COMMUNICATION DEVICE, CONTROL METHOD, AND PROGRAM

Abstract

To prevent transmission and reception from being performed in parallel in a communication device.SOLUTION: A communication device performs communications in conformity with IEEE 802.11 standard series together with the other device by use of a plurality of radio links. When a predetermined frame serving as a group address frame is transmitted via a first radio link included in the plurality of radio links, the communication device performs a control such that any frame addressed to the communication device does not come thereto via a second radio link included in the plurality of radio links and different from the first radio link.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a communication control technology considering a communication device with operating constraints.

Background Art

[0002] As a communication standard for Wireless Local Area Network (Wireless LAN), the IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard is known. The IEEE 802.11 standard is a standard series including IEEE 802.11a / b / g / n / ac / ax standards. Patent Document 1 describes that in the IEEE 802.11ax standard, communication using OFDMA (Orthogonal Frequency Division Multiple Access) is performed. According to wireless communication by OFDMA, high peak throughput can be realized, and the communication speed can be sufficiently ensured in a congested situation.

[0003] Currently, for further throughput improvement, as a new standard of the IEEE 802.11 standard series, the formulation of the IEEE 802.11be standard is in progress. In the IEEE 802.11be standard, multi-link communication is considered in which one access point (AP) establishes a plurality of wireless links in one or more frequency bands with one station (STA) and performs communication. In multi-link communication, for example, the AP uses a plurality of frequency channels in at least one of the frequency bands of 2.4 GHz, 5 GHz, or 6 GHz to establish a connection with the STA and communicates in parallel on each frequency channel. Note that due to hardware constraints of the device, although multi-link communication is possible, there may be an AP or STA that cannot perform a reception operation on the other link while executing a transmission operation on a predetermined link.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] An access point (AP) performing multilink communication needs to periodically transmit beacons on each link. However, if an AP is unable to receive on another link while transmitting on a given link, it cannot transmit a beacon on the other link while receiving data on that link. In addition to beacons, an AP may also need to transmit group address frames to send information to multiple devices at once, but it may be unable to transmit such frames for the same reason. Furthermore, even if the timing of beacon transmission by the AP on a given link is predetermined, the timing of beacon transmission may be shifted depending on the degree of congestion on that link. In such cases, the AP will still operate under the constraint that it cannot receive on the other link while transmitting on the given link.

[0006] The present invention provides a communication control technology to prevent transmission and reception from occurring in parallel in a communication device. [Means for solving the problem]

[0007] A communication device according to one aspect of the present invention includes communication means for performing communication with a partner device in accordance with the IEEE 802.11 standard series using a plurality of wireless links, and control means for controlling the communication means so that when a predetermined frame, which is a group address frame, is transmitted on a first wireless link among the plurality of wireless links, a frame addressed to the communication device does not arrive on a second wireless link, which is different from the first wireless link among the plurality of wireless links. [Effects of the Invention]

[0008] According to the present invention, it is possible to prevent transmission and reception from occurring in parallel in a communication device. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing an example configuration of a wireless communication system. [Figure 2] This figure shows an example of the hardware configuration of a communication device. [Figure 3] This figure shows an example of the functional configuration of a communication device. [Figure 4] This figure shows an example of the processing flow performed by an access point. [Figure 5] This diagram shows an example of the communication flow in a wireless communication system. [Figure 6] This figure shows an example of the processing flow performed by an access point. [Figure 7] This diagram shows an example of the communication flow in a wireless communication system. [Figure 8] This figure shows an example of the processing flow performed by an access point. [Figure 9] This diagram shows an example of the communication flow in a wireless communication system. [Figure 10] This diagram shows an example of the communication flow in a wireless communication system. [Modes for carrying out the invention]

[0010] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0011] (Configuration of the wireless communication system) Figure 1 shows an example of the configuration of the wireless communication system of this embodiment. The wireless communication system includes multiple communication devices, and these communication devices communicate by sending and receiving wireless signals to each other. In one example of the wireless communication system, an access point (AP102) constitutes a network 101, and a station (STA103) participates in the network 101. STA103 can participate in the network 101 and communicate with AP102. Figure 1 also shows a situation where there is an STA106 that is not participating in the network 101. STA106 cannot communicate with AP102, but is affected by interference from signals from AP102, and is located in a position where the signals it sends interfere with AP102's communication.

[0012] Here, AP102 and STA103 are configured to perform wireless communication compliant with the IEEE (Institute of Electrical and Electronics Engineers) 802.11be (EHT) standard. In addition, AP102 and STA103 may also support legacy standards that precede the IEEE 802.11be standard. For example, AP102 and STA103 may be configured to support at least one of the IEEE 802.11a / b / g / n / ac / ax standards. Furthermore, AP102 and STA103 may support other communication standards in addition to the IEEE 802.11 standard series, such as Bluetooth®, NFC, UWB, ZigBee, and MBOA. NFC, UWB, and MBOA are acronyms for Near Field Communication, Ultra Wide Band, and Multi Band OFDM Alliance, respectively. UWB includes Wireless USB, Wireless 1394, WiNET, etc. Furthermore, AP102 and STA103 may support wired communication standards such as wired LAN. AP102 may, but is not limited to, a wireless LAN router or a personal computer (PC). AP102 may also be an information processing device such as a wireless chip capable of performing wireless communication compliant with the IEEE 802.11be standard. STA103 may, but is not limited to, a camera, tablet, smartphone, PC, mobile phone, video camera, or headset. STA103 may also be an information processing device such as a wireless chip capable of performing wireless communication compliant with the IEEE 802.11be standard.

[0013] AP102 and STA103 can communicate in frequency bands such as the 2.4 Hz, 5 GHz, and 6 GHz bands. These are just examples; AP102 and STA103 may also be capable of using other frequency bands, such as the 60 GHz band. Furthermore, AP102 and STA103 can communicate using bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, or 320 MHz. Again, this is just an example; AP102 and STA103 may be configured to communicate using different bandwidths, such as 240 MHz or 4 MHz.

