WO2026014154A1 - Wireless communication device and wireless communication method - Google Patents

Abstract

A carrier sense unit 405 comprises two types of NAV: a basic NAV and an intra-BSS NAV. When all of conditions including at least four: [condition 1] the received frame is identified as an inter-BSS frame or cannot be identified as either an intra-BSS frame nor an inter-BSS frame; [condition 2] the continuous period information of the received frame is larger than the current basic NAV value; [condition 3] the receive address (RA) of the received frame is not the address of the own device; and [condition 4] the received frame is not an AP low-capability notification frame, are satisfied, the carrier sense unit 405 updates the value of the basic NAV with the value of the continuous period information of the received frame.

Description

Wireless communication device and wireless communication method

The present invention relates to a wireless communication device and a wireless communication method.
This application claims priority to Japanese Patent Application No. 2024-111783, filed on July 11, 2024, the contents of which are incorporated herein by reference.

The Institute of Electrical and Electronics Engineers, Inc. (IEEE) is continuously working on developing new standards for the wireless LAN (Local Area Network) standard, IEEE 802.11, in order to achieve higher efficiency, faster communication speeds, and improved frequency utilization efficiency in wireless LAN (Local Area Network) systems.

In the IEEE 802.11 series specifications, a wireless communication device in a wireless LAN system is called a station (STA), an STA that connects multiple other STAs and provides network services is called an access point station (AP STA), and an STA that connects to an AP STA and receives network services is called a non-access point station (non-AP STA). Below, an AP STA is also called an access point (AP), access point device, or base station device, and a non-AP STA is also called a terminal, user terminal, terminal device, or user terminal device.

The conventional IEEE 802.11 standard employs a power saving mechanism for non-AP STAs, one of the goals of which is to reduce power consumption in battery-powered devices such as personal computers, mobile phones, smartphones, and portable information devices (Non-Patent Document 1, Non-Patent Document 2).

On the other hand, the high power consumption of AP STAs has become a problem due to environmental considerations and the widespread use of battery-powered access point devices such as mobile routers. IEEE 802.11 Task Group bn (TGbn) has stipulated that it will work on reducing the power consumption of AP STAs when formulating next-generation wireless LAN standards (Non-Patent Document 3), and discussions have begun on this issue (Non-Patent Documents 4-7).

IEEE Std 802.11-2020, p.2111, 1641-1642, 1647-1649, 2080-2081 IEEE Std 802.11ax-2021, p.291-292, 314-315, 404-406, 435-439 IEEE P802.11bn PAR IEEE 802.11-23/1835r0 IEEE 802.11-23/1965r2 IEEE 802.11-24/0782r0 IEEE 802.11-24/0813r0

The challenge is to achieve both low power consumption in wireless communication devices and maintaining the communication quality of the wireless link.

The wireless communication device and wireless communication method according to one aspect of the present invention, which solve the above-mentioned problems, are as follows.

(1) That is, a wireless communication device according to one aspect of the present invention is a wireless communication device that belongs to a first basic service set (BSS) and performs wireless communication, and includes a wireless receiver and a carrier sense unit. The carrier sense unit performs virtual carrier sensing using a first network allocation vector (NAV) and a second NAV. When the wireless receiver receives a frame, if a first condition is met, the first NAV is updated with a first duration included in the received frame, and if a second condition is met, the second NAV is updated with the first duration. The first condition is that the received frame is identified as a frame of a BSS different from the first BSS, or is a frame of the first BSS but is not a frame of a BSS different from the first BSS. The second condition includes at least the following: the received frame cannot be identified as a frame of the first BSS; the first duration is greater than the current second NAV value; the receiving address of the received frame is not the address of the own device; and the received frame is not a frame notifying the access point device of its transition to a low capability mode; and the second condition includes at least the following: the received frame is identified as a frame of the first BSS; the first duration is greater than the current second NAV value; the receiving address of the received frame is not the address of the own device; the own device is not a transmission opportunity holder and the received frame is not a frame requiring an immediate response; or the own device is not a transmission opportunity holder and the received frame is a trigger frame.

(2) Furthermore, a wireless communication device according to one aspect of the present invention is an access point device, further comprising a communication control unit and a wireless transmission unit, wherein the communication control unit, when deciding to transition from high capability mode to low capability mode, generates a first frame notifying the transition to low capability mode, and the wireless transmission unit transmits the first frame, which includes at least information indicating the transition to the low capability mode and duration information indicating the duration of the low capability mode.

(3) Furthermore, in a wireless communication device according to one aspect of the present invention, if the received frame is a second frame notifying another access point device that it will transition to low capability mode, and the communication control unit determines that the device itself can transition to low capability mode, the communication control unit generates the first frame, and the wireless transmission unit transmits the first frame.

(4) In a wireless communication device according to one aspect of the present invention, the communication control unit sets the duration of the low capability mode based on the expiration time indicated by the duration information included in the second frame.

(5) Also, a communication method according to one aspect of the present invention is a communication method in a wireless communication device that belongs to a first BSS and performs wireless communication, comprising the steps of receiving a frame, performing virtual carrier sensing using a first NAV and a second NAV, updating the first NAV with a first duration included in the received frame if a first condition is met when the frame is received, and updating the second NAV with the first duration if a second condition is met when the frame is received, wherein the first condition is that the received frame is identified as a frame of a BSS different from the first BSS, or is a frame of the first BSS but is also a frame of a BSS different from the first BSS. the first duration is greater than the current second NAV value; the receiving address of the received frame is not the address of the own device; and the received frame is not a frame notifying the access point device of its transition to a low capability mode; and the second conditions include at least the following: the received frame is identified as a frame of the first BSS; the first duration is greater than the current second NAV value; the receiving address of the received frame is not the address of the own device; the own device is not a transmission opportunity holder and the received frame is not a frame requiring an immediate response; or the own device is not a transmission opportunity holder and the received frame is a trigger frame.

The wireless communication device and wireless communication method of the present invention make it possible to reduce power consumption in wireless communication devices, particularly access point devices, while maintaining the communication quality of wireless links.

1 is a diagram illustrating an example of a configuration of a wireless communication system according to an aspect of the present invention. FIG. 1 is a diagram illustrating an example of a PHY layer frame configuration in a wireless LAN system. FIG. 1 is a diagram illustrating an example of a MAC layer frame configuration in a wireless LAN system. 1 is a block diagram illustrating an example of a configuration of a wireless communication device according to an aspect of the present invention. FIG. 1 is a diagram illustrating an example of a timing chart in a wireless communication system according to an aspect of the present invention. FIG. 1 is a diagram illustrating an example of a timing chart in a wireless communication system according to an aspect of the present invention. FIG. 1 is a diagram illustrating an example of a timing chart in a wireless communication system according to an aspect of the present invention. FIG. 1 is a diagram illustrating an example of a timing chart in a wireless communication system according to an aspect of the present invention. FIG. 1 is a diagram illustrating an example of a timing chart in a wireless communication system according to an aspect of the present invention. FIG. 1 is a diagram illustrating an example of a timing chart in a wireless communication system according to an aspect of the present invention. FIG. 1 is a diagram illustrating an example of a timing chart in a wireless communication system according to an aspect of the present invention. FIG. 1 is a diagram illustrating an example of a timing chart in a wireless communication system according to an aspect of the present invention. FIG. 1 is a diagram illustrating an example of a timing chart in a wireless communication system according to an aspect of the present invention.

The wireless communication system in this embodiment comprises an access point device (also referred to as an AP STA or base station device) and multiple terminal devices (also referred to as non-AP STAs). The wireless communication system and network consisting of the access point device and the terminal devices connected to that access point device is called a BSS (Basic Service Set, management range). The terminal devices in this embodiment can have the functions of an access point device. Similarly, the access point device in this embodiment can have the functions of a terminal device. Below, simply referring to an STA or wireless communication device refers to both the access point device and the terminal devices.

The access point device and terminal devices within the BSS each perform wireless communication based on CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). This embodiment focuses on infrastructure mode, in which an access point device performs wireless communication with multiple terminal devices, but the method of this embodiment can also be implemented in ad hoc mode, in which terminal devices perform direct wireless communication with each other. In ad hoc mode, one terminal device acts as an access point device and forms a BSS. A BSS in ad hoc mode is also referred to as an IBSS (Independent Basic Service Set). Below, a terminal device that forms an IBSS in ad hoc mode can also be considered an access point device.

Figure 1 shows an example of a wireless communication system according to this embodiment. Figure 1 shows an example of an environment in which wireless communication system 100-1 (also referred to as BSS 100-1), which is composed of access point (AP) device 101-1, terminal device 102-1, and legacy terminal device 103-1, and wireless communication system 100-2 (also referred to as BSS 100-2), which is composed of access point (AP) device 101-2, terminal device 102-2, and legacy terminal device 103-2, exist with their communication areas partially or completely overlapping. In this embodiment, we will explain an example in which wireless frames transmitted by each wireless communication device are received by all other wireless communication devices (can be observed with a predetermined reception power or higher). Such other BSSs with overlapping communication areas are called OBSSs (Overlapping BSSs). In the example of the wireless communication system in Figure 1, BSS 100-1 and BSS 100-2 recognize each other's BSS as an OBSS. In this embodiment, a legacy terminal device refers to a conventional terminal device to which an aspect of the present invention is not applied, such as a terminal device conforming to the IEEE 802.11ax standard. Similarly, a legacy access point device refers to a conventional access point device to which an aspect of the present invention is not applied, such as an access point device conforming to the IEEE 802.11ax standard. Furthermore, legacy access point devices and legacy terminal devices are collectively referred to as legacy wireless communication devices. Wireless communication systems 100-1 and 100-2 form different BSSs, but this does not necessarily mean that their ESSs (Extended Service Sets), which represent service sets forming LANs, are different. In other words, wireless communication devices belonging to the same ESS can be considered to belong to the same network from a higher layer. Furthermore, BSSs can be connected via a DS (Distribution System) to form an ESS. Each of wireless communication systems 100-1 and 100-2 can further include multiple terminal devices, legacy terminal devices, or both.

