WO2019017590A1 - Method for transmitting or receiving frame in wireless lan system, and device therefor - Google Patents

Abstract

A method by which a station (STA) transmits/receives a frame in a wireless LAN (WLAN), according to one embodiment of the present invention, can comprise the steps of: receiving a trigger frame from an access point (AP); checking whether the trigger frame includes a simultaneous transmission and reception (STR) indicator; and transmitting an uplink (UL) frame and receiving a downlink (DL) frame simultaneously through a resource unit (RU) allocated by the trigger frame, if the trigger frame includes the STR indicator.

Description

Method and apparatus for transmitting or receiving frames in a wireless LAN system

The present invention relates to channel access in a wireless LAN system, and more particularly, to a method and apparatus for transmitting and receiving an UL frame and a DL frame.

The standard for wireless LAN technology is being developed as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. IEEE 802.11a and b 2.4. GHz or 5 GHz, the IEEE 802.11b provides a transmission rate of 11 Mbps, and the IEEE 802.11a provides a transmission rate of 54 Mbps. IEEE 802.11g employs Orthogonal Frequency-Division Multiplexing (OFDM) at 2.4 GHz to provide a transmission rate of 54 Mbps. IEEE 802.11n employs multiple input multiple output (OFDM), or OFDM (MIMO-OFDM), and provides transmission speeds of 300 Mbps for four spatial streams. IEEE 802.11n supports channel bandwidth up to 40 MHz, which in this case provides a transmission rate of 600 Mbps.

The IEEE 802.11ax standard, which supports a maximum of 160 MHz bandwidth and supports 8 spatial streams and supports a maximum speed of 1 Gbit / s, has been discussed in the IEEE 802.11ax standard.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for simultaneously transmitting and receiving an UL frame and a DL frame, a method thereof, and an apparatus therefor.

The present invention is not limited to the above-described technical problems, and other technical problems can be deduced from the embodiments of the present invention.

According to another aspect of the present invention, there is provided a method of transmitting and receiving a frame in a wireless local area network (WLAN), the method comprising: receiving a trigger frame from an access point; Checking whether the trigger frame includes a simultaneous transmission and reception (STR) indicator; And if the trigger frame includes the STR indicator, transmitting an uplink (UL) frame and a downlink (DL) frame through a resource unit (RU) allocated by the trigger frame .

According to another aspect of the present invention, there is provided a station (STA) including: a transceiver; And receiving a trigger frame from an access point (AP) through the transceiver, checking whether the trigger frame includes a simultaneous transmission and reception (STR) indicator, and if the trigger frame includes the STR indicator (UL) frame through a resource unit (RU) allocated by a trigger frame and a downlink (DL) frame.

The end of the UL frame and the end of the DL frame may be time aligned.

The UL frame may start after a predetermined gap from the L-preamble of the DL frame.

The STR indicator may be received via a reserved bit in the Trigger Dependent User Information field of the trigger frame.

Control information including at least one of STA ID, RU assignment, TXOP (transmission opportunity) period and frame length indicated by the trigger frame may be commonly applied to the DL frame and the UL frame.

In the signal (SIG) field of the DL frame, the control information may be omitted.

The STA may null a predetermined number of subcarriers located at both ends of the RU when transmitting the UL frame.

According to an embodiment of the present invention, reception of a DL frame and transmission of an UL frame are simultaneously performed through the same RU, so that not only radio resources can be used more efficiently but also system throughput can be improved.

Other technical advantages than the above-described technical effects can be deduced from the embodiments of the present invention.

1 is a diagram showing an example of a configuration of a wireless LAN system.

2 is a diagram showing another example of the configuration of the wireless LAN system.

3 is a diagram for explaining a general link setup process.

4 is a diagram for explaining a backoff process.

5 is a diagram for explaining hidden nodes and exposed nodes.

6 is a diagram for explaining RTS and CTS.

7 to 9 are diagrams for explaining the operation of the STA that has received the TIM.

10 is a diagram for explaining an example of a frame structure used in the IEEE 802.11 system.

FIG. 11 illustrates a contention free (CF) -END frame.

Figures 12-15 illustrate HE PPDUs.

16 is a diagram for explaining an uplink multi-user transmission situation based on a trigger frame.

17 shows an example of a trigger frame format.

18 shows an example of a user information field of a trigger frame.

19 is a view for explaining the type of STR.

20 is a diagram for explaining the magnetic interference of the STR.

Figures 21 and 22 illustrate DL frames containing an indicator for STR initiation.

23 is a diagram for explaining a UL frame transmitted by the STR scheme.

24 is a diagram for explaining an STR using a trigger frame.

FIG. 25 shows a flow of a method for simultaneously transmitting / receiving a DL / UL frame according to an embodiment of the present invention.

26 is a view for explaining an apparatus according to an embodiment of the present invention.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced.

The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are omitted or shown in block diagram form around the core functions of each structure and device in order to avoid obscuring the concepts of the present invention.

As described above, the following description relates to a method and apparatus for efficiently utilizing a channel having a wide bandwidth in a wireless LAN system. To this end, a wireless LAN system to which the present invention is applied will be described in detail.

1 is a diagram showing an example of a configuration of a wireless LAN system.

As shown in FIG. 1, a WLAN system includes one or more Basic Service Sets (BSSs). A BSS is a collection of stations (STAs) that can successfully communicate and synchronize with each other.

The STA is a logical entity including a medium access control (MAC) and a physical layer interface for a wireless medium. The STA includes an access point (AP) and a non-AP STA (Non-AP Station) . A portable terminal operated by a user in the STA is a non-AP STA, and sometimes referred to as a non-AP STA. The non-AP STA may be a terminal, a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile terminal, May also be referred to as another name such as a Mobile Subscriber Unit.

An AP is an entity that provides a connection to a distribution system (DS) via a wireless medium to an associated station (STA). The AP may be referred to as a centralized controller, a base station (BS), a Node-B, a base transceiver system (BTS), a site controller, or the like.

The BSS can be divided into an infrastructure BSS and an independent BSS (IBSS).

The BBS shown in FIG. 1 is an IBSS. The IBSS means a BSS that does not include an AP, and does not include an AP, so a connection to the DS is not allowed and forms a self-contained network.

2 is a diagram showing another example of the configuration of the wireless LAN system.

The BSS shown in FIG. 2 is an infrastructure BSS. The infrastructure BSS includes one or more STAs and APs. In the infrastructure BSS, communication between non-AP STAs is performed via an AP, but direct communication between non-AP STAs is possible when a direct link is established between non-AP STAs.

As shown in FIG. 2, a plurality of infrastructure BSSs may be interconnected via DS. A plurality of BSSs connected through a DS are referred to as an extended service set (ESS). The STAs included in the ESS can communicate with each other, and within the same ESS, the non-AP STA can move from one BSS to another while seamlessly communicating.

