KR20140035812A - Method for active scanning in wireless local area network system - Google Patents

Method for active scanning in wireless local area network system Download PDF

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Publication number
KR20140035812A
KR20140035812A KR1020130101510A KR20130101510A KR20140035812A KR 20140035812 A KR20140035812 A KR 20140035812A KR 1020130101510 A KR1020130101510 A KR 1020130101510A KR 20130101510 A KR20130101510 A KR 20130101510A KR 20140035812 A KR20140035812 A KR 20140035812A
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South Korea
Prior art keywords
probe request
request frame
information
frame
response
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KR1020130101510A
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Korean (ko)
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배영호
정양석
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주식회사 케이티
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Priority to KR1020120102425 priority
Application filed by 주식회사 케이티 filed Critical 주식회사 케이티
Publication of KR20140035812A publication Critical patent/KR20140035812A/en

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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W48/00Access restriction; Network selection; Access point selection
    • H04W48/08Access restriction or access information delivery, e.g. discovery data delivery
    • H04W48/14Access restriction or access information delivery, e.g. discovery data delivery using user query or user detection
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W48/00Access restriction; Network selection; Access point selection
    • H04W48/16Discovering, processing access restriction or access information
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W84/00Network topologies
    • H04W84/02Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10Small scale networks; Flat hierarchical networks
    • H04W84/12WLAN [Wireless Local Area Networks]

Abstract

An active search method is disclosed in a WLAN system. The active search method may include obtaining a first probe request frame transmitted by a first terminal through an arbitrary channel, generating a short probe request frame based on information excluding common information among the first probe request frames, and Transmitting a probe request frame through an arbitrary channel and transmitting a second probe request frame if a response to the short probe request frame is not received within a predefined time. Therefore, it is possible to reduce the air-time occupied by the probe request frame and the 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 in which a plurality of terminals and a plurality of access points exist, each terminal transmits its own probe request frame, and each access point transmits a probe response frame in response to the probe request frame. That is, a large number of probe request frames and probe response frames are transmitted, thereby increasing the air-time occupied by the probe request frame and the probe response frame.
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 an active search method, the method comprising: acquiring a first probe request frame transmitted by a first terminal through an arbitrary channel, and common information among the first probe request frames; Generating a short probe request frame based on the excluded information, transmitting the short probe request frame through the arbitrary channel, and if a response to the short probe request frame is not received within a predetermined time; And transmitting 2 probe request frames.
Here, in the transmitting of the second probe request frame, the second probe request frame may be transmitted through the arbitrary channel.
In the transmitting of the second probe request frame, the second probe request frame may be transmitted through a channel other than the arbitrary channel.
Here, the short probe request frame may further include reference information for identifying the referenced first probe request frame.
Here, the reference information may be generated based on source address information and order control information included in the first probe request frame.
Here, the reference information may be generated based on source address information included in the first probe request frame and time information on which the first 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 first probe request frame.
In accordance with another aspect of the present invention, there is provided an active scanning method, the method comprising: acquiring a first probe request frame transmitted by a first terminal, based on information excluding common information among the first probe request frames; Generating a short probe request frame, transmitting the short probe request frame, and obtaining an information request message from the access point indicating that there is insufficient information necessary to generate a probe response frame in response to the short probe request frame. Steps.
The active search method may further include transmitting a second probe request frame in response to the information request message and obtaining a probe response frame from the access point in response to the second probe request frame. can do.
The active search method may further include transmitting necessary information indicated by the information request message and obtaining, from the access point, a probe response frame generated based on the short probe request frame and the necessary information. can do.
Here, the necessary information 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.
Here, the short probe request frame may further include reference information for identifying the referenced first probe request frame.
According to another exemplary embodiment of the present invention, there is provided a method for acquiring a short probe request frame from a terminal, based on reference information included in the short probe request frame. Identifying the presence of the first probe request frame referenced to generate the frame and, if the first probe request frame does not exist, indicating information required to generate a probe response frame that is a response to the short probe request frame. Transmitting the information request message.
