KR20140009040A - Method for passive scanning in wireless local area network system - Google Patents

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

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Publication number
KR20140009040A
KR20140009040A KR1020130080737A KR20130080737A KR20140009040A KR 20140009040 A KR20140009040 A KR 20140009040A KR 1020130080737 A KR1020130080737 A KR 1020130080737A KR 20130080737 A KR20130080737 A KR 20130080737A KR 20140009040 A KR20140009040 A KR 20140009040A
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South Korea
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beacon
short
access point
long
information
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KR1020130080737A
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Korean (ko)
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정양석
김주영
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주식회사 케이티
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Publication of KR20140009040A publication Critical patent/KR20140009040A/en

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    • 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

A manual searching method for a wireless local area network (LAN) system is disclosed. The manual searching method includes a step of receiving a short beacon from an access point; a step of recognizing a transmission time of a long beacon transmitted from the access point after the short beacon based on a time information included in the short beacon; and a step of receiving the long beacon from the access point in the transmission time. Therefore, the manual searching method can improve the efficiency of using a wireless channel. [Reference numerals] (AA) Sleep mode; (S100) Transmitting a long beacon; (S110) Transmitting a short beacon; (S120) Recognizing a transmission time of a next long beacon; (S130) Transmitting the next long beacon

Description

Manual Search in Wireless LAN System {METHOD FOR PASSIVE SCANNING IN WIRELESS LOCAL AREA NETWORK SYSTEM}

The present invention relates to a manual search method, and more particularly, to a method for searching for an access point based on a manual search method 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 uses a unlicensed band at 5 GHz to provide a transmission rate of 54 Mbps. 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 applies multiple input multiple output OFDM (MIMO-OFDM) to provide a transmission rate of 300 Mbps for two spatial streams. IEEE 802.11n supports a channel bandwidth of up to 40 MHz, which in this case 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) WLAN technology is one of the IEEE 802.11 WLAN technologies that have been proposed to support data processing speeds of 1Gbps or more. Among them, IEEE 802.11ac is being developed as a standard for providing very high throughput in the band below 5 GHz, and IEEE 802.11ad is being developed as a standard for providing very high throughput in the 60 GHz band.

In a low power / low rate wireless LAN system (e.g., sensor network, etc.) based on such WLAN technology, an access point uses a minimum modulation and coding scheme (MCS) level of 100 Kbps (typically, Beacon is transmitted every 100ms. In this case, since a transmission time of about 8 ms is required to transmit a 100 byte beacon, considering a general beacon period, there is a problem of inefficient use of a wireless channel with about 8% overhead.

An object of the present invention for solving the above problems is to provide a manual search method performed in the terminal to perform a manual search using a short beacon frame containing only essential information.

Another object of the present invention for solving the above problems is to provide a beacon transmission method performed at an access point to transmit a short beacon frame including only essential information within a long beacon frame interval.

Manual search method according to an embodiment of the present invention for achieving the above object, receiving a short beacon from the access point, based on the time information contained in the short beacon, after the short beacon from the access point Recognizing a transmission point of a long beacon transmitted, and receiving a long beacon from the access point at the transmission point, wherein the short beacon is transmitted within an interval of the long beacon.

Here, the time information may include interval information of the short beacons and information on the number of short beacons transmitted until a transmission point of the next long beacon.

Here, the time information may include remaining time information until the transmission time of the next long beacon.

Here, the period of the long beacon may be an integer multiple of the short beacon period.

Here, the short beacon may further include traffic allocation information for a predefined terminal or a predefined group.

Here, the terminal may operate in the sleep mode until the transmission time of the next long beacon.

In accordance with another aspect of the present invention, there is provided a method of receiving data, the method comprising: receiving a short beacon from an access point, based on traffic allocation information included in the short beacon, data buffered for the terminal; And determining the presence of data, and receiving the data from the access point if there is data for the terminal, wherein the short beacon is transmitted from the access point within an interval of a long beacon.

Here, the traffic allocation information may indicate the presence of data buffered at the access point for a predefined terminal or a predefined group.

