Wireless communication method supporting relay communication, and wireless communication terminal using same

Abstract

A non-access point (AP) station communicating with an AP is disclosed. The non-AP station comprises a transceiving unit and a processor. The processor receives a downlink relay MPDU including traffic for a destination station from the AP, and transmits the downlink relay MPDU to the destination station.

Description

Wireless communication method supporting relay communication and wireless communication terminal using the same

[0001] The present invention relates to a wireless communication method supporting relay communication and a wireless communication terminal using the same.

[0002] With the recent proliferation of mobile devices, wireless LAN (WLAN) technology, which can provide them with fast wireless Internet service, is attracting significant attention. WLAN technology utilizes short-range wireless communication technology to enable mobile devices such as smartphones, tablets, laptops, portable multimedia players, and embedded devices to wirelessly connect to the Internet at home, in businesses, or in specific service areas.

[0003] Since supporting the initial wireless LAN technology using the 2.4 GHz frequency, the Institute of Electrical and Electronics Engineers (IEEE) 802.11 has been commercializing or developing various technology standards. First, IEEE 802.11b supports communication speeds of up to 11 Mbps while using the 2.4 GHz band. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses the 5 GHz band instead of the 2.4 GHz band, thereby reducing the impact of interference compared to the considerably crowded 2.4 GHz band. It also uses OFDM technology to increase communication speeds to up to 54 Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication range than IEEE 802.11b. And IEEE 802.11g, like IEEE 802.11b, uses the 2.4GHz band to achieve a communication speed of up to 54Mbps and satisfies backward compatibility, which has garnered considerable attention. It is also superior to IEEE 802.11a in terms of communication distance.

[0004] And to overcome the limitations of communication speed, which has been pointed out as a vulnerability in wireless LAN, there is IEEE 802.11n, a technical standard established. IEEE 802.11n aims to increase the speed and reliability of networks and extend the operating range of wireless networks. More specifically, IEEE 802.11n supports high throughput (HT) with data processing speeds of up to 540 Mbps or more, and is based on MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas at both the transmitter and receiver to minimize transmission errors and optimize data rates. In addition, this standard can use a coding method that transmits multiple redundant copies to increase data reliability.

[0005] As wireless LAN becomes more widespread and applications diversify, the need for new wireless LAN systems that support very high throughput (VHT) higher than the data processing speed supported by IEEE 802.11n has arisen. Among these, IEEE 802.11ac supports a wide bandwidth (80MHz to 160MHz) at the 5GHz frequency. Although the IEEE 802.11ac standard is defined only for the 5GHz band, early 11ac chipsets will also support operation in the 2.4GHz band to ensure backward compatibility with existing 2.4GHz band products. Theoretically, according to this specification, multi-station wireless LAN speeds can reach at least 1Gbps and a maximum single-link speed of at least 500Mbps. This is achieved by extending the wireless interface concepts accepted in 802.11n, such as wider radio frequency bandwidth (up to 160 MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256 QAM). In addition, there is IEEE 802.11ad, which transmits data using the 60 GHz band instead of the existing 2.4 GHz / 5 GHz. IEEE 802.11ad is a transmission standard that provides speeds of up to 7 Gbps using beamforming technology, making it suitable for streaming high-bitrate video such as large amounts of data or uncompressed HD video. However, the 60 GHz frequency band has a disadvantage in that it has difficulty passing through obstacles, so it can only be used between devices in short distances.

[0006] Meanwhile, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard, which follows 802.11ac and 802.11ad as a wireless LAN standard, is nearing completion to provide high-efficiency and high-performance wireless LAN communication technology in high-density environments with densely packed APs and terminals. In an 802.11ax-based wireless LAN environment, high-frequency efficient communication must be provided indoors and outdoors in the presence of high-density stations and APs (Access Points), and various technologies have been developed to achieve this.

[0007] Additionally, development of new wireless LAN standards has begun to increase maximum transmission speeds to support emerging multimedia applications such as high-definition video and real-time gaming. The 7th generation wireless LAN standard, IEEE 802.11be (Extremely High Throughput, EHT), is currently under development with the goal of supporting transmission rates of up to 30 Gbps in the 2.4 / 5 / 6 GHz bands through wider bandwidth, increased spatial streams, and multi-AP cooperation.

[0008] Recently, discussions have begun on Ultra High Reliability (UHR) wireless LAN communication technology, a successor to the 802.11be standard, to overcome reliability issues that have been identified as limitations of wireless LAN. The UHR standard is currently under development with the goal of supporting low latency and low jitter in wireless LAN traffic with a high probability (e.g., greater than 99.9999%).

[0009] An object of one embodiment of the present invention is to provide a wireless communication method supporting relay communication and a wireless communication terminal using the same.

[0010] According to one embodiment of the present invention, a non-AP station communicating with an access point (AP) includes a transceiver; and a processor. The processor receives a downlink relay MPDU containing traffic for a destination station from the AP, and transmits the downlink relay MPDU to the destination station.

[0011] The processor may not receive the downlink relay MPDU and may not transmit the downlink relay MPDU to the target station during a period other than the target wakeup time (TWT) service period (SP) of the non-AP station when the non-AP station performs a power save operation.

[0012] The TWT SP of the above non-AP station may be included in the TWT SP of the above destination station.

[0013] The processor may transmit information regarding the capabilities of the non-AP station related to relay operations to the AP. The information regarding the capabilities related to the relay operations may include information regarding a relay service period, which indicates a period during which the non-AP station can perform relay operations.

[0014] Information about the capabilities related to the above relay operation may further include information about the maximum frequency bandwidth supported by the non-AP station when transmitting / receiving for the above relay operation.

[0015] Information about the capabilities associated with the relay operation may further include information about the maximum transmission power that the non-AP station can use when transmitting a PPDU for the relay operation.

[0016] The processor can measure the reception sensitivity of a measurement frame received from the target station and transmit a reporting frame including information about the reception sensitivity of the measurement frame to the AP.

[0017] The above reporting frame may include information regarding the reception sensitivity of the request frame that triggers transmission of the above measurement frame.

[0018] The processor can receive an uplink relay MPDU containing traffic for the AP from the destination station and transmit the uplink relay MPDU to the AP.

[0019] The processor can receive an uplink relay MPDU from the destination station within a TXOP (transmission opportunity) allocated by the destination station to the non-AP station, and transmit the uplink relay MPDU to the AP.

[0020] Before transmitting the downlink relay MPDU, a first RTS (request to send) frame may be received from the AP, and a first CTS (clear to send) frame may be transmitted to the AP in response to the first RTS frame. Before transmitting the downlink relay MPDU, the AP and the destination station may exchange a second RTS frame and a second CTS frame.

[0021] According to an embodiment of the present invention, an AP (access point) communicating with a non-AP station

[0022] A transceiver; and a processor. The processor can transmit a downlink relay MPDU containing traffic for a destination station to a relay station.

[0023] When the relay station performs a power save operation, the relay station may not receive the downlink relay MPDU and may not transmit the downlink relay MPDU to the target station during a time period other than the target wakeup time (TWT) service period (SP) of the relay station. The processor may not transmit the downlink relay MPDU to the relay station during a time period other than the TWT service period when the relay station performs a power save operation.

[0024] The processor may receive information about the relay operation capability of the relay station from the relay station, and determine whether to perform a relay operation with the relay station based on the information about the relay operation capability. The information about the relay operation capability may include information about a relay service period, which indicates a period during which the non-AP station can perform a relay operation.

[0025] Information about the capabilities related to the above relay operation may further include information about the maximum frequency bandwidth supported by the non-AP station when transmitting / receiving for the above relay operation.

[0026] Information about the capabilities associated with the relay operation may further include information about the maximum transmission power that the non-AP station can use when transmitting a PPDU for the relay operation.

[0027] The processor can transmit a frame that triggers transmission of a measurement frame of the target station, and receive, from the relay station, a reporting frame including information about reception sensitivity of the measurement frame.

[0028] The above reporting frame may include information regarding the reception sensitivity of the request frame that triggers transmission of the above measurement frame.

[0029] Before transmitting the downlink relay MPDU, a first RTS (request to send) frame may be transmitted to the relay station, a first CTS (clear to send) frame may be received from the relay station in response to the first RTS frame, and before transmitting the downlink relay MPDU, a second RTS frame may be transmitted to the destination station, and a second CTS frame may be received from the destination station in response to the second RTS frame.

[0030] In an embodiment of the present invention, a non-AP station communicating with an access point (AP) includes a transceiver and a processor. The processor transmits an uplink relay MPDU containing traffic for the AP to the relay station.

[0031] When the relay station performs a power save operation, the relay station may not receive the uplink relay MPDU and may not transmit the uplink relay MPDU to the AP during a time period other than the target wakeup time (TWT) service period (SP) of the relay station. The processor may not transmit the uplink relay MPDU to the relay station during a time period other than the TWT service period when the relay station performs a power save operation. The TWT SP of the relay station may be included in the TWT SP of the non-AP station.

[0032] The processor can receive a frame that triggers transmission of a measurement frame of the target station, and transmit a measurement frame in response to the trigger frame.

[0033] The processor may transmit a first RTS (request to send) frame to the relay station before transmitting the uplink relay MPDU, receive a first CTS (clear to send) frame from the relay station in response to the first RTS frame, and transmit a second RTS frame to the AP before transmitting the uplink relay MPDU, and receive a second CTS frame from the AP in response to the second RTS frame.

[0034] According to an embodiment of the present invention, a method of operating a non-AP station communicating with an access point (AP) includes the steps of receiving a downlink relay MPDU including traffic for a destination station from the AP and transmitting the downlink relay MPDU to the destination station.

[0035] According to an embodiment of the present invention, a method of operating an access point (AP) communicating with a non-AP station includes a step of transmitting a downlink relay MPDU containing traffic for a destination station to a relay station.

[0036] According to an embodiment of the present invention, a method of operating a non-AP station communicating with an access point (AP) includes a step of transmitting an uplink relay MPDU containing traffic for the AP to the relay station.

[0037] One embodiment of the present invention provides a wireless communication method for efficiently supporting relay communication and a wireless communication terminal using the same.

[0038] Figure 1 illustrates a wireless LAN system according to one embodiment of the present invention.

[0039] Figure 2 illustrates a wireless LAN system according to another embodiment of the present invention.

[0040] Figure 3 shows the configuration of a station according to one embodiment of the present invention.

[0041] Figure 4 shows the configuration of an access point according to one embodiment of the present invention.

[0042] Figure 5 schematically illustrates the process by which a station establishes a link with an access point.

[0043] Figure 6 shows an example of a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0044] FIG. 7 shows various standard generation-specific physical layer protocol data unit (PPDU) formats according to an embodiment of the present invention.

[0045] Figure 8 shows an EHT / UHR PPDU format according to an embodiment of the present invention.

[0046] FIG. 9 shows a transmission / TXOP protection method using an RTS frame and a CTS frame according to an embodiment of the present invention.

[0047] FIG. 10 shows a transmission / TXOP protection method using an MU-RTS frame and a CTS frame according to an embodiment of the present invention.

[0048] Figure 11 shows the format of a trigger frame according to an embodiment of the present invention.

[0049] Figure 12 shows the format of the Common Info field of a trigger frame according to an embodiment of the present invention.

[0050] Figure 13 shows the format of the User Info field of a trigger frame according to an embodiment of the present invention.

[0051] FIG. 14 shows a network including a relay station according to an embodiment of the present invention.

[0052] FIG. 15 shows an MPDU and ACK exchange procedure using a relay station according to an embodiment of the present invention.

[0053] FIG. 16 shows a non-AP station searching for a non-AP station to operate as a relay station according to an embodiment of the present invention.

[0054] FIG. 17 shows that relay setup is completed according to an embodiment of the present invention, and that the destination station and relay station operate in relay operation.

[0055] Figure 18 shows the format of frames exchanged in a relay setup process according to an embodiment of the present invention.

[0056] FIG. 19 shows a relay operation performed within a TXOP allocated by an AP according to an embodiment of the present invention.

[0057] FIG. 20 shows an AP allocating an RU to a relay station and the relay station performing a relay operation in the allocated RU according to an embodiment of the present invention.

[0058] FIG. 21 shows an AP performing an SR operation on an RU allocated to a relay station according to an embodiment of the present invention.

[0059] FIG. 22 illustrates an operation of a relay station transmitting a relay PPDU for multiple destination stations according to an embodiment of the present invention.

[0060] FIG. 23 illustrates an operation of transmitting a relay PPDU including both an MPDU transmitted by a relay station to an AP and an MPDU transmitted to a destination station according to an embodiment of the present invention.

[0061] FIG. 24 shows that when a relay station transmits a UL PPDU to transmit an MPDU received from a destination station according to an embodiment of the present invention, the relay station includes an MPDU transmitted to an AP in the UL PPDU.

[0062] FIG. 25 shows the format of a UL PPDU including an MPDU received by a relay station from a destination station and an MPDU transmitted by the relay station to an AP according to an embodiment of the present invention.

[0063] Figure 26 shows the format of a commonly used BlockAck frame.

[0064] Figure 27 shows the format of a typical Multi-STA BlockAck frame.

[0065] FIG. 28 shows the format of a Multi-STA BlockAck frame transmitted by a relay station according to an embodiment of the present invention.

[0066] FIG. 29 shows an operation of an AP protecting relay downlink transmission by performing two RTS frame / CTS frame exchanges according to one embodiment of the present invention.

[0067] FIG. 30 shows an operation in which an AP protects relay downlink transmission by exchanging one RTS frame / CTS frame according to an embodiment of the present invention.

[0068] FIG. 31 shows an operation of a non-AP station protecting an uplink transmission relay by performing two RTS frame / CTS frame exchanges according to an embodiment of the present invention.

[0069] FIG. 32 shows an operation of an AP designating a relay station for a destination station according to an embodiment of the present invention.

[0070] FIG. 33 shows an operation in which a TWT agreement established between a relay station and an AP is applied to a destination station according to an embodiment of the present invention.

[0071] Figure 34 shows a Relay Support element according to an embodiment of the present invention.

[0072] FIG. 35 shows a relay operation performed based on a relay service section indicated by a relay station according to an embodiment of the present invention.

[0073] The terms used in this specification have been selected from widely used and current terms, taking into account the functions of the present invention. However, these terms may vary depending on the intentions of those skilled in the art, customs, or the emergence of new technologies. Furthermore, in certain cases, the applicant may arbitrarily select terms, in which case their meanings will be described in the description of the relevant invention. Therefore, it should be noted that the terms used in this specification should be interpreted based on their substantive meaning and the overall content of this specification, rather than simply their names.

[0074] Throughout the specification, when a component is said to be "connected" to another component, this includes not only the case where the component is "directly connected," but also the case where the component is "electrically connected" with another component intervening therebetween. Furthermore, when a component is said to "include" a particular component, this does not exclude the other component, but rather allows the inclusion of other components, unless specifically stated otherwise. Furthermore, the terms "more than" or "less than" with respect to a specific threshold may be appropriately replaced with "greater than" or "less than", respectively, depending on the embodiment.

[0075] Hereinafter, in the present invention, fields and subfields may be used interchangeably.

[0076] Figure 1 illustrates a wireless LAN system according to one embodiment of the present invention.

[0077] A wireless LAN system includes one or more Basic Service Sets (BSSs), which represent a collection of devices that have successfully synchronized and can communicate with each other. BSSs can generally be categorized as infrastructure BSSs and independent BSSs (IBSSs). Figure 1 illustrates an infrastructure BSS.

[0078] As illustrated in FIG. 1, the infrastructure BSS (BSS1, BSS2) includes one or more stations (STA1, STA2, STA3, STA4, STA5), an access point (AP-1, AP-2) that provides a distribution service, and a distribution system (DS) that connects multiple access points (AP-1, AP-2).

[0079] A station (STA) is any device that includes a medium access control (MAC) and a physical layer interface for a wireless medium that complies with the IEEE 802.11 standard, and broadly includes both non-access point (AP) stations and access points (APs). In addition, the term "terminal" in this specification may refer to a non-AP STA or an AP, or both. A station for wireless communication includes a processor and a communication unit, and may further include a user interface unit and a display unit, depending on the embodiment. The processor may generate a frame to be transmitted through a wireless network or process a frame received through the wireless network, and may perform various other processes for controlling the station. In addition, the communication unit is functionally connected to the processor and transmits and receives frames through the wireless network for the station. In the present invention, a terminal may be used as a term that includes a user equipment (UE).

[0080] An Access Point (AP) is an entity that provides access to a distribution system (DS) via a wireless medium for stations associated with it. In an infrastructure BSS, communication between non-AP stations is in principle performed via an AP, but direct communication is also possible between non-AP stations when a direct link is established. Meanwhile, in the present invention, the AP is used as a concept including a Personal BSS Coordination Point (PCP), and in a broad sense, it can include concepts such as a centralized controller, a base station (BS), a node-B, a base transceiver system (BTS), or a site controller. In the present invention, the AP may also be referred to as a base wireless communication terminal, and the base wireless communication terminal may be used as a term including, in a broad sense, an AP, a base station, an eNodeB (eNB), and a transmission point (TP). In addition, the base wireless communication terminal may include various types of wireless communication terminals that allocate communication medium resources and perform scheduling in communication with multiple wireless communication terminals.

[0081] Multiple infrastructure BSSs can be interconnected via a distribution system (DS). Multiple BSSs connected via the distribution system are referred to as an Extended Service Set (ESS).

[0082] FIG. 2 illustrates an independent BSS, a wireless LAN system, according to another embodiment of the present invention. In the embodiment of FIG. 2, portions identical or corresponding to those in the embodiment of FIG. 1 will be omitted for duplicative description.

[0083] BSS3, illustrated in Figure 2, is an independent BSS and does not include an AP. Therefore, all stations (STA6, STA7) are not connected to an AP. An independent BSS does not allow access to a distribution system and forms a self-contained network. In an independent BSS, each station (STA6, STA7) can be directly connected to one another.

[0084] FIG. 3 is a block diagram showing the configuration of a station (100) according to one embodiment of the present invention. As illustrated, the station (100) according to the embodiment of the present invention may include a processor (110), a communication unit (120), a user interface unit (140), a display unit (150), and a memory (160).

[0085] First, the communication unit (120) transmits and receives wireless signals such as wireless LAN packets, and may be built into or externally installed in the station (100). According to an embodiment, the communication unit (120) may include at least one communication module using different frequency bands. For example, the communication unit (120) may include communication modules of different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to one embodiment, the station (100) may include a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module may perform wireless communication with an AP or an external station according to the wireless LAN standard of the frequency band supported by the corresponding communication module. The communication unit (120) may operate only one communication module at a time or may operate multiple communication modules simultaneously, depending on the performance and requirements of the station (100). When the station (100) includes multiple communication modules, each communication module may be provided in an independent form, or the multiple modules may be integrated into a single chip. In the embodiment of the present invention, the communication unit (120) may represent an RF (Radio Frequency) communication module that processes RF (Radio Frequency) signals.

[0086] Next, the user interface unit (140) includes various types of input / output means provided in the station (100). That is, the user interface unit (140) can receive user input using various input means, and the processor (110) can control the station (100) based on the received user input. In addition, the user interface unit (140) can perform output based on a command of the processor (110) using various output means.

[0087] Next, the display unit (150) outputs an image on the display screen. The display unit (150) can output various display objects, such as content executed by the processor (110) or a user interface based on the control commands of the processor (110). In addition, the memory (160) stores a control program used in the station (100) and various data corresponding thereto. Such a control program may include a connection program required for the station (100) to connect to an AP or an external station.

[0088] The processor (110) of the present invention can execute various commands or programs and process data within the station (100). In addition, the processor (110) can control each unit of the above-described station (100) and control data transmission and reception between the units. According to an embodiment of the present invention, the processor (110) can execute a program for connection to an AP stored in the memory (160) and receive a communication setup message transmitted by the AP. In addition, the processor (110) can read information on the priority conditions of the station (100) included in the communication setup message and request connection to the AP based on the information on the priority conditions of the station (100). The processor (110) of the present invention may refer to the main control unit of the station (100), and according to an embodiment, may refer to a control unit for individually controlling some components of the station (100), such as the communication unit (120). That is, the processor (110) may be a modem or modulator and / or demodulator that modulates and / or demodulates wireless signals transmitted and received from the communication unit (120). The processor (110) controls various operations of transmitting and receiving wireless signals of the station (100) according to an embodiment of the present invention. A specific embodiment thereof will be described later.

