Access point

Abstract

An access point according to the present invention comprises a condition determination unit, a determination unit, and a simultaneous transmission request unit. The condition determination 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. The determination unit determines allocation of a resource unit (RU) to the terminal that satisfies the condition for simultaneous transmission so that the RU overlaps with a channel which is used by the other access point, and determines allocation of an RU to a terminal that does not satisfy the condition for simultaneous transmission so that the RU does not overlap with the channel which is used by the other access point. The simultaneous transmission request unit transmits, to the other access point, a request 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, it is assumed that multiple APs communicate in the same frequency band and the same bandwidth. However, if APs communicate in different bandwidths even in the same frequency band, a different simultaneous transmission method from the conventional method may be considered.

[0005] The embodiment provides an access point capable of simultaneous transmission suitable for communication using different bandwidths even in the same frequency band.

[0006] An access point according to one aspect includes a condition determination unit, a determination unit, and a simultaneous transmission request unit. The condition determination unit 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 subordinate terminals. The determination unit determines resource unit (RU) allocation so that a terminal that satisfies the simultaneous transmission condition overlaps with channels used by other access points, and so that a terminal that does not satisfy the simultaneous transmission condition does not overlap with channels used by other access points. The simultaneous transmission request unit transmits a request for simultaneous transmission to the other access points.

[0007] According to the embodiment, an access point is provided that can perform simultaneous transmission suitable for communication using different bandwidths even in the same frequency band.

[0008] FIG. 1 is a diagram showing an example of the configuration of a communication system according to an embodiment. FIG. 2 is a block diagram showing an example of the hardware configuration of an AP. FIG. 3 is a block diagram showing an example of the hardware configuration of a terminal. FIG. 4 is a block diagram showing an example of the functional configuration of an AP according to an embodiment. FIG. 5 is a diagram showing an example of the bandwidth of AP 10-1 and AP 10-2. FIG. 6 is a block diagram showing an example of the functional configuration of a terminal according to an embodiment. FIG. 7 is a flowchart showing the operation of one AP according to an embodiment. FIG. 8 is a diagram showing a specific example of RU allocation according to an embodiment. FIG. 9 is a diagram for explaining the operation of a communication system according to an embodiment. FIG. 10 is a diagram showing an example of the configuration of a communication system according to a second modified example of an embodiment. FIG. 11 is a diagram showing an example of the bandwidth of AP 10-1, AP 10-2, and AP 10-3. FIG. 12 is a diagram showing a specific example of RU allocation according to the second modified example. FIG. 13 is a diagram for explaining the operation of a communication system according to the second modified example. FIG. 14 is a diagram for explaining the operation of a communication system according to a third 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, a communication system 1 includes access points (APs) 10-1 and 10-2, terminals 20-1, 20-2, and 20-3, and a network 30.

[0010] The APs 10-1 and 10-2 and the terminals 20-1, 20-2, and 20-3 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, 20-2, and 20-3 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. However, as will be described later, AP 10-1 and AP 10-2 have different usable bandwidths. 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 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] Furthermore, in the embodiment, the APs 10-1 and 10-2 and the terminals 20-1, 20-2, and 20-3 support UL-OFDMA transmission and / or DL-OFDMA transmission. OFDMA is a method that combines orthogonal frequency division multiplexing (OFDM) and frequency division multiple access (FDMA). OFDM is a method of transmitting by dividing the bandwidth allocated to wireless communication into multiple subcarriers. In OFDM, subcarrier allocation for multiple STAs is performed in units of RUs (resource units), which are groups of subcarriers that make up one channel. By combining this with FDMA, OFDMA can finely change the subcarrier allocation depending on the radio wave conditions of each STA. This enables many-to-one transmission from multiple STAs to the AP, and therefore OFDMA can improve radio wave utilization efficiency compared to OFDM. Furthermore, the AP 10-1, AP 10-2 and terminals 20-1, 20-2 and 20-3 may support a DRU (distributed RU) that configures an RU using discretely allocated subcarriers during OFDMA transmission.

[0013] APs 10-1 and 10-2 can exchange traffic with terminals 20-1, 20-2, and 20-3. 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.

[0014] Terminals 20-1, 20-2, and 20-3 are, for example, smartphones or PCs (personal computers), and are wireless terminals conforming to the IEEE 802.11 standard. Although three terminals are shown in FIG. 1, the number of terminals is not limited to three. The communication system 1 may include one or more terminals. In the following, terminals 20-1, 20-2, and 20-3 have the same configuration. In the following, when there is no particular need to distinguish between terminals 20-1, 20-2, and 20-3, they may be referred to as terminal 20.

