Access point, shared access point, and terminal

Abstract

An access point according to an embodiment comprises a management unit. In response to receiving a notification for transferring a remaining period of a transmission opportunity from a first terminal to a first access point, the management unit allocates at least a part of the remaining period of the transmission opportunity to a second access point having a different communicable area than the first access point.

Description

Access points, shared access points and terminals

[0001] Embodiments relate to an access point, a shared access point and a terminal.

[0002] In a wireless communication network such as a wireless LAN (Local Area Network), for example, an access point (AP) and a terminal, which is a station (STA), are wirelessly connected, and data is transmitted and received between the AP and the terminal via wireless communication. In this case, when transmitting data from a terminal to the AP, the terminal that transmits the data acquires a transmission opportunity such as a channel occupation period (TXOP), and transmits the data to the AP during the acquired transmission opportunity.

[0003] Furthermore, the IEEE 802.11be standard allows TXOP sharing, which shares transmission opportunities between an AP and multiple communication stations among terminals located in the communication area of ​​the AP. This allows transmission opportunities to be shared among multiple communication stations within a single BSS (basic service set). For example, after one of the terminals located in the communication area of ​​the AP transmits data to the AP during an acquired transmission opportunity, a remaining period of the transmission opportunity may occur. In this case, TXOP sharing is performed by the terminal that transmitted data to the AP transferring the remaining period of the transmission opportunity to either the AP to which the data is to be transmitted or another terminal located in the communication area of ​​the AP.

[0004] In a wireless communication network, when a remaining period of a transmission opportunity occurs after a terminal transmits data to an AP as described above, it is required to be able to allocate the remaining period of the transmission opportunity to either an AP other than the AP to which the data is transmitted or a terminal located in the communication area of ​​the AP other than the AP to which the data is transmitted. In other words, it is required to be able to allocate the remaining period of the acquired transmission opportunity to communication stations belonging to different BSSs, and to enable the transmission opportunity to be shared among multiple communication stations belonging to different BSSs.

[0005] IEEE802.11 Standard (IEEE Std 802.11TM-2020), Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, Section 10.23.2.7 (Sharing an EDCA TXOP), December 2020 IEEE802.11be Standard Draft (IEEE P802.11beTM / D4.1), Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, Amendment 8: Enhancements for extremely high throughput (EHT), Section 35.2.1.2 (Triggered TXOP sharing procedure), September 2023Shikhar Verma, Tiago Koketsu Rodrigues, Yuichi Kawamoto, and Nei Kato, “A Survey on Multi-AP Coordination Approaches over Emerging WLANs: Future Directions and Open Challenges” arXiv:2306.04164v1 [cs.NI], 7 June 2023

[0006] An object of the present invention is to provide an access point, a shared access point, and a terminal that enable a plurality of communication stations that belong to different BSSs to share transmission opportunities.

[0007] In one embodiment of the present invention, the access point includes a management unit, and in response to receiving a notification from a first terminal to transfer the remaining period of a transmission opportunity to the first access point, the management unit allocates at least a portion of the remaining period of the transmission opportunity to a second access point having a communication coverage area different from that of the first access point.

[0008] According to the present invention, it is possible to provide an access point, a shared access point, and a terminal that enable a plurality of communication stations that belong to different BSSs to share transmission opportunities.

[0009] FIG. 1 is a block diagram showing an example of the configuration of a communication system according to an embodiment. FIG. 2 is a schematic diagram showing an example of the arrangement in a building of communication stations that constitute the communication system according to an embodiment. FIG. 3 is a block diagram showing an example of the hardware configuration of a sharing AP according to an embodiment. FIG. 4 is a block diagram showing an example of the hardware configuration of a shared AP according to an embodiment. FIG. 5 is a block diagram showing an example of the hardware configuration of a terminal according to an embodiment. FIG. 6 is a block diagram showing an example of the functional configuration of a sharing AP according to an embodiment. FIG. 7 is a block diagram showing an example of the functional configuration of a shared AP according to an embodiment. FIG. 8 is a block diagram showing an example of the functional configuration of a terminal according to an embodiment. FIG. 9 is a flowchart showing an example of processing performed by a sharing AP when a transmission opportunity is shared among a plurality of communication stations that belong to different BSSs with respect to each other in the communication system according to the embodiment. FIG. 10 is a sequence diagram showing an example of communication processing performed in an operation of sharing a transmission opportunity among a plurality of communication stations that belong to different BSSs with respect to each other in the communication system according to the embodiment. FIG. 11 is a sequence diagram showing another example of communication processing, different from that shown in FIG. 10, performed in an operation of sharing a transmission opportunity among a plurality of communication stations that belong to different BSSs with respect to each other in the communication system according to the embodiment. Fig. 12 is a sequence diagram showing another example of communication processing performed in an operation of sharing transmission opportunities among multiple communication stations belonging to different BSSs in a communication system according to an embodiment, which is different from Figs. 10 and 11 . Fig. 13 is a schematic diagram showing an example of a format of a remaining period allocation frame used in the embodiment. Fig. 14 is a flowchart showing an example of processing performed by a first AP, which is one of the shared APs, when sharing transmission opportunities among multiple communication stations belonging to different BSSs in a certain modification. Fig. 15 is a sequence diagram showing an example of communication processing performed in an operation of sharing transmission opportunities among multiple communication stations belonging to different BSSs in a communication system according to the modification of Fig. 14 .

[0010] 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.

[0011] 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 and shared APs 20-1 and 20-2 as access points (APs), and terminals 30-1A, 30-1B, 30-2A, and 30-2B as stations (STAs). The sharing AP 10, the shared APs 20-1 and 20-2, and the terminals 30-1A, 30-1B, 30-2A, and 30-2B each function as a communication station in the communication system 1. In addition, a wireless network such as a wireless LAN is formed in the communication system 1.

[0012] In the following description, the sharing AP 10 will also be referred to as AP0, and the shared APs 20-1 and 20-2 will also be referred to as AP1 and AP2, respectively. The terminals 30-1A, 30-1B, 30-2A, and 30-2B will also be referred to as STA1A, STA1B, STA2A, and STA2B, respectively. The shared APs 20-1 and 20-2 have the same configuration. Therefore, unless otherwise specified, the shared APs 20-1 and 20-2 will also be simply referred to as the shared AP 20. The terminals 30-1A, 30-1B, 30-2A, and 30-2B have the same configuration. Therefore, unless otherwise specified, the terminals 30-1A, 30-1B, 30-2A, and 30-2B will also be simply referred to as the terminals 30.

[0013] In the communication system 1, the sharing AP 10 is connected to a network 40 and can communicate, via wired or wireless communication, with a server (not shown) on the network 40. The sharing AP 10 can also communicate, via wired or wireless communication, with each of the shared APs 20-1 and 20-2.

[0014] The shared APs 20-1 and 20-2 are installed in locations physically separated from each other and have different communication areas. In one example, a portion of the communication area of ​​the shared AP 20-1 overlaps with a portion of the communication area of ​​the shared AP 20-2. However, in another example, there may be no overlapping portion between the communication areas of the shared APs 20-1 and 20-2. Each shared AP 20 is capable of wireless communication with each terminal 30 located in its communication area. Each shared AP 20 performs wireless communication with each terminal 30 located in its communication area in accordance with, for example, the IEEE 802.11 standard.

[0015] Each of the terminals 30 is a wireless terminal such as a smartphone or a PC (Personal Computer). In the example of Fig. 1, each of the terminals 30-1A and 30-1B is located within the communication area of ​​the shared AP 20-1 and can communicate wirelessly with the shared AP 20-1. Each of the terminals 30-2A and 30-2B is located within the communication area of ​​the shared AP 20-2 and can communicate wirelessly with the shared AP 20-2.

[0016] Furthermore, in the communication system 1, one BSS (basic service set) is formed by one shared AP 20 and terminals 30 located in the communication area of ​​the shared AP 20. In the example of Fig. 1, BSS1 is formed as a BSS by the shared AP 20-1 and terminals 30-1A, 30-1B, etc. located in the communication area of ​​the shared AP 20-1, and BSS2 is formed as a BSS by the shared AP 20-2 and terminals 30-2A, 30-2B, etc. located in the communication area of ​​the shared AP 20-2. Note that a BSS is also referred to as a "cell."

