Wireless communication method using ofdma random access and wireless communication terminal using the same

Abstract

To provide a wireless communication terminal using OFDMA (Orthogonal Frequency Division Multiple Access) random access.SOLUTION: A wireless communication terminal that wirelessly communicates with a base wireless communication terminal includes a transceiver and a processor. The processor is configured to set an integer selected from a range of 0 to a value equal to or smaller than an OFDMA Contention Window (OCW) as a counter for random access, receive a trigger frame for triggering random access using one or more resource units (RUs) allocated for the random access from the base wireless communication terminal using the transceiver, decrease a value of the counter based on the allocated RUs, randomly select the one or more RUs when the value of the counter is 0 or reaches 0, and attempt transmission to the base wireless communication terminal. The RU is a group of a plurality of subcarriers usable for uplink transmission and downlink transmission.SELECTED DRAWING: Figure 41

Description

[Technical Field]

[0001] The present invention relates to a wireless communication method and a wireless communication terminal using OFDMA random access. [Background technology]

[0002] Recently, as the popularity of mobile devices has increased, wireless LAN technology, which provides high-speed wireless Internet services to these devices, has been gaining attention. Wireless LAN technology is a technology that uses short-range wireless communication technology to wirelessly connect mobile devices such as smartphones, smart pads, laptop computers, portable multimedia players, and embedded devices to the Internet at home, in businesses, or in specific service areas.

[0003] Since supporting the initial wireless LAN technology using the 2.4GHz frequency band, IEEE (Institute of Electrical and Electronics Engineers) 802.11 has implemented or is currently developing various technology standards. First, IEEE 802.11b supports communication speeds of up to 11Mbps using the 2.4GHz frequency band. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses the 5GHz frequency band instead of the 2.4GHz band, reducing the impact of interference compared to the significantly more congested 2.4GHz frequency band, and uses OFDM technology to increase communication speeds to up to 54Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication distance than IEEE 802.11b. IEEE 802.11g has attracted considerable attention because it uses the 2.4GHz band like IEEE 802.11b to achieve a maximum communication speed of 54Mbps and is backward compatible, but it also has an advantage over IEEE 802.11a in terms of communication distance.

[0004] IEEE 802.11n is a technical standard established to overcome the communication speed limitations that have been identified as a weakness of wireless LANs. IEEE 802.11n aims to increase network speed and reliability and extend the operating distance of wireless networks. More specifically, IEEE 802.11n supports high throughput (HT) of up to 540 Mbps. It also relies on MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas on both the transmitter and receiver sides to minimize transmission errors and optimize data speed. This standard also uses a coding method that transmits multiple duplicate copies to increase data reliability.

[0005] As WLAN usage continues to grow and applications become more diverse, a need has arisen for new WLAN systems that support data rates higher than those supported by IEEE 802.11n (Very High Throughput, VHT). IEEE 802.11ac supports wide bandwidth (80MHz-160MHz) in the 5GHz frequency band. While the IEEE 802.11ac standard was defined only for the 5GHz band, initial 802.11ac chipsets also support operation in the 2.4GHz band for backward compatibility with existing 2.4GHz products. Theoretically, this standard enables multi-station WLAN speeds of at least 1Gbps and maximum single-link speeds of at least 500Mbps. This is achieved by expanding the air interface concepts adopted in 801.11n, including wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and denser modulation (up to 256QAM). Additionally, there is IEEE 802.11ad, a method of transmitting data using the 60 GHz band instead of the conventional 2.4 GHz / 5 GHz. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide speeds of up to 7 Gbps, making it suitable for streaming large amounts of data and high-bitrate video, such as uncompressed HD video. However, the 60 GHz frequency band has the disadvantage of being difficult to pass through obstacles and can only be used between devices in close proximity.

[0006] Meanwhile, discussions are currently underway to provide high-efficiency and high-performance wireless LAN communication technology in high-density environments as the next-generation wireless LAN standard after 801.11ac and 802.11ad. In other words, next-generation wireless LAN environments should provide high-frequency-efficient communication both indoors and outdoors in the presence of high-density stations and access points (APs), and various technologies are required to achieve this.

[0007] In particular, as the number of devices using wireless LANs increases, it becomes necessary to use designated channels efficiently. Therefore, there is a demand for technology that allows data transmission between multiple stations and APs simultaneously, thereby efficiently using bandwidth. Summary of the Invention [Problem to be solved by the invention]

[0008] An embodiment of the present invention aims to provide a wireless communication terminal using OFDMA random access. [Means for solving the problem]

[0009] According to one embodiment of the present invention, a wireless communication terminal for wirelessly communicating with a basic wireless communication terminal includes a transceiver unit and a processor. The processor sets a counter for random access to an integer selected within a range from 0 to an OFDMA contention window (OCW) or a smaller value, and receives, using the transceiver unit, a trigger frame for triggering random access using one or more resource units (RUs) allocated for random access from the basic wireless communication terminal. The processor decrements the value of the counter based on the one or more RUs allocated for random access. When the counter value is 0 or becomes 0, the processor randomly selects one or more RUs allocated for the random access and attempts transmission to the base wireless communication terminal using the selected RUs. In this case, the RUs may be a group of multiple subcarriers that can be used for uplink transmission and downlink transmission.

[0010] The processor can decrement the value of the counter based on one or more RUs assigned to the random access and the capability of the wireless communication terminal.

[0011] The processor may decrement the counter value by the number of RUs to which the wireless communication terminal can transmit a trigger-based PPDU according to the capability of the wireless communication terminal, among one or more RUs allocated for the random access.

[0012] When the value of the counter is 0 or becomes 0, the processor can arbitrarily select one of the RUs assigned to the random access and to which the wireless communication terminal can transmit a trigger-based PPDU according to the capabilities of the wireless communication terminal.

[0013] The capabilities of the wireless communication terminal may include a capability regarding the bandwidth over which the wireless communication terminal can transmit.

[0014] The capabilities of the wireless communication terminal may include capabilities regarding the length of a padding field included in the trigger-based PPDU.

[0015] The capabilities of the wireless communication terminal may include capabilities regarding modulation and coding schemes that the wireless communication terminal can transmit.

[0016] The wireless communication terminal may be a wireless communication terminal not coupled to the base wireless communication terminal, and the processor may set an OCW minimum value, which is a parameter representing a minimum value of the OCW, to a value previously designated as a default value of the OCW minimum value, and set an OCW maximum value, which is a parameter representing a maximum value of the OCW, to a value previously designated as a default value of the OCW maximum value, and the previously designated default value of the OCW minimum value and the previously designated default value of the OCW maximum value may not be values ​​designated by the base wireless communication terminal.

[0017] The wireless communication terminal may be a wireless communication terminal not coupled to the base wireless communication terminal. When the wireless communication terminal communicates with a base wireless communication terminal different from the base wireless communication terminal, the processor may initialize parameters for random access to the different wireless communication terminal. In this case, the parameters for random access may include the counter, an OCW minimum value which is a parameter representing a minimum value of the OCW, and an OCW maximum value which is a parameter representing a maximum value of the OCW.

[0018] The processor can set the OCW minimum value and the OCW maximum value according to information received from the base wireless communication terminal when the wireless communication terminal communicates with the base wireless communication terminal, and can set the OCW minimum value and the OCW maximum value according to information received from the different base wireless communication terminal when the wireless communication terminal communicates with the different base wireless communication terminal.

[0019] The wireless communication terminal may be connected to the base wireless communication terminal. In this case, the wireless communication terminal may set an OCW minimum value, which is a parameter indicating a minimum value of the OCW, and an OCW maximum value, which is a parameter indicating a maximum value of the OCW, according to information received from a base wireless communication terminal different from the base wireless communication terminal. In addition, the different base wireless communication terminal may belong to multiple BSSID (Basic Service Set Identification) sets to which the base wireless communication terminal belongs.

[0020] The processor may not decrement the counter value based on a trigger frame transmitted from the different base wireless communication terminal.

[0021] The different base wireless communication terminals may be wireless communication terminals that operate BSSs corresponding to transmitted Basic Service Set Identifications (BSSIDs) of the multiple BSSID sets.

[0022] The information received from the different base wireless communication terminal may not be information indicated in a signaling field allocated for the BSS in which the wireless communication terminal is included.

[0023] If the trigger frame instructs the wireless communication terminal to perform an upstream transmission, the processor may not decrement the value of the counter based on the trigger frame.

[0024] According to an embodiment of the present invention, a method for operating a wireless communication terminal that wirelessly communicates with a basic wireless communication terminal may include the steps of: setting an integer selected within a range from 0 to an OFDMA contention window (OCW) or a smaller value as a counter for random access; receiving a trigger frame from the basic wireless communication terminal that triggers random access using one or more resource units (RUs) allocated for random access; decrementing the value of the counter based on the one or more RUs allocated for the random access; randomly selecting one or more RUs allocated for the random access when the value of the counter is 0 or becomes 0; and attempting transmission to the base wireless communication terminal using the selected RU. In this case, the RU may be a group of a plurality of subcarriers that can be used for uplink transmission and downlink transmission.

[0025] The step of decreasing the counter value may include the step of decreasing the counter value based on one or more RUs assigned to the random access and the capability of the wireless communication terminal.

[0026] The step of decreasing the counter value based on one or more RUs allocated to the random access and the capabilities of the wireless communication terminal may include a step of decreasing the counter value by the number of RUs to which the wireless communication terminal can transmit a trigger-based PPDU according to the capabilities of the wireless communication terminal, among the one or more RUs allocated to the random access.

[0027] The step of randomly selecting one or more RUs allocated for the random access may include a step of randomly selecting one of the RUs allocated for the random access and to which the wireless communication terminal can transmit a trigger-based PPDU according to the capability of the wireless communication terminal.

[0028] The wireless communication terminal may be a wireless communication terminal not coupled to the base wireless communication terminal. In this case, the operating method may further include the steps of setting an OCW minimum value, which is a parameter representing a minimum value of the OCW, to a predetermined value as a default value of the OCW minimum value, and setting an OCW maximum value, which is a parameter representing a maximum value of the OCW, to a predetermined value as a default value of the OCW maximum value. In addition, the predetermined value as the default value of the OCW minimum value and the predetermined value as the default value of the OCW maximum value may not be values ​​designated by the base wireless communication terminal. [Effects of the Invention]

[0029] An embodiment of the present invention provides a wireless communication method using OFDMA random access and a wireless communication terminal using the same. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Figure 3]FIG. 2 is a block diagram showing the configuration of a station according to an embodiment of the present invention. [Figure 4] FIG. 2 is a block diagram showing the configuration of an access point according to an embodiment of the present invention. [Figure 5] 2 is a diagram illustrating a process in which a station establishes a link with an access point according to an embodiment of the present invention; [Figure 6] 1 illustrates UL MU transmission of a wireless communication terminal according to an embodiment of the present invention. [Figure 7] 1 shows a specific format of a trigger frame according to an embodiment of the present invention. [Figure 8] 10 shows specific formats of the Common Info field and the User Info field of the trigger frame according to an embodiment of the present invention. [Figure 9] 4 illustrates a random access operation of a wireless communication terminal according to an embodiment of the present invention. [Figure 10] 1 shows a specific format of a UORA parameter set element according to an embodiment of the present invention. [Figure 11] 10 shows a specific format of a multiple BSSID element according to an embodiment of the present invention. [Figure 12] 10 illustrates a random access operation of a wireless communication terminal associated with multiple BSSID sets according to an embodiment of the present invention. [Figure 13] 10 illustrates a random access operation of a wireless communication terminal associated with multiple BSSID sets according to an embodiment of the present invention. [Figure 14] 1 shows the types of RUs and subcarrier indexes that can be used when transmitting a PPDU with a 20 MHz bandwidth according to an embodiment of the present invention. [Figure 15] 1 shows the types of RUs and subcarrier indexes that can be used when transmitting a PPDU having a 40 MHz bandwidth according to an embodiment of the present invention. [Figure 16] 1 shows the types of RUs and subcarrier indexes that can be used when transmitting a PPDU having an 80 MHz bandwidth according to an embodiment of the present invention. [Figure 17] 11 shows an encoding value used to indicate an RU in the RU Allocation subfield of a trigger frame according to an embodiment of the present invention. [Figure 18] 10 illustrates an operation of a wireless communication terminal that supports only PPDUs having a 20 MHz frequency bandwidth performing random access according to an embodiment of the present invention. [Figure 19] 10 illustrates an operation of a wireless communication terminal that supports only PPDUs having a 20 MHz frequency bandwidth performing random access according to an embodiment of the present invention. [Figure 20] 10 illustrates an operation of a wireless communication terminal that supports only PPDUs having a frequency bandwidth of 80 MHz or less to perform random access according to an embodiment of the present invention. [Figure 21] 10 illustrates an operation of a wireless communication terminal that supports only PPDUs having a frequency bandwidth of 80 MHz or less to perform random access according to an embodiment of the present invention. [Figure 22] 4 illustrates a random access operation of an unassociated wireless communication terminal according to an embodiment of the present invention. [Figure 23] 4 illustrates a random access operation of an unassociated wireless communication terminal according to an embodiment of the present invention. [Figure 24] 4 illustrates a random access operation of an unassociated wireless communication terminal according to an embodiment of the present invention. [Figure 25] 4 illustrates a random access operation of an unassociated wireless communication terminal according to an embodiment of the present invention. [Figure 26] 1 illustrates a random access operation of a wireless communication terminal according to an embodiment of the present invention when an upstream transmission is scheduled by a trigger frame. [Figure 27] 1 illustrates a legacy PPDU format according to an embodiment of the present invention. [Figure 28] 1 illustrates a non-legacy PPDU format according to an embodiment of the present invention. [Figure 29] 1 shows the transmission coverage of an HE extended range SU PPDU and the transmission coverage of a legacy PPDU according to an embodiment of the present invention. [Figure 30] A base wireless communication terminal according to an embodiment of the present invention illustrates a dual beacon transmission operation. [Figure 31] 10 illustrates the format of a BSS Color Change Announcement element according to an embodiment of the present invention. [Figure 32] 10 illustrates a BSS color change operation of a base wireless communication terminal when the base wireless communication terminal uses dual beacons according to an embodiment of the present invention. [Figure 33] 10 illustrates a BSS color change operation of a base wireless communication terminal when the base wireless communication terminal uses dual beacons according to still another embodiment of the present invention. [Figure 34] 10 illustrates a BSS color change operation of a base wireless communication terminal when the base wireless communication terminal uses dual beacons according to still another embodiment of the present invention. [Figure 35] 3 shows a format of an A-MPDU according to an embodiment of the present invention. [Figure 36] 10 shows a specific format of a BlockAck according to an embodiment of the present invention. [Figure 37] 10 illustrates a Per STA Info subfield according to an embodiment of the present invention. [Figure 38] 1 illustrates the context of a Per STA Info subfield according to an embodiment of the present invention. [Figure 39] 1 shows an A-MPDU configuration according to an embodiment of the present invention. [Figure 40] 1 shows an A-MPDU configuration according to an embodiment of the present invention. [Figure 41] 4 illustrates an operation of the wireless communication terminal according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily understand the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, parts that are not relevant to the description are omitted to clarify the present invention, and similar parts are designated by similar reference numerals throughout the specification.

[0032] Furthermore, when a part "comprises" a certain element, this does not mean excluding other elements, but rather further including other elements, unless otherwise specified to the contrary.

[0033] This application claims priority based on Korean Patent Application Nos. 10-2016-0179781 (December 27, 2016), 10-2017-0000020 (January 2, 2017), 10-2017-0000437 (January 2, 2017), 10-2017-0002195 (January 6, 2017), and 10-2017-0002720 (January 9, 2017), and the descriptions, examples, and disclosures in each of the above priority applications are incorporated herein by reference.

[0034] 1 illustrates a wireless LAN system according to an embodiment of the present invention. A wireless LAN system includes one or more basic service sets (BSSs), which refer to a set of devices that can successfully synchronize and communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs), of which FIG. 1 illustrates an infrastructure BSS.

[0035] As shown in FIG. 1, the infrastructure BSs BSS1, BSS2 includes one or more stations STA1, STA2, STA3, STA4, STA5, access points PCP / AP-1, PCP / AP-2 which are stations providing distribution services, and a distribution system (SD) connecting multiple access points PCP / AP-1, PCP / AP-2.

[0036] A station (STA) is any device that includes a Medium Access Control (MAC) and a physical layer interface to the wireless medium according to the IEEE 802.11 standard. In a broad sense, it includes both non-APs and APs. In this specification, the term "terminal" refers to either a non-AP STA or an AP, or both. A station for wireless communication includes a processor and a transmit / receive unit, and, depending on the embodiment, may further include a user interface and a display unit. The processor generates frames to be transmitted over the wireless network, processes frames received over the wireless network, and performs various other processes for controlling the station. The transceiver is functionally connected to the processor and transmits and receives frames over the wireless network for the station.

[0037] An access point (AP) is an entity that provides a connection to a distribution system (DS) via a wireless medium for stations associated with it. In an infrastructure BSS, communication between non-AP stations is generally performed via the AP, but when a direct link is established, direct communication between non-AP stations becomes possible. Meanwhile, in the present invention, the term AP is used as a base including a personal BSS coordination point (PCP), and in a broad sense, it includes all concepts such as a central controller, base station (GS), Node B, base transceiver system (BTS), or site controller.

[0038] A plurality of infrastructure BSSs are interconnected via a distribution system, and the plurality of BSSs connected via the distribution system are referred to as an Extended Service Set (ESS).

[0039] 2 is a diagram showing an independent BSS, which is a wireless LAN system according to another embodiment of the present invention. In the embodiment of FIG. 2, the same or corresponding parts as those in the embodiment of FIG. 1 will not be described again.

[0040] BSS3 shown in Figure 2 is an independent BSS and does not include an AP, so all stations STA6 and STA7 are not connected to an AP. An independent BSS does not allow connections as a distribution system and forms a self-contained network. In an independent BSS, stations STA6 and STA7 are directly connected to each other.

[0041] FIG. 3 is a block diagram showing the configuration of a station 100 according to an embodiment of the present invention.

[0042] As shown, station 100 according to an embodiment of the present invention includes a processor 110 , a transceiver 120 , a user interface 140 , a display unit 150 , and a memory 160 .

[0043] First, the transceiver 120 transmits and receives wireless signals such as WLAN packets and is provided internally or externally in the station 100. According to an embodiment, the transceiver 120 includes at least one transceiver module using different frequency bands. For example, the transceiver 120 includes transceiver modules for different frequency bands such as 2.4 GHz, 5 GHz, and 50 GHz. According to one embodiment, the station 100 includes a transceiver module using a frequency band above 6 GHz and a transceiver module using a frequency band below 6 GHz. Each transceiver module performs wireless communication with an AP or an external station according to the WLAN standard of the frequency band supported by the corresponding transceiver module. The transceiver 120 operates only one transceiver module at a time or multiple transceiver modules simultaneously, depending on the performance and requirements of the station 100. If the station 100 includes multiple transceiver modules, each transceiver module may be provided independently, or multiple modules may be integrated into a single chip.

[0044] Next, the user interface unit 140 is provided in the station 100 and includes various types of input / output means. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the station 100 based on the received user input. Also, the user interface unit 140 performs output based on instructions from the processor 110 using various output means.

[0045] Next, the display unit 150 outputs an image on a display screen. The display unit 150 outputs various display objects, such as content processed by the processor 110 or a user interface based on a control command of the processor 110. The memory 140 also stores control programs and various data used by the station 110. Such control programs include connection programs required for the station 110 to connect to an AP or an external station.

