WO2023033184A1 - Communication device and communication method - Google Patents

Abstract

The present invention provides a wireless communication device that transmits a frame using two or more links. The communication device is provided with a multi-link control unit for selecting a retransmission destination link candidate in accordance with the load status of each of the links in a MAC layer. The control unit generates and sends control information about the retransmission destination link candidate and a retransmission method to a PHY layer. If an affirmative response with respect to the frame is not received, the control unit does not permit retransmission other than by the retransmission destination link candidate designated by the control information. In accordance with the IEEE802.11 standard, the present invention enables packet combining in a multi-link device, and contributes to reduction in latency and an improvement of reception SNR.

Description

Communication device and communication method

The present invention relates to a communication device and communication method.
This application claims priority to Japanese Patent Application No. 2021-144568 filed in Japan on September 6, 2021, the content of which is incorporated herein.

IEEE (The Institute of Electrical and Electronics Engineers Inc.) is working to update the specifications of IEEE802.11, a wireless LAN standard, in order to increase the speed of wireless LAN (Local Area Network) communication and improve frequency utilization efficiency. I'm in. In recent years, with the rapid spread of wireless LAN devices, it is expected that the use of wireless LAN devices will expand in real-time applications such as telemedicine and VR/AR. Standardization of IEEE802.11be, which realizes capacity enhancement, is underway.

　In the IEEE802.11 standard, error control is introduced as a technique for speeding up throughput. Error control is roughly divided into forward error correction (FEC) and automatic repeat request (ARQ). Forward error correction is a method of correcting errors that occur on a transmission line using an error correction code on the receiving side, and eliminates the need to request retransmission of erroneous packets to the transmitting side. The error correction capability is improved by increasing the ratio of redundant bits in codewords, but there is a trade-off with the increase in decoding processing and the decrease in transmission efficiency. ARQ, on the other hand, is a scheme for requesting the transmitting side to retransmit packets that were not properly decoded at the receiving side. Packet errors during decoding are detected by Medium Access Control (MAC) on the receiving side and discarded without being stored in a buffer. An acknowledgment (ACK) is conveyed to the sender if the packet is successfully decoded and a negative acknowledgment (NACK) if a packet error is detected. Packet retransmission processing is performed by ARQ when a NACK is signaled to the sender or no ACK is signaled to the sender within a certain period of time. In addition to error control in the IEEE802.11 standard described above, hybrid ARQ (HARQ), which combines forward error correction code and ARQ, is being considered in standardization activities of IEEE802.11be. In HARQ, the same packet is sent during retransmission, and the packets are combined on the receiving side to improve the signal-to-noise power ratio (SNR) of the received signal. Incremental redundancy (IR) combining, which increases the error correction decoding capability of the receiving side by newly transmitting a signal), is being studied.

　In IEEE802.11n and later standards, aggregation is introduced for each radio frame and ACK as a technique for speeding up throughput by reducing MAC layer overhead. Radio frame aggregation is roughly classified into A-MSDU (Aggregated MAC Service Data Unit) and A-MPDU (Aggregated MAC Protocol Data Unit). Aggregation of ACKs, for example, block ACK (Block Acknowledgment: BA) that can implement reception completion notification for multiple MPDUs, multi STA block ACK (Multi STA Block ACK: BA) that can implement reception completion notification for multiple users M-BA). Aggregation of radio frames allows many packets to be sent at once, improving transmission efficiency, but also increasing the possibility of transmission errors. For this reason, in IEEE 802.11ax and later standards, efficient error control for each MPDU is expected in addition to improvement in transmission efficiency by aggregation of radio frames as a main element technology for speeding up throughput. Therefore, in IEEE 802.11be standardization activities, improvement of transmission quality is being studied by obtaining time diversity by HARQ.

On the other hand, from the viewpoint of the frequency band used, the ETSI (European Telecommunications Standards Institute) in Europe and the FCC (Federal Communications Commission) in the United States have made it possible to use the 6 GHz band (5.935 to 7.125 GHz) as an unlicensed band. Similar considerations are underway in other countries around the world. This means that it is expected that the wireless LAN will be able to use the 6 GHz band in addition to the 2.4 GHz band and 5 GHz band. In order to cope with the expansion of target frequencies, the Wi-Fi Alliance has formulated Wi-Fi6E (registered trademark), which is an extended version of Wi-Fi6, and plans to use the 6 GHz band.

While the 2.4 GHz band has a relatively wide coverage (communication range), the usable bandwidth is relatively narrow and the influence of interference between communication devices is large. On the other hand, the 5 GHz band and the 6 GHz band can have a wide communication bandwidth, but cannot have a wide coverage. Therefore, in order to realize various services and applications on a wireless LAN, the frequency band (2.4 GHz band, 5 GHz band, 6 GHz band, etc.) to be used according to the use case. It is desirable to appropriately switch sub-channels included in However, in the conventional wireless LAN communication device, in order to switch the frequency band used for communication, it was necessary to once disconnect the current frequency band and connect to another frequency band.

From the above, in the IEEE 802.11be standardization, there is a discussion on multi-link operation (MLO), which enables a communication device to maintain multiple connections (links) using multiple frequency bands. (See Non-Patent Document 2). To give an example of MLO, in the IEEE802.11be standardization, combinations of various frequency bands, channels, and sub-channels such as 2.4 GHz band connection, 5 GHz band connection, 6 GHz band connection, and simultaneous connection of all bands are possible. It becomes possible. According to MLO, a communication device can maintain a plurality of connections with different radio resources to be used and settings related to communication. That is, by using MLO, the communication device can simultaneously maintain connections of different frequency bands, so that it is possible to change the frequency band for frame transmission/reception without performing reconnection operation.

In addition, IEEE802.11be standardization discusses a wireless communication method using a multi-link device (MLD) having two or more links. By transmitting frames using this multilink, it is expected to realize large-capacity communication that increases the throughput not only between a single terminal and a base station but also for the entire system. Also, each link constituting a multilink may not be bundled and used at the same time, but may be used independently for frame transmission/reception. For example, by avoiding congested radio channels and selecting an empty link as appropriate for frame transmission, it is possible to reduce the delay and latency that occur during transmission, thereby realizing low-latency communication. be. The characteristics of high-capacity communication and low-delay communication by these multilinks are that the quality of each link (less radio interference between wireless communication devices, high received signal strength, low frame reception error rate, etc.) is enhanced. The point is that the performance of the multilink is improved as much as possible.

In MLD, the entity that manages multi-links (Multi-link Management Entity: MLME) monitors the load of all links (load) and implements load balance, but the existing mechanism does not allow the effect of HARQ in MLD. may not be obtained. In the IEEE 802.11 standard, after sending the last buffered PPDU frame on the link, a field is updated to indicate whether there are any buffered frames after that frame. That is, when an erroneous PPDU frame is retransmitted on another link on a link that constitutes MLD, packet combining by HARQ may not be performed if the retransmission destination link is in Doze state (Non-Patent Document 1).

Therefore, in Non-Patent Document 1, a frame having the same Traffic ID (TID) as the frame so that the link does not shift to the Doze state after transmitting the last buffered PPDU frame of the link configuring the MLD. It proposes a mechanism that does not update the field indicating the presence or absence of buffered frames included in the frame until the transmission is completed. On the other hand, Non-Patent Document 2 discusses sharing acknowledgments between all links by MLME. However, in the IEEE 802.11 standard, Non-Patent Document 1 and Non-Patent Document 2 also propose an efficient packet combining method in MLD, such as a method of securing a retransmission destination link as an Awake State in advance for frame retransmission. Not yet.

The present invention has been made in view of such circumstances, and its object is to realize efficient packet combining in MLD in the IEEE802.11 standard, contributing to low-delay communication and improvement of received SNR. Disclosed is a communication device and a communication method.

The communication device and communication method according to the present invention for solving the above problems are as follows.

(1) A communication device that transmits frames using two or more links, wherein the communication device selects retransmission destination link candidates according to the load status of each link in the MAC layer. The control unit generates the retransmission destination link candidate and the retransmission method as control information and transmits the retransmission method to the PHY layer, and the communication device includes a transmission unit that generates a frame in the PHY layer, When no acknowledgment for the frame is received, retransmission on a link other than the retransmission destination link candidate specified by the control information is not permitted, and the communication device transmits the frame on the retransmission destination link candidate according to the control information. and a signal demodulator for packet-combining and decoding the frame.

(2) The communication apparatus according to (1) above, wherein the retransmission destination link candidate restricts retransmission by ARQ and does not restrict retransmission by HARQ as the retransmission method.

(3) The communication device according to (1) above, wherein the control unit does not include retransmission destination link candidates in the control information and sets a retransmission method when each of the links has the same load status.

(4) if the control unit does not receive an acknowledgment for the frame on each of the links or does not receive it within a predetermined time, it updates the retransmission destination link candidate; The communication device according to (1) above.

(5) When the control unit does not receive an acknowledgment for the frame in succession for a plurality of times in one link in each of the links, or when the frame is not received within a predetermined time, the control unit The communication device according to (1) above, wherein a link with the next lowest load status to the link is included in the candidates for the retransmission destination link.

