Wireless communication method using TXOP and wireless communication terminal using the same

Abstract

To provide a wireless communication terminal that wirelessly communicates.SOLUTION: The wireless communication terminal includes: a transceiver for transmitting and receiving a wireless signal; and a processor for processing the wireless signal. The processor is configured to perform a transmission based on a transmission opportunity (TXOP) limit which is a maximum value of a TXOP, which is a time interval in which a wireless communication terminal has a right to initiate a frame exchange sequence in a wireless medium.SELECTED DRAWING: Figure 19

Description

[Technical field]

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

[0002] Recently, as the use of mobile devices has become more widespread, wireless LAN technology that 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, embedded devices, etc. to the Internet at home, in a business, or in a specific service area.

[0003] Since IEEE (Institute of Electrical and Electronics Engineers) 802.11 supported early wireless LAN technology using 2.4GHz frequency, it has put into practical use or is currently developing various technology standards. First, IEEE 802.11b supports a maximum communication speed of 11Mbps using 2.4GHz frequency band. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses 5GHz frequency band instead of 2.4GHz band, reducing the impact of interference compared to the considerably congested 2.4GHz frequency band, and improves communication speed to a maximum of 54Mbps using OFDM technology. However, IEEE 802.11a has the disadvantage of a shorter communication distance compared to IEEE 802.11b. IEEE 802.11g has attracted considerable attention because it uses the 2.4GHz frequency band like IEEE 802.11b to achieve a maximum communication speed of 54Mbps and satisfies backward compatibility, but it also has an advantage over IEEE 802.11a in communication distance.

[0004] IEEE 802.11n is a technical standard established to overcome the communication speed limitations that have been pointed out as a weakness of wireless LAN. The purpose of IEEE 802.11n is to increase the network speed and reliability and extend the operating distance of wireless networks. More specifically, IEEE 802.11n supports high throughput (HT) with a data processing speed of up to 540 Mbps and is based on MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas on both the transmitting and receiving ends 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 the use of wireless LANs has become more widespread and applications using them have become more diverse, a new wireless LAN system is required to support a data processing rate (Very High Throughput, VHT) higher than that supported by IEEE 802.11n. Among these, IEEE 802.11ac supports a wide bandwidth (80MHz~160MHz) at 5GHz frequency. Although the IEEE 802.11ac standard was defined only in the 5GHz band, early 11ac chipsets also support operation in the 2.4GHz band for backward compatibility with existing 2.4GHz band products. Theoretically, this standard allows for a multi-station wireless LAN speed of at least 1Gbps and a maximum single link speed of at least 500Mbps. This is done by extending the wireless interface concept accepted by 801.11n, such as wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high density modulation (up to 256QAM). Also, there is IEEE 802.11ad, a method of transmitting data using the 60GHz band instead of the conventional 2.4GHz / 5GHz. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide speeds of up to 7Gbps, and is suitable for streaming large amounts of data and high bitrate videos such as uncompressed HD video. However, the 60GHz frequency band has the disadvantage that it is 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 standard for next-generation wireless LANs 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 APs (Access Points), and various technologies are required to realize this.

[0007] In particular, as the number of devices using wireless LAN increases, it becomes necessary to use the designated channels efficiently. Therefore, there is a demand for technology that uses the bandwidth efficiently by enabling data transmission between multiple stations and APs simultaneously. 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 terminal using a TXOP. [Means for solving the problem]

[0009] According to an embodiment of the present invention, a wireless communication terminal for wireless communication includes a transceiver for transmitting and receiving wireless signals, and a processor for processing the wireless signals, the processor performs transmission based on a TXOP limit, which is a maximum value of a transmission opportunity (TXOP), which is a time period during which the wireless communication terminal has the right to initiate a frame exchange sequence on a wireless medium.

[0010] The processor transmits a Beamforming Report Poll (BRP) trigger frame to another wireless communication terminal using a TXOP exceeding a TXOP limit, and receives a feedback frame in response to the BRP trigger frame from the other wireless communication terminal within the TXOP exceeding the TXOP limit. In this case, the BRP trigger frame triggers simultaneous transmission of feedback frames of one or more wireless communication terminals. The feedback frame indicates a channel state measured by the other wireless communication terminal, which is used for a Multi-Input Multi-Output (MIMO) transmission of the wireless communication terminal to the other wireless communication terminal, or a beamforming transmission of the wireless communication terminal to the other wireless communication terminal.

[0011] The processor transmits a Null Data Packet (NDP) frame used for measuring the channel state to the other wireless communication terminal after a predetermined time has elapsed since the wireless communication terminal transmitted a Null Data Packet Announcement (NDPA) frame informing the other wireless communication terminal of the start of a sounding protocol sequence. In this case, if the wireless communication terminal transmits the NDPA frame, the NDP frame, and the BRP trigger frame within the TXOP limit, the processor transmits the BRP trigger frame to the other wireless communication terminal using a TXOP exceeding the TXOP limit after a predetermined time has elapsed since the wireless communication terminal transmitted the NDP frame to the other wireless communication terminal.

[0012] If the wireless communication terminal transmits the BRP trigger frame within the TXOP limit, the processor transmits the BRP trigger frame using a TXOP that exceeds the TXOP limit.

[0013] The feedback frame is transmitted from the other wireless communication terminal after a pre-specified time has elapsed since the other wireless communication terminal received the BRP trigger frame.

[0014] The processor generates at least one fragment using dynamic fragmentation and transmits the at least one fragment to another wireless communication terminal, where dynamic fragmentation refers to fragmentation other than static fragmentation that requires all fragments except for a last fragment to be fragmented to the same size.

[0015] The processor first generates a first fragment of the at least one fragment based on a value specified by the other wireless communication terminal as a minimum fragment size, and transmits the first fragment to the other wireless communication terminal using a TXOP that exceeds the TXOP limit.

[0016] If the wireless communication terminal transmits the at least one fragment to the other wireless communication terminal without using an A (Aggregate)-MPDU including multiple MPDUs (MAC Protocol Data Units), the processor transmits the first fragment to the other wireless communication terminal using a TXOP that exceeds the TXOP limit.

[0017] The processor generates the first fragment with a size equal to a value designated by the other wireless communication terminal as a minimum fragment size.

[0018] The processor generates the at least one fragment up to the maximum number of fragments that the wireless communication terminal can generate, and transmits a first fragment, which is generated last among the at least one fragment, to the other wireless communication terminal using a TXOP that exceeds the TXOP limit.

[0019] The maximum number of fragments that the wireless communication terminal can generate is 16.

[0020] If the other wireless communication terminal explicitly fails to receive a first fragment, which is one of the at least one fragment, the processor generates a fourth fragment having a size different from that of the third fragment and the same sequence number and fragment number as the third fragment, based on at least one of whether the wireless communication terminal does not transmit a fragment following the first fragment and whether the other wireless communication terminal explicitly fails to receive a fragment following the first fragment, and in this case, the processor transmits the fourth fragment to the other wireless communication terminal instead of retransmitting the third fragment to the other wireless communication terminal.

[0021] If there is no BlockACK agreement between the wireless communication terminal and the other wireless communication terminal, the processor performs dynamic fragmentation according to a fragmentation level determined according to the capability of the other wireless communication terminal, where the fragmentation level indicates a method of transmitting fragments.

[0022] The wireless communication terminal is a TXOP holder.

[0023] According to an embodiment of the present invention, a method for operating a wireless communication terminal communicating wirelessly includes a step of transmitting based on a TXOP limit, which is a maximum value of a TXOP, which is a time period during which the wireless communication terminal has the right to initiate a frame exchange sequence on a wireless medium.

[0024] The step of transmitting based on the TXOP limit includes the steps of transmitting a beamforming report poll trigger frame to another wireless communication terminal using a TXOP exceeding the TXOP limit, and receiving a feedback frame from the other wireless communication terminal in response to the BRP trigger frame within the TXOP exceeding the TXOP limit. In this case, the BRP trigger frame triggers simultaneous transmission of feedback frames of one or more wireless communication terminals. Also, the feedback frame indicates a channel state measured by the other wireless communication terminal, which is used for MIMO transmission of the wireless communication terminal to the other wireless communication terminal, or beamforming transmission of the wireless communication terminal to the other wireless communication terminal.

[0025] The step of transmitting the BRP trigger frame includes a step of receiving an NDP frame used by the other wireless communication terminal to measure the channel state from the other wireless communication terminal after a predetermined time from when an NDPA frame notifying the other wireless communication terminal that a sounding protocol sequence is to begin, and if the wireless communication terminal transmits the NDPA frame, the NDP frame, and the BRP trigger frame within a TXOP limit, a step of transmitting the BRP trigger frame using a TXOP that exceeds the TXOP limit after a predetermined time from when the wireless communication terminal transmits the NDP frame to the other wireless communication terminal.

[0026] The step of transmitting the BRP trigger frame using a TXOP exceeding the TXOP limit includes the step of transmitting the BRP trigger frame using a TXOP exceeding the TXOP limit if the BRP trigger frame is transmitted within the TXOP limit.

[0027] The method further includes generating at least one fragment using dynamic fragmentation, and the transmitting step based on the TXOP limit includes transmitting the at least one fragment to another wireless communication terminal, where dynamic fragmentation refers to fragmentation other than static fragmentation that requires all fragments except the last fragment to be fragmented to the same size.

[0028] The step of generating the at least one fragment includes a step of generating a first fragment from the at least one fragment based on a value specified by the other wireless communication terminal as a minimum fragment size, and the step of transmitting the at least one fragment to the other wireless communication terminal includes a step of transmitting the first fragment to the other wireless communication terminal using a TXOP that exceeds the TXOP limit.