[0089] The station (100) illustrated in FIG. 3 is a block diagram according to one embodiment of the present invention, and the blocks shown separately are logically distinguished elements of the device. Accordingly, the elements of the above-described device may be mounted as one chip or as multiple chips depending on the design of the device. For example, the processor (110) and the communication unit (120) may be implemented by being integrated into one chip or may be implemented as separate chips. In addition, in the embodiment of the present invention, some components of the station (100), such as the user interface unit (140) and the display unit (150), may be selectively provided in the station (100).

[0090] Fig. 4 is a block diagram illustrating the configuration of an AP (200) according to one embodiment of the present invention. As illustrated, the AP (200) according to the embodiment of the present invention may include a processor (210), a communication unit (220), and a memory (260). In Fig. 4, redundant descriptions of portions of the configuration of the AP (200) that are identical or corresponding to the configuration of the station (100) of Fig. 3 will be omitted.

[0091] Referring to FIG. 4, the AP (200) according to the present invention has a communication unit (220) for operating a BSS in at least one frequency band. As described above in the embodiment of FIG. 3, the communication unit (220) of the AP (200) may also include a plurality of communication modules that utilize different frequency bands. That is, the AP (200) according to the embodiment of the present invention may include two or more communication modules for different frequency bands, such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP (200) may include a communication module that utilizes a frequency band of 7.125 GHz or higher and a communication module that utilizes a frequency band of 7.125 GHz or lower. Each communication module may perform wireless communication with a station according to the wireless LAN standard of the frequency band supported by the corresponding communication module. The communication unit (220) may operate only one communication module at a time or may operate multiple communication modules simultaneously, depending on the performance and requirements of the AP (200). In an embodiment of the present invention, the communication unit (220) may represent an RF communication module that processes an RF (Radio Frequency) signal.

[0092] Next, the memory (260) stores the control program used in the AP (200) and various data according to the control program. This control program may include a connection program that manages the connection of the station. In addition, the processor (210) controls each unit of the AP (200) and may control data transmission and reception between the units. According to an embodiment of the present invention, the processor (210) may execute a program for connection with a station stored in the memory (260) and transmit a communication setup message to one or more stations. At this time, the communication setup message may include information on the connection priority conditions of each station. In addition, the processor (210) performs connection setup according to a connection request from a station. According to one embodiment, the processor (210) may be a modem or a modulator and / or demodulator that modulates and demodulates a wireless signal transmitted and received from the communication unit (220). The processor (210) controls various operations of wireless signal transmission and reception of the AP (200) according to an embodiment of the present invention. Specific examples of this will be described later.

[0093] Figure 5 schematically illustrates the process by which a station establishes a link with an access point.

[0094] Referring to FIG. 5, the link between STA (100) and AP (200) is largely established through three stages: scanning, authentication, and association. First, the scanning stage is a stage in which STA (100) acquires access information of the BSS operated by AP (200). Methods for performing scanning include a passive scanning method in which information is acquired only by utilizing a beacon message (S101) periodically transmitted by AP (200), and an active scanning method in which STA (100) acquires access information by transmitting a probe request to AP (S103) and receiving a probe response from AP (S105).

[0095] The STA (100) that successfully receives wireless access information in the scanning step transmits an authentication request (S107a) and receives an authentication response from the AP (200) (S107b) to perform the authentication step. After the authentication step is performed, the STA (100) transmits an association request (S109a) and receives an association response from the AP (200) (S109b) to perform the association step. In this specification, association basically means wireless association, but the present invention is not limited thereto, and association in a broad sense may include both wireless association and wired association.

[0096] Meanwhile, an additional 802.1X-based authentication step (S111) and an IP address acquisition step (S113) via DHCP may be performed. In Fig. 5, the authentication server (300) is a server that processes STA (100) and 802.1X-based authentication, and may be physically connected to the AP (200) or may exist as a separate server.

[0097] Figure 6 shows an example of a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0098] A terminal performing wireless LAN communication performs carrier sensing before transmitting data to check whether the channel is busy. If a wireless signal above a certain strength is detected, the channel is determined to be busy, and the terminal delays access to the channel. This process is called clear channel assessment (CCA), and the level that determines whether the signal is detected is called the CCA threshold. If a wireless signal above the CCA threshold received by the terminal is intended for the terminal, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected on the channel or a wireless signal with a strength lower than the CCA threshold is detected, the channel is determined to be idle.

[0099] When the channel is determined to be idle, each terminal with data to transmit performs a backoff procedure after an IFS (Inter Frame Space) time, such as AIFS (Arbitration IFS) or PIFS (PCF IFS), depending on the status of each terminal. In some embodiments, the AIFS may be used as a configuration to replace the existing DIFS (DCF IFS). Each terminal waits while decreasing the slot time by a random number determined for the terminal during the idle interval of the channel, and a terminal that has exhausted all slot times attempts to access the channel. The period during which each terminal performs the backoff procedure is called a contention window period. At this time, the random number may be referred to as a backoff counter. That is, the initial value of the backoff counter is set by an integer, which is a random number obtained by the terminal. If the terminal detects that the channel is idle during the slot time, the terminal may decrease the backoff counter by 1. Additionally, if the backoff counter reaches 0, the terminal may be permitted to perform channel access on the channel. Accordingly, transmission by the terminal may be permitted if the channel is idle during the AIFS time and the slot time of the backoff counter.

[0100] If a specific terminal successfully accesses the channel, the terminal can transmit data through the channel. However, if the terminal attempting access collides with another terminal, the collided terminals are each assigned a new random number and perform a backoff procedure again. According to one embodiment, the random number newly assigned to each terminal may be determined within a range twice (2*CW) of the random number range (contention window, CW) previously assigned to the terminal. Meanwhile, each terminal performs the backoff procedure again in the next contention window period to attempt access, and at this time, each terminal performs the backoff procedure starting from the slot time remaining in the previous contention window period. In this way, each terminal performing wireless LAN communication can avoid collisions with each other for a specific channel.

[0101] <Various PPDU format examples>

[0102] FIG. 7 shows various standard generation-specific physical layer protocol data unit (PPDU) formats according to an embodiment of the present invention.

[0103] More specifically, FIG. 7(a) illustrates an embodiment of a legacy PPDU format based on 802.11a / g, FIG. 7(b) illustrates an embodiment of a HE PPDU format based on 802.11ax, and FIG. 7(c) illustrates an embodiment of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. In addition, FIG. 7(d) illustrates a detailed field configuration of L-SIG and RL-SIG commonly used in the above PPDU formats.

[0104] Referring to FIG. 7(a), the preamble of a legacy PPDU includes a legacy short training field (L-STF), a legacy long training field (L-LTF), and a legacy signal field (L-SIG). In an embodiment of the present invention, the L-STF, L-LTF, and L-SIG may be referred to as a legacy preamble.

[0105] Referring to FIG. 7(b), the preamble of the HE PPDU additionally includes RL-SIG (Repeated Legacy Short Training field), HE-SIG-A (High Efficiency Signal A field), HE-SIG-B (High Efficiency Signal B field), HE-STF (High Efficiency Short Training field), and HE-LTF (High Efficiency Long Training field) in addition to the legacy preamble. In an embodiment of the present invention, the RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF may be referred to as a HE preamble. The specific configuration of the HE preamble may be modified according to the HE PPDU format. For example, HE-SIG-B may be used only in the HE MU PPDU format.

[0106] Referring to FIG. 7(c), the preamble of the EHT PPDU additionally includes, in addition to the legacy preamble, an RL-SIG (Repeated Legacy Short Training field), a U-SIG (Universal Signal field), an EHT / UHR-SIG-A (Extremely High Throughput / Ultra High Reliability Signal A field), an EHT / UHR-SIG-A (Extremely High Throughput / Ultra High Reliability Signal B field), an EHT-STF (Extremely High Throughput Short Training field), and an EHT-LTF (Extremely High Throughput Long Training field). In an embodiment of the present invention, the RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF may be referred to as an EHT preamble. The specific configuration of the non-legacy preamble may be modified according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B can only be used in some of the EHT PPDU formats.

[0107] In this way, the PPDU used in the UHR standard may have a format similar to the PPDU format used in the EHT standard. This is because the EHT PPDU format defined in 802.11be includes a U-SIG field that multiple wireless LAN generations have agreed to use in common. At this time, the value of the PHY Version Identifier field of the U-SIG field included in the EHT PPDU may be 0, and the value of the PHY Version identifier field of the U-SIG field included in the UHR PPDU may have a non-zero value, such as 1. The EHT PPDU includes an EHT-STF (Extremely High Throughput Short Training field) field in the STF field, and an EHT-LTF (Extremely High Throughput Long Training field) field in the LTF field. The UHR PPDU includes a UHR-STF (Ultra High Reliability Short Training field) field in the STF field, and a UHR-LTF (Ultra High Reliability Long Training field) field in the LTF field.

[0108] The L-SIG field included in the PPDU preamble applies 64FFT OFDM and consists of a total of 64 subcarriers. Of these, 48 subcarriers, excluding the guard subcarrier, DC subcarrier, and pilot subcarrier, are used for L-SIG data transmission. Since L-SIG applies BPSK, Rate=1 / 2 Modulation and Coding Scheme (MCS), it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information structure of L-SIG.

[0109] Referring to Fig. 7(d), L-SIG includes an L_RATE field and an L_LENGTH field. The L_RATE field consists of 4 bits and indicates the MCS used for data transmission. Specifically, the L_RATE field indicates one of the transmission speeds of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps, which combine modulation methods such as BPSK / QPSK / 16-QAM / 64-QAM and inefficiencies such as 1 / 2, 2 / 3, and 3 / 4. Combining the information in the L_RATE field and the L_LENGTH field can indicate the total length of the corresponding PPDU. In non-legacy PPDU formats, the L_RATE field is set to the minimum speed of 6 Mbps.

[0110] The L_LENGTH field is allocated in bytes, with a total of 12 bits, allowing for signaling up to 4095. In combination with the L_RATE field, it can indicate the length of the corresponding PPDU. At this time, legacy and non-legacy terminals may interpret the L_LENGTH field in different ways.

[0111] First, the method by which a legacy terminal or non-legacy terminal interprets the length of the PPDU using the L_LENGTH field is as follows. If the value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) can be transmitted during 4 us, which is the duration of one symbol of 64 FFT. Therefore, by adding 3 bytes corresponding to the SVC field and Tail field to the L_LENGTH field value and dividing this by 3 bytes, which is the transmission amount of one symbol, the number of symbols based on 64 FFT after L-SIG is obtained. Multiplying the obtained number of symbols by 4 us, which is the duration of one symbol, and then adding 20 us required for transmission of L-STF, L-LTF, and L-SIG, the length of the PPDU, i.e., the reception time (RXTIME) is obtained. This can be expressed as a formula as shown in Mathematical Expression 1 below.

[0112]

[0113] At this time, represents the smallest natural number greater than or equal to x. Since the maximum value of the L_LENGTH field is 4095, the length of the PPDU can be set to a maximum of 5.484 ms. A non-legacy terminal transmitting the PPDU must set the L_LENGTH field as in Mathematical Expression 2 below.

[0114]

[0115] Here, TXTIME is the total transmission time that constitutes the corresponding PPDU, as shown in mathematical expression 3 below. In this case, TX represents the transmission time of X.

[0116]

[0117] Referring to the above formulas, the length of the PPDU is calculated based on the rounded value of L_LENGTH / 3. Therefore, for any value of k, three different values ​​of L_LENGTH={3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0118] Referring to Fig. 7(e), the U-SIG (Universal SIG) field continues to exist in EHT / UHR PPDUs and subsequent generation wireless LAN PPDUs, and serves to distinguish which generation of PPDU it is, including EHT / UHR. In addition, the U-SIG field can serve to facilitate spatial reuse of EHT / UHR and subsequent generation wireless LANs. U-SIG is an OFDM 2 symbol based on 64FFT and can convey a total of 52 bits of information. Of these, 43 bits, excluding the 9 bits of CRC / Tail, are largely divided into the VI (Version Independent) field and the VD (Version Dependent) field.

[0119] The VI bit maintains its current bit configuration in the future so that even if a subsequent generation PPDU is defined, current EHT / UHR terminals can obtain information about the PPDU through the VI fields of the PPDU. For this purpose, the VI field consists of PHY version, UL / DL, BSS Color, TXOP, and Reserved fields. The PHY version ID field is 3 bits and sequentially distinguishes EHT / UHR and subsequent generation wireless LAN standards by version. The PHY version ID field of the EHT (11be) PPDU has a value of 000b, and the PHY version ID field of the UHR PPDU has a value other than 000b. The UL / DL field distinguishes whether the PPDU is an uplink / downlink PPDU. BSS Color means an identifier for each BSS defined in 11ax and has a value of 6 bits or more. TXOP stands for Transmit Opportunity Duration transmitted in the MAC header. By adding it to the PHY header, the length of the TXOP containing the corresponding PPDU can be inferred without having to decode the MPDU, and has a value of 7 bits or more.

[0120] The VD field of EHT is signaling information that is only useful for PPDUs of version 11be. It can be composed of fields that are commonly used in any PPDU format, such as PPDU format and BW, and fields that are defined differently for each PPDU format. The PPDU format is a delimiter that distinguishes EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), and EHT ER (Extended Range) PPDUs.

[0121] The BW field largely signals five basic PPDU BW options of 20, 40, 80, 160 (80+80), and 320 (160+160) MHz (a BW that can be expressed in the form of an exponential of 20*2 can be called the basic BW), and various remaining PPDU BWs configured through Preamble Puncturing. In addition, some 80 MHz can be signaled in a punctured form after being signaled at 320 MHz. In addition, the punctured and modified channel form can be signaled directly in the BW field, or by using the BW field together with a field that appears after the BW field (for example, a field in the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signaling is possible, so only a maximum of 3 puncturing modes can be signaled. If the BW field is 4 bits, a total of 16 BW signaling is possible, so the puncturing mode can signal up to 11.

[0122] The VD field of the UHR is a field that indicates signaling information that is only useful for the UHR PPDU. However, the information indicated by each field included in the VD field of the UHR PPDU may be identical to or more extended than the information indicated by the field that plays the same role as the VD field of the EHT (11be). For example, the field indicating the puncturing pattern included in the VD field of the UHR PPDU may indicate a wider variety of patterns than the field indicating the puncturing pattern included in the VD field of the EHT PPDU. Alternatively, the field indicating the puncturing pattern included in the VD field of the UHR PPDU may be interpreted in conjunction with the BW field. This allows for indicating a wider variety of puncturing patterns.

[0123]

[0124] Figure 8 shows an EHT / UHR PPDU format according to an embodiment of the present invention.

[0125] The EHT / UHR PPDU format can be indicated by the PPDU Format field of the U-SIG field of the PPDU. Fig. 8 (a) shows an EHT / UHR SU PPDU according to an embodiment of the present invention. The EHT / UHR SU PPDU is a PPDU used for single-user transmission between an AP and a single station, and may include an EHT-SIG-A field for additional signaling after the U-SIG.

[0126] FIG. 8(b) illustrates an EHT / UHR Trigger-based PPDU according to an embodiment of the present invention. An EHT / UHR Trigger-based PPDU is an uplink PPDU used for transmission in response to a trigger frame, and may not have a separate EHT / UHR-SIG-A field after the U-SIG.

[0127] Figure 8(c) illustrates an EHT / UHR MU PPDU according to an embodiment of the present invention. An EHT / UHR MU PPDU is a PPDU used for transmission to one or more terminals. The EHT / UHR MU PPDU format may include a HE-SIG-B field after the U-SIG field.

[0128] Figure 8(d) illustrates an EHT / UHR ER SU PPDU according to an embodiment of the present invention. The EHT / UHR ER SU PPDU is used for single-user transmission to stations in an extended range. The EHT / UHR ER SU PPDU format allows the U-SIG to be repeated along the time axis.

[0129] The EHT / UHR MU PPDU described through (c) of FIG. 8 can be used by an AP to perform downlink transmission to multiple stations. At this time, the EHT / UHR MU PPDU can include scheduling information for multiple stations to simultaneously receive the PPDU. At this time, the EHT / UHR MU PPDU can convey AID information of the receiver or transmitter of the corresponding PPDU through the user specific field of EHT / UHR-SIG-B. A station that receives the EHT / UHR MU PPDU can perform a spatial reuse operation based on the AID information obtained from the preamble of the PPDU. More specifically, the resource unit allocation (RA) field of EHT / UHR-SIG-B can include information on a resource unit (RU) partitioning form in a specific bandwidth (e.g., 20 MHz) in the frequency domain. Additionally, information about the station assigned to each partitioned resource unit may be conveyed via a user-specific field of EHT / UHR-SIG-B. The user-specific field may include one or more user fields corresponding to each partitioned resource unit.

[0130] Among the multiple resource units divided, the AID of the receiver or sender may be inserted into the user field corresponding to the resource unit in which data transmission is performed. A pre-specified null STA ID may be inserted into the user field corresponding to the remaining resource units in which data transmission is not performed.

[0131] Two or more PPDUs described through FIG. 8 may be indicated by the same PPDU format. For example, the value of the U-SIG PPDU format subfield indicating an EHT / UHR SU PPDU and the value of the U-SIG PPDU format subfield indicating an EHT / UHR MU PPDU may be the same.

[0132] Some fields or some information within a field included in the PPDU format described above may be omitted. This may be referred to as compression mode or compressed mode.

[0133]

[0134] <Wi-Fi 단말의 채널 액세스 방법>

[0135] Wi-Fi terminals (APs, non-AP STAs, etc.) perform communication using unlicensed bands, so before transmitting a frame, they check whether the channel they want to transmit is in use by another device. CSMA (Carrier Sense Multiple Access) is a channel access method in which a terminal that wants to transmit a packet performs carrier sense to check whether the channel is in use by another device, and transmits only if the channel is determined to be idle. Since a terminal using CSMA can perform an action of not attempting transmission at least when it is determined that another device is using the medium (channel) (when it is determined to be busy), the transmission that was initiated first can be protected from other devices.

[0136] However, multiple terminals that recognize that the medium is occupied by another device experience a transmission collision by simultaneously attempting to transmit packets when it is confirmed that the medium occupation from the other device has ended (the medium has changed to Idle). That is, as multiple other terminals simultaneously attempt to transmit packets when a specific terminal attempts to transmit a packet, a terminal that is supposed to receive the packet transmitted by the specific terminal is unable to properly receive and decode the packet that it is supposed to receive due to interference caused by the transmissions performed by the multiple other terminals.

[0137] CSMA / CA (CSMA with collision avoidance) is a channel access mechanism that prevents multiple terminals from simultaneously attempting packet transmission when the medium has changed to Idle, as described above. Terminals accessing the medium (channel) using CSMA / CA attempt to transmit after waiting for a random amount of time when the state of the medium they observe changes to Idle. The random amount of time may be an aslottime (typically 9 microseconds) equal to a random number (random backoff counter) generated by each terminal attempting to transmit. In other words, terminals accessing the medium using CSMA / CA attempt to transmit after waiting for different random amounts of time, so they attempt to transmit at different times, unlike when CSMA alone is used. In this case, when a specific terminal that waited for the shortest random amount of time after the medium changed to Idle attempts to transmit first, other terminals can recognize that the medium has been occupied (changed to busy) by the specific terminal and abort the channel access procedure. At this time, the specific terminal may perform an operation of decreasing the backoff counter maintained by it by 1 every aslottime while the medium is maintained as Idle, and may attempt transmission when the backoff counter becomes 0, or when the aslottime has passed after the backoff counter becomes 0. At this time, the specific terminal that performed the transmission may generate a new random number (new backoff counter) after the transmission is finished, and may attempt transmission when the new random number becomes 0 again, or after it becomes 0.

[0138] The CSMA / CA and random backoff procedures briefly explained above are applied to DCF (Distributed coordination function) and EDCAF (Enhanced distributed channel access), which are the basic functions used by Wi-Fi terminals when attempting to access a channel. Since these are well-known and widely used unlicensed band channel access methods, a more detailed explanation will be omitted.

