Wireless device and wireless communication method

Abstract

According to one aspect of the present invention, a wireless device comprises an acquisition unit and a multilink control unit. The acquisition unit acquires a communication quality indicator that indicates the communication quality of a link for each of a plurality of links that form a multilink with another wireless device. The multilink control unit determines whether to suspend use of a first link that has the lowest communication quality of the plurality of links on the basis of a comparison of the communication quality indicator for the first link and a first threshold value.

Description

Technical Field

[0001] The present invention relates to wireless communication.

Background Art

[0002] As a wireless system that wirelessly connects a base station and a terminal, a wireless LAN (Local Area Network) is known. A base station and a terminal, which are wireless stations of a wireless LAN, perform carrier sensing based on CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) and transmit data when they acquire the right to transmit.

[0003] The multi-link function being considered in IEEE802.11be, which is being formulated as a successor standard to IEEE802.11ax, enables a terminal to establish a plurality of links with a base station. When a plurality of links are established, a wireless station performs carrier sensing based on CSMA / CA for each link and transmits a data frame using the link that has acquired the right to transmit. The multi-link function brings about improvements in throughput and delay characteristics.

[0004] On the other hand, in a case where there is a hidden terminal, even if a wireless station transmits a frame using the link that has acquired the right to transmit, a collision may occur between the frame transmitted by the wireless station and a frame transmitted by another wireless station that the wireless station cannot detect. Such frame collisions deteriorate the communication characteristics of multi-link communication.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a technique for preventing deterioration of communication characteristics in multi-link communication.

Means for Solving the Problems

[0007] A wireless device according to an aspect of the present invention includes an acquisition unit that acquires a communication quality index indicating the communication quality of each of a plurality of links constituting a multi-link with another wireless device, and among the plurality of links, a multi-link control unit that determines whether to suspend the use of the first link based on a comparison between the communication quality index of the first link with the lowest communication quality and a first threshold value.

Advantages of the Invention

[0008] According to the present invention, a technique for preventing deterioration of communication characteristics in multi-link communication is provided.

Brief Description of the Drawings

[0009]

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DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0011] FIG. 1 schematically shows a configuration example of a communication system 50 including a wireless network 45 according to an embodiment. The "system" and "network" described in this specification may be used interchangeably. As shown in FIG. 1, the communication system 50 includes a base station 10, a terminal 20, and a server 30. The base station 10 and the terminal 20 are included in the wireless network 45.

[0012] The base station 10 operates as an access point (AP) for a wireless LAN. The base station 10 can be wirelessly connected to one or more terminals. The number of terminals wirelessly connected to the base station 10 dynamically changes. In the example shown in FIG. 1, the base station 10 is wirelessly connected to the terminal 20. The base station 10 establishes one or more links with the terminal 20 and uses the one or more links to wirelessly communicate with the terminal 20. In this specification, the wireless connection using a plurality of links between a base station and a terminal is referred to as "multi-link". The base station 10 is connected, for example, wired to a communication network 40 that may include the Internet.

[0013] The terminal 20 is a wireless terminal device having a wireless communication function. Examples of the wireless terminal device include a smartphone, a mobile phone, a tablet PC (personal computer), a desktop PC, a laptop PC, and an IoT (Internet of things) sensor / device. The terminal 20 exchanges data with a computer such as a server 30 on the communication network 40 via the base station 10.

[0014] The server 30 is connected to the communication network 40. For example, the server 30 may be a service provider that provides services such as a network game, and exchanges service-related data with the terminal 20 via the communication network 40.

[0015] In the wireless network 45, the wireless communication between the base station 10 and the terminal 20 is based on the IEEE802.11 standard. Although the wireless communication based on the IEEE802.11 standard is described as an example in this specification, a wireless communication standard different from the IEEE802.11 standard may be used.

[0016] The IEEE 802.11 standard defines the first layer and the MAC (media access control) sublayer of the second layer of the OSI (Open Systems Interconnection) model. In the OSI model, communication functions are divided into seven layers (the first layer: physical layer, the second layer: data link layer, the third layer: network layer, the fourth layer: transport layer, the fifth layer: session layer, the sixth layer: presentation layer, the seventh layer: application layer). The data link layer includes, for example, the LLC (logical link control) layer and the MAC layer. The LLC layer forms an LLC packet by adding, for example, a DSAP (destination service access point) header and an SSAP (source service access point) header to the data input from the upper layer. The MAC layer generates a MAC frame by adding a MAC header to the LLC packet, for example. The physical layer generates a radio frame by adding a preamble and a PHY (physical layer) header to the MAC frame, for example. Here, the processing of the first layer and the MAC sublayer of the second layer defined by the IEEE 802.11 standard will be mainly described, and the description of the processing of other layers will be omitted.

[0017] Figure 2 schematically shows the frequency bands used in the wireless network 45. In the example shown in Figure 2, in the wireless communication between the base station 10 and the terminal 20, three frequency bands, namely, the 6 GHz band, the 5 GHz band, and the 2.4 GHz band, can be used. Each frequency band includes a plurality of channels. In this embodiment, the multi-link is formed using channels in different frequency bands. For example, three links using channels in the 6 GHz band, channels in the 5 GHz band, and channels in the 2.4 GHz band can be established between the base station 10 and the terminal 20. In other embodiments, a plurality of channels included in the same frequency band may be used to form the multi-link.

[0018] FIG. 3 schematically shows a link management table as link management information held by the base station 10. The link management information is information for managing the link states of each terminal wirelessly connected to the base station 10. In the example shown in FIG. 3, the link management table includes information about the STA function, multi-link, link, TID (Traffic Identifier), throughput, and delay.

[0019] The STA function corresponds to a radio signal processing unit that processes radio signals. In the present embodiment, the base station 10 includes three radio signal processing units: a radio signal processing unit configured to transmit and receive radio signals using a channel in the 6 GHz band, a radio signal processing unit configured to transmit and receive radio signals using a channel in the 5 GHz band, and a radio signal processing unit configured to transmit and receive radio signals using a channel in the 2.4 GHz band. In FIG. 3, STA1 represents a radio signal processing unit that uses a channel in the 6 GHz band, STA2 represents a radio signal processing unit that uses a channel in the 5 GHz band, and STA3 represents a radio signal processing unit that uses a channel in the 2.4 GHz band.

[0020] The multi-link information includes information indicating whether a multi-link is established between the base station 10 and the terminal, and information indicating which link is established when the multi-link is established. The link information includes information indicating whether the link is used for data transmission. In the example shown in FIG. 3, for terminal A, the multi-link information indicates that a multi-link is established between the base station 10 and terminal A, and three links corresponding to STA1, STA2, and STA3 are established. The link information indicates that the links corresponding to STA1 and STA3 are used for data transmission, and the link corresponding to STA2 is not used for data transmission. In other words, the links corresponding to STA1 and STA3 are in an active state, and the link corresponding to STA2 is in an inactive state. For terminal B, the multi-link information indicates that a multi-link is not established between the base station 10 and terminal B. The link information indicates that the link corresponding to STA2 is used for data transmission. That is, a single link is established between the base station 10 and terminal B. Terminal B may be a legacy terminal that does not support the multi-link function.

