JP2024012732A - Communication apparatus and communication method - Google Patents

Abstract

To enable effective packet synthesis at a retransmission in an IEEE802.11 standard and improve a reception SNR.SOLUTION: A station device is a communication apparatus that transmits a frame, and comprises: an upper layer part that compacts a plurality of MPDUs, and sets a deliminator to each of the MPDUs; and a transmission part that transmits a frame length of the plurality of MPDUs, and forms a block of the plurality of MPDUs on the basis of a predetermined information bit length. In the case where a HARQ is set to the frame, it is not permitted that information on two or more of the MPDUs is included in the one block.SELECTED DRAWING: Figure 12

Description

The present invention relates to a communication device and a communication method.

IEEE (The Institute of Electrical and Electronics Engineers Inc.) continues to update the specifications of IEEE 802.11, a wireless LAN standard, to achieve faster wireless LAN (Local Area Network) communication speeds and more efficient frequency use. We are working on this. In recent years, with the rapid spread of wireless LAN devices, their use as real-time applications such as telemedicine and VR/AR is expected to expand. The standardization of IEEE802.11be, which will realize the

The IEEE802.11 standard introduces error control as a throughput speed-up technique. Error control is broadly classified into forward error correction (FEC) and automatic repeat request (ARQ). Forward error correction is a method in which errors occurring on a transmission path are corrected on the receiving side using error correction codes, and there is no need to request retransmission to the transmitting side for erroneous packets. Error correction ability can be improved by increasing the proportion of redundant bits in the codeword, but there is a trade-off with increased decoding processing and decreased transmission efficiency. On the other hand, ARQ is a method that requests the transmitting side to retransmit packets that were not properly decoded on the receiving side. Packet errors during decoding are detected by a medium access control (MAC) on the receiving side and are discarded without being stored in a buffer. If the packet is successfully decoded, an acknowledgment (ACK) is transmitted to the transmitting side, and if a packet error is detected, a negative acknowledgment (NACK) is transmitted to the transmitting side. Packet retransmission processing is performed by ARQ when NACK is transmitted to the transmitting side or when ACK is not transmitted to the transmitting side within a certain period of time. In addition to the error control in the IEEE802.11 standard described above, hybrid ARQ (HARQ), which combines a forward error correction code and ARQ, is being considered in standardization activities for IEEE802.11be. HARQ uses chase combining, which improves the signal-to-noise power ratio (SNR) of the received signal by transmitting the same packet during retransmission and combining the packets on the receiving side, and redundant signal (parity) signal during retransmission. Incremental redundancy (IR) combining, which increases the error correction decoding ability of the receiving side by transmitting a new signal (signal), has been widely studied.

In the IEEE 802.11n and later standards, radio frame and ACK aggregation is introduced as a technology for increasing throughput by reducing MAC layer overhead. Radio frame aggregation is broadly classified into A-MSDU (Aggregated MAC Service Data Unit) and A-MPDU (Aggregated MAC Protocol Data Unit). Aggregation of radio frames allows many packets to be transmitted at once, improving transmission efficiency, but increases the possibility of transmission errors. Therefore, in the IEEE 802.11ax and later standards, efficient error control for each MPDU is expected to be a key elemental technology for increasing throughput, in addition to improving transmission efficiency through radio frame aggregation. Therefore, in the standardization activities of IEEE802.11be, it is expected that transmission quality will be improved by obtaining time diversity through HARQ.

IEEE 802.11-19/1578-00-0be, September. 2019 IEEE 802.11-20/482-01-0be, June. 2020

However, the conventional IEEE 802.11 standard does not take packet combining using HARQ into consideration, so there is a problem in that it is difficult to apply efficient packet combining.

The present invention has been made in view of the above circumstances, and its purpose is to provide a communication device and a communication method that enable efficient packet combining during retransmission and contribute to improving reception SNR in the IEEE802.11 standard. It is to be disclosed.

A communication device and a communication method according to the present invention for solving the above-mentioned problems are as follows.

(1) That is, a communication device according to one aspect of the present invention is a communication device that transmits frames, and includes an upper layer unit that aggregates a plurality of MPDUs and sets a delimiter to each MPDU, and a communication device that transmits frames. The controller includes a control unit that transmits the MPDU length, which is the length of each frame, to the PHY layer, and a transmitter that blocks the MPDU based on a predetermined encoded block length. One block is not allowed to include information on two or more MPDUs, and if HARQ is not configured in the frame, the one block includes information on two or more MPDUs. is allowed.

(2) Further, in the communication device according to one aspect of the present invention, the predetermined encoded block length is based on the MCS and the MPDU length set in the frame including the MPDU. is set.
(3) Further, in the communication device according to one aspect of the present invention, the predetermined encoded block length is based on the MCS and the MPDU length set in the frame including the MPDU. It is set from the number of blocks set.

(4) Furthermore, a communication method according to one aspect of the present invention is a communication method in a communication device that transmits frames, which includes the steps of aggregating a plurality of MPDUs and setting a delimiter to each MPDU; the MPDU length, which is the frame length of each frame, to the PHY layer; and the step of blocking the MPDU based on a predetermined encoded block length; If one block is not allowed to include information of two or more MPDUs, and if HARQ is not configured in the frame, one block includes information of two or more MPDUs. is allowed.

(5) Further, a communication device according to one aspect of the present invention is a communication device that receives frames, and includes an upper layer unit in which a plurality of MPDUs are aggregated and a delimiter is set in each MPDU, and a A control unit that transmits the MPDU length, which is the frame length of each frame, to the PHY layer, and a reception unit that blocks and decodes the MPDU based on a predetermined encoded block length, and HARQ is set in the frame. If HARQ is not configured in the frame, the one block is not allowed to include information of two or more MPDUs, and if the frame is not configured with HARQ, the one block contains information of two or more MPDUs. information is permitted to be included.

(6) Further, in the communication device according to one aspect of the present invention, the predetermined encoded block length is set based on the MCS set in the frame including the MPDU and the MPDU length. be done.

(7) Further, in the communication device according to one aspect of the present invention, the predetermined encoded block length is set based on the MCS set in the frame including the MPDU and the MPDU length. It is set from the number of blocks.

(8) Further, a communication method according to one aspect of the present invention is a communication method in a communication device that receives frames, which includes the step of aggregating a plurality of MPDUs and setting a delimiter to each MPDU; The method comprises a step of transmitting an MPDU length, which is the frame length of each MPDU, to a PHY layer, and a step of blocking and decoding the MPDU based on a predetermined encoded block length, and HARQ is configured in the frame. If HARQ is not configured in the frame, the one block is not allowed to contain information of two or more MPDUs, and if the frame is not configured with HARQ, the one block contains information of two or more MPDUs. information is allowed to be included.

According to the present invention, it is possible to efficiently combine packets during retransmission under the IEEE802.11 standard, and it can contribute to improving low-latency communication and increasing user throughput by improving reception SNR.

FIG. 2 is a schematic diagram illustrating an example of dividing radio resources according to one aspect of the present invention. FIG. 2 is a diagram illustrating an example of a frame configuration according to one aspect of the present invention. FIG. 2 is a diagram illustrating an example of a frame configuration 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 illustrating an example of a configuration of a communication system according to one aspect of the present invention. FIG. 1 is a block diagram illustrating a configuration example of a wireless communication device according to one aspect of the present invention. FIG. 1 is a block diagram illustrating a configuration example of a wireless communication device according to one aspect of the present invention. FIG. 2 is a schematic diagram illustrating an example of an encoding method according to one aspect of the present invention. FIG. 2 is a schematic diagram illustrating an example of a modulation and coding method according to one aspect of the present invention. FIG. 2 is a schematic diagram showing an example of block length of LDPC encoding processing according to one aspect of the present invention. FIG. 2 is a schematic diagram illustrating an example of blocking processing according to one aspect of the present invention. FIG. 2 is a schematic diagram illustrating an example of blocking processing according to one aspect of the present invention.

The communication system in this embodiment includes an access point device (or base station device) and a plurality of station devices (or terminal devices). In addition, a communication system or network composed of an access point device and a station device is called a basic service set (BSS, management range, cell). Furthermore, 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 function of a station device. Therefore, in the following, when a communication device is simply referred to, the communication device can refer to both a station device and an access point device.

