Access point and terminal device

Abstract

An access point according to an embodiment comprises a communication circuit and a processor. The communication circuit is configured to be capable of communicating with a plurality of access points. The processor is configured to establish, by using the communication circuit, a wireless connection between a terminal device and two or more access points selected from the plurality of access points, and to coordinate the selected two or more access points to communicate with the terminal device. The processor is further configured to reference one or more access point groups constructed on the basis of information on the clock frequency of each of the plurality of access points, select two or more access points included in one access point group selected from the one or more access point groups, and establish communication with the terminal device.

Description

Access Point and Terminal Device

[0001] An embodiment relates to an access point and a terminal device.

[0002] As a communication system for wirelessly connecting between an access point (AP: access point) and a terminal device, a wireless LAN (local area network) is known. The terminal device can access the network via an access point within a communicable area by means of the wireless LAN.

[0003] In IEEE802.11bn, a multi-access point (hereinafter referred to as "multi-AP") in which a plurality of access points operate in cooperation has been studied. The multi-AP can coordinate signal transmission among a plurality of access points to achieve enhanced beamforming and an increased number of MIMO (Multi Input Multi Output) paths. As one form of utilization of the multi-AP, joint transmission is known, in which a plurality of access points are made to cooperate to perform simultaneous transmission to achieve an increase in the number of streams. The joint transmission acts as distributed MIMO using antennas belonging to different access points.

[0004] I. L. Cherif, L. Zitoune and V. Veque, "Performance Evaluation of Joint Transmission Coordinated-MultiPoint in Dense Very High Throughput WLANs Scenario," 2015 IEEE 40th Conference on Local Computer Networks (LCN), Clearwater Beach, FL, USA, 2015, pp.426-429, doi:10.1109 / LCN.2015.7366344

[0005] In a multi-AP (Access Point) system, it is preferable that the operating (clock) frequencies of multiple access points used in coordination are synchronized with high precision. One method for synchronizing the clock frequencies of each access point is to exchange information for clock frequency synchronization between the multiple access points via wired or wireless connections. However, such a method requires the implementation of clock frequency synchronization circuits in each access point, which can increase costs.

[0006] Therefore, the object of the present invention is to provide an access point and terminal device that can realize the coordinated operation of multiple access points in a multi-AP at low cost.

[0007] The access point of the embodiment includes a communication circuit and a processor. The communication circuit is configured to communicate with a plurality of access points. The processor is configured to use the communication circuit to establish a wireless connection between two or more access points selected from the plurality of access points and a terminal device, and to coordinate the two or more selected access points to communicate with the terminal device. The processor is further configured to refer to one or more access point groups constructed based on information about the respective clock frequencies of the plurality of access points, and to select two or more access points included in one access point group selected from the one or more access point groups to establish communication with the terminal device.

[0008] According to the embodiment, it is possible to provide an access point and terminal device that can realize the coordinated operation of multiple access points in a multi-AP at low cost.

[0009] Figure 1 is a block diagram showing an example of the overall configuration of a communication system according to the first embodiment. Figure 2 is a block diagram showing an example of the hardware configuration of a sharing access point provided by the communication system according to the first embodiment. Figure 3 is a block diagram showing an example of the hardware configuration of a shared access point provided by the communication system according to the first embodiment. Figure 4 is a block diagram showing an example of the hardware configuration of a terminal device provided by the communication system according to the first embodiment. Figure 5 is a block diagram showing an example of the functional configuration of a sharing access point provided by the communication system according to the first embodiment. Figure 6 is a block diagram showing an example of the functional configuration of a shared access point provided by the communication system according to the first embodiment. Figure 7 is a block diagram showing an example of the functional configuration of a terminal device provided by the communication system according to the first embodiment. Figure 8 is a flowchart showing an example of the sequence for creating AP group information in the communication system according to the first embodiment. Figure 9 is a schematic diagram showing a specific example of an AP group in the communication system according to the first embodiment. Figure 10 is a table showing a specific example of AP group information in the communication system according to the first embodiment. Figure 11 is a flowchart showing an example of the sequence for establishing a multi-AP connection in the communication system according to the first embodiment. Figure 12 is a table showing a specific example of AP group information in the communication system according to the second embodiment. Figure 13 is a flowchart showing an example of the sequence for switching links used in a multi-AP connection in the communication system according to the second embodiment.

[0010] Each embodiment will be described below with reference to the drawings. Each embodiment illustrates an apparatus or method for realizing the technical idea of ​​the invention. The drawings are schematic or conceptual. Components having substantially the same function and configuration are given the same reference numeral. The numbers attached to the reference numerals are used to distinguish elements having similar configurations from each other.

[0011] In each embodiment of the multi-AP, multiple second access points belonging to the first access point operate in coordination. This allows the non-AP_MLD (non-access point multi-link device) of the terminal device to send and receive data to and from the first access point via the multiple second access points that operate in coordination. The non-AP_MLD corresponds to a functional block of the terminal device that manages wireless connections using the multi-AP.

[0012] In the following, the first access point in a multi-AP configuration will be referred to as a "sharing access point." A sharing access point may also be referred to as a "central control unit." In the following, the second access point in a multi-AP configuration will be referred to as a "shared access point." In the following, a state in which multiple links for communication using a multi-AP configuration are established will be referred to as a "multi-AP connection." In the following, "access point" will be abbreviated as "AP" as appropriate. A wireless LAN access point may also be referred to as a "base station."

[0013] <1>First Embodiment The communication system 1 according to the first embodiment groups a plurality of shared APs used in multi-AP based on predetermined conditions related to the operating frequency. The communication system 1 then establishes a multi-AP connection using shared APs in the same group. Details of the communication system 1 according to the first embodiment will be described below.

[0014] <1-1> Configuration First, the configuration of the communication system 1 according to the first embodiment will be described.

[0015] <1-1-1> The overall configuration diagram 1 of the communication system 1 is a block diagram showing an example of the overall configuration of the communication system 1 according to the first embodiment. As shown in Figure 1, the communication system 1 includes a sharing AP 10, a plurality of shared APs 20, and a terminal device 30. The following explanation assumes that a multi-AP connection using multiple APs has been established.

