Terminal device, shared access points, and communication method

Abstract

This terminal device is a terminal device in a communication system including sharing access points, a shared access point, another shared access point, and the terminal device. The terminal device is configured to exchange data with a sharing access point using both a first wireless link between the terminal device and the shared access point and a second wireless link between the terminal device and another shared access point, and on the basis of the amount of change in the distance from the shared access point, change a first transmission rate applied to the first wireless link to a value different from a second transmission rate applied to the second wireless link.

Description

Terminal device, shared access point, and communication method

[0001] The embodiments relate to a terminal device, a shared access point, and a communication method.

[0002] A multi-link transmission method using a wireless local area network (LAN) is known as a communication system that wirelessly connects an access point (AP) and a terminal. In the multi-link transmission method, data exchange between a multi-link device (AP MLD) in the access point and a multi-link device (non-AP MLD) in the terminal is realized by wireless links between multiple affiliated APs in the access point and multiple affiliated STAs in the terminal.

[0003] IEEE802.11be D3.0, “35.3 Multi-link operation”, p479-p586, January 2023

[0004] From the viewpoint of improving the wireless communication environment, it is desirable that a terminal be able to use wireless links with multiple affiliated APs of multiple access points in combination.

[0005] When such a transmission method (multi-AP transmission method) is implemented, the communication environment of multiple wireless links between the AP MLD and non-AP MLD may differ for each wireless link. Therefore, in the multi-AP transmission method, it may be necessary to adjust the settings for each wireless link to maintain a good wireless communication environment.

[0006] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide an access point and a terminal device that improve the wireless communication environment.

[0007] A terminal device according to one aspect is a terminal device in a communication system including a shared access point, a shared access point, another shared access point, and the terminal device, wherein the terminal device exchanges data with the shared access point using a first wireless link with the shared access point and a second wireless link with the other shared access point, and is configured to change a first transmission rate applied to the first wireless link to a value different from a second transmission rate applied to the second wireless link based on a change in distance from the shared access point.

[0008] According to the embodiment, it is possible to provide an access point and a terminal device that improve the wireless communication environment.

[0009] FIG. 1 is a block diagram showing a configuration of a communication system according to an embodiment. FIG. 2 is a block diagram showing an example of the hardware configuration of a sharing AP according to an embodiment. FIG. 3 is a block diagram showing an example of the hardware configuration of a shared AP according to an embodiment. FIG. 4 is a block diagram showing an example of the hardware configuration of a terminal according to an embodiment. FIG. 5 is a block diagram showing an example of the functional configuration of a sharing AP according to an embodiment. FIG. 6 is a diagram showing an example of the data structure of multi-AP management information stored in a sharing AP according to an embodiment. FIG. 7 is a diagram showing an example of the data structure of terminal management information stored in a sharing AP according to an embodiment. FIG. 8 is a block diagram showing an example of the functional configuration of a shared AP according to an embodiment. FIG. 9 is a diagram showing an example of the data structure of link management information stored in a shared AP according to an embodiment. FIG. 10 is a block diagram showing an example of the functional configuration of a terminal according to an embodiment. FIG. 11 is a diagram showing an example of the data structure of link management information stored in a terminal according to an embodiment. FIG. 12 is a sequence diagram showing an example of association processing in a communication system according to an embodiment. FIG. 13 is a flowchart showing an example of transmission rate control processing in a communication system according to an embodiment. FIG. 14 is a flowchart showing an example of channel occupancy rate control processing in a communication system according to an embodiment. FIG. 15 is a flowchart showing an example of transmission rate control processing in a communication system according to a first modified example. Fig. 16 is a flowchart showing an example of a channel occupancy ratio control process in a communication system according to Modification 2. Fig. 17 is a block diagram showing an example of the configuration of a communication system according to another modification.

[0010] Hereinafter, embodiments will be described with reference to the drawings. In the following description, components having the same functions and configurations will be given the same reference numerals.

[0011] 1. Embodiment 1.1 Configuration 1.1.1 Communication System Fig. 1 is a block diagram showing an example of the configuration of a communication system according to an embodiment. As shown in Fig. 1, the communication system 1 includes a sharing AP 10, shared APs 20-1, 20-2, and 20-3, a terminal 30, and a network 40.

[0012] The sharing AP 10, the shared APs 20-1, 20-2, and 20-3, and the terminal 30 have wireless communication functions based on, for example, the OSI (open systems interconnection) reference model. In the OSI reference model, wireless communication functions are 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, and layer 7: application layer). The data link layer includes a logical link control (LLC) sublayer and a media access control (MAC) sublayer.

[0013] Specifically, the sharing AP 10 is, for example, an access point of a wireless LAN. The sharing AP 10 includes an AP MLD. The AP MLD is a multi-link device (MLD) within the sharing AP 10, and is an entity configured to logically connect with the terminal 30 wirelessly. In other words, the AP MLD can be the end point on the sharing AP 10 side in data exchange with the terminal 30 via wireless communication. The AP MLD is configured to communicate with a server (not shown) on the network 40 via a wired or wireless connection. The AP MLD is configured to communicate with each of the shared APs 20-1, 20-2, and 20-3 via a wired or wireless connection.

[0014] Each of the shared APs 20-1, 20-2, and 20-3 is, for example, a wireless LAN access point. The shared APs 20-1, 20-2, and 20-3 are different access points and are located physically apart from one another. Therefore, the shared APs 20-1, 20-2, and 20-3 may have different communication areas. The shared APs 20-1, 20-2, and 20-3 include an affiliated AP 1, an affiliated AP 2, and an affiliated AP 3, respectively. The affiliated AP 1, the affiliated AP 2, and the affiliated AP 3 are entities configured to establish a physical wireless connection with the terminal 30. In other words, the affiliated AP 1, the affiliated AP 2, and the affiliated AP 3 each have a physical configuration for exchanging data with the terminal 30 via a wireless link. Each of Affiliated AP1, Affiliated AP2, and Affiliated AP3 belongs to an AP MLD. Here, "an affiliated AP belongs to an AP MLD" means that the affiliated AP can be used for data exchange between the AP MLD and a terminal.