[0139]

[0140] The DCF and EDCAF utilized by the MAC of the Wi-Fi terminal evaluate the channel status by considering not only the channel status (idle / busy) confirmed by each terminal performing its own physical CS (Carrier Sense) but also the results of a virtual CS. In more detail, even if the result of the physical CS performed on the channel is idle, if the result of the virtual CS is busy, the Wi-Fi terminal considers the channel status to be busy. At this time, the Virtual CS is a channel evaluation method that determines the channel to be busy if the NAV (Network allocation vector) is not 0. The NAV may be a value maintained for future traffic that is predicted to occupy the medium. To explain in more detail, when the MAC of Wi-Fi receives an RTS / CTS frame, it can set the NAV (NAV count) based on the duration information of the received frame, for example, the value of the duration field, and maintain the NAV as a non-zero value for the expected time that the medium will be occupied after the RTS / CTS frame exchange. In other words, the value maintained as NAV decreases over time. If the NAV value of a specific MAC is 0, it can be interpreted that the future traffic recognized by the specific MAC is no longer occupying the medium. If the NAV is 0, the MAC can determine the virtual CS result as Idle. At this time, the MAC of Wi-Fi can also set the NAV based on the duration value obtained from not only the RTS / CTS frame but also other received MAC frames.

[0141] The channel assessment method (determine the state of the medium) that considers the results of the physical CS and virtual CS briefly described above is also one of the well-known Wi-Fi MAC functions, so a detailed explanation is omitted.

[0142]

[0143] <EDCA와 TXOP>

[0144] EDCA provides a mechanism to differentiate and manage traffic into four types of ACs (access categories) according to the characteristics of the traffic. At this time, the four types of ACs are AC_VO (AC Voice), AC_VI (AC Video), AC_BE (AC Best effort), and AC_BK (AC Background), and each AC can have different CW (contention window), TXOP (transmit opportunity), and AIFSN parameters. Simply put, EDCA is a mechanism that differentiates the CW, TXOP, and AIFSN parameters for the four types of ACs and controls the transmission priority of traffic transmitted using each AC. To this end, EDCA can map traffic (MSDU) that the MAC must service to one of the four ACs according to the TC (traffic category) or TS (traffic stream). At this time, the traffic mapped to one of the four ACs by EDCA is divided and managed into four queues for each AC. At this time, the four queues may be logically separated rather than physically separated.

[0145] AC_VO is an AC that can be utilized for traffic that is vulnerable to transmission delays, although the absolute volume of traffic, such as voice traffic, is not large. It has relatively small CW and AIFSN parameter values ​​to increase the probability of being serviced preferentially over traffic from other ACs. The TXOP parameter of AC_VO is limited to a relatively small value compared to the TXOP parameters of other ACs, ensuring only a shorter transmission time than other ACs.

[0146] AC_VI is an AC that is more delay-tolerant than voice traffic, but can still be used for low-latency transmission and high-volume traffic such as video. AC_VI has larger CW and AIFSN parameter values ​​than AC_VO but smaller than other ACs. However, its TXOP is about twice as long as AC_VI.

[0147] AC_BE is an AC that can be utilized for traffic that is robust to transmission delays, and most general traffic, excluding voice data and streaming video data, can be classified as AC_BE. AC_BE uses CW and AIFSN parameters with values ​​greater than AC_VO and AC_VI. In addition, AC_BE does not have a separate TXOP. Therefore, traffic corresponding to AC_BE cannot be utilized in the TXOP transmission sequence, which transmits a PPDU, receives an ACK in response, and then transmits a PPDU again after SIFS.

[0148] AC_BK, similar to AC_BE, is a delay-tolerant traffic, but can be utilized for lower-priority traffic than BE traffic. AC_BK utilizes the same CW parameter values ​​as AC_BE, and the AIFSN parameter values ​​are larger than those of AC_BE. In addition, traffic corresponding to AC_BK does not have a separate TXOP like AC_BE, so it cannot be utilized in the TXOP transmission sequence.

[0149] The four types of EDCA AC described above are mapped to the UP (user-priority) of 802.1D, and the EDCA AC is determined based on the UP value of the traffic received through the wire or the TID of the MSDU indicated from the upper layer. At this time, if the TID of the MSDU indicates a value between 0 and 7, the value indicated by the TID can correspond one-to-one with the UP.

[0150] In addition, the four types of EDCA AC described above have default CW (CWmin, CWmax), AIFSN, and TXOP parameters defined in the standard, and the parameter values ​​of each AC can be changed by the AP, so that different values ​​can be used for each BSS.

[0151]

[0152] Using the EDCA mechanism, Wi-Fi traffic is stored in one of four queues corresponding to four ACs, and can be transmitted to the destination device only if the AC containing the traffic wins the channel access contention with other ACs. At this time, in the channel access contention between ACs, each AC competes using its assigned access parameters (CW[AC], AIFSN[AC]), and the channel access contention operation performed by each AC is identical to DCF. At this time, if a specific AC does not have any traffic to transmit in its queue, the specific AC may not participate in the contention.

[0153] However, as described above, since the CW and AIFSN parameter values ​​utilized by each AC are different, the AC_VO with the smallest CW and AIFSN parameters is more likely to win the channel access competition with other ACs, and thus the traffic of AC_VO is more likely to be serviced with priority over the traffic of other ACs.

[0154] In addition, the EDCA mechanism stipulates internal competition rules such as when an (internal) collision occurs between ACs, the AC with a higher priority wins, and increases the CW of the other AC that caused the collision, and rules for composing a PPDU including traffic from an AC other than the AC that won the competition (primary AC), but a detailed description is omitted because it is not closely related to the proposal of the present invention.

[0155] As described above, EDCA provides the EDCA TXOP (EDCA Transmission Opportunity) function along with the function of operating differentiated ACs according to the type of traffic (frames, packets, etc.) to enhance QoS. EDCA TXOP refers to the time during which the EDCAF (EDCA Function) of a specific AC can control the medium without being disturbed by other devices during the TXOP period (duration) when it obtains a channel access opportunity, i.e., becomes a TXOP holder. At this time, the EDCA TXOP may be limited by the TXOP limit advertised by the AP. The TXOP holder must ensure that its own transmission and the transmission of the response frame responded to by its own transmission can be terminated within the TXOP limit.

[0156] A TXOP holder can transmit multiple frames (multiple PPDUs) during an EDCA TXOP period. If the transmission of each frame is performed within the acquired TXOP period, the TXOP holder can transmit multiple frames continuously without performing a separate channel access procedure, such as a backoff procedure, between transmissions of each frame. At this time, if the multiple frames are MPDUs or A-MPDUs (Aggregated MAC protocol data units) that do not request an immediate ack, the transmission of the multiple frames can be performed at an interval of a short interframe space (SIFS) or a reduced interframe space (RIFS). At this time, if there is an MPDU or A-MPDU requesting an immediate ack among the multiple frames, the TXOP holder can transmit a frame requesting an immediate ack, receive the ack, and transmit the next frame after an SIFS.

[0157] At this time, traffic (packets, frames, etc.) of other ACs other than the specific AC that is the TXOP holder may also be transmitted together within the TXOP acquired by the TXOP holder (specific AC) when certain conditions are satisfied. The transmission of traffic of other ACs other than the TXOP holder within the TXOP may be an operation due to TXOP sharing between ACs, and detailed information regarding the above-mentioned certain conditions is omitted because it is not related to the present invention.

[0158]

[0159] As described above, a TXOP holder can perform continuous frame transmission without performing a separate channel access procedure within the TXOP. This may be an operation that can be achieved when other terminals understand and protect the TXOP interval acquired by the TXOP holder. In other words, in order for the TXOP holder to acquire medium control authority for the EDCA TXOP interval, a procedure may be required to notify other terminals of the acquired TXOP interval so that they can recognize it.

[0160] To this end, a terminal (AC) that becomes a TXOP holder or initiates transmission after completing a channel access procedure may attempt to allow other terminals to recognize the TXOP section by transmitting an RTS frame. At this time, the RTS frame means a frame in which the Type subfield (the fourth bit (B3), the third bit (B2) of the Frame Control field) of the Frame Control field of the MAC frame header is set to 01b (Type = Control frame) and the Subtype subfield (the eighth bit (B7), the seventh bit (B6), the sixth bit (B5), the fifth bit (B4) of the Frame Control field) is set to 1011b. Another terminal that receives an RTS frame from a TXOP holder may set an NAV based on information related to the duration included in the RTS frame, for example, the value of the Duration field. The set NAV may be maintained as a non-zero value for a time corresponding to the TXOP of the TXOP holder. However, the terminal indicated as the destination device of the RTS frame must respond with a CTS frame instead of setting the NAV based on the information in the RTS frame. At this time, the destination device of the RTS frame transmitted to start TXOP is a TXOP responder and must transmit a CTS frame in response to the RTS (SIFS after the RTS frame is received). At this time, the Duration field of the responding CTS frame is set to a value calculated as the value indicated in the Duration field of the received RTS frame - the CTS frame transmission time - SIFS. The terminals receiving the CTS frame can set the NAV based on information related to the duration included in the CTS frame (e.g., the value of the Duration field).

[0161] Therefore, the NAV of the terminal that received the RTS frame from the TXOP holder and the terminal that received the CTS frame from the TXOP responder are set to 0 after the TXOP acquired by the TXOP holder ends. This allows the Wi-Fi MAC mechanism to protect the TXOP holder and the TXOP responder from exchanging multiple frames without interruption during the TXOP.

[0162] However, if the TXOP holder transmits an RTS frame as a non-HT duplicate PPDU over the primary 80 MHz band, but the CTS frame (non-HT duplicate PPDU) responded to by the TXOP responder is responded to only in the primary 40 MHz band, the TXOP holder may use only the bandwidth of the primary 40 MHz or less than the primary 40 MHz, for example, the primary 20 MHz, for frame exchange during the acquired TXOP. The CH_BANDWIDTH (a type of TXVECTOR parameter) of the PPDU transmitted by the TXOP holder shall be set to a value equal to or smaller than the CH_BANDWIDTH_IN-NON_HT (a type of RXVECTOR parameter) of the received CTS frame. In this case, the RTS frame may be an RTS frame that allows the CTS frame to be responded to in a BW smaller than the BW in which the RTS frame was transmitted. An RTS frame may be an RTS frame transmitted with DYN_BANDWIDTH_IN_NON_HT (a type of TXVECTOR parameter) set to Dynamic. If DYN_BANDWIDTH_IN_NON_HT is set to Static and the RTS frame is transmitted from a TXOP holder, the TXOP responder may have to respond with a CTS frame with the same BW as the BW in which the RTS frame was received.

[0163]

[0164] FIG. 9 shows a transmission / TXOP protection method using an RTS frame and a CTS frame according to an embodiment of the present invention.

[0165] Before transmitting a PPDU, the first station (STA1) transmits an RTS frame to the second station (STA2), which is the destination of the PPDU, and the second station (STA2) recognizes that the received RTS frame is an RTS frame destined for itself and responds with a CTS frame after SIFS.

[0166] STA1_Neighbor, a neighbor station of the first station (STA1), sets the NAV based on the value indicated by the Duration field of the RTS frame after receiving the RTS frame transmitted by the first station (STA1). STA2_Neighbor, a neighbor station of the second station (STA2), sets the NAV based on the information indicated by the Duration field of the CTS frame after receiving the CTS frame transmitted by the second station (STA2). STA1_Neighbor and STA2_Neighbor determine that the virtual CS is busy while the set NAV (counter) is maintained at a non-zero value after receiving the RTS / CTS frame, and perform actions such as not decreasing the backoff counter. As a result, the neighboring terminals that received the RTS / CTS frame do not attempt transmission during the period in which the NAV is maintained at a non-zero value. Therefore, the first station (STA1) and the second station (STA2) may not be disturbed by surrounding terminals while exchanging PPDU and Ack frames.

[0167] Even if the first station (STA1) and STA2_Neighbor are in a relationship where signals due to each other's transmissions are not detected (hidden), STA2_Neighbor can perform an operation that takes into account that the channel (channel, WM, Wireless medium) is in use while the first station (STA1) transmits a PPDU.

[0168]

[0169] <MU-RTS 트리거 프레임을 이용한 TXOP 보호>

[0170] 11ax (6th generation Wi-Fi, Wi-Fi6, HEW, High Efficiency WLAN) defines the MU-RTS Trigger / CTS frame exchange procedure, and adds a function that enables the AP to start TXOP and protect the TXOP frame exchange procedure using the MU-RTS trigger frame (hereinafter referred to as MU-RTS, MU-RTS frame). The MU-RTS frame is a type of trigger frame. When the MU-RTS frame is received, the station whose AID12 (the LSB 12 bits of the Association ID) is indicated in the User field included in the MU-RTS frame simultaneously responds with a CTS frame. When the AP protects the TXOP using the MU-RTS frame, since multiple stations respond with CTS frames, the TXOP can be protected from the peripheral devices of each of the multiple stations that are the destination devices of the DL MU PPDU (Down link multi-user PPDU). In addition, the MU-RTS frame can be used to protect the UL MU PPDU. In more detail, before requesting a TB (Trigger based) PPDU from multiple stations through a trigger frame, the AP can transmit an MU-RTS frame to cause multiple stations that will respond to the TB PPDU to respond with a CTS frame. At this time, the CTS frames responded to by the multiple stations induce the surrounding stations of each station to set a NAV that protects the TB PPDU and the Ack frame (Ack, Block Ack, etc.) to be transmitted after the TB PPDU, and through this, legacy stations STAs that cannot recognize (interpret, decode) the trigger frame and TB PPDU may not perform channel access during the packet exchange sequence period (or TXOP) initiated through the trigger frame.

[0171]

[0172] FIG. 10 shows a transmission / TXOP protection method using an MU-RTS frame and a CTS frame according to an embodiment of the present invention.

[0173] In the embodiment of FIG. 10, before transmitting an MU PPDU, the AP transmits an MU-RTS frame to the first station (STA1) and the second station (STA2), which are the destination devices of the MU PPDU, and the first station (STA1) and the second station (STA2) receive the MU-RTS frame and, after SIFS, each respond to the MU-RTS frame with a CTS frame.

[0174]

[0175] STA1_Neighbor, a neighboring station of the first station (STA1), sets its NAV based on the information indicated by the Duration field of the CTS frame after receiving the CTS frame transmitted by the first station (STA1). STA2_Neighbor, a neighboring station of the second station (STA2), sets its NAV based on the information indicated by the Duration field of the CTS frame after receiving the CTS frame transmitted by the second station (STA2). STA1_Neighbor and STA2_Neighbor perform operations such as not decreasing the backoff counter, assuming that the Virtual CS (Virtual Carrier Sense) is busy while the NAV (counter) set after receiving the CTS frame remains at a non-zero value. Therefore, neighboring terminals that have received the CTS frame do not attempt to transmit during the period in which the NAV remains at a non-zero value. This allows the AP to transmit MU PPDUs and the first station (STA1) and the second station (STA2) to transmit Ack frames without being interrupted by surrounding terminals.

[0176] The trigger frame described above is a frame type defined in 11ax, and is a frame type in which the Type (fourth bit (B3) and third bit (B2)) and Subtype (eighth bit (B7), seventh bit (B6), sixth bit (B5), and fifth bit (B4)) subfields of the Frame Control field are set to 01b and 0010b, respectively. A trigger frame is a frame of Control Type in which the Type subfield of the Frame Control field is 01b, and the Subtype value 0010 indicates that it is a Trigger frame type. In 11ax, a trigger frame is defined so that an AP can request a response frame for multiple stations at once, and an MU-RTS frame is used so that an AP can request a CTS frame for multiple stations (non-AP STAs). Trigger Types other than the MU-RTS frame include the Basic Tigger frame requesting UL MU PPDU, the Beamforming Report Poll Tigger frame requesting Beamforming Report, the MU-BAR Tigger frame (BlockAck request), the BSRP trigger frame requesting Buffer Status Report, the GCR MU-BAR trigger frame, the Bandwidth Query Report Poll (BQRP) trigger frame, and the NDP Feedback Report Poll trigger frame. Trigger Types other than the MU-RTS frame are not related to the content of the present invention, so a detailed description thereof is omitted.

[0177]

[0178]

[0179] Figure 11 shows the format of a trigger frame according to an embodiment of the present invention.

[0180] The trigger frame includes a MAC header including a Frame Control field, a Common Info field, a User Info List field, a Padding field, and an FCS field.

[0181] The Frame Control field contains Type and Subtype subfields, and a trigger frame has the values ​​of these two subfields set to 01b and 0010b, respectively.

[0182] The Common Info field includes a Trigger Type subfield for indicating the type of trigger frame, a UL Length subfield for indicating the length of the UL transmission being responded to, and more details are described in detail through an embodiment of FIG. 12.

[0183] The User Info List field may include a User Info field containing information for indicating the target device of the trigger frame. In this case, in addition to the information for indicating the target device, the User Info field also includes information regarding parameters used by the target device when transmitting a response frame after receiving the trigger frame, such as UL DCM or UL MCS, depending on the Type of the Trigger frame. The User Info field is described in detail with reference to FIG. 13.

[0184] The Padding field is a field set to secure time for the station receiving the trigger frame to prepare to transmit a response frame, such as a UL TB PPDU or CTS frame. The AP transmitting the trigger frame can adjust the length of the Padding field considering the performance of the target devices. In addition, in 11be (Wi-Fi 7, EHT), the end time of the PPDU containing the trigger frame may be added / adjusted to align it with other PPDUs, but a detailed explanation is omitted.

[0185] The FCS (Frame Check Sequence) field contains a 32-bit CRC (Cyclic Redundancy Code), calculated from the MAC header and Frame Body fields. The function and setting method of the FCS field in the trigger frame are identical to those of the FCS field in a conventional MAC frame. A separate description thereof will be omitted.

[0186]

[0187] Figure 12 shows the format of the Common Info field of a trigger frame according to an embodiment of the present invention.

[0188] The Trigger Type subfield indicates the type (type, variant) of the trigger frame. If the value of the Trigger Type subfield is 0, the Trigger Type subfield indicates a basic trigger frame. If the value of the Trigger Type subfield is 1, the Trigger Type subfield indicates a BFRP (Beamforming Report Poll) trigger frame. If the value of the Trigger Type subfield is 2, the Trigger Type subfield indicates an MU-BAR frame. If the value of the Trigger Type subfield is 3, the Trigger Type subfield indicates an MU-RTS frame. If the value of the Trigger Type subfield is 4, the Trigger Type subfield indicates a BSRP frame. If the value of the Trigger Type subfield is 5, the Trigger Type subfield indicates a GCR MU-BAR frame. If the value of the Trigger Type subfield is 6, the Trigger Type subfield indicates a Bandwidth Query Report Poll (BQRP) frame. If the value of the Trigger Type subfield is 7, the Trigger Type subfield indicates an NFRP (NDP Feedback Report Poll) frame.

[0189] The UL Length subfield indicates the value to be set in the L-SIG LENGTH field of the TB PPDU responded to via the trigger frame.

[0190] The More TF subfield indicates whether there are more trigger frames to be transmitted after the trigger frame containing the More TF subfield.

[0191] The CS Required subfield indicates whether the destination device of the trigger frame must perform CS (Physical & Virtual CS, ED & NAV) when transmitting a response frame. If the value of the CS Required subfield is 1, the station that receives the trigger frame containing the CS Required subfield must perform CS before transmitting a response frame to the trigger frame.

[0192] The UL BW subfield indicates the value of the BW field that an STA responding with a TB PPDU after receiving a trigger frame must set in the preamble, e.g., HE-SIG-A or U-SIG.

[0193] The GI And HE / EHT-LTF Type subfield indicates the GI (Guard interval) and HE (EHT)-LTF values ​​of the TB PPDU to be responded to.

[0194] The MU-MIMO HE(EHT)-LTF Mode subfield indicates information regarding the HE(EHT)-LTF mode that should be applied to the TB PPDU to be responded to.

[0195] If the value of the Doppler subfield is 0, the Number Of HE(EHT / UHR)-LTF Symbols And Midamble Periodicity subfield indicates the number of HE(EHT)-LTF symbols that should be applied to the TB PPDU. If the value of the Doppler subfield is 1, the Number Of HE(EHT / UHR)-LTF Symbols And Midamble Periodicity subfield indicates information related to the number of HE(EHT)-LTF symbols and the periodicity of the midamble.

[0196] The UL STBC subfield indicates whether STBC encoding should be applied to the TB PPDU that is a response to a trigger frame containing the UL STBC subfield. If STBC encoding should be applied, the value of the UL STBC subfield is set to 1. The value of the UL STBC subfield of the trigger frame that triggers the EHT / UHR TB PPDU is reserved.