It is assumed that base station devices and terminal devices within a BSS perform communication based on CSMA/CA (Carrier sense multiple access with collision avoidance). In this embodiment, an infrastructure mode in which a base station apparatus communicates with a plurality of terminal apparatuses is targeted, 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, a terminal device forms a BSS in place of a base station device. BSS in ad hoc mode is also called IBSS (Independent Basic Service Set). In the following, a terminal device that forms an IBSS in ad hoc mode can also be regarded as a base station device. The method of this embodiment can also be implemented using WiFi Direct (registered trademark), in which terminal devices directly communicate with each other. In WiFi Direct, a terminal device forms a group in place of a base station device. In the following, 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 IEEE 802.11 system, each device can transmit frames of multiple frame types with a common frame format. Transmission frames are defined in a physical (PHY) layer, a medium access control (MAC) layer, and a logical link control (LLC) layer, respectively.

The transmission frame of the PHY layer is a physical protocol data unit (PPDU).
data unit (physical layer frame). A PPDU consists of a physical layer header (PHY header) that includes header information for signal processing on the physical layer, and a physical service data unit (PSDU) that is a data unit processed on the physical layer. MAC layer frame), etc. A PSDU can be composed of an aggregated MPDU (A-MPDU) in which a plurality of MAC protocol data units (MPDUs), which are retransmission units in a 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 obtain channel information for data demodulation, etc. , and a control signal such as a signal (SIG) containing control information for data demodulation. In addition, STF can be classified into legacy STF (L-STF), high throughput STF (HT-STF), and very high throughput STF (VHT-STF), depending on the corresponding standard. It is classified into high throughput-STF), high efficiency STF (HE-STF), and extremely high throughput STF (EHT-STF), and LTF and SIG are similarly classified into L- 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-A1-4 and HE-SIG-B. Furthermore, assuming technology updates in the same standard, a Universal SIGNAL (U-SIG) field containing additional control information may be included.

Furthermore, the PHY header can include information that identifies the BSS that is the 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. Further, the information identifying the BSS can be a value unique to the BSS (eg, BSS Color, etc.) other than the SSID or MAC address.

The PPDU is modulated according to the corresponding standard. For example, in the case of the IEEE802.11n standard, the signal is modulated into an orthogonal frequency division multiplexing (OFDM) signal.

MPDU consists of a MAC layer header (MAC header) containing header information for signal processing in the MAC layer, and a MAC service data unit (MSDU) or MAC service data unit (MSDU), which is a data unit processed in the MAC layer. It consists of a frame body and a frame check sequence (FCS) that checks whether there are any errors in the frame. Further, a plurality of MSDUs can be aggregated as an aggregated MSDU (A-MSDU).

The frame types of MAC layer transmission frames are broadly classified into three types: management frames that manage the connection status between devices, control frames that manage the communication status between devices, and data frames that include actual transmission data. Each of these is further classified into multiple subframe types. The control frame includes a reception completion notification (Ack: Acknowledgment).
ledge) frame, request to send (RTS) frame, clear to send (CTS) frame, etc. 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 frame, a polling (CF-poll) frame, and the like. Each device can understand the frame type and subframe type of the received frame by reading the contents of the frame control field included in the MAC header.

Note that Ack may include Block Ack. Block Ack can notify reception completion for multiple MPDUs. Further, the Ack may include a Multi STA Block Ack (M-BA) that includes a reception completion notification for multiple communication devices.

The beacon frame includes a field in which a beacon is transmitted (Beacon interval) and an SSID. The base station device can periodically broadcast a beacon frame within the BSS, and by receiving the beacon frame, the terminal device can know base station devices around the terminal device. The process in which a terminal device learns about a base station device based on a beacon frame broadcast from the base station device is called passive scanning. On the other hand, when a terminal device broadcasts a probe request frame within the BSS to search for a base station device, this is called active scanning. The base station device can transmit a probe response frame as a response to the probe request frame, and the content of the probe response frame is equivalent to that of a beacon frame.

After the terminal device recognizes the base station device, it performs a connection process to the base station device. The connection process is classified into an authentication procedure and an association procedure. A terminal device transmits an authentication frame (authentication request) to a base station device with which it wishes to connect. Upon receiving the authentication frame, the base station device transmits an authentication frame (authentication response) including a status code indicating whether or not the terminal device can be authenticated to the terminal device. By reading the status code written in the authentication frame, the terminal device can determine whether or not the terminal device is authorized to be authenticated by the base station device. Note that the base station device and the terminal device can exchange authentication frames multiple times.

Following the authentication procedure, the terminal device transmits a connection request frame to the base station device in order to perform a connection procedure. When the base station device receives the connection request frame, it determines whether or not to permit connection of the terminal device, and transmits a connection response frame to notify that fact. In addition to a status code indicating whether connection processing is possible or not, the connection response frame includes an association identifier (AID) for identifying the terminal device. The base station apparatus can manage a plurality of terminal apparatuses by setting a different AID for each terminal apparatus that has 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, there are a distributed control mechanism (DCF: Distributed Coordination Function), a centralized control mechanism (PCF: Point Coordination Function), and an expanded mechanism of these (enhanced distributed channel access (EDCA), A hybrid control function (HCF: Hybrid coordination function, etc.) is defined. In the following, a case where a base station device transmits a signal to a terminal device using DCF will be described as an example, but the same applies to a case where a signal is transmitted from a terminal device to a base station device using DCF.

In DCF, before communication, a base station device and a terminal device perform carrier sense (CS) to check the usage status of wireless channels in the vicinity of the base station device and the terminal device. For example, if a base station device that is a transmitting station receives a signal higher than a predetermined clear channel assessment level (CCA level) on the wireless channel, it stops transmitting the transmission frame on the wireless channel. put off. Hereinafter, a state in which a signal higher than the CCA level is detected in the radio channel will be referred to as a busy state, and a state in which a signal higher than the CCA level is not detected will be referred to as an idle state. In this way, CS performed by each device based on the power (reception power level) of the signal actually received is called physical carrier sense (physical CS). Note that the CCA level is also called a carrier sense level (CS level) or a CCA threshold (CCA threshold: CCAT). Note that when the base station device and the terminal device detect a signal of the CCA level or higher, they start an operation of demodulating at least the PHY layer signal.

The base station apparatus performs carrier sense on the transmission frame to be transmitted by a frame interval (IFS) depending on the type, and determines whether the wireless channel is in a busy state or an idle state. The period during which the base station device carries out carrier sensing differs depending on the frame type and subframe type of the transmission frame that the base station device will transmit from now on. In the IEEE 802.11 system, multiple IFS with different periods are defined.Short IFS (SIFS) is used for transmission frames given the highest priority, and Short IFS is used for transmission frames with relatively high priority. There are a polling frame interval (PCF IFS: PIFS) used, a distributed control frame interval (DCF IFS: DIFS) used for the lowest priority transmission frame, etc. When the base station device transmits a data frame using DCF, the base station device uses DIFS.

After waiting for DIFS, the base station apparatus further waits for a random backoff time to prevent frame collisions. In the IEEE 802.11 system, a random backoff time called a 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 transmitting stations transmit frames at the same timing, the frames will collide with each other, and the receiving station will not be able to receive the frames correctly. Therefore, frame collisions are avoided by each transmitting station waiting for a randomly set time before starting transmission. When the base station device determines that the wireless channel is in an idle state through carrier sense, it starts counting down the CW, and only when the CW reaches 0 does it acquire the transmission right and can transmit a transmission frame to the terminal device. Note that if the base station apparatus determines that the wireless channel is in a busy state through carrier sense during the CW countdown, the CW countdown is stopped. Then, when the wireless channel becomes idle, the base station device restarts the countdown of the remaining CW following the previous IFS.

Next, details of frame reception will be explained. A terminal device, which is a receiving station, receives a transmission frame, reads a PHY header of the transmission frame, and demodulates the received transmission frame. Then, by reading the MAC header of the demodulated signal, the terminal device can recognize whether the transmission frame is addressed to the terminal device itself. Note that the terminal device may also determine the destination of the transmission frame based on the information written in the PHY header (for example, the group identification number (GID: Group ID) written in VHT-SIG-A). It is possible.

