Access point

Abstract

An access point according to the present invention comprises a management unit. The management unit determines whether or not there is a terminal that satisfies a condition for simultaneous transmission with another access point, on the basis of information pertaining to interference from the other access point which is reported from a subordinate terminal, and transmits, to the other access point, a request for simultaneous transmission when there is a terminal that satisfies the condition for simultaneous transmission.

Description

Access Points

[0001] The embodiments relate to an access point.

[0002] Wireless LANs (Local Area Networks) are known as systems that wirelessly connect access points (APs) and terminals (STAs). IEEE 802.11TGbn, which is formulating the next generation of wireless LAN standards, is studying multi-APs, which transmit data by coordinating multiple APs. Coordinated spatial reuse (Co-SR) by multiple APs is also being considered as part of this study. Co-SR is a mechanism that adjusts the transmission power of multiple APs in cooperation with each other, enabling simultaneous transmission.

[0003] Jason Yuchen Guo et al., “Coordinated Spatial Reuse Design”, IEEE 802.11-23 / 1868r2, October 2023Kosuke Aio et al., “Coordinated Measurement”, IEEE 802.11-23 / 0668r2, July 2023Rui Yang et al., “On Joint C-SR and C-OFDMA M-AP Transmission Coordinated IEEE 802.11-20 / 1399r2, September 2020

[0004] In conventional simultaneous transmission, the criteria for grouping APs that perform simultaneous transmission are not clear. By clarifying the criteria for grouping APs that perform simultaneous transmission, it is expected that simultaneous transmission will be performed more efficiently.

[0005] The embodiments provide an access point that can perform more efficient simultaneous transmissions.

[0006] An access point according to one aspect includes a management unit that determines whether or not there is a terminal that satisfies a condition for simultaneous transmission with other access points based on information about interference from other access points reported by terminals under its control, and transmits a request for simultaneous transmission to the other access points if there is a terminal that satisfies the condition for simultaneous transmission.

[0007] According to the embodiment, an access point capable of more efficient simultaneous transmission is provided.

[0008] FIG. 1 is a diagram illustrating an example of the configuration of a communication system according to an embodiment. FIG. 2 is a block diagram illustrating an example of the hardware configuration of an AP. FIG. 3 is a block diagram illustrating an example of the hardware configuration of a terminal. FIG. 4 is a block diagram illustrating an example of the functional configuration of an AP according to an embodiment. FIG. 5 is a block diagram illustrating an example of the functional configuration of a terminal according to an embodiment. FIG. 6 is a flowchart illustrating the operation of one AP according to an embodiment. FIG. 7 is a flowchart illustrating the operation of another AP according to an embodiment. FIG. 8 is a diagram illustrating the operation of a communication system according to an embodiment. FIG. 9 is a diagram illustrating an example of the configuration of a communication system according to a second modified example. FIG. 10 is a diagram illustrating an example of the configuration of a communication system according to a third modified example. FIG. 11 is a diagram illustrating an example of the configuration of a communication system according to a first modified example of a fourth modified example. FIG. 12 is a diagram illustrating an example of scheduling of simultaneous transmissions in the case of FIG. 11. FIG. 13 is a diagram illustrating an example of the configuration of a communication system according to a second example of the fourth modified example. FIG. 14 is a diagram illustrating an example of scheduling of simultaneous transmissions in the case of FIG. 13. FIG. 15 is a diagram illustrating the operation of a communication system according to a fifth modified example.

[0009] Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 is a 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 access points (AP) 10-1 and 10-2, terminals 20-1 and 20-2, and a network 30.

[0010] The APs 10-1 and 10-2 and the terminals 20-1 and 20-2 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.

[0011] In an embodiment, AP 10-1 and AP 10-2 and terminals 20-1 and 20-2 may support multi-link communication, which performs communication using two or more different wireless links. In an embodiment, AP 10-1 and AP 10-2 are configured to use at least one wireless link of the same channel. Also, in an embodiment, at least a portion of the coverage areas of AP 10-1 and AP 10-2 overlap. Therefore, when AP 10-1 and AP 10-2 simultaneously communicate in the same frequency band, one of them may become a source of interference to the other. In an embodiment, AP 10-1 and AP 10-2 may simultaneously transmit in the same frequency band through cooperative operation.

[0012] APs 10-1 and 10-2 can exchange traffic with terminals 20-1 and 20-2. Here, in FIG. 1, AP 10-1 is connected to network 30, and AP 10-2 is not connected to network 30. Both APs 10-1 and 10-2 may be connected to network 30, or neither may be connected to network 30. Although two APs are shown in FIG. 1, the number of APs is not limited to two. The communication system 1 may include two or more APs. In the following, AP 10-1 and AP 10-2 have the same configuration. In the following, when APs 10-1 and 10-2 are not particularly distinguished from each other, they may be referred to as AP 10.