In an IEEE 802.11 wireless communication system, each wireless communication device can transmit multiple types of frames that share a common frame format. The frames are defined in the physical (PHY) layer, medium access control (MAC) layer, and logical link control (LLC) layer.

A PHY layer frame is called a physical protocol data unit (PPDU: PHY Protocol Data Unit, physical layer frame). Hereinafter, a PHY layer frame will also be referred to as a radio frame. Unless otherwise specified, the term "frame" will refer to a radio frame. A PPDU is composed of a training field (TF) used to assist in signal detection, propagation path estimation, and demodulation processing at the physical layer, a signal field (SIG) containing information for signal processing at the physical layer, and a physical service data unit (PSDU: PHY Service Data Unit), which is a data unit processed at the physical layer. A PSDU can also be composed of an aggregated MPDU (A-MPDU: Aggregated MPDU), which aggregates multiple MAC protocol data units (MPDU: MAC Protocol Data Unit, MAC layer frames), which serve as the unit of retransmission in the wireless section.

Figure 2 shows an example of a PHY layer frame and PPDU configuration in a wireless LAN system. Figure 2 shows an example of a PPDU configuration for the following standards: IEEE 802.11n (also known as HT: High Throughput), IEEE 802.11ac (also known as VHT: Very High Throughput), IEEE 802.11ax (also known as HE: High Efficiency), and IEEE 802.11be (also known as EHT: Extremely High Throughput). The PPDU contains multiple short training fields (STF: Short Training Fields) used for signal detection and synchronization, and long training fields (LTF: Long Training Fields) used to acquire channel information for data demodulation. STF is classified into L-STF (non-HT Short Training Field), HT-STF (High Throughput Short Training Field), VHT-STF (Very High Throughput Short Training Field), HE-STF (High Efficiency Short Training Field), EHT-STF (Extremely High Throughput Short Training Field), etc. depending on the corresponding standard. LTF is similarly classified into L-LTF, HT-LTF, VHT-LTF, HE-LTF, EHT-LTF, etc. depending on the corresponding standard. PPDUs that comply with standards prior to IEEE 802.11n are also called non-HT PPDUs.

The SIGNAL field contained in the PPDU is similarly classified into L-SIG, HT-SIG, VHT-SIG, HE-SIG, EHT-SIG, etc. depending on the corresponding standard. VHT-SIG is further classified into VHT-SIG-A1, VHT-SIG-A2, and VHT-SIG-B. Similarly, HE-SIG is classified into HE-SIG-A1 to HE-SIG-A4 and HE-SIG-B. As shown in Figure 2, the L-SIG field contains multiple subfields such as RATE and LENGTH. The LENGTH subfield of the L-SIG field indicates information about the length of the PPDU, such as the number of octets and duration. In addition, in anticipation of specification updates within the same standard, a U-SIG (Universal SIG) field containing additional control information can be included. The RL-SIG field included in the PPDUs (HE PPDU and EHT PPDU) of the IEEE 802.11ax and IEEE 802.11 11be standards is a repetition of the L-SIG field, and can be used to distinguish the HE PPDU and EHT PPDU from PPDUs of earlier standards.

Furthermore, the PPDU may contain information identifying the BSS that sent the frame (hereinafter also referred to as BSS identification information). The information identifying the BSS may be, for example, the SSID (Service Set Identifier) of the BSS or the MAC address of the access point device of the BSS. The information identifying the BSS may also be a value unique to the BSS (such as a BSS Color) other than an SSID or MAC address. Information indicating the BSS Color may be included in a HE-SIG-A or U-SIG, etc.

In PPDUs conforming to the IEEE 802.11ax and IEEE 802.11be standards, a PE field (Packet Extension field) may be added to ensure the time required for receiving and processing the PPDU.

Figure 3 shows an example of the structure of an MPDU, which is a MAC layer frame in a wireless LAN system. The MPDU consists of a MAC header containing information for signal processing at the MAC layer, a MAC Service Data Unit (MSDU) or frame body, which is a data unit input to the MAC layer for processing, and a Frame Check Sequence (FCS) field, which checks for errors in the MAC layer frame. Multiple MSDUs can also be aggregated as an aggregated MSDU (A-MSDU) and included in the frame body.

Each wireless communication device can recognize the frame type and subframe type of a received MAC layer frame by reading the contents of the frame control field contained in the MAC header. MAC layer frame types are broadly classified into three types: management frames that manage the connection status between wireless communication devices, control frames that manage the communication status between wireless communication devices, and data frames that contain the actual transmitted data. Each type is further classified into multiple subframe types. Control frames include acknowledgement (Ack or ACK) frames, block acknowledgement (BA or BlockAck) frames, request to send (RTS: Request To Send) frames, and clear to send (CTS: Clear To Send) frames. BA can issue acknowledgements (notification of completion of reception) for multiple MPDUs. Management frames include beacon frames, probe request frames, probe response frames, authentication frames, association request frames, and association response frames. Data frames include data frames and polling (CF-Poll) frames.

The MAC header also includes a Duration/ID field. In some frame types, the Duration/ID field indicates the association identification number (AID: Association IDentifier) of the sender of the frame, and in other frame types, it can indicate the duration of occupation of the wireless medium by the transmission of the frame, or the duration of occupation of the wireless medium by the transmission of the frame and the exchange of a series of frames associated with it. Note that the Duration/ID field is also simply called the Duration field when it indicates the duration.

The MAC header can also contain up to four address fields indicating MAC addresses, with the BSS identifier (BSSID), source address (SA), destination address (DA), transmitting address (TA), and receiving address (RA) displayed in the address fields at positions determined according to the frame type, etc. Hereinafter, the various address information shown in the address fields of the MAC header will be collectively referred to as address information or MAC address information.

A beacon frame includes fields indicating the period at which beacons are transmitted (Beacon interval) and the SSID, a string used to identify the BSS. Access point devices can periodically broadcast beacon frames within the BSS, and terminal devices can recognize surrounding access point devices by receiving beacon frames. When a terminal device recognizes an access point device based on a beacon frame broadcast by an access point device, this is called passive scanning. On the other hand, when a terminal device searches for an access point device by broadcasting a probe request frame within the BSS, this is called active scanning. The access point device can send a probe response frame in response to the probe request frame, and the content of the probe response frame is the same as the content of the beacon frame.

After recognizing an access point device, a terminal device performs a connection process with the access point device. The connection process is divided into an authentication procedure and an association procedure. The terminal device sends an authentication request frame to the access point device to which it wishes to connect. When the access point device receives the authentication request frame, it sends an authentication response frame to the terminal device, which includes a status code indicating whether the terminal device has been authenticated. By reading the status code included in the authentication response frame, the terminal device can determine whether its authentication request has been approved by the access point device. Note that the access point device and terminal device can exchange authentication request frames and authentication response frames (collectively referred to as authentication frames) multiple times.

Following the authentication procedure, the terminal device sends a connection request frame to the access point device to carry out the connection procedure. When the access point device receives the connection request frame, it determines whether to allow the terminal device to connect and sends a connection response frame to notify the decision. The connection response frame contains an AID for identifying the terminal device, in addition to a status code indicating whether the connection process is successful. The access point device can manage multiple terminal devices by setting different AIDs for each terminal device that it has granted connection permission to.

After the connection process is completed, the access point device and terminal device carry out actual data transmission. In the IEEE 802.11 system, the Distributed Coordination Function (DCF) and Point Coordination Function (PCF), as well as their extended form, the Hybrid Coordination Function (HCF), are defined as media access methods. Specific implementation methods for HCF include Enhanced Distributed Channel Access (EDCA) and HCF Controlled Channel Access (HCCA).

An example of the operation when a wireless communication device transmits a wireless frame based on DCF is described below. In DCF, a wireless communication device performs carrier sense (CS) to check the usage status of wireless channels surrounding the wireless communication device prior to communication. For example, if a wireless communication device that is about to transmit a frame receives a signal with a received power higher than a predetermined clear channel assessment level (CCA level) on that wireless channel during the carrier sense period performed prior to transmission, it postpones the transmission of the frame on that wireless channel. Hereinafter, a state in which a signal with a received power equal to or higher than the CCA level is detected on the wireless channel is referred to as the wireless medium being in a busy state, and a state in which a signal with a received power equal to or higher than the CCA level is not detected is referred to as the wireless medium being in an idle state. In this way, carrier sense performed by each wireless communication device based on the power level of the signal actually received is referred to as physical carrier sense (physical CS). The CCA level is also called the carrier sense level (CS level) or CCA threshold (CCAT). When a wireless communication device detects a signal with a received power equal to or greater than the CCA level, it begins demodulating the signal at least in the PHY layer.