[0197] The LDPC Extra Symbol Segment subfield indicates whether an LDPC extra symbol segment should appear in the TB PPDU that is a response to a trigger frame containing the LDPC Extra Symbol Segment subfield. If the value of the LDPC Extra Symbol Segment subfield is 1, the TB PPDU that is a response to a trigger frame containing the LDPC Extra Symbol Segment subfield contains an LDPC extra symbol segment.

[0198] The AP Tx Power subfield indicates a value related to the transmission power used by the AP that transmitted the trigger frame when transmitting the trigger frame. A station that receives the trigger frame can adjust the transmission power of the response frame to the trigger frame based on the value indicated by the AP Tx Power subfield.

[0199] The Pre-FEC Padding Factor and PE Disambiguity subfields indicate whether the Pre-FEC Padding Factor is 1, 2, 3, or 4, and provide information to clarify the length of the PE (Packet Extension).

[0200] The UL Spatial Reuse subfield contains four Spatial Reuse subfields and indicates the value to be set in the Spatial Reuse field of a TB PPDU that is a response to a trigger frame containing a UL Spatial Reuse subfield.

[0201] The Doppler subfield indicates whether a midamble is included in the TB PPDU, which is a response to a trigger frame containing a Doppler subfield. A trigger frame that triggers an EHT / UHR TB PPDU may have the value of the Doppler subfield set to reserved. In this case, setting the subfield to reserved may indicate that the station operates without considering the presence and value of the Doppler subfield after receiving the trigger frame.

[0202] The Special User Info Field Present subfield indicates whether the User Info field, among the User Info fields, represents a User Info field whose AID12 subfield is indicated as 2007 or a predefined value.

[0203] The Trigger Dependent Common Info subfield is a field included in a trigger frame only when the type of trigger frame indicated by the Trigger Type field is a basic trigger frame or an NFRP trigger frame.

[0204]

[0205] Figure 13 shows the format of the User Info field of a trigger frame according to an embodiment of the present invention.

[0206] The AID12 subfield indicates information regarding which station the User Info field containing the AID12 subfield is for. A station with an AID equal to the AID indicated by the AID12 subfield can determine that a trigger frame containing the AID12 subfield includes the station as a destination. In this case, the AID12 subfield can be set to 1 to 2006 (1 to 2007 if the trigger frame is a HE Trigger) when indicating one associated station.

[0207] At this time, if the value of the AID12 subfield is 0, the AID12 subfield may indicate that one or more RA-RUs (Random Access RUs) are allocated to a station associated with the AP that transmitted the trigger frame. If the trigger frame received by the station associated with the AP that transmitted the trigger frame does not have a User Info field including an AID12 subfield indicating the AID of the station, and has a User Info field with a value of 0 in the AID12 subfield, the station may attempt to transmit a TB PPDU using RA-RU.

[0208] Additionally, if the value of the AID12 subfield is 2045, the AID12 subfield may indicate that one or more RA-RUs (Random Access RUs) are allocated to a station that is not associated with the AP that transmitted the trigger frame. A station that is not associated with an AP may attempt to transmit a TB PPDU using RA-RUs if the trigger frame received by the station includes a User Info field with the value of the AID12 subfield being 2045.

[0209] Additionally, if the value of the AID12 subfield is 4095, the station receiving the trigger frame may determine that a padding field starts from the AID12 subfield. In this case, the station may not attempt to parse the remaining portion of the MAC frame after the AID12 subfield with the value 4095.

[0210] Additionally, when the value of the AID12 subfield is 2046, the AID12 subfield may indicate that the User Info field containing the AID12 subfield indicates information about an unallocated RU, which is an RU that is not allocated to any station.

[0211] Except for the MU-RTS trigger frame, the RU Allocation subfield of other trigger frames indicates the size and location information of the RU (Resource Unit) / MRU (Multiple Resource Unit) allocated to the destination device of the User Info field including the RU Allocation subfield. The station can determine the information of the RU / MRU allocated to the station by interpreting the RU Allocation subfield and the PS160 subfield included in the User Info field together. The station can determine the information of the RU / MRU allocated to the station by interpreting the RU Allocation subfield and the PS160 subfield and PS320 subfield included in the User Info field together. At this time, the PS320 subfield indicates whether the allocated RU is included in the primary 320 MHz band or the secondary 320 MHz band among the 640 MHz band. The PS160 subfield indicates whether the RU is allocated within a 160 MHz band located higher on the frequency axis or within a 160 MHz band located lower on the frequency axis within the 320 MHz band indicated by the PS320 subfield (primary 320 MHz or secondary 320 MHz). However, if the 320 MHz band indicated by the PS320 subfield is the primary 320 MHz, the information indicated by the PS160 subfield may indicate whether it is the primary 160 MHz or the secondary 160 MHz, rather than the high / low on the frequency axis. Specifically, the 320 MHz band indicated by the PS320 subfield may be the primary 320 MHz. In this case, if the value of the PS160 subfield is 0, the PS160 subfield may indicate that the allocated RU is included in the primary 160 MHz band.When the value of the PS160 subfield is 1, the PS160 subfield may indicate that the allocated RU is included in the secondary 160 MHz band. In this case, the value of the PS160 subfield is an example. When the value of the PS160 subfield is 1, the PS160 subfield may indicate that the allocated RU is included in the primary 160 MHz band. When the value of the PS160 subfield is 0, the PS160 subfield may indicate that the allocated RU is included in the secondary 160 MHz band.

[0212] Within each 160 (and 320) MHz band indicated in this manner, the method of indicating the location of the allocated RU may be the same as or similar to the method of indicating the RU Allocation subfield of the trigger frame defined in EHT.

[0213] The RU Allocation subfield of the MU-RTS indicates the channel on which the destination device in the User Info field responds to the CTS frame. Specifically, the RU Allocation subfield of the MU-RTS frame indicates whether the destination device transmits the CTS frame only on the primary 20 MHz channel, or on the primary 40 MHz channel, primary 80 MHz channel, primary 160 MHz channel, 80 + 80 MHz channel, primary 320 MHz channel, or primary Primary 640 MHz channel when transmitting the CTS frame. At this time, MRU represents an RU that is a combination of two or more RUs, and 52+26, 106+26, 484+242, 996+484, 996+484+242, 2x996+484, 3x996, 3x996+484, 4x996, 4x996+4x996-tone size MRUs can be used in UHR.

[0214] The UL FEC Coding Type subfield indicates the code type of the TB PPDU to be responded to. If the value of the UL FEC Coding Type subfield is 0 and the value of BCC (binary convolution coding) is 1, the UL FEC Coding Type subfield indicates LDPC (low density parity check).

[0215] The UL EHT / UHR-MCS subfield indicates the EHT / UHR-MCS to be applied to the TB PPDU transmission in response to the trigger frame.

[0216] The SS Allocation / RA-RU Information subfield can be used as the SS Allocation subfield when the AID12 subfield is not allocated an RA-RU. The 6 bits of the SS Allocation subfield can include a 4-bit Starting Spatial Stream subfield and a 2-bit Number Of Spatial Streams subfield. When the value of the AID12 subfield is 0, 2044, or 2045, the User Info field containing the AID12 subfield indicates information about the RA-RU.

[0217]

[0218] The UL Target Receive Power subfield indicates the predicted signal strength (power) that the TB PPDU, which is a response to the trigger frame, will receive at the AP's antenna side. When a station transmits a TB PPDU, the station can adjust the transmission power of the TB PPDU according to the value of the UL Target Receive Power subfield. This allows the AP to receive the TB PPDU at the power it expects.

[0219] The PS160 subfield, together with the RU Allocation subfield, indicates information about the location and size of the RU / MRU allocated by the User Info field containing the PS160 subfield.

[0220] The Trigger Dependent User Info (sub) field does not appear in the MU-RTS frame, so a detailed description is omitted.

[0221]

[0222]

[0223] <BSS 커버리지 인핸스먼트>

[0224] Ultra High Reliability (UHR) aims to improve the reliability of wireless LANs. This improvement is achieved by providing lower transmission delay, more stable jitter management, and more stable connectivity than 7th-generation Wi-Fi (EHT). However, this improved connectivity has raised concerns about connection drops caused by limited Basic Service Set (BSS) coverage and by stations moving beyond BSS coverage.

[0225] The coverage of a BSS is determined physically and electrically by the characteristics of the frequency band in which the BSS operates (signal attenuation, etc.), the transmission power of the terminals, and the reception sensitivity of the receiving device. This can be difficult to improve. In mobile communications, the location of each base station is determined based on its coverage, and connectivity is ensured by connecting each node to the appropriate base station based on its location. Base stations are placed so that all service areas fall within the coverage of at least one base station, ensuring mobile connectivity. Unlike mobile communications, wireless LAN environments built using Wi-Fi are not managed by operators. Therefore, it is difficult to expect planned AP placement that takes service areas into account. For general users building a home wireless LAN environment using a single AP, while not experiencing issues in areas close to the AP, they may encounter slow communication speeds and disconnections in areas where the AP signal is weak or where the AP signal cannot reach. One solution to this problem is to build a mesh system (a system using mesh Access Points). However, it is not easy for general users to build a mesh system due to the difficulty of building a mesh system, such as having to install additional mesh APs, deciding where to install the mesh APs, and establishing connections.

[0226] Accordingly, in UHR, the introduction of a technology is being considered to expand the coverage of AP signals by having non-AP stations perform relays, rather than installing separate mesh APs.

[0227]

[0228] <Expanding Coverage Through Relay>

[0229] The term "relay" used in this specification refers to multi-hop communication using an intermediate device, and refers to a communication method supported by a relay station (Relay STA) in the process of an MPDU transmitted by a transmitting device reaching a destination device. After the relay station receives an MPDU transmitted by an AP, the relay station performs an operation of transmitting the received MPDU to the destination station (Destination STA), which is the destination device of the MPDU, and performs an operation of transmitting the MPDU transmitted by the destination station to the AP. This allows frame exchange between two devices that do not directly reach each other's transmissions.

[0230] It is difficult for a signal transmitted to an AP to be directly received by the destination station. Therefore, the operation of the relay station may be performed according to a relay operation environment set in advance between at least two of the AP, the destination station, and the relay station.

[0231] In this specification, the term "relay PPDU" does not refer to a specific PPDU format, but rather refers to a PPDU for transmitting an MPDU received from a transmitting device to a destination station. Specifically, a relay PPDU is a PPDU used by a relay station for transmission to a destination station. A relay PPDU may be an UL PPDU or a TB PPDU. In this case, the UL PPDU may be an MU PPDU or an SU PPDU.

[0232]

[0233] FIG. 14 shows a network including a relay station according to an embodiment of the present invention.

[0234] In the embodiment of FIG. 14, the destination station (D_STA) is located outside the signal coverage of the AP. The AP transmits an MPDU to the destination station (D_STA) via the relay station (R_STA). In addition, the destination station (D_STA) transmits an MPDU to the AP via the relay station (R_STA).

[0235] FIG. 15 shows an MPDU and ACK exchange procedure using a relay station according to an embodiment of the present invention.

[0236] The AP transmits the MPDU to be transmitted to the destination station (D_STA) to the relay station (R_STA). The relay station (R_STA) determines that the MPDU received from the AP is an MPDU that must be transmitted to the destination station (D_STA). At this time, the relay station (R_STA) transmits the received MPDU to the destination station (D_STA). The destination station (D_STA) that received the MPDU from the relay station (R_STA) transmits an Ack frame to the relay station (R_STA) indicating that the MPDU was successfully received. The relay station (R_STA) transmits the Ack frame received from the destination station (D_STA) to the AP.

[0237]

[0238] Relay Discovery

[0239] When the AP's signal cannot reach the destination station or is detected to be weaker than a certain level, the destination station can decide whether to perform relay operation through a relay station. The destination station can check whether there are non-AP stations that can act as relay stations in the BSS to which the destination station belongs. Specifically, a non-AP station that wishes to exchange frames with the AP through relay communication can search for a non-AP station that will act as a relay station. This operation is called relay discovery.

[0240] The destination station can determine whether the received PPDU is transmitted by a non-AP station that can operate as a relay station. If the PPDU received by the destination station is an Intra-BSS PPDU and the station that transmitted the PPDU is a non-AP station that can operate as a relay station, the destination station can request the non-AP station that transmitted the PPDU to operate as a relay station. The non-AP station can signal that the non-AP station can operate as a relay station in the signaling field of the physical layer of the PPDU or in the MAC header. Specifically, the non-AP station can indicate that the non-AP station can operate as a relay station by setting the value of a pre-designated field of the signaling field of the physical layer of the PPDU to a pre-designated value. If the value of the pre-designated field of the signaling field of the physical layer of the PPDU received by the destination station is a pre-designated value, the destination station can determine that the station that transmitted the PPDU can operate as a relay station. A pre-designated field of a signaling field of a physical layer may be included in a U-SIG field. In addition, the pre-designated field may be referred to as a Relay support bit. In this case, when the value of the Relay support bit is the first pre-designated value, the Relay support bit may indicate that a non-AP station transmitting a PPDU can operate as a relay station. In addition, when the value of the Relay support bit is the second pre-designated value, the Relay support bit may indicate that a non-AP station transmitting a PPDU cannot operate as a relay station.Additionally, non-AP stations that do not support operating as relay stations, as well as non-AP stations that do not want to operate as relay stations, may set the value of the Relay support bit to a second predetermined value. The first predetermined value may be 1, and the second predetermined value may be 0. Additionally, the DL PPDU may not include the Relay support bit or it may be reserved. In this case, the Relay support bit may be included only in the UL PPDU. Additionally, the Relay support bit may be included in the Disreard field or the Validate field of the U-SIG field.

[0241] Additionally, a non-AP station can indicate that the non-AP station can operate as a relay station by setting the value of a pre-designated field of the MAC header of the MPDU to a pre-designated value. If the value of the pre-designated field of the MAC header of the MPDU received by the destination station is a pre-designated value, the destination station can determine that the station that transmitted the MPDU can operate as a relay station. Additionally, the pre-designated field may be referred to as a Relay support bit. In this case, if the value of the Relay support bit is a first pre-designated value, the Relay support bit may indicate that the non-AP station transmitting the MPDU can operate as a relay station. Additionally, if the value of the Relay support bit is a second pre-designated value, the Relay support bit may indicate that the non-AP station transmitting the MPDU cannot operate as a relay station. Additionally, not only non-AP stations that do not support operating as relay stations but also non-AP stations that do not want to operate as relay stations may set the value of the Relay support bit to the second pre-designated value. The first predefined value may be 1, and the second predefined value may be 0.

[0242]

[0243] Additionally, if the AP allows a non-AP station associated with the AP to signal whether it supports relay operation, the non-AP station may signal whether the non-AP station can operate as a relay station. In this case, if the AP does not allow a non-AP station associated with the AP to signal whether it supports relay operation, the non-AP station may not be permitted to signal whether the non-AP station can operate as a relay station. In addition, the AP may use a management frame to indicate whether it allows a non-AP station associated with the AP to signal whether it supports relay operation. In this case, the management frame may include at least one of a beacon frame, a probe frame, and an operating mode notification frame.

[0244] FIG. 16 shows a non-AP station searching for a non-AP station to operate as a relay station according to an embodiment of the present invention.

[0245] A second non-AP station (non-AP STA2) overhears a UL PPDU transmitted by a first non-AP station (non-AP STA1) to an AP. The second non-AP station (non-AP STA2) determines whether the PPDU is an Intra-BSS PPDU. The second non-AP station (non-AP STA2) determines the received PPDU as an Intra-BSS PPDU. At this time, the second non-AP station (non-AP STA2) can determine whether the first non-AP station (non-AP STA1) supports a relay operation based on a value of a pre-designated field of a signaling field of a physical layer of the PPDU or a value of a pre-designated field of a MAC header of the MPDU according to the embodiments described above. The second non-AP station (non-AP STA2) can request a relay operation with the first non-AP station (non-AP STA1).

[0246]

[0247] Relay setup

[0248] The destination station can attempt to establish a relay with a non-AP station that can act as a relay station discovered through the discovery operation described above. The destination station can request a relay establishment from the discovered non-AP station. Once the relay establishment between the destination station and the non-AP station is complete, the non-AP station acts as a relay station for the destination station.

[0249] A station requesting relay setup can transmit a request frame requesting relay setup to a non-AP station. For convenience of explanation, during the relay setup process, the non-AP station transmitting the request frame is referred to as a relay request station. At this time, the request frame can include information of the relay request station. Specifically, the request frame can include at least one of the AID of the relay request station, TID mapping information negotiated between the relay request station and the AP, and QoS requirements. The TID mapping information can be set for each transmission direction (UL / DL). In addition, if there is no TID mapping separately agreed upon between the relay request station and the AP, the request frame may not include TID mapping information.

[0250] A non-AP station that receives a request frame can accept the relay request by transmitting a response frame to the relay establishment request request to the station requesting the relay establishment. For convenience of explanation, a non-AP station that receives a request frame and transmits a response frame is referred to as a relay request responding station. The response frame may include information regarding the capabilities supported by the relay request responding station in the relay operation. Specifically, the response frame may include at least one of a data rate supported by the relay request responding station in the relay operation, a queue size, whether BlockAck is supported, TWT information, and the number of target stations for which relay establishment has already been completed. The data rate may be set for each transmission direction (UL / DL). In addition, the queue size may be a queue size for the relay operation. In addition, the queue size may be set in bytes. In addition, whether BlockAck is supported may indicate whether transmitting and receiving BlockAck is supported in the relay operation. In addition, the TWT information may be information regarding the TWT that the relay request responding station is operating.

[0251] The relay request station can determine whether to complete the relay setup based on the received response frame. Specifically, the relay request station can determine whether to complete the relay setup based on the capabilities that the relay request responding station supports in the relay operation as indicated in the received response frame. If the relay request station decides to complete the relay setup, the relay request station can transmit an activation frame to the relay request responding station to initiate the relay operation. In addition, if the relay request station decides not to complete the relay setup, the relay request station can search for another station to perform the relay operation or move to a BSS.

[0252] When an activation frame is received, the relay request station acts as the destination station, and the relay request response station acts as the relay station. The relay station can transmit a report frame containing information about the destination station for which the relay station supports relay operation to the AP. The AP can transmit the MPDU that it transmits to the destination station to the relay station. The relay station can transmit the MPDU received from the AP to the destination station.

[0253] A relay station may transmit a report frame to an AP that includes the AIDs of destination stations for which the relay station supports relay operations. If the relay station supports relay operations for multiple destination stations, the relay station may transmit a report frame to the AP that includes the AIDs of multiple destination stations for which the relay station supports relay operations.

[0254] FIG. 17 shows that relay setup is completed according to an embodiment of the present invention, and that the destination station and relay station operate in relay operation.

[0255] In the embodiment of FIG. 17, a second non-AP station (non-AP STA2) discovers a first non-AP station (non-AP STA1) that supports relay operation through relay discovery. The second non-AP station (non-AP STA2) transmits a request frame (Relay Request) requesting relay setup to the first non-AP station (non-AP STA1). At this time, the request frame (Relay Request) may include information of the second non-AP station (non-AP STA2) as described above. The first non-AP station (non-AP STA1) may determine whether to set up a relay for the second non-AP station (non-AP STA2) based on the information of the second non-AP station (non-AP STA2). A first non-AP station (non-AP STA1) decides to set up a relay for a second non-AP station (non-AP STA2) and transmits a response frame (Relay Response) to the second non-AP station (non-AP STA2). The response frame (Relay Response) includes capabilities supported by the relay operation of the first non-AP station (non-AP STA1). The second non-AP station (non-AP STA2) decides whether to complete the relay setup based on the capabilities supported by the relay operation of the first non-AP station (non-AP STA1). The second non-AP station (non-AP STA2) transmits an activation frame (Relay Activation) to the first non-AP station (non-AP STA1) to request initiation of the relay operation. The first non-AP station (non-AP STA1) receiving the activation frame starts the relay operation. The second non-AP station (non-AP STA2) starts the relay operation.The first non-AP station (non-AP STA1) transmits a report frame containing information about the second non-AP station (non-AP STA2) to the AP. The AP transmits the MPDU that is to be transmitted to the second non-AP station (non-AP STA2) to the first non-AP station (non-AP STA1). The first non-AP station (non-AP STA1) transmits the MPDU received from the AP to the second non-AP station (non-AP STA2).

[0256]

[0257] Figure 18 shows the format of frames exchanged in a relay setup process according to an embodiment of the present invention.