[0013] Terminals 20-1 and 20-2 are, for example, smartphones or PCs (personal computers), and are wireless terminals conforming to the IEEE 802.11 standard. Although two terminals are shown in FIG. 1, the number of terminals is not limited to two. The communication system 1 may include one or more terminals. In the following, terminals 20-1 and 20-2 have the same configuration. In the following, when there is no particular need to distinguish between terminals 20-1 and 20-2, they may be referred to as terminal 20.

[0014] Next, the hardware configuration of the AP and the terminal in the communication system according to the embodiment will be described.

[0015] 2 is a block diagram showing an example of the hardware configuration of an AP 10. As shown in FIG. 2, the 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, and a wired communication module 15.

[0016] The CPU 11 is a processing circuit that controls the overall operation of the AP 10. The ROM 12 is, for example, a non-volatile semiconductor memory. The ROM 12 stores programs and data for controlling the 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 30.

[0017] Although the wired communication module 15 is described as a means for connecting the AP 10 and the network 30, a wireless communication module different from the wireless communication module 14 may alternatively be used, or the wireless communication module 14 may communicate with the network 30 during times when it is not communicating with the terminal 20.

[0018] 3 is a block diagram showing an example of the hardware configuration of the terminal 20. As shown in FIG. 3, the terminal 20 includes, for example, a CPU 21, a ROM 22, a RAM 23, a wireless communication module 24, a display 25, and a storage 26.

[0019] The CPU 21 is a processing circuit that controls the overall operation of the terminal 20. The ROM 22 is, for example, a non-volatile semiconductor memory. The ROM 22 stores programs and data for controlling the terminal 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 transmitting and receiving data via wireless signals. The wireless communication module 24 is connected to an antenna. The display 25 is, for example, an LCD (liquid crystal display) or an EL (electro-luminescence) display. The display 25 displays a GUI (graphical user interface) corresponding to application software, etc. The storage 26 is a non-volatile storage device. The storage 26 stores system software, etc. of the terminal 20.

[0020] Next, the functional configuration of the AP and the terminal in the communication system according to the embodiment will be described.

[0021] FIG. 4 is a block diagram showing an example of the functional configuration of an AP according to an embodiment. The AP 10 functions as a computer including a data processing unit 110, a frame processing unit 120, a management unit 130, a radio signal processing unit 140, a radio signal processing unit 150, and a radio signal processing unit 160. 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 frame processing unit 120 and the management unit 130 are functional blocks that execute processing corresponding to the MAC sublayer of Layer 2. The radio signal processing units 140, 150, and 160 are functional blocks that execute processing corresponding to Layer 1. The data processing unit 110, the frame processing unit 120, and the management unit 130 may operate as an AP MLD. The frame processing unit 120 and the radio signal processing units 140, 150, and 160 may operate as an affiliated AP. The AP MLD is a multilink device (MLD) in the AP 10 and is an entity configured to logically establish a wireless connection with the terminal 20. The affiliated AP is an entity configured to physically establish a wireless connection with the terminal 20. That is, the affiliated AP has a physical configuration for exchanging data with the terminal via a wireless link.

[0022] The data processing unit 110 outputs data input from the network 30 via the LLC layer to the frame processing unit 120. The data processing unit 110 also outputs data input from the frame processing unit 120 to the network 30 via the LLC layer.

[0023] When data is input to frame processing unit 120 from data processing unit 110 or management unit 130, frame processing unit 120 adds a MAC header to the input data to generate a MAC frame. Frame processing unit 120 then outputs the MAC frame to radio signal processing unit 140. When a MAC frame is input from radio signal processing unit 140, frame processing unit 120 extracts data from the MAC frame and outputs the extracted data to data processing unit 110 or management unit 130 depending on the type of MAC frame. Specifically, when the MAC frame is a data frame, frame processing unit 120 inputs the data to data processing unit 110. When the MAC frame is a management frame or a control frame, frame processing unit 120 inputs the data to management unit 130.

[0024] The management unit 130 controls the logical wireless connection between the AP 10 and the terminal 20. For example, the management unit 130 executes wireless connection processing in response to an association request from the terminal 20. The wireless connection processing includes multilink connection processing. The management unit 130 also includes a determination unit 131 and a simultaneous transmission management unit 132. The determination unit 131 determines whether conditions for simultaneous transmission with other APs are met. The condition for simultaneous transmission is that there is a terminal under the control of the local station that experiences minimal interference from other APs. Interference from other APs can be measured, for example, by the received power level from other APs or the ratio of the received power level from the local station to the received power level from other APs. Furthermore, when a simultaneous transmission request is received from another AP, the determination unit 131 determines whether simultaneous transmission with this AP is possible. The determination of whether simultaneous transmission is possible is based on the received power level of the subordinate terminal. For example, if the reception power level of the subordinate terminal from its own station is equal to or greater than a certain value, or if the reception power level of the subordinate terminal from another AP relative to its own station is equal to or less than a certain value, the determination unit 131 determines to perform simultaneous transmission with another AP. The simultaneous transmission management unit 132 transmits a simultaneous transmission request to another access point via the wireless signal processing unit 140, 150, or 160. The frame format of the simultaneous transmission request is not particularly limited. Furthermore, when the simultaneous transmission management unit 132 receives a simultaneous transmission request from another AP via the wireless signal processing unit 140, 150, or 160, it transmits a response including the result of the determination unit 131 as to whether simultaneous transmission is possible via the wireless signal processing unit 140, 150, or 160.

