CN117898019A

CN117898019A - Method and apparatus for EMLSR operation in wireless LAN

Info

Publication number: CN117898019A
Application number: CN202280058387.9A
Authority: CN
Inventors: 金龙浩
Original assignee: Hyundai Motor Co; Industry Academic Cooperation Foundation of KNUT; Kia Corp
Current assignee: Hyundai Motor Co; Industry Academic Cooperation Foundation of KNUT; Kia Corp
Priority date: 2021-06-28
Filing date: 2022-06-27
Publication date: 2024-04-16

Abstract

A method and apparatus for EMLSR operation in a wireless LAN are disclosed. The method of the first device comprises the steps of: receiving a first data frame from a second device via a first link using a multi-spatial stream; transmitting a receive response frame to the first data frame to the second device via the first link; transmitting a third data frame including configuration information for transmitting the second data frame to the second device via the first link; and transmitting the second data frame to the second device via the second link based on the configuration information.

Description

Method and apparatus for EMLSR operation in wireless LAN

Technical Field

The present disclosure relates to wireless Local Area Network (LAN) communication technology, and more particularly, to a technique for transmitting and receiving frames based on enhanced multi-link single radio (EMLSR) operation.

Background

Recently, with the popularization of mobile devices, wireless lan technology capable of providing a rapid wireless communication service to mobile devices has been a focus of attention. The wireless LAN technology may be a technology supporting wireless access to the internet by a mobile device such as a smart phone, a smart tablet, a laptop computer, a portable multimedia player, an embedded device, etc., based on a wireless communication technology.

With the advent of applications requiring higher throughput and applications requiring real-time transmission, the IEEE 802.11be standard as an ultra high throughput (EHT) wireless LAN technology is being developed. The IEEE 802.11be standard may target to support high throughput of 30 Gbps. The IEEE 802.11be standard may support techniques for reducing transmission delay. Further, the IEEE 802.11be standard may support more extended frequency bandwidths (e.g., 320MHz bandwidth), multi-link transmission and aggregation operations including multi-band operations, multi-Access Point (AP) transmission operations, and/or efficient retransmission operations (e.g., hybrid automatic repeat request (HARQ) operations).

However, since the multilink operation is an operation which is not defined in the existing wireless LAN specification, it may be necessary to define a detailed operation depending on an environment in which the multilink operation is performed. In particular, a device (e.g., station (STA)) supporting enhanced multi-link single radio (EMLSR) operation may wait for reception on multiple links. The device supporting EMLSR operation may be referred to as an "EMLSR device". When frame transmission and reception operations are initiated, the EMLSR device may operate on a single link in which the frame transmission and reception operations are performed. When frame transmission and reception operations are performed on a single link, other links may be in a state where frame transmission and reception operations cannot be performed. In EMLSR devices, time for switching transceivers between links may be required. Accordingly, a method for transmitting and receiving frames considering the operating characteristics of an EMLSR device over a single link may be required.

Meanwhile, the technology written as background of the disclosure is for the purpose of improving understanding of the background of the disclosure and may include what is not yet known to one of ordinary skill in the art to which the disclosure pertains.

Disclosure of Invention

[ problem ]

The present disclosure is directed to a method and apparatus for transmitting and receiving frames based on EMLSR operation in a wireless LAN.

[ technical solution ]

According to a first exemplary embodiment of the present disclosure, a method of a first apparatus for achieving the above object may include: receiving a first data frame from a second device over a first link using a multi-spatial stream; transmitting a receive response frame to the first data frame over the first link to the second device; transmitting a third data frame comprising configuration information for transmitting the second data frame to the second device over the first link; and transmitting the second data frame to the second device over the second link based on the configuration information.

The method may further comprise: receiving a multi-user (MU) request-to-send (RTS) frame from a second device over a first link; and transmitting a Clear To Send (CTS) frame to the second device in response to the MU-RTS frame on the first link, wherein the first data frame is received after the CTS frame is transmitted.

During a first period from a time when the CTS frame is transmitted to a completion time of switching the radio chain of the first device, a receiving operation may not be performed on the second link, and the first period may include (time required for transmitting the CTS frame + time required for receiving the first data frame + time required for transmitting the reception response frame + time required for transmitting the third data frame + time required for switching the radio chain).

The receive response frame and the third data frame may be configured in the form of an aggregate (a) -Medium Access Control (MAC) protocol data unit (MPDU), and the third data frame may be a quality of service (QoS) null frame.

The configuration information may include at least one of information indicating a link on which the second data frame is transmitted, information indicating an Access Category (AC) of the second data frame, or information indicating a scheme of a transmission/reception procedure of the second data frame.

The method may further comprise: a trigger frame is received from the second device over the second link in response to the configuration information indicating that a transmission/reception process of the second data frame is performed based on the first scheme, wherein the transmission/reception process of the second data frame is initiated by the trigger frame.

The method may further comprise: receiving, from the second device, a MU-RTS frame over the second link in response to the configuration information indicating that the transmission/reception process of the second data frame is performed based on the second scheme; and transmitting a CTS frame to the MU-RTS frame to the second device over the second link, wherein the transmission/reception process of the second data frame is initiated by the MU-RTS frame.

According to a second exemplary embodiment of the present disclosure, a method of a second apparatus for achieving the above object may include: transmitting a first data frame to a first device over a first link using a multi-spatial stream; receiving a receive response frame to the first data frame from the first device over the first link; receiving a third data frame comprising configuration information for transmitting the second data frame from the first device over the first link; and receiving a second data frame from the first device over the second link based on the configuration information.

The method may further comprise: transmitting a multi-user (MU) request-to-send (RTS) frame to the first device over the first link; and receiving a Clear To Send (CTS) frame for the MU-RTS frame from the first device over the first link, wherein the first data frame is transmitted after receiving the CTS frame.

The receiving operation of the first apparatus may not be performed on the second link during a first period from a time of receiving the CTS frame to a completion time of switching a radio chain of the first apparatus, and the first period may include a time required to receive the CTS frame + a time required to transmit the first data frame + a time required to receive the receive response frame + a time required to receive the third data frame + a time required to switch the radio chain.

The method may further comprise: transmitting a trigger frame to the first device over the second link in response to the configuration information indicating that a transmission/reception process of the second data frame is performed based on the first scheme, wherein the transmission/reception process of the second data frame is initiated by the trigger frame.

The method may further comprise: transmitting the MU-RTS frame to the first device over the second link in response to the configuration information indicating that the transmission/reception process of the second data frame is performed based on the second scheme; and receiving a CTS frame for the MU-RTS frame from the first device over the second link, wherein the transmission/reception process of the second data frame is initiated by the MU-RTS frame.

According to a third exemplary embodiment of the present disclosure, a method of a first apparatus for achieving the above object may include: receiving a first data frame from a second device over a first link using a multi-spatial stream; transmitting a first receive response frame to the first data frame over the first link to the second device; and performing a receiving operation on the first link without switching a radio chain of the first device in response to information included in the first data frame indicating that a second data frame to be transmitted to the first device exists in the second device.

The method may further comprise: receiving a second data frame from a second device over the first link using the multi-spatial stream; transmitting a second receive response frame to the second data frame over the first link to the second device; and performing a receiving operation on the plurality of links by switching the radio link of the first device in response to the information included in the second data frame indicating that the third data frame to be transmitted to the first device does not exist in the second device.

When the data frame transmission/reception process using the multi-spatial stream is performed on the first link, the reception operation of the first device may not be performed on the second link.

The method may further comprise: receiving a multi-user (MU) request-to-send (RTS) frame from a second device over a first link; and transmitting a Clear To Send (CTS) frame to the MU-RTS frame to the second device over the first link, wherein the transmission/reception process of the first data frame is initiated by the MUR-TS frame.

The control frame for initiating the transmission/reception process of the second data frame may not be used, and the second data frame may be transmitted when the backoff operation in the second apparatus is successful.

The number of multi-spatial streams may correspond to the number of radio chains comprised in the first device.