[0015] Next, the hardware configuration of the AP and the terminal in the communication system according to the embodiment will be described.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] Next, the functional configuration of the AP and the terminal in the communication system according to the embodiment will be described.

[0022] 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 have a physical wireless connection with the terminal 20. That is, the affiliated AP has a physical configuration for exchanging data with the terminal through a wireless link.

[0023] 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.

[0024] 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.

[0025] 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 multi-link connection processing. The management unit 130 also includes a condition determination unit 131, a determination unit 132, and a simultaneous transmission request unit 133. The condition determination unit 131 determines whether a condition for simultaneous transmission with other APs is met. The condition for simultaneous transmission is that a terminal under the control of the local station is one 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. The determination unit 132 determines the allocation of RUs for simultaneous transmission. As will be described in detail later, in this embodiment, the APs 10-1 and 10-2 can use wireless links in the same frequency band, but have different usable bandwidths. The determination unit 132 allocates RUs to communication with terminals that meet the conditions for simultaneous transmission so that the channels overlap with those used by other APs, and allocates RUs to communication with terminals that do not meet the conditions for simultaneous transmission so that the channels do not overlap with those used by other APs. The simultaneous transmission request unit 133 transmits a simultaneous transmission request to other access points via the radio signal processing unit 140, 150, or 160. The frame format of the simultaneous transmission request is not particularly limited.

[0026] Returning now to the description of FIG. 4 , 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.

[0027] As described above, in the embodiment, AP 10-1 and AP 10-2 have different usable bandwidths. FIG. 5 is a diagram showing an example of the bandwidths of AP 10-1 and AP 10-2. In one example, AP 10-1 can use both sidebands of 40 MHz each from the center frequency. In other words, the bandwidth of AP 10-1 is 80 MHz. On the other hand, AP 10-2 can use the lower sideband of 40 MHz from the center frequency. In other words, the bandwidth of AP 10-2 is 40 MHz.

[0028] FIG. 6 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.

[0029] 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.

[0030] 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.

[0031] 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. The management unit 230 can store information on the RU assigned to each terminal.

[0032] 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.

[0033] 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.

[0034] Next, the operation of the communication system according to the embodiment will be described. FIG. 7 is a flowchart showing the operation of one AP 10 according to the embodiment. One AP 10 may be either AP 10-1 or 10-2. In the following, for example, it is assumed that AP 10-1 performs the operation shown in FIG. 7. 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 using the wireless signal processing unit 150 with terminals 20-1 and 20-2, and that AP 10-2 has established a wireless link using the wireless signal processing unit 150 with terminal 20-3. 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.

[0035] In step S1, the AP 10-1 determines whether it has received reports of received power levels from the subordinate terminals 20-1 and 20-2 via the wireless signal processing unit 150. The terminals 20-1 and 20-2 periodically, or upon request from the AP 10-1, perform, for example, a CCA (Clear Channel Assessment) operation to measure the received power levels from each AP and report 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 levels. Here, the received power levels may be reported as absolute values ​​of the received power from each AP, or as ratios 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 levels may be reported. If it is determined in step S1 that a report of the received power levels has been received, the process proceeds to step S2. If it is determined in step S1 that a report of the received power levels has not been received, the process proceeds to step S8.

[0036] In step S2, AP 10-1 determines whether there is a terminal 20 that satisfies the conditions for simultaneous transmission based on the reported received power level. A terminal 20 that satisfies the conditions for simultaneous transmission is a terminal that experiences little interference from other APs. For example, if there is a terminal whose received power level from AP 10-2 is below a certain level and / or a terminal whose received power level from AP 10-2 is below a certain value relative to the received power level from 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 conditions for simultaneous transmission, the process proceeds to step S3. If it is determined in step S2 that there is no terminal 20 that satisfies the conditions for simultaneous transmission, the process proceeds to step S8.

[0037] In step S3, the AP 10-1 determines the allocation of RUs to the subordinate terminals 20-1 and 20-2. The allocation of RUs will be explained below using a specific example.