[0258] For convenience of explanation, during the relay setup process, a non-AP station that transmits a request frame is referred to as a relay request station, and a non-AP station that receives the request frame and transmits a response frame is referred to as a relay request response station.

[0259] As described above, the request frame, response frame, and report frame exchanged during the relay setup process may include various information. The request frame may include a TID-to-link mapping element. In addition, the request frame may include a Relay Request Control field. The Relay Request Control field may include a TID-to-Link mapping element present subfield. The TID-to-Link mapping element present subfield indicates whether the request frame includes a TID-to-Link mapping element. For example, when the request frame includes a TID-to-Link mapping element, the value of the TID-to-Link mapping element present subfield may be set to 1. In addition, if the requesting station is included in a multi-link device, and TID-to-Link mapping negotiation is performed between the multi-link device and the AP and does not correspond to the default mapping, the relay requesting station may not be permitted to transmit a request frame that does not include a TID-to-Link mapping element. The request frame may include an AID12 subfield indicating AID12 of the relay requesting station. The request frame may include a QoS Requirement subfield indicating information related to the QoS requirements of the relay requesting station. In this case, the information related to the QoS requirements may indicate a delay / latency bound or a minimum required data rate. In addition, if the non-AP station that received the request frame determines that it cannot support the QoS requirements of the relay requesting station, the non-AP station that received the request frame may reject the relay setup.

[0260] The response frame may include a UL / DL Data Rate subfield indicating a data rate that the relay request responding station can provide to the relay requesting station. The data rate may be indicated for each transmission direction (UL / DL). In addition, the response frame may include a Queue Size subfield indicating the size of a queue that the relay request responding station can use for the relay requesting station. In addition, the response frame may include a BlockAck Support subfield indicating whether the relay request responding station supports transmitting and receiving BlockAcks for MPDUs exchanged in relay operation. In addition, the response frame may include a Number of Relay Stations subfield indicating the number of non-AP stations for which the relay request responding station currently supports relay operation. In addition, the response frame may include a TWT information subfield indicating information about an individual TWT agreement established by the relay request responding station with the AP. If the number of individual TWT agreements established by the relay request response station and the AP is multiple, the TWT information subfield may indicate information about each of the multiple individual TWT agreements. Additionally, the Relay Response Control field included in the request frame may include a field indicating the number of individual TWT agreements indicated by the TWT information subfield.

[0261] The relay request station can determine whether to complete the relay setup based on the information indicated in the response frame. Specifically, if the response frame indicates that the relay request responding station does not support BlockAck, the relay request station can abort the relay setup. Furthermore, if the doze state maintenance period of the TWT setup of the relay responding station indicated in the response frame is longer than a predetermined time, the relay request station can abort the relay setup. Through these embodiments, the relay request station can determine the communication quality that can be expected when the relay responding station performs the relay operation. Furthermore, through this, the relay request station can decide whether to proceed with the relay setup based on the communication quality that can be expected.

[0262] As previously described, the report frame can indicate information about newly added destination stations to a relay station that has completed relay setup. The report frame can include a Number of STAs subfield, which indicates the number of destination stations for which the relay station supports relay operations. Additionally, the report frame can include an AID12 subfield, which indicates the AID12 of the destination stations for which the relay station supports relay operations.

[0263] The format of the specific request frame, response frame, and report frame may be as shown in Fig. 18.

[0264]

[0265] Relay Protocol

[0266] Relay stations must transmit and receive not only traffic for the destination device but also traffic for themselves. Relay station performance can degrade the efficiency of transmitting and receiving traffic for relay stations due to relay operation. Furthermore, power management efficiency can be reduced. Therefore, a relay protocol that considers relay stations is needed to encourage participation of many non-AP stations in relay operation.

[0267]

[0268] <Operation of the relay station>

[0269] A relay station needs to determine whether the MPDU it receives is for itself or for the destination station. At this time, the relay station can determine whether the MPDU received is for itself or for the destination station based on the receiver address of the MPDU. The receiver address of the MPDU can be indicated by either the value of the Receiver Address field of the MAC header or the value of the Destination Address field. Specifically, the relay station can operate as follows.

[0270] The relay station can check the receiver address of the received MPDU. At this time, if the receiver address of the received MPDU is the MAC address of the relay station, the relay station can MAC process the received MPDU and forward it to the upper layer. In addition, if the receiver address of the received MPDU is the MAC address of the destination station, the relay station can queue the received MPDU in a buffer for relay operation. The relay station can operate a buffer for relay operation for each destination station. In addition, the relay station can operate a buffer for each of multiple TIDs for each destination station. In addition, if the received MPDU requests ACK / BA, the relay station can transmit ACK / BA for the received MPDU. At this time, the relay station can transmit ACK / BA regardless of the receiver address of the received MPDU. If the relay station is allocated a resource for transmitting a PPDU to the destination station, the relay station can transmit the MPDU queued in the buffer for relay operation to the destination station. At this time, the resource for transmitting the PPDU to the destination station may include at least one of time, for example, TXOP, and RU (resource unit) allocated for transmission. If the transmission of the relay station to the destination station fails, the relay station may retransmit the failed MPDU. If the transmission of the relay station to the destination station succeeds, the relay station may delete the successfully transmitted MPDU from the buffer for relay operation.

[0271] A relay station can transmit a broadcast frame received from an AP to a destination station. At this time, the broadcast frame may be a group addressed frame. Specifically, the relay station can transmit a non-individually addressed MPDU (MPDU) to the destination station using a relay PPDU. This allows the AP's announcement to be delivered to the destination station. In addition, the relay station can select information that needs to be delivered to the destination station among the information announced by the AP and transmit it to the destination station. In a specific embodiment, if the AP indicates critical update information using a beacon frame, the relay station can transmit a relay PPDU including an element corresponding to the critical update to the destination station. For example, if the AP indicates a critical update that changes an EDCA parameter using a beacon frame, the relay station can transmit a relay PPDU including information regarding the EDCA parameter to the destination station. Additionally, if the AP transmits a Channel Switch Announcement element, the relay station can transmit information generated based on the Channel Switch Announcement element to the destination station. This can ensure the destination station's channel switch.

[0272]

[0273] Resource Allocation for Relay Stations

[0274] A relay station requires resources to exchange MPDUs for itself as well as resources to exchange MPDUs for the destination station. If a relay station uses acquired TXOP and frequency resources to exchange MPDUs for relay operation, the processing of MPDU exchanges for the relay station may be delayed. Therefore, non-AP stations are more likely to not participate as relay stations in relay operation.

[0275] An AP can allocate resources for relay operation to a relay station. Specifically, the AP can allocate a TXOP for relay operation to the relay station within the TXOP acquired by the AP. The relay station can perform relay operation within the TXOP allocated for relay operation from the AP. The AP can allocate a TXOP for relay operation to the relay station using an MU-RTS TXS trigger frame. The MU-RTS TXS trigger frame can indicate the time interval allocated by the MU-RTS TXS trigger frame and the station to which the TXOP is allocated.

[0276] FIG. 19 shows a relay operation performed within a TXOP allocated by an AP according to an embodiment of the present invention.

[0277] After the AP acquires the TXOP, it transmits the first PPDU (DL PPDU#1) to the relay station. The first PPDU (DL PPDU#1) is a PPDU including an MPDU whose destination is the relay station. The relay station receives the first PPDU (DL PPDU#1) and transmits the first BlockAck (BlockAck#1). The AP receives the first BlockAck (BlockAck#1) from the relay station and transmits the second PPDU (DL PPDU#2). The second PPDU (DL PPDU#2) is a PPDU including an MPDU whose destination is the relay station. The relay station receives the second PPDU (DL PPDU#2) and transmits the second BlockAck (BlockAck#2) to the AP indicating whether reception of the MPDU included in the second PPDU (DL PPDU#2) was successful. At this time, the AP can delete the MPDU (MSDU) indicated by the receipt of the second BlockAck (BlockAck#2) from the queue.

[0278] The AP receives the second BlockAck (BlockAck#2) from the relay station and allocates a TXOP for relay operation to the relay station within the TXOP acquired by the AP. Specifically, the AP allocates a TXOP for relay operation to the relay station using a TXS trigger frame. The relay station, which has received the TXS trigger frame, transmits a CTS frame to the AP in response to the TXS trigger frame. The relay station transmits a relay PPDU to the destination station within the allocated TXOP. The destination station transmits a response frame to the relay station, indicating whether or not the MPDU (MSDU) included in the relay PPDU has been received. At this time, the response frame may be a BlockAck or an AcK frame. If the relay station determines that the transmission of the MPDU (MSDU) included in the relay PPDU has failed, the relay station may perform a MAC level recovery operation. Specifically, the relay station may perform retransmission for the MPDU (MSDU) that has failed to be transmitted.

[0279]

[0280] An AP can use a trigger frame to assign an RU to a relay station for relay operation. This is described in FIG. 20.

[0281] FIG. 20 shows an AP allocating an RU to a relay station and the relay station performing a relay operation in the allocated RU according to an embodiment of the present invention.

[0282] A relay station can transmit a relay PPDU to a destination station in an RU allocated for relay operation in a trigger frame. At this time, the format of the relay PPDU may not be a TB PPDU. The trigger frame can allocate both an RU for relay operation and an RU for UL transmission. For example, the trigger frame can allocate a 242-tone RU of a primary 20 MHz band as an RU for RU operation to the relay station, a 242-tone RU of a secondary 20 MHz band to the first station, and a 484-tone RU of a 40 MHz band to the second station. In addition, the relay station can transmit the relay PPDU simultaneously with the TB PPDU transmission of a station that has been allocated an RU through the trigger frame that allocated the RU to the relay station. At this time, the relay station and the station that has been allocated an RU through the trigger frame can use OFDMA (orthogonal frequency division multiple access). Additionally, the end time of the relay PPDU may be restricted to be the same as or earlier than the end time of the TB PPDU.

[0283] Additionally, the trigger frame may indicate the purpose for which the RU is allocated. Specifically, the trigger frame may indicate that the RU is allocated for relay operation. For example, the trigger frame may include an indicator indicating that the RU is allocated for relay operation. Additionally, when the AP transmits an MPDU to be transmitted to the destination station to the relay station and then transmits a trigger frame immediately thereafter or within a predetermined time, the RU indicated by the trigger frame may be implicitly indicated as being allocated for relay operation.

[0284] An AP may perform SR (spatial reuse) for an RU allocated to a relay station for relay operation. Specifically, the AP may transmit a PPDU to a station corresponding to a hidden station of the relay station from the RU allocated to the relay station for relay operation. At this time, the station corresponding to the hidden station of the relay station may receive the DL PPDU without being affected by interference caused by the relay PPDU transmission of the relay station. In this embodiment, the length of the DL PPDU transmitted by the AP may be limited within the length of the relay PPDU transmitted by the relay station. Specifically, the length of the DL PPDU may be the same as the length of the relay PPDU. At this time, the end time of the relay PPDU and the end time of the DL PPDU may be a time corresponding to a length indicated by the UL Length field of the trigger frame, that is, a time when the PPDU indicated by the UL Length field ends in SIFS. In addition, the AP may set the interval between the trigger frame and the DL PPDU to PIFS (PCF inter-frame space). This ensures that relay PPDUs are transmitted before DL PPDUs. For this embodiment, a procedure for identifying hidden stations may be implemented. The AP may transmit a response indicating whether a frame transmitted by the relay station has been received by a non-AP station in the BSS operated by the AP. The AP may determine a station that has not received a frame transmitted by the relay station as a hidden station.

[0285] A relay station can receive a trigger frame and transmit a relay PPDU at intervals within a pre-specified time interval. The pre-specified time interval can be equal to or greater than the short inter-frame space (SIFS) and within the PIFS. A station that receives a trigger frame transmits a response frame at SIFS intervals, but the relay PPDU is a PPDU transmitted to the destination station, not the AP.

[0286] In the embodiment of FIG. 20, the AP transmits an MU-RTS frame. The first station (STA1) and the relay station (R_STA) transmit a CTS frame in response to the MU-RTS frame. The AP transmits a DL MU PPDU to the first station (STA1) and the relay station (R_STA). The DL MU PPDU includes an MPDU to be transmitted by the relay station (R_STA) to the destination station (D_STA). The AP transmits a trigger frame that allocates RUs to the first station (STA1) and the relay station (R_STA). At this time, the trigger frame allocates a 242-tone RU of the primary 20MHz channel to the relay station (R_STA) as an RU for relay operation. In addition, the trigger frame allocates a 484-tone RU of the secondary 40MHz band to the first station (STA1). The relay station transmits a relay PPDU to the destination station in the 242-tone RU of the allocated primary 20MHz channel. The first station (STA1) transmits a PPDU (TX TB PPDU) to the AP in the 484-tone RU of the secondary 40MHz band. The relay station (STA1) starts transmitting the relay PPDU after the first station (STA1) starts transmitting the PPDU (TX TB PPDU). As in the embodiments described above, the relay station (R_STA) can determine the interval between the trigger frame and the relay PPDU within a predetermined time interval. The predetermined time interval can be greater than or equal to SIFS and less than or equal to PIFS. The end time of the relay PPDU can be the time indicated by the UL Length field of the trigger frame, that is, the time when a PPDU of a length indicated by the UL Length field in SIFS ends.

[0287] However, the Relay PPDU is terminated at the time indicated by the Trigger frame (the time indicated by the UL Length field included in the Trigger frame). That is, the Relay PPDU is terminated at the same time as the TB PPDU that was responded to together.

[0288] FIG. 21 shows an AP performing an SR operation on an RU allocated to a relay station according to an embodiment of the present invention.

[0289] The operation up to the transmission of the trigger frame in Fig. 21 is the same as in Fig. 20. However, in Fig. 21, the AP transmits a DL PPDU to the first station (STA1), which is a hidden station, while the relay PPDU is being transmitted. At this time, the interval between the trigger frame and the DL PPDU is PIFS, as described above.

[0290]

[0291] <Restrictions on relay operation>

[0292] When an AP transmits an MPDU to a relay station to transmit to a destination device, the AP can transmit based on the physical layer capabilities of the relay station. This is because the relay station, not the destination station, directly performs the reception. In addition, the AP can configure the MPDU to be transmitted to the destination station based on the MAC layer capabilities of the relay station. Specifically, the AP can configure the MPDU to be transmitted to the destination station based on not only the MAC layer capabilities of the destination station but also the MAC layer capabilities of the relay station. Therefore, the AP can configure the MPDU to be transmitted to the relay station based on the minimum supported function between the MAC layer capabilities of the destination station and the MAC layer capabilities of the relay station. In addition, the relay station can configure the MPDU to be transmitted to the AP based on the MAC layer capabilities of the relay station. Specifically, the relay station can configure the MPDU to be transmitted to the AP based on not only the MAC layer capabilities of the AP but also the MAC layer capabilities of the relay station. Therefore, the destination station can configure the MPDU to be transmitted to the relay station based on the minimum supported function between the MAC layer capabilities of the AP and the MAC layer capabilities of the relay station. Specifically, the capabilities of the MAC layer of the relay station may include at least one of the following: maximum number of MSDUs that can be included in an A-MSDU, support for Multi-TID A-MPDU, capability for fragmentation, support for All Ack, maximum value of extension of A-MPDU length, and support for ACK other than BA frame for A-MSDU. The capabilities for fragmentation may include at least one of: support for dynamic fragmentation, maximum number of fragmented MSDUs / A-MSDUs, and maximum value of fragments.For example, the AP and the destination station may support Multi-TID A-MPDUs, and the relay station may only support Single-TID A-MPDUs. In this case, the AP and the destination station may not be permitted to perform frame exchange with the relay station by configuring A-MPDUs with multiple TIDs. In addition, if the destination device supports A-MPDUs with four TIDs, but the relay station supports A-MPDUs with two TIDs, the AP may not configure the A-MPDU transmitted to the relay station for transmission to the destination device to have three or more TIDs.

[0293] These embodiments can prevent problems that may arise when a non-AP station operating as a relay station has limited capabilities compared to an AP. This is because generating and transmitting MPDUs based solely on the capabilities of the AP and destination station can burden the relay station or prevent relay operation from occurring. Furthermore, these embodiments can reduce the processing burden on the relay station's MAC layer.

[0294]

[0295] Relay PPDU for Multiple Stations

[0296] A relay PPDU may include MPDUs transmitted to multiple stations. Specifically, the relay PPDU may be an MU (multiuser) PPDU. In addition, the MPDUs transmitted to multiple stations may be transmitted according to the RUs allocated to each of the multiple stations. In addition, the relay PPDU may be transmitted using MU-MIMO or OFDMA. In addition, the relay PPDU may indicate information about a frequency range in which the MPDUs that each station must receive are transmitted, such as RUs. In this case, the information about the RUs may include at least one of RU location information and RU allocation information. In addition, the information about the frequency range may be included in a preamble of the relay PPDU, such as a UHR signaling field. Multiple stations may determine a frequency range in which the MPDUs for each of the multiple stations are transmitted based on the preamble of the relay PPDU. In addition, the preamble of the relay PPDU may be repeated in units of 20 MHz. At this time, a station receiving a relay PPDU can check the preamble of any 20MHz band and determine the frequency range in which the MPDU for the station is transmitted. Furthermore, even if the relay PPDU only contains MPDUs for a single station, it can include information indicating the frequency range in which the MPDU for the station is transmitted.

[0297] Additionally, the plurality of stations may include not only the destination station but also non-destination stations. Specifically, the plurality of stations may include not only the destination station but also an AP.

[0298] Additionally, a relay station may exchange MU-RTS frames and CTS frames before transmitting a PPDU containing an MPDU to be transmitted to multiple stations.

[0299] FIG. 22 illustrates an operation of a relay station transmitting a relay PPDU for multiple destination stations according to an embodiment of the present invention.

[0300] In the embodiment of FIG. 22, the AP transmits a first DL PPDU (DL PPDU#1) including an MPDU to be transmitted to a first destination station (D_STA1) to a relay station (R_STA). The relay station transmits a Block Ack for the first DL PPDU (DL PPDU#1) to the AP. The AP transmits a second DL PPDU (DL PPDU#2) including an MPDU to be transmitted to a second destination station (D_STA2) to the relay station (R_STA). The relay station transmits a Block Ack for the second DL PPDU (DL PPDU#2) to the AP. At this time, the relay station can determine to which destination station the MPDU should be transmitted based on the receiver address field of the MPDU. The AP transmits a TXS trigger frame (TXS Trigger) to allocate a TXOP to the relay station (R_STA). The relay station (R_STA) transmits a CTS frame to the AP in response to the TXS trigger frame (TXS Trigger).

[0301] The relay station (R_STA) exchanges MU-RTS frames / CTS frames with the first destination station (D_STA1) and the second destination station (D_STA2) within the allocated TXOP. The relay station (R_STA) transmits a relay PPDU containing MPDUs to be transmitted to each of the first destination station (D_STA1) and the second destination station (D_STA2) using MU-MIMO or OFDMA. The first destination station (D_STA1) and the second destination station (D_STA2) transmit a Block Ack frame to the relay station (R_STA).

[0302] FIG. 23 illustrates an operation of transmitting a relay PPDU including both an MPDU transmitted by a relay station to an AP and an MPDU transmitted to a destination station according to an embodiment of the present invention.

[0303] In Fig. 23, the AP and the relay station (R_STA) exchange RTS frames and CTS frames. The AP transmits a DL PPDU to the relay station (R_STA). The relay station (R_STA) transmits a Block Ack. The relay station (R_STA) exchanges MU-RTS frames and CTS frames with the AP and the destination station (D_STA). The relay station (R_STA) transmits a relay PPDU, which includes both an MPDU transmitted to the AP and an MPDU transmitted to the destination station, to the AP and the destination station (D_STA). The relay PPDU indicates an RU in which the MPDU transmitted to the destination station (D_STA) is transmitted and an RU in which the MPDU transmitted to the AP is transmitted. The AP and the destination station receive the MPDU transmitted to the AP and the destination station, respectively, according to the RU indicated by the relay PPDU.

[0304]

[0305] When a relay station transmits an UL PPDU to transmit an MPDU received from a destination station, the relay station may include an MPDU that the relay station transmits to the AP in the UL PPDU. At this time, the UL PPDU includes an MPDU including traffic received from the destination station and an MPDU including traffic that the relay station transmits to the AP. In addition, the UL PPDU may include information indicating a frequency resource through which the MPDU is transmitted for each transmitting station. Specifically, the UHR-SIG field of the UL PPDU may include information indicating a resource through which the MPDU is transmitted for each station. At this time, the frequency resource may be RU. The AP may determine from which station the MPDU included in the UL PPDU was transmitted based on the information indicating a resource through which the MPDU is transmitted for each station.