[0029] The step of initially generating a first fragment of the at least one fragment includes the step of generating the first fragment with a size equal to a value designated by the other wireless communication terminal as a minimum fragment size.

[0030] The step of generating the at least one fragment includes a step of generating the at least one fragment up to the maximum number of fragments that the wireless communication terminal can generate, and the step of transmitting the at least one fragment to another wireless communication terminal includes a step of transmitting a second fragment, which is generated last among the at least one fragment, to the other wireless communication terminal using a TXOP that exceeds the TXOP limit.

[0031] The operating method includes the steps of: when the other wireless communication terminal explicitly fails to receive a third fragment, which is one of the at least one fragment, by the processor generating a fourth fragment having a different size from the third fragment and having the same sequence number and fragment number as the third fragment for retransmitting the third fragment based on at least one of whether the wireless communication terminal has transmitted a fragment that follows the third fragment or the other wireless communication terminal has explicitly failed to receive a fragment that follows the third fragment; and transmitting the fourth fragment to the other wireless communication terminal instead of retransmitting the third fragment to the other wireless communication terminal. Effect of the Invention

[0032] An embodiment of the present invention provides a wireless communication method using a TXOP and a wireless communication terminal using the same. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Diagram 2] FIG. 11 is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Diagram 3] FIG. 2 is a block diagram showing a configuration of a station according to an embodiment of the present invention. [Figure 4] 2 is a block diagram showing a configuration of an access point according to an embodiment of the present invention. FIG. [Diagram 5] 2 is a diagram illustrating a process in which a station sets up a link with an access point according to one embodiment of the present invention. [Figure 6] A diagram showing the operation of a wireless communication terminal performing frame exchange based on a TXOP limit according to an embodiment of the present invention. [Figure 7] FIG. 13 is a diagram showing dynamic fragmentation in a wireless communication terminal according to an embodiment of the present invention; [Figure 8] 5A and 5B are diagrams illustrating an operation of a wireless communication terminal determining a reception failure of a receiver and an operation of retransmission according to an embodiment of the present invention; [Figure 9] A diagram showing the operation of a wireless communication terminal retransmitting within the TXOP limit according to an embodiment of the present invention. [Figure 10] A diagram showing the operation of a wireless communication terminal retransmitting within the TXOP limit according to an embodiment of the present invention. [Figure 11] 13 is a diagram illustrating an operation of a wireless communication terminal retransmitting a fragment included in the same sequence as a retransmitted fragment within the TXOP limit after retransmission according to another embodiment of the present invention. [Figure 12] 13 is a diagram illustrating a transmission operation that exceeds the TXOP limit if a wireless communication terminal uses dynamic fragmentation according to an embodiment of the present invention. [Figure 13] 13 is a diagram illustrating a transmission operation that exceeds the TXOP limit if a wireless communication terminal uses dynamic fragmentation according to an embodiment of the present invention. [Figure 14] A diagram illustrating the retransmission operation of a wireless communication terminal that is not a TXOP holder according to an embodiment of the present invention. [Figure 15]A diagram illustrating the retransmission operation of a wireless communication terminal that is not a TXOP holder according to yet another embodiment of the present invention. [Figure 16] A diagram illustrating the retransmission operation of a wireless communication terminal that is not a TXOP holder according to yet another embodiment of the present invention. [Figure 17] A diagram showing a wireless communication terminal according to an embodiment of the present invention performing a sounding protocol operation regarding a TXOP limit. [Figure 18] A diagram showing a wireless communication terminal according to an embodiment of the present invention performing a sounding protocol operation regarding a TXOP limit. [Figure 19] FIG. 4 is a diagram illustrating the operation of a wireless communication terminal according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out 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 related to the description are omitted in order to clarify the present invention, and similar parts are designated by similar reference numerals throughout the specification.

[0035] Furthermore, when a part "comprises" a certain element, this does not mean excluding other elements, but rather further includes other elements, unless otherwise specified to the contrary.

[0036] This application claims priority based on Korean Patent Application Nos. 10-2017-0003137 (2017.01.09), 10-2017-0008306 (2017.01.17), 10-2017-0024265 (2017.02.23) and 10-2017-0057098 (2017.05.05), and the embodiments and descriptions in each of the above applications which serve as the basis for priority are incorporated herein by reference in their entirety.

[0037] FIG 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 (BSS), which refers to a collection 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.

[0038] As shown in FIG. 1, the infrastructure BS S BSS1, BSS2 includes one or more stations STA1, STA2, STA3, STA4, STA5, access points PCP / AP-1, PCP / AP-2 which are stations providing distribution services, and a distribution system (SD) connecting multiple access points PCP / AP-1, PCP / AP-2.

[0039] A station (STA) is any device that includes a medium access control (MAC) based on the IEEE 802.11 standard and a physical layer interface for a wireless medium, and in a broad sense includes not only a non-AP but also an AP. In this specification, the term "terminal" refers to a non-AP STA or an AP, or is used as a term that refers to both. A station for wireless communication includes a processor and a transmit / receive unit, and further includes a user interface unit and a display unit, etc., depending on the embodiment. The processor generates frames to be transmitted through a wireless network, processes frames received through the wireless network, and performs various other processes for controlling the station. The transmit / receive unit is functionally connected to the processor and transmits and receives frames through the wireless network for the station.

[0040] 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 set up, direct communication between non-AP stations becomes possible. Meanwhile, in the present invention, the AP is used as a base including a PCP (Personal BSS Coordination Point), and in a broad sense, includes all concepts such as a central controller, a base station (GS), a Node B, a BTS (Base Transceiver System), or a site controller.

[0041] A plurality of infrastructure BSSs are interconnected through a distribution system, and the plurality of BSSs connected through the distribution system are referred to as an Extended Service Set (ESS).

[0042] 2 is a diagram showing an independent BSS, which is a wireless LAN system according to another embodiment of the present invention, in which the same or corresponding parts in the embodiment of FIG. 2 are the same as or correspond to the embodiment of FIG.

[0043] The 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 is a self-contained network that is not allowed to be connected to a distribution system. In an independent BSS, each station STA6 and STA7 is directly connected to each other.

[0044] FIG. 3 is a block diagram showing a configuration of a station 100 according to an embodiment of the present invention.

[0045] As shown, station 100 according to an embodiment of the present invention includes a processor 110 , a transceiver 120 , a user interface 140 , a display unit 150 , and a memory 160 .

[0046] First, the transceiver 120 transmits and receives wireless signals such as wireless LAN packets, and is provided inside or outside 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 using different frequency bands such as 2.4 GHz, 5 GHz, and 50 GHz. According to an embodiment, the station 100 includes a transceiver module using a frequency band of 6 GHz or more and a transceiver module using a frequency band of 6 GHz or less. Each transceiver module performs wireless communication with an AP or an external station according to the wireless LAN standard of the frequency band supported by the corresponding transceiver module. The transceiver 120 operates only one transceiver module at a time or operates multiple transceiver modules simultaneously according to the performance and requirements of the station 100. When the station 100 includes multiple transceiver modules, each transceiver module may be provided in an independent form, or multiple modules may be integrated into one chip.

[0047] 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 a command from the processor 110 using various output means.

[0048] Next, the display unit 150 outputs an image on a display screen. The display unit 150 outputs various display objects such as a user interface based on the contents or control commands of the processor 110. The memory 140 also stores control programs and various data used by the station 110. Such control programs include connection programs required for the station 100 to connect to an AP or an external station.

[0049] 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 described above 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 to an AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information on the priority conditions of the station 100 included in the communication setup message and requests a connection to the AP based on the information on the priority conditions of the station 100. The processor 110 of the present invention may refer to a main control unit of the station 100, or may refer to a control unit for individually controlling some components of the station 100, for example, the transceiver 120, depending on the embodiment. That is, the processor 110 is a modulation unit or demodulation unit (MPDUlator and / or deMPDUlator) that modulates a wireless signal transmitted and received from the transceiver 120. The processor 110 controls various operations of wireless signal transmission and reception of the station 100 according to an embodiment of the present invention. A specific embodiment of this will be described later.

[0050] The station 100 shown in FIG. 3 is a block diagram according to an embodiment of the present invention, and the separate blocks are used to logically distinguish the elements of the device. The above-mentioned device elements may be implemented in one chip or multiple chips depending on the design of the device. For example, the processor 110 and the transceiver 120 may be integrated and implemented in one chip, or may be implemented in separate chips. In addition, in an embodiment of the present invention, some components of the station 100, such as the user interface unit 140 and the display unit 150, may be selectively provided in the station 100.

[0051] FIG. 4 is a block diagram showing a configuration of an AP 200 according to an embodiment of the present invention.

[0052] As shown, an AP 200 according to an embodiment of the present invention includes a processor 210, a transceiver 220, and a memory 260. In Fig. 4, a duplicated description of parts of the configuration of the AP 200 that are the same as or correspond to the configuration of the station 100 in Fig. 3 will be omitted.

[0053] Referring to FIG. 4, the AP 200 according to the present invention includes a transceiver 220 for operating a BSS in at least one frequency band. As described in the embodiment of FIG. 3, the transceiver 220 of the AP 200 also includes a plurality of transceiver modules using different frequency bands. That is, the AP 200 according to the embodiment of the present invention includes two or more transceiver modules using different frequency bands, for example, 2.4 GHz, 5 GHz, and 60 GHz. Preferably, the AP 200 includes a transceiver module using a frequency band of 6 GHz or more and a transceiver module using a frequency band of 6 GHz or less. Each transceiver module performs wireless communication with a station according to the WLAN standard of the frequency band supported by the corresponding transceiver module. The transceiver 220 may operate only one transceiver module at a time or operate multiple transceiver modules simultaneously depending on the performance and requirements of the AP 200.