[0025] The radio signal processing units 140, 150, and 160 generate radio frames by adding preambles and the like to the MAC frames input from the frame processing unit 120. The radio signal processing units 140, 150, and 160 convert the generated radio frames into radio signals. The radio signal processing units 140, 150, and 160 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 processing units 140, 150, and 160 also convert radio signals received via 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 processing units 140, 150, and 160 extract MAC frames from the converted radio frames and output the extracted MAC frames to the frame processing unit 120. The radio signal processing units 140, 150, and 160 are configured to transmit and receive radio signals using different frequency bands. The radio signal processing units 140, 150, and 160 may also be configured to transmit and receive radio signals using different channels in the same frequency band.

[0026] FIG. 5 is a block diagram showing an example of the functional configuration of a terminal according to an embodiment. The terminal 20 functions as a computer equipped with a data processing unit 210, a frame processing unit 220, a management unit 230, radio signal processing units 240, 250, and 260, and an application execution unit 270. The data processing unit 210 is a functional block that executes processing corresponding to the LLC sublayer of layer 2 and layers 3 to 7. The frame processing unit 220 and management unit 230 are functional blocks that execute processing corresponding to the MAC sublayer of layer 2. The radio signal processing units 240, 250, and 260 are functional blocks that execute processing corresponding to layer 1. The data processing unit 210, the frame processing unit 220, and the management unit 230 can operate as a non-AP MLD. The frame processing unit 220 and the radio signal processing units 240, 250, and 260 can operate as an affiliated STA. Here, the terminal 20 in this example is equipped with multiple radio signal processing units to enable multi-link communication, similar to the AP 10. On the other hand, the terminal 20 does not necessarily need to be capable of multi-link communication, and may be equipped with only one radio signal processing unit.

[0027] The data processing unit 210 outputs data input from the application execution unit 270 via the LLC layer to the frame processing unit 220. The data processing unit 210 also outputs data input from the frame processing unit 220 to the application execution unit 270 via the LLC layer.

[0028] When data is input to frame processing unit 220 from data processing unit 210 or management unit 230, frame processing unit 220 adds a MAC header to the input data to generate a MAC frame. Frame processing unit 220 then outputs the MAC frame to radio signal processing unit 240. When a MAC frame is input from radio signal processing unit 240, frame processing unit 220 extracts data from the MAC frame and outputs the extracted data to data processing unit 210 or management unit 230 depending on the type of MAC frame. Specifically, when the MAC frame is a data frame, frame processing unit 220 inputs the data to data processing unit 210. When the MAC frame is a management frame or a control frame, frame processing unit 220 inputs the data to management unit 230.

[0029] The management unit 230 controls the logical wireless connection between the terminal 20 and the AP 10. For example, the management unit 230 generates an association request based on a beacon frame from the AP 10.

[0030] The radio signal processing units 240, 250, and 260 generate radio frames by adding preambles and the like to the MAC frames input from the frame processing unit 220. The radio signal processing units 240, 250, and 260 convert the generated radio frames into radio signals. The radio signal processing units 240, 250, and 260 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 processing units 240, 250, and 260 also convert radio signals received via 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 processing units 240, 250, and 260 extract MAC frames from the converted radio frames. Then, the radio signal processing units 240, 250, and 260 output the extracted MAC frames to the frame processing unit 220. The radio signal processing units 240, 250, and 260 are configured to transmit and receive radio signals using different frequency bands. That is, the radio signal processing units 240, 250, and 260 may form different wireless links with the AP 10. Each wireless link may be distinguished by a link ID. For example, the radio signal processing unit 240 is configured to transmit and receive radio signals using the same frequency band as the radio signal processing unit 140. The radio signal processing unit 250 is configured to transmit and receive radio signals using the same frequency band or channel as the radio signal processing unit 150. The radio signal processing unit 260 is configured to transmit and receive radio signals using the same frequency band as the radio signal processing unit 160. The radio signal processing units 240, 250, and 260 may also be configured to transmit and receive radio signals using different channels in the same frequency band.

[0031] The application execution unit 270 executes an application based on data input from the data processing unit 210. The application execution unit 270 also inputs data to the data processing unit 210. For example, the application execution unit 270 can display application information on the display 25. The application execution unit 270 can also operate based on operations on an input interface.