[0021] The TID is an identifier indicating the type of traffic (data). Each STA function transmits and receives traffic of the TID assigned to itself. The traffic is classified into multiple access categories. In one example, the traffic may be classified into four access categories: "VO (Voice)", "VI (Video)", "BE (Best Effort)", and "BK (Background)". In another example, the traffic may be classified into five access categories: "VO", "VI", "BE", "BK", and "LL (Low Latency)". The traffic of the access category "LL" is latency-sensitive traffic such as traffic generated from real-time applications such as network games. For example, the traffic of TID#1 is classified into the access category "VO", the traffic of TID#2 is classified into the access category "VI", the traffic of TID#3 is classified into the access category "BE", and the traffic of TID#4 is classified into the access category "BK". In the example shown in Figure 3, for terminal A, TID#1 is assigned to STA1, TID#2 is assigned to STA1 and STA3, TID#3 is assigned to STA1 and STA3, and TID#4 is assigned to STA1. In other words, STA1 is used to transmit and receive traffic of TID#1 to TID#4, and STA3 is used to transmit and receive traffic of TID#2 and TID#3. For terminal B, a single link corresponding to STA2 is established, and TID#1 to TID#4 are assigned to STA2.

[0022] The links corresponding to the STA function are associated with the TID when the multi-link between the base station 10 and the terminal is established. For example, in the association between the TID and the link (TID-to-link mapping), each TID may be associated with all the links. Alternatively, the association between the TID and the link may be set so that the traffic volume (data volume) is equal among the plurality of links constituting the multi-link. Also, traffic of similar types to each other may be associated with a specific link. The frequency band assigned for the transmission and reception of traffic is preferably selected according to the type of traffic and the data volume. For example, it is conceivable to associate voice (VO) with a small data volume with the 2.4 GHz band and video (VI) with a large data volume with the 5 GHz band.

[0023] The base station 10 measures (monitors) the throughput and delay regarding data transmission between the base station 10 and the terminal for each terminal and for each link (STA function), and registers those measured values in the link management table. In FIG. 3, symbols (such as T1, D1, etc.) are described in the columns of throughput and delay, but actually specific numerical values are stored.

[0024] FIG. 4 schematically shows an example of the arrangement of radio stations included in the wireless network 45. In the example shown in FIG. 4, the wireless network 45 includes basic service sets (BSSs) 41 and 42 adjacent to each other. BSS 41 includes the base station 10-1 and terminals 20-1, 20-2, and 20-3. A multi-link is established between the base station 10-1 and the terminal 20-1, and the multi-link includes three links corresponding to the 6 GHz band, 5 GHz band, and 2.4 GHz band. The terminals 20-2 and 20-3 are legacy terminals, and a single link corresponding to the 5 GHz band is established between the base station 10-1 and each of the terminals 20-2 and 20-3. BSS 42 includes the base station 10-2 and the terminal 20-4. A multi-link is established between the base station 10-2 and the terminal 20-4, and the multi-link includes three links corresponding to the 6 GHz band, 5 GHz band, and 2.4 GHz band.

[0025] Base stations 10-2 and terminal 20-4 are hidden terminals for base station 10-1. Therefore, a situation may occur where while base station 10-1 transmits a frame to terminal 20-1 on a 5 GHz band link, base station 10-2 or terminal 20-4 transmits a frame to terminal 20-4 or base station 10-2 on a 5 GHz band link. In this case, frame collision occurs at terminal 20-1, and terminal 20-1 may fail to receive the frame from base station 10-1. Frame collision leads to a decrease in throughput and / or an increase in delay, deteriorating the communication characteristics of the multi-link communication between base station 10-1 and terminal 20-1.

[0026] Also, when using the RTS (Request to Send) / CTS (Clear to Send) function for communication between base station 10-1 and terminal 20-1, terminal 20-1 sets a NAV (Network Allocation Vector) period for the 5 GHz band link in response to the detection of an RTS frame or data frame transmitted on the 5 GHz band link by base station 10-2 or terminal 20-4. Even if terminal 20-1 receives an RTS frame from base station 10-1, it does not transmit a CTS frame to base station 10-1 during the NAV period. If base station 10-1 cannot receive a CTS frame from terminal 20-1, it will retransmit the RTS frame. Although the use of the RTS / CTS function can effectively prevent the above-mentioned frame collision, there may be many situations where retransmission of the RTS frame is required. Thus, even when using the RTS / CTS function, the communication characteristics of the multi-link communication between base station 10-1 and terminal 20-1 may deteriorate.

[0027] Furthermore, when there are many legacy terminals that use only links corresponding to a specific frequency band (5 GHz band in the example of FIG. 4) such as terminals 20-2 and 20-3, the competition of links corresponding to the specific frequency band increases. Regarding the links corresponding to the specific frequency band, the throughput decreases and / or the delay increases. As a result, the communication characteristics of the multi-link communication between base station 10-1 and terminal 20-1 deteriorate.

[0028] In this embodiment, the base station 10-1 measures the packet error rate (PER), which is a communication quality index indicating the communication quality of a link, for each terminal and each link. The base station 10-1 determines that a link with a measured PER value exceeding a predetermined threshold is a link where many frame collisions occur, and suspends the use of this link. In the example shown in FIG. 4, the base station 10-1 suspends the use of the 5 GHz band link established between the base station 10-1 and the terminal 20-1. As shown in the right part of FIG. 4, the base station 10-1 and the terminal 20-1 communicate with each other using the 6 GHz link and the 2.4 GHz link. By avoiding the use of the 5 GHz link determined to be a link where many frame collisions occur, it is possible to prevent the communication characteristics of the multi-link communication between the base station 10-1 and the terminal 20-1 from deteriorating.

[0029] FIG. 5 schematically shows an example of the hardware configuration of the base station 10. As shown in FIG. 5, the base station 10 includes, for example, a CPU (Central Processing Unit) 101, a program memory 102, a RAM (Random Access Memory) 103, a wireless communication module 104, and a wired communication module 105.

[0030] The CPU 101 is an integrated circuit capable of executing various programs, and controls the overall operation of the base station 10. The program memory 102 is a non-volatile semiconductor memory such as a ROM (read only memory) or a flash memory, and stores programs and control data for controlling the base station 10. The RAM 103 is, for example, a volatile semiconductor memory and is used as a working area for the CPU 101. The wireless communication module 104 is a circuit used for transmitting and receiving data by wireless signals and is connected to an antenna. The wireless communication module 104 includes a plurality of communication modules corresponding to a plurality of frequency bands respectively. The wired communication module 105 is a circuit used for transmitting and receiving data by wired signals and is connected to the communication network 40.

[0031] The hardware configuration shown in FIG. 5 is an example, and the base station 10 may have a hardware configuration different from that shown in FIG. 5. For example, when the base station 10 is wirelessly connected to the communication network 40, the wired communication module 105 may be omitted from the base station 10.

[0032] FIG. 6 schematically shows an example of the functional configuration of the base station 10. As shown in FIG. 6, the base station 10 includes an LLC processing unit 110, a link management unit 150, and radio signal processing units 160, 170, and 180. The LLC processing unit 110 can be realized by a combination of the CPU 101 and the wired communication module 105. The data processing unit 120, the MAC frame processing unit 130, the link management unit 150, and the radio signal processing units 160, 170, and 180 can be realized by the wireless communication module 104 or a combination of the wireless communication module 104 and the CPU 101.

[0033] The LLC processing unit 110 performs LLC layer processing and upper layer (layers 3 to 7) processing on the input data. For example, the LLC processing unit 110 adds a DSAP header and an SSAP header, etc., to the data received from a computer on the communication network 40 (e.g., the server 30 shown in FIG. 1) to generate an LLC packet, and sends the LLC packet to the link management unit 150. Also, the LLC processing unit 110 receives the LLC packet from the link management unit 150, extracts the data from the LLC packet, and transmits the data to a computer on the communication network 40.

[0034] The link management unit 150 performs MAC layer processing on the input data. Further, the link management unit 150 manages the links with each terminal wirelessly connected to the base station 10. The link management unit 150 includes a data processing unit 120, a MAC frame processing unit 130, and a management unit 140.

