KR20140034072A - Method for active scanning in wireless local area network system - Google Patents

Abstract

Disclosed is an active search method in a wireless local area network (LAN) system. The active search method includes: a step of obtaining a second probe request frame which a second terminal transmits; a step of generating a short probe request frame based on information excluding common information among the second probe request frame; and a step of transmitting the short probe request frame. Therefore, air-time occupied by the probe request frame can be reduced. [Reference numerals] (S100) Transmit a second probe request frame; (S110) Obtain the second probe request frame; (S120) Generate a short probe request frame based on the second probe request frame; (S130) Transmit the short probe request frame; (S140) Transmit a probe response frame

Description

METHOOD FOR ACTIVE SCANNING IN WIRELESS LOCAL AREA NETWORK SYSTEM}

The present invention relates to an active search method, and more particularly, to an active search method for access point search in a WLAN system.

With the development of information and communication technology, various wireless communication technologies are being developed. Among these, a wireless local area network (WLAN) is a wireless local area network (WLAN) based on radio frequency technology such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player It is a technology that allows a portable terminal to access the Internet wirelessly in a home, a business, 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. IEEE 802.11a provides a transmission rate of 54 Mbps using an unlicensed band at 5 GHz. IEEE 802.11b applies a direct sequence spread spectrum (DSSS) at 2.4 GHz to provide a transmission rate of 11 Mbps. IEEE 802.11g applies orthogonal frequency division multiplexing (OFDM) at 2.4 GHz to provide a transmission rate of 54 Mbps. IEEE 802.11n employs multiple input multiple output (OFDM), or OFDM (MIMO-OFDM), and provides a transmission rate of 300 Mbps for two spatial streams. IEEE 802.11n supports a channel bandwidth of up to 40 MHz, in which case it provides a transmission rate of 600 Mbps.

As the spread of the WLAN is activated and the applications using the WLAN are activated, a need for a new WLAN technology to support a higher throughput than the data processing speed supported by IEEE 802.11n is increasing. Very high throughput (VHT) Wireless LAN technology is one of the proposed IEEE 802.11 wireless LAN technologies to support data rates of more than 1 Gbps. Among them, IEEE 802.11ac is being developed as a standard for providing ultra high throughput in a band below 5 GHz, and IEEE 802.11ad is being developed as a standard for providing ultra high throughput in the 60 GHz band.

In a system based on the WLAN technology, when the terminal searches for an access point through an active search method, the terminal transmits a probe request frame, and the access point transmits a probe request frame. In response to the probe response frame (probe response frame) is transmitted. In an environment where a plurality of terminals exist, each terminal transmits its own probe request frame, thereby increasing the occupation of air-time due to probe request frames.

An object of the present invention for solving the above problems is to provide an active search method for performing the search of the access point using a short probe request frame.

Another object of the present invention for solving the above problems is to provide an active search response method for performing a search of an access point using a short probe request frame.

In accordance with another aspect of the present invention, there is provided a method of actively searching for an object, the method comprising: acquiring a second probe request frame transmitted by a second terminal, based on information excluding common information among the second probe request frames; Generating a short probe request frame, and transmitting the short probe request frame.

The active search method may further include receiving a probe response frame that is a response of the short probe request frame.

Here, the short probe request frame may further include reference information for identifying the referenced second probe request frame.

Here, the reference information may be generated based on source address information and order control information included in the second probe request frame.

Here, the reference information may be generated based on source address information included in the second probe request frame and time information on which the second probe request frame is transmitted.

Here, the reference information may be generated based on source address information and frame check order information included in the second probe request frame.

Here, the common information of the second probe request frame includes at least one of a service set identifier, a supported rate, request information, an extended supported rate, a high processing capability, a 20/40 basic service set coexistence, and an extended capability. can do.

In accordance with another aspect of the present invention, there is provided an active search response method. The method includes: receiving a short probe request frame, based on reference information included in the short probe request frame, Identifying the presence of the referenced full probe request frame to generate, and if the referenced full probe request frame exists, transmitting a probe response frame corresponding to the referenced full probe request frame.

Here, when the referenced full probe request frame does not exist, the method may further include transmitting a probe response frame corresponding to another full probe request frame.

Here, the short probe request frame may include information other than common information among the referenced full probe request frames and the reference information.

Here, the common information among the referenced full probe request frames may include at least one of a service set identifier, a supported rate, request information, an extended supported rate, a high processing capability, a 20/40 basic service set coexistence, and an extended capability. It may include.