If the terminal device determines that the received transmission frame is addressed to its own device and is able to demodulate the transmission frame without error, it transmits an ACK frame indicating that the frame was correctly received to the base station device that 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 is taken). The base station device ends a series of communications upon receiving the ACK frame transmitted from the terminal device. Note that if the terminal device cannot correctly receive the frame, the terminal device does not transmit an ACK. Therefore, if the base station apparatus does not receive an ACK frame from the receiving station for a certain period (SIFS+ACK frame length) after transmitting the frame, the base station apparatus considers the communication to have failed and terminates the communication. In this way, the end of one communication (also called a burst) in the IEEE 802.11 system occurs in special cases such as when transmitting a broadcast signal such as a beacon frame, or when fragmentation is used to divide transmitted data. Except for the following cases, the determination is always made based on whether or not an ACK frame is received.

If the terminal device determines that the received transmission frame is not addressed to itself, it uses a network allocation vector (NAV) based on the length of the transmission frame written in the PHY header etc. vector). The terminal device does not attempt communication during the period set in NAV. In other words, since the terminal device performs the same operation for a period set in NAV as when it determines that the wireless channel is in a busy state based on physical CS, communication control using NAV is also called virtual carrier sense (virtual CS). In addition to being set based on the information described in the PHY header, NAV is also set based on request to send (RTS) frames, which are introduced to solve the hidden terminal problem, and clear ready to receive (CTS) frames. to send) frame.

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

The communication period by PCF includes a contention free period (CFP) and a contention period (CP). Communication is performed between the CPs based on the DCF described above, and the PC controls transmission rights between the CFPs. A base station device, which is a PC, broadcasts a beacon frame in which a CFP period (CFP Max duration) and the like are described within the BSS prior to PCF communication. Note that PIFS is used to transmit the beacon frame broadcast at the start of PCF transmission, and is transmitted without waiting for CW. The terminal device that has received the beacon frame sets the CFP period written in the beacon frame to NAV. From then on, the terminal device sends a signal to acquire the transmission right transmitted from the PC until the NAV elapses or a signal notifying the end of CFP is received within the BSS (for example, a data frame including CF-end). The transmission right can be acquired only when a signal (for example, a data frame including CF-poll) is received. Note that within the CFP period, packet collisions within the same BSS do not occur, so each terminal device does not take the random backoff time used in DCF.

A wireless medium may be divided into multiple resource units (RUs). FIG. 1 is a schematic diagram showing an example of a divided state of a wireless medium. For example, in resource division example 1, the wireless communication device can divide the frequency resource (subcarrier), which is a wireless medium, into nine RUs. Similarly, in resource division example 2, the wireless communication device can divide the subcarrier, which is a wireless medium, into five RUs. Naturally, the example of resource division shown in FIG. 1 is just one example, and for example, a plurality of RUs can be configured with different numbers of subcarriers. Furthermore, the wireless medium divided into RUs can include not only frequency resources but also spatial resources. A wireless communication device (for example, an AP) can simultaneously transmit frames to multiple terminal devices (for example, multiple STAs) by arranging frames addressed to different terminal devices in each RU. The AP can write information (resource allocation information) indicating the state of division of the wireless medium as common control information in the PHY header of the frame transmitted by the AP itself. Further, the AP can write information (resource unit assignment information) indicating the RU in which frames addressed to each STA are allocated as unique control information in the PHY header of the frame transmitted by the AP.

Furthermore, multiple terminal devices (for example, multiple STAs) can simultaneously transmit frames by arranging and transmitting frames in respective assigned RUs. After receiving a frame (Trigger frame: TF) containing trigger information transmitted from the AP, the plurality of STAs can wait for a predetermined period and then transmit the frame. Each STA can grasp the RU assigned to its own device based on the information described in the TF. Further, each STA can acquire an RU by random access based on the TF.

The AP can simultaneously allocate multiple RUs to one STA. The plurality of RUs can be made up of continuous subcarriers or can be made up of 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 is a Resource
The frame may include common control information for multiple terminal devices that transmit allocation information.

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

The AP can assign multiple AIDs to one STA. The AP can allocate RUs to each of multiple AIDs allocated 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 of different frame types.

One STA can be assigned multiple AIDs by the AP. One STA can be assigned RUs to each of a plurality of assigned AIDs. One STA recognizes that the RUs assigned to each of the multiple AIDs assigned to the own device are all RUs assigned to the own device, and transmits one frame using the multiple assigned RUs. can do. Furthermore, one STA can transmit multiple frames using the assigned multiple RUs. At this time, information indicating the AID associated with each allocated RU can be written 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 may be of different frame types.

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

The wireless communication device has either or both of a function of transmitting a PPDU and a function of receiving a PPDU. FIG. 2 is a diagram illustrating an example of a PPDU configuration transmitted by a wireless communication device. PPDU compatible with the IEEE802.11a/b/g standard has a structure that includes L-STF, L-LTF, L-SIG, and Data frames (MAC Frame, MAC frame, payload, data part, data, information bits, etc.). be. P compatible with IEEE802.11n standard
The PDU has a configuration including L-STF, L-LTF, L-SIG, HT-SIG, HT-STF, HT-LTF, and Data frame. PPDUs compatible with the IEEE802.11ac standard include part or all of L-STF, L-LTF, L-SIG, VHT-SIG-A, VHT-STF, VHT-LTF, VHT-SIG-B, and MAC frames. The structure is as follows. The PPDUs considered in the IEEE802.11ax standard are L-STF, L-LTF, L-SIG, RL-SIG in which L-SIG is temporally repeated, HE-SIG-A, HE-STF, HE- This configuration includes part or all of LTF, HE-SIG-B, and Data frames. The PPDUs considered in the IEEE802.11be standard are L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, EHT-SIG, EHT-STF, EHT-LTF, and part of the Data frame or This is a configuration that includes everything.

L-STF, L-LTF, and L-SIG surrounded by dotted lines in Figure 2 are configurations commonly used in the IEEE802.11 standard (below, L-STF, L-LTF, and L-SIG are (also collectively referred to as L-header). For example, a wireless communication device compatible with the IEEE 802.11a/b/g standard can appropriately receive an L-header in a PPDU compatible with the IEEE 802.11n/ac standard. A wireless communication device compatible with the IEEE 802.11a/b/g standard can receive a PPDU compatible with the IEEE 802.11n/ac standard, regarding it as a PPDU compatible with the IEEE 802.11a/b/g standard. .

However, wireless communication devices compatible with the IEEE 802.11a/b/g standards cannot demodulate the PPDU that follows the L-header and supports the IEEE 802.11n/ac standards. ), the receiving address (RA), and information regarding the Duration/ID field used for setting the NAV cannot be demodulated.

IEEE 802.11 inserts Duration information into L-SIG as a method for wireless communication devices compatible with the IEEE 802.11a/b/g standards to appropriately set NAV (or perform reception operations for a predetermined period). It stipulates how to do so. Information regarding the transmission rate (RATE field, L-RATE field, L-RATE, L_DATARATE, L_DATARATE field) and information regarding the transmission period (LENGTH field, L-LENGTH field, L-LENGTH) within L-SIG is based on IEEE 80. 2. A wireless communication device compatible with the 11a/b/g standard is used to appropriately set the NAV.

FIG. 3 is a diagram illustrating an example of a method for inserting Duration information into L-SIG. Although FIG. 3 shows a PPDU configuration compatible with the IEEE802.11ac standard as an example, 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 includes information regarding the length of the PPDU, aPreambleLength includes information regarding the length of the preamble (L-STF+L-LTF), and aPLCPHeaderLength includes information regarding the length of the PLCP header (L-SIG). L_LENGTH is Signal Extension, which is a virtual period set for compatibility with the IEEE 802.11 standard, N _ops related to L_RATE, and aSymbolLength, which is information regarding the period of one symbol (symbol, OFDM symbol, etc.). 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. In addition, the wireless communication device is an L-SI
G Duration can be calculated. L-SIG Duration indicates information regarding the total period of the PPDU including L_LENGTH and the period of the Ack and SIFS expected to be transmitted from the destination wireless communication device in response.