[0017] In the communication system 1, each of the terminals 30 can communicate with the sharing AP 10 via one or more of the shared APs 20 that are capable of wireless communication. Therefore, each of the terminals 30 can communicate with a server on the network 40 via one or more of the corresponding shared APs 20 and the sharing AP 10. In the example of FIG. 1 , each of the terminals 30-1A and 30-1B is connected to the sharing AP 10 via the shared AP 20-1, and each of the terminals 30-2A and 30-2B is connected to the sharing AP 10 via the shared AP 20-2. The connection method between each of the terminals 30 and the sharing AP 10 as described above is also referred to as a "multi-AP connection method." Furthermore, each of the shared APs 20 is also referred to as an "access point belonging" to the sharing AP 10 in the multi-AP connection method. Therefore, the sharing AP 10 is also referred to as an "associated AP," and each of the shared APs 20 is also referred to as an "associated AP."

[0018] 2 is a schematic diagram showing an example of the arrangement of communication stations constituting a communication system in a building in an embodiment. In the example shown in FIG. 2, a building 50 is divided into four rooms 51, 52, 53, and 54, and a sharing AP 10 (AP0) is arranged in the center of the building 50. Each of shared APs 20-1 and 20-2 is capable of communicating with the sharing AP 10.

[0019] In the example of FIG. 2, rooms 51 and 52 are included in the communication range of shared AP 20-1 (AP1). Therefore, terminal 30-1A (STA1A) located in room 51 and terminal 30-1B (STA1B) located in room 52 can each wirelessly communicate with shared AP 20-1 and are connected to sharing AP 10 via shared AP 20-1. Also, in the example of FIG. 2, rooms 53 and 54 are included in the communication range of shared AP 20-2 (AP2). Therefore, terminal 30-2A (STA2A) located in room 53 and terminal 30-2B (STA2B) located in room 54 can each wirelessly communicate with shared AP 20-2 and are connected to sharing AP 10 via shared AP 20-2.

[0020] Each of the sharing AP 10, the shared AP 20, and the terminal 30 has a wireless communication function based on, for example, the OSI (Open Systems Interconnection) reference model. In the OSI reference model, the wireless communication function is divided into seven layers (Layer 1: Physical Layer, Layer 2: Data Link Layer, Layer 3: Network Layer, Layer 4: Transport Layer, Layer 5: Session Layer, Layer 6: Presentation Layer, and Layer 7: Application Layer). The data link layer includes a Logical Link Control (LLC) sublayer and a Media Access Control (MAC) sublayer.

[0021] Fig. 3 is a block diagram showing an example of the hardware configuration of a sharing AP according to an embodiment. Fig. 3 shows an example in which the sharing AP 10 communicates with a server on a network 40 via wired communication and with each of the shared APs 20 via wireless communication. As shown in Fig. 3, the sharing AP 10 includes, for example, a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a wireless communication module 14, and a wired communication module 15.

[0022] 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. In the example of FIG. 3 , the wireless communication module 14 can be connected (wirelessly connected) to the shared APs 20-1 and 20-2. The wired communication module 15 can be connected to a network 40.

[0023] Note that when the sharing AP 10 communicates wirelessly with a server on the network 40 and also communicates wired with each of the shared APs 20, the wireless communication module 14 can be connected to the network 40, and the wired communication module 15 can be connected (wirelessly) to the shared APs 20-1 and 20-2. Also, when the sharing AP 10 communicates wired with both the server on the network 40 and the shared AP 20, the sharing AP 10 does not have a wireless communication module 14. In this case, the wired communication module 15 can be connected to the network 40 and can be connected (wired) to the shared APs 20-1 and 20-2. Also, when the sharing AP 10 communicates wirelessly with both the server on the network 40 and the shared AP 20, the sharing AP 10 does not have a wired communication module 15. In this case, the wireless communication module 14 can be connected to the network 40 and can be connected (wirelessly) to the shared APs 20-1 and 20-2.

[0024] Fig. 4 is a block diagram showing an example of the hardware configuration of a shared AP according to an embodiment. Fig. 4 shows an example of a case where the shared AP 20 communicates wirelessly with the sharing AP 10. In one example, each of the shared APs 20-1 and 20-2 has the same hardware configuration as the example shown in Fig. 4. As shown in Fig. 4, the shared AP 20 includes, for example, a CPU 21, a ROM 22, a RAM 23, and a wireless communication module 24.

[0025] 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 for sending and receiving data via wireless signals. The wireless communication module 24 is connected to an antenna. The wireless communication module 24 can be connected (wirelessly connected) to the sharing AP 10 and to terminals 30 located in the communication area.

[0026] When the shared AP 20 communicates with the sharing AP 10 via a wired connection, the shared AP 20 is further provided with a wired communication module (not shown). In this case, the wireless communication module 24 can be connected to a terminal 30 located in a communication area, and the wired communication module can be connected (wired) to the sharing AP 10.

[0027] Fig. 5 is a block diagram showing an example of the hardware configuration of a terminal according to an embodiment. In one example, each of terminals 30-1A, 30-1B, 30-2A, and 30-2B has the same hardware configuration as the example shown in Fig. 5. As shown in Fig. 5, the terminal 30 includes, for example, a CPU 31, a ROM 32, a RAM 33, a wireless communication module 34, a display 35, and storage 36.

[0028] 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 wireless communication module 34 can be connected (wirelessly connected) to one or more corresponding shared APs 20. 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.

[0029] 6 is a block diagram showing an example of the functional configuration of a sharing AP according to an embodiment. As shown in FIG. 6, the sharing AP 10 functions as a computer including an upper layer processing unit 110, a management unit 120, a frame processing unit 130, and a transceiver unit 140. The upper layer processing unit 110 is a functional block that executes processing corresponding to the LLC sublayer of the second layer and layers 3 to 7. The management unit 120 and the frame processing unit 130 are functional blocks that execute processing corresponding to the MAC sublayer of the second layer. Furthermore, when the sharing AP 10 wirelessly communicates with each of the shared APs 20, the transceiver unit 140 is a functional block that executes processing corresponding to the MAC sublayer of the second layer and layer 1.

[0030] For example, upper layer processing unit 110 generates LLC packets by adding a DSAP (Destination Service Access Point) header, an SSAP (Source Service Access Point) header, etc. to data received from network 40. Then, upper layer processing unit 110 inputs the generated LLC packets to frame processing unit 130. Furthermore, upper layer processing unit 110 extracts data from the LLC packets input from frame processing unit 130. Then, upper layer processing unit 110 transmits the extracted data to network 40.

[0031] The management unit 120 manages the connection (logical connection) between the sharing AP 10 and each of the terminals 30 in the multi-AP connection method. In the multi-AP connection method, data is exchanged between the sharing AP 10 and each of the terminals 30 in a state where each of the terminals 30 is wirelessly connected to one or more corresponding shared APs 20. The management unit 120 manages, for each of the terminals 30, the wireless connection between the terminal 30 and one or more corresponding shared APs 20. In this way, the management unit 120 manages, for each of the multiple shared APs 20, the wireless connection between the terminal 30 and each of the terminals 30 located in the communication area.

[0032] The management unit 120 stores management information 121 related to the multi-AP connection method. The management unit 120 manages connections between the sharing AP 10 and each of the terminals 30 in the multi-AP connection method based on the management information 121. The management information 121 includes information related to access points used in the multi-AP connection method, i.e., information related to each of the sharing AP 10 and the shared AP 20. The information related to the access points used in the multi-AP connection method indicates, for example, information related to an identifier, a frequency band, and operation parameters for each of the access points used.

[0033] The AP information indicates, for each AP used, information about an identifier, such as a MAC address, and information about a frequency band used in a multi-AP connection method, such as a frequency band. Examples of applicable frequency bands include the 2.4 GHz band, the 5 GHz band, the 6 GHz band, the 45 GHz band, and the 60 GHz band. Each frequency band may include multiple channels. In this case, the AP information may indicate, for each AP used, information about a channel instead of or in addition to the information about the frequency band.

[0034] Furthermore, the information about APs indicates, for each AP used, information about operational parameters such as CWmin, CWmax, arbitration interframe space (AIFS), and transmission opportunity (TXOP) limit. CWmin and CWmax indicate the minimum and maximum values ​​of the contention window, respectively. The contention window is a parameter used to calculate backoff, which is a transmission waiting time for collision avoidance. AIFS is a fixed transmission waiting time set for each access category of traffic. Examples of traffic access categories include "VO (Voice)", "VI (Video)", "BE (Best Effort)", "BK (Background)", and "LL (Low Latency)". TXOP Limit indicates the upper limit of TXOP, which is the channel occupation period.

