Access point, terminal device, and communication method therefor

Abstract

An access point as a first access point according to one aspect constitutes a communication system together with a second access point, a third access point, and a terminal device. The first access point is configured to transmit a time stamp related to a first timer corresponding to the first access point to the second access point and the third access point, receive a first offset between the first timer and a second timer corresponding to the second access point from the second access point, receive a second offset between the first timer and a third timer corresponding to the third access point from the third access point, and transmit the first offset and the second offset to each of the second access point and the third access point.

Description

Access point, terminal device, and communication method therefor

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

[0002] 2. Description of the Related Art A multi-link transmission method using a wireless local area network (LAN) is known as a communication system for wirelessly connecting an access point (AP) and a terminal device.

[0003] In the multi-link transmission method, data exchange between a multi-link device (AP MLD) in an access point and a multi-link device (non-AP MLD) in a terminal device is realized by wireless links between multiple affiliated APs in the access point and multiple affiliated STAs in the terminal.

[0004] As a cooperative operation between a plurality of affiliated APs in a multi-link transmission system, a technique such as R-TWT (restricted target wake time) has been proposed.

[0005] IEEE802.11be D3.0, “35.3 Multi-link operation”, “35.8 Restricted TWT (R-TWT)”, p479-p586, p617-p621, January 2023

[0006] From the viewpoint of improving the wireless communication environment, it is desirable that a transmission method (multi-AP transmission method) be established in which a terminal device can use wireless links with multiple affiliated APs of multiple access points in combination.

[0007] However, since each of the access points operates based on different time information, when the access points cooperate with each other in the multi-AP transmission method, it may be necessary to synchronize the time between the access points and the terminal device in order to maintain a good wireless communication environment.

[0008] The present invention has been made in light of the above circumstances, and its object is to provide a shared access point, a terminal device, and a communication method therefor that improve the wireless communication environment.

[0009] In one aspect, an access point as a first access point constitutes a communication system together with a second access point, a third access point, and a terminal device, wherein the first access point is configured to transmit a timestamp related to a first timer corresponding to the first access point to the second access point and the third access point, receive from the second access point a first offset between the first timer and a second timer corresponding to the second access point, receive from the third access point a second offset between the first timer and a third timer corresponding to the third access point, and transmit the first offset and the second offset to each of the second access point and the third access point.

[0010] According to the embodiments, it is possible to provide a shared access point, a terminal device, and a communication method therefor that improve the wireless communication environment.

[0011] FIG. 1 is a block diagram showing the configuration of a communication system according to the first embodiment. FIG. 2 is a block diagram showing an example of the hardware configuration of a sharing AP according to the first embodiment. FIG. 3 is a block diagram showing an example of the hardware configuration of a shared AP according to the first embodiment. FIG. 4 is a block diagram showing an example of the hardware configuration of a terminal device according to the first embodiment. FIG. 5 is a block diagram showing an example of the functional configuration of a sharing AP according to the first 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 the first embodiment. FIG. 7 is a diagram showing an example of the data structure of terminal management information stored in a sharing AP according to the first embodiment. FIG. 8 is a diagram showing an example of the data structure of time management information stored in a sharing AP according to the first embodiment. FIG. 9 is a diagram showing an example of a beacon frame related to time synchronization transmitted from a sharing AP according to the first embodiment. FIG. 10 is a block diagram showing an example of the functional configuration of a shared AP according to the first embodiment. FIG. 11 is a diagram showing an example of the data structure of link management information stored in a shared AP according to the first embodiment. FIG. 12 is a diagram showing an example of a beacon frame related to time synchronization transmitted from a shared AP according to the first embodiment. FIG. 13 is a block diagram showing an example of the functional configuration of a terminal device according to the first embodiment. FIG. 14 is a diagram showing an example of a data structure of link management information stored in a terminal device according to the first embodiment. FIG. 15 is a sequence diagram showing an example of time synchronization processing in the communication system according to the first embodiment. FIG. 16 is a sequence diagram showing an example of R-TWT coordination processing in the communication system according to the first embodiment. FIG. 17 is a block diagram showing an example of the functional configuration of a sharing AP according to the second embodiment. FIG. 18 is a sequence diagram showing an example of reference timer generation processing in the communication system according to the second embodiment. FIG. 19 is a block diagram showing an example of the functional configuration of a sharing AP according to the first modified example. FIG. 20 is a block diagram showing the configuration of a communication system according to the second modified example.

[0012] Hereinafter, embodiments will be described with reference to the drawings. In the following description, components having the same functions and configurations will be denoted by the same reference numerals.

[0013] 1. First 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 the first embodiment. As shown in Fig. 1, the communication system 1 includes a sharing access point (AP) 10 as a first access point, shared access points (APs) 20-1 and 20-2 as second and third access points, a terminal device 30, and a network 40.

[0014] The sharing AP 10, the shared APs 20-1 and 20-2, and the terminal device 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.

[0015] 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 device 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 device 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 and 20-2 via a wired or wireless connection.

[0016] Each of the shared APs 20-1 and 20-2 is, for example, a wireless LAN access point. The shared APs 20-1 and 20-2 are different access points and are located at locations physically separated from each other. Therefore, the shared APs 20-1 and 20-2 may have different communication areas. The shared APs 20-1 and 20-2 include an affiliated AP 1 and an affiliated AP 2, respectively. The affiliated AP 1 and the affiliated AP 2 are each entities configured to establish a physical wireless connection with the terminal device 30. In other words, the affiliated AP 1 and the affiliated AP 2 each have a physical configuration for exchanging data via a wireless link with the terminal device 30. The affiliated AP 1 and the affiliated AP 2 each belong 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 device.

