JP7707018B2 - COMMUNICATION DEVICE, CONTROL METHOD FOR COMMUNICATION DEVICE, AND PROGRAM THEREOF - Google Patents

Description

The present invention relates to a communication device that performs wireless communication, a control method for the communication device, and a program for the same.

With the increase in the amount of data being communicated in recent years, the development of communication technologies such as wireless LANs (Local Area Networks) is progressing. The IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard series is known as the main communication standard for wireless LANs. The IEEE 802.11 standard series includes standards such as IEEE 802.11a/b/g/n/ac/ax. For example, the latest standard, IEEE 802.11ax, uses OFDMA (orthogonal frequency division multiple access) to standardize technology that improves communication speeds under congested conditions in addition to a high peak throughput of up to 9.6 gigabits per second (Gbps) (see Patent Document 1). OFDMA stands for Orthogonal frequency-division multiple access.

A task group called IEEE802.11be was launched as a successor standard aimed at further improving throughput, frequency efficiency, and communication latency.

IEEE 802.11be is considering multi-link communication, in which one AP and one STA (station) build multiple links in frequency bands such as 2.4 GHz, 5 GHz, and 6 GHz and communicate simultaneously. In multi-link communication, the AP is called an AP MLD (Access point multi-link device), and the STA is called a non-AP MLD (non-Access point multi-link device).

In addition, IEEE 802.11be is considering Enhanced multi-link multi-radio (EMLMR) operation in multi-link communication. A non-AP MLD operating in EMLMR mode performs an initial frame exchange with the number of spatial streams according to the per-link spatial stream capability for each EMLMR link, and then operates as follows until the end of the frame exchange sequence on the link where the initial frame exchange was performed. This operation involves receiving a PPDU (Physical layer convergence protocol data unit) with the number of spatial streams up to the value presented in the EMLMR SUPPORTED MCS AND NSS SET subfield of the Common Info field of the Basic variant Multi-Link element, and transmitting a PPDU with the number of spatial streams presented in the EMLMR SUPPORTED MCS AND NSS SET subfield.

JP 2018-50133 A

When multiple EMLMR links are established, it was not considered that a frame exchange sequence would be executed with the number of spatial streams according to the spatial stream capability of each EMLMR link.

The present invention aims to provide a communication device that executes a frame exchange sequence with the number of spatial streams according to the spatial stream capability of each link in which an EMLMR link is established.

The communication device of the present invention is a communication device that operates as a Multi-Link Device compliant with the IEEE 802.11 series standard, and is characterized by having a control means that, when a frame exchange sequence is executed on two links, a first EMLMR (Enhanced multi-link multi-radio) link and a second EMLMR (Enhanced multi-link multi-radio) link, controls the frame exchange sequence to be executed with the respective numbers of spatial streams of the first EMLMR link and the second EMLMR link.

According to the present invention, it is possible to provide a communication device that executes a frame exchange sequence with the number of spatial streams according to the spatial stream capability of each link in which an EMLMR link is established.

FIG. 1 is a diagram showing a network configuration according to the present invention. FIG. 2 is a diagram illustrating a hardware configuration of a communication device according to the present invention. FIG. 2 is a diagram showing a functional configuration of a communication device according to the present invention. FIG. 1 is a diagram showing an overview of Multi-Link communication. 13A is a diagram showing a Basic variant Multi-Link element included in an Association Request frame, and FIG. 13B is a diagram showing an EMLMR Capabilities subfield included in a Common Info field of the Basic variant Multi-Link element. 11 is a flowchart of a process executed to start a frame exchange sequence in an EMLMR link in the present invention. 11 is a flowchart of a process executed to start a frame exchange sequence in an EMLMR link in the present invention.

The following describes in detail an embodiment of the present invention with reference to the attached drawings. Note that the configurations shown in the following embodiments are merely examples, and the present invention is not limited to the configurations shown in the drawings.

(Configuration of wireless communication system)
1 shows the configuration of a network searched by a communication device 101 (hereinafter, Non-AP MLD 101) according to this embodiment. A communication device 102 (hereinafter, AP MLD 102) is an access point (AP) that serves to construct a wireless network 100. The AP MLD 102 is capable of communicating with the Non-AP MLD 101. This embodiment is applied to the Non-AP MLD 101 and the AP MLD 102.

Each of the Non-AP MLD 101 and the AP MLD 102 can perform wireless communication conforming to the IEEE 802.11be (EHT) standard. IEEE is an abbreviation for the Institute of Electrical and Electronics Engineers. The Non-AP MLD 101 and the AP MLD 102 can communicate at frequencies of 2.4 GHz, 5 GHz, and 6 GHz. The frequency bands used by each communication device are not limited to these, and different frequency bands such as the 60 GHz band may be used. The Non-AP MLD 101 and the AP MLD 102 can also communicate using bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz. The bandwidth used by each communication device is not limited to this, and may use a different bandwidth, such as 240 MHz or 4 MHz.