[0035] The management information 121 also includes information about the terminals 30 (e.g., terminals 30-1A, 30-1B, 30-2A, and 30-2B) connected to the sharing AP 10 in the multi-AP connection method. The information about the terminals indicates, for each of the terminals 30 connected to the sharing AP 10, information about the identifier of the terminal 30 and the identifier of the shared AP 20 through which the connection to the sharing AP 10 is made, for example. The information about the identifier of each connected terminal 30 indicates, for example, the MAC address of the terminal 30. The information about the identifier of the shared AP 20 through which the connection to the sharing AP 10 is made indicates, for example, the MAC address of the shared AP 20.

[0036] An LLC packet containing data is input to frame processing unit 130 from upper layer processing unit 110. When sharing AP 10 communicates wirelessly with each of shared APs 20, frame processing unit 130 generates a MAC frame by adding a MAC header to the LLC packet input from upper layer processing unit 110. Frame processing unit 130 then outputs the generated MAC frame to transceiver unit 140. When sharing AP 10 communicates wirelessly with each of shared APs 20, frame processing unit 130 extracts the LLC packet from the MAC frame input from transceiver unit 140. Frame processing unit 130 then outputs the extracted LLC packet to upper layer processing unit 110. In the following description, a MAC frame containing data is also referred to as a "data frame."

[0037] When sharing AP 10 communicates with each of shared APs 20 via wired communication, frame processing unit 130 outputs the LLC packet input from upper layer processing unit 110 to transceiver unit 140. Frame processing unit 130 also outputs the LLC packet input from transceiver unit 140 to upper layer processing unit 110.

[0038] Furthermore, notification information and control information are input to the frame processing unit 130 from the management unit 120. The notification information from the management unit 120 includes notification information to be notified to either the shared AP 20 or the terminal 30, and may include the information indicated by the management information 121 described above. Furthermore, the control information from the management unit 120 includes control information related to control of the operation of either the shared AP 20 or the terminal 30. When the sharing AP 10 communicates wirelessly with each of the shared APs 20, the frame processing unit 130 generates, as MAC frames, a management frame including the notification information from the management unit 120 and a control frame including the control information from the management unit 120. The frame processing unit 130 then outputs the generated management frame and control frame to the transmission / reception unit 140.

[0039] Furthermore, data, notification information, control information, etc. are input to frame processing unit 130 from transceiver unit 140. The notification information from transceiver unit 140 includes notification information notified from either shared AP 20 or terminal 30. Furthermore, the control information from transceiver unit 140 includes control information related to control of the operation of either sharing AP 10, shared AP 20, or terminal 30. When a data frame or LLC packet including data is input from transceiver unit 140, frame processing unit 130 outputs the LLC packet including data to upper layer processing unit 110. Furthermore, when either notification information or control information is input from transceiver unit 140, frame processing unit 130 outputs the input notification information, control information, etc. to management unit 120.

[0040] When the sharing AP 10 communicates wirelessly with each of the shared APs 20, a management frame and a control frame are input as MAC frames from the transmitting / receiving unit 140 to the frame processing unit 130. The frame processing unit 130 then outputs the notification information contained in the management frame from the transmitting / receiving unit 140 and the control information contained in the control frame from the transmitting / receiving unit 140 to the management unit 120. The management unit 120 also updates the above-mentioned management information 121 based on the notification information and the like input from the frame processing unit 130.

[0041] The transceiver 140 transmits and receives data, notification information, control information, and the like to and from each of the shared APs 20 to which it belongs via wireless or wired communication. When the sharing AP 10 communicates wirelessly with each of the shared APs 20, the transceiver 140 generates a wireless frame by adding a preamble or the like to a MAC frame (such as a data frame, management frame, or control frame) input from the frame processor 130, and converts the generated wireless frame into a wireless signal. The transceiver 140 then transmits (radiates) the converted wireless signal via an antenna. The conversion process from the wireless frame to the wireless signal includes, for example, convolutional coding, interleaving, subcarrier modulation, inverse fast Fourier transform, Orthogonal Frequency Division Multiplexing (OFDM) modulation, and frequency conversion.

[0042] Furthermore, when the sharing AP 10 communicates wirelessly with each of the shared APs 20, the transceiver 140 converts a wireless signal received from one of the shared APs 20 via an antenna into a wireless frame. The conversion process from a wireless signal to a wireless frame includes, for example, frequency conversion, OFDM demodulation, fast Fourier transform, subcarrier demodulation, deinterleaving, and Viterbi decoding. Each of the transceivers 140 extracts a MAC frame from the converted wireless frame and outputs the extracted MAC frame to the frame processor 130. In one example, multiple shared APs 20 belong to the sharing AP 10, and the multiple shared APs 20 transmit and receive wireless signals to and from the transceiver 140 of the sharing AP 10 using different frequency bands or channels.

[0043] When the sharing AP 10 communicates with each of the shared APs 20 via a wired network, the transmitting / receiving unit 140 is connected to each of the shared APs 20 to which the sharing AP 10 belongs via a wired network, and transmits and receives data, notification information, control information, etc. via the wired network to and from each of the shared APs 20. In this case, the transmitting / receiving unit 140 is configured from a network interface for the wired network.

[0044] The management unit 120 cooperates with the shared AP 20 and the terminal 30 to which it belongs, to perform allocation (mapping) of traffic transmitted and received between the sharing AP 10 and the terminal 30. As a result, traffic such as data transmitted from the sharing AP 10 is allocated to the shared AP 20 to which it belongs. Based on the traffic allocation result, the management unit 120 instructs the frame processing unit 130 on the destination of the traffic. Then, the frame processing unit 130 causes the transmission / reception unit 140 to transmit the traffic to the shared AP 20 corresponding to the instruction from the management unit 120.

[0045] FIG. 7 is a block diagram showing an example of the functional configuration of a shared AP according to an embodiment. In one example, each of the shared APs 20-1 and 20-2 has the same functional configuration as the example shown in FIG. 7. As shown in FIG. 7, the shared AP 20 functions as a computer including a management unit 210, a frame processing unit 220, a transmission / reception unit 230, and a wireless communication unit 240. The management unit 210 and the frame processing unit 220 are functional blocks that perform processing corresponding to the MAC sublayer of the second layer. The wireless communication unit 240 is a functional block that performs processing corresponding to the MAC sublayer of the second layer and the first layer. Furthermore, when the sharing AP 10 communicates wirelessly with each of the shared APs 20, the transmission / reception unit 230 is a functional block that performs processing corresponding to the MAC sublayer of the second layer and the first layer. When the sharing AP 10 communicates wired with each of the shared APs 20, the transmission / reception unit 230 is a functional block that performs processing corresponding to the MAC sublayer of the second layer.

[0046] The transmitter / receiver 230 transmits and receives data, notification information, control information, and the like to and from the sharing AP 10 via wireless communication or wired communication. When the shared AP 20 communicates wirelessly with the sharing AP 10, the transmitter / receiver 230 generates a wireless frame by adding a preamble or the like to a MAC frame (data frame, management frame, control frame, etc.) input from the frame processor 220. The transmitter / receiver 230 then converts the generated wireless frame into a wireless signal and transmits (radiates) the converted wireless signal to the sharing AP 10 via an antenna. The conversion process from a wireless frame to a wireless signal is performed as described above.

[0047] The transmitter / receiver 230 also converts wireless signals received from the sharing AP 10 via the antenna into wireless frames. The conversion process from wireless signals to wireless frames is performed as described above. The transmitter / receiver 230 extracts MAC frames from the converted wireless frames and outputs the extracted MAC frames to the frame processor 220.

[0048] When the shared AP 20 communicates with the sharing AP 10 via a wired network, the transmitting / receiving unit 230 is connected to the sharing AP 10 via a wired network, and transmits and receives data, notification information, control information, etc. to and from the sharing AP 10 via the wired network. In this case, the transmitting / receiving unit 230 is configured from a network interface for the wired network.