[0014] AP102 and STA103 can perform multi-user (MU) communication with multiple user signals multiplexed by executing OFDMA (Orthogonal Frequency Division Multiple Access) communication compliant with the IEEE 802.11be standard. In OFDMA communication, the available frequency bandwidth is divided into Resource Units (RUs), and non-overlapping frequency resources are allocated to each STA in units of RUs. Furthermore, the subcarriers in an RU are configured to be orthogonal to the subcarriers in other RUs. As a result, AP102 can communicate in parallel with multiple STAs within a defined bandwidth.

[0015] In addition, the AP 102 and the STA 103 can establish a plurality of wireless links respectively established via a plurality of frequency channels, and are configured to execute multi-link communication for communicating via one or more wireless links. Hereinafter, the wireless link is simply referred to as a "link". In the IEEE 802.11 standard series, the bandwidth of each frequency channel is defined as 20 MHz. Also, the frequency channels here are the frequency channels defined in the IEEE 802.11 standard series. In the IEEE 802.11 standard series, a plurality of frequency channels are defined in each of the frequency bands of 2.4 GHz band, 5 GHz band, 6 GHz band, and 60 GHz band. Also, in the IEEE 802.11 standard series, by bonding two adjacent frequency channels to each other, a bandwidth of 40 MHz can be utilized in one frequency channel. Similarly, it is also possible to bond four frequency channels to utilize a bandwidth of 80 MHz, and it is also possible to bond eight frequency channels to utilize a bandwidth of 160 MHz. Further, it is also possible to bond 16 frequency channels or, for example, utilize two bandwidths of 160 MHz to utilize a bandwidth of 320 MHz.

[0016] In this embodiment, as an example, the AP 102 is assumed to communicate with the STA 103 by establishing a link 104 via a first frequency channel in the 2.4 GHz band and a link 105 via a second frequency channel in the 6 GHz band. The AP 102 and the STA 103 can execute multi-link communication for maintaining the link 104 via the first frequency channel and the second link 105 via the second frequency channel in parallel. According to this, the AP 102 and the STA 103 can improve the communication throughput by the links via a plurality of frequency channels. In this embodiment, it is assumed that the link 104 is established with a 20 MHz bandwidth in the 6ch of the 2.4 GHz band, and the link number of this link 104 is set to "1". Also, it is assumed that the link 105 is established with a 320 MHz bandwidth in the 113ch of the 6 GHz band, and the link number of this link 105 is set to "2".

[0017] Furthermore, multilink communication may utilize links established in different frequency bands, or at least some of the multiple links may be established in a common frequency band. For example, multilink communication may be performed between AP102 and STA103 by establishing one link each in the 2.4GHz band, the 5GHz band, and the 6GHz band. Alternatively, multilink communication may be performed between AP102 and STA103 by establishing separate links in the 2.4GHz band, specifically on channels 1 and 6. Furthermore, multilink communication may be performed between AP102 and STA103 by establishing two or more links in the 2.4GHz band, and one or more additional links in the 5GHz band and 6GHz band, using these links. In other words, multilink communication establishes links using two or more frequency channels defined in multiple frequency bands, but the frequency channels of those two or more links can be arbitrary as long as they do not overlap with each other. AP102 and STA103 can establish multiple links on different frequency channels, allowing communication to continue on other frequency bands even if one frequency band is congested, thus preventing throughput degradation and communication delays.

[0018] When AP102 and STA103 perform multi-link communication, they split one piece of data and transmit it to the peer device via multiple links. Also, AP102 and STA103 may be able to execute MIMO (Multiple-Input Multiple-Output) communication on each link. In this case, AP102 and STA103 have multiple antennas, and the transmitting device transmits multiple data streams in parallel on the same frequency channel from multiple transmitting antennas. The receiving device uses multiple receiving antennas to receive in parallel the multiple signals sent from the multiple transmitting antennas, and separates and decodes multiple data streams from those signals. Thus, AP102 and STA103 can transmit and receive more data in a common time-frequency resource by MIMO communication. Also, when performing multi-link communication, AP102 and STA103 may execute MIMO communication only on some of the links.

[0019] Note that in FIG. 1, the configuration of a system including one AP102, one STA103 connected to AP102, and STA106 not connected to AP102 is shown, but the number and arrangement of APs and STAs are not limited to these. For example, one or more STAs connected to AP102 may be added. At this time, the frequency band of the link established with this STA, the number of links, and the bandwidth can be arbitrarily set.

[0020] STA106 can be any device that operates on a specific link among the links established between AP102 and STA103, without considering other links. For example, although STA106 is assumed not to participate in network 101, it may participate in network 101. In this case, STA106 may not comply with IEEE802.11be, but rather be an STA that complies only with, for example, IEEE802.11b. In this case, STA106 may establish a link with AP102 on channel 6 of the 2.4GHz band. STA106 may also be a wireless communication device that does not comply with the IEEE802.11 standard series, or a noise source that generates radio noise that is not a communication device, such as a microwave oven. Furthermore, STA106 may be a communication device that supports multilink communication and may be configured to establish multiple links with AP102 for communication. In any case, STA106 can communicate on other links while ignoring its operation on a given link.

[0021] (Device configuration) Figure 2 shows an example of the hardware configuration of AP102 according to this embodiment. AP102 includes, for example, a storage unit 201, a control unit 202, a function unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207. STA103 may have a similar configuration.

[0022] The memory unit 201 is configured to include one or more memories, such as ROM or RAM, and stores various information such as computer programs for performing various operations described later, and communication parameters for wireless communication. ROM is an acronym for Read Only Memory, and RAM is an acronym for Random Access Memory. In addition to or instead of ROM or RAM, the memory unit 201 may also include storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, and DVDs. Furthermore, the memory unit 201 may include multiple memories.

