the STA device that is closest to the first AP device is given higher priority as the first STA device.

[0023] According to the above aspect, in a communication system, one AP device can more easily determine a designated STA device by using the distances from the AP device to each of a plurality of STA devices. By determining the designated STA device using distances, it can contribute to more appropriate wireless communication (e.g., low-latency wireless communication or low-loss-rate wireless communication) between the one AP device and the designated STA device. As a result, the communication system can contribute to more appropriate wireless communication while reducing the occurrence of communication interruption time in wireless communication.

[0024] (8) The communication system according to (1), wherein the one AP device has the function of an AP in an infrastructure mode compliant with the IEEE802.11 standard.

[0025] According to the above aspect, in a communication system, by using a device having the function of an AP in an infrastructure mode compliant with the IEEE802.11 standard as the one AP device, it can contribute to more appropriate wireless communication between the one AP device and the designated STA device. As a result, the communication system can contribute to more appropriate wireless communication while reducing the occurrence of communication interruption time in wireless communication.

[0026] (9) An AP device that is movable within a predetermined area together with a mobile body, the AP device including a first wired interface connected to the mobile body by wired communication, a first wireless interface having a function of maintaining a state of establishing a wireless communication link with at least two of the plurality of STA devices, and a first transfer unit that transfers frames between the first wired interface and the first wireless interface, wherein the area is set to a position where any position within the area is within the communication range of a second wireless interface included in two or more of the plurality of STA devices.

[0027] According to the above aspect, the AP device has the same effect as the above communication system.

[0028] (10) An STA device comprising one of a plurality of STA devices, a second wired interface connected by wired communication to a communication partner of a mobile body, a second wireless interface that establishes a wireless communication link with an AP device connected by wired communication to the mobile body and which is mobile within a predetermined area, and a second transfer unit that transfers frames between the second wired interface and the second wireless interface, wherein the plurality of STA devices are arranged so that any position within the area is within the communication range of the second wireless interface provided by two or more of the plurality of STA devices.

[0029] According to the above embodiment, the STA device has the same effect as the above communication system.

[0030] (11) A control method for a communication system comprising one AP device and a plurality of STA devices, wherein the one AP device is movable together with a mobile body within a predetermined area and comprises a first wired interface connected to the mobile body by wired communication, a first wireless interface having the function of maintaining a state in which a wireless communication link is established with at least two of the plurality of STA devices, a first transfer unit that transfers frames between the first wired interface and the first wireless interface, and a first control unit, and each of the plurality of STA devices comprises a second wired interface connected to the communication partner of the mobile body by wired communication, a second wireless interface that establishes a wireless communication link with the one AP device, a second transfer unit that transfers frames between the second wired interface and the second wireless interface, and a second control unit, and the plurality of STA devices are such that any position within the area is such that two or more of the plurality of STA devices have the second wireless interface A control method comprising: a first control unit positioned within the communication area of ​​a face; the first control unit generates designation information that designates one STA device among the plurality of STA devices to which the second transfer unit transfers the frame from the second wired interface to the second wireless interface; the first transfer unit transmits the generated designation information to the plurality of STA devices; the first transfer unit controls the first transfer unit to transfer the first frame received by the first wired interface from the mobile body to the first wireless interface; the first wireless interface transmits the first frame only to the one STA device among the plurality of STA devices; and the second control unit of each of the plurality of STA devices receives the designation information transmitted by the one AP device and controls the second transfer unit of that STA device to transfer the second frame received by the second wired interface to the second wireless interface only if that STA device is the one STA device designated by the designation information received from the one AP device.

[0031] According to the above embodiment, the same effects as the above communication system are achieved.

[0032] (12) A method for controlling an AP device, wherein the AP device is movable together with a mobile body within a predetermined area and comprises a first wired interface connected to the mobile body by wired communication, a first wireless interface having the function of maintaining a state in which wireless communication links are established with at least two of a plurality of STA devices, a first transfer unit that transfers frames between the first wired interface and the first wireless interface, and a first control unit, wherein each of the plurality of STA devices comprises a second wired interface connected to the mobile body's communication partner by wired communication, a second wireless interface that establishes a wireless communication link with the AP device, and a second transfer unit that transfers frames between the second wired interface and the second wireless interface, A control method comprising a second control unit, wherein the plurality of STA devices are arranged such that any position within the area is within the communication area of ​​the second wireless interface provided by two or more of the plurality of STA devices, the first control unit generates designation information that specifies one of the plurality of STA devices which the second transfer unit transfers the frame from the second wired interface to the second wireless interface, transmits the generated designation information to the plurality of STA devices, controls the first transfer unit to transfer the first frame received by the first wired interface from the mobile body to the first wireless interface, and the first wireless interface transmits the first frame to only the one of the plurality of STA devices.

[0033] According to the above embodiment, the same effects as the AP device described above are achieved.