[0049] When the shared AP 20 communicates with the sharing AP 10 via a wired connection, the frame processing unit 220 generates a MAC frame including any of data, notification information, control information, etc. received by the transceiver unit 230 from the sharing AP 10. For example, the frame processing unit 220 adds a MAC header to an LLC packet received from the sharing AP 10 to generate a data frame, which is a MAC frame. When the shared AP 20 communicates with the sharing AP 10 via a wired connection, the frame processing unit 220 receives a data frame, which is a MAC frame, from the wireless communication unit 240, extracts an LLC packet from the input data frame, and outputs the extracted LLC packet to the transceiver unit 230. The frame processing unit 220 also outputs notification information, control information, etc. from the management unit 210 to the transceiver unit 230. The transceiver unit 230 then transmits the LLC packet, notification information, control information, etc. to the sharing AP 10 via wired communication.

[0050] The wireless communication unit 240 can transmit and receive data, notification information, control information, and the like to and from the wirelessly connected terminals 30 via wireless communication. Therefore, the wireless communication unit 240 of the shared AP 20 can establish a wireless connection with each of the terminals 30 located within the communication area. The wireless communication unit 240 generates a wireless frame by adding a preamble or the like to a MAC frame (data frame, management frame, control frame, etc.) input from the frame processing unit 220. The wireless communication unit 240 then converts the generated wireless frame into a wireless signal and transmits (radiates) the converted wireless signal to the corresponding terminal 30 via an antenna. The conversion process from the wireless frame to the wireless signal is performed as described above.

[0051] The wireless communication unit 240 also converts wireless signals received from the terminal 30 via the antenna into wireless frames. The conversion process from wireless signals to wireless frames is performed as described above. The wireless communication unit 240 extracts MAC frames from the converted wireless frames and outputs the extracted MAC frames to the frame processing unit 220.

[0052] When the shared AP 20 communicates wirelessly with the sharing AP 10, it is preferable that the transceiver 230 be configured to transmit and receive using a frequency band or channel different from that of the wireless communication unit 240. When the shared AP 20 communicates wirelessly with the sharing AP 10, the transceiver 230 may not be provided. In this case, the shared AP 20 communicates wirelessly with the sharing AP 10 via the wireless communication unit 240.

[0053] The frame processing unit 220 outputs a data frame, which is a MAC frame, to the wireless communication unit 240. When notification information or control information is input to the frame processing unit 220 from either the transmission / reception unit 230 or the wireless communication unit 240, the frame processing unit 220 outputs the input notification information and control information to the management unit 210. Furthermore, when notification information, control information, etc. to be transmitted to the sharing AP 10 is input to the frame processing unit 220 from the management unit 210, the frame processing unit 220 outputs the input notification information, control information, etc. to the transmission / reception unit 230. The frame processing unit 220 generates, as MAC frames, management frames including notification information to be transmitted to the terminal 30 and control frames including control information to be transmitted to the terminal 30. The frame processing unit 220 then outputs the generated management frames and control frames, etc. to the wireless communication unit 240. For example, a wireless signal converted from the management frame is transmitted from the wireless communication unit 240, thereby notifying the terminal 30 of the notification information included in the management frame.

[0054] The notification information notified from the shared AP 20 includes information about the sharing AP 10, information about the shared AP 20 of the own station, and information about the shared AP 20 of another station that belongs to the sharing AP 10. Furthermore, the shared AP 20 may receive the information indicated by the above-mentioned management information 121 from the sharing AP 10 as notification information, and the management unit 210 may notify the information indicated by the management information 121 as notification information.

[0055] The management unit 210 also stores management information 211 related to the terminals 30 wirelessly connected to the local shared AP 20 in the multi-AP connection method. The management information 211 indicates, for example, information related to an identifier for each of the terminals 30 wirelessly connected to the local shared AP 20. The management information 211 also indicates, for example, a MAC address or the like as information related to the identifier for each of the terminals 30 wirelessly connected to the local shared AP 20.

[0056] The transmitting / receiving unit 230 also receives instructions from the sharing AP 10 regarding transmission of traffic (data) between the sharing AP 10 and the terminal 30 wirelessly connected to the local station. The management unit 210 controls data transmission (transmission and reception of data) between the sharing AP 10 and the terminal 30 wirelessly connected to the shared AP 20 of the local station in accordance with the instructions from the sharing AP 10.

[0057] FIG. 8 is a block diagram showing an example of the functional configuration of a terminal according to an embodiment. In one example, each of terminals 30-1A, 30-1B, 30-2A, and 30-2B has the same functional configuration as the example shown in FIG. 8. As shown in FIG. 8, the terminal 30 functions as a computer including an upper layer processing unit 310, a management unit 320, a frame processing unit 330, and a wireless communication unit 340. The upper layer processing unit 310 is a functional block that executes processing corresponding to the LLC sublayer of the second layer and layers 3 to 7. The management unit 320 and frame processing unit 330 are functional blocks that execute processing corresponding to the MAC sublayer of the second layer. The wireless communication unit 340 is a functional block that executes processing corresponding to the MAC sublayer of the second layer and layer 1.

[0058] The upper layer processing unit 310 generates LLC packets by adding DSAP headers, SSAP headers, etc. to the data. The upper layer processing unit 310 then outputs the generated LLC packets to the frame processing unit 330. The upper layer processing unit 310 also extracts data from the LLC packets input from the frame processing unit 330. The upper layer processing unit 310 then executes an application based on the extracted data. For example, the upper layer processing unit 310 can display application information on the display 35. The upper layer processing unit 310 can also operate based on operations on an input interface.

[0059] The management unit 320 controls the connection (logical wireless connection) between the sharing AP 10 and its own terminal 30 in the multi-AP connection method. In the terminal 30, the management unit 320 acquires the notification information, control information, etc. by receiving notification information or control information, etc. from the shared AP 20 that is wirelessly connected. In one example, in the terminal 30, the management unit 320 acquires the information indicated in the management information 121 described above by receiving notification information from the shared AP 20. The management unit 320 controls the wireless connection with the shared AP 20 that is the connection destination, based on the notification information, control information, etc. from the shared AP 20.

[0060] The management unit 320 also stores management information 321 related to the shared APs 20 that are wireless connection destinations of the local terminal 30 in the multi-AP connection method. The management information 321 indicates, for example, information related to an identifier for each shared AP 20 that is a connection destination of the local terminal 30. The management information 321 indicates, for example, a MAC address or the like as information related to an identifier for each shared AP 20 that is a connection destination of the local terminal 30.

[0061] Frame processing unit 330 generates a MAC frame by adding a MAC header to the LLC packet input from upper layer processing unit 310. Frame processing unit 330 then outputs the generated MAC frame to wireless communication unit 340. Frame processing unit 330 also extracts any of LLC packets, notification information, control information, etc. from the MAC frame input from wireless communication unit 340 (data frame, management frame, control frame, etc.). Frame processing unit 330 then outputs the LLC packet to upper layer processing unit 310 and outputs the notification information, control information, etc. to management unit 320.

[0062] The wireless communication unit 340 generates a wireless frame by adding a preamble and the like to the MAC frame input from the frame processing unit 330. The wireless communication unit 340 then converts the generated wireless frame into a wireless signal and transmits (radiates) the converted wireless signal via an antenna. The conversion process from the wireless frame to the wireless signal is performed as described above.

[0063] The wireless communication unit 340 also converts wireless signals received via an antenna from the shared AP 20, which is the destination of the wireless connection, into wireless frames. The conversion process from wireless signals to wireless frames is performed as described above. The wireless communication unit 340 extracts MAC frames from the converted wireless frames and outputs the extracted MAC frames to the frame processing unit 330.

[0064] Next, the operation of the communication system 1 according to the embodiment will be described, and in particular, the operation of sharing a transmission opportunity among multiple communication stations belonging to different BSSs will be described. Each terminal 30 acquires a transmission opportunity, such as a channel occupation period (TXOP), when transmitting data. Each terminal 30 then transmits data to the wirelessly connected shared AP 20 during the acquired transmission opportunity. Furthermore, after transmitting data to the shared AP 20 during the acquired transmission opportunity, a remaining period of the transmission opportunity may occur in each terminal 30. When a remaining period of the transmission opportunity occurs, each terminal 30 can transfer the remaining period of the transmission opportunity to another communication station. This enables TXOP sharing, in which a transmission opportunity is shared among multiple communication stations.