Here, the reference information may be generated based on source address information and order control information included in the referenced full probe request frame.

Here, the reference information may be generated based on source address information included in the referenced full probe request frame and time information on which the referenced full probe request frame is transmitted.

Here, the reference information may be generated based on source address information and frame check order information included in the referenced full probe request frame.

The transmitting of the probe response frame may include transmitting the probe response frame in a broadcast manner.

According to the present invention, the terminal may search for an access point using a short probe request frame instead of a full probe request frame, thereby reducing the air-time occupied by the probe request frame.

1 is a conceptual diagram showing an embodiment of a configuration of an IEEE 802.11 wireless LAN system.
2 is a conceptual diagram illustrating a connection process of a terminal in an infrastructure BSS.
3 is a conceptual diagram showing an embodiment of a data transmission process of an access point.
4 is a flowchart illustrating an active search method according to an embodiment of the present invention.
5 is a conceptual diagram illustrating a configuration of a probe request frame.
6 is a conceptual diagram illustrating information included in a probe request frame.
7 is a conceptual diagram illustrating an embodiment of reference information.
8 is a conceptual diagram illustrating another embodiment of reference information.
9 is a conceptual diagram illustrating another embodiment of reference information.
10 is a flowchart illustrating an active search response method according to an embodiment of the present invention.
11 is a flow diagram illustrating one embodiment of an access point search.
12 is a flowchart illustrating another embodiment of an access point search.
13 is a flowchart illustrating an environment overlapped between access points.

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.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. 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. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination 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.

Throughout the specification, a station is a physical layer for medium access control (MAC) and a medium access control (MAC) compliant with the IEEE 802.11 standard. Means any functional medium including an interface. A station (STA) can be divided into a station (STA) which is an access point (AP) and a station (STA) which is a non-AP. A station (STA), which is an access point (AP), may be referred to simply as an access point (AP), and a station (STA) that is a non-AP may be simply referred to as a terminal.

The station STA includes a processor and a transceiver, and may further include a user interface and a display device. A processor is a unit designed to generate a frame to be transmitted over a wireless network or to process a frame received through a wireless network, and performs various functions for controlling the station (STA). A transceiver is a unit that is functionally connected to a processor and is designed to transmit and receive frames over a wireless network for a station (STA).

An access point (AP) may refer to a centralized controller, a base station (BS), a node-B, an eNode-B, a base transceiver system (BTS), a site controller, May include some or all of the functions of the < / RTI >

The terminal may be a wireless transmit / receive unit (WTRU), a user equipment (UE), a user terminal (UT), an access terminal (AT), a mobile station (MS), May refer to a mobile terminal, a subscriber unit, a subscriber station (SS), a wireless device, or a mobile subscriber unit, and some of them. Or all of the functions may be included.

Here, a desktop computer, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone, and an e-communication capable of communicating with a terminal may be used. book readers, portable multimedia players (PMPs), portable game consoles, navigation devices, digital cameras, digital multimedia broadcasting (DMB) players, digital audio recorders, digital audio players ), A digital picture recorder, a digital picture player, a digital video recorder, a digital video player, and the like can be used.

1 is a conceptual diagram illustrating an embodiment of a configuration of an IEEE 802.11 WLAN system.

Referring to FIG. 1, an IEEE 802.11 WLAN system includes at least one basic service set (BSS). A BSS is a set of stations (STA 1, STA 2 (AP 1), STA 3, STA 4, STA 5 (AP 2)) that are able to successfully communicate and communicate with each other, no.

BSS can be classified into Infrastructure BSS (Independent BSS) and Independent BSS (IBSS), and BSS 1 and BSS 2 represent Infrastructure BSS. The BSS 1 connects the access point STA 2 (AP 1) and the access points STA 2 (AP 1) and STA 5 (AP 2), which provide a terminal STA 1, a distribution service And a distribution system (DS). In BSS 1, the access point (STA 2 (AP 1)) manages the terminal (STA 1).

BSS 2 connects a terminal (STA 3, STA 4), an access point (STA 5 (AP 2)) providing a distribution service and a plurality of access points (STA 2 (AP 1), STA 5 (AP 2)) It may include a distribution system. In BSS 2, the access point (STA 5 (AP 2)) manages the terminals STA 3 and STA 4.

