Wireless communication method using trigger information and wireless communication terminal using the same

Abstract

To provide a wireless communication method and a wireless communication terminal in a high-density environment including overlapping basic service sets.SOLUTION: Disclosed is a wireless communication terminal that communicates wirelessly. The wireless communication terminal includes a transceiver and a processor. The processor receives trigger information from a base wireless communication terminal using the transceiver, and transmits an Aggregate-MAC Protocol Data Unit (A-MPDU) to the base wireless communication terminal based on the trigger information.SELECTED DRAWING: Figure 24

Description

[Technical Field]

[0001] The present invention relates to a wireless communication method and a wireless communication terminal that use trigger information. [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 early wireless LAN technology using the 2.4 GHz frequency band, IEEE (Institute of Electrical and Electronics Engineers) 802.11 has implemented or is currently developing various technology standards. IEEE 802.11b supports a maximum communication speed of 11 Mbps using the 2.4 GHz frequency band. IEEE 802.11a, commercialized after IEEE 802.11b, uses the 5 GHz frequency band instead of the 2.4 GHz band, reducing interference compared to the much more congested 2.4 GHz frequency band, and uses OFDM technology to increase communication speeds to a maximum of 54 Mbps. 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 adoption accelerates and applications become more diverse, the need for a new WLAN system is emerging to support data rates higher than those supported by IEEE 802.11n (Very High Throughput, VHT). IEEE 802.11ac supports a wide bandwidth (80MHz-160MHz) in the 5GHz frequency band. While the IEEE 802.11ac standard was defined only in 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 object of one embodiment of the present invention is to provide a wireless communication method and a wireless communication terminal in a high density environment including overlapping basic service sets. [Means for solving the problem]

[0009] According to an embodiment of the present invention, a wireless communication terminal for wireless communication includes a transceiver unit and a processor, wherein the processor receives trigger information from a base wireless communication terminal using the transceiver unit and transmits an Aggregate-MAC Protocol Data Unit (A-MPDU) to the base wireless communication terminal based on the trigger information.

[0010] The processor determines whether to aggregate MPDUs requesting an immediate response and generate the A-MPDU based on the trigger information.

[0011] The trigger information is a trigger frame, and the trigger frame includes a signaling field indicating whether the wireless communication terminal is allowed to aggregate MPDUs requesting an immediate response and generate the A-MPDU, and the processor aggregates MPDUs requesting an immediate response based on the signaling field and generates the A-MPDU.

[0012] If the value of the signaling field is a predetermined value, the processor generates the A-MPDU without including an MPDU requesting an immediate response. In this case, if the value of the signaling field is within a predetermined range, the signaling field indicates the maximum number of TIDs that the A-MPDU can have when the wireless communication terminal generates the A-MPDU, and the processor generates the A-MPDU according to the maximum number of TIDs.

[0013] In addition, if the value of the signaling field is within a predetermined range, the processor aggregates MPDUs that do not require an immediate response regardless of the maximum number of TIDs that the A-MPDU can have, and generates the A-MPDU.

[0014] The MPDU that does not request an immediate response includes a Quality of Service (QoS) Null frame that does not request an ACK for data transmission.

[0015] The MPDU that does not request an immediate response includes an action No Ack frame that does not request an ACK for data transmission. Also, the MPDU requesting an immediate response includes an action frame.

[0016] At this time, if the value of the signaling field is within a predetermined range, the processor aggregates the action frames and generates the A-MPDU regardless of the maximum number of TIDs that the A-MPDU can have.

[0017] If the trigger information is included in the MAC header, the processor generates the A-MPDU without including an MPDU requesting an immediate response.

[0018] If the trigger information is included in the MAC header, the processor aggregates one of an ACK frame and a BA (Block ACK) frame without the MPDU requesting an immediate response and an MPDU not requesting an immediate response to generate the A-MPDU.

[0019] The MPDU that does not request an immediate response includes at least one of a Qos Null frame that does not request an ACK for data transmission and an Action No Ack frame that does not request an ACK for data transmission.

[0020] According to an embodiment of the present invention, a base wireless communication terminal for wireless communication includes a transceiver unit and a processor, wherein the processor transmits trigger information to a plurality of wireless communication terminals using the transceiver unit and receives an A-MPDU generated based on the trigger information from at least one of the plurality of wireless communication terminals.

[0021] The trigger information is a trigger frame, and the trigger frame includes a first signaling field indicating information about the type of MPDU included in the A-MPDU. At this time, if the wireless communication terminal corresponding to the first signaling field is not allowed to generate the A-MPDU by aggregating MPDUs requesting an immediate response, the processor sets a value of the first signaling field to a predetermined value.

[0022] If the wireless communication terminal corresponding to the first signaling field is allowed to generate the A-MPDU by aggregating MPDUs requesting an immediate response, the processor sets the value of the first signaling field according to the maximum number of TIDs that the A-MPDU can have.

[0023] The maximum number of TIDs that the A-MPDU can have indicates the maximum number of TIDs that the A-MPDU can have and that request an immediate response.

[0024] A Qos Null frame that does not request an ACK for data transmission may not correspond to a TID that requests an immediate response.

[0025] The trigger frame includes a second signaling field indicating whether channel sensing is required when transmitting the trigger-based PPDU (Physical Layer Data Unit),

[0026] The processor sets a value of the first signaling field based on a value of the second signaling field.

[0027] The processor sets the value of the first signaling field to a pre-specified value if the second signaling field is set to indicate that channel sensing is not required for transmitting the trigger-based PPDU.

[0028] The trigger frame includes a third signaling field indicating information about a length of a trigger-based PPDU, and the processor sets a value of the first signaling field based on a value of the third signaling field.

[0029] According to an embodiment of the present invention, a method for operating a wireless communication terminal that communicates without prior notice includes the steps of receiving trigger information from a base wireless communication terminal and transmitting an A-MPDU to the base wireless communication terminal based on the trigger information. [Effects of the Invention]

[0030] An embodiment of the present invention provides a wireless communication method using trigger information and a wireless communication terminal using the same. [Brief explanation of the drawings]

[0031] [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] A diagram showing a method in which a wireless communication terminal generates an A-MPDU according to an embodiment of the present invention. [Figure 7] 10 is a diagram illustrating a method in which a wireless communication terminal transmits a Block ACK (BA) frame for an A-MPDU according to an embodiment of the present invention. [Figure 8] 10 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on maximum number information of TIDs according to an embodiment of the present invention. [Figure 9] 10 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on maximum number information of TIDs according to another embodiment of the present invention. [Figure 10] 10 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on maximum number information of TIDs according to still another embodiment of the present invention. [Figure 11] 10 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on maximum number information of TIDs according to yet another embodiment of the present invention. [Figure 12] 10 is a diagram illustrating an operation of a wireless communication terminal according to an embodiment of the present invention for setting maximum number information of TIDs of a trigger frame. [Figure 13] 10 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on an UL MU RS according to an embodiment of the present invention. [Figure 14] 10 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on an UL MU RS according to another embodiment of the present invention. [Figure 15]10 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on an UL MU RS according to still another embodiment of the present invention. [Figure 16] FIG. 10 is a diagram illustrating an embodiment of the present invention in which an AP uses a trigger frame to signal the transmission power of the trigger frame to multiple wireless communication terminals, and the multiple wireless communication terminals adjust the transmission power of the MU PPDU based on the transmission power of the trigger frame. [Figure 17] 4 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to an embodiment of the present invention; [Figure 18] 10 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to another embodiment of the present invention. [Figure 19] 10 is a diagram illustrating a method for a wireless communication terminal to measure a received signal strength of an MU PPDU according to still another embodiment of the present invention. [Figure 20] FIG. 10 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to yet another embodiment of the present invention. [Figure 21] FIG. 10 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to yet another embodiment of the present invention. [Figure 22] FIG. 10 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to yet another embodiment of the present invention. [Figure 23] FIG. 10 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to yet another embodiment of the present invention. [Figure 24] 1 is a diagram illustrating an operation of a wireless communication terminal according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] 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.

[0033] 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.

[0034] This application claims priority based on Korean Patent Application Nos. 10-2016-0085764 (July 6, 2016), 10-2016-0117898 (September 13, 2016), and 10-2017-0048145 (April 13, 2017), and the examples and descriptions in each of the above priority applications are incorporated herein by reference.

[0035] 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.

[0036] As shown in FIG. 1, an infrastructure BSS (BSS1, BSS2) includes one or more stations (STA1, STA2, STA3, STA4, STA5), access points (PCP / AP-1, PCP / AP-2) that provide distribution services, and a distribution system (SD) that connects multiple access points (PCP / AP-1, PCP / AP-2).

[0037] 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.

[0038] 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 to include a personal BSS coordination point (PCP), and in a broad sense, includes all concepts such as a central controller, base station (GS), node B, base transceiver system (BTS), or site controller.

[0039] 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).

[0040] 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.

[0041] 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.

[0042] FIG. 3 is a block diagram showing the configuration of a station 100 according to an embodiment of the present invention.

[0043] As shown, station 100 according to an embodiment of the present invention includes a processor 110 , a transceiver unit 120 , a user interface unit 140 , a display unit 150 , and a memory 160 .

[0044] 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.

[0045] 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.

[0046] Next, the display unit 150 outputs an image on a display screen. The display unit 150 outputs various display objects, such as content executed by the processor 110 or a user interface based on a control command of the processor 110. The memory 160 also stores control programs used by the processor 110 and various data associated therewith. Such control programs include connection programs required for the station 100 to connect to an AP or an external station.

[0047] 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.

[0048] 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.

[0049] FIG. 4 is a block diagram showing the configuration of an AP 200 according to an embodiment of the present invention.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] FIG. 5 shows a schematic diagram of a process in which a STA establishes a link with an AP.

[0054] 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) and receives a probe response from the AP (S105) to acquire access information.

[0055] 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 (S107b), and performs the authentication step. After the authentication step is performed, the STA 100 transmits an association request (S109a), receives an association response from the AP 200 (S109b), and performs the association step. 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 and wired association.

[0056] 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.

[0057] 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.

[0058] A wireless communication terminal according to an embodiment of the present invention transmits and receives data using a data unit, which is a data processing unit for each layer. Specifically, the wireless communication terminal generates a MAC Protocol Data Unit (MPDU) from a Medium Access Control (MAC) layer and generates a PPDU from a physical layer. A wireless communication terminal receiving data receives the PPDU and acquires the MPDU from the PPDU. Through these operations, the wireless communication terminal improves the reliability and efficiency of data transmission. For convenience of explanation, a wireless communication terminal transmitting data is referred to as a transmitter, and a wireless communication terminal receiving data is referred to as a recipient. The transmitter aggregates multiple MPDUs to generate an A-MPDU including multiple MPDUs. The transmitter transmits the generated A-MPDU to the recipient. Specific operations of the wireless communication terminal regarding the A-MPDU will be described with reference to FIGS. 6 to 24.