[0015] The shared APs 20-1, 20-2, and 20-3 have the same configuration. Hereinafter, when there is no need to distinguish between the shared APs 20-1, 20-2, and 20-3, they may be referred to as the shared AP 20. Furthermore, when there is no need to distinguish between the affiliated AP 1, affiliated AP 2, and affiliated AP 3, they may be referred to as the affiliated AP.

[0016] The terminals 30 are, for example, smartphones, personal computers (PCs), etc., and are portable wireless terminal devices that comply with the IEEE 802.11 standard. The terminals 30 include a non-AP MLD, an affiliated STA1, and an affiliated STA2.

[0017] The non-AP MLD is a multi-link device within the terminal 30, and is an entity configured to logically establish a wireless connection with the sharing AP 10. In other words, the non-AP MLD can be the terminal 30 end point for data exchange via wireless communication with the sharing AP 10. The non-AP MLD is connected to affiliated STA1 and affiliated STA2 via wired connections.

[0018] Each of Affiliated STA1 and Affiliated STA2 is an entity configured to have a physical wireless connection with the Affiliated AP. That is, each of Affiliated STA1 and Affiliated STA2 has a physical configuration for exchanging data via a wireless link with the Affiliated AP. Each of Affiliated STA1 and Affiliated STA2 belongs to a non-AP MLD. Here, "an affiliated STA belongs to a non-AP MLD" means that the affiliated STA can be used for data exchange between the non-AP MLD and the AP MLD.

[0019] The affiliated STA1 and the affiliated STA2 have the same configuration. Hereinafter, when there is no need to particularly distinguish between the affiliated STA1 and the affiliated STA2, they may be referred to as the affiliated STA.

[0020] In this embodiment, AP MLD and non-AP MLD are configured to exchange data via wireless links between multiple affiliated APs installed in different access points and multiple affiliated STAs installed in the same terminal 30. This type of data transmission method is also called a multi-AP transmission method.

[0021] The example of FIG. 1 shows a case where the AP MLD and the non-AP MLD exchange data using the wireless link between affiliated AP1 and affiliated STA1, and the wireless link between affiliated AP2 and affiliated STA2.

[0022] For convenience of explanation, the following description will be given of a case where the sharing AP 10 and the shared AP 20 are connected via a wired connection.

[0023] 1.1.2 Hardware Configuration Next, the hardware configuration of the sharing AP, the shared AP, and the terminal in the communication system according to the embodiment will be described.

[0024] 1.1.2.1 Hardware Configuration of Sharing AP Fig. 2 is a block diagram showing an example of the hardware configuration of a sharing AP according to an embodiment. As shown in Fig. 2, the sharing AP 10 includes, for example, a central processing unit (CPU) 11, a read only memory (ROM) 12, a random access memory (RAM) 13, a wired communication module 14, and a wired communication module 15.

[0025] The CPU 11 is a processing circuit that controls the overall operation of the sharing AP 10. The ROM 12 is, for example, a non-volatile semiconductor memory. The ROM 12 stores programs and data for controlling the sharing AP 10. The RAM 13 is, for example, a volatile semiconductor memory. The RAM 13 is used as a work area for the CPU 11. The wired communication modules 14 and 15 are circuits used to send and receive data via wired signals. The wired communication module 14 is connected to the shared APs 20-1, 20-2, and 20-3. The wired communication module 15 is connected to a network 40.

[0026] 1.1.2.2 Hardware Configuration of Shared AP Fig. 3 is a block diagram showing an example of the hardware configuration of a shared AP according to an embodiment. As shown in Fig. 3, the shared AP 20 includes, for example, a CPU 21, a ROM 22, a RAM 23, a wireless communication module 24, and a wired communication module 25.

[0027] The CPU 21 is a processing circuit that controls the overall operation of the shared AP 20. The ROM 22 is, for example, a non-volatile semiconductor memory. The ROM 22 stores programs and data for controlling the shared AP 20. The RAM 23 is, for example, a volatile semiconductor memory. The RAM 23 is used as a working area for the CPU 21. The wireless communication module 24 is a circuit used to send and receive data via wireless signals. The wireless communication module 24 is connected to an antenna. The wired communication module 25 is a circuit used to send and receive data via wired signals. The wired communication module 25 is connected to the sharing AP 10.

[0028] 1.1.2.3 Hardware Configuration of Terminal Fig. 4 is a block diagram showing an example of the hardware configuration of a terminal according to an embodiment. As shown in Fig. 4, the terminal 30 includes, for example, a CPU 31, a ROM 32, a RAM 33, a wireless communication module 34, a display 35, and a storage 36.

[0029] The CPU 31 is a processing circuit that controls the overall operation of the terminal 30. The ROM 32 is, for example, a non-volatile semiconductor memory. The ROM 32 stores programs and data for controlling the terminal 30. The RAM 33 is, for example, a volatile semiconductor memory. The RAM 33 is used as a work area for the CPU 31. The wireless communication module 34 is a circuit used to send and receive data via wireless signals. The wireless communication module 34 is connected to an antenna. The display 35 is, for example, an LCD (liquid crystal display) or an EL (electro-luminescence) display. The display 35 displays a GUI (graphical user interface) corresponding to application software, etc. The storage 36 is a non-volatile storage device. The storage 36 stores system software, etc. of the terminal 30.

[0030] 1.1.3 Functional Configuration Next, the functional configuration of the sharing AP, the shared AP, and the terminal in the communication system according to the embodiment will be described.

[0031] 1.1.3.1 Functional Configuration of Sharing AP FIG. 5 is a block diagram showing an example of the functional configuration of a sharing AP according to this embodiment.

[0032] The sharing AP 10 functions as a computer including an LLC processing unit 110, a management unit 120, and a frame processing unit 130. The LLC processing unit 110 is a functional block that executes processing corresponding to the LLC sublayer of layer 2 and layers 3 to 7. The management unit 120 and frame processing unit 130 are functional blocks that execute processing corresponding to the MAC sublayer of layer 2. The LLC processing unit 110, the management unit 120, and the frame processing unit 130 function as, for example, an AP MLD.