In this case, the traffic allocation information may be set based on count information included in the short beacon.

Here, the period of the long beacon may be an integer multiple of the short beacon period.

Here, the short beacon may include time information used to recognize the transmission time of the long beacon transmitted from the access point after the short beacon.

Here, the time information may include interval information of the short beacons and information on the number of short beacons transmitted until a transmission point of the next long beacon.

Here, the time information may include remaining time information until the transmission time of the next long beacon.

A beacon transmission method according to an embodiment of the present invention for achieving the another object, the step of transmitting a long beacon at a predetermined time point, and a short beacon having a size smaller than the long beacon within the interval of the long beacon And transmitting, wherein the short beacon includes time information used to recognize a transmission time of the long beacon transmitted after the short beacon from the access point.

Here, the time information may include interval information of the short beacons and information on the number of short beacons transmitted until a transmission point of the next long beacon.

Here, the time information may include remaining time information until the transmission time of the next long beacon.

Here, the period of the long beacon may be an integer multiple of the short beacon period.

Here, the short beacon may further include traffic allocation information for a predefined terminal or a predefined group.

In this case, the traffic allocation information may be set based on count information included in the short beacon.

According to the present invention, by setting a relatively long period of the existing beacons (ie, long beacons) and transmitting short beacons including only essential information between the existing beacons, it is possible to improve the use efficiency of the wireless channel.

In addition, by using the counter information and interval information included in the short beacon, the terminal can recognize the transmission time of the existing beacon transmitted later, and can maintain a sleep state until the transmission time of the existing beacon to reduce power consumption Can be.

In addition, by using a short beacon including TIM information for a specific terminal (or group), the specific terminal (or group) does not have to wait until the transmission time of the existing beacon to receive data, thereby improving the data transmission speed. . In addition, since the channel access attempts of the terminals for data reception are distributed in time, collision between the terminals can be prevented.

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 an embodiment of beacon transmission in a WLAN system.
5 is a block diagram showing the configuration of a beacon.
6 is a block diagram showing the configuration of a TIM element.
7 is a conceptual diagram illustrating an operation of a terminal in a manual search method.
8 is a flowchart illustrating a manual search method according to an embodiment of the present invention.
9 is a block diagram showing the configuration of a short beacon.
FIG. 10 is a block diagram illustrating an embodiment of a configuration of a short beacon information field included in a short beacon.
11 is a block diagram illustrating another embodiment of the configuration of a short beacon information field included in a short beacon.
12 is a block diagram illustrating a hierarchical AID structure.
13 is a flowchart illustrating a data receiving method according to an embodiment of the present invention.
14 is a conceptual diagram illustrating an embodiment of short beacon transmission.
15 is a conceptual diagram illustrating an embodiment of a terminal operation in a manual search method according to an embodiment of the present invention.
FIG. 16 is a conceptual diagram illustrating an embodiment of short beacon transmission including TIM information. FIG.

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 "have" 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 manual search method according to an embodiment of the present invention to be described later may be applied to the IEEE 802.11 WLAN system described above, as well as a wireless personal area network (WPAN) and a wireless body area network (WBAN) as well as an IEEE 802.11 WLAN system. 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.

4 is a conceptual diagram illustrating an embodiment of beacon transmission in a WLAN system.

Referring to FIG. 4, in an infrastructure BSS of a traditional WLAN system (eg, IEEE 802.11a / b / g / n), an access point (AP) informs UEs of its existence and coverage. The beacon is transmitted in a broadcast manner at a target beacon transmit time (TBTT).

The terminal that is not associated with the access point (AP) checks the presence and connection compatibility of the access point (AP) based on the received beacon, and predicts the coverage of the access point (AP). A terminal connected to an access point (AP) uses a beacon for the purpose of maintaining a connection state with the access point (AP), mobility support, and receiving information for data transmission.

5 is a block diagram showing the configuration of a beacon.

Referring to FIG. 5, a beacon generally has a size of 100 bytes or more and has a size of about 230 bytes in an enterprise environment. The MAC header includes a frame control field, a duration field, an address (address 1, address 2, address 3) field, a sequence control field, and an HT control field.