The DS is a mechanism for connecting a plurality of APs. It is not necessarily a network, and there is no limitation on the form of DS if it can provide a predetermined distribution service. For example, the DS may be a wireless network such as a mesh network, or may be a physical structure that links APs together.

Hierarchy

The operation of the STA operating in the wireless LAN system can be described in terms of the layer structure. In terms of device configuration, the hierarchy can be implemented by a processor. The STA may have a plurality of hierarchical structures. For example, the hierarchical structure covered in the 802.11 standard document is mainly a MAC sublayer and a physical (PHY) layer on a DLL (Data Link Layer). The PHY may include a Physical Layer Convergence Procedure (PLCP) entity, a PMD (Physical Medium Dependent) entity, and the like. The MAC sublayer and the PHY conceptually include management entities called a MAC sublayer management entity (MLME) and a physical layer management entity (PLME), respectively. These entities provide a layer management service interface in which a layer management function operates .

In order to provide correct MAC operation, a Station Management Entity (SME) exists in each STA. An SME is a layer-independent entity that may be present in a separate management plane or may appear to be off-the-side. Although the exact functions of the SME are not described in detail in this document, they generally include the ability to collect layer-dependent states from various Layer Management Entities (LMEs) and to set similar values for layer-specific parameters It can be seen as responsible. An SME typically performs these functions on behalf of a generic system management entity and can implement a standard management protocol.

The aforementioned entities interact in various ways. For example, they can interact by exchanging GET / SET primitives between entities. A primitive is a set of elements or parameters related to a specific purpose. The XX-GET.request primitive is used to request the value of a given MIB attribute. The XX-GET.confirm primitive returns the appropriate MIB attribute information value if the Status is "Success", otherwise it is used to return an error indication in the Status field. The XX-SET.request primitive is used to request that the indicated MIB attribute be set to the given value. If the MIB attribute indicates a specific operation, it is requested that the corresponding operation be performed. The XX-SET.confirm primitive confirms that the indicated MIB attribute is set to the requested value if the status is "success", otherwise it is used to return an error condition to the status field. If the MIB attribute indicates a specific operation, this confirms that the corresponding operation has been performed.

In addition, MLME and SME can exchange various MLME_GET / SET primitives through MLME_SAP (Service Access Point). In addition, various PLME_GET / SET primitives can be exchanged between PLME and SME via PLME_SAP and exchanged between MLME and PLME through MLME-PLME_SAP.

Link Setup Process

3 is a diagram for explaining a general link setup process.

In order for a STA to set up a link to a network and transmit and receive data, the STA first discovers a network, performs authentication, establishes an association, establishes an authentication procedure for security, . The link setup process may be referred to as a session initiation process or a session setup process. Also, the process of discovery, authentication, association, and security setting of the link setup process may be collectively referred to as an association process.

An exemplary link setup procedure will be described with reference to FIG.

In step S510, the STA can perform a network discovery operation. The network discovery operation may include a scanning operation of the STA. In other words, in order for the STA to access the network, it must find a network that can participate. The STA must identify a compatible network before joining the wireless network. The process of identifying a network in a specific area is called scanning.

The scanning methods include active scanning and passive scanning.

FIG. 3 illustrates a network discovery operation that includes an exemplary active scanning process. The STA performing the scanning in the active scanning transmits the probe request frame and waits for a response in order to search for the existence of an AP in the surroundings while moving the channels. The responder sends a probe response frame in response to the probe request frame to the STA that transmitted the probe request frame. Here, the responder may be the STA that last transmitted the beacon frame in the BSS of the channel being scanned. In the BSS, the AP transmits the beacon frame, so the AP becomes the responder. In the IBSS, the STAs in the IBSS transmit the beacon frame while the beacon frame is transmitted. For example, the STA that transmits the probe request frame in channel 1 and receives the probe response frame in channel 1 stores the BSS-related information included in the received probe response frame and transmits the next channel (for example, Channel) and perform scanning in the same manner (i.e., transmitting / receiving a probe request / response on the second channel).

Although not shown in Fig. 3, the scanning operation may be performed in a passive scanning manner. In passive scanning, the STA performing the scanning waits for the beacon frame while moving the channels. A beacon frame is one of the management frames in IEEE 802.11, and is transmitted periodically to notify the presence of a wireless network and allow the STA performing the scanning to find the wireless network and participate in the wireless network. In the BSS, the AP periodically transmits the beacon frame. In the IBSS, the beacon frames are transmitted while the STAs in the IBSS are running. Upon receiving the beacon frame, the scanning STA stores information on the BSS included in the beacon frame and records beacon frame information on each channel while moving to another channel. The STA receiving the beacon frame stores the BSS-related information included in the received beacon frame, moves to the next channel, and performs scanning in the next channel in the same manner.

Comparing active scanning with passive scanning, active scanning has the advantage of less delay and less power consumption than passive scanning.

After the STA finds the network, the authentication procedure may be performed in step S520. This authentication process can be referred to as a first authentication process in order to clearly distinguish from the security setup operation in step S540 described later.

The authentication process includes an STA transmitting an authentication request frame to the AP, and an AP transmitting an authentication response frame to the STA in response to the authentication request frame. The authentication frame used for the authentication request / response corresponds to the management frame.

The authentication frame includes an authentication algorithm number, an authentication transaction sequence number, a status code, a challenge text, a robust security network (RSN), a finite cyclic group Group), and the like. This corresponds to some examples of information that may be included in the authentication request / response frame, may be replaced by other information, or may include additional information.

The STA may send an authentication request frame to the AP. Based on the information included in the received authentication request frame, the AP can determine whether or not to allow authentication for the STA. The AP can provide the result of the authentication process to the STA through the authentication response frame.

After the STA has been successfully authenticated, the association process may be performed in step S530. The association process includes an STA transmitting an association request frame to an AP, and an AP transmitting an association response frame to the STA in response to the association request frame.

For example, the association request frame may include information related to various capabilities, a listening interval, a service set identifier (SSID), supported rates, supported channels, an RSN, , Supported operating classes, TIM broadcast request, interworking service capability, and the like.

For example, the association response frame may include information related to various capabilities, a status code, an association ID (AID), a support rate, an enhanced distributed channel access (EDCA) parameter set, a Received Channel Power Indicator (RCPI) A timeout interval (an association comeback time), a overlapping BSS scan parameter, a TIM broadcast response, a QoS map, and the like.

This corresponds to some examples of information that may be included in the association request / response frame, may be replaced by other information, or may include additional information.