The method may further include obtaining a second probe request frame that is a response to the information request message from the terminal, and transmitting a probe response frame in response to the second probe request frame. can do.
The active search response method may further include obtaining necessary information indicated by the information request message from the terminal and transmitting a short probe request frame and a probe response frame generated based on the necessary information. can do.
Here, the short probe request frame may be generated based on information except common information among the first probe request frames.
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 conceptual diagram illustrating a general active search method in a WLAN system.
5 is a conceptual diagram illustrating an embodiment of transmission of a short probe request frame.
6 is a conceptual diagram illustrating another embodiment of the transmission of a short probe request frame.
7 is a conceptual diagram illustrating an environment in which a plurality of access points and a plurality of terminals exist.
8 is a conceptual diagram illustrating an embodiment of an active search method in an environment in which a plurality of access points and a plurality of terminals exist.
9 is a conceptual diagram illustrating an active search method according to an embodiment of the present invention.
10 is a conceptual diagram illustrating another embodiment of short probe request frame transmission.
11 is a flowchart illustrating an active search method according to another embodiment of the present invention.
12 is a conceptual diagram illustrating an active search method according to another embodiment of the present invention.
13 is a flowchart illustrating an active search method according to another embodiment of the present invention.
14 is a conceptual diagram illustrating an active search method according to another embodiment of the present invention.
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 a connection to the distribution system (DS) over the wireless medium for the terminal (STA 1, STA 3, STA 4) . 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 perform authentication with the detected access point AP and may perform authentication with the plurality of detected access points APs. 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.
Lastly, the terminal STA selects one of the authenticated access points APs and performs a connection process with the selected 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.
In an environment in which a plurality of terminals and a plurality of access points exist, most radio sections are occupied by a plurality of probe response frames that are responses of the plurality of probe request frames and probe request frames when each terminal transmits a probe request frame. do.
4 is a conceptual diagram illustrating a general active search method in a WLAN system.
Referring to FIG. 4, the terminal STA may transmit a probe request frame, and the first access point AP 1 that receives the probe request frame may transmit a probe response frame after a distributed interframe space (DIFS). Upon receiving the probe response frame, the STA may transmit an ACK frame after a short interframe space (SIFS). Thereafter, the second access point AP 2 may transmit a probe response frame after performing a backoff procedure, and the terminal STA that receives the probe response frame may transmit an ACK frame after SIFS.
In the case of performing an active search, the information contained in the probe request frames transmitted by each UE is almost the same, and since the probe request frame and the probe response frame are transmitted at a low data rate, most of the UEs located in the vicinity can receive the information. Can be.
Since the WLAN system operates based on carrier sense multiple access / collision avoidance (CSMA / CA) and random backoff, when a first terminal and a second terminal, which are neighboring terminals, attempt to transmit a probe request frame, contention Only one terminal can transmit a probe request frame through the other terminal, the other terminal does not transmit the probe request frame is to wait.
For example, when there is a neighboring first terminal and a second terminal, when the first terminal transmits a probe request frame, the access point transmits a probe response frame in response to the probe request frame and receives a probe response frame. One first terminal transmits an ACK frame in response thereto. On the other hand, since the wireless section is occupied by the first terminal, the second terminal cannot transmit the probe request frame during the active search period between the first terminal and the access point.
5 is a conceptual diagram illustrating an embodiment of transmission of a short probe request frame.
Referring to FIG. 5, when the first terminal STA 1 transmits the first probe request frame PRQ 1, the second terminal STA 2 receives or listens to the first probe request frame PRQ 1. can be overhear). The second terminal STA 2 may determine whether the first probe request frame PRQ 1 is identical to the second probe request frame to be transmitted. When the information common to the first probe request frame PRQ 1 and the second probe request frame exists, the second terminal STA 2 may shorten the short probe request frame based on the information excluding the common information (that is, simplify). Generate a simplified probe request frame (SPQ). Here, the first probe request frame PRQ 1 and the second probe request frame may mean a general probe request frame according to IEEE 802.11.