(6) If a frame containing the same identifier as the last frame buffered in each of the links on the transmitting side has been subsequently buffered in a link other than each of the links, the control unit The communication apparatus according to (1) above, wherein control data for setting a NAV for the another link is added to the control information for a predetermined period of time until an acknowledgment for a frame containing the same identifier is received.

(7) The communication device according to (1) above, wherein the communication device includes a control unit that sets an access category for retransmission to each of the links and transmits frames of the access category for retransmission with top priority. .

(8) The communication device according to (1) above, wherein the control unit in the communication device retransmits the frame with the highest priority by performing buffer reordering in each of the links.

(9) The above-described (1), wherein when another frame is being transmitted on the retransmission destination link, the control unit retransmits the frame on another link specified by the retransmission destination link candidate. Communication device.

(10) A signal demodulator that receives a frame using two or more links, assigns retransmission of the frame to the link specified by the control information, and demodulates and decodes the frame; The communication device according to (1) above, wherein packet synthesis of the frame is performed when is set.

(11) A communication method for transmitting frames using two or more links, wherein the communication method comprises a step of selecting retransmission destination link candidates according to the load status of each of the links in the MAC layer. and generating the retransmission destination link candidate and the retransmission method as control information and transmitting it to the PHY layer, the communication method comprising the step of generating a frame in the PHY layer, and receiving an acknowledgment for the frame if not, retransmission is not permitted on any other than the retransmission destination link candidate specified by the control information, and the communication method comprises the step of: receiving the frame on the retransmission destination link candidate according to the control information; and packetizing and decoding frames.

The present invention realizes efficient packet combining in MLD according to the IEEE802.11 standard, and improves low-delay communication by improving reception SNR, speeding up user throughput, and features of multilink communication. It contributes to large-capacity communication and low-delay communication.

1 is a schematic diagram showing an example of division of radio resources according to one aspect of the present invention; FIG. FIG. 4 is a diagram showing an example of a frame structure according to one aspect of the present invention; FIG. 4 is a diagram showing an example of a frame structure according to one aspect of the present invention; FIG. 3 is a diagram illustrating an example of communication according to one aspect of the present invention; 1 is a diagram showing one configuration example of a communication system according to one aspect of the present invention; FIG. FIG. 3 illustrates frame transmission and reception according to one aspect of the present invention; 1 is a block diagram showing one configuration example of a wireless communication device according to one aspect of the present invention; FIG. 1 is a block diagram showing one configuration example of a wireless communication device according to one aspect of the present invention; FIG. 1 is a block diagram showing one configuration example of a wireless communication device according to one aspect of the present invention; FIG. 1 is a schematic diagram illustrating an example of an encoding scheme according to one aspect of the present invention; FIG. 1 is a schematic diagram showing an example of a modulation and coding scheme according to one aspect of the present invention; FIG. FIG. 4 is a schematic diagram illustrating an example of block lengths for LDPC encoding processing according to an aspect of the present invention; 1 is a schematic diagram showing an example of a frame retransmission method according to an aspect of the present invention; FIG. 1 is a schematic diagram showing an example of a frame retransmission method according to an aspect of the present invention; FIG.

A communication system in this embodiment is called a base station device or an access point device (Access point: AP), and includes a plurality of terminal devices or station devices (Station: STA). A communication system or network composed of access point devices and station devices is called a basic service set (BSS: Basic service set, management range, cell). Also, the station device according to this embodiment can have the function of an access point device. Similarly, the access point device according to this embodiment can have the functions of the station device. Therefore, hereinafter, when simply referring to a communication device, the communication device can indicate both a station device and an access point device.

It is assumed that the base station apparatus and the terminal apparatus within the BSS perform communication based on CSMA/CA (Carrier sense multiple access with collision avoidance). This embodiment targets the infrastructure mode in which a base station apparatus communicates with a plurality of terminal apparatuses, but the method of this embodiment can also be implemented in an ad-hoc mode in which terminal apparatuses directly communicate with each other. In ad-hoc mode, the terminal device forms a BSS on behalf of the base station device. A BSS in ad-hoc mode is also called an IBSS (Independent Basic Service Set). In the following, a terminal device forming an IBSS in ad-hoc mode can also be regarded as a base station device. The method of the present embodiment can also be implemented in WiFi Direct (registered trademark) in which terminal devices directly communicate with each other. WiFi
In Direct, a terminal device forms a group instead of a base station device. In the following description, a terminal device of a group owner that forms a group in WiFi Direct can also be regarded as a base station device.

In the IEEE802.11 system, each device can transmit transmission frames of multiple frame types with a common frame format. A transmission frame is defined in a physical (PHY) layer, a medium access control (MAC) layer, and a logical link control (LLC) layer, respectively. The physical layer is also called the PHY layer, and the MAC layer is also called the MAC layer.

A PHY layer transmission frame is called a physical protocol data unit (PPDU: PHY protocol data unit, physical layer frame). A PPDU consists of a physical layer header (PHY header) that includes header information for performing signal processing in the physical layer, and a physical service data unit (PSDU: PHY service data unit) that is a data unit processed in the physical layer. MAC layer frame) and the like. PSDU can be composed of aggregated MPDU (A-MPDU: Aggregated MPDU) in which multiple MAC protocol data units (MPDU: MAC protocol data units) that are retransmission units in the wireless section are aggregated.

The PHY header includes a short training field (STF) used for signal detection and synchronization, a long training field (LTF) used to acquire channel information for data demodulation, etc. and a control signal such as a signal (Signal: SIG) containing control information for data demodulation. In addition, STF can be legacy STF (L-STF: Legacy-STF), high-throughput STF (HT-STF: High throughput-STF), or ultra-high-throughput STF (VHT-STF: Very high throughput-STF), high efficiency STF (HE-STF), ultra-high throughput STF (EHT-STF: Extremely High Throughput-STF), etc. LTF and SIG are also L- It is classified into LTF, HT-LTF, VHT-LTF, HE-LTF, L-SIG, HT-SIG, VHT-SIG, HE-SIG and EHT-SIG. VHT-SIG is further classified into VHT-SIG-A1, VHT-SIG-A2 and VHT-SIG-B. Similarly, HE-SIG is classified into HE-SIG-A1 to 4 and HE-SIG-B. Also, in anticipation of technical updates in the same standard, a Universal SIGNAL (U-SIG) field containing additional control information can be included.

Furthermore, the PHY header can include information identifying the BSS that is the transmission source of the transmission frame (hereinafter also referred to as BSS identification information). The information identifying the BSS can be, for example, the SSID (Service Set Identifier) of the BSS or the MAC address of the base station device of the BSS. Also, the information that identifies the BSS can be a value unique to the BSS (for example, BSS Color, etc.) other than the SSID and MAC address.

The PPDU is modulated according to the corresponding standard. For example, according to the IEEE 802.11n standard, it is modulated into an Orthogonal Frequency Division Multiplexing (OFDM) signal.

MPDU is a MAC layer header that contains header information etc. for signal processing in the MAC layer, and a MAC service data unit (MSDU: MAC service data unit) that is a data unit processed in the MAC layer or It consists of a frame body and a frame check sequence (FCS) that checks if there are any errors in the frame. Also, multiple MSDUs can be aggregated as an aggregated MSDU (A-MSDU: Aggregated MSDU).

The frame type of the transmission frame of the MAC layer is roughly classified into three types: a management frame that manages the connection state between devices, a control frame that manages the communication state between devices, and a data frame that contains actual transmission data. Each is further classified into a plurality of types of subframe types. The control frame includes a reception completion notification (ACK: Acknowledge) frame, a transmission request (RTS: Request to send) frame, a reception preparation completion (CTS: Clear to send) frame, and the like. Management frames include Beacon frames, Probe request frames, Probe response frames, Authentication frames, Association request frames, Association response frames, etc. included. The data frame includes a data (Data) frame, a polling (CF-poll) frame, and the like. Each device can recognize the frame type and subframe type of the received frame by reading the contents of the frame control field included in the MAC header.

　The ACK may include a Block ACK. Block ACK can implement reception completion notification for multiple MPDUs. Also, the ACK may include a Multi STA Block ACK containing reception completion notifications for a plurality of communication devices.

A beacon frame contains a field describing the beacon interval and the SSID. The base station apparatus can periodically broadcast a beacon frame within the BSS, and the terminal apparatus can recognize base station apparatuses around the terminal apparatus by receiving the beacon frame. It is called passive scanning that a terminal device recognizes a base station device based on a beacon frame broadcast from the base station device. On the other hand, searching for a base station apparatus by broadcasting a probe request frame in the BSS by a terminal apparatus is called active scanning. The base station apparatus can transmit a probe response frame as a response to the probe request frame, and the description content of the probe response frame is equivalent to that of the beacon frame.