[ beneficial effects ]

According to the present disclosure, an EMLSR device may wait to receive frames on links corresponding to the number of antennas. When a frame is received on a first one of the links, the EMLSR device may switch the radio link to the first link and receive the frame quickly over the multi-spatial stream. When the frame transmission and reception operations are completed, the EMLSR device may wait again to receive frames from the plurality of links. Thus, an EMLSR device may use multiple antennas to transmit and receive frames at high speed over a single link without communication interruption.

Drawings

Fig. 1 is a conceptual diagram illustrating a first exemplary embodiment of a wireless LAN system.

Fig. 2 is a block diagram showing a first exemplary embodiment of a communication node constituting a wireless LAN system.

Fig. 3 is a conceptual diagram illustrating a first exemplary embodiment of a multilink configured between multilink devices (MLDs).

Fig. 4 is a sequence diagram showing an association procedure of stations in the wireless LAN system.

Fig. 5 is a timing diagram illustrating a first exemplary embodiment of a method of operation of an EDCA-based communication node.

Fig. 6 is a block diagram illustrating a first exemplary embodiment of an enhanced multi-link single radio (EMLSR) device in a wireless LAN.

Fig. 7 is a timing diagram illustrating a first exemplary embodiment of a communication method in an apparatus supporting an EMLSR mode.

Fig. 8 is a timing diagram illustrating a second exemplary embodiment of a communication method in an apparatus supporting an EMLSR mode.

Fig. 9 is a timing diagram illustrating a third exemplary embodiment of a communication method in an apparatus supporting an EMLSR mode.

Fig. 10 is a timing diagram illustrating a fourth exemplary embodiment of a communication method in an apparatus supporting an EMLSR mode.

Fig. 11A is a timing chart illustrating a fifth exemplary embodiment of a communication method in an apparatus supporting an EMLSR mode.

Fig. 11B is a timing chart showing a sixth exemplary embodiment of a communication method in an apparatus supporting an EMLSR mode.

Fig. 12 is a timing chart showing a seventh exemplary embodiment of a communication method in an apparatus supporting an EMLSR mode.

Detailed Description

As the present disclosure is susceptible to various modifications and alternative forms, specific exemplary embodiments have been shown in the drawings and will be described in detail herein. It should be understood, however, that there is no intent to limit the disclosure to the particular exemplary embodiments, but on the contrary, the disclosure is to cover all modifications and alternatives falling within the spirit and scope of the disclosure.

Relational terms such as first, second, and the like may be used to describe various elements, but should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. The term "and/or" refers to any one or combination of a plurality of related and described items.

In exemplary embodiments of the present disclosure, "at least one of a and B" may refer to "at least one of a or B" or "at least one of a combination of one or more of a and B". Further, "one or more of a and B" may refer to "one or more of a or B" or "one or more of a and B in combination.

When an element is referred to as being "coupled" or "connected" to another element, it is understood that the element is directly "coupled" or "connected" to the other element or additional elements may be disposed therebetween. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it should be understood that no additional element is provided therebetween.

The terminology used in the present disclosure is for the purpose of describing particular example embodiments only and is not intended to be limiting of the disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this disclosure, terms such as "comprises" or "comprising" are intended to specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but it is to be understood that the terms do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Terms commonly used in dictionaries should be interpreted as having meanings that match the contextual meaning in the art. In this description, terms are not necessarily to be construed as having formal meanings unless clearly defined otherwise.

Hereinafter, forms of the present disclosure will be described in detail with reference to the accompanying drawings. In describing the present disclosure, in order to facilitate the overall understanding of the present disclosure, like numerals refer to like elements throughout the description of the drawings, and repetitive descriptions thereof will be omitted.

Hereinafter, a wireless communication system to which exemplary embodiments according to the present disclosure are applied will be described. The wireless communication system to which the exemplary embodiments according to the present disclosure are applied is not limited to what is described below, and the exemplary embodiments according to the present disclosure may be applied to various wireless communication systems. A wireless communication system may be referred to as a "wireless communication network".

As shown in fig. 1, the wireless LAN system may include at least one Basic Service Set (BSS). A BSS may refer to a group of stations (e.g., STA1, STA2 (AP 1), STA3, STA4, STA5 (AP 2), STA6, STA7, and STA 8) that may communicate with each other by successful synchronization, and may not refer to a specific region. In the following exemplary embodiments, a station that performs a function as an access point may be referred to as an "Access Point (AP)", and a station that does not perform a function as an access point may be referred to as a "non-AP station" or a "station".

BSSs may be classified into infrastructure BSSs and Independent BSSs (IBSS). Here, BSS1 and BSS2 may refer to infrastructure BSSs, and BSS3 may refer to IBSS. The BSS1 may include a first station (STA 1), a first access point (STA 2 (AP 1)) providing a distribution service, and a Distribution System (DS) connecting a plurality of access points (STA 2 (AP 1) and STA5 (AP 2)). In BSS1, a first access point STA2 (AP 1) may manage the first station STA1.

The BSS2 may include a third station (STA 3), a fourth station (STA 4), a second access point (STA 5 (AP 2)) providing a distribution service, and a DS connecting a plurality of access points (STA 2 (AP 1) and STA5 (AP 2)). In BSS2, the second access point STA5 (AP 2) may manage the third station STA3 and the fourth station STA4.

BSS3 may refer to an IBSS operating in ad hoc mode. An access point as a centralized management entity may not exist in the BSS 3. That is, in the BSS3, the stations STA6, STA7, and STA8 may be managed in a distributed manner. In BSS3, all stations STA6, STA7 and STA8 may refer to mobile stations and may constitute a self-contained network since they are not allowed to access the DS.

Access points STA2 (AP 1) and STA5 (AP 2) may provide access to the DS for their associated stations STA1, STA3, and STA4 via a wireless medium. In BSS1 or BSS2, communication between stations STA1, STA3, and STA4 is generally performed through access points STA2 (AP 1) and STA5 (AP 2), but when a direct link is established, direct communication between stations STA1, STA3, and STA4 is possible.

Multiple infrastructure BSSs may be interconnected by a DS. The BSSs connected through the DS may be referred to as Extended Service Sets (ESS). Communication nodes STA1, STA2 (AP 1), STA3, STA4, and STA5 (AP 2) included in the ESS may communicate with each other, and any station (STA 1, STA3, or STA 4) may move from one BSS to another BSS within the same ESS while communicating without interruption.

The DS may be a mechanism for one access point to communicate with another access point, according to which the access point may transmit frames for stations associated with its managed BSS, or for any station that has moved to another BSS. In addition, the access point may transmit frames to and receive frames from an external network, such as a wired network. Such a DS is not necessarily a network, and its form is not limited if it can provide a predetermined distribution service specified in the IEEE 802.11 standard. For example, the DS may be a wireless network such as a mesh network, or a physical structure that connects access points to each other. Communication nodes STA1, STA2 (AP 1), STA3, STA4, STA5 (AP 2), STA6, STA7, and STA8 included in the wireless LAN system may be configured as follows.

As shown in fig. 2, the communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to a network to perform communication. The transceiver 230 may be referred to as a transceiver, a Radio Frequency (RF) unit, an RF module, etc. In addition, the communication node 200 may further comprise an input interface device 240, an output interface device 250, a storage device 260, etc. The respective components included in the communication node 200 may be connected to communicate with each other through a bus 270.

However, the respective components included in the communication node 200 may be connected by separate interfaces or separate buses centered on the processor 210 instead of the common bus 270. For example, the processor 210 may be connected to at least one of the memory 220, the transceiver 230, the input interface device 240, the output interface device 250, and the storage device 260 through a dedicated interface.

Processor 210 may execute program commands stored in at least one of memory 220 and storage 260. Processor 210 may refer to a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), or a special-purpose processor on which methods according to exemplary embodiments of the present invention are performed. Each of the memory 220 and the storage 260 may be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be configured with at least one of a Read Only Memory (ROM) and a Random Access Memory (RAM).