The independent BSS, on the other hand, is a BSS operating in an ad-hoc mode. Since the IBSS does not include an access point, there is no centralized management entity in the center. That is, in the IBSS, terminals are managed in a distributed manner. In the IBSS, all terminals can be made as mobile terminals, and self-contained networks can be established because access is not allowed to the distribution system (DS).

The access points STA 2 (AP 1) and STA 5 (AP 2) provide access to the distributed system DS through the wireless medium for the terminals STA 1, STA 3, and STA 4 coupled thereto. . Communication between terminals STA 1, STA 3, and STA 4 in BSS 1 or BSS 2 is generally performed through an access point STA 2 (AP 1) or STA 5 (AP 2), but a direct link (direct link) If the link is configured, direct communication between the terminals STA 1, STA 3, and STA 4 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 called an extended service set (ESS). Stations included in the ESS may communicate with each other, and the UE may move from one BSS to another BSS while seamlessly communicating within the same ESS.

The distribution system (DS) is a mechanism for one access point to communicate with another access point, whereby the access point transmits frames to, or moves to, another BSS for the terminals that are associated with the BSS it manages. A frame may be transmitted for one 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 need to be a network, and there is no limitation on its form as long as 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 a physical structure that connects access points to each other.

The active search method according to an embodiment of the present invention to be described below can be applied to the IEEE 802.11 WLAN system described above, and in addition to the IEEE 802.11 WLAN system, a wireless personal area network (WPAN) and a wireless body area network (WBAN). It can be applied to various networks such as.

2 is a conceptual diagram illustrating a connection process of a terminal in an infrastructure BSS.

In order for the STA to transmit and receive data in the intra-structure BSS, the terminal STA must first be connected to the access point AP.

Referring to FIG. 2, the connection process of the STA in the infrastructure BSS is largely 1) a probe step (AP), 2) an authentication step with the detected access point (AP). ) And 3) an association step with an authenticated access point (AP).

The STA may first detect neighboring access points (APs) through a detection process. The detection process is divided into a passive scanning method and an active scanning method. The passive scanning method may be performed by overhearing beacons transmitted by neighboring access points (APs). Meanwhile, the active scanning method may be performed by broadcasting a probe request frame. The AP that receives the probe request frame may transmit a probe response frame corresponding to the probe request frame to the corresponding STA. The STA may know the presence of neighboring access points (APs) by receiving a probe response frame.

Thereafter, the terminal STA may select one access point AP among the plurality of detected access points and perform authentication with the selected access point AP. An authentication algorithm according to the IEEE 802.11 standard is divided into an open system algorithm for exchanging two authentication frames and a shared key algorithm for exchanging four authentication frames. Through the process of exchanging an authentication request frame and an authentication response frame based on the authentication algorithm, the terminal STA may perform authentication with the access point AP.

Finally, the STA performs a connection process with an authenticated access point (AP). That is, the terminal STA transmits an association request frame to the selected access point AP, and the access point AP that receives the association request frame receives an association response frame corresponding to the association request frame. frame is transmitted to the corresponding STA. As such, through the process of exchanging the connection request frame and the connection response frame, the STA may perform a connection process with the access point AP.

3 is a conceptual diagram showing an embodiment of a data transmission process of an access point.

Referring to FIG. 3, an access point (AP) periodically broadcasts a beacon, and can broadcast a beacon including DTIM at three beacon intervals. The terminal (STA 1, STA 2) of the power save mode (PSM) periodically wakes up (awake) to receive the beacon, checks the TIM or DTIM included in the beacon, Make sure it is buffered. In this case, when the buffered data is present, the terminals STA 1 and STA 2 remain awake to receive data from the access point AP, and when the buffered data does not exist, the terminals STA 1 and STA 2. ) Returns to the power saving state (ie the doze state).

That is, if the bit in the TIM corresponding to its AID is set to 1, the STA (STA 1, STA 2) is a PS (Power Save) -Poll frame (notifying that it is awake and ready to receive data) Or, transmit a trigger (trigger frame) to the access point (AP), the access point (AP) confirms that the terminal (STA 1, STA 2) is ready for data reception by receiving a PS-Poll frame, Data or an acknowledgment (ACK) may be transmitted to the terminals STA 1 and STA 2. When the ACK is transmitted to the terminals STA 1 and STA 2, the access point AP transmits data to the terminals STA 1 and STA 2 at an appropriate time. On the other hand, when the bit in the TIM corresponding to its own AID is set to 0, the terminals STA 1 and STA 2 return to the power saving state.