[0034] (13) A method for controlling one STA device among a plurality of STA devices, wherein one AP device is movable together with a mobile body within a predetermined area and comprises a first wired interface connected to the mobile body by wired communication, a first wireless interface having the function of maintaining a state in which a wireless communication link is established with at least two of the plurality of STA devices, a first transfer unit for transferring frames between the first wired interface and the first wireless interface, and a first control unit, and each of the plurality of STA devices comprises a second wired interface connected to the communication partner of the mobile body by wired communication, a second wireless interface for establishing a wireless communication link with the one AP device, a second transfer unit for transferring frames between the second wired interface and the second wireless interface, and a second control unit, and the plurality of STA devices are such that any position within the area is such that two or more of the plurality of STA devices have the second wireless interface A control method comprising: being positioned within a communication area; the first control unit generates designation information that designates one STA device from among the plurality of STA devices to which the second transfer unit transfers the frame from the second wired interface to the second wireless interface; transmitting the generated designation information to the plurality of STA devices; controlling the first transfer unit to transfer the first frame received by the first wired interface from the mobile device to the first wireless interface; the first wireless interface transmits the first frame only to the one STA device among the plurality of STA devices; and the second control unit of the one STA device receives the designation information transmitted by the one AP device and controls the second transfer unit of the one STA device to transfer the second frame received by the second wired interface to the second wireless interface only if the one STA device is the one STA device designated by the designation information received from the one AP device.

[0035] According to the above embodiment, the same effects as the STA device described above are achieved.

[0036] (14) A program that causes a computer to execute the control methods described in (12).

[0037] According to the above embodiment, the same effects as the AP device described above are achieved.

[0038] (15) A program that causes a computer to execute the control methods described in (13).

[0039] According to the above embodiment, the same effects as the STA device described above are achieved.

[0040] Furthermore, the present invention can be implemented not only as a device, but also as a method in which the processing means constituting the device are steps, as a program that causes a computer to execute those steps, as a recording medium such as a computer-readable CD-ROM on which the program is recorded, or as information, data, or signals that represent the program. These programs, information, data, and signals may be distributed via a communication network such as the Internet. [Effects of the Invention]

[0041] The present invention makes it possible to reduce the occurrence of communication interruptions in wireless communication systems. [Brief explanation of the drawing]

[0042] [Figure 1] This is a schematic diagram showing the configuration of a communication system according to an embodiment. [Figure 2] This is a block diagram showing an example of the functional configuration of an AP device according to an embodiment. [Figure 3] This is a block diagram showing an example of the functional configuration of the STA device according to the embodiment. [Figure 4] This is a schematic diagram showing an example of the position of the STA device according to the embodiment. [Figure 5] This is a flowchart showing a first example of the processing of the AP device according to the embodiment. [Figure 6]This is a flowchart showing a second example of the processing of the AP device according to the embodiment. [Figure 7] This is a flowchart showing an example of processing by the STA device according to the embodiment. [Figure 8] This is an explanatory diagram showing an example of communication in a communication system according to an embodiment. [Figure 9] This is an explanatory diagram showing an example of a communication link in a communication system according to an embodiment. [Figure 10] This is an explanatory diagram showing an example of a communication link in a communication system related to a comparative example. [Modes for carrying out the invention]

[0043] The embodiments will be described in detail below with reference to the drawings.

[0044] The embodiments described below all represent preferred specific examples of the present invention. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, those components that are not described in the independent claims representing the highest-level concept of the present invention are described as any components that constitute a more preferred form. Note that identical components may be denoted by the same reference numeral and their descriptions may be omitted.

[0045] (Embodiment) In this embodiment, a communication system that reduces the occurrence of communication interruptions in wireless communication will be described.

[0046] Figure 1 is a schematic diagram showing the configuration of the communication system 1 according to this embodiment.

[0047] As shown in Figure 1, the communication system 1 comprises an AP device 11 and STA devices 21, 22, and 23 (also referred to as STA device 21, etc.). The communication system 1 is also connected to a mobile device 41, a server 5, and a LAN 6. The communication system 1 may further include a mobile device 41 and a server 5.

[0048] Communication system 1 is a system that relays communication between the mobile device 41 and the server 5, using at least the LAN 6 and the wireless link between the STA device 21 and the AP device 11.

[0049] Server 5 is a server device, which is a computer that communicates with the mobile device 41. Server 5 is connected to LAN 6 via a wired interface and is connected to STA devices 21, 22, and 23 via LAN 6. Server 5 is the communication partner of the mobile device 41. Server 5 transmits communication frames (also called simply frames) to the mobile device 41 via the communication system 1 and receives frames from the mobile device 41 via the communication system 1. Note that Server 5 may be a general-purpose communication device.

[0050] LAN6 is a network to which server 5 and multiple STA devices 21, etc., are connected. The communication standard for LAN6 could be, for example, Ethernet.

[0051] Mobile device 41 is a mobile communication terminal. Mobile device 41 is a mobile computer, for example, a portable terminal or a personal computer. Mobile device 41 may also be a mobile cart that carries computer-controlled transported objects or a drone that performs wireless communication. Mobile device 41 is connected to AP device 11 via a wired interface and communication lines (including signal lines on a circuit board). Mobile device 41 is a communication partner of server 5. Mobile device 41 transmits frames to server 5 via communication system 1 and receives frames from mobile device 41 via communication system 1. Mobile device 41 may also be a general-purpose communication device.