[0059] FIG. 6 is a diagram illustrating a method for generating an A-MPDU by a wireless communication terminal according to an embodiment of the present invention.

[0060] The wireless communication terminal generates an A-MPDU as described above and transmits the A-MPDU to a receiver. Specifically, the wireless communication terminal generates an A-MPDU by inserting multiple MPDUs having the same TID. This increases transmission efficiency. Specifically, the wireless communication terminal reduces the number of channel access contention procedures required for data transmission, thereby increasing transmission efficiency. The wireless communication terminal generates an A-MPDU by inserting a delimiter indicating information about the MPDU and inserting one or more MPDUs. The A-MPDU is divided into pre-EOF padding and EOF padding. The delimiter includes an EOF field indicating the end of the pre-EOF padding portion included in the A-MPDU. The EOF field indicates that the MPDU corresponding to the delimiter requests an ACK that does not include a BA bitmap. The delimiter also includes an MPDU Length field indicating the length of the MPDU. The delimiter also includes a CRC field indicating a CRC value for detecting a delimiter error. The delimiter also includes a Delimiter Signature field indicating a pattern for detecting the delimiter. The wireless communication terminal inserts a delimiter whose EOF field value is 0 and whose MPDU Length field value is non-zero into the A-MPDU, and inserts an MPDU after the delimiter. The wireless communication terminal inserts one or more MPDUs and multiple delimiters indicating information about each of the one or more MPDUs into the A-MPDU to generate a Pre-EOF Padding A-MPDU. At this time, the inserted MPDU is a data MPDU corresponding to the TID agreed upon in the Block ACK agreement. The wireless communication terminal inserts EOF Padding after the Pre-EOF Padding A-MPDU. At this time, the EOF Padding indicates one or more delimiters whose EOF field value is 1 and whose MPDU Length field value is 0. When the receiver detects a delimiter whose EOF field value is 1 and whose MPDU Length field value is 0, the receiver determines that the A-MPDU transmission has ended.

[0061] When a wireless communication terminal transmits a large amount of data, it uses A-MPDU to improve transmission efficiency. However, a receiver that receives an A-MPDU should transmit a BA (Block ACK) frame containing a BA bitmap in response to the A-MPDU. Therefore, it is inefficient for a wireless communication terminal to transmit a single MPDU using an A-MPDU. Therefore, a receiver that receives a single MPDU (S-MPDU), which is an A-MPDU containing one MPDU, transmits an ACK frame, not a BA frame, to the transmitter in response to the A-MPDU. Specifically, regardless of the BA agreement for one MPDU, the receiver transmits an ACK frame, not a BA frame, to the transmitter in response to the A-MPDU. In addition, the transmitter sets the EOF field value in the delimiter located before the MPDU to 1 and sets the MPDU Length field value to a non-zero value. In addition, if the EOF field value of the delimiter included in the A-MPDU received by the receiver is 1 and the MPDU Length field value is 0, the receiver determines that the received A-MPDU is an S-MPDU. In addition, the transmitter inserts EOF padding after the MPDU in the S-MPDU.

[0062] In the embodiment of FIG. 6(a), the wireless communication terminal generates an A-MPDU by assembling multiple MPDUs with a TID of 2 and multiple delimiters (Pre EOF Padding) indicating information about each of the multiple MPDUs. At this time, the MPDUs are located after the delimiters indicating information about the corresponding MPDUs. The wireless communication terminal also inserts EOF padding. In the embodiment of FIG. 6(b), the wireless communication terminal generates an S-MPDU by assembling one MPDU with a TID of 2 and a delimiter (Pre EOF Padding) indicating information about the corresponding MPDU. At this time, the EOF field of the delimiter has a value of 1, and the MPDU Legnth field has a value other than 0. The wireless communication terminal also inserts EOF padding into the S-MPDU. Referring to FIG. 7, the operation of a transmitter transmitting an A-MPDU and a receiver transmitting a response to the A-MPDU will be described in detail.

[0063] FIG. 7 is a diagram illustrating a method in which a wireless communication terminal transmits a Block ACK (BA) frame for an A-MPDU according to an embodiment of the present invention.

[0064] As described above, the wireless communication terminal generates an A-MPDU by combining only MPDUs having the same traffic identifier (TID). In another specific embodiment, the wireless communication terminal generates one A-MPDU by combining multiple MPDUs having different TIDs. For convenience of explanation, an A-MPDU including multiple MPDUs corresponding to different TIDs is referred to as a multi-TID A-MPDU (multi-TID A-MPDU) or an A-MPDU with multiple TIDs (A-MPDU with Multiple TIDs). This improves the transmission efficiency of the A-MPDU. Furthermore, the wireless communication terminal transmits an A-MPDU with multiple TIDs using a physical layer protocol data unit (HE PPDU). In this case, the HE PPDU may be a multi-user PPDU (MEMU). Furthermore, the HE PPDU may be a HE trigger-based PPDU.

[0065] The wireless communication terminal sets parameters related to A-MPDU and BA frame transmission during a link setup procedure. The wireless communication terminal sets parameters related to A-MPDU transmission having multiple TIDs during the ring setup procedure. Specifically, the wireless communication terminal transmits the maximum number of TIDs, which indicates the maximum number of TIDs that the wireless communication terminal can simultaneously receive, during the link setup procedure. In this case, the wireless communication terminal transmits the maximum number of TIDs information using an HE capability information element, which is information indicating the terminal's capabilities. This is because the greater the number of TIDs in an A-MPDU having multiple TIDs, the higher the processing capability required of the wireless communication terminal receiving the A-MPDU. The maximum number of TIDs information is the maximum number of TIDs field of the HE capability information element. The maximum number of TIDs information transmitted by an AP to a non-AP wireless communication terminal indicates the maximum number of TIDs that an MPDU included in an uplink (UL) A-MPDU can have when transmitted by a wireless communication terminal that is not the corresponding AP. In addition, the maximum TID number information transmitted by a wireless communication terminal other than an AP to an AP indicates the maximum number of TIDs that can be included in a downlink (DL) A-MPDU transmitted by the corresponding AP. In a link establishment procedure, the wireless communication terminal transmits the maximum TID number information using a management frame. In this case, the management frame is at least one of a probe request frame, a probe response frame, an authentication request frame, an authentication response frame, an association request frame, an association response frame, and a beacon frame. In addition, if the AP transmits the maximum TID number information using a beacon frame, the maximum TID number information indicates the number of TIDs that the AP can simultaneously receive.In particular, if the AP transmits the maximum number of TIDs information using a beacon frame, the maximum number of TIDs information indicates the maximum number of TIDs that can be transmitted in a multi-hop transmission, rather than the maximum number of TIDs that an MPDU included in an A-MPDU transmitted from any one wireless communication terminal to the AP. This is because the AP transmits the beacon frame to all wireless communication terminals in the BSS operated by the AP. In other specific embodiments, the maximum number of TIDs information in the beacon frame may be used for other purposes. In still another specific embodiment, the maximum number of TIDs field in the beacon frame may be a reserved field.

[0066] During the link establishment procedure, the wireless communication terminal receives an All ACK from the receiver and transmits an All ACK capable indicator indicating whether it can process the All ACK. In this case, the All ACK is an ACK indicating that the receiver has received all MPDUs including an A-MPDU or multiple TID A-MPDUs transmitted by any one transmitter. When the All ACK is transmitted, the transmitter cannot know information about the transmitted fragments from the All ACK. To process the All ACK, the transmitter should store information about the fragments transmitted by the transmitter. This is because the transmitter may not be able to store information about the fragments transmitted by the transmitter depending on its capability. Specifically, the wireless communication terminal transmits the All ACK capable indicator, indicating whether it can process the All ACK, using an HE capability information element.

[0067] A wireless communication terminal fragments and transmits at least one of one MAC service data unit (MSDU), one Aggregate (A-MSDU), and one management protocol data unit (MMPDU). For convenience of explanation, a portion of an MSDU, a portion of an A-MSDU, or a portion of an MMPDU generated through fragmentation is referred to as a fragment. In addition, a wireless communication terminal that transmits data is referred to as a transmitter, and a wireless communication terminal that receives data is referred to as a receiver.

[0068] Specifically, the wireless communication terminal fragments at least one of one MSDU, one A-MSDU, and one MMPDU to generate a plurality of fragments. At this time, the wireless communication terminal transmits the generated plurality of fragments as a plurality of MPDUs. Furthermore, the wireless communication terminal receiving the plurality of fragments defragments the plurality of fragments to obtain at least one of one MSDU, one A-MSDU, and one MMPDU. At this time, the MPDU may be an S-MPDU or an A-MPDU.

[0069] The receiver needs sufficient buffer capacity and processing capability to defragment multiple fragments. Specifically, the receiver should store all fragments until it receives all fragments of an MSDU corresponding to the same sequence number. Therefore, if the receiver supports the capabilities required to receive fragments, the transmitter can transmit fragments to the receiver. Ultimately, the transmitter needs to know the fragmentation level supported by the receiver. The wireless communication terminal signals the fragmentation level. Specifically, the wireless communication terminal transmits information about the fragmentation level of fragments that the wireless communication terminal can receive during a link establishment procedure with the AP, and receives information about the fragmentation level of fragments that the AP can receive. Specifically, the wireless communication terminal transmits information about the fragmentation level using an HE Capability information element. In this case, the HE Capability information element indicates the capabilities of the wireless communication terminal. In addition, the wireless communication terminal transmits information about the fragmentation level using at least one of a probe request frame, a probe response frame, an authentication request frame, an authentication response frame, an association request frame, and an association response frame.

[0070] As described above, the HE Capability information element includes a Max number of TID field, an All ACK capable indicator, and information indicating the fragmentation level supported by the wireless communication terminal (fragmentation support level).

[0071] Furthermore, the wireless communication terminal sets BA parameters in an ADDBA (Add Block ACK) procedure. In this case, the BA parameters are parameters used for BA frame transmission and BA frame reception. The wireless communication terminal uses an ADDBA request frame to request an ACK in the form of a BA frame. In addition, the wireless communication terminal uses an ADDBA response frame to transmit a response to the ADDBA request frame. The ADDBA request frame and the ADDBA response frame include a Block Ack Parameter Set element. In this case, the Block Ack Parameter Set element includes information about the BA parameters. In addition, the wireless communication terminal sets BA parameters for each TID. More specifically, the wireless communication terminal negotiates BA parameter settings for each TID. In a specific embodiment, the wireless communication terminal specifies a TID that is the target of BA parameter setting negotiation using a TID field included in the Block Ack Parameter Set element. The transmitter transmits an ADDBA request frame to request BA parameter setting. The receiver receives the ADDBA request frame and transmits an ADDBA response frame in response to the ADDBA request frame to confirm the BA parameter setting. After the transmitter receives the ADDBA response frame and transmits an ACK frame for the ADDBA response frame, the transmitter and receiver can set the BA parameters.