[0033] The LLC processing unit 110 adds, for example, a destination service access point (DSAP) header or a source service access point (SSAP) header to data received from the network 40 and inputs the data to the frame processing unit 130. The LLC processing unit 110 also transmits the data input from the frame processing unit 130 to the network 40.

[0034] The management unit 120 controls the logical wireless connection between the AP MLD and the non-AP MLD in the multi-AP transmission method. For example, the management unit 120 executes multi-AP connection processing in response to an association request from the terminal 30. The management unit 120 also stores multi-AP management information 121 and terminal management information 122.

[0035] FIG. 6 is a diagram illustrating an example of a data structure of multi-AP management information stored in a sharing AP according to the embodiment.

[0036] 6, information about various entities (i.e., AP MLD, affiliated AP1, affiliated AP2, and affiliated AP3) on the access point side used in the multi-AP transmission scheme is stored in the multi-AP management information 121. The information about various entities on the access point side used in the multi-AP transmission scheme specifically includes, for example, an identifier, a frequency band, capability information, and operation parameters.

[0037] The identifier may include, for example, the MAC address of the corresponding entity.

[0038] The frequency band includes information indicating a frequency band used by the corresponding entity. The frequency band may be, for example, 2.4 GHz, 5 GHz, 6 GHz, 45 GHz, or 60 GHz. Each frequency band includes multiple channels.

[0039] The capability information includes, for example, information indicating whether the corresponding entity supports the multi-AP transmission method.

[0040] The operational parameters include, for example, CWmin, CWmax, arbitration interframe space (AIFS), and transmission opportunity (TXOP) limit. CWmin and CWmax respectively indicate the minimum and maximum values ​​of the contention window. The contention window is a parameter used to calculate backoff, which is a transmission waiting time for collision avoidance. AIFS is a fixed transmission waiting time set for each access category of traffic. Traffic access categories include, for example, "VO (voice)", "VI (video)", "BE (best effort)", "BK (background)", and "LL (low latency)". TXOP limit indicates the upper limit of the channel occupation period TXOP.

[0041] It should be noted that the frequency band, capability information, and operation parameters related to AP MLD do not necessarily need to be stored.

[0042] FIG. 7 is a diagram illustrating an example of a data structure of terminal management information stored in the sharing AP according to the embodiment.

[0043] 7, the terminal management information 122 stores information about the connection status of the terminal 30 wirelessly connected to the sharing AP 10 using the multi-AP transmission method. Specifically, for example, the terminal management information 122 stores a non-AP MLD identifier, a set of an identifier of affiliated STA1 and an identifier of an affiliated AP wirelessly connected to affiliated STA1, and a set of an identifier of affiliated STA2 and an identifier of an affiliated AP wirelessly connected to affiliated STA2. Here, the identifiers include the MAC address of the target entity.

[0044] In the connection example shown in FIG. 1, the affiliated AP wirelessly connected to affiliated STA1 and the affiliated AP wirelessly connected to affiliated STA2 are affiliated AP1 and affiliated AP2, respectively.

[0045] Referring again to FIG. 5, the functional configuration of the sharing AP 10 will be described.

[0046] Prior to starting the multi-AP transmission method, frame processing unit 130 transmits multi-AP management information 121 input from management unit 120 to shared APs 20-1, 20-2, and 20-3.

[0047] After the multi-AP transmission method is initiated, the frame processing unit 130 performs processing such as deaggregation on the data transmitted from the shared APs 20-1, 20-2, and 20-3, and then inputs the data to the LLC processing unit 110. Furthermore, when the frame processing unit 130 receives data from the LLC processing unit 110, it performs processing such as aggregation on the data, and then distributes the data to one of the shared APs 20-1, 20-2, and 20-3 via a wired connection. The frame processing unit 130 may determine the data distribution destination by referencing the terminal management information 122. When multiple affiliated APs belong to the AP MLD, the frame processing unit 130 may determine the data distribution destination according to a traffic identifier (TID) associated with an access category.

[0048] 1.1.3.2 Functional Configuration of Shared AP FIG. 8 is a block diagram showing an example of the functional configuration of a shared AP according to this embodiment.

[0049] The shared AP 20 functions as a computer including a management unit 210, a frame processing unit 220, a radio signal processing unit 230, and a radio environment monitoring unit 240. The management unit 210 and the frame processing unit 220 are functional blocks that execute processing corresponding to the MAC sublayer of the second layer. The radio signal processing unit 230 and the radio environment monitoring unit 240 are functional blocks that execute processing corresponding to the first layer. The management unit 210, the frame processing unit 220, the radio signal processing unit 230, and the radio environment monitoring unit 240 function as an affiliated AP.

[0050] Prior to starting the multi-AP transmission method, the management unit 210 generates a beacon frame including information about the multi-AP transmission method. The beacon frame includes the multi-AP management information 121 received from the sharing AP 10. More specifically, the beacon frame includes an AP MLD identifier, as well as the identifiers, frequencies, and operation parameters of all affiliated APs that belong to the AP MLD and support the multi-AP transmission method. The management unit 210 notifies the terminal 30 of the generated beacon frame via the wireless signal processing unit 230.

[0051] The management unit 210 also manages the state of the physical wireless connection with the affiliated STA in the multi-AP transmission method. Specifically, for example, the management unit 210 stores link management information 211. The management unit 210 may also store multi-AP management information 121 transmitted from the sharing AP 10.

[0052] FIG. 9 is a diagram illustrating an example of a data structure of link management information stored in a shared AP according to the embodiment.

[0053] 9 , in the multi-AP transmission method, the link management information 211 stores information about affiliated STAs that are physically connected wirelessly to affiliated APs in the shared AP 20. The information about affiliated STAs connected to affiliated APs in the shared AP 20 specifically includes, for example, an identifier, an MCS (modulation and coding scheme) index, mobility information, and a channel occupancy rate.