[0054] Next, the memory 260 stores control programs used by the AP 200 and various data associated therewith. Such control programs include a management program for managing station connections. Also, the processor 210 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 for one or more stations. At this time, the communication setup message includes information regarding connection priority conditions of each station. Also, the processor 210 performs connection setup in response to a connection request from a station. According to an embodiment, the processor 210 is a modulation unit or demodulation unit that modulates a wireless signal transmitted and received from the transceiver unit 220. The processor 210 controls various operations of 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.

[0055] FIG. 5 illustrates a process in which a STA establishes a link with an AP.

[0056] 5, the link between the STA 100 and the AP 200 is set up through three steps: scanning, authentication, and association. First, the scanning step is a step in which the STA 100 acquires access information of the BSS operated by the AP 200. There are two methods for performing scanning: a passive scanning method in which the AP 200 acquires information only by using a beacon message S101 periodically transmitted by the AP 200, and an active scanning method in which the STA 10 transmits a probe request to the AP S103, receives a probe response from the AP S105, and acquires access information.

[0057] The STA100 that successfully receives wireless access information in the scanning step transmits an authentication request (S107a), receives an authentication response from the AP 200, and performs an authentication step (S107b). After the authentication step is performed, the STA100 transmits an association request (S109a), receives an association response from the AP 200, and performs an association step (S109b). In this specification, association basically means wireless association, but the present invention is not limited to this, and association in a broad sense includes both wireless association and wired association.

[0058] Meanwhile, an 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are additionally performed. In FIG 5, the authentication server 300 is a server that processes 802.1X-based authentication with the STA 100, and may be physically connected to the AP 200 or may exist as a separate server.

[0059] In a specific embodiment, the AP (200) may be a wireless communication terminal that allocates communication medium resources and performs scheduling in an independent network that is not connected to an external distribution service, such as an ad-hoc network. The AP (200) may be at least one of a base station, an eNB, and a transmission point (TP). The AP (200) may be referred to as a base wireless communication terminal.

[0060] Also, the base wireless communication terminal may be a wireless communication terminal that allocates communication medium resources and performs scheduling in communication with a plurality of wireless communication terminals. Specifically, the base wireless communication terminal may perform a role of a cell coordinator. In a specific embodiment, the base wireless communication terminal may be a wireless communication terminal that allocates communication medium resources and performs scheduling in an independent network that is not connected to an external distribution service, such as an ad-hoc network.

[0061] The wireless communication terminal fragments traffic and transmits it. In this case, the traffic includes at least one of an MSDU (MAC service data unit), an A-MSDU, and an MMPDU (management protocol data unit). In particular, the wireless communication terminal fragments at least one of one MSDU, one A-MSDU, and one MMPDU and transmits it. For convenience of explanation, a portion of the MSDU, a portion of the A-MSDU, or a portion of the MMPDU refined through fragmentation is referred to as a fragmentation. In addition, a wireless communication terminal that transmits data is referred to as an originator, and a wireless communication terminal that receives data is referred to as a recipient.

[0062] In detail, 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 to a plurality of MPDUs. Also, 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.

[0063] A receiver is required to have sufficient buffer capacity and processing capability to defragment multiple fragments. To this end, a transmitter needs to know the defragmentation level that the receiver can support. In this case, the fragmentation level indicates a method of transmitting fragments. Thus, the wireless communication terminal signals the fragmentation level that the wireless communication terminal supports. The fragmentation level is divided into four levels. Level 0 indicates that the wireless communication terminal does not support fragmentation for the MSDU it receives. Also, level 1 indicates that the wireless communication terminal can receive an MPDU including one fragment. In this case, the MPDU is a single MPDU that is not aggregated with other MPDUs, or an MPDU that is not an A-MPDU. Furthermore, level 2 indicates that the wireless communication terminal can receive an A-MPDU including one fragment per MSDU. In particular, level 2 indicates that the wireless communication terminal can receive an A-MPDU including one or less fragments per MSDU. Level 3 indicates that the wireless communication terminal can receive an A-MPDU including multiple fragments per MSDU. In particular, level 3 indicates that the wireless communication terminal can receive A-MPDUs including up to four fragments per MSDU.

[0064] Also, wireless communication terminals acquire the right to use a wireless medium through a contention procedure or are granted permission. A time period during which a wireless communication terminal has the right to start a frame exchange sequence on a wireless medium is called a TXOP. A TXOP is defined by a start time and a maximum duration. Also, frames are exchanged in the form of an immediate response in a TXOP. In this case, an immediate response indicates that a response frame is transmitted at a pre-specified time interval. The pre-specified time is a Short Inter-Frame Space (SIFS). A wireless communication terminal that acquires a TXOP through a contention procedure or is granted a TXOP is called a TXOP holder. Also, a wireless communication terminal that transmits a frame in response to a frame transmitted from a TXOP holder in a frame exchange sequence is called a TXOP responder. In this case, the frame is a MAC frame and is used in the same sense as the above-mentioned MPDU. In order to prevent any one wireless communication terminal from monopolizing the wireless medium for a long time, a maximum value of a TXOP duration is defined. The maximum value of the TXOP duration is called the TXOP limit, which is defined for each Enhanced Distributed Channel Access Function (EDCAF).

[0065] Regarding the fragmentation operation of a wireless communication terminal, the TXOP limit can be a problem, which will be explained with reference to FIGS.

[0066] FIG. 6 is a diagram illustrating an operation of a wireless communication terminal performing frame exchange based on a TXOP limit according to an embodiment of the present invention.

[0067] The wireless communication terminal receives an EDCA parameter set from the base wireless communication terminal. In this case, the wireless communication terminal sets a management information base (MIB) attribute based on the received EDCA parameter set. The wireless communication terminal exchanges data in frames within a duration equal to or smaller than the TXOP limit. In this case, the TXOP limit is set for each EDCAF. If the TXOP limit corresponding to the EDCAF of the traffic to be transmitted by the wireless communication terminal is 0, the wireless communication terminal transmits only one MPDU regardless of the duration of the MPDU. In this case, one MPDU indicates one A-MPDU. If the TXOP limit corresponding to the EDCAF of the traffic to be transmitted by the wireless communication terminal is not 0, the wireless communication terminal is restricted to transmitting data or a management frame within the TXOP limit. In more detail, if it is determined that the wireless communication terminal exceeds the TXOP limit due to the duration of the data exchange sequence, the wireless communication terminal fragments the data and transmits the fragments. In this case, the data indicates the MSDU, which is the payload of the MAC frame. In certain cases, the wireless communication terminal cannot fragment the data. In a specific situation, the wireless communication terminal exceeds the TXOP limit. The specific situation is a case where the wireless communication terminal transmits one data (MSDU) or MMPDU. In addition, the specific situation does not include a case where the wireless communication terminal aggregates and transmits two or more MPDUs. FIG. 6(a) shows that the wireless communication terminal fragments the MSDU and transmits the fragments within the TXOP limit. In addition, when the wireless communication terminal attempts to transmit an A-MSDU, if it is determined that the TXOP limit will be exceeded due to the transmission of the A-MSDU, the wireless communication terminal cancels the aggregation of the A-MSDU. Therefore, when the wireless communication terminal attempts to transmit an A-MSDU, the wireless communication terminal cannot exceed the TXOP limit.

[0068] A wireless communication terminal exceeds the TXOP limit if at least one of the following circumstances exists:

[0069] 1) When a wireless communication terminal transmits an MSDU corresponding to a TID with a Block ACK agreement, the wireless communication terminal transmits the MSDU using a TXOP that exceeds the TXOP limit. In this case, the Block ACK agreement indicates an agreement on a method of transmitting a Block ACK frame. In this specification, a frame is used to refer to a MAC frame. Figure 6(b) shows an operation of transmitting an MSDU using a TXOP that exceeds the TXOP limit when a wireless communication terminal transmits an MSDU corresponding to a TID with a Block ACK agreement.

[0070] 2) If the wireless communication terminal further transmits a previously transmitted MPDU, the wireless communication terminal transmits the MPDU using a TXOP that exceeds the TXOP limit. In this case, the wireless communication terminal transmits the same MPDU as the previously transmitted MPDU. This is because if a receiver receives an MPDU having the same sequence number and fragment number as a previously received MPDU, the receiver may discard the previously received MPDU. In the embodiment of FIG. 6(c), the wireless communication terminal attempts to transmit an MPDU using MCS3 (Modulation & Coding Scheme 3). The wireless communication terminal fails to transmit the MPDU and retransmits the same MPDU using MCS2. In this case, the wireless communication terminal retransmits the same MPDU exceeding the TXOP limit.

[0071] 3) The wireless communication terminal fragments the MSDU, MMPDU, or A-MSDU such that all fragments except the last fragment have the same size and the last fragment is smaller than the other fragments. According to this rule, when the wireless communication terminal generates fragments as many as the maximum number of fragments, the wireless communication terminal transmits the fragments using a TXOP that exceeds the TXOP limit. In this case, the maximum number of fragments is 16. In more detail, when the wireless communication terminal generates fragments as many as the maximum number of fragments at the time when the wireless communication terminal attempts to transmit the first fragment, the wireless communication terminal transmits the fragments using a TXOP that exceeds the TXOP limit regardless of the fragment number of the fragment to be transmitted. This is because the wireless communication terminal generates fragments as many as the maximum number of fragments allowed, but the transmission of the fragments exceeds the TXOP limit. In the embodiment of FIG. 6(d), the wireless communication terminal fragments the MSDU or MMPDU to generate 16 fragments. In this case, 16 is the maximum number of fragments allowed. Therefore, the wireless communication terminal transmits the fragments in excess of the TXOP limit.