Wireless communication devices perform carrier sensing during the inter-frame space (IFS) period, which is set according to the frame type and subframe type being transmitted, to determine whether the wireless channel is busy or idle. IEEE 802.11 systems define several IFS periods with different durations, including the short inter-frame space (SIFS: Short IFS) used for frames assigned the highest priority, the polling inter-frame space (PIFS: PCF IFS) used for frames with relatively high priority, and the distributed arbitration inter-frame space (DIFS: DCF IFS) used for frames with low priority. When transmitting data frames using DCF, wireless communication devices use DIFS.

After waiting for the DIFS period, the wireless communication device waits an additional random backoff time to prevent frame collisions. In IEEE 802.11 systems, a random backoff time based on the contention window (CW) is used. CSMA/CA assumes that a frame transmitted by a transmitting station will be received by a receiving station without interference from other transmitting stations. Therefore, if multiple transmitting stations transmit frames at the same time, the frames may collide, preventing the receiving station from receiving the frames correctly. Therefore, each transmitting station waits for a randomly set time before starting transmission to avoid frame collisions. When the wireless communication device determines through carrier sense that the wireless channel is idle, it begins counting down the backoff counter set based on the CW. Only when the backoff counter reaches 0 does it acquire a transmission opportunity (TXOP) and become able to transmit a frame. The wireless communication device continues carrier sensing even while the backoff counter is counting down, and if it determines that the wireless channel is busy again, it stops counting down the backoff counter. Then, if the wireless channel becomes idle again, the wireless communication device waits for the same period as the previous IFS, and then resumes counting down the remaining part of the previous backoff counter. The TXOP acquisition procedure using the above-mentioned backoff counter is also called the backoff procedure.

The wireless communication device, which is the receiving station, receives the frame, reads information such as the SIGNAL field according to the frame's compatible standard, and demodulates the received frame. The wireless communication device can then identify whether the frame is addressed to the device itself by reading the MAC header of the demodulated signal. The wireless communication device can also determine the destination of the frame based on information contained in the SIGNAL field, such as the group identification number (GID: Group Identifier, Group ID) contained in VHT-SIG-A.

If a wireless communication device determines that a received frame is intended for that device and can demodulate the frame without error, it must send an Ack frame to the wireless communication device (transmitting station) indicating that the frame was received correctly. The Ack frame is one of the highest priority frames, and is transmitted after only waiting for the SIFS period (without a random backoff time). The wireless communication device (transmitting station) terminates a series of communications upon receiving the Ack frame transmitted from the wireless communication device (receiving station). Note that if the wireless communication device (receiving station) fails to receive the frame correctly, the wireless communication device (receiving station) will not transmit an Ack frame. Therefore, if the wireless communication device (transmitting station) does not receive an Ack frame from the receiving station within a certain period of time (SIFS + Ack frame length) after transmitting the frame, it determines that the communication has failed and terminates the communication. In this way, the end of a single communication (also called a burst) in an IEEE 802.11 system is always determined by whether or not an Ack frame is received, except in special cases such as when transmitting an announcement signal such as a beacon frame, or when fragmentation is used to divide the transmitted data.

Next, we will explain an example of the operation when an access point device transmits a signal to a terminal device based on PCF. Unlike DCF, in which each device performs carrier sensing and autonomously acquires transmission rights, in PCF a control station called a point coordinator controls the transmission rights of each device within the BSS. Generally, the access point device acts as the point coordinator and acquires transmission rights for terminal devices within the BSS.

The communication period using PCF includes a contention-free period (CFP) and a contention period (CP). During the CP, communication is carried out based on the DCF described above, and it is during the CFP that the point coordinator controls the transmission rights. The access point device, which is the point coordinator, broadcasts a beacon frame containing information such as the maximum duration of the CFP (CFP Max duration) within the BSS prior to PCF communication. Note that the beacon frame broadcast at the start of PCF transmission uses PIFS and is transmitted without going through the backoff procedure. The terminal device that receives this beacon frame sets the value of the CFP Max duration contained in the beacon frame to the NAV (Network Allocation Vector), which maintains the period during which no frames are transmitted to the wireless medium. From then on, until the duration set in the NAV has elapsed or a signal announcing the end of the CFP within the BSS (for example, a data frame containing CF-End) is received, the terminal device can only acquire the transmission right if it receives a signal from the point coordinator signaling acquisition of the transmission right for that device (for example, a data frame containing CF-Poll). Note that, since packet collisions do not occur within the same BSS during the CFP period, each terminal device does not take the random backoff time used in DCF.

Furthermore, we will also explain TXOP in EDCA, a data transmission method different from DCF. The IEEE 802.11e standard is related to EDCA, and specifies TXOP from the perspective of guaranteeing QoS (Quality of Service) for various services such as video transmission and VoIP (Voice over IP). Services are broadly classified into four access categories: VO (VOice), VI (VIdeo), BE (Best Effort), and BK (Background). Generally, the order of priority is VO, VI, BE, and BK. Each access category has parameters for the minimum CW value (CWmin), the maximum CW value (CWmax), AIFS (Arbitration IFS), which is a type of IFS, and TXOP limit, which is the upper limit of transmission opportunities, and these values are set to differentiate between high and low priorities. For example, by setting the CWmin, CWmax, and AIFS of VO, which has the highest priority for audio transmission, to relatively small values compared to other access categories, data transmission can be prioritized over other access categories. For example, in VI, which transmits a relatively large amount of data for video transmission, setting the TXOP limit to a large value makes it possible to secure longer transmission opportunities than other access categories. In this way, the values of the four parameters for each access category are adjusted to guarantee QoS according to the various services.

Furthermore, TIDs (Traffic Identifiers) can be used to set the QoS for MSDUs input from higher layers to the MAC layer, with eight of the TIDs being able to identify traffic categories (TCs) and the remaining eight being able to identify parameterized traffic streams (TSs).

FIG. 4 is a diagram showing an example of the configuration of a wireless communication device 400 according to this embodiment. The example configuration of the wireless communication device 400 shown in FIG. 4 is a configuration common to the access point devices 101-1 and 101-2 and terminal devices 102-1 and 102-2 in FIG. 1. Note that the basic block configuration of the legacy terminal devices 103-1 and 103-2 in FIG. 1 is the same as that of the wireless communication device 400, but the operation of some blocks differs.

The wireless communication device 400 includes an upper layer unit (upper layer step) 401, a communication control unit (communication control step) 402, a wireless transmission unit (wireless transmission step) 403, a wireless reception unit (wireless reception step) 404, a carrier sense unit (carrier sense step) 405, and an antenna unit 406.

The upper layer unit 401 may, for example, implement some or all of the functions of the layers above the MAC layer and perform processing. Note that the functions of the upper layer unit 401 are not limited to this, and may, for example, also include some functions of the MAC layer.

The communication control unit 402 generates MPDUs for control frames and management frames, outputs them to the wireless transmission unit 403, and instructs it to transmit. The communication control unit 402 also uses the data unit (MSDU) input from the upper layer unit 401 as the frame body, and adds a MAC header containing address information such as the BSSID of the BSS to which the wireless communication device 400 belongs, source address, destination address, sending address, and receiving address, QoS control information related to the MSDU, and fields such as duration, as well as an FCS (Frame Check Sequence) for error detection to generate an MPDU for the data frame, and outputs it to the wireless transmission unit 403 to instruct it to transmit. The duration can be set to the duration of wireless medium occupation by the transmission of the frame, the duration of wireless medium occupation by the transmission of the frame and the associated exchange of a series of frames, or the duration of the TXOP desired. The communication control unit 402 may also output an A-MPDU, which aggregates multiple MPDUs, to the wireless transmission unit 403.

The instruction to transmit a frame to the wireless transmitter 403 may be executed when the carrier sense result from the carrier sense unit 405 is in the idle state and after a TXOP has been acquired based on the backoff procedure. Note that the above carrier sense and backoff procedures can be omitted for frames that can be transmitted without carrier sense, such as an ACK frame for a received frame or a response frame for a frame addressed to the device itself from the TXOP holder.

The communication control unit 402 also processes the received MPDU input from the wireless receiving unit 404. The communication control unit 402 performs a cyclic redundancy check (CRC) on the received MPDU and compares it with the value in the FCS field to confirm that the MPDU is error-free. If the communication control unit 402 confirms that the MPDU is error-free, it extracts the MAC header of the MPDU and identifies the frame type and subframe type from the frame control field. Based on the identified frame type and subframe type, the communication control unit 402 extracts the remaining fields of the MAC header and obtains information such as duration information, address information, and QoS control information indicated in each field. Note that an A-MPDU may also be input from the wireless receiving unit 404; in this case, the wireless control unit 402 separates the A-MPDU into individual MPDUs and performs the above-mentioned reception processing.

The communication control unit 402 uses the acquired address information to identify whether the received MPDU is addressed to its own device (including multicast and broadcast frames that include its own device), and whether it is a frame within the BSS to which its own device belongs (referred to as an intra-BSS frame) or a frame from another BSS (referred to as an inter-BSS frame). The communication control unit 402 inputs the address information, the identification result as to whether it is an intra-BSS frame, and duration information to the carrier sense unit 405. Furthermore, if the communication control unit 402 identifies the received MPDU as addressed to its own device and the MPDU contains a frame body, i.e., an MSDU, it outputs the MSDU to the upper layer unit 401. The communication control unit 402 may also output information such as the address information and QoS control information acquired along with the MSDU to the upper layer unit 401.