4 is a flowchart illustrating an active search method according to an embodiment of the present invention.

Referring to FIG. 4, a first terminal (STA 1) 10 and a second terminal (STA 2) 20 exist within a cell range served by an access point (AP) 30. . The first terminal 10 may obtain a frame transmitted by the second terminal 20, and the second terminal 20 may obtain a frame transmitted by the first terminal 10.

The second terminal 20 may transmit the second probe request frame (S100) and may transmit the second probe request frame to the access point 30 in a broadcast or unicast manner. The second probe request frame refers to a probe request frame defined in IEEE 802.11, and may include information necessary for active scanning.

The first terminal 10 may obtain a second probe request frame transmitted by the second terminal 20 (S110). When the second probe request frame is transmitted to the access point 30 in a unicast manner, the first terminal 10 may acquire the second probe request frame by overhearing the second probe request frame.

The first terminal 10 may generate a short probe request frame based on information other than common information among the second probe request frames (S120). The first terminal 10 may generate a short probe request frame (that is, a simplified probe request frame) with reference to the second probe request frame. That is, the first terminal 10 may obtain information included in the second probe request frame, and generate a short probe request frame based on information other than the common information among the acquired information. The short probe request frame has a smaller size than the second probe request frame.

FIG. 5 is a conceptual diagram illustrating a configuration of a probe request frame, and FIG. 6 is a conceptual diagram illustrating information included in a probe request frame.

5 and 6, the probe request frame defined in IEEE 802.11 is a frame control field, a duration / ID field, an address 1 field, an address 2 field, an address 3 field, and a sequence. A control control field, a high throughput control, a frame body field, and a frame check sequence (FCS) field.

In this case, the information included in the frame body may include a service set identifier (SSID), supported rates, request information, extended supported rates, and high processing capability ( high throughput capabilities, 20/40 basic service set coexistence, extended capabilities, and the like.

The probe request frame described above may mean a second probe request frame transmitted by the second terminal 20 of FIG. 4. The information common to the second probe request frame may include at least one of a service set identifier, a supported rate, request information, an extended supported rate, high processing capability, 20/40 basic service set coexistence, and an extended capability. That is, the first terminal 10 of FIG. 4 may generate a short probe request frame based on information except common information among information included in the frame body of the second probe request frame.

Referring back to FIG. 4, in step S120, the first terminal 10 may generate a short probe request frame including reference information. The reference information may be used to identify the referenced second probe request frame to generate a short probe request frame.

7 is a conceptual diagram illustrating an embodiment of reference information.

Referring to FIG. 7, the reference information may include a source address (or partial source address) field and an order control field. The source address (or partial source address) field has the size of A bits (A is any value) and the order control field has the size of B bits (B is any value). A and B may be different values, or may be the same value.

The source address of the reference information may be generated based on the source address of the referenced frame request frame (eg, the second probe request frame in FIG. 4). That is, the source address of the referenced frame request frame may be used as the source address of the reference information, or a part of the source address of the referenced frame request frame may be used as the source address of the reference information.

When a part of the source address of the referenced frame request frame is used as the source address of the reference information, the most significant bits (MSBs) part, the least significant bits part (LSBs) part or the middle part of the source address of the referenced frame request frame (Less than 48 bits) can be used as a source address of reference information. In addition, a hash algorithm may be used to process the source address of the referenced frame request frame, and the hashed source address may be used as the source address of the reference information.

The order control of the reference information may be generated based on the order control of the referenced frame request frame (eg, the second probe request frame in FIG. 4). That is, the order control of the referenced frame request frame may be used as the order control of the reference information.

8 is a conceptual diagram illustrating another embodiment of reference information.

Referring to FIG. 8, the reference information may include a source address (or partial source address) field and a time stamp (or partial time stamp) field. The source address (or partial source address) field has a size of A bits (A is any value) and the time stamp (or partial time stamp) field has a B bit size (B is any value). A and B may be different values, or may be the same value.

The source address of the reference information may be generated based on the source address of the referenced frame request frame (eg, the second probe request frame in FIG. 4). That is, the source address of the referenced frame request frame may be used as the source address of the reference information, or a part of the source address of the referenced frame request frame may be used as the source address of the reference information.