After the terminal device recognizes the base station device, it performs connection processing to the base station device. Connection processing is classified into an authentication procedure and an association procedure. A terminal device transmits an authentication frame (authentication request) to a base station device that desires connection. Upon receiving the authentication frame, the base station apparatus transmits to the terminal apparatus an authentication frame (authentication response) including a status code indicating whether or not the terminal apparatus can be authenticated. By reading the status code described in the authentication frame, the terminal device can determine whether or not the terminal device is permitted to be authenticated by the base station device. Note that the base station apparatus and the terminal apparatus can exchange authentication frames multiple times.

Following the authentication procedure, the terminal device transmits a connection request frame to perform the connection procedure to the base station device. Upon receiving the connection request frame, the base station apparatus determines whether or not to permit the connection of the terminal apparatus, and transmits a connection response frame to notify that effect. The connection response frame contains an association identifier (AID) for identifying the terminal device, in addition to a status code indicating whether connection processing is possible. The base station apparatus can manage a plurality of terminal apparatuses by setting different AIDs for the terminal apparatuses that have issued connection permission.

After the connection process is performed, the base station device and the terminal device perform actual data transmission. In the IEEE802.11 system, a distributed control mechanism (DCF: Distributed Coordination Function), a centralized control mechanism (PCF: Point Coordination Function), and enhanced mechanisms of these (enhanced distributed channel access (EDCA), A hybrid control mechanism (HCF: Hybrid coordination function) is defined. In the following, a case where the base station apparatus transmits a signal to the terminal apparatus using DCF will be described as an example, but the same applies to the case where the terminal apparatus transmits a signal to the base station apparatus using DCF.

In DCF, base station equipment and terminal equipment perform carrier sense (CS) to check the usage status of wireless channels around their own equipment prior to communication. For example, when a base station apparatus, which is a transmitting station, receives a signal higher than a predetermined clear channel evaluation level (CCA level: Clear channel assessment level) on the radio channel, the transmission of the transmission frame on the radio channel is performed. put off. Hereinafter, a state in which a signal of the CCA level or higher is detected in the radio channel is called a busy state, and a state in which a signal of the CCA level or higher is not detected is called an idle state. Thus, CS performed based on the power (reception power level) of the signal actually received by each device is called physical carrier sense (physical CS). The CCA level is also called a carrier sense level (CS level) or a CCA threshold (CCAT). When the base station apparatus and the terminal apparatus detect a signal of the CCA level or higher, they start the operation of demodulating at least the PHY layer signal.

The base station device performs carrier sense for the frame interval (IFS: Inter frame space) according to the type of transmission frame to be transmitted, and determines whether the radio channel is busy or idle. The period during which the base station apparatus performs carrier sensing differs depending on the frame type and subframe type of the transmission frame to be transmitted by the base station apparatus. In the IEEE 802.11 system, multiple IFSs with different durations are defined. There are the polling frame interval (PCF IFS: PIFS) used, the distributed control frame interval (DCF IFS: DIFS) used for the lowest priority transmission frame, and the like. When the base station apparatus transmits data frames in DCF, the base station apparatus uses DIFS.

After waiting for DIFS, the base station device further waits for a random backoff time to prevent frame collision. In the IEEE 802.11 system, a random backoff time called contention window (CW) is used. CSMA/CA assumes that a transmission frame transmitted by a certain transmitting station is received by a receiving station without interference from other transmitting stations. Therefore, if the transmitting stations transmit transmission frames at the same timing, the frames collide with each other and the receiving stations cannot receive the frames correctly. Therefore, each transmitting station waits for a randomly set time before starting transmission, thereby avoiding frame collision. When the base station apparatus determines that the radio channel is in an idle state by carrier sense, it starts counting down the CW and acquires the transmission right only when the CW becomes 0, and can transmit the transmission frame to the terminal apparatus. If the base station apparatus determines that the radio channel is busy by carrier sense during the CW countdown, the CW countdown is stopped. Then, when the radio channel becomes idle, following the previous IFS, the base station apparatus resumes counting down remaining CWs.

Next, the details of frame reception will be explained. A terminal device, which is a receiving station, receives the transmission frame, reads the PHY header of the transmission frame, and demodulates the received transmission frame. By reading the MAC header of the demodulated signal, the terminal device can recognize whether or not the transmission frame is addressed to itself. In addition, the terminal device may determine the destination of the transmission frame based on the information described in the PHY header (for example, the group identification number (GID: Group identifier, Group ID) described in VHT-SIG-A). It is possible.

When the terminal device determines that the received transmission frame is addressed to itself and demodulates the transmission frame without error, the terminal device transmits an ACK frame indicating that the frame has been correctly received to the base station device, which is the transmitting station. Must. The ACK frame is one of the highest priority transmission frames that is transmitted only waiting for the SIFS period (no random backoff time). The base station apparatus terminates a series of communications upon receiving the ACK frame transmitted from the terminal apparatus. In addition, when the terminal device cannot receive the frame correctly, the terminal device does not transmit ACK. Therefore, if the base station apparatus does not receive an ACK frame from the receiving station for a certain period of time (SIFS+ACK frame length) after frame transmission, it assumes that the communication has failed and terminates the communication. As described above, the end of one communication (also called a burst) in the IEEE 802.11 system is limited to special cases such as the transmission of a notification signal such as a beacon frame, or the use of fragmentation to divide transmission data. Except for this, the determination is always based on whether or not an ACK frame has been received.

When the terminal device determines that the received transmission frame is not addressed to itself, the network allocation vector (NAV: Network allocation vector). The terminal device does not attempt communication during the period set in NAV. In other words, the terminal device performs the same operation as when the radio channel is determined to be busy by the physical CS for the period set in the NAV. Therefore, communication control by the NAV is also called virtual carrier sense (virtual CS). In addition to being set based on the information in the PHY header, NAV is a request to send (RTS) frame introduced to solve the hidden terminal problem, and a clear reception (CTS) frame. to send) frame.

In contrast to DCF, in which each device performs carrier sense and acquires the transmission right autonomously, in PCF, a control station called a point coordinator (PC) controls the transmission right of each device within the BSS. In general, the base station apparatus becomes a PC and acquires the transmission right of the terminal apparatus within the BSS.

The communication period by PCF includes a contention-free period (CFP: Contention free period) and a contention period (CP: Contention period). During the CP, communication is performed based on the DCF described above, and it is during the CFP that the PC controls the transmission right. A base station apparatus, which is a PC, notifies a beacon frame in which a CFP duration (CFP Max duration) and the like are described within the BSS prior to PCF communication. It should be noted that PIFS is used to transmit the beacon frame notified at the start of PCF transmission, and is transmitted without waiting for the CW. A terminal device that receives the beacon frame sets the period of the CFP described in the beacon frame to NAV. Thereafter, until the NAV elapses or until a signal announcing the end of the CFP within the BSS (for example, a data frame containing CF-end) is received, the terminal equipment signals acquisition of the transmission right transmitted from the PC. The right to transmit can only be obtained when a signal (eg a data frame containing a CF-poll) is received. Note that during the CFP period, packet collisions do not occur within the same BSS, so each terminal device does not take the random backoff time used in DCF.

The wireless medium can be divided into multiple resource units (RU). FIG. 1 is a schematic diagram showing an example of a division state of a wireless medium. For example, in resource division example 1, the wireless communication device can divide frequency resources (subcarriers), which are wireless media, into nine RUs. Similarly, in resource division example 2, the wireless communication device can divide subcarriers, which are wireless media, into five RUs. Of course, the example of resource division shown in FIG. 1 is only an example, and for example, a plurality of RUs can be configured with different numbers of subcarriers. Also, the wireless medium divided as RUs can include spatial resources as well as frequency resources. A wireless communication device (for example, an AP) can simultaneously transmit frames to a plurality of terminal devices (for example, a plurality of STAs) by arranging frames addressed to different terminal devices in each RU. The AP can write information (Resource allocation information) indicating the division state of the wireless medium in the PHY header of the frame transmitted by the AP as common control information. Furthermore, the AP can describe information (resource unit assignment information) indicating the RU in which the frame addressed to each STA is allocated as unique control information in the PHY header of the frame transmitted by the AP itself.

Also, a plurality of terminal devices (for example, a plurality of STAs) can transmit frames simultaneously by arranging frames in assigned RUs and transmitting the frames. A plurality of STAs can transmit a frame after waiting for a predetermined period after receiving a frame (Trigger frame: TF) containing trigger information transmitted from the AP. Each STA can grasp the RU assigned to itself based on the information described in the TF. Also, each STA can acquire RUs through random access based on the TF.

The AP can allocate multiple RUs to one STA at the same time. The plurality of RUs can be composed of continuous subcarriers or discontinuous subcarriers. The AP can transmit one frame using multiple RUs assigned to one STA, or can transmit multiple frames by assigning them to different RUs. At least one of the plurality of frames can be a frame containing common control information for a plurality of terminal devices transmitting resource allocation information.

One STA can be assigned multiple RUs by the AP. A STA can transmit one frame using multiple assigned RUs. Also, the STA can use the assigned multiple RUs to assign multiple frames to different RUs and transmit them. The plurality of frames can be frames of different frame types.