[0035] The data processing unit 120 receives LLC packets from the LLC processing unit 110, adds a MAC header to the LLC packets to generate MAC frames, and then sends the MAC frames to the MAC frame processing unit 130. Also, the data processing unit 120 receives MAC frames from the MAC frame processing unit 130, extracts LLC packets from the MAC frames, and then sends the LLC packets to the LLC processing unit 110.

[0036] The MAC frame processing unit 130 receives MAC frames, which are data frames, from the data processing unit 120 and temporarily stores the MAC frames. Then, the MAC frame processing unit 130 performs carrier sense to check the status of the channel corresponding to the link associated with the TID of the data included in the MAC frame. If the channel is busy, the MAC frame processing unit 130 continues carrier sense. If the channel is idle, the MAC frame processing unit 130 sends the MAC frame to the wireless signal processing unit corresponding to the link associated with the TID of the data included in the MAC frame. The MAC frame processing unit 130 receives MAC frames, which are management frames or control frames, from the management unit 140 and sends the MAC frames to any of the wireless signal processing units 160, 170, and 180.

[0037] Also, the MAC frame processing unit 130 receives MAC frames from the wireless signal processing units 160, 170, and 180 and sends the MAC frames to the data processing unit 120 or the management unit 140 according to the type of the MAC frames. For example, if the MAC frame is a data frame, the MAC frame processing unit 130 sends the MAC frame to the data processing unit 120. If the MAC frame is a management frame or a control frame, the MAC frame processing unit 130 sends the MAC frame to the management unit 140. Furthermore, the MAC frame processing unit 130 executes processing based on the instructions of the management unit 140 or exchanges information with the management unit 140.

[0038] The management unit 140 manages the link with the terminal based on the information included in the management frame received from the wireless signal processing units 160, 170, 180 via the MAC frame processing unit 130. In one example, the management unit 140 includes link management information 141, an association processing unit 142, an authentication processing unit 143, a measurement unit 144, a multi-link control unit 145, and a notification unit 146.

[0039] The link management information 141 includes information about the terminal wirelessly connected to the base station 10. The link management information 141 is stored, for example, in the RAM 103 and is referenced by the MAC frame processing unit 130. For example, the MAC frame processing unit 130 uses the link management information 141 to identify the link corresponding to the TID of the data included in the MAC frame to be transmitted. When the link management information 141 includes the information shown in FIG. 3, for terminal A, TID#1 is associated with the link corresponding to STA1 (i.e., the wireless signal processing unit 160). When the MAC frame processing unit 130 receives a MAC frame including data addressed to terminal A with TID#1 from the data processing unit 120, the MAC frame is sent to the wireless signal processing unit 160.

[0040] When the association processing unit 142 receives a connection request from the terminal via any of the wireless signal processing units 160, 170, 180, it executes the protocol regarding association. The authentication processing unit 143 executes the protocol regarding authentication following the association.

[0041] The measurement unit 144 measures at least one type of metric related to the communication quality or performance of the link. Some of the metrics can be statistical quantities. At least one type of metric to be measured includes a communication quality metric indicating the communication quality of the link. The measurement unit 144 measures the communication quality metric for each terminal and for each link. The communication quality metric may include at least one of PER, the collision rate divided by the air time, and the retransmission rate of RTS (Request to Send). PER indicates the ratio of frames that the terminal could not receive out of the frames transmitted by the base station 10 to the terminal. The collision rate indicates the ratio of frames transmitted by the base station 10 to the terminal that collided with frames transmitted by other radio stations (e.g., other terminals and / or other base stations) at the terminal. The air time indicates the total time the channel (link) was used to transmit a frame to the terminal. The RTS retransmission rate indicates the ratio at which RTS frames from the base station 10 to the terminal are retransmitted.

[0042] At least one type of metric to be measured may further include throughput and delay related to data transmission between the base station 10 and the terminal. The measurement unit 144 measures throughput and delay for each terminal and for each link. At least one type of metric to be measured may further include an Ack response rate. The Ack response rate indicates the ratio of Ack frames received by the base station 10 from the terminal to the frames transmitted by the base station 10 to the terminal. The Ack frame is a frame used for a confirmation response to frame reception. The measurement unit 144 measures the Ack response rate for each terminal and for each link. At least one type of metric to be measured may further include the reception success probability of a dummy frame. The dummy frame is a data frame containing dummy data and is used to determine whether to resume the use of an idle link. The reception success probability of the dummy frame indicates the probability that the terminal successfully receives the dummy frame transmitted by the base station 10.

[0043] The multi-link control unit 145 controls the use of a plurality of links that constitute a multi-link for each terminal. The multi-link control unit 145 performs multi-link control based on the measurement results of at least one type of metric obtained by the measurement unit 144. The multi-link control includes a process of suspending the use of a link, a process of resuming the use of a link, and an association between a TID and a link accompanying the suspension or resumption of the use of the link. For example, when the PER for a certain link of a certain terminal exceeds a predetermined threshold, the multi-link control unit 145 suspends the use of the link. For example, the multi-link control unit 145 resumes the use of the link when the total throughput does not improve after suspending the use of the link. Also, for example, the multi-link control unit 145 includes a transmission unit that transmits a dummy frame to the terminal using a suspended link, the measurement unit 144 measures the reception success probability of the dummy frame, and the multi-link control unit 145 resumes the use of the link in response to the reception success probability of the dummy frame exceeding a predetermined threshold.

[0044] Furthermore, the multi-link control unit 145 performs an association between a TID and a link. The association between a TID and a link is executed, for example, when establishing a multi-link between the base station 10 and the terminal.

[0045] The notification unit 146 notifies the terminal of multi-link control information for controlling the use of a plurality of links that constitute a multi-link. In one example, the multi-link control information is generated by the multi-link control unit 145 and includes information indicating a link whose use is to be suspended or resumed. The multi-link control information may be transmitted to the terminal in a management frame (e.g., beacon). In another example, the multi-link control information includes the measurement results obtained by the measurement unit 144.

[0046] The wireless signal processing unit 160 transmits and receives data between the base station 10 and the terminal by wireless communication. Specifically, the wireless signal processing unit 160 performs physical layer processing on the input data or wireless signal. For example, the wireless signal processing unit 160 receives a MAC frame from the MAC frame processing unit 130, adds a preamble, a PHY header, etc. to the MAC frame to generate a wireless frame. Then, the wireless signal processing unit 160 performs a predetermined modulation operation on the wireless frame to convert the wireless frame into a wireless signal, and radiates the wireless signal via an antenna. The predetermined modulation operation includes, for example, convolutional coding, interleaving, subcarrier modulation, inverse fast Fourier transform (IFFT), orthogonal frequency division multiplexing (OFDM) modulation, and frequency conversion. Also, the wireless signal processing unit 160 receives a wireless signal from the terminal via an antenna, performs a predetermined demodulation operation on the received wireless signal to obtain a wireless frame. The predetermined demodulation operation includes, for example, frequency conversion, OFDM demodulation, fast Fourier transform (FFT), subcarrier demodulation, deinterleaving, and Viterbi decoding. Then, the wireless signal processing unit 160 extracts a MAC frame from the wireless frame and sends the MAC frame to the MAC frame processing unit 130.

[0047] The wireless signal processing units 170 and 180 perform the same processing as the wireless signal processing unit 160. Therefore, the description of the wireless signal processing units 170 and 180 is omitted. In this example, the wireless signal processing units 160, 170, and 180 handle wireless signals in the 6 GHz band, 5 GHz band, and 2.4 GHz band, respectively. Note that the wireless signal processing units 160, 170, and 180 may use a common antenna or individual antennas.

[0048] FIG. 7 schematically shows the channel access function of the MAC frame processing unit 130. As shown in FIG. 7, the MAC frame processing unit 130 includes a classification unit 131, transmission queues 132A, 132B, 132C, 132D, 132E, carrier sense execution units 133A, 133B, 133C, 133D, 133E, and a collision management unit 134.