[0038] 8 is a diagram showing a specific example of RU allocation. In the following example, it is assumed that terminal 20-1 is a terminal that is located relatively far from AP 10-2 and experiences little interference from AP 10-2, i.e., a terminal that satisfies the conditions for simultaneous transmission, and terminal 20-2 is a terminal that is located relatively close to AP 10-2 and experiences significant interference from AP 10-2, i.e., a terminal that does not satisfy the conditions for simultaneous transmission.

[0039] AP 10-1 and AP 10-2 communicate with terminal 20 using wireless links in the same frequency band. Meanwhile, as shown in FIG. 5, the bandwidth available for wireless communication by AP 10-1 is wider than the bandwidth available for wireless communication by AP 10-2. If AP 10-1 performs OFDMA transmission with terminals 20-1 and 20-2, for example, a 40 MHz subchannel corresponding to the upper sideband and a 40 MHz subchannel corresponding to the lower sideband may be configured as RUs and assigned to terminals 20-1 and 20-2. Here, AP 10-2 communicates with terminal 20-3 using 40 MHz corresponding to the lower sideband, as shown in FIG. 8. Therefore, if AP 10-1 communicates using 40 MHz corresponding to the lower sideband, there is a possibility that it will be subject to interference from AP 10-2.

[0040] Therefore, as shown in Figure 8, AP 10-1 assigns an RU consisting of a 40 MHz subchannel corresponding to the lower sideband that may be subject to interference from AP 10-2 to terminal 20-1, which satisfies the conditions for simultaneous transmission, i.e., terminal 20-1 that experiences little interference from AP 10-2. On the other hand, as shown in Figure 8, AP 10-1 assigns an RU consisting of a 40 MHz subchannel corresponding to the upper sideband to terminal 20-2, which does not meet the conditions for simultaneous transmission, i.e., terminal 20-2 that experiences much interference from AP 10-2. In other words, AP 10-1 assigns an RU that overlaps with the channel used by AP 10-2 to terminals that meet the conditions for simultaneous transmission, and assigns an RU that does not overlap with the channel used by AP 10-2 to terminals that do not meet the conditions for simultaneous transmission.

[0041] In this way, in an embodiment, in a communication system in which there are multiple APs with different available bandwidths, simultaneous transmission by multiple APs is enabled by combining Co-SR and OFDMA transmission and appropriately allocating RUs.

[0042] 7, in step S4, AP 10-1 transmits a simultaneous transmission request to AP 10-2 using wireless signal processing unit 140. The simultaneous transmission request includes, for example, information about the time when simultaneous transmission will be performed, information about the terminal with which AP 10-1 will communicate during simultaneous transmission, and the like.

[0043] In step S5, AP 10-1 determines whether or not it has received a response to the simultaneous transmission request from AP 10-2. In response to the simultaneous transmission request, AP 10-2 determines whether or not to perform simultaneous transmission. For example, if the conditions for performing simultaneous transmission are met, such as when there is no conflict with the communication destination, AP 10-2 transmits a response indicating that simultaneous transmission can be performed. If the conditions for performing simultaneous transmission are not met, such as when there is conflict with the communication destination or when communication is not necessary, AP 10-2 transmits a response indicating that simultaneous transmission cannot be performed. AP 10-1 waits until it receives a response to the simultaneous transmission request from AP 10-2. If it is determined in step S5 that a response to the simultaneous transmission request from AP 10-2 has been received, the process proceeds to step S6.

[0044] In step S6, AP 10-1 determines whether simultaneous transmission is OK based on the response reception result. When AP 10-1 receives a response indicating that simultaneous transmission can be performed, it determines that simultaneous transmission is OK, and when AP 10-1 receives a response indicating that simultaneous transmission cannot be performed, it determines that simultaneous transmission is not OK. If it is determined in step S6 that simultaneous transmission is OK, the process proceeds to step S7. If it is determined in step S6 that simultaneous transmission is not OK, the process proceeds to step S8.

[0045] In step S7, AP 10-1 performs simultaneous transmission with AP 10-2. Thereafter, the process returns to step S1. For example, in a DL-OFDMA transmission operation in which data is transmitted to terminals 20-1 and 20-2, AP 10-1 first transmits a multi-user request to send (MU-RTS) frame addressed to the subordinate terminals 10-1 and 10-2, and waits to receive a clear to send (CTS) frame from the terminals 20-1 and 20-2. Upon receiving the CTS frames from the terminals 20-1 and 20-2, AP 10-1 assigns data (OFDMA frames) addressed to each terminal to the RU determined in step S3, and transmits wireless signals including these OFDMA frames to terminals 20-1 and 20-2 at the time of simultaneous transmission. Also, for example, in the case of UL-OFDMA transmission operation for receiving data from the terminals 20-1 and 20-2, the AP 10-1 transmits a trigger frame including information on the RU allocation determined in step S3 to the subordinate terminals 10-1 and 10-2. Then, the AP 10-1 receives wireless signals including the data (OFDMA frames) transmitted from the terminals 20-1 and 20-2 at the time of simultaneous transmission.