[0023] The control unit 202 is composed of one or more processors, such as a CPU or MPU, and controls the entire AP102 by executing a computer program stored in the memory unit 201, for example. CPU stands for Central Processing Unit, and MPU stands for Micro Processing Unit. In addition to controlling the entire AP102, the control unit 202 may be configured to perform processing to generate data and signals (wireless frames) to be transmitted in communication with other communication devices (e.g., STA103). The control unit 202 may also be configured to perform processing such as overall control of the AP102 through cooperation between a computer program stored in the memory unit 201 and the OS (Operating System). Furthermore, the control unit 202 may include multiple processors, such as a multi-core processor, and the multiple processors may perform processing such as overall control of the AP102. The control unit 202 may also be composed of an ASIC (Application-Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field-Programmable Gate Array), etc.

[0024] Furthermore, the control unit 202 controls the functional unit 203 to perform predetermined processes such as imaging, printing, and projection. The functional unit 203 is the hardware that enables the AP102 to perform predetermined processes. For example, if the AP102 is a camera, the functional unit 203 is the imaging unit and performs imaging processing. Also, for example, if the AP102 is a printer, the functional unit 203 is the printing unit and performs printing processing. Also, for example, if the AP102 is a projector, the functional unit 203 is the projection unit and performs projection processing. The data processed by the functional unit 203 may be data stored in the storage unit 201, or it may be data communicated with other communication devices (e.g., STA103) via the communication unit 206, which will be described later.

[0025] The input unit 204 receives various operations from the user. The output unit 205 provides various outputs to the user. Here, the output from the output unit 205 includes at least one of the following: display on a screen, audio output from a speaker, vibration output, etc. Note that both the input unit 204 and the output unit 205 may be implemented in a single module, such as a touch panel. Furthermore, the input unit 204 and the output unit 205 may be built into the AP102, or they may be configured as external devices connected to a communication device.

[0026] The communication unit 206 controls wireless communication compliant with the IEEE 802.11 standard series and IP communication. In this embodiment, the communication unit 206 is configured to control wireless communication compliant with the IEEE 802.11be standard. The communication unit 206 controls the antenna 207 to transmit and receive signals for wireless communication generated by, for example, the control unit 202. Furthermore, if the AP102 supports the NFC standard, Bluetooth standard, etc., the communication unit 206 can also control wireless communication compliant with these communication standards. In addition, if the AP102 is configured to perform wireless communication compliant with multiple communication standards, a separate communication unit 206 and antenna 207 corresponding to each communication standard may be provided. The AP102 communicates data such as image data, document data, and video data with a communication partner device (e.g., STA103) via the communication unit 206. Note that the antenna 207 may be provided separately from the communication unit 206, or it may be configured as a single module together with the communication unit 206.

[0027] Antenna 207 is an antenna capable of communication in the sub-GHz band, 2.4GHz band, 5GHz band, and 6GHz band. AP102 may have a multiband antenna as antenna 207, or it may have multiple antennas corresponding to each frequency band. Furthermore, if AP102 has multiple antennas 207, it may have one communication unit 206 for each of the multiple antennas, or it may have multiple communication units 206 corresponding to each of the multiple antennas 207. Antenna 207 may be a single antenna or an antenna array. That is, antenna 207 may have multiple antenna elements and be configured to perform multi-antenna communication such as MIMO.

[0028] Figure 3 shows an example of the functional configuration of AP102. Note that STA103 may have a similar functional configuration. The functional units shown in Figure 3 of AP102 include a wireless LAN control unit 301, a frame generation unit 302, a transmission time control unit 303, a beacon control unit 304, a UI control unit 305, and a storage control unit 306.

[0029] The wireless LAN control unit 301 performs control for sending and receiving wireless signals with other wireless LAN communication devices. The wireless LAN control unit 301 performs wireless LAN communication control based on the frames generated by the frame generation unit 302, following the procedures specified in the IEEE 802.11 standard series. Note that AP102 may have two or more wireless LAN control units 301, for example, one for each frequency band or one for each link.

[0030] The frame generation unit 302 generates a wireless control frame to be transmitted to another device under the control of the wireless LAN control unit 301. The content of the wireless control frame generated by the frame generation unit 302 may be constrained based on setting information held in the storage unit 201. Furthermore, the content of the wireless control frame generated by the frame generation unit 302 may be modified by user settings received via the UI control unit 305. The generated wireless control frame is transmitted to the other device via the communication unit 206 under the control of the wireless LAN control unit 301.

[0031] The transmission time control unit 303 outputs an instruction on when to transmit a frame, according to the time interval obtained from the beacon control unit 304. The wireless LAN control unit 301 controls the communication unit 206 to transmit the frame generated by the frame generation unit 302, according to the instruction from the transmission time control unit 303.

[0032] The beacon control unit 304 outputs instructions to the frame generation unit 302 and the transmission time control unit 303 regarding the timing of beacon transmission and the information to be included in the beacon. When AP102 starts operating as an AP, the beacon control unit 304 outputs setting information for the time interval for periodically transmitting beacons to the transmission time control unit 303. Based on the setting information, the transmission control unit 303 can output a beacon transmission instruction to the wireless LAN control unit 301. In addition, when the transmission time control unit 303 outputs a beacon transmission instruction, the beacon control unit 304 outputs instructions to the frame generation unit 302 regarding the information to be included in the beacon. Based on these instructions, the frame generation unit 302 obtains information from the storage unit 201 via the storage control unit 306 and generates a beacon based on the obtained information.

[0033] The UI control unit 305 controls the input unit 204 to accept operations on AP102 by a user (not shown), and controls the output unit 205 to present information to the user, such as displaying images or outputting audio. The memory control unit 306 performs control processing such as storing data in the memory unit 201 and reading data stored in the memory unit 201.

[0034] (Communication flow) Next, we will explain an example of the communication flow when AP102 communicates with one or more STAs, such as STA103. Note that, in the following explanation, we will assume that the communication partner of AP102 is STA103, but AP102 can communicate with multiple STAs, including STA103, in parallel.

