KR101657004B1

KR101657004B1 - Operation method of station in wireless local area network

Info

Publication number: KR101657004B1
Application number: KR1020150082686A
Authority: KR
Inventors: 안재현; 장석호
Original assignee: 단국대학교 산학협력단
Priority date: 2015-03-27
Filing date: 2015-06-11
Publication date: 2016-09-12

Abstract

Disclosed is an operation method of a station in a wireless local area network. The operation method of a first station comprises the steps of: generating a first frame including a first indicator for indicating whether to control a CCA critical value; and transmitting the first frame. Accordingly, the present invention can improve the performance of a wireless local area network.

Description

{OPERATION METHOD OF STATION IN WIRELESS LOCAL AREA NETWORK}

The present invention relates to wireless LAN technology, and more particularly, to a method of operating a station based on dynamic clear channel assessment (CCA).

With the development of information and communication technology, various wireless communication technologies are being developed. Among them, a wireless local area network (WLAN) may be a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), a smart phone A smart phone, a tablet PC, or the like, to wirelessly connect to the Internet in a home, an enterprise, or a specific service providing area.

The standard for wireless LAN technology is being developed as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. A wireless LAN system according to IEEE 802.11a uses a unlicensed band at 5 GHz and provides a transmission speed of 54 Mbps. A wireless LAN system according to IEEE 802.11b applies a direct sequence spread spectrum (DSSS) at 2.4 GHz to provide a transmission speed of 11 Mbps. The IEEE 802.11g wireless LAN system adopts orthogonal frequency division multiplexing (OFDM) at 2.4 GHz to provide a transmission rate of 54 Mbps. The IEEE 802.11n wireless LAN system employs multiple input multiple output (OFDM) and multiple input multiple output (OFDM) to provide a transmission rate of 300 Mbps for four spatial streams. The IEEE 802.11n wireless LAN system supports a channel bandwidth of up to 40 MHz, and provides a transmission speed of 600 Mbps in this case.

As the spread of the wireless LAN is activated and the application using the wireless LAN is activated, a need for a new wireless LAN technology to support a higher throughput than the data processing speed supported by IEEE 802.11n has increased. Very high throughput (VHT) Wireless LAN technology is one of the proposed IEEE 802.11 wireless LAN technologies to support data processing speeds of 1 Gbps or higher. Among them, IEEE 802.11ac is a standard for providing ultra high throughput in a band below 6 GHz, and IEEE 802.11ad is a standard for providing ultra high throughput in a 60 GHz band.

In addition, standards for various wireless LAN technologies have been defined and standards development is in progress. Typically, IEEE 802.11af is a standard prescribed for operation of a wireless LAN in TV idle white space, IEEE 802.11ah is a standard prescribed to support a large number of terminals operating at low power, and IEEE 802.11ai Is a defined standard for fast initial link setup (FILS) in WLAN systems. Recently, the development of IEEE 802.11ax for the purpose of improving frequency efficiency in a dense environment in which a plurality of base stations and terminals exist is proceeding.

In a system based on such a wireless LAN technology, a first station belonging to an overlapping basic service set (OBSS) transmits a frame to a first station based on a clear channel assessment (CCA) ) To a first access point. In this case, the second station belonging to the OBSS may not successfully receive the frame transmitted from the second access point to which the second station is connected due to the frame transmitted from the first station.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of operating a station based on dynamic CCA.

According to an aspect of the present invention, there is provided a method of operating a first station, the method comprising: generating a first frame including a first indicator indicating whether a CCA threshold is adjusted; To the base station.

Here, the first indicator may be included in a signal field of the first frame.

Here, the first frame may be a control frame or a management frame.

Here, the first frame may further include a second indicator indicating a BSS to which the first station belongs.

Here, the second indicator may be included in the signal field of the first frame.

According to another aspect of the present invention, there is provided a method of operating a second station, the method comprising: acquiring a preamble of a first frame; receiving a preamble of a first station, Obtaining a first indicator indicating whether to adjust the CCA threshold included in the preamble when the BSS to which the first station transmitting the first frame belongs is the OBSS, And performing a CCA operation based on the CCA threshold value indicated by the first indicator.

Here, the first indicator may be included in a signal field of the first frame.

Here, the first frame may be a control frame or a management frame.