[0072] After receiving data in the ADDBA procedure, the wireless communication terminal transmits buffer size information indicating the number of MPDUs that can be stored before transmitting a BA frame. Specifically, the wireless communication terminal transmits the buffer size information using a Block Ack Parameter Set element in the ADDBA procedure. The wireless communication terminal sets the length of the BA bitmap based on the range of values ​​that the buffer size information can have. Specifically, if the range of values ​​that the buffer size information can have is between 1 and X, the wireless communication terminal sets the length of the BA bitmap to X bits. At this time, if the wireless communication terminal cannot receive information about the length of the BA bitmap, the wireless communication terminal sets the length of the BA bitmap to X bits.

[0073] When the AP performs downlink transmission to the wireless communication terminal, the AP transmits an A-MPDU based on the capability of the wireless communication terminal signaled in the link establishment procedure and the BA parameter set in the ADDBA procedure. At this time, the wireless communication terminal transmits a BA frame or an M-BA (Multi-STA Block ACK) frame to the AP based on the capability of the AP and the BA parameter set in the ADDBA procedure.

[0074] If an AP simultaneously receives A-MPDUs from multiple wireless communication terminals, the AP may store the received MPDUs in a buffer, making it difficult to maintain a scoreboard. In this case, the scoreboard indicates information recorded by the AP on the reception status of each MPDU. Therefore, the AP uses a trigger frame to indicate the maximum number of TIDs that each A-MPDU transmitted by a wireless communication terminal may have. Specifically, the AP uses the User Info field of the trigger frame to indicate the maximum TID that the wireless communication terminal will transmit in the User Info field. In this case, the wireless communication terminal that receives the trigger frame sets the maximum number of TIDs that the A-MPDU may have based on the trigger frame. Specifically, the wireless communication terminal that receives the trigger frame sets the number of TIDs that the MPDU contained in the A-MPDU to be transmitted has based on the maximum number of TIDs indicated by the trigger frame, and transmits the A-MPDU to the AP. For example, a wireless communication terminal that receives a trigger frame sets the number of TIDs contained in the MPDU included in the A-MPDU to be transmitted so that the number does not exceed the maximum number of TIDs indicated by the trigger frame, and transmits the A-MPDU to the AP.

[0075] Furthermore, the wireless communication terminal transmits an A-MPDU having multiple TIDs in SU transmission. Specifically, if the wireless communication terminal uses an HE MU PPDU in SU (Single User) uplink transmission, the wireless communication terminal may be restricted from transmitting an A-MPDU having multiple TIDs. The wireless communication terminal uses an HE MU PPDU in SU UL transmission to use a narrow frequency band and a relatively wide transmission range. In this case, if the wireless communication terminal is allowed to transmit an A-MPDU including an A-MPDU having multiple TIDs, an issue of fairness may arise in terms of competition with other wireless communication terminals. Therefore, if the wireless communication terminal uses an HE MU PPDU in SU UL transmission, the wireless communication terminal may be restricted from transmitting an A-MPDU having multiple TIDs. Specific operations of a transmitter and a receiver regarding multiple A-MPDUs will be described with reference to FIGS. 8 to 15.

[0076] As described above, when a receiver receives data with a BA agreement, the receiver maintains a scoreboard that records the received data by TID and AID. When the receiver receives a BAR frame requesting BA frame transmission, the receiver should transmit the BA frame based on the data reception record in the scoreboard within a certain time period. In this case, the certain time period is SIFS. The receiver implements the scoreboard in the form of a one-chip memory for efficient processing. In addition, the receiver records records related to multiple BA sessions in one scoreboard. Therefore, if an AP simultaneously receives A-MPDUs from multiple wireless communication terminals, the AP may find it difficult to maintain the scoreboard as the number of wireless communication terminals increases. Therefore, the AP can limit the number of TIDs in MPDUs transmitted by wireless communication terminals participating in UL MU transmission.

[0077] The AP uses trigger information to indicate the maximum number of TIDs that can be included in an A-MPDU transmitted by each wireless communication terminal. In this case, the trigger information is at least one of a trigger frame and UL MU response scheduling (UL MU RS) information included in a MAC header. The operation of the AP using a trigger frame to indicate the maximum number of TIDs that can be included in an A-MPDU transmitted by each wireless communication terminal will be described with reference to Figures 8 to 12.

[0078] FIG. 8 illustrates an operation of a wireless communication terminal transmitting an A-MPDU based on information about the maximum number of TIDs according to an embodiment of the present invention.

[0079] The AP uses the trigger frame to indicate information regarding the type of MPDU included in the A-MPDU transmitted by the wireless communication terminal to the AP. As described above, the AP uses the trigger frame to indicate the maximum number of TIDs that the A-MPDU transmitted by the wireless communication terminal to the AP can have. Specifically, the AP uses the User Info field of the trigger frame to indicate the maximum TID that the wireless communication terminal will transmit, corresponding to the User Info field. In a specific embodiment, the AP uses the TID Aggregation Limit field of the User Info field of the trigger frame to indicate the maximum TID that the wireless communication terminal will transmit, corresponding to the User Info field. At this time, the wireless communication terminal that receives the trigger frame sets the number of TIDs that the A-MPDU can have based on the trigger frame. Specifically, the wireless communication terminal that receives the trigger frame sets the number of TIDs that the MPDU included in the A-MPDU will have based on the maximum number of TIDs indicated by the trigger frame, and transmits the A-MPDU to the AP. For example, a wireless communication terminal that receives a trigger frame sets the number of TIDs in the MPDU included in the A-MPDU so that the number does not exceed the maximum number of TIDs indicated by the trigger frame, and transmits the corresponding A-MPDU to the AP. This allows the AP to efficiently manage the scoreboard. Also, the length of the BA bitmap for each wireless communication terminal can be adjusted.

[0080] In a specific embodiment, the value of the TID Aggregation Limit field indicates the maximum number of TIDs that can be included in an A-MPDU that a wireless communication terminal that has received the trigger frame transmits to an AP. For example, if the TID Aggregation Limit field is a 3-bit field having a value from 0 to 7, each of the values ​​from 0 to 7 indicates that the maximum number of TIDs that an A-MPDU that is transmitted to an AP corresponds to one of 1 to 8.

[0081] In another specific embodiment, the AP uses a trigger frame to indicate that the wireless communication terminal designated by the trigger frame cannot aggregate MPDUs having a TID to generate an A-MPDU to be transmitted to the AP. Specifically, the AP sets the TID Aggregation Limit field to 0 to indicate that the wireless communication terminal designated by the trigger frame cannot aggregate MPDUs having a TID to generate an A-MPDU to be transmitted to the AP. However, even if the A-MPDU does not have a TID, if it includes an MPDU requesting an immediate response, the size of the BA frame transmitted by the receiver as a response to the A-MPDU may increase. In addition, this may increase the burden of managing the scoreboard on the receiver. In this case, an immediate response indicates that the receiver transmits a response to the transmitter within a pre-specified period within the same Transmission Opportunity (TXOP). Specifically, the pre-specified period is a Short Inter-Frame Space (SIFS).

[0082] In another specific embodiment, the AP uses a trigger frame to indicate that the wireless communication terminal indicated by the trigger frame cannot aggregate MPDUs requesting an immediate response to generate an A-MPDU to be transmitted to the AP. The MPDU requesting an immediate response includes an MPDU containing Quality of Service (QoS) data having a TID. The MPDU requesting an immediate response also includes a Management MPDU (MMPDU) requesting an immediate response. Specifically, the MPDU requesting an immediate response includes an action frame. The AP sets the value of the TID Aggregation Limit field in the User Info field of the trigger frame to 0 to indicate that the wireless communication terminal corresponding to the User Info field cannot aggregate MPDUs requesting an immediate response to generate an A-MPDU to be transmitted to the AP. If the value of the TID Aggregation Limit field indicates a value other than 0, it indicates the maximum number of TIDs that can be included in the A-MPDU to be transmitted to the AP by the wireless communication terminal indicated by the trigger frame. Furthermore, if the trigger frame indicates that the wireless communication terminal cannot aggregate MPDUs requiring an immediate response to generate an A-MPDU to be transmitted to the AP, the wireless communication terminal aggregates MPDUs requiring no immediate response to generate an A-MPDU to be transmitted to the AP. Specifically, if the value of the TID Aggregation Limit field in the User Info field corresponding to the wireless communication terminal in the trigger frame is 0, the wireless communication terminal aggregates MPDUs requiring no immediate response to generate an A-MPDU to be transmitted to the AP. In a specific embodiment, the MPDU requiring no immediate response includes an MPDU including QoS data whose ACK Policy is set to No Ack. Setting the ACK Policy to No Ack means that no ACK is requested for the corresponding frame. Furthermore, the MPDU requiring no immediate response includes a QoS Null frame. In this case, the QoS Null frame is a QoS Null frame whose ACK Policy is set to No Ack. Furthermore, the MPDU requiring no immediate response includes an Action No Ack frame.

[0083] In addition, the AP uses the trigger frame to instruct the wireless communication terminals indicated by the trigger frame to aggregate MPDUs without any limit on the number of TIDs to generate A-MPDUs and transmit the generated A-MPDUs to the AP. Specifically, the AP sets the value of the TID Aggregation Limit field in the User Info field of the trigger frame to 7, instructing the wireless communication terminals indicated by the User Info field to aggregate MPDUs without any limit on the number of TIDs to generate A-MPDUs and transmit the generated A-MPDUs to the AP.

[0084] In the embodiment of Figure 8, the AP sets the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame to 3, indicating that the maximum number of TIDs that the A-MPDU that the third station STA3 can have to transmit to the AP is 3. The third station STA3 determines the number of TIDs in the A-MPDU to be transmitted to the AP based on the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame. Specifically, the third station STA3 determines the number of TIDs in the A-MPDU to be transmitted to the AP to be 3 based on the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame. The third station STA1 aggregates MPDUs with TID 1, MPDUs with TID 2, MPDUs with TID 3, action frames, and QoS Null frames to generate an A-MPDU to be transmitted to the AP. The third station STA3 transmits the generated A-MPDU to the AP. The AP transmits M-BA frames to multiple wireless communication terminals including the third station STA3 based on the A-MPDU received from the third station STA3. In this embodiment, the AP adjusts the duration of the M-BA frame. In the embodiment of FIG. 8, the third station STA3 processes MPDUs without TIDs, such as QoS Null frames and action frames, as not being included in the number of TIDs indicated by the maximum number of TIDs. However, if there is no BA agreement for a specific TID, a response to an MPDU without the corresponding TID does not affect the M-BA frame. Also, as described above, an immediate response can be requested even for an MPDU that does not correspond to a specific TID. Therefore, a specific example of comparing the number of TIDs in an A-MPDU transmitted by a wireless communication terminal to an AP with the maximum number of TIDs is needed. This will be described in detail with reference to FIGS. 9 to 12.

[0085] FIG. 9 illustrates an operation of a wireless communication terminal transmitting an A-MPDU based on information about the maximum number of TIDs according to another embodiment of the present invention.