[0052] The content of the communication between the server 5 and the mobile device 41 may be anything. For example, the content of the frame that the server 5 sends to the mobile device 41 may be notification information in which the server 5 notifies the mobile device 41 of its destination, notification information in which the server 5 notifies the mobile device 41 of the status of its own device, or control information in which the server 5 starts or stops a predetermined function of the mobile device 41. Also, the content of the frame that the server 5 receives from the mobile device 41 may be report information in which the mobile device 41 reports to the server 5 about its own movement (position, speed, or direction of movement, etc.), notification information in which the mobile device 41 notifies the server 5 of the status of its own device, or result information showing the result of processing performed by the mobile device 41 in accordance with the control information received from the server 5.

[0053] The AP device 11 is connected to the mobile unit 41 via a wired interface and communication lines (in other words, it is connected via wired communication). The AP device 11 also has the function of maintaining a state in which it has established wireless communication links with at least two STA devices, such as the STA device 21. In other words, the AP device 11 is capable of establishing wireless communication links with at least two STA devices, such as the STA device 21, at any given time.

[0054] The AP device 11 is mobile along with the mobile unit 41 and is mobile within a predetermined area (described later). The AP device 11 is a communication device that has the function of maintaining a state in which wireless communication links are established simultaneously with multiple STA devices, but it is desirable that it has the functionality of an AP compliant with the IEEE 802.11 standard, for example. That is, the AP device 11 may have the functionality of an AP in infrastructure mode of the IEEE 802.11 standard, which allows communication between the mobile unit 41 and the server 5 to take place through the device itself.

[0055] The STA device 21 is connected to LAN 6 via wired communication. The STA device 21 can establish a wireless communication link 31 with the AP device 11. The STA device 21 has the functionality of an STA in infrastructure mode according to the IEEE 802.11 standard.

[0056] STA devices 22 and 23 are STA devices similar to STA device 21, and operate independently of STA device 21. STA devices 22 and 23 can establish wireless communication links 32 and 33 with AP device 11, respectively.

[0057] The STA devices 21, etc., are positioned such that any location within the area where the AP device 11 can move is within the communication range of two or more of the STA devices (more specifically, the wireless IF 212 of the STA devices) (as described later). More specifically, the STA devices 21 are fixedly installed at the above location. The above location may be a location predetermined in the communication system 1 (in other words, a location predetermined in the design of the communication system 1, etc.).

[0058] The functions of the AP device 11 and the STA device 21, etc., will be explained in detail below.

[0059] Figure 2 is a block diagram showing an example of the functional configuration of the AP device 11 according to this embodiment.

[0060] As shown in Figure 2, the AP device 11 comprises a wired IF 111, a wireless IF 112, a transfer unit 113, and a control unit 114. The transfer unit 113 and the control unit 114 may be implemented by the processor (e.g., CPU (Central Processing Unit)) of the AP device 11 executing a program using memory, or they may be implemented by dedicated hardware.

[0061] The wired IF111 is a communication interface capable of wired communication. The wired IF111 corresponds to the first wired interface. The wired IF111 may be, for example, an Ethernet communication interface. The wired IF111 is connected to the mobile device 41.

[0062] Wireless IF112 is a communication interface capable of wireless communication. Wireless IF112 corresponds to the first wireless interface. Wireless IF112 has the function of maintaining a state in which a wireless communication link has been established with at least two of the multiple STA devices 21, etc. To realize this function, Wireless IF112 may be composed of at least two or more wireless circuits (modules), or it may be composed of wireless IC chips capable of communicating using at least two or more different frequency bands (e.g., 2.4 GHz and 5 GHz bands).

[0063] Wireless IF 112 can establish a wireless communication link with wireless IF 212 when AP device 11 moves and enters the communication range of wireless IF 112. Wireless IF 112 can also disconnect the wireless communication link established with wireless IF 212 when AP device 11 moves and deviates from the communication range of wireless IF 112.

[0064] The transfer unit 113 transfers frames between the wired IF 111 and the wireless IF 112. Whether the transfer unit 113 transfers frames or prohibits transfer can be controlled by the control unit 114. The transfer unit 113 corresponds to the first transfer unit.

[0065] The control unit 114 controls the transfer of frames by the transfer unit 113. Specifically, the control unit 114 controls the transfer unit 113 to transfer frames received by the wired IF 111 from the mobile device 41 to the wireless IF 112. At this time, the control unit 114 controls the wireless IF 112 to transmit frames only to the designated STA device (described later). The control unit 114 corresponds to the first control unit.

[0066] Furthermore, the control unit 114 generates designation information and transmits the generated designation information to multiple STA devices 21, etc. via the wireless IF 112. The designation information is information that designates one STA device (also called a designated STA device) from among the multiple STA devices 21, etc., for which the transfer unit 213 will transfer frames from the wired IF 211 to the wireless IF 212. The transmission of the designation information to the multiple STA devices 21, etc. by the control unit 114 may be a broadcast transmission or a unicast transmission with each of the multiple STA devices 21, etc. as the destination. For example, the control unit 114 can broadcast a beacon signal containing the designation information to the multiple STA devices 21, etc. via the wireless IF 112.

[0067] Figure 3 is a block diagram showing an example of the functional configuration of the STA device 21 according to this embodiment.

[0068] As shown in Figure 3, the STA device 21 comprises a wired IF 211, a wireless IF 212, a transfer unit 213, and a control unit 214. The transfer unit 213 and the control unit 214 may be implemented by a processor (e.g., CPU) in the STA device 21 executing a program using memory, or they may be implemented by dedicated hardware.