[0065] The following describes a process in which a remaining period occurs during a transmission opportunity in which a first terminal 30α, which is any one of the terminals 30, transmits data to a first AP 20α, which is a shared AP 20 to which the first terminal 30α is wirelessly connected, and the first terminal 30α transfers the remaining period of the transmission opportunity to another communication station. When transferring the remaining period of the transmission opportunity from the first terminal 30α to another communication station, the management unit 320 of the first terminal 30α causes the wireless communication unit 340 to transmit notification information to the first AP 20α, which is the destination of the data at the transmission opportunity, informing the first AP 20α that the remaining period of the transmission opportunity has been transferred. This notifies the first AP 20α that the remaining period of the transmission opportunity has been transferred.

[0066] In one example, the management unit 320 of the first terminal 30α transmits a notification to transfer the remaining period of the transmission opportunity after completing data transmission to the first AP 20α during the transmission opportunity. In another example, the management unit 320 of the first terminal 30α transmits an RTS (request to send) signal including a notification to transfer the remaining period of the transmission opportunity before transmitting data to the first AP 20α during the transmission opportunity. In this case, for example, notification information to transfer the remaining period of the transmission opportunity is embedded in the management frame that becomes the RTS signal. In yet another example, the management unit 320 of the first terminal 30α transmits a notification to transfer the remaining period of the transmission opportunity together with data to be transmitted to the first AP 20α during the transmission opportunity. In this case, for example, notification information to transfer the remaining period of the transmission opportunity is embedded in a data unit including data to be transmitted to the first AP 20α.

[0067] The first AP 20α may allocate the remaining period of the transmission opportunity transferred from the first terminal 30α to itself or to a terminal 30 located in its communication area. The first AP 20α may also allocate the remaining period of the transmission opportunity transferred from the first terminal 30α to a communication station belonging to a BSS different from that of the first AP 20α. In this case, the remaining period of the transmission opportunity transferred from the first terminal 30α is allocated to one or more of a shared AP 20 whose communication area is different from that of the first AP 20α and a terminal 30 wirelessly connected to a shared AP 20 whose communication area is different from that of the first AP 20α.

[0068] When transferring the remaining period of the transmission opportunity to a communication station belonging to a BSS different from the first AP 20α, the management unit 210 of the first AP 20α causes the transceiver unit 230 to transmit, as notification information, a notification transferring the remaining period of the transmission opportunity from the first terminal 30α to the first AP 20α to the sharing AP 10. For example, after the first AP 20α has completed receiving data from the first terminal 30α during the transmission opportunity, the notification transferring the remaining period of the transmission opportunity is transmitted to the sharing AP 10.

[0069] FIG. 9 is a flowchart illustrating an example of processing performed by a sharing AP when a transmission opportunity is shared among multiple communication stations belonging to different BSSs in an embodiment. The example processing of FIG. 9 is performed when the remaining period of a transmission opportunity from a first terminal 30α to the first AP 20α is transferred to a communication station belonging to a BSS different from that of the first AP 20α. When the example processing of FIG. 9 starts, the transceiver unit 140 of the sharing AP 10 receives notification information from the first terminal 30α informing the first AP 20α of the transfer of the remaining period of the transmission opportunity (S401). At this time, the transceiver unit 140 receives the notification information transmitted from the first AP 20α. As a result, the first terminal 30α notifies the sharing AP 10, via the first AP 20α, that the remaining period of the transmission opportunity will be transferred.

[0070] Then, the management unit 120 of the sharing AP 10 selects one or more shared APs 20 other than the first AP 20α to which the remaining period of the transmission opportunity is to be allocated based on the communication status in the multi-AP connection method including the management information 121 (S402). As a result, one or more shared APs 20 that belong to the sharing AP 10 and have communication areas different from those of the first AP 20α are selected to which the remaining period of the transmission opportunity is to be allocated. In one example, a shared AP 20 that is waiting to transmit or receive low-latency traffic with the terminal 30 is preferentially selected as the shared AP 20 to which the remaining period of the transmission opportunity is to be allocated. In another example, a shared AP 20 with large fluctuations in throughput is preferentially selected as the shared AP 20 to which the remaining period of the transmission opportunity is to be allocated.

[0071] Then, the management unit 120 of the sharing AP 10 causes the transceiver unit 140 to transmit notification information to each of the one or more selected shared APs 20, informing them that at least a portion of the remaining period of the transmission opportunity is allocated as a communication-enabled period (S403). This notifies one or more shared APs 20 other than the first AP 20α that the remaining period of the transmission opportunity is allocated. In one example, the management unit 120 allocates the remaining period of the transmission opportunity to only one shared AP 20. In another example, the management unit 120 allocates the remaining period of the transmission opportunity to multiple shared APs 20. In this case, a portion of the remaining period is allocated as a communication-enabled period to each of the multiple shared APs 20 so that the communication-enabled periods allocated among the multiple shared APs 20 do not overlap.

[0072] Here, any one of the one or more shared APs 20 to which the remaining period of the transmission opportunity is allocated is referred to as the second AP 20β. The second AP 20β has a different communication area than the first AP 20α. When the example process of FIG. 9 is performed by the sharing AP 10, the transceiver 230 of the second AP 20β receives notification information from the sharing AP 10 informing the second AP 20β that at least a portion of the remaining period of the transmission opportunity is allocated to the second AP 20β as a communication-enabled period. This notifies the second AP 20β that at least a portion of the remaining period of the transmission opportunity is allocated to the second AP 20β as a communication-enabled period.

[0073] 9 , the management unit 120 of the sharing AP 10 notifies one or more shared APs 20 other than the first AP 20α, including the second AP 20β, that it will allocate at least a portion of the remaining period of the transmission opportunity to the second AP 20β as a communication available period, in response to receiving a notification from the first AP 20α to transfer the remaining period of the transmission opportunity. This allows the management unit 120 to allocate (transfer) at least a portion of the remaining period of the transmission opportunity to each of one or more shared APs 20, including the second AP 20β, whose communication available areas are different from those of the first AP 20α.

[0074] When the communication period is allocated to the second AP 20β as described above, the management unit 210 of the second AP 20β allocates the communication period to one or more of the communication stations constituting the BSS to which the second AP 20β belongs. In this case, the management unit 210 may allocate the communication period to the second AP 20β, which is the second AP 20β, or may allocate the communication period to a terminal 30 located in the communication area of ​​the second AP 20β. In one example, at least a portion of the communication period is allocated to a second terminal 30β that is different from the first terminal 30α located in the communication area of ​​the second AP 20β.

[0075] Here, as long as the communication period is allocated to the communication stations constituting the BSS to which the second AP 20β belongs, the management unit 210 of the second AP 20β may allocate the communication period to only one communication station or may allocate the communication period to multiple communication stations. However, when allocating the communication period to multiple communication stations, a portion of the communication period is allocated to each of the multiple communication stations so that the allocated periods do not overlap among the multiple communication stations. Furthermore, when a portion of the remaining period of the transmission opportunity is allocated as the communication period to each of multiple shared APs 20 including the second AP 20β, the management unit 210 of each shared AP 20 other than the second AP 20β also allocates the communication period to one or more of the communication stations constituting the BSS to which the shared AP 20 belongs, in the same manner as the second AP 20β.

[0076] 10 is a sequence diagram showing an example of communication processing performed in an operation in which a transmission opportunity is shared among multiple communication stations belonging to different BSSs in a communication system according to an embodiment. In the example shown in FIG. 10, a terminal 30-1A (STA1A) corresponds to the first terminal 30α, and a shared AP 20-1 (AP1) corresponds to the first AP 20α. The terminal 30-1A acquires a TXOP or the like as a transmission opportunity to transmit data to the shared AP 20-1.

[0077] 10 , STA1A transmits an RTS signal before transmitting data to AP1 (S501). Then, AP1 transmits a CTS (clear to send) signal to STA1 in response to receiving the RTS signal (S502). Then, STA1A transmits data (DATA) to AP1 at the acquired transmission opportunity in response to receiving the CTS signal (S503). Then, AP1 transmits a block acknowledgement (BA) to STA1A in response to completing reception of data from STA1A (S504).

[0078] 10, after STA1A transmits data to AP1, a remaining period of the acquired transmission opportunity occurs. Therefore, after STA1A receives a block acknowledgment from AP1, STA1A transmits a notification (TX-G) to AP1 to transfer the remaining period of the transmission opportunity as notification information (S505). Then, in response to receiving the notification information from STA1A, AP1 transmits a notification (TX-G) to sharing AP10 (AP0) to transfer the remaining period of the transmission opportunity as notification information (S506).