[0035] In this embodiment, we will focus on the situation in which AP102 transmits a group address frame on links 104 and 105 established with STA103. A group address frame is primarily used when transmitting simultaneously to multiple STAs. In a group address frame, the MAC Address included in the Destination Address (DA) or A1 field has a Group Bit of 1. For example, a beacon is a broadcast frame, and in that case, the Group Bit is set to 1. Therefore, a beacon is a group address frame. Similarly, a multicast address also has a Group Bit set to 1, and is therefore a group address frame.

[0036] In this embodiment, as described above, AP102 cannot receive signals on either link 104 or link 105 while transmitting a signal on the other. On the other hand, it is assumed that AP102 needs to transmit beacons on each frequency channel (each link). Therefore, in each of the following processes, while AP102 is transmitting a beacon (group address frame) on one link, signals addressed to AP102 from surrounding STAs or other APs are not transmitted on the frequency channels of other links. An example of such a process flow is described below. Note that beacons are just an example, and the same process can be performed when transmitting any group address frame. Furthermore, the following process is also applicable when a predetermined signal should be transmitted, for example, with a predetermined transmission timing such as a predetermined period. That is, the following process can be applied when there is any predetermined frame (which may be a unicast frame) with a predetermined transmission timing on any of the links.

[0037] The following example describes a case where AP102 attempts to transmit beacons (group address frames) on all established links, but it is not limited to this. That is, AP102 may perform the following processing on two or more links that are part of a group of established links. For example, this processing may be performed when it is necessary to transmit group address frames such as beacons on only some of the links, and there is no need to transmit such frames on the other links. In that case, AP102 may, for example, ignore frames that arrive on other links while it is transmitting frames on some of the links.

[0038] Furthermore, while the following describes an example of sending a beacon, the following discussion can also be applied to sending any group address frame or multicast frame destined for a multicast address. For example, the beacon in the following description may be replaced with a FILS Discovery frame or an Unsolicited Probe Response frame. Note that the FILS Discovery frame is a frame sent between beacons at intervals of 20 TUs. Here, TU is an acronym for Time Unit, and 1 TU is 1024 microseconds. The beacon in the following description may also be replaced with other management frames, such as the Probe Response frame or the Action frame.

[0039] (Processing Example 1) In this example, AP102 attempts to transmit beacons in parallel on both Link 104 and Link 105 at the same time (at least during a time when the transmission periods overlap). However, AP102 is not required to transmit beacons on Link 104 and Link 105 simultaneously; it is permitted to transmit beacons on Link 104 and Link 105 at different times.

[0040] Figure 4 shows an example of the processing flow executed by AP102 in the first processing example. The processing in Figure 4 starts, for example, when AP102 starts operating as an AP. For example, the processing in Figure 4 can be realized by the control unit 202 of AP102 executing a program stored in the memory unit 201 of AP102. However, it is not limited to this, and for example, part or all of the processing in Figure 4 may be realized by dedicated hardware. Also, the processing in Figure 4 is just an example, and unless there is a particular reason for not doing so, the order of each process may be changed, part of the process may be omitted, or it may be replaced with other similar processes.

[0041] In this process, AP102 first waits until the timing to transmit a beacon (hereinafter referred to as the beacon transmission time) (S401). This beacon transmission time can be determined, for example, based on the transmission interval setting value stored in the memory unit 201. When AP102 reaches the beacon transmission time (YES in S401), it executes the beacon transmission process on all of the established links (S402). Note that the above-mentioned beacon transmission time may be a predetermined timing prior to the timing when the beacon should actually be transmitted (Target Beacon Transmission Time, TBTT). At that predetermined timing, AP102 may start preparing to transmit the beacon and execute processing so that it can start transmitting the beacon at TBTT. Then, while observing the status of the links, AP102 attempts to transmit the beacon on all links at the timing when the beacon should be transmitted. Then, AP102 determines whether it was not possible to transmit the beacon on any of the established links, for example, due to channel congestion (S403). AP102 determines that it cannot transmit a beacon on a link of that frequency channel if, for example, STA106 is transmitting data to another AP on the same frequency channel as link 104 or link 105, and TBTT arrives during the period when that data is being transmitted. In such a situation, AP102 will delay the timing of the beacon transmission.

[0042] If AP102 determines that it is unable to transmit a beacon on any link and that the beacon timing is off (YES in S403), it will transmit a signal on the other links during the beacon transmission period on the link with the off-timing. In this example, AP102 first determines whether there is an additional group address frame to be transmitted following the beacon transmission (S404). If AP102 can transmit the additional group address frame on a second link different from the first link with the off-timing, it will transmit the additional group address frame on the second link during the beacon transmission period on the first link. In this case, while the additional group address frame is being transmitted on the second link, the beacon transmission on the first link may be completed, and then another AP or surrounding STA may transmit a frame addressed to AP102. Therefore, in such cases, AP102 can prevent the transmission of a signal addressed to AP102 on the first link from occurring even while the group address frame is being transmitted on the second link.

[0043] If AP102 determines that an additional group address frame exists (YES in S404), it determines whether the group address frame should be transmitted on all links (S405). If AP102 determines that the additional group address frame should be transmitted on all links (YES in S405), it performs adjustment processing to ensure that the transmission of that frame is completed simultaneously (or nearly simultaneously) on all links (S406). This adjustment processing can be done, for example, by additionally transmitting another frame such as an empty frame, or by adding padding bits to the end of the data for frames that are short in length and can be transmitted quickly. In addition, AP102 may perform processing in the adjustment processing to transmit additional group address frames that are scheduled to be sent in the next beacon on other links in accordance with the transmission period of the additional group address frame transmitted on a given link. In addition, AP102 may perform processing in the adjustment processing to transmit a duplicate of the additional group address frame on other links in accordance with the transmission period of the additional group address frame transmitted on a given link.

[0044] Furthermore, AP102 may ensure a transmission opportunity (TXOP) on other links while it is transmitting beacons or additional group address frames on a given link. By ensuring a TXOP, AP102 can prevent other STAs from transmitting frames. AP102 can ensure a TXOP, for example, by sending a CTS (Clear-To-Send)-to-self on another link. A CTS-to-self is a CTS sent to the sender itself. Upon receiving the CTS-to-self, STAs and other APs around AP102 will be unable to transmit frames for the period specified in the CTS-to-self. This prevents other devices from transmitting data to AP102 while AP102 is transmitting additional group address frames, in cases where AP102 cannot transmit and receive in parallel.