[0069] The wired IF211 is a communication interface capable of wired communication. The wired IF211 corresponds to the second wired interface. The wired IF211 may be, for example, an Ethernet communication interface. The wired IF211 is connected to LAN6 and connected to server 5 via LAN6.

[0070] Wireless IF212 is a communication interface capable of wireless communication. Wireless IF212 corresponds to the second wireless interface. Wireless IF212 establishes a wireless communication link with AP device 11.

[0071] The transfer unit 213 transfers frames between the wired IF 211 and the wireless IF 212. Whether the transfer unit 213 transfers frames or prohibits transfer can be controlled by the control unit 214. The transfer unit 213 corresponds to a second transfer unit.

[0072] The control unit 214 controls the transfer of frames by the transfer unit 213. The control unit 214 controls the transfer of frames by the transfer unit 213 according to the specified information transmitted by the AP device 11. The control unit 214 corresponds to the second control unit.

[0073] Specifically, the control unit 214 receives the designated information transmitted by the AP device 11 via the wireless IF 212, and controls the transfer unit 213 to transfer the frame from the wired IF 211 to the wireless IF 212 if the designated STA device included in the received designated information is the local device. The control unit 214 also controls the transfer unit 213 to prohibit the transfer of the frame from the wired IF 211 to the wireless IF 212 if the designated STA device included in the designated information is not the local device. As a result, the control unit 214 can control the wireless IF 212 to transmit frames only to the designated STA device.

[0074] Figure 4 is a schematic diagram showing an example of the position of the STA device 21 and the like according to this embodiment.

[0075] Figure 4 shows the fixedly installed STA devices 21, 22, and 23, and the movable AP device 11. Region 55 is shown as the movable area of ​​the AP device 11, and the positions of the AP device 11 when it moves are shown as AP device 11a and 11b. It should also be noted that the movable area of ​​the AP device 11 is the movable area of ​​the mobile body 41.

[0076] Area 51 indicates the communication area of ​​the wireless IF212 of STA device 21. Area 52 indicates the communication area of ​​the wireless IF212 of STA device 22. Area 53 indicates the communication area of ​​the wireless IF212 of STA device 23. Note that the communication area of ​​the wireless IF212 of STA device 21, etc., is not limited to the shape shown in the diagram.

[0077] As shown in Figure 4, the multiple STA devices 21 are positioned such that any location within the region 55 is within the communication range of the wireless IF 212 provided by two or more of the multiple STA devices 21.

[0078] For example, the location indicated as AP device 11 is located within areas 51, 52, and 53, which are the communication areas of the three STA devices 21, 22, and 23. The location indicated as AP device 11a is located within areas 51 and 52, which are the communication areas of the two STA devices 21 and 22. The location indicated as AP device 11b is located within areas 52 and 53, which are the communication areas of the two STA devices 22 and 23.

[0079] The shape of the region 55 can vary depending on the manner in which the moving body moves. For example, the region 55 may be a three-dimensional region defined by its position and range in the width, depth, and height directions (for example, the x, y, and z directions shown in Figure 4). Such a shape of the region 55 can be used when the moving body 41 is movable in the three directions mentioned above.

[0080] Furthermore, for example, the region 55 may be a two-dimensional region defined by the position and range in two of the three directions: width, depth, and height. Such a shape of region 55 can be used when the mobile body 41 is movable along a certain plane.

[0081] Furthermore, for example, the region 55 may be a one-dimensional region defined by its position and range in one of the width, depth, and height directions. Such a shape of region 55 can be used when the mobile body 41 is able to move along a certain trajectory.

[0082] The processing of the AP device 11 and STA device 21, etc., configured as described above, will now be explained.

[0083] Figure 5 is a flowchart showing a first example of the processing performed by the AP device 11 according to this embodiment. The processing shown in Figure 5 is an example of the processing performed when the AP device 11 sets a designated STA device and transmits the designated information.

[0084] In step S101, the control unit 114 executes the process of setting the designated STA device. If a designated STA device has already been set, the control unit 114 sets a new designated STA device and updates the previous setting.

[0085] Specifically, the control unit 114 receives radio waves from each of the multiple STA devices 21 etc. via the wireless IF 112, and can set as the designated STA device the STA device with the higher received signal strength (RSSI (Received Signal Strength Indicator)) of the radio waves received from that STA device among the multiple STA devices 21 etc. More specifically, the control unit 114 can set as the designated STA device the STA device with the highest received signal strength of the radio waves received from that STA device among the multiple STA devices 21 etc.

[0086] The control unit 114 may also send a trigger frame to each of the multiple STA devices 21, etc., which serves as a trigger for each of them to transmit a frame. In that case, the above setting can be made using the received signal strength of the radio waves when the wireless IF 112 receives the frame that the STA device 21, etc. transmits in response to receiving the trigger frame.

[0087] Furthermore, the control unit 114 receives radio waves from each of the multiple STA devices 21 etc. via the wireless IF 112, and can prioritize setting the STA device that is closest to the AP device 11 as the designated STA device. More specifically, the control unit 114 can set the STA device that is closest to the AP device 11 as the designated STA device.