[0017] The shared APs 20-1 and 20-2 have the same configuration. In the following, when there is no need to distinguish between the shared APs 20-1 and 20-2, they may be referred to as the shared AP 20. Furthermore, when there is no need to distinguish between the affiliated AP 1 and the affiliated AP 2, they may be referred to as the affiliated AP.

[0018] The terminal devices 30 are, for example, smartphones, personal computers (PCs), etc., and are portable wireless terminal devices that comply with the IEEE 802.11 standard. The terminal devices 30 include a non-AP MLD, an affiliated STA1, and an affiliated STA2.

[0019] The non-AP MLD is a multi-link device within the terminal device 30, and is an entity configured to logically connect wirelessly to the sharing AP 10. In other words, the non-AP MLD can be the end point on the terminal device 30 side in 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.

[0020] 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.

[0021] 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.

[0022] In this embodiment, AP MLD and non-AP MLD are configured to exchange data via wireless links between multiple affiliated APs provided in different access points and multiple affiliated STAs provided in the same terminal device 30. This type of data transmission method is also called a multi-AP transmission method.

[0023] The example of Figure 1 shows a case where the AP MLD in the sharing AP 10 and the non-AP MLD in the terminal device 30 exchange data using a wireless link between the affiliated AP 1 in the shared AP 20-1 and the affiliated STA 1 in the terminal device 30, and a wireless link between the affiliated AP 2 in the shared AP 20-2 and the affiliated STA 2 in the terminal device 30.

[0024] 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 wireless communication.

[0025] 1.1.2 Hardware Configuration Next, the hardware configuration of the sharing AP, the shared AP, and the terminal device in the communication system according to the first embodiment will be described.

[0026] 2 is a block diagram showing an example of the hardware configuration of a sharing AP according to embodiment 1. 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 wireless communication module 14, a wired communication module 15, and an oscillator 16.

[0027] 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 wireless communication module 14 is a circuit used to send and receive data via wireless signals. The wireless communication module 14 is connected to an antenna. The wired communication module 15 is a circuit used to send and receive data via wired signals. The wired communication module 15 is connected to the network 40. The oscillator 16 functions as a clock that generates time information used within the sharing AP 10. The time information is also called a TSF (time synchronization function) timer. The accuracy of the TSF timer generated by the oscillator 16 is high enough to be used as a TSF timer (reference timer) that serves as a reference when the sharing AP 10, the shared AP 20, and the terminal device 30 operate in synchronization with each other. In the first embodiment, the TSF timer generated by the oscillator 16 coincides with the reference timer.

[0028] 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 embodiment 1. 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 an oscillator 25.

[0029] 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 work area for the CPU 21. The wireless communication module 24 is a circuit used for sending and receiving data via wireless signals. The wireless communication module 24 is connected to an antenna. The oscillator 25 operates independently of the oscillator 16 and functions as a clock for generating a TSF timer used in the shared AP 20. The accuracy of the TSF timer generated by the oscillator 25 does not need to be high enough to be used as a reference timer. In other words, the TSF timer generated by the oscillator 25 may have an offset from the reference timer.

[0030] 1.1.2.3 Hardware Configuration of Terminal Device Fig. 4 is a block diagram showing an example of the hardware configuration of a terminal device according to Embodiment 1. As shown in Fig. 4, the terminal device 30 includes, for example, a CPU 31, a ROM 32, a RAM 33, a wireless communication module 34, a display 35, a storage 36, and an oscillator 37.

[0031] The CPU 31 is a processing circuit that controls the overall operation of the terminal device 30. The ROM 32 is, for example, a non-volatile semiconductor memory. The ROM 32 stores programs and data for controlling the terminal device 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 device 30. The oscillator 37 operates independently of the oscillators 16 and 25 and functions as a clock for generating a TSF timer used within the terminal device 30. The accuracy of the TSF timer generated by the oscillator 37 does not need to be high enough to be usable as a reference timer. That is, the TSF timer generated by the oscillator 37 may have an offset with respect to the reference timer.

[0032] 1.1.3 Functional Configuration Next, the functional configuration of the sharing AP, the shared AP, and the terminal device in the communication system according to the first embodiment will be described.

[0033] 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 the first embodiment.

[0034] The sharing AP 10 functions as a computer including a reference timer generation unit 100, a data processing unit 110, a management unit 120, a frame processing unit 130, and radio signal processing units 140 and 150. The data 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 radio signal processing units 140 and 150 are functional blocks that execute processing corresponding to layer 1. The reference timer generation unit 100, the data processing unit 110, the management unit 120, and the frame processing unit 130 function as an AP MLD.

[0035] The reference timer generating unit 100 generates a reference timer based on the output of the oscillator 16. The reference timer generating unit 100 outputs the generated reference timer to the management unit 120.

[0036] The data processing unit 110 outputs data input from the network 40 via the LLC layer to the frame processing unit 130. The data processing unit 110 also outputs data input from the frame processing unit 130 to the network 40 via the LLC layer.

[0037] 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 a multi-AP connection process in response to an association request from the terminal device 30. The management unit 120 also manages the offset between the reference timer and the TSF timer applied to each of the shared APs 20-1 and 20-2. The management unit 120 stores multi-AP management information 121, terminal management information 122, and time management information 123.

[0038] FIG. 6 is a diagram illustrating an example of the data structure of multi-AP management information stored in a sharing AP according to the first embodiment.

[0039] 6, information about various entities (i.e., AP MLD, affiliated AP1, and affiliated AP2) on the access point side used in the multi-AP transmission method 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 method specifically includes, for example, an identifier, a frequency band, capability information, and operation parameters.