[0046] The processor 110 of the present invention executes various commands or programs to process data within the station 100. The processor 110 also controls each unit of the station 100 and controls data transmission and reception between the units. According to an embodiment of the present invention, the processor 110 executes a program for connection with an AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information about the station 100's priorities contained in the communication setup message and requests connection to the AP based on the information about the station 100's priorities. The processor 110 of the present invention may refer to a main control unit of the station 100, or, depending on the embodiment, may refer to a control unit for individually controlling some components of the station 100, such as the transceiver 120. That is, the processor 110 is a modulator or demodulator (MPDUlator and / or deMPDUlator) that modulates wireless signals transmitted and received by the transceiver 120. The processor 110 controls various operations for transmitting and receiving wireless signals in the station 100 according to an embodiment of the present invention. A specific embodiment of this will be described later.

[0047] The station 100 shown in FIG. 3 is a block diagram according to one embodiment of the present invention, and the separate blocks indicate the logically separated elements of the device. Therefore, the above-described device elements may be implemented on a single chip or multiple chips depending on the device design. For example, the processor 110 and the transceiver 120 may be integrated into a single chip or may be implemented on separate chips. Furthermore, in some embodiments of the present invention, some components of the station 100, such as the user interface 140 and the display unit 150, may be selectively provided in the station 100.

[0048] FIG. 4 is a block diagram showing the configuration of an AP 200 according to an embodiment of the present invention.

[0049] As shown, the AP 200 according to one embodiment of the present invention includes a processor 210, a transceiver 220, and a memory 260. In Fig. 4, the same or corresponding parts of the configuration of the AP 200 as those of the station 100 in Fig. 3 will not be described again.

[0050] Referring to FIG. 4, the AP 200 according to the present invention includes a transceiver unit 220 for operating a BSS in at least one frequency band. As described in the embodiment of FIG. 3, the transceiver unit 220 of the AP 200 also includes multiple transceiver modules that use different frequency bands. That is, the AP 200 according to the embodiment of the present invention includes two or more transceiver modules that use different frequency bands, for example, 2.4 GHz, 5 GHz, and 60 GHz. Preferably, the AP 200 includes a transceiver module that uses a frequency band above 6 GHz and a transceiver module that uses a frequency band below 6 GHz. Each transceiver module performs wireless communication with stations according to the WLAN standard of the frequency band supported by the corresponding transceiver module. The transceiver unit 220 may operate only one transceiver module at a time or multiple transceiver modules simultaneously, depending on the performance and requirements of the AP 200.

[0051] Next, the memory 260 stores control programs used by the AP 200 and various data associated therewith. These control programs include a management program for managing station connections. The processor 210 also controls each unit of the AP 200 and controls data transmission and reception between the units. According to an embodiment of the present invention, the processor 210 executes a program for connecting with a station stored in the memory 260 and transmits a communication setup message to one or more stations. At this time, the communication setup message includes information regarding connection preferences of each station. The processor 210 also performs connection setup in response to a station connection request. According to one embodiment, the processor 210 is a modulation unit or demodulation unit that modulates wireless signals transmitted and received from the transceiver unit 220. The processor 210 controls various operations for transmitting and receiving wireless signals of the AP 200 according to an embodiment of the present invention. A specific embodiment of this will be described later.

[0052] FIG. 5 shows a schematic diagram of a process in which a STA establishes a link with an AP.

[0053] 5, a link between the STA 100 and the AP 200 is established through three steps: scanning, authentication, and association. First, the scanning step is a step in which the STA 100 acquires access information of a BSS operated by the AP 200. There are two scanning methods: a passive scanning method in which the STA 100 acquires information using only a beacon message S101 periodically transmitted by the AP 200, and an active scanning method in which the STA 100 transmits a probe request to the AP S103, receives a probe response from the AP S105, and acquires access information.

[0054] The STA 100 that successfully receives wireless access information in the scanning step transmits an authentication request (S107a), receives an authentication response from the AP 200, and performs the authentication step (S107b). After the authentication step is performed, the STA 100 transmits an association request (S109a), receives an association response from the AP 200, and performs the association step (S109b). In this specification, association basically means wireless association, but the present invention is not limited to this, and association in a broad sense includes both wireless association and wired association.

[0055] Meanwhile, an 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are additionally performed. In Fig. 5, authentication server 300 is a server that processes 802.1X-based authentication with STA 100, and may be physically connected to AP 200 or may exist as a separate server.

[0056] In a specific embodiment, the AP (200) may be a wireless communication terminal that allocates and schedules communication medium resources in an independent network not connected to an external distribution service, such as an ad-hoc network. The AP (200) may be at least one of a base station, an eNB, and a transmission point (TP). The AP (200) may also be referred to as a base wireless communication terminal.

[0057] In addition, the base wireless communication terminal may be a wireless communication terminal that allocates communication medium resources and performs scheduling in communication with multiple wireless communication terminals. Specifically, the base wireless communication terminal may perform the role of a cell coordinator. In a specific embodiment, the base wireless communication terminal may be a wireless communication terminal that allocates communication medium resources and performs scheduling in an independent network that is not connected to an external distribution service, such as an ad-hoc network.

[0058] A base wireless communication terminal can simultaneously communicate with multiple wireless communication terminals using Orthogonal Frequency Division Multiple Access (OFDMA) or Multi-user Multiple Input Multiple Output (MU-MIMO). In this case, the base wireless communication terminal can transmit trigger information to the multiple wireless communication terminals to trigger the multiple wireless communication terminals to perform uplink (UL) multi-user (MU) transmission using OFDMA. This will be described with reference to FIG. 6.

[0059] FIG. 6 illustrates UL MU transmission of a wireless communication terminal according to an embodiment of the present invention.

[0060] The base wireless communication terminal can transmit trigger information to multiple wireless communication terminals to trigger UL MU transmissions of the multiple wireless communication terminals. Specifically, the base wireless communication terminal can transmit trigger information to multiple wireless communication terminals to trigger the multiple wireless communication terminals to simultaneously transmit immediate response frames. In this case, the immediate response can refer to transmitting a response frame within a pre-specified time from receiving trigger information within the same Transmission Opportunity (TXOP). In this case, the predetermined time can be a Short Inter-Frame Space (SIFS) defined in the 802.11 standard. The base wireless communication terminal can transmit the trigger information using a trigger frame. In addition, the base wireless communication terminal can transmit the trigger information using a MAC header.

[0061] A plurality of wireless communication terminals can transmit a response frame to the trigger information using a trigger-based (TB) PPDU. In this case, the plurality of wireless communication terminals can transmit the trigger-based PPDU after a certain time has elapsed since receiving the trigger information. In addition, the plurality of wireless communication terminals can transmit the trigger-based PPDU using at least one of UL OFDMA and UL MU-MIMO. If the trigger type of the trigger information is transmitted via a MU-RTS (Request To Send) frame, the plurality of wireless communication terminals can transmit a response frame to the MU-RTS frame using a non-HT PPDU.

[0062] In the embodiment of Figure 6, the AP transmits a trigger frame to the first station STA1, the second station STA2, the third station STA3, and the fourth station STA4. The first station STA1, the second station STA2, the third station STA3, and the fourth station STA4 receive the trigger frame. The first station STA1, the second station STA2, the third station STA3, and the fourth station STA4 transmit a trigger-based PPDU (HE trigger-based PPDU) when SIFS has elapsed since the AP received the trigger frame. The AP receives the trigger-based PPDU and transmits an ACK to the first station STA1, the second station STA2, the third station STA3, and the fourth station STA4.

[0063] As described above, the base wireless communication terminal can transmit trigger information using a trigger frame or a MAC header. Specifically, the base wireless communication terminal can transmit trigger information using a UL MU Response Scheduling (UMRS) A-Control subfield of the MAC header. In a specific embodiment, a wireless communication terminal that receives a MAC frame including a UMRS A-Control subfield transmits a trigger-based PPDU in response to the UMRS A-Control subfield. In addition, a wireless communication terminal indicated by the User Info field of the trigger frame can transmit a trigger-based PPDU in response to the trigger frame. A specific format of the trigger frame will be described in detail with reference to FIG. 7.

[0064] FIG. 7 shows a specific format of a trigger frame according to an embodiment of the present invention.

[0065] The trigger frame may include at least one of a Frame Control field, a Duration field, an RA field, a TA field, a Common Info field, a User Info field, a Padding field, and an FCS field. The response requested by the trigger frame may vary depending on the trigger type. In addition, the fields included in the trigger frame may vary depending on the trigger type.

[0066] The RA field indicates the recipient address of the trigger frame. If the trigger frame triggers transmission of one wireless communication terminal, the RA field may indicate the MAC address of the wireless communication terminal. If the trigger frame triggers transmission of two or more wireless communication terminals, the RA field may indicate a broadcast address. If the trigger type of the trigger frame is GCR MU-BAR, the RA field may indicate a group address corresponding to multiple wireless communication terminals triggered by the trigger frame.

[0067] The TA field indicates the sender address of the trigger frame. If the wireless communication terminal transmitting the trigger frame does not use multiple BSSIDs, the TA field may indicate the MAC address of the wireless communication terminal transmitting the trigger frame. Also, if the wireless communication terminal transmitting the trigger frame uses multiple BSSIDs and the trigger frame triggers multiple wireless communication terminals in a multiple BSSID set, the TA field may indicate the transmitted BSSID of the multiple BSSID set to which the wireless communication terminal transmitting the trigger frame belongs. In this case, the transmitted BSSID indicates a BSS that can signal information about other BSSs included in the multiple BSSID set. The identifier of a BSS that does not correspond to a transmitted BSSID among the BSSs included in the multiple BSSID set is called a nontransmitted BSSID. Specifically, a base wireless communication terminal operating a BSS corresponding to a transmitted BSSID can signal information about a BSS corresponding to a nontransmitted BSSID using a multiple BSSID element. A management frame transmitted from a BSS corresponding to a transmitted BSSID can include a Multiple BSSID element. In this case, the management frame can include a beacon frame and a probe response frame. Also, one Transmitted BSSID can exist for each Multiple BSSID set. This will be described in detail with reference to FIG. 11.

[0068] The Common Info field indicates information commonly required for at least one wireless communication terminal triggered by the trigger frame to transmit a response to the trigger frame. The User Info field indicates information individually required for each of multiple wireless communication terminals indicated by the trigger frame to transmit a response to the trigger frame. Specifically, the trigger frame may include multiple User Info fields. Specific formats of the Common field and the User Info field will be described with reference to FIG. 8.

[0069] The Padding field includes padding bits. Specifically, the Padding field can help a wireless communication terminal transmitting a response frame to a trigger frame to secure time to prepare for transmission of the response frame. Therefore, the length of the Padding field can be determined depending on the capability of the wireless communication terminal transmitting the response frame to the trigger frame. Also, the trigger frame may not include a Padding field. The Padding field can indicate the start of the Padding field with a pre-specified value. In this case, the pre-specified value may be 0xFFF. Also, the remaining fields of the Padding field, excluding the Padding field including the pre-specified value, can include a value other than the pre-specified value or the pre-specified value. The specific format of the trigger frame is as shown in the embodiment of FIG. FIG. 8 shows a specific format of the Common Info field and the User Info field of the trigger frame according to an embodiment of the present invention.

[0070] Specifically, the format of the Common Info field and the format of the User Info field according to an embodiment of the present invention may be as shown in Figures 8(a) and 8(b), respectively. The User Info field may indicate a wireless communication terminal to be triggered by the trigger frame. Specifically, if the User Info field includes an AID (Association Identifier) ​​of a wireless communication terminal or a portion of the AID, the wireless communication terminal corresponding to the AID may determine that the trigger frame will trigger the corresponding wireless communication terminal. In a specific embodiment, the AID12 subfield of the User Info field may indicate 12 LSBs (Least Significant Bits) of the AID of the wireless communication terminal to be triggered by the trigger frame.

[0071] In addition, the User Info field may indicate a resource unit (RU) allocated to the wireless communication terminal triggered by the trigger frame. The RU may indicate a grouping of a plurality of subcarriers that can be used for uplink transmission and downlink transmission according to the size of the frequency band. In this case, at least one of OFDM, OFDMA, and MU-MIMO may be used for the uplink transmission and downlink transmission. In addition, the grouping may be referred to as subchannelization. In a specific embodiment, the RU Allocation subfield may indicate an RU allocated to the wireless communication terminal indicated by the AID12 subfield.

[0072] The base wireless communication terminal can trigger an upstream transmission of an arbitrary wireless communication terminal using a trigger frame. Specifically, the base wireless communication terminal can trigger random access to a designated RU. At this time, the base wireless communication terminal can set the User Info field of the trigger frame to indicate a pre-designated value instead of the AID of a specific wireless communication terminal. In a specific embodiment, the base wireless communication terminal can set the AID12 subfield of the User Info field of the trigger frame to a pre-designated value. Also, if the User Info field of the trigger frame indicates a pre-designated value instead of the AID of a specific wireless communication terminal, the wireless communication terminal receiving the trigger frame can randomly access the RU indicated by the corresponding User Info field. In a specific embodiment, if the AID12 subfield of the User Info field of the trigger frame received by the wireless communication terminal indicates a pre-designated value, the wireless communication terminal can randomly access the RU indicated by the RU Allocation subfield of the corresponding User Info field. The pre-designated value may be 0. Alternatively, the pre-designated value may be 2045. A specific operation of the wireless communication terminal performing random access based on the trigger frame will be described with reference to FIG. 9.

[0073] FIG. 9 shows a random access operation of a wireless communication terminal according to an embodiment of the present invention.

[0074] The wireless communication terminal can perform an OFDMA random access operation through the following operation. The wireless communication terminal selects an integer within an OFDMA contention window (OCW). Specifically, the wireless communication terminal can select an integer within a range from 0 to OCW, or less than OCW. In this case, OCW may be greater than or equal to an OCW minimum value (OCWmin), which is a positive integer, and greater than or equal to an OCW maximum value (OCWmax). The wireless communication terminal sets the selected number as an OFDMA random access backoff (OBO) counter. The wireless communication terminal can receive a trigger frame and decrement the OBO counter based on the RUs for which the trigger frame instructs random access. Specifically, the wireless communication terminal can receive a trigger frame and decrement the OBO counter by the number of RUs for which the trigger frame instructs random access. If the OBO counter is 0 or becomes 0, the wireless communication terminal can arbitrarily select one of the RUs instructed by the random access and attempt transmission via the selected RU. In this case, the wireless communication terminal determines whether the selected RU is idle, and if the selected RU is idle, it can transmit a pending frame to the base wireless communication terminal via the selected RU. Also, if the wireless communication terminal determines that the corresponding RU is busy in either physical carrier sense or virtual carrier sense, the wireless communication terminal can determine that the corresponding RU is busy. The physical carrier sense can include Clear Channel Assessment (CCA). The physical carrier sense can also include Energy Detect (ED). If the wireless communication terminal determines that the selected RU is busy, it can maintain the OBO counter at 0 without transmitting a pending frame to the base wireless communication.

[0075] The wireless communication terminal can set OCWmin and OCWmax according to the OBO-related parameter values ​​signaled by the base wireless communication terminal associated with the wireless communication terminal. The wireless communication terminal can initialize the OBO procedure when it first attempts random access, when it receives OBO-related parameters signaled by the base wireless communication terminal, or when the wireless communication terminal successfully transmits via random access. The initialization of the OBO procedure can include at least one of initialization of the OBO counter and initialization of the OCW. When the wireless communication terminal initializes the OCW, the wireless communication terminal can set the OCW to OCWmin. If the wireless communication terminal's transmission via random access fails, the wireless communication terminal can update the OCW value to (2xOCW+1). The wireless communication terminal selects an arbitrary integer within the updated OCW and sets the selected integer as the OBO counter. If the OCW value reaches OCWmax, the wireless communication terminal can maintain the OCW at OCWmax even if the wireless communication terminal's transmission via random access fails.

[0076] In the embodiment of FIG. 9, the OBO counter of the first station STA1 is 5, and the OBO counter of the second station STA2 is 1. The AP transmits a trigger frame to trigger random access to the first RU (RU1) and the second RU (RU2). Because the number of RUs allocated for random access is two, the first station STA1 decrements its OBO counter by 2 to set it to 3, and the second station STA2 sets its OBO counter to 0. Because the OBO counter of the second station STA2 has become 0, the second station STA2 randomly selects one of the first RU (RU1) and the second RU (RU2) allocated for random access and attempts transmission through it. After 1FS from the time the second station STA2 receives the trigger frame, the second station STA2 transmits a trigger-based PPDU to the AP via the randomly selected RU. The AP receives the trigger-based PPDU from the second station STA2. After 1FS from the time the AP receives the trigger-based PPDU, the AP transmits an ACK to the second station for the frame transmitted by the second station.

[0077] The second station STA2, which has successfully transmitted to the AP, sets the OCW to OCWmin and selects a random number within the set OCW. At this time, the second station STA2 selects 6 and sets the OBO counter to 6. The AP transmits a trigger frame to trigger random access to the first RU (RU1), the second RU (RU2), and the third RU (RU3). Because the number of RUs allocated for random access is three, the first station STA1 decrements the OBO counter by 3 and sets it to 0, and the second station STA2 decrements the OBO counter by 3 and sets it to 3. Now that the OBO counter of the first station STA1 is 0, the first station STA1 randomly selects one of the first RU (RU1), the second RU (RU2), and the third RU (RU3) allocated for random access and attempts to transmit the trigger frame. After a SIFS from the time the first station STA1 receives the trigger frame, the first station STA1 transmits a trigger-based PPDU to the AP through the randomly selected RU. The AP receives the trigger-based PPDU from the first station STA1. After SIFS from when the AP receives the trigger-based PPDU, the AP transmits an ACK to the first station for the frame transmitted by the first station.

[0078] As described above, the wireless communication terminal can set OCWmin and OCWmax according to the OBO-related parameter values ​​signaled by the base wireless communication terminal associated with the wireless communication terminal. Specifically, the wireless communication terminal can receive an element including the OBO-related parameter values ​​from the base wireless communication terminal associated with the wireless communication terminal. In this case, the element can be referred to as a UORA (UL OFDMA-based Random Access) parameter set element. A specific format of the UORA parameter set element will be described with reference to FIG. 10.

[0079] FIG. 10 shows a specific format of a UORA parameter set element according to an embodiment of the present invention.

[0080] A UORA parameter set element can include an Element ID field, a Length field, an Element ID Extension field, and an OCW Range field. The Element ID field indicates an element identifier that identifies the UORA parameter set element. The Length field indicates the length of the UORA element. The Element ID Extension field indicates an extension identifier that is combined with the element identifier to create the extended ID of the UORA parameter set element. The OCW Range field indicates information about the range of the OCW.

[0081] The OCW Range field can include information about OCWmin and OCWmax. Specifically, the OCW Range field can include an EOCWmin field, an EOCWmax field, and a Reserved field. In this case, the wireless communication terminal can set OCWmin according to the value indicated by the EOCWmin field. In a specific embodiment, the wireless communication terminal sets OCWmin by 2 EOCWmin In a specific embodiment, the wireless communication terminal sets OCWmax to 2. EOCWmax Can be set to -1.

[0082] A wireless communication terminal can set OCWmin and OCWmax according to the most recently received UORA parameter set element. Also, a wireless communication terminal can set OCWmin and OCWmax according to the most recently received UORA parameter set element regardless of the access category (AC) of the traffic to be transmitted. A base wireless communication terminal can transmit a UORA parameter set element using a beacon frame. Also, a base wireless communication terminal can transmit a UORA parameter set element using a probe response frame.

[0083] The specific format of the UORA parameter set element may be as shown in FIG.

[0084] When multiple physical access points exist within a network, the time that data transmission frames can occupy the channel can be significantly reduced due to management frames transmitted by the multiple access points. Therefore, a single base station wireless communication terminal in a network can operate multiple BSSs. This will be described with reference to FIG. 11.