[0045] On the other hand, if AP102 determines in S405 that it will not send additional group address frames on all links (NO in S405), AP102 performs processing to synchronize the transmission end times on all links (S407). For example, AP102 may send a frame similar to the additional group address frame, or an empty group address frame, on a link other than the link on which it plans to send the additional group address frame. AP102 may also secure a TXOP by sending a CTS-to-self on a link on which it does not plan to send the additional group address frame, as explained in relation to S406. AP102 may also send a unicast frame with the MAC address of its own device or the source MAC address on another link set as the destination, for example. AP102 may also perform the processing in S407 by sending control frames, action frames, and data frames, including management frames, trigger frames, and Ack frames related to the connection. In this case, by specifying the value of the Duration field in the transmitted frame, a TXOP can be secured for the specified period. However, this is just one example, and TXOP may be secured using a different field or subfield than the Duration field. Furthermore, AP102 may, for example, secure TXOP in advance using an RTS frame or CTS-to-self frame before sending a beacon, rather than when sending an additional group address frame.

[0046] Furthermore, in S404, if AP102 determines that no additional group address frames exist (NO in S404), it will send a frame on another link when sending a beacon on a link where the beacon transmission timing is staggered (S408). Note that AP102 does not need to send a frame if other links that are not sending beacons are in the NAV (Network Allocation Vector) period. In this case, for example, unicast frames, group address frames, RTS (Request-To-Send) frames, and FILS Discovery frames may be sent to the connected STA. Alternatively, empty data may be sent, or a unicast frame with the destination set to AP102's own MAC address or the source MAC address on that link may be sent.

[0047] If AP102 determines that the timing of the beacons is not out of sync on each link (NO in S403), it determines whether to send an additional group address frame (S409). If AP102 determines not to send an additional group address frame (NO in S409), it sends beacons with synchronized transmission periods on each link (S413) and terminates processing. On the other hand, if AP102 determines to send an additional group address frame (YES in S409), it determines whether to send that additional group address frame on all links (S410). If AP102 determines to send the additional group address frame on all links (YES in S410), it sends the additional group address frame with synchronized transmission periods on each link (S412). On the other hand, if AP102 determines to send the additional group address frame on only some links (NO in S410), it secures a TXOP on the links that do not send the group address frame (S411). This allows AP102 to prevent multiple devices from sending signals to AP102 on another link while an additional group address frame is being sent on one link.

[0048] Figure 5 shows an example of the communication flow when AP102 operates based on the processing shown in Figure 4. Here, AP102 is assumed to send an additional group address frame following the beacon on both Link 104 and Link 105. Here, it is assumed that the timing of the beacon transmission on Link 105 is delayed due to channel congestion.

[0049] In one example, let's assume that timing 531, after AP102 receives a frame from STA103 during period 511, is the timing when a beacon should be transmitted. At this time, AP102 is able to transmit beacon 512 as planned on link 104. On the other hand, let's assume that link 105 is in NAV period 521, for example, because STA106 is transmitting a data frame to another AP. At timing 532, after the end of that NAV period, AP102 is able to transmit beacon 522 on link 105 as well. At this time, AP102 has transmitted an additional group address frame 513 after transmitting beacon 512 on link 104, and is transmitting frames in parallel on both link 104 and link 105. Then, AP102 transmits an additional group address frame 523 after transmitting beacon 522 on link 105.

[0050] Here, the group address frame 513 on link 104 and the group address frame 523 on link 105 have different transmission end times. Therefore, AP102 secures TXOP 514 on link 104, for example, by one of the methods described above, in accordance with the end time 533 of the group address frame 523 on link 105, which has a later transmission end time. This ensures that AP102 secures transmission rights for all links, preventing a situation where AP102 must transmit a frame on one link while receiving a frame on another.

[0051] Furthermore, in this example, AP102 can transmit data to a specific STA while TXOP is secured. Therefore, AP102 can efficiently utilize frequency resources while preventing simultaneous transmission and reception. Additionally, even if some links are unavailable due to reasons unrelated to wireless communication, such as interference from microwave ovens, AP102 can select an available link and transmit a beacon.

[0052] Furthermore, as shown in link 105 of Figure 5, if the timing of a beacon is off, the opportunity to transmit the next beacon after the off-timing beacon has been transmitted can be determined based on the timing and period in which the beacon should have been transmitted. For example, suppose the beacon transmission period is 100 TU, and the first beacon is transmitted at 0 TU, and then, due to a timing shift, the next beacon is transmitted at 110 TU. In this case, the timing of the next beacon transmission can be determined to be at 200 TU, based on the original transmission timing of 100 TU. Note that this is just one example, and the beacon transmission timing may be determined by other criteria. For example, in the above example, the next beacon may be determined to be transmitted at 210 TU, based on the timing after the shift.

[0053] (Processing Example 2) In this example, AP102 will attempt to transmit beacons in parallel on both Link 104 and Link 105 at the same time (at least during a time when the transmission periods overlap). However, in this example, AP102 is not required to transmit beacons simultaneously on Link 104 and Link 105; it is permitted to transmit beacons on Link 104 and Link 105 at different times.

[0054] Figure 6 shows an example of the processing flow executed by AP102 in the second processing example. The processing in Figure 6 starts, for example, when AP102 starts operating as an AP. For example, the processing in Figure 6 can be realized by the control unit 202 of AP102 executing a program stored in the memory unit 201 of AP102. However, it is not limited to this, and for example, part or all of the processing in Figure 6 may be realized by dedicated hardware. Also, the processing in Figure 6 is just an example, and unless there is a particular reason for not doing so, the order of each process may be changed, part of the process may be omitted, or it may be replaced with other similar processes.