[0040] The identifier may include, for example, the MAC address of the corresponding entity.

[0041] 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.

[0042] The capability information includes, for example, information indicating whether the corresponding entity supports the multi-AP transmission method.

[0043] 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.

[0044] It should be noted that the frequency band, capability information, and operation parameters related to AP MLD do not necessarily need to be stored.

[0045] FIG. 7 is a diagram illustrating an example of a data structure of terminal management information stored in the sharing AP according to the first embodiment.

[0046] 7, the terminal management information 122 stores information about the connection status of the terminal device 30 that is 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 that is wirelessly connected to affiliated STA1, and a set of an identifier of affiliated STA2 and an identifier of an affiliated AP that is wirelessly connected to affiliated STA2. Here, the identifiers include the MAC address of the target entity.

[0047] 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.

[0048] Prior to the start of the multi-AP connection, the management unit 120 transmits a MAC frame (beacon frame) including information stored in the multi-AP management information 121 to the shared APs 20-1 and 20-2 belonging to the sharing AP 10 using the wireless signal processing units 140 and 150. During the association process, the management unit 120 also transmits an association notification based on the multi-AP management information 121 and the terminal management information 122 to the shared APs 20-1 and 20-2 belonging to the sharing AP 10 using the wireless signal processing units 140 and 150.

[0049] FIG. 8 is a diagram showing an example of the data structure of time management information stored in the sharing AP according to the first embodiment.

[0050] As shown in FIG. 8, the time management information 123 stores information about the offset of the TSF timer applied to each of the shared APs 20-1 and 20-2 relative to a reference timer at a certain time (timestamp).

[0051] For example, if the offset of the TSF timer of shared AP 20-1 relative to the reference timer is +X (>0) seconds, the TSF timer of shared AP 20-1 is X seconds ahead of the reference timer. If the offset of the TSF timer of shared AP 20-2 relative to the reference timer is −X (<0) seconds, the TSF timer of shared AP 20-2 is X seconds behind the reference timer.

[0052] After the multi-AP connection is started, the management unit 120 transmits beacon frames related to time synchronization to the shared APs 20-1 and 20-2 belonging to the sharing AP 10 using the wireless signal processing units 140 and 150.

[0053] FIG. 9 is a diagram illustrating an example of a beacon frame related to time synchronization transmitted from a sharing AP according to the first embodiment.

[0054] 9, the beacon frame related to time synchronization transmitted from the sharing AP 10 includes information stored in the time management information 123. Specifically, for example, the beacon frame includes the identifier of the sharing AP 10, the timestamp of the reference timer, the offset of the TSF timer of the shared AP 20-1 relative to the reference timer, and the offset of the TSF timer of the shared AP 20-2 relative to the reference timer. Here, the identifier of the sharing AP 10 may be read as the identifier of the AP MLD.

[0055] Referring again to FIG. 5, the functional configuration of the sharing AP 10 will be described.

[0056] When data is input from data processing unit 110 or management unit 120, frame processing unit 130 generates a MAC frame by adding a MAC header to the input data. Frame processing unit 130 then distributes the MAC frame to either radio signal processing unit 140 or 150. Frame processing unit 130 may determine the distribution destination of the MAC frame according to a traffic identifier (TID) associated with an access category.

[0057] Furthermore, when a MAC frame is input from radio signal processing units 140 and 150, frame processing unit 130 extracts data from the MAC frame and outputs the extracted data to data processing unit 110 or management unit 120 depending on the type of MAC frame. Specifically, when the MAC frame is a data frame, frame processing unit 130 inputs the data to data processing unit 110. When the MAC frame is a management frame or a control frame, frame processing unit 130 inputs the data to management unit 120.

[0058] Each of the radio signal processing units 140 and 150 generates a radio frame by adding a preamble or the like to the MAC frame input from the frame processing unit 130. Each of the radio signal processing units 140 and 150 converts the generated radio frame into a radio signal. Each of the radio signal processing units 140 and 150 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, OFDM modulation, and frequency conversion. Each of the radio signal processing units 140 and 150 also converts the radio signal received from the corresponding shared AP 20 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. Each of the radio signal processing units 140 and 150 extracts a MAC frame from the converted radio frame, and then outputs the extracted MAC frame to the frame processing unit 130.

[0059] The wireless signal processing units 140 and 150 are configured to transmit and receive wireless signals using different frequency bands or channels. For example, the wireless signal processing unit 140 is used to transmit wireless signals individually to one wireless signal processing unit of the shared AP 20-1. The wireless signal processing unit 150 is used to transmit wireless signals individually to one wireless signal processing unit of the shared AP 20-2. For example, the wireless signal processing units 140 and 150 may be used to transmit wireless signals containing the same information to multiple shared APs.

[0060] 1.1.3.2 Functional Configuration of Shared AP FIG. 10 is a block diagram showing an example of the functional configuration of a shared AP according to the first embodiment.

[0061] The shared AP 20 functions as a computer including a management unit 210, a frame processing unit 220, and radio signal processing units 230 and 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 units 230 and 240 are functional blocks that execute processing corresponding to the first layer. The management unit 210, the frame processing unit 220, and the radio signal processing unit 240 function as an affiliated AP.

[0062] Prior to starting the multi-AP transmission method, the management unit 210 generates a beacon frame including information related to the multi-AP transmission method. The beacon frame related to the multi-AP transmission method includes the multi-AP management information 121 received from the sharing AP 10. More specifically, the beacon frame related to the multi-AP transmission method 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 device 30 of the generated beacon frame related to the multi-AP transmission method via the wireless signal processing unit 240.

[0063] 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.

[0064] FIG. 11 is a diagram showing an example of the data structure of link management information stored in the shared AP according to the first embodiment.