As shown in fig. 3, the MLD may have a Medium Access Control (MAC) address. In an exemplary embodiment, the MLD may refer to an AP MLD and/or a non-AP MLD. The MAC address of the MLD may be used in a multi-link establishment procedure between the non-AP MLD and the AP MLD. The MAC address of the AP MLD may be different from the non-AP MLD. The APs affiliated to the AP MLD may have different MAC addresses, and the stations affiliated to the AP MLD may have different MAC addresses. Each of the APs having different MAC addresses within the AP MLD may be responsible for each link and may perform the task of an independent AP.

Each of the STAs having different MAC addresses within the non-AP MLD may be responsible for each link and may perform the tasks of an independent STA. The non-AP MLD may be referred to as STA MLD. MLD may support Simultaneous Transmit and Receive (STR) operations. In this case, the MLD may perform a transmission operation in link 1 and may perform a reception operation in link 2. MLDs that support STR operations may be referred to as STR MLDs (e.g., STR AP MLD, STR non-AP MLD). In an exemplary embodiment, a link may refer to a channel or a frequency band. Devices that do not support STR operation may be referred to as non-STR (NSTR) AP MLD or NSTR non-AP MLD (or NSTR STA MLD).

MLD can transmit and receive frames in multiple links by using a discontinuous bandwidth extension scheme (e.g., 80mhz+80mhz). The multilink operation may include multi-band transmission. The AP MLD may include a plurality of APs, and the plurality of APs may operate in different links. Each of the plurality of APs may perform the functions of a lower MAC layer. Each of the plurality of APs may be referred to as a "communication node" or "lower entity. The communication node (i.e., AP) may operate under control of an upper layer (or processor 210 shown in fig. 2). The non-AP MLD may include a plurality of STAs, and the plurality of STAs may operate in different links. Each of the plurality of STAs may be referred to as a "communication node" or "lower entity. The communication node (i.e., STA) may operate under control of an upper layer (or processor 210 shown in fig. 2).

The MLD may perform communication in a plurality of frequency bands (i.e., multiple frequency bands). For example, the MLD may perform communication using an 80MHz bandwidth according to a channel extension scheme (e.g., a bandwidth extension scheme) in a 2.4GHz band, and perform communication using a 160MHz bandwidth according to a channel extension scheme in a 5GHz band. The MLD may perform communication using 160MHz bandwidth in the 5GHz band and may perform communication using 160MHz bandwidth in the 6GHz band. One frequency band (e.g., one channel) used by the MLD may be defined as one link. Alternatively, a plurality of links may be configured in one frequency band used by the MLD. For example, the MLD may configure one link in the 2.4GHz band and two links in the 6GHz band. The respective links may be referred to as a first link, a second link, and a third link. Alternatively, each link may be referred to as link 1, link 2, link 3, and so on. The link number may be set by the access point and an Identifier (ID) may be assigned to each link.

The MLD (e.g., AP MLD and/or non-AP MLD) may configure the multilink by performing an access procedure and/or a negotiation procedure for multilink operation. In this case, the number of links and/or links to be used in the multilink may be configured. The non-AP MLD (e.g., STA) may identify information on a frequency band capable of communicating with the AP MLD. In a negotiation process for multi-link operation between the non-AP MLD and the AP MLD, the non-AP MLD may configure one or more of the links supported by the AP MLD for multi-link operation. Stations that do not support multi-link operation (e.g., IEEE 802.11a/b/g/n/ac/ax STAs) may connect to one or more links of the multi-links supported by the AP MLD.

Each of the AP MLD and the STA MLD may have an MLD MAC address, and each of the AP and the STA operating in each link may have a MAC address. The MLD MAC address of the AP MLD may be referred to as an AP MLD MAC address, and the MLD MAC address of the STA MLD may be referred to as a STA MLD MAC address. The MAC address of the AP may be referred to as an AP MAC address, and the MAC address of the STA may be referred to as an STA MAC address. In the multilink negotiation process, an AP MLD MAC address and a STA MLD MAC address may be used. The address of the AP and the address of the STA may be exchanged and/or configured during the multilink negotiation process.

When the multilink negotiation process is completed, the AP MLD may generate an address table and manage and/or update the address table. One AP MLD MAC address may be mapped to one or more AP MAC addresses, and corresponding mapping information may be included in the address table. One STA MLD MAC address may be mapped to one or more STA MAC addresses and corresponding mapping information may be included in the address table. The AP MLD may identify address information based on the address table. For example, upon receiving the STA MLD MAC address, the AP MLD may identify one or more STA MAC addresses mapped to the STA MLD MAC address based on the address table.

In addition, the STA MLD may manage and/or update the address table. The address table may include "mapping information between AP MLD MAC address and AP MAC address" and/or "mapping information between STA MLD MAC address and STA MAC address". The AP MLD may receive a packet from the network, identify an address of the STA MLD included in the packet, identify a link supported by the STA MLD, and may identify an STA responsible for the link from the address table. The AP MLD may set the STA MAC address of the identified STA as the receiver address, and may generate and transmit a frame including the receiver address.

Meanwhile, the association process in the wireless LAN system may be performed as follows.

As shown in fig. 4, the association procedure of the STA in the infrastructure BSS can be generally divided into a probe step of detecting the AP, an authentication step with the detected AP, and an association step with the authenticated AP. The STA may be an STA MLD or an STA affiliated to the STA MLD, and the AP may be an AP MLD or an AP affiliated to the AP MLD.

The STA may detect the neighboring AP using a passive scanning scheme or an active scanning scheme. When using the passive scanning scheme, the STA may detect neighboring APs by overheard beacons transmitted by the APs. When the active scanning scheme is used, the STA may transmit a probe request frame and may detect the neighboring AP by receiving a probe response frame from the AP as a response to the probe request frame.

When a neighboring AP is detected, the STA may perform an authentication step with the detected AP. In this case, the STA may perform an authentication step with a plurality of APs. Authentication algorithms according to the IEEE 802.11 standard can be classified into an open system algorithm that exchanges two authentication frames, a shared key algorithm that exchanges four authentication frames, and the like.

The STA may transmit an authentication request frame based on an authentication algorithm according to the IEEE 802.11 standard, and may complete authentication with the AP by receiving an authentication response frame from the AP as a response to the authentication request frame.

When authentication with the AP is completed, the STA may perform an association step with the AP. In this case, the STA may select one AP from among APs with which the STA has performed the authentication step, and perform the association step with the selected AP. That is, the STA may transmit an association request frame to the selected AP, and may complete association with the selected AP by receiving an association response frame from the selected AP as a response to the association request frame.

Meanwhile, a communication node (e.g., an access point, a station, etc.) belonging to the wireless LAN system may perform transmission and reception operations of frames based on a Point Coordination Function (PCF), a Hybrid Coordination Function (HCF), HCF-controlled channel access (HCCA), a Distributed Coordination Function (DCF), an Enhanced Distributed Channel Access (EDCA), etc.

In the wireless LAN system, frames can be classified into management frames, control frames, and data frames. The management frames may include association request frames, association response frames, reassociation request frames, reassociation response frames, probe request frames, probe response frames, beacon frames, disassociation frames, authentication frames, deauthentication frames, action frames, and the like.

The control frames may include an Acknowledgement (ACK) frame, a Block ACK Request (BAR) frame, a Block ACK (BA) frame, a Power Save (PS) poll frame, a Request To Send (RTS) frame, a Clear To Send (CTS) frame, and so forth. Data frames may be classified into quality of service (QoS) data frames and non-QoS data frames. QoS data frames may refer to data frames that need to be transmitted according to QoS, and non-QoS data frames may indicate data frames that do not need to be transmitted according to QoS. The QoS data frame may include a QoS null frame and the QoS null frame may not include a payload.

Meanwhile, in a wireless LAN system, a communication node (e.g., an access point or station) may operate based on the EDCA scheme.