After the STA is successfully associated with the network, a security setup procedure may be performed at step S540. The security setup process in step S540 may be referred to as an authentication process through a Robust Security Network Association (RSNA) request / response. The authentication process in step S520 may be referred to as a first authentication process, May also be referred to simply as an authentication process.

The security setup process of step S540 may include a private key setup through 4-way handshaking over an Extensible Authentication Protocol over LAN (EAPOL) frame, for example . In addition, the security setup process may be performed according to a security scheme not defined in the IEEE 802.11 standard.

Medium access mechanism

In a wireless LAN system compliant with IEEE 802.11, the basic access mechanism of Medium Access Control (MAC) is a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism. The CSMA / CA mechanism is also referred to as the Distributed Coordination Function (DCF) of the IEEE 802.11 MAC, which basically adopts a "listen before talk" access mechanism. According to this type of access mechanism, the AP and / or the STA may sense a radio channel or medium for a predetermined time interval (e.g., DCF Inter-Frame Space (DIFS) If the medium is judged to be in an idle status, the frame transmission is started through the corresponding medium, whereas if the medium is occupied status, The AP and / or the STA does not start its own transmission but sets a delay period (for example, a random backoff period) for the medium access and waits for a frame transmission after waiting With the application of an arbitrary backoff period, several STAs are expected to attempt frame transmission after waiting for different time periods, so that collisions can be minimized.

In addition, the IEEE 802.11 MAC protocol provides HCF (Hybrid Coordination Function). The HCF is based on the DCF and the PCF (Point Coordination Function). The PCF is a polling-based, synchronous access scheme that refers to periodically polling all receiving APs and / or STAs to receive data frames. In addition, HCF has EDCA (Enhanced Distributed Channel Access) and HCCA (HCF Controlled Channel Access). EDCA is a contention-based access method for a provider to provide data frames to a large number of users, and HCCA uses a contention-based channel access method using a polling mechanism. In addition, the HCF includes a medium access mechanism for improving QoS (Quality of Service) of the WLAN, and can transmit QoS data in both a contention period (CP) and a contention free period (CFP).

4 is a diagram for explaining a backoff process.

An operation based on an arbitrary backoff period will be described with reference to FIG. When a medium that is in an occupy or busy state is changed to an idle state, several STAs may attempt to transmit data (or frames). At this time, as a method for minimizing the collision, each of the STAs may attempt to transmit after selecting an arbitrary backoff count and waiting for a corresponding slot time. An arbitrary backoff count has a packet number value and can be determined to be one of values in the range of 0 to CW. Here, CW is a contention window parameter value. The CW parameter is given an initial value of CWmin, but it can take a value twice in the case of a transmission failure (for example, in the case of not receiving an ACK for a transmitted frame). If the CW parameter value is CWmax, the data transmission can be attempted while maintaining the CWmax value until the data transmission is successful. If the data transmission is successful, the CWmin value is reset to the CWmin value. The values of CW, CWmin and CWmax are preferably set to 2 ⁿ -1 (n = 0, 1, 2, ...).

When an arbitrary backoff process is started, the STA continuously monitors the medium while counting down the backoff slot according to the determined backoff count value. When the medium is monitored in the occupied state, the countdown is stopped and waited, and when the medium is idle, the remaining countdown is resumed.

In the example of FIG. 4, when a packet to be transmitted to the MAC of the STA3 arrives, the STA3 can confirm that the medium is idle by DIFS and transmit the frame immediately. Meanwhile, the remaining STAs monitor and wait for the medium to be in a busy state. In the meanwhile, data to be transmitted may also occur in each of STA1, STA2 and STA5, and each STA waits for DIFS when the medium is monitored in an idle state and then counts down the backoff slot according to the arbitrary backoff count value selected by each STA. Can be performed. In the example of FIG. 4, STA2 selects the smallest backoff count value, and STA1 selects the largest backoff count value. That is, the case where the remaining backoff time of the STA5 is shorter than the remaining backoff time of the STA1 at the time when the STA2 finishes the backoff count and starts the frame transmission is illustrated. STA1 and STA5 stop countdown and wait for a while while STA2 occupies the medium. When the occupation of STA2 is ended and the medium becomes idle again, STA1 and STA5 wait for DIFS and then resume the stopped backoff count. That is, the frame transmission can be started after counting down the remaining backoff slots by the remaining backoff time. Since the remaining backoff time of STA5 is shorter than STA1, STA5 starts frame transmission. On the other hand, data to be transmitted may also occur in the STA 4 while the STA 2 occupies the medium. At this time, in STA4, if the medium becomes idle, it can wait for DIFS, count down according to an arbitrary backoff count value selected by the STA4, and start frame transmission. In the example of FIG. 6, the remaining backoff time of STA5 coincides with the arbitrary backoff count value of STA4, in which case a collision may occur between STA4 and STA5. If a collision occurs, neither STA4 nor STA5 receive an ACK, and data transmission fails. In this case, STA4 and STA5 can double the CW value, then select an arbitrary backoff count value and perform a countdown. On the other hand, the STA1 waits while the medium is occupied due to the transmission of the STA4 and the STA5, waits for the DIFS when the medium becomes idle, and starts frame transmission after the remaining backoff time.

STA sensing behavior

As described above, the CSMA / CA mechanism includes virtual carrier sensing in addition to physical carrier sensing in which the AP and / or STA directly senses the medium. Virtual carrier sensing is intended to compensate for problems that may occur in media access, such as hidden node problems. For the virtual carrier sensing, the MAC of the wireless LAN system may use a network allocation vector (NAV). NAV is a value indicating to another AP and / or STA the time remaining until the media and / or the STA that is currently using or authorized to use the media are available. Therefore, the value set to NAV corresponds to the period in which the medium is scheduled to be used by the AP and / or the STA that transmits the frame, and the STA receiving the NAV value is prohibited from accessing the medium during the corresponding period. The NAV may be set according to the value of the " duration " field of the MAC header of the frame, for example.

In addition, a robust collision detection mechanism has been introduced to reduce the probability of collision. This will be described with reference to Figs. 5 and 7. Fig. The actual carrier sensing range and the transmission range may not be the same, but are assumed to be the same for convenience of explanation.

5 is a diagram for explaining hidden nodes and exposed nodes.

FIG. 5A is an example of a hidden node, and STA A and STA B are in communication and STA C has information to be transmitted. Specifically, STA A is transmitting information to STA B, but it can be determined that STA C is idle when performing carrier sensing before sending data to STA B. This is because the STA A transmission (ie, media occupancy) may not be sensed at the STA C location. In this case, STA B receives information of STA A and STA C at the same time, so that collision occurs. In this case, STA A is a hidden node of STA C.