[0046] In step S8, 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 S6 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 terminals 20-1 and 20-2 using normal procedures. The communication may or may not be performed using OFDMA transmission. In addition to the individual transmission, the AP 10-1 may request the AP 10-2 to adjust its transmission power, as in normal Co-SR, or may request that the AP 10-2's communication be suppressed.

[0047] The operation of Fig. 7 will be specifically described below using Fig. 9. The communication system shown in Fig. 9 includes APs 10-1 and 10-2 and terminals 20-1, 20-2, and 20-3, similar to Fig. 1. AP 10-1 controls terminals 20-1 and 20-2, and AP 10-2 controls terminal 20-3.

[0048] AP 10-1 receives reports of received power levels from subordinate terminals 20-1 and 20-2. Based on this result, AP 10-1 determines whether there are any terminals that satisfy the conditions for simultaneous transmission. For example, assume that terminal 20-1 is determined to be a terminal that satisfies the conditions for simultaneous transmission with AP 10-2, and terminal 20-2 is determined to be a terminal that does not satisfy the conditions for simultaneous transmission with AP 10-2. In this case, as shown in FIG. 8, AP 10-1 determines the allocation of RUs so that terminal 20-1 that satisfies the conditions for simultaneous transmission is assigned an RU that overlaps with the channel used by AP 10-2, and terminal 20-2 that does not satisfy the conditions for simultaneous transmission is assigned an RU that does not overlap with the channel used by AP 10-2. After this, AP 10-1 transmits a simultaneous transmission request Req to AP 10-2.

[0049] AP 10-2 returns a response indicating that simultaneous transmission can be performed to communicate with terminal 20-3 at the same time as AP 10-1. In response to this, AP 10-1 performs simultaneous transmission with AP 10-2. FIG. 8 shows an example of DL-OFDMA transmission in which data Data1 is transmitted from AP 10-1 to terminal 20-1, and data Data2 is transmitted from AP 10-1 to terminal 20-2. Simultaneously with this transmission, data Data3 is transmitted from AP 10-2 to terminal 20-3. The subchannel used for communication between AP 10-1 and terminal 20-1 overlaps with the channel used for communication between AP 10-2 and terminal 20-3. However, because terminal 20-1 is a terminal that experiences little interference from AP 10-2, it is expected that data transmission between AP 10-1 and terminal 20-1 and data transmission between AP 10-2 and terminal 20-3 will be performed with high reliability. Furthermore, the subchannel used for communication between the AP 10-1 and the terminal 20-2 does not overlap with the channel used for communication between the AP 10-2 and the terminal 20-3, so data transmission between the AP 10-1 and the terminal 20-2 is expected to be highly reliable.

[0050] As described above, according to the embodiment, the allocation of terminals to be subjected to simultaneous transmission and RUs to be used for communication with each terminal is determined assuming that the frequency bandwidths used by the multiple APs are different. As a result, it is expected that simultaneous transmission by multiple APs can be performed with high reliability when communication is performed using different bandwidths even if the same frequency band is used.

[0051] (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 also be AP 10-2. However, as shown in FIG. 5, AP 10-2 has a narrower bandwidth than AP 10-1. Therefore, for simultaneous transmission, AP 10-2 needs to cause AP 10-1 to perform RU allocation similar to that shown in FIG. 8. For this reason, it is desirable that the simultaneous transmission request transmitted from AP 10-2 to AP 10-1 include information on the time at which simultaneous transmission will be performed, information on the terminal with which AP 10-2 will communicate during simultaneous transmission, and also information on the RU allocation performed by AP 10-1.

[0052] 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 20-3 via AP 10-2.

[0053] (Second Modification) In the embodiment, the number of APs is two. As described above, the number of APs may be three or more. Even when there are three or more APs, the allocation of RUs may be determined so that a terminal that satisfies the condition for simultaneous transmission with other APs is assigned an RU that overlaps with the channel used by the other APs, and a terminal that does not satisfy the condition for simultaneous transmission with other APs is assigned an RU that does not overlap with the channel used by the other APs. A specific example will be described below.