As shown in fig. 5, a communication node desiring to transmit a control frame (or a management frame) may perform a channel state monitoring operation (e.g., a carrier sensing operation) during a predetermined period of time (e.g., a short inter-frame space (SIFS) or a PCF IFS (PIFS)), and when it is determined that the channel state is idle during the predetermined period of time (e.g., SIFS or PIFS), the communication node may transmit the control frame (or the management frame). For example, when the channel state is determined to be idle during SIFS, the communication node may transmit an ACK frame, a BA frame, a CTS frame, etc. Further, when the channel state is determined to be idle during PIFS, the communication node may transmit a beacon frame or the like. On the other hand, when it is determined that the channel state is busy during a predetermined period (e.g., SIFS or PIFS), the communication node may not transmit a control frame (or a management frame). Here, the carrier sensing operation may refer to a Clear Channel Assessment (CCA) operation.

A communication node desiring to transmit a non-QoS data frame may perform a channel state monitoring operation (e.g., a carrier sensing operation) during DCF IFS (DIFS), and when the channel state is determined to be idle during DIFS, the communication node may perform a random backoff procedure. For example, the communication node may select a backoff value (e.g., a backoff counter) within the contention window according to a random backoff procedure, and may perform a channel state monitoring operation (e.g., a carrier sensing operation) during a period corresponding to the selected backoff value (hereinafter referred to as a "backoff period"). The communication node may transmit a non-QoS data frame when the channel state is determined to be idle in the backoff period.

A communication node desiring to transmit QoS data frames may perform a channel state monitoring operation (e.g., a carrier sensing operation) during an Arbitration IFS (AIFS), and when the channel state is determined to be idle during the AIFS, the communication node may perform a random backoff procedure. The AIFS may be configured according to an Access Category (AC) of a data unit (e.g., a Protocol Data Unit (PDU)) included in the QoS data frame. The AC of the data unit may be as shown in table 1 below.

TABLE 1

Ac_bk may indicate background data, ac_be may indicate data transmitted in a best effort manner, ac_vi may indicate video data, and ac_vo may indicate voice data. For example, the length of the AIFS of the QoS data frame corresponding to each of ac_vo and ac_vi may be configured to be equal to the length of the DIFS. The length of the AIFS of the QoS data frame corresponding to each of the ac_be and the ac_bk may BE configured to BE longer than the length of the DIFS. Here, the length of the AIFS of the QoS data frame corresponding to the ac_bk may BE configured to BE longer than the length of the AIFS of the QoS data frame corresponding to the ac_be.

During random backoff, the communication node may select a backoff value (e.g., a backoff counter) within a contention window of the AC according to the QoS data frame. The contention window according to the AC may be as shown in table 2 below. CW (continuous wave) _min Can indicate the minimum value of the contention window, CW _max The maximum value of the contention window may be indicated, and each of the minimum value and the maximum value of the contention window may be represented by the number of slots.

TABLE 2

AC	CW _min	CW _max
			AC_BK	31	1023
AC_BE	31	1023
			AC_VI	15	31
AC_VO	7	15

The communication node may perform a channel state monitoring operation (e.g., a carrier sensing operation) in the backoff period and may transmit the QoS data frame when the channel state is determined to be idle in the backoff period.

Hereinafter, a data transmission and reception method in the wireless LAN system will be described. Even when a method (e.g., transmission or reception of a signal) performed at a first communication node of the communication nodes is described, a corresponding second communication node may perform a method (e.g., reception or transmission of a signal) corresponding to the method performed at the first communication node. That is, when describing the operation of the STA, the AP corresponding thereto may perform the operation corresponding to the operation of the STA. Conversely, when describing the operation of an AP, a STA corresponding thereto may perform an operation corresponding to the operation of the AP. In an exemplary embodiment, the operation of the STA may be interpreted as the operation of the STA MLD, the operation of the STA MLD may be interpreted as the operation of the STA, the operation of the AP may be interpreted as the operation of the AP MLD, and the operation of the AP MLD may be interpreted as the operation of the AP.

As shown in fig. 6, the EMLSR device 600 may be an MLD that supports MLSR operation and/or EMLSR operation. EMLSR device 600 may be referred to as an MLSR device. An EMLSR STA (or MLSR STA) may be an STA supporting MLSR operation and/or EMLSR operation, and an EMLSR AP (or MLSR AP) may be an AP supporting MLSR operation and/or EMFSR operation. The MLSR operation may refer to an MLSR mode, and the EMLSR operation may refer to an EMLSR mode. EMLSR device 600 may include antennas 610-1 and 610-2, EMLSR control message detection blocks 620-1 and 620-2, spatial stream processing block 630, modulation and demodulation block 640, wireless LAN modem 650, and/or higher layer block 660. In an exemplary embodiment, the spatial stream may be referred to as "SS".

EMLSR device 600 may include multiple antennas 610-1 and 610-2. The first antenna 610-1 may be used for sensing operations and/or receiving operations of signals on the first link. The second antenna 610-2 may be used for sensing operations and/or receiving operations of signals on the second link. The frequency at which the first link operates may be different from the frequency at which the second link operates. The sensing operation and/or the receiving operation performed by the first antenna and/or the second antenna may be referred to as a "listening operation". To simultaneously receive the spatial stream signals, the first antenna 610-1 and the second antenna 610-2 may perform a sensing operation and/or a receiving operation of the signals on one of the first link and the second link. Of the plurality of antennas 610-1 and 610-2 included in the EMLSR device 600, one antenna may be a main antenna and the remaining antennas may be auxiliary antennas. The primary and secondary antennas may be preconfigured. Alternatively, the primary and secondary antennas may be configured during a negotiation process between the EMLSR device 600 and another device (e.g., an AP MLD supporting EMLSR operation). An antenna performing a listening operation on a link having a low number (e.g., low index) may be configured as a primary antenna, and the remaining antennas may be configured as secondary antennas.

The first EMLSR control frame detection block 620-1 may be connected to or cooperate with the first antenna 610-1 and the second EMLSR control frame detection block 620-2 may be connected to or cooperate with the second antenna 610-2. Electromagnetic waves (e.g., signals) detected by antennas 610-1 and 610-2 may be input to EMLSR control frame detection blocks 620-1 and 620-2. The EMLSR control frame detection blocks 620-1 and 620-2 may determine whether an electromagnetic wave (e.g., signal) corresponds to a particular control frame (e.g., initial control frame). The EMLSR control frame detection blocks 620-1 and 620-2 may support only predefined Modulation and Coding Schemes (MCSs) and may identify only predefined control frame formats. The format of the predefined control frames (e.g., specific control frames, initial control frames) may include a Request To Send (RTS) frame, a multi-user (MU) -RTS trigger frame, and/or a Buffer Status Report Poll (BSRP) trigger frame.

When a specific control frame is detected by the EMLSR control frame detection blocks 620-1 and/or 620-2, the EMLSR device 600 may perform a reception operation for receiving data through a plurality of SSs by simultaneously using as many spatial streams as the number of spatial streams (e.g., the number of antennas) supported by the EMLSR device 600. In order to perform a reception operation for simultaneously receiving the multi-space stream, a Clear To Send (CTS) frame may be transmitted through the first antenna 610-1 after a short inter-frame space (SIFS) from a time when a specific control frame is detected on the first link, and the second antenna 610-2 may be operated on a second link where the specific control frame is not detected may be switched to and operated on the first link. In other words, the receiving radio chain (i.e., the RX radio chain) may be switched to operate on the first link. In this disclosure, an RX radio chain may refer to a radio chain. Further, in the present disclosure, a radio chain may refer to an RX radio chain or an RX chain. A radio chain may refer to a Radio Frequency (RF) chain. The switching of the operating link (e.g., switching of the radio link) of the second antenna 610-2 may start after a time when a specific control frame on the first link is detected, and may be completed after transmitting a CTS signal after passing through the SIFS until the SIFS is completed. Thereafter, multiple spatial streams (e.g., two spatial streams) may be received through the multiple antennas 610-1 and 610-2. The operation of receiving MU-RTS trigger frames and the operation of switching radio chains to receive multi-spatial streams may be referred to as "EMLSR operation.