[0049] The classification unit 131 classifies the MAC frames received from the data processing unit 120 and inputs them to the transmission queues 132A, 132B, 132C, 132D, 132E. In the example shown in FIG. 7, the classification unit 131 classifies the MAC frames into five access categories "LL", "VO", "VI", "BE", "BK", inputs the MAC frames classified into the access category "LL" to the transmission queue 132A, inputs the MAC frames classified into the access category "VO" to the transmission queue 132B, inputs the MAC frames classified into the access category "VI" to the transmission queue 132C, inputs the MAC frames classified into the access category "BE" to the transmission queue 132D, and inputs the MAC frames classified into the access category "BK" to the transmission queue 132E. The transmission queues 132A, 132B, 132C, 132D, 132E buffer the input MAC frames. The transmission queues 132A, 132B, 132C, 132D, 132E are realized by, for example, the RAM 103.

[0050] The carrier sense execution units 133A, 133B, 133C, 133D, and 133E execute carrier sense based on CSMA / CA according to the access parameters preset for each of them. The access parameters are set for each access category so that the transmission of wireless signals is prioritized in the order of, for example, "LL", "VO", "VI", "BE", and "BK". The carrier sense execution units 133A, 133B, 133C, 133D, and 133E each execute carrier sense for the MAC frames stored in the transmission queues 132A, 132B, 132C, 132D, and 132E. For example, when the carrier sense execution unit 133A acquires the right to transmit (when the channel is idle), it extracts the MAC frame from the transmission queue 132A and outputs the MAC frame to the wireless signal processing unit corresponding to the link associated with the access category "LL" via the collision management unit 134.

[0051] When multiple carrier sense execution units among the carrier sense execution units 133A, 133B, 133C, 133D, and 133E acquire the right to transmit for the same link, the collision management unit 134 prevents transmission collisions. The collision management unit 134 prioritizes the transmission of data in the access category with a higher priority. The access category "LL" has the highest priority. Suppose the carrier sense execution unit 133A and any one of the carrier sense execution units 133B, 133C, 133D, and 133E simultaneously acquire the right to transmit for the link corresponding to the wireless signal processing unit 160. In this case, the collision management unit 134 prioritizes the transmission right acquired by the carrier sense execution unit 133A and outputs the MAC frame received from the carrier sense execution unit 133A to the wireless signal processing unit 160.

[0052] In the embodiment, an example in which the MAC frame processing unit 130 implements the channel access function is described, but the wireless signal processing units 160, 170, and 180 may implement the channel access function.

[0053] FIG. 8 schematically shows an example of the hardware configuration of the terminal 20. As shown in FIG. 8, the terminal 20 includes, for example, a CPU 201, a program memory 202, a RAM 203, a wireless communication module 204, a display 205, and a storage 206.

[0054] The CPU 201 is an integrated circuit capable of executing various programs and controls the overall operation of the terminal 20. The program memory 202 is a non-volatile semiconductor memory such as a ROM and stores programs and control data for controlling the terminal 20. The storage 206 may be used as the program memory 202. The RAM 203 is, for example, a volatile semiconductor memory and is used as a work area for the CPU 201. The wireless communication module 204 is a circuit used for transmitting and receiving data by wireless signals and is configured to be connectable to an antenna. Further, the wireless communication module 204 includes, for example, a plurality of communication modules respectively corresponding to a plurality of frequency bands. The display 205 displays information such as a GUI (Graphical User Interface) provided by application software. The display 205 may have a function as an input interface of the terminal 20. For example, a touch panel may be provided on the display 205. The storage 206 is a non-volatile storage device and stores data including, for example, the system software of the terminal 20.

[0055] The hardware configuration shown in FIG. 8 is an example, and the terminal 20 may have a hardware configuration different from that shown in FIG. 8. For example, when the terminal 20 is an IoT device or the like, the display 205 may be omitted from the terminal 20.

[0056] Figure 9 schematically shows an example of the functional configuration of the terminal 20. As shown in Figure 9, the terminal 20 includes an LLC processing unit 210, a link management unit 250, wireless signal processing units 260, 270, 280, and an application execution unit 290. The LLC processing unit 210 and the application execution unit 290 can be implemented by the CPU 201. The link management unit 250 and the wireless signal processing units 260, 270, 280 can be implemented by the wireless communication module 204 or a combination of the wireless communication module 204 and the CPU 201.

[0057] The LLC processing unit 210 executes LLC layer and upper layer processing on the input data. For example, the LLC processing unit 210 receives data from the application execution unit 290, adds a DSAP header, an SSAP header, etc. to the data to generate an LLC packet, and sends the LLC packet to the link management unit 250. Also, the LLC processing unit 210 receives an LLC packet from the link management unit 250, extracts the data from the LLC packet, and sends the data to the application execution unit 290.

[0058] The link management unit 250 executes MAC layer processing on the input data. Further, the link management unit 250 manages the link with the base station 10 wirelessly connected to the terminal 20. The link management unit 250 includes a data processing unit 220, a MAC frame processing unit 230, and a management unit 240.

[0059] The data processing unit 220 receives an LLC packet from the LLC processing unit 210, adds a MAC header to the LLC packet to generate a MAC frame. Then, the data processing unit 220 sends the MAC frame to the MAC frame processing unit 230. Also, the data processing unit 220 receives a MAC frame from the MAC frame processing unit 230, extracts the LLC packet from the MAC frame. Then, the data processing unit 220 sends the LLC packet to the LLC processing unit 210.

[0060] The MAC frame processing unit 230 receives a MAC frame, which is a data frame, from the data processing unit 220 and temporarily stores the MAC frame. Then, the MAC frame processing unit 230 performs carrier sensing to check the status of the channel corresponding to the link associated with the TID of the data included in the MAC frame. When the channel is busy, the MAC frame processing unit 230 continues carrier sensing. When the channel is idle, the MAC frame processing unit 230 sends the MAC frame to the radio signal processing unit corresponding to the link associated with the TID of the data included in the MAC frame. Since the channel access function of the MAC frame processing unit 230 is the same as that of the MAC frame processing unit 130 of the base station 10 described with reference to FIG. 7, the description of the channel access function of the MAC frame processing unit 230 is omitted.

[0061] The MAC frame processing unit 230 receives a MAC frame, which is a management frame or a control frame, from the management unit 240 and sends the MAC frame to any one of the radio signal processing units 260, 270, and 280.

[0062] In addition, the MAC frame processing unit 230 receives a MAC frame from the radio signal processing units 260, 270, and 280 and sends the MAC frame to the data processing unit 220 or the management unit 240 according to the type of the MAC frame. For example, when the MAC frame is a data frame, the MAC frame processing unit 230 sends the MAC frame to the data processing unit 220. When the MAC frame is a management frame or a control frame, the MAC frame processing unit 230 sends the MAC frame to the management unit 240. Furthermore, the MAC frame processing unit 230 executes processing based on an instruction from the management unit 240 or exchanges information with the management unit 240.

[0063] The management unit 240 manages the link with the base station 10 based on the information (e.g., multi-link control information) contained in the management frame received from the radio signal processing units 260, 270, 280 via the MAC frame processing unit 230. The management unit 240 includes link management information 241, an association processing unit 242, an authentication processing unit 243, a multi-link control information acquisition unit 244, and a multi-link control unit 245.