The frame control field indicates the type and basic information of the frame, and the duration field indicates the occupancy time of the radio channel. The address field indicates a transmission / reception address, the sequence control field indicates a frame transmission order, and the HT control field supports a high throughput (HT) function.

The frame body field is mandatory and includes timestamp, capability, service set identifier (SSID), supported rates information, and multiple options as needed. May contain information. The option information may include a traffic indication map (TIM) element indicating that there is data to transmit to the terminal.

Here, the timestamp information has a size of 8 bytes, the performance information has a size of 2 bytes, the SSID information has a size of 2 to 34 bytes, and the supported rate information has a size of 3 to 11 bytes.

6 is a block diagram showing the configuration of a TIM element.

Referring to FIG. 6, the TIM element includes an element ID field having a size of one octet, a length field having a size of one octet, a DTIM count field having a size of one octet, A DTIM period field having a size of one octet, a bitmap control field having a size of one octet, and a partial virtual bitmap field having a size of 1 to 251 octets are included.

7 is a conceptual diagram illustrating an operation of a terminal in a manual search method.

Referring to FIG. 7, an AP transmits a DTIM beacon by a broadcasting method at a 400 ms period, and transmits a beacon by a broadcasting method at a 100 ms period within an interval of the DTIM beacon. The AP may transmit a beacon in which the DTIM count is set. For example, the access point AP may set the DTIM count of the first beacon transmitted after the DTIM beacon to 3, and then set the DTIM counter of the next transmitted beacon to 2. That is, each time the AP transmits the beacon, the AP may subtract one DTIM counter and transmit the DTIM counter, and the DTIM beacon has a DTIM count of zero.

A STA operating in a power save state wakes up just before transmission of the DTIM beacon and may receive a DTIM beacon transmitted from the AP. Upon receiving the DTIM beacon, the STA may check whether its AID bit is set in the bitmap control field and the partial virtual bitmap field included in the TIM element.

If its AID bit is set to 1, this indicates that data to be transmitted to the AP exists in the AP, so that the STA transmits the PS-Poll frame to the AP. It may inform that it is ready to receive. The AP receiving the PS-Poll frame transmits the buffered data to the terminal STA.

When the TBTT, which is a beacon period, is long or the DTIM period is long, a period for transmitting data to the terminal STA becomes long. In this case, the AP needs to allocate a large storage space for temporarily storing data to be transmitted to the terminal STA. In addition, in this case, since a data transmission delay occurs in the MAC layer, the transmission speed of the transmission control protocol (TCP) layer becomes slow.

An access point (AP) periodically transmits a beacon using the lowest modulation and coding scheme (MCS) level to ensure backward version compatibility with terminals in coverage and stable frame transmission. In a WLAN system according to IEEE 802.11b / g, an access point (AP) transmits a beacon every 100 ms using an MCS level of 1 Mbps. In a WLAN system according to IEEE 802.11a, an access point (AP) is an MCS level of 6 Mbps. Send beacons every 100ms using.

In a low power / low data rate WLAN system (eg, sensor network, etc.) based on such WLAN technology, an access point (AP) transmits a beacon every 100 ms using a minimum MCS level of 100 Kbps. In this case, since a transmission time of about 8 ms is required to transmit a beacon of about 100 bytes, in consideration of a general beacon period, there is a problem of inefficient use of a wireless channel with about 8% overhead.

8 is a flowchart illustrating a manual search method according to an embodiment of the present invention.

Referring to FIG. 8, the access point 10 may periodically transmit a long beacon in a broadcast manner at a predetermined time point (for example, TBTT) (S100). Long beacon means a beacon that is commonly used (ie, the beacon shown in FIG. 5). The terminal 20 may receive a long beacon transmitted from the access point 10 when waking at the time of transmitting the long beacon, but may operate the long beacon when operating in the sleep mode at the time of transmitting the long beacon. I do not receive it.