When a signal is detected by one of the plurality of antennas 610-1 and 610-2 and the signal is determined by the EMLSR control frame detection blocks 620-1 and 620-2 to be not a specific control frame, the signal may be transferred to the modulation/demodulation block 640 without passing through the spatial stream processing block 630. One antenna of the detection signal may be the main antenna.

When the EMLSR control frame detection blocks 620-1 and 620-2 detect a specific control frame and perform a multi-spatial stream reception process, the spatial stream processing block 630 may perform a rearrangement operation on signals (e.g., symbols) received through the plurality of antennas 610-1 and 610-2. When a space-time code is used, a single symbol may be generated into a plurality of symbols through an encoding operation, and the plurality of symbols may be transmitted. The space-time code may be an Alamouti code. The spatial stream processing block 630 may perform an operation of recovering the redundancy symbols into a single symbol during the decoding process.

The output symbols of spatial stream processing block 630 may be input to a modulation/demodulation block 640. The modulation/demodulation block 640 may generate bits by performing demodulation operations on the symbols. The modulation/demodulation block 640 may perform channel coding operations and/or channel decoding operations. The output bits of the modulation/demodulation block 640 may be transmitted to the wireless LAN modem 650. The wireless LAN modem 650 may perform a Medium Access Control (MAC) operation defined in the IEEE 802.11 standard. The output of the wireless LAN modem 650 may be passed to a higher layer block 660. Higher layer block 660 may perform higher layer operations defined in the IEEE 802.11 standard. The series of operations performed after the specific control frame is detected by the EMLSR control frame detection block may be operations performed during the EMLSR operation.

In the EMLSR device 600, the transmission operation may be performed in reverse order of the above-described reception operation.

As shown in fig. 7, the AP MLD and the STA MLD may support the EMLSR mode. In an exemplary embodiment, STA MLD may refer to STA MLD1 and/or STA MLD2. The frame transmission and reception procedure between the AP MLD and the STA MLD may be initiated by a specific control frame (e.g., MU-RTS frame) agreed between the AP MLD and the STA MLD. The AP MLD may initiate the multi-spatial streaming process by transmitting a multi-user request to send (MU-RTS) frame on one of the multiple links. In this case, the channel state of each link may not be considered. Thus, the AP MLD may transmit MU-RTS frames over multiple available links. STA MLD1 may receive the MU-RTS frame from the AP MLD. STA MLD1 may select a link (e.g., a first link) having the best reception state (e.g., the best reception quality) among links on which MU-RTS frames are received, and transmit a clear-to-send (CTS) frame on the selected link.

STA MLD1 may perform a radio link switching operation from when a link is selected. STA MLD1 may receive the MU-RTS frame and transmit a CTS frame to MU-RTS. STA MLD1 may receive a frame (e.g., a data frame) over a link (e.g., a first link) over which STA MLD1 transmits a CTS frame by using multiple spatial frames (e.g., two spatial frames). The number of multi-spatial streams may correspond to the number of radio chains included in the STA MLD 1. When performing the radio chain switching operation, it may take time of EMLSR Delay1 in STA MLD 1. In an exemplary embodiment, the data frame may be a data unit, a Physical Protocol Data Unit (PPDU), or a PPDU frame, or a medium access control layer (MAC) protocol data unit (MPDU).

STA MLD1 (e.g., STA 1) may receive the data frame from AP MLD (e.g., AP 1) on the first link and may transmit the reception response frame after SIFS passes from the time of receiving the data frame. In an exemplary embodiment, the reception response frame may be an Acknowledgement (ACK) frame or a Block ACK (BA) frame. STA MLD1 may transmit the reception response frame by using two or more spatial streams or one spatial stream.

After the frame transmission and reception process (e.g., after transmitting a reception response frame), STA MLD1 may restore the switched radio link to the original link to await reception of MU-RTS frames on multiple links. When restoring the radio chain to the original link, time of EMLSR Delay2 may be required in STA MLD 1. The EMLSR device may receive the MU-RTS frame after a time of EMLSR Delay2 has elapsed after transmitting the receive response frame on the second link. In an exemplary embodiment, the operation of waiting to receive a frame (e.g., a receiving operation) may refer to an operation of monitoring a link (or channel) to receive the frame.

AP1 may transmit a MU-RTS frame on a first link and AP2 may transmit a MU-RTS frame on a second link. STA1 may initiate the data frame transmission and reception process by transmitting a CTS frame over the primary link. The Medium Access Control (MAC) header of the MU-RTS frame may include a duration field. The other communication node (e.g., MLD, AP, STA) may set a Network Allocation Vector (NAV) to a time corresponding to the value of the duration field, and may not perform a transmission operation during a time corresponding to the set NAV. The duration field included in the MAC header of the MU-RTS frame may be set to indicate a period including a time required for the STA MLD to transmit the reception response frame.

Although the AP2 of the AP MLD transmits the MU-RTS frame on the second link, the STA1 of the STA MLD1 transmits the CTS frame on the first link, and thus it is not necessary to set the NAV on the second link. Thus, the STA may wait on the second link during the time after receiving the MU-RTS frame (sifs+the time required to detect the preamble of the frame (e.g., data frame)) and may release the NAV if the preamble of the frame is not detected. The time required to detect the preamble of the frame may be replaced with the time required to detect the MAC header or the time required to transmit the CTS frame.

When STA1 of STA MLD1 transmits a CTS frame on a first link and performs a radio link switching operation, a second link may be in a state where it is impossible to receive a frame (e.g., a data frame). That is, the channel sensing operation may not be performed on the second link. The above-described state (i.e., the link state when EMLSR operation is performed) may be the same or similar to the state of the blind period in a non-simultaneous transmission and reception (NSTR) link pair. When the first link and the second link are NSTR link pairs, the blind period on the second link may begin at the time of transmitting the CTS frame on the first link even when a radio link switching operation is not performed. When the first link and the second link are STR link pairs, a blind period on the second link may begin when a radio link switching operation is performed. The end time of the blind period may be the time when the transmission of the reception response frame and the recovery of the radio chain are completed. The end time of the blind period may be a time after the time of EMLSR Delay2 has elapsed from the time of transmitting the reception response frame. The timer Medium SynDelay may be operated since channel sensing operations are not performed during the blind periods on the second link. The timer Medium SynDelay may be started after the end of the blind period. During the time corresponding to the timer Medium SynDelay, no transmission operation may be performed. The channel sensing operation may be performed during a time corresponding to the timer Medium SynDelay.

As shown in fig. 8, the AP MLD and the STA MLD may support the EMLSR mode. In an exemplary embodiment, STA MLD may refer to STA MLD1 and/or STA MLD2.AP1 may transmit a MU-RTS frame on a first link and AP2 may transmit a MU-RTS frame on a second link. STA1 may initiate the data frame transmission and reception procedure by transmitting a CTS frame on the primary link in response to the MU-RTS frame. The MAC header of the MU-RTS frame may include a duration field. The other communication node (e.g., MLD, AP, STA) may set the NAV to a time corresponding to the value of the duration field, and may not perform the transmission operation during the time corresponding to the set NAV. The duration field included in the MAC header of the MU-RTS frame may be set to indicate a period including a time required for the STA MLD to transmit the reception response frame.

Although the AP2 of the AP MLD transmits the MU-RTS frame on the second link, the STA1 of the STA MLD1 transmits the CTS frame on the first link, and thus it is not necessary to set the NAV on the second link. In order to release the needlessly set NAV, AP2 of AP MLD1 may transmit a CF-END frame or QoS null frame (e.g., qoS null data frame) including a duration field set to 0 on the second link. AP2 may transmit a CF-END frame or QoS null frame after identifying that no CTS frame was transmitted on the second link. Thus, when a CTS frame is received on a first link, AP2 may transmit a CF-END frame or QoS null frame on a second link. The time at which the AP2 may transmit the CF-END frame or the QoS null frame on the second link may be immediately after the time at which the CTS frame is detected. The time of detecting the CTS frame may be a time of detecting a preamble of a frame (e.g., PPDU frame, CTS frame), a time of detecting a MAC header of the CTS frame, or a time of an entire transmission of the CTS frame.