[0054] The identifier includes, for example, the MAC address of the affiliated STA. In the connection example shown in FIG. 1, the link management information 211 in the shared AP 20-1 includes the MAC address of affiliated STA 1. Furthermore, the link management information 211 in the shared AP 20-2 includes the MAC address of affiliated STA 2.

[0055] The MCS index corresponds to a transmission rate applied to data exchange with an affiliated STA. Specifically, for example, the MCS index corresponds to a combination of a spatial stream, a modulation scheme, and a coding rate. The magnitude of the MCS index correlates with the transmission rate.

[0056] The movement information indicates the speed at which the affiliated STA is moving away (or approaching) from the perspective of the affiliated AP with which the wireless link is established. In other words, the movement information may indicate the amount of change in distance. The movement information is obtained based on information such as the relative coordinates of the affiliated STA from the perspective of the affiliated AP with which the wireless link is established, and parameters that change depending on the distance from the affiliated AP with which the wireless link is established to the affiliated STA. Parameters that change depending on distance include, for example, received signal strength indicator (RSSI) and radio wave arrival direction.

[0057] The channel occupancy rate is information indicating the degree to which the affiliated STA occupies the channel used for data exchange, and is acquired based on information such as the transmission airtime and transmission time of the affiliated STA, for example.

[0058] Referring again to FIG. 8, the functional configuration of the shared AP 20 will be described.

[0059] The management unit 210 acquires the above-mentioned movement information and channel occupancy rate from the radio environment monitor unit 240 and stores them as link management information 221. Then, the management unit 210 executes a transmission rate control process and a channel occupancy rate control process based on the acquired movement information and channel occupancy rate.

[0060] The transmission rate control process is a process for realizing efficient data exchange while suppressing packet loss and sudden communication interruptions by changing the transmission rate of the wireless link according to the MCS index. In the transmission rate control process, the management unit 210 determines the MCS index to be applied to data exchange with the affiliated STA based on the acquired mobility information. For example, the management unit 210 determines the magnitude of the MCS index to be changed depending on the speed at which the connected affiliated STA moves away from (or approaches) the affiliated AP. Note that the management unit 210 may previously store information indicating the relationship between the magnitude of the MCS index to be changed and the speed. Details of the transmission rate control process will be described later.

[0061] The channel occupancy rate control process is a process for preventing a wireless link with a high channel occupancy rate from decreasing the throughput of the entire communication system 1 by disconnecting the wireless link with the high channel occupancy rate. In the channel occupancy rate control process, the management unit 210 determines whether or not to maintain the wireless link established with the affiliated STA based on the acquired channel occupancy rate. Details of the channel occupancy rate control process will be described later.

[0062] The frame processing unit 220 adds a MAC header to the data input from the sharing AP 10 to generate a MAC frame, and inputs the MAC frame to the wireless signal processing unit 230. The frame processing unit 220 also performs a CRC (Cyclic Redundancy Check) on the MAC frame input from the wireless signal processing unit 230 to perform error detection. The frame processing unit 220 then inputs the data that has been confirmed to be error-free to the sharing AP 10.

[0063] The radio signal processing unit 230 generates a radio frame by adding a preamble and the like to the MAC frame input from the frame processing unit 220. The radio signal processing unit 230 converts the generated radio frame into a radio signal. The radio signal processing unit 230 then radiates (transmits) the converted radio signal via an antenna. The conversion process from the radio frame to the radio signal includes, for example, convolutional coding, interleaving, subcarrier modulation, inverse fast Fourier transform, orthogonal frequency division multiplexing (OFDM) modulation, and frequency conversion. The radio signal processing unit 230 also converts a radio signal received from the terminal 30 via the antenna into a radio frame. The conversion process from the radio signal to the radio frame includes, for example, frequency conversion, OFDM demodulation, fast Fourier transform, subcarrier demodulation, deinterleaving, and Viterbi decoding. The radio signal processing unit 230 extracts a MAC frame from the converted radio frame. Then, the radio signal processing unit 230 inputs the extracted MAC frame to the frame processing unit 220 .

[0064] The radio environment monitor unit 240 monitors the radio environment of the radio signal received by the radio signal processor 230. Specifically, the radio environment monitor unit 240 monitors parameters that change depending on the distance to the affiliated STA that is the sender, such as the received signal strength and the radio wave arrival direction of the radio signal. Then, the radio environment monitor unit 240 calculates movement information of the affiliated STA based on the monitored parameters.

[0065] The radio environment monitor 240 also monitors information such as the transmission airtime and transmission time of the affiliated STA that is the source of the radio signal, and calculates the channel occupancy rate for data exchange with the affiliated STA based on the monitored information.

[0066] The radio environment monitor 240 inputs the acquired movement information and channel occupancy rate to the management unit 210 .

[0067] 1.1.3.3 Functional Configuration of Terminal FIG. 10 is a block diagram showing an example of the functional configuration of a terminal according to this embodiment.

[0068] The terminal 30 functions as a computer including an application execution unit 300, an LLC processing unit 310, a management unit 320, a frame processing unit 330, and radio signal processing units 340 and 350. The application execution unit 300 is a functional block that executes processing corresponding to layer 7. The LLC processing unit 310 is a functional block that executes processing corresponding to the LLC sublayer of layer 2 and layers 3 to 6. The management unit 320 and frame processing unit 330 are functional blocks that execute processing corresponding to the MAC sublayer of layer 2. The radio signal processing units 340 and 350 are functional blocks that execute processing corresponding to layer 1. The application execution unit 300, the LLC processing unit 310, the management unit 320, and the frame processing unit 330 function as a non-AP MLD. The radio signal processing unit 340 functions as an affiliated STA1. The radio signal processing unit 350 functions as an affiliated STA2.

[0069] The application execution unit 300 executes an application based on data input from the LLC processing unit 310. The application execution unit 300 also inputs data to the LLC processing unit 310. For example, the application execution unit 300 can display application information on the display 35. The application execution unit 300 can also operate based on operations on an input interface.