The short probe request frame SPQ may include reference information indicating the first probe request frame PRQ 1 referred to to generate the short probe request frame SPQ. The reference information includes source address information, sequence control information, frame check sequence, and first probe request frame PRQ 1 included in the first probe request frame PRQ 1. It can be generated by a combination of the transmitted time information (timestamp).
For example, the reference information may include the source address information and the sequence control information included in the referenced probe request frame, or the time at which the source address information and the referenced probe request frame included in the referenced probe request frame are transmitted. Information, or may include source address information and frame check order included in the referenced probe request frame.
Common information between probe request frames includes service set identifier (SSID), supported rates, request information, extended supported rates, and high throughput. throughput capabilities, 20/40 basic service set coexistence, extended capabilities, and the like.
The second terminal STA 2 may perform a random backoff procedure after the 'first probe request frame PRQ 1 transmission time + DIFS' passes, and after the random backoff procedure is completed, a short probe request frame SPQ Can be transmitted.
The AP may receive the first probe request frame PRQ 1 and the short probe request frame SPQ, and perform a random backoff procedure after the short probe request frame SPQ transmission time + DIFS. Can be done. Here, the access point AP may know that the short probe request frame SPQ is generated by referring to the first probe request frame PRQ 1 through analysis of reference information included in the short probe request frame SPQ. Accordingly, the access point AP may generate a probe response frame PRS corresponding to the first probe request frame PRQ 1.
After the random backoff procedure is completed, the access point AP may transmit the probe response frame PRS in response to the first probe request frame PRQ 1 and the short probe request frame SPQ. In this case, the AP may transmit a probe response frame PRS to each terminal in a unicast manner, or may transmit a probe response frame PRS in a broadcast manner.
6 is a conceptual diagram illustrating another embodiment of the transmission of a short probe request frame.
Referring to FIG. 6, when the first terminal STA 1 transmits the first probe request frame PRQ 1, the second terminal STA 2 may receive or overhear the first probe request frame PRQ 1. have. The second terminal STA 2 may determine whether the first probe request frame PRQ 1 is identical to the second probe request frame to be transmitted. When information common to both the first probe request frame PRQ 1 and the second probe request frame exists, the second terminal STA 2 may perform a short probe request frame (ie, a simplified probe request) based on information other than the common information. Frame) (SPQ).
The second terminal STA 2 may perform a random backoff procedure after the 'first probe request frame PRQ 1 transmission time + DIFS' passes to transmit a short probe request frame SPQ, and simultaneously access point. The AP may perform a random backoff procedure to transmit a probe response frame PRS that is a response to the first probe request frame PRQ 1.
If the random backoff procedure of the access point AP is completed before the second terminal STA 2 and the probe response frame PRS is transmitted, the second terminal STA 2 may generate a short probe request frame SPQ. An access process with the AP may be performed based on the probe response frame PRS without transmitting. That is, the second terminal STA 2 may omit the transmission of the short probe request frame SPQ.
7 is a conceptual diagram illustrating an environment in which a plurality of access points and a plurality of terminals exist. 8 is a conceptual diagram illustrating an embodiment of an active search method in an environment in which a plurality of access points and a plurality of terminals exist.
7 and 8, a plurality of access points AP 1, AP 2,..., AP n and a plurality of terminals STA 1, STA 2,..., STA k exist. Is positive). The first terminal STA 1 is located within a range (ie, a communicable area) of the first access point AP 1, and the second terminal STA 2 is located within a range (ie, a communication) of the second access point AP 2. Available area). The first access point AP 1 may receive information transmitted from the first terminal STA 1, but may not receive information transmitted from the second terminal STA 2, and may not receive information transmitted from the second terminal STA 2. The UE may receive information transmitted from the second terminal STA 2, but may not receive information transmitted from the first terminal STA 1. The first terminal STA 1 may receive information transmitted from the second terminal STA 2, and the second terminal STA 2 may receive information transmitted from the first terminal STA 1.