Here, the step of determining whether the OBSS is included in the preamble may include determining whether the first station included in the preamble includes a first indicator indicating a BSS to which the first station transmitting the first frame belongs, It can be determined whether the BSS to which it belongs is an OBSS.

The method may further include performing a CCA operation based on a default value of the CCA threshold value when the BSS to which the first station transmitting the first frame belongs is the BSS to which the second station belongs have.

Here, the step of performing the CCA operation may perform the CCA operation based on the default value of the CCA threshold value when the first indicator indicates that the CCA threshold value is not adjusted.

Herein, the step of performing the CCA operation may perform the CCA operation based on a value larger than the default value of the CCA threshold value when the first indicator indicates that the CCA threshold value is to be adjusted.

According to another aspect of the present invention, there is provided a method of operating a second station, including: acquiring a preamble of a first frame; receiving a first indicator indicating whether the CCA threshold value included in the preamble is adjusted; And performing a CCA operation based on the CCA threshold value indicated by the first indicator.

Here, the first indicator may be included in a signal field of the first frame.

Here, the first frame may be a control frame or a management frame.

According to the present invention, the performance of the wireless LAN system can be improved.

1 is a block diagram illustrating one embodiment of a station performing methods in accordance with the present invention.
2 is a conceptual diagram showing an embodiment of a configuration of a wireless LAN according to the IEEE 802.11 standard.
3 is a flowchart illustrating a connection procedure of a terminal in an infrastructure BSS.
4 is a conceptual diagram showing an OBSS (overlapping BSS).
5 is a flowchart illustrating an operation method of a station according to an embodiment of the present invention.
6 is a flowchart illustrating a method of performing a CCA operation according to an embodiment of the present invention.
7 is a block diagram showing the structure of a frame.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

In the specification, a station (STA) refers to any functional medium including a medium access control (MAC) layer according to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, a physical layer, . A station STA can be divided into a station STA, which is an access point, and a station STA, which is a non-AP. A station (STA), which is an access point, may be referred to simply as an access point, and a station (STA) that is a non-AP may be referred to simply as a terminal.

The access point may be a centralized controller, a base station (BS), a radio access station, a node B, an evolved node B, a relay, a mobile multihop relay (MMR) -BS, a base transceiver system (BTS), a site controller, and the like, and may include some or all of the functions thereof.

A terminal may be a wireless transmit / receive unit (WTRU), a user equipment (UE), a user terminal (UT), an access terminal (AT), a mobile station May refer to a mobile terminal, a subscriber unit, a subscriber station (SS), a wireless device, a mobile subscriber unit, etc., and some or all of them Function.

The terminal may be a desktop computer, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone, a smart watch, smart watch, smart glass, e-book reader, portable multimedia player (PMP), portable game machine, navigation device, digital camera, digital multimedia broadcasting (DMB) A digital audio recorder, a digital audio player, a digital picture recorder, a digital picture player, a digital video recorder, a digital video player ) And the like.

1 is a block diagram illustrating one embodiment of a station performing methods in accordance with the present invention.

Referring to FIG. 1, a station 100 may include at least one processor 110, a memory 120, and a network interface device 130 for communicating with a network. In addition, the station 100 may further include an input interface device 140, an output interface device 150, a storage device 160, and the like. Each component included in the station 100 may be connected by a bus 170 and communicate with each other.

The processor 110 may execute a program command stored in the memory 120 and / or the storage device 160. The processor 110 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which the methods of the present invention are performed. The memory 120 and the storage device 160 may be composed of a volatile storage medium and / or a non-volatile storage medium. For example, memory 120 may be comprised of read only memory (ROM) and / or random access memory (RAM).

Embodiments of the present invention can be applied to a wireless local area network (WLAN) conforming to the IEEE 802.11 standard, and can be applied to other communication networks as well as a wireless LAN according to the IEEE 802.11 standard.

For example, embodiments of the present invention may be implemented in a portable Internet such as a wireless personal area network (WPAN), a wireless body area network (WBAN), a wireless broadband internet (WiBro) or a world interoperability for microwave access (WiMax) a 3G mobile communication network such as WCDMA (wideband code division multiple access) or cdma1000, a high speed downlink packet access (HSDPA) or a high speed uplink (HSUPA) a 3.5G mobile communication network such as a packet access, a 4G mobile communication network such as LTE (Long Term Evolution) or LTE-Advanced, and a 5G mobile communication network.

2 is a conceptual diagram showing an embodiment of a configuration of a wireless LAN according to the IEEE 802.11 standard.