[0070] The LLC processing unit 310 adds a DSAP header, an SSAP header, etc. to the data input from the application execution unit 300 and inputs the data to the frame processing unit 330. The LLC processing unit 310 also inputs the data input from the frame processing unit 330 to the application execution unit 300.

[0071] The management unit 320 controls the logical wireless connection between the AP MLD and the non-AP MLD in the multi-AP transmission method. For example, the management unit 320 generates an association request based on a beacon frame from the shared AP 20. The management unit 320 also stores link management information 321. The management unit 320 also stores information included in the beacon frame from the shared AP 20, part of the multi-AP management information 121.

[0072] 11 is a diagram illustrating an example of the data structure of link management information stored in the terminal according to the embodiment. In FIG. 11, the data structure of link management information 321 is illustrated as an example of information stored in the terminal 30 in addition to the information included in the beacon frame.

[0073] 11 , in the multi-AP transmission method, link management information 321 stores information about affiliated APs that are physically connected to affiliated STA1 and affiliated STA2 in terminal 30. The information about the affiliated APs that are physically connected to affiliated STA1 and affiliated STA2 includes, specifically, for example, an identifier and an MCS index.

[0074] The identifier includes, for example, the MAC address of the affiliated AP. In the connection example shown in Figure 1, the link management information 321 stores the MAC address of affiliated AP 1 connected to affiliated STA 1 and the MAC address of affiliated AP 2 connected to affiliated STA 2.

[0075] The MCS index corresponds to the MCS index stored in the link management information 221. That is, in the case of the connection example shown in Fig. 1 , the link management information 321 stores an MCS index applied to data exchange with affiliated AP1 connected to affiliated STA1, and an MCS index applied to data exchange with affiliated AP2 connected to affiliated STA2.

[0076] Referring again to FIG. 10, the functional configuration of the terminal 30 will be described.

[0077] When data is input from LLC processing unit 310, frame processing unit 330 performs processing such as aggregation. Then, frame processing unit 330 adds a MAC header to the data to generate a MAC frame, and distributes the data to either radio signal processing unit 340 or 350. Note that frame processing unit 330 may determine the distribution destination of the data based on the TID. Furthermore, frame processing unit 330 performs CRC on the MAC frames input from radio signal processing units 340 and 350 to perform error detection. Then, frame processing unit 330 performs processing such as deaggregation on data that has been confirmed to be error-free, and then inputs the data to LLC processing unit 310.

[0078] The radio signal processors 340 and 350 generate radio frames by adding a preamble and the like to the MAC frames input from the frame processor 330. The radio signal processors 340 and 350 convert the generated radio frames into radio signals. The radio signal processors 340 and 350 then radiate (transmit) the converted radio signals via antennas. The conversion process from radio frames to radio signals includes, for example, convolutional coding, interleaving, subcarrier modulation, inverse fast Fourier transform, OFDM modulation, and frequency conversion. The radio signal processors 340 and 350 also convert radio signals received from the corresponding shared AP 20 via the antennas into radio frames. The conversion process from radio signals to radio frames includes, for example, frequency conversion, OFDM demodulation, fast Fourier transform, subcarrier demodulation, deinterleaving, and Viterbi decoding. The radio signal processors 340 and 350 extract MAC frames from the converted radio frames. Then, the radio signal processing units 340 and 350 input the extracted MAC frames to the frame processing unit 330 .

[0079] 1.2 Operation Next, the operation of the communication system according to the embodiment will be described.

[0080] 1.2.1 Association Processing Fig. 12 is a sequence diagram showing an example of association processing in the communication system according to the embodiment. Fig. 12 shows the flow of information exchanged among the AP MLD, affiliated AP1, affiliated AP2, affiliated AP3, affiliated STA1, affiliated STA2, and non-AP MLD during the association processing.

[0081] The AP MLD transmits the multi-AP management information 121 to each of affiliated AP1, affiliated AP2, and affiliated AP3 (S1).

[0082] Affiliated AP1, Affiliated AP2, and Affiliated AP3 each generate a beacon frame based on the multi-AP management information 121 received in the process of S1. Then, Affiliated AP1, Affiliated AP2, and Affiliated AP3 each broadcast the generated beacon frame to Affiliated STA1 and Affiliated STA2 (S2).

[0083] Affiliated STA1 and affiliated STA2 each receive the beacon frame broadcast in the process of S2, and then each of affiliated STA1 and affiliated STA2 inputs the multi-AP management information 121 in the beacon frame to the non-AP MLD (S3).

[0084] The non-AP MLD generates an association request for establishing a multi-AP connection based on the multi-AP management information 121 input in the process of S3, and transmits the generated association request to the sharing AP 10 (S4). The association request includes, for example, information about the affiliated APs to which Affiliated STA1 and Affiliated STA2 each wish to connect for the multi-AP connection. The association request is transmitted to the AP MLD via at least one Affiliated STA among Affiliated STA1 and Affiliated STA2, and at least one Affiliated AP among Affiliated AP1, Affiliated AP2, and Affiliated AP3.

[0085] The AP MLD generates an association notification based on the association request sent in the process of S4. Then, the AP MLD transmits the generated association notification to each of affiliated AP1, affiliated AP2, and affiliated AP3 (S5). The association notification includes information notifying which affiliated AP and which affiliated STA will exchange data over the wireless link established between the AP MLD and the non-AP MLD. The association notification may include information equivalent to that of the association request sent in the process of S4.

[0086] The AP MLD also generates an association response based on the association request sent in the process of S4. The AP MLD then transmits the generated association response to the non-AP MLD (S6). The association response is transmitted to the non-AP MLD via at least one affiliated AP among Affiliated AP1, Affiliated AP2, and Affiliated AP3, and at least one affiliated STA among Affiliated STA1 and Affiliated STA2.

[0087] The non-AP MLD generates an association notification based on the association response sent in the process of S6, and then inputs the generated association notification to each of affiliated STA1 and affiliated STA2 (S7).