[0085] FIG. 11 shows a specific format of a multiple BSSID element according to an embodiment of the present invention.

[0086] A base wireless communication terminal can signal information about multiple BSSs by transmitting one management frame. Specifically, the base wireless communication terminal can signal information about each BSS corresponding to multiple basic service identifiers (BSSIDs) included in a multiple BSSID set by transmitting one management frame. A multiple BSSID set is a set of BSSIDs corresponding to multiple BSSs classified into one group. When a basic wireless communication terminal uses a multiple BSSID set, the wireless communication terminal transmits one management frame to signal information about multiple BSSs, thereby increasing the time that data frames can occupy the channel. In a specific embodiment, the wireless communication terminal can set a reference BSSID representing the multiple BSSID set as BSS information represented by the management frame and insert information about the multiple BSSID set into the management frame. The information about the multiple BSSID set can include information related to the maximum number of multiple BSSIDs included in the multiple BSSID set. In this case, the reference BSSID can be a BSSID that serves as a reference when identifying BSSIDs included in the multiple BSSID set. Specifically, the information about the multiple BSSID set may be the multiple BSSID element in Figure 11. In this case, the information about the multiple BSSID set may include subelements.

[0087] The multiple BSSID element may include an Element ID field. The Element ID field is an identifier representing the multiple BSSID element. The multiple BSSID element may also include a Length field. The Length field represents the length of the multiple BSSID element. The multiple BSSID element may also include a Max BSSID indicator field. In this case, the Max BSSID indicator field represents information related to the maximum number of BSSIDs that the multiple BSSID set can include. Specifically, if the value represented by the Max BSSID indicator field is n, the maximum number of BSSIDs that the multiple BSSID set can include is 2. n In this case, the maximum number of BSSIDs includes the number of BSSIDs for the reference BSSID.

[0088] The multiple BSSID element may also include an Optional Subelements field. The Optional Subelements may include information about the BSS represented by the non-transmitted BSSID. The non-transmitted BSSID represents a BSSID included in the multiple BSSID set other than the reference BSSID. Specifically, the Optional Subelements field may include a non-transmitted BSSID profile, which is information about the BSS represented by the non-transmitted BSSID. The Optional Subelements field may include only information about some of the BSSs represented by the non-transmitted BSSID. In this case, the wireless communication terminal can obtain information about the BSSs represented by the remaining non-transmitted BSSIDs based on a beacon frame or a probe response frame.

[0089] The information about the BSS represented by the non-transmitted BSSID may be a non-transmitted BSSID Capability element and an element that can be included in the beacon frame body. Specifically, the elements that can be included in the beacon frame body may be at least one of an SSID, a multiple BSSID-index subelement, and an FMD Descriptor element. Furthermore, information about the BSS represented by the non-transmitted BSSID that is the same as information about the BSS represented by the reference BSSID may be omitted. Specifically, at least one of the following elements of the BSS represented by the non-transmitted BSSID: Timestamp and Beacon Interval field, DSSS Parameter Set, IBSS Parameter Set, Country, Channel Switch Announcement, Extended Channel Switch Announcement, Wide Bandwidth Channel Switch, Transmit Power Envelope, Supported Operating Classes, IBSS DFS, ERP Information, HT Capabilities, HT Operation, VHT Capabilities, and VHT Operation may be the same as that of the BSS represented by the reference BSSID. The Optional sub-element field can also contain vendor specific elements.

[0090] A wireless communication terminal that receives a management frame including information about a multiple BSSID set can acquire the information about the multiple BSSID set from the management frame. In this case, the wireless communication terminal can acquire the BSSIDs included in the multiple BSSID set based on the information about the multiple BSSID set and the reference BSSID. Specifically, the wireless communication terminal can acquire the BSSIDs included in the multiple BSSID set using the following equation: BSSID(i)=BSSID_A|BSSID_B

[0091] In this case, BSSID_A is a BSSID whose (48-n) most significant bits (MSB) values ​​are the same as the (48-n) MSB values ​​of the reference BSSID, and whose n least significant bits (LSB) values ​​are 0. BSSID_B is a BSSID whose (48-n) MSB values ​​are 0, and whose n LSB values ​​are 2 times the sum of the n LSBs of the reference BSSID and i. n This is the BSSID that is the remainder (mod) when divided by .

[0092] In addition, the base station wireless communication terminal can signal information about multiple BSSID sets using an Operation element. The Operation element can include a MaxBSSID Indicator field and a Tx BSSID Indicator field. The MaxBSSID Indicator field can represent the same information as the MAX BSSID Indicator field of the multiple BSSID element. Therefore, the wireless communication terminal can obtain the BSSID of the BSS from which a management frame is transmitted using the MaxBSSID Indicator field in the same way as obtaining the BSSID of the BSS from which a management frame is transmitted using the MAX BSSID Indicator field of the multiple BSSID element. The Tx BSSID Indicator field indicates whether the BSS from which a management frame containing an Operation element is transmitted corresponds to a non-transmitted BSSID. Specifically, if the Tx BSSID Indicator field is 1, the BSS from which a management frame containing an Operation element is transmitted corresponds to a transmitted BSSID. If the Tx BSSID Indicator field is 0, the BSS from which a management frame containing an Operation element is transmitted corresponds to a non-transmitted BSSID.

[0093] In addition, the wireless communication terminal can signal information about capabilities related to a multiple BSSID set using the Capabilities element of the management frame. Specifically, the wireless communication terminal can transmit an Rx Control Frame to MultiBSS field using the Capabilities element of the management frame. The Rx Control Frame to MultiBSS field can indicate whether the wireless communication terminal can receive frames transmitted from a transmitted BSSID when associated with a BSS corresponding to a non-transmitted BSSID. Specifically, the Rx Control Frame to MultiBSS field can indicate whether the wireless communication terminal can receive control frames transmitted from a transmitted BSSID when associated with a BSS corresponding to a non-transmitted BSSID.

[0094] When a BSS containing a wireless communication terminal corresponds to a multiple BSSID set, the wireless communication terminal's OFDMA random access operation becomes an issue. Although the BSSs included in the multiple BSSID set are technically different BSSs, due to the purpose of using the multiple BSSID set, the BSSs included in the multiple BSSID set can be treated as the same BSS (intra-BSS) in the operation of a specific wireless communication terminal. Also, a trigger frame transmitted from a transmitted BSSID can trigger upstream transmissions of wireless communication terminals included in a BSS corresponding to a non-transmitted BSSID. Specifically, the wireless communication terminal's operations related to OBO-related parameter setting, OBO procedure initialization, OBO counter decrement operation, and random access RU selection become issues.

[0095] When the BSS of the wireless communication terminal is included in the multiple BSSID set and the wireless communication terminal is associated with a BSS corresponding to a non-transmitted BSSID, the wireless communication terminal can configure OBO-related parameters based on the UORA parameter set transmitted by the transmitted BSSID. When the BSS of the wireless communication terminal is included in the multiple BSSID set and the wireless communication terminal is associated with a BSS corresponding to a non-transmitted BSSID, the wireless communication terminal can update OCWmin and OCWmax according to the UORA parameter set transmitted by the transmitted BSSID. In this embodiment, the UORA parameter set does not have to be included in the non-transmitted BSSID profile. Furthermore, the UORA parameter set may be commonly applied to at least one other BSS included in the multiple BSSID set. Therefore, when the BSS of the wireless communication terminal is included in the multiple BSSID set and the wireless communication terminal is associated with a BSS corresponding to a non-transmitted BSSID, the wireless communication terminal can configure OBO-related parameters according to the UORA parameter set transmitted by the transmitted BSSID. In addition, when the BSS of the wireless communication terminal is included in the multiple BSSID set and the wireless communication terminal is associated with a BSS corresponding to a non-transmitted BSSID, the non-transmitted BSSID Profile sub-element corresponding to the BSS to which the wireless communication terminal is associated may not include a UORA parameter set element. In this way, when the non-transmitted BSSID Profile sub-element does not include a UORA parameter set element, the wireless communication terminal can set OBO-related parameters according to the UORA parameter set transmitted by the transmitted BSSID.

[0096] When the base wireless communication terminal transmits a management frame from a BSS corresponding to a transmitted BSSID, the base wireless communication terminal can signal OBO-related parameters used by wireless communication terminals of multiple BSSs corresponding to a multiple BSSID set using the UORA parameter set transmitted by the transmitted BSSID. Also, when the base wireless communication terminal transmits a management frame from a BSS corresponding to a transmitted BSSID, the base wireless communication terminal can signal OBO-related parameters to wireless communication terminals of a BSS corresponding to a non-transmitted BSSID separately from other BSSs of the multiple BSSID set using a non-transmitted BSSID Profile subelement. Through this embodiment, the base wireless communication terminal can efficiently signal OBO-related parameters to multiple wireless communication terminals included in a BSS corresponding to a multiple BSSID set.

[0097] As described above, when the wireless communication terminal receives information on OBO-related parameters from the base wireless communication terminal, the wireless communication terminal can initiate the OBO procedure. Therefore, if the BSS of the wireless communication terminal is included in the multiple BSSID set and the wireless communication terminal is associated with a BSS corresponding to a non-transmitted BSSID, the wireless communication terminal can initiate the OBO procedure when it receives a UORA parameter set transmitted by the transmitted BSSID. If the BSS of the wireless communication terminal is included in the multiple BSSID set and the wireless communication terminal is associated with a BSS corresponding to a non-transmitted BSSID, the wireless communication terminal can initiate the OBO procedure when it receives a UORA parameter set transmitted by the transmitted BSSID. Also, if the BSS of the wireless communication terminal is included in the multiple BSSID set and the wireless communication terminal is associated with a BSS corresponding to a non-transmitted BSSID, the non-transmitted BSSID Profile sub-element corresponding to the BSS to which the wireless communication terminal is associated may not include a UORA parameter set element. In this case, the wireless communication terminal can initiate the OBO procedure. In a specific embodiment, when a wireless communication terminal initiates an OBO procedure, the wireless communication terminal sets OCW to OCWmin, and can arbitrarily select an OBO counter within the OCW.

[0098] When the transmitter address (Transmitter Address, TA) of the trigger frame is the BSSID of the BSS to which the wireless communication terminal is associated, the wireless communication terminal can decrement the OBO counter based on the RU indicated by the trigger frame. Therefore, even when the BSS of the wireless communication terminal is included in the multiple BSSID set, the wireless communication terminal can decrement the OBO counter based on the RU indicated by the trigger frame if the transmitter address (Transmitter Address, TA) of the trigger frame is the BSSID of the BSS to which the wireless communication terminal is associated. Specifically, when the BSS of the wireless communication terminal is included in the multiple BSSID set and the transmitter address of the trigger frame is the transmitted BSSID, wireless communication terminals associated with a BSS having a non-transmitted BSSID cannot decrement based on the RU indicated by the corresponding trigger frame. Also, when the BSS of the wireless communication terminal is included in the multiple BSSID set and the transmitter address of the trigger frame is the non-transmitted BSSID, wireless communication terminals associated with a BSS having a transmitted BSSID cannot decrement based on the RU indicated by the corresponding trigger frame.

[0099] In yet another specific embodiment, if the sender address of the trigger frame is the transmitted BSSID, wireless communication terminals associated with a BSS having a non-transmitted BSSID may be allowed to decrement their OBO counters based on the trigger frame. However, in this embodiment, fairness with wireless communication terminals associated with a BSS having the transmitted BSSID may be an issue. Also, if the recipient address of the trigger frame is a BSSID included in the multiple BSSID set, wireless communication terminals associated with the BSS included in the multiple BSSID set may be allowed to decrement their OBO counters based on the trigger frame. In this embodiment, wireless communication terminals associated with a BSS corresponding to the transmitted BSSID may decrement their OBO counters based on a trigger frame that cannot trigger the wireless communication terminal, which may result in issues with random access operation and fairness for wireless communication terminals not associated with a BSS corresponding to the multiple BSSID set. Also, wireless communication terminals associated with a non-transmitted BSSID may be allowed to decrement their OBO counters based on the trigger frame only if the sender address of the trigger frame is the transmitted BSSID and the trigger frame triggers transmission for wireless communication terminals associated with the non-transmitted BSSID. In order to determine whether a trigger frame whose sender address is a transmitted BSSID triggers transmission for a wireless communication terminal associated with a non-transmitted BSSID, the wireless communication terminal must decode the User Info field. Therefore, this embodiment may increase the complexity of the random access operation of the wireless communication terminal.

[0100] Specific operations of the wireless communication terminal related to setting OBO-related parameters, initializing the OBO procedure, decrementing the OBO counter, and selecting an RU to randomly access will be described in detail with reference to FIG.

[0101] 12 and 13 illustrate a random access operation of a wireless communication terminal associated with multiple BSSID sets according to an embodiment of the present invention.

[0102] In the embodiment of Figure 12, a first station STA1 is associated with a BSS corresponding to a transmitted BSSID of a multiple BSSID set. A second station STA2 is associated with a BSS corresponding to a non-transmitted BSSID of the multiple BSSID set. The first station STA1 and the second station STA2 receive a beacon frame transmitted from the transmitted BSSID. At this time, the first station STA1 and the second station STA2 update their OCWmin and OCWmax according to the UORA parameter set element included in the beacon frame. In a specific embodiment, the UORA parameter set of the beacon frame is advertised by the transmitted BSSID and is not included in the non-transmitted BSSID Profile subelement, so the second station STA2 can update its OCWmin and OCWmax according to the UORA parameter set element.

[0103] Furthermore, the first station STA1 and the second station STA2 have received information about OBO-related parameters from the base wireless communication terminal, and therefore initialize the OBO procedure. Specifically, the first station STA1 and the second station STA2 arbitrarily select an OBO counter in the OCW. The first station STA1 selects 3, and the second station STA2 selects 5.

[0104] The first station STA1 and the second station STA2 receive a trigger frame having the transmitted BSSID as a sender address (TA). At this time, the trigger frame indicates two RUs allocated for random access. In the embodiment of Figure 12, it is assumed that a wireless communication terminal associated with a BSS included in a multiple BSSID set can decrement its OBO counter based on a trigger frame having one of the BSSIDs included in the multiple BSSID set as a sender address. Therefore, the first station STA1 decrements its OBO counter by 2 in response to the trigger frame and sets the OBO counter to 1, and the second station STA2 associated with a BSS corresponding to the non-transmitted BSSID decrements its OBO counter by 2 in response to the trigger frame and sets the OBO counter to 3.

[0105] The first station STA1 and the second station STA2 receive a trigger frame having the non-transmitted BSSID as a sender address (TA). At this time, the trigger frame indicates two RUs allocated for random access. The first station STA1 decrements its OBO counter by 2 in response to the trigger frame, sets the OBO counter to 0, and randomly selects and attempts to transmit one of the two RUs indicating that the trigger frame is allocated for random access. The second station STA2, which is associated with the BSS corresponding to the non-transmitted BSSID, decrements its OBO counter by 2 in response to the trigger frame, and sets the OBO counter to 1.

[0106] If the first station STA1 and the second station STA2 receive a beacon frame that does not include a UORA parameter set element, the first station STA1 and the second station STA2 maintain the conventional OBO procedure. The first station STA1 and the second station STA2 receive a beacon frame transmitted from the transmitted BSSID. At this time, the beacon frame includes a UORA parameter set element. Therefore, the first station STA1 and the second station STA2 update their OCWmin and OCWmax according to the UORA parameter set element included in the beacon frame and initialize the OBO procedure.

[0107] The OBO counter decrement operation described in Fig. 12 may complicate the random access operation of the wireless communication terminal as described above, and may cause problems with fairness with other wireless communication terminals. Therefore, even when the BSS of the wireless communication terminal is included in a multiple BSSID set as shown in Fig. 13, the wireless communication terminal can decrement the OBO counter based on the RU indicated by the trigger frame if the transmitter address (TA) of the trigger frame is the BSSID of the BSS to which the wireless communication terminal is associated.

[0108] 12. The same operations and situations in the embodiment of FIG. 13 as in the embodiment of FIG. 12 will not be described. The first station STA1 and the second station STA2 receive a trigger frame having the transmitted BSSID as a sender address (TA). At this time, the trigger frame indicates two RUs allocated for random access. The first station STA1, which is associated with the BSS corresponding to the transmitted BSSID, decrements its OBO counter by 2 in response to the trigger frame and sets the OBO counter to 1. The second station STA2, which is associated with the BSS corresponding to the non-transmitted BSSID, maintains its OBO counter at 5.

[0109] In addition, the first station STA1 and the second station STA2 receive a trigger frame having the non-transmitted BSSID as a sender address (TA). At this time, the trigger frame indicates two RUs allocated for random access. Since the first station STA1 is associated with the BSS corresponding to the transmitted BSSID, it maintains its OBO counter at 1. The second station STA2, associated with the BSS corresponding to the non-transmitted BSSID, decrements its OBO counter by 2 and sets it to 3.

[0110] Even if a trigger frame triggers random access, if the capability of the wireless communication terminal does not support the upward transmission condition indicated by the trigger frame, the wireless communication terminal cannot perform random access even if the OBO counter reaches 0. For example, if the wireless communication terminal does not support transmission for the frequency bandwidth of the RU indicated by the trigger frame in the RU allocated for random access, the wireless communication terminal cannot perform random access to the corresponding RU. Therefore, a random access operation taking into account the capability of the wireless communication terminal is required.

[0111] When the wireless communication terminal receives the trigger frame, the wireless communication terminal can decrement the OBO counter according to the capability of the wireless communication terminal. Specifically, when the wireless communication terminal receives the trigger frame, the wireless communication terminal can decrement the OBO counter based on the RUs allocated for random access and the capability of the wireless communication terminal. In a specific embodiment, the wireless communication terminal can decrement the OBO counter by the number of RUs to which the wireless communication terminal can transmit a trigger-based PPDU according to the capability of the wireless communication terminal, among the RUs allocated for random access. As described above, the RUs allocated for random access can be indicated by the trigger frame. Furthermore, the wireless communication terminal can determine whether it can transmit a trigger-based PPDU via an RU based on the transmission condition indicated by the trigger frame.

[0112] In addition, when the OBO counter reaches 0, the wireless communication terminal can select an RU according to the capability of the wireless communication terminal. In a specific embodiment, when the OBO counter reaches 0, the wireless communication terminal can arbitrarily select any one of the RUs that are assigned for random access and to which the wireless communication terminal can transmit a trigger-based PPDU according to the capability of the wireless communication terminal.

[0113] When the OBO counter reaches 0, the wireless communication terminal can suspend random access and maintain the OBO counter. Specifically, if data of the response length indicated by the trigger frame is not buffered in the wireless communication terminal, the wireless communication terminal can suspend random access and maintain the OBO counter at 0. In this case, the wireless communication terminal can perform random access in response to the next trigger frame that triggers random access. Also, if there is no RU to which the wireless communication terminal can transmit a trigger-based PPDU according to the capability of the wireless communication terminal among the RUs allocated for random access, the wireless communication terminal can maintain the OBO counter at 0. In this case, the wireless communication terminal can perform random access in response to the next trigger frame that triggers random access.

[0114] In addition, the wireless communication terminal capability may include at least one of the wireless communication terminal capability related to a transmission bandwidth, a modulation and coding scheme (MCS), a dual carrier modulation (DCM), the number of spatial streams, a guard interval (GI) length, a long training field (LTF) type, a space-time block coding (STBC), transmission power, and a padding field length. The padding field length may represent the length of a padding field included in a trigger-based PPDU. Specific operations of the wireless communication terminal will be described with reference to FIGS. 14 to 21.

[0115] Figure 14 shows RU types and subcarrier indexes that can be used when transmitting a PPDU with a 20 MHz bandwidth according to an embodiment of the present invention. Figure 15 shows RU types and subcarrier indexes that can be used when transmitting a PPDU with a 40 MHz bandwidth according to an embodiment of the present invention. Figure 16 shows RU types and subcarrier indexes that can be used when transmitting a PPDU with an 80 MHz bandwidth according to an embodiment of the present invention.