[0065] 11 , in the multi-AP transmission method, information about affiliated STAs that are physically connected wirelessly to affiliated APs in the shared AP 20 is stored in the link management information 211. The information about affiliated STAs that are connected to affiliated APs in the shared AP 20 specifically includes, for example, identifiers.

[0066] 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.

[0067] After the start of the multi-AP connection, the management unit 210 manages the TSF timer applied to its own station so that the offset from the reference timer falls within a threshold value (for example, ±15 μs), and shares the offset with the sharing AP 10. The management unit 210 then transmits a beacon frame used for time synchronization with the terminal device 30 to the terminal device 30 using the wireless signal processing unit 240. The management unit 210 may further store time management information 123 transmitted from the sharing AP 10.

[0068] FIG. 12 is a diagram illustrating an example of a beacon frame related to time synchronization transmitted from a shared AP according to the first embodiment.

[0069] As shown in FIG. 12 , a beacon frame related to time synchronization transmitted from the shared AP 20 includes information related to the TSF timer applied to the shared AP 20 itself. Specifically, for example, the beacon frame includes an identifier of the sharing AP 10, an identifier of the shared AP 20 of the shared AP 20 itself, a timestamp of the TSF timer of the shared AP 20 of the shared AP 20 itself, and an offset of the TSF timer of the shared AP 20 of the other station. Here, the offset of the TSF timer of the shared AP 20 of the other station may be an offset relative to the TSF timer of the shared AP 20 of the shared AP 20 of the own station or an offset relative to the reference timer. If the offset of the TSF timer of the shared AP 20 of the other station is an offset relative to the reference timer, the beacon frame further includes a timestamp of the reference timer or an offset of the TSF timer of the shared AP 20 of the own station relative to the reference timer. Note that the offset of the TSF timer of the shared AP 20 of the other station may not be included in the beacon frame and may be transmitted to the terminal device 30 in response to a request from the terminal device 30.

[0070] Referring again to FIG. 10, the functional configuration of the shared AP 20 will be described.

[0071] When a MAC frame is input from sharing AP 10 via wireless signal processing unit 230, frame processing unit 220 extracts data from the MAC frame and performs processing according to the type of MAC frame. Specifically, if the MAC frame is a data frame, frame processing unit 220 re-attaches a MAC header to the data and inputs it to wireless signal processing unit 240. If the MAC frame is a management frame or control frame, frame processing unit 220 inputs the data to management unit 210. Furthermore, when a MAC frame is input from a wirelessly connected affiliated STA via wireless signal processing unit 240, frame processing unit 220 re-attaches a MAC header to the data extracted from the MAC frame and inputs it to wireless signal processing unit 230.

[0072] The radio signal processing units 230 and 240 generate radio frames by adding a preamble and the like to the MAC frames input from the frame processing unit 220. The radio signal processing units 230 and 240 convert the generated radio frames into radio signals. The radio signal processing units 230 and 240 then radiate (transmit) the converted radio signals via antennas to the sharing AP 10 and the wirelessly connected affiliated STAs, respectively. The conversion process from radio frames to radio signals 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 radio signals received from the sharing AP 10 via the antenna into radio frames. The radio signal processing unit 240 converts radio signals received from the terminal device 30 via the antenna into radio frames. 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 units 230 and 240 extract MAC frames from the converted radio frames. The radio signal processing units 230 and 240 then input the extracted MAC frames to the frame processing unit 220.

[0073] 1.1.3.3 Functional Configuration of Terminal Device FIG. 13 is a block diagram showing an example of the functional configuration of the terminal device according to the first embodiment.

[0074] The terminal device 30 functions as a computer including an application execution unit 300, a data processing unit 310, a management unit 320, a frame processing unit 330, radio signal processing units 340 and 350, and TSF timer management units 360 and 370. The application execution unit 300 is a functional block that executes processing corresponding to layer 7. The data 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, and the TSF timer management units 360 and 370 are functional blocks that execute processing corresponding to layer 1. The data 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 and the TSF timer management unit 360 function as an affiliated STA1. The radio signal processing unit 350 and the TSF timer management unit 370 function as the affiliated STA2.

[0075] The application execution unit 300 executes an application based on data input from the data processing unit 310. The application execution unit 300 also inputs data to the data 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.

[0076] The data processing unit 310 outputs data input from the application execution unit 300 via the LLC layer to the frame processing unit 330. The data processing unit 310 also outputs data input from the frame processing unit 330 to the application execution unit 300 via the LLC layer.

[0077] 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 related to the multi-AP connection from the shared AP 20. The management unit 320 stores link management information 321. The management unit 320 also stores information included in the beacon frame related to the multi-AP connection from the shared AP 20, which is part of the multi-AP management information 121.

[0078] Fig. 14 is a diagram showing an example of the data structure of link management information stored in the terminal device according to the first embodiment. Fig. 14 shows the data structure of link management information 321 as an example of information stored in the terminal device 30 in addition to the information included in the beacon frame.

[0079] 14, in the multi-AP transmission method, link management information 321 stores information about the affiliated APs that are physically connected to affiliated STA1 and affiliated STA2 within terminal device 30. The information about the affiliated APs that are physically connected to affiliated STA1 and affiliated STA2 specifically includes, for example, identifiers.

[0080] 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.

[0081] Referring again to FIG. 10, the functional configuration of the terminal device 30 will be described.