[0086] The AP uses a trigger frame to indicate the maximum number of TIDs with a BA agreement that may be included in an A-MPDU transmitted by the wireless communication terminal. The wireless communication terminal calculates the number of TIDs included in the A-MPDU based on the number of TIDs with a BA agreement. In the above-described embodiment, when the wireless communication terminal compares the number of TIDs included in the A-MPDU to be transmitted to the AP with the maximum number of TIDs, the wireless communication terminal compares the number of TIDs with a BA agreement with the maximum number of TIDs. Specifically, when the wireless communication terminal compares the number of TIDs included in the A-MPDU to be transmitted to the AP with the maximum number of TIDs, the wireless communication terminal does not calculate TIDs without a BA agreement as the number of TIDs in the A-MPDU. This is because the receiver does not buffer data corresponding to TIDs without a BA agreement and directly transmits them to an upper layer, so the reception of data corresponding to TIDs without a BA agreement does not affect scoreboard management. In addition, if the wireless communication terminal calculates TIDs without a BA agreement as the number of TIDs, buffer management and A-MPDU configuration would be limited. Specifically, if the value of the TID Aggregation Limit field is 1 to 6, the wireless communication terminal generates an A-MPDU in which the number of TIDs with a BA agreement is equal to or less than the value of the TID Aggregation Limit field, and transmits the generated A-MPDU to the AP. At this time, the wireless communication terminal adds MPDUs corresponding to TIDs without a BA agreement to the A-MPDU regardless of the value of the TID Aggregation Limit field. In addition, the AP sets the value of the TID Aggregation Limit field of the Per User Info of the trigger frame to 0, instructing the wireless communication terminal to aggregate MPDUs that do not require an immediate response, regardless of whether the TIDs corresponding to the Per User Info field have a BA agreement, generate an A-MPDU, and transmit the A-MPDU to the AP. Specifically, if the value of the TID Aggregation Limit field of the User Info field corresponding to the wireless communication terminal of the trigger frame is 0, the wireless communication terminal aggregates MPDUs that do not require an immediate response, and generates an A-MPDU to transmit to the AP.

[0087] In the embodiment of Figure 9, the AP sets the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame to 3, indicating that the maximum number of TIDs with BA agreement that the A-MPDU that the third station STA3 may transmit to the AP is 3. The third station STA3 determines the number of TIDs with BA agreement that the A-MPDU that it will transmit to the AP has based on the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame. The third station STA3 determines that the A-MPDU that it will transmit to the AP has three TIDs with BA agreement based on the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame. TIDs 1, 2, and 4 have BA agreement, and TID 5 does not have BA agreement. Therefore, the third station STA1 aggregates the MPDUs with TID 1, TID 2, TID 3, TID 5, the action No Ack frame, and the QoS Null frame to generate an A-MPDU to transmit to the AP. The third station STA3 transmits the generated A-MPDU to the AP. The AP transmits M-BA frames to multiple wireless communication terminals including the third station STA3 based on the A-MPDU received from the third station STA3. Through this embodiment, the AP adjusts the duration of the M-BA frame.

[0088] Data corresponding to a TID without a BA agreement can also request ACK frame transmission. In this case, the receiver transmits an M-BA frame including a Per AID TID field without a BA bitmap in response to an MPDU corresponding to a TID without a BA agreement. Therefore, even an MPDU corresponding to a TID without a BA agreement may affect the duration of the M-BA frame. Therefore, the maximum number of TIDs that an A-MPDU can have is calculated based on the number of TIDs requiring an immediate response and the number of frames without a TID requiring an immediate response. This will be described in detail with reference to FIG. 10.

[0089] FIG. 10 illustrates an operation of a wireless communication terminal transmitting an A-MPDU based on information about the maximum number of TIDs according to still another embodiment of the present invention.

[0090] The AP uses a trigger frame to limit the number of MPDUs that request an immediate response that may be included in an A-MPDU transmitted by the wireless communication terminal. Specifically, the AP uses a trigger frame to indicate the number of TIDs that request an immediate response that may be included in an A-MPDU transmitted by the wireless communication terminal. The wireless communication terminal calculates the number of TIDs included in the A-MPDU based on the number of TIDs that request an immediate response. In the above embodiment, when the wireless communication terminal compares the number of TIDs included in the A-MPDU to be transmitted to the AP with the maximum number of TIDs, the wireless communication terminal compares the number of TIDs included in the A-MPDU that request an immediate response with the maximum number of TIDs. When comparing the number of TIDs included in the A-MPDU to be transmitted to the AP with the maximum number of TIDs, the wireless communication terminal calculates the number of TIDs in the A-MPDU without taking into account MPDUs that do not request an immediate response. Therefore, the wireless communication terminal collects MPDUs corresponding to TIDs that do not require an immediate response, regardless of the maximum number of TIDs. The wireless communication terminal also collects frames without TIDs that do not require an immediate response, regardless of the maximum number of TIDs. The number of TIDs that require an immediate response is the sum of the number of frames without TIDs that require an immediate response, which are included in the A-MPDU, and the number of TIDs that require an immediate response, which are included in the A-MPDU. The number of frames without TIDs indicates the type of frame without a TID. An action frame with a TID of 15 in the per AID TID of an M-BA frame is also one of the frames without a TID that requires an immediate response. An MPDU corresponding to a TID that does not require an immediate response is an MPDU corresponding to a TID whose ACK policy is set to No Ack. An MPDU corresponding to a TID that does not require an immediate response is a QoS Null frame. The ACK Policy of the QoS Null frame is No Ack. Also, a frame without a TID that does not request an immediate response is an Action No Ack frame.

[0091] As described above, the AP sets the value of the TID Aggregation Limit field of the Per User Info field of the trigger frame to 0, and instructs the wireless communication terminal corresponding to the Per User Info field to aggregate MPDUs that do not require an immediate response, regardless of whether the TID has a BA agreement, to generate an A-MPDU and transmit it to the AP. In particular, if the value of the TID Aggregation Limit field of the User Info field corresponding to the wireless communication terminal of the trigger frame is 0, the wireless communication terminal aggregates MPDUs that do not require an immediate response and generates an A-MPDU to transmit to the AP.

[0092] 10, the AP sets the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame to 3, indicating that the maximum sum of the number of TIDs requesting an immediate response that the third station STA3 may have in the A-MPDU to transmit to the AP and the number of frames without a TID requesting an immediate response that the A-MPDU contains is 3. The third station STA3 determines the sum of the number of TIDs requesting an immediate response that the A-MPDU to transmit to the AP has and the number of frames without a TID requesting an immediate response based on the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame. The third station STA3 determines the sum of the number of TIDs requesting an immediate response that the A-MPDU to transmit to the AP has and the number of frames without a TID requesting an immediate response based on the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame. TIDs 1 and 2 request an immediate response, and TIDs 4 and 5 have an ACK policy set to No Ack. Also, the action frame requests an immediate response. Therefore, the third station STA1 aggregates the MPDUs with TIDs 1, 2, 4, 5, the action frame, the action No Ack frame, and the QoS Null frame, and generates an A-MPDU to transmit to the AP. The third station STA3 transmits the generated A-MPDU to the AP. The AP transmits M-BA frames to multiple wireless communication terminals including the third station STA3 based on the A-MPDU received from the third station STA3. In this embodiment, the AP adjusts the duration of the M-BA frame.

[0093] FIG. 11 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on information about the maximum number of TIDs according to still another embodiment of the present invention.

[0094] A multiple TID A-MPDU does not contain multiple action frames. Therefore, a multiple TID A-MPDU contains only one action frame. Also, if an A-MPDU contains an additional action frame, the length of the M-BA frame increases by about two octets. Therefore, the change in M-BA duration caused by adding an action frame to an A-MPDU is negligible. Also, action frames are considered to be more important than QoS data frames.

[0095] When the wireless communication terminal compares the number of TIDs in the A-MPDU to be transmitted to the AP with the maximum number of TIDs, the wireless communication terminal does not calculate the number of action frames as the number of TIDs in the A-MPDU. Specifically, if the value of the TID Aggregation Limit field is within a predetermined range, the wireless communication terminal aggregates action frames regardless of the value of the TID Aggregation Limit field to generate an A-MPDU to be transmitted to the AP. Specifically, in the embodiments of Figures 8 to 10, the wireless communication terminal does not calculate the number of action frames as the number of TIDs in the A-MPDU.

[0096] 11, the AP sets the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame to 2, and indicates that the maximum value of the sum of the number of TIDs requesting an immediate response that the third station STA3 may have in the A-MPDU transmitted to the AP and the number of frames without TIDs requesting an immediate response that the A-MPDU contains, excluding action frames, is 3. In this case, action frames are excluded from the calculation of the maximum value. The third station STA3 determines the sum of the number of TIDs requesting an immediate response that the A-MPDU may have in the A-MPDU transmitted to the AP and the number of frames without TIDs requesting an immediate response that the A-MPDU contains, excluding action frames, based on the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame. Based on the value of the TID Aggregation Limit field in the User Info field corresponding to the third station in the trigger frame, the third station STA3 determines that the A-MPDU to be transmitted to the AP has two TIDs that require an immediate response. TIDs 1 and 2 require an immediate response, and the ACK policy for TIDs 4 and 5 is set to No Ack. Additionally, action frames are excluded from the count calculation. Therefore, the third station STA1 aggregates MPDUs with TIDs 1, 2, and 4, MPDUs with TIDs 5, action frames, action No Ack frames, and QoS Null frames, and generates an A-MPDU to be transmitted to the AP. The third station STA3 transmits the generated A-MPDU to the AP. The AP transmits M-BA frames to multiple wireless communication terminals, including the third station STA3, based on the A-MPDUs received from the third station STA3. In this embodiment, the AP adjusts the duration of the M-BA frame.

[0097] The AP uses the trigger information to instruct a wireless communication terminal transmitting a response to the trigger information to perform channel sensing before transmitting the response. Specifically, the AP sets a CS Required field value in the trigger information to instruct a wireless communication terminal transmitting a response to the trigger information to perform channel sensing before transmitting the response. The CS Required field indicates whether channel sensing is required when the wireless communication terminal transmits a response to the corresponding trigger information. In this case, if the CS Required field is set to 1, the CS Required field indicates that channel sensing is required. In addition, the wireless communication terminal receiving the trigger information determines whether to perform channel sensing based on the CS Required field of the trigger information when transmitting a response to the trigger information. In particular, if the CS Required field value of the trigger information is set to 1, the wireless communication terminal receiving the trigger information performs channel sensing when transmitting a response to the trigger information. In this case, channel sensing indicates detecting whether the channel transmitting the response to the trigger information is idle. In addition, channel sensing indicates a CCA operation.

[0098] FIG. 12 is a diagram illustrating an operation of a wireless communication terminal setting information on the maximum number of TIDs of a trigger frame according to an embodiment of the present invention.