FIG. 5B is an example of an exposed node, and STA B is a case of transmitting data to STA A, and STA C has information to be transmitted in STA D. FIG. In this case, if the STA C carries out the carrier sensing, it can be determined that the medium is occupied due to the transmission of the STA B. Accordingly, even if STA C has information to be transmitted to STA D, it is sensed that the media is occupied, and therefore, it is necessary to wait until the medium becomes idle. However, since the STA A is actually out of the transmission range of the STA C, the transmission from the STA C and the transmission from the STA B may not collide with each other in the STA A. Therefore, the STA C is not necessary until the STA B stops transmitting It is to wait. In this case, STA C can be regarded as an exposed node of STA B.

6 is a diagram for explaining RTS and CTS.

5, short signaling packets such as RTS (request to send) and CTS (clear to send) can be used in order to efficiently use the collision avoidance mechanism. The RTS / CTS between the two STAs may allow the surrounding STA (s) to overhear, allowing the surrounding STA (s) to consider whether to transmit information between the two STAs. For example, if the STA to which data is to be transmitted transmits an RTS frame to the STA receiving the data, the STA receiving the data can notify that it will receive the data by transmitting the CTS frame to surrounding STAs.

FIG. 6A is an example of a method for solving a hidden node problem, and it is assumed that both STA A and STA C attempt to transmit data to STA B. FIG. When STA A sends RTS to STA B, STA B transmits CTS to both STA A and STA C around it. As a result, STA C waits until the data transmission of STA A and STA B is completed, thereby avoiding collision.

6 (b) is an illustration of a method for solving the exposed node problem, where STA C overrides the RTS / CTS transmission between STA A and STA B, D, the collision does not occur. That is, STA B transmits RTS to all surrounding STAs, and only STA A having data to be transmitted transmits CTS. Since STA C only receives RTS and does not receive CTS of STA A, it can be seen that STA A is outside the carrier sensing of STC C.

Power Management

As described above, in the wireless LAN system, the STA must perform channel sensing before performing transmission / reception, and always sensing the channel causes continuous power consumption of the STA. The power consumption in the reception state does not differ much from the power consumption in the transmission state, and maintaining the reception state is also a large burden on the STA which is limited in power (that is, operated by the battery). Thus, if the STA keeps listening for sustained channel sensing, it will inefficiently consume power without special benefits in terms of WLAN throughput. To solve this problem, the wireless LAN system supports the power management (PM) mode of the STA.

The STA's power management mode is divided into an active mode and a power save (PS) mode. STA basically operates in active mode. An STA operating in active mode maintains an awake state. The awake state is a state in which normal operation such as frame transmission / reception and channel scanning is possible. Meanwhile, the STA operating in the PS mode operates by switching between a sleep state (or a doze state) and an awake state. The STA operating in the sleep state operates with minimal power and does not perform frame scanning nor transmission and reception of frames.

As the STA sleeps for as long as possible, power consumption is reduced, which increases the operating time of the STA. However, since it is impossible to transmit / receive frames in the sleep state, it can not be operated unconditionally for a long time. If the STA operating in the sleep state exists in the frame to be transmitted to the AP, it can switch to the awake state and transmit the frame. On the other hand, when there is a frame to be transmitted to the STA by the AP, the STA in the sleep state can not receive it, and it is unknown that there is a frame to receive. Therefore, the STA may need to switch to the awake state according to a certain period to know whether there is a frame to be transmitted to it (and to receive it if it exists).

The AP may transmit a beacon frame to the STAs in the BSS at regular intervals. The beacon frame may include a Traffic Indication Map (TIM) information element. The TIM information element may include information that indicates that the AP has buffered traffic for the STAs associated with it and will transmit the frame. The TIM element includes a TIM used for indicating a unicast frame and a delivery traffic indication map (DTIM) used for indicating a multicast or broadcast frame.

7 to 9 are views for explaining the operation of the STA receiving the TIM in detail.

Referring to FIG. 7, in order to receive a beacon frame including a TIM from an AP, the STA changes from a sleep state to an awake state, and analyzes the received TIM element to find that there is buffered traffic to be transmitted to the STA . After the STA performs contending with other STAs for medium access for PS-Poll frame transmission, it may transmit a PS-Poll frame to request AP to transmit data frame. The AP receiving the PS-Poll frame transmitted by the STA can transmit the frame to the STA. The STA may receive a data frame and send an acknowledgment (ACK) frame to the AP. The STA can then be switched to the sleep state again.

As shown in FIG. 7, the AP operates according to an immediate response scheme for transmitting a data frame after a predetermined time (for example, SIFS (Short Inter-Frame Space)) after receiving the PS-Poll frame from the STA . On the other hand, if the AP does not prepare the data frame to be transmitted to the STA after receiving the PS-Poll frame for the SIFS time, the AP can operate according to a deferred response method, which will be described with reference to FIG.

In the example of FIG. 8, the operation of switching the STA from the sleep state to the awake state, receiving the TIM from the AP, competing, and transmitting the PS-Poll frame to the AP is the same as the example of FIG. If the AP receives the PS-Poll frame and fails to prepare the data frame for SIFS, it can send an ACK frame to the STA instead of transmitting the data frame. After the AP transmits the ACK frame and the data frame is ready, it can transmit the data frame to the STA after performing the contention. The STA transmits an ACK frame indicating that the data frame has been successfully received to the AP, and can be switched to the sleep state.

Figure 9 is an example of an AP transmitting a DTIM. STAs may transition from the sleep state to the awake state to receive a beacon frame containing the DTIM element from the AP. STAs can know that a multicast / broadcast frame will be transmitted through the received DTIM. The AP can transmit data (i.e., multicast / broadcast frame) directly without transmitting / receiving a PS-Poll frame after transmitting a beacon frame including DTIM. The STAs may receive data while continuing to hold the awake state after receiving the beacon frame including the DTIM, and may switch to the sleep state again after the data reception is completed.

Frame structure general

10 is a diagram for explaining an example of a frame structure used in the IEEE 802.11 system.

The Physical Layer Protocol Data Unit (PPDU) frame format may include a Short Training Field (STF) field, a Long Training Field (LTF) field, a SIGN (SIGNAL) field, and a Data field. The most basic (e.g., non-HT (High Throughput)) PPDU frame format may consist of L-STF (Legacy-STF), L-LTF (Legacy-LTF), SIG field and data field only.

STF is a signal for signal detection, AGC (Automatic Gain Control), diversity selection, precise time synchronization, etc., and LTF is a signal for channel estimation and frequency error estimation. STF and LTF may be collectively referred to as a PLCP preamble, and the PLCP preamble may be a signal for synchronization and channel estimation of the OFDM physical layer.

The SIG field may include a RATE field and a LENGTH field. The RATE field may contain information on the modulation and coding rate of the data. The LENGTH field may contain information on the length of the data. Additionally, the SIG field may include a parity bit, a SIG TAIL bit, and the like.