[0032] Next, the operation of the communication system according to the embodiment will be described. FIG. 6 is a flowchart showing the operation of one AP 10 according to the embodiment. One AP 10 is the AP that transmits a simultaneous transmission request out of APs 10-1 and 10-2. In the following, for example, it is assumed that AP 10-2 performs the operation shown in FIG. 6. In the following example, it is assumed that AP 10-1 and AP 10-2 have established a wireless link using the wireless signal processing unit 140. It is also assumed that AP 10-1 has established a wireless link with terminal 20-1 using the wireless signal processing unit 150, and AP 10-2 has established a wireless link with terminal 20-2 using the wireless signal processing unit 150. Here, communication between AP 10-1 and AP 10-2 does not necessarily have to be performed wirelessly, but may be performed via wired communication.

[0033] In step S1, the AP 10-1 determines whether it has received a report of the received power level from the subordinate terminal 20-1 via the wireless signal processing unit 150. The terminal 20-1 measures the received power level from each AP, for example, by performing a CCA (Clear Channel Assessment) operation, either periodically or upon request from the AP 10-1, and reports the results to the AP 10-1. Upon receiving this report, the AP 10-1 determines that it has received a report of the received power level. Here, the received power level may be reported as the absolute value of the received power from each AP, or as the ratio of the received power level from another AP to the received power level from a reference AP, such as the ratio of the received power level from AP 10-2 to the received power level from AP 10-1. Both the absolute value and the ratio of the received power level may be reported. If it is determined in step S1 that a report of the received power level has been received, the process proceeds to step S2. If it is determined in step S1 that a report of the received power level has not been received, the process proceeds to step S7.

[0034] In step S2, the AP 10-1 determines whether there is a terminal 20 that satisfies the simultaneous transmission condition based on the reported received power level. A terminal 20 that satisfies the simultaneous transmission condition is a terminal that experiences little interference from other APs. For example, if there is a terminal whose received power level from the AP 10-2 is below a certain level and / or if there is a terminal whose received power level from the AP 10-2 is below a certain value relative to the received power level from the AP 10-1, it is determined that there is a terminal 20 that experiences little interference from other APs. If it is determined in step S2 that there is a terminal 20 that satisfies the simultaneous transmission condition, the process proceeds to step S3. If it is determined in step S2 that there is no terminal 20 that satisfies the simultaneous transmission condition, the process proceeds to step S7. Here, if there are two or more terminals 20 that satisfy the simultaneous transmission condition, the AP 10-1 may select one of those terminals 20. For example, the AP 10-1 may select the terminal 20 that has the lowest received power level from the AP 10-2 among the two or more terminals 20 that satisfy the simultaneous transmission condition.

[0035] In step S3, the AP 10-1 transmits a simultaneous transmission request to the AP 10-2 using the wireless signal processing unit 140. The simultaneous transmission request includes, for example, information on the time when the simultaneous transmission will be performed, information on the terminal with which the AP 10-1 will communicate during the simultaneous transmission, and the like.

[0036] In step S4, AP 10-1 determines whether or not a response to the simultaneous transmission request has been received from AP 10-2. AP 10-1 waits until a response to the simultaneous transmission request has been received from AP 10-2. If it is determined in step S4 that a response to the simultaneous transmission request has been received from AP 10-2, the process proceeds to step S5.

[0037] In step S5, AP 10-1 determines whether simultaneous transmission is OK based on the response reception result. If it is determined in step S5 that simultaneous transmission is OK, the process proceeds to step S6. If it is determined in step S6 that simultaneous transmission is not OK, the process proceeds to step S7.

[0038] In step S6, AP 10-1 performs simultaneous transmission with AP 10-2. Thereafter, the process returns to step S1. For example, when transmitting data to terminal 20-1, AP 10-1 transmits a wireless signal including a data frame addressed to the terminal to terminal 20-1 at a predetermined time. Also, for example, when receiving data from terminal 20-1, AP 10-1 notifies subordinate terminal 20-1 of the time of simultaneous transmission. Then, AP 10-1 receives the wireless signal including the data frame transmitted from terminal 20-1 at the time of simultaneous transmission.

[0039] In step S7, if it is determined in step S1 that a report of the received power level has not been received, if it is determined in step S2 that there is no terminal 20 that satisfies the conditions for simultaneous transmission, or if it is determined in step S5 that simultaneous transmission is not OK, the AP 10-1 performs individual transmission. Thereafter, the process returns to step S1. Individual transmission is an operation that does not involve cooperative operation with the AP 10-2. In this case, the AP 10-1 communicates with the terminal 20-1 using the normal procedure.

[0040] 7 is a flowchart showing the operation of the other AP 10 in this embodiment. The other AP 10 is the AP that receives the simultaneous transmission request from either AP 10-1 or 10-2. In the following, it is assumed that AP 10-2 performs the operation shown in FIG. 7, for example.