FIG. 4 is a diagram showing an example of L-SIG Duration in L-SIG TXOP Protection. DATA (frame, payload, data, etc.) is composed of a MAC frame and a part or both of a PLCP header. Moreover, BA is Block Ack or Ack. The PPDU can be configured to include L-STF, L-LTF, and L-SIG, and further include one or more of DATA, BA, RTS, and CTS. Although the example shown in FIG. 4 shows L-SIG TXOP Protection using RTS/CTS, CTS-to-Self may also be used. Here, MAC Duration is a period indicated by the value of Duration/ID field. Additionally, 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 a 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 must include information for identifying the BSS (BSS color, BSS identification information, a value unique to the BSS) in the PPDU. It is preferable to insert it. Information indicating the BSS color can be written in HE-SIG-A.

The wireless communication device can transmit L-SIG multiple times (L-SIG Repetition). For example, by receiving L-SIG transmitted multiple times using MRC (Maximum Ratio Combining), a wireless communication device on the receiving side improves the demodulation accuracy of L-SIG. Furthermore, when the wireless communication device completes correctly receiving the L-SIG using MRC, it can interpret that the PPDU including the L-SIG is a PPDU that complies with the IEEE802.11ax standard.

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

Ack and BA can also be called a response (response frame). Further, a probe response, an authentication response, and a connection response can be called a response.
[1. First embodiment]

FIG. 5 is a diagram showing an example of a wireless communication system according to this embodiment. The wireless communication system 3-1 includes a wireless communication device 1-1 and wireless communication devices 2-1 to 2-3. Note that the wireless communication device 1-1 is also referred to as the base station device 1-1, and the wireless communication devices 2-1 to 2-3 are also referred to as the terminal devices 2-1 to 2-3. Furthermore, the wireless communication devices 2-1 to 2-3 and the terminal devices 2-1 to 2-3 are also referred to as the wireless communication device 2A and the 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 where they can send and receive PPDUs to and from each other. Further, the wireless communication system according to this embodiment may include a wireless communication system 3-2 in addition to the wireless communication system 3-1. The wireless communication system 3-2 includes a wireless communication device 1-2 and wireless communication devices 2-4 to 2-6. Note that the wireless communication device 1-2 is also referred to as the base station device 1-2, and the wireless communication devices 2-4 to 2-6 are also referred to as the terminal devices 2-4 to 2-6. Furthermore, the wireless communication devices 2-4 to 6 and the terminal devices 2-4 to 6 are also referred to as the wireless communication device 2B and the terminal device 2B as devices connected to the wireless communication device 1-2. Although the wireless communication system 3-1 and the wireless communication system 3-2 form different BSSs, this does not necessarily mean that their ESSs (Extended Service Sets) are different. ESS indicates a service set forming a LAN (Local Area Network). In other words, wireless communication devices belonging to the same ESS can be considered by the upper layer to belong to the same network. Further, the BSSs are combined via a DS (Distribution System) to form an ESS. Note that each of the wireless communication systems 3-1 and 3-2 may further include a plurality of wireless communication devices.

In FIG. 5, in the following description, it is assumed that a signal transmitted by the wireless communication device 2A reaches the wireless communication device 1-1 and the wireless communication device 2B, but does not reach the wireless communication device 1-2. do. In other words, when the wireless communication device 2A transmits a signal using a certain channel, the wireless communication device 1-1 and the wireless communication device 2B determine that the channel is busy, while the wireless communication device 1-2 The channel is determined to be in an idle state. Further, it is assumed that a signal transmitted by the wireless communication device 2B reaches the wireless communication device 1-2 and the wireless communication device 2A, but does not reach the wireless communication device 1-1. In other words, when the wireless communication device 2B transmits a signal using a certain channel, the wireless communication device 1-2 and the wireless communication device 2A determine that the channel is busy, while the wireless communication device 1-1 The channel is determined to be in an idle state.

FIG. 6 shows an example of the device configuration of wireless communication devices 1-1, 1-2, 2A, and 2B (hereinafter also collectively referred to as wireless communication device 10-1 or station device 10-1 or simply station device). This 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. The configuration includes (receiving step) 10004-1 and an antenna section 10005-1.

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

FIG. 7 is a diagram showing an example of the device configuration of the autonomous decentralized control unit 10002-1. The control unit 10002-1 has a configuration including a CCA unit (CCA step) 10002a-1, a backoff unit (backoff step) 10002b-1, and a transmission determination unit (transmission determination step) 10002c-1.

The CCA section 10002a-1 receives either or both of the information regarding the received signal power received via the radio resource and the information regarding the received signal (including information after decoding), which is notified from the receiving section 10004-1. can be used to determine the status of the wireless resource (including determining whether it is busy or idle). The CCA unit 10002a-1 can notify the backoff unit 10002b-1 and the transmission determination unit 10002c-1 of the status determination information of the radio resource.

The backoff unit 10002b-1 can perform backoff using the wireless resource state determination information. The backoff unit 10002b-1 generates a CW and has a countdown function. For example, when the wireless resource status determination information indicates idle, the CW countdown can be executed, and when the wireless resource status 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 determination unit 10002c-1 makes a transmission determination using either or both of the radio resource state determination information and the CW value. For example, when the wireless resource status determination information indicates idle and the CW value is 0, transmission determination information can be notified to the transmitter 10003-1. Further, when the wireless resource state determination information indicates idle, transmission determination information can be notified to the transmitter 10003-1.

The transmitting unit 10003-1 has a configuration including a physical layer frame generating unit (physical layer frame generating step) 10003a-1 and a wireless transmitting unit (wireless transmitting step) 10003b-1. The physical layer frame generation unit 10003a-1 has a function of generating a physical layer frame (PPDU) based on the transmission determination information notified from the transmission determination unit 10002c-1. The physical layer frame generation unit 10003a-1 performs error correction encoding, modulation, precoding filter multiplication, etc. on the transmission frame sent from the upper layer. Physical layer frame generation section 10003a-1 notifies wireless transmission section 10003b-1 of the generated physical layer frame.

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

The wireless transmitter 10003b-1 converts the physical layer frame generated by the physical layer frame generator 10003a-1 into a signal in a radio frequency (RF) band, and generates a radio frequency signal. The processing performed by the wireless transmitter 10003b-1 includes digital-to-analog conversion, filtering, frequency conversion from a baseband band to an 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 regarding received signal power from the RF band signal received by antenna section 10005-1. The receiving section 10004-1 can notify the CCA section 10002a-1 of information regarding received signal power and information regarding the received signal.

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

The signal demodulator 10004b-1 has a function of demodulating the physical layer signal generated by the wireless receiver 10004a-1. Processing performed by signal demodulation section 10004b-1 includes channel equalization, demapping, error correction decoding, and the like. The signal demodulation unit 10004b-1 can extract, for example, information included in the physical layer header, information included in the MAC header, and information included 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. Note that the signal demodulator 10004b-1 can extract any or all of the information included in the physical layer header, the MAC header, and the transmission frame.

Antenna section 10005-1 has a function of transmitting a radio frequency signal generated by radio transmitting section 10003b-1 into radio space. Furthermore, the antenna section 10005-1 has a function of receiving a radio frequency signal and passing 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 and MAC header of the frame to be transmitted, thereby informing wireless communication devices around the wireless communication device of the wireless communication device 10-1. NAV can be set only for a certain period. For example, the wireless communication device 10-1 can write information indicating the period in the Duration/ID field or Length field of the frame to be transmitted. The NAV period set in wireless communication devices around the own wireless communication device will be referred to as the TXOP period (or simply TXOP) acquired by the wireless communication device 10-1. The wireless communication device 10-1 that has acquired the TXOP is called a TXOP acquirer (TXOP holder). The frame type of the frame that the wireless communication device 10-1 transmits to obtain TXOP is not limited to any particular type, 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 between the TXOPs. If the wireless communication device 1-1 is a TXOP holder, the wireless communication device 1-1 can transmit a frame to the wireless communication device 2A within the period of the TXOP. Furthermore, the wireless communication device 1-1 can instruct the wireless communication device 2A to transmit a frame addressed to the wireless communication device 1-1 within the TXOP period. The wireless communication device 1-1 can transmit a trigger frame including information instructing the wireless communication device 1-1 to transmit a frame to the wireless communication device 2A within the TXOP period.