When the first terminal STA 1 transmits the first probe request frame PRQ 1, the first access point AP 1 may receive the first probe request frame PRQ 1, and the second terminal STA may receive the first probe request frame PRQ 1. 2) may receive or overhear the first probe request frame PRQ 1. On the other hand, the second access point AP 2 does not receive the first probe request frame PRQ 1.
The second terminal STA 2 may determine whether the first probe request frame PRQ 1 is identical to the second probe request frame to be transmitted. When information common to both the first probe request frame PRQ 1 and the second probe request frame exists, the second terminal STA 2 may perform a short probe request frame (ie, a simplified probe request) based on information other than the common information. Frame) (SPQ). Here, the specific method of generating the short probe request frame SPQ is the same as the content described with reference to FIG. 5.
After the 'first probe request frame PRQ 1 transmission time + DIFS' passes, the first access point AP 1 goes through a random backoff procedure and a probe response frame that is a response to the first probe request frame PRQ 1. Send (PRS). Meanwhile, since the second terminal STA 2 is located outside the range of the first access point AP 1 and is not related to the transmission of the probe response frame PRS, the transmission time of the first probe request frame PRQ 1 + DIFS is increased. After a short probe request frame (SPQ) is transmitted. That is, the first access point AP 1 may not receive the short probe request frame SPQ transmitted from the second terminal STA 2, and the second terminal STA 2 may not receive the first access point AP 1. It is not possible to receive the probe response frame (PRS) transmitted from.
The second access point AP 2 may receive the short probe request frame SPQ and may be referred to to use the short probe request frame SPQ based on reference information included in the short probe request frame SPQ. The probe request frame can be identified. The reference information indicates that the short probe request frame SPQ refers to the first probe request frame PRQ 1, but the second access point AP 2 did not receive the first probe request frame PRQ 1. There is a problem that a probe response frame corresponding to a short probe request frame SPQ cannot be transmitted.
In this case, the access point may operate in three ways as follows.
Method 1) The access point generates a probe response frame for any probe request frame among previously received probe request frames, and transmits the generated probe response frame in response to the short probe request frame. (Or, a probe response frame is generated according to a preset criterion, and the generated probe response frame is transmitted in response to a short probe request frame.)
Scheme 2) The access point does not send a response to the short probe request frame.
Scheme 3) The access point transmits an information request message indicating that information for generating a probe response frame corresponding to a short probe request frame is insufficient.
9 is a conceptual diagram illustrating an active search method according to an embodiment of the present invention. This represents an active search method according to the method 1 described above.
9, a plurality of access points AP 1, AP 2,..., AP n and a plurality of terminals STA 1, STA 2,..., STA k exist, and a plurality of access points and a plurality of terminals are present. The relationship between is as shown in FIG.
The first terminal STA 1 may transmit a first probe request frame PRQ 1, and the first access point AP 1 may respond to the first probe request frame PRQ 1 in response to the probe response frame PRS. Can be transmitted. Meanwhile, the second terminal STA 2 may receive the first probe request frame PRQ 1, and determine the sameness between the first probe request frame PRQ 1 and the second probe request frame that it wants to transmit. Can be. Here, the second terminal STA 2 does not receive the probe response frame PRS transmitted from the first access point AP 1. When information common to both the first probe request frame PRQ 1 and the second probe request frame exists, the second terminal STA 2 may perform a short probe request frame (ie, a simplified probe request) based on information other than the common information. Frame) (SPQ). A detailed method of generating a short probe request frame SPQ is the same as that described with reference to FIG. 5.
The second terminal STA 2 may transmit a short probe request frame SPQ, and the second access point AP 2 may receive a short probe request frame SPQ. The second access point AP 2 may identify the probe request frame referred to to generate the short probe request frame SPQ through analysis of reference information included in the short probe request frame SPQ. The reference information indicates that the first probe request frame PRQ 1 was referred to to generate a short probe request frame, but the second access point AP 2 did not receive the first probe request frame PRQ 1. The probe response frame corresponding to the first probe request frame PRQ 1 may not be generated.