[0055] In this process, AP102 first waits until it is time to send a beacon (S601), and when it is time to send a beacon (YES in S601), it verifies that each link is not busy (S602, S603). AP102 determines that a link is busy if data is being transmitted on the frequency channel used by another wireless communication device, or if TXOP is secured and the link is in NAV state. If AP102 determines that all links are not busy (NO in S602, NO in S603), it sends a beacon on all of those links (S604). For example, AP102 may measure the elapsed time from the time when a beacon should be sent, and if any link remains busy until that elapsed time reaches a predetermined timeout period, it may terminate this process without sending a beacon.

[0056] AP102 determines whether to send an additional group address frame after sending the beacon (S605). If AP102 does not send an additional group address frame (NO in S605), it sends the beacons with synchronized transmission periods (S609) and terminates processing. On the other hand, if AP102 decides to send an additional group address frame (YES in S605), it determines whether to send that additional group address frame on all links (S606). If AP102 decides to send the additional group address frame on all links (YES in S606), it sends the additional group address frame on all links with synchronized transmission periods (S608). In order to synchronize the transmission periods, padding bits may be added or another frame may be sent as described above. Also, AP102 may, when sending the beacon on each link, take into account the transmission period of the additional group address frame and ensure a common TXOP with other links. On the other hand, if AP102 sends an additional group address frame following a beacon on only one link (NO in S606), it reserves a TXOP on the link that does not send that group address frame (S607). This TXOP may be reserved for the duration until the transmission of group address frames on the other links is completed. AP102 can reserve a TXOP in the same manner as in the processing example 1 described above.

[0057] Figure 7 shows an example of the communication flow when AP102 operates based on the processing in Figure 6. Here, we describe an example where an additional group address frame is sent after the beacon is sent on all links. In the example in Figure 7, at the beacon transmission timing 731, TXOP 711 by STA103 has finished on link 104 and it is not busy. On the other hand, link 105 is busy because the NAV period 721 is set, for example, because the frequency channel is being used for communication by another STA106. Therefore, AP102 is unable to send beacons on both links 104 and 105 simultaneously and waits without sending beacons on either link. Subsequently, at timing 732, when link 105 is no longer busy and both links 104 and 105 are not busy, AP102 sends beacons 712 and 722 on both links 104 and 105. Subsequently, AP102 transmits an additional group address frame 713 on link 104, and then another additional group address frame 723 on link 105. At this time, AP102 performs control to synchronize the transmission periods of these frames, and synchronizes the end-of-transmission timing 733 of the group address frames on links 104 and 105. These additional group address frames are optional, but even if only beacons are transmitted, control is performed to synchronize the end-of-transmission timing of those beacons.

[0058] This ensures that AP102 transmits frames on all links, preventing situations where a frame is transmitted on one link while a frame is received on another. This example also allows for handling situations where a beacon transmission timing arrives while data is being received from another STA on link 105. In other words, AP102 can prevent simultaneous frame reception on link 105 and beacon transmission on link 104 through the same process as described above.

[0059] The above processing example is just one example, and different processing may be performed. For example, in the above processing example, the beacon transmission timing of link 104 was changed based on the NAV period of link 105, but this is not limited to this. AP102 may, for example, set link 104 as the primary link and link 105 as the sub-link, and only perform the control to shift the beacon transmission timing as described above if the beacon transmission timing is shifted on the primary link. That is, if the beacon transmission timing arrives while link 104 is in the NAV period, AP102 will shift the beacon transmission timing on both link 104 and link 105. On the other hand, if the beacon transmission timing arrives while link 105 is in the NAV period, AP102 will only shift the beacon transmission timing on link 105, and not shift the beacon transmission timing on link 104. In other words, AP102 may operate with priority given to the primary link.

[0060] Furthermore, in addition to the processing described above, AP102 may, for example, require connection to the primary link and only allow connection to communication devices capable of multilink communication on the sub-links. This allows AP102 to operate as a multilink communication AP while taking into consideration the operation of communication devices that do not support multilink communication operating on link 104. In this case, AP102 does not need to transmit a beacon on link 105 if it is unable to transmit a beacon at the beacon transmission timing, such as when it is in the NAV period at the beacon transmission timing. This is because each STA connected to AP102 can maintain synchronization with AP102 even if it only receives beacons on link 104. However, since there are operations that need to be performed on each link, such as recovery from power saving mode and correction of time drift, AP102 will transmit beacons on each link at the timing when transmission is possible.

[0061] (Processing Example 3) In this example, AP102 attempts to transmit beacons on link 104 and link 105 at different times (at times when the transmission periods do not overlap). However, AP102 is not required to transmit beacons in a way that avoids overlapping transmission periods between link 104 and link 105; at least a partial overlap in the transmission periods of the beacons on link 104 and link 105 is permitted.

[0062] Figure 8 shows an example of the processing flow executed by AP102 in the third processing example. The processing in Figure 4 is started, for example, when AP102 starts operating as an AP. For example, the processing in Figure 4 can be realized by the control unit 202 of AP102 executing a program stored in the memory unit 201 of AP102. However, it is not limited to this, and for example, part or all of the processing in Figure 4 may be realized by dedicated hardware. Also, the processing in Figure 8 is just an example, and unless there is a particular reason for not doing so, the order of each process may be changed, part of the process may be omitted, or it may be replaced with other similar processes.

[0063] In this process, AP102 first waits until the beacon transmission time (S801). Then, when AP102 transmits the beacon, it checks the status of other links other than the link on which the beacon is being transmitted. Note that the order of the procedure for checking other links in the following description is an example, and the order of these procedures may be changed. For example, AP102 first determines whether frames are being transmitted on the other link (S802). Then, if frames are being transmitted on the other link (YES in S802), AP102 transmits the beacon and additional group address frames in sync with the transmission time of this other link (S810). Note that various frames may be transmitted on the other link, for example, management frames including beacon frames, data frames of unicast frames, and control frames including trigger frames may be transmitted. Also, group address frames and action frames destined for multicast addresses or broadcast addresses may be transmitted on the other link.