[0099] When the AP uses the trigger information to trigger an immediate response to data transmission, the AP also uses the trigger information to indicate that channel sensing is not required when the wireless communication terminal transmits a response to the trigger information. Specifically, when the AP uses the trigger information to trigger an immediate response to data transmission and the value of the length field in the common info field of the trigger information is equal to or less than a predetermined value, the AP also uses the trigger information to indicate that channel sensing is not required when the wireless communication terminal transmits a response to the trigger information. In this case, the length field indicates information about the length of the trigger-based PPDU. Specifically, the length field indicates information about the length of the trigger-based PPDU. The predetermined value is 418 bytes. This prevents the wireless communication terminal transmitting the response to the trigger information from being unable to transmit the immediate response due to channel sensing. In this case, the operation of the wireless communication terminal to transmit both the response to the trigger information and data becomes an issue. This is because when a wireless communication terminal operating in EDCA transmits data, the wireless communication terminal always performs channel sensing before transmitting the data. Also, if a wireless communication terminal transmitting a response to trigger information transmits an MPDU requesting an immediate response, an additional transmission sequence is required.

[0100] If channel sensing is not required when a wireless communication terminal indicated by the trigger frame transmits a response to the trigger information, the AP uses the trigger frame to instruct the wireless communication terminal indicated by the trigger frame to aggregate MPDUs requesting an immediate response to generate an A-MPDU and not transmit the generated A-MPDU. Specifically, if channel sensing is not required when a wireless communication terminal indicated by the trigger frame transmits a response to the trigger information, the AP sets the value of the TID Aggregation Limit field in the User Info field of the trigger frame to 0 to instruct the wireless communication terminal corresponding to the User Info field to aggregate MPDUs requesting an immediate response to generate an A-MPDU. Specifically, when the AP uses the trigger information to trigger an immediate response to data transmission, if the value of the common info field of the trigger information is equal to or less than a predetermined value, the AP instructs the wireless communication terminal indicated by the trigger frame to aggregate MPDUs requesting an immediate response to generate an A-MPDU and not transmit the generated A-MPDU. In this embodiment, the wireless communication terminal generates an A-MPDU by aggregating MPDUs that do not require an immediate response, and transmits the generated A-MPDU to the AP.

[0101] In the embodiment of FIG. 12, an AP transmits an HE MU PPDU to multiple stations. At this time, the HE MU PPDU includes a trigger frame requesting an immediate response to the data MPDU included in the HE MU PPDU. The length field value of the Common Info field of the trigger frame is 418. The CS Required bit of the trigger frame is set to 0. Therefore, the AP sets the TID Aggregation Limit field value of the User Info field of the trigger frame to 0. A wireless communication terminal that receives the trigger frame transmits both a response to the data MPDU included in the HE MU PPDU and an A-MPDU including an MPDU that does not request an immediate response. The length field value of the trigger frame that triggers a trigger-based PPDU (HE TB PPDU) including the A-MPDU is less than or equal to 418. Therefore, the first station transmits an A-MPDU including a BA frame and an MPDU including data whose ACK policy is No Ack. The second station transmits an A-MPDU including a BA frame and an Action No Ack frame, and the third and fourth stations transmit A-MPDUs including a BA frame and a QoS Null frame.

[0102] The operation of triggering A-MPDU transmission of a wireless communication terminal using a trigger frame has been described with reference to Figures 7 to 12. As described above, the AP triggers the wireless communication terminal to transmit a trigger-based PPDU to the AP using the MAC header. More specifically, the AP inserts trigger information into the HE variant HT control field of the MAC header to trigger the wireless communication terminal to transmit a trigger-based PPDU to the AP. In this case, the trigger information included in the MAC header is referred to as UL MU Response Scheduling (UL MU RS). The operation of the AP using the UL MU RS to trigger the wireless communication terminal to transmit a trigger-based PPDU including an A-MPDU will be described with reference to Figures 13 to 15.

[0103] FIG. 13 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on an UL MU RS according to an embodiment of the present invention.

[0104] Since the UL MU RS is included in the MAC header, the size of the field that the UL MU RS can use is limited. Specifically, the UL MU RS is identified by a 4-bit Control ID field in the HE variant HT control field, and trigger information is indicated using 26 bits. The UL MU RS also triggers the transmission of an ACK / BA frame for the payload included in the MAC frame containing the UL MU RS. The UL MU RS also triggers the transmission of a wireless communication terminal whose recipient address is the MAC frame containing the UL MU RS. In this embodiment, the UL MU RS contains less information than the trigger frame. Therefore, the UL MU RS may not contain information on the maximum number of TIDs. A wireless communication terminal that receives a MAC frame containing the UL MU RS transmits a trigger-based PPDU (TB PPDU) within the UL PPDU length indicated by the UL MU RS. Therefore, a wireless communication terminal that receives a MAC frame containing the UL MU RS generates an A-MPDU to be transmitted to the AP regardless of the number of TIDs that the A-MPDU may have.

[0105] In the embodiment of Figure 13, the AP transmits a data MPDU and an HE MU PPDU including a broadcast trigger frame to each of the first station STA1 to the third station STA3. At this time, the MAC header of the data MPDU for each of the first station STA1 to the third station STA3 includes an UL MU RS. Each of the first station STA1 to the third station STA3 generates an A-MPDU including an ACK / BA frame, a data MPDU, and an MPDU based on the UL MU RS. Each of the first station STA1 to the third station STA3 transmits the generated A-MPDU to the AP using the HE MU PPDU. The first station STA1 generates an A-MPDU by aggregating the ACK / BA frame, MPDUs and MMPDUs corresponding to each of multiple TIDs.

[0106] If a wireless communication terminal that has received a MAC frame containing a UL MU RS transmits an A-MPDU to an AP with a TID that exceeds the total number of TIDs that the AP can receive, the AP may not receive the A-MPDU or may malfunction. Therefore, a method for preventing this is needed.

[0107] FIG. 14 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on an UL MU RS according to still another embodiment of the present invention.

[0108] As described above, a wireless communication terminal that receives an UL MU RS generates an A-MPDU including an ACK / BA frame. The wireless communication terminal that receives an UL MU RS transmits the generated A-MPDU to the AP using information indicated by the UL MU RS. At this time, the MPDUs that the wireless communication terminal that receives an UL MU RS can aggregate with the ACK / BA frame are limited to at least one of an MPDU corresponding to one TID and one MMPDU. Therefore, the wireless communication terminal that receives an UL MU RS generates an A-MPDU by aggregating the ACK / BA frame with at least one of an MPDU corresponding to one TID and one MMPDU. At this time, the M-BA frame transmitted by the AP includes up to two BA information fields per wireless communication terminal. This is because the MMPDU in the M-BA frame is treated as having a TID of 1111. In the embodiment of FIG. 14, the AP transmits an HE MU PPDU to the first station STA1 to the third station STA3, as in the embodiment of FIG. 13. At this time, the first station STA1 transmits an A-MPDU to the AP based on the UL MU RS included in the MAC frame transmitted to the first station STA1. In the embodiment of Fig. 14(a), the first station STA1 generates an A-MPDU by assembling an ACK / BA frame, an MPDU with a TID of 3, and an MMPDU.

[0109] In another specific embodiment, the MPDUs that a wireless communication terminal that receives the UL MU RS can aggregate with an ACK / BA frame are limited to either an MPDU corresponding to one TID or one MMPDU. Therefore, a wireless communication terminal that receives the UL MU RS generates an A-MPDU by aggregating an ACK / BA frame with either an MPDU corresponding to one TID or one MMPDU. In this case, an M-BA frame transmitted by an AP includes a maximum of one BA information field per wireless communication terminal. In the embodiment of Figure 14(b), a first station STA1 generates an A-MPDU by aggregating an ACK / BA frame and an MPDU corresponding to TID 3.

[0110] In another specific embodiment, the MPDUs that a wireless communication terminal that receives the UL MU RS can aggregate with an ACK / BA frame are limited to at least one of an MMPDU and an MPDU corresponding to a high-priority TID. A wireless communication terminal that receives the UL MU RS generates an A-MPDU by aggregating an ACK / BA frame, an MMPDU, or an MPDU having a high-priority TID. A highly preferred TID indicates a TID with a higher priority than a fixed priority. Specifically, the fixed priority is designated by an AP. In a specific embodiment, the AP designates the fixed priority in a link establishment procedure. For example, the AP designates the fixed priority using at least one of a beacon frame, an association response frame, and an authentication response frame. In the embodiment of FIG. 14(c), a first station STA1 generates an A-MPDU by aggregating an ACK / BA frame, an MPDU with a TID of 1 that has a higher priority than the fixed priority, and an MMPDU.

[0111] In yet another specific embodiment, the MPDU that a wireless communication terminal that receives an UL MU RS can aggregate with an ACK / BA frame is limited to an MMPDU. Therefore, a wireless communication terminal that receives an UL MU RS aggregates an ACK / BA frame and an MMPDU to generate an A-MPDU. In the embodiment of Figure 14(d), a first station STA1 aggregates an ACK / BA frame and an MMPDU to generate an A-MPDU.

[0112] Furthermore, the wireless communication terminal that has received the UL MU RS collects MPDUs corresponding to TIDs without ACK / BA frames and BA agreements in the above-described embodiment without any restrictions.

[0113] In yet another specific embodiment, the MPDUs that a wireless communication terminal that receives a UL MU RS can aggregate with an ACK / BA frame are limited to MPDUs that do not require an immediate response. Therefore, a wireless communication terminal that receives a UL MU RS aggregates an ACK / BA frame with an MPDU that does not require an immediate response to generate an A-MPDU. In the embodiment of Figure 14(e), a first station STA1 aggregates an ACK / BA frame with an MPDU that does not require an immediate response to generate an A-MPDU. The wireless communication terminal prevents an increase in transmission sequences through this embodiment.

[0114] In yet another specific embodiment, the wireless communication terminal that receives the UL MU RS transmits an A-MPDU including the ACK / BA frame without aggregating the ACK / BA frame with other MPDUs, thereby maximizing the reliability of the ACK / BA frame transmission.

[0115] FIG. 15 is a diagram illustrating an operation of a wireless communication terminal transmitting an A-MPDU based on an UL MU RS according to still another embodiment of the present invention.

[0116] While transmitting the UL MU RS, the AP signals that aggregation of MPDUs other than the ACK / BA frame transmitted based on the UL MU RS is restricted. Specifically, the AP sets a bit indicating whether aggregation of the UL MU RS is permitted to 0 to signal that aggregation of MPDUs other than the ACK / BA frame transmitted based on the UL MU RS is restricted. If the UL MU RS indicates that aggregation of MPDUs other than the ACK / BA frame transmitted based on the UL MU RS is restricted, the wireless communication terminal receiving the UL MU RS generates an A-MPDU including an ACK / BA frame according to various embodiments described with reference to FIG. 14. Specifically, if the UL MU RS indicates that aggregation of MPDUs other than the ACK / BA frame is restricted, the wireless communication terminal receiving the UL MU RS transmits an A-MPDU including an ACK / BA frame to the AP without aggregation with other MPDUs. In another specific embodiment, if the UL MU RS indicates that the set of MPDUs other than the ACK / BA frame is restricted, the wireless communication terminal receiving the UL MU RS transmits to the AP an A-MPDU including an ACK / BA frame and an MPDU that does not request an immediate response.