As shown in fig. 9, the AP MLD and the STA MLD may support the EMLSR mode. AP1 of AP MLD may transmit a MU-RTS frame on the first link. STA1 of STA MLD may receive the MU-RTS frame from AP1 on the first link and transmit a CTS frame on the first link in response to the MU-RTS frame. AP1 may receive a CTS frame from STA1 over the primary link. According to the above operation, a frame transmission and reception procedure (hereinafter, referred to as an "EMLSR communication procedure") based on an EMLSR operation using multi-spatial streams may be initiated. Accordingly, a procedure for transmitting and receiving frames (e.g., data frames, receive response frames) may be performed between the AP MLD and the STA MLD. The number of multi-spatial streams may correspond to the number of radio chains included in the STA MLD.

When a data unit (e.g., data, packet) is present in a queue of the STA MLD while the EMLSR communication procedure is performed, a procedure of transmitting and receiving a data frame may be initiated using one of a plurality of links after the EMLSR communication procedure. After the EMLSR communication process, a time medium syncdelay may be set on the second link (e.g., a timer medium syncdelay is set). Thus, during the time corresponding to the timer, transmission of data or frames on the second link may not be performed. Since the EMLSR communication process is performed on the first link, the medium syncdelay is not provided on the first link, and the frame transmission and reception process may be performed using multiple spatial streams in multiple radio chains, the data frame may be transmitted only on the first link. In order to transmit a data frame, the STA1 may perform a backoff operation after passing through an arbitrary inter-frame space (AIFS) according to an Access Category (AC) of the data frame from a time of transmitting a reception response frame (e.g., BA frame). When the backoff operation is successful, STA1 may transmit a data frame using multiple spatial streams (e.g., two spatial streams). After transmitting the data frame, STA1 may receive a reception response frame for the data frame from AP 1.

When the first link and the second link are NSTR link pairs, medium syncdelay may be released in STA2 during the time required for STA1 to transmit data frames on the first link. The time required for STA1 to transmit a data frame on the first link may be a blind period on the second link. The channel sensing operation may not be performed in the blind period. STA2 may again set medium syncdelay after the blind period. Even when the first link and the second link are STR link pairs (e.g., when the first link and the second link are not NSTR link pairs), since STA MLD is EMLSR STA MLD (e.g., EMLSR STA), the time at which STA MLD transmits data frames on the first link may be a dead zone period on the second link. Therefore, medium SyncDelay may be set on the second link.

As shown in fig. 10, the AP MLD and the STA MLD may support the EMLSR mode. AP1 of AP MLD may transmit a MU-RTS frame on the first link. STA1 of STA MLD may receive the MU-RTS frame from AP1 on the first link and transmit a CTS frame on the first link in response to the MU-RTS frame. AP1 may receive a CTS frame from STA1 over the primary link. According to the above operation, a frame transmission and reception procedure (i.e., an EMLSR communication procedure) based on an EMLSR operation using multi-spatial streams may be initiated. Accordingly, a procedure for transmitting and receiving frames (e.g., data frames, receive response frames) may be performed between the AP MLD and the STA MLD. The number of multi-spatial streams may correspond to the number of radio chains included in the STA MLD.

When there are data units (e.g., data, packets, MPDUs, PPDUs) in the queue while the EMLSR communication process is being performed, a process for transmitting and receiving data frames may be initiated using one of the plurality of links after the EMLSR communication process. A Traffic Identifier (TID) may be determined from the AC of the data frame and a link over which the data frame is transmitted may be determined based on a TID-to-link mapping. For example, the link on which the data frame is transmitted may be determined as the second link.

In order to transmit a data frame on the second link, STA2 may perform a backoff operation after an elapsed time (time EMLSR Delay2+ AIFS according to AC of the data frame) from the transmission of a reception response frame (e.g., BA frame) on the first link. The time EMLSR Delay2 may be the time required to switch the radio chain. The timer medium syncdelay on the second link may begin after a time EMLSR Delay2 has elapsed since the time the receive response frame was transmitted on the first link. When the timer Medium SyncDelay operates, only data frame transmission and reception procedures initiated by a particular control frame (e.g., short control frame, RTS frame) may be allowed.

When a reception response frame is transmitted using a single spatial stream, the radio chain may be switched before a time EMLSRDelay2 from the transmission end time of the reception response frame. When the transmission of the reception response frame is completed, the second link may be in a state in which the channel sensing operation may be performed. In this case, the timer medium syncdelay on the second link may start to operate from the transmission end time of the reception response frame of the first link, which is the time when the channel sensing operation may be performed. The backoff operation for transmitting the data frame may be performed after an AIFS elapses from a transmission end time of the reception response frame on the first link, which is a time when the channel sensing operation may be performed.

Fig. 11A is a timing chart showing a fifth exemplary embodiment of a communication method in an apparatus supporting an EMLSR mode, and fig. 11B is a timing chart showing a sixth exemplary embodiment of a communication method in an apparatus supporting an EMLSR mode.

As shown in fig. 11A and 11B, the AP MLD and the STA MLD may support the EMLSR mode. AP1 of AP MLD may transmit a MU-RTS frame on the first link. STA1 of STA MLD may receive the MU-RTS frame from AP1 on the first link and transmit a CTS frame on the first link in response to the MU-RTS frame. AP1 may receive a CTS frame from STA1 over the primary link. According to the above operation, a frame transmission and reception procedure (i.e., an EMLSR communication procedure) based on an EMLSR operation using multi-spatial streams may be initiated. Accordingly, a procedure for transmitting and receiving frames (e.g., data frames, receive response frames) may be performed between the AP MLD and the STA MLD. The number of multi-spatial streams may correspond to the number of radio chains included in the STA MLD.

When a data unit (e.g., data, packet) exists in a queue of the STA MLD while the EMLSR communication procedure is performed, the procedure for transmitting and receiving the data frame may be initiated using one of a plurality of links after the EMLSR communication procedure. The TID may be determined from the AC of the data frame and the link over which the data frame is transmitted may be determined based on the TID-to-link mapping. For example, the link over which the data frame is transmitted may be determined as the second link.

STA MLD1 (e.g., STA 1) may notify AP1 of information indicating that a data unit exists in a queue and/or information of a data frame. The above information may be configuration information for transmitting the data frame. STA1 may transmit the above configuration information along with the BA frame. Since the size of the MAC header of the BA frame is fixed, it may be difficult to transmit additional information (e.g., configuration information for transmitting the data frame) through the MAC header. On the other hand, the MAC header of the QoS null frame (e.g., qoS null data frame) may include additional information. Accordingly, STA1 may transmit a QoS null frame including the above configuration information (e.g., additional information) together with the BA frame. That is, the QoS null frame may include configuration information for transmitting a data frame (e.g., a data unit). The BA frames and QoS null frames may be configured in the form of aggregate (a) -MAC Protocol Data Units (MPDUs) or as separate frames.

The duration of the transmission opportunity (TXOP) may be set by a duration field included in the MAC header of the MU-RTS frame. The TXOP may include the time required to transmit the BA frame. However, to transmit information indicating the presence of data units in the queue, it may be allowed to transmit QoS null frames having a short length. That is, the duration of the TXOP may be extended for transmitting QoS null frames. To extend the duration of the TXOP, a duration field included in the MAC header of the CTS frame as a response to the MU-RTS frame may indicate a period of time (i.e., an extended TXOP) including the time required to transmit the QoS null frame. The value indicated by the duration field included in the MAC header of the CTS frame may be greater than the value indicated by the duration field included in the MAC header of the MU-RTS frame.

The duration of the TXOP may be set to not exceed the TXOP limit. The TXOP limit may be a maximum duration of the TXOP. The period including the time required to transmit QoS null frames may not exceed the TXOP limit. If the time required to transmit the QoS null frame exceeds the TXOP limit, the QoS null frame may not be transmitted. If the duration of the TXOP is not allowed to be extended, STA1 may transmit a QoS null frame by performing a channel access procedure after transmitting the BA frame. That is, STA1 may perform the backoff operation again to transmit the QoS null frame on the first link, and when the backoff operation is completed, STA1 may transmit the QoS null frame.