[0082] The management unit 320 stores information equivalent to the time management information 123 based on beacon frames related to time synchronization from the shared AP 20. The management unit 320 then manages the discrepancy between the TSF timer of the shared AP 20 and the TSF timers applied to the non-AP MLD, affiliated STA1, and affiliated STA2. Specifically, the management unit 320 notifies the TSF timer management unit 360 of information related to the TSF timer of the shared AP 20-1, which includes the affiliated AP 1 that is the wireless connection destination of the affiliated STA1. The management unit 320 notifies the TSF timer management unit 370 of information related to the TSF timer of the shared AP 20-2, which includes the affiliated AP 2 that is the wireless connection destination of the affiliated STA2. Furthermore, if the beacon frame related to time synchronization from the shared AP 20 includes information about the reference timer, the management unit 320 may synchronize the TSF timer of the non-AP MLD with the reference timer.

[0083] When data is input from data processing unit 310, frame processing unit 330 generates a MAC frame by adding a MAC header to the input data. Frame processing unit 330 then distributes the MAC frame to either radio signal processing unit 340 or 350. Frame processing unit 330 may determine the distribution destination of the MAC frame according to the TID.

[0084] Furthermore, when a MAC frame is input from radio signal processing units 340 and 350, frame processing unit 330 extracts data from the MAC frame and outputs the extracted data depending on the type of MAC frame to data processing unit 310 or management unit 320. Specifically, when the MAC frame is a data frame, frame processing unit 330 inputs the data to data processing unit 310. When the MAC frame is a management frame or a control frame, frame processing unit 330 inputs the data to management unit 320.

[0085] 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 .

[0086] TSF timer management units 360 and 370 each manage the TSF timer of affiliated STA1 and the TSF timer of affiliated STA2 based on information related to the offset notified by management unit 320. Specifically, TSF timer management unit 360 synchronizes the TSF timer of affiliated STA1 with the TSF timer of shared AP 20-1 notified by management unit 320. TSF timer management unit 370 synchronizes the TSF timer of affiliated STA2 with the TSF timer of shared AP 20-1 notified by management unit 320.

[0087] In this way, the terminal device 30 generates three types of TSF timers to be applied respectively to the non-AP MLD, affiliated STA1, and affiliated STA2 from the oscillator 37. Then, the terminal device 30 synchronizes the TSF timer of the non-AP MLD with the reference timer, synchronizes the TSF timer of affiliated STA1 with the TSF timer of shared AP 20-1, and synchronizes the TSF timer of affiliated STA2 with the TSF timer of shared AP 20-2.

[0088] 1.2 Operation Next, the operation of the communication system according to the first embodiment will be described.

[0089] 1.2.1 Time Synchronization Processing Fig. 15 is a sequence diagram showing an example of time synchronization processing in the communication system according to the first embodiment. Fig. 15 shows the flow of information exchanged among the sharing AP 10 (AP MLD), shared AP 20-1 (affiliated AP 1), shared AP 20-2 (affiliated AP 2), affiliated STA 1, affiliated STA 2, and non-AP MLD during time synchronization processing when a multi-AP connection is established.

[0090] The sharing AP 10 transmits a beacon frame including the time management information 123 to each of the shared APs 20-1 and 20-2 (S10).

[0091] The shared AP 20-1 executes synchronization processing with the reference timer based on the beacon frame related to time synchronization received in the processing of S10 (S11). Specifically, the shared AP 20-1 compares the timestamp of the reference timer included in the beacon frame received in the processing of S10 with the TSF timer of the shared AP 20-1. If the comparison shows that the offset between the timestamp of the reference timer and the TSF timer of the shared AP 20-1 is equal to or greater than a threshold, the shared AP 20-1 overwrites the TSF timer of the shared AP 20-1 with the timestamp of the reference timer. If the offset between the timestamp of the reference timer and the TSF timer of the shared AP 20-1 is less than the threshold, the shared AP 20-1 uses the TSF timer of the shared AP 20-1 as is.

[0092] After the synchronization process in S11, the shared AP 20-1 calculates the offset of the TSF timer of the shared AP 20-1 relative to the reference timer (S12).

[0093] Similarly, the shared AP 20-2 executes synchronization processing with the reference timer based on the beacon frame related to time synchronization received in the processing of S10 (S13). Specifically, the shared AP 20-2 compares the timestamp of the reference timer included in the beacon frame received in the processing of S10 with the TSF timer of the shared AP 20-2. If the comparison shows that the offset between the timestamp of the reference timer and the TSF timer of the shared AP 20-2 is equal to or greater than a threshold, the shared AP 20-2 overwrites the TSF timer of the shared AP 20-2 with the reference timer. If the offset between the timestamp of the reference timer and the TSF timer of the shared AP 20-2 is less than the threshold, the shared AP 20-2 uses the TSF timer of the shared AP 20-2 as is.

[0094] After the synchronization process in S13, the shared AP 20-2 calculates the offset of the TSF timer of the shared AP 20-2 relative to the reference timer (S14).

[0095] After the processes of S13 and S14, each of the shared APs 20-1 and 20-2 notifies the sharing AP 10 of the calculated offset (S15).

[0096] The sharing AP 10 updates the offset stored in the time management information 123 based on the offset notified in the process of S15 (S16). The offset updated in the process of S16 is reflected in the next beacon frame related to time synchronization transmitted from the sharing AP 10. In this way, the sharing AP 10 periodically broadcasts a beacon frame related to time synchronization and manages the TSF timer of the shared AP 20 to which it belongs by obtaining information on the latest offset.

[0097] Each of the shared APs 20-1 and 20-2 transmits a beacon frame related to time synchronization to the non-AP MLD via the affiliated STA connected wirelessly (S17).