[0054] 10 is a diagram illustrating an example of the configuration of a communication system according to a second modification of the embodiment. As illustrated in FIG. 10, the communication system 1 according to the second modification includes APs 10-1, 10-2, and 10-3, terminals 20-1, 20-2, 20-3, and 20-4, and a network 30.

[0055] APs 10-1, 10-2, and 10-3 have the hardware configuration shown in FIG. 2 and the functional configuration shown in FIG. 4. Similarly, terminals 20-1, 20-2, 20-3, and 20-4 have the hardware configuration shown in FIG. 3 and the functional configuration shown in FIG. 6. However, even in the second modified example, APs 10-1, 10-2, and 10-3 have different usable bandwidths. FIG. 11 is a diagram showing an example of the bandwidths of APs 10-1, 10-2, and 10-3. In one example, AP 10-1 can use both sidebands of 40 MHz each from the center frequency. That is, the bandwidth of AP 10-1 is 80 MHz. AP 10-2 can use the lower sideband of 40 MHz from the center frequency. That is, the bandwidth of AP 10-2 is 40 MHz. Furthermore, AP 10-3 can use the upper sideband of 40 MHz from the center frequency. That is, the bandwidth of AP10-3 is 40 MHz.

[0056] The operation of an AP making a simultaneous transmission request is the same as the operation shown in FIG. 7. In the following example, it is assumed that AP 10-1 is the AP making the simultaneous transmission request. In the following example, it is assumed that AP 10-1 and AP 10-2 have established a wireless link using wireless signal processing unit 140. It is assumed that AP 10-1 and AP 10-3 have established a wireless link using wireless signal processing unit 150. It is assumed that AP 10-1 has established a wireless link using wireless signal processing unit 160 with terminals 20-1 and 20-2, and that AP 10-2 has established a wireless link using wireless signal processing unit 160 with terminal 20-3. It is assumed that AP 10-3 has established a wireless link using wireless signal processing unit 160 with terminal 20-4. Here, communication between AP 10-1 and AP 10-2 and communication between AP 10-1 and AP 10-3 do not necessarily have to be performed wirelessly, but may be performed via wired communication.

[0057] In the example of FIG. 10, AP 10-1 receives reports of received power levels from subordinate terminals 20-1 and 20-2. Based on the results, AP 10-1 determines whether or not there are any terminals that satisfy the conditions for simultaneous transmission. For example, assume that terminal 20-1 is determined to be a terminal that satisfies the conditions for simultaneous transmission with AP 10-2 but does not satisfy the conditions for simultaneous transmission with AP 10-3, and terminal 20-2 is determined to be a terminal that satisfies the conditions for simultaneous transmission with AP 10-3 but does not satisfy the conditions for simultaneous transmission with AP 10-2. In this case, as shown in FIG. 12, AP 10-1 assigns an RU consisting of a 40 MHz subchannel corresponding to the lower sideband to terminal 20-1, and assigns an RU consisting of a 40 MHz subchannel corresponding to the upper sideband to terminal 20-2. That is, AP 10-1 determines the allocation of RUs so that terminal 20-1, which does not satisfy the conditions for simultaneous transmission with AP 10-3 but satisfies the conditions for simultaneous transmission with AP 10-2, is assigned an RU that does not overlap with the channel used by AP 10-3 and overlaps with the channel used by AP 10-2. Also, AP 10-1 determines the allocation of RUs so that terminal 20-2, which does not satisfy the conditions for simultaneous transmission with AP 10-2 but satisfies the conditions for simultaneous transmission with AP 10-3, is assigned an RU that does not overlap with the channel used by AP 10-2 and overlaps with the channel used by AP 10-3.

[0058] Thereafter, the AP 10-1 transmits a simultaneous transmission request Req to the APs 10-2 and 10-3 as shown in FIG.