The wireless transmitter 403 generates a PPDU by treating the MPDU or A-MPDU input from the communication controller 402 as a PSDU and adding a training field and a SIGNAL field to the PSDU. For example, in the case of a PPDU compliant with the IEEE 802.11be standard, the PPDU is generated by adding L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, EHT-SIG, EHT-STF, and EHT-LTF before the PSDU. Furthermore, the wireless transmitter 403 may add a PE field to the end of the PPDU as necessary.

The wireless transmission unit 403 performs processes on the generated PPDU, such as error correction coding, digital modulation, mapping, frequency-time conversion, digital-to-analog conversion, filtering, and upconversion to radio frequency (RF), to generate a wireless signal, which is then transmitted from the antenna unit 406 at the transmission timing instructed by the communication control unit 402.

The wireless receiver 404 downconverts the wireless signal received by the antenna 406 and performs processing such as filtering and analog-to-digital conversion to obtain a digital received signal. If the wireless receiver 404 detects L-STF and L-LTF from the received signal and successfully synchronizes with the received frame, it can further perform time-frequency conversion, demapping, digital demodulation, error correction decoding, etc. on the obtained digital received signal to obtain a received PPDU. The wireless receiver 404 outputs the obtained PPDU to the communication control unit 402. Note that if the wireless receiver 404 fails to obtain the L-SIG field, i.e., if the parity check of the L-SIG field is not successful, it may abort the acquisition of the frame. Furthermore, if a BSS-specific value such as BSS Color is obtained from HE-SIG-A or U-SIG, and the BSS-specific value differs from that of the BSS to which the device belongs, the wireless receiver 404 may abort the acquisition of the frame.

The wireless receiving unit 404 monitors the received signal from the antenna unit 406, and if it does not detect a signal with a received power equal to or greater than a predetermined CCA level (hereinafter referred to as the CCA-ED level) for energy detection (ED), it sets the CCA indication (also referred to as the PHY-CCA indication), which indicates whether the wireless medium is available, to an idle state and outputs it to the carrier sense unit 405. If it detects a signal with a received power equal to or greater than the CCA-ED level, it sets the CCA indication to a busy state and notifies the carrier sense unit 405.

If the radio receiving unit 404 detects L-STF and L-LTF from the received signal at a received power equal to or greater than a predetermined CCA level for signal detection (SD) (hereinafter also referred to as the CCA-SD level), it sets the CCA indication to a busy state and notifies the carrier sense unit 405. This received power detection is also called preamble detection. Furthermore, if the radio receiving unit 404 successfully acquires the L-SIG field, it maintains the CCA indication in a busy state for a period based on the LENGTH subfield in the L-SIG field. Note that the radio receiving unit 404 may set the CCA-ED level higher than the CCA-SD level; for example, the CCA-SD level may be set to -82 dBm and the CCA-ED level to -62 dBm. Furthermore, if a BSS-specific value such as BSS Color is obtained from HE-SIG-A or U-SIG and that value differs from that of the BSS to which the device belongs, the wireless receiver 404 may change the CCA-SD level to a higher value. In this case, it is preferable for the wireless transmitter 403 to reduce the transmission power in conjunction with raising the CCA-SD level.

The carrier sense unit 405 receives a CCA indication from the wireless receiver 404, and receives from the communication control unit 402 the identification result of whether the received MPDU is addressed to the device itself, whether it is an intra-BSS frame or an inter-BSS frame, and duration information. This carrier sense based on the CCA indication is called physical carrier sense (physical CS).

The carrier sense unit 405 has an indicator called a Network Allocation Vector (NAV), which maintains time periods during which the device does not transmit frames to the wireless medium, regardless of the state of the physical CS. The NAV can be expressed as a countdown timer and is also called a NAV timer or NAV counter. In the following, the NAV will be described as being expressed as a countdown timer, but this is not limited to this. The carrier sense unit 405 of a terminal device has two types of NAV: a basic NAV and an intra-BSS NAV. The carrier sense unit 405 of an access point device can have two types of NAV: a basic NAV and an intra-BSS NAV. Details on updating the NAV value will be explained later.

The carrier sense unit 405 determines that the virtual carrier sense (virtual CS) is in an idle state if both the basic NAV and the intra-BSS NAV are 0, and determines that the virtual CS is in a busy state if at least one NAV is non-zero.

The carrier sense unit 405 outputs to the communication control unit 402 that the carrier sense result is in an idle state when both the physical CS and the virtual CS are in an idle state, and that the carrier sense result is in a busy state when either the physical CS or the virtual CS is in a busy state.

Next, the low power consumption mode of the access point device according to this embodiment will be described. The access point device according to this embodiment has a low power consumption mode designed to reduce power consumption. In low power consumption mode, the access point device can impose operational limitations, such as not transmitting frames from the device itself, or reducing or limiting all or part of its reception processing capability. From the perspective of reception processing capability, power consumption can be reduced, for example, by stopping all reception processing capabilities, or by limiting the receivable frequency bandwidth, modulation and coding scheme (MCS), spatial multiplexing number, number of wireless links, PPDU format, etc. to specific configurations, such as a frequency bandwidth of 20 MHz, an MCS with the minimum transmission rate, a spatial multiplexing number of 1, and one wireless link, or by limiting them to non-HT PPDUs only; however, the configurations, methods, and combinations thereof are not limited to these. Low power consumption modes that reduce or limit all or part of the processing capabilities as described above include power save mode, doze mode, sleep mode, lower capability mode, and low power listening mode. States that are not low power consumption modes include active mode, higher capability mode, and normal mode. In the following, low capability mode will be used as an example of a low power consumption mode, and high capability mode as an example of a state that is not low capability mode, but this is not limiting and other modes listed above may also be used.

When an access point device is in low-capability mode, for example, frames addressed to the access point device may not be received and may be continually retransmitted, or a necessary response frame may not be returned from the access point device, resulting in a disconnection or the inability of new terminal devices to connect.

Therefore, when an access point device transitions to low capability mode, it transmits a frame notifying surrounding wireless communication devices that it is transitioning to low capability mode. The frame notifying the transition to low capability mode includes at least information indicating the transition to low capability mode and duration information indicating the duration of low capability mode. The frame notifying the transition to low capability mode can be, for example, a frame that can include information indicating the transition to low capability mode and duration information, such as a CTS-to-self frame, which is a CTS frame with the MAC address of the device set in the receiving address (RA). As another example, a frame that includes a broadcast address in the RA may be used. Alternatively, a frame that includes a pre-set unicast address in the RA may be used. Hereinafter, the frame notifying the access point device that it is transitioning to low capability mode will be referred to as an AP low capability notification frame (AP LC notification frame).

When the communication control unit 402 in the access point device decides to transition from high capability mode to low capability mode, it generates an AP low capability notification frame and outputs it to the wireless transmission unit 403 to instruct it to transmit. After confirming that the wireless transmission unit 403 has completed transmission of the AP low capability notification frame, the communication control unit 402 may output an instruction to the wireless transmission unit 403 and wireless reception unit 404 to transition to low capability mode. Furthermore, when the duration of low capability mode has expired or when it has decided to return from low capability mode to high capability mode, the communication control unit 402 in the access point device may output an instruction to the wireless transmission unit 403 and wireless reception unit 404 to transition from low capability mode to high capability mode.

The communications control unit 402 in the access point device may make the decision to transition from high-capacity mode to low-capacity mode based on criteria such as whether there is data in the transmission buffer, whether there is data in the transmission buffer with a high priority or a short allowable delay time in terms of QoS settings or access category, the communication status (frequency, transmission rate, data QoS settings and access category, etc.) with the terminal device connected to the device itself, and, if the device itself is battery-powered, the remaining battery power.

When an instruction to transition to low-capacity mode is input from the communication control unit 402, the wireless transmission unit 403 in the access point device may reduce power consumption by stopping the operation of circuits involved in the transmission processing of wireless frames, such as digital-to-analog conversion circuits, filters, oscillators, upconverters, and power amplifiers.

When an instruction to transition to low-capacity mode is input from the communication control unit 402, the wireless receiving unit 404 in the access point device may reduce power consumption by, for example, halting all or part of the operation of circuits involved in the reception processing of wireless frames, such as low-noise amplifiers (LNAs), oscillators, downconverters, filters, and analog-to-digital converters.

In this way, when an access point device transitions to low capability mode, it transmits an AP low capability notification frame, thereby setting a NAV for surrounding wireless communication devices that may become communication partners during low capability mode. This prevents surrounding wireless communication devices from transmitting frames addressed to the access point device while the access point device is in low capability mode, and prevents frequent frame retransmissions and disconnections with terminal devices due to limitations in the processing power of the access point device.

However, if there are nearby wireless communication devices that belong to a different BSS from the BSS formed by the access point device and are able to receive the AP low capability notification frame, simply transmitting the AP low capability notification frame will prevent these wireless communication devices, i.e., the wireless communication devices in the OBSS from the perspective of the access point device, from transmitting frames. To avoid this problem, the NAV update conditions in the carrier sense unit 405 are set as follows:

First, the carrier sense unit 405 updates the basic NAV value with the value of the duration information of the received frame when all of the following four conditions are met: [Condition 1] The received frame is identified as an inter-BSS frame, or cannot be identified as either an intra-BSS frame or an inter-BSS frame. [Condition 2] The duration information of the received frame is greater than the current basic NAV value. [Condition 3] The receiving address (RA) of the received frame is not the address of the device itself. [Condition 4] The received frame is not an AP low capability notification frame.