The access point 10 may transmit, in a broadcast manner, a short beacon having a size smaller than that of the long beacon within an interval of the long beacon. That is, the access point 10 may transmit N (N = integer) short beacons in a broadcast manner within a long beacon interval, and may inform the terminal 20 of the transmission period of short beacons through the long beacon. The long beacon period may be an integer multiple of the short beacon period. For example, when the short beacon period is 100 ms, the long beacon may have a 700 ms period.

The short beacon may be used to convey at least one of information necessary for the new terminal to search for an access point, information necessary for terminals in the BSS to maintain a connection, and information necessary for data transmission. That is, the presence of the access point can be notified through the short beacon, synchronization between the access point and the terminal can be established, and the presence or absence of data to be transmitted to the terminal in the power saving state can be known. Other information may be transmitted to the terminal through a probe response frame in an active scanning process, an association response frame in an association process, and an existing long beacon transmitted in a TBTT period.

The short beacon may include time information used for recognizing the transmission time of the long beacon transmitted from the access point 10 after the short beacon. The time information may include interval information of short beacons and information on the number of short beacons transmitted until a transmission point of the next long beacon. Here, the number of short beacons may include the currently transmitted short beacons. In addition, the time information may include remaining time information until the transmission time of the next long beacon.

9 is a block diagram showing the configuration of a short beacon.

Referring to FIG. 9, a short beacon includes a frame control field, a source address field, a timestamp field, a change sequence field, a short beacon information field, It may include a compressed SSID field, an access network options field, an optional information elements (IEs) field, and a CRC field.

Since the short beacon is a frame transmitted in a broadcast manner rather than transmitted to a specific terminal, the short beacon may have only a source address field as an address field. The timestamp field is used to synchronize the time between the access point and the terminals in the BBS, and the change sequence field is used to indicate whether the configuration information of the access point has changed. If the change sequence field indicates that there is a change in the setting information, the terminal may obtain and update the changed information from the long beacon. The access point may use a compressed SSID that represents the entire SSID. The access network options represent access network information connected to the access point.

The short beacon information field may include time information used to recognize a transmission time of a long beacon transmitted from the access point after the short beacon. That is, the short beacon information field may include interval information of short beacons and information on the number of short beacons transmitted until a transmission point of the next long beacon. The time information may also include remaining time information until the transmission time of the next long beacon.

The frame control field includes a protocol version field, a type field, a subtype field, a short beacon information present field, an SSID present field, and an interworking present. presnet), a BBS bandwidth field, a security field, and a reserved field.

The type field / subtype field may indicate that the corresponding beacon is a short beacon, the short beacon information present field may indicate the presence or absence of short beacon information, the SSID present field may indicate the presence or absence of a compressed SSID, and the inter The working present field may indicate the presence or absence of access network options.

FIG. 10 is a block diagram illustrating an embodiment of a configuration of a short beacon information field included in a short beacon.

Referring to FIG. 10, the short beacon information field may include a short beacon count field having a size of one octet and a short beacon interval field having a size of one octet. The short beacon count field may include information on the number of short beacons transmitted until the next long beacon transmission time, and the number of short beacons may include a short beacon currently transmitted. The short beacon count is initialized to a preset value in the first short beacon transmitted after the transmission of the long beacon, and decremented or increased by one each time the next short beacon is transmitted. Due to this feature, the short beacon count may serve as an ID for distinguishing short beacons from long beacons.

The Short Beacon Interval field contains interval information of the short beacon. When using 100TU (1TU = 1024us) as an embodiment of the short beacon interval, the short beacon period may be set within the range of 100ms ~ 25.5s.

The terminal receiving the short beacon may recognize the transmission time of the next long beacon based on the short beacon information field. That is, the terminal may obtain a transmission time of the next long beacon through Equation 1 below.

Figure pat00001

11 is a block diagram illustrating another embodiment of the configuration of a short beacon information field included in a short beacon.