[0079] In the example of FIG. 10 , in response to receiving notification information from AP1, AP0 selects shared AP 20-2 (AP2) as the shared AP 20 to which it will allocate the remaining period of the transmission opportunity. Therefore, in the example of FIG. 10 , AP2 corresponds to the second AP 20β described above. Then, AP0 transmits notification information (TX-G) to AP2, allocating at least a portion of the remaining period of the transmission opportunity to AP2 as a communication-enabled period (S507). Then, in the example of FIG. 10 , in response to receiving notification information from AP0, AP2 transmits notification information (TX-G) to STA2A, allocating a communication-enabled period to terminal 30-2A (STA2A) located in the communication-enabled area of ​​AP2 (S508). Therefore, in the example of FIG. 10 , among the communication stations constituting the BSS to which AP2 belongs, the communication-enabled period is allocated to STA2A, and STA2A corresponds to the second terminal 30β described above.

[0080] Then, STA2A transmits data (DATA) to AP2 during the allocated communication period, i.e., during at least a part of the remaining period of the transmission opportunity (S509).Then, AP2 transmits a block acknowledgement (BA) to STA2A in response to the completion of receiving the data from STA2A (S510).

[0081] Fig. 11 is a sequence diagram showing another example of communication processing performed in an operation in which a transmission opportunity is shared among multiple communication stations belonging to different BSSs in the communication system according to the embodiment. In the example of Fig. 11, a terminal 30-1A (STA1A) corresponding to the first terminal 30α acquires a transmission opportunity to transmit data to a shared AP 20-1 (AP1) corresponding to the first AP 20α, and a remaining period occurs in the transmission opportunity acquired by STA1A.

[0082] However, in the example of FIG. 11 , before transmitting data to AP1, the management unit 320 of STA1A determines that a remaining period of the transmission opportunity will occur based on the amount of data to be transmitted and the length of the TXOP, etc., which will be the transmission opportunity. Therefore, in the example of FIG. 11 , STA1A transmits an RTS signal including a notification (TX-G) to AP1 to transfer the remaining period of the transmission opportunity (S511). At this time, the notification included in the RTS signal indicates, for example, that only a portion of the acquired transmission opportunity will be used to transmit data to AP1. This notifies AP1 that the remaining period of the transmission opportunity that is not used for data transmission will be transferred.

[0083] In the example of Figure 11, when AP1 receives the RTS signal, similarly to the example of Figure 10, the following sequence occurs: AP1 transmits a CTS signal to STA1 (S512), STA1A transmits data (DATA) to AP1 (S513), and AP1 transmits a block acknowledgment (BA) to STA1A (S514). Here, in the example of Figure 11, before transmitting the data, AP1 is notified that the remaining period of the transmission opportunity will be transferred. Therefore, after transmitting the block acknowledgment to STA1A, AP1 transmits a notification (TX-G) to the sharing AP 10 (AP0) as notification information, without performing wireless communication with STA1A or the like (S515).

[0084] In the example of Figure 11, when AP0 receives notification information from AP1, similar to the example of Figure 10, AP0 transmits a notification (TX-G) to AP2, which corresponds to the second AP 20β, allocating at least a portion of the remaining period of the transmission opportunity as a communication period to shared AP 20-2 (AP2) as notification information (S516). Then, AP2 transmits a notification (TX-G) to STA2A, which corresponds to terminal 30-2A (STA2A), which corresponds to the second terminal 30β, allocating the communication period as notification information (S517). Then, similar to the example of Figure 10, during the allocated communication period, data (DATA) is transmitted from STA2A to AP2 (S518), and a block acknowledgment (BA) is transmitted from AP2 to STA2A (S519).

[0085] 12 is a sequence diagram showing another example of communication processing performed in an operation in which a transmission opportunity is shared among multiple communication stations belonging to different BSSs in a communication system according to an embodiment, which is different from that shown in FIGS. 10 and 11. In the example of FIG. 12, a terminal 30-1A (STA1A) corresponding to a first terminal 30α acquires a transmission opportunity to transmit data to a shared AP 20-1 (AP1) corresponding to a first AP 20α, and a residual period occurs in the transmission opportunity acquired by STA1A. Then, as in the example of FIG. 10, an RTS signal is transmitted from STA1 to AP1 (S521), and a CTS signal is transmitted from AP1 to STA1 (S522) in sequence.

[0086] However, in the example of FIG. 12 , the management unit 320 of STA1A determines that a remaining period of the transmission opportunity will occur before data transmission to AP1 is completed, based on the amount of data to be transmitted and the length of the TXOP, etc., which will be the transmission opportunity. Then, in the example of FIG. 12 , STA1A transmits a notification (TX-G) to AP1, along with the data (DATA), to transfer the remaining period of the transmission opportunity (S523). At this time, for example, notification information notifying the transfer of the remaining period of the transmission opportunity is embedded in a data unit containing the data to AP1. This notifies AP1 that the remaining period of the transmission opportunity will be transferred in response to the completion of AP1's reception of data from STA1A. In the example of FIG. 12 , AP1 also transmits a block acknowledgment (BA) to STA1A in response to the completion of data reception from STA1A (S524).

[0087] 12, before the data transmission is completed, AP1 is notified that the remaining period of the transmission opportunity will be transferred. Therefore, after AP1 transmits a block acknowledgment to STA1A, AP1 transmits a notification (TX-G) to the sharing AP 10 (AP0) to transfer the remaining period of the transmission opportunity as notification information without performing wireless communication with STA1A (S525).

[0088] In the example of Figure 12, when AP0 receives notification information from AP1, similar to the example of Figure 10, AP0 transmits a notification (TX-G) to AP2, which corresponds to the second AP 20β, allocating at least a portion of the remaining period of the transmission opportunity as a communication period to shared AP 20-2 (AP2) as notification information (S526). Then, AP2 transmits a notification (TX-G) to STA2A, which corresponds to terminal 30-2A (STA2A), which corresponds to the second terminal 30β, allocating the communication period as a communication period (S527). Then, similar to the example of Figure 10, during the allocated communication period, data (DATA) is transmitted from STA2A to AP2 (S528), and a block acknowledgment (BA) is transmitted from AP2 to STA2A (S529).

[0089] Furthermore, when transferring the remaining period of a transmission opportunity from the first terminal 30α to the first AP 20α, a management frame or the like containing notification information for allocating (transferring) the remaining period of the transmission opportunity is used as the remaining period allocation frame. FIG. 13 is a schematic diagram showing an example of the format of a remaining period allocation frame used in an embodiment. In the example of FIG. 13, two shared APs 20β and 20γ other than the first AP 20α are selected by the sharing AP 10 as the destinations for the remaining period of the transmission opportunity. That is, in addition to the second AP 20β, a communication-enabled period is allocated to a third AP 20γ, which is a shared AP 20 other than the first AP 20α and the second AP 20β. The example of FIG. 13 shows a remaining period allocation frame used in the notification from the sharing AP 10 to the shared APs 20β and 20γ.

[0090] In the example of FIG. 13 , the remaining period allocation frame includes address fields (RA and TA) and a frame check sequence (FCS) field, as well as a notification field for each of one or more allocated communication periods. Each notification field indicates the start time and duration of the corresponding communication period, as well as the identifier of the communication station to which the corresponding communication period is allocated. The identifier of the communication station to which the communication period is allocated is indicated, for example, by the MAC address of the communication station. In the example of FIG. 13 , the notification field for the communication period allocated to the second AP 20β indicates the start time and duration of the communication period, as well as the identifier of the second AP 20β to which the communication period is allocated. Then, the notification field for the communication period allocated to the third AP 20γ indicates the start time and duration of the communication period, as well as the identifier of the third AP 20γ to which the communication period is allocated.

[0091] Furthermore, in a notification from the first terminal 30α to the first AP 20α, the remaining period allocation frame used includes a notification field regarding the remaining period of the transmission opportunity to be transferred to the first AP 20α. The notification field indicates the start time and duration of the remaining period to be transferred, as well as the identifier of the first AP 20α to which the remaining period is to be transferred. The identifier of the first AP 20α is indicated, for example, by the MAC address of the first AP 20α. Furthermore, in a notification from the first AP 20α to the sharing AP 10, the remaining period allocation frame used includes a notification field regarding the remaining period of the transmission opportunity to be transferred to the sharing AP 10. The notification field indicates the start time and duration of the remaining period to be transferred, as well as the identifier of the sharing AP 10 to which the remaining period is to be transferred. The identifier of the sharing AP 10 is indicated, for example, by the MAC address of the sharing AP 10.