The data field may include a SERVICE field, a physical layer service data unit (PSDU), a PPDU TAIL bit, and may also include a padding bit if necessary. Some bits in the SERVICE field may be used for synchronization of the descrambler at the receiving end. The PSDU corresponds to an MPDU (MAC Protocol Data Unit) defined in the MAC layer and may include data generated / used in an upper layer. The PPDU TAIL bit can be used to return the encoder to the 0 state. The padding bits may be used to match the length of the data field to a predetermined unit.

The MPDU is defined according to various MAC frame formats, and the basic MAC frame is composed of a MAC header, a frame body, and a frame check sequence (FCS). The MAC frame is composed of MPDUs and can be transmitted / received via the PSDU of the data part of the PPDU frame format.

The MAC header includes a Frame Control field, a Duration / ID field, an Address field, and the like. The frame control field may contain control information necessary for frame transmission / reception. The period / ID field may be set to a time for transmitting the frame or the like.

The period / ID field included in the MAC header can be set to a 16-bit length (e.b., B0 to B15). The content included in the period / ID field may vary depending on the frame type and subtype, whether it is transmitted during the contention free period (CFP), the QoS capability of the transmitting STA, and the like. (i) In a control frame whose subtype is PS-Poll, the period / ID field may contain the AID of the transmitting STA (e.g., via 14 LSB bits) and 2 MSB bits may be set to one. (ii) In frames transmitted during the CFP by a point coordinator (PC) or a non-QoS STA, the duration / ID field may be set to a fixed value (e.g., 32768). (iii) In other frames transmitted by other non-QoS STAs or control frames transmitted by the QoS STA, the duration / ID field may include a duration value defined for each frame type. In a data frame or a management frame transmitted by the QoS STA, the duration / ID field may include a duration value defined for each frame type. For example, if B15 = 0 in the duration / ID field indicates that the duration / ID field is used to indicate TXOP Duration, B0-B14 can be used to indicate the actual TXOP duration. The actual TXOP Duration indicated by B0 to B14 may be any of 0 to 32767, and the unit may be microseconds (us). However, when the period / ID field indicates a fixed TXOP Duration value (e.g., 32768), B15 = 1 and B0 to B14 = 0. In addition, if B14 = 1 and B15 = 1 are set, the period / ID field is used to indicate AID, and B0 to B13 indicate one of AIDs from 1 to 2007. The specific contents of the Sequence Control, QoS Control, and HT Control subfields of the MAC header can refer to the IEEE 802.11 standard document.

 The frame control field of the MAC header may include Protocol Version, Type, Subtype, To DS, From DS, More Fragment, Retry, Power Management, More Data, Protected Frame, Order subfields. The contents of each subfield of the frame control field may reference an IEEE 802.11 standard document.

FIG. 11 illustrates a contention free (CF) -END frame.

For convenience of explanation, it is assumed that a CF-END frame is transmitted by a non-DMG (directional multi-gigabit, 11ad) STA. The CF-END frame may be sent to truncate the TXOP duration. Therefore, the duration field in the CF-END frame is set to zero. The Receiver Address (RA) field may be set to a broadcast group address. The BSSID field may be set to the address of the STA included in the AP. However, in the case of a non-HT or non-HT duplicate CF-END frame transmitted by the VHT STA to the VHT AP, the Individual / Group bit of the BSSID field may be set to one.

Example of HE PPDU structure

Hereinafter, an example of a HE PPDU (High Efficiency Physical Layer Protocol Data Unit) format in a wireless LAN system supporting 11ax will be described.

Figures 12-15 illustrate HE PPDUs.

The HE-SIG A field is located after the L-Part (e.g., L-STF, L-LTF, L-SIG) and is duplicated in 20MHz units as in the L-Part. HE-SIG A may be included in all HE PPDUs, whereas HE-SIG B may be omitted from SU PPDUs and UL trigger based PPDUs (e.g., UL PPDUs transmitted based on trigger frames).

HE-SIG A contains common control information (e.g., BW, GI length, BSS Color, CRC, Tail, etc.) for STAs. The HE-SIG A field contains information for interpreting the HE PPDU, so the information contained in the HE-SIG A field will vary depending on the format of the HE PPDU (eg, SU PPDU, MU PPDU, or trigger-based PPDU) .

For example, (i) in the HE SU PPDU format, the HE-SIG A field includes a DL / UL indicator, an HE PPDU format indicator, a BSS Color, a TXOP Duration, a BW (bandwidth), an MCS, a CP + LTF length, Number, STBC (eg, STBC use), transmission beamforming (TxBF) information, CRC, and Tail. For HE SU PPDU format, the HE-SIG B field may be omitted. (ii) HE MU In the PPDU format, the HE-SIG A field includes the DL / UL indicator, the BSS Color, the TXOP Duration, the bandwidth, the MCS information of the SIG B field, the number of symbols of the SIG B field, , A full band MU-MIMO use indicator, a CP + LTF length, transmission beamforming (TxBF) information, CRC and Tail. (iii) In the HE trigger based PPDU format, the HE-SIG A field may include at least one of a format indicator (e.g., SU PPDU or trigger based PPDU), BSS Color, TXOP Duration, BW, CRC, and Tail have.

In addition to the common control information, the HE-SIG A may include at least one of user allocation information such as STA identifier such as PAID or GID, allocated resource information, and the number of streams Nsts have.

The BSS color information included in the HE-SIG A field is information for identifying the BSS, and has a length shorter than the BSSID. For example, the BSSID may have a length of 48 bits, whereas the BSS color information may have a length of 6 bits. The STA can determine whether it is an intra-BSS frame using the BSS color information. That is, even if only the HE-SIG A field is decoded, the STA can distinguish the intra BSS PPDU from the inter BSS PPDU through the BSS color information without decoding the entire HE PPDU.

HE-SIG B can be independently encoded every 20 MHz channel unit. The HE-SIG B encoded per 20 MHz channel unit may be referred to as the HE-SIG-B content channel.

According to one embodiment, if the bandwidth is not greater than 20 MHz, one HE-SIG B content channel may be transmitted. When the bandwidth is greater than 20 MHz, the channels of the 20 MHz size are allocated to the first HE-SIG B content channel (HE-SIG B [1]) or the second HE-SIG B content channel (HE-SIG B [ 2]) can be transmitted. For example, HE-SIG B [1] and HE-SIG B [2] can be transmitted alternately. The odd 20 MHz channel transmits HE-SIG B [1] and the even 20 MHz channel can transmit HE-SIG B [2]. More specifically, for a 40 MHz bandwidth, HE-SIG B [1] is transmitted on the first 20 MHz channel and HE-SIG B [2] is transmitted on the second 20 MHz channel. SIG B [1] is transmitted on the first 20 MHz channel, HE-SIG B [2] is transmitted on the second 20 MHz channel, and the same HE-SIG B [1] 20 MHz channel, and the same HE-SIG B [2] is repeatedly transmitted on the fourth 20 MHz channel. The 160 MHz bandwidth is similarly transmitted.