When using a part of the source address of the referenced frame request frame as the source address of the reference information, refer to some bits (less than 48 bits) of the MSBs part, the LSBs part, or the middle part of the source address of the referenced frame request frame. Can be used as a starting address for. In addition, a hash algorithm may be used to process the source address of the referenced frame request frame, and the hashed source address may be used as the source address of the reference information.

The time stamp of the reference information may be generated based on a time when the referenced frame request frame (eg, the second probe request frame in FIG. 4) is transmitted. That is, time information on which the referenced frame request frame is transmitted may be used as a time stamp of reference information, or a part of time information on which the referenced frame request frame is transmitted may be used as a time stamp of reference information.

When some of the time information in which the referenced frame request frame is transmitted is used as a time stamp of the reference information, some bits of the MSBs part, LSBs part, or the middle part of the time information in which the referenced frame request frame is transmitted are referred to as the time of the reference information. Can be used as a stamp. In addition, a hash algorithm may process time information in which the referenced frame request frame is transmitted, and the hashed time information may be used as a time stamp of the reference information.

9 is a conceptual diagram illustrating another embodiment of reference information.

Referring to FIG. 9, the reference information may include a source address (or partial source address) field and a frame check sequence (FCS) (or partial frame check order) field. The source address (or partial source address) field has the size of A bits (A is any value), and the frame check order (or partial frame check order) field has the size of B bits (B is any value). Have A and B may be different values, or may be the same value.

The source address of the reference information may be generated based on the source address of the referenced frame request frame (eg, the second probe request frame in FIG. 4). That is, the source address of the referenced frame request frame may be used as the source address of the reference information, or a part of the source address of the referenced frame request frame may be used as the source address of the reference information.

When using a part of the source address of the referenced frame request frame as the source address of the reference information, refer to some bits (less than 48 bits) of the MSBs part, the LSBs part, or the middle part of the source address of the referenced frame request frame. Can be used as a starting address for. In addition, a hash algorithm may be used to process the source address of the referenced frame request frame, and the hashed source address may be used as the source address of the reference information.

The frame check order of the reference information may be generated based on a frame check sequence (FCS) of the referenced frame request frame (eg, the second probe request frame in FIG. 4). That is, the FCS of the referenced frame request frame can be used as the frame checking order of the reference information, or a part of the FCS of the referenced frame request frame can be used as the frame checking order of the reference information.

When using a part of the FCS of the referenced frame request frame as the frame checking order of the reference information, some bits of the MSBs part, the LSBs part, or the middle part of the FCS of the referenced frame request frame may be used as the frame checking order of the reference information. . In addition, a hash algorithm may be used to process the FCS of the referenced frame request frame, and the hashed FCS may be used as a frame check order of the reference information.

Referring back to FIG. 4, the first terminal 10 may transmit a short probe request frame to the access point 30 in a broadcast or unicast manner (S130). Meanwhile, the access point 30 may receive a second probe request frame from the terminal 2 20, and may receive a short probe request frame from the terminal 1 10. The access point 30 may obtain reference information included in the short probe request frame and recognize that the short probe request frame is generated with reference to the second probe request frame through the obtained reference information. Accordingly, the access point 30 may generate a probe response frame corresponding to the second probe request frame without generating a probe response frame corresponding to the second probe request frame and the short probe request frame, respectively. The access point 30 may transmit the generated probe response frame as a response of the second probe request frame and the short probe request frame (S140).

10 is a flowchart illustrating an active search response method according to an embodiment of the present invention.

Referring to FIG. 10, the access point may receive a short probe request frame from the terminal (S200). Here, the short probe request frame refers to the short probe request frame described with reference to FIGS. 4 to 9 above, and is a full probe request frame transmitted by another terminal (that is, a probe request frame defined by IEEE 802.11). It includes information and reference information except common information. The reference information is used to identify the full probe request frame referenced to generate the short probe request frame.

The reference information may include a (partial) source address field and an order control field, which may be generated based on the source address information and the order control information included in the referenced full probe request frame. Alternatively, the reference information may include a (partial) source address field and a (partial) time stamp field, which are based on the source address included in the referenced full probe request frame and the time information at which the referenced full probe request frame was transmitted. Can be generated as Alternatively, the reference information may include a (partial) source address field and a (partial) frame check order field, which may be generated based on the source address information and the frame check order information included in the referenced full probe request frame. .

Common information in the full probe request frame may include at least one of a service set identifier, a supported rate, request information, an extended supported rate, high processing capability, 20/40 basic service set coexistence, and an extended capability.