[0098] The non-AP MLD executes synchronization processing with the reference timer based on the beacon frame related to time synchronization received in the processing of S17 (S18). Specifically, the non-AP MLD calculates the TSF timers of the shared APs 20-1 and 20-2 based on the timestamp and offset of the shared AP 20 included in the beacon frame received in the processing of S17. The non-AP MLD then overwrites the TSF timer of the non-AP MLD with the calculated TSF timer. Note that if the reference timer can be calculated based on the timestamp and offset of the shared AP 20 included in the beacon frame received in the processing of S17, the non-AP MLD may overwrite the TSF timer of the non-AP MLD with the reference timer.

[0099] The non-AP MLD notifies the corresponding affiliated STAs of the TSF timers of the shared APs 20-1 and 20-2 calculated in the process of S18 (S19).

[0100] Based on the TSF timer received in the process of S19, the affiliated STA1 executes a synchronization process with the TSF timer of the wirelessly connected shared AP 20-1 (S20). Specifically, the affiliated STA1 overwrites the TSF timer of the affiliated STA1 with the TSF timer of the shared AP 20-1.

[0101] Similarly, the affiliated STA2 executes a synchronization process with the TSF timer of the wirelessly connected shared AP 20-2 based on the TSF timer received in the process of S19 (S21). Specifically, the affiliated STA2 overwrites the TSF timer of the affiliated STA2 with the TSF timer of the shared AP 20-2.

[0102] This completes the time synchronization process.

[0103] 1.2.2 R-TWT Collaboration Processing Fig. 16 is a sequence diagram showing an example of R-TWT collaboration processing in the communication system according to the first embodiment. Fig. 16 shows, as an example, a series of processes up to the execution of communication processing in the R-TWT SP (service period) based on the occurrence of periodic low-latency traffic between the sharing AP 10 and the non-AP MLD.

[0104] When the application execution unit 300 expects low-latency traffic to occur (starts), the non-AP MLD transmits a bandwidth allocation request in the R-TWT SP to the sharing AP 10 (S30).

[0105] Upon receiving the bandwidth allocation request for the R-TWT SP, the sharing AP 10 inquires of each of the shared APs 20-1 and 20-2 whether the R-TWT SP can be set and whether a bandwidth to be used for traffic transmission and reception can be allocated (S31).

[0106] In response to the inquiry received in the process of S31, each of the shared APs 20-1 and 20-2 responds to the sharing AP 10 with the determination result as to whether or not the R-TWT SP can be set and whether or not a band to be used for transmitting and receiving traffic can be allocated (S32).

[0107] Based on the response received in the process of S32, the sharing AP 10 determines the shared AP 20 that will set up the R-TWT SP, and transmits the response to the bandwidth allocation request received in the process of S30 to the non-AP MLD (S33). If multiple shared APs 20-1 and 20-2 are compatible, highly reliable bandwidth allocation can be performed by aligned link processing, which simultaneously communicates via multiple wireless links in the same R-TWT SP.

[0108] When receiving a response to the bandwidth allocation request, the non-AP MLD determines the affiliated STA that will transmit and receive low latency traffic in the R-TWT SP, and notifies each of affiliated STA1 and affiliated STA2 (S34).

[0109] The sharing AP 10 notifies the shared APs 20-1 and 20-2 of information regarding the start of the R-TWT SP (S35). The information regarding the start of the R-TWT SP includes, for example, the start time, period, and interval length of the R-TWT SP. Here, the start time of the R-TWT SP notified by the sharing AP 10 is notified by a reference timer.

[0110] Each of the shared APs 20-1 and 20-2 transmits a beacon frame including information regarding the start of the R-TWT SP received in the process of S35 to the non-AP MLD via the affiliated STA connected wirelessly (S36).

[0111] Here, the start time of the R-TWT SP notified from each of the shared APs 20-1 and 20-2 is notified by the TSF timer of the local station so as to be synchronized with the start time of the R-TWT SP notified by the reference timer. In other words, if there is an offset between the reference timer and the TSF timer of the local station, the start time of the R-TWT SP in the TSF timer of the local station is set to a time shifted by the offset from the start time of the R-TWT SP in the reference timer. Specifically, if the reference timer is X seconds ahead of the TSF timer of the shared AP 20-1, the shared AP 20-1 sets the start time of the R-TWT SP in the TSF of the shared AP 20-1 to a time delayed by X seconds from the start time of the R-TWT SP in the reference timer.

[0112] When the align link process is executed, the beacon frame transmitted in the process of S36 includes information indicating that multiple wireless links are assigned to the same R-TWT SP.

[0113] When the R-TWT SP starts, the shared AP 20 to which the bandwidth is allocated, out of the shared APs 20-1 and 20-2, transmits a trigger frame to the corresponding affiliated STA (S37).

[0114] When low-latency traffic occurs in the application execution unit 300, the non-AP MLD outputs data to the corresponding affiliated STA (S38).

[0115] The affiliated STA that received the data in the process of S38 transmits the data to the corresponding shared AP 20 based on the information regarding bandwidth allocation included in the trigger frame received in the process of S37 (S39).

[0116] The shared AP 20 that received the data in the process of S39 transfers the data to the sharing AP 10 (S40).

[0117] The processes of S37 to S40 are repeatedly executed for a plurality of R-TWT SPs set for each interval length included in the information relating to the start of the R-TWT SP.

[0118] This completes the R-TWT cooperation process.

[0119] 1.3 Effects of the First Embodiment According to the first embodiment, the sharing AP 10 transmits a timestamp related to the reference timer to the shared APs 20-1 and 20-2. Each of the shared APs 20-1 and 20-2 transmits the offset of its own TSF timer relative to the reference timer to the sharing AP 10 based on the timestamp related to the reference timer. The sharing AP 10 shares the offset received from each of the shared APs 20-1 and 20-2 with the shared APs 20-1 and 20-2. This allows the sharing AP 10 and each of the shared APs 20-1 and 20-2 to share information related to time synchronization.