Note that legacy wireless communication devices, including legacy terminal devices 103-1 and 103-2, cannot identify AP low capability notification frames, and therefore do not take into account condition 4 of the basic NAV update conditions described above.

Similarly, the carrier sense unit 405 updates the intra-BSS NAV value with the value of the duration information of the received frame when at least the following three conditions are met: [Condition 1] The received frame is identified as an intra-BSS frame. [Condition 2] The duration information of the received frame is greater than the current intra-BSS NAV value. [Condition 3] The RA of the received frame is not the address of the own device, the own device is not a TXOP holder and the received frame is a frame requesting an immediate response, or the own device is not a TXOP holder and the received frame is a trigger frame intended to prompt a response action from the communication partner.

The carrier sense unit 405 determines that the virtual CS is in an idle state if both the basic NAV and intra-BSS NAV are 0, and determines that the virtual CS is in a busy state if at least one NAV is non-zero.

As a result of the above, a wireless communication device does not need to update its NAV when it receives an AP low capability notification frame from an access point device of a BSS different from the BSS to which the device belongs, thereby reducing the impact of access point devices of different BSSs transitioning to low capability mode.

Figure 5 shows an example of a timing chart for the wireless communication system according to this embodiment. The configuration of the wireless communication devices in Figure 5 is the same as that in Figure 1, and includes access point device 101-1, terminal device 102-1, and legacy terminal device 103-1 that make up BSS 100-1, and access point device 101-2, terminal device 102-2, and legacy terminal device 103-2 that make up BSS 100-2. It is assumed that the basic NAV and intra-BSS NAV of all wireless communication devices are 0 as the initial state, and that neither of the two access point devices is in low capability mode. Also, Figure 5 assumes an example in which a CTS-to-self frame is used as the AP low capability notification frame, but this is not limited to this. Figure 5 shows an example of a timing chart from when access point device 101-1 transitions to low capability mode until it returns to high capability mode.

The access point device 101-1 is initially in high capability mode M501, and if it decides to transition to low capability mode, it generates an AP low capability notification frame F510 and transmits it after the backoff procedure S506. Between the time T504 when the AP low capability notification frame F510 is transmitted and the time T505 when the low capability mode duration expires, the access point device 101-1 transitions to low capability mode M502.

When terminal device 102-1 and legacy terminal device 100-1 belonging to BSS 100-1 configured by access point device 101-1 receive AP low capability notification frame F510, the above-mentioned intra-BSS NAV update conditions are met, so the intra-BSS NAV is updated according to the value of the duration information in AP low capability notification frame F510, resulting in non-zero states S507 and S508, and virtual carrier sense entering a busy state from time T504 to time T505.

Meanwhile, the access point device 101-2, terminal device 102-2, and legacy terminal device 103-2 belonging to BSS 100-2 identify AP low capability notification frame F510 as an inter-BSS frame. The access point device 101-2 and terminal device 102-2 identify frame F510 as an AP low capability notification frame and do not update their basic NAV, but the legacy terminal device 103-2 cannot identify the AP low capability notification frame F510, so like other inter-BSS frames, its basic NAV is updated based on the value of the duration information in the AP low capability notification frame F510, resulting in a non-zero state S509, and the virtual CS enters a busy state from time T504 to time T505.

As a result of the above, frame transmissions addressed to access point device 101-1 can be suppressed while access point device 101-1 is in low-capability mode, thereby avoiding frequent frame retransmissions and disconnections of terminal devices belonging to BSS 100-1.

When the low capability mode duration expires at time T505, access point device 101-1 transitions from low capability mode M502 to high capability mode M503, and the intra-BSS NAV of terminal device 102-1 and legacy terminal device 103-1 becomes 0 and the virtual carrier sense enters the idle state. Similarly, the basic NAV of legacy terminal device 103-2 becomes 0 and the virtual CS enters the idle state.

FIG. 6 shows an example of a timing chart for the wireless communication system according to this embodiment. FIG. 6 is an example of a timing chart for when terminal device 102-2 belonging to BSS 100-2 transmits data after access point device 101-1 transitions to low capability mode M502 using the same flow as in FIG. 5, and parts with the same reference numerals as in FIG. 5 are the same as in FIG. 5. Explanations of parts similar to those in FIG. 5 will be omitted.

Because the basic NAV of terminal device 102-2 is not updated by the AP low capability notification frame F510, the virtual CS remains in an idle state and frame transmission is possible. Even if access point device 101-1 is in low capability mode M502, when data to be transmitted to access point device 101-2 occurs, terminal device 102-2 transmits an RTS frame F608 to access point device 101-2 after a backoff procedure S603. At this time, the duration information of RTS frame F608 may be set to a duration calculated by adding together the durations of the CTS frame F609, data frame F610, and Ack frame F611 scheduled to follow RTS frame F608, plus three SIFS intervals between those frames.

A wireless communication device belonging to BSS100-1 that receives an RTS frame F608 not addressed to itself updates its basic NAV with the value of the duration information in RTS frame F608, causing the basic NAV to become non-zero (S604, S605, S606). Furthermore, another wireless communication device belonging to BSS100-2 that receives an RTS frame F608 not addressed to itself updates its intra-BSS NAV with the value of the duration information in RTS frame F608, causing the intra-BSS NAV to become non-zero (S607).

If the access point device 101-2 receives an RTS frame F608 addressed to itself and is in a state where it can receive data, it will not go through the backoff procedure and will transmit a CTS frame F609 to the terminal device 102-2 after the specified IFS period, SIFS, following the RTS frame F608.

The terminal device 102-2, which receives the CTS frame F609, does not follow the backoff procedure and transmits a data frame F610 to the access point device 101-2 SIFS after the CTS frame F609.

Upon receiving data frame F610, access point device 101-2 performs error detection on data frame F610, and if no error is detected, transmits Ack frame F611 to terminal device 102-2 SIFS after data frame F610 without following the backoff procedure.

Note that Figure 6 shows an example in which terminal device 102-2 exchanges RTS frame F608 and CTS frame F609 before transmitting data frame F610. However, if the length of data frame F610 is shorter than a predetermined length, data frame F610 may be transmitted after backoff procedure S603 without exchanging RTS frame F608 and CTS frame F609.

As a result of the above, even if access point device 101-1 transmits AP low capability notification frame F510, wireless communication devices (access point device 101-2, terminal device 102-2) belonging to BSS 100-2, which is a different BSS from access point device 101-1, can continue to communicate without being affected by access point device 101-1's transition to low capability mode.
(Variation 1)

Furthermore, when an access point device in the OBSS transitions to low capability mode, the access point device itself may transition to low capability mode. For example, when access point device 101-1 transitions to low capability mode, access point device 101-2 may also transition to low capability mode.

FIG. 7 shows an example of a timing chart for a wireless communication system according to this embodiment. FIG. 7 is an example of a timing chart for when access point device 101-1 transitions to low capability mode M502 using the same flow as FIG. 5, and then access point device 101-2 also transitions to low capability mode; parts with the same reference numerals as FIG. 5 are the same as FIG. 5. Explanations of parts similar to FIG. 5 will be omitted.

When access point device 101-2, which is in high capability mode M701, receives AP low capability notification frame F510 from access point device 101-1, it determines whether it can also transition to low capability mode. If access point device 101-2 determines that it can transition to low capability mode, it generates AP low capability notification frame F709 and transmits it after backoff procedure S705. The example of Figure 7 shows a case where the low capability mode expiration time of access point device 101-2 is set to coincide with the low capability mode expiration time T505 of access point device 101-1, but this is not limited to this, and low capability mode may be set to expire earlier or later than time T505. In the example of Figure 7, the duration information of AP low capability notification frame F709 is set to a duration until time T505. The access point device 101-2 transitions to low capability mode M702 from time T704 when the AP low capability notification frame F709 is transmitted until time T505 when the low capability mode duration expires.

As a result of the above, in an environment where multiple access point devices exist, the probability that one access point device will transition to low capacity mode in response to the transition of other access point devices to low capacity mode increases, and it becomes possible to avoid frequent periods in which the virtual CS becomes busy due to each access point device transitioning to low capacity mode asynchronously, which would significantly hinder the acquisition of transmission opportunities for legacy wireless communication devices in particular.
(Variation 2)

Another example of a wireless communication device 400 according to this embodiment will now be described. The configuration of the wireless communication device 400 is the same as the configuration example shown in Figure 4, but the operation of the carrier sense unit 405 is different. Below, we will explain the differences from the previous example, and will omit a description of the similarities.

In addition to the basic NAV and intra-BSS NAV, the carrier sense unit 405 has a third NAV. The third NAV is a NAV associated with the low capability mode of the access point device within the BSS to which the device belongs, and is hereafter referred to as the low capability NAV (LC NAV: Lower Capability NAV).