[0116] As described above, an RU can represent a grouping of multiple subcarriers that can be used for upstream and downstream transmissions depending on the size of the frequency band.

[0117] A wireless communication terminal according to an embodiment of the present invention can perform uplink transmission or downlink transmission using at least one of an RU using 26 subcarriers (26-tone RU), an RU using 52 subcarriers (52-tone RU), an RU using 106 subcarriers (106-tone RU), an RU using 242 subcarriers (242-tone RU), an RU using 484 subcarriers (484-tone RU), an RU using 996 subcarriers (996-tone RU), and an RU using 1992 subcarriers (2*996-tone RU). Specifically, the wireless communication terminal can transmit an HE MU PPDU or an HE trigger-based PPDU via OFDMA using a designated RU. In this case, if the frequency bandwidth of the PPDU is any one of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 80+80 MHz, the wireless communication terminal can transmit the PPDU using any one of 26-tone RU, 52-tone RU, 106-tone RU, and 242-tone RU. Also, if the frequency bandwidth of the PPDU is any one of 40 MHz, 80 MHz, 160 MHz, and 80+80 MHz, the wireless communication terminal can transmit the PPDU using 484-tone RU. Also, if the frequency bandwidth of the PPDU is any one of 80 MHz, 160 MHz, and 80+80 MHz, the wireless communication terminal can use 996-tone RU. Also, if the frequency bandwidth of the PPDU is any one of 160 MHz and 80+80 MHz, the wireless communication terminal can transmit the PPDU using 2*996-tone RU.

[0118] Furthermore, the wireless communication terminal can transmit an HE SU (Single User) PPDU using a specified RU. In this case, if the frequency bandwidth of the HE SU PPDU is 20 MHz, the wireless communication terminal can transmit the HE SU PPDU using a 242-tone RU. Furthermore, if the frequency bandwidth of the HE SU PPDU is 40 MHz, the wireless communication terminal can transmit the HE SU PPDU using a 484-tone RU. Furthermore, if the frequency bandwidth of the HE SU PPDU is 80 MHz, the wireless communication terminal can transmit the HE SU PPDU using a 996-tone RU. Furthermore, if the frequency bandwidth of the HE SU PPDU is 160 MHz or 80+80 MHz, the wireless communication terminal can transmit the HE SU PPDU using 2*996-tone RU.

[0119] A 26-tone RU may include 24 subcarriers for transmitting data and 2 subcarriers for transmitting pilot signals. Specific locations of the 26-tone RU may be as shown in FIG. 14, FIG. 15, and FIG. 16. When the frequency bandwidth of a PPDU transmitted by a wireless communication terminal is 160 MHz or 80+80 MHz PPDU, the 26-tone RU transmitted via each 80 MHz frequency band may be as shown in FIG. 15. A 52-tone RU may include 48 subcarriers for transmitting data and 4 subcarriers for transmitting pilot signals. Specific locations of the 52-tone RU may be as shown in FIG. 14, FIG. 15, and FIG. 16. When the frequency bandwidth of a PPDU transmitted by a wireless communication terminal is 160 MHz or 80+80 MHz PPDU, the 52-tone RU transmitted via each 80 MHz frequency band may be as shown in FIG. 15.

[0120] A 106-tone RU may include 102 subcarriers for transmitting data and 4 subcarriers for transmitting pilot signals. Specific locations of the 106-tone RUs may be as shown in FIG. 14, FIG. 15, and FIG. 16. When the frequency bandwidth of a PPDU transmitted by a wireless communication terminal is 160 MHz or 80+80 MHz PPDU, the 106-tone RUs transmitted via each 80 MHz frequency band may be as shown in FIG. 15. A 242-tone RU may include 234 subcarriers for transmitting data and 8 subcarriers for transmitting pilot signals. Specific locations of the 242-tone RUs may be as shown in FIG. 14, FIG. 15, and FIG. 16. When the frequency bandwidth of a PPDU transmitted by a wireless communication terminal is 160 MHz or 80+80 MHz PPDU, the 242-tone RUs transmitted via each 80 MHz frequency band may be as shown in FIG. 15.

[0121] A 484-tone RU may include 468 subcarriers for transmitting data and 16 subcarriers for transmitting pilot signals. Specific locations of the 484-tone RUs may be as shown in FIG. 15 and FIG. 16. When the frequency bandwidth of a PPDU transmitted by a wireless communication terminal is 160 MHz or 80+80 MHz PPDU, the 484-tone RUs transmitted via each 80 MHz frequency band may be as shown in FIG. 15. A 996-tone RU may include 980 subcarriers for transmitting data and 16 subcarriers for transmitting pilot signals. Specific locations of the 996-tone RUs may be as shown in FIG. 15. When the frequency bandwidth of a PPDU transmitted by a wireless communication terminal is 160 MHz or 80+80 MHz PPDU, the 996-tone RUs transmitted via each 80 MHz frequency band may be as shown in FIG. 15. When a wireless communication terminal transmits a PPDU with a 160 MHz or 80+80 MHz bandwidth, the subcarriers included in the 996-tone RU are located at [-1012:-515, -509:-12] and [12:509, 515:1012] in each 80 MHz frequency band. Here, "x:y" represents subcarrier indexes x to y. Therefore, even when using 2*996-tone RUs, the wireless communication terminal can use subcarriers located at subcarrier indexes [-1012:-515, -509:-12] and [12:509, 515:1012].

[0122] When a wireless communication terminal transmits an HE MU PPDU or HE trigger-based PPDU having a frequency bandwidth of 20 MHz and the PPDU includes two or more RUs, the wireless communication terminal can transmit seven DC (Direct Current) subcarriers in [-3:3]. When a wireless communication terminal transmits an HE SU PPDU having a frequency bandwidth of 20 MHz using a 242-tone RU, the wireless communication terminal can transmit three DC subcarriers in [-1:1]. When a wireless communication terminal transmits an HE SU PPDU having a frequency bandwidth of 40 MHz using a 484-tone RU, the wireless communication terminal can transmit five DC subcarriers in [-2:2]. When a wireless communication terminal transmits an HE MU PPDU or HE trigger-based PPDU having a frequency bandwidth of 80 MHz and the PPDU includes two or more RUs, the wireless communication terminal can transmit seven DC subcarriers in [-3:3]. When the wireless communication terminal transmits an HE SU PPDU having an 80 MHz frequency bandwidth using 996-tone RU, the wireless communication terminal can transmit five DC subcarriers at [-2:2]. When the wireless communication terminal transmits a PPDU having a 160 MHz or 80+80 MHz bandwidth, the wireless communication terminal can transmit DC subcarriers at the same positions as when transmitting an HE SU PPDU having an 80 MHz frequency bandwidth using 996-tone RU in each 80 MHz band.

[0123] When a wireless communication terminal transmits a PPDU having a 20 MHz frequency bandwidth, it can transmit 11 guard subcarriers at [-128:-123] and [123:127]. When a wireless communication terminal transmits a PPDU having a 40 MHz frequency bandwidth, it can transmit 23 guard subcarriers at [-256:-245] and [245:255]. When a wireless communication terminal transmits a PPDU having an 80 MHz frequency bandwidth, it can transmit 23 guard subcarriers at [-512:-501] and [501:511]. When a wireless communication terminal transmits a PPDU having a 160 MHz or 80+80 MHz frequency bandwidth, it can transmit the guard subcarriers used when transmitting a PPDU having an 80 MHz frequency bandwidth at both ends.

[0124] FIG. 17 illustrates encoding values ​​used to indicate RUs in the RU Allocation subfield of a trigger frame according to an embodiment of the present invention.

[0125] The RU Allocation subfield indicates the RU that the wireless communication terminal triggered by the trigger frame uses for transmission. The RU Allocation subfield may be an 8-bit field. In this case, one bit of the RU Allocation subfield, for example, B12, may indicate whether the RU indicated by the RU Allocation subfield is in a primary 80 MHz channel or a secondary (non-primary) 80 MHz channel. The primary channel represents a frequency band that serves as the basis for frequency band extension. The primary channel may also refer to a continuous frequency band including a frequency band with a 20 MHz frequency bandwidth that serves as the basis for frequency band extension. If the RU has a frequency bandwidth of 80 MHz or less, seven bits of the RU Allocation subfield, for example, B19-B13, indicate which RU is indicated within the 80 MHz bandwidth. If the RU has a frequency bandwidth greater than 80 MHz, seven bits of the RU Allocation subfield, for example, B19-B13, indicate which RU is indicated by the RU in a frequency bandwidth greater than 80 MHz. The specific values ​​of the RU Allocation field may be as shown in FIG.

[0126] Specifically, for a PPDU with a 20 MHz, 40 MHz, or 80 MHz frequency bandwidth, B12 can be set to 0. Also, for a 2*996-tone RU, B12 can be set to 1. Also, B19-B13 can be set as follows:

[0127] When a wireless communication terminal transmits a PPDU having a 20 MHz frequency bandwidth, the wireless communication terminal may specify the RU indexes of FIG. 14 in B19-B13 in ascending order. When the values ​​of B19-B13 are 0000000, the RU Allocation subfield may indicate 26-tone RU1. When the values ​​of B19-B13 are 0001000, the RU Allocation subfield may indicate 26-tone RU9. Values ​​of B19-B13 from 0001001 to 0100100 may not be used. When the values ​​of B19-B13 are 0100101, the RU Allocation subfield may indicate 52-tone RU1. When the value of B19-B13 is 0101000, the RU Allocation subfield may indicate 52-tone RU4. Values ​​of B19-B13 from 0101001 to 0110100 may not be used. If the value of B19-B13 is 0110101, the RU Allocation subfield can indicate a 106-tone RU1. If the value of B19-B13 is 0110110, the RU Allocation subfield can indicate a 106-tone RU2. Values ​​0110111 to 0111100 cannot be used for B19-B13. If the value of B19-B13 is 0111101, the RU Allocation subfield can indicate a 242-tone RU1. Values ​​0111110 to 1000000 cannot be used for B19-B13.

[0128] When a wireless communication terminal transmits a PPDU having a 40 MHz frequency bandwidth, the wireless communication terminal may specify the RU indexes of FIG. 15 in B19-B13 in ascending order. When the values ​​of B19-B13 are 0000000, the RU Allocation subfield may indicate a 26-tone RU1. When the values ​​of B19-B13 are 0010001, the RU Allocation subfield may indicate a 26-tone RU18. Values ​​of 0010010 to 0100100 may not be used for B19-B13. When the values ​​of B19-B13 are 0100101, the RU Allocation subfield may indicate a 52-tone RU1. When the value of B19-B13 is 0101100, the RU Allocation subfield may indicate a 52-tone RU8. Values ​​of 0101101 to 0110100 may not be used for B19-B13. The values ​​of B19-B13 can be specified according to rules such as 26-tone RU and 52-tone RU for 106-tone, 242-tone and 484-tone RU.

[0129] When a wireless communication terminal transmits a PPDU having an 80 MHz, 160 MHz, or 80+80 MHz frequency bandwidth, the wireless communication terminal may specify the RU indexes of FIG. 12 in B19-B13 in ascending order. When the values ​​of B19-B13 are 0000000, the RU Allocation subfield may indicate a 26-tone RU1. When the values ​​of B19-B13 are 0100100, the RU Allocation subfield may indicate a 26-tone RU37. When the values ​​of B19-B13 are 0100101, the RU Allocation subfield may indicate a 52-tone RU1. When the values ​​of B19-B13 are 0110100, the RU Allocation subfield may indicate a 52-tone RU16. The values ​​of B19-B13 can be specified according to rules such as 26-tone RU and 52-tone RU for 106-tone, 242-tone, 484-tone, and 996-tone RU. If a wireless communication terminal transmits a 160 MHz or 80+80 MHz PPDU and the values ​​of B19-B13 are 1000100, the RU Allocation subfield can indicate 2*996-tone RU.

[0130] A wireless communication terminal can only support PPDU transmission and reception having a frequency bandwidth equal to or less than a certain size. For example, a wireless communication terminal can only support PPDU transmission and reception having a frequency bandwidth of 20 MHz. Alternatively, a wireless communication terminal can only support PPDU transmission and reception having a frequency bandwidth equal to or less than 80 MHz. When a wireless communication terminal only supports PPDU transmission and reception having a frequency bandwidth equal to or less than a certain size, the wireless communication terminal can decrement the OBO counter based on the number of RUs included in a frequency bandwidth equal to or less than a certain size among RUs allocated for random access. In this case, the RUs allocated for random access can be indicated by a trigger frame. Furthermore, the wireless communication terminal decrements the OBO counter upon receiving a trigger frame. Specifically, when a wireless communication terminal only supports PPDU transmission and reception having a frequency bandwidth equal to or less than a certain size, the wireless communication terminal can decrement the OBO counter based on the number of RUs included in a primary channel having a frequency bandwidth equal to or less than a certain size among RUs allocated for random access. This is because the wireless communication terminal may have difficulty switching channels within a certain time and may not be able to support a secondary channel. In this case, the secondary channel may refer to a channel other than the primary channel. For example, if the wireless communication terminal supports only PPDU transmission and reception having a frequency bandwidth of 20 MHz or less, the wireless communication terminal can decrement the OBO counter based on the number of RUs allocated for random access whose B19-B13 values ​​of the RU Allocation subfield are 0000000 to 0001000, 0100101 to 0101000, 0110101 to 0110110, or 0111101. In yet another specific embodiment, if the wireless communication terminal supports only PPDU transmission and reception having a frequency bandwidth of a certain size or less, the wireless communication terminal can decrement the OBO counter based on the number of RUs allocated for random access that are included in a frequency bandwidth of a certain size or less, regardless of whether the RUs are included in a primary channel.For example, if a wireless communication terminal only supports PPDU transmission and reception with a frequency bandwidth of 20 MHz or less, the wireless communication terminal can reduce the OBO count based on the number of RUs allocated for random access whose B19-B13 values ​​in the RU Allocation subfield are 1000000 or less.

[0131] Furthermore, when the OBO counter reaches 0 and the wireless communication terminal supports only PPDU transmission and reception having a frequency bandwidth equal to or smaller than a certain size, the wireless communication terminal can arbitrarily select any one of the RUs allocated for random access that are included in the frequency bandwidth equal to or smaller than the certain size. In this case, the wireless communication terminal can attempt transmission via the selected RU. The RU allocated for random access can be indicated by the trigger frame as described above. If there is no frequency bandwidth equal to or smaller than the certain size among the RUs allocated for random access, the wireless communication terminal can maintain the OBO counter without attempting transmission. In this case, the wireless communication terminal can attempt random access in response to the next trigger frame transmitted. In this embodiment, when the wireless communication terminal decrements the OBO counter, the wireless communication terminal can ignore its own capabilities. Specifically, the wireless communication terminal decrements the OBO counter regardless of whether the RU is included in the frequency bandwidth equal to or smaller than a certain size. When the OBO counter reaches 0, the wireless communication terminal can arbitrarily select any one of the RUs allocated for random access that are included in the frequency bandwidth equal to or smaller than the certain size.

[0132] In addition, in a specific embodiment, the wireless communication terminal may arbitrarily select any one of the RUs allocated for random access and included in a primary channel having a bandwidth equal to or less than a certain size. This is because the wireless communication terminal may have difficulty switching channels within a certain time and may not be able to support a secondary channel. For example, if the wireless communication terminal supports only PPDU transmission and reception having a frequency bandwidth equal to or less than 20 MHz, the wireless communication terminal may arbitrarily select any one of the RUs allocated for random access and having a B19-B13 value of 0000000 to 0001000, 0100101 to 0101000, 0110101 to 0110110, or 0111101. In yet another specific embodiment, if the wireless communication terminal supports only PPDU transmission and reception having a frequency bandwidth equal to or less than a certain size, the wireless communication terminal may arbitrarily select any one of the RUs allocated for random access and included in a frequency bandwidth equal to or less than a certain size, regardless of whether the RU is included in a primary channel. For example, if a wireless communication terminal only supports PPDU transmission and reception with a frequency bandwidth of 20 MHz or less, the wireless communication terminal can arbitrarily select one of the RUs that are allocated for random access and whose B19-B13 values ​​of the RU Allocation subfield corresponding to the RU are 1000000 or less.

[0133] 18 and 19 illustrate a random access operation performed by a wireless communication terminal that supports only PPDUs having a 20 MHz frequency bandwidth according to an embodiment of the present invention.

[0134] In the embodiments of Figures 18 to 21, the wireless communication terminal decrements the OBO counter based on the frequency bandwidth that the wireless communication terminal can support. In the embodiments of Figures 18 and 20, if an RU allocated for random access is included in a primary channel having a frequency bandwidth equal to or smaller than a certain size, the wireless communication terminal decrements the OBO count based on the corresponding RU.

[0135] In the embodiment of FIG. 18, the first station STA1 supports only frequency bands below 20 MHz. The second station STA2 supports frequency bands above 20 MHz. The first station STA1 and the second station STA2 receive beacon frames from a first AP (AP1). The first station STA1 and the second station STA2 acquire UORA parameter set elements from the beacon frames and initialize the OBO procedure. Specifically, the first station STA1 sets OCWmin and OCWmax according to the UORA parameter set element to initialize the OCW. The first station STA1 randomly selects 10 within the OCW and sets the OBO counter to 10. The second station STA2 sets OCWmin and OCWmax according to the UORA parameter set element to initialize the OCW. The second station STA2 randomly selects 12 within the OCW and sets the OBO counter to 12.

[0136] The first station STA1 and the second station STA2 receive a trigger frame from the first AP (AP1). At this time, the trigger frame indicates two RUs to be assigned for random access. One RU is included in the primary channel having a 20 MHz frequency bandwidth, and the other RU is not included in the primary channel having a 20 MHz frequency bandwidth. Because the first station STA1 only supports frequency bandwidths of 20 MHz or less, the first station STA1 decrements the OBO counter by 1 and sets the OBO counter to 9. Because the second station STA2 also supports frequency bandwidths of 20 MHz or more, the second station STA2 decrements the OBO counter by 2 and sets the OBO counter to 10.

[0137] In the embodiment of Fig. 19, the first station STA1 supports only a frequency band of 20 MHz or less, and the second station STA2 supports a frequency band of 20 MHz or more, as in the embodiment of Fig. 18. The operations of the first station STA1 and the second station STA2, which are the same as those in the embodiment of Fig. 18, will not be described here.

[0138] The first station STA1 and the second station STA2 receive a trigger frame from the first AP (AP1). At this time, the trigger frame indicates two RUs to be assigned for random access. One RU has a frequency bandwidth equal to or smaller than 20 MHz, and the other RU has a frequency bandwidth greater than 20 MHz. Because the first station STA1 only supports frequency bandwidths of 20 MHz or less, the first station STA1 decrements the OBO counter by 1 and sets the OBO counter to 9. Because the second station STA2 also supports frequency bandwidths greater than 20 MHz, the second station STA2 decrements the OBO counter by 2 and sets the OBO counter to 10.

[0139] 20 and 21 illustrate a random access operation performed by a wireless communication terminal that supports only PPDUs having a frequency bandwidth of 80 MHz or less according to an embodiment of the present invention.

[0140] In the embodiment of Figure 20, the first station STA1 supports only the frequency band below 80 MHz, and the second station STA2 supports the frequency band above 80 MHz (160 MHz, 80+80 MHz). The operation of the first station STA1 and the second station STA2, which are the same as those in the embodiments of Figures 18 and 19, will not be described.