The wireless communication device 1-1 may secure TXOP for all communication bands (for example, Operation bandwidth) in which frames may be transmitted, or may secure TXOP for all communication bands (for example, Operation bandwidth) in which frames may be transmitted (for example, Transmission bandwidth). may be reserved for a specific communication band.

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

Furthermore, 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 specifies TXOP from the viewpoint of guaranteeing QoS (Quality of Service) for various services such as video transmission and VoIP. Services are broadly divided into VO (VOice), VI (VIdeo), and BE (Best).
It is classified into four access categories: Effort) and BK (BacK ground). Generally, the order of priority is VO, VI, BE, and BK. Each access category has parameters such as the minimum CW value CWmin, the maximum value CWmax, AIFS (Arbitration IFS), which is a type of IFS, and TXOP limit, which is the upper limit of transmission opportunities. The value is set. For example, the CWmin, CWmax, and AIFS of a VO with the highest priority for audio transmission can be set to relatively small values compared to other access categories, thereby allowing data to be prioritized over other access categories. Transmission becomes possible. For example, in a VI where the amount of data to be transmitted is relatively large due to video transmission, by setting a large TXOP limit, it is possible to take a longer transmission opportunity than in other access categories. In this way, the values of the four parameters for each access category are adjusted for the purpose of guaranteeing QoS according to various services.

FIG. 8 is a diagram showing an example of error correction encoding by the physical layer frame generation unit 10003a-1 according to this embodiment. As shown in FIG. 8, information bit (systematic bit) sequences are placed in the shaded area, and redundant (parity) bit sequences are placed in the white area. A bit interleaver is appropriately applied to each of the information bits and redundant bits. The physical layer frame generation unit 10003a-1 can read out the required number of bits from the arranged bit sequence as a starting position determined according to the value of the redundancy version (RV). By adjusting the number of bits, the coding rate can be changed flexibly, that is, puncturing can be performed. Note that in FIG. 8, a total of four types of RV are shown, but in the error correction encoding according to this embodiment, the options for RV are not limited to specific values. The location of the RV needs to be shared between the station devices. Needless to say, the error correction encoding method according to this embodiment is not limited to the example shown in FIG. 8, and any method may be used as long as the encoding rate can be changed and the decoding process on the receiving side can be achieved.

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. This is not limited to 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. Note that 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 described using FIGS. 6 and 7, unless otherwise specified.

The upper layer unit 10001-1 of the wireless communication device 1-1 according to the present embodiment generates a MAC layer payload A- After composing the MPDU, it is transferred to the transmitter 10003-1. Further, upper layer section 10001-1 transfers control information including retransmission method settings to transmitting section 10003-1. The retransmission method setting is, for example, information indicating either ARQ or HARQ, or HARQ setting information. The HARQ configuration information is information indicating whether HARQ is configured. Note that if HARQ is not configured, the PHY layer determines that ARQ is configured. When the information bit sequence is composed of one MPDU, the settings of the MPDU, MPDU length, and retransmission method are transferred to the lower layer transmitter. On the other hand, when the information bit sequence is composed of A-MPDUs and the retransmission scheme setting indicates ARQ, the A-MPDUs and A-MPDU lengths are transferred to the lower layer transmitter. When the retransmission method setting indicates HARQ, part or all of the A-MPDU, A-MPDU length, each MPDU length, and the number of MPDUs are transferred to the lower layer transmitter. The MPDU may constitute one MSDU or an A-MSDU that is an aggregation of two or more MSDUs. Note that the MAC layer control information of the upper layer section 10001-1 does not necessarily include an information field that stores the MPDU length and the number of MPDUs when the retransmission method is not specified as HARQ.

The physical layer frame generation unit 10003a-1 of the wireless communication device 1-1 according to the present embodiment first generates a PSDU, which is a PHY layer payload, from the A-MPDU transferred by the upper layer unit 10001-1. The PSDU is attached with a PHY header to generate a PPDU of a transmission frame. The PHY header includes a PLCP preamble for synchronization detection, a PLCP header for determining a modulation and coding scheme (MCS) according to the received signal strength, and a MAC layer of the upper layer section 10001-1. Control information, and when an information field of MPDU length is added to the control information, an information field of a predetermined information bit length (encoded block length) to which error correction encoding is applied corresponding to each information field. include. Note that when the MAC layer of the upper layer section 10001-1 does not set MPDU aggregation, the PHY header may store the predetermined information bit length in the information field.

For example, error correction encoding using low density parity check code (LDPC) of the IEEE802.11 standard first obtains a generator matrix from a low density parity check matrix, and then combines the generator matrix with a matrix of information bits. Generate a parity bit calculated from the product. Next, the parity bit is added to the information bit sequence to form a code word. That is, the physical layer frame generation unit 10003a-1 calculates a predetermined information bit length to be subjected to error correction encoding based on the size of the parity check matrix set by the MCS coding rate. Note that the information bit sequence used for LDPC encoding is also referred to as an LDCP information block, and the bit sequence obtained by LDPC encoding the LDPC information block is also referred to as an LDPC codeword block.

FIG. 9 shows an example of association between MCS, modulation method, and coding rate. For example, when MCS is 1, the modulation method is QPSK and the coding rate is 1/2, and when MCS is 4, the modulation method is 16QAM and the coding rate is 3/4. Further, FIG. 10 shows an example of the association between the coding rate, the LDPC information block length, and the LDPC codeword block length. Multiplying the LDPC code word block length by the coding rate gives the LDPC information block length. For example, when the coding rate is 1/2, the candidates for (LDPC information block length, LDPC code word 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 be different from the information block length and codeword block length to be transmitted.

FIG. 11 is a schematic diagram showing an example of the blocking process of the physical layer frame generation unit 10003a-1 when the retransmission method setting indicates ARQ. The physical layer frame generation unit 10003a-1 in the figure divides the PSDU into information blocks, which are multiple payloads, with a predetermined information bit length determined by the MCS included in the PHY header, and performs error correction on each information block. A transmission frame is generated by encoding. Note that an information block encoded by error correction is also called a code word block. In the blocking process shown in the figure, the predetermined bit length by which the MAC layer delimits PSDUs may not match the predetermined bit length by which the PHY layer delimits PSDUs. That is, the physical layer frame generation unit 10003a-1 allows each information block to include two or more MPDUs. Block #3 and block #6 in FIG. 11 each contain two or more MPDUs, the former storing a part of the information bit sequence contained in MPDU #1-2, and the latter storing a part of the information bit sequence contained in MPDU #2-3. become. Note that in this example, the MAC layer of the upper layer section 10001-1 that has received the Block Ack in the transmission frame retransmits MPDU #2 because an error has been detected in MPDU #2. When retransmitting MPDU #2, the PHY layer divides the PSDU into blocks and transmits them. However, if a PHY layer block includes multiple MPDUs, it may be divided into blocks different from those at the time of initial transmission, and in this case , different codeword blocks are transmitted. In this case, the receiving side cannot combine the first transmitted MPDU #2 and the retransmitted MPDU #2.

An example of a procedure in which the physical layer frame generation unit 10003a-1 divides a PSDU (A-MPDU) into information blocks when the retransmission method setting indicates ARQ will be described. The LDPC codeword block length is determined by the encoded bit length (also referred to as the first encoded bit length) calculated based on at least the PSDU length (A-MPDU length) and the encoding rate. For example, in the example of FIG. 10, when the first encoded bit length is 648 bits or less, the LDPC codeword block length ( _LCW ) is 648 bits. Next, when the first encoded bit length is greater than 648 bits and less than or equal to 1296 bits, the LDPC codeword block length is 1296 bits. When the first encoded bit length is greater than 1296 bits and less than or equal to 1944 bits, the LDPC codeword block length is 1944 bits. Note that when the first encoded bit length is 1944 bits or less, the number of LDPC codeword blocks (N _CW ) is 1. When the first encoded bit length is greater than 1944 bits and less than or equal to 2592 bits, the LDPC codeword block length is 1296 bits and the number of LDPC codeword blocks is 2. When the LDPC codeword block length is larger than 2592 bits, the LDPC codeword block length is 1944 bits, and the number of LDPC codeword blocks is calculated from the first coded bit length and the LDPC codeword block length of 1944 bits to ceil(th). It can be calculated as the encoded bit length of 1/1944). Note that ceil(x) is a ceiling function and represents the smallest integer greater than or equal to x.