[0072] 4) If the wireless communication terminal first transmits a fragment that corresponds to the MSDU or MMPDU of a fragment that was previously retransmitted, the wireless communication terminal transmits the fragment using a TXOP that exceeds the TXOP limit. In the embodiment of FIG. 6(e), the wireless communication terminal attempts to transmit the first fragment (FN:0) using MCS3. The wireless communication terminal fails to transmit the fragment and retransmits the first fragment (FN:0) using MCS2. At this time, the wireless communication terminal retransmits the first fragment (FN:0) using a TXOP that exceeds the TXOP limit. Also, after the wireless communication terminal retransmits the first fragment (FN:0), the wireless communication terminal transmits the first fragment (FN:0) and the second fragment (FN:1), which is a fragment of the corresponding MSDU or MMPDU, using a TXOP that exceeds the TXOP limit. In this case, the second fragment (FN:1) is the first fragment to be transmitted after the first fragment (FN:0) is transmitted among the fragments of the corresponding MSDU or MMPDU.

[0073] 5) If the wireless communication terminal cannot fragment the MSDU or MMPDU, the wireless communication terminal transmits the MSDU or MMPDU using a TXOP that exceeds the TXOP limit. In particular, the wireless communication terminal cannot fragment an MMPDU that has a group address. In addition, the wireless communication terminal cannot fragment a control frame. In the embodiment of FIG. 6(f), the wireless communication terminal cannot fragment the MSDU or MMPDU. Therefore, the wireless communication terminal transmits the MSDU or MMPDU using a TXOP that exceeds the TXOP limit.

[0074] In the above description, the wireless communication terminal is a TXOP holder, and the wireless communication terminal exceeds the TXOP limit, which means that the wireless communication terminal transmits using a TXOP that exceeds the TXOP limit.

[0075] FIG. 7 is a diagram illustrating dynamic fragmentation performed by a wireless communication terminal according to an embodiment of the present invention.

[0076] The wireless communication terminal performs not only static fragmentation but also dynamic fragmentation. Static fragmentation refers to a wireless communication terminal generating fragments such that all fragments except the last fragment have the same size and the size of the last fragment is smaller than the sizes of the different fragments. Static fragments refer to fragments generated by static fragmentation. Dynamic fragmentation refers to fragmentation in which the wireless communication terminal is not required to have each fragment have the same size. In particular, in dynamic fragmentation, the wireless communication terminal is not required to fragment all fragments except the last fragment to have the same size. Dynamic fragments refer to fragments generated by dynamic fragmentation.

[0077] In dynamic fragmentation, the wireless communication terminal operates according to at least one of the following principles: 1) The wireless communication terminal signals whether it supports dynamic fragmentation. 2) The wireless communication terminal should transmit the first fragment that is larger than or equal to the initial size signaled by the receiver. 3) The wireless communication terminal sets the fragmentation level for each TID via the ADDBA extension element during the Block ACK agreement process. 4) The wireless communication terminal fragments the A-MSDU. 5) If the fragmentation level is level 2 or level 3, the wireless communication terminal transmits one fragment of the MMPDU per A-MPDU. If the fragmentation level is level 1, the wireless communication terminal transmits the fragment of the MMPDU using a single MPDU (Single-MPDU, S-MPDU).

[0078] The wireless communication terminal determines a fragmentation level for traffic to be transmitted through a BLOCKACK agreement with a receiver, and fragments the traffic to be transmitted according to the determined fragmentation. If there is no BLOCKACK agreement with a receiver for traffic to be transmitted, the wireless communication terminal performs dynamic fragmentation according to a fragmentation level determined based on the receiver's capability. At this time, the wireless communication terminal determines the receiver's capability based on a Capabilities Information field transmitted by the receiver. In a specific embodiment, if there is no BLOCKACK agreement but the value of the receiver's Capabilities Information field is a pre-specified value, the wireless communication terminal transmits to the receiver an MMPDU or MSDU fragmented according to fragmentation level 1. At this time, the pre-specified value is 1. Also, if there is no BLOCKACK agreement but the value of the receiver's Capabilities Information field is a pre-specified value, the wireless communication terminal transmits to the receiver an MMPDU or MSDU fragmented according to fragmentation level 1 or level 2. At this time, the pre-specified value is 2. In a specific embodiment, if there is no BLOCKACK agreement but the value of the receiver's Capabilities Information field is a pre-specified value, the wireless communication terminal transmits to the receiver an MMPDU or MSDU fragmented according to fragmentation level 1 or level 3. In this case, the pre-specified value is 3. In the embodiment of FIG. 7, there is no BLOCKACK agreement between the transmitter and the receiver. In this case, the transmitter determines the fragmentation level to be level 1 based on the Capabilities Information field value transmitted by the receiver. The transmitter generates three dynamic fragments according to fragmentation level level 1. In such an embodiment, the wireless communication terminal transmits the sequence and fragments in the order of the sequence number and the fragment number.In this case, if the wireless communication terminal receives a fragment of a specific sequence before a fragment having a fragment number smaller than the fragment number of the specific fragment that includes the fragment in the same sequence, the wireless communication terminal deletes all MPDUs including the fragment of the specific sequence from the cache. Also, if the wireless communication terminal receives a specific sequence before a sequence having a sequence number smaller than the sequence number of the specific sequence, the wireless communication terminal deletes all MPDUs including the specific sequence from the cache.

[0079] Also includes a case where the wireless communication terminal transmits an MMPDU if there is no BLOCKACK agreement with a receiver regarding traffic that the wireless communication terminal intends to transmit. Also includes a case where the wireless communication terminal transmits an MPDU corresponding to a TID designated as QoS No Ack if there is no BLOCKACK agreement with a receiver regarding traffic that the wireless communication terminal intends to transmit. Since retransmission is not requested for an MPDU corresponding to a QoS No Ack, the wireless communication terminal does not apply the exceptional operation of the TXOP limit to an MPDU corresponding to a QoS No Ack.

[0080] Once the sender and receiver have negotiated dynamic fragmentation for one or more TIDs, the sender fragments traffic to be transmitted to the receiver according to the highest fragmentation level of the signaled TID among the one or more TIDs. The sender and receiver negotiate dynamic fragmentation using the ADDBA extension, and the receiver signals the fragmentation level for each TID using the ADDBA response.

[0081] In this way, if the wireless communication terminal uses dynamic fragmentation, it is possible to generate fragments more flexibly than when the wireless communication terminal uses static fragmentation. If the wireless communication terminal uses static fragmentation, even in a situation where the TXOP limit cannot be observed, the wireless communication terminal can use dynamic fragmentation to observe the TXOP limit. Also, if the wireless communication terminal uses dynamic fragmentation, there is a risk that the wireless communication terminal may transmit while harming fairness with other wireless communication terminals in an exceptional situation with respect to the TXOP limit. Therefore, it is necessary to newly define the operation related to the TXOP limit of the wireless communication terminal.

[0082] With regard to retransmission by a wireless communication terminal, a case where the wireless communication terminal retransmits using a TXOP that exceeds the TXOP limit will be described with reference to Figures 8 to 11. In this specification, the wireless communication terminal exceeds the TXOP limit refers to performing a data exchange sequence from the start point of the corresponding TXOP to beyond the maximum duration indicated by the TXOP limit.

[0083] FIG. 8 illustrates an operation of a wireless communication terminal determining whether a receiver has failed to receive a signal and an operation of retransmission according to an embodiment of the present invention.

[0084] When the wireless communication terminal according to the embodiment of the present invention transmits a frame indicating whether data can be received, such as an ACK reply frame, a C (Compressed)-BA frame, or an M (Multi-Station)-BA frame, using the A-MPDU, the wireless communication terminal inserts the frame indicating whether data can be received into the first MPDU of the A-MPDU. This re-reception indicates that the wireless communication terminal has successfully received traffic. Successful reception of traffic indicates that traffic received by the wireless communication terminal has passed verification using a Frame Check Sequence (FCD) field. Also, in this specification, successful transmission indicates that traffic transmitted by the wireless communication terminal has passed verification by the receiver using an FCS field. Therefore, the wireless communication terminal according to the present invention determines whether the receiver has successfully received traffic based on whether the A-MPDU received by the wireless communication terminal includes a frame indicating whether data can be received at a pre-specified position. In particular, if the A-MPDU received by the wireless communication terminal does not include a frame indicating whether data can be received at a pre-specified position, the wireless communication terminal determines that the receiver has failed to receive traffic previously transmitted by the wireless communication terminal. In addition, the wireless communication terminal according to the embodiment of the present invention determines whether the receiver has failed to receive traffic previously transmitted by the wireless communication terminal based on a BA bitmap field included in a frame indicating reception availability. In particular, if each bit of the BA bitmap field of the BA frame received by the wireless communication terminal indicates 0, the wireless communication terminal determines that the transmission of the traffic corresponding to the bit has failed. In this case, the BA frame is any one of an M-BA frame, a C-BA frame, and a general BA frame.

[0085] In the embodiment of Fig. 8, the access point transmits a trigger frame to trigger an upstream transmission of the first station. The first station receives the trigger frame and transmits a trigger-based PPDU (HE TB PPDU) based on the trigger frame. At this time, the access point fails to receive one MPDU (SN:2) included in the trigger-based PPDU. The access point transmits a multi-user PPDU (HE MU PPDU) including a BA frame indicating whether the MPDU received from the first station can be received.