[0306] FIG. 24 shows that when a relay station transmits a UL PPDU to transmit an MPDU received from a destination station according to an embodiment of the present invention, the relay station includes an MPDU transmitted to an AP in the UL PPDU.

[0307] The destination station (D_STA) exchanges RTS frames and CTS frames with the relay station (R_STA). The destination station (D_STA) transmits to the relay station (R_STA) an SU PPDU containing an MPDU to be transmitted to the AP. The relay station (R_STA) transmits to the destination station (D_STA) a BlockAck. The relay station (R_STA) exchanges RTS frames and CTS frames with the AP. The relay station (R_STA) transmits an UL PPDU containing an MPDU that the destination station (D_STA) transmits to the AP and an MPDU that the relay station (R_STA) transmits to the AP. The AP receives both the MPDU that the destination station (D_STA) transmits to the AP and the MPDU that the relay station (R_STA) transmits to the AP, included in the UL PPDU. The AP transmits to the relay station a Multi-STA BlockAck frame indicating whether the MPDU that the destination station (D_STA) transmits to the AP and the MPDU that the relay station (R_STA) transmits to the AP were successful. The Multi-STA BlockAck frame includes a Per AID TID Info field corresponding to the relay station and a Per AID TID Info field corresponding to the destination station. At this time, the value of the AID11 subfield of the Per AID TID Info field corresponding to the relay station (R_STA) is the AID11 of the relay station (R_STA). AID11 represents the value of 11 bits of the AID value. The value of the AID11 subfield of the Per AID TID Info field corresponding to the destination station (D_STA) is the AID11 of the destination station (D_STA).

[0308] FIG. 25 shows the format of a UL PPDU including an MPDU received by a relay station from a destination station and an MPDU transmitted by the relay station to an AP according to an embodiment of the present invention.

[0309] As described above, a relay station can transmit together an MPDU including traffic received from a destination station and an MPDU including traffic transmitted by the relay station to an AP. The relay station can generate a first A-MPDU by aggregating MPDUs including traffic received from the destination station. In addition, the relay station can generate a second A-MPDU by aggregating MPDUs including traffic transmitted by the relay station to an AP. The relay station can transmit the first A-MPDU and the second A-MPDU using a single PPDU. In this case, the PPDU can be transmitted using OFDM. The first A-MPDU and the second A-MPDU can have the same length. In addition, when the lengths of the first A-MPDU and the second A-MPDU are different, the first A-MPDU or the second A-MPDU can include padding so that the first A-MPDU and the second A-MPDU have the same length. The first A-MPDU and the second A-MPDU may be transmitted via independent frequency resources, such as RU, via OFDM. In this case, information regarding the frequency resources through which the first A-MPDU and the second A-MPDU are transmitted may be indicated in the UHR-SIG field of the UL PPDU.

[0310] In the embodiment of FIG. 25, a first A-MPDU is transmitted through a 40 MHz band corresponding to a Low 484-tone RU area, and a second A-MPDU is transmitted through a 40 MHz band corresponding to a High 484-tone RU area. At this time, information regarding frequency resources is indicated equally for every 20 MHz band in the preamble of the physical layer.

[0311]

[0312] <BlockAck Frame Format for Relay Operation>

[0313] A relay station can send a BlockAck to an AP. Specifically, the relay station can send a BlockAck indicating whether the AP has received an MPDU (MSDU) transmitted to the relay station and whether the AP has received an MPDU (MSDU) transmitted to the destination station.

[0314] The AP can transmit a BlockAck to the relay station to indicate whether the relay station has received the MPDU (MSDU) transmitted by the AP and whether the destination station has received the MPDU (MSDU) transmitted by the AP. Specifically, when the relay station transmits a UL PPDU containing the MPDU (MSDU) transmitted by the relay station to the AP and the MPDU (MSDU) transmitted by the destination station to the AP, the AP can transmit a BlockAck to the relay station to indicate whether the relay station has received the MPDU (MSDU) transmitted by the relay station to the AP and whether the destination station has received the MPDU (MSDU) transmitted by the AP.

[0315] This BlockAck can be transmitted as a Multi-STA BlockAck frame. At this time, the value of the AID11 subfield of the Per AID TID Info subfield, which indicates whether the MPDU (MSDU) transmitted by the destination station to the AP has been received, can indicate the AID11 of the destination station.

[0316] Figure 26 shows the format of a commonly used BlockAck frame.

[0317] Figure 26 (a) shows the BA Information field format when the type of BA indicated in the BA Control field is indicated as Compressed BlockAck.

[0318] The Compressed BlockAck variant format of the BA Information field consists of a 2-octet Block Ack Starting Sequence Control subfield and an 8 / 32 / 64 / 128-octet Block Ack Bitmap subfield. Since the Block Ack Bitmap subfield has a maximum size of 128 octets, it can indicate compressed BAs for up to 1024 MPDUs. Devices that can use the 64 / 128-octet Block Ack Bitmap subfield may be limited to EHT / UHR devices or subsequent generation UHR devices that can respond / receive 512 / 1024-bit BAs. Since the Block Ack Bitmap subfield can be of various lengths, a device that receives a BlockAck frame must know the size of the Block Ack Bitmap subfield included in the BlockAck frame in order to interpret the Block Ack frame. Information regarding the size of the Block Ack Bitmap subfield is indicated together with the SSN in the Block Ack Starting Sequence Control subfield preceding the Block Ack Bitmap subfield.

[0319] Figure 26 (d) shows the format of the Block Ack Starting Sequence Control subfield, and the Block Ack Starting Sequence Control subfield having a 2-octet size can be composed of a 4-bit Fragment Number subfield and a 12-bit Starting Sequence Number subfield. The Block Ack Starting Sequence Control subfield can be commonly included in the BA Information field of various BlockAck variants, as illustrated through Figures 26 (a), (b), and (c). In the case of the format of the BA Information field of the Multi-STA BlockAck variant of Figure 26 (c), the Block Ack Starting Sequence Control subfield can be omitted if a specific condition is satisfied. In this case, when the Block Ack Starting Sequence Control subfield is omitted, the Block Ack Bitmap subfield can also be omitted.

[0320] The length of the Block Ack Bitmap subfield is indicated through the 4-bit Fragment Number subfield, and the device that received the BA can determine the size of the Block Ack Bitmap subfield and the information indicated in the bitmap based on the information indicated through the Fragment Number subfield.

[0321] Depending on the type of TID and the number of AID-TIDs included in the BlockAck frame, the BlockAck frame may include multiple Multi-TID BlockAcks and Multi-TID BlockAck variants as shown in (b) and (c) of FIG. 26.

[0322] The Per TID Info field of (b) of FIG. 26 includes a TID subfield indicating which TID each Multi-TID BlockAck variant is for. If the TID subfields of two Multi-TID BlockAck variants transmitted to a specific STA indicate 0 and 1, respectively, the Multi-TID BlockAck frame received by the station indicates whether the MPDUs corresponding to TID0 and TID1 were successfully received.

[0323] The Per AID TID Info field of (c) of Fig. 26 includes an AID11 subfield indicating which station each Multi-STA BlockAck variant is for. The Per AID TID Info field includes a TID subfield indicating which TID MPDU (MSDU) each Multi-STA BlockAck variant is for. The four Multi-STA BlockAck variants transmitted to the first and second stations<AID11 subfield, TID subfield> Each of the first STA may include <AID11, 0 of the first STA>, <AID11, 1 of the first STA>, <AID11, 2 of the second STA>, and <AID11, 3 of the second STA>. At this time, the Multi-STA BlockAck frame indicates whether reception of an MPDU having a TID of 0 or 1 among the MPDUs transmitted by the first STA was successful, and whether reception of an MPDU having a TID of 2 or 3 among the MPDUs transmitted by the second STA was successful.

[0324]

[0325] Figure 27 shows the format of a typical Multi-STA BlockAck frame.

[0326] Fig. 27 (a) shows the format of the BA Information field, Fig. 27 (b) shows the format of the Per AID TID Info subfield included in the BA Information field, and Fig. 27 (c) shows the format of the AID TID Info subfield included in the Per AID TID Info subfield. The BA Information field of the Multi-STA BlockAck frame includes a Per AID TID Info subfield for each combination of AID and TID. Each Per AID TID Info subfield includes an AID TID Info subfield, as shown in Fig. 27 (b). The AID TID Info subfield indicates the structure of the Per AID TID Info subfield including the AID TID Info subfield and the identifier of the station corresponding to the Per AID TID Info subfield, for example, the AID and the TID corresponding to the Per AID TID Info subfield. A station receiving a Multi-STA BlockAck may determine that the Per AID TID Info subfield, which includes an AID TID Info subfield containing an AID11 subfield indicating the station's AID11, is information for the station.

[0327] Each of the multiple Per AID TID Info subfields included in the Multi-STA BlockAck frame may include information corresponding to a different station. A station receiving a Multi-STA BlockAck may selectively obtain information indicated by a Per AID TID Info subfield including an AID11 subfield indicating the AID of the station among the multiple Per AID TID Info subfields included in the BA Information field. The station may determine whether to receive an MPDU indicated by a Block Ack Bitmap subfield of a BA Information field of a Per AID TID Info subfield including an AID11 subfield indicating the AID of the station.

[0328] A station receiving a Multi-STA BlockAck frame may acquire a Per AID TID Info subfield including an AID11 subfield indicating an AID of the station, and update the status of an MPDU in the station's transmission buffer based on a Block Ack Bitmap subfield included in the acquired Per AID TID Info subfield. In addition, a station receiving a Multi-STA BlockAck frame may not determine information indicated by a Per AID TID Info subfield including an AID11 subfield not indicating an AID of the station. A station receiving a Multi-STA BlockAck frame may determine information related to a start position of a next Per AID TID Info subfield in the Multi-STA BlockAck frame based on the length of a Block Ack Bitmap subfield indicated by a Fragment Number subfield. At this time, the station can determine the position of the AID11 subfield of the next Per AID TID Info subfield in the Multi-STA BlockAck frame based on the length of the Block Ack Bitmap subfield indicated by the Fragment Number subfield. The station receiving the Multi-STA BlockAck frame can sequentially determine whether multiple Per AID TID Info subfields included in the Multi-STA BlockAck frame indicate the station's AID.

[0329]

[0330] As described above, the AP can transmit a BlockAck frame to the relay station to indicate whether it has received an MPDU (MSDU) containing the traffic of the relay relay station as well as an MPDU (MSDU) containing the traffic of the destination station. The relay station can obtain the information indicated by the Per AID TID Info subfield corresponding to the AID of the relay station as well as the information indicated by the Per AID TID Info subfield corresponding to the AID of the destination station for which the relay station supports the relay operation. The relay station can determine whether the value of the AID11 subfield included in the Per AID TID Info field indicates the AID11 of the relay station or the AID11 of the destination station for which the relay station supports the relay operation. The relay station can delete the received MPDU (MSDU) from the transmission buffer and perform retransmission for the MPDU (MSDU) that has not been received depending on whether the MPDU (MSDU) indicated by the Per AID TID Info field corresponding to the AID of the relay station has been received. The relay station can delete the received MPDU (MSDU) from the buffer for relay operation and perform retransmission for the MPDU (MSDU) that is not received, depending on whether the MPDU (MSDU) indicated by the Per AID TID Info field corresponding to the AID of the destination station has been received.

[0331] An AP may transmit an ACK frame in response to an MPDU (MSDU) containing traffic from a relay station and an MPDU (MSDU) containing traffic from a destination station. The AP may respond with an ACK frame to a UL PPDU containing an MPDU (MSDU) containing traffic from a relay station and an MPDU (MSDU) containing traffic from a destination station. In a specific embodiment, if the AP successfully receives all MPDUs (MSDUs) from a UL PPDU containing an MPDU (MSDU) containing traffic from a relay station and an MPDU (MSDU) containing traffic from a destination station, the AP may respond with an ACK frame to the UL PPDU. In this case, the ACK frame indicates that all MPDUs (MSDUs) contained in the UL PPDU have been successfully received.

[0332] In addition, the relay station can transmit a Multi-STA BlockAck frame to the AP to indicate whether the MPDU (MSDU) received from the AP has been received, distinguishing between an MPDU (MSDU) containing traffic for the relay station and an MPDU (MSDU) containing traffic for the destination station. Specifically, the Multi-STA BlockAck frame can indicate whether the MPDU (MSDU) containing traffic for the relay station has been received and whether the MPDU (MSDU) containing traffic for the destination station has been received using separate Per AID TID Info fields. At this time, when the relay station performs relay operation for multiple destination stations, the Multi-STA BlockAck frame can indicate whether the MPDU (MSDU) containing traffic for each of the multiple destination stations has been received by distinguishing between the MPDUs. At this time, the Multi-STA BlockAck frame can indicate whether the MPDU (MSDU) containing traffic for each of the multiple destination stations has been received by using Per AID TID Info fields corresponding to each of the multiple destination stations.

[0333] In these embodiments, the station receiving the Multi-STA BlockAck frame is distinguished from the use of the conventional Multi-STA BlockAck frame, which is used to indicate to multiple stations by the AP whether or not to receive MPDUs (MSDUs). In this case, the value of the AID11 subfield of the Per AID TID Info field corresponding to the destination station may be the AID11 of the destination station. In addition, the value of the AID11 subfield of the Per AID TID Info field corresponding to the relay station may be the AID11 of the relay station or a pre-specified value.

[0334] In the embodiments described above, whether or not an individual MPDU is successfully received can be indicated by the value of the sequence number of each MPDU (MSDU) in the Block ACK Bitmap included in the Per AID TID Info field. Specifically, a bit having 1 in the Block ACK Bitmap can indicate that the MPDU (MSDU) of the sequence number corresponding to the bit was successfully received. In addition, a bit having 0 in the Block ACK Bitmap indicates that the MPDU (MSDU) of the sequence number corresponding to the bit was not received or failed to be received.

[0335] FIG. 28 shows the format of a Multi-STA BlockAck frame transmitted by a relay station according to an embodiment of the present invention.

[0336] As described above, the Multi-STA BlockACK frame includes multiple BA Information fields. In the embodiment of FIG. 28, the AID11 field included in the first BA Information field indicates the AID11 of the relay station (R_STA) or 0, which is a pre-designated value for the relay station (R_STA). Therefore, the first BA Information field corresponds to the TID indicated by the TID field included in the BA Information field, and indicates whether the MPDU including traffic for the relay station (R_STA) has been successfully received. The AID11 field included in the second BA Information field indicates the AID11 value of the destination station (D_STA). Therefore, the second BA Information field corresponds to the TID indicated by the TID field included in the BA Information field, and indicates whether the MPDU including traffic for the destination station (D_STA) has been successfully received.

[0337] In the embodiments described above, whether or not a reception has been made may indicate whether or not the reception has been successful.

[0338]

[0339] <Channel Access Method for Uplink Transmission Relay>

[0340] A relay station receives traffic from a destination station, and the relay station can transmit the traffic received from the destination station to the AP. This is called uplink relaying. The relay station can perform channel access to perform uplink relaying. If the relay station performs separate channel access to perform uplink relaying, it is burdensome for the relay station and can harm the fairness between the relay station and the destination station. A method is needed to guarantee channel access for the relay station performing uplink relaying.

[0341] An AP can cause a relay station to perform uplink transmission relaying based on the TXOP acquired by the AP. Specifically, the AP can transmit a trigger frame to the relay station to trigger transmission for uplink transmission relaying of the relay station. In addition, the AP can share the TXOP acquired by the AP, and the relay station can perform transmission for uplink transmission relaying based on the shared TXOP. However, the AP is unaware of information related to traffic that the destination station intends to transmit. The destination station can transmit information about the traffic that it intends to transmit through the relay station to the AP in advance. In another specific embodiment, the destination station can transmit information about the traffic transmitted through the relay station to the AP in advance. In the embodiments described above, the information about the traffic may be the amount of traffic or the type of traffic. In addition, the destination station can directly transmit information about the traffic to the AP. In this case, the destination station and the AP may be capable of directly exchanging frames at a relatively low data rate. In another specific embodiment, the destination station can transmit information about the traffic to the AP through the relay station. In the embodiments described above, the AP can determine the resources to allocate to the relay station based on traffic information. Specifically, the AP can determine the amount of resources to allocate to the relay station based on traffic information. For example, the AP can determine at least one of the RU size or TXOP length to allocate to the relay station based on traffic information.

[0342] In another specific embodiment, within the TXOP acquired by the destination station, the relay station can transmit traffic received from the destination station to the AP. Specifically, the destination station can allocate the TXOP acquired by the destination station to the relay station. Within the allocated TXOP, the relay station can transmit traffic received from the destination station to the AP. As described above, when the AP intends to transmit traffic to the destination station through the relay station, the AP can share the TXOP with the relay station. When the destination station intends to transmit traffic to the AP through the relay station, the destination station can share the TXOP with the relay station. The destination station's allocation of the TXOP to the relay station can implicitly indicate that the destination station intends to be an uplink transmission relay. Furthermore, after the transmitting station transmits the traffic to be transmitted to the destination station, the transmitting station can allocate the TXOP acquired by the transmitting station to the relay station. The transmitting station is a station that intends to transmit traffic through the relay station. The transmitting station can be a non-AP station, or the AP can be a relay station. At this time, the allocation of TXOP can implicitly indicate relay transmission, as described above. Furthermore, the relay station can transmit traffic to the destination station after receiving a TXOP allocation from the transmitting station.

[0343]

[0344] Protection of Relay Transmission

[0345] As previously explained, when relay transmission is performed, the distance between the destination station and the AP may be relatively far, necessitating relay transmission. In such a situation, the NAV settings of the destination station and the AP may differ. For example, when the destination station completes the backoff procedure, the NAV may have been set by a frame transmitted by the destination station and another non-AP station to the AP, or the AP may be receiving a frame from another non-AP station. Furthermore, when the destination station completes the backoff procedure, the relay station may also not be able to receive the destination station's transmission. Therefore, the relay station may not be able to receive the destination station's transmission, or the AP may not be able to receive the relay station's transmission. Furthermore, when the AP completes the backoff procedure, the NAV may have been set by a frame transmitted by a non-AP station to the destination station, or the destination station may be receiving a frame from a non-AP station. Therefore, when the AP completes the backoff procedure, the relay station may not be able to receive, or when the relay station completes the backoff procedure, the destination station may not be able to receive. Therefore, a method for protecting frame exchanges between the AP, the relay station, and the destination station may be required. At this time, an RTS (request to send) frame / CTS (clear to send) frame exchange may be performed to protect the frame exchange. In this specification, the RTS frame may be replaced with an MU-RTS frame unless otherwise specified. In another specific embodiment, a non-HT PPDU exchange may be performed to protect the frame exchange.

[0346] The destination station can perform RTS frame / CTS frame exchange between the destination station and the AP, and RTS frame / CTS frame exchange between the destination station and the relay station. In another specific embodiment, the destination station can perform RTS frame / CTS frame exchange between the destination station and the relay station, and RTS frame / CTS frame exchange between the destination station and the AP. Through this, the destination station can obtain a TXOP for performing uplink transmission relay, and protect the uplink transmission relay from the hidden nodes of the destination station, the relay station, and the AP, respectively.

[0347] If either of the two RTS frame / CTS frame exchanges fails, the destination station may consider it as having failed to acquire a TXOP. At this time, the destination station may perform an action corresponding to a TXOP acquisition failure. Specifically, the destination station may restart the backoff procedure. If the destination station succeeds in the first RTS frame / CTS frame exchange and fails in the second RTS frame / CTS frame exchange, the destination station may perform the backoff procedure using the minimum value of the CW (contention window) when attempting the RTS frame / CTS frame exchange again. In addition, if the destination station succeeds in the first RTS frame / CTS frame exchange and fails in the second RTS frame / CTS frame exchange, the destination station may transmit a CF-End frame. At this time, the station that receives the CF-End frame may transmit the CF-End frame. Through this embodiment, the NAV set by the RTS frame / CTS frame exchange may be released.