[0064] The link management information 241 includes information about the base station 10 wirelessly connected to the terminal 20. The link management information 241 may include information about the STA function, multi-link, link, TID, throughput, and delay. The link management information 241 may match the information about the terminal 20 included in the link management information 141 of the base station 10. The terminal 20 measures (monitors) the throughput and delay for each terminal and for each link (STA function), and registers those measured values in the link management information 241. The link management information 241 is stored, for example, in the RAM 203 and is referred to by the MAC frame processing unit 230. For example, the MAC frame processing unit 230 uses the link management information 241 to identify the link corresponding to the TID of the data included in the MAC frame to be transmitted.

[0065] The association processing unit 242 executes a protocol related to the association including the transmission of a connection request to the base station 10. The authentication processing unit 243 executes a protocol related to the authentication following the association.

[0066] The multi-link control information acquisition unit 244 acquires multi-link control information from the base station 10 and sends the multi-link control information to the multi-link control unit 245. The management frame including the multi-link control information transmitted by the base station 10 is received by any one of the radio signal processing units 260, 270, 280 and is provided to the multi-link control information acquisition unit 244 via the MAC frame processing unit 230. The multi-link control information acquisition unit 244 extracts the multi-link control information from the management frame.

[0067] The multi-link control unit 245 controls the use of a plurality of links that constitute a multi-link between the base station 10 and the terminal 20 based on multi-link control information. In an example where the multi-link control information includes information indicating a link whose use is to be suspended or resumed, the multi-link control unit 245 controls the use of each link according to the multi-link control information. For example, when the multi-link control information includes information indicating that the use of a certain link is to be suspended, the multi-link control unit 245 identifies the link whose use is to be suspended based on the multi-link control information, and updates the link management information 241 to switch the identified link to a suspended state. In an example where the multi-link control information includes the measurement result of a communication quality index obtained by the measurement unit 144 of the base station 10, the multi-link control unit 245 uses the same algorithm as the multi-link control unit 145 of the base station 10 to control the use of each link based on the measurement result included in the multi-link control information.

[0068] Furthermore, the multi-link control unit 245 determines the association between the TID and the link. The association between the TID and the link is executed at a predetermined timing such as when establishing a multi-link between the base station 10 and the terminal 20. For example, at the time of setting up the multi-link, the multi-link control unit 245 determines the association between the TID and the link, and requests the multi-link control unit 145 of the base station 10 to apply the association. Then, when the terminal 20 receives an affirmative response to the request from the base station 10, the association between the TID and the link is determined.

[0069] Note that the management unit 240 may further include a measurement unit that performs the same processing as the measurement unit 144 (FIG. 6) of the base station 10. When the management unit 240 includes a measurement unit, the measurement result obtained by the measurement unit is notified to the base station 10 and used by the base station 10 for multi-link control.

[0070] The wireless signal processing unit 260 transmits and receives data between the base station 10 and the terminal 20 through wireless communication. Specifically, the wireless signal processing unit 260 performs physical layer processing on the input data or wireless signal. For example, the wireless signal processing unit 260 receives a MAC frame from the MAC frame processing unit 230, adds a preamble, a PHY header, etc. to the MAC frame to generate a wireless frame. Then, the wireless signal processing unit 260 performs a predetermined modulation operation on the wireless frame to convert the wireless frame into a wireless signal, and radiates the wireless signal via an antenna. Also, the wireless signal processing unit 260 receives a wireless signal from the base station 10 via the antenna, performs a predetermined demodulation operation on the received wireless signal to obtain a wireless frame. Then, the wireless signal processing unit 260 extracts a MAC frame from the wireless frame and sends the MAC frame to the MAC frame processing unit 230.

[0071] The wireless signal processing units 270 and 280 perform the same processing as the wireless signal processing unit 260. Therefore, the description of the wireless signal processing units 270 and 280 is omitted. In this example, the wireless signal processing units 260, 270, and 280 handle wireless signals in the 6 GHz band, 5 GHz band, and 2.4 GHz band, respectively. Note that the wireless signal processing units 260, 270, and 280 may use a common antenna or individual antennas.

[0072] The application execution unit 290 executes an application that utilizes the data received from the LLC processing unit 210. The application execution unit 290 sends data to the LLC processing unit 210 or receives data from the LLC processing unit 210 according to the operation of the application. The application execution unit 290 can display information from the application on the display 205. Also, the application execution unit 290 can execute processing according to a user operation on the input interface.

[0073] Referring to FIG. 10, an operation example related to the multi-link setup between the base station 10 and the terminal 20 will be described. The multi-link setup is executed using a management frame.

[0074] In step S10, the terminal 20 sends (broadcasts) a probe request. The probe request is a signal for checking whether a base station exists around the terminal 20. When the base station 10 receives the probe request from the terminal 20, it executes the process of step S11.

[0075] In step S11, the base station 10 sends a probe response to the terminal 20. The probe response is a signal used for the base station 10 to respond to the probe request from the terminal 20. When the terminal 20 receives the probe response from the base station 10, it executes the process of step S12. Here, the probe response includes information necessary for establishing a multi-link.

[0076] In step S12, the terminal 20 sends an association request to the base station 10 via any one of the STA functions of the terminal 20. The association request includes a signal for requesting the base station 10 to establish a multi-link. For example, the association request is generated by the management unit 240 of the terminal 20. When the management unit 140 of the base station 10 receives the association request including a signal for requesting the establishment of a multi-link, it executes the process of step S13. Note that, as the association request, one obtained by adding information for multi-link connection to a normal association request may be used.

[0077] In step S13, the management unit 140 of the base station 10 executes multi-link association processing using one STA function. Specifically, first, the base station 10 executes association processing of the first STA function with the terminal 20. Then, when a link is established in the first STA function, the management unit 140 of the base station 10 uses the first STA function in which the link is established to execute association processing of the second STA function. That is, the STA function in which the link is established is used for the association processing of the STA function in which the link is not established. When the association processing of at least two STA functions is completed, the base station 10 recognizes that the multi-link with the terminal 20 has been established and executes the processing of step S14.

[0078] In step S14, the management unit 140 of the base station 10 updates the link management information 141.

[0079] In step S15, the base station 10 transmits a multi-link establishment response to the terminal 20. The multi-link establishment response is a signal used for the response to the multi-link request. When the management unit 240 of the terminal 20 receives the multi-link establishment response from the base station 10, it recognizes that the multi-link with the base station 10 has been established and executes the processing of step S16.

[0080] In step S16, the management unit 240 of the terminal 20 updates the link management information 241.

[0081] By updating the link management information at both the base station 10 and the terminal 20, the setup of the multi-link is completed. Thereafter, data communication using the multi-link becomes possible between the base station 10 and the terminal 20.

[0082] Here, in the example shown in FIG. 10, after the probe request from the terminal 20 and the probe response from the base station 10, connection processing for establishing a multi-link is performed. Alternatively, the base station 10 may periodically transmit a beacon, and the terminal 20 that has received this beacon may transmit an association request for establishing a multi-link, whereby connection processing for establishing a multi-link may be performed.

[0083] Next, an operation for controlling the use of a multi-link will be described. Here, it is assumed that the PER is used as a communication quality indicator. Instead of the PER, the collision rate divided by the air time or the RTS retransmission rate may be used.

[0084] FIG. 11 schematically shows an example of a method for controlling a multi-link executed by the base station 10. The flow shown in FIG. 11 may start when the multi-link setup shown in FIG. 10 is completed. When a multi-link is established between the base station 10 and a plurality of terminals, the flow shown in FIG. 11 is executed for each terminal.

[0085] Here, a method for controlling a multi-link between the base station 10 and the terminal 20 will be described. The multi-link between the base station 10 and the terminal 20 includes three links, namely, a first link, a second link, and a third link, and all of these are used for data transmission.

[0086] As shown in FIG. 11, when a predetermined time has elapsed (step S1101), the process proceeds to step S1102.