An AP can allocate multiple AIDs to one STA. The AP can assign RUs to multiple AIDs assigned to one STA. The AP can transmit different frames to multiple AIDs assigned to one STA using the assigned RUs. The different frames can be frames of different frame types.

A single STA can be assigned multiple AIDs by the AP. One STA can be assigned RUs for each of the assigned AIDs. One STA recognizes all RUs assigned to multiple AIDs assigned to itself as RUs assigned to itself, and uses the assigned multiple RUs to transmit one frame. can do. Also, one STA can transmit multiple frames using the multiple assigned RUs. At this time, information indicating the AID associated with each assigned RU can be described in the plurality of frames and transmitted. The AP can transmit different frames to multiple AIDs assigned to one STA using the assigned RUs. The different frames can be frames of different frame types.

Below, base station devices and terminal devices are also collectively referred to as wireless communication devices or communication devices. Information exchanged when one wireless communication device communicates with another wireless communication device is also called data. That is, a wireless communication device includes a base station device and a terminal device.

A wireless communication device has either or both of a function to transmit and a function to receive PPDU. FIG. 2 is a diagram showing an example of the configuration of a PPDU transmitted by a wireless communication device. A PPDU that supports the IEEE802.11a/b/g standard has a configuration that includes L-STF, L-LTF, L-SIG and Data frames (MAC frames, MAC frames, payloads, data parts, data, information bits, etc.). be. A PPDU corresponding to the IEEE 802.11n standard has a configuration including L-STF, L-LTF, L-SIG, HT-SIG, HT-STF, HT-LTF and Data frames. PPDU corresponding to the IEEE802.11ac standard includes part or all of L-STF, L-LTF, L-SIG, VHT-SIG-A, VHT-STF, VHT-LTF, VHT-SIG-B and MAC frames. configuration. PPDUs in the IEEE 802.11ax standard are L-STF, L-LTF, L-SIG, RL-SIG with L-SIG temporally repeated, HE-SIG-A, HE-STF, HE-LTF, HE- This configuration includes part or all of SIG-B and Data frames. The PPDU considered in the IEEE802.11be standard is L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, EHT-SIG, EHT-STF, EHT-LTF and part of Data frame or It is an all-inclusive configuration.

L-STF, L-LTF and L-SIG surrounded by dotted lines in FIG. collectively referred to as the L-header). For example, a wireless communication device compatible with the IEEE 802.11a/b/g standard can properly receive an L-header in a PPDU compatible with the IEEE 802.11n/ac standard. A wireless communication device conforming to the IEEE802.11a/b/g standard can receive a PPDU conforming to the IEEE802.11n/ac standard as a PPDU conforming to the IEEE802.11a/b/g standard.

However, since the wireless communication device compatible with the IEEE802.11a/b/g standard cannot demodulate the PPDU compatible with the IEEE802.11n/ac standard following the L-header, the transmission address (TA: Transmitter Address) , receiver address (RA), and Duration/ID field used for setting NAV cannot be demodulated.

IEEE 802.11 inserts Duration information into L-SIG as a method for a wireless communication device compatible with IEEE 802.11a/b/g standards to appropriately set NAV (or perform reception operation for a predetermined period). stipulates the method. Information about the transmission rate in L-SIG (RATE field, L-RATE field, L-RATE, L_DATARATE, L_DATARATE field), information about the transmission period (LENGTH field, L-LENGTH field, L-LENGTH) is IEEE802.11a A wireless communication device supporting the /b/g standard is used to properly set the NAV.

FIG. 3 is a diagram showing an example of how Duration information is inserted into L-SIG. FIG. 3 shows a PPDU configuration corresponding to the IEEE802.11ac standard as an example, but the PPDU configuration is not limited to this. A PPDU configuration compatible with the IEEE802.11n standard and a PPDU configuration compatible with the IEEE802.11ax standard may be used. TXTIME comprises information on the length of the PPDU, aPreambleLength comprises information on the length of the preamble (L-STF+L-LTF), and aPLCPHeaderLength comprises information on the length of the PLCP header (L-SIG). L_LENGTH is Signal Extension, which is a virtual duration set for compatibility with the IEEE 802.11 standard; _Nops related to L_RATE; It is calculated based on aPLCPServiceLength indicating the number of bits included in the PLCP Service field and aPLCPConvolutionalTailLength indicating the number of tail bits of the convolutional code. The wireless communication device can calculate L_LENGTH and insert it into L-SIG. Also, the wireless communication device can calculate the L-SIG Duration. L-SIG Duration indicates information on the total duration of the PPDU including L_LENGTH and the duration of ACK and SIFS expected to be transmitted from the destination wireless communication device as a response.

FIG. 4 is a diagram showing an example of L-SIG Duration in L-SIG TXOP Protection. DATA (frame, payload, data, etc.) consists of part or both of the MAC frame and the PLCP header. Also, BA is Block ACK or ACK. The PPDU includes L-STF, L-LTF, L-SIG, and may include any or more of DATA, BA, RTS, or CTS. Although the example shown in FIG. 4 shows L-SIG TXOP Protection using RTS/CTS, CTS-to-Self may be used. Here, MAC Duration is the period indicated by the value of Duration/ID field. Also, the Initiator can transmit a CF_End frame to notify the end of the L-SIG TXOP Protection period.

Next, a method for identifying a BSS from a frame received by the wireless communication device will be described. In order for the wireless communication device to identify the BSS from the received frame, the wireless communication device that transmits the PPDU should include information for identifying the BSS (BSS color, BSS identification information, value unique to the BSS) in the PPDU. It is preferable to insert, and it is possible to describe information indicating the BSS color in HE-SIG-A.

The wireless communication device can transmit L-SIG multiple times (L-SIG Repetition). For example, the radio communication apparatus on the receiving side receives the L-SIG transmitted multiple times using MRC (Maximum Ratio Combining), thereby improving the demodulation accuracy of the L-SIG. Furthermore, when the L-SIG is correctly received by the MRC, the wireless communication device can interpret that the PPDU including the L-SIG is a PPDU conforming to the IEEE802.11ax standard.

The wireless communication device shall perform the reception operation of a part of the PPDU other than the PPDU (for example, the preamble, L-STF, L-LTF, PLCP header, etc. specified by IEEE 802.11) even during the reception operation of the PPDU. (also called double receive operation). When a wireless communication device detects part of a PPDU other than the relevant PPDU during a PPDU reception operation, the wireless communication device updates part or all of the information on the destination address, the source address, the PPDU, or the DATA period. can be done.

ACK and BA can also be called responses (response frames). Also, probe responses, authentication responses, and connection responses can be referred to as responses.

FIG. 5 is a diagram showing an example of a wireless communication system according to this embodiment. The radio communication system 3-1 includes a radio communication device 1-1 and radio communication devices 2-1 to 2-3. The wireless communication device 1-1 is also called the base station device 1-1, and the wireless communication devices 2-1 to 2-3 are also called terminal devices 2-1 to 2-3. The wireless communication devices 2-1 to 2-3 and the terminal devices 2-1 to 2-3 are also referred to as a wireless communication device 2A and a terminal device 2A as devices connected to the wireless communication device 1-1. The wireless communication device 1-1 and the wireless communication device 2A are wirelessly connected and are in a state of being able to transmit and receive PPDUs to and from each other. Also, the radio communication system according to this embodiment may include a radio communication system 3-2 in addition to the radio communication system 3-1. The radio communication system 3-2 includes a radio communication device 1-2 and radio communication devices 2-4 to 2-6. The wireless communication device 1-2 is also called the base station device 1-2, and the wireless communication devices 2-4 to 2-6 are also called terminal devices 2-4 to 2-6. The wireless communication devices 2-4 to 2-6 and the terminal devices 2-4 to 2-6 are also referred to as a wireless communication device 2B and a terminal device 2B as devices connected to the wireless communication device 1-2. Although the radio communication system 3-1 and the radio communication system 3-2 form different BSSs, this does not necessarily mean that ESSs (Extended Service Sets) are different. ESS indicates a service set forming a LAN (Local Area Network). That is, wireless communication devices belonging to the same ESS can be regarded as belonging to the same network from higher layers. Also, the BSSs are combined via a DS (Distribution System) to form an ESS. Each of the radio communication systems 3-1 and 3-2 can further include a plurality of radio communication devices.

In FIG. 5, in the following description, it is assumed that the signal transmitted by the radio communication device 2A reaches the radio communication devices 1-1 and 2B, but does not reach the radio communication device 1-2. do. That is, when the radio communication device 2A transmits a signal using a certain channel, the radio communication device 1-1 and the radio communication device 2B determine that the channel is busy, while the radio communication device 1-2 The channel is determined to be idle. It is also assumed that the signal transmitted by the radio communication device 2B reaches the radio transmission device 1-2 and the radio communication device 2A, but does not reach the radio communication device 1-1. That is, when radio communication device 2B transmits a signal using a certain channel, radio communication device 1-2 and radio communication device 2A determine that the channel is busy, while radio communication device 1-1 The channel is determined to be idle.