The access point may identify the existence of the referenced full probe request frame to generate the short probe request frame based on the reference information included in the short probe request frame (S210 and S220). The access point may determine whether there is a full probe request frame indicated by the reference information (that is, the full probe request frame referenced to generate the short probe request frame) among the already received full probe request frames.

If there is a full probe request frame indicated by the reference information, the access point may generate a probe response frame in consideration of the information included in the referenced full probe request frame and the short probe request frame, and the generated probe response frame May be transmitted in response to the referenced full probe request frame and the short probe request frame (S230). In this case, the AP may transmit a probe response frame in a broadcast manner.

On the other hand, if the full probe request frame indicated by the reference information does not exist, the access point detects a probe response frame corresponding to another full probe request frame (that is, a full probe request frame not referenced to generate a short probe request frame). In operation S240, the generated probe response frame may be transmitted as a response of the short probe request frame. In this case, the AP may transmit a probe response frame to the terminal in a unicast manner.

11 is a flow diagram illustrating one embodiment of an access point search.

Referring to FIG. 11, a first terminal STA 1 and a second terminal STA 2 are located within a cell range served by an access point AP. The first terminal STA 1 may receive a frame transmitted by the second terminal STA 2, and the second terminal STA 2 may receive a frame transmitted by the first terminal STA 1.

The first terminal STA 1 may transmit a first probe request frame (that is, a probe request frame defined in IEEE 802.11). The second terminal STA 2 may obtain a first probe request frame transmitted by the first terminal STA 1, and generate a short probe request frame based on the first probe request frame. Here, the short probe request frame refers to the short probe request frame described above with reference to FIGS. 4 to 9, and includes information and reference information except common information among the first probe request frames. The reference information is used to identify the probe request frame referenced to generate the short probe request frame. The second terminal STA 2 may transmit a short probe request frame.

The access point AP may receive a first probe request frame from the first terminal STA 1, and may receive a short probe request frame from the second terminal STA 2. The AP may acquire reference information from the short probe request frame, and recognize that the short probe request frame is generated with reference to the first probe request frame through the obtained reference information. Accordingly, the access point AP may generate a probe response frame corresponding to the first probe request frame, and transmit the generated probe response frame in response to the first probe request frame and the short probe request frame. In this case, the AP may transmit a probe response frame in a broadcast manner.

12 is a flowchart illustrating another embodiment of an access point search.

Referring to FIG. 12, a first terminal STA 1, a second terminal STA 2, and a third terminal STA 3 are located within a cell range served by the access point AP. The first terminal STA 1 may receive a frame transmitted by the second terminal STA 2 and the third terminal STA 3, and the second terminal STA 2 may be connected to the first terminal STA 1 and the first terminal STA 1. The third terminal STA 3 may receive a frame, and the third terminal STA 3 may receive a frame transmitted by the first terminal STA 1 and the second terminal STA 2.

The first terminal STA 1 may continuously transmit the first probe request frame and the second probe request frame. The first probe request frame and the second probe request frame may refer to probe request frames defined in IEEE 802.11. The second terminal STA 2 may receive a first probe request frame transmitted by the first terminal STA 1, generate a first short probe request frame based on the first probe request frame, and generate the first probe request frame. The first short probe request frame may be transmitted. The third terminal STA 3 may receive a second probe request frame transmitted by the first terminal STA 1, generate a second short probe request frame based on the second probe request frame, and generate the second probe request frame. The second short probe request frame may be transmitted.

Here, the short probe request frame refers to the short probe request frame described above with reference to FIGS. 4 to 9, and includes information and reference information except common information among probe request frames transmitted by the first terminal STA 1. do. The reference information is used to identify the probe request frame referenced to generate the short probe request frame.

The access point AP may receive the first probe request frame and the second probe request frame from the first terminal STA 1, and may receive the first short probe request frame from the second terminal STA 2. The second short probe request frame may be received from the third terminal STA 3.

The access point AP may obtain reference information from the first short probe request frame, and recognize that the first short probe request frame is generated with reference to the first probe request frame through the obtained reference information. In addition, the AP may acquire reference information from the second short probe request frame, and recognize that the second short probe request frame is generated with reference to the second probe request frame through the obtained reference information. have.

Accordingly, the AP may generate a probe response frame corresponding to the first probe request frame and the second probe request frame, and generate the first probe request frame, the second probe request frame, and the first probe request frame. It can be transmitted in response to the first short probe request frame and the second short probe request frame. In this case, the AP may transmit a probe response frame in a broadcast manner.