[0087] In step S1102, the measurement unit 144 measures the PER for each of the plurality of links included in the multi-link. For example, the measurement unit 144 obtains a measurement result including a first measurement value that is the measured value of the PER for the first link, a second measurement value that is the measured value of the PER for the second link, and a third measurement value that is the measured value of the PER for the third link.

[0088] In step S1103, the multi-link control unit 145 determines whether there is a link whose PER exceeds a predetermined PER threshold value. For example, the multi-link control unit 145 determines whether the maximum value among the measured values of the PER exceeds the PER threshold value. For example, when the first measured value is higher than the second measured value and the second measured value is higher than the third measured value, the multi-link control unit 145 determines whether the first measured value exceeds the PER threshold value. When the maximum measured value exceeds the PER threshold value, the multi-link control unit 145 determines that there is a link whose PER exceeds the PER threshold value, and when the maximum measured value is equal to or less than the PER threshold value, the multi-link control unit 145 determines that there is no link whose PER exceeds the PER threshold value. If there is no link whose PER exceeds the PER threshold value (step S1103; No), the process returns to step S1101. If there is a link whose PER exceeds the PER threshold value (step S1103; Yes), the process proceeds to step S1104.

[0089] In step S1104, the multi-link control unit 145 suspends the use of the link whose PER exceeds the PER threshold value. For example, the multi-link control unit 145 determines to suspend the use of the link whose measured value of the PER is the maximum and exceeds the PER threshold value, and updates the link management information 141 to switch the link to the suspended state. Further, the notification unit 146 notifies the terminal 20 of the suspension of the use of the link. The notification unit 146 may transmit the multi-link control information indicating the link to be suspended to the terminal 20 using any of the radio signal processing units 160, 170, and 180. For example, when the first measured value is higher than the second and third measured values and exceeds the PER threshold value, the multi-link control unit 145 determines to suspend the use of the first link. Then, the multi-link control unit 145 updates the link management information 141 to switch the first link to the suspended state, and the notification unit 146 notifies the terminal 20 of the suspension of the use of the first link. When the multi-link control unit 245 of the terminal 20 receives the notification from the base station 10, it identifies the link to be suspended based on this notification and updates the link management information 241 to switch the identified link to the suspended state.

[0090] After a predetermined time has elapsed after the process of step S1104 is executed (step S1105), in step S1106, the multi-link control unit 145 determines whether the total throughput has improved. The total throughput may be the total throughput regarding data transmission between the base station 10 and the terminal 20, that is, the sum of the throughputs regarding data transmission by the links established between the base station 10 and the terminal 20. Also, the total throughput may be the total throughput regarding data transmission between the base station 10 and all terminals wirelessly connected to the base station 10, that is, the sum of the throughputs regarding data transmission by the links established between the base station 10 and all terminals wirelessly connected to the base station 10. For example, the multi-link control unit 145 compares the total throughput before link suspension and the total throughput after link suspension in order to determine whether the total throughput has improved. For example, the multi-link control unit 145 determines that the total throughput has improved when the total throughput after link suspension exceeds the total throughput before link suspension, and determines that the total throughput has not improved otherwise. Instead of or in addition to the total throughput, the multi-link control unit 145 may determine whether the delay regarding data transmission between the base station 10 and the terminal 20 has improved. Alternatively, the multi-link control unit 145 may determine whether the Ack response rate regarding data transmission between the base station 10 and the terminal 20 has improved.

[0091] If the total throughput has improved (step S1106; Yes), the process proceeds to step S1107. In step S1107, the multi-link control unit 145 maintains the link in the suspended state.

[0092] If the total throughput has not improved (step S1106; No), the process proceeds to step S1108. In step S1108, the multi-link control unit 145 resumes the use of the link that was put into the idle state. For example, the multi-link control unit 145 updates the link management information 141 in order to switch the first link to the active state. Further, the notification unit 146 notifies the terminal 20 of the resumption of the use of the first link. When the multi-link control unit 245 of the terminal 20 receives the notification from the base station 10, it identifies the link for which the use is to be resumed based on this notification, and updates the link management information 241 in order to switch the identified link to the active state.

[0093] FIG. 12 schematically shows another example of a method for controlling multi-links, which is executed by the base station 10. In FIG. 12, the same steps as those shown in FIG. 11 are denoted by the same reference numerals, and the description thereof is omitted. The flow shown in FIG. 12 is obtained by changing step S1101 to step S1201 in the flow shown in FIG. 11.

[0094] In step S1201 of FIG. 12, the measurement unit 144 measures the Ack response rate of the terminal 20 over a predetermined period, and compares the measured Ack response rate with a predetermined Ack response rate threshold. If the measured value of the Ack response rate exceeds the Ack response rate threshold (step S1201; No), the process of step S1201 is repeated. If the measured value of the Ack response rate is equal to or less than the Ack response rate threshold (step S1201; Yes), the process proceeds to step S1102. Since the processing after step S1102 has been described with reference to FIG. 11, the description thereof is omitted here.

[0095] FIG. 13 schematically shows another example of a method for controlling multi-links, which is executed by the base station 10. In FIG. 13, the same steps as those shown in FIG. 11 are denoted by the same reference numerals, and the description thereof is omitted. The flow shown in FIG. 13 is obtained by adding steps S1301 to S1303 to the flow shown in FIG. 11. Steps S1301 to S1303 are added between step S1103 and step S1104.

[0096] In the example shown in FIG. 13, when there is a link where the PER exceeds the PER threshold (step S1103; Yes), the process proceeds to step S1301. In step S1301, the multi-link control unit 145 determines whether the desired data rate for the data being transmitted to the terminal 20 using the link where the PER exceeds the PER threshold exceeds a predetermined desired data rate threshold. The desired data rate indicates the data rate required for the data. For example, for data generated from a real-time application, a higher desired data rate is set compared to data generated from an application that does not require real-time performance.

[0097] When the desired data rate exceeds the desired data rate threshold (step S1301; Yes), the process proceeds to step S1104. In step S1104, the multi-link control unit 145 suspends the use of the link determined in step S1103 to have a PER exceeding the PER threshold.

[0098] When the desired data rate does not exceed the desired data rate threshold (step S1301; No), the process proceeds to step S1302. In step S1302, the multi-link control unit 145 calculates the difference between the PER of the link determined in step S1103 to have a PER exceeding the PER threshold and the PER of the other links. Specifically, the multi-link control unit 145 calculates the difference by subtracting the PER of the other links from the PER of the link determined in step S1103 to have a PER exceeding the PER threshold.

[0099] In step S1303, the multi-link control unit 145 determines whether the difference calculated in step S1302 exceeds a predetermined difference threshold. If the calculated difference does not exceed the difference threshold (step S1302; No), the process returns to step S1101. If the calculated difference exceeds the difference threshold (step S1302; Yes), the process proceeds to step S1104. In step S1104, the multi-link control unit 145 suspends the use of the link for which it was determined in step S1103 that the PER exceeds the PER threshold.

[0100] Referring again to the example referred to in the description of FIG. 11, the multi-link control unit 145 determines whether the first measurement value exceeds the PER threshold (step S1103). If the first measurement value exceeds the PER threshold, the multi-link control unit 145 determines whether the desired data rate for the data being transmitted to the terminal 20 using the first link exceeds the desired data rate threshold (step S1301). If the desired data rate exceeds the desired data rate threshold, the multi-link control unit 145 suspends the use of the first link (step S1104).

[0101] If the desired data rate does not exceed the desired data rate threshold, the multi-link control unit 145 calculates the difference obtained by subtracting the second measurement value from the first measurement value (step S1302). In response to the calculated difference exceeding the difference threshold, the multi-link control unit 145 suspends the use of the first link (step S1104).