N _CW・L If _CW・R is different from the PSDU length, shortening processing is performed. Note that R indicates a coding rate. N _CW・L The difference between _CW・R and the PSDU length is expressed as N _shrt . N _shrt is equally distributed to each information block. That is, the shortening bit N _shblk of each information block becomes floor(N _shrt /N _CW ). However, floor(x) is a floor function and represents the largest integer less than or equal to x. Note that the first N _short mod N _CW block has one more shortening bit than the other blocks. However, mod represents the remainder. The shortening process adds N _shblk (or N _shblk +1) bits to the information block to generate an LDPC information block. Therefore, the PSDU is divided into information blocks in consideration of shortening processing. The LDPC information block is LDPC encoded to generate an LDPC codeword block, but the shortening bits are discarded.

If N _CW ·L _CW and (first encoded bit length+N _shrt ) are different, puncturing processing is performed to discard (thin out) parity bits. The difference between N _CW ·L _CW and (first encoded bit length+N _shrt ) is expressed as N _punc . N _punc is equally distributed to each codeword block. That is, the puncturing bit N _pcblk of each codeword block becomes floor(N _punc /N _CW ). Note that the first N _punc mod N _CW block has one more puncturing bit than the other blocks. In the puncturing process, the last N _pcblk (or N _pcblk +1) bits of the LDPC codeword block are discarded. The codeword block to be transmitted is generated by the shortening process and the puncturing process.

FIG. 12 is a schematic diagram showing an example of the blocking process of the physical layer frame generation unit 10003a-1 when the MAC layer control information includes the MPDU length information field (when the retransmission method setting indicates HARQ). It is. The physical layer frame generation unit 10003a-1 in the figure divides each MPDU constituting the PSDU into multiple pieces based on the MPDU length of the control information in addition to the predetermined information bit length defined by the MCS included in the PHY header. Split into information blocks. The physical layer frame generation unit 10003a-1 also calculates the information block length and stores it in the information field of the header. Note that when the MPDU length is an integral multiple of the information block length, the number of information blocks may be stored in the PHY header. Thereafter, each information block is subjected to error correction encoding to generate a transmission frame. In the blocking process shown in the figure, one MPDU is composed of one or more information blocks. That is, the physical layer frame generation unit 10003a-1 is not permitted to allow each block to include two or more MPDUs. Blocks #4 to #6 in the figure each store an information bit sequence of MPDU #2. Note that in this example, the MAC layer of the upper layer section 10001-1 that has received the Block Ack in the transmission frame retransmits MPDU #2 because an error has been detected in MPDU #2. Since each MPDU is divided into information blocks, it is possible to transmit the same code word block at the time of retransmission as at the time of initial transmission. In this case, on the receiving side, it is possible to improve the reception quality by combining the first transmitted MPDU #2 and the retransmitted MPDU #2.

When the retransmission scheme setting indicates HARQ, the LDPC codeword block length is at least MP
It is determined by the encoding bit length (also referred to as the second encoding bit length) calculated based on the DU length and the encoding rate. Note that when the MPDU length changes for each MPDU, the second encoded bit length is calculated for each MPDU. For example, when the second encoded bit length is 648 bits or less, the LDPC codeword block length is 648 bits. Furthermore, when the second encoded bit length is greater than 648 bits and less than or equal to 1296 bits, the LDPC codeword block length is 1296 bits. Furthermore, when the second encoded bit length is greater than 1296 bits and less than or equal to 1944 bits, the LDPC codeword block length is 1944 bits. Note that when the second encoded bit length is 1944 bits or less, the number of LDPC code word blocks is 1. When the second encoded bit length is greater than 1944 bits and less than or equal to 2592 bits, the LDPC codeword block length is 1296 bits and the number of LDPC codeword blocks is 2. When the LDPC codeword block length is larger than 2592 bits, the LDPC codeword block length becomes 1944 bits, and the number of LDPC codeword blocks is calculated from the second coded bit length and the LDPC codeword block length of 1944 bits to ceil(th). It can be calculated as the encoding bit length of 2/1944).

When the retransmission method setting indicates HARQ, shortening processing is performed for each MPDU. N _CW・L If _CW・R is different from the MPDU length, shortening processing is performed. The difference between N _CW L _CW R and the MPDU length is expressed as N _shrt . N _shrt is equally distributed to each information block. That is, the shortening bit N _shblk of each information block becomes floor(N _shrt /N _CW ). Note that the first N _short mod N _CW block has one more shortening bit than the other blocks. However, mod represents the remainder. The shortening process adds N _shblk (or N _shblk +1) bits to the information block to generate an LDPC information block. Therefore, the PSDU is divided into information blocks in consideration of shortening processing. The LDPC information block is LDPC encoded to generate an LDPC codeword block, but the shortening bits are discarded.

When the retransmission method setting indicates HARQ, puncturing processing is performed for each MPDU. If N _CW ·L _CW and (second encoded bit length+N _shrt ) are different, puncturing processing is performed. The difference between N _CW ·L _CW and (second encoded bit length+N _shrt ) is expressed as N _punc . N _punc is equally distributed to each codeword block. That is, the puncturing bit N _pcblk of each codeword block becomes floor(N _punc /N _CW ). Note that the first N _punc mod N _CW block has one more puncturing bit than the other blocks. In the puncturing process, the last N _pcblk (or N _pcblk +1) bits of the LDPC codeword block are discarded. The codeword block to be transmitted is generated by the shortening process and the puncturing process.

On the other hand, when the MAC layer control information includes an information field of MPDU length (when the retransmission method setting indicates ARQ), the physical layer frame generation unit 10003a-1 according to the present embodiment responds to the MCS and MPDU length. By referring to a table or calculation formula that can calculate the encoded block length, it is also possible to perform blocking processing of PSDUs using the encoded block length.

Note that the encoding method according to this embodiment is not limited to LDPC. For example, the transmitting device according to this embodiment can also use a binary convolutional code (BCC). In this case, the transmitting device can use the BCC to use the blocking processing method described above, that is, the blocking processing when ARQ is set and when HARQ is set. For example, when HARQ is configured, the transmitting device can match the number of information bits included in the information block to the number of bits included in the MPDU. Further, the transmitting device can match an integral multiple of the number of information bits included in the information block to the number of bits included in the MPDU.

Further, the transmitting device according to the present embodiment can switch blocking processing depending on the error correction encoding method set in the PHY layer. For example, when BCC is set as the error correction encoding method, the transmitting device performs blocking processing assuming ARQ, and when LDPC is set, performing blocking processing assuming HARQ. can do. Further, the transmitting device can perform blocking processing assuming HARQ when BCC is set, and perform blocking processing assuming ARQ when LDPC is set.

The table or calculation formula includes a plurality of MPDU length candidate values for each maximum MPDU size (for example, 3895, 7991, and 11454 bytes for 11ac), and predetermined information to be encoded for each MCS in each MPDU length. Bit length candidate values can be stored. For example, if the length of one MPDU constituting the A-MPDU transferred from the upper layer unit 10001-1 according to the present embodiment is 3895 bytes or less, the transmitting unit may refer to the above table or calculation formula. Then, a candidate value that is the same as the MPDU length of the MPDU or a candidate value with the closest MPDU length is selected, and candidate values of the encoded block length according to the MCS can be acquired in a series as an index. Note that the station device, access point, etc. according to this embodiment can update the table or calculation formula using a management frame such as a beacon frame, and can share the index of the encoded block length.

In the blocking process using the table and calculation formula, the PHY header included in the transmission frame includes a PLCP preamble for synchronization detection, a PLCP header for determining the modulation and coding scheme (MCS) according to the received signal strength, and an upper layer section 10001. -1 MAC layer includes control information for notifying ARQ/HARQ and an index that can refer to the encoded block length.