Referring to FIG. 2, a wireless LAN according to the IEEE 802.11 standard may include at least one basic service set (BSS). BSS means a set of stations (STA1, STA2 (AP1), STA3, STA4, STA5 (AP2), STA6, STA7, STA8) that can successfully communicate with each other and communicate with each other, .

The BSS can be divided into an infrastructure BSS (infrastructure BSS) and an independent BSS (IBSS). Here, BSS1 and BSS2 denote an infrastructure BSS, and BSS3 denotes an IBSS.

The BSS1 is a distribution system for connecting a first terminal STA1, a first access point STA2 (AP1) providing a distribution service and a plurality of access points STA2 (AP1), STA5 (AP2) distribution system, DS). In the BSS1, the first access point STA2 (AP1) can manage the first terminal STA1.

The BSS2 connects the third terminal STA3, the fourth terminal STA4, the second access point STA5 (AP2) providing the distribution service and the plurality of access points STA2 (AP1) and STA5 (AP2) And a distribution system (DS). The second access point STA5 (AP2) in the BSS2 can manage the third terminal STA3 and the fourth terminal STA4.

BSS3 means an IBSS operating in an ad-hoc mode. In BSS3, there is no access point which is a centralized management entity. That is, the terminals STA6, STA7, and STA8 in the BSS3 are managed in a distributed manner. In the BSS3, all terminals STA6, STA7, and STA8 may denote a mobile terminal and form a self-contained network since access is not permitted to the distribution system DS.

The access points STA2 (AP1) and STA5 (AP2) can provide a connection to the distributed system (DS) via a wireless medium for the terminals STA1, STA3 and STA4 connected thereto. The communication between the terminals STA1, STA3 and STA4 in the BSS1 or BSS2 is generally performed through the access points STA2 and STA5 and when the direct link is established, STA1, STA3, STA4) is possible.

A plurality of infrastructure BSSs may be interconnected via a distribution system (DS). A plurality of BSSs connected through a distribution system (DS) is referred to as an extended service set (ESS). (STA1, STA3, and STA4) in the same ESS can communicate with each other without interrupting the communication between the terminals (STA1, STA2, APA, STA3, STA4, From the BSS to another BSS.

The distribution system DS is a mechanism by which one access point communicates with another access point, whereby the access point transmits a frame for terminals coupled to the BSS it manages, or moves to another BSS A frame can be transmitted for an arbitrary terminal. The access point can also transmit and receive frames to and from an external network, such as a wired network. Such a distribution system (DS) does not necessarily have to be a network, and there is no restriction on the form if it can provide a predetermined distribution service defined in the IEEE 802.11 standard. For example, the distribution system may be a wireless network, such as a mesh network, or may be a physical structure that connects the access points to each other.

Next, the frames used in the wireless LAN according to the IEEE 802.11 standard will be described.

In the IEEE 802.11 standard, frames exchanged between stations are classified into a management frame, a control frame, and a data frame. The management frame may mean a frame used for exchange of management information not provided to an upper layer. The management frame may be a random backoff after an inter frame space (IFS) such as DIFS (distributed coordination function) interframe space (DCF), PIFS (point coordination function) interframe space (PCF) may be transmitted after a contention window (CW) according to a random backoff procedure.

A control frame may refer to a frame used to control media access. The control frame may be transmitted after the contention window according to the random backoff procedure after the elapse of the IFS when the frame is not a response frame of another frame. Alternatively, the control frame may be transmitted without a random backoff procedure after a short inter frame space (SIFS) in the case of a response frame of another frame. A data frame is a frame used for transmission of data provided to an upper layer, and may be transmitted after a contention window according to a random backoff procedure after an IFS has passed.

3 is a flowchart illustrating a connection procedure of a terminal in an infrastructure BSS.

Referring to FIG. 3, the connection procedure of the STA in the infrastructure BSS includes a probe step for detecting an access point (AP), an authentication step for a detected access point (AP) And an association step with an access point (AP) that has performed the association process.

The terminal STA may first detect neighboring APs using a passive scanning method or an active scanning method. When the passive scanning method is used, the terminal STA can detect neighboring access points APs by overhearing the beacon frame transmitted by the access points APs. When the active scanning method is used, the terminal STA transmits a probe request frame and receives a probe response frame, which is a response to the probe request frame from the access points APs, It can detect one of the access points APs.