[0102] FIG. 14 schematically shows another example of a method for controlling multi-links, which is executed by the base station 10. In FIG. 14, the same steps as those shown in FIGS. 11 and 13 are denoted by the same reference numerals, and the description thereof is omitted. The flow shown in FIG. 14 is obtained by changing step S1301 to step S1401 in the flow shown in FIG. 13.

[0103] In the example shown in FIG. 14, when there is a link where the PER exceeds the PER threshold (step S1103; Yes), the process proceeds to step S1401. In step S1401, the multi-link control unit 145 determines whether the MCS (Modulation and Coding Scheme) value that identifies the MCS used for data transmission on the link where the PER exceeds the PER threshold is less than or equal to a predetermined MCS threshold. The MCS value is information that identifies a combination of a modulation method and an error correction coding rate. For example, in IEEE802.11ax, 12 types of MCSs from MCS0 to MCS11 are defined. The higher the MCS value, the higher the data rate at which data can be transmitted. For example, the MCS value is selected to satisfy the desired data rate. The MCS value is also referred to as the MCS index.

[0104] If the MCS value is less than or equal to the MCS threshold (step S1401; Yes), the process proceeds to step S1104, and the multi-link control unit 145 suspends the use of the link determined in step S1103 to have a PER exceeding the PER threshold.

[0105] If the MCS value exceeds the MCS threshold (step S1401; No), the process proceeds to step S1302. The processing after step S1302 has been described with reference to FIGS. 10 and 12, and thus the description here is omitted.

[0106] Referring again to the example referred to in the description of FIG. 11, the multi-link control unit 145 determines whether the MCS value used for the first link is less than or equal to the MCS threshold (step S1401). If the MCS value used for the first link is less than or equal to the MCS threshold, the multi-link control unit 145 suspends the use of the first link (step S1104). If the MCS value exceeds the threshold, the multi-link control unit 145 calculates the difference obtained by subtracting the second measurement value from the first measurement value (step S1302). If the calculated difference exceeds the difference threshold, the multi-link control unit 145 suspends the use of the first link (step S1104).

[0107] In FIG. 13 or FIG. 14, the process of step S1101 may be replaced with the process of step S1201 shown in FIG. 12.

[0108] FIG. 15 schematically shows another example of a method for controlling multi-link executed by the base station 10. Specifically, FIG. 15 schematically shows an example of a method for resuming the use of a link in a dormant state among the links constituting the multi-link between the base station 10 and the terminal 20. Here, it is assumed that one link has transitioned to the dormant state based on the control flow as shown in FIGS. 11 to 14. The flow shown in FIG. 15 can be executed, for example, after the control flow shown in any of FIGS. 11 to 14 ends. Note that the link may transition to the dormant state for some other reason.

[0109] As shown in FIG. 15, when a predetermined time has elapsed (step S1501), the process proceeds to step S1502.

[0110] In step S1502, the multi-link control unit 145 transmits a dummy frame to the terminal 20 using the link in the dormant state, and the measurement unit 144 measures the reception success probability of the dummy frame. For example, the multi-link control unit 145 generates a predetermined number of MAC frames including dummy data. Then, the multi-link control unit 145 sends these MAC frames to the MAC frame processing unit 130 and instructs the MAC frame processing unit 130 to transmit these MAC frames using the link in the dormant state. The MAC frame processing unit 130 repeats the processes including carrier sense execution and MAC frame transmission to transmit a predetermined number of MAC frames. The measurement unit 144 measures the ratio of the MAC frames successfully received by the terminal 20 for a predetermined number of MAC frames as the reception success probability of the dummy frame.

[0111] In step S1503, the multi-link control unit 145 determines whether the reception success probability of the dummy frame exceeds a predetermined probability threshold.

[0112] If the reception success probability of the dummy frame does not exceed the probability threshold (step S1503; No), the process ends. The flow shown in FIG. 15 may be executed again immediately after the process ends. Alternatively, the flow shown in FIG. 15 may be executed again after a predetermined time has elapsed after the process ends.

[0113] If the reception success probability of the dummy frame exceeds the probability threshold (step S1503; Yes), the process proceeds to step S1504. In step S1504, the multi-link control unit 145 resumes the use of the link in the inactive state. For example, the multi-link control unit 145 updates the link management information 141 to switch the link to an active state. Further, the notification unit 146 transmits multi-link control information indicating the link to resume use to the terminal 20.

[0114] FIG. 16 schematically shows another example of a method for resuming the use of an inactive link among the links constituting the multi-link between the base station 10 and the terminal 20. In FIG. 16, the same steps as those shown in FIG. 15 are denoted by the same reference numerals, and the description thereof is omitted. The flow shown in FIG. 16 is obtained by changing step S1501 to step S1601 in the flow shown in FIG. 15.

[0115] In step S1601 of FIG. 16, the multi-link control unit 145 determines whether the total throughput regarding data transmission between the base station 10 and the terminal 20 is equal to or less than a predetermined throughput threshold. Instead of or in addition to the total throughput, the delay or Ack response rate regarding data transmission between the base station 10 and the terminal 20 may be used.

[0116] If the total throughput exceeds the throughput threshold (step S1601; No), the process of step S1601 is repeated.

[0117] When the total throughput is less than or equal to the throughput threshold (step S1601; Yes), the process proceeds to step S1502. Since the processes after step S1502 have been described with reference to FIG. 15, the description here is omitted.

[0118] It is also possible to combine the flow shown in FIG. 15 and the flow shown in FIG. 16. Specifically, in FIG. 15, step S1601 may be provided between step S1501 and step S1502. In this case, when the total throughput exceeds the throughput threshold, the process returns to step S1501.

[0119] As described above, the base station 10 measures the communication quality index for each of the plurality of links constituting the multi-link between the base station 10 and the terminal 20, and based on the comparison between the largest communication quality index and a predetermined communication quality index threshold, determines whether to suspend the use of the link with the largest communication quality index (i.e., the lowest communication quality). According to this configuration, it is possible to avoid using a link with low communication quality, such as a link in a situation where frame collisions are likely to occur. As a result, it is possible to prevent the communication characteristics of the multi-link communication from deteriorating.

[0120] As the communication quality index, an index that increases as the communication quality decreases may be used. For example, the communication quality index may include at least one of the packet error rate, the frame collision rate divided by the air time, and the RTS retransmission rate. Each of these indexes increases when there is a hidden terminal. The base station 10 determines a link with a communication quality index exceeding the communication quality index threshold as a link where many frame collisions occur, and suspends the use of this link. According to this configuration, it is possible to suspend the use of a link in a situation where frame collisions are likely to occur. As a result, it is possible to prevent the deterioration of the communication characteristics of the multi-link communication.

[0121] The base station 10 may suspend the use of the link with the largest communication quality indicator in response to the largest communication quality indicator exceeding the communication quality indicator threshold and the desired data rate for the data transmitted to the terminal 20 using the link with the largest communication quality indicator exceeding the predetermined desired data rate threshold. According to this configuration, it is possible to avoid transmitting large-capacity data (for example, data that requires transmission at a high MCS value) on a link with low communication quality, such as a link in a situation where frame collisions are likely to occur.

[0122] When the largest communication quality indicator exceeds the communication quality indicator threshold and the desired data rate for the data transmitted to the terminal 20 using the link with the largest communication quality indicator does not exceed the desired data rate threshold, the base station 10 may calculate the difference between the largest communication quality indicator and the second-largest communication quality indicator. The base station 10 may suspend the use of the link with the largest communication quality indicator in response to the calculated difference exceeding the predetermined difference threshold. The calculated difference exceeding the difference threshold indicates that only the communication quality of one link is extremely low. According to this configuration, it is possible to avoid using a link with extremely low communication quality.