Note that when the retransmission method setting indicates HARQ, it is also possible to limit the MPDU length and /MCS so that one information block does not include bits of multiple MPDUs. For example, the MPDU length is limited to an integral multiple of the LDPC information block length where the LDPC code word block length is 1944 bits, and the use of MCS other than the coding rate that makes the LDPC block length a divisor of the MPDU is limited. For example, when multiple 1458-byte MPDUs are aggregated to form a PSDU, the MPDU length is divisible by LDPC information blocks with coding rates of 1/2, 2/3, and 3/4, so the PSDU is processed into blocks. Even if the blocking process is performed for each MPDU, the result will not change. Therefore, when the retransmission method setting indicates HARQ and the MPDU length is 1458 bytes, if MCS7 and MCS9 with a coding rate of 5/6, which is an indivisible LDPC information block length, are not used, the retransmission method can be Similarly to the case where the setting indicates ARQ, even if PSDUs are subjected to flocking processing, HARQ combining is possible on the receiving side. Further, even if the retransmission method setting is HARQ, it may also mean ARQ when using limited MCS. For example, when MCS7 is applied when the MPDU length is 1458 bytes, the retransmission method may indicate ARQ. In this case, even if the retransmission method setting indicates HARQ, the wireless communication device 1-1 blocks the PSDU and transmits it.

The wireless communication device 1-1 according to the present embodiment specifies the retransmission method included in the control information notified by the MAC layer of the upper layer section 10001-1 as ARQ/HARQ, thereby adding A-MPDU to the control information. It is possible to set whether or not to add an information field for the length of each constituent MPDU, and it is possible to switch between blocking processing for PSDUs and blocking processing for MPDUs using control information. shall be.

The wireless communication device 1-1 according to the present embodiment uses a beacon frame, a probe response frame, etc. to determine the function information (Capability, Capability element, Capability
information), information indicating whether or not HARQ is set in the frame transmitted by the wireless communication device 1-1 can be included in the function information. Further, the wireless communication device 1-1 can refuse connection to the wireless communication device 1-1 from a communication device that cannot interpret a frame in which HARQ is set.

Further, the wireless communication device 1-1 can determine whether to set HARQ to a frame including the PSDU, based on the length of the PSDU transmitted by the wireless communication device 1-1. For example, if the length of a PSDU exceeds a predetermined length, the wireless communication device may not set HARQ to a frame including the PSDU. Here, the length of the PSDU can be the number of information bits included in the PSDU, the number of bits included in the code word block after error correction encoding, the time length of the frame included in the PSDU, etc. .

Further, the wireless communication device 1-1 can set HARQ in a transmission frame only within a TXOP period acquired by a control frame such as an RTS frame or a CTS frame. The wireless communication device includes information indicating that HARQ is set or that there is a possibility that HARQ is set in frames transmitted within the period of the TXOP in a frame that acquires the TXOP. Can be done. The wireless communication device can transmit a frame for acquiring the TXOP to multiple wireless communication devices. Further, the wireless communication device can include information indicating a plurality of destination wireless communication devices (for example, information including a plurality of AIDs or information directly indicating a plurality of AIDs) in a frame for acquiring the TXOP. A wireless communication device that receives a frame that acquires the TXOP and includes itself as a destination can transmit a response frame to the frame that acquires the TXOP. At this time, the response frame may include information indicating whether the HARQ configured frame can be interpreted. Furthermore, a response frame can be transmitted to the frame for which the TXOP is acquired only if the own device can interpret the frame in which HARQ is configured.

The wireless communication device 2-1 according to this embodiment receives a transmission frame from the wireless communication device 1-1. The signal demodulation unit 10004b-1 of the wireless communication device 2-1 according to this embodiment decodes the code word of the PSDU included in the received transmission frame. The decoding result is then transferred to the upper layer section 10001-1. The upper layer section 10001-1 performs error detection on the frame and determines whether it has been correctly decoded. Error detection uses error detection codes (e.g., cyclic redundancy check (CRC) codes) added to received transmission frames, or error detection using error correction codes (e.g., low-density parity check codes) that originally have an error detection function (e.g., low-density parity check codes). Includes error detection by LDPC).

When the retransmission method setting indicates ARQ, the signal demodulator 10004b-1 in FIG. 11 of the wireless communication device 2-1 according to this embodiment reads the predetermined information bit length and coding rate defined by the MCS from the PHY header, A predetermined information bit length (code word block length) to be decoded is calculated. Then, decoding processing is performed on the error correction encoded PSDU for each code word block. The MAC layer of the upper layer section 10001-1 determines whether the MPDU or A-MPDU has been correctly decoded from the decoded PSDU. For example, in the example of FIG. 11, the MAC layer of the upper layer unit 10001-1 detects an error in MPDU #2, and therefore transmits a Block Ack indicating that MPDU #2 is a NACK to the wireless communication device 1-1. . In order to transmit the new MPDU #4-5 following the MPDU #2, the wireless communication device 1-1 generates a block #9-16 with the encoded block length and generates a retransmission frame. Note that the retransmission frame can also include only the MPDU #2. In the blocking process of FIG. 11, the predetermined bit length by which the MAC layer delimits PSDUs does not match the predetermined bit length by which the PHY layer delimits PSDUs. Therefore, since MPDU #2 included in the retransmission frame and MPDU #2 of the first transmission constitute different code words, the signal demodulation unit 10004b-1 of the wireless communication device 2-1 does not perform packet combining.

An example of a procedure for decoding by the signal demodulating section 10004b-1 of the wireless communication device 2-1 when the retransmission method setting indicates ARQ will be described. First, the first encoded bit length for the PSDU is determined based on the number of OFDM symbols and MCS of the received frame. Then, the LDPC codeword block length is determined from the first encoded bit length. For example, in the example of FIG. 10, when the first encoded bit length is 648 bits or less, the LDPC code word block length is 648 bits. Furthermore, when the first encoded bit length is greater than 648 bits and less than or equal to 1296 bits, the LDPC codeword block length is 1296 bits. If the first encoded bit length is greater than 1296 bits and less than 1944 bits, the LDPC codeword block length is 1944 bits. Note that when the first encoded bit length is 1944 bits or less, the number of LDPC code word blocks is 1. When the first encoded bit length is greater than 1944 bits and less than or equal to 2592 bits, the LDPC codeword block length is 1296 bits and the number of LDPC codeword blocks is 2. When the LDPC codeword block length is larger than 2592 bits, the LDPC codeword block length is 1944 bits, and the number of LDPC codeword blocks is calculated from the first coded bit length and the LDPC codeword block length of 1944 bits to ceil(th). It can be calculated as the encoded bit length of 1/1944). Then, the shortening bit length and puncturing bit length are calculated to obtain the codeword block length. The first coded bits are then divided into codeword blocks. The shortening process and puncturing process performed on the transmitting side are reversely processed on the codeword block to generate an LDCP codeword block. In the reverse process of the shortening process, an LLR (Log Likelihood Ratio) with a large absolute value indicating bit 0 is inserted at the position of the discarded shortening bit on the transmitting side. In the reverse process of the puncturing process, an LLR with a value of 0 is inserted at the position of the discarded puncturing bit on the transmitting side. Error correction decoding is performed on the LDPC code word block to obtain an LDPC information block.

When the retransmission method setting indicates HARQ, the signal demodulator 10004b-1 in FIG. 12 of the wireless communication device 2-1 according to this embodiment extracts the information field of the coding rate and coding block length defined by the MCS from the PHY header. Read and calculate the codeword block length. Then, the PSDU is subjected to decoding processing for each code word block, and the decoding results are transferred to the upper layer section 10001-1. The MAC layer of the upper layer section 10001-1 performs error detection and determines whether the MPDU or A-MPDU has been correctly decoded from the decoded PSDU. In the example of FIG. 12, the MAC layer of the upper layer section 10001-1 detects an error in MPDU #2, and therefore transmits a Block Ack indicating that MPDU #2 is a NACK to the wireless communication device 1-1. The Block Ack frame may include in the information field the sequence number of the information block corresponding to the sequence number of the MPDU in which the error was detected. The wireless communication device 1-1 can transmit the MPDU #2 and a new MPDU #4-5 following the MPDU #2, generate a block #10-18 with the information block length, and configure a retransmission frame. Note that the retransmission frame can also include only the MPDU #2. When the retransmission method setting indicates HARQ, the predetermined bit length by which the MAC layer delimits PSDUs matches a plurality of predetermined bit lengths by which the PHY layer delimits PSDUs. Therefore, the signal demodulator 10004b-1 of the wireless communication device 2-1 can packet-synthesize the retransmitted MPDU #2 and the initially transmitted MPDU #2 stored in the buffer, improving reception power, time diversity effect, etc. It will be done.