A MLD (Multi-link Device) is a wireless communication device capable of multi-link communication. An access point device and a station device of this embodiment, which will be described later, are MLDs that support multilink communication. The radio communication devices 1-1, 1-2, 2A, and 2B described above are described as being MLDs, but in actual operation, even if all the radio communication devices in the radio communication system do not support multilink communication, good.

In the following embodiment, a case will be described in which the wireless communication device 1-1 (base station device 1-1) transmits and the wireless communication device 2-1 (terminal device 2-1) receives. However, it also includes the case where the wireless communication device 2-1 (terminal device 2-1) transmits and the wireless communication device 1-1 (base station device 1-1) receives. Unless otherwise specified, the device configurations of the wireless communication device 1-1 and the wireless communication device 2-1 are the same as the device configuration examples shown in FIGS. 8 and 9, which will be described later.

FIG. 6 shows an example of the overview of the multilink setup of this embodiment. In the figure, an MLD wireless communication device 1-1 and an MLD wireless communication device 2-1 are used as examples of wireless communication devices compatible with MLD. The MLD radio communication device 1-1 implements procedures for establishing a multilink (a multilink establishment request 10-1 and a multilink establishment response 10-2) to establish a multilink and maintain the multilink. be able to. Here, maintaining multilink means that frames can be transmitted and received based on a predetermined setting for multilink. In addition, the MLD radio communication device 1-1 maintains the multilink, and in addition to the procedure for changing the multilink setting (multilink change request 10-3, multilink change response 10-4), It is also possible to carry out a procedure for canceling the multilink using the multilink change request 10-3 and the multilink change response 10-4, thereby canceling the multilink.

The MLD wireless communication device 2-1 in FIG. 6 is also called an initiator (multilink initiator), and transmits a multilink establishment request 10-1 to the MLD wireless communication device 1-1. Note that the multilink initiator may be the MLD wireless communication device 1-1 instead of the MLD wireless communication device 2-1. The multilink establishment request 10-1 may include control information such as multilink capability information (Capability information) and multilink operation mode information of its own wireless communication device. The multilink measurement information (measurement information) is the radio signal quality of the frequency band (or channel or subchannel) that can be used by the own radio communication device, and may be included in the multilink establishment request 10-1. and may be reported to the MLD wireless communication device 1-1 using another frame. The radio signal quality is, for example, received power level, SNR (Signal to Noise Ratio), etc., but is not limited to these. Just do it. The object of measurement of the received power level and SNR may be a broadcast frame (announcement frame) such as a beacon transmitted by each sub access point device constituting the MLD wireless communication device 2-1. Since the broadcast frame is broadcast to the wireless communication devices 2A connected to the MLD wireless communication device 1-1, each wireless communication device 2A can measure the wireless signal quality of the same frame, and can check the reception status of each wireless communication device 2A. A relative comparison may be made. In addition to beacons, broadcast and multicast management frames and control frames may also be measured. The measurement of the multilink measurement information is independently performed by the receiving section of the sub wireless communication device (substation device) and transmitted to the upper layer processing section 10001-1. The measured value may be handled for each sub-radio communication device unit, or may be handled by integrating all sub-stations.

The number of links forming the MLD wireless communication device 1-1 and the MLD wireless communication device 2-1 is any number of two or more. The carrier frequency of each link can be set to 6 GHz band, 60 GHz band, etc. in addition to 2.4 GHz band and 5 GHz band, but it may change according to the legal regulations of each country.

The multilink capability information includes channel information (frequency, bandwidth, etc.) usable by the own wireless communication device, STR (Simultaneously Transmission and Reception) availability, frame synchronization availability, multilink aggregation availability, multilink switching availability, multilink Information such as TXOP (max, min, etc.) may be included. The multilink operation mode information includes channel information (frequency, bandwidth, etc.) of each link that configures the multilink, multilink TXOP limit, multilink aggregation, multilink switch, frame synchronization, frame asynchronization, STR, non-STR, Response frame method (response frame connection information, response frame timing information, etc.), response frame parameters (frame length threshold, response frame transmission time limit, etc.), etc. may be included.

The multilink establishment request may be sent independently and separately on each link, or may be sent on one of the links that make up the multilink. Similarly, the multilink measurement information may be sent independently and separately on each link, or may be sent on one of the links that make up the multilink (multilink in the multilink establishment request). not include link measurement information). When transmission is performed by one link, the link for transmitting and receiving frames for multilink management is also called a multilink management link (multilink management link).

A configuration example of the MLD according to this embodiment is shown in FIG. In the figure, an access point device 20000-1 (hereinafter also referred to as AP-MLD) supporting multilink and a station device 30000-1 (hereinafter also referred to as STA-MLD) supporting multilink are multilink consists of a plurality of sub-radio communication devices corresponding to the frequency bands (or channels or sub-channels) of each link that constitutes the . The AP-MLD consists of three sub wireless communication devices, in this case three sub access point devices (20000-2, 200000-3, 20000-4). Similarly, the STA-MLD is composed of three sub-radio communication devices, in this case three sub-station devices (30000-2, 300000-3, 30000-4). The sub-radio communication device (sub-access point device, sub-station device, etc.) may be composed of a part of the circuits in the radio communication device, and is called a sub-radio communication unit (sub-access point unit, sub-station unit). You may

In FIG. 7, a plurality of sub wireless communication devices are shown as logically separate blocks (squares) for explanation. Physically, it may consist of one wireless communication device. Alternatively, physically, separate sub-wireless communication devices may be configured, each sub-access point device transmitting and receiving necessary information via connections 9-1 and 9-2, and each substation device Necessary information is transmitted and received through connections 9-3 and 9-4. In this case, the separate sub-radio communication devices are managed by the MLME. In the example of the present embodiment, mainly the former case, that is, physically composed of one wireless communication device 10-1, the configuration of the wireless communication device 10-1 will be described later with reference to FIGS. 8 and 9. .

The number of sub-access point devices included in one AP-MLD and the number of sub-station devices included in one STA-MLD change according to the performance installed in each wireless communication device. That is, the number of sub wireless communication devices (sub access point devices, sub station devices) possessed by each wireless communication device positioned within one wireless communication system does not have to match.

In FIG. 7, substation device 30000-2 establishes link 1 by connecting (associating) with subaccess point device 20000-2. Substation device 30000-3 establishes link 2 by connecting (associating) with sub access point device 20000-3. Substation device 30000-4 establishes link 3 by connecting (associating) with sub access point device 20000-4. In the example of this embodiment, the number of links forming the multilink is three, but the number is not limited to this and may be any number of two or more. The carrier frequency of link 1 is 2.4 GHz band, the carrier frequency of link 2 is 5 GHz band, and the carrier frequency of link 3 is 6 GHz band. However, the frequency used by each link can be arbitrarily set from 2.4 GHz band, 5 GHz band, 6 GHz band, 60 GHz band, and other frequency bands, channels, and sub-channels supported by the wireless communication system. , may vary according to the laws and regulations of each country.

FIG. 8 shows an example of the device configuration of radio communication devices 1-1, 1-2, 2A and 2B, AP-MLD and STA-MLD (hereinafter also collectively referred to as radio communication device 10-1). It is a diagram. The wireless communication device 10-1 includes an upper layer section (upper layer processing step) 10001-1, an autonomous distributed control section (autonomous distributed control step) 10002-1, a transmitting section (transmitting step) 10003-1, and a receiving section. (Receiving step) This configuration includes 10004-1 and antenna section 10005-1.

The upper layer section 10001-1 handles information handled within its own wireless communication device (information related to transmission frames, MIB (Management Information Base), etc.) and frames received from other wireless communication devices, a layer higher than the physical layer, For example, it performs information processing in the MAC layer and the LLC layer. The multilink control section 10001a-1 may be included in the upper layer section 10001-1, or may be independent.

The upper layer section 10001-1 measures the load status of the links that have established multilinks in the MAC layer, and the multilink control section 10001a-1 selects retransmission destination link candidates according to the measurement results. The retransmission destination link candidate includes information designating a retransmission destination link for the frame. The multilink control section 10001a-1 generates the retransmission destination link candidate or control information including the retransmission method (ARQ/HARQ) for the retransmission destination link candidate, and transmits the control information to the PHY layer. For example, the multilink control unit 10001a-1 retransmits the frame by ARQ when no retransmission destination link candidate is set in the control information, and when HARQ is set in the control information, the Perform packet combining on candidate retransmission destination links.

The load status of each link includes the channel usage status in the MAC layer of the upper layer section 10001-1, the allocation status of frames for each RU (Resource allocation), and the BSS load information indicating the operation status of the AP. ), BSS average access delay, and BSS access category delay. Also, the load status of each link may be the measurement reported by all STAs or STA-MLDs establishing multi-links with the AP-MLD. Instead of the measured value, the link load status may be an identifier that reflects the load status in stages.