[0016] Sharing AP 10 is a type of wireless LAN access point. Sharing AP 10 is connected to the network NW. Sharing AP 10 can communicate via wired or wireless connection with a server (not shown) on the network NW, and is configured to communicate wirelessly with each of the multiple shared APs 20. Sharing AP 10 establishes a multi-AP connection with the non-AP_MLD of the terminal device 30.

[0017] A shared AP 20 is a type of wireless LAN access point. A shared AP 20 is configured to communicate wirelessly with both the sharing AP 10 and the terminal device 30. The communication area of ​​each shared AP 20 may overlap with the communication area of ​​other shared APs 20. Figure 1 shows two shared APs 20-1 and 20-2 connected to the sharing AP 10. Note that a wired connection may be used between the shared APs 20 and the sharing AP 10.

[0018] Terminal device 30 is a wireless terminal such as a smartphone or a PC (Personal Computer). Terminal device 30 has multiple affiliated STAs (affiliated stations) (hereinafter also referred to as "A-STAs") and a non-AP_MLD. In this example, the multiple affiliated STAs include A-STA1 wirelessly connected to shared AP20-1 and A-STA2 wirelessly connected to shared AP20-2. The wireless connection between the shared AP20 and the affiliated STAs corresponds to the connection between a conventional pair of access points and an STA. The non-AP_MLD is a multi-link device (MLD) that manages the link status and wireless communication of each of the multiple A-STAs. The non-AP_MLD can establish a multi-AP connection with the sharing AP10 via multiple shared AP20s using the multiple affiliated STAs.

[0019] In communication system 1, when establishing a multi-AP connection, information on multiple shared APs 20 under the sharing AP 10 and information on multiple affiliated STAs under the non-AP_MLD are exchanged between the sharing AP 10 and the non-AP_MLD. This allows communication system 1 to collectively establish a comprehensive connection between the sharing AP 10 and the non-AP_MLD, targeting multiple shared APs 20 and multiple affiliated STAs. In addition, in a multi-AP connection, terminal device 30 may establish a multilink with the shared APs 20.

[0020] In the communication system 1, the multiple shared APs 20 are grouped based on predetermined conditions related to the operating (clock) frequency. In the first embodiment, the grouping of the multiple shared APs 20 is performed by the sharing AP 10. Details of the method for grouping the multiple shared APs 20 will be described later.

[0021] The wireless communication used in communication system 1 conforms to the IEEE 802.11 standard, for example. The IEEE 802.11 standard has wireless communication functionality based on the OSI (Open Systems Interconnection) reference model. In the OSI reference model, wireless communication functionality is divided into seven layers (Layer 1: Physical Layer, Layer 2: Data Link Layer, Layer 3: Network Layer, Layer 4: Transport Layer, Layer 5: Session Layer, Layer 6: Presentation Layer, Layer 7: Application Layer). The data link layer includes the LLC (Logical Link Control) sublayer and the MAC (Media Access Control) sublayer. The frequency bands used for wireless communication in communication system 1 may include, for example, the 2.4 GHz band, 5 GHz band, 6 GHz band, 45 GHz band, and 60 GHz band. Multiple channels may be assigned to each frequency band. Different or identical channels may be assigned to A-STA1 and A-STA2. Furthermore, A-STA1 and A-STA2 may use the same frequency band, or they may use different frequency bands.

[0022] <1-1-2> Hardware Configuration of Communication System 1 The hardware configuration of the communication system 1 according to the first embodiment will be described below.

[0023] (1: Hardware configuration of the sharing AP 10) Figure 2 is a block diagram showing an example of the hardware configuration of the sharing AP 10 provided in the communication system 1 according to the first embodiment. As shown in Figure 2, the sharing AP 10 includes, for example, a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a wireless communication module 14, and a wired communication module 15.

[0024] The CPU 11 is an integrated circuit capable of executing various programs and controls the overall operation of the sharing AP 10. The ROM 12 is, for example, a non-volatile semiconductor memory and stores programs and control data for controlling the sharing AP 10. The RAM 13 is, for example, a volatile semiconductor memory and is used as a workspace for the CPU 11. The wireless communication module 14 is configured to send and receive wireless signals via an antenna. The wireless communication module 14 is used to send and receive data, etc., between each shared AP 20. The wired communication module 15 is a circuit used to send and receive data, etc., via wired signals. The wired communication module 15 is configured to be connectable to a network NW.

[0025] The sharing AP 10 may have other hardware configurations. For example, if the sharing AP 10 is wirelessly connected to the network NW, the wired communication module 15 may be omitted from the sharing AP 10. If the sharing AP 10 is wiredly connected to both the network NW and the shared AP 20, the wireless communication module 14 may be omitted from the sharing AP 10. The antenna may be built into the sharing AP 10 or connected externally.

[0026] (2: Hardware configuration of the shared AP20) Figure 3 is a block diagram showing an example of the hardware configuration of the shared AP20 provided in the communication system 1 according to the first embodiment. As shown in Figure 3, the shared AP20 includes, for example, a CPU 21, a ROM 22, a RAM 23, a wireless communication module 24, and an oscillator 25.

[0027] The CPU 21 is an integrated circuit capable of executing various programs and controls the overall operation of the shared AP 20. The ROM 22 is, for example, a non-volatile semiconductor memory and stores programs and control data for controlling the shared AP 20. The RAM 23 is, for example, a volatile semiconductor memory and is used as a workspace for the CPU 21. The wireless communication module 24 is configured to send and receive wireless signals via an antenna. The wireless communication module 24 is used for sending and receiving data with the sharing AP 10 and with the terminal device 30. The oscillation frequency of the oscillator 25 corresponds to the clock frequency of the shared AP 20. The transmission of wireless signals by the wireless communication module 24 is performed based on the oscillation frequency of the oscillator 25.

[0028] The shared AP 20 may have other hardware configurations. For example, the antenna may be built into the shared AP 20 or connected externally. When the shared AP 20 is connected to the sharing AP 10 by wire, it further includes a wired communication module configured to communicate with the sharing AP 10. The communication system 1 may include both a shared AP 20 connected to the sharing AP 10 by wire and a shared AP 20 connected to the sharing AP 10 by wireless. Although not shown in the diagram, the oscillator 25 also includes the sharing AP 10 and the terminal device 30.