The Enhanced Distributed Channel Access (EDCA) parameter used in the backoff operation for transmitting the QoS null frame may be an EDCA parameter of an AC of the data frame for which assistance is requested to be transmitted from the AP MLD. That is, the EDCA parameter used in the backoff operation for transmitting the QoS null frame may be EDCA of AC of the data unit existing in the queue of the STA MLD. When the AC of the data unit existing in the queue of the STA MLD is ac_vo, the STA1 may perform a backoff operation for transmitting the QoS null frame using EDCA parameters of the ac_vo, and when the backoff operation is completed, the STA1 may transmit the QoS null frame.

Alternatively, the AP may set the transmission duration (e.g., TXOP) set by the MU-RTS frame to be longer than the actual TXOP. Thus, the STA may transmit a BA frame configured with the QoS null frame in the designated TXOP. The transmission end of the received response frame (e.g., BA frame or BA frame configured with QoS null frame) may be earlier than the end time of the configured TXOP. The AP may terminate the TXOP early when the transmission procedure ends within the TXOP.

An Auxiliary AP Request (AAR) control field included in the MAC header of the QoS null frame may be used to transmit configuration information of data units present in the queue of the STA MLD. In order to transmit data units present in the queue of STA MLD during a period corresponding to medium syncdelay, STA1 may request assistance from AP MLD by transmitting a QoS null frame including an AAR control field (e.g., request transmission of a trigger frame for ensuring an earlier transmission opportunity).

The AAR control field may include at least one of: a supplementary AP link ID bitmap of 16 bits in size, an AC indicator of 2 bits in size, an immediate/default indicator of 1 bit in size, or a reserved bit of 1 byte in size. The auxiliary AP link ID bitmap may indicate links of APs that transmit data units present in a queue of the auxiliary STA MLD among APs affiliated with the AP MLD. The order of bits included in the auxiliary AP link ID bitmap may be the order of APs affiliated with the AP MLD. A bit set to 1 in the auxiliary AP link ID bitmap may indicate the AP (e.g., link) corresponding to the bit. The AC indicator may indicate the AC of the data units present in the queue of the STA MLD. The AC indicator may be referred to as an Access Category Index (ACI). An ACI set to 00 may indicate ac_be, an ACI set to 01 may indicate ac_bk, an ACI set to 10 may indicate ac_vi, and an ACI set to 11 may indicate ac_vo. The immediate/default indicator may indicate a scheme of a procedure for transmitting and receiving the data frame. For example, in a first scheme, a procedure for transmitting and receiving data frames may be initiated by a trigger frame. In a second scheme, the procedure for transmitting and receiving data frames may be initiated by MU-RTS frames.

In the exemplary embodiment of fig. 11A, if the immediate/default indicator included in the QoS null frame indicates an immediate scheme (e.g., a first scheme), this may indicate that the STA MLD may immediately receive a default control frame (e.g., a trigger frame). The trigger frame may be referred to as "TF". STA MLD may switch both radio chains to the link indicated by the auxiliary AP link ID bitmap (e.g., the second link) after transmitting the BA frame and QoS null frame on the first link, and may receive a default control frame (e.g., trigger frame) or data frame instead of a specific control frame (e.g., MU-RTS frame) on the second link.

In the exemplary embodiment of fig. 11B, if the immediate/default indicator included in the QoS null frame indicates a default scheme (e.g., a second scheme), this may indicate that the STA MLD may receive a particular control frame (e.g., MU-RTS frame). STA MLD may switch both radio chains to the link indicated by the auxiliary AP link ID bitmap (e.g., the second link) after transmitting the BA frame and QoS null frame on the first link, and may wait for a frame transmission/reception procedure initiated by a specific control frame (e.g., MU-RTS frame) to be performed on the second link. Alternatively, the STA MLD may wait to perform a frame transmission/reception procedure indicated by a specific control frame on the second link while operating both radio chains on the respective operation links (e.g., the first link and the second link). When a specific control frame is received on the second link, the STA MLD may operate the radio link on the second link to perform frame transmission and reception procedures.

The AP MLD (e.g., AP 1) may receive the BA frame and the QoS null frame from STA1 on the first link and may identify configuration information included in the QoS null frame. AP2 of AP MLD may perform a backoff operation for transmitting the MU-RTS frame on the second link using EDCA parameters corresponding to AC indicated by ACI included in the QoS null frame. Alternatively, the AP2 of the AP MLD may perform a backoff operation using EDCA parameters (e.g., EDCA parameters corresponding to ac_vo or ac_vi) for transmitting the trigger frame.

When receiving the MU-RTS frame on the second link, the STA MLD may switch the radio chain waiting to receive the MU-RTS frame on the first link to the second link. STA2 of STA MLD may transmit a CTS frame in response to the MU-RTS frame and wait for receipt of the frame. Considering the time required for switching the radio chain for EMLSR Delay1, STA MLD may complete the switching operation of the radio chain before receiving the trigger frame. The AP2 of the AP MLD may receive the CTS frame from the STA2 and may transmit the trigger frame after the SIFS elapses from the time of receiving the CTS frame. One or two spatial streams may be used to transmit the trigger frame. The preamble of the trigger frame may include information indicating the number of spatial streams used to transmit the trigger frame. STA2 of the STA MLD may receive the trigger frame from the AP2 and may identify the radio resource indicated by the trigger frame. The STA2 may transmit a data frame including a data unit existing in the queue using the radio resource indicated by the trigger frame after the SIFS elapses from the time when the trigger frame is received.

The AAR control field included in the QoS null frame may not indicate the length of the data units present in the queue. Thus, STA1 may transmit QoS null frames including Buffer Status Reports (BSRs) in a control. The BSR may indicate the length of data units present in the queues of the STA MLD. The AP MLD may receive the QoS null frame from the STA MLD and identify the BSR included in the QoS null frame. The AP MLD may allocate radio resources by using the trigger frame so that the STA MLD may transmit the entire data unit having the length indicated by the BSR or may transmit the data unit having the length indicated by the BS as much as possible. That is, the AP MLD may allocate an accurate amount of radio resources to the STA MLD based on the BSR.

As shown in fig. 12, the AP MLD and the STA MLD may support the EMLSR mode. When there is a data frame to be transmitted to the STA MLD, the AP MLD may initiate a process of transmitting and receiving the data frame by transmitting the MU-RTS frame on one of the plurality of links. The AP MLD may set the duration of the TXOP within the TXOP limit according to the AC of the data frame and transmit a MU-RTS frame including a MAC header including a duration field indicating the duration of the TXOP. The STA MLD may receive the MU-RTS frame from the AP MLD and identify a duration field included in a MAC header of the MU-RTS frame. Among STAs attached to the STA MLD, STAs that are not recipients of the data frame may set the NAV based on the value of the duration field.

AP1 of AP MLD may transmit multiple data frames with the same AC within the TXOP. AP1 may transmit a plurality of data frames using spatial streams corresponding to the number of radio chains. STA MLD (e.g., STA 1) may receive multiple data frames with multiple spatial streams. The number of multi-spatial streams may correspond to the number of radio chains included in the STA MLD. Additional data units to be transmitted to the STA MLD may exist in a queue of the AP MLD. The additional data units may be remaining data units that were not transmitted during the previous transmission. The AC of the data unit transmitted in the previous transmission may be the same as the AC of the additional data unit. Alternatively, the additional data unit may be a new data unit to be transmitted to the STA MLD (e.g., STA 1). The AC of the data unit transmitted during the previous transmission may be the same as or different from the AC of the additional data unit.