[0120] Furthermore, the terminal device 30 receives beacon frames related to time synchronization from the shared APs 20-1 and 20-2. This allows the TSF timers of the non-AP MLD in the terminal device 30, the TSF timer of the affiliated STA1, and the TSF timer of the affiliated STA2 to be synchronized with the reference timer, the TSF timer of the shared AP 20-1, and the TSF timer of the shared AP 20-2, respectively. Therefore, in the collaborative processing in the R-TWT SP, it is possible to synchronize the affiliated STA1 and the affiliated STA2 with the wirelessly connected shared APs 20-1 and 20-2, respectively, while also performing time synchronization between the wireless links.

[0121] Furthermore, the aligned link process allows affiliated STA1 and affiliated STA2 to transmit data in the same R-TWT SP via wireless links with shared APs 20-1 and 20-2, respectively. This allows, for example, redundant communication in which the same data is transmitted over multiple wireless links in the same R-TWT SP. This allows for highly reliable data communication.

[0122] 2. Second Embodiment Next, a second embodiment will be described. The second embodiment differs from the first embodiment in that the TSF timer generated by the oscillator 16 is not used as a reference timer. The following mainly describes configurations and operations that differ from the first embodiment. Descriptions of configurations and operations that are equivalent to those of the first embodiment will be omitted as appropriate.

[0123] 2.1 Sharing AP Fig. 17 is a block diagram showing an example of the functional configuration of a sharing AP according to the second embodiment. Fig. 17 corresponds to Fig. 5 in the first embodiment.

[0124] As shown in FIG. 17, the sharing AP 10A includes a reference timer generation unit 100A instead of the reference timer generation unit 100.

[0125] The reference timer generation unit 100A generates a reference timer based on the TSF timers of the shared APs 20-1 and 20-2, in addition to the output of the oscillator 16. The reference timer generation unit 100A outputs the generated reference timer to the management unit 120.

[0126] Specifically, for example, the reference timer generation unit 100A updates the reference timer with the average value of the TSF timer generated by the oscillator 16, the TSF timer of the shared AP 20-1, and the TSF timer of the shared AP 20-2. When updating the reference timer, any TSF timer that deviates from the reference timer before the update by a threshold value or more may be excluded from the calculation of the average value.

[0127] In the second embodiment, the accuracy of the TSF timer generated by the oscillator 25 included in the shared AP 20 is high enough to be used as a reference timer.

[0128] 2.2 Reference Timer Generation Process Fig. 18 is a sequence diagram showing an example of a reference timer generation process in the communication system according to the second embodiment. Fig. 18 shows the exchange of information between the sharing AP 10A and the shared AP 20 when the sharing AP 10A generates a reference timer.

[0129] The sharing AP 10A periodically requests information about the TSF timer from the shared APs 20-1 and 20-2 (S50).

[0130] In response to the request from the TSF timer, each of the shared APs 20-1 and 20-2 notifies the sharing AP 10A of information relating to its own TSF timer (S51).

[0131] The sharing AP 10A updates the reference timer based on the TSF timers of the shared APs 20-1 and 20-2 received in the process of S51 and the TSF timer generated by the oscillator 16 (S52).

[0132] This completes the reference timer generation process.

[0133] 2.3 Effects of the Second Embodiment According to the second embodiment, the reference timer is generated as the average value of the TSF timers of multiple access points. As a result, even if the accuracy of any of the TSF timers of multiple access points deteriorates, the reference timer can be generated without being affected by the deterioration. Therefore, a more stable reference timer can be generated than when the reference timer is generated from a single TSF timer.

[0134] 3. Modifications, etc. Various modifications can be applied to the first and second embodiments described above.

[0135] 3.1 First Modification In the first and second embodiments described above, the oscillator 16 included in the sharing APs 10 and 10A is described as being capable of generating a TSF timer with sufficient accuracy to be used as a reference timer. However, this is not limited to this. For example, the oscillator 16 included in the sharing APs 10 and 10A does not have to be capable of generating a TSF timer with sufficient accuracy to be used as a reference timer. In this case, the sharing APs 10 and 10A may obtain the TSF timer from outside the communication system 1.

[0136] Fig. 19 is a block diagram showing an example of the functional configuration of a sharing AP according to Modification 1. Fig. 19 corresponds to Fig. 5 in the first embodiment.

[0137] 19 , the sharing AP 10B includes a reference timer generation unit 100B. The reference timer generation unit 100B acquires, via the network 40, a TSF timer that has sufficient accuracy to be usable as a reference timer from outside the communication system 1.

[0138] Specifically, for example, the reference timer generation unit 100B may acquire the TSF timer from a time server on the network 40. The time server may be implemented as an NTP (network time protocol) server. In this case, communication between the reference timer generation unit 100B and the NTP server may be performed according to the NTP. To achieve more accurate time synchronization, communication between the reference timer generation unit 100B and the NTP server may be performed according to the IEEE 802.1AS-2011 standard.

[0139] Furthermore, for example, the sharing AP 10B may include a global positioning system (GPS) receiver. In this case, the reference timer generation unit 100B may generate the TSF timer based on time information acquired from the GPS receiver.

[0140] According to the first modification, the sharing AP 10B can generate a reference timer for synchronizing various devices in the communication system 1 even if it does not have an oscillator 16 capable of generating a highly accurate TSF timer.

[0141] Furthermore, when time synchronization processing is performed in a wider area communication system using a plurality of multi-AP connections by a plurality of sharing APs, time synchronization between the plurality of sharing APs can be easily performed.