[0029] (3: Hardware configuration of terminal device 30) Figure 4 is a block diagram showing an example of the hardware configuration of a terminal device 30 provided in the communication system 1 according to the first embodiment. As shown in Figure 4, the terminal device 30 includes, for example, a CPU 31, ROM 32, RAM 33, wireless communication module 34, display 35, and storage 36.

[0030] The CPU 31 is an integrated circuit capable of executing various programs and controls the overall operation of the terminal device 30. The ROM 32 is, for example, a non-volatile semiconductor memory and stores programs and control data for controlling the terminal device 30. The RAM 33 is, for example, a volatile semiconductor memory and is used as a workspace for the CPU 31. The wireless communication module 34 is configured to send and receive wireless signals via an antenna. The wireless communication module 34 is used to send and receive data with the shared AP 20. The display 35 is, for example, an LCD (Liquid Crystal Display) or an EL (Electro-Luminescence) display. The display 35 displays, for example, a GUI (Graphical User Interface) corresponding to application software. The storage 36 is a non-volatile storage device and stores, for example, the system software of the terminal device 30.

[0031] The terminal device 30 may have other hardware configurations. For example, if the terminal device 30 is an IoT (Internet of Things) terminal, the display 35 may be omitted from the terminal device 30. The display 35 may also function as an input interface for the terminal device 30. The antenna may be built into the terminal device 30 or connected externally.

[0032] <1-1-3> Functional Configuration of Communication System 1 The functional configuration of the communication system 1 according to the first embodiment will be described below.

[0033] (1: Functional Configuration of Sharing AP 10) Figure 5 is a block diagram showing an example of the functional configuration of the sharing AP 10 provided in the communication system 1 according to the first embodiment. As shown in Figure 5, the sharing AP 10 functions as a computer, for example, comprising an LLC processing unit 110, a data processing unit 120, a management unit 130, a frame processing unit 140, and a transmitting / receiving unit 150. The LLC processing unit 110 is a functional block that executes processing corresponding to the LLC sublayer of the second layer and layers 3 through 7. The data processing unit 120, the management unit 130, and the frame processing unit 140 are functional blocks that execute processing corresponding to the MAC sublayer of the second layer. The transmitting / receiving unit 150 is a functional block that executes processing corresponding to the first layer.

[0034] The LLC processing unit 110 generates an LLC packet by adding a DSAP (Destination Service Access Point) header, an SSAP (Source Service Access Point) header, etc., to the data received from the network NW. The LLC processing unit 110 then inputs the generated LLC packet to the data processing unit 120. The LLC processing unit 110 also extracts data from the LLC packet input from the data processing unit 120. Finally, the LLC processing unit 110 transmits the extracted data to the network NW.

[0035] The data processing unit 120 adds a MAC header to the LLC packets input from the LLC processing unit 110 to generate a MAC frame. The data processing unit 120 then inputs the generated MAC frame to the frame processing unit 140. The data processing unit 120 also extracts LLC packets from the MAC frame input from the frame processing unit 140. The data processing unit 120 then inputs the extracted LLC packets to the LLC processing unit 110. A MAC frame containing data is also called a "data frame".

[0036] The management unit 130 establishes a wireless connection (wireless link) with the non-AP_MLD of the terminal device 30, maps data types to links, and sets up BlockAck, etc. For example, the management unit 130 executes multi-AP association processing in response to a multi-AP association request from the terminal device 30. For example, if the terminal device 30 uses two A-STA1 and A-STA2, the multi-AP association processing causes A-STA1 to establish a wireless link with shared AP20-1, and A-STA2 to establish a wireless link with shared AP20-2. As a result, a multi-AP connection using shared AP20-1 and AP20-2 is established between the sharing AP10 and the terminal device 30.

[0037] Furthermore, the management unit 130 includes, for example, multi-AP management information 131, link management information 132, and AP group information 133. The multi-AP management information 131 includes information about the access points used for the multi-AP connection (i.e., the sharing AP 10, and the shared APs 20-1 and 20-2) and the terminal device 30. For example, the multi-AP management information 131 is provided for each terminal device 30 that establishes the multi-AP connection. The link management information 132 includes information about the status of the links established in the multi-AP connection. The AP group information 133 includes information about the shared APs 20 that are grouped based on predetermined conditions related to the clock frequency. Hereinafter, a group of shared APs 20 will be referred to as an "access point group (AP group)". In the communication system 1, shared APs 20 included in the same AP group are used for the multi-AP connection. Since an AP group can be used for joint transmission, it may also be referred to as a "joint transmission group (joint transmission set)".

[0038] When a MAC frame is input from the data processing unit 120 or the management unit 130, the frame processing unit 140 outputs the input MAC frame to the transmission / reception unit 150. Furthermore, when a MAC frame is input from the transmission / reception unit 150, the frame processing unit 140 outputs the input frame to the data processing unit 120 or the management unit 130 according to the frame type. For example, when a data frame is input from the transmission / reception unit 150, the frame processing unit 140 outputs the input frame to the data processing unit 120. When a management frame or control frame is input from the transmission / reception unit 150, the frame processing unit 140 outputs the input frame to the management unit 130. Management frames or control frames may include, for example, management information. This management information may include notification information for either the shared AP 20 or the terminal device 30, or control information related to the control of the operation of either the shared AP 20 or the terminal device 30.

[0039] The transmitting / receiving unit 150 transmits and receives data and management information to and from each of the multiple shared APs 20 belonging to the sharing AP 10. The transmitting / receiving unit 150 is provided with, for example, one wireless signal processing unit for each of the multiple shared APs 20 belonging to the sharing AP 10. Each wireless signal processing unit of the transmitting / receiving unit 150 is configured to transmit and receive wireless signals using different frequency bands or channels.