[0348] In addition, the AP may perform an RTS frame / CTS frame exchange between the AP and the destination station, and an RTS frame / CTS frame exchange between the AP and the relay station. In another specific embodiment, the AP may perform an RTS frame / CTS frame exchange between the AP and the relay station, and an RTS frame / CTS frame exchange between the AP and the destination station. This may protect the downlink relay. If either of the two RTS frame / CTS frame exchanges fails, the AP may consider it as a failure to acquire the TXOP. In addition, in a specific embodiment, the AP may perform another frame exchange instead of the first RTS frame / CTS frame exchange. Specifically, the AP may perform an MU-RTS frame / CTS frame exchange instead of the first RTS frame / CTS frame exchange. In this case, the MU-RTS frame may indicate a station other than the destination device as the destination station. In this embodiment, if the AP receives a CTS frame from either station, the AP may determine that the MU-RTS frame / CTS frame has been successfully exchanged.

[0349] Additionally, the AP can first perform transmissions that do not utilize the relay station within the acquired TXOP, such as transmitting DL PPDUs and receiving TB PPDUs, and then perform downlink relaying. Therefore, frame exchange protection between the AP and the relay station may already be established. In this case, the AP can perform downlink relaying after the RTS frame / CTS frame exchange between the AP and the destination station.

[0350]

[0351] The previously described embodiments for protecting uplink or downlink relays involve two RTS / CTS frame exchanges. The need for two frame exchanges reduces transmission efficiency and can be burdensome for stations performing protection operations. Therefore, a method for protecting relay transmissions with a single frame exchange may be needed.

[0352] A transmitting station, a non-AP station, or an AP, or a relay station can transmit a trigger frame designated to protect relay transmissions to a destination station, an AP, or a non-AP station. For convenience of explanation, the trigger frame defined to protect relay transmissions is referred to as a Relay RTS frame. The relay station and the destination station that receive the Relay RTS frame can transmit a CTS frame designated to protect relay transmissions. For convenience of explanation, the CTS frame designated to protect relay transmissions is referred to as a Relay CTS frame.

[0353] Each of the relay station and the destination station can transmit the Relay CTS frame using different RUs or frequency tones. At this time, the transmitting station can determine the station that transmitted the Relay CTS frame based on the RU or frequency tone in which the Relay CTS frame was received. Each of the relay station and the destination station can transmit the payload of the Relay CTS frame on different RUs or frequency tones. For example, the relay station can transmit the payload of the Relay CTS frame in a lower 10 MHz frequency band among the primary 20 MHz subchannel, and the destination station can transmit the payload of the Relay CTS frame in a higher 10 MHz frequency band among the primary 20 MHz subchannel. Furthermore, if the transmitting station determines that the Relay CTS frame received has energy in the entire primary 20 MHz, the transmitting station can determine that both the relay station and the destination station transmitted the Relay CTS frame.

[0354] In another specific embodiment, the relay station and the destination station can each transmit the Relay CTS frame at different times. The transmitting station can determine the station that transmitted the Relay CTS frame based on the time at which the Relay CTS frame was received. Specifically, the relay station and the destination station can transmit the Relay CTS frames in a predefined order. The transmitting station can determine the station that transmitted the received Relay CTS frames in a predefined order. For example, the transmitting station can determine that the first received Relay CTS frame was transmitted by the relay station, and can determine that the second received Relay CTS frame was transmitted by the destination station. In a specific embodiment, the relay station can transmit the Relay CTS frame at a short inter frame space (SIFS) interval from the Relay RTS frame, and the destination station can transmit the Relay CTS frame at a 2xSIFS interval from the Relay RTS frame. At this time, the transmitting station can determine that the Relay CTS frame transmitted at an interval of SIFS between the Relay RTS frame and the Relay CTS frame is transmitted by the relay station, and the Relay CTS frame transmitted at an interval of 2xSIFS between the Relay RTS frame and the Relay CTS frame is transmitted by the destination station. In the embodiment described above, it was described that the Relay CTS frame is transmitted at an interval of SIFS units. Depending on the specific embodiment, a time interval shorter than SIFS may be used instead of SIFS.

[0355]

[0356] FIG. 29 shows an operation of an AP protecting relay downlink transmission by performing two RTS frame / CTS frame exchanges according to one embodiment of the present invention.

[0357] The AP transmits an RTS frame to the relay station (R_STA). The relay station (R_STA) responds to the RTS frame by transmitting a CTS frame to the AP. The interval between the RTS and CTS frames is SIFS. The AP, upon receiving the CTS frame, determines that the relay station (R_STA) is capable of receiving DL PPDUs.

[0358] The AP transmits an RTS frame to the destination station (D_STA). The destination station (D_STA) responds to the RTS frame by transmitting a CTS frame to the AP. The interval between the RTS and CTS frames is SIFS. The AP, upon receiving the CTS frame, determines that the destination station (D_STA) is capable of receiving relay PPDUs.

[0359] Two RTS / CTS frame exchanges establish NAVs for each of the AP, relay station, and destination station's neighboring stations. This protects the downlink relay.

[0360] The AP transmits a DL PPDU containing traffic to be transmitted to the destination station to the relay station (R_STA). The relay station (R_STA) transmits a BlockAck to the AP. The AP can determine whether the traffic transmission is successful by receiving the BlockAck from the relay station (R_STA). If the traffic transmission is successful, the AP allocates the TXOP acquired by the AP to the relay station (R_STA). Specifically, the AP allocates the TXOP acquired by the AP by transmitting a TXS Trigger frame to the relay station (R_STA). As described above, in the embodiment of FIG. 29, the AP allocating the TXOP to the relay station (R_STA) can indicate that relay PPDU transmission is about to begin.

[0361] The relay station (R_STA) transmits the traffic received from the AP to the destination station (D_STA) as a relay PPDU. The destination station (D_STA) receives the relay PPDU. The destination station (D_STA) transmits a BlockAck to the relay station (R_STA) indicating whether it has received the MPDU included in the relay PPDU.

[0362] FIG. 30 shows an operation in which an AP protects relay downlink transmission by exchanging one RTS frame / CTS frame according to an embodiment of the present invention.

[0363] The same operation as described in Fig. 29 is omitted. The AP transmits a Relay RTS frame. The relay station (R_STA) and the destination station (D_STA) transmit a Relay CTS frame in response to the Relay RTS frame. This allows the AP to protect the downlink relay. The AP receives Relay CTS frames from the relay station (R_STA) and the destination station (D_STA) and transmits a DL PPDU to the relay station (R_STA). As described above, if the AP does not receive a Relay CTS frame from either the relay station (R_STA) or the destination station (D_STA), the AP does not transmit a DL PPDU to the relay station (R_STA).

[0364]

[0365] FIG. 31 shows an operation of a non-AP station protecting an uplink transmission relay by performing two RTS frame / CTS frame exchanges according to an embodiment of the present invention.

[0366] The destination station (D_STA) transmits an RTS frame to the relay station (R_STA). The relay station (R_STA) transmits a CTS frame to the destination station (D_STA) in response to the RTS frame. The destination station (D_STA) transmits an RTS frame to the AP. The AP transmits a CTS frame to the destination station (D_STA) in response to the RTS frame. Through these operations, the destination station (D_STA) can determine that the relay station (R_STA) is in a state where it can receive UL PPDUs and that the AP is in a state where it can receive relay PPDUs.

[0367] Two RTS / CTS frame exchanges establish NAVs for each of the AP, relay station, and destination station's neighboring stations. This protects the uplink relay.

[0368] The destination station (D_STA) transmits a UL PPDU containing the traffic to be transmitted to the AP to the relay station (R_STA). The relay station (R_STA) receives the UL PPDU. The relay station (R_STA) transmits a BlockAck to the destination station (D_STA) indicating whether the MPDU contained in the UL PPDU has been received. If the transmission of the traffic contained in the UL PPDU is successful, the destination station (D_STA) assigns the TXOP it acquired to the relay station (R_STA).

[0369] If the traffic transmission is successful, the destination station (D_STA) allocates the TXOP acquired by the AP to the relay station (R_STA). Specifically, the destination station (D_STA) transmits a TXS trigger frame (TXS Trigger) to the relay station (R_STA) to allocate the TXOP acquired by the destination station (D_STA). As described above, in the embodiment of FIG. 31, the destination station (D_STA) allocating the TXOP to the relay station (R_STA) may indicate that relay PPDU transmission is about to begin. At this time, the type of the TXS trigger frame may be designated as a different type from the type of the TXS trigger frame transmitted by the AP. The relay station (R_STA) transmits the traffic received from the destination station (D_STA) to the AP through the relay PPDU. The AP receives the relay PPDU and transmits a BlockAck to the relay station (R_STA).

[0370]

[0371] <How to designate a relay station>

[0372] As described above, an AP can perform setup for relay operation with a non-AP station. At this time, the non-AP station can notify the AP that the relay operation is possible. Specifically, multiple non-AP stations can perform negotiation, and at least one non-AP station can notify the AP that the relay operation is possible. In another specific embodiment, the AP can designate a specific non-AP station as a relay station. This allows the AP to determine whether to transmit an MPDU to a non-AP station directly to the non-AP station or through the relay station. To this end, the AP can perform an operation to find a non-AP station that supports relay operation. The AP can determine a non-AP station that can perform the relay operation based on information acquired when associating with the non-AP station or information acquired for relay operation, such as information acquired during the relay discovery process. If there are multiple non-AP stations that support relay operation, a method is needed for the AP to determine which non-AP station to designate as a relay station.

[0373] First, we describe embodiments for determining whether an AP performs relay operation.

[0374] If the signal strength received from a non-AP station among the non-AP stations to which the AP intends to transmit traffic is lower than a predetermined value, the AP may transmit the traffic to the non-AP station using relay transmission. In another specific embodiment, if the transmission performed by the AP at a predetermined data rate or higher to a non-AP station fails a predetermined number of times, the AP may transmit the traffic to the non-AP station using relay transmission. In this case, the AP may transmit the traffic to the non-AP station without using relay transmission using a data rate lower than the predetermined data rate. In another specific embodiment, the AP may determine whether to transmit a PPDU including traffic using relay transmission based on a coding method of the PPDU including traffic. Specifically, if the AP intends to transmit a PPDU including traffic at a data rate lower than a predetermined data rate or a MCS lower than a predetermined MCS, the AP may transmit the PPDU including traffic at a data rate lower than a predetermined MCS to the non-AP station without using relay transmission, regardless of the presence of a relay station.

[0375] An AP may designate any one of a plurality of non-AP stations supporting relay operation as a relay station using the following embodiments. For convenience of explanation, a plurality of non-AP stations supporting relay operation or a non-AP station that can be designated as a relay station is referred to as a relay station candidate.

[0376] An AP can acquire information about multiple relay station candidates and, based on the acquired information, designate one of the multiple relay station candidates as a relay station. The information about the relay station candidates can include signal sensitivity between the relay station and the AP.

[0377] This describes a relay station discovery procedure. An AP may transmit a Relay Sounding Request frame to indicate the start of a discovery procedure. The Relay Sounding Request frame may include information indicating a destination device that wishes to participate in relay transmission. The Relay Sounding Request frame may include information related to the AID or MAC address of the destination station that wishes to participate in relay transmission. In addition, the Relay Souding Request frame may indicate a relay station candidate that will receive a measurement frame and perform reporting. The Relay Souding Request frame may include information indicating the relay station candidate. In addition, the Relay Souding Request frame may indicate information regarding the allocation of resource units (RUs) to be used by the relay station candidate when transmitting a measurement frame. When a destination station receives a Relay Souding Request frame from an AP requesting transmission of a measurement frame of the destination station, the destination station may determine that the AP will use relay transmission for communication between the destination stations. When a destination station receives a Relay Sounding Request frame from an AP requesting transmission of a measurement frame of the destination station, the destination station can transmit UL traffic through the relay station. The destination station indicated by the Relay Sounding Request frame can transmit a measurement frame after receiving the Relay Sounding Request frame and a predetermined time interval. The predetermined time interval can be SIFS or PIFS. In addition, the measurement frame can be a frame that does not include a payload. Specifically, the measurement frame can be an NDP (null data PPDU).In a specific embodiment, the measurement frame may be replaced with a frame of a type other than an NDP frame.

[0378] A station that receives a Relay Souding Request frame and is not instructed to transmit a measurement frame by the Relay Souding Request frame may receive a measurement frame transmitted after the Relay Souding Request frame and measure a reception signal sensitivity of the measurement frame. The reception signal sensitivity may include at least one of a received signal strength indicator (RSSI) or a signal to noise ratio (SNR). In addition, the station that received the measurement frame may transmit a reporting frame including the reception signal sensitivity and related information after a predetermined time interval from the reception of the measurement frame. In this case, the predetermined time interval is a SIFS or PIFS. In addition, the reporting frame may include information regarding the reception signal sensitivity of the Relay Souding Request frame measured by the station. In addition, the station may transmit the reporting frame through an RU allocated to the station. In this case, the Relay Sounding Request frame may indicate the RU allocated to the station. In another specific embodiment, a trigger frame transmitted by an AP may indicate an RU assigned to a station.

[0379] An AP receiving a reporting frame can designate a relay station from among a plurality of relay station candidates based on at least one of the reception sensitivity for the measurement frame or the reception sensitivity of the Relay Souding Request frame. If the AP receives one reporting frame, the AP can designate the station that transmitted the reporting frame as the relay station. Specifically, an AP receiving a reporting frame can designate a relay station from among a plurality of relay station candidates based on the reception sensitivity for the measurement frame or the reception sensitivity of the Relay Souding Request frame. For example, even if the measurement frame reception sensitivity of a relay station candidate is better than the measurement frame reception sensitivity of the remaining relay station candidates, the reception sensitivity of the Relay Souding Request frame of the relay station candidate may not be better than the measurement frame reception sensitivity of the remaining relay station candidates. In this case, the AP may not designate the relay station candidate as a relay station.

[0380] After a relay station is designated, the AP and the destination station can exchange traffic through the relay station. At this time, the AP can attempt to transmit directly to the destination station. Afterwards, the AP and the destination station can exchange traffic directly without performing relay transmission. Specifically, if the RA field of the MAC frame received by the destination station from the AP indicates the station's MAC address, the destination station can determine that the relay transmission has ended.

[0381] FIG. 32 shows an operation of an AP designating a relay station for a destination station according to an embodiment of the present invention.

[0382] The AP transmits a Relay Souding Request frame. The Relay Souding Request frame instructs the destination station (D_STA) to transmit a measurement frame (NDP). The Relay Souding Request frame also indicates the RUs to which the first station (STA1) and the second station (STA2) will transmit a reporting frame (Report).

[0383] The destination station (D_STA) receives a Relay Sounding Request frame and transmits an NDP frame at a predetermined time interval with the Relay Sounding Request frame. The predetermined time interval may be SIFS or PIFS. The first station (STA1) and the second station (STA2) measure the reception sensitivity of the NDP frame. The first station (STA1) and the second station (STA2) transmit a reporting frame (Report) frame to the AP at a predetermined interval with the NDP frame. The reporting frame includes information about the reception sensitivity of the NDP frame. In addition, the reporting frame may further include information about the reception sensitivity of the Relay Sounding Request frame. The first station (STA1) and the second station (STA2) transmit a reporting frame (Report) to the AP in an RU allocated to each of the first station (STA1) and the second station (STA2) by the Relay Sounding Request frame.

[0384] The AP designates the first station (STA1) as a relay station (R_STA) based on information obtained from the reporting frames (Report) received from the first station (STA1) and the second station (STA2). After designating the first station (STA1) as a relay station (R_STA), the AP transmits the traffic to be transmitted to the destination station (D_STA) to the first station (STA1). The first station (STA1) transmits a relay PPDU (Relay PPDU) containing the traffic received from the AP to the destination station (D_STA).

[0385]

[0386] <Relay 전송과 TWT 동작의 상관 관계>

[0387] A relay station can perform a power-save operation. Relay transmission may be interrupted when the relay station maintains a doze state. Specifically, the relay station maintains an awake state during the TWT service period (SP) and a doze state during non-TWT SP periods. In the doze state, the relay station may not perform any operations except for essential operations. For example, the relay station may not support transmission and reception operations in the doze state. Therefore, the relay station may not perform relay operations during non-TWT SP periods. During non-TWT SP periods, the relay station may not receive a downlink relay MPDU from the AP and may not transmit a downlink relay MPDU to the destination station. In addition, the relay station may not receive an uplink relay MPDU from the destination station and may not transmit an uplink relay MPDU to the AP. In this case, the downlink relay MPDU refers to an MPDU including traffic that the AP intends to transmit to the destination station. In addition, the uplink relay MPDU refers to an MPDU including traffic that the destination station intends to transmit to the AP. Additionally, in the active state, a relay station can support all operations. For example, a non-AP station with 10 ms of a 100 ms time interval set to TWT SP performs transmission and reception with the AP during the TWT SP. It can maintain a power-saving state during the 90 ms non-TWT SP. This allows the non-AP station to reduce power consumption.

[0388] A TWT SP can be established through an individual TWT agreement or operated through a broadcast TWT operation. An individual TWT agreement can be established through negotiation between two stations, for example, an AP and a non-AP station. Once an individual TWT agreement is established, a non-AP station can transition to a power-saving state during a time period other than the TWT SP. In a broadcast TWT operation, a TWT scheduling AP schedules a TWT SP and indicates information related to the TWT SP through a broadcast TWT element included in a management frame, for example, a beacon frame. A non-AP station that obtains information about the broadcast TWT SP through the received broadcast TWT element can become a TWT scheduled station of the TWT SP by transmitting a TWT request frame to the TWT scheduling AP. At this time, the TWT scheduling AP is an AP that establishes a broadcast TWT, and the TWT scheduled station is a non-AP station that participates in the broadcast TWT SP and performs a power save operation.

[0389] A relay station may also perform a power-save operation according to its TWT SP. Specifically, the time period during which the relay station can support relay transmission for the destination station may be the relay station's TWT SP. As previously described, the relay station may not perform relay operations during non-TWT SP periods. During non-TWT SP periods, the relay station may not receive downlink relay MPDUs from the AP and may not transmit downlink relay MPDUs to the destination station. Furthermore, the relay station may not receive uplink relay MPDUs from the destination station and may not transmit uplink relay MPDUs to the AP. The AP determines whether the relay station is in an operational state during the period, and may transmit to the destination station through the relay station when the relay station is in an operational state. The destination station may change its power state depending on the TWT SP in which the relay station participates. Specifically, the destination station may enter a power-saving state when the relay station is in a power-saving state. This is because, when the relay station is in a power-saving state, the destination station cannot expect transmission or reception through the relay station. The destination station can enter the operational state when the relay station is in the operational state. Therefore, the TWT SP in which the relay station participates can be applied to the destination station as is.

[0390] When an AP establishes a TWT agreement with a relay station, the AP can signal information about the TWT agreement established between the AP and the relay station to the destination station. The destination station can change its power state based on the information about the TWT agreement. Furthermore, the relay station can convey information about the TWT agreement established between the AP and the relay station to the destination station.

[0391] Additionally, the AP can operate a broadcast TWT SP. If the relay station is a member station of the broadcast TWT SP, the destination station can participate as a member station of the relay station's broadcast TWT SP. At this time, information of the broadcast TWT SP can be delivered to the destination station by the AP or the relay station. At this time, information of the broadcast TWT SP can be delivered to the destination station through a frame including a TWT element. Information of the TWT SP can be delivered through a TWT element in which the TWT Setup Command field is set to 1 (Suggest TWT) or 2 (Demand TWT).

[0392] The destination station can perform additional power-saving operations by participating in a TWT SP that the relay station does not participate in. The TWT SP of the destination station may include the TWT SP of the relay station. Specifically, the destination station can remain in a power-saving state even while the relay station is in an operating state. The destination station can set the TWT SP of the destination station based on the TWT SP of the relay station. Specifically, the destination station can set the TWT SP of the destination station to the same TWT SP as the TWT SP of the relay station.

[0393] An AP may transmit MPDUs containing traffic intended for a destination station to a relay station only during a time period in which the destination station is expected to be operational. Even if the relay station is operational, for example, within a TWT SP period in which the relay station participated, or if the relay station is not performing a power save operation, if the destination station is determined to be in a power-saving state, the AP may not be permitted to transmit traffic intended for a destination station to the relay station. This is because the destination station cannot receive from the relay station when the destination station is in a power-saving state.

[0394] FIG. 33 shows an operation in which a TWT agreement established between a relay station and an AP is applied to a destination station according to an embodiment of the present invention.