[0059] AP 10-2 responds that it can perform simultaneous transmission to communicate with terminal 20-3 at the same time as AP 10-1. AP 10-3 also responds that it can perform simultaneous transmission to communicate with terminal 20-4 at the same time as AP 10-1. In response to this, AP 10-1 performs simultaneous transmission with APs 10-2 and 10-3. FIG. 13 shows an example of DL-OFDMA transmission in which data Data1 is transmitted from AP 10-1 to terminal 20-1, and data Data2 is transmitted from AP 10-1 to terminal 20-2. Simultaneously with this transmission, data Data3 is transmitted from AP 10-2 to terminal 20-3, and data Data4 is transmitted from AP 10-3 to terminal 20-4. The subchannel used for communication between AP 10-1 and terminal 20-1 overlaps with the channel used for communication between AP 10-2 and terminal 20-3, but does not overlap with the channel used for communication between AP 10-3 and terminal 20-4. Because terminal 20-1 is a terminal that experiences little interference from AP 10-2, data transmission between AP 10-1 and terminal 20-1 is expected to be carried out with high reliability. Furthermore, the subchannel used for communication between AP 10-1 and terminal 20-2 overlaps with the channel used for communication between AP 10-3 and terminal 20-4, but does not overlap with the channel used for communication between AP 10-2 and terminal 20-3. Because terminal 20-2 is a terminal that experiences little interference from AP 10-3, data transmission between AP 10-1 and terminal 20-2 is also expected to be carried out with high reliability. Furthermore, data transmission between the AP 10-2 and the terminal 20-3 and data transmission between the AP 10-3 and the terminal 20-4 are also expected to be performed with high reliability.

[0060] In this way, according to the second modification, the technology of the embodiment can be applied to a communication system including three or more APs.

[0061] (Third Modification) In a second modification, AP 10-1 transmits a simultaneous transmission request to APs 10-2 and 10-3. That is, AP 10-1 essentially operates as a sharing AP, and AP 10-2 essentially operates as a shared AP. In contrast, one AP may operate as both a sharing AP and a shared AP. Figure 14 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 of Figure 13. That is, AP 10-1 operates as a sharing AP for AP 10-2 and as a shared AP for AP 10-3.

[0062] In the example of Fig. 14, AP 10-1 receives reports of received power levels from subordinate terminals 20-1 and 20-2. Also, AP 10-3 receives a report of received power levels from subordinate terminal 20-4. From the results, AP 10-1 and AP 10-3 determine whether 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. 13. AP 10-1 performs RU allocation in the same manner as shown in Fig. 12.

[0063] After this, AP 10-3 transmits a simultaneous transmission request Req to AP 10-1. In response, AP 10-1 transmits a simultaneous transmission request Req to AP 10-2. AP 10-2 returns a response indicating that simultaneous transmission can be performed in order to communicate with terminal 20-3 at the same time as APs 10-1 and 10-3. In response, AP 10-1 returns a response indicating that simultaneous transmission can be performed to AP 10-3. In response, AP 10-3 performs simultaneous transmission with APs 10-1 and 10-2. FIG. 14 shows an example of DL-OFDMA transmission in which data Data1 is transmitted from AP 10-1 to terminal 20-1, and data Data2 is transmitted from AP 10-1 to terminal 20-2. Simultaneously with this transmission, data Data3 is transmitted from AP 10-2 to terminal 20-3, and data Data4 is transmitted from AP 10-3 to terminal 20-4.

[0064] (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.

[0065] 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.

[0066] 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, 20-2, 20-3, 20-4...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...Condition judgment unit 132...Decision unit 133...Simultaneous transmission request unit 140, 150, 160...Wireless signal processing unit 210...Data processing unit 220...Frame processing unit 230...Management unit 240, 250, 260...Wireless signal processing unit 270...Application execution unit

Claims

1. An access point comprising: a condition determination unit that determines whether or not 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; a determination unit that determines resource unit (RU) allocation so that terminals that satisfy the conditions for simultaneous transmission overlap with channels used by the other access points, and so that terminals that do not satisfy the conditions for simultaneous transmission are assigned RUs that do not overlap with channels used by the other access points; and a simultaneous transmission request unit that transmits a request for simultaneous transmission to the other access points.

2. The access point according to claim 1, wherein the simultaneous transmission request unit transmits the simultaneous transmission request together with information on the allocation of the RUs.

3. The access point according to claim 1, wherein the other access points include two or more access points, the condition determination unit determines whether or not there is a terminal that satisfies the conditions for simultaneous transmission for each of the two or more access points, and the determination unit determines the allocation of RUs for each of the two or more access points so that the RU is allocated to a terminal that satisfies the conditions for simultaneous transmission so as to overlap with the channel used by the corresponding access point, and the RU is allocated to a terminal that does not satisfy the conditions for simultaneous transmission so as not to overlap with the channel used by the corresponding access point.

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.

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