[0086] A wireless communication terminal according to an embodiment of the present invention distinguishes between a receiver's ACK frame transmission failure and a wireless communication terminal's transmission failure through the following embodiment. If the wireless communication terminal retransmits traffic with an MCS lower than the MCS previously used, the wireless communication terminal fragments the failed traffic and transmits fragments having a changed size. Thereby, the wireless communication terminal can retransmit traffic without exceeding the TXOP limit. This will be described with reference to FIG. 9.

[0087] 9 and 10 are diagrams illustrating a retransmission operation within the TXOP limit by a wireless communication terminal according to an embodiment of the present invention.

[0088] When the wireless communication terminal retransmits a fragment, the wireless communication terminal performs different retransmission operations depending on whether the receiver has successfully received a fragment having a fragment number higher than the fragment number of the fragment that the receiver failed to receive in a sequence including the fragment that the receiver failed to receive. For convenience of explanation, the fragment that the receiver failed to receive is referred to as a failed fragment. Also, a fragment having a fragment number higher than the fragment number of the fragment is referred to as a following fragment following the failed fragment. If the wireless communication terminal does not know that it has received an ACK for the fragment following the failed fragment or that the receiver has received a fragment following the failed fragment, the wireless communication terminal cannot generate a fragment having a size different from the size of the failed fragment for retransmission. In this case, the wireless communication terminal further transmits a fragment having the same size as the failed fragment. Also, the wireless communication terminal transmits a fragment having the same size as the failed fragment within the TXOP limit.

[0089] Based on at least one of the following: the wireless communication terminal did not transmit a fragment succeeding the failed fragment, and the receiver explicitly failed to receive the fragment succeeding the failed fragment, the wireless communication terminal generates a fragment having a size different from the size of the failed fragment for retransmission. In this case, the wireless communication terminal retransmits the fragment having a size different from the size of the failed fragment instead of retransmitting the failed fragment. In particular, if the wireless communication terminal did not transmit a fragment succeeding the failed fragment or the receiver explicitly failed to receive the fragment succeeding the failed fragment, the wireless communication terminal generates a fragment having a size different from the size of the failed fragment for retransmission. In a specific embodiment, the wireless communication terminal further fragments the failed fragment. Also, the wireless communication terminal assigns the same sequence number and fragment number as the failed fragment to the fragment having a size different from the size of the failed fragment. Also, the wireless communication terminal transmits the fragment having a size different from the size of the failed fragment using a TXOP exceeding the TXOP limit instead of retransmitting the failed fragment.

[0090] In the embodiment of FIG. 9, the wireless communication terminal transmits a fragment with a fragment number of 0 to MCS3. The wireless communication terminal determines that the receiver explicitly fails to receive the fragment with fragment number 0. Therefore, the fragment with fragment number 0 is a failed fragment. In the same sequence, no fragment with a fragment number larger than the failed fragment has been transmitted. Therefore, the wireless communication terminal generates a fragment with a size smaller than the failed fragment for retransmission and assigns fragment number 0 to the generated fragment. Instead of transmitting the same fragment as the previously transmitted fragment, the wireless communication terminal transmits the generated fragment to MCS2. At this time, the wireless communication terminal transmits the generated fragment within the TXOP limit.

[0091] In addition, the receiver may fail to receive multiple fragments that are included in the same sequence and have consecutive fragmentation numbers. In this case, the wireless communication terminal generates a fragment for retransmission that has a size different from at least one of the multiple failed fragments, regardless of whether the receiver successfully receives a fragment that follows the multiple failed fragments. In particular, the wireless communication terminal changes the size of the failed fragment, regardless of whether the receiver successfully receives a fragment that follows the multiple failed fragments.

[0092] In the embodiment of FIG. 10, the access point transmits a trigger frame to trigger an upward transmission of the first wireless communication terminal. The first station receives the trigger frame and transmits a trigger-based PPDU (HE TB PPDU) based on the trigger frame. At this time, the trigger-based PPDU includes an A-MPDU including three fragments included in the same sequence and having fragment numbers 1, 2, and 3, respectively. The access point receives the trigger-based PPDU (HE TB PPDU) from the first station. At this time, the access point fails to receive a fragment having a fragment number of 0 and a fragment having a fragment number of 1. The access point transmits a multi-user PPDU including an M-BA frame that explicitly indicates that it fails to receive a fragment having a fragment number of 0 and a fragment having a fragment number of 1. Since the transmission of two fragments having consecutive fragment numbers has failed, the first station generates a fragment having a different size from the failed fragment for retransmission and assigns fragment number 0 to the generated fragment. The wireless communication terminal transmits the generated fragment within the TXOP limit.

[0093] FIG. 11 is a diagram illustrating an operation of a wireless communication terminal retransmitting fragments included in the same sequence as a retransmitted fragment within a TXOP limit after retransmission according to another embodiment of the present invention.

[0094] As described above, when the wireless communication terminal transmits a fragment corresponding to the MSDU or MMPDU of a retransmitted fragment for the first time after the retransmission, the wireless communication terminal transmits the fragment using a TXOP that exceeds the TXOP limit. This is because if the wireless communication terminal fails in a previous transmission and retransmits with a lowered MCS, there is a high possibility that the lowered MCS will be maintained even in the transmission after the retransmission. If the wireless communication terminal uses dynamic fragmentation, the wireless communication terminal adjusts the size of the fragment to be transmitted after the retransmission. Therefore, if the wireless communication terminal uses dynamic fragmentation, even if the wireless communication terminal transmits a fragment corresponding to the MSDU or MMPDU of a previously retransmitted fragment for the first time after the retransmission, the wireless communication terminal is not allowed to transmit the fragment using a TXOP that exceeds the TXOP limit. In more detail, if the wireless communication terminal uses dynamic fragmentation, even if the wireless communication terminal transmits a fragment corresponding to the MSDU or MMPDU of a previously retransmitted fragment for the first time after the retransmission, the wireless communication terminal can transmit the corresponding fragment only within the TXOP limit.

[0095] In the embodiment of FIG. 11, the wireless communication terminal transmits a fragment with a fragment number of 0 to MCS3. The receiver fails a fragment with a fragment number of 0. No fragment with a fragment number greater than 0 has been transmitted in the same sequence. Therefore, the wireless communication terminal generates a further fragment with a size smaller than the fragment whose transmission failed, and assigns fragment number 0 to the generated fragment. The wireless communication terminal transmits the corresponding fragment to MCS2 within the TXOP limit. The wireless communication terminal also generates a fragment of the same sequence as the fragment whose transmission failed, and assigns fragment number 1 to the generated fragment. The wireless communication terminal transmits for the first time after the retransmission, but because dynamic fragmentation is used, the wireless communication terminal transmits a fragment with a fragmentation number of 1 within the TXOP limit.

[0096] 12 and 13 are diagrams illustrating a transmission operation in which a wireless communication terminal exceeds a TXOP limit when dynamic fragmentation is used according to an embodiment of the present invention.

[0097] If the wireless communication terminal generates the maximum number of fragments that can be generated by dynamic fragmentation, the wireless communication terminal transmits the last fragment of the generated fragments using a TXOP that exceeds the TXOP limit. Also, the maximum number of fragments that the wireless communication terminal can generate by dynamic fragmentation is 16. Therefore, the wireless communication terminal transmits the 16th fragment of the traffic using a TXOP that exceeds the TXOP limit. Also, the traffic is MSDU, MMPDU, or A-MSDU as described above. In a specific embodiment, the wireless communication terminal determines the fragmentation level to level 1 or level 2, and fragments the MSDU, MMPDU, or A-MSDU according to the determined fragmentation level. Also, the wireless communication terminal is a TXOP holder. Also, if the wireless communication terminal transmits a trigger-based PPDU based on a trigger frame, it fragments and transmits the A-MSDU. In this case, the wireless communication terminal is not a TXOP holder. Therefore, even in this case, the wireless communication terminal transmits the last fragment of the fragments generated using a TXOP that exceeds the TXOP limit.

[0098] In the embodiment of Fig. 12, the wireless communication terminal generates fragments for dynamically fragmenting traffic and transmits the generated fragments. In this case, the wireless communication terminal generates 16 fragments, which is the maximum number of fragments that the wireless communication terminal can generate. The wireless communication terminal transmits the 16th fragment to be transmitted using a TXOP that exceeds the TXOP limit.

[0099] As described above, when the wireless communication terminal generates the first dynamic fragment in dynamic fragmentation, the wireless communication terminal is requested to generate a dynamic fragment having a size equal to or larger than the initial size designated by the receiver. In this case, the initial dynamic fragment indicates a dynamic fragment generated first. Therefore, when the wireless communication terminal generates the first dynamic fragment based on a value designated by the receiver as the initial size of the fragment, the wireless communication terminal transmits the first dynamic fragment using a TXOP exceeding the TXOP limit. In detail, when the wireless communication terminal generates the first dynamic fragment based on a value designated by the receiver as the initial size of the fragment and transmits the first dynamic fragment without using an A-MPDU including multiple MPDUs, the wireless communication terminal transmits the first dynamic fragment using a TXOP exceeding the TXOP limit. When the wireless communication terminal transmits the first dynamic fragment without using an A-MPDU including multiple MPDUs, this indicates a case of transmitting a fragment using a single MPDU. In addition, the wireless communication terminal is restricted from generating a first dynamic fragment having a size equal to the value designated by the receiver as the initial size of the fragment. This is because if the wireless communication terminal generates an excessively large dynamic fragment, fairness with other wireless communication terminals may be an issue.