[0142] 3.2 Second Modification In the above-described first and second embodiments, the AP MLD and each of the multiple affiliated APs are located at positions separated from each other, but the present invention is not limited to this.

[0143] Fig. 20 is a block diagram showing an example of the configuration of a communication system according to Modification 2. Fig. 20 corresponds to Fig. 1 in the first embodiment.

[0144] 20 , in communication system 1C, at least one affiliated AP (affiliated AP1) among a plurality of affiliated APs may be provided in the same housing 5 as AP MLD. In this case, communication between AP MLD and affiliated AP1 may be performed via a wired connection.

[0145] According to the above-described configuration, the sharing AP 10 having the AP MLD and the shared AP 20-1 having the affiliated AP 1 are provided in the same housing 5. Therefore, the TSF timer of the sharing AP 10 and the TSF timer of the shared AP 20-1 may be the same.

[0146] According to the second modification, by matching the TSF timer of affiliated AP 1 with the reference timer and synchronizing the TSF of affiliated AP 2 with the reference timer, it is possible to perform time synchronization of the entire communication system 1C.

[0147] 3.3 Others The TSF timer and offset between the sharing AP 10, the shared AP 20, and the terminal device 30 may be values ​​that take into account propagation delays due to wireless communication and processing delays within the devices.

[0148] Furthermore, the time synchronization process, R-TWT cooperative control process, and reference timer generation process in the sharing AP 10, the shared AP 20, and the terminal device 30 can be stored as a program that can be executed by a processor, which is a computer. Alternatively, they can be stored and distributed in a storage medium of an external storage device such as a magnetic disk, optical disk, or semiconductor memory. The processors of the sharing AP 10, the shared AP 20, and the terminal device 30 can then load the program stored in the storage medium of the external storage device, and their operations can be controlled by the loaded program, thereby executing the time synchronization process, the R-TWT cooperative control process, and the reference timer generation process.

[0149] 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.

[0150] DESCRIPTION OF SYMBOLS 1, 1C...Communication system 5...Housing 10...Sharing AP 20...Shared AP 30...Terminal device 40...Network 11, 21, 31...CPU 12, 22, 32...ROM 13, 23, 33...RAM 14, 24, 34...Wireless communication module 15...Wired communication module 16, 25, 37...Oscillator 35...Display 36...Storage 100, 100A, 100B...Reference timer generation unit 110, 310...Data processing unit 120, 210, 320...Management unit 130, 220, 330...Frame processing unit 140, 150, 230, 240, 340, 350...Wireless signal processing unit 300...Application execution unit 360, 370...TSF timer management unit 121...Multi-AP management information 122...Terminal management information 123...Time management information 211, 321...Link management information

Claims

1. An access point serving as the first access point in a communication system including a first access point, a second access point, a third access point, and a terminal device, wherein the first access point is configured to: transmit a timestamp relating to a first timer corresponding to the first access point to the second access point and the third access point; receive from the second access point a first offset between the first timer and a second timer corresponding to the second access point; receive from the third access point a second offset between the first timer and a third timer corresponding to the third access point; and transmit the first offset and the second offset to each of the second access point and the third access point.

2. The access point of claim 1, wherein the first access point is configured to receive data from the terminal device, in response to a request from the terminal device, from a first time based on the first timer for a first period of time, via each of a first wireless link between the second access point and the terminal device and a second wireless link between the third access point and the terminal device.

3. An access point serving as the second access point in a communication system including a first access point, a second access point, a third access point, and a terminal device, wherein the second access point is configured to: receive from the first access point information indicating a first period starting from a first time based on a first timer corresponding to the first access point; and receive data from the terminal device via a first wireless link between the second access point and the terminal device for a second period starting from a second time based on the second timer and coinciding with the first period, based on a first offset between the first timer and a second timer corresponding to the second access point and the information.

4. A terminal device in a communication system including a first access point, a second access point, a third access point, and a terminal device, wherein the terminal device is configured to receive information regarding a second timer corresponding to the second access point and a third timer corresponding to the third access point, communicate with the second access point via a first wireless link based on the second timer, and communicate with the third access point via a second wireless link based on the third timer.

5. The terminal device according to claim 4, configured to: transmit data to the first access point via a first wireless link with the second access point over a second period starting from a second time based on the second timer, the second period being a period that coincides with a first period starting from a first time based on a first timer corresponding to the first access point; and transmit data to the first access point via a second wireless link with the third access point over a third period starting from a third time based on the third timer, the third period being a period that coincides with the first period.

6. A communication method by an access point as the first access point in a communication system including a first access point, a second access point, a third access point, and a terminal device, comprising: transmitting a timestamp related to a first timer corresponding to the first access point to the second access point and the third access point; receiving a first offset between the first timer and a second timer corresponding to the second access point from the second access point; receiving a second offset between the first timer and a third timer corresponding to the third access point from the third access point; and transmitting the first offset and the second offset to each of the second access point and the third access point.

7. A communication method by an access point serving as the second access point in a communication system including a first access point, a second access point, a third access point, and a terminal device, comprising: receiving information from the first access point indicating a first period starting from a first time based on a first timer corresponding to the first access point; and receiving data from the terminal device via a first wireless link between the second access point and the terminal device, for a second period starting from a second time based on the second timer and coinciding with the first period, based on a first offset between the first timer and a second timer corresponding to the second access point and the information.

8. A communication method by a terminal device in a communication system including a first access point, a second access point, a third access point, and the terminal device, comprising: receiving information regarding a second timer corresponding to the second access point and a third timer corresponding to the third access point; communicating with the second access point via a first wireless link based on the second timer; and communicating with the third access point via a second wireless link based on the third timer.

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