[0040] Each wireless signal processing unit of the transmitting / receiving unit 150 generates a wireless frame by adding a preamble and the like to the MAC frame input from the frame processing unit 140, and converts the generated wireless frame into a wireless signal. Then, each wireless signal processing unit transmits (radiates) the converted wireless signal to the wirelessly connected shared AP 20 via the antenna. In addition, each wireless signal processing unit of the transmitting / receiving unit 150 converts the wireless signal received from any of the shared AP 20 via the antenna into a wireless frame. Then, each wireless signal processing unit extracts the MAC frame from the converted wireless frame and outputs the extracted MAC frame to the frame processing unit 140. Note that the transmitting / receiving unit 150 may use multicast or broadcast when notifying multiple shared AP 20 simultaneously. Multicast and broadcast are used, for example, for transmitting beacons.

[0041] The multi-AP management information 131 may include information such as frequency band, channel, operational parameters, and access category. The frequency band information indicates, for example, the frequency band used by A-STA for the radio link. The channel information indicates, for example, the channel used by A-STA for the radio link. The operational parameter information includes, for example, CWmin, CWmax, AIFS (arbitration interframe space), and TXOP (transmission opportunity) Limit. CWmin and CWmax indicate the minimum and maximum values ​​of the contention window, respectively. The contention window is a parameter used to calculate backoff, which is the transmission waiting time for collision avoidance. AIFS is a fixed transmission waiting time set for each traffic access category. TXOP Limit indicates the upper limit of the channel occupancy period TXOP. Access category information is indicated, for example, by “VO (Voice)”, “VI (Video)”, “BE (Best Effort)”, and “BK (Background)”.

[0042] Link management information 132 may include information indicating whether the wireless link is enabled or disabled. Multi-AP management information 131 and link management information 132 may be integrated. Based on the multi-AP management information 131, the frame processing unit 140 may output data to be transmitted to shared AP 20-1 to the wireless signal processing unit associated with shared AP 20-1, and data to be transmitted to shared AP 20-2 to the wireless signal processing unit associated with shared AP 20-2. The frame processing unit 140 may determine the destination of the MAC frame input from the data processing unit 120 according to the TID (traffic identifier) ​​associated with the access category. This process of associating TIDs with links is also called "TID-to-link mapping". The transmitting / receiving unit 150 may be provided with a wireless signal processing unit assigned to transmitting and receiving data, as well as a wireless signal processing unit assigned to transmitting management information.

[0043] (2: Functional Configuration of Shared AP20) Figure 6 is a block diagram showing an example of the functional configuration of the shared AP20 provided in the communication system 1 according to the first embodiment. As shown in Figure 6, the shared AP20 functions as a computer, for example, comprising a transmitting / receiving unit 210-1 and 210-2, a management unit 220, a frame processing unit 230-1 and 230-2, and a data processing unit 240. The transmitting / receiving units 210-1 and 210-2 are functional blocks that execute processing corresponding to the first layer. The management unit 220, and the frame processing units 230-1 and 230-2, are functional blocks that execute processing corresponding to the MAC sublayer of the second layer.

[0044] The transmission / reception unit 210-1 transmits and receives data, management information, etc. to and from the sharing AP 10 via wireless communication. The transmission / reception unit 210-2 transmits and receives data, management information, etc. to and from the terminal device 30 via wireless communication. The transmission / reception units 210-1 and 210-2 are respectively associated with the frame processing units 230-1 and 230-2. When the transmission / reception unit 210-2 notifies the terminal device 30, it may use multicast or broadcast. Multicast or broadcast is used, for example, for transmitting beacons and the like that include information regarding multi-AP connection. Each of the transmission / reception units 210-1 and 210-2 includes a wireless signal processing unit.

[0045] The wireless signal processing unit of the transmission / reception unit 210-1 adds a preamble and the like to the MAC frame (data frame, management frame, etc.) input from the frame processing unit 230-1 to generate a wireless frame. Then, the wireless signal processing unit of the transmission / reception unit 210-1 converts the generated wireless frame into a wireless signal, and transmits (radiates) the converted wireless signal to the sharing AP 10 via an antenna. Also, the wireless signal processing unit of the transmission / reception unit 210-1 converts the wireless signal received from the sharing AP 10 via the antenna into a wireless frame. Then, the wireless signal processing unit of the transmission / reception unit 210-1 extracts the MAC frame from the converted wireless frame, and outputs the extracted MAC frame to the frame processing unit 230-1.

[0046] The wireless signal processing unit of the transmission / reception unit 210-2 adds a preamble and the like to the MAC frame (data frame, management frame, etc.) input from the frame processing unit 230-2 to generate a wireless frame. Then, the wireless signal processing unit of the transmission / reception unit 210-2 converts the generated wireless frame into a wireless signal, and transmits (radiates) the converted wireless signal to the terminal device 30 via an antenna. Also, the wireless signal processing unit of the transmission / reception unit 210-2 converts the wireless signal received from the terminal device 30 via the antenna into a wireless frame. The wireless signal processing unit of the transmission / reception unit 210-2 extracts the MAC frame from the converted wireless frame, and outputs the extracted MAC frame to the frame processing unit 230-2.

[0047] The management unit 220 controls the establishment of a wireless connection (wireless link) between the sharing AP 10 and the non-AP MLD of the terminal device 30 in multi-AP connection. Also, based on the notification from the sharing AP 10, the management unit 220 generates and distributes beacons required for multi-AP connection, manages the state of the wireless link between the shared AP 20 and the affiliated STA of the terminal device 30 in multi-AP connection, etc. Further, the management unit 220 has a function of determining the type and content of frames to be transmitted for each link. Also, the management unit 220 includes, for example, link management information 221, a beacon generation unit 222, and oscillator information 223.

[0048] The link management information 221 stores management information regarding the state of the wireless link used in multi-AP connection. Also, the link management information 221 includes, for example, the identifier of the sharing AP 10 to which the local station belongs and the identifier of the A-STA of the terminal device 30 that has established a wireless link with the local station. The link management information 221 may store the information included in the multi-AP management information 131 and the link management information 132. The management unit 220 manages the validity and invalidity of the wireless link using the link management information 221.