[0117] In the embodiment of Figure 15, the AP sets the value of the Aggregation allowed field included in the UL MU RS to indicate that aggregation of MPDUs other than the ACK / BA frame transmitted based on the UL MU RS is restricted. In this case, if the value of the Aggregation allowed field is 0, the first station STA1 transmits an A-MPDU including an ACK / BA frame and padding to the AP. On the other hand, if the value of the Aggregation allowed field is 1, the first station STA1 transmits an A-MPDU including an ACK / BA frame, an MPDU with TID 1, and an MMPDU to the AP. Through such an embodiment, the form of the A-MPDU transmitted based on the UL MU RS becomes diverse.

[0118] If there is a large difference in received signal strength (RSSI) between MU PPDUs transmitted by multiple wireless communication terminals, it may be difficult for the AP to properly receive the MU PPDUs from the multiple wireless communication terminals. Therefore, the AP uses trigger information to adjust the transmission power of the MU PPDUs transmitted by each wireless communication terminal. This will be explained with reference to Figures 16 to 23.

[0119] Figure 16 is a diagram showing an embodiment of the present invention in which an AP uses a trigger frame to signal the transmission power of the trigger frame to multiple wireless communication terminals, and the multiple wireless communication terminals adjust the transmission power of the MU PPDU based on the transmission power of the trigger frame.

[0120] Depending on the location of the wireless communication terminal, the magnitude of path loss occurring during transmission to the AP may vary. Path loss refers to the attenuation of signal strength as a wireless signal is transmitted along a specific path. In FIG. 16, the second station STA2 is located farther from the AP than the first station STA1, and the path loss PL2 occurring during transmission between the second station STA2 and the AP is greater than the path loss PL1 occurring during transmission between the first station STA1 and the AP. Therefore, in order to adjust the received signal strength of the MU PPDU received by the AP to the received signal strength designated by the AP, the wireless communication terminal should estimate the path loss occurring along the transmission path from the wireless communication terminal to the AP. To this end, the AP inserts information regarding the transmission power for transmitting the PPDU containing the trigger information into the trigger information. Specifically, the AP inserts the transmission power into at least one of the trigger frame and the UL MU RS. In this case, the received signal strength designated by the AP is referred to as the target RSSI. Furthermore, the transmission power for transmitting the PPDU containing the trigger information is referred to as the DL TX power. For example, the AP inserts information about DL TX power into the Common Info field of the trigger frame as shown in Figure 16. The AP also inserts information about the target RSSI into the Trigger Dependent Info field of the Per User Info field of the trigger frame as shown in Figure 16. The AP also inserts information about DL TX power into the HE variant HT control field as shown in Figure 16. The AP also inserts information about the target RSSI into the HE variant HT control field as shown in Figure 16.

[0121] The wireless communication terminal acquires information about DL TX power based on the trigger information received from the AP. The wireless communication terminal estimates the path loss occurring on the transmission path between the wireless communication terminal and the AP based on the DL TX power and the received signal strength of the PPDU containing the trigger information. Specifically, as shown in Figure 16, the wireless communication terminal estimates the path loss occurring on the transmission path between the wireless communication terminal and the AP by subtracting the received signal strength of the PPDU containing the trigger information from the DL TX power based on the trigger information. Specifically, the DL TX power is displayed in 20 MHz units in the trigger information.

[0122] The wireless communication terminal measures the received signal strength of the PPDU on the physical layer and acquires information on DL TX power and target RSSI included in the trigger information from the MAC layer. In this case, the wireless communication terminal measures the received signal strength in advance and determines the transmission power of the trigger-based PPDU based on the DL TX power information and target SRRI information acquired from the MAC layer. Specifically, as shown in FIG. 16, the wireless communication terminal adds the path loss occurring on the transmission path between the AP and the wireless communication terminal to the target RSSI based on the received signal strength and DL TX power to determine the transmission power (Target UL TX power) of the trigger-based PPDU. The wireless communication terminal transmits the trigger-based PPDU at the determined transmission power.

[0123] Even for the same PPDU, the amount of power allocated may vary depending on frequency and time. Therefore, depending on the method by which the wireless communication terminal measures the received signal strength of the PPDU containing trigger information, the estimation of the path loss occurring in the transmission between the AP and the wireless communication terminal may be inaccurate. In particular, if the PPDU containing trigger information is transmitted through a bandwidth of 80 MHz or more and a center Resource Unit (26RU) is located at the center of the 80 MHz bandwidth, the center Resource Unit (26RU) is located at the center of two consecutive 20 MHz frequency bands. Specifically, the center Resource Unit (26RU) refers to an RU including subcarriers with indexes -16 to -4 and 4 to 16 and including seven Direct Current (DC) subcarriers located at the center of the frequency band. Therefore, a question arises as to which frequency band the wireless communication terminal receiving the PPDU payload through the center Resource Unit (26RU) should measure the received signal strength of. A method by which the wireless communication terminal measures the received signal strength of the MU PPDU will be described with reference to FIGS. 17 to 23. In this case, the MU PPDU contains trigger information as described above.

[0124] FIG. 17 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to an embodiment of the present invention.

[0125] The wireless communication terminal measures the received signal strength of the legacy preamble of the PPDU transmitted from a primary channel having a 20 MHz bandwidth as the received signal strength of the PPDU. In this case, the legacy preamble indicates a preamble that can be decoded not only by the wireless communication terminal according to the embodiment of the present invention but also by legacy wireless communication terminals. Specifically, the wireless communication terminal measures the received signal strength of the legacy training field of the PPDU transmitted from the primary channel having a 20 MHz bandwidth as the received signal strength of the PPDU. In a specific embodiment, the wireless communication terminal measures the received signal strength of the legacy long training field (L-LTF) transmitted from the primary channel having a 20 MHz bandwidth as the received signal strength of the PPDU. In another specific embodiment, the wireless communication terminal measures the average value of the received signal strengths of the L-LTF and the legacy short training field (L-STF) transmitted from the primary channel having a 20 MHz bandwidth as the received signal strength of the PPDU. In this case, L-LTF refers to a long training signal, which is a training signal having a relatively long signal length. Specifically, the wireless communication terminal estimates the frequency offset and channel of the OFDM symbol including the L-SIG field based on the LTF. Also, L-STF refers to a short training signal, which is a training signal having a relatively short length. Specifically, the wireless communication terminal performs AGC (Automatic Gain Control) on the OFDM symbol including the L-LTF field and the L-SIG field based on the L-STF. Also, the wireless communication terminal synchronizes the timing and frequency with the OFDM symbol including the L-SIG field based on the L-STF. The wireless communication terminal adjusts transmission power based on the received signal strength of the PPDU measured through the above-described embodiment.

[0126] In the embodiment of FIG. 17, an AP transmits an HE-MU PPDU having an 80 MHz bandwidth including a center 26RU to multiple wireless communication terminals. The HE-MU PPDU includes an L-STF, an L-LTF, an L-SIG, an RL-SIG, an HE-SIG-A, an HE-SIG-B, an HE-STF, an HE-LTF, a payload (Data), and a packet extension (PE). At this time, the multiple wireless communication terminals measure the received signal strength of the L-STF and L-LTF transmitted via a primary channel having a 20 MHz bandwidth. Based on the measured received signal strength and DL TX power, the multiple wireless communication terminals estimate the path loss occurring from the transmission from the AP to each of the multiple wireless communication terminals. At this time, the multiple wireless communication terminals acquire DL TX power from a trigger frame or an UL MU RS. Based on the estimated path loss and target RSSI, the multiple wireless communication terminals determine the transmission power of the trigger-based PPDU. The multiple wireless communication terminals transmit the trigger-based PPDU to the AP in accordance with information indicated by the trigger frame or the UL MU RS.

[0127] The wireless communication terminal senses the main channel having a 20 MHz bandwidth regardless of the location of the RU to which the payload received by the wireless communication terminal is transmitted. Furthermore, a legacy preamble is transmitted with the same power in the frequency bandwidth in which the PPDU is transmitted. Therefore, if the wireless communication terminal measures the received signal strength of the PPDU based on the legacy preamble transmitted through the 20 MHz band, the wireless communication terminal can efficiently measure the received signal strength of the PPDU. Furthermore, a wireless communication terminal receiving a PPDU payload through the center 26RU can also accurately measure the received signal strength of the PPDU. Furthermore, the wireless communication terminal measures the received signal strength of the PPDU in the same way when receiving a trigger frame transmitted in the form of a non-HT PPDU.

[0128] FIG. 18 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to yet another embodiment of the present invention.

[0129] The wireless communication terminal measures the received signal strength of the PPDU over the entire frequency band in which the PPDU is transmitted. At this time, the wireless communication terminal averages the received signal strength measured over the entire frequency band in which the PPDU is transmitted in 20 MHz units. More specifically, the wireless communication terminal measures the received signal strength of the legacy preamble over the entire frequency band in which the PPDU is transmitted as the received signal strength of the PPDU. More specifically, the wireless communication terminal measures the received signal strength of the PPDU based on a value obtained by averaging the received signal strength of the legacy preamble over the entire frequency band in which the PPDU is transmitted in 20 MHz bandwidth units. However, unlike the PPDU payload, which is transmitted using 256FFT, the legacy preamble is transmitted using 64FFT. Therefore, if the wireless communication terminal measures the received signal strength of the PPDU based on the legacy preamble, an error may occur.

[0130] The wireless communication terminal measures the received signal strength of the PPDU based on the non-legacy training field. The wireless communication terminal measures the received signal strength of the non-legacy training field as the received signal strength of the PPDU in the entire frequency band in which the PPDU is transmitted. Specifically, the wireless communication terminal measures the received signal strength of the PPDU based on an average value of the received signal strength of the non-legacy training field in the entire frequency band in which the PPDU is transmitted per 20 MHz bandwidth. In a specific embodiment, the wireless communication terminal estimates the path loss occurring in the transmission path between the wireless communication terminal and the AP by subtracting the average value of the received signal strength of the non-legacy training field in 20 MHz bandwidth from the entire frequency bandwidth in which the PPDU is transmitted using the DL TX power acquired from the trigger information. In this embodiment, the wireless communication terminal acquires information regarding the bandwidth of the PPDU signaled by the MU PPDU and measures the received signal strength of the non-legacy training field in the entire frequency band in which the PPDU is transmitted. In addition, the non-legacy training field may be a non-legacy long training field. The wireless communication terminal estimates the frequency offset and channel of the OFDM symbol including the non-legacy signaling field and the payload based on the non-legacy long training field. Specifically, the wireless communication terminal estimates the channel through which data is transmitted based on the non-legacy long training field. The wireless communication terminal also estimates the frequency offset of the OFDM symbol based on the non-legacy long training field. The wireless communication terminal also performs AGC on the OFDM symbol including the non-legacy long training field, the non-legacy signaling field, and the payload based on the short training signal. The wireless communication terminal also synchronizes the timing and frequency of the OFDM symbol including the non-legacy long training field, the non-legacy signaling field, and the payload based on the non-legacy short training field.