[0141] The first station STA1 and the second station STA2 receive a trigger frame from the first AP (AP1). At this time, the trigger frame indicates two RUs to be assigned for random access. One RU is included in the primary channel having an 80 MHz frequency bandwidth, and the other RU is not included in the primary channel having an 80 MHz frequency bandwidth. Because the first station STA1 only supports frequency bandwidths of 80 MHz or less, the first station STA1 decrements the OBO counter by 1 and sets the OBO counter to 9. Because the second station STA2 also supports frequency bandwidths of 80 MHz or more, the second station STA2 decrements the OBO counter by 2 and sets the OBO counter to 10.

[0142] In the embodiment of Figure 21, the first station STA1 supports only the frequency band below 80 MHz, as in the embodiment of Figure 20, and the second station STA2 supports the frequency band above 80 MHz (160 MHz, 80+80 MHz). The operations of the first station STA1 and the second station STA2, which are the same as those in the embodiments of Figures 18 to 20, will not be described.

[0143] The first station STA1 and the second station STA2 receive a trigger frame from the first AP (AP1). At this time, the trigger frame indicates two RUs to be assigned for random access. One RU has a frequency bandwidth equal to or smaller than 80 MHz, and the other RU has a frequency bandwidth greater than 80 MHz. Because the first station STA1 only supports frequency bandwidths of 80 MHz or less, the first station STA1 decrements the OBO counter by 1 and sets the OBO counter to 9. Because the second station STA2 also supports frequency bandwidths of 20 MHz or more, the second station STA2 decrements the OBO counter by 2 and sets the OBO counter to 10.

[0144] In the random access operation of the wireless communication terminal described above, the wireless communication terminal receives information on OBO-related parameters from a base wireless communication terminal associated with the wireless communication terminal and sets the OBO-related parameters according to the received information. Specifically, the wireless communication terminal receives a UORA parameter set element from the base wireless communication terminal associated with the wireless communication terminal and sets the OBO-related parameters based on the UORA parameter set element. A wireless communication terminal that is not associated with a base wireless communication terminal can perform random access based on a trigger frame transmitted by the base wireless communication terminal. In this case, a method for an unassociated wireless communication terminal to set OBO-related parameters and initialize an OBO procedure becomes an issue. This will be described in detail with reference to FIGS. 22 to 25. Unless otherwise specified in this specification, an unassociated wireless communication terminal may refer to a wireless communication terminal that is not associated with any base wireless communication terminal.

[0145] FIG. 22 illustrates a random access operation of an unassociated wireless communication terminal according to an embodiment of the present invention.

[0146] When a wireless communication terminal receives a trigger frame for triggering a random access of the wireless communication terminal from a base wireless communication terminal that is not associated with the wireless communication terminal, the wireless communication terminal can start an OBO procedure based on information on OBO-related parameters transmitted by the corresponding base wireless communication terminal. Specifically, the wireless communication terminal can receive a UORA parameter set element from a base wireless communication terminal that is not associated with the wireless communication terminal. In this case, when the wireless communication terminal receives a trigger frame for triggering a random access of the wireless communication terminal from the corresponding base wireless communication terminal, the wireless communication terminal can set OCWmin and OCWmax according to the UORA parameter set element and start an OBO procedure.

[0147] When a wireless communication terminal receives a trigger frame triggering a random access of the wireless communication terminal from a wireless communication terminal other than the base wireless communication terminal that transmitted the UORA parameter set element, the wireless communication terminal does not need to perform an OBO-related procedure in accordance with the received UORA parameter set element. Specifically, when a wireless communication terminal receives a trigger frame triggering a random access of the wireless communication terminal from a wireless communication terminal other than the base wireless communication terminal that transmitted the UORA parameter set element, the wireless communication terminal does not need to decrement the OBO counter based on the trigger frame. To this end, the wireless communication terminal can compare the identifier of the base wireless communication terminal that transmitted the UORA parameter set element with the identifier of the base wireless communication terminal that transmitted the trigger frame. In this case, the identifier of the base wireless communication terminal may be a MAC address or a BSSID. In the above-described embodiment, the trigger frame triggering a random access may be a trigger frame that triggers a random access of an unassociated wireless communication terminal.

[0148] Furthermore, when a wireless communication terminal receives a new UORA parameter set element from a wireless communication terminal other than the base wireless communication terminal that transmitted the UORA parameter set element, the wireless communication terminal does not need to initialize the OBO procedure based on the newly received UORA parameter set element. In this case, the initialization of the OBO procedure includes at least one of OBO counter initialization and OCW initialization. Furthermore, when a wireless communication terminal receives a new UORA parameter set element from a wireless communication terminal other than the base wireless communication terminal that transmitted the UORA parameter set element, the wireless communication terminal does not need to configure OBO-related parameters based on the newly received UORA parameter set element. In this case, the configuration of OBO-related parameters may include at least one of OCWmin configuration and OCWmax configuration. To this end, the wireless communication terminal can compare the identifier of the base wireless communication terminal that transmitted the UORA parameter set element with the identifier of the base wireless communication terminal that transmitted the new UORA parameter set element. In this case, the identifier of the base wireless communication terminal may be a MAC address or a BSSID. This embodiment can prevent an unassociated wireless communication terminal from continuing to initialize the OBO procedure or from performing random access that disrupts fairness with other wireless communication terminals.

[0149] In the embodiment of Figure 22, the first station STA1 is a wireless communication terminal that is not associated with any base wireless communication terminal. The first station STA1 receives a beacon frame from a first AP (AP1) and acquires a UORA parameter set element from the received beacon frame. The first station STA1 sets OBO-related parameters according to the acquired UORA parameter set element and initializes the OBO procedure. Specifically, the first station STA1 sets OCWmin and OCWmax according to the acquired UORA parameter set element and selects an arbitrary integer within the OCW. In this case, the arbitrarily selected integer is 10, and the first station STA1 sets an OBO counter to 10.

[0150] The first station STA1 receives a trigger frame from the first AP (AP1) indicating two RUs allocated for random access. At this time, the first station STA1 decrements the OBO count by 2 and sets the OBO count to 8.

[0151] The first station STA1 receives a trigger frame from the second AP (AP2) indicating two RUs allocated for random access. Because the first AP (AP1) and the second AP (AP2) that sent the UORA parameter set element used to set the OBO-related parameters have different identifiers, the first station STA1 maintains the OBO counter.

[0152] The first station STA1 receives a beacon frame from a second AP (AP2), and the received beacon frame includes a UORA parameter set element. Because the first AP (AP1) and the second AP (AP2) that transmitted the UORA parameter set element used to set the OBO-related parameters have different identifiers, the first station STA1 does not update the OBO-related parameters.

[0153] The first station STA1 receives a beacon frame from the first AP (AP1) and acquires a UORA parameter set element from the received beacon frame. Since the first station STA1 receives a UORA parameter set element again from the first AP (AP1) that transmitted the UORA parameter set element used to set the OBO-related parameters, the first station STA1 updates the OBO-related parameters according to the newly received UORA parameter set element.

[0154] In the embodiment described with reference to Fig. 22, a non-associated wireless communication terminal cannot participate in random access triggered by a base wireless communication terminal other than the base wireless communication terminal that first received the UORA parameter set element. Therefore, a method for solving this problem is required.

[0155] FIG. 23 illustrates a random access operation of an unassociated wireless communication terminal according to an embodiment of the present invention.

[0156] When an unassociated wireless communication terminal performs an OBO procedure with a second base wireless communication terminal while performing an OBO procedure with a first base wireless communication terminal, the unassociated wireless communication terminal can initialize the OBO procedure. Specifically, the unassociated wireless communication terminal can maintain OBO-related parameters and an OBO procedure for each base wireless communication terminal. In a specific embodiment, the unassociated wireless communication terminal can set OBO-related parameters for each base wireless communication terminal. Specifically, the unassociated wireless communication terminal can set OBO-related parameters for each base wireless communication terminal based on information on the OBO-related parameters received from each base wireless communication terminal. In a specific embodiment, when the wireless communication terminal receives a UORA parameter set element from one of the base wireless communication terminals, the wireless communication terminal can update the OBO-related parameters for the corresponding UORA parameter set element. In this case, the OBO-related parameters may be at least one of OCWmin and OCWmax.

[0157] In addition, an unassociated wireless communication terminal can initialize an OBO procedure for each base wireless communication terminal. Specifically, an unassociated wireless communication terminal can maintain an OBO counter for each base wireless communication terminal. In a specific embodiment, when an unassociated wireless communication terminal receives a trigger frame that triggers random access from any one of the base wireless communication terminals, the unassociated wireless communication terminal can decrement the OBO counter for the corresponding base wireless communication terminal based on the number of RUs for random access indicated by the corresponding trigger frame.

[0158] In the embodiment of Figure 23, the first station STA1 is a wireless communication terminal not associated with any base wireless communication terminal. The first station STA1 receives a beacon frame from a first AP (AP1) and acquires a UORA parameter set element from the received beacon frame. The first station STA1 sets OBO-related parameters (Set1) for the first AP (AP1) according to the acquired UORA parameter set element and initializes the OBO procedure. Specifically, the first station STA1 sets OCWmin and OCWmax for the first AP (AP1) according to the acquired UORA parameter set element and selects an arbitrary integer within the first AP (AP1) OCW. In this case, the arbitrarily selected integer is 10, and the first station STA1 sets an OBO counter for the first AP (AP1) to 10.

[0159] The first station STA1 receives a trigger frame from the first AP (AP1) indicating two RUs allocated for random access, and then decrements the OBO count for the first AP (AP1) by 2 to set the OBO count for the first AP (AP1) to 8.

[0160] The first station STA1 receives a beacon frame from the second AP (AP2) and acquires a UORA parameter set element from the received beacon frame. Because the first AP (AP1) and the second AP (AP2) that transmitted the UORA parameter set element used to set the OBO-related parameters have different identifiers, the first station STA1 sets the OBO-related parameters (Set2) for the second AP (AP2) according to the acquired UORA parameter set element and initializes the OBO procedure for the second AP (AP2). Specifically, the first station STA1 sets OCWmin and OCWmax for the second AP (AP2) according to the acquired UORA parameter set element and selects an arbitrary integer within the OCW for the second AP (AP2). In this case, the arbitrarily selected integer is 12, and the first station STA1 sets the OBO counter for the second AP (AP2) to 12. In this case, the first station STA1 does not update the OBO-related parameters for the first AP (AP1) or initialize the OBO procedure.

[0161] The first station STA1 receives a trigger frame from the second AP (AP2) indicating two RUs allocated for random access. At this time, the first station STA1 decreases the OBO count for the second AP (AP2) by 2 and sets the OBO count for the second AP (AP2) to 10. At this time, the first station STA1 maintains the OBO counter for the first AP (AP1) at 8.

[0162] 22 and 23, if the wireless communication terminal does not receive information about OBO-related parameters from the base wireless communication terminal, the wireless communication terminal cannot participate in random access. Therefore, an operation of the wireless communication terminal to solve this problem is required.

[0163] FIG. 24 illustrates a random access operation of an unassociated wireless communication terminal according to an embodiment of the present invention.

[0164] An unassociated wireless communication terminal can perform random access using default values ​​pre-specified for each OBO-related parameter. Specifically, an unassociated wireless communication terminal can set OCWmin to a value pre-specified as the default value of OCWmin. Also, an unassociated wireless communication terminal can set OCWmax to a value pre-specified as the default value of OCWmax. In this case, the value pre-specified as the default value of OCWmin may be different from the value specified by the base wireless communication terminal. Also, the value pre-specified as the default value of OCWmax may be different from the value specified by the base wireless communication terminal. Specifically, if an unassociated wireless communication terminal does not receive information about OBO-related parameters from the base wireless communication terminal, the unassociated wireless communication terminal can use default values ​​pre-specified for each OBO-related parameter. In this case, if an unassociated wireless communication terminal receives information about OBO-related parameters from the base wireless communication terminal, the unassociated wireless communication terminal can set the OBO-related parameters according to the information about the OBO-related parameters.

[0165] In a specific embodiment, when an unassociated wireless communication terminal uses default values ​​pre-specified for each OBO-related parameter, the unassociated wireless communication terminal does not need to set the OBO-related parameters according to the information on the OBO-related parameters even when receiving information on the OBO-related parameters from the base wireless communication terminal. Also, in a specific embodiment, when an unassociated wireless communication terminal uses default values ​​pre-specified for each OBO-related parameter and performs random access to a second base wireless communication terminal while performing random access to a first base wireless communication terminal, the unassociated wireless communication terminal does not need to initialize the OBO procedure. For example, when an unassociated wireless communication terminal uses default values ​​pre-specified for each OBO-related parameter and performs random access to a second base wireless communication terminal while performing random access to a first base wireless communication terminal, the unassociated wireless communication terminal can also use the OBO counter value used in the OBO procedure for the first base wireless communication terminal when randomly accessing the second base wireless communication terminal.

[0166] 24, the first station STA1 sets OCWmin as the default value of OCWmin and OCWmax as the OCWmax value when it has not received a UORA parameter set element from the base wireless communication terminal. At this time, the first station STA1 initializes the OBO procedure and selects 10 as an arbitrary integer in the OCW. The first station STA1 sets the arbitrarily selected 10 as the OBO count.

[0167] The first station STA1 receives a beacon frame from the first AP (AP1), acquires the UORA parameter set element from the beacon frame, and maintains the values ​​of the OBO-related parameters without initiating the OBO procedure.

[0168] The first station STA1 receives a trigger frame from the first AP (AP1) indicating two RUs allocated for random access. At this time, the first station STA1 decrements the OBO count by 2 and sets the OBO count to 8.

[0169] In addition, the first station STA1 receives a trigger frame from the second AP (AP2) indicating two RUs allocated for random access. At this time, the first station STA1 decrements the OBO count by 2 and sets the OBO count to 6.

[0170] FIG. 25 illustrates a random access operation of an unassociated wireless communication terminal according to an embodiment of the present invention.

[0171] An unassociated wireless communication terminal can randomly access the base wireless communication terminal and transmit a management frame. Specifically, an unassociated wireless communication terminal can randomly access the base wireless communication terminal and transmit at least one of a probe request frame, an authentication request frame, and an association request frame. When a wireless communication terminal transmits a trigger-based PPDU in response to a trigger frame, the wireless communication terminal must transmit the trigger-based PPDU in the form of an Aggregate-MAC Protocol Data Unit (A-MPDU) according to a MAC padding rule. However, since the probe request frame, authentication request frame, and association request frame are MAC Management Protocol Data Units (MMPDUs) that do not request an immediate response, transmission using A-MPDUs may not be permitted. In this case, an immediate response may represent transmission of a response within a certain period within one transmission opportunity (TXOP). The certain period may be SIFS. For transmission via random access by an unassociated wireless communication terminal, it may be permitted to aggregate and transmit an MMPDU into an A-MPDU. In this case, the MMPDU may include at least one of a probe request frame, an authentication request frame, an association request frame, and a reassociation request frame. Specifically, the transmission of the MMPDU may be included in a context including data that does not require an immediate response (the data enabled no immediate response context) among contexts related to the content of the A-MPDU.In a specific embodiment, a probe request frame, an authentication request frame, and an association request frame may be defined as MPDU types that can be aggregated in a context including data that does not require an immediate response (the data enabled no immediate response context) among the contexts related to the content of the A-MPDU. In yet another specific embodiment, a context related to the content of the A-MPDU may be defined. Specifically, a context for an aggregation procedure is set, and it may be specified that an A-MPDU defined in the context for the aggregation procedure does not require an immediate response and can aggregate a QoS Null frame or an Action No ACK frame with an MMPDU. For example, it may be specified that an A-MPDU defined in the context for the aggregation procedure does not require an immediate response and can aggregate a QoS Null frame or an Action No ACK frame with a probe request frame, an authentication request frame, or an association request frame.

[0172] In the embodiment of Figure 25, a first station STA1, which is not associated, receives a beacon frame from the AP. The first station STA1 acquires a UORA parameter set element from the beacon frame and initiates an OBO procedure according to the acquired UORA parameter set element. The first station STA1 sets an OBO counter to 3. The first station STA1 receives a trigger frame from the AP indicating four RUs allocated for random access. The first station STA1 decrements the OBO counter to 0 based on the trigger frame. Then, the first station STA1 transmits a trigger-based PPDU (HE TRIG PPDU) including an A-MPDU in which probe request frames or association request frames are aggregated to the AP via the RUs allocated for random access. The AP transmits a Multi-STA Block Ack (M-BA) to multiple stations.

[0173] When a wireless communication terminal performing random access is scheduled for upstream transmission by a trigger frame, the operation of the wireless communication terminal will be described with reference to FIG.

[0174] FIG. 26 illustrates a random access operation of a wireless communication terminal when an upstream transmission is scheduled by a trigger frame according to an embodiment of the present invention.

[0175] When a wireless communication terminal performing random access is scheduled for upstream transmission by a trigger frame, the question arises as to whether the wireless communication terminal can decrement the OBO counter based on the RUs allocated to the random access indicated by the trigger frame. If a wireless communication terminal performing random access is scheduled for upstream transmission by a trigger frame but decrements the OBO counter based on the RUs allocated to the random access indicated by the trigger frame, the wireless communication terminal may have excessive priority over other wireless communication terminals. Therefore, fairness among wireless communication terminals may be disrupted. When a wireless communication terminal performing random access is scheduled for upstream transmission by a trigger frame, the wireless communication terminal may maintain the OBO counter regardless of the number of RUs allocated to the random access indicated by the trigger frame.

[0176] The trigger frame may indicate that carrier sensing is required when a wireless communication terminal, whose uplink transmission is scheduled by the trigger frame, performs uplink transmission. In this case, if it is determined as a result of carrier sensing that the RU used for uplink transmission is busy, the wireless communication terminal may not attempt uplink transmission. Specifically, the trigger frame may use a CS required field to indicate that carrier sensing is required when a wireless communication terminal, whose uplink transmission is scheduled by the trigger frame, performs uplink transmission. In addition, carrier sensing may include energy detection (ED). If it is determined through carrier sensing that the RU used for uplink transmission is busy, the random access operation of the wireless communication terminal, whose uplink transmission is scheduled by the trigger frame, becomes problematic. This is because the wireless communication terminal was instructed to perform uplink transmission by the trigger frame but was unable to perform uplink transmission.

[0177] When a trigger frame schedules an uplink transmission for a wireless communication terminal performing random access and indicates that carrier sensing is required for the uplink transmission, the wireless communication terminal performing random access can operate as follows. If it is determined through carrier sensing that an RU used for uplink transmission is in use, the wireless communication terminal performing random access can decrement the OBO counter based on the RU allocated to the random access indicated by the trigger frame. Specifically, the wireless communication terminal performing random access can decrement the OBO counter by the number of RUs allocated to the random access indicated by the trigger frame. Furthermore, when it is determined through carrier sensing that an RU used for uplink transmission is in use, even if the OBO counter is 0 or reaches 0, the wireless communication terminal performing random access can maintain the OBO counter at 0 and not attempt uplink transmission. In yet another specific embodiment, when it is determined through carrier sensing that an RU used for uplink transmission is in use and the OBO counter is 0 or reaches 0, the wireless communication terminal performing random access can arbitrarily select one of the RUs allocated to the random access to attempt uplink transmission.

[0178] In the embodiment of Figure 26, the first station STA1 receives a beacon frame from the AP. The first station STA1 acquires a UORA parameter set element from the beacon frame and initializes an OBO procedure according to the acquired UORA parameter set element. The first station STA1 sets an OBO counter to 3. The first station STA1 receives a trigger frame from the AP indicating four RUs allocated for random access and scheduling the first station STA1's upstream transmission. The first station STA1 maintains the OBO counter as it is because the trigger frame schedules the first station STA1's upstream transmission. The first station STA1 also transmits a trigger-based PPDU (HE TRIG PPDU) to the AP according to the information indicated in the trigger frame. The AP transmits a multi-station block ACK (Multi-STA Block Ack, M-BA) to multiple stations.