[0041] In step S11, AP 10-2 determines whether or not a simultaneous transmission request has been received from AP 10-1 via wireless signal processing unit 140. If it is determined in step S11 that a simultaneous transmission request has been received, the process proceeds to step S12. If it is determined in step S11 that a simultaneous transmission request has not been received, the process proceeds to step S17.

[0042] In step S12, AP 10-2 receives a report of the received power level from subordinate terminal 20-2 via wireless signal processing unit 150. Terminal 20-2 measures the received power level from each AP, for example, by performing a CCA operation, either periodically or upon request from AP 10-2, and reports the results to AP 10-2. The received power level may be reported as an absolute value of the received power from each AP, or may be reported as a ratio of the received power level from another AP to the received power level from a reference AP, such as the ratio of the received power level from AP 10-1 to the received power level from AP 10-2.

[0043] In step S13, AP 10-2 determines whether to perform simultaneous transmission with AP 10-1 based on the reported received power level. For example, if the received power level of subordinate terminal 20-2 is equal to or greater than a certain value and / or the received power level from AP 10-1 relative to the received power level from AP 10-2 is equal to or less than a certain value, it is determined that simultaneous transmission will be performed. If it is determined in step S13 that simultaneous transmission will be performed, the process proceeds to step S14. If it is determined in step S13 that simultaneous transmission will not be performed, the process proceeds to step S16.

[0044] In step S14, the AP 10-2 transmits a response indicating that simultaneous transmission is OK using the wireless signal processing unit 140. In step S15, the AP 10-2 performs simultaneous transmission with the AP 10-1. Thereafter, the process returns to step S11.

[0045] In step S16, the AP 10-2 transmits a response indicating that simultaneous transmission is not permitted using the wireless signal processing unit 140. Thereafter, the process proceeds to step S17.

[0046] If it is determined in step S11 that a simultaneous transmission request has not been received, or after transmitting a response indicating that simultaneous transmission is not permitted in step S16, the AP 10-2 performs individual transmission in step S17. Then, the process returns to step S11.

[0047] The operations of Figures 6 and 7 will be specifically described below using Figure 8. The communication system shown in Figure 8 includes APs 10-1 and 10-2 and terminals 20-1 and 20-2, similar to Figure 1. AP 10-1 is subordinate to terminal 20-1, and AP 10-2 is subordinate to terminal 20-2.

[0048] The AP 10-1 receives a report of the received power level from the terminal 20-1 under its control. Based on this result, the AP 10-1 determines whether there is a terminal that satisfies the conditions for simultaneous transmission. For example, suppose that the terminal 20-1 is determined to be a terminal that satisfies the conditions for simultaneous transmission with the AP 10-2. After this, the AP 10-1 transmits a simultaneous transmission request Req to the AP 10-2.

[0049] Upon receiving a simultaneous transmission request Req from AP 10-1, AP 10-2 receives a report of the received power level from the subordinate terminal 20-2. Based on this result, AP 10-2 determines whether to perform simultaneous transmission with AP 10-1. For example, if the received power level from AP 10-1 reported by terminal 20-2 is equal to or lower than a threshold, it is determined that simultaneous transmission is to be performed. If simultaneous transmission is to be performed, AP 10-2 returns a response Res to AP 10-1 indicating that simultaneous transmission is OK.

[0050] Upon receiving a response Res from AP 10-2 indicating that simultaneous transmission is OK, AP 10-1 performs simultaneous transmission with AP 10-2. In FIG. 8, data Data1 is transmitted from AP 10-1 to terminal 20-1, and at the same time, data Data2 is transmitted from AP 10-2 to terminal 20-2. The channel used for communication between AP 10-1 and terminal 20-1 overlaps with the channel used for communication between AP 10-2 and terminal 20-2. However, because terminal 20-1 is a terminal that experiences little interference from AP 10-2 and terminal 20-2 is a terminal that experiences little interference from AP 10-1, it is expected that data transmission between AP 10-1 and terminal 20-1 and data transmission between AP 10-2 and terminal 20-2 will be performed with high reliability.

[0051] As described above, according to the embodiment, the terminals to be subjected to simultaneous transmission are determined taking into consideration interference from other APs with respect to terminals subordinate to each AP, which is expected to enable simultaneous transmission by multiple APs with high reliability.

[0052] (First Modification) A modification of the embodiment will be described below. In the embodiment, the AP making the simultaneous transmission request is AP 10-1, but the AP making the simultaneous transmission request may be AP 10-2.

[0053] Here, in the multi-AP system under consideration in IEEE 802.11TGbn, a system in which one AP manages one or more APs under its control is also being considered. In this system, an AP that manages other APs is called a sharing AP, and an AP managed by the sharing AP is called a shared AP. In the example of FIG. 8, AP 10-1 can be a sharing AP, and AP 10-2 can be a shared AP. On the other hand, in the first modified example, AP 10-2 can be a sharing AP, and AP 10-1 can be a shared AP. Note that an AP operating as a shared AP can also communicate with a terminal under the AP operating as a shared AP via the shared AP. For example, AP 10-1 can receive data from terminal 20-2 via AP 10-2.