An example of a procedure for decoding by the signal demodulating section 10004b-1 of the wireless communication device 2-1 when the retransmission method setting indicates HARQ will be described. First, the second encoding bit length for the MPDU is determined based on the number of OFDM symbols and MCS of the received frame. Then, the LDPC codeword block length is determined from the second encoded bit length. For example, when the second encoded bit length is 648 bits or less, the LDPC codeword block length is 648 bits. Next, when the second encoded bit length is greater than 648 bits and less than or equal to 1296 bits, the LDPC codeword block length is 1296 bits. If the second encoded bit length is greater than 1296 bits but less than or equal to 1944 bits, the LDPC codeword block length is 1944 bits. Note that when the second encoded bit length is 1944 bits or less, the number of LDPC code word blocks is 1. When the second encoded bit length is greater than 1944 bits and less than or equal to 2592 bits, the LDPC codeword block length is 1296 bits and the number of LDPC codeword blocks is 2. When the LDPC codeword block length is larger than 2592 bits, the LDPC codeword block length becomes 1944 bits, and the number of LDPC codeword blocks is calculated from the second coded bit length and the LDPC codeword block length of 1944 bits to ceil(th). It can be calculated as the encoding bit length of 2/1944). Then, the shortening bit length and puncturing bit length are calculated to obtain the codeword block length. The second coded bits are then divided into codeword blocks. The shortening process and puncturing process performed on the transmitting side are reversely processed on the codeword block to generate an LDCP codeword block. In the reverse process of the shortening process, an LLR (Log Likelihood Ratio) with a large absolute value indicating bit 0 is inserted at the position of the discarded shortening bit on the transmitting side. In the reverse process of the puncturing process, an LLR with a value of 0 is inserted at the position of the discarded puncturing bit on the transmitting side. Error correction decoding is performed on the LDPC code word block to obtain an LDPC information block. In the case of retransmission, error correction decoding is performed after LLR combining the first transmitted LDPC codeword block and the retransmitted LDCP codeword block.

On the other hand, when the information field of the PHY header of the received transmission frame stores an index of the coded block length, in the decoding process of the signal demodulation section 10004b-1 according to this embodiment, the index is stored in the table or The codeword block length can also be calculated by referring to the calculation formula. Then, the signal demodulation section 10004b-1 decodes each MPDU for each code word block length, and transfers the decoding results to the upper layer section 10001-1. When storing multiple block lengths corresponding to the lengths of each MPDU constituting an A-MPDU in the PHY header, as the number of MPDU aggregations increases in the MAC layer, the proportion of overhead occupying the PHY layer increases. This suggests a decrease in transmission efficiency. In the decoding process using the table or calculation formula, the length of each MPDU can be referenced from the index, and it is possible to combine packets with high transmission efficiency by reducing overhead.

Note that when the retransmission method setting indicates HARQ, when a predetermined MCS is applied with a predetermined MPDU length, the wireless communication device 2-1 generates a code word block for decoding from the first encoded bit length for the PSDU. You may also ask for

As described above, the communication device according to the present embodiment improves communication quality and transmission efficiency by reducing the overhead of the PHY layer and MAC layer and performing effective packet combining in the PHY layer while maintaining the retransmission function of the MAC layer. can contribute to the improvement of
[2. Common to all embodiments]

The communication device according to the present invention can communicate in a frequency band (frequency spectrum) called a so-called unlicensed band, which does not require permission from the country or region. is not limited to this. For example, the communication device according to the present invention uses 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. (For example, frequency bands allocated for television broadcasting but not used in some areas) and shared spectrum (shared frequency bands) that are expected to be shared by multiple carriers. It is possible to demonstrate the effect.

The program that operates on the wireless communication device according to the present invention is a program that controls the CPU, etc. (a program that causes the computer to function) so as to realize the functions of the above embodiments related to the present invention. The information handled by these devices is temporarily stored in the 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 (for example, ROM, nonvolatile memory card, etc.), optical recording media (for example, DVD, MO, MD, CD, BD, etc.), magnetic recording media (for example, magnetic tape, flexible disk, etc.). Furthermore, by executing the loaded program, the functions of the embodiments described above are not only realized, but also the functions of the embodiment described above are realized by processing in collaboration with the operating system or other application programs based on the instructions of the program. In some cases, the functions of the invention may be realized.

Furthermore, when distributing the program on the market, the program can be stored in a portable recording medium and distributed, 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. Further, part or all of the communication device in the embodiments described above may be realized as an LSI, which is typically an integrated circuit. Each functional block of the communication device may be individually formed into a chip, or some or all of them may be integrated into a chip. When each functional block is integrated into an integrated circuit, an integrated circuit control section is added to control the functional blocks.

Moreover, the method of circuit integration is not limited to LSI, but may be implemented using a dedicated circuit or a general-purpose processor. Further, if an integrated circuit technology that replaces LSI emerges due to advances in semiconductor technology, it is also possible to use an integrated circuit based on this technology.

Note 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 is also applicable to stationary or non-movable electronic devices installed indoors or outdoors, such as AV devices, kitchen devices, cleaning/laundry devices, etc. Needless to say, it can be applied to appliances, air conditioning equipment, office equipment, vending machines, and other household equipment.

The embodiments of this invention have been described above in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and designs etc. within the scope of the gist of this invention may also be claimed. Included in the range.

INDUSTRIAL APPLICABILITY 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 device 3-1, 3-2 Management range 10-1 Wireless communication device 10001-1 Upper layer section 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 Receiving section 10004a-1 Radio receiving section 10004b-1 Signal demodulation section 10005 -1 Antenna part

Claims (8)

A communication device that transmits frames,
an upper layer unit that aggregates multiple MPDUs and sets a delimiter for each MPDU;
a control unit that transmits an MPDU length that is a frame length of each of the plurality of MPDUs to a PHY layer;
comprising a transmitter that blocks the MPDU based on a predetermined encoded block length,
When HARQ is configured in the frame, the one block is not allowed to include information of two or more MPDUs,
If HARQ is not configured in the frame, the one block is permitted to include information on two or more MPDUs. The communication device according to claim 1, wherein the predetermined encoded block length is set based on MCS and the MPDU length set in the frame including the MPDU. The communication device according to claim 1, wherein the predetermined encoded block length is set from a number of blocks set based on MCS and the MPDU length set in the frame including the MPDU. A communication method in a communication device that transmits frames,
aggregating multiple MPDUs and setting a delimiter for each MPDU;
transmitting an MPDU length, which is a frame length of each of the plurality of MPDUs, to a PHY layer;
Blocking the MPDU based on a predetermined encoded block length,
When HARQ is configured in the frame, the one block is not allowed to include information of two or more MPDUs,
If HARQ is not configured in the frame, the one block is allowed to include information on two or more MPDUs. A communication device that receives frames,
an upper layer unit in which a plurality of MPDUs are aggregated and a delimiter is set in each MPDU;
a control unit that transmits an MPDU length that is a frame length of each of the plurality of MPDUs to a PHY layer;
a receiving unit that blocks and decodes the MPDU based on a predetermined encoded block length,
When HARQ is configured in the frame, the one block is not allowed to include information of two or more MPDUs,
If HARQ is not configured in the frame, the one block is permitted to include information on two or more MPDUs. The communication device according to claim 5, wherein the predetermined encoded block length is set based on the MCS set in the frame including the MPDU and the MPDU length. The communication device according to claim 5, wherein the predetermined encoded block length is set from a number of blocks set based on an MCS set in the frame including the MPDU and the MPDU length. A communication method in a communication device that receives frames, the method comprising:
a step in which a plurality of MPDUs are aggregated and a delimiter is set for each MPDU;
transmitting an MPDU length, which is a frame length of each of the plurality of MPDUs, to a PHY layer;
Blocking and decoding the MPDU based on a predetermined encoded block length,
When HARQ is configured in the frame, the one block is not allowed to include information of two or more MPDUs,
If HARQ is not configured in the frame, the one block is allowed to include information on two or more MPDUs.

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