The upper layer section 10001-1 generates an MPDU or an A-MPDU frame by aggregating the MPDUs from the frame transmitted to the MAC layer. The multilink control unit 10001a-1 implements TID to link mapping for allocating TIDs to the frame and each link. Note that each link can be assigned multiple TIDs. Also, the multilink control unit 10001a-1 transfers the frame to the PHY layer and generates a PPDU including the control information in the PHY header. The PHY header contains information necessary for frame decoding, such as a PLCP preamble for synchronization detection and a PLCP header for determining the modulation and coding scheme (MCS) according to the received signal strength. shall be The transmitting section 10003-1 in the AP-MLD transmits the frame on the link to which the same TID as the PPDU is assigned.

The upper layer section 10001-1 is connected to another network and can notify the autonomous distributed control section 10002-1 of information on frames and traffic. Information about traffic may be, for example, control information included in a management frame such as a beacon, or may be measurement information reported by another wireless communication device addressed to the wireless communication device itself. Furthermore, the destination is not limited (it may be addressed to its own device, may be addressed to another device, or may be broadcast or multicast), even if it is control information included in a management frame or control frame. good.

FIG. 9 is a diagram showing an example of the device configuration of the autonomous decentralized control unit 10002-1. The control section 10002-1 includes a CCA section (CCA step) 10002a-1, a backoff section (backoff step) 10002b-1, and a transmission determination section (transmission determination step) 10002c-1.

CCA section 10002a-1 receives one or both of information about received signal power received via radio resources and information about received signals (including information after decoding) notified from receiving section 10004-1. can be used to determine the state of the radio resource (including busy or idle determination). The CCA section 10002a-1 can notify the back-off section 10002b-1 and the transmission decision section 10002c-1 of the radio resource state determination information.

The backoff unit 10002b-1 can perform backoff using the radio resource state determination information. The backoff unit 10002b-1 generates a Contention Window (CW) and has a countdown function. For example, when the radio resource state determination information indicates idle, the CW countdown can be executed, and when the radio resource state determination information indicates busy, the CW countdown can be stopped. The backoff unit 10002b-1 can notify the transmission determination unit 10002c-1 of the CW value.

The transmission decision unit 10002c-1 makes a transmission decision using either one or both of the radio resource status decision information and the CW value. For example, when the radio resource state determination information indicates idle and the value of CW is 0, the transmission determination information can be notified to the transmitting section 10003-1. Further, when the radio resource state determination information indicates idle, the transmission determination information can be notified to the transmitting section 10003-1.

The transmission section 10003-1 includes a physical layer frame generation section (physical layer frame generation step) 10003a-1 and a radio transmission section (radio transmission step) 10003b-1. The physical layer frame generation unit 10003a-1 has a function of generating a physical layer frame (hereinafter also referred to as PPDU) based on transmission determination information notified from the transmission determination unit 10002c-1. Physical layer frame generation section 10003a-1 performs error correction coding, modulation, precoding filter multiplication, and the like on a transmission frame sent from an upper layer. The physical layer frame generator 10003a-1 notifies the radio transmitter 10003b-1 of the generated physical layer frame.

Control information is included in the frame generated by the physical layer frame generation unit 10003a-1. The control information includes information indicating in which RU (here, RU includes both frequency resources and space resources) data addressed to each wireless communication device is allocated. Also, the frame generated by the physical layer frame generation unit 10003a-1 includes a trigger frame that instructs the wireless communication device, which is the destination terminal, to transmit the frame. The trigger frame contains information indicating the RU used when the wireless communication device instructed to transmit the frame transmits the frame.

The radio transmission unit 10003b-1 converts the physical layer frame generated by the physical layer frame generation unit 10003a-1 into a radio frequency (RF) band signal to generate a radio frequency signal. Processing performed by the radio transmission unit 10003b-1 includes digital/analog conversion, filtering, frequency conversion from the baseband band to the RF band, and the like.

The receiving section 10004-1 includes a radio receiving section (radio receiving step) 10004a-1 and a signal demodulating section (signal demodulating step) 10004b-1. Receiving section 10004-1 generates information about received signal power from the RF band signal received by antenna section 10005-1. Receiving section 10004-1 can report information on received signal power and information on received signals to CCA section 10002a-1.

The receiving section 10004-1 includes a radio receiving section (radio receiving step) 10004a-1 and a signal demodulating section (signal demodulating step) 10004b-1. Receiving section 10004-1 generates information about received signal power from the RF band signal received by antenna section 10005-1. Receiving section 10004-1 can report information on received signal power and information on received signals to CCA section 10002a-1.

The radio receiving section 10004a-1 has a function of converting an RF band signal received by the antenna section 10005-1 into a baseband signal and generating a physical layer signal (for example, a physical layer frame). The processing performed by the radio reception unit 10004a-1 includes frequency conversion processing from the RF band to the baseband band, filtering, and analog/digital conversion.

The signal demodulator 10004b-1 has a function of demodulating the physical layer signal generated by the radio receiver 10004a-1. Processing performed by the signal demodulator 10004b-1 includes channel equalization, demapping, error correction decoding, and the like. The signal demodulator 10004b-1 can extract, for example, information contained in the physical layer header, information contained in the MAC header, and information contained in the transmission frame from the physical layer signal. The signal demodulation section 10004b-1 can notify the extracted information to the upper layer section 10001-1. The signal demodulator 10004b-1 can extract any or all of the information included in the physical layer header, the information included in the MAC header, and the information included in the transmission frame.

The antenna section 10005-1 has a function of transmitting a radio frequency signal generated by the radio transmission section 10003b-1 to radio space. Also, the antenna section 10005-1 has a function of receiving a radio frequency signal and transferring it to the radio receiving section 10004a-1.

The wireless communication device 10-1 writes information indicating the period during which the wireless communication device uses the wireless medium in the PHY header or MAC header of the frame to be transmitted, thereby notifying wireless communication devices around the wireless communication device 10-1 of the period. NAV can be set only for a period of time. For example, wireless communication device 10-1 can write information indicating the duration in the Duration/ID field or Length field of the frame to be transmitted. The NAV period set in the wireless communication devices around the own wireless communication device is called the TXOP period (or simply TXOP) acquired by the wireless communication device 10-1. Then, the wireless communication device 10-1 that has acquired the TXOP is called a TXOP holder. The frame type of the frame that is transmitted by the wireless communication device 10-1 to acquire the TXOP is not limited to anything, and may be a control frame (for example, an RTS frame or a CTS-to-self frame) or a data frame. But it's okay.

The wireless communication device 10-1, which is a TXOP holder, can transmit frames to wireless communication devices other than its own wireless communication device during the TXOP. If the radio communication device 1-1 is a TXOP holder, the radio communication device 1-1 can transmit frames to the radio communication device 2A within the period of the TXOP. Further, the radio communication device 1-1 can instruct the radio communication device 2A to transmit a frame addressed to the radio communication device 1-1 within the TXOP period. Within the TXOP period, the radio communication device 1-1 can transmit to the radio communication device 2A a trigger frame containing information instructing frame transmission addressed to the radio communication device 1-1.

The wireless communication device 1-1 may secure TXOP for all communication bands (for example, operation bandwidth) in which frame transmission may be performed, or a communication band for actually transmitting frames (for example, transmission bandwidth). may be reserved for a specific communication band (Band).

The wireless communication device that instructs the frame transmission within the period of the TXOP acquired by the wireless communication device 1-1 is not necessarily limited to the wireless communication device connected to the own wireless communication device. For example, a wireless communication device is not connected to its own wireless communication device in order to transmit a management frame such as a Reassociation frame or a control frame such as an RTS/CTS frame to wireless communication devices around itself. A wireless communication device can be instructed to transmit a frame.

　In addition, TXOP in EDCA, which is a data transmission method different from DCF, will also be explained. The IEEE802.11e standard is related to EDCA, and defines TXOP from the viewpoint of QoS (Quality of Service) assurance for various services such as video transmission and VoIP. Services are broadly classified into four access categories: VO (VOice), VI (VIdeo), BE (BestEffort), and BK (Back ground). In general, the order of priority is VO, VI, BE, and BK. Each access category has parameters for the minimum CW value CWmin, maximum value CWmax, AIFS (arbitration IFS), which is a type of IFS, and TXOP limit, which is the upper limit of transmission opportunities. Value is set. For example, CWmin, CWmax, and AIFS of the VO with the highest priority for voice transmission are set to relatively small values compared to other access categories, thereby giving priority to other access categories. Transmission becomes possible. For example, in VI where the amount of data to be transmitted is relatively large due to video transmission, setting a large TXOP limit makes it possible to secure a longer transmission opportunity than in other access categories. Thus, the values of the four parameters of each access category are adjusted for the purpose of guaranteeing QoS according to various services.

In this embodiment, the signal demodulation section 10004b-1 of the transmission section can perform decoding processing and error detection on the received signal in the physical layer. The decoding processing here includes decoding processing for the error correction code applied to the received signal. Here, the error detection includes error detection using an error detection code (for example, a cyclic redundancy check (CRC) code) assigned in advance to the received signal, or error correction code (for example, a low-density parity code) originally provided with an error detection function. Includes error detection by check code (Low Density Parity Check: LDPC). A decoding process in the physical layer can be applied for each coded block.