[0054] (Second Modification) In the embodiment, the number of APs is two. As described above, the number of APs may be three or more. FIG. 9 is a diagram showing an example of the configuration of a communication system according to the second modification. As shown in FIG. 9, a communication system 1 according to the second modification includes APs 10-1, 10-2, and 10-3, terminals 20-1, 20-2, and 20-3, and a network 30. When the number of APs is three or more, the partner of simultaneous transmission can be switched.

[0055] APs 10-1, 10-2, and 10-3 have the hardware configuration shown in Figure 2 and the functional configuration shown in Figure 4. Similarly, terminals 20-1, 20-2, and 20-3 have the hardware configuration shown in Figure 3 and the functional configuration shown in Figure 5. In the following example, it is assumed that APs 10-1 and 10-2 have established a wireless link using wireless signal processing unit 140. It is also assumed that APs 10-2 and 10-3 have established a wireless link using wireless signal processing unit 150. It is also assumed that AP 10-1 has established a wireless link with terminal 20-1 using wireless signal processing unit 160, and AP 10-2 has established a wireless link with terminal 20-2 using wireless signal processing unit 160. It is also assumed that AP 10-3 has established a wireless link with terminal 20-3 using wireless signal processing unit 160. Here, the communication between AP 10-1 and AP 10-2 and the communication between AP 10-2 and AP 10-3 do not necessarily have to be performed wirelessly, but may be performed by wired communication. Also, in the example of Fig. 9, simultaneous transmission is performed between AP 10-1 and AP 10-2. In this case, it is assumed that a simultaneous transmission request is sent from AP 10-3 to AP 10-2.

[0056] The operation of AP 10-3 making a simultaneous transmission request is the same as the operation shown in Fig. 6. AP 10-3 receives a report of the received power level from terminal 20-3 under its control. From this result, AP 10-3 determines whether there is a terminal that satisfies the conditions for simultaneous transmission. For example, suppose AP 10-3 determines that terminal 20-3 is a terminal that satisfies the conditions for simultaneous transmission with AP 10-2. After this, AP 10-3 sends a simultaneous transmission request Req to AP 10-2.

[0057] Upon receiving a simultaneous transmission request Req from AP 10-3, AP 10-2 receives a report of the received power level from the subordinate terminal 20-2. Based on this result, AP 10-2 determines whether to perform simultaneous transmission with AP 10-3. For example, if the received power from AP 10-3 is lower than the received power level from AP 10-1 reported by terminal 20-2, that is, if the interference received from AP 10-3 is less than the interference received from AP 10-1, it is determined that simultaneous transmission with AP 10-3 will be performed. If simultaneous transmission is to be performed, AP 10-2 transmits a wireless signal Cancel to AP 10-1 to cancel the simultaneous transmission, and returns a response Res to AP 10-3 to indicate that simultaneous transmission is OK. Upon receiving the wireless signal Cancel from AP 10-2 to cancel the simultaneous transmission, AP 10-1 stops simultaneous transmission with AP 10-2 and switches to individual transmission. On the other hand, upon receiving a response Res from the AP 10-3 indicating that simultaneous transmission is OK, the AP 10-3 performs simultaneous transmission with the AP 10-2.

[0058] As described above, in the second modified example, in a wireless system in which three or more APs exist, switching of the AP that is the target of simultaneous transmission is performed, and it is expected that communication will be performed with higher reliability.

[0059] (Third Modification) In the embodiment, the number of terminals subordinate to each AP is 1. However, the number of terminals subordinate to each AP may be 2 or more. When the number of subordinate terminals is 2 or more, a terminal to be subjected to simultaneous transmission may be selected.

[0060] Fig. 10 is a diagram showing an example of the configuration of a communication system according to the third modified example. As shown in Fig. 10, the communication system 1 according to the third modified example includes APs 10-1 and 10-2, terminals 20-1, 20-2, and 20-3, and a network 30. The AP 10-1 controls the terminals 20-1 and 20-3, and the AP 10-2 controls the terminal 20-2.

[0061] The operation of AP 10-1 making a simultaneous transmission request is similar to the operation shown in FIG. 6. AP 10-1 receives reports of received power levels from subordinate terminals 20-1 and 20-3. Based on this result, AP 10-1 determines whether there are any terminals that satisfy the conditions for simultaneous transmission. For example, suppose that both terminals 20-1 and 20-3 are determined to be terminals that satisfy the conditions for simultaneous transmission with AP 10-2. In this case, AP 10-1 selects one of them as the target terminal for simultaneous transmission. For example, AP 10-1 selects the terminal with the lower received power level reported from terminal 20-1 or terminal 20-3, i.e., the terminal with the least interference from AP 10-2. For example, suppose AP 10-1 selects terminal 20-3 as the target terminal for simultaneous transmission. After this, AP 10-1 transmits a simultaneous transmission request Req to AP 10-2.