First, the carrier sense unit 405 updates the basic NAV value with the value of the duration information of the received frame when all of the following three conditions are met: [Condition 1] The received frame is identified as an inter-BSS frame, or cannot be identified as either an intra-BSS frame or an inter-BSS frame. [Condition 2] The duration information of the received frame is greater than the current basic NAV value. [Condition 3] The receiving address (RA) of the received frame is not the address of the device itself.

Similarly, the carrier sense unit 405 updates the intra-BSS NAV value with the value of the duration information of the received frame when at least the following four conditions are met: [Condition 1] The received frame is identified as an intra-BSS frame. [Condition 2] The duration information of the received frame is greater than the current intra-BSS NAV value. [Condition 3] The RA of the received frame is not the address of the own device, the own device is not a TXOP holder and the received frame is a frame requesting an immediate response, or the own device is not a TXOP holder and the received frame is a trigger frame intended to prompt a response action from the communication partner. [Condition 4] The received frame is not an AP low capability notification frame.

Furthermore, the carrier sense unit 405 updates the LC NAV value with the value of the duration information of the received frame when at least the following three conditions are met: [Condition 1] The received frame is identified as an intra-BSS frame. [Condition 2] The duration information of the received frame is greater than the current LC NAV value. [Condition 3] The received frame is an AP low capability notification frame.

The carrier sense unit 405 determines that the virtual CS is in an idle state if all three NAVs, the basic NAV, intra-BSS NAV, and LC NAV, are 0, and determines that the virtual CS is in a busy state if at least one NAV is non-zero. However, the carrier sense unit 405 does not take the LC NAV into account for QoS settings, such as frames with high priority set in the access category or TID, or frames requiring low latency, and determines that the virtual CS is in an idle state if both the basic NAV and intra-BSS NAV are 0, and determines that the virtual CS is in a busy state if either the basic NAV or intra-BSS NAV is non-zero.

Figure 8 shows an example of a timing chart for the wireless communication system according to this embodiment. The wireless communication device configuration in Figure 8 is the same as in Figure 1, and includes access point device 101-1, terminal device 102-1, and legacy terminal device 103-1 that make up BSS 100-1, and access point device 101-2, terminal device 102-2, and legacy terminal device 103-2 that make up BSS 100-2. It is assumed that the basic NAV and intra-BSS NAV of all wireless communication devices, and the LC NAV of wireless communication devices other than legacy terminal devices 103-1 and 103-2 that do not have an LC NAV, are 0 as the initial state, and that neither of the two access point devices is in low capability mode. Furthermore, Figure 8 assumes an example in which a CTS-to-self frame is used as the AP low capability notification frame, but this is not limited to this. Figure 8 shows an example of a timing chart from when access point device 101-1 transitions to low capability mode until it returns to high capability mode.

The access point device 101-1 is initially in high capability mode M801. If it decides to transition to low capability mode, it generates an AP low capability notification frame F812 and transmits it after the backoff procedure S806. From the time T804 when the AP low capability notification frame F812 is transmitted until the time T805 when the low capability mode duration expires, the access point device 101-1 transitions to low capability mode M802. At this time, the access point device 101-1 transitions to low capability mode, which restricts its reception capabilities. It may be able to receive frames with specified settings, such as frames restricted by parameters such as a frequency bandwidth of 20 MHz, a minimum transmission rate MCS, a spatial multiplexing number of 1, and one wireless link, or non-HT PPDU frames, but the restricted frame configuration (parameters) is not limited to these. The access point device 101-1 may also be in a state where it does not transmit frames.

When terminal device 102-1, which belongs to BSS 100-1 made up of access point device 101-1, receives AP low capability notification frame F812, it meets the above-mentioned LC NAV update conditions, so the LC NAV is updated based on the value of the duration information in AP low capability notification frame F812, resulting in a non-zero state S807, and virtual carrier sense is busy from time T804 to time T805, with the exception of some frames.

When legacy terminal device 100-1 belonging to BSS 100-1 configured by access point device 101-1 receives AP low capability notification frame F812, the above-mentioned intra-BSS NAV update conditions are met, so the intra-BSS NAV is updated according to the value of the duration information in AP low capability notification frame F812, resulting in a non-zero state S808, and virtual carrier sense is in a busy state from time T804 to time T805.

Meanwhile, in the access point device 101-2, terminal device 102-2, and legacy terminal device 103-2 belonging to BSS 100-2, the AP low capability notification frame F812 is identified as an inter-BSS frame, the basic NAV is updated based on the value of the duration information in the AP low capability notification frame F810, and the basic NAV is set to non-zero states S809, S810, and S811, and the virtual CS is placed in a busy state from time T804 to time T805.

At expiration time T805 of the low capability mode duration, access point device 101-1 transitions from low capability mode M802 to high capability mode M803, the LC NAV of terminal device 102-1 and the intra-BSS NAV of legacy terminal device 103-1 become 0, and the virtual carrier sense enters the idle state. Similarly, in access point device 101-2, terminal device 102-2, and legacy terminal device 103-2 belonging to BSS 100-2, the basic NAV becomes 0 and the virtual CS enters the idle state.

As a result of the above, frame transmissions addressed to access point device 101-1 can be suppressed while access point device 101-1 is in low-capability mode, thereby avoiding frequent frame retransmissions and disconnections of terminal devices belonging to BSS 100-1.

FIG. 9 shows an example of a timing chart for the wireless communication system according to this embodiment. FIG. 9 is an example of a timing chart for when the terminal device 101-2 transmits a frame requiring low latency after the access point device 101-1 transitions to low capability mode M901 using the same flow as in FIG. 8. Parts with the same reference numerals as in FIG. 8 are the same as in FIG. 8. Descriptions of parts similar to FIG. 8 will be omitted. Note that FIG. 8 illustrates an example of transmitting a frame requiring low latency, but this is not limited to this. The frame may be for transmitting data for which a high priority is set in a QoS setting, such as an access category or TID, or for transmitting data that has been in the transmission buffer for a longer period than a predetermined time. Furthermore, the access point device 101-1 may notify information regarding frames that are permitted to be transmitted to itself even when in low capability mode by including it in the AP low capability notification frame F812 or beacon frame.

The terminal device 102-1 receives the AP low capability notification frame F812 and is in state S807, with the LC NAV being non-zero. When data requiring low latency occurs while in state S807, the terminal device 102-1 does not consider the LC NAV, but instead references the two NAVs, the basic NAV and the intra-BSS NAV, to determine that the virtual CS is in an idle state. After a random backoff procedure S906, the terminal device 102-1 transmits an RTS frame F907 to the access point device 101-1 requesting permission to transmit.

When the access point device 101-1 detects and receives an RTS frame F907 that can be received in low capability mode, it transitions from low capability mode M901 to high capability mode M902, and at time T904, SIFS after the RTS frame F907, it transmits a CTS frame F908, which is a response frame to the RTS frame F907. Note that while Figure 9 shows the timing at which the access point device 101-1 switches from low capability mode M901 to high capability mode M902 as starting to transmit the CTS frame F908, it may also switch earlier.

When the terminal device 102-1 receives the CTS frame F908, it transmits a data frame F909, which transmits data requiring low latency, to the access point device 101-1 after an SIFS.

When the access point device 101-1 receives the data frame F909 without error, it transmits an Ack frame F910 to the terminal device 102-1 after an SIFS. If the duration notified in the AP low capability notification frame F812 remains at time T905 when transmission of the Ack frame F910 is completed, the access point device 101-1 may again transition from high capability mode M902 to low capability mode M903.

Note that Figure 9 shows an example in which terminal device 102-2 exchanges an RTS frame F907 and a CTS frame F908 before transmitting a data frame, but if the length of data frame F909 is shorter than a predetermined length, data frame F909 may be transmitted after backoff procedure S603 without exchanging RTS frame F907 and CTS frame F908.

As a result of the above, when a high-priority frame, such as a frame requiring low latency, occurs in terminal device 102-1 during the low-capability mode of access point device 101-1, terminal device 102-1 can transmit the frame with low latency and priority.
(Variation 3)

Another example of a wireless communication device 400 according to this embodiment will now be described. The configuration of the wireless communication device 400 is the same as the configuration example shown in Figure 4, but the operation of the carrier sense unit 405 is different. Below, we will explain the differences from the previous example, and will omit a description of the similarities.

In addition to the basic NAV and intra-BSS NAV, the carrier sense unit 405 also has a third NAV. The third NAV is a NAV associated with the low capability mode of the access point device within the BSS to which the device belongs, and is hereafter referred to as the low capability NAV (LC NAV).

First, the carrier sense unit 405 updates the basic NAV value with the value of the duration information of the received frame when all of the following four conditions are met: [Condition 1] The received frame is identified as an inter-BSS frame, or cannot be identified as either an intra-BSS frame or an inter-BSS frame. [Condition 2] The duration information of the received frame is greater than the current basic NAV value. [Condition 3] The receiving address (RA) of the received frame is not the address of the device itself. [Condition 4] The received frame is not an AP low capability notification frame.

Similarly, the carrier sense unit 405 updates the intra-BSS NAV value with the value of the duration information of the received frame when at least the following four conditions are met: [Condition 1] The received frame is identified as an intra-BSS frame. [Condition 2] The duration information of the received frame is greater than the current intra-BSS NAV value. [Condition 3] The RA of the received frame is not the address of the own device, the own device is not a TXOP holder and the received frame is a frame requesting an immediate response, or the own device is not a TXOP holder and the received frame is a trigger frame intended to prompt a response action from the communication partner. [Condition 4] The received frame is not an AP low capability notification frame.