[0088] Furthermore, the control unit 114 can transmit and receive frames with each of the multiple STA devices 21, etc., and measure the distance from each of the multiple STA devices 21, etc. to the AP device 11 using the round-trip time (so-called round-trip time), and can make the above settings using the distance measured in this way.

[0089] In step S102, the control unit 114 generates designation information indicating the designated STA device set in step S101, and transmits the generated designation information to multiple STA devices 21, etc. As mentioned above, the transmission of the designation information may be by unicast, broadcast, or beacon. Each of the multiple STA devices 21, etc. receives the transmitted designation information, and if the information indicates that it is the designated STA device, it stores that information in a storage unit (not shown). Also, if a device is currently the designated STA device, but newly received designation information indicates that another STA device is the designated STA device, it erases that information from the storage unit.

[0090] In step S103, the control unit 114 determines whether or not the update timing for the designated STA device has arrived. The update timing may be, for example, a predetermined time after the designated STA device was set in step S101. The predetermined time is, for example, several hundred milliseconds to several seconds, but is not limited to this. If it is determined that the update timing has arrived (Yes in step S103), the process proceeds to step S101; otherwise (No in step S103), the process proceeds to step S102. If the process proceeds to step S102, the process may proceed after waiting for an appropriate waiting time (for example, about 100 milliseconds to 1 second).

[0091] The control unit 114 may execute the process in step S102 at a different timing than the series of processes shown in Figure 5. For example, the control unit 114 may execute the process in step S102 when the relative magnitudes of the received signal strengths of the radio waves received from the STA devices 21, etc., are changed by the control unit 114 transmitting trigger frames to multiple STA devices 21, etc. For example, when the control unit 114 periodically updates the received signal strengths of the radio waves from the STA devices 21 and 22, the control unit 114 may execute the process in step S102 when the received signal strength of the radio waves from the STA device 21 changes from a state where it is higher than the received signal strength of the radio waves from the STA device 22 to a state where it is lower.

[0092] Through the series of processes shown in Figure 5, the AP device 11 can perform periodic setting or updating of specified information and periodic transmission of specified information.

[0093] Figure 6 is a flowchart showing a second example of the processing performed by the AP device 11 according to this embodiment. The processing shown in Figure 6 is an example of the processing performed by the AP device 11 when transferring a frame.

[0094] In step S201, the control unit 114 determines whether the wired IF 111 has received a frame sent by the mobile unit 41 and destined for the server 5. If the wired IF 111 determines that it has received the frame (Yes in step S201), the process proceeds to step S202; otherwise (No in step S201), step S201 is executed again. In other words, the control unit 114 remains in a waiting state in step S201 until it receives the frame.

[0095] In step S202, the control unit 114 identifies a designated STA device from among the multiple STA devices 21, etc. The identified designated STA device may be the designated STA device set or updated in step S101 (see Figure 5).

[0096] In step S203, the control unit 114 transmits the frame received in step S201 to the wireless IF 112 via the wireless IF 112 by having the transfer unit 113 do so. The designated STA device receives the transmitted frame and transmits the received frame to the server 5, which is its destination.

[0097] Through the series of processes shown in Figure 6, the AP device 11 can forward the frame sent by the mobile device 41 to the designated STA device, which is destined for the server 5.

[0098] Figure 7 is a flowchart showing an example of processing by the STA device 21, etc., according to this embodiment. The processing shown in Figure 7 is an example of processing that is executed when the STA device 21, etc., receives a frame transmitted by the server 5.

[0099] In step S301, the control unit 214 determines whether the wired IF 211 has received a frame sent by the server 5 to the mobile device 41. If the wired IF 211 determines that it has received the frame (Yes in step S301), the process proceeds to step S302; otherwise (No in step S301), step S301 is executed again. In other words, the control unit 214 remains in a waiting state in step S301 until it receives the frame. It is assumed that the frame sent by the server 5 to the mobile device 41 is broadcast via LAN 6 so that it can be received by each of the multiple STA devices 21, etc.

[0100] In step S302, the control unit 214 determines whether its own device is a designated STA device. The control unit 214 determines whether the designation information received from the AP device 11 in step S102 indicates its own device as a designated STA device, and if it determines that the designation information indicates its own device, it can determine that its own device is a designated STA device. If it determines that its own device is a designated STA device (Yes in step S302), it proceeds to step S303; otherwise (No in step S302), it terminates the series of processes shown in Figure 7.

[0101] In step S303, the control unit 214 transmits the frame received in step S301 to the wireless IF 212 via the wireless IF 212 by having the transfer unit 213 do so. The AP device 11 receives the transmitted frame and transmits the received frame to the mobile device 41, which is its destination.

[0102] Through the series of processes shown in Figure 7, the STA device 21 and the like can forward the frame sent by the server 5 to the AP device 11, which is destined for the mobile object 41.

[0103] The following describes an example of the operation of communication system 1.

[0104] Figure 8 is an explanatory diagram showing an example of communication in the communication system 1 according to this embodiment.

[0105] In Figure 8, the communication path for the frame from server 5 to mobile device 41 (corresponding to the first frame) is shown by a solid arrow, and the communication path for the frame from mobile device 41 to server 5 (corresponding to the second frame) is shown by a dashed arrow.

[0106] Server 5 broadcasts (or multicasts) a first frame destined for the mobile device 41 via LAN 6 so that each of the multiple STA devices 21, etc., can receive it. Each of the multiple STA devices 21, etc., receives the transmitted first frame.