In this case, the second access point AP 2 may generate a probe response frame PRS based on an arbitrary probe request frame among previously received probe request frames, and shortens the generated probe response frame PRS. It can be transmitted in response to the probe request frame SPQ. Alternatively, the second access point AP 2 may generate a probe response frame PRS according to a preset criterion, and transmit the generated probe response frame PRS in response to the short probe request frame SPQ. have. Here, the second access point AP 2 may transmit the probe response frame PRS to the second terminal STA 2 in a unicast manner, or may transmit the probe response frame PRS in a broadcast manner.
According to the above method, the terminals STA 3,..., STA k located within the range of the second access point AP 2 receive the probe response frame PRS transmitted from the second access point AP 2. Or may overhear it, and thus may not transmit a probe request frame or a short probe request frame. As a result, the air-time occupied by the probe request frame can be reduced.
10 is a conceptual diagram illustrating another embodiment of short probe request frame transmission.
Referring to FIG. 10, when the first terminal STA 1 transmits the first probe request frame PRQ 1, the second terminal STA 2 may receive or overhear the first probe request frame PRQ 1. have. The second terminal STA 2 may determine whether the first probe request frame PRQ 1 is identical to the second probe request frame to be transmitted. When information common to both the first probe request frame PRQ 1 and the second probe request frame exists, the second terminal STA 2 may perform a short probe request frame (ie, a simplified probe request) based on information other than the common information. Frame) (SPQ).
The second terminal STA 2 may perform a random backoff procedure after a 'first probe request frame PRQ 1 transmission time + DIFS' passes to transmit a short probe request frame SPQ, and simultaneously The access point AP 1 may perform a random backoff procedure to transmit a probe response frame PRS that is a response to the first probe request frame PRQ 1.
Meanwhile, the other terminals STA 3,..., STA k located in the communicable area of the second access point AP 2 to the n-th access point AP n are short probes transmitted from the second terminal STA 2. The request frame SPQ may be received or eavesdropped, and may wait in a reception state to receive a probe response frame that is a response to the short probe request frame SPQ. However, when the access points AP 2,..., AP n do not transmit a response to the short probe request frame SPQ, the other terminals STA 3,..., STA k have their short probe request frames ( SPQ) can be sent. In this case, there is a problem that air time is occupied by short probe request frames SPQs transmitted by a plurality of terminals.
11 is a flowchart illustrating an active search method according to another embodiment of the present invention, and FIG. 12 is a conceptual diagram illustrating an active search method according to another embodiment of the present invention. This represents an active search method according to the scheme 2 described above.
11 and 12, there are a plurality of access points AP 1, AP 2,..., AP n and a plurality of terminals STA 1, STA 2,..., STA k, and a plurality of access points. The relationship between the plurality of terminals is as shown in FIG.
The first terminal STA 1 may transmit the first probe request frame PRQ 1, and the second terminal STA 2 may receive or overhear the first probe request frame PRQ 1 through an arbitrary channel. There is (S100). The second terminal STA 2 may generate a short probe request frame (that is, a simplified probe request frame) SPQ based on information other than common information among the first probe request frames PRQ 1 (S110). .
In operation S110, the second terminal STA 2 may determine the sameness between the first probe request frame PRQ 1 and the second probe request frame that it intends to transmit. When information common to both the first probe request frame PRQ 1 and the second probe request frame exists, the second terminal STA 2 may generate a short probe request frame SPQ based on information other than the common information. have. A detailed method of generating a short probe request frame SPQ is the same as that described with reference to FIG. 5.
Here, the common information between probe request frames may mean a service set identifier, a supported rate, request information, an extended supported rate, a high processing capability, a 20/40 basic service set coexistence, an extended capability, and the like. The short probe request frame SPQ may include reference information, and the reference information indicates a probe request frame referred to to generate the short probe request frame SPQ. The reference information may be generated by a combination of source address information included in the referenced probe request frame, order control information, a frame inspection order, and time information in which the referenced probe request frame is transmitted.