Furthermore, the carrier sense unit 405 updates the LC NAV value with the value of the duration information of the received frame when at least the following three conditions are met: [Condition 1] The received frame is identified as an intra-BSS frame. [Condition 2] The duration information of the received frame is greater than the current LC NAV value. [Condition 3] The received frame is an AP low capability notification frame.

The carrier sense unit 405 determines that the virtual CS is in an idle state if all three NAVs, the basic NAV, intra-BSS NAV, and LC NAV, are 0, and determines that the virtual CS is in a busy state if at least one NAV is non-zero. However, the carrier sense unit 405 does not take the LC NAV into account for QoS settings, such as frames with high priority set in the access category or TID, or frames requiring low latency, and determines that the virtual CS is in an idle state if both the basic NAV and intra-BSS NAV are 0, and determines that the virtual CS is in a busy state if either the basic NAV or intra-BSS NAV is non-zero.

Figure 10 shows an example of a timing chart for the wireless communication system of this embodiment. The configuration of the wireless communication devices in Figure 10 is the same as that in Figure 1, and includes access point device 101-1, terminal device 102-1, and legacy terminal device 103-1 that make up BSS 100-1, and access point device 101-2, terminal device 102-2, and legacy terminal device 103-2 that make up BSS 100-2. It is assumed that the basic NAV and intra-BSS NAV of all wireless communication devices, and the LC NAV of wireless communication devices other than legacy terminal devices 103-1 and 103-2 that do not have an LC NAV, are 0 as the initial state, and that neither of the two access point devices is in low capability mode. Furthermore, Figure 10 assumes an example in which a CTS-to-self frame is used as the AP low capability notification frame, but this is not limited to this. Figure 10 shows an example of a timing chart from when access point device 101-1 transitions to low capability mode to when it returns to high capability mode.

The access point device 101-1 is initially in high capability mode M1001. If it decides to transition to low capability mode, it generates an AP low capability notification frame F1010 and transmits it after the backoff procedure S1006. Between the time T1004 when the AP low capability notification frame F1010 is transmitted and the time T1005 when the low capability mode duration expires, the access point device 101-1 transitions to low capability mode M1002. At this time, the access point device 101-1 transitions to low capability mode, which restricts its reception capabilities. It may be able to receive frames with specified settings, such as frames restricted by parameters such as a frequency bandwidth of 20 MHz, a minimum transmission rate MCS, a spatial multiplexing number of 1, and one wireless link, or non-HT PPDU frames, although the restricted frame configuration (parameters) is not limited to these. The access point device 101-1 may also be in a state where it does not transmit frames.

When terminal device 102-1 belonging to BSS 100-1 comprising access point device 101-1 receives AP low capability notification frame F1010, the LC NAV update conditions described above are met, so the LC NAV is updated based on the value of the duration information in AP low capability notification frame F1010, resulting in a non-zero state S1007, and the virtual carrier sense is busy from time T1004 to time T1005, with the exception of some frames.

When legacy terminal device 100-1 belonging to BSS 100-1 configured by access point device 101-1 receives AP low capability notification frame F1010, the above-mentioned intra-BSS NAV update conditions are met, so the intra-BSS NAV is updated according to the value of the duration information in AP low capability notification frame F1010, resulting in a non-zero state S1008, and virtual carrier sense entering a busy state from time T1004 to time T1005.

Meanwhile, the access point device 101-2, terminal device 102-2, and legacy terminal device 103-2 belonging to BSS 100-2 identify the AP low capability notification frame F1010 as an inter-BSS frame. The access point device 101-2 and terminal device 102-2 identify frame F1010 as an AP low capability notification frame and do not update their basic NAV, but the legacy terminal device 103-2 cannot identify the AP low capability notification frame F1010, so like other inter-BSS frames, its basic NAV is updated based on the value of the duration information in the AP low capability notification frame F1010, resulting in a non-zero state S1009, and the virtual CS enters a busy state from time T1004 to time T1005.

When the low capability mode duration expires at time T1005, access point device 101-1 transitions from low capability mode M1002 to high capability mode M1003, terminal device 102-1's LC NAV becomes 0 and the virtual carrier sense enters an idle state, and legacy terminal device 103-1's intra-BSS NAV becomes 0 and the virtual carrier sense enters an idle state. Similarly, legacy terminal device 103-2's basic NAV becomes 0 and the virtual CS enters an idle state.

As a result of the above, frame transmissions addressed to access point device 101-1 can be suppressed while access point device 101-1 is in low-capability mode, thereby avoiding frequent frame retransmissions and disconnections of terminal devices belonging to BSS 100-1.

FIG. 11 shows an example of a timing chart for the wireless communication system according to this embodiment. FIG. 11 is an example of a timing chart for when the terminal device 101-2 transmits a frame requiring low latency after the access point device 101-1 transitions to low capability mode M1101 using the same flow as in FIG. 10. Parts with the same reference numerals as in FIG. 10 are the same as in FIG. 10. Descriptions of parts similar to FIG. 10 will be omitted. Note that FIG. 10 illustrates an example of transmitting a frame requiring low latency, but this is not limited to this. It may also be a frame for transmitting data for which a high priority is set in a QoS setting, such as an access category or TID, or a frame for transmitting data that has been in the transmission buffer for a longer period than a predetermined time. Furthermore, the access point device 101-1 may notify information regarding frames that are permitted to be transmitted to itself even when in low capability mode by including it in an AP low capability notification frame F1010 or a beacon frame.

The terminal device 102-1 receives the AP low capability notification frame F1010 and is in state S1007, with the LC NAV being non-zero. When data requiring low latency occurs while in state S1007, the terminal device 102-1 determines that the virtual CS is in an idle state by referencing the two NAVs, the basic NAV and the intra-BSS NAV, without considering the LC NAV, and after a random backoff procedure S1106, transmits an RTS frame F1109 requesting permission to transmit to the access point device 101-1. At this time, the duration information of the RTS frame F1109 may be set to the sum of the durations of the CTS frame F1110, low latency data frame F1111, and Ack frame F1112 that are scheduled to follow the RTS frame F1109, plus three SIFS intervals between those frames.

When access point device 101-1 detects and receives an RTS frame F1109 that can be received in low capability mode, it transitions from low capability mode M1101 to high capability mode M1102, and transmits a CTS frame F1110, which is a response frame to the RTS frame F1109, at time T1104, SIFS after the RTS frame F1109. Note that while Figure 11 shows the timing at which access point device 101-1 switches from low capability mode M1101 to high capability mode M1102 as starting to transmit CTS frame F1110, the switching may occur earlier.

When access point device 101-2 and terminal device 102-2, which belong to a different BSS from terminal device 102-1, receive RTS frame F1109, they identify it as an inter-BSS frame and update their basic NAVs with the value of the duration information contained in RTS frame F1109. As a result, the basic NAVs of access point device 101-2 and terminal device 102-2 become non-zero (S1107, S1108), and the virtual CS enters a busy state from time T1104 to time T1105.

When the terminal device 102-1 receives the CTS frame F1110, it transmits a data frame F1111, which transmits data requiring low latency, to the access point device 101-1 after an SIFS.

When the access point device 101-1 receives the data frame F1111 without error, it transmits an Ack frame F1112 to the terminal device 102-1 after an SIFS. If the duration notified in the AP low capability notification frame F1010 remains at time T1105 when transmission of the Ack frame F1112 is completed, the access point device 101-1 may again transition from high capability mode M1102 to low capability mode M1103.

Note that, in FIG. 11, an example is shown in which terminal device 102-2 exchanges an RTS frame F1109 with a CTS frame F1110 before transmitting a data frame F1111. However, if the length of data frame F1111 is shorter than a predetermined length, data frame F1111 may be transmitted after backoff procedure S603 without exchanging RTS frame F1109 with a CTS frame F1110.

As a result of the above, if a high-priority frame, such as a frame requiring low latency, occurs in terminal device 102-1 while access point device 101-1 is in low-capability mode, terminal device 102-1 can transmit the frame with low latency and priority.

FIG. 12 shows an example of a timing chart for the wireless communication system according to this embodiment. FIG. 12 is an example of a timing chart for when terminal device 102-2 belonging to BSS 100-2 transmits data after access point device 101-1 transitions to low capability mode M1002 using the same flow as in FIG. 10, and parts with the same reference numerals as in FIG. 10 are the same as in FIG. 10. Explanations of parts similar to those in FIG. 10 will be omitted.

Since the basic NAV of terminal device 102-2 is not updated by the AP low capability notification frame F1010, the virtual CS remains in an idle state and frame transmission is possible. Even if access point device 101-1 is in low capability mode M1002, when data to be transmitted to access point device 101-2 occurs, terminal device 102-2 transmits an RTS frame F1207 to access point device 101-2 after a backoff procedure S1203. At this time, the duration information of RTS frame F1207 may be set to a duration calculated by adding together the durations of the CTS frame F1208, data frame F1209, and Ack frame F1210 scheduled to follow RTS frame F1207, plus three SIFS intervals between those frames.