[0179] In the above embodiment, it has been described that the wireless communication terminal can acquire information about the OBO counter from the beacon frame. In this way, the wireless communication terminal can acquire information about the BSS from the beacon frame. In addition, the base wireless communication terminal can periodically transmit a beacon frame to signal information about the BSS. Specific transmission methods for the beacon frame will be described with reference to FIGS. 27 to 35.

[0180] FIG. 27 illustrates a legacy PPDU format according to an embodiment of the present invention.

[0181] The types of legacy PPDUs that can be transmitted by a legacy wireless communication terminal may include at least one of a Non-HT PPDU, an HT-mixed PPDU, an HT-greenfield PPDU, and a VHT PPDU.

[0182] Figure 27(a) shows the format of a Non-HT PPDU. The Non-HT PPDU format includes a Short Training field containing a relatively short training signal, a Long Training field containing a relatively long training signal, a Signal field containing signaling information, and a Data field containing the PPDU payload. Figure 27(b) shows the format of an HT-mixed PPDU. The HT-mixed PPDU includes an L-STF, an L-LTF, and an L-SIG field for legacy wireless communication terminals that do not support HT-mixed PPDUs. The HT-mixed PPDU also includes an HT-SIG field containing signaling information, an HT-STF containing a relatively short training signal, at least one HT-LTF containing a relatively long training signal, and a Data field containing the PPDU payload. Figure 27(c) shows the format of an HT-greenfield PPDU. The HT-greenfield PPDU includes an HT-GF-STF containing a relatively short training signal, an HT-SIG field containing signaling information, at least one HT-LTF containing a relatively long training signal, and a Data field containing the PPDU payload. Figure 27(d) shows the format of a VHT PPDU. The VHT PPDU includes an L-STF, an L-LTF, and an L-SIG field for legacy wireless communication terminals that do not support the VHT PPDU. The VHT PPDU also includes a VHT-SIG-A field containing signaling information, a VHT-STF containing a relatively short training signal, at least one VHT-LTF containing a relatively long training signal, and a Data field containing the PPDU payload. The VHT PPDU can also include a VHT-SIG-B field for signaling additional information.

[0183] FIG. 28 shows a non-legacy PPDU format according to an embodiment of the present invention.

[0184] A wireless communication terminal according to an embodiment of the present invention may support one or more non-legacy PPDU formats. Furthermore, the wireless communication terminal according to an embodiment of the present invention may select and use one of a plurality of non-legacy PPDU formats depending on the use and purpose of transmitting the PPDU. Specifically, the wireless communication terminal may support at least one of an HE SU PPDU, an HE MU PPDU, an HE extended range SU PPDU, and an HE trigger-based PPDU. The HE-SIG-A field and the HE-SIG-B field of the non-legacy PPDU may be referred to as pre-HE modulated fields. Furthermore, the HE-STF, HE-LTF, and Date fields of the non-legacy PPDU may be referred to as HE modulated fields. The pre-HE modulated field and the HE modulated fields may be modulated with different numerologies.

[0185] FIG. 28(a) shows the format of an HE SU PPDU. A wireless communication terminal can use the HE SU PPDU for single-user (SU) transmission. The HE SU PPDU can include an L-STF, L-LTF, and L-SIG field for legacy wireless communication terminals. The HE SU PPDU also includes an RL-SIG for signaling a non-legacy PPDU, an HE-SIG-A field including signaling information, an HE-STF including a relatively short training signal, at least one HE-LTF including a relatively long training signal, and a Data field including the PPDU payload. The HE SU PPDU can also include a Packet Extension (PE) field to ensure processing time. The duration of the PE field can be determined by the TXVECTOR parameter PE_DURATION. The HE SU PPDU can deliver one PSDU.

[0186] Figure 28(b) shows the format of an HE-MU PPDU. A wireless communication terminal can use the HE-MU PPDU for transmission to one or more users. In this case, the wireless communication terminal does not need to use the HE-MU PPDU as a response to a trigger. The HE-MU PPDU has a format similar to that of the HE-SU PPDU, and can further include an HE-SIG-B field compared to the HE-SU PPDU. The HE-SIG-B field includes information for multi-user (MU) transmission. The HE-MU PPDU can carry one or more PSDUs.

[0187] 28(c) shows the format of an HE trigger-based PPDU. In the above-described embodiments, the trigger-based PPDU may refer to the HE trigger-based PPDU. A wireless communication terminal may use the HE trigger-based PPDU to respond to a trigger frame or a UL MU Response Scheduling A-Control field. The HE trigger-based PPDU may include an HE-STF having a longer duration than the HE SU PPDU format.

[0188] FIG. 28(d) shows the format of an HE extended range SU PPDU. A wireless communication terminal can use the HE extended range SU PPDU for extended range transmission. The HE extended range SU PPDU has a format similar to that of the HE SU PPDU, except that the duration of the HE-SIG-A field of the HE extended range SU PPDU is twice the duration of the HE-SIG-A field of the HE SU PPDU. The wireless communication terminal can transmit using four symbols. For example, four symbols can be used to transmit the HE-SIG-A field of the HE extended range SU PPDU. The four symbols used to transmit the HE-SIG-A field can be repeated in the time domain. The four symbols used to transmit the HE-SIG-A field are referred to as HE-SIG-A1, HE-SIG-A2, HE-SIG-A3, and HE-SIG-A4 in time order. In this case, HE-SIG-A1 and HE-SIG-A2 can transmit the same signal, and HE-SIG-A3 and HE-SIG-A4 can transmit the same signal. Furthermore, when transmitting an HE extended range SU PPDU, the wireless communication terminal can boost the transmission power by 3 dB compared to when transmitting the L-STF and L-LTF of other non-legacy PPDUs. Furthermore, when transmitting four extra tons (subcarrier index k = -28, -27, 27, 28) in the L-SIG and RL-SIG fields, the wireless communication terminal can boost the transmission power by 3 dB compared to when transmitting the L-STF and L-LTF of other non-legacy PPDUs. Through this operation, the wireless communication terminal can increase the probability of receiving the HE extended range SU PPDU.

[0189] FIG. 29 illustrates the transmission coverage of an HE extended range SU PPDU and the transmission coverage of a legacy PPDU according to an embodiment of the present invention.

[0190] As described in FIG. 28, when transmitting an HE extended range SU PPDU, the wireless communication terminal performs various operations for long-distance transmission. Therefore, the transmission coverage of the HE extended range SU PPDU is wider than that of a legacy PPDU. As a result, even a wireless communication terminal that can receive the HE extended range SU PPDU may not be able to receive the legacy PPDU format. For example, in the situation shown in FIG. 29, the transmission coverage of the HE extended range SU PPDU is wider than that of a legacy PPDU (non-HE PPDU). Therefore, the first station STA1 can receive both the legacy PPDU (non-HE PPDU) and the HE extended range SU PPDU. The second station STA2 cannot receive the legacy PPDU (non-HE PPDU) and can only receive the HE extended range SU PPDU. If there is information transmitted via the legacy PPDU format, wireless communication terminals located outside the coverage of the legacy PPDU format cannot use the information. A wireless communication terminal transmits a beacon frame using a legacy PPDU format. A wireless communication terminal located outside the coverage of the legacy PPDU format may be unable to communicate with the base wireless communication terminal because it cannot receive BSS information, even though it can communicate with the base wireless communication terminal using the HE extended range SU PPDU. Therefore, the base wireless communication terminal can transmit a dual beacon frame. This will be described with reference to FIG. 30.

[0191] FIG. 30 shows a dual beacon transmission operation of a base wireless communication terminal according to an embodiment of the present invention.

[0192] The base wireless communication terminal can transmit beacon frames using multiple PPDU formats. Specifically, the base wireless communication terminal can transmit beacon frames using two PPDU formats with different transmission coverages. The wireless communication terminal can transmit beacon frames using a legacy PPDU format and a PPDU format for wideband transmission. In this case, the PPDU format for wideband transmission can be the above-mentioned HE extended range SU PPDU. Through this operation, the base wireless communication terminal can increase the likelihood that wireless communication terminals surrounding the base wireless communication terminal will receive the beacon frame. For ease of explanation, transmitting beacon frames by the base wireless communication terminal using two PPDU formats with different transmission coverages is referred to as dual beacon.

[0193] The base wireless communication terminal can transmit a beacon frame based on a fixed period. In this case, the time when the base wireless communication terminal attempts to transmit a beacon frame can be referred to as a target beacon transmission time (TBTT). The TBTT can continue at a fixed time interval. In this case, the fixed time interval can be referred to as a beacon interval. If the channel on which the base wireless communication terminal attempts to transmit a beacon frame is busy, the base wireless communication terminal can attempt to transmit a beacon frame again after the scheduled time. For example, if the channel on which the base wireless communication terminal attempts to transmit a beacon frame is idle during a PIFS, the base wireless communication terminal can transmit a beacon frame.

[0194] The base station wireless communication terminal may attempt to transmit a legacy PPDU including a beacon frame at the TBTT and may attempt to transmit a PPDU for broadband transmission including a beacon frame a predetermined time after the TBTT. In this case, the predetermined time may be half the time interval between TBTTs. For example, the TBTT of the beacon frame included in the legacy PPDU may have a timing synchronization function (TSF) value of 0, and the TBTT of the beacon frame included in the legacy PPDU may be repeated at every beacon interval. The TBTT of the beacon frame included in the PPDU for broadband transmission may be a point half the beacon interval after the TSF value of 0. In addition, the TBTT of the beacon frame included in the PPDU for broadband transmission may also be repeated at every beacon interval.

[0195] The base wireless communication terminal may signal whether or not dual beacons are used using an Operation element. In this case, the Operation element may be an HE Operation element. In addition, beacon frames transmitted through different PPDU formats may include different types of signaling information. Specifically, beacon frames transmitted through different PPDU formats may include different types of elements.

[0196] In the embodiment of Figure 30, the base wireless communication terminal attempts to transmit a legacy PPDU including a beacon frame in the TBTT for the legacy PPDU including a beacon frame. The base wireless communication terminal transmits the legacy PPDU including the beacon frame, and a first station STA1 receives the legacy PPDU including the beacon frame. A second station STA2, which is located at a distance farther from the base wireless communication terminal than the first station STA1, cannot receive the legacy PPDU including the beacon frame.

[0197] The base wireless communication terminal attempts to transmit an HE extended range SU PPDU including a beacon frame when half the beacon interval of the legacy PPDU including a beacon frame has elapsed since the TBTT for the legacy PPDU including a beacon frame. The base wireless communication terminal transmits the HE extended range SU PPDU including a beacon frame, and both the first station STA1 and the second station STA2 receive the HE extended range SU PPDU including a beacon frame.

[0198] When the beacon interval has elapsed since the TBTT for the legacy PPDU including the beacon frame, the base wireless communication terminal attempts to transmit the legacy PPDU including the beacon frame. When half the beacon interval has elapsed since this time, the base wireless communication terminal attempts to transmit the HE extended range SU PPDU including the beacon frame.

[0199] The base station wireless communication terminal can signal information about a specific time point using the above-mentioned TBTT. For example, the base station wireless communication terminal can signal the start time of changing the BSS color, which is an identifier representing the BSS, using the TBTT. This will be described in detail with reference to FIG. 31.

[0200] FIG. 31 illustrates the format of a BSS Color Change Announcement element according to an embodiment of the present invention.

[0201] The base station wireless communication terminal may transmit a beacon frame including a BSS Color Change Announcement element to notify the new BSS color value after the BSS color has been changed. In this case, the BSS Color Change Announcement element may include a field indicating the time when the BSS color will be changed. The BSS Color Change Announcement element may also include a field indicating the changed BSS color value. For example, the BSS Color Change Announcement element may include a Color Switch Countdown field. The Color Switch Countdown field may indicate the number of TBTTs remaining until the BSS color is changed. The BSS Color Change Announcement element may include a New BSS Color Information field. The New BSS Color Information field may indicate a new BSS color value to be used as the BSS color of the corresponding BSS. The New BSS Color Information field may include a New BSS Color subfield, and the New BSS Color subfield may indicate a new BSS color value to be used as the BSS color of the corresponding BSS. A specific format of the BSS Color Change Announcement element is shown in FIG. 31.

[0202] For ease of explanation, the TBTT at which the Color Switch Countdown value reaches 0 and the BSS color is changed is referred to as the BSS Color change TBTT. Until the BSS Color change TBTT is reached, the base wireless communication terminal inserts the BSS color value before the BSS change in the BSS Color subfield of the HE Operation element. Furthermore, when the BSS Color change TBTT is reached, the base wireless communication terminal sets the BSS Color Disabled subfield of the HE Operation element to 0, inserts the changed BSS color value in the BSS Color subfield of the HE Operation element, and begins to use the changed BSS color value. Furthermore, a wireless communication terminal that receives a BSS Color Change Announcement element can use the changed BSS color value from the BSS Color change TBTT. In this case, the wireless communication terminal obtains the changed BSS color value from the BSS Color Change Announcement element.

[0203] In order for all wireless communication terminals within a BSS to use the same BSS color value, the base wireless communication terminal and the wireless communication terminal can operate as follows. A base wireless communication terminal that has transmitted a BSS Color Change Announcement element can use the previous BSS color value until the BSS Color change TBTT is reached, and can use the changed BSS Color value after the BSS Color change TBTT. In addition, a base wireless communication terminal that has transmitted a BSS Color Change Announcement element may not be allowed to change the BSS Color change TBTT indicated by the BSS Color Change Announcement element until the BSS Color change TBTT is reached. When the base wireless communication terminal uses dual beacons, the time of the BSS color change can be determined differently depending on the format of the PPDU that the wireless communication terminal can receive. This will be described with reference to FIG. 32.

[0204] FIG. 32 shows a BSS color change operation of a base wireless communication terminal when the base wireless communication terminal uses dual beacons according to an embodiment of the present invention.

[0205] Depending on the distance between the wireless communication terminal and the base station, the wireless communication terminal may receive only one of the PPDU formats used for dual beacons. In this case, a wireless communication terminal that receives only one of the PPDU formats used for dual beacons can determine the BSS Color change TBTT differently from a wireless communication terminal that receives all of the PPDU formats used for dual beacons. Specifically, the wireless communication terminal cannot recognize the transmission of a beacon frame included in a PPDU format that the wireless communication terminal cannot receive, and therefore cannot accurately determine the number of TBTTs remaining until the BSS color change. Furthermore, a wireless communication terminal that receives all of the PPDU formats used for dual beacons may be confused about how to define the TBTT criteria when determining the BSS Color change TBTT. For example, a wireless communication terminal that receives all of the PPDU formats used for dual beacons may have difficulty determining whether the value represented by the Color Switch Countdown field represents the TBTTs of all types of PPDU formats, including beacon frames, or only the TBTTs of a specific type of PPDU format, including beacon frames.

[0206] In the embodiment of Figure 32, the base wireless communication terminal attempts to transmit a legacy PPDU including a beacon frame during the TBTT for the legacy PPDU including a beacon frame. The base wireless communication terminal transmits the legacy PPDU including the beacon frame, and a first station STA1 receives the legacy PPDU including the beacon frame. A second station STA2, which is located at a distance farther from the base wireless communication terminal than the first station STA1, cannot receive the legacy PPDU including the beacon frame.

[0207] When half the beacon interval of the legacy PPDU containing the beacon frame has elapsed since the TBTT for the legacy PPDU containing the beacon frame, the base wireless communication terminal attempts to transmit an HE extended range SU PPDU containing the beacon frame. The base wireless communication terminal transmits the HE extended range SU PPDU containing the beacon frame, and both the first station STA1 and the second station STA2 receive the HE extended range SU PPDU containing the beacon frame.

[0208] In this case, the beacon frame included in the legacy PPDU signals the BSS Color change TBTT based on the TBTT of the beacon frame included in the legacy PPDU. The beacon frame included in the legacy PPDU may signal the remaining TBTT count up to the first point in time (BSS Color change TBTT 1) when the BSS color is changed and the legacy PPDU including the beacon frame is transmitted for the first time. The beacon frame included in the PPDU for wideband transmission signals the BSS Color change TBTT based on the TBTT of the beacon frame included in the PPDU for wideband transmission. The beacon frame included in the PPDU for wideband transmission may signal the remaining TBTT count up to the second point in time (BSS Color change TBTT 2) when the BSS color is changed and the PPDU for wideband transmission including the beacon frame is transmitted for the first time. Because the first station STA1 can receive both PPDU formats including the beacon frame, it may be unable to determine at which of the first time point (BSS Color change TBTT 1) and the second time point (BSS Color change TBTT 2) the BSS color will change. Furthermore, the second station STA2 cannot receive information about the first time point (BSS Color change TBTT 1). Therefore, the first station STA1 and the second station STA2 may change their BSS color at different times. Consequently, even though they are wireless communication terminals in the same BSS, they may use different BSS color values, causing interference.

[0209] The wireless communication terminal may perform operations other than the BSS color change operation based on the TBTT. For example, the wireless communication terminal may receive a UORA parameter element set in association with random access at the TBTT and perform an operation associated with the reception of the UORA parameter element set. The operation associated with the reception of the UORA parameter element set may include at least one of OBO-related parameter configuration and OBO procedure initialization. As a result, when the base wireless communication terminal uses dual beacons, a problem may occur in which it is unclear when the wireless communication terminal receives a UORA parameter element set in association with random access and performs an operation associated with the reception of the UORA parameter element set. Furthermore, a wireless communication terminal located relatively close to the base wireless communication terminal may receive a UORA parameter element set more frequently than a wireless communication terminal located relatively far from the base wireless communication terminal. As a result, a wireless communication terminal located relatively close to the base wireless communication terminal may perform the OBO procedure more frequently than a wireless communication terminal located relatively far from the base wireless communication terminal. As a result, fairness among wireless communication terminals regarding random access may become an issue. For convenience of explanation, an operation in which the time to perform an operation by the wireless communication terminal is determined based on the TBTT will be referred to as a TBTT-based operation. An embodiment in which the wireless communication terminal can perform the TBTT-based operation without any problems even when the base wireless communication terminal uses dual beacons will be described with reference to FIGS. FIG. 33 shows a BSS color change operation of a base wireless communication terminal when the base wireless communication terminal uses dual beacons according to yet another embodiment of the present invention.

[0210] When a base wireless communication terminal uses dual beacons, the wireless communication terminal may perform a TBTT-based operation on the TBTT of a beacon frame included in one PPDU format, but may not perform a TBTT-based operation on the TBTT of a beacon frame included in another PPDU format. Specifically, the wireless communication terminal may perform a TBTT-based operation on the TBTT of a beacon frame included in a legacy PPDU, but may not perform a TBTT-based operation on the TBTT of a beacon frame included in a PPDU for broadband transmission. In yet another specific embodiment, the wireless communication terminal may not perform a TBTT-based operation on the TBTT of a beacon frame included in a legacy PPDU, but may perform a TBTT-based operation on the TBTT of a beacon frame included in a PPDU for broadband transmission. For convenience of explanation, a PPDU format including a beacon frame transmitted at a TBTT for which the wireless communication terminal performs a TBTT-based operation is referred to as a reference PPDU format. Beacons included in PPDU formats other than the reference PPDU format may also signal information related to the TBTT-based operation. In this case, the information related to the TBTT reference operation signaled by the beacon included in the reference PPDU format and the information related to the TBTT reference operation signaled by the beacon included in a PPDU format other than the reference PPDU format may indicate the same information.