[0092] Furthermore, when a communication period is allocated from the second AP 20β to a terminal 30 such as the second terminal 30β, the remaining period allocation frame used in the notification from the second AP 20β to the terminal 30 to which the period is allocated includes a notification field for each of the periods allocated to one or more terminals 30. Each notification field indicates the start time and duration of the corresponding period, as well as the identifier of the terminal 30 to which the corresponding period is allocated. The identifier of the terminal 30 to which the period is allocated is indicated, for example, by the MAC address of the terminal 30. Furthermore, when a communication period is allocated to a terminal 30 from a shared AP 20 other than the first AP 20α and the second AP 20β, the remaining period allocation frame used in the notification from that shared AP 20 to the terminal 30 to which the period is allocated includes a notification field for each of the periods allocated to one or more terminals 30, similar to the remaining period allocation frame used in the notification from the second AP 20β to the terminal 30 to which the period is allocated.

[0093] In one example, the aforementioned notification field is added to a management frame used for notification of notification information other than information related to the transfer of the remaining period of a transmission opportunity, and information about the remaining period, information about the allocated communication period, etc. is notified. In another example, the aforementioned notification field is added to a control frame used for transmitting and receiving control information, and information about the remaining period, information about the allocated communication period, etc. is notified.

[0094] As described above, in the embodiments, in response to receiving a notification from the first terminal 30α to transfer the remaining period of the transmission opportunity to the first AP 20α, the sharing AP 10 allocates at least a portion of the remaining period of the transmission opportunity to the second AP 20β, which has a different communication coverage area from the first AP 20α. This makes it possible to allocate the remaining period of the transmission opportunity to an AP other than the first AP 20α, which is the destination of data transmission during the acquired transmission opportunity. Therefore, the remaining period of the acquired transmission opportunity can be allocated to a shared AP 20 belonging to a different BSS from the first terminal 30α, making it possible to share the transmission opportunity among multiple communication stations belonging to different BSSs.

[0095] Furthermore, in the embodiments, when at least a portion of the remaining period of the transmission opportunity is allocated to the second AP 20β as a communication enabled period, the second AP 20β can allocate at least a portion of the communication enabled period to a second terminal 30β, etc., other than the first terminal 30α, located in the communication enabled area of ​​the second AP 20β. This makes it possible to allocate the remaining period of the transmission opportunity acquired by the first terminal 30α to a terminal 30 belonging to a different BSS from the first terminal 30α. Therefore, it becomes possible to share the transmission opportunity among multiple terminals 30 belonging to different BSSs.

[0096] In one example of the embodiment, when the sharing AP 10 notifies the second AP 20β of the allocation of a communication period, the sharing AP 10 notifies the second AP 20β of the start time and duration of the communication period and the identifier of the second AP 20β to which the communication period is allocated, by including the notification information. As a result, information about the allocated communication period is notified to the second AP 20β without transmitting a trigger signal or the like to the second AP 20β at the start time of the allocated communication period separately from the notification of the allocation of the communication period. As a result, in TXOP sharing, in which transmission opportunities are shared among multiple communication stations belonging to different BSSs, the number of frame exchanges between communication stations is reduced, thereby reducing overhead.

[0097] In one modified example, the first AP 20α can wirelessly communicate with other shared APs 20 located in the communication area without the sharing AP 10 in between. For example, the first AP 20α can perform D2D (device-to-device) communication with other shared APs 20 located in the communication area. Fig. 14 is a flowchart showing an example of processing performed by the first AP, which is one of the shared APs, when a transmission opportunity is shared among multiple communication stations belonging to different BSSs with respect to each other in one modified example. The example processing of Fig. 14 is performed when the remaining period of a transmission opportunity from the first terminal 30α to the first AP 20α is transferred to a communication station belonging to a BSS different from the first AP 20α.

[0098] When the process of the example of FIG. 14 starts, the wireless communication unit 240 of the first AP 20α receives notification information from the first terminal 30α informing the first AP 20α of the transfer of the remaining period of the transmission opportunity (S411). At this time, the wireless communication unit 240 receives the notification information transmitted from the first terminal 30α. As a result, the first terminal 30α directly notifies the first AP 20α of the transfer of the remaining period of the transmission opportunity. Then, the management unit 210 of the first AP 20α selects one or more shared APs 20 to which the remaining period of the transmission opportunity is to be allocated, from among the shared APs 20 that can wirelessly communicate with the first AP 20α without the sharing AP 10 being involved, based on the communication status in the multi-AP connection mode (S412). As a result, one or more shared APs 20 to which the remaining period of the transmission opportunity is to be allocated are selected from among the shared APs 20 that belong to the sharing AP 10 and have a communication coverage area different from that of the first AP 20α.

[0099] Then, the management unit 210 of the first AP 20α causes the wireless communication unit 240 to transmit, as notification information, a notification that at least a part of the remaining period of the transmission opportunity is allocated as a communication available period to each of the selected one or more shared APs 20 (S413). As a result, the first AP 20α notifies one or more shared APs 20 other than the first AP 20α that the remaining period of the transmission opportunity is allocated to them without going through the sharing AP 10.

[0100] Here, as in the above-described embodiment, any one of the one or more shared APs 20 to which the remaining period of the transmission opportunity is allocated is designated as the second AP 20β. In this modification, the example process of FIG. 14 is performed by the first AP 20α, and the wireless communication unit 240 of the second AP 20β receives notification information from the first AP 20α informing the second AP 20β that at least a portion of the remaining period of the transmission opportunity is allocated to the second AP 20β as a communication-enabled period. As a result, the second AP 20β is notified, without the sharing AP 10 being involved, that at least a portion of the remaining period of the transmission opportunity is allocated to the second AP 20β as a communication-enabled period.

[0101] As described above, in this modification, by performing the example process of FIG. 14 , the management unit 210 of the first AP 20α, in response to receiving a notification from the first terminal 30α to transfer the remaining period of the transmission opportunity, notifies one or more shared APs 20 other than the first AP 20α, including the second AP 20β, that it will allocate at least a portion of the remaining period of the transmission opportunity to the second AP 20β as a communication available period. This allows the management unit 210 to allocate (transfer) at least a portion of the remaining period of the transmission opportunity to each of one or more shared APs 20 that have communication available areas different from those of the first AP 20α, including the second AP 20β. In this modification, when the communication available period is allocated to the second AP 20β, the management unit 210 of the second AP 20β allocates the communication available period to one or more communication stations that constitute the BSS to which the second AP 20β belongs, in a manner similar to the above-described embodiment.

[0102] Fig. 15 is a sequence diagram showing an example of communication processing performed in an operation in which a transmission opportunity is shared among multiple communication stations belonging to different BSSs in a communication system according to a modified example of Fig. 14. In the example of Fig. 15, as in the example of Fig. 10, terminal 30-1A (STA1A) corresponding to first terminal 30α acquires a transmission opportunity to transmit data to shared AP 20-1 (AP1) corresponding to first AP 20α, and a residual period occurs in the transmission opportunity acquired by STA1A. Then, as in the example of Fig. 10, transmission of an RTS signal from STA1 to AP1 (S531), transmission of a CTS signal from AP1 to STA1 (S532), transmission of data (DATA) from STA1A to AP1 (S533), and transmission of a block acknowledgment (BA) from AP1 to STA1A (S534) are performed sequentially. Then, similar to the example of FIG. 10, after receiving the block acknowledgment from AP1, STA1A transmits a notification (TX-G) to AP1 to transfer the remaining period of the transmission opportunity as notification information (S535).

[0103] However, in the example of Figure 15, AP1 can wirelessly communicate with AP2, which corresponds to the second AP 20β, described above, by D2D communication or the like, without AP0 being involved. Therefore, in the example of Figure 15, in response to receiving the notification information from STA1A, AP1 transmits to AP2 a notification (TX-G) that allocates at least a portion of the remaining period of the transmission opportunity as a communication available period to AP2 (S536). At this time, the notification information is transmitted from AP1 to AP2 without AP0 being involved.