[0131] In the embodiment of FIG. 18, an AP transmits an HE-MU PPDU having an 80 MHz bandwidth including a center 26RU to multiple wireless communication terminals. The HE-MU PPDU includes an L-STF, an L-LTF, an L-SIG, an RL-SIG, an HE-SIG-A, an HE-SIG-B, an HE-STF, an HE-LTF, a payload (Data), and a packet extension (PE). At this time, the multiple wireless communication terminals cross-correlate the HE-LTF, which is a non-legacy short training field, and measure the received signal strength of the HE-LTF. Based on the measured received signal strength and DL TX power, the multiple wireless communication terminals estimate the path loss occurring from the transmission from the AP to each of the multiple wireless communication terminals. Other operations of the multiple wireless communication terminals are the same as those described in the embodiment of FIG. 17.

[0132] However, when the AP transmits the HE MU PPDU using OFDMA, the AP may set different transmit power for each RU. More specifically, when the AP transmits the HE MU PPDU using OFDMA, the AP sets different transmit power for each RU from the HE-STF, a non-legacy short training field. In particular, when 256FFT is used, the impact of frequency selectivity for each RU becomes even greater. A method of measuring received signal strength that takes into account such differences in transmit power for each RU will be described with reference to FIG. 19.

[0133] FIG. 19 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to still another embodiment of the present invention.

[0134] The wireless communication terminal measures the received signal strength of the non-legacy training field in the RU to which the PPDU payload is transmitted as the received signal strength of the PPDU. In this case, the non-legacy training field is a non-legacy long training field (HE-LTF). The RU to which the PPDU payload is transmitted indicates the RU to which the trigger frame for triggering the wireless communication terminal or the UL MU RS is transmitted. Specifically, if the bandwidth of the RU to which the PPDU payload is transmitted is smaller than 20 MHz, the wireless communication terminal scales the measured received signal strength to 20 MHz units.

[0135] In the embodiment of FIG. 19, an AP transmits an HE-MU PPDU having an 80 MHz bandwidth including 26 center RUs to multiple wireless communication terminals. The HE-MU PPDU includes an L-STF, an L-LTF, an L-SIG, an RL-SIG, an HE-SIG-A, an HE-SIG-B, an HE-STF, an HE-LTF, a payload (Data), and a packet extension (PE). The multiple wireless communication terminals cross-correlate the HE-LTF in the RU to which the payload for each of the multiple wireless communication terminals is transmitted, and measure the received signal strength of the HE-LTF. The multiple wireless communication terminals estimate the path loss occurring from the transmission from the AP to each of the multiple wireless communication terminals based on the measured received signal strength and DL TX power. If the bandwidth of the RU is smaller than 20 MHz, the measured received signal strength value is scaled to 20 MHz units. Other operations of the multiple wireless communication terminals are the same as those described in the embodiment of FIG. 17.

[0136] In this embodiment, if the frequency band of the RU to which the payload of the PPDU corresponding to the wireless communication terminal is transmitted is too narrow, the number of sample symbols that the wireless communication terminal can use to measure the received signal strength may be too small, and therefore the accuracy of the received signal strength measured by the wireless communication terminal may be reduced.

[0137] FIG. 20 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to yet another embodiment of the present invention.

[0138] The wireless communication terminal measures the received signal strength of the non-legacy training field as the received signal strength of the PPDU in a frequency band having a 20 MHz bandwidth including the RU to which the PPDU payload is transmitted, which corresponds to the wireless communication terminal. In this case, the non-legacy training field is a non-legacy long training field (HE-LTF). In addition, the RU to which the PPDU payload is transmitted indicates the RU to which the trigger frame for triggering the wireless communication terminal or the UL MU RS is transmitted.

[0139] In the embodiment of FIG. 20, an AP transmits an HE-MU PPDU having an 80 MHz bandwidth including 26 center RUs to multiple wireless communication terminals. The HE-MU PPDU includes an L-STF, an L-LTF, an L-SIG, an RL-SIG, an HE-SIG-A, an HE-SIG-B, an HE-STF, an HE-LTF, a payload (Data), and a packet extension (PE). The multiple wireless communication terminals measure the received signal strength of the HE-LTF by cross-correlating the HE-LTF in a frequency band having a 20 MHz bandwidth including the RU to which the payload for each of the multiple wireless communication terminals is transmitted. The multiple wireless communication terminals estimate the path loss occurring from the transmission from the AP to each of the multiple wireless communication terminals based on the measured received signal strength and DL TX power. If the bandwidth of the RU is smaller than 20 MHz, the measured received signal strength value is scaled to 20 MHz units. Other operations of the multiple wireless communication terminals are the same as those described in the embodiment of FIG. 17.

[0140] In such an embodiment, the question arises as to in which frequency band a wireless communication terminal receiving the payload of the PPDU via the center 26RU should measure the received signal strength of the non-legacy signaling field.

[0141] FIG. 21 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to yet another embodiment of the present invention.

[0142] In the above embodiment, when a wireless communication terminal receives a PPDU payload via the center 26RU, the wireless communication terminal measures the received signal strength of a non-legacy signaling field in a frequency band in which a SIG-B content channel signaling information about the center 26RU is transmitted. Specifically, the HE-SIG-B signaling field signals information about a plurality of wireless communication terminals receiving the HE-MU PPDU. Specifically, the information about the plurality of wireless communication terminals includes information about resource allocation. In this case, the information about resource allocation includes information about the RUs where the plurality of wireless communication terminals receive the HE-MU PPDU payload. The AP transmits HE-SIG-B fields including different information for each 20 MHz frequency band. Specifically, when the AP transmits the HE-MU PPDU over a frequency band having a bandwidth of 40 MHz or more, the AP repeatedly transmits a first SIG-B content channel having a 20 MHz bandwidth and a second SIG-B content channel having a 20 MHz bandwidth for each 40 MHz bandwidth. In this case, the AP transmits information about the center 26RU of the primary channel having an 80 MHz bandwidth via a first SIG-B content channel. The AP also transmits information about the center 26RU of the secondary channel having an 80 MHz bandwidth via a second SIG-B content channel. Therefore, when the wireless communication terminal receives the PPDU payload via the center 26RU included in the primary channel having an 80 MHz bandwidth, the wireless communication terminal measures the received signal strength of the non-legacy signaling field in the frequency band in which the first SIG-B content channel is transmitted. Also, when the wireless communication terminal receives the PPDU payload via the center 26RU included in the secondary channel having an 80 MHz bandwidth, the wireless communication terminal measures the received signal strength of the non-legacy signaling field in the frequency band in which the second SIG-B content channel is transmitted. The non-legacy training field is a non-legacy long training field (HE-LTF).

[0143] In the embodiment of FIG. 21 , an AP transmits an HE-MU PPDU having an 80 MHz bandwidth including a center 26RU to multiple wireless communication terminals. The HE-MU PPDU includes an L-STF, an L-LTF, an L-SIG, an RL-SIG, an HE-SIG-A, an HE-SIG-B, an HE-STF, an HE-LTF, a payload (Data), and a packet extension (PE). At this time, the wireless communication terminal receiving the payload via the center 26RU cross-correlates the HE-LTF from a frequency band having a 20 MHz bandwidth in which the first SIG-B content channel is transmitted, and measures the received signal strength of the HE-LTF. The wireless communication terminal estimates the path loss occurring from the transmission from the AP to the wireless communication terminal based on the measured received signal strength and DL TX power. The wireless communication terminal also acquires DL TX power from a trigger frame or an UL MU RS. The multiple wireless communication terminals determine the transmission power of the trigger-based PPDU based on the estimated path loss and target RSSI. A plurality of wireless communication terminals transmit trigger-based PPDUs to the PA in response to the trigger frame or information indicated by the UL MU RS.

[0144] When the wireless communication terminal measures the received signal strength of the non-legacy signaling field in the frequency band in which the SIG-B content channel signaling information about the center 26RU is transmitted, the wireless communication terminal acquires the HE-SIG-B field and measures the received signal strength from the same frequency band. However, there is a drawback in that the payload received by the wireless communication terminal is not transmitted in the frequency band in which the wireless communication terminal measured the received signal strength.

[0145] FIG. 22 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to yet another embodiment of the present invention.

[0146] In the above embodiment, when the wireless communication terminal receives a PPDU payload via the center 26RU, the wireless communication terminal measures the received signal strength of the non-legacy signaling field in a frequency band close to a SIG-B content channel that signals information about the center 26RU, among two frequency bands having a 20 MHz bandwidth including the center 26RU. In another specific embodiment, the wireless communication terminal measures the received signal strength of the non-legacy signaling field in two frequency bands having a 20 MHz bandwidth including the center 26RU. At this time, the wireless communication terminal averages the measured received signal strength in 20 MHz units. In addition, the non-legacy training field is a non-legacy long training field, HE-LTF.

[0147] In the embodiment of Figure 22, an AP transmits an HE-MU PPDU having an 80 MHz bandwidth including a center 26RU to multiple wireless communication terminals. The HE-MU PPDU includes an L-STF, an L-LTF, an L-SIG, an RL-SIG, an HE-SIG-A, an HE-SIG-B, an HE-STF, an HE-LTF, a payload (Data), and a packet extension (PE). The wireless communication terminals receiving the payload via the center 26RU measure the received signal strength of the HE-LTF by cross-correlating the HE-LTF in a frequency bandwidth close to the first SIG-B content channel among two frequency bands having a 20 MHz bandwidth including the center 26RU. In another specific embodiment, the wireless communication terminals receiving the payload via the center 26RU measure the received signal strength of the HE-LTF by cross-correlating the HE-LTF in two frequency bands having a 20 MHz bandwidth including the center 26RU, and average the received signal strength in 20 MHz units. Other operations of the wireless communication terminal are the same as those described in the embodiment of FIG.

[0148] FIG. 23 is a diagram illustrating a method for a wireless communication terminal to measure the received signal strength of an MU PPDU according to yet another embodiment of the present invention.

[0149] The AP may be restricted from transmitting trigger information through the center 26RU. Specifically, the AP may not transmit trigger information through the center 26RU. Specifically, the AP may not transmit trigger frames through the center 26RU. Furthermore, the AP may not transmit UL MU RSs through the center 26RU. This is because the center 26RU is used only when the bandwidth of the frequency band is 80 MHz or more, and the size of the center 26RU in the entire frequency band is not large.