[0100] In the embodiment of FIG. 13, the wireless communication terminal generates a plurality of fragments by dynamic fragmentation of traffic. In this case, the wireless communication terminal generates the first fragment (FN:0) with the size of the first fragment size specified by the receiver. The wireless communication terminal transmits the corresponding fragment to the receiver using a TXOP that exceeds the TXOP limit. Next, the wireless communication terminal retransmits the second and third transmitted fragments (FN:1, FN:2) within the TXOP limit.

[0101] In addition, in a specific embodiment, if the wireless communication terminal transmits the first fragment of the A-MSDU, the embodiment for the exception to the TXOP limit compliance described in FIG. 13 does not apply because there is a high possibility that the wireless communication terminal disassembles the A-MSDU.

[0102] The embodiments described with reference to Figures 5 to 13 are applied to the transmission operation of a TXOP holder. A wireless communication terminal that is not a TXOP holder may also transmit data. In particular, if a wireless communication terminal participates in an Uplink (UL) Multi-User (MU) transmission, a wireless communication terminal that is not a TXOP holder also transmits data. In this way, if a transmitter that is not a TXOP holder transmits data, an operation regarding the transmitter's TXOP limit becomes an issue. This will be described with reference to Figures 14 to 16.

[0103] FIG. 14 is a diagram illustrating a retransmission operation of a wireless communication terminal that is not a TXOP holder according to an embodiment of the present invention.

[0104] If a wireless communication terminal participates in UL MU transmission, the wireless communication terminal can transmit data even if it is not a TXOP holder. In this case, the wireless communication terminal sets a TXOP limit different from that of the base wireless communication terminal which is the TXOP holder. Therefore, the wireless communication terminal may use a TXOP much larger than the TXOP limit used in single user (SU) transmission to improve the efficiency of UL MU transmission. If the wireless communication terminal performs an upward transmission using a TXOP much larger than the TXOP limit used in SU transmission, the base wireless communication terminal may not be able to successfully receive the data transmitted through the upward transmission. In this case, the wireless communication terminal attempts retransmission again using a very large TXOP. Therefore, if the wireless communication terminal is allowed to perform retransmission using a TXOP that exceeds the TXOP limit when performing retransmission, fairness with other wireless communication terminals may be impaired. In order to prevent this, if the wireless communication terminal attempts retransmission due to a failure in UL MU transmission, the wireless communication terminal may perform retransmission only using UL MU transmission.

[0105] In the embodiment of Figure 14, a wireless communication terminal that is not a TXOP holder transmits one fragment (FN:0) to a base wireless communication terminal via UL MU transmission. The base wireless communication terminal transmits an M-BA frame (M-BA) indicating that the transmission of one fragment (FN:0) to the wireless communication terminal was unsuccessful. The wireless communication terminal receives the M-BA frame from the base wireless communication terminal. The wireless communication terminal fails to transmit the MU. Therefore, the wireless communication terminal retransmits another fragment (FN:1) other than the fragment (FN:0) that failed to be transmitted via SU transmission.

[0106] The embodiment described with reference to Fig. 14 can also be applied to transmissions other than UL MU transmission. This is because a wireless communication terminal that is not a TXOP holder may transmit data other than UL MU transmission. In particular, if the base wireless communication terminal and the wireless communication terminal use a reverse direction method of 1:1 transmission, the wireless communication terminal that is not a TXOP holder transmits data. This will be described with reference to Figs. 15 and 16.

[0107] 15 and 16 are diagrams illustrating a retransmission operation of a wireless communication terminal that is not a TXOP holder according to another embodiment of the present invention.

[0108] The retransmission of the MPDU transmitted in the UL MU transmission and the retransmission of the MPDU transmitted in the reverse transmission have a very small impact on the management of the TXOP. Therefore, if the retransmission is a retransmission for a transmission failure using the trigger-based PPDU, the wireless communication terminal can only perform the retransmission using the trigger-based PPDU.

[0109] In the embodiment of Figure 15, a wireless communication terminal that is not a TXOP holder transmits one fragment (FN:0) to a base wireless communication terminal via UL MU transmission. The base wireless communication terminal transmits an M-BA frame (M-BA) indicating that the transmission of one fragment (FN:0) to the wireless communication terminal was unsuccessful. The wireless communication terminal receives the M-BA frame from the base wireless communication terminal. The wireless communication terminal fails to transmit using the trigger-based PPDU. Therefore, the wireless communication terminal transmits another fragment (FN:1) other than the fragment (FN:0) that was unsuccessfully transmitted, via SU transmission.

[0110] According to the embodiment described through FIG. 14 and FIG. 15, the wireless communication terminal cannot retransmit all MPDUs transmitted to the UL MU using SU transmission. If the wireless communication terminal attempts retransmission due to failure of transmission using a trigger-based PPDU, and the duration of a transmission sequence required for the wireless communication terminal's retransmission does not exceed the TXOP limit, the wireless communication terminal performs the corresponding retransmission using SU transmission. At this time, the transmission sequence required for retransmission includes a certain time interval between retransmission and a response transmission to the retransmission, and a time required to receive the response to the retransmission. In particular, the response to the retransmission is an immediate response transmitted within a certain time from the reception of a frame to be responded to. Also, the certain time interval between retransmission and a response transmission to the retransmission is SIFS. The response to the retransmission is an ACK frame. At this time, the required time of the retransmission sequence is calculated based on the MCS used in the UL MU transmission. Also, the required time of the retransmission sequence is calculated based on a specific frequency bandwidth. At this time, the specific frequency bandwidth is the maximum frequency bandwidth allowed for SU transmission in a BSS including the wireless communication terminal. The specific frequency bandwidth is 20 MHz. The specific frequency bandwidth is the frequency bandwidth obtained by rounding up the size of the RU (Resource Unit) used during UL MU transmission to a multiple of 20 MHz.

[0111] In the embodiment of FIG. 16, a wireless communication terminal that is not a TXOP holder transmits one fragment (FN:0) to a base wireless communication terminal via UL MU transmission. The base wireless communication terminal transmits an M-BA frame (M-BA) indicating that the transmission of one fragment (FN:0) was unsuccessful to the wireless communication terminal. The wireless communication terminal receives the M-BA frame from the base wireless communication terminal. The wireless communication terminal fails in the MU transmission. The wireless communication terminal calculates the required time of the transmission sequence required to retransmit one fragment (FN:0). The time required for the transmission sequence calculated by the wireless communication terminal exceeds the TXOP limit. Therefore, the wireless communication terminal transmits another fragment (FN:1) other than the fragment (FN:0) that failed to be transmitted via SU transmission.

[0112] In order for a wireless communication terminal to perform MIMO or beamforming, it is necessary to receive the channel state from a receiver. A wireless communication terminal that is to perform MIMO or beamforming receives the channel state through the following sounding protocol sequence. For convenience of explanation, a wireless communication terminal that is to perform MIMO or beamforming transmission is called a beamformer, and a wireless communication terminal that is to perform MIMO or beamforming reception is called a beamformee. The beamformer transmits an NDPA frame to notify that a sounding protocol sequence has started. At this time, the NDPA frame includes information about the beamformee, which is a wireless communication terminal that measures the channel state. The beamformer transmits an NDP frame that is used to measure the channel state but does not include a data field. At this time, the beamformer transmits an NDP frame after a pre-specified time from the time of transmitting the NDPA frame. At this time, the pre-specified time is SIFS. The beamformee measures the channel state based on the NDP frame. The beamformee transmits a feedback frame indicating the measured channel state to the wireless communication terminal that transmitted the NDP frame. In this case, the feedback frame is a compressed feedback frame including a field that is more compressed than a general feedback frame. Since the size of the feedback frame may be very large, the beamformee needs to occupy the wireless medium for a long time. Therefore, if a very small TXOP limit is set for the AC in which the beamformer attempts to transmit a frame that starts the sounding sequence, the sounding protocol sequence may not be completed within the TXOP limit. Therefore, since the sounding protocol sequence is an essential operation in MIMO and beamforming transmission, an exception to the TXOP limit is allowed. However, if the exception to the TXOP limit is widely applied in the sounding protocol sequence, fairness with other wireless communication terminals may become an issue.Therefore, in the sounding protocol sequence, the wireless communication terminal operation regarding the TXOP limit becomes an issue.

[0113] 17 and 18 are diagrams illustrating a wireless communication terminal according to an embodiment of the present invention performing a sounding protocol operation regarding a TXOP limit.

[0114] The beamformer transmits the NDPA frame and the NDP frame using a TXOP that exceeds the TXOP limit. More specifically, if the NDP frame is transmitted within the TXOP limit, the beamformer transmits the NDPA frame and the NDP frame using a TXOP that exceeds the TXOP limit. Also, the beamformer receives a feedback frame as a response to the NDPA frame from the beamformee in a TXOP that exceeds the TXOP limit. The interval between the transmission of the NDPA frame and the transmission of the NDP frame is SIFS. Also, the time interval between the NDP frame and the feedback frame is SIFS. More specifically, the beamformee transmits the feedback frame SIFS after receiving the NDP frame.

[0115] Also, if the feedback frame exceeds the maximum A-MPDU length, the beamformee divides the feedback frame into multiple segments before transmitting it. At this time, the beamformer transmits a beamforming report poll (BRP) frame to the beamformee to request a subsequent segment for the previously transmitted feedback frame. At this time, the beamformer transmits the BRP frame using a TXOP that exceeds the TXOP limit. More specifically, if the beamformer transmits the BRP frame within the TXOP limit, the beamformer transmits the BRP frame using a TXOP that exceeds the TXOP limit. Also, the beamformer receives a feedback frame from the beamformee within a TXOP that exceeds the TXOP limit. The time interval between the BRP frame and the feedback frame is SIFS. More specifically, the beamformee transmits the feedback frame after SIFS from the time when it receives the BRP frame.