The terminal STA may perform an authentication step with a detected access point (AP) when it detects neighboring access points (APs). In this case, the terminal STA can perform the authentication step with a plurality of access points APs. The authentication algorithm according to the IEEE 802.11 standard can be classified into an open system algorithm for exchanging two authentication frames, a shared key algorithm for exchanging four authentication frames, and the like.

Based on an authentication algorithm according to the IEEE 802.11 standard, a terminal (STA) transmits an authentication request frame to an access point (AP) and receives an authentication response frame (a response to an authentication request frame) authentication with the access point (AP) can be completed by receiving the authentication response frame.

When the terminal STA has completed the authentication, the terminal STA can perform a connection step with the access point (AP). In this case, the terminal STA can select one of the access points (APs) that have performed the authentication step with the terminal STA, and can perform the connection step with the selected access point (AP). That is, the terminal STA transmits an association request frame to the selected access point (AP) and receives an association response frame, which is a response to the connection request frame, from the selected access point (AP) The connection with the selected access point (AP) can be completed.

On the other hand, stations in the WLAN can access channels based on distributed coordination function (DCF) or enhanced distributed channel access (EDCA). That is, a station can access a channel based on a carrier sense multiple access (CSMA) / collision avoidance (CA) scheme to avoid collision between frames in a channel. The station may transmit a frame after the contention window according to the random backoff procedure if the channel is in an idle state.

When the station receives a signal with RX sensitivity or more, the station can determine the occupied state of the channel based on the received signal. A method for determining the occupation state of a channel can be classified into a physical carrier sensing method and a virtual carrier sensing method. A clear channel assessment (CCA) operation method can be used as a physical carrier sensing method. The CCA operation method can be classified into an energy detection (ED) based CCA operation method and a CS (carrier sensing) based CCA operation method. In the ED-based CCA operation method, a station that performs a CCA operation transmits a signal having a radio frequency (RF) energy exceeding a CCA threshold value or a signal having an RF energy of 20 dB or more It can be determined that the corresponding channel is in a busy state. In a CS-based CCA operation method, a station performing a CCA operation can determine that a corresponding channel is in a busy state when a physical layer convergence procedure (PLCP) preamble is detected.

4 is a conceptual diagram showing an OBSS (overlapping BSS).

Referring to FIG. 4, a first STA1 may be connected to a first access point AP1, and a first STA1 and a first AP AP1 may form a BSS1. The second terminal STA2 and the third terminal STA3 can be connected to the second access point AP2 and the second terminal STA2, the third terminal STA3 and the second access point AP2 can be connected to the BSS2 . The first terminal STA1 and the second terminal STA2 may be located in the OBSS in which the BSS1 and the BSS2 are overlapped. The terminals STA1 and STA2 located in the OBSS can determine that the channel is in the busy state by the frame transmitted from the station belonging to each of the BSS1 and the BSS2. That is, when it is determined that the channel is busy, it may occur more frequently in the OBSS than non-OBSS. Therefore, the terminals STA1 and STA2 located in the OBSS can obtain a smaller frame transmission opportunity than the station located in one BSS.

For example, if the first terminal STA1 wants to transmit a frame to the first access point AP1, the first terminal STA1 may first determine the occupancy state of the channel. At this time, if the first terminal STA1 detects a frame transmitted from the second access point AP2 to the third terminal STA3, the first terminal STA1 may determine that the channel is in a busy state, The frame transmission opportunity may not be obtained. However, since the transmission between the second access point AP2 and the third terminal STA3 is not affected by the frame transmitted from the first terminal STA1, the first terminal STA1 can transmit the frame And fails to transmit the frame.

This problem can be overcome by adjusting the CCA threshold. For example, the first terminal STA1 may perform a CCA operation based on a value (e.g., -72 dB) greater than a default value (e.g., -82 dB) of the CCA threshold. In this case, when the signal strength of the frame transmitted from the second access point AP2 is -80 dB, the first terminal STA1 can determine that the channel is in the idle state, Lt; / RTI > On the other hand, when the CCA operation is performed based on the default value of the CCA threshold, the first terminal STA1 can determine that the channel is in the busy state when the signal strength of the frame transmitted from the second access point AP2 is -80 dB , Thereby failing to acquire the transmission opportunity of the frame.