[0107] Of the multiple STA devices 21, the designated STA device (in this case, STA device 22) transmits the received first frame to the AP device 11 (Yes in step S302, step S303, see Figure 7).

[0108] Among the multiple STA devices 21, etc., STA devices that are not designated STA devices (in this case, STA devices 21 and 23) are prohibited from transmitting the received first frame to the AP device 11 (see No. in step S302, see Figure 7).

[0109] AP device 11 receives the first frame transmitted by the designated STA device and transmits it to mobile device 41.

[0110] Mobile device 41 transmits a second frame destined for server 5 to AP device 11. AP device 11 receives the transmitted second frame. AP device 11 transmits the received second frame to a designated STA device (in this case, STA device 22) (step S203, see Figure 6). STA device 22 receives the transmitted second frame and transmits the received second frame to server 5.

[0111] In this way, the communication system 1 can realize bidirectional communication between the server 5 and the mobile device 41.

[0112] Figure 9 is an explanatory diagram showing an example of a communication link in the communication system 1 according to this embodiment.

[0113] In Figure 9, the AP device 11 and the mobile body 41 are initially located in the positions indicated as AP device 11 and mobile body 41, respectively. They then move to the positions indicated as AP device 11a and mobile body 41a, and then sequentially move to the positions indicated as AP device 11b and mobile body 41b.

[0114] When AP device 11 is located in the position indicated as AP device 11, AP device 11 establishes a wireless communication link 31 with STA device 21 and a wireless communication link 32 with STA device 22. The designated STA device in this case may be STA device 21.

[0115] When AP device 11 moves to the position indicated as AP device 11a, AP device 11 can establish a new wireless communication link 33 with STA device 23. At this time, AP device 11 has established a wireless communication link 31 with STA device 21, a wireless communication link 32 with STA device 22, and a wireless communication link 33 with STA device 23. The designated STA device at this time may be STA device 22.

[0116] When AP device 11 moves to the position indicated as AP device 11b, AP device 11 disconnects the wireless communication link 31. At this time, AP device 11 has established a wireless communication link 32 with STA device 22 and a wireless communication link 33 with STA device 23. The designated STA device at this time may be STA device 23.

[0117] Thus, since the AP device 11 has established wireless communication links with at least two STA devices 21, etc., it is always possible to communicate between one of the STA devices and the server 5. In other words, there is no time when it is not connected to any STA device. As a result, the communication system 1 can reduce the occurrence of communication interruptions in bidirectional communication between the server 5 and the mobile device 41.

[0118] Figure 10 is an explanatory diagram showing an example of a communication link in the communication system 9 according to the comparative example.

[0119] In the comparative example, the communication system 9 comprises AP devices 91, 92, and 93 (also referred to as AP device 91, etc.) and an STA device 81.

[0120] The communication system 9 is connected to the mobile unit 41, the server 5, and the LAN 6, and is a system that relays communication between the mobile unit 41 and the server 5, at least using wireless communication.

[0121] Server 5 and mobile device 41 are the same as the devices of the same name in the above embodiment. Here, the communication system 9, which is a comparative example, communicates between the mobile device 41 and server 5 by relaying multiple AP devices, whereas the communication system 1 according to the above embodiment of the present invention differs in that it communicates between the mobile device 41 and server 5 by relaying multiple STA devices.

[0122] The STA device 81 is connected to the mobile unit 41 via a wired interface and communication lines. Furthermore, the STA device 81 establishes a wireless communication link with at most one AP device among the AP devices 91, etc. In other words, at any given time, the STA device 81 can only establish a wireless communication link with at most one AP device among the AP devices 91, etc.

[0123] The STA device 81 is movable together with the mobile unit 41. The STA device 81 has the functionality of an STA in infrastructure mode according to the IEEE 802.11 standard.

[0124] AP device 91 is connected to LAN6 via wired communication and is permanently installed at a predetermined location. AP device 91 can establish a wireless communication link 71 with STA device 81. AP device 91 has AP functionality in infrastructure mode according to the IEEE 802.11 standard.

[0125] AP devices 92 and 93 are AP devices similar to AP device 91, and operate independently of AP device 91. AP devices 92 and 93 can establish wireless communication links 72 and 73 with STA device 81, respectively.

[0126] In Figure 10, the STA device 81 is initially located in the position indicated as STA device 81, and then moves sequentially to the positions indicated as STA device 81a and 81b.

[0127] When the STA device 81 is located in the position indicated as the STA device 81, the STA device 81 has established a wireless communication link 71 with the AP device 91. Even if the STA device 81 is within the communication range of the AP device 92, it cannot immediately establish a wireless communication link 72 with the AP device 92.

[0128] When STA device 81 moves to the position indicated as STA device 81a, STA device 81 establishes a new wireless communication link 72 with AP device 92. At this time, AP device 81 must have previously disconnected wireless communication link 71. Then, a communication interruption occurs between the disconnection of wireless communication link 71 and the establishment of wireless communication link 72. Note that even if STA device 81 is still within the communication range of AP device 91, it cannot maintain wireless communication link 71 with AP device 91. Also, even if STA device 81 is already within the communication range of AP device 93, it cannot establish wireless communication link 73 with AP device 93. The reason for the communication interruption is that the previously established wireless link is disconnected, and then STA device 81 needs to perform connection procedures for communication with each AP device (e.g., connection request / response, authentication, exchange of encryption keys, etc.) in order to establish a wireless communication link with AP device 91, etc., and therefore it is not possible to immediately establish wireless communication link 72 with AP device 91, etc.