[0104] In the example of Fig. 15, when AP2 receives the notification information, AP2 transmits a notification (TX-G) to STA2A (S537) allocating a communication period to terminal 30-2A (STA2A) corresponding to second terminal 30β, as notification information, in the same manner as in the example of Fig. 10. Then, in the allocated communication period, data (DATA) is transmitted from STA2A to AP2 (S538), and a block acknowledgement (BA) is transmitted from AP2 to STA2A (S539), in sequence.

[0105] In one example, similar to the example in Fig. 15, AP1 transmits notification information to AP2 without AP0 being involved, and STA1A transmits a notification (TX-G) to transfer the remaining period of the transmission opportunity to AP1 in an RTS signal, similar to the example in Fig. 11. In another example, similar to the example in Fig. 15, AP1 transmits notification information to AP2 without AP0 being involved, and STA1A transmits a notification (TX-G) to transfer the remaining period of the transmission opportunity to AP1 together with data (DATA), similar to the example in Fig. 12.

[0106] In the modified example of Figure 14, in response to receiving a notification from the first terminal 30α that transfers the remaining period of the transmission opportunity to the first AP 20α, the first AP 20α, which is one of the shared APs 20, allocates at least a portion of the remaining period of the transmission opportunity to the second AP 20β, which has a different communication coverage area from the first AP 20α. This makes it possible, even in this modified example, to allocate the remaining period of the transmission opportunity to an AP other than the first AP 20α, which is the destination of data transmission during the acquired transmission opportunity. Therefore, even in this modified example, it is possible to allocate the remaining period of the acquired transmission opportunity to a communication station belonging to a different BSS from the first terminal 30α, making it possible to share the transmission opportunity among multiple communication stations belonging to different BSSs.

[0107] Note that there is no particular limitation on the number of shared APs 20 belonging to the sharing AP 10, as long as it is plural. That is, in a multi-AP connection method in which plural shared APs 20 belong to the sharing AP 10, the remaining period of a transmission opportunity from the first terminal 30α to the first AP 20α can be allocated to a communication station belonging to a BSS different from that of the first terminal 30α, and the transmission opportunity can be shared among plural communication stations belonging to different BSSs from each other.

[0108] Furthermore, in the above-described embodiment, the functions of the sharing AP and the shared AP are completely separate, but in a modified example, the sharing AP may also have the functions of a shared AP. For example, in a communication system 1 similar to that shown in FIG. 1, the sharing AP 10 may perform the processing of the shared AP 20-1 in addition to the processing described above. In this case, the sharing AP 10 has, as its functional configuration, an upper layer processing unit 110, a management unit 120, a frame processing unit 130, and a transmission / reception unit 140, as well as a management unit 210, a frame processing unit 220, and a wireless communication unit 240.

[0109] In a sharing AP 10 having the functionality of a shared AP, the transmitter / receiver 140 transmits and receives data, management information, control information, and the like to and from each of the shared APs 20 to which it belongs, such as shared AP 20-2, via wireless or wired communication. In the sharing AP 10, the wireless communication unit 240 can transmit and receive data, management information, control information, and the like to and from each of the terminals 30 located in the communication area via wireless communication. In addition, data, management information, control information, and the like are exchanged between a frame processing unit 130 included in the functionality of the sharing AP 10 and a frame processing unit 220 included in the functionality of the shared AP.

[0110] In a communication system 1 provided with a sharing AP 10 having shared AP functionality, for example, a remaining period occurs in an opportunity for transmitting data from a first terminal 30α to the sharing AP (first AP) 10. In this case, by performing processing similar to that of the above-described embodiment, at least a portion of the remaining period of the opportunity for transmission from the first terminal 30α to the sharing AP 10 can be allocated to a second AP 20β, which is one of the shared APs 20 belonging to the sharing AP 10. As a result, even in a communication system 1 provided with a sharing AP 10 having shared AP functionality, transmission opportunities can be shared among multiple communication stations belonging to different BSSs.

[0111] Furthermore, in the above-described embodiment and the like, the connection between the sharing AP 10 and the terminal 30 passes through one shared AP 20, but in a modified example, the connection between the sharing AP 10 and the terminal 30 may pass through two or more shared APs. That is, the processing of the above-described embodiment and the like can also be applied to a multi-AP connection method with a multi-stage configuration in which two or more shared APs 20 are interposed between the sharing AP 10 and the terminal 30.

[0112] In the multi-AP connection method with a multi-stage configuration, by performing the same processing as in the above-described embodiment, it is possible to allocate at least a portion of the remaining period of a transmission opportunity from the first terminal 30α to the first AP 20α, which is one of the shared APs 20, to the second AP 20β, which is a shared AP 20 having a different communication area from the first AP 20α. This makes it possible to share transmission opportunities among multiple communication stations that belong to different BSSs, even in the multi-AP connection method with a multi-stage configuration.

[0113] The processes of the above-described embodiments and the like can be stored as a program that can be executed by a processor, which is a computer. Furthermore, the program that executes the above-described processes can be stored and distributed in a storage medium of an external storage device, such as a magnetic disk, an optical disk, or a semiconductor memory. The processor can then read the program stored in the storage medium of the external storage device, and its operation can be controlled by the read program, thereby executing the processes of the embodiments and the like.

[0114] 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.

[0115] 1...Communication system 10...Sharing AP 11, 21, 31...CPU 12, 22, 32...ROM 13, 23, 33...RAM 14, 24, 34...Wireless communication module 15...Wired communication module 20 (20-1, 20-2)...Shared AP 30 (30-1A, 30-1B, 30-2A, 30-2B)...Terminal 35...Display 36...Storage 40...Network 50...Building 51, 52, 53, 54...Room 110, 310...Upper layer processing unit 120, 210, 320...Management unit 121, 211, 321...Management information 130, 220, 330...Frame processing unit 140, 230...Transmission / reception unit 240, 340...Wireless communication unit

Claims

1. An access point comprising a management unit that, in response to receiving a notification from a first terminal to transfer the remaining period of a transmission opportunity to a first access point, allocates at least a portion of the remaining period of the transmission opportunity to a second access point having a communication coverage area different from that of the first access point.

2. The access point of claim 1, wherein the access point is a sharing access point to which at least the first access point and the second access point belong as shared access points, and the management unit, in response to receiving the notification from the first access point to transfer the remaining period of the transmission opportunity, notifies the second access point that it will allocate at least a portion of the remaining period of the transmission opportunity to the second access point as a communication available period.

3. The access point of claim 1, wherein the access point is the first access point that belongs to a shared access point that is common to the second access point as a shared access point, and the management unit, in response to receiving the notification from the first terminal to transfer the remaining period of the transmission opportunity, notifies the second access point, without going through the shared access point, that at least a portion of the remaining period of the transmission opportunity will be allocated to the second access point as a communication available period.

4. The access point of claim 1, wherein, in response to receiving a notification to transfer the remaining period of the transmission opportunity, the management unit notifies the second access point that at least a portion of the remaining period of the transmission opportunity will be allocated to the second access point as a communication period, and the management unit notifies the second access point of allocating the communication period to the second access point by including in the notification information the start time and length of the communication period and an identifier of the second access point to which the communication period will be allocated.

5. A shared access point capable of communicating with the access point of any one of claims 1 to 4 as the second access point, comprising a management unit that, in response to receiving a notification that at least a portion of the remaining period of the transmission opportunity is allocated to the second access point as a communication period, allocates at least a portion of the communication period to a second terminal other than the first terminal located in the communication area of the second access point.

6. A terminal used as the first terminal together with an access point according to any one of claims 1 to 4, comprising: a wireless communication unit; and a management unit that notifies the access point that will become the first access point directly, or notifies the access point that will become a sharing access point via the first access point, of the transfer of the remaining period of the transmission opportunity by causing the wireless communication unit to transmit the notification of the transfer of the remaining period of the transmission opportunity.

7. The terminal of claim 6, wherein the management unit causes the notification to be transmitted after completing transmission of data to the first access point during the transmission opportunity.

8. The terminal of claim 6, wherein the management unit causes the terminal to transmit an RTS signal including the notification of transferring the remaining period of the transmission opportunity before transmitting data to the first access point at the transmission opportunity, or causes the management unit to transmit the notification of transferring the remaining period of the transmission opportunity together with the data to be transmitted to the first access point at the transmission opportunity.

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