The Non-AP MLD 101 and AP MLD 102 can realize multi-user (MU, Multi User) communication by multiplexing signals from multiple users by performing OFDMA communication conforming to the IEEE 802.11be standard. OFDMA stands for Orthogonal Frequency Division Multiple Access. In OFDMA communication, a portion of the divided frequency band (RU, Resource Unit) is assigned to each STA so that they do not overlap, and the carrier waves of each STA are orthogonal. Therefore, the AP can communicate with multiple STAs in parallel within a specified bandwidth.

It is generally known that the range of radio waves varies depending on the frequency; the lower the frequency, the greater the diffraction of the radio waves and the farther they can reach, while the higher the frequency, the less the diffraction of the radio waves and the shorter the distance they can reach. Even if there is an obstacle in the way, low-frequency radio waves can go around the obstacle, but high-frequency radio waves have a high degree of directivity and therefore have difficulty going around them, so they may not reach their destination. On the other hand, the 2.4 GHz frequency is often used by other devices, and microwave ovens are known to emit radio waves in the same frequency band. Thus, even when radio waves are emitted by the same device, the strength of the radio waves that reach the destination and the signal-to-noise (SN) ratio may differ depending on the frequency band, depending on the location and environment in which they are placed.

Although the Non-AP MLD 101 and the AP MLD 102 are described as being compatible with the IEEE 802.11be standard, they may also be compatible with a legacy standard that is a standard that precedes the IEEE 802.11be standard. Specifically, the Non-AP MLD 101 and the AP MLD 102 may be compatible with at least one of the IEEE 802.11a/b/g/n/ac/ax standards. In addition to the IEEE 802.11 series standards, they may also be compatible with other communication standards such as Bluetooth (registered trademark), NFC, UWB, ZigBee, and MBOA. UWB stands for Ultra Wide Band, and MBOA stands for Multi Band OFDM Alliance. Additionally, NFC is an abbreviation for Near Field Communication. UWB includes wireless USB, wireless 1394, WiNET, and the like. It may also be compatible with communication standards for wired communication such as wired LAN. Specific examples of the AP MLD 102 include, but are not limited to, a wireless LAN router and a personal computer (PC).

The AP MLD 102 may be an information processing device such as a wireless chip capable of performing wireless communication conforming to the IEEE 802.11be standard. Specific examples of the Non-AP MLD 101 include, but are not limited to, a camera, a tablet, a smartphone, a PC, a mobile phone, a video camera, and a headset. The Non-AP MLD 101 may be an information processing device such as a wireless chip capable of performing wireless communication conforming to the IEEE 802.11be standard. Each communication device can communicate using bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz.

The Non-AP MLD 101 and the AP MLD 102 also perform Multi-Link communication by establishing links and communicating via multiple frequency channels. In the IEEE 802.11 series standard, the bandwidth of each frequency channel is defined as 20 MHz except for the 60 GHz band, which is defined as 2.16 GHz. Here, the frequency channel is a frequency channel defined in the IEEE 802.11 series standard, and in the IEEE 802.11 series standard, multiple frequency channels are defined in each of the 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz frequency bands. Note that a bandwidth of 40 MHz or more may be used in one frequency channel by bonding with adjacent frequency channels.

For example, AP MLD 102 is capable of establishing a link with Non-AP MLD 101 via a first frequency channel in the 2.4 GHz band and communicating with it. Non-AP MLD 101 is capable of establishing a link with AP MLD 102 via a second frequency channel in the 5 GHz band in parallel with this and communicating with it. In this case, Non-AP MLD 101 executes Multi-Link communication that maintains a second link via the second frequency channel in parallel with the link via the first frequency channel. In this way, AP MLD 102 can improve the throughput in communication with Non-AP MLD 101 by establishing links with Non-AP MLD 101 via multiple frequency channels.

In addition, in the multi-link communication, the links between the communication devices may establish multiple links of different frequency bands. For example, the Non-AP MLD 101 may be able to establish links in the 2.4 GHz band, the 5 GHz band, and the 6 GHz band. Or, links may be established via multiple different channels included in the same frequency band. For example, a 6ch link in the 2.4 GHz band may be established as the first link, and a 1ch link in the 2.4 GHz band may be established as the second link in addition to this. Note that links of the same frequency band and links of different frequency bands may be mixed. For example, the Non-AP MLD 101 may be able to establish a 1ch link in the 2.4 GHz band and a 149ch link in the 5 GHz band in addition to the first link of 6ch in the 2.4 GHz band. By establishing multiple connections at different frequencies between the Non-AP MLD 101 and the AP, even if one band is congested, communication can be established between the Non-AP MLD 101 and the AP in another band. This makes it possible to prevent a decrease in throughput and communication delays in communication with the Non-AP MLD 101.