[0062] Upon receiving a simultaneous transmission request Req from AP 10-1, AP 10-2 receives a report of the received power level from the subordinate terminal 20-2. Based on this result, AP 10-2 determines whether to perform simultaneous transmission with AP 10-1. For example, if the received power level from AP 10-1 reported by terminal 20-2 is equal to or lower than a threshold, it is determined that simultaneous transmission is to be performed. If simultaneous transmission is to be performed, AP 10-2 returns a response Res to AP 10-1 indicating that simultaneous transmission is OK.

[0063] Upon receiving a response Res from AP 10-2 indicating that simultaneous transmission is OK, AP 10-1 performs simultaneous transmission with AP 10-2. In Fig. 10, data Data3 is transmitted from AP 10-1 to terminal 20-3, and at the same time, data Data2 is transmitted from AP 10-2 to terminal 20-2. Because AP 10-1 is communicating with terminal 20-3, which is subject to less interference from AP 10-2, it is expected that data transmission will be carried out with higher reliability.

[0064] FIG. 10 illustrates an example in which the target terminals for simultaneous transmission are determined based on the received power level. Alternatively, the target terminals for simultaneous transmission may be determined based on the priority of simultaneous transmission assigned to each terminal. For example, a high priority may be assigned to a terminal that handles low-latency traffic. When determining which terminals satisfy the conditions for simultaneous transmission, the AP 10-1 may change the threshold for the received power level according to the priority. For example, the threshold value for a terminal with a high priority may be changed to a smaller value. In this case, the AP with which simultaneous transmission is performed is likely to be an AP with less interference, i.e., an AP located further away. Furthermore, when it is determined that multiple terminals simultaneously satisfy the conditions, the AP 10-1 may select terminals with higher priorities in preference to terminals with lower priorities. As a result, terminals with higher priorities may be prioritized as the target terminals for simultaneous transmission.

[0065] (Fourth Modification) When the number of APs is three or more, an AP making a simultaneous transmission request may perform simultaneous transmission with a plurality of APs at different times.

[0066] Fig. 11 is a diagram showing an example of the configuration of a communication system according to a first example of the fourth modified example. As shown in Fig. 11, the communication system 1 according to the first example includes APs 10-1, 10-2, and 10-3, terminals 20-11, 20-12, 20-21, and 20-31, and a network 30. AP 10-1 is subordinate to terminals 20-11 and 20-12, AP 10-2 is subordinate to terminal 20-21, and AP 10-3 is subordinate to terminal 20-31.

[0067] The operation of AP 10-1 making a simultaneous transmission request is similar to the operation shown in Fig. 6. AP 10-1 receives reports of received power levels from subordinate terminals 20-11 and 20-12. From these results, AP 10-1 determines whether there are any terminals that satisfy the conditions for simultaneous transmission. In the example of Fig. 11, it is determined that terminal 20-11 has little interference from AP 10-2 and much interference from AP 10-3, and terminal 20-12 has little interference from both AP 10-2 and AP 10-3.

[0068] In this case, AP 10-1 determines the time periods in which terminals that satisfy the conditions for simultaneous transmission exist for each of AP 10-2 and AP 10-3, and schedules simultaneous transmission based on the determined time periods, for example, as shown in Figure 12. That is, AP 10-1 schedules simultaneous transmission so that it performs simultaneous transmission with AP 10-2 at the timing of data communication with terminal 20-11, and performs simultaneous transmission with AP 10-3 at the timing of data communication with terminal 20-12. In this way, since terminal 20-11 is susceptible to interference from AP 10-3, simultaneous transmission is scheduled so that AP 10-3 is not the partner of simultaneous transmission during data communication between AP 10-1 and terminal 20-11. Here, in Figure 12, communication with terminal 20-11 is performed first, and then communication with terminal 20-12 is performed, but this may be reversed.

[0069] Fig. 13 is a diagram showing an example of the configuration of a communication system according to a second example of the fourth modified example. As shown in Fig. 13, a communication system 1 according to the first example includes APs 10-1, 10-2, and 10-3, terminals 20-11, 20-21, and 20-31, and a network 30. AP 10-1 is subordinate to terminal 20-11, AP 10-2 is subordinate to terminal 20-21, and AP 10-3 is subordinate to terminal 20-31. The differences from Fig. 11 are that the position of terminal 20-11 has been changed to the position of terminal 20-12, and that terminal 20-12 is not present.

[0070] The operation of AP 10-1 making a simultaneous transmission request is similar to the operation shown in Fig. 6. AP 10-1 receives a report of the received power level from terminal 20-11 under its control. From this result, AP 10-1 determines whether there is a terminal that satisfies the conditions for simultaneous transmission. In the example of Fig. 13, it is assumed that terminal 20-11 is determined to have little interference from both AP 10-2 and AP 10-3.