[0211] In this embodiment, all BSS Color Change Announcement elements may indicate the same BSS color change time regardless of the format of the PPDU in which the BSS Color Change Announcement element is included. Furthermore, the Color Switch Countdown field may indicate the number of times a reference PPDU format including a remaining beacon frame is transmitted until the BSS color is changed. If the Color Switch Countdown field included in a PPDU format other than the reference PPDU format is set to 0, the Color Switch Countdown field may indicate that the BSS color is changed when the reference PPDU format including a beacon frame is transmitted. For example, if the wireless communication terminal changes the BSS color at the TBTT of a beacon frame included in a legacy PPDU, the Color Switch Countdown field may indicate the number of times a legacy PPDU including a remaining beacon frame is transmitted until the BSS color is changed. In this case, if the Color Switch Countdown field of a beacon frame included in a PPDU for broadband transmission indicates 0, the wireless communication terminal may determine that the BSS color is changed at the TBTT of a beacon frame included in a legacy PPDU transmitted next to the corresponding beacon frame. Also, if the Color Switch Countdown field of the beacon frame included in the legacy PPDU indicates 0, the wireless communication terminal can determine that the BSS color will be changed in the TBTT of the corresponding beacon frame.

[0212] In yet another specific embodiment, when the wireless communication terminal changes the BSS color to the TBTT of a beacon frame included in a PPDU for broadband transmission, the Color Switch Countdown field may indicate the number of times a PPDU for broadband transmission including the remaining beacon frames is transmitted until the BSS color is changed. In this case, when the Color Switch Countdown field of a beacon frame included in a legacy PPDU indicates 0, the wireless communication terminal may determine that the BSS color is changed to the TBTT of a beacon frame included in a PPDU for broadband transmission that is transmitted next to the corresponding beacon frame. Also, when the Color Switch Countdown field of a beacon frame included in a PPDU for broadband transmission indicates 0, the wireless communication terminal may determine that the BSS color is changed to the TBTT of the corresponding beacon frame.

[0213] In the embodiment of Figure 33, the BSS color is changed based on the TBTT of the beacon frame included in the legacy PPDU (non-HE format). Therefore, both the beacon frame included in the HE extended range SU PPDU and the beacon frame included in the legacy PPDU (non-HE format) signal the TBTT of the beacon frame included in the legacy PPDU (non-HE format) at the time of BSS color change. Therefore, the first station STA1 and the second station STA2 can change the BSS color based on the same time point. Among the operations of the base wireless communication terminal, the first station STA1, and the second station STA2, descriptions of the same operations as in the embodiment of Figure 31 will be omitted.

[0214] In yet another specific embodiment, the wireless communication terminal may update OBO-related parameters based on the UORA parameter set element in the TBTT of a beacon frame included in a PPDU for wideband transmission, and may not update OBO-related parameters based on the UORA parameter set element in the TBTT of a beacon frame included in a legacy PPDU. Also, the wireless communication terminal may initialize an OBO procedure based on the UORA parameter set element in the TBTT of a beacon frame included in a PPDU for wideband transmission, and may not initialize an OBO procedure based on the UORA parameter set element in the TBTT of a beacon frame included in a legacy PPDU.

[0215] FIG. 34 shows a BSS color change operation of a base wireless communication terminal when the base wireless communication terminal uses dual beacons according to yet another embodiment of the present invention.

[0216] When the base wireless communication terminal uses dual beacons, the base wireless communication terminal may signal information related to TBTT-based operation through a beacon frame included in one of the PPDU formats, and may not signal information related to the TBTT-based operation through a beacon frame included in another type of PPDU format. Specifically, the base wireless communication terminal may signal information related to the TBTT-based operation through a beacon frame included in a legacy PPDU, and may not signal information related to the TBTT-based operation through a beacon frame included in a PPDU for wideband transmission. Also, in this embodiment, the reference PPDU format described with reference to FIG. 33 may be specified. The reference PPDU format may be a PPDU format including a beacon signaling information related to the TBTT-based operation. Also, the PPDU format including a beacon signaling information related to the TBTT-based operation may be a PPDU format having a wider transmission coverage than other PPDU formats. This is because the larger the transmission coverage of the PPDU format including the beacon signaling information related to the TBTT-based operation, the more wireless communication terminals can receive the information related to the TBTT-based operation.

[0217] In a specific embodiment, the base wireless communication terminal may signal the BSS Color Change Announcement element through a beacon frame included in a PPDU for wideband transmission, but may not signal the BSS Color Change Announcement element through a beacon frame included in a legacy PPDU. Even in this embodiment, a reference PPDU format may be specified. Specifically, the reference PPDU format may be a PPDU for wideband transmission.

[0218] In the embodiment of Fig. 34, the base wireless communication terminal transmits a BSS Color Change Announcement element via a beacon frame included in an HE extended range SU PPDU, but does not transmit the BSS Color Change Announcement element via a beacon frame included in a legacy PPDU (non-HE format). Furthermore, the BSS color is changed based on the TBTT of the beacon frame included in the HE extended range SU PPDU. Of the operations of the base wireless communication terminal, first station STA1, and second station STA2, those that are the same as those in the embodiment of Fig. 31 will not be described.

[0219] In yet another specific embodiment, the base wireless communication terminal may transmit a UORA parameter set element via a beacon frame included in a PPDU for wideband transmission, and may not transmit a UORA parameter set element via a beacon frame included in a legacy PPDU.

[0220] The base wireless communication terminal can transmit a beacon frame using STBC. In this case, the transmitted beacon frame can be referred to as an STBC beacon frame. When the base wireless communication terminal uses both the STBC beacon frame and the beacon frame included in the HE extended range SU PPDU, the transmission time of the STBC beacon frame and the transmission time of the HE extended range SU PPDU can overlap. In addition, it can be difficult for a wireless communication terminal receiving a beacon frame to determine what beacon frame is transmitted at what time. Therefore, the base wireless communication terminal can not operate both the STBC beacon frame and the beacon frame included in the HE extended range SU PPDU. For example, when the base wireless communication terminal uses the beacon frame included in the HE extended range SU PPDU, the base wireless communication terminal cannot use the STBC beacon frame. In addition, when the base wireless communication terminal starts using the beacon frame included in the HE extended range SU PPDU, the base wireless communication terminal can stop using the STBC beacon frame.

[0221] The base wireless communication terminal can indicate whether to use an STBC beacon frame using the Dual Beacon field of the HT Operation element. The base wireless communication terminal can also indicate whether to use a beacon frame included in the HE extended range SU PPDU using the Dual Beacon field of the HT Operation element. When the Dual Beacon field of the HT Operation element signals using one of the STBC beacon frame and the beacon frame included in the HE extended range SU PPDU, it can indicate that the other beacon frame is not used. For example, if the Dual Beacon field of the HE Operation element indicates that an STBC beacon frame is used, the Dual Beacon field of the HE Operation element can indicate that the beacon frame included in the HE extended range SU PPDU is not used. Therefore, if the Dual Beacon field of the HE Operation element is set to 1, the Dual Beacon field of the HE Operation element can indicate that an STBC beacon frame is not used.

[0222] A wireless communication terminal can transmit one MPDU or A-MPDU (Aggregate-MPDU) in a PSDU (Physical layer Service Data Unit) of a PPDU. In this case, the wireless communication terminal can combine multiple MPDUs to generate one A-MPDU (Aggregate-MAC Protocol Data Unit). The wireless communication terminal can improve transmission efficiency by transmitting A-MPDU instead of dividing multiple MPDUs into multiple PPDUs and transmitting them. A specific format of A-MPDU will be described with reference to FIG. 35.

[0223] FIG. 35 shows a format of an A-MPDU according to an embodiment of the present invention.

[0224] An A-MPDU can include a sequence of one or more A-MPDU subframes and EOF padding. The boundary between A-MPDU subframes can be defined by an MPDU delimiter field. An MPDU can follow the MPDU delimiter field. If an A-MPDU subframe is not the last A-MPDU subframe, it can include padding octets. The wireless communication terminal can set padding octets so that the length of each A-MPDU subframe is a multiple of 4 octets. The length of the padding subfield included in the last A-MPDU subframe can be 0 to 3 octets.

[0225] The length of the MPDU delimiter field may be 4 octets. A specific format of the MPDU delimiter field may be as shown in FIG. 35. In this case, the MPDU delimiter field may be the format of an MPDU delimiter field transmitted by a non-DMG wireless communication terminal. The MPDU delimiter field may include at least one of an EOF subfield, a Reserved subfield, an MPDU Length subfield, a CRC subfield, and a Delimiter Signature subfield. The EOF subfield may be a 1-bit field. A wireless communication terminal may set the MPDU Length subfield of an A-MPDU subframe to 0 and the EOF subfield to 1 to indicate that the corresponding A-MPDU subframe is an EOF Padding subframe. Alternatively, a wireless communication terminal may set the EOF subfield to 1 and the MPDU Length subfield to a non-zero value to indicate that the corresponding A-MPDU subframe is a VHT single MPDU or a single MPDU (S-MPDU). The VHT single MPDU or single MPDU is the only MPDU in the corresponding A-MPDU. The wireless communication terminal may set the EOF field to 0 in other cases. The MPDU Length subfield may indicate the length of the MPDU included in the A-MPDU subframe in octets. If the A-MPDU subframe does not include an MPDU, the wireless communication terminal sets the MPDU Length field to 0. The CRC subfield may include a CRC value for the 16 bits included in the MPDU delimiter field. The CRC field may be an 8-bit field. The Delimiter Signature subfield may include a value set to identify the MPDU delimiter. In this case, the set value may be 0x4E.

[0226] The length of the EOF Padding field may be variable. The EOF Padding field may include an EOF Padding subframe and EOF Padding Octets. The EOF Padding field may optionally include one or more EOF Padding subframes. The MPDU delimiter field may include an MPDU Length field and an EOF field. A wireless communication terminal may set the MPDU Length subfield of an A-MPDU subframe to 0 and the EOF subfield to 1 to indicate that the corresponding A-MPDU subframe is an EOF Padding subframe. The length of the EOF Padding Octets subfield may be 0 to 3 octets.

[0227] As described above, the wireless communication terminal can signal information about the A-MPDU subframe through the value of the EOF field. In this case, the wireless communication terminal can configure the A-MPDU according to the following rules.

[0228] An A-MPDU subframe with the EOF subfield set to 0 in an A-MPDU is not located after an A-MPDU subframe with the EOF subfield set to 1.

[0229] An A-MPDU subframe in which the EOF subfield is set to 1 and the MPDU Length subfield is set to 0 in the A-MPDU is not located before an A-MPDU subframe containing a VHT single MPDU.

[0230] In addition, the wireless communication terminal can solicit an immediate response to the MPDU included in the A-MPDU by setting a pre-specified value in the EOF subfield. Specifically, the wireless communication terminal transmitting the PPDU can solicit an immediate response by setting the Ack Policy field of a QoS Data frame or a QoS Null frame, transmitting a specific type of frame (e.g., an Action frame, a BAR frame, or an MU-BAR frame), or by setting a pre-specified value in the EOF subfield if the frame is an A-MPDU or a multi-TID A-MPDU.

[0231] A Multi-TID A-MPDU refers to an MPDU generated by combining multiple MPDUs having different traffic identifiers (TIDs). Specifically, a multi-TID A-MPDU may be an A-MPDU including multiple QoS Data frames having different TIDs. A wireless communication terminal can solicit a specific type of response to an MPDU included in an A-MPDU subframe using the value of a subfield of an MPDU delimiter field included in the Multi-TID A-MPDU. Specifically, when a wireless communication terminal generates a Multi-TID A-MPDU, the wireless communication terminal can set the MPDU Length subfield of the MPDU delimiter field to a non-zero value and set the value of the EOF subfield to 0 to immediately transmit an ACK frame for a QoS data frame or an action frame included in the A-MPDU subframe corresponding to the MPDU delimiter field. Furthermore, the wireless communication terminal can solicit ACKs for MPDUs included in each of the plurality of MPDU delimiter fields by setting a plurality of noncontiguous MPDU delimiter fields whose EOF subfield is 1 and whose MPDU Length field is a nonzero value. Furthermore, the wireless communication terminal can solicit BlockAcks for MPDUs included in each of the plurality of MPDU delimiter fields by setting a plurality of noncontiguous MPDU delimiter fields whose EOF subfield is 0 and whose MPDU Length field is a nonzero value. The wireless communication terminal can aggregate A-MPDUs by mixing A-MPDU subframes including MPDU delimiter fields whose EOF subfield is 1 and whose MPDU Length subfield is not 0 and A-MPDU subframes including MPDU delimiter fields whose EOF subfield is 0 and whose MPDU Length subfield is not 0.Furthermore, the wireless communication terminal can generate a Multi-TID A-MPDU by discontinuously aggregating A-MPDU subframes having the same TID.

[0232] A wireless communication terminal that receives a Multi-TID A-MPDU can transmit a Multi-STA BlockAck in response to the Multi-TID A-MPDU. In this case, the Multi-STA BlockAck can include the following Per STA Info field.

[0233] A Per STA Info field indicating an ACK for successful reception of an MPDU corresponding to an MPDU Length field having a non-zero length and an EOF subfield value of 1 (in this case, the TID value of the MPDU may represent the TID of a QoS data frame or a QoS Null frame. The TID value of the MPDU may also be 15, which represents an action frame).

[0234] -Per STA Info field indicating a BlockAck for successful reception of an MPDU corresponding to an MPDU Length field having a non-zero length when the EOF subfield value is 0 (in this case, the TID value of the MPDU may be the TID value of the QoS data frame).

[0235] The specific format of BlockAck will be explained with reference to FIG.

[0236] FIG. 36 shows a specific format of a BlockAck according to an embodiment of the present invention.

[0237] The BlockAck frame may include at least one of a Frame Control field, a Duration field, an RA field, a TA field, a BA Control field, a BA Information field, and an FCS field. The Frame Control field, the Duration field, the RA field, and the TA field correspond to a MAC header. When the BlockAck frame is not a Multi-STA BlockAck variant, the wireless communication terminal may set the RA field as the TA field of the frame that induces the BlockAck frame. Also, when the BlockAck frame is not a Multi-STA BlockAck variant, the wireless communication terminal may set the RA field as the address of the wireless communication terminal that transmitted the data / management frame that is acknowledged by the BlockAck frame.

[0238] If the BlockAck frame is a Multi-STA BlockAck variant and the AID subfield of the Per STA Info subfield included in the Multi-STA BlockAck variant has a value of 2 or more, the wireless communication terminal can set the RA field as a broadcast address. If the BlockAck frame is a Multi-STA BlockAck variant and the AID subfield of the Per STA Info subfield included in the Multi-STA BlockAck variant has a value of 1, the wireless communication terminal can set the RA field as the address of the wireless communication terminal that requested the BlockAck or as a broadcast address. If the BlockAck frame is a Multi-STA BlockAck variant and the AID subfield of the Per STA Info subfield included in the Multi-STA BlockAck variant has a value of one, the wireless communication terminal can set the RA field as the address of the wireless communication terminal that requested the BlockAck or as the address of the wireless communication terminal that transmitted the data / management frame that is acknowledged in the BlockAck frame. Also, if the AID subfield of the Per STA Info subfield included in the Multi-STA BlockAck variant has a value of one, the Multi-STA BlockAck variant can include only one AID subfield of the Per STA Info subfield, or multiple AID subfields of the Per STA Info subfield with the same value.

[0239] Also, the BA Control field may include at least one of a BA Ack Policy subfield, a BA Type subfield, a TID_INFO subfield, and a Reserved subfield, as shown in FIG. 36. The BA Type subfield may include at least one of a conventional Multi-TID subfield, a Compressed Bitmap subfield, and a GCR subfield. Specifically, B1 of the BA Type may be the same as the conventional Multi-TID subfield, B2 of the BA Type may be the same as the conventional Compressed Bitmap subfield, and B3 of the BA Type may be the same as the conventional GCR subfield.

[0240] In a specific embodiment, the wireless communication terminal can signal the type of this BlockAck frame using the BA Type subfield. The wireless communication terminal can indicate that the BlockAck frame is a Multi-STA BlockAck variant by setting the BA Type subfield to a pre-specified value. For example, the wireless communication terminal can indicate that the BlockAck frame is a Multi-STA BlockAck variant by setting B1-B4 of the BA Type subfield to 1101. A BlockAck frame that is a Multi-STA BlockAck variant can be called a Multi-STA BlockAck frame. In addition, the wireless communication terminal can indicate whether the BlockAck frame is a Basic BlockAck, a Compressed BlockAck, a GLK-GCR BlockAck, a GCR BlockAck, an Extended Compressed BlockAck, a Multi-TID BlockAck, or a Multi-STA BlockAck using the BA Type subfield.

[0241] Furthermore, the information represented by the TID_INFO subfield may vary depending on the BlockAck frame variant type. Specifically, the information represented by the TID_INFO subfield may vary depending on the type of BlockAck frame. If the BlockAck frame is a Multi-STA BlockAck, the TID_INFO subfield may be a reserved field.

[0242] In addition, the information represented by the BA Information field may vary depending on the BlockAck frame variant type. Specifically, when the BlockAck frame is a Multi-STA BlockAck variant, the BA Information field may include one or more Per STA Info subfields shown in FIG. 37. A specific format of the Per STA Info subfield will be described in detail with reference to FIG. 37. In this specification, receiving an MPDU / frame may mean successfully receiving an MPDU or frame. Specifically, when a frame check sequence (FCS) value acquired based on the received MPDU / frame is the same as the value of the FCS field, the wireless communication terminal may determine that the MPDU / frame has been successfully received.

[0243] FIG. 37 illustrates a Per STA Info subfield according to an embodiment of the present invention.

[0244] The BA Information field of the Multi-STA BlockAck can contain one or more Per STA Info fields.

[0245] The Per STA Info subfield may include a Per AID TID Info subfield. The Per AID TID Info subfield may include at least one of an AID subfield, an Ack Type subfield, and a TID subfield. If the Multi-STA BlockAck frame is intended to be transmitted to a wireless communication terminal that is not a base wireless communication terminal, the wireless communication terminal may set the AID subfield to 11 LSBs of the AID of the corresponding wireless communication terminal. If the Multi-STA BlockAck frame is intended to be transmitted to a wireless communication terminal that is not a base wireless communication terminal, the wireless communication terminal may set the AID subfield to the AID of the corresponding wireless communication terminal. If the Multi-STA BlockAck frame is intended to be transmitted to a base wireless communication terminal, the wireless communication terminal may set the AID subfield to 0.

[0246] One Multi-STA BlockAck frame may include multiple Per STA Info subfields with the same AID subfield value, where the TID subfield values ​​of the multiple Per STA Info subfields may be different from each other.

[0247] The TID subfield indicates the TID of the frame that the Per AID TID Info subfield acknowledges. When the Per AID TID Info subfield of the Multi-STA BlockAck variant acknowledges a management frame, the wireless communication terminal can set the TID subfield to 15.

[0248] In addition, the Ack Type subfield can indicate whether a Block Ack Starting Sequence Control subfield and a Block Ack Bitmap subfield exist in the Per STA Info subfield corresponding to the Ack Type subfield, which will be described in detail with reference to FIG.

[0249] FIG. 38 shows the context of the Per STA Info subfield according to an embodiment of the present invention.

[0250] If the Ack Type subfield is 1 and the value of the TID subfield of the Per AID TID Info subfield is less than 8 or 15, the Ack Type subfield and TID subfield can indicate that the Block Ack Starting Sequence Control subfield and Block Ack Bitmap subfield are not present. In this case, the Per STA Info subfield corresponding to the Ack Type field can acknowledge the successful reception of one MPDU (a single MPDU) indicated by the TID subfield of the Per AID TID Info subfield.

[0251] Also, if the Ack Type subfield is 1 and the TID subfield value of the Per AID TID Info subfield is 14, the Ack Type subfield and TID subfield may indicate that the Block Ack Starting Sequence Control subfield and Block Ack Bitmap subfield are not present. In this case, the Per STA Info subfield corresponding to the Ack Type field may acknowledge the successful reception of all MPDUs in the A-MPDU including the frame indicated by the TID subfield of the Per AID TID Info subfield.