[0049] The beacon generation unit 222 generates, for example, a beacon frame including information regarding multi-AP connection based on the management information received from the sharing AP 10. The beacon generation unit 222 notifies the terminal device 30 of the generated beacon frame via the frame processing unit 230-1 and the transmission / reception unit 210-1. The beacon frame includes, for example, information of the sharing AP 10, information of the local station's shared AP 20, and information of the other station's shared AP 20 included in multi-AP connection. Also, the beacon frame may include the multi-AP management information 131 and the link management information 132 transferred from the sharing AP 10. The transmission of the beacon frame may be performed by broadcast or multicast.

[0050] The oscillator information 223 stores information about the oscillation frequency (clock frequency) of its own oscillator 25. The clock frequency of oscillator 25 may vary from one shared AP 20 to another, even if it is within the specifications of the device. The shared AP 20 may transmit the oscillator information 223 to the sharing AP 10 based on instructions from the sharing AP 10, or it may transmit it to the sharing AP 10 periodically. The sharing AP 10 may construct a group of multiple shared APs 20 for use in a multi-AP based on the multiple oscillator information 223 that it has collected.

[0051] When a MAC frame is input from the data processing unit 240, the frame processing unit 230-1 outputs the input frame to the transmit / receive unit 210-1. When a MAC frame is input from the transmit / receive unit 210-1, the frame processing unit 230-1 outputs the input MAC frame to the management unit 220 or the data processing unit 240, depending on the frame type. For example, when a data frame is input from the transmit / receive unit 210-1, the frame processing unit 230-1 outputs the input frame to the data processing unit 240. When a management frame or control frame for its own station is input from the transmit / receive unit 210-1, the frame processing unit 230-1 outputs the input frame to the management unit 220.

[0052] When a MAC frame is input from the data processing unit 240, the frame processing unit 230-2 outputs the input frame to the transmit / receive unit 210-2. When a MAC frame is input from the transmit / receive unit 210-2, the frame processing unit 230-2 outputs the input MAC frame to the management unit 220 or the data processing unit 240, depending on the frame type. For example, when a data frame is input from the transmit / receive unit 210-2, the frame processing unit 230-2 outputs the input frame to the data processing unit 240. When a management frame or control frame for its own station is input from the transmit / receive unit 210-2, the frame processing unit 230-2 outputs the input frame to the management unit 220.

[0053] The data processing unit 240 outputs MAC frames received from the frame processing unit 230-1 to the frame processing unit 230-2. The data processing unit 240 also outputs MAC frames received from the frame processing unit 230-2 to the frame processing unit 230-1.

[0054] (3: Functional Configuration of Terminal Device 30) Figure 7 is a block diagram showing an example of the functional configuration of a terminal device 30 provided in the communication system 1 according to the first embodiment. As shown in Figure 7, the terminal device 30 functions as a computer comprising, for example, an application execution unit 300, an LLC processing unit 310, a data processing unit 320, a management unit 330, a frame processing unit 340, and a transmission / reception unit 350. The transmission / reception unit 350 includes a plurality of affiliated STAs, including A-STA1 and A-STA2. The application execution unit 300 is a functional block that executes processing corresponding to the seventh layer. The LLC processing unit 310 is a functional block that executes processing corresponding to the second layer's LLC sublayer and layers 3 through 6. The data processing unit 320, the management unit 330, and the frame processing unit 340 are functional blocks that execute processing corresponding to the second layer's MAC sublayer. The transmission / reception unit 350 is a functional block that executes processing corresponding to the second layer's MAC sublayer and layer 1. For example, a set consisting of an LLC processing unit 310, a data processing unit 320, a management unit 330, and a frame processing unit 340 corresponds to non-AP_MLD.

[0055] The application execution unit 300 executes the application based on the data input from the LLC processing unit 310. The application execution unit 300 also outputs data to the LLC processing unit 310. For example, the application execution unit 300 can display application information on the display 35. Furthermore, the application execution unit 300 can operate based on the operation of the input interface.

[0056] The LLC processing unit 310 generates an LLC packet by adding DSAP headers, SSAP headers, etc., to the data input from the application execution unit 300 (upper layer). The LLC processing unit 310 then outputs the generated LLC packet to the data processing unit 320. The LLC processing unit 310 also extracts data from the LLC packet input from the data processing unit 320. The LLC processing unit 310 then outputs the extracted data to the application execution unit 300 (upper layer).

[0057] The data processing unit 320 adds a MAC header to the LLC packets input from the LLC processing unit 310 to generate a MAC frame. The data processing unit 320 then outputs the generated MAC frame to the frame processing unit 340. The data processing unit 320 also extracts LLC packets from the MAC frames input from the frame processing unit 340. The data processing unit 320 then outputs the extracted LLC packets to the LLC processing unit 310.

[0058] The management unit 330 establishes a wireless connection (wireless link) with the sharing AP 10, maps data types to links, and sets up BlockAck, etc. The management unit 330 can, for example, obtain management information from beacons received from the shared AP 20. The management unit 330 also manages the status of wireless links between the multiple shared APs 20 used in the multi-AP connection and the multiple affiliated STAs used in the multi-AP connection, and includes, for example, link management information 331.

[0059] Link management information 331 stores management information regarding the status of the wireless link used in the multi-AP connection. Link management information 331 also includes, for example, information regarding the identifier of the sharing AP 10 to which the station belongs and the identifier of the shared AP 20 with which the station has established a wireless link. Link management information 331 may also store information contained in multi-AP management information 131 and link management information 132. The management unit 330 manages the enablement and disablement of the wireless link using link management information 331.

[0060] When a MAC frame is input from the data processing unit 320, the frame processing unit 340 outputs the input frame to at least one of the multiple affiliated STAs in the transmitting / receiving unit 350 according to the traffic assignment. Furthermore, when a MAC frame is input from any of the multiple affiliated STAs, the frame processing unit 340 outputs the input frame to the management unit 330 or the data processing unit 320 according to the frame type. For example, when a data frame is input from any of the multiple affiliated STAs, the frame processing unit 340 outputs the input frame to the data processing unit 320. When a data frame is input from the data processing unit 320, the frame processing unit 340 outputs the input frame to any of the multiple affiliated STAs. When a management frame or control frame intended for the local station is input from any of the multiple affiliated STAs, the frame processing unit 340 outputs the input frame to the management unit 330.