The second terminal STA 2 may transmit the short probe request frame SPQ to the second access point AP 2 in a unicast manner through an arbitrary channel, or the short probe request frame SPQ in a broadcast manner. It may be transmitted (S120).
If a response to the short probe request frame SPQ is not received from the second access point AP 2 within a predefined time, the second terminal STA 2 may access the channel through any channel or a channel other than any channel. 2 probe request frame (PRQ 2) may be transmitted (S130). Here, the predefined time may mean a maximum probe response time (max_probe_response_time).
13 is a flowchart illustrating an active search method according to another embodiment of the present invention, and FIG. 14 is a conceptual diagram illustrating an active search method according to another embodiment of the present invention. This represents an active search method according to the scheme 3 described above.
13 and 14, there are a plurality of access points AP 1, AP 2,..., AP n and a plurality of terminals STA 1, STA 2,..., STA k, and a plurality of access points. The relationship between the plurality of terminals is as shown in FIG.
The first terminal STA 1 may transmit the first probe request frame PRQ 1, and the second terminal STA 2 may receive or overhear the first probe request frame PRQ 1 (S200). The second terminal STA 2 may generate a short probe request frame (ie, a simplified probe request frame) SPQ based on information other than common information among the first probe request frames PRQ 1 (S210). .
In operation S210, the second terminal STA 2 may determine the sameness between the first probe request frame PRQ 1 and the second probe request frame to which the second probe request frame PRQ 1 transmits. When information common to both the first probe request frame PRQ 1 and the second probe request frame exists, the second terminal STA 2 may generate a short probe request frame SPQ based on information other than the common information. have. A detailed method of generating a short probe request frame SPQ is the same as that described with reference to FIG. 5.
Here, the common information between probe request frames may mean a service set identifier, a supported rate, request information, an extended supported rate, a high processing capability, a 20/40 basic service set coexistence, an extended capability, and the like. The short probe request frame SPQ may include reference information, and the reference information indicates a probe request frame referred to to generate the short probe request frame SPQ. The reference information may be generated by a combination of source address information included in the referenced probe request frame, order control information, a frame inspection order, and time information in which the referenced probe request frame is transmitted.
The second terminal STA 2 may transmit the short probe request frame SPQ to the second access point AP 2 in a unicast manner, or may transmit the short probe request frame SPQ in a broadcast manner ( S220).
The second access point AP 2 may obtain the short probe request frame SPQ from the second terminal STA 2 and refer to the first probe request frame PRQ referred to to generate the short probe request frame SPQ. It may be determined whether 1) exists (S230). That is, the second access point AP 2 may determine whether the first probe request frame PRQ 1 exists based on reference information included in the short probe request frame SPQ. Since the second access point AP 2 does not receive the first probe request frame PRQ 1 transmitted by the first terminal STA 1, it is determined that the first probe request frame PRQ 1 does not exist. Can be.
Since the information included in the short probe request frame SPQ alone cannot generate a probe response frame that is a response to the short probe request frame SPQ, the second access point AP 2 may not generate the probe response frame SPQ. An information request message (NRS) indicating information required to generate a probe response frame as a response may be generated (S240). The information request message (NRS) may explicitly indicate the type of information required for generating the probe response frame, or may indicate that the information required for generating the probe response frame is insufficient.
The second access point AP 2 may transmit the information request message NRS to the second terminal STA 2 in a unicast manner, or may transmit the information request message NRS in a broadcast manner (S250). . The second access point AP 2 may reset the time point at which the information request message NRS is transmitted to give priority to the transmission of the information request message NRS. For example, the second access point AP 2 may transmit an information request message NRS by performing a random backoff procedure after a short probe request frame transmission time + SIFS.
The second terminal STA 2 may obtain an information request message NRS from the second access point AP 2, and transmit a response to the information request message NRS to the second access point AP 2. There is (S260).
In operation S260, the second terminal STA 2 may transmit necessary information indicated by the second probe request frame or the information request message to the second access point AP 2 in response to the information request message NRS.