[0116] In the embodiment of FIG. 17, the beamformer transmits an NDPA frame (HE NDPA) and an NDP frame (HE NDP) within the TXOP limit. Since the beamformer transmits an NDPA frame (HE NDPA) and an NDP frame (HE NDP) within the TXOP limit, the beamformer transmits an NDPA frame (HE NDPA) and an NDP frame (HE NDP) using a TXOP that exceeds the TXOP limit. In particular, the beamformer receives a feedback frame (SU Compressed Feedback) within a TXOP that exceeds the TXOP limit. The beamformee transmits the feedback frame SIFS after receiving the NDP frame (HE NDP).

[0117] Also, the beamformer transmits a BRP trigger frame to request feedback frames from multiple beamformees. More specifically, the beamformer transmits an NDPA frame instructing multiple beamformees. At this time, the NDPA frame includes multiple user info fields supporting multiple beamformees, respectively. Also, the receiver address (Receiver Address, RA) of the NDPA frame is a broadcast address. After a pre-specified time from when the beamformer transmits the NDPA frame, the beamformer transmits an NDP frame. After transmitting the NDP frame, the beamformer transmits a BRP trigger frame. At this time, the pre-specified time is SIFS. The beamformer transmits a BRP trigger frame after a pre-specified time from when the beamformer transmits the NDPA frame. At this time, the pre-specified time is SIFS. Multiple beamformees receive the BRP trigger frame and simultaneously transmit feedback frames after a pre-specified time from when the BRP trigger frame is received. At this time, the pre-specified time is SIFS. Also, multiple beamformees simultaneously transmit feedback frames using orthogonal frequency multiple access (OFDMA). If the TXOP limit is applied without exception when the beamformer transmits the BRP trigger frame, it may be difficult for the beamformer to trigger the transmission of the feedback frame of the beamformee. Therefore, the beamformer should perform a sounding protocol sequence for each beamformee individually. Regarding this problem, the wireless communication terminal operates according to the following specific embodiment.

[0118] The beamformer transmits the BRP trigger frame using a TXOP that exceeds the TXOP limit. In a specific embodiment, the beamformer transmits the NDPA frame, the NDP frame, and the BRP trigger frame using a TXOP that exceeds the TXOP limit. In this case, if the beamformer transmits the NDPA frame, the NDP frame, and the BRP trigger frame within the TXOP limit, the beamformer transmits the NDPA frame, the NDP frame, and the BRP trigger frame using a TXOP that exceeds the TXOP limit. As described above, the transmission interval between the NDPA frame, the NDP frame, and the BRP trigger frame is SIFS. In addition, the time interval between the BRP trigger frame and the feedback frame is SIFS. In particular, the beamformee transmits the feedback frame SIFS after receiving the BRP trigger frame.

[0119] If the beamformer uses the BRP trigger frame to trigger the transmission of feedback frames of many beamformees, fairness with the conventional sounding protocol sequence may become an issue. In consideration of fairness with the conventional sounding protocol sequence, the wireless communication terminal operates according to the following specific embodiment.

[0120] In another specific embodiment, even if the beamformer uses the NDPA frame to indicate multiple beamformees, the beamformer triggers the transmission of feedback frames of a specific number of beamformees in the BRP trigger frame. In this case, the specific number is 1. Also, the specific number is set based on the TXOP limit. Also, the BRP trigger frame includes a pre-specified number of user info fields. Thus, the beamformer receives feedback frames from a pre-specified number of beamformees. In the TXOP following the TXOP in which the first BRP trigger frame is transmitted, the beamformer further transmits a BRP trigger frame to trigger the transmission of feedback frames of a specific number of beamformees among the remaining beamformees other than the beamformees previously specified by the BRP trigger frame among the multiple beamformees specified by the NDPA frame. In this case, the BRP trigger frame includes a user info field indicating each of a specific number of beamformees among the remaining beamformees other than the beamformees previously specified by the BRP trigger frame among the multiple beamformees specified by the NDPA frame. In addition, in the next TXOP after the TXOP that transmitted the first BRP trigger frame, the beamformer may not further transmit an NDPA frame and an NDP frame. In addition, if the beamformer transmits the BRP trigger frame within the TXOP limit in the next TXOP after the TXOP that transmitted the first BRP trigger frame, the beamformer transmits the BRP trigger frame using a TXOP that exceeds the TXOP limit. In more detail, the beamformee transmits a feedback frame after SIFS from the time when it receives the BRP trigger frame.

[0121] Also, in the above embodiment, the beamformee uses a trigger-based PPDU to transmit a feedback frame in response to the BRP trigger frame.

[0122] In the embodiment of FIG. 18, the beamformer transmits an NDPA frame (HE NDPA) and an NDP frame (HE NDP) within the TXOP limit. At this time, the NDPA frame (HE NDPA) has multiple beamformees. In addition, the beamformer transmits a first BRP trigger frame (Beamforming Report Poll trigger variant) after SIFS from the time of transmitting the NDP frame (NE NDP). At this time, the BRP trigger frame indicates one beamformee. The beamformer receives a trigger-based PPDU (HE TP PPDU compressed feedback) including a feedback frame from one beamformee. At this time, the trigger-based PPDU including the feedback frame is transmitted SIFS from the time the beamformee receives the first BRP and the trigger frame. In the next TXOP, the beamformer transmits a second BRP trigger frame. At this time, the second BRP trigger frame indicates one of the remaining beamformees other than the beamformee indicated by the first BRP trigger frame among the multiple beamformees indicated by the NDPA frame (HE NDPA). Since the beamformer transmitted the second BRP trigger frame within the TXOP limit, the beamformer transmits the second BRP trigger frame using a TXOP that exceeds the TXOP limit. In more detail, the beamformer receives a trigger-based PPDU including a feedback frame in a TXOP that exceeds the TXOP limit. At this time, the beamformer receives a trigger-based PPDU including a feedback frame from the beamformee indicated by the second BRP trigger frame. At this time, the beamformee transmits a trigger-based PPDU including a feedback frame after SIFS from the time of receiving the second BRP trigger frame.

[0123] FIG. 19 is a diagram illustrating the operation of a wireless communication terminal according to an embodiment of the present invention.

[0124] The wireless communication terminal performs transmission based on the TXOP limit. More specifically, the wireless communication terminal acquires information on the TXOP limit S1901, and performs transmission based on the information on the TXOP limit S1903. More specifically, the wireless communication terminal acquires information on the TXOP limit from the base wireless communication terminal. At this time, the information on the TXOP limit is an EDCA parameter set element. The wireless communication terminal performs transmission according to the rules on the TXOP limit described with reference to Figs. 6 to 7.

[0125] The wireless communication terminal transmits a beamforming report poll (BRP) trigger frame to another wireless communication terminal using a TXOP that exceeds the TXOP limit. In this case, the wireless communication terminal receives a feedback frame as a response to the BRP trigger frame from the other wireless communication terminal within the TXOP that exceeds the TXOP limit. In this case, the BRP trigger frame triggers simultaneous transmission of feedback frames of one or more wireless communication terminals. The feedback frame indicates a channel state measured by the other wireless communication terminal, which is used for MIMO transmission of the wireless communication terminal to the other wireless communication terminal, or for beamforming transmission of the wireless communication terminal to the other wireless communication terminal. In a specific embodiment, a beamformer for MIMO transmission or beamforming transmission transmits an NDPA frame, an NDP frame, and a BRP trigger frame using a TXOP that exceeds the TXOP limit. For example, after a pre-specified time has elapsed since the wireless communication terminal transmitted an NDPA frame informing the other wireless communication terminal that a sounding protocol sequence is to start, the wireless communication terminal transmits an NDP frame used to measure a channel state to the other wireless communication terminal. In this case, when a wireless communication terminal transmits an NDPA frame, an NDP frame, and a BRP trigger frame within the TXOP limit, after a predetermined time has elapsed since transmitting an NDP frame to another wireless communication terminal, the wireless communication terminal transmits the BRP trigger frame to the other wireless communication terminal using a TXOP that exceeds the TXOP limit.

[0126] In addition, the BRP trigger frame is used to request a subsequent segment for a feedback frame previously transmitted by another wireless communication terminal. In this case, if the beamformer transmits the BRP trigger frame within the TXOP limit, the beamformer transmits the BRP trigger frame using a TXOP that exceeds the TXOP limit.

[0127] The feedback frame is transmitted from the other wireless communication terminal after a pre-specified time has elapsed since the other wireless communication terminal received the BRP trigger frame. The above-mentioned pre-specified time is SIFS. In detail, the beamformee and the beamformer operate according to the embodiment described in FIG. 17 to FIG. 18.

[0128] The wireless communication terminal generates at least one fragment using dynamic fragmentation and transmits the at least one fragment to another wireless communication terminal. Dynamic fragmentation, as described above, refers to fragmentation in which all fragments except the last fragment are not required to be the same size.

[0129] The wireless communication terminal determines the fragmentation level to be applied to the fragment to be transmitted to the other wireless communication terminal based on the Block ACK agreement with the other wireless communication terminal. If there is no Block ACK agreement between the wireless communication terminal and the other wireless communication terminal, the wireless communication terminal performs dynamic fragmentation according to the fragmentation level determined according to the capability of the other wireless communication terminal. In this case, the fragmentation level indicates the method of transmitting the fragment as described above.