[0061] Each affiliated STA (A-STA) functions as a wireless signal processing unit configured to send and receive data and management information, etc., to and from a wirelessly connected shared AP 20 via wireless communication. The affiliated STA generates a wireless frame by adding a preamble, etc., to the MAC frame input from the frame processing unit 340. The affiliated STA then converts the generated wireless frame into a wireless signal. The affiliated STA then transmits (radiates) the converted wireless signal to the wirelessly connected shared AP 20 via the antenna. The affiliated STA also converts the wireless signal received from the wirelessly connected shared AP 20 via the antenna into a wireless frame. The affiliated STA extracts the MAC frame from the converted wireless frame and outputs the extracted MAC frame to the frame processing unit 340.

[0062] <1-2> Operation Next, the operation of the communication system 1 according to the first embodiment will be described.

[0063] <1-2-1> How to create an AP group The method for creating an AP group is explained below.

[0064] (1: AP Group Creation Sequence) Figure 8 is a flowchart showing an example of the AP group information 133 creation sequence in the communication system 1 according to the first embodiment. The sharing AP 10 starts (starts) the series of processes shown in Figure 8 based on a predetermined schedule, for example.

[0065] First, the sharing AP 10 acquires oscillator information 223 from multiple shared APs 20 belonging to its own station (step ST11). The sharing AP 10 may also be configured to acquire oscillator information 223 from the CSI (Channel State Information) contained in the beacon signal transmitted periodically by each shared AP 20.

[0066] Next, the sharing AP 10 performs a grouping process (step ST12). In the grouping process, the sharing AP 10 constructs at least one AP group. For example, based on the oscillator information 223 acquired in step ST11, the sharing AP 10 sets shared APs 20 whose clock frequency differences are below a certain level into the same AP group. Note that the process in step ST12 may be performed by the CPU 11 or by other configurations within the sharing AP 10.

[0067] Next, the sharing AP 10 saves the information of the constructed AP group to the AP group information 133 (step ST13). Once the processing in step ST13 is complete, the sharing AP 10 terminates the series of processes shown in Figure 8 (termination).

[0068] Furthermore, the sharing AP 10 may construct AP groups based on other conditions. For example, when the sharing AP 10 acquires oscillator information 223 multiple times, it can calculate the clock frequency fluctuation for each shared AP 20. The sharing AP 10 may then set shared APs 20 in the same AP group if the correlation of the clock frequency fluctuations is higher than a predetermined threshold. Also, when the sharing AP 10 acquires oscillator information 223 multiple times, it can calculate the phase fluctuation of the clock frequency for each shared AP 20. The sharing AP 10 may then exclude shared APs 20 from the AP group if the correlation of the phase fluctuations of the clock frequency is greater than a predetermined threshold. In other words, if the clock frequency fluctuation of a shared AP 20 is greater than the average value of all its subordinate shared APs, or a specific threshold, the sharing AP 10 may consider that the clock frequency of that shared AP 20 is unstable and unsuitable for use, for example, joint transmission.

[0069] (2: Specific Example of AP Group) Figure 9 is a schematic diagram showing a specific example of an AP group in the communication system 1 according to the first embodiment. Figure 9 illustrates a case where a sharing AP 10 groups five shared APs 20-1 to 20-5 located within the area of ​​the terminal device 30. Note that the illustration of the sharing AP 10 is omitted.

[0070] As shown in Figure 9, in this example, shared APs 20-1, 20-2, and 20-3 are configured in AP group GR1, and shared APs 20-3, 20-4, and 20-5 are configured in AP group GR2. In this case, sharing AP 10 can select either AP group GR1 or GR2 and establish a multi-AP connection using the multiple shared APs 20 included in the selected AP group GR.

[0071] As in this example, depending on the variation in oscillator operating frequencies, the same shared AP20-3 may be included in different AP groups GR1 and GR2. The sharing AP10 can determine the number of shared AP20s used for multi-AP connection according to the capability information of the terminal device 30. For multi-AP connection, it is sufficient that at least two shared AP20s included in AP group GR are used.

[0072] (3: Specific Examples of AP Group Information) Figure 10 is a table showing a specific example of AP group information 133 in the communication system 1 according to the first embodiment. As shown in Figure 10, the AP group information 133 stores, for example, an AP group ID and information about the APs belonging to the AP group AI. The AP group ID is an identifier for the AP group. Each AP group ID may include information on multiple shared APs 20. In this example, shared APs 20-1, 20-2, and 20-3 are associated with AP group ID "GR1". Shared APs 20-1, 20-2, and 20-3 are associated with AP group ID "GR2".

[0073] Furthermore, the AP group information 133 may record information used for grouping, associated with the AP group ID. Such information may include a reference value for the clock frequency. In addition, the AP group information 133 may record the magnitude of the difference in clock frequencies, the magnitude of the correlation of clock frequency fluctuations, etc., associated with the AP group ID.

[0074] <1-2-2> Multi-AP Connection Sequence Diagram 11 is a flowchart showing an example of a sequence for establishing a multi-AP connection in the communication system 1 according to the embodiment. For example, when a user requests to start using a multi-AP by operating the user's terminal device 30, the series of processes shown in Figure 11 are started (start).

[0075] First, terminal device 30 sends a multi-AP connection request to sharing AP 10 via shared AP 20 (step ST21). The multi-AP connection request includes capability information of terminal device 30. Capability information of terminal device 30 may include information about shared AP 20 within terminal device 30's area, information about the number of APs available for multi-AP connection, etc. The shared AP 20 that forwards the multi-AP request between terminal device 30 and sharing AP 10 may be any shared AP 20 within terminal device 30's communication area. Capability information of terminal device 30 may be sent to sharing AP 10 at a different time than the multi-AP connection request.

[0076] When the sharing AP 10 receives a multi-AP connection request, it selects a shared AP 20 to be used for the multi-AP connection based on the AP group information 133 and the capability information of the terminal device 30 (step ST22). In the process of step ST22, the sharing AP 10 selects at least two shared APs 20 to be used for the multi-AP connection from the same AP group. Specifically, the management unit 130 of the sharing AP 10 (for example, the CPU 11) refers to one or more AP groups (AP group information 133) constructed based on information about the respective clock frequencies of multiple shared APs 20. Then, the management unit 130 selects one AP group from the one or more AP groups based on the capability information of the terminal device 30, and further selects two or more shared APs 20 included in the selected AP group.