Note that the wireless network in Figure 1 has one AP MLD and one Non-AP MLD, but the number and arrangement of AP MLDs and Non-AP MLDs are not limited to this. For example, one Non-AP MLD may be added to the wireless network in Figure 1. In this case, the frequency band, number of links, and frequency width of each link established are not important.

When performing multi-link communication, the AP MLD 102 and the Non-AP MLD 101 transmit and receive data to and from the other device via multiple links. Data may be transmitted and received via one of the links that make up the multi-link.

The AP MLD 102 and the Non-AP MLD 101 may also be capable of performing MIMO (Multiple-Input and Multiple-Output) communication. In this case, the AP MLD 102 and the Non-AP MLD 101 have multiple antennas, and one of them sends different signals from each antenna using the same frequency channel. The receiving side simultaneously receives all signals arriving from multiple streams using multiple antennas, and separates and decodes the signals of each stream. In this way, by performing MIMO communication, the AP MLD 102 and the Non-AP MLD 101 can communicate more data in the same amount of time compared to when they do not perform MIMO communication. Furthermore, the AP MLD 102 and the Non-AP MLD 101 may perform MIMO communication in some links when performing multi-link communication.

(Configuration of AP MLD and Non-AP MLD)
2 shows an example of the hardware configuration of the Non-AP MLD 101 in this embodiment. The Non-AP MLD 101 has 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. Note that there may be multiple antennas.

The storage unit 201 is composed of one or more memories such as ROM and RAM, and stores various information such as computer programs for performing various operations described below and communication parameters for wireless communication. ROM stands for Read Only Memory, and RAM stands for Random Access Memory. In addition to memories such as ROM and RAM, storage units 201 may also use 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. The storage unit 201 may also include multiple memories.

The control unit 202 is configured with one or more processors such as a CPU or MPU, and controls the entire Non-AP MLD 101 by executing a computer program stored in the storage unit 201. The control unit 202 may control the entire Non-AP MLD 101 in cooperation with the computer program stored in the storage unit 201 and an OS (Operating System). The control unit 202 also generates data and signals (radio frames) to be transmitted in communication with other communication devices. The CPU stands for Central Processing Unit, and the MPU stands for Micro Processing Unit. The control unit 202 may also include multiple processors such as multi-core processors, and the entire Non-AP MLD 101 may be controlled by the multiple processors.

The control unit 202 also controls the function unit 203 to perform predetermined processes such as wireless communication, image capture, printing, and projection. The function unit 203 is hardware that enables the Non-AP MLD 101 to perform predetermined processes.

The input unit 204 receives various operations from the user. The output unit 205 outputs various types of information to the user via a monitor screen or a speaker. Here, the output by the output unit 205 may be a display on a monitor screen, a sound output by a speaker, a vibration output, or the like. Note that both the input unit 204 and the output unit 205 may be realized by a single module, such as a touch panel. Also, the input unit 204 and the output unit 205 may be integrated with the Non-AP MLD 101, or may be separate.

The communication unit 206 controls wireless communication conforming to the IEEE 802.11be standard. The communication unit 206 may also control wireless communication conforming to other IEEE 802.11 series standards in addition to the IEEE 802.11be standard, and control wired communication such as a wired LAN. The communication unit 206 controls the antenna 207 to transmit and receive signals for wireless communication generated by the control unit 202.

If the Non-AP MLD 101 supports the NFC standard, Bluetooth standard, etc. in addition to the IEEE 802.11be standard, it may control wireless communication in accordance with these communication standards. If the Non-AP MLD 101 can perform wireless communication in accordance with multiple communication standards, it may be configured to have separate communication units and antennas compatible with each communication standard. The Non-AP MLD 101 communicates data such as image data, document data, and video data with the Non-AP MLD 101 via the communication unit 206. The antenna 207 may be configured as a separate entity from the communication unit 206, or may be configured together with the communication unit 206 as a single module.

The antenna 207 is an antenna capable of communication in the 2.4 GHz band, the 5 GHz band, and the 6 GHz band. In this embodiment, the Non-AP MLD 101 has one antenna, but it may have three antennas. Alternatively, it may have a different antenna for each frequency band. Furthermore, if the Non-AP MLD 101 has multiple antennas, it may have a communication unit 206 corresponding to each antenna.

Note that AP MLD 102 has the same hardware configuration as Non-AP MLD 101.