[0395] In the embodiment of FIG. 33, the relay station and the AP establish a TWT agreement by exchanging a TWT Setup frame and a TWT Response frame. Through this, the relay station transmits a TWT Setup frame requesting the establishment of an individual TWT agreement, and the AP accepts the individual TWT agreement. The TWT Setup frame is a frame containing a TWT element with the TWT Request subfield set to 1. The TWT Response frame is a frame containing a TWT element with the TWT Request subfield set to 0.

[0396] After an individual TWT agreement is established, the relay station transmits a frame (TWT Information) containing information about the established TWT agreement to the destination station. The destination station, upon receiving the frame (TWT Information), transmits an Ack frame to the relay station. As described above, the destination station performs a power-save operation according to the TWT SP of the TWT agreement established between the relay station and the AP. At this time, the destination station may have the same TWT SP as the relay station.

[0397]

[0398] <Relay service period>

[0399] A relay station can set a relay service interval to support relay transmission. A relay station may only support relay transmission within the relay service interval and may not support relay transmission outside the relay service interval. This is because relay transmission by a relay station is not for its own benefit, but for the benefit of other non-AP stations and the AP. Excessive relay operation can strain the relay station's processing and power efficiency.

[0400] A station supporting relay operation can transmit information about capabilities related to the relay operation to an AP. At this time, the information about capabilities related to the relay operation may include a relay service interval. The information about capabilities related to the relay operation may include information about a maximum frequency bandwidth (BW) that the station supports when transmitting / receiving a relay PPDU. The information about capabilities related to the relay operation may include information about whether the station supports transmitting / receiving Multi-TID A-MPDUs for the relay operation. The information about capabilities related to the relay operation may include information about a maximum transmission power that the station can use when transmitting a Relay PPDU. An element including information about capabilities related to the relay operation is referred to as a Relay Support element.

[0401] When a station supporting relay operation associates with an AP, the station may transmit a Relay Support element to the AP. Specifically, the station may transmit an Association Request frame including a Relay Support element to the AP. Furthermore, when the station receives a Relay Request frame from the AP, the station may transmit a Relay Support element to the AP. Furthermore, the relay station may transmit the Relay Support element to the destination station via the first relay PPDU. In another specific embodiment, the relay station may transmit the Relay Support element to the destination station using a separate PPDU before transmitting the first relay PPDU to the destination station. The AP and the destination station may perform the relay operation according to the Relay Support element most recently received from the relay station.

[0402]

[0403] Figure 34 shows a Relay Support element according to an embodiment of the present invention.

[0404] The Relay Support element may include at least one of a Control field, a Relay Support Interval field, a Relay Support Duration field, a Relay Max Tx Power field, a Relay Max Tx Bandwidth (BW) field, and a Relay Multi-TID Support field.

[0405] The Control field of the Relay Support element has a size of 1 octet and can indicate the type of relay operation supported by the station that transmitted the Relay Support element and whether fields that can be included in the Relay Support element are included.

[0406] The Type subfield may indicate the type of relay operation supported by the station transmitting the Relay Support element. If the value of the Type subfield is 0, the Type subfield may indicate that the station transmitting the Relay Support element supports single TXOP relay operation. Single TXOP relay operation is an operation in which the relay station receives traffic for relay transmission from an AP or a destination station in one TXOP and transmits a Relay PPDU to the destination station or AP in the corresponding TXOP. If the value of the Type subfield is 0, the Type subfield may indicate that the station transmitting the Relay Support element supports separate TXOP relay operation. Separate TXOP relay operation is an operation in which the station receives relay traffic from the AP or a destination station in the first TXOP and transmits a relay PPDU using the second TXOP. Therefore, in separate TXOP relay operation, the TXOP in which the relay station receives relay traffic and the TXOP in which the relay station transmits a relay PPDU are distinguished. Values ​​2 and 3 of the Type subfield are reserved values.

[0407] The Relay SP Present subfield can indicate whether the Relay Support element includes a Relay SP field. If the value of the Relay SP Present subfield is 1, the Relay Support element includes a Relay SP field. If the value of the Relay SP Present subfield is 0, the Relay support element does not include a Relay SP field. The value of the Relay SP Present subfield of the Relay support element included in the Association Request frame can always be set to 0. In this case, the Relay Support element included in the Association Request frame does not include a Relay SP field.

[0408] The Relay SP field included in the Relay Support element can indicate information about the start time of the next relay service period that the station that transmitted the Relay Support element can operate. Specifically, the Relay SP field can indicate the TSF of the start time of the immediately next relay service period that the station that transmitted the Relay Support element can operate. The destination station or AP that received the Relay Support element can attempt communication for relay transmission after the start time of the relay service period indicated by the Relay SP field.

[0409] The Relay Support Time Information Present subfield can indicate whether the Relay Support element includes a Relay Support Interval field and a Relay Support Duration field. If the value of the Relay Support Time Information Present subfield is 1, the Relay Support element includes a Relay Support Interval field and a Relay Support Duration field. If the value of the Relay Support Time Information Present subfield is 0, the Relay Support element does not include a Relay Support Interval field and a Relay Support Duration field. If the value of the Relay Support Time Information Present subfield is 0, the station that transmitted the Relay Support element does not operate a relay service interval and can always support relay operation. Specifically, since a separate relay service interval is not defined, all time intervals can be interpreted as relay service intervals.

[0410] The Relay Support Interval field indicates the expected average time interval between two consecutive relay service periods (Relay Service Periods). As previously explained, a Relay Service Period is the time interval during which a station supports relay operations. The Relay Support Interval field may be a field with a size of 1 octet or 2 octets. The unit of the time value indicated by the Relay Support Interval field may be the same as the TWT Wake Interval Mantissa field of the TWT element.

[0411] The Relay Support Duration field can indicate the maximum time length of each relay service interval. If the Relay Support Duration field indicates a specific time value, the maximum time length of the started relay service interval can only be maintained for a time equal to or shorter than the specific time value. In this case, the maximum time indicated by the Relay Support Duration field can be shorter than or equal to the time indicated by the Relay Support Interval field.

[0412] A transmitting device, such as an AP or a destination station, for relay transmission, having a relay service interval specified based on the Relay Support Interval field and the Relay Support Duration field, can perform relay transmission according to the relay service interval of the relay station. Specifically, the transmitting device can transmit an MPDU (PPDU) for a destination device to the relay station only within the relay service interval of the relay station. In addition, the transmitting device can adjust the length of a PPDU transmitted by the transmitting device so that the relay PPDU transmitted by the relay station can be completely transmitted within the relay service interval. The relay station may determine that the amount of traffic received from the transmitting device is impossible to transmit to the destination device within the remaining relay service interval. In this case, the relay station may not transmit the relay PPDU. In addition, the relay station may respond to the transmitting device that it could not transmit the received traffic due to insufficient remaining relay service interval.

[0413] The Relay Max Tx Power Present service field can indicate whether the Relay Support element includes a Relay Max Tx Power field. If the value of the Relay Max Tx Power Present subfield is 1, the Relay Support element includes a Relay Max Tx Power field. If the value of the Relay Max Tx Power Present subfield is 0, the Relay Support element does not include a Relay Max Tx Power field.

[0414] The Relay Max Tx Power field can indicate the maximum transmit power that a station that has transmitted a Relay Support element can use when transmitting a Relay PPDU. Specifically, the relay station can transmit a relay PPDU with a value that is equal to or less than the value indicated by the Relay Max Tx Power field. In addition, the maximum transmit power of a UL PPDU transmitted by a relay station to an AP may be different from the maximum transmit power of a relay PPDU transmitted to a destination station.

[0415] The Relay Max Tx BW Present subfield indicates whether the Relay Support element includes the Relay Max Tx BW field. If the value of the Relay Max Tx BW Present subfield is 1, the Relay Support element includes the Relay Max Tx BW field. If the value of the Relay Max Tx BW Present subfield is 0, the Relay Support element does not include the Relay Max Tx BW field.

[0416] The Relay Max Tx BW field indicates the maximum frequency bandwidth (BW) that the station that transmitted the Relay Support element supports when transmitting / receiving relay PPDUs. If the value of the Relay Max Tx BW field is 0, the maximum frequency bandwidth of the PPDU that the station that transmitted the Relay Support element supports through relay transmission is 20 MHz. If the value of the Relay Max Tx BW field is 1, the maximum frequency bandwidth of the PPDU that the station that transmitted the Relay Support element supports through relay transmission is 40 MHz. If the value of the Relay Max Tx BW field is 2, the maximum frequency bandwidth of the PPDU that the station that transmitted the Relay Support element supports through relay transmission is 80 MHz. Therefore, the transmitting device can determine the frequency bandwidth of the PPDU that is transmitted to the relay station based on the maximum frequency bandwidth supported by the relay station. Specifically, the transmitting device can determine the frequency bandwidth of the PPDU that is transmitted to the relay station so as to have a bandwidth that is equal to or less than the maximum frequency bandwidth supported by the relay station.

[0417] The Relay Multi-TID Support Present subfield can indicate whether the Relay Support element includes a Relay Multi-TID Support field. If the value of the Relay Multi-TID Support Present subfield is 1, the Relay Support element includes a Relay Multi-TID Support field. If the value of the Relay Multi-TID Support Present subfield is 0, the Relay Support element does not include a Relay Multi-TID Support field.

[0418] The Relay Multi-TID Support field may indicate whether the station transmitting the Relay Support element supports transmitting and receiving Multi-TID A-MPDUs for relay operation. If the value of the Relay Multi-TID Support field is 0, the Relay Multi-TID Support field may indicate that the station transmitting the Relay Support element does not support Mulit-TID A-MPDUs in relay operation. In this case, a transmitting device, such as an AP or a destination station, may configure the A-MPDUs transmitted and received in relay transmission as a single TID A-MDPU. If the value of the Relay Multi-TID Support field is 1, the Relay Multi-TID Support field may indicate that the station transmitting the Relay Support element supports Mulit-TID A-MPDUs in relay operation. In this case, a transmitting device, such as an AP or a destination station, may configure the A-MPDUs transmitted and received in relay transmission as Multi-TID A-MDPU. Additionally, the value of the Relay Multi-TID Support field may indicate the maximum number of TIDs that the relay station can support in an A-MPDU - 1. For example, if the value of the Relay Multi-TID Support field is 3, the Relay Support element may indicate that the station transmitting the Relay Support element supports A-MPDUs with 4 TIDs in relay operation.

[0419] As previously explained, a relay station can support relay operation only during the time period selected by the relay station. To this end, the relay station can operate a relay service period. The relay station and the AP and destination station attempting to perform relay operation must attempt relay operation according to the relay service period. Specifically, the relay station and the AP and destination station attempting to perform relay operation can transmit relay traffic to the relay station only during the relay service period. At this time, even if the relay station and the AP and destination station attempting to perform relay operation have completed channel access, they can postpone transmission of relay traffic during times other than the relay station's relay service period. In addition, the AP and destination station can restart the backoff procedure to postpone transmission. At this time, the size of the contention window, CW[AC], and the QoS station retry counter (station Retry Counter), QSRC[AC] are maintained. This is because the backoff procedure is not restarted due to a transmission failure.

[0420] FIG. 35 shows a relay operation performed based on a relay service section indicated by a relay station according to an embodiment of the present invention.

[0421] As described above, when a relay station transmits a reporting frame to an AP, it can transmit information about the capability related to the relay operation of the relay station. In addition, the relay station can transmit information about the capability related to the relay operation to the destination station through the first relay PPDU transmitted in the relay transmission. The information about the capability related to the relay operation may be the Relay Support element described above. In the embodiment of FIG. 35, the relay station (R_STA) transmits a Relay Support element to the AP through a reporting frame (Report) and transmits the Relay Support element through the first relay PPDU (Relay PPDU) transmitted to the destination station (D_STA). The value of the Relay Support Inverval field of the Relay Support element is X, and the value of the Relay Support Duration field is Y. The value of the Relay SP field of the Relay Support element transmitted to the AP is T1, and the value of the Relay SP field of the Relay Support element transmitted to the destination station (D_STA) is T2.

[0422] The AP and the destination station (D_STA) determine the relay service interval (Relay SP) of the relay station (R_STA) based on the values ​​of the Relay SP field and the Relay Support Duration field. The AP transmits a DL PPDU to the relay station (R_STA) within the relay service interval (Relay SP) of the relay station (R_STA). The relay station (R_STA) receives the DL PPDU and responds to the AP with a BlockAck frame (BA). The relay station (R_STA) transmits a relay PPDU (Relay PPDU) containing a Relay Support element to the destination station (D_STA). The destination station (D_STA) receives the relay PPDU (Relay PPDU) and transmits a BlockAck frame (BA) to the relay station (R_STA). The relay station (R_STA) receives a BlockAck frame (BA) from the destination station (D_STA) and transmits information (End-to-End BA) indicating whether transmission to the destination station was successful to the AP.

[0423] The operation of the relay station (R_STA) performing relay transmission is within the relay service period (Relay SP). Specifically, the time at which the AP transmits a DL PPDU to the relay station (R_STA) and the time at which the relay station (R_STA) transmits information (End-to-End BA) indicating to the AP whether transmission to the destination station was successful or not are within the relay service period (Relay SP). Specifically, the time at which the AP transmits a DL PPDU to the relay station (R_STA) is after T1, and the time at which the AP transmits information (End-to-End BA) indicating to the AP whether transmission to the destination station was successful or not is before Y elapses from T1.

[0424] The AP and the destination station (D_STA) do not perform transmission for relay operation to the relay station (R_STA) during time periods other than the relay service period (Relay SP) of the relay station (R_STA).

[0425] After T2, the destination station (D_STA) transmits a UL PPDU to the relay station (R_STA). The relay station (R_STA) receives the UL PPDU and transmits a BlockAck frame (BA) to the destination station (D_STA). The relay station (R_STA) transmits a Relay PPDU to the AP. The AP receives the Relay PPDU and transmits a BlockAck frame (BA) to the relay station (R_STA). The relay station (R_STA) transmits information (End-to-End BA) indicating whether transmission to the AP was successful to the destination station (D_STA). At this time, the time when the destination station (D_STA) transmits the UL PPDU to the relay station (R_STA) is after T2, and the time when the destination station (D_STA) transmits information (End-to-End BA) indicating whether transmission to the AP was successful to the destination station (D_STA) is before Y time elapses from T2.

[0426]

[0427] While the present invention has been described using wireless LAN communication as an example, it is not limited thereto and can be equally applied to other communication systems, such as cellular communication. Furthermore, while the methods, devices, and systems of the present invention have been described with reference to specific embodiments, some or all of the components and operations of the present invention can be implemented using a computer system with a general-purpose hardware architecture.

[0428] The features, structures, effects, etc. described in the embodiments above are included in at least one embodiment of the present invention, and are not necessarily limited to just one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified in other embodiments by those skilled in the art to which the embodiments pertain. Therefore, the contents related to such combinations and modifications should be construed as being included within the scope of the present invention.

[0429] Although the above has been described focusing on embodiments, these are merely examples and do not limit the present invention. Those skilled in the art to which the present invention pertains will appreciate that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present embodiment. For example, each component specifically shown in the embodiments can be modified and implemented. In addition, differences related to such modifications and applications should be interpreted as being included within the scope of the present invention defined in the appended claims.

Claims

1. At a non-AP station communicating with an AP (access point), Transmitter and receiver; and Contains a processor, The above processor Receive a downlink relay MPDU containing traffic for a destination station from the AP, Transmitting the above downlink relay MPDU to the above destination station non-AP station.

2. In paragraph 1, The above processor When the non-AP station performs a power save operation, the downlink relay MPDU is not received and the downlink relay MPDU is not transmitted to the target station during a period other than the target wakeup time (TWT) service period (SP) of the non-AP station. non-AP station.

3. In paragraph 2, The TWT SP of the above non-AP station is included in the TWT SP of the above destination station. non-AP station.

4. In paragraph 1, The above processor Transmits information about the capabilities of the non-AP station related to relay operation to the AP, Information about the capability related to the above relay operation includes information about the relay service period, which indicates the period in which the non-AP station can perform the relay operation. non-AP station.

5. In paragraph 4, Information about the capabilities associated with the above relay operation Further including information about the maximum frequency bandwidth supported by the non-AP station when transmitting / receiving for the relay operation. non-AP station.

6. In paragraph 4, Information about the capabilities associated with the above relay operation Further including information about the maximum transmission power that the non-AP station can use when transmitting a PPDU for the relay operation. non-AP station.

7. In paragraph 1, The above processor Measure the reception sensitivity of the measurement frame received from the above target station, Transmitting a reporting frame containing information about the reception sensitivity of the above measurement frame to the AP non-AP station.

8. In paragraph 7, The above reporting frame contains information about the reception sensitivity of the request frame that triggers the transmission of the above measurement frame. non-AP station.

9. In paragraph 1, The above processor Receive an uplink relay MPDU containing traffic for the AP from the destination station, and transmit the uplink relay MPDU to the AP. non-AP station.

10. In paragraph 9, The above processor The destination station receives an uplink relay MPDU from the destination station within the TXOP (transmission opportunity) allocated to the non-AP station, and transmits the uplink relay MPDU to the AP. non-AP station.

11. In paragraph 1, Before transmitting the above downlink relay MPDU, receive a first RTS (request to send) frame from the AP, and transmit a first CTS (clear to send) frame to the AP in response to the first RTS frame, Before the above downlink relay MPDU is transmitted, the AP and the destination station exchange a second RTS frame and a second CTS frame. non-AP station.

12. At an AP (access point) communicating with a non-AP station, Transmitter and receiver; and Contains a processor, The above processor Transmitting a downlink relay MPDU containing traffic for the destination station to the relay station. AP.

13. In paragraph 12, When the relay station performs a power save operation, the relay station does not receive the downlink relay MPDU and does not transmit the downlink relay MPDU to the destination station during a period other than the target wakeup time (TWT) service period (SP) of the relay station. The above processor When the relay station performs a power save operation, the relay station does not transmit the downlink relay MPDU to the relay station during a time period other than the TWT service period. AP.

14. In paragraph 12, The above processor Receive information about the capabilities related to the relay operation of the relay station from the relay station, Decide whether to perform the relay operation with the relay station based on information about the capabilities related to the above relay operation, Information about the capability related to the above relay operation includes information about the relay service period, which is the period during which the non-AP station can perform the relay operation. AP.

15. In paragraph 14, Information about the capabilities associated with the above relay operation Further including information about the maximum frequency bandwidth supported by the non-AP station when transmitting / receiving for the relay operation. AP.

16. In paragraph 14, Information about the capabilities associated with the above relay operation Further including information about the maximum transmission power that the non-AP station can use when transmitting a PPDU for the relay operation. AP.

17. In paragraph 12, The above processor Transmitting a frame that triggers the transmission of a measurement frame of the above target station, Receive a reporting frame including information on the reception sensitivity of the measurement frame from the relay station. AP.

18. In paragraph 17, The above reporting frame contains information about the reception sensitivity of the request frame that triggers the transmission of the above measurement frame. AP.

19. In paragraph 12, Before transmitting the above downlink relay MPDU, transmit a first RTS (request to send) frame to the relay station, and receive a first CTS (clear to send) frame from the relay station in response to the first RTS frame, Before transmitting the above downlink relay MPDU, transmit a second RTS frame to the destination station, and receive a second CTS frame from the destination station in response to the second RTS frame. AP.

20. At a non-AP station communicating with an AP (access point), Transmitter and receiver; and Contains a processor, The above processor Transmitting an uplink relay MPDU containing traffic for the AP to the relay station. non-AP station.

21. In paragraph 20, When the relay station performs a power save operation, the relay station does not receive the uplink relay MPDU and does not transmit the uplink relay MPDU to the AP during a period other than the target wakeup time (TWT) service period (SP) of the relay station. The above processor When the relay station performs a power save operation, the relay station does not transmit the uplink relay MPDU to the relay station during a time period other than the TWT service period. non-AP station.

22. In paragraph 21, The TWT SP of the above relay station is included in the TWT SP of the above non-AP station. non-AP station.

23. In paragraph 20, The above processor Receive a frame that triggers the transmission of a measurement frame of the above target station, Transmitting a measurement frame in response to the above trigger frame non-AP station.

24. In paragraph 20, Before transmitting the above-mentioned upstream relay MPDU, transmit a first RTS (request to send) frame to the relay station, and receive a first CTS (clear to send) frame from the relay station in response to the first RTS frame, Before transmitting the above uplink relay MPDU, transmit a second RTS frame to the AP, and receive a second CTS frame from the AP in response to the second RTS frame. non-AP station.

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