[0088] This completes the association process for establishing a wireless link via a multi-AP connection between the AP MLD and the non-AP MLD. This comprehensively establishes associations between the AP MLD and the non-AP MLD for the wireless links via Affiliated AP1, Affiliated AP2, and Affiliated AP3. Based on the contents of the association notification, data exchange can be performed using the wireless links connecting at least one Affiliated AP from among Affiliated AP1, Affiliated AP2, and Affiliated AP3 with the corresponding Affiliated STA.

[0089] 1.2.2 Transmission Rate Control Processing Fig. 13 is a flowchart showing an example of a transmission rate control processing in the communication system according to the embodiment. Fig. 13 shows, as an example, a transmission rate control processing for a wireless link between affiliated AP1 and affiliated STA1.

[0090] When the transmission rate control process starts (START), the radio environment monitor unit 240 acquires movement information regarding the affiliated STA1 (including the terminal 30) with which the radio link is established (S11). The radio environment monitor unit 240 inputs the acquired movement information to the management unit 210.

[0091] Based on the movement information acquired in the process of S11, the management unit 210 determines whether the affiliated STA1 with which the wireless link is established is moving away from the affiliated AP1 at a speed equal to or greater than a threshold (S12).

[0092] If affiliated STA1 is moving away from affiliated AP1 at a speed equal to or greater than the threshold (S12; yes), management unit 210 lowers the transmission rate applied to the wireless link in accordance with the speed (S13). Specifically, management unit 210 determines that the higher the moving speed, the lower the MCS index applied to the wireless link with affiliated STA1. Management unit 210 applies the newly determined MCS index to data exchange between affiliated AP1 and affiliated STA1, and notifies non-AP MLD of the MCS index. This allows affiliated AP1 and affiliated STA1 to perform subsequent data exchange using a smaller MCS index.

[0093] If the affiliated STA1 is not moving away from the affiliated AP1 at a speed equal to or greater than the threshold (S12; no), the management unit 210 determines, based on the movement information acquired in the process of S11, whether the affiliated STA1, with which the wireless link has been established, is approaching the affiliated AP1 at a speed equal to or greater than the threshold (S14). Note that the threshold used in the process of S14 may be the same as or different from the threshold used in the process of S12.

[0094] If affiliated STA1 is approaching affiliated AP1 at a speed equal to or greater than the threshold (S14; yes), the management unit 210 increases the transmission rate applied to the wireless link in accordance with the speed (S15). Specifically, the management unit 210 determines that the higher the approaching speed, the higher the MCS index applied to the wireless link with affiliated STA1. The affiliated AP1 applies the newly determined MCS index to data exchange with affiliated STA1, and notifies the non-AP MLD of the MCS index. This allows the affiliated AP1 and affiliated STA1 to apply the higher MCS index to perform subsequent data exchange.

[0095] After the process of S13 or the process of S15, the transmission rate control process for the wireless link between the affiliated AP 1 and the affiliated STA 1 ends (END).

[0096] 1.2.3 Channel Occupancy Ratio Control Processing Fig. 14 is a flowchart illustrating an example of a channel occupancy ratio control processing in the communication system according to the embodiment. Fig. 14 illustrates, as an example, a channel occupancy ratio control processing for a wireless link between affiliated AP1 and affiliated STA1.

[0097] When the channel occupancy rate control process starts (START), the radio environment monitor 240 acquires the channel occupancy rate for the radio link established with the affiliated STA 1 (S21). The radio environment monitor 240 inputs the acquired channel occupancy rate to the management unit 210.

[0098] The management unit 210 determines whether the channel occupancy rate acquired in the process of S21 is equal to or greater than a threshold value (S22). Note that the threshold value used in the channel occupancy rate control process is different from the threshold value used in the transmission rate control process.

[0099] If the channel occupancy rate is equal to or greater than the threshold (S22; yes), the management unit 210 determines to disconnect the wireless link with the affiliated STA1 (i.e., set the transmission rate to 0). Then, the communication system 1 executes a process to disconnect the wireless link based on this determination (S23). Specifically, first, the AP MLD transmits a wireless link disconnection notification to the affiliated STA1 and the affiliated AP1. Upon receiving the wireless link disconnection notification, the affiliated AP1 and the affiliated STA1 stop data exchange in accordance with the notification.

[0100] If the channel occupation ratio is less than the threshold value (S22; no), or after the process of S23, the channel occupation ratio control process ends (END).

[0101] 1.3 Effects of the Embodiment In the multi-AP transmission method, the distances between the terminal 30 and multiple shared APs 20 with which wireless links are established change independently as the terminal 30 moves. Therefore, the appropriate wireless environment in the multi-AP transmission method changes independently and dynamically for each wireless link.

[0102] According to an embodiment, the shared AP 20 and the terminal 30 that have established a wireless link using the multi-AP transmission method monitor the amount of change in the distance between them. This allows the transmission rate to be changed before packet loss or communication interruption occurs, without triggering the change in transmission rate due to packet loss or communication interruption. Therefore, even when the wireless environment changes independently and dynamically for each wireless link as the terminal 30 moves, it is possible to apply an optimal transmission rate for each wireless link while avoiding packet loss or communication interruption due to the changes. Therefore, it is possible to lower the transmission rate for wireless links that are at risk of packet loss or communication interruption due to distance increases, and to raise the transmission rate for wireless links that are expected to improve throughput due to closer distance increases.

[0103] Furthermore, the shared AP 20 and the terminal 30 stop data exchange based on the channel occupancy rate of the wireless link. This allows for disconnection of a wireless link whose channel occupancy rate has increased due to, for example, a prolonged state of a reduced transmission rate caused by the movement of the terminal 30. This prevents a decrease in the throughput of the entire communication system 1 caused by a wireless link whose channel occupancy rate has increased. This therefore improves the wireless communication environment of the communication system 1.

[0104] 2. Modifications, etc. Various modifications can be applied to the above-described embodiment.

[0105] 2.1 First Modification For example, one of multiple wireless links established in the multi-AP connection mode may be designated as an anchor link to be distinguished from other wireless links. The anchor link is a wireless link that is treated to be less susceptible to communication interruptions than other wireless links. In this case, a lower MCS index may be applied to the anchor link than to the other wireless links.