Figure 3 shows a block diagram of the functional configuration of Non-AP MLD 101 in this embodiment. AP MLD 102 has a similar configuration. Here, Non-AP MLD 101 is assumed to have a wireless LAN control unit 301. The number of wireless LAN control units is not limited to one, and may be two, or three or more. Non-AP MLD 101 further has a frame processing unit 302, an EMLMR management unit 303, a UI control unit 304, a memory unit 305, and a wireless antenna 306.

The wireless LAN control unit 301 is configured to include an antenna and circuit for transmitting and receiving wireless signals to and from other wireless LAN devices, and a program for controlling them. The wireless LAN control unit 301 executes wireless LAN communication control based on the frames generated by the frame processing unit 302 in accordance with the IEEE 802.11 standard series.

The frame processing unit 302 processes wireless control frames transmitted and received by the wireless LAN control unit 301. The contents of the wireless control generated and analyzed by the frame processing unit 302 may be restricted by settings stored in the memory unit 305. They may also be changed by user settings from the UI control unit 304. The information of the generated frame is sent to the wireless LAN control unit 301 and transmitted to the communication partner. The information of the frame received by the wireless LAN control unit 301 is passed to the frame processing unit 302 and analyzed.

The EMLMR management unit 303 performs management control to determine which links are EMLMR links. Management control includes the establishment of EMLMR links and the deletion of EMLMR links. Establishment of an EMLMR link refers to the state in which an EMLMR link is identified when a multi-link is established or after a multi-link is established. Deletion of an EMLMR link refers to canceling the state of a link that has been identified as an EMLMR link.

The UI control unit 304 is configured to include hardware related to a user interface, such as a touch panel or buttons for accepting operations on the Non-AP MLD 101 by a user (not shown) of the Non-AP MLD 101, and a program for controlling these. The UI control unit 304 also has a function for presenting information to the user, such as displaying images, or outputting audio.

The memory unit 305 is a storage device that can be configured with ROM, RAM, etc., for storing the programs and data that the Non-AP MLD 101 operates on.

Figure 4 shows the configuration of AP MLD and Non-AP MLD for Multi-Link communication.

A communication device that operates on a multi-link is called an MLD (multi-link device), and one MLD has multiple STAs and APs (access points) associated with each link. An MLD with AP functionality is called an AP MLD, and an MLD without AP functionality is called a non-AP MLD.

In FIG. 4, AP1 401 and STA1 404 establish Link1 407 via a first frequency channel. Similarly, AP2 402 and STA2 405 establish Link2 408 via a second frequency channel, and AP3 403 and STA3 406 establish Link3 409 via a third frequency channel.

Here, the AP MLD and Non-AP MLD establish connections via frequency channels in the sub-GHz band, the 2.4 GHz band, the 3.6 GHz band, the 4.9 and 5 GHz bands, the 60 GHz band, and the 6 GHz band. The AP MLD and Non-AP MLD maintain a connection of a second link via a second frequency channel in parallel with a connection of a first link via a first frequency channel. Also, instead of connections in different frequency bands, multiple connections via different frequency channels in the same frequency band may be established.

In addition, each of Link 1, Link 2, and Link 3 is assigned a number of spatial streams according to the spatial stream capability. If it is assumed that there are six antennas, each link uses two antennas. That is, the spatial stream capability of each link is "2". As will be described later, if Link 1, Link 2, and/or Link 3 are EMLMR links, the spatial stream capability during EMLMR operation of Link 1 is "4" or "6", and Link 2 and/or Link 3 is "0". As a result, it becomes possible to transmit and receive each data obtained by dividing one piece of data, or multiple different data, at the same timing and at the same frequency via Link 1 using multiple antennas so as not to cause spatial interference. The number of spatial streams is determined by the EHT Capabilities element or EHT Operation element included in the frame that declares that no-AP MLD supports EHT. Specifically, it is determined based on the value of the Supported EHT-MCS And NSS Set field or the Basic EHT-MCS And NSS Set field included in the EHT Capabilities element or the EHT Operation element.

Figure 5 (a) shows a Basic variant Multi-Link element in an Association Request frame. Figure 5 (b) shows the EMLMR Capabilities subfield included in the Common Info field of the Basic variant Multi-Link element. When the EMLMR Support field is "0", it indicates that EMLMR is not supported, and when it is "1", it indicates that EMLMR is supported. When Multi-Link communication is established, all links establish EMLMR links. Although the Basic variant Multi-Link element is described as being included in the Association Request frame when establishing a Multi-Link, it may also be included in a probe request frame, a probe response frame, an association response frame, a Beacon frame, etc.