A wireless communication device belonging to BSS100-1 that receives an RTS frame F1207 not addressed to itself updates its basic NAV with the value of the duration information in the RTS frame F1207 (S1204, S1205). Furthermore, another wireless communication device belonging to BSS100-2 that receives an RTS frame F1207 not addressed to itself updates its intra-BSS NAV with the value of the duration information in the RTS frame F1207 (S1206).

If the access point device 101-2 receives the RTS frame F1207 addressed to itself and is in a state where it can receive data, it will not go through the backoff procedure and will instead send a CTS frame F1208 to the terminal device 102-2 after the SIFS following the RTS frame F1207.

After receiving the CTS frame F1208, the terminal device 102-2 transmits a data frame F1209 to the access point device 101-2 SIFS after the CTS frame F1208 without performing the backoff procedure.

Upon receiving data frame F1209, access point device 101-2 performs error detection on data frame F1209, and if no error is detected, transmits Ack frame F1210 to terminal device 102-2 SIFS after data frame F1209 without performing the backoff procedure.

Note that Figure 12 shows an example in which terminal device 102-2 exchanges RTS frame F1207 and CTS frame F1208 before transmitting data frame F1209. However, if the length of data frame F1209 is shorter than a predetermined length, data frame F1209 may be transmitted after backoff procedure S603 without exchanging RTS frame F1207 and CTS frame F1208.

As a result of the above, even when access point device 101-1 transmits AP low capability notification frame F1010, wireless communication devices (access point device 101-2, terminal device 102-2) belonging to BSS 100-2, a different BSS from access point device 101-1, can continue to communicate without being affected by access point device 101-1's transition to low capability mode.

FIG. 13 shows an example of a timing chart for a wireless communication system according to this embodiment. FIG. 13 is an example of a timing chart for when access point device 101-1 transitions to low capability mode M1002 using the same flow as FIG. 10, and then access point device 101-2 also transitions to low capability mode; parts with the same reference numerals as FIG. 10 are the same as FIG. 10. Explanations of parts similar to FIG. 10 will be omitted.

When access point device 101-2, which is in high capability mode M1301, receives AP low capability notification frame F1010 from access point device 101-1, it determines whether it can also transition to low capability mode. If access point device 101-2 determines that it can transition to low capability mode, it generates AP low capability notification frame F1309 and transmits it after backoff procedure S1305. The example of Figure 13 shows a case where the low capability mode expiration time of access point device 101-2 is set to coincide with the low capability mode expiration time T1005 of access point device 101-1, but this is not limited to this, and low capability mode may be set to expire earlier or later than time T1005. In the example of Figure 13, the duration information of AP low capability notification frame F1309 is set to a duration until time T1005. Between the time T1304 when the AP low capability notification frame F1309 is transmitted and the time T1005 when the low capability mode duration expires, the access point device 101-2 transitions to low capability mode M1302.

As a result of the above, in an environment where multiple access point devices exist, the probability that one access point device will transition to low capacity mode in response to the transition of other access point devices to low capacity mode increases, and it becomes possible to avoid frequent periods in which the virtual CS becomes busy due to each access point device transitioning to low capacity mode asynchronously, which would significantly hinder the acquisition of transmission opportunities for legacy wireless communication devices in particular.
(Common to all embodiments)

A wireless communication device according to one aspect of the present invention can communicate in frequency bands (frequency spectrum) known as unlicensed bands, which do not require permission to use from a country or region, but the frequency bands that can be used are not limited to this. A wireless communication device according to one aspect of the present invention can also be effective in frequency bands known as white bands (for example, frequency bands allocated for television broadcasting but unused in some regions) that are not actually used despite permission to use specific services from a country or region for the purpose of preventing interference between frequencies, or in shared spectrum (shared frequency bands) that are expected to be shared by multiple operators.

The program that runs on a wireless communication device according to one aspect of the present invention is a program that controls a CPU and other components (a program that causes a computer to function) so as to implement the functions of the above-described embodiment according to one aspect of the present invention. Information handled by these devices is temporarily stored in RAM during processing, and is then stored in various ROMs or HDDs, from which it is read, modified, and written as needed by the CPU. The recording medium for storing the program may be any of semiconductor media (e.g., ROM, non-volatile memory card, solid state drive, etc.), optical recording media (e.g., DVD, MO, MD, CD, BD, etc.), and magnetic recording media (e.g., magnetic tape, flexible disk, etc.). Executing a loaded program not only implements the functions of the above-described embodiment, but may also implement the functions of the present invention by processing in cooperation with an operating system or other application programs based on instructions from the program.

Furthermore, when distributing the program on the market, the program can be stored and distributed on a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer also falls within one aspect of the present invention. Furthermore, some or all of the wireless communication devices in the above-described embodiments may be realized as an LSI, which is typically an integrated circuit. Each functional block of the wireless communication device may be formed into an individual chip, or some or all may be integrated into a chip. When each functional block is formed into an integrated circuit, an integrated circuit control unit that controls them is added. Needless to say, downloading programs and setting information from a server computer to implement at least some of the functions of the above-described embodiments also falls within one aspect of the present invention.

Furthermore, the integrated circuit method is not limited to LSI, and may be realized using dedicated circuits or general-purpose processors. Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology, it may also be possible to use integrated circuits using that technology.

Note that one aspect of the present invention is not limited to the above-described embodiment. The wireless communication device of the present invention is not limited to application to mobile station devices, but can, of course, be applied to stationary or non-mobile electronic devices installed indoors or outdoors, such as AV equipment, kitchen equipment, cleaning/washing appliances, air conditioning equipment, office equipment, vending machines, and other household appliances.

The above describes in detail an embodiment of the present invention with reference to the drawings, but the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included in the scope of the claims.

One aspect of the present invention is suitable for use in wireless communication devices and wireless communication methods.

100-1, 100-2 Basic service sets 101-1, 101-2 Access point devices 102-1, 102-2 Terminal devices 103-1, 103-2 Legacy terminal device 400 Wireless communication device 401 Upper layer unit 402 Communication control unit 403 Wireless transmission unit 404 Wireless reception unit 405 Carrier sense unit 406 Antenna unit M501, M503, M701, M703, M801, M803, M902, M1001, M1003, M1102 High capability mode M502, M702, M802, M901, M903, M1002, M1101, M1103 Low capability mode F510, F709, F812, F1010 CTS-to-self frame (AP low capability notification frame)
F608, 907, F1109, F1207 RTS frame F609, F908, F1110, F1208 CTS frame F610, F1209 Data frame F611, F910, F1112, F1210 Ack frame F909, F1111 Low latency data frame

Claims (5)

A wireless communication device that belongs to a first basic service set (BSS) and performs wireless communication,
A radio receiver and a carrier sense unit are provided,
the carrier sense unit performs virtual carrier sense using a first network allocation vector (NAV) and a second NAV;
When the wireless receiving unit receives a frame, if a first condition is satisfied, the first NAV is updated with a first duration period included in the received frame, and if a second condition is satisfied, the second NAV is updated with the first duration period;
The first condition is:
the received frame is identified as a frame of a BSS different from the first BSS, or is identifiable as neither a frame of the first BSS nor a frame of a BSS different from the first BSS;
the first duration is greater than the current first NAV value;
The receiving address of the received frame is not the address of the own device.
The received frame is not a frame informing the access point device of its transition to a low capability mode.
At least
The second condition is:
the received frame is identified as a frame of the first BSS;
the first duration is greater than the current second NAV value;
The receiving address of the received frame is not the address of the own device, the own device is not a transmission opportunity holder and the received frame is not a frame requiring an immediate response, or the own device is not a transmission opportunity holder and the received frame is a trigger frame.
A wireless communication device including at least: The wireless communication device is an access point device,
Further comprising a communication control unit and a wireless transmission unit,
When the communication control unit determines to transition from the high capacity mode to the low capacity mode, the communication control unit generates a first frame notifying the transition to the low capacity mode;
the wireless transmission unit transmits the first frame;
The wireless communication device according to claim 1 , wherein the first frame includes at least information indicating a transition to the low capability mode and duration information indicating a duration of the low capability mode. When the received frame is a second frame notifying that another access point device will transition to a low capability mode, the communication control unit generates the first frame if it determines that its own device can transition to the low capability mode;
The wireless communication device according to claim 2 , wherein the wireless transmission unit transmits the first frame. The wireless communication device according to claim 3 , wherein the communication control unit sets the duration of the low capability mode based on an expiration time according to duration information included in the second frame. A communication method in a wireless communication device that belongs to a first basic service set (BSS) and performs wireless communication, comprising:
receiving a frame;
performing a virtual carrier sense using a first network allocation vector (NAV) and a second NAV;
When a frame is received, if a first condition is satisfied, updating the first NAV with a first duration included in the received frame;
and updating the second NAV with the first duration if a second condition is met when receiving a frame;
The first condition is:
the received frame is identified as a frame of a BSS different from the first BSS, or is identifiable as neither a frame of the first BSS nor a frame of a BSS different from the first BSS;
the first duration is greater than the current first NAV value;
The receiving address of the received frame is not the address of the own device.
The received frame is not a frame informing the access point device of its transition to a low capability mode.
At least
The second condition is:
the received frame is identified as a frame of the first BSS;
the first duration is greater than the current second NAV value;
The receiving address of the received frame is not the address of the own device, the own device is not a transmission opportunity holder and the received frame is not a frame requiring an immediate response, or the own device is not a transmission opportunity holder and the received frame is a trigger frame.
A wireless communication method including at least the following.