[0071] In this case, the AP 10-1 schedules simultaneous transmission as shown in Fig. 14. That is, the AP 10-1 schedules simultaneous transmission so that simultaneous transmission with both the APs 10-2 and 10-3 is performed at the same time as data communication with the terminal 20-11.

[0072] In this way, in the fourth modification, the combination of the target terminal and the AP with which the simultaneous transmission will be performed and the time period for the simultaneous transmission are determined taking into consideration the interference of multiple APs with each terminal. This is also expected to result in more reliable communication.

[0073] (Fifth Modification) In the above-described embodiments and modifications, one AP may operate as both a sharing AP and a shared AP. Fig. 15 shows an example in which AP 10-1 operates as both a sharing AP and a shared AP in a communication system 1 similar to that shown in Fig. 11. In other words, AP 10-1 operates as a sharing AP for AP 10-2 and as a shared AP for AP 10-3.

[0074] In the example of Fig. 15, AP 10-1 receives reports of received power levels from subordinate terminals 20-11 and 20-12. AP 10-2 also receives a report of received power levels from subordinate terminal 20-21. AP 10-3 receives a report of received power levels from subordinate terminal 20-31. From the results, AP 10-1, AP 10-2, and AP 10-3 determine whether or not there are any terminals that satisfy the conditions for simultaneous transmission. The terminals that satisfy the conditions for simultaneous transmission are the same as those in the example of Fig. 11.

[0075] After this, AP 10-3 sends a simultaneous transmission request Req to AP 10-1. In response, AP 10-1 sends a simultaneous transmission request Req to AP 10-2. AP 10-2 replies that simultaneous transmission is possible in order to communicate with terminal 20-21 at the same time as APs 10-1 and 10-3. In response, AP 10-1 replies to AP 10-3 that simultaneous transmission is possible.

[0076] (Other Modifications) The above-described processing in the AP 10 and the terminal 20 can be stored as a program that can be executed by a processor, which is a computer. Alternatively, the program can be stored in a storage medium of an external storage device such as a magnetic disk, optical disk, or semiconductor memory and distributed. The processors of the AP 10 and the terminal 20 can then load the program stored in the storage medium of the external storage device and execute various processes by having their operations controlled by the loaded program.

[0077] 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.

[0078] 1...Communication system 10, 10-1, 10-2, 10-3...Access point (AP) 11...CPU 12...ROM 13...RAM 14...Wireless communication module 15...Wired communication module 20, 20-1, 20-11, 20-12, 20-2, 20-21, 20-3, 20-31...Terminal 21...CPU 22...ROM 23...RAM 24...Wireless communication module 25...Display 26...Storage 30...Network 110...Data processing unit 120...Frame processing unit 130...Management unit 131...Determination unit 132...Simultaneous transmission management unit 140, 150, 160...Wireless signal processing unit 210...Data processing unit 220...Frame processing unit 230...Management unit 240...Wireless signal processing unit 250...Wireless signal processing unit 260...Wireless signal processing unit 270...Application execution unit

Claims

1. An access point having a management unit that determines whether there is a terminal that satisfies the conditions for simultaneous transmission with other access points based on information about interference from other access points reported by subordinate terminals, and if there is a terminal that satisfies the conditions for simultaneous transmission, transmits a request for simultaneous transmission to the other access points.

2. The access point according to claim 1, wherein the other access points include two or more access points, and the management unit determines whether or not there is a terminal that satisfies the condition for simultaneous transmission for each of the two or more access points.

3. The access point according to claim 2, wherein the management unit further determines a time period during which a terminal that satisfies the condition for simultaneous transmission exists for each of the two or more access points.

4. The access point according to claim 1, wherein the access point operates as a sharing access point for a first access point among the other access points and as a shared access point for a second access point among the other access points.

5. The access point according to claim 1, wherein a priority for simultaneous transmission is set for the other access points, and the management unit determines whether or not there is a terminal that satisfies the simultaneous transmission conditions by making the conditions for simultaneous transmission for a second other access point that has a lower priority stricter than those for a first other access point that has a higher priority.

6. An access point having a management unit that receives a simultaneous transmission request from another access point, determines whether or not simultaneous transmission with the other access point is possible based on information on interference from the other access point reported by a subordinate terminal, transmits a response to the other access point indicating that the simultaneous transmission is permitted if the simultaneous transmission is permitted, and transmits a response to the other access point indicating that the simultaneous transmission is not permitted if the simultaneous transmission is not permitted.

7. The access point according to claim 6, wherein the other access points include two or more access points, and the management unit, when receiving a request for simultaneous transmission from a second other access point while permitting simultaneous transmission with a first other access point, determines whether simultaneous transmission with the second other access point is possible based on information on interference from the first other access point and information on interference from the second other access point reported from the subordinate terminal, and when permitting simultaneous transmission with the second other access point, transmits a request to the first other access point to cancel the simultaneous transmission and transmits a response to the second other access point to permit simultaneous transmission.

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