Referring to FIG. 11, the short beacon information field includes a long beacon period field having a size of one octet, a short beacon count field having a size of one octet, and a short beacon interval having a size of one octet. (SB interval) field may be included. The long beacon period field includes the period information of the long beacon, and the period of the long beacon is an integer multiple of the short beacon period. The short beacon count field may include information on the number of short beacons transmitted until the next long beacon transmission time, and the number of short beacons may include a short beacon currently transmitted. The Short Beacon Interval field contains interval information of the short beacon.

The terminal receiving the short beacon may obtain a transmission time point of the next long beacon through Equation 1, and may obtain an interval of the long beacon through Equation 2 below.

Figure pat00002

Meanwhile, the short beacon may further include traffic allocation information for a predefined terminal or a predefined group, and the traffic allocation information may mean TIM information.

12 is a block diagram illustrating a hierarchical AID structure.

Referring to FIG. 12, an access point may group and manage AIDs of terminals in a hierarchical structure. One page may include a plurality of blocks, one block may include a plurality of sub-blocks, and one sub-block may include a plurality of terminals.

The access point may map TIM information to short beacons in units of pages, blocks, or sub-blocks. For example, the access point may map TIM information for block 1 to a short beacon in which the short beacon count is set to 3, so that the terminals belonging to block 1 may receive data based on the short beacon having the short beacon count 3. Can be received. In addition, the access point may map TIM information for block 2 to a short beacon in which the short beacon count is set to 2, and thus terminals belonging to block 2 receive data based on the short beacon having the short beacon count 2. can do.

Referring back to FIG. 8, when waking up immediately before the transmission of the short beacon, the terminal 20 may receive the short beacon transmitted from the access point 10. Upon receiving the short beacon, the terminal 20 may recognize the transmission time of the long beacon transmitted from the access point 10 after the short beacon using information included in the short beacon (S120). Since the short beacon includes short beacon count information and short beacon interval information, the terminal 20 may obtain a transmission time of the next long beacon based on Equation 1 above. The terminal 20 having obtained the transmission point of the next long beacon may operate in the sleep mode until the transmission point of the next long beacon.

In addition, since the short beacon may further include the long beacon period information, the terminal 20 may obtain a long beacon interval based on the equation (2). Accordingly, the terminal 20 may operate in a sleep mode within a long beacon interval.

The terminal 20 operating in the sleep mode may wake up just before the transmission point of the next long beacon, and may receive the long beacon transmitted from the access point 10 (S130). Upon receiving the long beacon, the terminal 20 may perform the following operation with the access point 10 based on the information included in the long beacon. For example, the terminal 20 to be connected to the access point 10 may perform a connection process with the access point 10 based on information included in the long beacon. On the other hand, when the setting information of the access point 10 is changed (when the change sequence field indicates the change of the setting information), the terminal 20 selects the setting information of the access point 10 based on the information included in the long beacon. Can be updated.

13 is a flowchart illustrating a data receiving method according to an embodiment of the present invention.

Referring to FIG. 13, the access point 10 may periodically transmit a long beacon in a broadcast manner at a predetermined time point (for example, TBTT) (S200). Here, the long beacon means a beacon (ie, beacon shown in FIG. 5) which is generally used. The terminal 20 may receive a long beacon transmitted from the access point 10 when waking at the transmission time of the long beacon, but may not receive the long beacon when operating in the sleep mode at the transmission time of the long beacon.

The access point 10 may transmit a short beacon having a size smaller than the long beacon in a broadcast manner within the interval of the long beacon (S210). That is, the access point 10 may transmit N (N = integer) short beacons in a broadcast manner within a long beacon interval, and may inform the terminal 20 of the transmission period of short beacons through the long beacon. The period of the long beacon may be an integer multiple of the short beacon period.

The short beacon may be used to convey at least one of information necessary for the new terminal to search for an access point, information necessary for terminals in the BSS to maintain a connection, and information necessary for data transmission. That is, the presence of the access point can be notified through the short beacon, synchronization between the access point and the terminal can be established, and the existence of data to be transmitted to the terminal in the power saving state can be announced. Other information may be transmitted to the terminal through a probe response frame in the active search process, a connection response frame in the connection process, and the existing long beacon transmitted in the TBTT period.