However, if the adjusted CCA threshold (e.g., -72 dB) is used for CCA operation for a frame transmitted from a station belonging to the same BSS as the first terminal STA1, the frame may be collided. That is, when the signal strength of the frame transmitted from the first access point AP1 is -77 dB, the first terminal STA1 can determine that the channel is in the idle state, and accordingly the frame is transmitted to the first access point AP1 Lt; / RTI > In this case, the frame transmitted from the first access point AP1 to the station belonging to the BSS1 may collide with the frame transmitted from the first STA1 to the first access point AP1.

This problem can be overcome by using a second indicator that indicates the BSS to which the frame was sent (i.e., the BSS to which the station that transmitted the frame belongs). The second indicator may refer to color bits defined in IEEE 802.11ah. The first terminal STA1 can perform the CCA operation based on the default value of the CCA threshold value when the second indicator included in the received frame indicates that the BSS to which the station transmitting the corresponding frame belongs is BBS1, If the second indicator included in the frame indicates that the BSS to which the station transmitting the frame belongs is BBS2 (i.e., OBSS), the CCA operation can be performed based on a value larger than the default value of the CCA threshold value.

For example, the first terminal STA1 may detect a frame transmitted from the second access point AP2 to the second terminal STA2 when the frame is to be transmitted to the first access point AP1. The first terminal STA1 can recognize that the BSS to which the second access point that transmitted the corresponding frame through the second indicator included in the detected frame is the OBSS. The first terminal STA1 may determine that the channel is in the idle state if the signal strength of the detected frame is less than or equal to a value greater than a default value of the CCA threshold. Accordingly, the first terminal STA1 can transmit the frame to the first access point AP1. However, a frame transmitted from the first STA1 to the first access point AP1 may interfere with the second STA2, and accordingly, the second STA2 may transmit the frame from the second access point AP2 The frame can not be received successfully. Particularly, when the frame transmitted from the second access point AP2 to the second terminal STA2 is a control frame or a management frame, the performance of the wireless LAN system may be significantly degraded.

Hereinafter, a method performed at a terminal and a corresponding access point will be described. Even when a method performed in the first communication entity among the communication entities (for example, transmission or reception of a frame) is described, the corresponding second communication entity corresponds to the method performed in the first communication entity Method (e.g., receiving or transmitting a frame). That is, when the operation of the terminal is described, the corresponding access point can perform an operation corresponding to the operation of the terminal. Conversely, when the operation of the access point is described, the corresponding terminal can perform an operation corresponding to the operation of the access point.

FIG. 5 is a flowchart illustrating an operation method of a station according to an embodiment of the present invention, and FIG. 6 is a flowchart illustrating a method of performing a CCA operation according to an embodiment of the present invention.

Referring to FIGS. 5 and 6, the first station STA1 may belong to the same BSS as the second station STA2, or may belong to a different BSS than the second station STA2. Each of the first station STA1 and the second station STA2 may mean an access point or a terminal. The first station STA1 may generate a first frame including a first indicator indicating whether the CCA threshold is adjusted (S500). Here, the first frame may mean a control frame or a management frame. The first indicator may be represented by 1 bit. For example, if the first indicator is a binary number '0', this may indicate that the CCA threshold is not adjusted. If the first indicator is a binary number '1', this may indicate that the CCA threshold is adjusted. In addition, the first frame may further include a second indicator indicating a BSS to which the first station STA1 belongs. Here, the second indicator may indicate a color bit defined in IEEE 802.11ah. The first indicator and the second indicator may be included in a signal field of the first frame. The structure of the first frame is as follows.

7 is a block diagram showing the structure of a frame.

7, the frame 700 may include a preamble and a payload 780. The preamble includes a legacy-short training field (L-STF) 710, a legacy-long training field (L-LTF) 720, a legacy-signal (L-SIG) field 730, ), an ax-STF 750, an ax-LTF 760, and an ax-SIG B field 770. The ax-SIG A field 740, the ax-STF 750, the ax-LTF 760, and the ax-SIG B field 770 may refer to fields defined in IEEE 802.11ax. Each of the first and second indicators may be included in at least one of the ax-SIG A field 740 and the ax-SIG B field 770.

5 and 6, the first station STA1 may transmit the first frame (S510). The second station STA2 may perform the CCA operation based on the information included in the preamble of the first frame (S520). Specifically, the second station STA2 may acquire the preamble of the first frame (S521), and may determine whether the BSS to which the first frame is transmitted based on the information included in the preamble is the OBSS (S522 ).