On the other hand, the content of each of HE-SIG B [1] and HE-SIG B [2] may be different. However, HE-SIG-B [1] all have the same contents. Similarly, HE-SIG B [2] all have the same content.

HE-SIG B may include a common field and a user specific field. The common field may precede the user specific field. The common field and the user-specific field may be divided into bits, not OFDM symbols.

The common field of HE-SIG B contains information for all of the STAs designated to receive PPDUs in that bandwidth. The common field may include resource unit (RU) allocation information. For example, when dividing the four 20 MHz channels constituting 80 MHz into [LL, LR, RL, RR], a common block for LL and RL is included in the common field of HE-SIG B [ A common block for LR and RR may be included in the common field of SIG B [2].

The user-specific field of HE-SIG B may include a plurality of user fields, and each user field may include information specific to the individual STA designated to receive PPDUs. In one example, the user field may include, but is not limited to, at least one of station ID, MCS per STA, number of streams (Nsts), Coding (e.g., instructions for using LDPC), DCM indicator, and transmit beamforming information.

Trigger Frame

16 is a diagram for explaining an uplink multi-user transmission situation based on a trigger frame.

As described above, in the 802.11ax system, the UL MU transmission scheme can be used. This is because the AP transmits a trigger frame to a plurality of STAs (for example, STA 1 to STA 4) ≪ / RTI > The AP may acquire a TXOP to transmit the trigger frame through a contention process to access the medium.

The trigger frame may include UL MU assignment information. The UL MU allocation information may include, for example, at least one of resource location and size, STA IDs or receiving STA addresses, MCS and MU type (MIMO, OFDMA, etc.). The contents of the specific trigger frame will be described later.

 STAs can transmit UL data frames from the PPDU including the trigger frame in SIFS and HE trigger based PPDU format.

The AP may acknowledge the UL MU data frame over a BA (Block ACK) frame.

17 shows a trigger frame format according to one embodiment. Specifically, FIG. 17A shows the entire trigger frame, FIG. 17B shows the common information field of the trigger frame, and FIG. 17C shows the user information field of the trigger frame.

Referring to FIG. 17A, a trigger frame includes a frame control field, a duration field, a recipient STA address field, a transmitting STA address field, a common information field, , One or more Per User Info fields, padding, and a Frame Check Sequence (FCS). The RA field indicates the address or ID of the receiving STA, and may be omitted depending on the embodiment. The TA field indicates the address of the transmitting STA.

Referring to FIG. 17B, the common information field includes a trigger type, a length, a cascade indicator, a carrier sensing required, a bandwidth (BW), a guard interval (GI) The number of HE-LTF symbols, the number of HE-LTF symbols, the STBC, the LDPC Extra symbol segment, the AP TX power, the packet extension, the spatial reuse, the Doppler, the HE- Reserved and Trigger-dependent Common Info subfields. The trigger type subfield indicates the type of the trigger frame. The trigger type may be, for example, a basic trigger type (eg, type 0), a beamforming report poll trigger type (eg, type 1), a multi-user block ack request (eg, Type 2), MU-RTS (eg, Type 3), Buffer Status Report Poll (eg, Type 4), GCR MU BAR (eg, Type 5), or BW Query Report Poll But the present invention is not limited thereto. The length subfield indicates the L-SIG length of the HE trigger-based PPDU (e.g., UL MU PPDU). The cascade indicator indicates whether there is a transmission of a subsequent trigger frame following the current trigger frame. The CS Required subfield indicates whether the corresponding STA should determine whether to respond based on the medium sensing result and the NAV. The BW subfield indicates the bandwidth to the HE SIG A of the HE trigger-based PPDU.

Referring to FIG. 17C, the user information field includes an AID 12 subfield, an RU (resource unit) allocation subfield, a coding type subfield, an MCS field, a dual sub-carrier modulation (DCM) field, an RSSI sub-field, a target RSSI sub-field, a Reserved, and a Trigger-dependent Per User Info sub-field. The AID12 subfield indicates the LSB 12 bits of the AID of the STA to receive the corresponding user information field. AID12 subfield = 0 or 2045 indicates that the corresponding user information field is an RU allocation for random access. AID12 Subfield = 4095 indicates that the padding field is started in the trigger frame.

The padding field may optionally be provided in the trigger frame. The padding field extends the length of the trigger frame to give the receiver STA time to prepare the SIFS response after receiving the trigger frame. If a padding field is provided, the padding field has a length of at least two octets and is all set to one.

18 shows a user information field of a trigger frame according to an embodiment of the present invention.

As described above, the AID 12 field of the user information field of the trigger frame shown in FIG. 17 indicates the LSB 12 bits of the AID of the STA to use resources allocated in the trigger frame.

On the other hand, since the existing AID range is from 1 to 2007, the values of 1 to 2007 can be sufficiently represented by the AID field of 11 bits. Thus, according to the example of FIG. 18, the AID 12 field in the user information field of the trigger frame is reduced by one bit to the AID 11 field, and the remaining one bit can be used for another purpose. For example, B0 to B10 denote AID11, and the other bit B11 corresponds to reserved.

For example, when the AID is reduced to the AID 11 field, the 11 bits (B0 to B10) corresponding to the AID 11 field of the corresponding user information field may be set to 2047 if the user information field indicates trigger frame padding . In the AID 12 field scheme, if the AID 12 field = 4095 indicates the start of padding, then in the AID 11 field scheme, the AID 11 field = 2047 may be changed to indicate the start of padding.

An example of setting the Reserved field of the remaining 1 bit (B11) may be as follows.

- Example 1: Regardless of the value of AID11, the Reserved field can be set to 1 by default. If the Reserved field of B11 is used for other purposes, it can be set to 0 as an exception to indicate this.

- Example 2: The Reserved field can be set to 1 only when AID 11 is set to all 1s (i.e., 2047). For example, if AID11 is set to a value other than 2047, the Reserved field is set to zero.

- Example 3: Trigger frame padding may be indicated when AID 11 ([B0: B10]) is set to all 1s (ie, 2047), regardless of the B11 value.

In-band Simultaneous Transmission and Reception (STR)

In-band STR (Simultaneous Transmission and Reception) is a technique that allows simultaneous transmission and reception in the same frequency band. It is also called FDR (full-duplex radio).

19 is a view for explaining the type of STR. In Fig. 19, the client may be an STA.