If a data unit to be transmitted to STA MLD (e.g., STA 1) during the TXOP exists in a queue of the AP MLD, the AP1 in the AP MLD may set a "more data" field included in a MAC header of the data frame to 1 and transmit the data frame to STA1 of the STA MLD. STA1 of the STA MLD may receive the data frame from the AP1 and may recognize that the "more data" field included in the MAC header of the data frame is set to 1. That is, STA1 may determine that a data unit to be transmitted to STA1 exists in the queue of the AP MLD based on the value of the more data field. STA1 may transmit a reception response frame (e.g., BA frame) for the data frame to AP 1. Thereafter, the STA MLD may not perform an operation of switching the radio link to the second link, and may keep the radio link on the first link.

In order to transmit the data units existing in the queue to STA1 of the STA MLD, AP1 of the AP MLD may perform a backoff operation after an AIFS elapses from the time of receiving the reception response frame. When the backoff operation is successful, the AP1 of the AP MLD may transmit a data frame to the STA1 by using multi-spatial streams (e.g., two spatial streams) supported by the STA MLD, without transmitting the MU-RTS frame. STA1 of the STA MLD may receive the data frame using the multi-spatial stream. The STA MLD may identify that additional data frames are to be transmitted based on the more data fields. Therefore, the STA MLD may not switch the radio chain to another link. In this case, the time required to switch one radio chain to another (e.g., EMLSR Delay1 and/or EMLSR Delay 2) may not be necessary.

When the "more data" field included in the MAC header of the data frame received from the AP1 of the AP MLD is set to 0, the STA MLD may determine that there is no data frame to be transmitted by the AP MLD. In this case, the radio chain may wait to receive MU-RTS frames on multiple links. Thus, STA1 of STA MLD may switch the radio link to another link after receiving a reception response frame (e.g., BA frame). Switching the radio chain to another link may take time EMLSR Delay2. When a data frame transmission and reception process using a multi-spatial stream is performed between the AP1 of the AP MLD and the STA1 of the STA MLD, the second link may be in a state where a reception operation cannot be performed. That is, the channel sensing operation cannot be performed on the second link. Accordingly, a period from a time when the STA MLD transmission receives the response frame to a time when the radio chain switches to the second link may be a blind period. The blind period may include the time required to transmit the data frame, including the "more data" field set to 1 and the time required to perform the backoff operation.

The exemplary embodiments of the present disclosure may be implemented as program instructions executable by various computers and recorded on computer-readable media. The computer readable medium may include program instructions, data files, data structures, or combinations thereof. The program instructions recorded on the computer-readable medium may be specially designed and configured for the present disclosure, or may be well known and available to those having skill in the computer software arts.

Examples of computer readable media may include hardware devices such as ROM, RAM, and flash memory that are specially configured to store and perform program instructions. Examples of program instructions include machine code, such as produced by a compiler, and high-level language code that may be executed by the computer using an interpreter. The above-described exemplary hardware devices may be configured to operate as at least one software module in order to perform embodiments of the present disclosure, and vice versa.

Although exemplary embodiments of the present disclosure and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the disclosure.

Claims

1. A method of a first apparatus, comprising:

Receiving a first data frame from a second device over a first link using a multi-spatial stream;

transmitting a receive response frame to the first data frame over the first link to the second device;

transmitting a third data frame comprising configuration information for transmitting a second data frame to the second device over the first link; and

the second data frame is transmitted to the second device on a second link based on the configuration information.

2. The method of claim 1, further comprising:

receiving a multi-user (MU) -request-to-send (RTS) frame from the second device over the first link; and

a Clear To Send (CTS) frame is transmitted to the second device on the first link in response to the MU-RTS frame,

wherein the first data frame is received after the CTS frame is transmitted.

3. The method of claim 2, wherein no receive operation is performed on the second link during a first period from a time of transmission of the CTS frame to a completion time of switching a radio chain of the first device, and the first period comprises: time required to transmit CTS frame + time required to receive the first data frame + time required to transmit the receive response frame + time required to transmit the third data frame + time required to switch the radio chain.

4. The method of claim 1, wherein the receive response frame and the third data frame are configured in the form of an aggregate (a) -Medium Access Control (MAC) protocol data unit (MPDU), and the third data frame is a quality of service (QoS) null frame.

5. The method of claim 1, wherein the configuration information comprises at least one of information indicating a link over which the second data frame is transmitted, information indicating an Access Category (AC) of the second data frame, or information indicating a scheme of a transmission/reception procedure of the second data frame.

6. The method of claim 5, further comprising: a trigger frame is received from the second device over the second link in response to the configuration information indicating that the transmission/reception process of the second data frame is performed based on a first scheme, wherein the transmission/reception process of the second data frame is initiated by the trigger frame.

7. The method of claim 5, further comprising:

receiving a MU-RTS frame from the second device over the second link in response to the configuration information indicating that the transmission/reception process of the second data frame is performed based on a second scheme; and

Transmitting a CTS frame to the MU-RTS frame over the second link to the second device,

wherein the transmission/reception process of the second data frame is initiated by the MU-RTS frame.

8. A method of a second apparatus, comprising:

transmitting a first data frame to a first device over a first link using a multi-spatial stream;

receiving a receive response frame to the first data frame from the first device over the first link;

receiving a third data frame comprising configuration information for transmitting a second data frame from the first device over the first link; and

the second data frame is received from the first device over a second link based on the configuration information.

9. The method of claim 8, further comprising:

transmitting a multi-user (MU) -request-to-send (RTS) frame to the first device over the first link; and

a Clear To Send (CTS) frame for the MU-RTS frame is received from the first device over the first link,

wherein the first data frame is transmitted after receiving the CTS frame.

10. The method of claim 9, wherein a receiving operation of the first apparatus is not performed on the second link during a first period from a time of receiving the CTS frame to a completion time of switching a radio chain of the first apparatus, and the first period comprises: time required to receive CTS frame + time required to transmit the first data frame + time required to receive the receive response frame + time required to receive a third data frame + time required to switch the radio chain.

11. The method of claim 8, wherein the receive response frame and the third data frame are configured in the form of an aggregate (a) -Medium Access Control (MAC) protocol data unit (MPDU), and the third data frame is a quality of service (QoS) null frame.

12. The method of claim 8, wherein the configuration information comprises at least one of information indicating a link over which the second data frame is transmitted, information indicating an Access Category (AC) of the second data frame, or information indicating a scheme of a transmission/reception procedure of the second data frame.

13. The method of claim 12, further comprising: transmitting a trigger frame to the first device over the second link in response to the configuration information indicating that the transmission/reception process of the second data frame is performed based on a first scheme, wherein the transmission/reception process of the second data frame is initiated by the trigger frame.

14. The method of claim 12, further comprising:

transmitting a MU-RTS frame to the first device over the second link in response to the configuration information indicating that the transmission/reception process of the second data frame is performed based on a second scheme; and

A CTS frame for the MU-RTS frame is received from the first device over the second link,

15. A method of a first apparatus, comprising:

transmitting a first receive response frame to the first data frame to the second device over the first link; and

in response to information included in the first data frame indicating that a second data frame to be transmitted to the first device is present in the second device, a receiving operation is performed on the first link without switching a radio chain of the first device.

16. The method of claim 15, further comprising:

receiving the second data frame from the second device over the first link using the multi-spatial stream;

transmitting a second receive response frame to the second data frame over the first link to the second device; and

a receiving operation is performed on a plurality of links by switching a radio chain of the first device in response to information included in the second data frame indicating that a third data frame to be transmitted to the first device is not present in the second device.

17. The method of claim 15, wherein the receiving operation of the first apparatus is not performed on the second link while a data frame transmission/reception process using the multi-spatial stream is performed on the first link.

18. The method of claim 15, further comprising:

a Clear To Send (CTS) frame for the MU-RTS frame is transmitted over the first link to the second device,

wherein the transmission/reception process of the first data frame is initiated by the MU-RTS frame.

19. The method of claim 15, wherein a control frame for initiating a transmission/reception procedure of the second data frame is not used, and the second data frame is transmitted when a backoff operation in the second apparatus is successful.

20. The method of claim 15, wherein the number of multi-spatial streams corresponds to a number of radio chains included in the first apparatus.