[0106] Fig. 15 is a flowchart showing an example of a transmission rate control process in a communication system according to Modification 1. Fig. 15 corresponds to Fig. 13 in the embodiment.

[0107] When the transmission rate control process starts (START), the radio environment monitor 240 acquires movement information about the affiliated STA 1 with which the radio link is established (S31). The radio environment monitor 240 inputs the acquired movement information to the management unit 210.

[0108] Based on the movement information acquired in the process of S31, the management unit 210 determines whether the affiliated STA1 with which the wireless link is established is moving away from the affiliated AP1 at a speed equal to or greater than a threshold (S32).

[0109] If affiliated STA1 is moving away from affiliated AP1 at a speed equal to or greater than the threshold (S32; yes), the management unit 210 lowers the transmission rate applied to the wireless link in accordance with the speed (S33).

[0110] After the process of S33, the management unit 210 determines whether the wireless link is an anchor link (S34).

[0111] If the affiliated STA1 is far from the affiliated AP1 and the wireless link is an anchor link (S34; yes), the management unit 210 further reduces the transmission rate applied to the wireless link (S35).

[0112] If the affiliated STA1 is not moving away from the affiliated AP1 at a speed greater than or equal to the threshold (S32; no), the management unit 210 determines, based on the movement information acquired in the processing of S31, whether the affiliated STA1, which has established a wireless link, is approaching the affiliated AP1 at a speed greater than or equal to the threshold (S36).

[0113] If affiliated STA1 is approaching affiliated AP1 at a speed equal to or greater than the threshold (S36; yes), the management unit 210 increases the transmission rate applied to the wireless link in accordance with the speed (S37).

[0114] After the process of S37, the management unit 210 determines whether the wireless link is an anchor link (S38).

[0115] If the affiliated STA1 is approaching from the affiliated AP1 and the wireless link is not an anchor link (S38; no), the management unit 210 further increases the transmission rate applied to the wireless link (S39).

[0116] If the wireless link is not an anchor link when affiliated STA1 is away from affiliated AP1 (S34; no), or if the wireless link is an anchor link when affiliated STA1 is approaching affiliated AP1 (S38; yes), after processing S35 or after processing S39, the transmission rate control processing for the wireless link between affiliated AP1 and affiliated STA1 is terminated (end).

[0117] According to the first modification, when the speed at which the terminal 30 is moving away is equal to or greater than a threshold, the shared AP 20 that has established an anchor link reduces the transmission rate to a greater extent than when another wireless link other than the anchor link is established. Furthermore, when the speed at which the terminal 30 is approaching is equal to or greater than a threshold, the shared AP 20 that has established another wireless link other than the anchor link increases the transmission rate to a greater extent than when the anchor link is established. This prevents the transmission rate of the anchor link from becoming excessively high compared to the transmission rates of the other wireless links. This prevents communication interruptions in the anchor link.

[0118] 2.2 Second Modification Furthermore, for example, when disconnecting a wireless link with a high channel occupancy rate, a handover process may be executed to switch to a wireless link with an affiliated AP with a relatively low channel occupancy rate.

[0119] Fig. 16 is a flowchart showing an example of a channel occupancy ratio control process in a communication system according to Modification 2. Fig. 16 corresponds to Fig. 14 in the embodiment.

[0120] When the channel occupancy rate control process starts (START), the radio environment monitor 240 acquires the channel occupancy rate for the radio link established with the affiliated STA 1 (S41). The radio environment monitor 240 inputs the acquired channel occupancy rate to the management unit 210.

[0121] The management unit 210 determines whether the channel occupation rate acquired in the process of S41 is equal to or greater than a threshold value (S42).

[0122] If the channel occupancy rate is equal to or greater than the threshold (S42; yes), the management unit 210 determines to disconnect the wireless link with the affiliated STA1. Then, the management unit 210 searches for an affiliated AP that is a handover candidate for newly exchanging data with the affiliated STA1 (S43). Specifically, for example, the management unit 210 searches for the affiliated AP that is closest to the terminal 30 among the affiliated APs that have not established a wireless link with the terminal 30. Alternatively, the management unit 210 may search for the affiliated AP that has the smallest product of the inverse of the channel occupancy rate and the distance from the terminal 30 among the affiliated APs that have not established a wireless link with the terminal 30.

[0123] If an affiliated AP that is a candidate for handover is found (S44; yes), the management unit 210 determines to execute handover processing. Then, the communication system 1 executes handover processing based on this determination (S45). Specifically, first, the AP MLD transmits a handover notification to the affiliated STA1, the affiliated AP1, and the affiliated AP found in the processing of S43. This allows the affiliated STA1 to stop data exchange with the affiliated AP1 and start data exchange with the affiliated AP found in the processing of S43.

[0124] If no affiliated AP is found to be a candidate for handover (S44; no), the management unit 210 determines to disconnect the wireless link with the affiliated STA1. Then, the communication system 1 executes a wireless link disconnection process based on this determination (S46). Specifically, first, the AP MLD transmits a wireless link disconnection notification to the affiliated STA1 and the affiliated AP1. Upon receiving the wireless link disconnection notification, the affiliated AP1 and the affiliated STA1 stop data exchange in accordance with the notification.

[0125] If the channel occupation ratio is less than the threshold value (S42; no), the channel occupation ratio control process ends after the process of S45 or after the process of S46 (END).

[0126] According to the second modification, when the channel occupancy rate of the wireless link with the terminal 30 is equal to or greater than a threshold, the shared AP 20 searches for a shared AP 20 with a lower channel occupancy rate. Then, the communication system 1 terminates the wireless link whose channel occupancy rate has reached the threshold and executes a handover process to start data exchange between the shared AP 20 discovered by the search and the terminal 30. This makes it possible to suppress deterioration of the wireless environment of the terminal 30 without deteriorating the throughput of the entire communication system 1.