The upper layer section 10001-1 transfers the decoding result of the physical layer in the signal demodulation section to the MAC layer. In the MAC layer, the signal of the MAC layer is restored from the transferred decoding result of the physical layer. Then, in the MAC layer, error detection is performed, and it is determined whether or not the MAC layer signal transmitted by the station device that is the transmission source of the received frame has been correctly restored.

FIG. 10 is a diagram showing an example of error correction coding of the physical layer frame generator 10003a-1 according to this embodiment. As shown in FIG. 10, information bit (systematic bit) sequences are arranged in hatched areas, and redundant (parity) bit sequences are arranged in white areas. Information bits and redundant bits are appropriately bit interleaved. The physical layer frame generator 10003a-1 can read out the necessary number of bits from the allocated bit sequence as the start position determined according to the value of the redundancy version (RV). By adjusting the number of bits, it is possible to flexibly change the coding rate, that is, puncturing. Although FIG. 10 shows a total of four RVs, RV options are not limited to specific values in the error correction coding according to this embodiment. The position of the RV must be shared between station devices. Needless to say, the error correction coding method according to the present embodiment is not limited to the example of FIG. 10, and any method may be used as long as the coding rate can be changed and decoding processing on the receiving side can be achieved.

For example, in error correction coding using IEEE802.11 standard low-density parity check codes, first, a generator matrix is obtained from a low-density parity check matrix, and parity bits calculated from the matrix product of the generator matrix and information bits are obtained. Generate. Next, the parity bit is added to the information bit sequence to form a codeword. That is, the physical layer frame generating section 10003a-1 calculates a predetermined information bit length for error correction coding based on at least the size of the parity check matrix set by the coding rate of MCS. An information bit sequence used for LDPC encoding is also called an LDCP information block, and a bit sequence obtained by LDPC-encoding an LDPC information block is also called an LDPC codeword block.

FIG. 11 shows an example of associations between MCS, modulation schemes, and coding rates. For example, when the MCS is 1, the modulation scheme is QPSK and the coding rate is 1/2, and when the MCS is 4, the modulation scheme is 16QAM and the coding rate is 3/4. Also, FIG. 12 shows an example of the association between the coding rate, the LDPC information block length, and the LDPC codeword block length. The LDPC information block length is obtained by multiplying the LDPC codeword block length by the coding rate. For example, when the coding rate is ½, candidates for (LDPC information block length, LDPC codeword block length) are (972, 1944), (648, 1296), and (324, 648). Note that the LDPC information block length and the LDPC codeword block length are values determined by the parity check matrix size, and may differ from the transmitted information block length and codeword block length.

　In this embodiment, an example of a frame retransmission method during downlink communication is shown in FIGS. Note that acknowledgments corresponding to frames are omitted in both figures. In both figures, AP-MLD establishes multi-links with STA-MLD with three links and measures the load status of each link. For each link, the upper layer section 10001-1 assigns TID1 and TID3 to link 1, and TID3 to links 2 and 3. FIG. Assume that the frames following PPDU14 and PPDU23 have already been buffered in link 1 and link 2, respectively, and that link 2 has not received an acknowledgment corresponding to PPDU 22 and a frame error has occurred. In FIG. 13, PPDU 31 indicates the last frame buffered on link 3 . On the other hand, in FIG. 14, PPDU 32 to PPDU 33 that follow are already buffered in PPDU 31 of link 3 . In both figures, the multilink control unit 10001a-1 selects the link 3 with the lowest load condition as a retransmission destination link candidate based on the load conditions of the links measured by the upper layer unit 10001-1, Generates control information on how to retransmit frames.

　In FIGS. 13 and 14, an outline of a frame retransmission method when the control information includes only retransmission destination link candidates will be described. First, in FIG. 13, the AP-MLD transmits the PPDU31 of the last frame buffered on the link 3 and the PPDU22 of the same TID3 following the PPDU31 on the link 2 to the STA-MLD. The AP-MLD retransmits the erroneous PPDU 22 on link 2 with the highest priority using ARQ in the retransmission destination link candidates specified by the control information. The multilink control unit 10001a-1 allows the PPDU 31 to update a field (for example, a More data field) indicating whether or not there is a frame buffered after the frame until the transmission of the PPDU 22 is completed. First, control data for setting the NAV for link 3, which is a candidate for the retransmission destination link, is added to the control information. That is, according to the control information, the AP-MLD retransmits the PPDU 22 of the link 2 with the highest priority by ARQ immediately after the transmission of the PPDU 31 of the link 3 is completed. NAV settings may be, without limitation, RTS, CTS, or CTS-to-self. Next, FIG. 14 shows a retransmission method when PPDU 33 has already been buffered prior to PPDU 22 on link 3 when retransmitting PPDU 22 on link 3 . The multilink control unit 10001a-1 reorders the buffer of the link 3 so that the PPDU22 can be retransmitted prior to the PPDU33. That is, according to the control information, the AP-MLD retransmits the PPDU 22 with the highest priority using ARQ on link 3, which is a candidate for the retransmission destination link.

Next, with reference to FIGS. 13 and 14, outlines of a frame retransmission method and a packet combining method when the control information includes a retransmission destination link candidate and a retransmission method will be described. If the control information includes two or more retransmission destination link candidates, ARQ/HARQ may be configured for each link. However, in this case, multilink control section 10001a-1 limits retransmission of frames by ARQ and does not limit retransmission of frames by HARQ in the retransmission destination link candidates. First, in FIG. 13, AP-MLD retransmits the PPDU 22 with highest priority when the retransmission method is ARQ on link 3, which is a candidate for the retransmission destination link specified by the control information, and the retransmission method is HARQ. In this case, the PPDU 22 is retransmitted with the highest priority and packet combining is performed. The multilink control unit 10001a-1 does not allow the PPDU31 to update the field (More data field) indicating the presence or absence of a buffered frame after the frame until the transmission of the PPDU22 is completed. Control data for setting the NAV for link 3, which is a candidate for the retransmission destination link, is added to the control information. When the retransmission method is HARQ, by including information (MCS, coding rate) related to the packet combining method in the control information, the frame may be retransmitted using a different coding rate from the initial transmission. NAV settings may be, without limitation, RTS, CTS, or CTS-to-self. That is, according to the control information, the AP-MLD retransmits the PPDU 22 of the link 2 immediately after the transmission of the PPDU 31 on the link 3 is completed with the highest priority when the retransmission method is ARQ, and the retransmission method is HARQ. If so, retransmit with highest priority and perform packet combining. Next, in FIG. 14, the multilink control unit 10001a-1 reorders the buffer of link 3 so that PPDU22 can be retransmitted prior to PPDU33. According to the control information, the AP-MLD retransmits the PPDU 22 on link 3, which is a candidate for the retransmission destination link, with the highest priority when the retransmission method is ARQ, and gives the highest priority when the retransmission method is HARQ. retransmit to and perform packet combining.

A method of measuring the load status of the link of the upper layer section 10001-1 according to this embodiment will be described. The measurement of the load status of the link may be performed independently by the receiving section of the sub wireless communication device (substation device), or may be performed by integrating all the substations. The measured value of the load status of each link is not limited to a specific index, and may be any value that can be used to determine the load status of the links that constitute the MLD. For example, as a link load status measurement value, the MAC layer indicates the frame buffer size allocated to each link, the channel usage status, the frame allocation status for each RU (Resource allocation), and the AP operation status. BSS load information, BSS average access delay, BSS access category access delay (BSS Access Category Access Delay), etc. In addition, at the PHY layer, at the time of multi-link establishment request in multi-link setup , the ratio of Busy in the carrier sense time of each link, or the like may be used as the measurement value. Further, the load status of the plurality of links may be an identifier (Busy, High, Middle, Low, Idle, Null, etc.) that reflects the load status of the links in stages according to a predetermined threshold.

A method for selecting retransmission destination link candidates by the multilink control unit 10001a-1 based on the load status of each link measured by the upper layer unit 10001-1 will be described. The multilink control unit 10001a-1 selects the link with the lowest link load status based on the measurement result of the upper layer unit 10001-1, or creates a list of the measurement results in ascending order. Two or more links are elected as resend-to links. Also, when the load conditions of the respective links are the same, the multilink control unit 10001a-1 does not select retransmission destination link candidates. If a frame error occurs in multiple links forming the MLD, the same retransmission destination link may be set for each frame. Further, when there is an empty link for which the multilink establishment response 10-2 has not been received, the upper layer section 10001-1 establishes a new link by transmitting the multilink establishment request 10-1, When the load status of the link is lower than the existing load status, the link is set as a retransmission destination link candidate, and control information is generated together with the retransmission method.