[0064] If AP102 determines that it is not transmitting frames on another link (NO in S802) as part of checking the status of another link, it then determines whether or not it is in a NAV period on that other link (S803). If AP102 determines that it is not in a NAV period on the other link (NO in S803), it secures TXOP until the beacon transmission period (and the transmission period of any additional group address frames associated with the beacon) ends (S809). By securing transmission rights on the other link in this way, AP102 can prevent signals from being received on the other link during the beacon transmission period (and the transmission period of any additional group address frames). The method for securing TXOP is as described above, so it will not be repeated here, and the same applies below.

[0065] If AP102 determines that another link is in a NAV period (YES in S803) as a way to check the status of another link, it then determines whether or not it is currently receiving a frame (S804). If AP102 is receiving a frame on another link (YES in S804), it cannot transmit a frame while receiving that frame. Therefore, in this case, AP102 waits until it is possible to transmit a frame before transmitting the beacon (S808). AP102 also ensures that a TXOP is available on the other link during the period when the beacon is being transmitted. In this case, since AP102 had just received a frame on the other link, it may need to send an acknowledgment of receipt (Ack frame or Block Ack frame) for that frame. Therefore, AP102 may ensure a TXOP is available for sending that acknowledgment. Ack frames and Block Ack frames are a type of control frame.

[0066] If AP102 is not receiving frames during the NAV period of another link (NO in S804), it is assumed that, for example, STA106 is sending or receiving data frames with another AP. In this situation, it is assumed that AP102 will not receive data during the NAV period. In this case, if AP102 completes the transmission of the beacon during the NAV period, it can transmit only the beacon without receiving any data addressed to itself on the other link. Therefore, AP102 determines whether the NAV period of the other link will expire during the beacon transmission period (and the transmission period of any additional group address frames associated with the beacon) (S805). If AP102 determines that the NAV period of the other link will not expire during the transmission period of the beacon, etc. (NO in S805), it will transmit the beacon, etc. as is (S807). On the other hand, if the NAV period of another link expires during the transmission period of a beacon or other signal (YES in S805), AP102 will secure a TXOP (Time-Out Operation) on the other link to prevent the transmission of signals destined for AP102 during that transmission period (S806). AP102 will begin transmitting beacons on one of the links during the beacon transmission time. AP102 may also transmit any frame during the TXOP period secured in S806.

[0067] As described above, when AP102 transmits beacons independently on each link, it can prevent frames addressed to itself from arriving on other links while one link is transmitting beacons or the like.

[0068] Figure 9 shows an example of the communication flow when AP102 operates based on the processing in Figure 8. Figure 9 shows an example of the communication flow when the NAV period expires during the transmission of a beacon and its associated additional group address frame. In the example in Figure 9, at the beacon transmission timing 931, TXOP911 by STA103 has finished on link 104. Meanwhile, on link 105, the NAV period 921 is set, for example, because the frequency channel is being used for communication by another STA106. Meanwhile, on link 104, if beacon transmission starts at transmission timing 931, the transmission of the series of frames is completed at timing 933. At this time, since the NAV period 921 expires before timing 933, AP102 secures TXOP922 on link 105 during the period from timing 932 to timing 933, when it becomes possible to secure transmission rights. AP102 may also transmit some frame during TXOP922. In this way, AP102 can prevent frames destined for itself from arriving on link 105 during the transmission period of beacon 912 and additional group address frame 913 on link 104.

[0069] Figure 10 shows another example of the communication flow when AP102 operates based on the processing in Figure 8. Figure 10 shows an example where AP102 is receiving a data frame from STA103 on link 105 during the beacon transmission time on link 104. That is, in the example in Figure 10, at the beacon transmission timing 1031, TXOP1011 by STA103 has finished on link 104, but TXOP1021 by STA103 is continuing on link 105, and AP102 is receiving a frame. Therefore, AP102 waits without transmitting a beacon until TXOP1021 by STA103 on link 105 has finished. Note that Figure 10 shows the case where STA103 is an STA operating in multilink, but it may also be a communication device that does not support multilink communication. Then, at timing 1032, when AP102 has finished receiving frames from STA103 and can secure transmission rights on link 105, it begins transmitting the beacon 1012 and the additional group address frame 1013 on link 104. At this time, AP102 secures TXOP 1022 on link 105 so that no frames destined for itself arrive. TXOP 1022 is set to the period until the transmission of the beacon 1012 and the additional group address frame 1013 (and any further frames transmitted) is completed on link 104. In other words, in the example in Figure 10, TXOP 1022 is secured on link 105 until timing 1033, when the transmission of the additional group address frame 1013 on link 104 is completed. Note that in the example in Figure 10, since AP102 has just received a frame during the period of STA103's TXOP 1021, it may send an acknowledgment of receipt of that frame in TXOP 1022. In this way, AP102 can prevent frames destined for itself on link 105 from arriving during the transmission period of beacon 1012 and additional group address frame 1013 on link 104.

[0070] In this example, AP102 can communicate (transmit beacons, etc.) on another link even if there is interference on one link that is not due to communication, such as from a microwave oven. Furthermore, if AP102 is receiving data on the link that is not transmitting a beacon, it can postpone the transmission, thereby preventing simultaneous transmission and reception. Note that by having different beacon transmission timings for each link, as in this example, the degree of freedom of communication on each link can be improved. On the other hand, by aligning the beacon transmission timing as in the above-mentioned Examples 1 and 2, it becomes unnecessary to perform processes such as securing a TXOP on one link while a beacon is being transmitted on another, thus reducing overhead. Note that the above examples can be used in combination. For example, Examples 1 and 3 may be used during NAV periods or when there is interference not due to communication, such as from a microwave oven, while Example 2 may be used when a frame is being received on the link that is not transmitting a beacon. This makes it possible to effectively utilize the advantages of each of the above examples while preventing simultaneous transmission and reception on AP102.

[0071] In the embodiments described above, AP102 and STA103 are described assuming channel access via EDCA (Enhanced Distributed Channel Access). However, the invention is not limited to this. For example, AP102 may allow only trigger frame-based communication for UL (uplink) communication from the connected STA. In this case, AP102 performs channel allocation so that UL communication does not occur on another link when a beacon is transmitted on one link. This prevents frames destined for the device from arriving from the STA during the beacon transmission period.