As shown in FIG. 19A, there is a method in which an AP and a STA pair transmit and receive at the same time, as shown in FIG. 19A. As shown in FIG. 19B, STAs transmit or receive only, . In the latter case, an interference cancellation between the STAs may occur and a separate interference cancellation technique may be required.

20 is a diagram for explaining the magnetic interference of the STR.

Since the TX antenna and the RX antenna are adjacent to each other, the transmission signal may cause interference on reception. Therefore, self-interference cancellation can be performed by various methods.

The present invention proposes a necessary PHY or MAC structure (e.g., a frame structure and an operation method) when an in-band STR scheme is applied to a WiFi system. STR should be designed considering coexistence with existing WiFi system.

Although the method of FIG. 19 (a) will be described below, the present invention can also be applied to the method of FIG. 19 (b) when the STAs are sufficiently spaced apart from each other so that interference does not occur

The following assumptions apply to the following examples.

- Assumptions: In general DL means transmission from AP to STA, and UL means transmission from STA to AP. In the present invention, since the DL / UL is assumed for convenience of explanation, the AP can be interpreted as AP, Mesh, Relay, STA and the like, and the STA can also be interpreted as AP, Mesh, Relay, STA and the like. In addition, the fields such as STF and LTF are not described in order to prevent blurring of the problem.

The present invention proposes a method of applying an STR in a WiFi system by initiating an STR.

There are two ways in which the AP initiates.

(a) In order to initiate the STR, the AP transmits a DL frame in a DL frame including signal information for an UL frame

(b) a method using a separate trigger frame

Figures 21 and 22 illustrate DL frames containing an indicator for STR initiation.

For the (a) scheme, the AP may transmit signal information for the UL frame in the DL frame when the DL frame is transmitted to initiate the STR. The STA reads the signal information for the UL frame and transmits its UL frame. Since the STA needs processing time from receiving the signal information for the UL frame to decoding and generating the UL frame, the STA can transmit the UL frame after the gap time after receiving the signal information. The time of the 'gap' may be, for example, SIFS, DIFS, and the like.

A SIG field for a UL frame may be newly added to a DL frame for transmission of Signal information (e.g., UL SIG in FIG. 21) for an UL frame, or UL frame allocation information may be transmitted to an existing SIG of a DL frame It is also possible to add only the contents.

However, information indicating that UL SIG information (e.g., signal information for UL frame) is included in the DL frame (e.g., STR indication) should be included before UL SIG. The STR indication can be transmitted by reusing the reserved bits of the existing SIG field of the DL frame, or a new frame type including the STR indication can be defined.

Or a new PHY structure may be defined for the STR indication. The UL SIG included in the SIG field basically includes the STA ID to transmit the UL frame. Or a SIG including the STA ID, such as HE-SIG-B, is already included in the DL frame so that the STA ID may be omitted in the UL SIG (e.g., if all STAs receiving DL frame data transmit the UL to the STR ).

In addition, information included in the existing SIG such as TXOP value for UL transmission, RU allocation (for example, when MU OFDMA is applied), frame length, MCS and / or coding type can all be included in the UL SIG of the DL frame . However, if the DL frame, the TXOP, the RU allocation, or the frame length are applied to the UL frame, these values may be omitted from the UL SIG. In addition, when the STA determines the MCS, the coding type, and the like when the UL frame is transmitted, these values may also be omitted from the UL SIG.

If all of the mentioned values can be omitted from the UL SIG, the AP may trigger the STR with only the STR indication.

Alternatively, if all values mentioned are required, the AP uses the reserved bit (eg, B14) of the HE-SIG-A in the DL frame transmitted to the HE SU PPDU or HE ER SU PPDU, And inserts HE-SIG-B to inform UL SIG information. In this case, the HE-SIG-B is transmitted to inform the UL frame configuration method, not the DL frame.

In order to support the STR in the DL frame transmitted to the HE MU PPDU, the AP uses the reserved bit (eg, B7) of the HE-SIG-A field for the STR indication and the HE-SIG- After the transmission of B, an additional HE-SIG field for the UL frame can be transmitted. The UL SIG field may be set similar to HE-SIG-B, but the UL SIG field may not include the values if there are optional values as mentioned above.

Alternatively, as shown in FIG. 22, a STR indication may be transmitted through a reserved bit of L-SIG for fast transmission of an UL frame. In this case, the UL SIG field may be transmitted before the DL SIG field. The STA can start transmitting UL frames after 'gap' time after receiving the UL SIG field. The UL SIG field shall include the STA ID value, since the STAs must verify that the STR transmission is directed to them. In addition, the UL SIG field may include a BSS ID (e.g., BSS color), RU allocation for configuring an UL frame, BW, TXOP duration, UL PPDU length, MCS, and / or coding type.

Next, referring to FIG. 23, a UL frame transmitted by the STR scheme will be described.

The UL Frame transmitted in the STR may include an L-preamble and a common SIG (e.g., HE-SIG-A in case of 11ax format) for protection from the 3rd party and decoding and transmission time of the transmitting STA. The common SIG may include TXOP duration and UL frame length. In this case, the TXOP duration value may be a value obtained by subtracting the value of the L-preamble of the DL frame from the L-preamble of the UL frame in the TXOP duration included in the DL frame.

The UL SIG information included in the UL frame may be changed according to the UL SIG included in the DL frame. If the MCS and the coding type of the UL frame are indicated in the UL SIG field of the DL frame, such information need not be included again in the UL SIG of the UL frame. For example, there is no need for additional SIG information in the UL frame since it is similar to the UL MU procedure of 11ax (e.g., when the AP determines the structure of the UL frame). Thus, for example, the UL frame for the STR can use the 11 PPs TB PPDU structure.

Or if the DL frame only informs the STA ID and RU allocation information to transmit the UL frame, each STA must inform the MCS and the Coding type prior to data transmission of the UL frame, so that the additional SIG information is transmitted in the UL frame Should be transmitted. When 11ax frame structure is used, when a MU OFDMA transmission is performed, a SIG structure to be transmitted according to RU allocation is not defined, so a new SIG structure must be defined. Or if the STR transmission is a SU structure other than an MU, HE SU PPDU and HE ER SU PPDU format can be used.

Or a new STR UL frame structure, it is necessary to define a SIG structure to be transmitted in accordance with RU allocation after the common SIG. As described above, the newly defined SIG structure may include information such as MCS and coding type for data transmission per STA.

24 is a diagram for explaining an STR using a trigger frame.

The AP can send a separate trigger frame for the STR.

Unlike the UL MU precedence that uses the trigger frame in the existing 11ax, in the STR, not only the UL frame but also the DL frame are transmitted simultaneously after the trigger frame. Alternatively, the UL frame may be transmitted after a gap time after the STA receives the L-preamble of the DL frame, or after the STA receives the SIG information of the DL frame after the gap time.