[0077] Then, the sharing AP 10 sets up a multi-AP connection using the selected multiple shared APs 20 (step ST23). In setting up the multi-AP connection, the processes necessary to establish a link between each of the selected multiple shared APs 20 and the terminal device 30 are executed. In the process of step ST23, the sharing AP 10 performs, for example, authentication processing and association processing.

[0078] Once the multi-AP connection setup is complete, the sharing AP 10 sends a multi-AP connection response to the terminal device 30 via the shared AP 20 (step ST24). When the terminal device 30 receives the multi-AP connection response and confirms the establishment of the multi-AP connection, it terminates the series of processes shown in Figure 11 (end).

[0079] <1-3> Effects of the First Embodiment As described above, the communication system 1 according to the first embodiment groups together shared APs 20 with similar clock frequencies of oscillators 25 to form AP groups. The sharing AP 10 then selects an AP group and then selects a set of shared APs 20 to be used for multi-AP connection from within the selected AP group.

[0080] As a result, the communication system 1 according to the first embodiment can establish a multi-AP connection using a combination of shared APs 20 with suppressed differences in clock frequencies. Consequently, the communication system 1 according to the first embodiment can perform cooperative operations such as joint transmission, which require highly accurate synchronization of the clock frequencies of the shared APs 20. Furthermore, since the communication system 1 according to the first embodiment does not require a synchronization circuit for the oscillator 25 for each shared AP 20, joint transmission in a multi-AP environment can be realized at low cost. Therefore, the communication system 1 according to the first embodiment can realize cooperative operation of multiple access points in a multi-AP environment at low cost.

[0081] <2> Second Embodiment The communication system 1 according to the second embodiment changes the combination of shared APs 20 used by the multi-AP depending on the frame size of the data to be communicated. The following mainly describes the differences between the communication system 1 according to the second embodiment and the first embodiment.

[0082] <2-1> The configuration diagram 12 is a table showing a specific example of AP group information 133 in the communication system 1 according to the second embodiment. As shown in Figure 12, the AP group information 133 in the second embodiment has a configuration in which, for example, information on the permissible threshold for transmission frame length is added to the AP group information 133 shown in Figure 10.

[0083] The transmit frame length tolerance threshold indicates the threshold for the transmittable frame length in the associated AP group ID. The transmit frame length tolerance threshold is set high when the difference in clock frequencies within the AP group is small, and low when the difference is large. The transmit frame length tolerance threshold may also be set high when the correlation of clock frequency fluctuations is large, and low when the correlation is small. In other words, for long frames, the tolerance value for the difference or correlation of clock frequency fluctuations is set strictly (i.e., small). For short frames, the tolerance value for the difference or correlation of clock frequency fluctuations is set loosely (i.e., large). Furthermore, the transmit frame length tolerance threshold may be set considering both the magnitude of the difference in clock frequencies and the magnitude of the correlation of clock frequencies. The configuration of the communication system 1 according to the second embodiment is the same as in the first embodiment.

[0084] <2-2> Operation diagram 13 is a flowchart showing an example of a sequence for switching links used in a multi-AP connection in the communication system 1 according to the second embodiment. For example, when the sharing AP 10 receives a request from the terminal device 30 to download data on the network NW, it starts the series of processes shown in Figure 11 (start).

[0085] First, the sharing AP 10 receives downlink data from the network NW based on instructions from the terminal device 30 (step ST31). Then, the sharing AP 10 checks the frame length of the downlink data (step ST32).

[0086] Next, the sharing AP 10 checks whether the AP group used in the multi-AP connection meets the acceptance conditions (step ST33). Specifically, the sharing AP 10 refers to the AP group information 133 and compares the transmission frame length acceptance threshold in the currently used AP group with the frame length of the downlink data. For example, if the frame length of the downlink data is smaller than the transmission frame length acceptance threshold, it indicates that the acceptance conditions are met. If the frame length of the downlink data is greater than or equal to the transmission frame length acceptance threshold, it indicates that the acceptance conditions are not met.

[0087] If the AP group used in the multi-AP connection meets the acceptable conditions (step ST33: YES), the sharing AP 10 transmits downlink data to the terminal device 30 via the multiple shared APs 20 used in the multi-AP connection (step ST34). In other words, downlink data is transmitted without changing the multiple shared APs 20 used in the multi-AP connection. Once the transmission of downlink data is complete, the sharing AP 10 terminates the series of processes shown in Figure 11 (termination).

[0088] On the other hand, if the AP group used in the multi-AP connection does not meet the acceptable conditions (step ST33: NO), the sharing AP 10 changes the AP group used for the multi-AP connection (step ST35). At this time, the sharing AP 10 selects an AP group that meets the acceptable conditions based on the AP group information 133, the capability information of the terminal device 30, and the frame length of the downlink data. The sharing AP 10 then instructs the terminal device 30 to switch to the shared AP 20 in the multi-AP connection via, for example, at least one of the shared APs 20 currently used in the multi-AP connection. Then, the non-AP_MLD of the terminal device 30 switches the shared AP 20 to which each A-STA in the multi-AP connection is connected based on the instruction from the sharing AP 10. After that, the sharing AP 10 transmits the downlink data to the terminal device 30 via the multiple shared APs 20 used in the switched multi-AP connection (step ST34). In other words, the downlink data is transmitted using the multiple shared APs 20 that have been switched in the multi-AP connection. Once the transmission of downlink data is complete, the sharing AP 10 terminates the series of processes shown in Figure 11 (termination).

[0089] In the second embodiment, the terminal device 30 may be configured to request the sharing AP 10 to switch the multi-AP connection via at least one of the shared APs 20 used in the multi-AP connection, depending on the frame length of the uplink data. In this case, the management unit 330 of the terminal device 30 is configured to store AP group information similar to that in 133. The sharing AP 10 then selects an AP group that satisfies the acceptable conditions based on the frame length of the uplink data, based on the request from the terminal device 30, and switches the shared AP 20 used in the multi-AP connection.