[0129] When STA device 81 moves to the position indicated as STA device 81b, STA device 81 establishes a new wireless communication link 73 with AP device 93. At this time, STA device 81 must have previously disconnected wireless communication link 72. Then, a communication interruption occurs between the disconnection of wireless communication link 72 and the establishment of wireless communication link 73. Note that even if STA device 81 is still within the communication range of AP device 92, it cannot maintain wireless communication link 72 with AP device 92.

[0130] Thus, when the STA device 81 switches the partner with whom it establishes a wireless communication link from AP device 91 to AP device 92, and when it switches the partner with whom it establishes a wireless communication link from AP device 92 to AP device 93, a communication interruption occurs. Therefore, in the communication system 9, a communication interruption may occur in bidirectional communication between the server 5 and the mobile device 41.

[0131] In contrast, the communication system 1 in this embodiment, by adopting at least the configuration shown in Figure 1, can reduce the occurrence of communication interruptions in bidirectional communication between the server 5 and the mobile device 41.

[0132] Furthermore, the present invention can be implemented not only as a device, but also as a method in which the processing means constituting the device are steps, as a program that causes a computer to execute those steps, as a recording medium such as a computer-readable CD-ROM on which the program is recorded, or as information, data, or signals that represent the program. These programs, information, data, and signals may be distributed via a communication network such as the Internet.

[0133] Although the communication system and the like of the present invention have been described above based on embodiments, the present invention is not limited to these embodiments. Within the scope of the present invention, various modifications that a person skilled in the art could conceive of are applied to these embodiments, as well as forms constructed by combining components from different embodiments, are also included without departing from the spirit of the present invention. [Industrial applicability]

[0134] This invention can be used in communication systems, AP devices, and STA devices that perform wireless communication. [Explanation of symbols]

[0135] 1.9 Communication Systems 5 Servers 6 LAN 11, 11a, 11b, 91, 92, 93 AP device 21, 22, 23, 81, 81a, 81b STA device 31, 32, 33, 71, 72, 73 Wireless communication links 41, 41a, 41b Mobile objects 51, 52, 53, 55 areas 111, 211 Wired Interface 112, 212 Wireless IF 113, 213 Transfer section 114, 214 Control Unit

Claims

1. A communication system comprising one AP device and multiple STA devices, The aforementioned AP device is It can move along with the mobile body within a predetermined area. A first wired interface connected to the mobile device via wired communication, A first wireless interface having the function of maintaining a state in which a wireless communication link is established with at least two of the plurality of STA devices, The system includes a first transfer unit that transfers frames between the first wired interface and the first wireless interface, Each of the aforementioned plurality of STA devices is A second wired interface connected to the communication partner of the aforementioned mobile device via wired communication, A second wireless interface that establishes a wireless communication link with the aforementioned AP device, The system includes a second transfer unit that transfers frames between the second wired interface and the second wireless interface, The aforementioned multiple STA devices are, Any position within the aforementioned region is located within the communication range of the second wireless interface provided by two or more of the plurality of STA devices. Communication system.

2. The aforementioned multiple STA devices are, Any position within the aforementioned region is fixedly positioned so that it falls within the communication range of the second wireless interface provided by the two or more STA devices. The first wireless interface is, As the first AP device moves, it establishes the wireless communication link with the second wireless interface which has entered the communication range of the first wireless interface. The first AP device moves, thereby disconnecting the wireless communication link established between it and the second wireless interface, which has deviated from the communication range of the first wireless interface. The communication system according to claim 1.

3. The aforementioned AP device further, The system includes a first control unit which generates designation information that specifies one of the plurality of STA devices, from which the second transfer unit transfers the frame from the second wired interface to the second wireless interface, and transmits the generated designation information to the plurality of STA devices. The communication system according to claim 1 or 2.

4. The first control unit is, The first transfer unit controls the first transfer unit to transfer the first frame received by the first wired interface from the mobile body to the first wireless interface. The first wireless interface is, The first frame is transmitted to only one of the multiple STA devices. Each of the aforementioned plurality of STA devices further, The system includes a second control unit that receives the specified information transmitted by the first AP device, The second control unit of each of the plurality of STA devices controls the second transfer unit of the STA device to transfer the second frame received by the second wired interface to the second wireless interface only when the STA device is the one specified by the designation information received from the one AP device. The second wireless interface of only one of the plurality of STA devices transmits the second frame to the one AP device. The communication system according to claim 3.

5. The first control unit transmits a beacon signal containing the specified information to the plurality of STA devices. The communication system according to claim 3.

6. The first control unit is, The designation information is generated to designate, with higher priority, the STA device from which the first wireless interface receives a higher received signal strength of radio waves, among the plurality of STA devices, as the first STA device. The communication system according to claim 3.

7. The first control unit is, The system generates the designation information which designates, among the plurality of STA devices, the STA device that is closest to the first AP device as the first STA device, with higher priority. The communication system according to claim 3.