To use a trigger frame, a STR indication must be included in the trigger frame. For example, the STR indicator can be added to the Trigger frame type.

 Alternatively, the Trigger frame type is set to a basic Trigger variant, and a reserved bit (e.g., B5) of the Trigger Dependent User Infor field may be used for the STR indication.

When STR is applied in the MU OFDMA structure, the same DL and UL RU allocation applied to one STA and the same DL and UL frame end points may be advantageous for interference cancellation and hidden node problems. In this case, SIG information such as STA ID, RU allocation, TXOP duration, or frame length may be omitted in the DL frame following the trigger frame. For example, when information such as STA ID, RU allocation, TXOP duration, or frame length is instructed to transmit UL frames through the trigger frame and the same information is also applied to the DL frame, corresponding information is omitted in the SIG field of the DL frame .

The following rules can be applied to both an STR scheme (e.g., FIGS. 21 to 23) that does not use a trigger frame and an STR scheme that uses a trigger frame (e.g., FIG. 24).

(i) In order to avoid the hidden node problem, the point at which DL transmission and UL transmission ends can be aligned. After DL / UL transmission, UL / DL Ack / BA frame can also be transmitted based on STR if necessary.

(ii) If MU OFDMA is used in the STR, the UL transmission may be performed using a portion of the RU or DL RU such as the DL RU assigned to each STA. When some RUs are used, some subcarriers of both ends of the RU to which a DL frame is allocated may be nulled and an UL frame may be transmitted for interference mitigation from other STA packets.

Meanwhile, the STA receiving the DL frame and the STA transmitting the UL frame may be different. In this case, the DL SIG and UL SIG information included in the DL STR frame must include STA ID and RU allocation information, respectively. The remaining information can be configured as described above.

FIG. 25 shows a flow of a method for simultaneously transmitting / receiving a DL / UL frame according to an embodiment of the present invention.

The STA receives the trigger frame from the access point (AP) (2505).

The STA checks whether the trigger frame includes a simultaneous transmission and reception (STR) indicator (2510).

When the trigger frame includes the STR indicator, the STA transmits the UL frame through the resource unit (RU) allocated by the trigger frame and receives the DL frame (2515).

If the trigger frame does not include the STR indicator, the STA transmits only the uplink (UL) frame (2520) through the resource unit (RU) allocated by the trigger frame.

The end of the UL frame and the end of the DL frame may be time aligned.

The UL frame may start after a predetermined gap from the L-preamble of the DL frame.

The STR indicator may be received via the reserved bits of the Trigger Dependent User Information field of the trigger frame.

Control information including at least one of STA ID, RU assignment, TXOP (transmission opportunity) duration, and frame length indicated by the trigger frame may be commonly applied to the DL frame and the UL frame.

In the signal (SIG) field of the DL frame, the control information may be omitted.

The STA may null a predetermined number of subcarriers located at both ends of the RU when transmitting an UL frame.

26 is a view for explaining an apparatus for implementing the above-described method.

The wireless device 800 of FIG. 26 may correspond to the specific STA of the above description, and the wireless device 850 of the above description.

The STA 800 may include a processor 810, a memory 820, a transceiver 830 and an AP 850 may include a processor 860, a memory 870, and a transceiver 880. The transceivers 830 and 880 transmit / receive radio signals and may be implemented in a physical layer such as IEEE 802.11 / 3GPP. Processors 810 and 860 are implemented in the physical and / or MAC layer and are coupled to transceivers 830 and 880. Processors 810 and 860 may perform the UL MU scheduling procedure described above.

Processors 810 and 860 and / or transceivers 830 and 880 may include application specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processors. Memory 820 and 870 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage media and / or other storage units. When an embodiment is executed by software, the method described above may be executed as a module (e.g., process, function) that performs the functions described above. The module may be stored in memory 820, 870 and executed by processor 810, 860. The memory 820, 870 may be located inside or outside the processes 810, 860 and may be coupled to the processes 810, 860 by well known means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The foregoing description of the preferred embodiments of the present invention has been presented for those skilled in the art to make and use the invention. While the foregoing is directed to preferred embodiments of the present invention, those skilled in the art will appreciate that various modifications and changes may be made by those skilled in the art from the foregoing description. Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The present invention can be applied to various wireless communication systems including IEEE 802.11.

Claims (14)

1. A method for a station (STA) transmitting and receiving a frame in a wireless local area network (WLAN)

   Receiving a trigger frame from an access point (AP);

   Checking whether the trigger frame includes a simultaneous transmission and reception (STR) indicator; And

   (UL) frame through a resource unit (RU) allocated by the trigger frame and receiving a DL frame when the trigger frame includes the STR indicator. / RTI >
2. The method according to claim 1,

   Wherein an end of the UL frame and an end of the DL frame are time aligned.
3. 3. The method of claim 2,

   Wherein the UL frame starts after a predetermined gap from the L-preamble of the DL frame.
4. The method according to claim 1,

   Wherein the STR indicator is received via a reserved bit of a Trigger Dependent User Information field of the trigger frame.
5. The method according to claim 1,

   Wherein control information including at least one of a STA ID, an RU assignment, a transmission opportunity (DTA) period, and a frame length indicated by the trigger frame is commonly applied to the DL frame and the UL frame.
6. 6. The method of claim 5,

   Wherein the control information is omitted in a signal (SIG) field of the DL frame.
7. The method according to claim 1,

   Wherein the STA nulls a predetermined number of subcarriers located at both ends of the RU when transmitting the UL frame.
8. In the station (STA)

   A transceiver; And

   Receiving a trigger frame from an access point (AP) through the transceiver, checking whether the trigger frame includes a simultaneous transmission and reception (STR) indicator, and, if the trigger frame includes the STR indicator, (UL) frame through a resource unit (RU) allocated by a frame, and receives a downlink (DL) frame.
9. 9. The method of claim 8,

   Wherein an end of the UL frame and an end of the DL frame are time aligned.
10. 10. The method of claim 9,

    Wherein the UL frame starts after a predetermined gap from an L-preamble of the DL frame.
11. 9. The method of claim 8,

    Wherein the STR indicator is transmitted on a reserved bit of a Trigger Dependent User Information field of the trigger frame.
12. 9. The method of claim 8,

    Wherein control information including at least one of a STA ID, an RU assignment, a transmission opportunity (DTA) period, and a frame length indicated by the trigger frame is commonly applied to the DL frame and the UL frame.
13. 13. The method of claim 12,

    Wherein the control information is omitted in a signal (SIG) field of the DL frame.
14. 9. The method of claim 8,

    Wherein the processor nulls a predetermined number of subcarriers located at both ends of the RU when transmitting the UL frame.

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