[0150] In the embodiment of Figure 23, an AP transmits an HE-MU PPDU having an 80 MHz bandwidth including a center 26RU to multiple wireless communication terminals. The HE-MU PPDU includes an L-STF, an L-LTF, an L-SIG, an RL-SIG, an HE-SIG-A, an HE-SIG-B, an HE-STF, an HE-LTF, a payload (Data), and a packet extension (PE). In this case, the AP transmits the PPDU payload that does not include trigger information via the center 26RU. Through this embodiment, the AP prevents problems that may occur when wireless communication terminals receiving the PPDU payload via the center 26RU measure the received signal strength of the non-legacy signaling field.

[0151] FIG. 24 is a diagram illustrating the operation of the wireless communication terminal according to the embodiment of the present invention.

[0152] The base wireless communication terminal 2401 transmits trigger information to one or more wireless communication terminals 2403 (S2401). At this time, the trigger information is the above-mentioned trigger frame or UL MU RU.

[0153] The trigger information is a trigger frame, and the trigger frame includes a first signaling field related to the type of MPDU included in the A-MPDU. At this time, if the wireless communication terminal 2403 is not allowed to aggregate MPDUs requesting an immediate response and generate an A-MPDU to transmit to the base wireless communication terminal 2401, the base wireless communication terminal 2401 sets the value of the first signaling field to a pre-designated value. Also, if the base wireless communication terminal 2401 is allowed to aggregate MPDUs requesting an immediate response corresponding to the first signaling field and generate an A-MPDU to transmit to the base wireless communication terminal 2401, the base wireless communication terminal 2401 sets the value of the first signaling field according to the maximum number of TIDs that the A-MPDU can have. The maximum number of TIDs that the A-MPDU can have indicates the maximum number of TIDs that the A-MPDU can have, requesting an immediate response. The maximum number of TIDs for which an immediate response is requested indicates the maximum value of the sum of the number of TIDs for which an immediate response is requested and the number of frames without TIDs for which an immediate response is requested. In another specific embodiment, the maximum number of TIDs that an A-MPDU can have indicates the maximum number of TIDs for which a BA agreement is made.

[0154] In this case, an immediate response indicates that the receiver transmits a response to the transmitter within a pre-specified period within the same TXOP. Specifically, the pre-specified period is SIFS. An MPDU corresponding to a TID for which no immediate response is requested is an MPDU corresponding to a TID for which the ACK policy is set to No Ack. Also, an MPDU corresponding to a TID for which no immediate response is requested is a QoS Null frame. In this case, the ACK Policy of a QoS Null frame is No Ack. Also, a frame without a TID for which no immediate response is requested is an action No Ack frame.

[0155] The trigger frame includes a second signaling field indicating whether channel sensing is required when the wireless communication terminal 2403 transmits a trigger-based PPDU. The base wireless communication terminal 2401 sets the value of the first signaling field based on the value of the second signaling field. Specifically, if the second signaling field is set to indicate that channel sensing is not required for transmitting the trigger-based PPDU, the base wireless communication terminal 2401 sets the value of the first signaling field to a predetermined value. The trigger frame includes a third signaling field indicating information regarding the length of the trigger-based PPDU. In this case, the base wireless communication terminal sets the value of the first signaling field based on the value of the third signaling field. Specifically, if the value of the third signaling field is equal to or less than a predetermined value, the base wireless communication terminal 2401 sets the value of the first signaling field to a predetermined value. The predetermined value indicates that it is not possible to aggregate MPDUs requesting an immediate response and generate an A-MPDU to be transmitted to the base wireless communication terminal 2401.

[0156] The first signaling field is the TID Aggregation Limit field described above. The second signaling field is the CS required field described above. The base wireless communication terminal 2401 operates according to the embodiments described with reference to FIGS. 8 to 15.

[0157] The wireless communication terminal 2403 transmits an A-MPDU based on the trigger information (S2403). The wireless communication terminal 2403 determines whether to aggregate MPDUs requesting an immediate response and generate the A-MPDU based on the trigger information. The trigger frame includes a signaling field indicating whether the wireless communication terminal 2403 is allowed to aggregate MPDUs requesting an immediate response and generate an A-MPDU to transmit to the base wireless communication terminal 2401. The wireless communication terminal 2403 aggregates MPDUs requesting an immediate response based on the signaling field and generates an A-MPDU to transmit to the base wireless communication terminal 2401. If the value of the signaling field is a predetermined value, the wireless communication terminal 2403 generates the A-MPDU that does not include an MPDU requesting an immediate response. Also, if the value of the signaling field is within a predetermined range, the signaling field wireless communication terminal 2403 indicates the maximum number of TIDs that the A-MPDU can have when generating an A-MPDU to be transmitted to the base wireless communication terminal 2401, and the wireless communication terminal 2403 generates an A-MPDU to be transmitted to the base wireless communication terminal 2401 according to the maximum number of TIDs. If the value of the signaling field is within a predetermined range, the wireless communication terminal 2403 generates an A-MPDU by aggregating MPDUs that do not request an immediate response, regardless of the maximum number of TIDs that the A-MPDU can have. MPDUs that do not request an immediate response include a QoS Null frame that does not request an ACK for data transmission. MPDUs that do not request an immediate response also include an action No Ack frame that does not request an ACK for data transmission. MPDUs that request an immediate response also include an action frame. Furthermore, if the value of the signaling field is within a pre-specified range, the wireless communication terminal 2403 aggregates action frames to generate an A-MPDU regardless of the maximum number of TIDs that an A-MPDU can have. The signaling field is the TID Aggregation Limit field described above. The pre-specified value described above may be 0. The pre-specified range may be 1 or greater. The wireless communication terminal 2403 operates as in the embodiments described with reference to FIGS. 8 to 12.

[0158] If the trigger information is included in the MAC header, the wireless communication terminal 2403 generates an A-MPDU that does not include an MPDU requesting an immediate response as an A-MPDU to be transmitted to the base wireless communication terminal 2401. At this time, the trigger information is included in the HE variant HT control field of the MAC header. Specifically, the trigger information is the above-mentioned UL MU RU. In a specific embodiment, if the trigger information is included in the MAC header, the wireless communication terminal 2403 generates the A-MPDU by assembling one of an ACK frame and a BA frame and an MPDU that does not request an immediate response without an MPDU that requests an immediate response. At this time, the MPDU that does not request an immediate response includes at least one of a Qos Null frame that does not request an ACK for data transmission and an Action No Ack frame that does not request an ACK for data transmission. Specifically, the wireless communication terminal 2403 operates as in the embodiments described with reference to FIGS. 13 to 15.

[0159] The wireless communication terminal 2403 measures the received signal strength of the PPDU including the trigger frame and determines the transmission power of the trigger-based PPDU based on the measured received signal strength. Specifically, the wireless communication terminal 2403 measures the received signal strength of the legacy preamble of the PPDU transmitted from the primary channel having a 20 MHz bandwidth as the received signal strength of the PPDU. In this case, the legacy preamble indicates a preamble that can be decoded not only by the wireless communication terminal according to an embodiment of the present invention but also by legacy wireless communication terminals.

[0160] The wireless communication terminal 2403 also measures the received signal strength of the PPDU over the entire frequency band over which the PPDU is transmitted. At this time, the wireless communication terminal 2403 averages the received signal strength measured over the entire frequency band over which the PPDU is transmitted in 20 MHz units. More specifically, the wireless communication terminal 2403 measures the received signal strength of the legacy preamble over the entire frequency band over which the PPDU is transmitted as the received signal strength of the PPDU. The wireless communication terminal 2403 measures the received signal strength of the PPDU based on the non-legacy training field.

[0161] In addition, the wireless communication terminal 2403 measures the received signal strength of the non-legacy training field in the entire frequency band in which the PPDU is transmitted as the received signal strength of the PPDU. Specifically, the wireless communication terminal 2403 measures the received signal strength of the PPDU based on an average value of the received signal strength of the non-legacy training field in the entire frequency band in which the PPDU is transmitted in 20 MHz bandwidth units.

[0162] In addition, the wireless communication terminal 2403 measures the received signal strength of the non-legacy training field as the received signal strength of the PPDU in a frequency band having a 20 MHz bandwidth including the RU to which the PPDU payload is transmitted, which corresponds to the wireless communication terminal. When the wireless communication terminal 2403 receives the PPDU payload via the center 26RU, the wireless communication terminal 2403 measures the received signal strength of the non-legacy signaling field in a frequency band in which the SIG-B content channel signaling information about the center 26RU is transmitted. When the wireless communication terminal 2403 receives the PPDU payload via the center 26RU, the wireless communication terminal 2403 measures the received signal strength of the non-legacy signaling field in a frequency band close to the SIG-B content channel signaling information about the center 26RU, out of two frequency bandwidths having a 20 MHz bandwidth including the center 26RU. In another specific embodiment, the wireless communication terminal 2403 measures the received signal strength of the non-legacy signaling field in two frequency bands having a 20 MHz bandwidth including the center 26RU. At this time, the wireless communication terminal 2403 averages the measured received signal strength in 20 MHz units. In still another specific embodiment, the base wireless communication terminal 2401 is restricted from transmitting trigger information via the center 26RU. More specifically, the base wireless communication terminal 2401 does not need to transmit trigger information via the center 26RU. More specifically, the base wireless communication terminal 2401 does not need to transmit trigger frames via the center 26RU. More specifically, the wireless communication terminal 2403 and the base wireless communication terminal 2401 operate as in the embodiments described with reference to Figures 16 to 23.

[0163] 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.

[0164] 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.

[0165] 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. [Explanation of symbols]

[0166] 100...Station 110...Processor 120...Transmitter / receiver 140...User interface section 150...Display unit 160…Memory 210...processor 220...Transmitter / receiver 260…Memory 300...Authentication server 2401...Base wireless communication terminal 2403...Wireless communication terminal

Claims

[Claim 1] A wireless communication terminal that communicates wirelessly, the wireless communication terminal comprising: a transmitter / receiver; a processor; The processor: receiving trigger information from a base wireless communication terminal using the transceiver unit, the trigger information triggering transmission of a trigger-based physical layer protocol data unit (PPDU) by the wireless communication terminal; if the trigger information is included in a trigger frame, the trigger frame including a TID Aggregation Limit field in a User Info field corresponding to the wireless communication terminal, the TID Aggregation Limit field indicating whether or not the wireless communication terminal is enabled to generate an Aggregate-MAC Protocol Data Unit (A-MPDU) by aggregating one or more MPDUs requesting an immediate response, and indicating the maximum number of TIDs that can be aggregated into the A-MPDU if the wireless communication terminal generates the A-MPDU; If the trigger information is included in the trigger frame and the value of the TID Aggregation Limit field is a pre-specified value, the A-MPDU is generated so as not to include one or more MPDUs requesting an immediate response, and the pre-specified value is 0; If the trigger information is included in the trigger frame and the value of the TID Aggregation Limit field is within a predetermined range, generating the A-MPDU according to the maximum number of TIDs; If the trigger information is included in a MAC header, the processor generates the A-MPDU so as not to include one or more MPDUs requesting an immediate response; transmitting the trigger-based PPDU including the A-MPDU to the base wireless communication terminal; A wireless communication terminal configured to:

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