The EMLMR link is established by transmitting, receiving, or exchanging a frame including an EMLMR Support subfield with a value of 1 on each link that constitutes the Multi-Link. In this case, the EMLMR link may be established on only some of the links that constitute the Multi-Link by performing this on only some of the links. Also, the EMLMR link may be established on multiple links including other links by transmitting, receiving, or exchanging a frame including an EMLMR Support subfield with a value of 1 on one link. In this case, the EMLMR link may be established on all of the links that constitute the Multi-Link, or on only some of the links. In order to specify the link on which the EMLMR link is to be established, the link on which the EMLMR link is to be established may be specified by including information for identifying the link on which the EMLMR link is to be established in a frame including an EMLMR Support subfield with a value of 1. Information that can be used to identify a link includes the link ID (Link Identifier), the BSSID (Basic service set identifier) corresponding to the link, and the TID (Traffic Identifier).

The EMLMR Supported MCS and NSS Set subfield indicates the maximum number of spatial streams when transmitting and receiving a PPDU during EMLMR operation. When a specific link operates in EMLMR, the number of spatial streams assigned to links other than the link operating in EMLMR is reduced, and the specific link becomes able to transmit and receive a PPDU with an increased number of spatial streams.

Although an instruction to establish an EMLMR link was given when the Multi-Link was established, the establishment of the EMLMR link may be specified in an Action frame sent after the Multi-Link is established. In that case, a frame called an EML (Enhanced Multi-Link) Operating Mode Notification frame may be prepared and an instruction to establish an EMLMR link may be given. For example, in the case of Non AP MLD, when a frame including an EMLMR Support subfield with a value of 1 is received and an EML Operating Mode Notification frame including an EMLMR Mode subfield with a value of 1 is transmitted, the link that transmitted and received those frames establishes an EMLMR link. Alternatively, some or all of the other links that make up the Multi-Link may establish an EMLMR link. In the case of AP MLD, when a frame including an EMLMR Support subfield with a value of 1 is transmitted and an EML Operating Mode Notification frame including an EMLMR Mode subfield with a value of 1 is received, the link that transmitted and received the frames establishes an EMLMR link. Alternatively, some or all of the other links constituting the multi-link may establish an EMLMR link. In that case, the link that establishes the EMLMR link may be specified by including information for identifying the link that establishes the EMLMR link in the EML Operating Mode Notification frame. As information for identifying the link, a link ID (Link identifier), a BSSID (Basic service set identifier) corresponding to the link, a TID (Traffic identifier), etc. can be used.

Although it has been explained that the non-AP MLD is the one that takes the initiative in establishing the EMLMR link, the AP MLD may also instruct the establishment of the EMLMR link. Note that the EML Operating Mode Notification frame is an Action frame that the non-AP MLD sends to operate in EMLMR mode, and is a frame that must be sent to operate in EMLMR mode if the EMLMR link is not established when Multi-Link communication is established, or if the EMLMR link is established but then deleted.

Next, the behavior of the AP MLD 102 when operating in EMLMR mode and exchanging frames after establishing an EMLMR link will be explained using Figures 6 and 7. The main action in the following is the action of the frame processing unit 302 or the EMLMR control unit 303, but the action as a communication device is the action of the AP MLD 102. Therefore, the main action in the following explanation will be the control unit 202 of the communication device. Note that this action may also be executed by the non-AP MLD 101.

First, the operation when a start frame is transmitted will be described with reference to FIG. 6. Since the frame exchange sequence begins from the timing when the start frame is transmitted, the present invention expresses that the EMLMR link operating in EMLMR continues the frame exchange sequence. In S0, the control unit 202 determines that there is data to be transmitted to the communication device that is the communication partner. The data to be transmitted may be data requested to be transmitted from any communication device to the communication device that is the communication partner, or data generated by the function unit 203.

In S1, the control unit 202 judges whether multiple EMLMR links are established. For example, if not only Link1 but also Link2 are established, the result is judged as Yes, and if only Link1 is established, the result is judged as No. A possible method for checking whether multiple EMLMR links are established is to judge whether each of the multiple links transmits and receives a frame including an EMLMR Support subfield with a value of 1. Alternatively, a possible method is to judge whether each of the multiple links transmits a frame including an EMLMR Support subfield with a value of 1 and receives an EML Operating Mode Notification frame including an EMLMR Mode subfield with a value of 1. Alternatively, it is possible to check whether multiple EMLMR links are established by making the above-mentioned judgment on any of the links constituting the multi-link, rather than on each of the multiple links.

In this case, frames including an EMLMR Support subfield with a value of 1 and information for identifying the link that establishes the EMLMR link may be exchanged, and if there are multiple links in which the information for identifying the link matches in the frames sent by both parties, it may be determined that multiple EMLMR links have been established. Here, in the case of non-AP MLD, instead of a frame including an EMLMR Support subfield and information for identifying the link that establishes the EMLMR link, an EML Operating Mode Notification frame including information for identifying the link that establishes the EMLMR link may be transmitted. In the case of AP MLD, instead of a frame including an EMLMR Support subfield and information for identifying the link that establishes the EMLMR link, an EML Operating Mode Notification frame including information for identifying the link that establishes the EMLMR link may be received.