When the second probe request frame is received in response to the information request message (NRS), the second access point AP 2 transmits the probe response frame, which is a response to the second probe request frame, to the second terminal STA in a unicast manner. 2) or may be transmitted in a broadcast manner (S270).
On the other hand, when receiving the necessary information indicated by the information request message (NRS) in response to the information request message (NRS), the second access point (AP 2) is based on the short probe request frame (SPQ) and the necessary information The probe response frame may be generated, and the generated probe response frame may be transmitted to the second terminal STA 2 in a unicast manner or transmitted in a broadcast manner (S270). Here, the necessary information may include a service set identifier, a supported rate, request information, an extended supported rate, high processing capability, 20/40 basic service set coexistence, extended capability, and the like.
Thereafter, the second terminal STA 2 may perform an association process and an authentication process with the second access point AP 2 based on the received probe response frame.
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 (16)

  1. In the active search method performed in the second terminal,
    Obtaining a first probe request frame transmitted by the first terminal through an arbitrary channel;
    Generating a short probe request frame based on information other than the common information among the first probe request frames;
    Transmitting the short probe request frame on the arbitrary channel; And
    And if a response to the short probe request frame is not received within a predefined time period, transmitting a second probe request frame.
  2. The method according to claim 1,
    The transmitting of the second probe request frame may include:
    And transmitting the second probe request frame through the arbitrary channel.
  3. The method according to claim 1,
    The transmitting of the second probe request frame may include:
    And transmitting the second probe request frame through a channel other than the arbitrary channel.
  4. The method according to claim 1,
    The short probe request frame is
    And reference information identifying the referenced first probe request frame.
  5. The method of claim 4,
    The reference information,
    And generating based on source address information and sequence control information included in the first probe request frame.
  6. The method of claim 4,
    The reference information,
    And a source address information included in the first probe request frame and time information when the first probe request frame is transmitted.
  7. The method of claim 4,
    The reference information,
    And generating based on source address information and frame check sequence information included in the first probe request frame.
  8. In the active search method performed in the second terminal,
    Obtaining a first probe request frame transmitted by the first terminal;
    Generating a short probe request frame based on information other than the common information among the first probe request frames;
    Transmitting the short probe request frame; And
    And obtaining an information request message from an access point indicating that there is a lack of information required to generate a probe response frame that is a response to the short probe request frame.
  9. The method according to claim 8,
    In the active search method,
    Transmitting a second probe request frame in response to the information request message; And
    Acquiring a probe response frame from the access point that is a response to the second probe request frame.
  10. The method according to claim 8,
    In the active search method,
    Transmitting necessary information indicated by the information request message; And
    And acquiring a probe response frame generated based on the short probe request frame and the necessary information from the access point.
  11. The method of claim 10,
    The necessary information,
    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.
  12. The method according to claim 8,
    The short probe request frame is
    And reference information identifying the referenced first probe request frame.
  13. In an active search response method performed in an access point,
    Obtaining a short probe request frame from the terminal;
    Identifying the presence of a referenced first probe request frame to generate the short probe request frame based on the reference information included in the short probe request frame; And
    And if the first probe request frame does not exist, transmitting an information request message indicating information required to generate a probe response frame that is a response to the short probe request frame.
  14. The method according to claim 13,
    Wherein the active search response method comprises:
    Obtaining a second probe request frame which is a response to the information request message from the terminal; And
    And transmitting a probe response frame in response to the second probe request frame.
  15. The method according to claim 13,
    Wherein the active search response method comprises:
    Obtaining necessary information indicated by the information request message from the terminal; And
    And transmitting a probe response frame generated based on the short probe request frame and the necessary information.
  16. The method according to claim 13,
    The short probe request frame is
    Active search response method characterized in that the generated based on the information other than the common information of the first probe request frame.
KR1020130101510A 2012-09-14 2013-08-27 Method for active scanning in wireless local area network system KR20140035812A (en)

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