[0252] Also, if the Ack Type subfield is 0, the Ack Type subfield may indicate the presence of a Block Ack Starting Sequence Control subfield and a Block Ack Bitmap subfield. Other specific contexts of the Per STA Info subfield may be as shown in FIG. 38.

[0253] A specific method for generating a Multi-STA BlockAck frame by a wireless communication terminal receiving a Multi-TID A-MPDU will be described with reference to Figures 39 and 40. For convenience of description, a wireless communication terminal transmitting a Multi-TID A-MPDU is referred to as a Multi-TID A-MPDU sender, and a wireless communication terminal receiving a Multi-TID A-MPDU is referred to as a Multi-TID A-MPDU receiver.

[0254] 39 to 40 show A-MPDU configurations according to an embodiment of the present invention.

[0255] As described above, the wireless communication terminal can aggregate A-MPDUs by mixing A-MPDU subframes including an MPDU delimiter field whose EOF subfield is 1 and whose MPDU Length subfield is not 0 with A-MPDU subframes including an MPDU delimiter field whose EOF subfield is 0 and whose MPDU Length subfield is not 0. The wireless communication terminal can also generate a Multi-TID A-MPDU by discontinuously aggregating A-MPDU subframes having the same TID. If the EOF subfield of the MPDU delimiter field is 1 and the MPDU Length subfield is not 0, the Multi-TID A-MPDU receiver can acknowledge the MPDU corresponding to the MPDU delimiter field by using the Per AID TID Info field in which the Block Ack Starting Sequence Control field and the Block Ack Bitmap field are omitted. Also, if the EOF subfield of the MPDU delimiter field is 0 and the MPDU Length subfield is not 0, the Multi-TID A-MPDU receiver can ACK the MPDU corresponding to the MPDU delimiter field using the Per AID TID Info field, which includes both the Block Ack Starting Sequence Control field and the Block Ack Bitmap field. For efficient Multi-STA BlockAck frame construction, when a Multi-TID A-MPDU sender generates a Multi-TID A-MPDU, the Multi-TID A-MPDU sender can limit the number of MPDUs corresponding to TIDs requesting ACK other than BlockAck to one MPDU per TID.Specifically, when a Multi-TID A-MPDU sender aggregates a Multi-TID A-MPDU, the Multi-TID A-MPDU sender adds an MPDU to the Multi-TID A-MPDU whose EOF subfield is 1 and whose MPDU Length subfield is not 0, but does not add an MPDU with the same TID as the TID of the corresponding MPDU to the Multi-TID A-MPDU.

[0256] Furthermore, if the MPDU contained in any one A-MPDU subframe is the only MPDU that corresponds to a specific TID among the MPDUs contained in the Multi-TID A-MPDU, the Multi-TID A-MPDU sender may set the EOF subfield of the A-MPDU subframe to 1. If the MPDU contained in any one A-MPDU subframe is the only MPDU that corresponds to a specific TID among the MPDUs contained in the Multi-TID A-MPDU and whose MPDU Length field value is not 0, the Multi-TID A-MPDU sender may set the EOF subfield of the A-MPDU subframe to 1. If the MPDU contained in any one A-MPDU subframe is not the only MPDU that corresponds to a specific TID among the MPDUs contained in the Multi-TID A-MPDU, the Multi-TID A-MPDU sender may set the EOF subfield of the A-MPDU subframe to 0. If the MPDU contained in any one A-MPDU subframe is not the only MPDU corresponding to a specific TID among the MPDUs contained in the Multi-TID A-MPDU and the MPDU Length field value is not 0, the Multi-TID A-MPDU sender can set the EOF subfield of the A-MPDU subframe to 0.

[0257] In a specific embodiment, when a Multi-TID A-MPDU transmitter uses a PPDU of a pre-specified format for transmitting the Multi-TID A-MPDU, the transmitter may set the EOF subfield according to the above-described embodiment. For example, when a Multi-TID A-MPDU transmitter uses a non-legacy PPDU for transmitting the Multi-TID A-MPDU, the transmitter may set the EOF subfield according to the above-described embodiment. In this case, the non-legacy PPDU may represent the PPDU format described with reference to FIG. 28.

[0258] The Multi-TID A-MPDU receiver can generate a Multi-STA BlockAck frame as follows: If the Multi-TID A-MPDU receiver receives all MPDUs corresponding to the MPDU delimiter field with an EOF subfield of 0 and an MPDU Length subfield of non-zero, the Multi-TID A-MPDU receiver can determine that it has received all MPDUs requesting BlockAck included in the Multi-TID A-MPDU. Also, if the EOF subfield of the MPDU delimiter field corresponding to all MPDUs not received by the Multi-TID A-MPDU receiver is 1 and the MPDU Length subfield is non-zero, the Multi-TID A-MPDU receiver can determine that it has received all MPDUs requesting BlockAck included in the Multi-TID A-MPDU. When the EOF subfield of the MPDU delimiter field corresponding to all MPDUs that the Multi-TID A-MPDU receiver has not received is 1, the Multi-TID A-MPDU receiver can determine that it has received all MPDUs that request BlockAck contained in the Multi-TID A-MPDU.

[0259] The Multi-TID A-MPDU receiver can determine whether the EOF subfield of the MPDU delimiter field corresponding to an unreceived MPDU is 1 in the following manner: If an A-MPDU subframe whose EOF subfield is set to 0 in an A-MPDU is restricted to not be located after an A-MPDU subframe whose EOF subfield is set to 1, the Multi-TID A-MPDU receiver can determine whether the EOF subfield of the MPDU delimiter field corresponding to an unreceived MPDU is 1 in the following manner: If the Multi-TID A-MPDU receiver does not receive an MPDU included in an A-MPDU subframe that is located after an A-MPDU subframe including an MPDU delimiter field whose EOF subfield is 1, the Multi-TID A-MPDU receiver can determine that it has not received an MPDU corresponding to an MPDU delimiter field whose EOF subfield is 1. In yet another specific embodiment, if a Multi-TID A-MPDU receiver receives an MPDU delimiter field but does not receive an MPDU corresponding to the MPDU delimiter field, the Multi-TID A-MPDU receiver can check the EOF subfield value of the MPDU delimiter field to determine whether the Multi-TID A-MPDU receiver has received an MPDU corresponding to an MPDU delimiter field whose EOF subfield is 1.

[0260] Receipt of all MPDUs requesting BlockAck contained in a Multi-TID A-MPDU may mean that all MPDUs contained in the Multi-TID A-MPDU have the TID of an MPDU corresponding to an MPDU delimiter field whose EOF subfield is 0 and whose MPDU Length subfield is not 0 and have been received.

[0261] When the Multi-TID A-MPDU receiver has received all MPDUs that require Block Ack and are included in the Multi-TID A-MPDU, the Multi-TID A-MPDU receiver can acknowledge MPDUs that correspond to an MPDU delimiter field whose EOF subfield is 0 and whose MPDU Length subfield is not 0 using a Per AID TID Info field with the Block Ack Starting Sequence Control field and Block Ack Bitmap field omitted. Specifically, the Multi-TID A-MPDU receiver can acknowledge MPDUs that correspond to an MPDU delimiter field whose EOF subfield is 0 and whose MPDU Length subfield is not 0 using a Per AID TID Info field with the Ack Type subfield set to 1. In this embodiment, the Multi-TID A-MPDU receiver can set the TID subfield of the Per AID TID Info field as the TID of the received MPDU. In a specific embodiment, the Multi-TID A-MPDU receiver may transmit a Multi-STA BlockAck frame including Per AID TID Info with the Block Ack Starting Sequence Control subfield and Block Ack Bitmap subfield omitted, indicating that all MPDUs of the TID indicated by the TID subfield of the Per AID TID Info field have been received to the Multi-TID A-MPDU sender. In this case, the Per AID TID Info field may further include an indicator indicating that all MPDUs of the TID indicated by the TID subfield of the Per AID TID Info field have been received.

[0262] The Multi-TID A-MPDU receiver transmits the generated Multi-STA BlockAck frame to the Multi-TID A-MPDU sender. If the TID subfield of the Per AID TID Info field has a value between 0 and 7 and the Ack Type subfield has a value of 1, the Multi-TID sender can determine that the Multi-TID receiver has received a single MPDU or all MPDUs corresponding to the TID indicated by the TID subfield included in the Multi-TID A-MPDU that solicited the Multi-STA BlockAck frame, including the Per AID TID Info field.

[0263] 39, the MPDUs that the Multi-TID A-MPDU receiver could not receive are all MPDUs corresponding to MPDU delimiter fields whose EOF subfield is 1 and whose MPDU Length subfield is not 0. Therefore, the Multi-TID A-MPDU receiver acknowledges MPDUs corresponding to MPDU delimiter fields whose EOF subfield is 0 and whose MPDU Length subfield is not 0 using a Per AID TID Info field in which the Block Ack Starting Sequence Control field and Block Ack Bitmap field are omitted. Specifically, the Multi-TID A-MPDU receiver can transmit to the Multi-TID A-MPDU sender a Multi-STA BlockAck that includes one or more Per AID TID Info fields in which the Block Ack Starting Sequence Control field and Block Ack Bitmap field are omitted.

[0264] In the embodiment of Figure 40, an A-MPDU subframe whose EOF subfield is set to 0 in an A-MPDU is restricted to not be located after an A-MPDU subframe whose EOF subfield is set to 1. The receiver of the Multi-TID A-MPDU was unable to receive the MPDU delimiter field corresponding to the MPDU that was not received. The receiver of the Multi-TID A-MPDU can determine that the EOF subfield of the MPDU delimiter field that was not received is 1 because the EOF subfield of the MPDU delimiter field corresponding to the MPDU that was located before the MPDU that was not received is 1. Therefore, the receiver of the Multi-TID A-MPDU can determine that the receiver has received all MPDUs corresponding to MPDU delimiter fields whose EOF subfield is 0 and whose MPDU Length subfield is not 0. The Multi-TID A-MPDU receiver acknowledges an MPDU whose EOF subfield is 0 and whose MPDU Length subfield is not 0 using a Per AID TID Info field with the Block Ack Starting Sequence Control and Block Ack Bitmap fields omitted. Specifically, the Multi-TID A-MPDU receiver can send a Multi-STA BlockAck to the Multi-TID A-MPDU sender, containing one or more Per AID TID Info fields with the Block Ack Starting Sequence Control and Block Ack Bitmap fields omitted.

[0265] FIG. 41 shows the operation of the wireless communication terminal according to the embodiment of the present invention.

[0266] The wireless communication terminal receives a trigger frame that triggers random access (S4101). The wireless communication terminal performs random access based on the trigger frame (S4103). At this time, the wireless communication terminal can perform random access according to the above-mentioned OBO procedure. Specifically, the wireless communication terminal can perform random access according to the embodiments described with reference to FIGS. 6 to 26.

[0267] The wireless communication terminal can set a random access counter to an integer selected within a range from 0 to the same as or smaller than the OFDMA contention window (OCW). In this case, the random access counter can be the OBO counter described above. When the wireless communication terminal attempts random access for the first time, when the wireless communication terminal receives OBO-related parameters signaled by the base wireless communication terminal, or when the wireless communication terminal has successfully transmitted via random access, the wireless communication terminal can initialize the OBO procedure. The initialization of the OBO procedure can include at least one of initialization of a counter for random access and initialization of an OCW. Furthermore, when the wireless communication terminal initializes an OCW, the wireless communication terminal can set the OCW as OCWmin. If the wireless communication terminal's transmission via random access fails, the wireless communication terminal can update the OCW value to (2xOCW+1). In this case, the wireless communication terminal selects an arbitrary integer within the updated OCW and sets the selected integer as the random access counter. Furthermore, when the value of OCW reaches OCWmax, even if transmission via random access of the wireless communication terminal fails, the wireless communication terminal can maintain the OCW at OCWmax.

[0268] The trigger frame may indicate random access using one or more RUs allocated for random access. Specifically, the trigger frame may indicate one or more RUs allocated for random access. In this case, the wireless communication terminal may decrement a counter value for random access based on the one or more RUs allocated for random access. If the trigger frame indicates an uplink transmission of the wireless communication terminal, the wireless communication terminal may not decrement the counter value based on the trigger frame. Specific operations of the wireless communication terminal may be the same as those of the embodiment described with reference to FIG. 26.

[0269] In this case, an RU is a group of multiple subcarriers that can be used for uplink transmission and downlink transmission as described above.

[0270] The wireless communication terminal can reduce the value of the counter for random access based on one or more RUs allocated for random access and the capabilities of the wireless communication terminal. When the value of the counter for random access is 0 or becomes 0, the wireless communication terminal can arbitrarily select one or more RUs allocated for random access.

[0271] The wireless communication terminal can perform a random access operation depending on its capability. In this case, the wireless communication terminal can operate as follows.

[0272] The wireless communication terminal may decrement a counter value for random access by the number of RUs to which the wireless communication terminal can transmit a trigger-based PPDU according to its capability, among one or more RUs allocated for random access. The capability of the wireless communication terminal may include a capability related to a bandwidth that the wireless communication terminal can transmit. The capability of the wireless communication terminal may also include a capability related to a length of a padding field included in the trigger-based PPDU. The capability of the wireless communication terminal may also include a capability related to a modulation and coding scheme that the wireless communication terminal can transmit. The capability of the wireless communication terminal may include a capability related to at least one of dual carrier modulation (DCM), the number of spatial streams, a guard interval (GI) length, a long training field (LTF) type, space-time block coding (STBC), and transmission power.

[0273] Furthermore, when the value of the counter for random access is 0 or becomes 0, the wireless communication terminal can arbitrarily select one of the RUs allocated for random access to which the wireless communication terminal can transmit a trigger-based PPDU according to its capability. If there is no RU to which the wireless communication terminal can transmit a trigger-based PPDU among one or more RUs allocated for random access, the wireless communication terminal can maintain the counter for random access at 0. Operations related to the capability of the wireless communication terminal may be the same as those of the wireless communication terminal in the embodiments shown in FIGS. 14 to 21.

[0274] The wireless communication terminal may be a wireless communication terminal that is not associated with the base wireless communication terminal that transmitted the trigger frame. In this case, the wireless communication terminal may operate as follows.

[0275] The wireless communication terminal can set the OCW minimum value, which is a parameter representing the minimum value of the OCW, to a value previously designated as a default value of the OCW minimum value, and can set the OCW maximum value, which is a parameter representing the maximum value of the OCW, to a value previously designated as a default value of the OCW maximum value. In this case, the values ​​previously designated as the default values ​​of the OCW minimum value and the OCW maximum value may not be values ​​designated by the base wireless communication terminal. The OCW minimum value may be the above-mentioned OCWmin. Also, the OCW maximum value may be the above-mentioned OCWmax.

[0276] When a wireless communication terminal communicates with a base wireless communication terminal other than the base wireless communication terminal that transmitted the trigger frame, the wireless communication terminal can initialize parameters for random access to the other wireless communication terminal. The parameters for random access can include a counter for random access, an OCW minimum value, and an OCW maximum value, which are parameters representing the maximum value of the OCW. When the wireless communication terminal communicates with the base wireless communication terminal that transmitted the trigger frame, the wireless communication terminal sets the OCW minimum value and the OCW maximum value according to information received from the base wireless communication terminal that transmitted the trigger frame. When the wireless communication terminal communicates with another base wireless communication terminal, the wireless communication terminal can set the OCW minimum value and the OCW maximum value according to information received from the other base wireless communication terminal. In this case, the information received by the wireless communication terminal from the base wireless communication terminal that transmitted the trigger frame or the base wireless communication terminal can be information related to OBO parameters. Specifically, it can be the UORA parameter set element described above. The wireless communication terminal can maintain OBO-related parameters and OBO procedures for each base wireless communication terminal. In a specific embodiment, the wireless communication terminal can set OBO-related parameters for each base wireless communication terminal. Specifically, the wireless communication terminal can set OBO-related parameters for each base wireless communication terminal based on information on OBO-related parameters received from each base wireless communication terminal. Specific operations of the wireless communication terminal not connected to the base wireless communication terminal may be the same as those described with reference to FIGS. 21 to 25.

[0277] The wireless communication terminal may be a wireless communication terminal coupled to the base wireless communication terminal that transmitted the trigger frame. Also, the base wireless communication terminal that transmitted the trigger frame may belong to multiple BSSID sets. In this case, the wireless communication terminal may operate as follows.

[0278] The OCW minimum value and the OCW maximum value can be set according to information received from another base wireless communication terminal belonging to a multiple BSSID set to which the base wireless communication terminal that transmitted the trigger frame belongs. In this case, the other base wireless communication terminal may be a base wireless communication terminal that operates a BSS corresponding to a transmitted BSSID of the multiple BSSID set. In addition, the wireless communication terminal may not decrement the counter value based on the trigger frame transmitted from the other base wireless communication terminal. The other base wireless communication terminal may be a base wireless communication terminal that operates a BSS corresponding to a transmitted BSSID of the multiple BSSID set. The information received from the other base wireless communication terminal does not have to be information indicated in a signaling field allocated only for the BSS in which the wireless communication terminal is included. Specifically, the signaling field allocated only for the BSS in which the wireless communication terminal is included may represent the non-transmitted profile described above. In this case, the information may be the UORA parameter set element described above. When a multiple BSSID set is used, specific operations of the wireless communication terminal may be the same as those of the embodiments described with reference to FIGS. 11 to 13.

[0279] The wireless communication terminal can attempt transmission to the base wireless communication terminal using a selected RU. In this case, the wireless communication terminal determines whether the selected RU is idle, and if the selected RU is idle, it can transmit a pending frame to the base wireless communication terminal via the selected RU. In addition, if the wireless communication terminal determines that the corresponding RU is busy in either physical carrier sense or virtual carrier sense, the wireless communication terminal can determine that the corresponding RU is busy. The physical carrier sense can include Clear Channel Assessment (CCA). If the wireless communication terminal determines that the selected RU is busy, the wireless communication terminal can maintain the OBO counter at 0 without transmitting a pending frame to the base wireless communication.

[0280] As described above, the present invention has been described using wireless LAN communication as an example, but the present invention is not limited thereto and can be similarly applied to other communication systems such as mobile phone communication, etc. Furthermore, although the method, device, and system of the present invention have been described in relation to specific embodiments, some or all of the components and operations of the present invention can be implemented using a computer system having a general-purpose hardware architecture.

[0281] The features, structures, effects, etc. described in the embodiments are included in at least one embodiment of the present invention, but are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment may be combined or modified in other embodiments by a person skilled in the art to which the embodiment belongs. Therefore, the contents relating to such combinations and modifications should be interpreted as being included within the scope of the present invention.

[0282] While the present invention has been described with reference to the preferred embodiments, these are merely illustrative and are not intended to limit the scope of the present invention. Those skilled in the art will appreciate that various modifications and applications not exemplified above are possible within the scope of the present invention. For example, the components specifically illustrated in the preferred embodiments may be modified. Such modifications and variations are to be construed as falling within the scope of the present invention as defined by the appended claims.

Claims

[Claim 1] A wireless communication terminal that wirelessly communicates with a base wireless communication terminal, a transmitter / receiver; a processor; The processor: setting a counter for random access to an integer selected within the range from 0 to a value equal to or less than the OFDMA contention window (OCW); receiving a trigger frame for triggering the random access using one or more resource units (RUs) allocated for random access from the base wireless communication terminal using the transceiver unit; decrementing the counter based on the one or more RUs allocated to the random access; When the value of the counter is 0 or becomes 0, randomly selecting any one RU from the one or more RUs allocated for the random access. A wireless communication terminal configured as above.

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