8. The aforementioned AP device has AP functionality in infrastructure mode compliant with the IEEE 802.11 standard. The communication system according to claim 1.

9. An AP device that is movable within a predetermined area along with a mobile body, A first wired interface connected to the mobile device via wired communication, A first wireless interface having the function of maintaining a state in which a wireless communication link is established with at least two of the multiple STA devices, The system includes a first transfer unit that transfers frames between the first wired interface and the first wireless interface, The aforementioned region is Any position within the aforementioned region is set to be within the communication range of the second wireless interface provided by two or more of the plurality of STA devices. AP device.

10. One of several STA devices, A second wired interface that connects to the mobile device's communication partner via wired communication, An AP device connected to the aforementioned mobile body by wired communication, comprising a second wireless interface that establishes a wireless communication link with an AP device that is mobile within a predetermined area, The system includes a second transfer unit that transfers frames between the second wired interface and the second wireless interface, The aforementioned multiple STA devices are, Any position within the aforementioned region is located within the communication range of the second wireless interface provided by two or more of the plurality of STA devices. STA device.

11. A control method for a communication system comprising one AP device and multiple STA devices, The aforementioned AP device is It can move along with the mobile body within a predetermined area. A first wired interface connected to the mobile device via wired communication, A first wireless interface having the function of maintaining a state in which a wireless communication link is established with at least two of the plurality of STA devices, A first transfer unit that transfers frames between the first wired interface and the first wireless interface, It comprises a first control unit, Each of the aforementioned plurality of STA devices is A second wired interface connected to the communication partner of the aforementioned mobile device via wired communication, A second wireless interface that establishes a wireless communication link with the aforementioned AP device, A second transfer unit that transfers frames between the second wired interface and the second wireless interface, It comprises a second control unit, The aforementioned multiple STA devices are, Any position within the aforementioned region is located within the communication range of the second wireless interface provided by two or more of the plurality of STA devices. The first control unit is, The second transfer unit generates designation information to specify one of the plurality of STA devices that transfers the frame from the second wired interface to the second wireless interface, and transmits the generated designation information to the plurality of STA devices. The first transfer unit controls the first transfer unit to transfer the first frame received by the first wired interface from the mobile body to the first wireless interface. The first wireless interface transmits the first frame to only one of the plurality of STA devices. Each of the above-mentioned plurality of STA devices has a second control unit, Upon receiving the designated information transmitted by the first AP device, The second transfer unit of the STA device is controlled to transfer the second frame received by the second wired interface to the second wireless interface only if the STA device is the STA device specified by the designation information received from the first AP device. Control method.

12. A control method for an AP device, The AP device is It can move along with the mobile body within a predetermined area. A first wired interface connected to the mobile device via wired communication, A first wireless interface having the function of maintaining a state in which a wireless communication link is established with at least two of the multiple STA devices, A first transfer unit that transfers frames between the first wired interface and the first wireless interface, It comprises a first control unit, Each of the aforementioned plurality of STA devices is A second wired interface connected to the communication partner of the aforementioned mobile device via wired communication, A second wireless interface that establishes a wireless communication link with the AP device, A second transfer unit that transfers frames between the second wired interface and the second wireless interface, It comprises a second control unit, The aforementioned multiple STA devices are, Any position within the aforementioned region is located within the communication range of the second wireless interface provided by two or more of the plurality of STA devices. The first control unit is, The second transfer unit generates designation information to specify one of the plurality of STA devices that transfers the frame from the second wired interface to the second wireless interface, and transmits the generated designation information to the plurality of STA devices. The first transfer unit controls the first transfer unit to transfer the first frame received by the first wired interface from the mobile body to the first wireless interface. The first wireless interface transmits the first frame to only one of the plurality of STA devices. Control method.

13. A method for controlling one of several STA devices, One AP device is It can move along with the mobile body within a predetermined area. A first wired interface connected to the mobile device via wired communication, A first wireless interface having the function of maintaining a state in which a wireless communication link is established with at least two of the plurality of STA devices, A first transfer unit that transfers frames between the first wired interface and the first wireless interface, It comprises a first control unit, Each of the aforementioned plurality of STA devices is A second wired interface connected to the communication partner of the aforementioned mobile device via wired communication, A second wireless interface that establishes a wireless communication link with the aforementioned AP device, A second transfer unit that transfers frames between the second wired interface and the second wireless interface, It comprises a second control unit, The aforementioned multiple STA devices are, Any position within the aforementioned region is located within the communication range of the second wireless interface provided by two or more of the plurality of STA devices. The first control unit is, The second transfer unit generates designation information to specify one of the plurality of STA devices that transfers the frame from the second wired interface to the second wireless interface, and transmits the generated designation information to the plurality of STA devices. The first transfer unit controls the first transfer unit to transfer the first frame received by the first wired interface from the mobile body to the first wireless interface. The first wireless interface transmits the first frame to only one of the plurality of STA devices. The second control unit of the first STA device is Upon receiving the designated information transmitted by the first AP device, The second transfer unit of the first STA device is controlled to transfer the second frame received by the second wired interface to the second wireless interface only if the first STA device is the first STA device specified by the designation information received from the first AP device. Control method.

14. A program that causes a computer to execute the control method described in claim 12.

15. A program that causes a computer to execute the control method described in claim 13.

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