If the result of S1 is No, the process proceeds to S8. In S8, the control unit 202 transmits a start frame via the EMLMR link. The start frame of the EMLMR link is the first frame transmitted in the frame exchange sequence defined in the IEEE 802.11 standard Annex G. For example, this is an RTS (Request To Send) frame or an MU-RTS Trigger frame. This start frame is an instruction to start frame exchange on the EMLMR link after the EMLMR link is established.

In S9, the control unit 202 determines whether a response frame has been received. A response frame for an EMLMR link is a frame that is transmitted in response to a start frame from a communication device that has received the start frame in a frame exchange sequence defined in the IEEE 802.11 standard Annex G. For example, there is a CTS (Clear To Send) frame.

In S10, the control unit 202 starts a frame exchange sequence with the maximum number of spatial streams presented in the EMLMR SUPPORTED MCS AND NSS SET subfield of the Common Info field of the Basic variant Multi-Link element sent by the non-AP MLD before the start of this flow. This causes one EMLMR link to operate as EMLMR. In S17, it is determined whether the frame exchange sequence has ended, and the process ends if the determination is Yes. The explanation up to this point is based on the assumption of normal EMLMR operation.

Next, the behavior when S1 is judged as Yes, that is, when multiple EMLMR links are established, will be described. In S2, it is judged whether the conditions for transmitting a start frame on multiple EMLMR links are met based on the prediction of communication performance. A possible method for predicting communication performance is to predict the congestion level of the channel corresponding to each link, that is, the number of non-AP MLDs connected to the AP MLD. Another possible method is to measure the received signal strength and/or signal-to-noise power ratio of each link and predict the communication performance of each link. For example, if the channel of one of Link1 and Link2 is significantly more congested than the other link or the received signal strength is low, both links cannot be operated well, so a transition is made to S8 to operate either Link1 or Link2 as EMLMR. However, if the channels on both Link 1 and Link 2 are equally congested or sufficiently clear, or the received signal strength is low or sufficiently high, then EMLMR operation is unlikely to improve communication performance, and the system transitions to S3 to transmit and receive data with the number of spatial streams according to the spatial stream capabilities of each link.

In S3, the control unit 202 transmits a start frame over multiple EMLMR links. However, the number of spatial streams specified at this time is the number of spatial streams according to the spatial stream capability of each link. In other words, the number is determined by the EHT Capabilities element or the EHT Operation element included in the frame that declares that the non-AP MLD supports EHT. Other links that do not establish an EMLMR link are not links on which a frame exchange sequence is performed.

In S4, the control unit 202 determines whether or not a response frame has been received in at least one EMLMR link. If a response frame has not been received within a specific period of time, it is determined that the frame exchange sequence will not be executed in the EMLMR link, and the process ends. On the other hand, if a response frame has been received, the process transitions to S5. In S5, the control unit 202 determines whether or not the response frame has been received in multiple EMLMR links. If the determination in S5 is No, the process transitions to S10. If the determination in S5 is Yes, the process transitions to S6. In S6, the control unit 202 executes frame exchange in the EMLMR link that received the response frame, with the number of spatial streams according to the spatial stream capability for each link. In S7, it is determined whether or not the frame exchange sequence has ended, and if the determination is Yes, the process ends.

Next, the operation when a start frame is received will be described with reference to FIG. 7. The steps numbered in FIG. 7 that overlap with those numbered in FIG. 6 have already been described in FIG. 6, and therefore will not be described again. In S11, this flow is executed after the control unit 202 receives a start frame via the EMLMR link. In S12, the control unit 202 detects whether or not another start frame has been received via an EMLMR link other than the selected EMLMR link during the period from when the control unit 202 starts receiving the start frame to when it starts sending a response frame. If the determination in S12 is No, the process proceeds to S18. In S18, the control unit 202 sends a response frame in response to the received start frame. The rest is as described in FIG. 6.

If the answer in S12 is Yes, the process proceeds to S13. In S13, it is determined whether the conditions for transmitting a response frame over multiple EMLMR links are met based on the predicted communication performance. As with S2, the prediction of communication performance can be based on the degree of congestion of the channel corresponding to each link, i.e., the number of non-AP MLDs connected to the AP MLD. Alternatively, the received signal strength and/or signal-to-noise power ratio of each link can be measured to predict the communication performance of each link.