[0072] In the above embodiment, AP102 described a method to prevent data addressed to itself from occurring on links where it does not transmit beacons, such as by acquiring transmission rights. Alternatively, or in addition to this, AP102 may operate in a way that reduces the probability of data addressed to itself occurring. For example, AP102 may receive an RTS frame requesting data transmission from an STA connected to it. In this case, AP102 identifies the period of TXOP that the STA that sent the RTS is trying to secure from the value indicated in the Duration field of the RTS, and determines whether that period overlaps with the beacon transmission period on another link. If the period of TXOP that the STA is trying to secure and the beacon transmission period on another link overlap at least partially, AP102 may reject the RTS by not sending a CTS, which is a response to the received RTS. This prevents the STA from securing TXOP, and reduces the probability that a frame addressed to AP102 will be transmitted during AP102's beacon transmission period.

[0073] <<Other Embodiments>> The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0074] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of symbols]

[0075] 102: Access point, 103: Station, 202: Control unit, 206: Communication unit, 301: Wireless LAN control unit, 303: Transmission time control unit, 304: Beacon control unit

Claims

1. A communication device, a communication means for performing communication with a partner device using a plurality of wireless links in accordance with the IEEE 802.11 standard series; a control means for controlling the communication means so that, when a predetermined frame that is a group address frame is transmitted through a first wireless link among the plurality of wireless links, a frame addressed to the communication device does not arrive through a second wireless link among the plurality of wireless links that is different from the first wireless link; A communication device having:

2. 2. The communication device according to claim 1, wherein the control means controls the communication means so as to reserve a transmission right on the second wireless link during a period in which the predetermined frame is transmitted on the first wireless link.

3. 3. The communication device according to claim 2, wherein the control means controls the communication means so as to secure the transmission right by transmitting a frame on the second wireless link during a period in which the specified frame is transmitted on the first wireless link.

4. 4. The communication device according to claim 3, wherein the frame transmitted to reserve the transmission right on the second wireless link includes an empty frame.

5. 4. The communication device according to claim 3, wherein the frame transmitted to reserve the transmission right on the second wireless link includes a group address frame.

6. 6. The communication device according to claim 3, wherein the frame transmitted to secure the transmission right on the second wireless link includes padding bits based on the length of the period during which the specified frame is transmitted on the first wireless link.

7. The communication device according to any one of claims 2 to 6, characterized in that the control means controls the communication means to transmit either a CTS (Clear-To-Send) or RTS (Request-To-Send) frame on the second wireless link during a period in which the specified frame is transmitted on the first wireless link so as to secure the transmission right before the period begins.

8. 8. The communication device according to claim 3, wherein the control means controls the communication means to set the value of a Duration field in a frame transmitted to secure the transmission right to a period corresponding to the period during which the specified frame is transmitted on the first wireless link and transmit the frame on the second wireless link.

9. 9. The communication device according to claim 2, wherein the control means controls the communication means to secure the transmission right in the second wireless link during a period in which the specified frame is transmitted in the first wireless link, based on a deviation of the timing of transmitting the specified frame in the first wireless link from a predetermined transmission timing.

10. 10. The communication device according to claim 9, wherein the control means controls the communication means to shift the timing of transmitting the specified frame on the first wireless link so that, when a frame addressed to the communication device is received on the second wireless link at the predetermined transmission timing of the specified frame, the specified frame is transmitted on the first wireless link after reception of the frame is completed.

11. The communication device according to claim 9 or 10, characterized in that, if the control means cannot secure the transmission right in the second wireless link at the predetermined transmission timing of the specified frame and a frame addressed to the communication device is not received, the control means controls the communication means to transmit the specified frame at the predetermined transmission timing in the first wireless link.

12. The communication device according to claim 11, characterized in that, if it becomes possible to secure the transmission right in the second wireless link while transmitting the specified frame at the predetermined transmission timing in the first wireless link, it controls the communication means so as to secure the transmission right in the second wireless link from the time the transmission right becomes possible to the time transmission of the specified frame is completed.

13. the communication means is configured to transmit a first predetermined frame, which is a group address frame, over the first wireless link and to transmit a second predetermined frame, which is a group address frame, over the second wireless link; 2. The communication device according to claim 1, wherein the control means controls the communication means to transmit the second predetermined frame on the second wireless link during a period for transmitting the first predetermined frame on the first wireless link after the timing of transmitting the first predetermined frame on the first wireless link has shifted from a predetermined transmission timing.

14. 14. The communication device according to claim 13, wherein the control means controls the timing at which the transmission of the first predetermined frame and the second predetermined frame starts to coincide with the timing at which the transmission ends.

15. 15. The communication device according to claim 14, wherein when the timing of the end of transmission based on the frame length of the first predetermined frame in the first wireless link and the frame length of the second predetermined frame in the second wireless link differ, the control means includes padding bits in the frame whose transmission ends first, and performs control so that the timing of the end of transmission coincides.

16. 15. The communication device according to claim 14, wherein, when the timing of the end of transmission based on the frame length of the first predetermined frame in the first wireless link and the frame length of the second predetermined frame in the second wireless link differ, the control means controls the communication means to transmit another frame in the wireless link in which transmission ends first so that the timing of the end of transmission coincides.

17. 17. The communication device according to claim 1, wherein the predetermined frame includes a beacon.

18. 18. The communication device according to claim 1, wherein the communication device is an access point.

19. A control method executed by a communication device that communicates with a partner device using multiple wireless links in accordance with the IEEE 802.11 standard series, comprising: A control method comprising: when a predetermined frame, which is a group address frame, is transmitted on a first wireless link among the plurality of wireless links, controlling so that a frame addressed to the communication device does not arrive on a second wireless link among the plurality of wireless links that is different from the first wireless link.

20. A program for causing a computer to function as each of the means included in the communication device according to any one of claims 1 to 18.

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