[0090] In addition, the sharing AP 10 according to the second embodiment may be configured to form AP groups based on information about the transmission frame length. Specifically, if the transmission frame length is greater than a threshold, the sharing AP constructs an AP group by tightening (i.e., reducing) the limit on the difference in clock frequency, and if the transmission frame length is less than or equal to the threshold, it constructs an AP group by relaxing the limit on the difference in clock frequency. The sharing AP 10 then establishes a multi-AP connection using the constructed AP group. In this case, the sharing AP 10 is configured to construct AP groups based on the transmission frame length and to further set an allowable value for the correlation of the difference or fluctuation of clock frequency. Information about the transmission frame length may be notified by the terminal device 30 or obtained from the network NW.

[0091] <2-3> Effects of the Second Embodiment As described above, in the communication system 1 according to the second embodiment, groups of offsets (AP groups) that are appropriately allowed are constructed according to the data transmission frame length. For example, when the transmission frame length is short, the frequency difference constraint is set loosely, and when the transmission frame length is long, the frequency difference constraint is set strictly. Furthermore, the communication system 1 according to the second embodiment is configured to change the AP group used in multi-AP connection according to the data transmission frame length.

[0092] As a result, the communication system 1 according to the second embodiment can establish a multi-AP connection that satisfies the synchronization accuracy of the clock frequency required according to the frame length. Since the communication system 1 according to the second embodiment can change the AP group according to the required synchronization accuracy, it can utilize the resources of the shared AP 20 more efficiently than the communication system 1 according to the first embodiment.

[0093] <4> In the above embodiment, an example was given of a case in which a multi-AP connection is established between the sharing AP 10 and the terminal device 30 using multiple shared APs 20, but the embodiment is not limited to this. The sharing AP 10 does not have to be used in the multi-AP connection. In this case, the communication system 1 may omit the sharing AP 10, and each shared AP 20 may have the same functional configuration as the sharing AP 10 shown in Figure 5. In this example, the terminal device 30 is configured to establish a multi-AP connection using multiple access points (shared APs 20) and to communicate with the network NW. If the sharing AP 10 is not used, information for cooperative operation may be sent and received between the multiple access points. Each access point may collect the information necessary for building an AP group and create an AP group in the same manner as in the above embodiment.

[0094] The conversion process from wireless frames to wireless signals described in the above embodiments includes, for example, convolution coding, interleaving, subcarrier modulation, inverse fast Fourier transform, OFDM modulation, and frequency conversion. The conversion process from wireless signals to wireless frames described in the embodiments includes, for example, frequency conversion, OFDM demodulation, fast Fourier transform, subcarrier demodulation, deinterleaving, and Viterbi decoding. A wireless communication standard other than the IEEE 802.11 standard may be used as the wireless communication standard.

[0095] In the above embodiments, each of the CPUs 11, 21, and 31 may be other circuits. For example, instead of a CPU, an MPU (Micro Processing Unit) or the like may be provided. Each of the processes described in each embodiment may be implemented by dedicated hardware. Each of the processes described in the above embodiments may be a mixture of processes executed by software and processes executed by hardware, or it may be one or the other. Each of the sharing AP 10 and the terminal device 30 operates based on the clock frequency of the oscillator 25, similar to the shared AP 20.

[0096] It should be noted that the present invention is not limited to the embodiments described above, and can be modified in various ways during implementation without departing from its essence. Furthermore, each embodiment may be combined as appropriate, and in that case, the combined effects can be obtained. Moreover, the above embodiments include various inventions, and various inventions can be extracted by selecting combinations from the multiple constituent elements disclosed. For example, if the problem can be solved and effects can be obtained even if some constituent elements are deleted from all the constituent elements shown in the embodiment, then the configuration with these deleted constituent elements can be extracted as an invention.

[0097] 1...Communication system 10...Sharing AP 20, 20-1, 20-2...Shared AP 30, 30-1, 30-2...Terminal device 11, 21, 31...CPU 12, 22, 32...ROM 13, 23, 33...RAM 14, 24, 34...Wireless communication module 15...Wired communication module 25...Oscillator 35...Display 36...Storage 110, 310...LLC processing unit 120, 240, 320...Data processing unit 130, 220, 330...Management unit 131...Multi-AP management information 132, 221, 331...Link management information 133...AP group information 223...Oscillator information 140, 230-1, 230-2, 340...Frame processing unit 150, 210-1, 210-2, 350... Transmit / receive unit; 222... Beacon generation unit; 300... Application execution unit

Claims

1. An access point comprising: a communication circuit configured to communicate with a plurality of access points; and a processor configured to use the communication circuit to establish a wireless connection between two or more access points selected from the plurality of access points and a terminal device, and to coordinate the two or more selected access points to communicate with the terminal device, wherein the processor is further configured to refer to one or more access point groups constructed based on information regarding the respective clock frequencies of the plurality of access points, and to select two or more access points included in one access point group selected from the one or more access point groups to communicate with the terminal device.

2. The access point according to claim 1, wherein the processor is further configured to select an access point group and an access point to be used for the wireless connection based on capability information of the terminal device included in a request from the terminal device.

3. The access point group is comprised of access points whose clock frequency differences are below a threshold, as described in claim 1.

4. The access point group is comprised of access points whose correlation of clock frequency fluctuations is greater than or equal to a threshold, as described in claim 3.

5. The access point according to claim 1, wherein the processor is further configured not to assign to the access point group any access point whose phase fluctuation of the clock frequency is greater than or equal to a threshold.

6. The access point according to claim 1, wherein the processor is further configured to change the access point group used for the wireless connection according to the frame length of the data to be transmitted to the terminal device.

7. A terminal device comprising: a communication circuit configured to communicate with a plurality of access points; and a processor configured to use the communication circuit to establish wireless connections with two or more access points included in the plurality of access points and to communicate by utilizing the coordinated operation of the two or more access points, wherein the processor is further configured to communicate by utilizing two or more access points included in one access point group selected from one or more access point groups constructed based on information regarding the respective clock frequencies of the plurality of access points.

8. The terminal device according to claim 7, wherein the processor is further configured to request any of the plurality of access points to change the access point group used in the wireless connection, depending on the frame length of the uplink data.

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