For example, if the second indicator included in the preamble of the first frame indicates the BSS to which the second station STA2 belongs, the second station STA2 determines that the BSS to which the first frame is transmitted is not the OBSS . In this case, the second station STA2 may perform the CCA operation based on the default value of the CCA threshold (e.g., -82dB) (S523). That is, the second station STA2 can determine that the channel is busy if the signal strength of the first frame is greater than the default value of the CCA threshold, and if the signal strength of the first frame is lower than the CCA threshold, It can be judged as an idle state.

On the other hand, if the second indicator included in the preamble of the first frame does not indicate the BSS to which the second station STA2 belongs, the second station STA2 may determine that the BSS to which the first frame is transmitted is the OBSS .

The second station STA2 may acquire a first indicator included in the preamble of the first frame when the BSS in which the first frame is transmitted is determined to be the OBSS (S524). Here, it is described that the step S524 is performed after the step S522 is performed, but the step S522 may be omitted. That is, after acquiring the preamble of the first frame, the second station STA2 can acquire the first indicator included in the preamble of the first frame regardless of whether the BSS to which the first frame is transmitted is the OBSS.

The second station STA2 may adjust the CCA threshold to a value greater than the default value (e.g., -72 dB) if the first indicator included in the preamble of the first frame indicates that the CCA threshold is adjusted, The CCA operation may be performed based on the adjusted CCA threshold (S526). That is, when the signal strength of the first frame is greater than the adjusted threshold, the second station STA2 may determine that the channel is busy. If the signal strength of the first frame is equal to or less than the adjusted threshold, .

On the other hand, if the first indicator included in the preamble of the first frame indicates that the CCA threshold is not adjusted, the second station STA2 may perform the CCA operation based on the default value of the CCA threshold (S527) . That is, the second station STA2 can determine that the channel is busy if the signal strength of the first frame is greater than the default value of the CCA threshold, and if the signal strength of the first frame is lower than the CCA threshold, It can be judged as an idle state.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

Claims

delete

A method of operating a second station,
Obtaining a preamble of a first frame;
Determining whether a basic service set (BSS) to which the first station transmitting the first frame based on the preamble belongs is an OBSS (overlapping BSS);
If the BSS to which the first station transmitting the first frame belongs is the OBSS, a first indicator indicating whether to adjust a clear channel assessment (CCA) threshold included in the preamble is acquired step; And
And performing a CCA operation based on the CCA threshold indicated by the first indicator.

The method of claim 6,
Wherein the first indicator is included in a signal field of the first frame.

The method of claim 6,
Wherein the first frame is a control frame or a management frame.

The method of claim 6,
Wherein the step of determining whether the OBSS is an OBSS comprises:
And determining whether the BSS to which the first station transmitting the first frame belongs based on a second indicator indicating the BSS to which the first station that transmitted the first frame included in the preamble belongs is an OBSS, How it works.

The method of claim 9,
Wherein the second indicator is included in a signal field of the first frame.

The method of claim 6,
The operating method comprises:
Further comprising performing a CCA operation based on a default value of a CCA threshold when the BSS to which the first station transmitting the first frame belongs is a BSS to which the second station belongs .

The method of claim 6,
The step of performing the CCA operation includes:
And performing the CCA operation based on the default value of the CCA threshold if the first indicator indicates that the CCA threshold is not adjusted.

The method of claim 6,
The step of performing the CCA operation includes:
And performing a CCA operation based on a value greater than a default value of the CCA threshold if the first indicator indicates that the CCA threshold is to be adjusted.

A method of operating a second station,
Obtaining a preamble of a first frame;
Obtaining a first indicator indicating whether to adjust a clear channel assessment (CCA) threshold included in the preamble; And
And performing a CCA operation based on the CCA threshold indicated by the first indicator.

15. The method of claim 14,
Wherein the first indicator is included in a signal field of the first frame.

15. The method of claim 14,
Wherein the first frame is a control frame or a management frame.

15. The method of claim 14,
The step of performing the CCA operation includes:
And performing a CCA operation based on a default value of the CCA threshold if the first indicator indicates that the CCA threshold is not adjusted.

15. The method of claim 14,
The step of performing the CCA operation includes:
And performing a CCA operation based on a value greater than a default value of the CCA threshold if the first indicator indicates that the CCA threshold is to be adjusted.