When the multilink control unit 10001a-1 according to the present embodiment does not receive an acknowledgment corresponding to a frame within a predetermined time on a link on which a multilink has been established or a retransmission destination link, the multilink control unit 10001a-1 selects retransmission destination link candidates. Update. For example, when another frame has already been buffered on the retransmission destination link, the multilink control unit 10001a-1 sets the link with the next lowest load status included in the retransmission destination link candidates as the retransmission destination link. may Also, if no acknowledgment corresponding to the frame is received within a predetermined time, or if acknowledgments for the frame are not received a plurality of times consecutively, another link among the retransmission destination link candidates is retransmitted. Set as destination link. For example, if there are two or more candidates for the retransmission destination link, the link with the next lowest link load condition is selected as the retransmission destination link.

Also, the link load status according to this embodiment may be measured using a trigger frame. For example, in FIG. 13 or 14, AP-MLD transmits a trigger frame to all wireless communication devices such as STA-MLD that have established multilinks with them. On the other hand, the STA-MLD that received the trigger frame measures the load status of each link and notifies the AP-MLD of the measurement results. In each of the links, if the measurement result corresponding to the trigger frame is not received within a predetermined time, or if the measurement result for the trigger frame is not received continuously for a plurality of times, the AP- The MLD determines that the load status of the link is Busy and does not set it as a retransmission destination link candidate.

Regarding the method of retransmitting frames in the retransmission destination link candidate according to the present embodiment, the upper layer unit 10001-1 may set an access category for retransmission with a higher priority than the EDCA access category of the IEEE 802.11e standard. good. The multilink control unit 10001a-1 does not permit transmission of frames other than the retransmission-only access category on the retransmission destination link.

The STA-MLD according to this embodiment receives the frame transmitted from the AP-MLD in the receiving section 10004-1. The signal demodulator 10004b-1 of the STA-MLD can perform decoding processing and error detection on the received signal in the PHY layer. First, the signal demodulation unit 10004b-1 decodes the PHY header of the PPDU, which is the received transmission frame, performs packet synthesis of the frame when HARQ is set in the PHY header, Decode the word. The decoding result is transferred to the MAC layer in the upper layer section 10001-1. The MAC layer restores the frame of the MAC layer from the forwarded decoding result, performs error detection, and determines whether the frame of the MAC layer transmitted by the station device which is the transmission source of the received frame has been correctly restored. to judge. For error detection, error detection using an error detection code (for example, a cyclic redundancy check (CRC) code) attached to a received frame, or error correction code originally provided with an error detection function (for example, a low density parity check code (LDPC )) includes error detection. The decoding processing here includes decoding processing for the error correction code applied to the received signal. A decoding process in the PHY layer can be applied for each coded block. On the other hand, when ARQ is set in the PHY header of the received frame, the signal demodulation unit 10004b-1 does not perform packet synthesis of the frame in the decoding process, decodes the codeword of the PPDU, and outputs the decoding result. It is transferred to the upper layer section 10001-1.

As described above, the communication device according to the present embodiment maintains the retransmission function of the MAC layer, reduces the overhead of the PHY layer and the MAC layer, and enables effective packet combining in the PHY layer. It can contribute to improvement of transmission efficiency.

The communication device according to the present invention can communicate in a frequency band (frequency spectrum) called an unlicensed band that does not require a license from a country or region. is not limited to this. The communication device according to the present invention is, for example, a white band that is not actually used for the purpose of preventing interference between frequencies, even though the country or region has given permission to use it for a specific service. Also in the frequency band called (for example, the frequency band allocated for television broadcasting but not used in some areas) and the shared spectrum (shared frequency band) that is expected to be shared by multiple operators It is possible to exert an effect.

The program that operates in the wireless communication device according to the present invention is a program that controls the CPU and the like (a program that causes a computer to function) so as to implement the functions of the above-described embodiments related to the present invention. Information handled by these devices is temporarily stored in RAM during processing, then stored in various ROMs and HDDs, and read, modified, and written by the CPU as necessary. Recording media for storing programs include semiconductor media (eg, ROM, nonvolatile memory cards, etc.), optical recording media (eg, DVD, MO, MD, CD, BD, etc.), magnetic recording media (eg, magnetic tapes, flexible disk, etc.). By executing the loaded program, the functions of the above-described embodiments are realized. In some cases, inventive features are realized.

Also, when distributing to the market, the program can be distributed by storing it in a portable recording medium, or it can be transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention. Also, part or all of the communication device in the above-described embodiments may be typically implemented as an LSI, which is an integrated circuit. Each functional block of the communication device may be individually chipped, or part or all of them may be integrated and chipped. When each functional block is integrated, an integrated circuit control unit for controlling them is added.

Also, the method of circuit integration is not limited to LSIs, but may be realized with dedicated circuits or general-purpose processors. In addition, when a technology for integrating circuits to replace LSIs emerges due to advances in semiconductor technology, it is possible to use an integrated circuit based on this technology.

It should be noted that the present invention is not limited to the above-described embodiments. The wireless communication device of the present invention is not limited to application to mobile station devices, but can be applied to stationary or non-movable electronic devices installed indoors and outdoors, such as AV equipment, kitchen equipment, cleaning/washing equipment, etc. Needless to say, it can be applied to equipment, air conditioners, office equipment, vending machines, and other household equipment.

Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and designs and the like within the scope of the scope of the present invention can be applied within the scope of claims. Included in the scope.

The present invention is suitable for use in communication devices and communication methods.

1-1, 1-2, 2-1 to 6, 2A, 2B Wireless communication devices 3-1, 3-2 Control range 10-1 Wireless communication device 10001-1 Upper layer unit 10001a-1 Multilink control unit 10002- 1 Control section 10002a-1 CCA section 10002b-1 Backoff section 10002c-1 Transmission judgment section 10003-1 Transmission section 10003a-1 Physical layer frame generation section 10003b-1 Radio transmission section 10004-1 Reception section 10004a-1 Radio reception section 10004b-1 Signal demodulation unit 10005-1 Antenna unit 20000-1 Access point device 20000-2, 20000-3, 20000-4 Sub wireless communication device (sub access point device)
30000-1 Station device 30000-2, 30000-3, 30000-4 Sub wireless communication device (substation device)
10-1 Multilink establishment request 10-2 Multilink establishment response 10-3 Multilink change request 10-4 Multilink change response

Claims (11)

1. A communication device that transmits frames using two or more links, the communication device comprising a control unit that selects retransmission destination link candidates according to the load status of each of the links in the MAC layer. wherein the control unit generates the retransmission destination link candidate and the retransmission method as control information and transmits the same to a PHY layer; the communication device includes a transmission unit that generates a frame in the PHY layer; When no response is received, retransmission is not permitted on any other than the retransmission destination link candidate specified by the control information, and the communication device receives the frame on the retransmission destination link candidate according to the control information. A communication device, comprising: a receiver; and a signal demodulator that packet-synthesizes and decodes the frame.
2. The communication apparatus according to claim 1, wherein the retransmission destination link candidate restricts retransmission by ARQ and does not restrict retransmission by HARQ as the retransmission method.
3. The communication device according to claim 1, wherein the control unit sets a retransmission method without including retransmission destination link candidates in the control information when each of the links has the same load status.
4. 2. The control unit updates the retransmission destination link candidates when an acknowledgment for the frame is not received on each of the links or when no acknowledgment is received within a predetermined time. The communication device according to .
5. If the control unit does not receive a plurality of consecutive acknowledgments for the frame in one link in each of the links, or if the acknowledgment for the frame is not received within a predetermined time, 2. The communication device according to claim 1, wherein a link with a low load status is included in the retransmission destination link candidates.
6. If a frame containing the same identifier as the last frame buffered in each of the links on the transmitting side is subsequently buffered in a link other than the respective link, the control unit 2. The communication apparatus according to claim 1, wherein control data for setting a NAV for said another link is added to said control information for a predetermined time until receiving an acknowledgment for a frame containing .
7. The communication device according to claim 1, wherein the communication device comprises a control unit that sets an access category for retransmission to each of the links and transmits frames of the access category for retransmission with top priority.
8. The communication device according to claim 1, wherein the control unit in the communication device retransmits the frame with the highest priority by performing buffer reordering in each of the links.
9. The communication device according to claim 1, wherein when another frame is being transmitted on the retransmission destination link, the control unit retransmits the frame on another link specified by the retransmission destination link candidate.
10. A signal demodulator that receives a frame using two or more links, assigns the frame to the link specified by the control information, and demodulates and decodes the frame, and the signal demodulator has HARQ set to the frame. 2. The communication device according to claim 1, wherein packet combining of said frames is performed when a frame is received.
11. A communication method for transmitting frames using two or more links, the communication method comprising the step of selecting retransmission destination link candidates according to the load status of each of the links in the MAC layer, When the retransmission destination link candidate and the retransmission method are generated as control information and transmitted to the PHY layer, and the communication method includes the step of generating a frame in the PHY layer, and an acknowledgment for the frame is not received and retransmission is not permitted on any link other than the retransmission destination link candidate specified by the control information, and the communication method comprises: receiving the frame on the retransmission destination link candidate according to the control information; combining and decoding.

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