If the result in S13 is No, the process proceeds to S16. In S16, the control unit 202 selects one EMLMR link from among the EMLMR links that have transmitted or received a start frame, based on a predetermined criterion. The EMLMR operation is performed on the selected EMLMR link. The method of determining based on a predetermined criterion is as follows. There are three main methods of determining: (1) selection based on information for identifying the link (such as a link ID), (2) selection based on the order in which the EMLMR links were established, and (3) selection based on at least one of the communication performance (the degree of congestion of the channel corresponding to the link (the number of STAs connected to the AP), etc.).

When making a selection based on information for identifying a link (such as a link ID), the Link ID subfield of the Multi-Link element shown in FIG. 5(a) is referenced and determined. A Link ID is an ID that is assigned to each link when a Multi-Link is established. When IDs are assigned in the order in which the link IDs are established, the link with the lowest link ID number among multiple EMLMR links is selected as the single EMLMR link. Alternatively, the link with the highest link ID number may be selected as the single EMLMR link.

When the selection is based on the order in which the EMLMR link was established, more specifically, the selection is based on at least one of the following orders:
- The order in which a frame containing an EMLMR Support subfield with a value of 1 was transmitted. - The order in which a frame containing an EMLMR Support subfield with a value of 1 was received. - The order in which a frame containing an EMLMR Support subfield with a value of 1 was transmitted and received. - The order in which an EML Operating Mode Notification frame containing an EMLMR Mode subfield with a value of 1 was transmitted (in the case of non-AP MLD).
The order in which an EML Operating Mode Notification frame containing an EMLMR Mode subfield with a value of 1 was received (in the case of AP MLD)
The sequence of receiving a frame including an EMLMR Support subfield with a value of 1 and transmitting an EML Operating Mode Notification frame including an EMLMR Mode subfield with a value of 1 (in the case of non-AP MLD)
The sequence of transmitting a frame including an EMLMR Support subfield with a value of 1 and receiving an EML Operating Mode Notification frame including an EMLMR Mode subfield with a value of 1 (in the case of AP MLD)
If the frame includes information for identifying a link for establishing an EMLMR link, the EMLMR link identified by the information may be selected based on the order in which the information is transmitted or received.Also, the EMLMR link identified by the information may be selected based on the order in which the transmitted information for identifying a link for establishing an EMLMR link matches the received information.

According to this order, each EMLMR link is assigned a number starting from 1. In other words, the EMLMR link with a link number of 1 is the EMLMR link selected based on a specified criterion. For example, when selecting an EMLMR link in the order in which a frame containing an EMLMR Support subfield with a value of 1 is received, if it is assumed that the AP MLD receives a frame containing an EMLMR Support subfield with a value of 1 on Link 1 and then on Link 2, Link 1 is assigned a number of 1, so Link 1 will be selected. As will be explained in other embodiments, when multiple EMLMR links are selected, they will be selected from the lowest number up to the specified value at which an EMLMR link can be established.

When selecting based on communication performance, the degree of congestion of the channel corresponding to each EMLMR link is measured, and the EMLMR link with the least degree of congestion is selected as the EMLMR link. Measurement methods include judging based on the number of STAs connected to the AP, as well as a method of calculating the channel occupancy rate for each link of the Multi-Link.

If the answer in S13 is Yes, the process proceeds to S14. In S14, the control unit 202 transmits a response frame on the multiple EMLMR links that received the start frame, and then proceeds to S15. In S15, the control unit 202 executes frame exchange on the EMLMR links that transmitted the response frame with the number of spatial streams according to the spatial stream capability for each link. In S7, the control unit 202 determines whether the frame exchange sequence has ended, and ends the process if the answer is Yes.

In the above, in the first embodiment, a method for appropriately controlling operation in EMLMR mode when multiple start frames are exchanged with the other communication device before the start of EMLMR operation has been described. A specific method for appropriately controlling is a control method for performing frame exchange in one EMLMR link or multiple EMLMR links, depending on whether or not the frame exchange sequence is to be exchanged in multiple EMLMR links. The frame exchange sequence continues in the selected EMLMR link, and if there is an EMLMR link that has not been selected, the frame exchange sequence in that EMLMR link is temporarily stopped.

[Other Examples]
In the first embodiment, in S5 of Fig. 6, it is determined whether a response frame was received from a plurality of EMLMR links, and depending on the result, the process proceeds to either step S6 or step S10. However, S5 may be skipped. In this case, it is determined in S4 whether a response frame was received from at least one EMLMR link, and if the result is Yes, the process proceeds to step S6.