[0130] In a specific embodiment, a first fragment is generated from the at least one fragment based on a value designated by the other wireless communication terminal as a minimum fragment size. In this case, the wireless communication terminal transmits the first fragment to the other wireless communication terminal using a TXOP that exceeds a TXOP limit. If the wireless communication terminal transmits at least one fragment to the other wireless communication terminal without using an A-MPDU including multiple MPDUs, the wireless communication terminal transmits the first fragment to the other wireless communication terminal using a TXOP that exceeds a TXOP limit. In this case, the wireless communication terminal generates the first fragment with a size equal to the value designated by the other wireless communication terminal as a minimum fragment size.

[0131] In addition, the wireless communication terminal generates the at least one fragment up to the maximum number of fragments that the wireless communication terminal can generate, and transmits a second fragment, which is generated last, of the at least one fragment to another wireless communication terminal using a TXOP that exceeds the TXOP limit. In a specific embodiment, the wireless communication terminal can generate up to 16 fragments.

[0132] When the wireless communication terminal explicitly fails to receive a third fragment, which is one of the at least one fragment, the wireless communication terminal generates a fourth fragment having a size different from that of the third fragment based on at least one of whether the wireless communication terminal did not transmit a fragment following the third fragment or whether the other wireless communication terminal explicitly failed to receive a fragment following the third fragment. The wireless communication terminal assigns the sequence number and fragment number of the third fragment to the fourth fragment. In this case, the wireless communication terminal transmits the fourth fragment to the other wireless communication terminal instead of retransmitting the third fragment to the other wireless communication terminal. In particular, the wireless communication terminal transmits the fourth fragment using a TXOP that exceeds the TXOP limit. If the wireless communication terminal uses dynamic fragmentation, the wireless communication terminal operates as in the embodiment described with reference to FIGS. 7 to 16. The wireless communication terminal is a TXOP holder. Also, the specific operation when the wireless communication terminal is not a TXOP holder is as shown in Figures 14 to 16.

[0133] 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. Also, 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.

[0134] 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. The features, structures, effects, etc. exemplified in each embodiment may be combined or modified in other embodiments by a person having ordinary skill in the art to which the embodiment belongs. Therefore, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

[0135] Although the present invention has been described with a focus on the embodiments, these are merely illustrative and do not limit the present invention, and a person having ordinary skill in the art to which the present invention pertains should understand that various modifications and applications not exemplified above are possible within the scope of the essential characteristics of the present invention. For example, each component specifically illustrated in the embodiments may be modified and implemented. Such modifications and differences in applications should be interpreted as being included in the scope of the present invention as defined in the appended claims. [Explanation of symbols]

[0136] 100 Stations 110 Processor 120 Transmitter / receiver 140 User Interface 150 display units 160 Memory

Claims

1. In a wireless communication terminal that communicates wirelessly, A transceiver unit for transmitting and receiving wireless signals; a processor for processing the wireless signal; The processor, A wireless communication terminal transmits a frame on a wireless medium based on a TXOP limit, which is a maximum value of a transmission opportunity (TXOP), which is a time period during which the wireless communication terminal has the right to start a frame exchange sequence on the wireless medium. Wireless communication terminal.

2. The processor, Transmitting a Beamforming Report Poll (BRP) trigger frame to another wireless communication terminal using a TXOP exceeding the TXOP limit; receiving a feedback frame in response to the BRP trigger frame from the other wireless communication terminal within a TXOP that exceeds the TXOP limit; The BRP trigger frame triggers simultaneous transmission of feedback frames of one or more wireless communication terminals; The feedback frame indicates a state of a channel measured by the other wireless communication terminal, which is used for MIMO (Multi Input Multi Output) transmission of the wireless communication terminal to the other wireless communication terminal, or for beamforming transmission of the wireless communication terminal to the other wireless communication terminal.

2. The wireless communication terminal according to claim 1.

3. The processor, After a pre-specified time has elapsed since the wireless communication terminal transmitted a Null Data Packet Announcement (NDPA) frame to the other wireless communication terminal to inform the other wireless communication terminal that a sounding protocol sequence is to start, the wireless communication terminal transmits a Null Data Packet (NDP) frame used for measuring the state of the channel to the other wireless communication terminal; If the wireless communication terminal transmits the NDPA frame, the NDP frame, and the BRP trigger frame within the TXOP limit, after a pre-specified time has elapsed since the wireless communication terminal transmitted the NDP frame to the other wireless communication terminal, the wireless communication terminal transmits the BRP trigger frame to the other wireless communication terminal using a TXOP that exceeds the TXOP limit. The wireless communication terminal according to claim 2.

4. The processor, If the wireless communication terminal transmits the BRP trigger frame within the TXOP limit, the processor transmits the BRP trigger frame using a TXOP that exceeds the TXOP limit. The wireless communication terminal according to claim 2.

5. The feedback frame is transmitted from the other wireless communication terminal after a pre-specified time has elapsed since the other wireless communication terminal received the BRP trigger frame. The wireless communication terminal according to claim 2.

6. The processor, generating at least one fragment using dynamic fragmentation; transmitting the at least one fragment to another wireless communication terminal; The dynamic fragmentation refers to fragmentation other than static fragmentation, which requires that all fragments except the last fragment have the same size.

2. The wireless communication terminal according to claim 1.

7. The processor, the other wireless communication terminal generates a first fragment among the at least one fragment based on a value designated as a minimum fragment size; Transmitting the first fragment to the other wireless communication terminal using a TXOP exceeding the TXOP limit.

7. The wireless communication terminal according to claim 6.

8. If the wireless communication terminal transmits the at least one fragment to the other wireless communication terminal without using an A (Aggregate)-MPDU including a plurality of MPDUs (MAC Protocol Data Units), the processor transmits the first fragment to the other wireless communication terminal using a TXOP that exceeds the TXOP limit.

8. The wireless communication terminal according to claim 7.

9. The processor, The other wireless communication terminal generates the first fragment with a size equal to a value designated as the minimum fragment size.

8. The wireless communication terminal according to claim 7.

10. The processor, generating the at least one fragment a maximum number of times that the wireless communication terminal can generate fragments; A first fragment, which is generated last among the at least one fragment, is transmitted to the other wireless communication terminal using a TXOP exceeding the TXOP limit.

7. The wireless communication terminal according to claim 6.

11. The maximum number of fragments that the wireless communication terminal can generate is 16. The wireless communication terminal according to claim 10.

12. if the other wireless communication terminal explicitly fails to receive a first fragment, which is one of the at least one fragment, the processor generates a second fragment having a size different from that of the first fragment and having the same sequence number and fragment number as the first fragment, based on at least one of whether the wireless communication terminal did not transmit a fragment following the first fragment or whether the other wireless communication terminal explicitly failed to receive a fragment following the first fragment; and transmitting the second fragment to the wireless communication terminal instead of retransmitting the first fragment to the other wireless communication terminal.

7. The wireless communication terminal according to claim 6.

13. If there is no BlockACK agreement between the wireless communication terminal and the other wireless communication terminal, the processor performs dynamic fragmentation according to a fragmentation level determined according to a capability of the other wireless communication terminal; The fragmentation level indicates how the fragments are transmitted.

7. The wireless communication terminal according to claim 6.

14. The wireless communication terminal is a TXOP holder.

2. The wireless communication terminal according to claim 1.

15. A method for operating a wireless communication terminal that communicates wirelessly, comprising: The method includes a step of performing transmission based on a TXOP limit, which is a maximum value of a TXOP, which is a time period during which a wireless communication terminal has the right to start a frame exchange sequence on a wireless medium. How it works.

16. The step of transmitting based on the TXOP limit includes: transmitting a beamforming report poll trigger frame to another wireless communication terminal using a TXOP exceeding the TXOP limit; receiving a feedback frame in response to the BRP trigger frame from the other wireless communication terminal within a TXOP that exceeds the TXOP limit; The BRP trigger frame triggers simultaneous transmission of feedback frames of one or more wireless communication terminals; The feedback frame indicates a state of a channel measured by the other wireless communication terminal, the state being used for MIMO transmission from the wireless communication terminal to the other wireless communication terminal, or for beamforming transmission from the wireless communication terminal to the other wireless communication terminal.

14. The method of claim 13.

17. The step of transmitting the BRP trigger frame includes: receiving an NDP frame used by the other wireless communication terminal to measure the state of the channel from the other wireless communication terminal after a pre-specified time from when an NDPA frame informing the other wireless communication terminal of the start of a sounding protocol sequence is transmitted; If the wireless communication terminal transmits the NDPA frame, the NDP frame, and the BRP trigger frame within a TXOP limit, transmitting the BRP trigger frame using a TXOP exceeding the TXOP limit after a pre-specified time from when the wireless communication terminal transmits the NDP frame to the other wireless communication terminal.

20. The method of claim 16.

18. Transmitting the BRP trigger frame using a TXOP that exceeds the TXOP limit includes: If the BRP trigger frame is transmitted within the TXOP limit, transmitting the BRP trigger frame using a TXOP that exceeds the TXOP limit.

20. The method of claim 16.

19. The method of operation includes: generating at least one fragment using dynamic fragmentation; The step of transmitting based on the TXOP limit includes: transmitting the at least one fragment to another wireless communication terminal; The dynamic fragmentation refers to fragmentation other than static fragmentation, which requires that all fragments except the last fragment have the same size.

16. The method of claim 15.

20. The step of generating at least one fragment comprises: generating a first fragment from the at least one fragment based on a value designated as a minimum fragment size by the other wireless communication terminal; The step of transmitting the at least one fragment to another wireless communication terminal includes: transmitting the first fragment to the other wireless communication terminal using a TXOP that exceeds the TXOP limit.

20. The method of claim 19.

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