[0127] 2.3 Others In the above-described embodiment and second modification, a case has been described in which a wireless link whose acquired channel occupancy rate is equal to or greater than a threshold is disconnected regardless of whether the wireless link is an anchor link or not. However, this is not limited to this. For example, among wireless links whose channel occupancy rate is equal to or greater than a threshold, an anchor link may be maintained without being disconnected. This can prevent communication interruptions in the anchor link.

[0128] In the above-described embodiment and first modification, the management unit 210 of the shared AP 20 determines whether to change the transmission rate based on the mobility information in the transmission rate control process. However, this is not limiting. For example, the management unit 120 of the sharing AP 10 may determine whether to change the transmission rate in the transmission rate control process. In this case, the transmission rate control process can be performed comprehensively for multiple wireless links. This makes it possible to make adjustments such as lowering the MCS index of the anchor link and raising the MCS index of other wireless links so as not to reduce the throughput of the entire communication system 1.

[0129] In the above-described embodiment and second modification, the management unit 210 of the shared AP 20 determines whether to perform a handover or disconnect a wireless link based on the channel occupancy rate in the channel occupancy rate control process. However, this is not limiting. For example, the management unit 120 of the shared AP or the management unit 320 of the terminal 30 may determine whether to perform a handover or disconnect a wireless link based on the channel occupancy rate in the channel occupancy rate control process. In this case, the channel occupancy rate control process can be performed comprehensively for multiple wireless links. This allows the threshold applied to the determination to be dynamically changed based on, for example, the trade-off between the throughput of the entire communication system 1 and the connectivity of each individual wireless link. Note that when the management unit 320 performs the determination in the channel occupancy rate control process, the terminal 30 further includes a wireless environment monitor that monitors the wireless environments of the wireless signal processors 340 and 350.

[0130] Alternatively, the decision to change the transmission rate based on mobility information in the transmission rate control process, and the decision to handover or disconnect the wireless link based on the channel occupancy rate in the channel occupancy rate control process may be performed by a control device that manages traffic related to multiple sharing APs.

[0131] Fig. 17 is a block diagram showing an example of the configuration of a communication system according to another modification, which corresponds to Fig. 1 in the embodiment.

[0132] As shown in Figure 17, the communication system 1A includes a traffic control device 5, sharing APs 10-1 and 10-2, shared APs 20-1, 20-2, and 20-3, a terminal 30, and a network 40. The sharing AP 10-1 corresponds to the sharing AP 10 in the embodiment and includes an AP MLD1. The sharing AP 10-2 includes an AP MLD2. The AP MLD1 and AP MLD2 have the same configuration. The configuration under the sharing AP 10-2 includes a plurality of affiliated APs, a plurality of affiliated STAs, and a non-AP MLD (not shown).

[0133] According to the configuration of FIG. 17, the traffic control device 5 can comprehensively manage the traffic in the AP MLD1 and its subordinate configuration, and the traffic in the AP MLD2 and its subordinate configuration.

[0134] Furthermore, the transmission rate control process and the channel occupancy ratio control process in the sharing AP 10, the shared AP 20, and the terminal 30 according to the above-described embodiments can be stored as a program that can be executed by a processor, which is a computer. Alternatively, the programs can be stored in a storage medium of an external storage device such as a magnetic disk, an optical disk, or a semiconductor memory and distributed. The processors of the sharing AP 10, the shared AP 20, and the terminal 30 can then load the programs stored in the storage medium of the external storage device, and their operations can be controlled by the loaded programs, thereby executing the transmission rate control process and the channel occupancy ratio control process.

[0135] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention.

[0136] DESCRIPTION OF SYMBOLS 1, 1A...Communication system 5...Traffic control device 10...Sharing AP 20...Shared AP 30...Terminal 40...Network 11, 21, 31...CPU 12, 22, 32...ROM 13, 23, 33...RAM 14, 15, 25...Wired communication module 24, 34...Wireless communication module 35...Display 36...Storage 110, 310...LLC processing unit 120, 210, 320...Management unit 130, 220, 330...Frame processing unit 230, 340, 350...Wireless signal processing unit 240...Wireless environment monitoring unit 300...Application execution unit 121...Multi-AP management information 122...Terminal management information 211, 321...Link management information

Claims

1. A terminal device in a communication system including a shared access point, a shared access point, another shared access point, and a terminal device, wherein the terminal device is configured to exchange data with the shared access point using a first wireless link between the shared access point and the other shared access point and to change a first transmission rate applied to the first wireless link to a value different from a second transmission rate applied to the second wireless link based on an amount of change in distance from the shared access point.

2. The terminal device according to claim 1, configured to: reduce the first transmission rate when the speed at which the terminal device moves away from the shared access point is equal to or greater than a first threshold; and increase the first transmission rate when the speed at which the terminal device moves toward the shared access point is equal to or greater than a second threshold.

3. The terminal device according to claim 1, wherein the terminal device is configured to stop the data exchange via the first wireless link based on a channel occupancy rate of the first wireless link.

4. A shared access point in a communication system including a sharing access point, a shared access point, another shared access point, and a terminal device, wherein the shared access point is configured to change a first transmission rate applied to the first wireless link to a value different from a second transmission rate applied to the second wireless link based on a change in distance from the terminal device, in data exchange between the terminal device and the shared access point using a first wireless link between the terminal device and the shared access point and a second wireless link between the terminal device and the other shared access point.

5. The shared access point according to claim 4, configured to: reduce the first transmission rate when the speed at which the terminal device moves away from the shared access point is equal to or greater than a first threshold; and increase the first transmission rate when the speed at which the terminal device approaches the shared access point is equal to or greater than a second threshold.

6. The shared access point according to claim 4, wherein the shared access point is configured to stop the data exchange via the first wireless link when a channel occupancy rate of the first wireless link is equal to or greater than a third threshold.

7. A communication method in a communication system including a shared access point, a shared access point, another shared access point, and a terminal device, comprising: exchanging data between the terminal device and the shared access point using a first wireless link between the terminal device and the shared access point and a second wireless link between the terminal device and the other shared access point; and changing a first transmission rate applied to the first wireless link to a value different from a second transmission rate applied to the second wireless link based on an amount of change in distance from the shared access point to the terminal device.

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