[0123] The base station 10 may suspend the use of the link with the largest communication quality indicator in response to the largest communication quality indicator exceeding the communication quality indicator threshold and the MCS value used for data transmission on the link with the largest communication quality indicator being lower than the predetermined MCS threshold. According to this configuration, it is possible to avoid using a link with a large number of transmission failures despite a low transmission rate, that is, a link with a lot of interference.

[0124] When the largest communication quality index of the base station 10 exceeds the communication quality index threshold value, and the MCS value used for data transmission on the link with the largest communication quality index exceeds the MCS threshold value, the base station 10 may calculate the difference between the largest communication quality index and the second largest communication quality index. In response to the calculated difference exceeding a predetermined difference threshold value, the base station 10 may suspend the use of the link with the largest communication quality index. According to this configuration, it is possible to avoid using a link with extremely low communication quality.

[0125] After the use of the link is suspended, if the total throughput, delay, or Ack response rate regarding data transmission between the base station 10 and the terminal 20 is improved, the base station 10 may continue to suspend the use of the link. After the use of the link is suspended, if the total throughput, delay, or Ack response rate regarding data transmission between the base station 10 and the terminal 20 is not improved, the base station 10 may resume the use of the link. According to this configuration, it is possible to cancel the suspension when the communication characteristics of multi-link communication do not improve even if the use of the link is suspended.

[0126] After the use of the link is suspended, the base station 10 may transmit a dummy frame to the terminal 20 using this link, and in response to the reception success probability of the dummy frame exceeding the probability threshold value, the base station 10 may resume the use of the link. According to this configuration, it is possible to resume the use of a link that has escaped from a situation where frame collisions are likely to occur.

[0127] [Modification Example] In the above-described embodiment, the base station 10 measures an index regarding the communication quality or performance of the link for each terminal and each link.

[0128] In other embodiments, each terminal may perform measurements instead of or in addition to the base station 10. For example, the management unit 240 of the terminal 20 includes a measurement unit that measures at least one type of indicator related to the communication quality or performance of a link for each of a plurality of links that constitute a multi-link between the terminal and the base station 10. At least one type of indicator to be measured includes a communication quality indicator indicating the communication quality of the link. The communication quality indicator may be a PER, a value obtained by dividing the collision rate by the air time, or an RTS retransmission rate. In this case, for example, the PER indicates the ratio of frames that the base station 10 could not receive with respect to the frames transmitted from the terminal 20 to the base station 10. The management unit 240 of the terminal 20 may include a measurement result transmission unit that transmits the measurement results obtained by the measurement unit to the base station 10. The transmission of the measurement results may be performed using a management frame. In this case, the management unit 140 of the base station 10 includes a measurement result reception unit that receives the measurement results from the terminal, and the multi-link control unit 145 of the management unit 140 performs multi-link control based on the measurement results received by the measurement result reception unit.

[0129] In this way, the base station 10 acquires an indicator related to the communication quality or performance of the link by measuring the indicator and / or receiving the measurement result of the indicator from the terminal.

[0130] In the above-described embodiments, as the communication quality indicator, an indicator whose value increases as the communication quality of the link decreases is used. In other embodiments, an indicator whose value decreases as the communication quality of the link decreases may be used as the communication quality indicator.

[0131] The wireless communication function provided by the wireless stations (base station 10 and terminal 20) may be implemented by individual components such as chips. For example, chips may be incorporated into the substrate of the wireless station during the manufacture of the wireless station. The wireless device referred to here may refer to the wireless station or individual components that implement the wireless communication function of the wireless station.

[0132] Note that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof at the implementation stage. Also, the respective embodiments may be implemented in appropriate combination, and in that case, the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combinations selected from the plurality of disclosed components. For example, even if some components are deleted from all the components shown in the embodiments, if the problem can be solved and the effects can be obtained, the configuration from which these components are deleted can be extracted as an invention.

Explanation of Reference Numerals

[0133] 10…Base station 20…Terminal 30…Server 40…Communication network 45…Wireless network 50…Communication system 101…CPU 102…Program memory 103…RAM 104…Wireless communication module 105…Wired communication module 110…LLC processing unit 120…Data processing unit 130…MAC frame processing unit 131…Classification unit 132A, 132B, 132C, 132D, 132E…Transmission queue 133A, 133B, 133C, 133D, 133E…Carrier sense execution unit 134…Collision management unit 140…Management unit 141…Link management information 142…Association processing unit 143…Authentication processing unit 144…Measurement unit 145…Multi-link control unit 146…Notification unit 150…Link management unit 160, 170, 180…Wireless signal processing unit 201…CPU 202…Program memory 203…RAM 204…Wireless communication module 205…Display 206…Storage 210…LLC processing unit 220…Data processing unit 230…MAC frame processing unit 240…Management unit 241…Link management information 242…Association processing unit 243…Authentication processing unit 244…Multi-link control information acquisition unit 245…Multi-link control unit 250…Link management unit 260, 270, 280…Wireless signal processing unit 290…Application execution unit

Claims

1. An acquisition unit that acquires a communication quality index indicating the communication quality of all a plurality of links established between the access point and a wireless terminal for wireless communication with the wireless terminal; A multi-link control unit that determines whether to suspend the use of the first link based on a comparison between the communication quality index of the first link having the lowest communication quality among the plurality of links and a first threshold; An access point comprising the same.

2. The communication quality index includes at least one of a packet error rate, a value obtained by dividing a collision rate by air time, and a retransmission rate of RTS (Request to Send). The access point according to Claim 1.

3. The multi-link control unit suspends the use of the first link in response to the communication quality index of the first link exceeding the first threshold. The access point according to Claim 1 or 2.

4. The multi-link control unit suspends the use of the first link in response to the communication quality index of the first link exceeding the first threshold and a desired data rate of data being transmitted to the wireless terminal using the first link exceeding a second threshold. The access point according to Claim 3.

5. When the communication quality index of the first link exceeds the first threshold and the desired data rate is equal to or lower than the second threshold, the multi-link control unit calculates a difference between the communication quality index of the first link and the communication quality index of a second link included in the plurality of links, and suspends the use of the first link in response to the calculated difference exceeding a third threshold. The access point according to Claim 4.

6. The multi-link control unit suspends the use of the first link in response to the communication quality index of the first link exceeding the first threshold and an MCS (Modulation and Coding Scheme) value specifying the MCS used for data transmission on the first link being lower than a second threshold. The access point according to Claim 3.

7. When the communication quality index for the first link exceeds the first threshold and the MCS value exceeds the second threshold, the multi-link control unit calculates the difference between the communication quality index for the first link and the communication quality index for a second link included in the plurality of links, and in response to the calculated difference exceeding a third threshold, suspends the use of the first link. The access point according to claim 6.

8. After the use of the first link is suspended, if the total throughput, delay, or Ack response rate regarding data transmission between the access point and the wireless terminal is improved, the multi-link control unit continues to suspend the use of the first link; if the total throughput, delay, or Ack response rate regarding data transmission between the access point and the wireless terminal is not improved after the use of the first link is suspended, the multi-link control unit resumes the use of the first link. The access point according to any one of claims 1 to 7.

9. After the use of the first link is suspended, it further includes a transmission unit that transmits a dummy frame to the wireless terminal using the first link. In response to the reception success probability of the dummy frame exceeding a fourth threshold, the multi-link control unit resumes the use of the first link. The access point according to any one of claims 1 to 8.

10. A wireless communication method executed by an access point, comprising: acquiring a communication quality index indicating the communication quality of all of the plurality of links established between the access point and the wireless terminal for wireless communication with the wireless terminal; determining whether to suspend the use of the first link based on a comparison between the communication quality index for the first link, which has the lowest communication quality among the plurality of links, and a first threshold; A wireless communication method comprising the above.

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