13 is a flowchart illustrating an environment overlapped between access points.

Referring to FIG. 13, a cell in which a first terminal STA 1 and a third terminal STA 3 are positioned within a cell range served by the first access point AP 1 and served by the second access point AP 2 is served. The second terminal STA 2 and the third terminal STA 3 are located within the range. The third terminal STA 3 is located in an area where the first access point AP 1 and the second access point AP 2 overlap.

When the first terminal STA 1 transmits a probe request frame, the first terminal STA 1 transmits the first access point AP 1, the second terminal STA 2, and the third terminal STA 3 by the first terminal STA 1. Although one probe request frame may be received, the second access point AP 2 may not receive the probe request frame transmitted by the first terminal STA 1. In this case, in order to reduce the air-time required to send the probe request frame, the second terminal STA 2 and the third terminal STA 3 trust the probe request frame transmitted by the first terminal STA 1 and make their own probe. If the request frame is not transmitted, the second access point AP 2 that does not receive the probe request frame of the first terminal STA 1 may not transmit the probe response frame, and thus, the second terminal STA 2 may not be transmitted. The third terminal STA 3 may not recognize the existence of the second access point AP 2.

According to the active scanning method according to an embodiment of the present invention, the second terminal STA 2 and the third terminal STA 3 are short probe request frames based on probe request frames transmitted by the first terminal STA 1. May be generated, and the generated short probe request frame may be transmitted. In this case, the first access point AP 1 may generate a probe response frame in consideration of the probe request frame transmitted by the first terminal STA 1 and the short probe request frame transmitted by the third terminal STA 3. In addition, the generated probe response frame may be transmitted. On the other hand, since the access point AP 2 has not received the probe request frame of the first terminal STA 1 but received the short probe request frame transmitted by the second terminal STA 2 and the third terminal STA 3, In consideration of the short probe request frame, the probe response frame may be transmitted. In this manner, the terminals can effectively determine whether there is a neighboring access point.

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.

10: first terminal (STA 1)
20: second terminal (STA 2)
30: access point (AP)

Claims (15)

In the active search method performed in the first terminal,
Obtaining a second probe request frame transmitted by the second terminal;
Generating a short probe request frame based on information other than the common information among the second probe request frames; And
Transmitting the short probe request frame. The method according to claim 1,
In the active search method,
Receiving a probe response frame which is a response of the short probe request frame. The method according to claim 1,
The short probe request frame is
And reference information identifying the referenced second probe request frame. The method according to claim 3,
The reference information,
The active search method, characterized in that the generated based on the source address (source address) information and the sequence control (sequence control) information included in the second probe request frame. The method according to claim 3,
The reference information,
And an origin address information included in the second probe request frame and time information when the second probe request frame is transmitted. The method according to claim 3,
The reference information,
And generating based on source address information and frame check sequence information included in the second probe request frame. The method according to claim 1,
Common information among the second probe request frames is
Service set identifier (SSID), supported rates, request information, extended supported rates, high throughput capabilities, 20/40 basic And at least one of basic service set coexistence and extended capabilities. In an active search response method performed in an access point,
Receiving a short probe request frame;
Identifying the presence of a referenced full probe request frame to generate the short probe request frame based on reference information included in the short probe request frame; And
And transmitting a probe response frame generated based on the referenced full probe request frame and the short probe request frame when the referenced full probe request frame exists. The method according to claim 8,
And transmitting a probe response frame corresponding to another full probe request frame when the referenced full probe request frame does not exist. The method according to claim 8,
The short probe request frame is
And the reference information and information excluding common information among the referenced full probe request frames. The method of claim 10,
Common information among the referenced full probe request frames is
Service set identifier (SSID), supported rates, request information, extended supported rates, high throughput capabilities, 20/40 basic Active service response method comprising at least one of basic service set coexistence and extended capabilities. The method according to claim 8,
The reference information,
And generating based on source address information and sequence control information included in the referenced full probe request frame. The method according to claim 8,
The reference information,
And a source address information included in the referenced full probe request frame and time information when the referenced full probe request frame is transmitted. The method according to claim 8,
The reference information,
And generating based on the source address information and the frame check sequence information included in the referenced full probe request frame. The method according to claim 8,
Transmitting the probe response frame,
And transmitting the probe response frame in a broadcast manner.

Images