In the first embodiment, a method of selecting one EMLMR link is disclosed, but multiple EMLMR links may be operated in EMLMR mode. For example, assume that four links, Link 1 to Link 4, are formed between a communication device and a counterpart communication device. When Link 1 and Link 2 are operated as EMLMR links, a method may be used in which the spatial stream of Link 3 is assigned to Link 1 and the spatial stream of Link 4 is assigned to Link 2. As a result, the number of spatial streams of Link 1 and Link 2 increases, and the number of spatial streams of Link 3 and Link 4 decreases. Since such a case is also conceivable, if multiple EMLMR links that increase the number of spatial streams can exist, multiple EMLMR links may be selected according to a predetermined criterion in S8 of FIG. 6 and S16 of FIG. 7. Then, in S9 of FIG. 6, it is determined whether a response frame has been received on each selected EMLMR link, and in S10, the EMLMR operation is executed on each EMLMR link that has received the response frame. Also, in S18 of FIG. 7, a response frame is transmitted on each selected EMLMR link, and in S10, the EMLMR operation is executed on each EMLMR link that has transmitted the response frame.

In the first embodiment, when selecting based on the order in which the EMLMR links were established, the selection was made from the lowest order, but the selection may be made from the highest order, or the middle order may be selected first.

In the first embodiment, the Basic variant Multi-Link element is described, but the Basic Multi-Link element may be used, and the EMLMR Supported MCS And NSS Set subfield may be the EMLMR Rx NSS subfield and the EMLMR Tx NSS subfield. In this case, the EMLMR Rx NSS subfield indicates the maximum number of spatial streams in reception, and the EMLMR Tx NSS subfield indicates the maximum number of spatial streams in transmission.

A recording medium on which the program code of the software that realizes the above-mentioned functions is recorded may be supplied to the system or device, and the computer (CPU, MPU) of the system or device may read and execute the program code stored in the recording medium. In this case, the program code read from the storage medium itself realizes the functions of the above-mentioned embodiments, and the storage medium on which the program code is stored constitutes the above-mentioned device.

Storage media for supplying program code may include, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memory card, a ROM, a DVD, etc.

In addition, not only can the above-mentioned functions be realized by the computer executing the program code it has read, but the OS running on the computer can also perform some or all of the actual processing based on the instructions of the program code to realize the above-mentioned functions. OS is an abbreviation for Operating System.

The program code read from the storage medium is then written to memory on a function expansion board inserted into the computer or on a function expansion unit connected to the computer. Then, based on the instructions of the program code, a CPU on the function expansion board or function expansion unit may perform some or all of the actual processing to realize the above-mentioned functions.

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

201 Storage unit 202 Control unit 203 Functional unit 204 Input unit 205 Output unit 206 Communication unit

Claims (9)

A communication device that operates as a Multi-Link Device conforming to the IEEE 802.11 series standard,
and a control means for controlling, when a frame exchange sequence is executed in two links, a first EMLMR (Enhanced multi-link multi-radio) link and a second EMLMR (Enhanced multi-link multi-radio) link, to execute the frame exchange sequence with the respective numbers of spatial streams of the first EMLMR link and the second EMLMR link. The communication device according to claim 1, characterized in that the control means determines the first EMLMR link or the second EMLMR link as a link for EMLMR operation, and controls the other communication device operating as non-AP MLD to continue frame exchange after the initial frame exchange in the frame exchange sequence with the number of spatial streams up to the value defined in the EMLMR SUPPORTED MCS AND NSS SET subfield, instead of the respective number of spatial streams, in the link determined as the link for EMLMR operation. The communication device according to claim 2, characterized in that the control means continues the frame exchange sequence with one of the control described in claim 1 and the control described in claim 2 based on a prediction of communication performance. The communication device according to any one of claims 1 to 3, characterized in that the control means deletes the EMLMR link that performed the frame exchange sequence when the frame exchange sequence ends. A method for controlling a communication device that operates as a Multi-Link Device conforming to the IEEE 802.11 series standard, comprising:
A control method, comprising: when a frame exchange sequence is executed on two links, a first EMLMR (Enhanced multi-link multi-radio) link and a second EMLMR (Enhanced multi-link multi-radio) link, a control step of controlling so that a frame exchange sequence is executed with the respective numbers of spatial streams of the first EMLMR link and the second EMLMR link. The control method according to claim 5, characterized in that in the control step, the first EMLMR link or the second EMLMR link is determined as a link for EMLMR operation, and in the link determined as a link for EMLMR operation, instead of the respective number of spatial streams, the control method performs frame exchange after the initial frame exchange in the frame exchange sequence with the number of spatial streams that is the maximum value defined by the own device or another communication device operating as non-AP MLD in the EMLMR SUPPORTED MCS AND NSS SET subfield. The control method according to claim 6, characterized in that in the control step, the frame exchange sequence is continued with one of the control described in claim 1 and the control described in claim 2 based on a prediction of communication performance. The control method according to any one of claims 5 to 7, characterized in that in the control step, the EMLMR link that performed the frame exchange sequence is deleted when the frame exchange sequence ends. A program for causing a computer to function as each of the means of the communication device according to any one of claims 1 to 4.

Images