The short beacon may include time information used for recognizing the transmission time of the long beacon transmitted from the access point 10 after the short beacon. The time information may include interval information of short beacons and information on the number of short beacons transmitted until a transmission time point of the next long beacon. Here, the number of short beacons may include the currently transmitted short beacons. The time information may also include remaining time information until the transmission time of the next long beacon. The short beacon may be configured as shown in FIG. 9, and the short beacon information field included in the short beacon may be configured as shown in FIG. 10 or 11.

The short beacon may further include traffic allocation information for a predefined terminal or a predefined group, and the traffic allocation information may mean TIM information. The access point 10 may manage the AIDs of the terminal 20 by grouping them in a hierarchical structure (see FIG. 12). In this case, the access point 10 may include a TIM information for one page group and one page in a short beacon. TIM information for a block group, or TIM information for one sub-block may be added, and a short beacon added with TIM information may be transmitted.

When waking up immediately before the transmission of the short beacon, the terminal 20 may receive the short beacon transmitted from the access point 10. Upon receiving the short beacon, the terminal 20 may determine whether data to be transmitted to the user is stored in the access point 10 using traffic allocation information (for example, TIM information) included in the short beacon (S220). ).

When the data to be transmitted to the terminal 20 is buffered in the access point 10, the terminal 20 may receive the corresponding data from the access point 10. That is, the terminal 20 may transmit a PS-Poll frame indicating that it is ready to receive data to the access point 10 (S230), and then receive data transmitted from the access point 10. (S240).

14 is a conceptual diagram illustrating an embodiment of short beacon transmission.

Referring to FIG. 14, the AP may periodically transmit a long beacon FB, and may transmit a short beacon SB within an interval of the long beacon FB. For example, when the interval between the long beacons FB is 700 ms, the short beacons SB have an interval of 100 ms. That is, the access point AP may periodically transmit six short beacons SB within the interval of the long beacons FB.

The AP may transmit a short beacon SB at a short beacon interval after transmitting the long beacon FB, and count the first short beacon SB transmitted immediately after the long beacon FB. Can be set. The short beacon count 6 refers to the number of short beacons SB transmitted until the next long beacon transmission time, and includes the first short beacon SB currently transmitted.

The access point AP may decrease the short beacon SB count by one each time the short beacon SB is transmitted. When the short beacon count is 0, this means the long beacon FB.

15 is a conceptual diagram illustrating an embodiment of a terminal operation in a manual search method according to an embodiment of the present invention.

Referring to FIG. 15, the AP may periodically transmit a long beacon FB and may transmit a short beacon SB within an interval of the long beacon FB. When the terminal STA wakes up immediately before the third short beacon SB is transmitted, the terminal STA may receive the short beacon SB transmitted from the access point AP. Since the short beacon SB includes a short beacon interval and a short beacon count, the terminal STA may obtain short beacon interval information and short beacon count information from the received short beacon SB.

The terminal STA may recognize a transmission time of the next long beacon through 'short beacon count x short beacon interval'. For example, if the short beacon count is 4 and the short beacon interval is 100 ms, the next long beacon (FB) is 400 ms after the transmission of the corresponding short beacon (SB) (i.e., the short beacon with the short beacon count set to 4). Is sent. Accordingly, the terminal STA may operate in the sleep mode after acquiring the transmission time point of the next long beacon FB, and wake up immediately before the transmission of the next long beacon FB, and then the long beacon transmitted from the AP. FB) can be received.

FIG. 16 is a conceptual diagram illustrating an embodiment of short beacon transmission including TIM information. FIG.

Referring to FIG. 16, the AP may periodically transmit a long beacon FB, and may transmit a short beacon SB within an interval of the long beacon FB. The short beacon SB includes a short beacon interval and a short beacon count, and the access point AP may add TIM information for a particular group to the short beacon. In this case, the AP may map TIM information for a specific group according to the value of the short beacon count. For example, the access point AP may add the TIM information for the block ID 1 to the short beacon SB having the short beacon count 6 and to block the short beacon SB having the short beacon count 5 or 6. TIM information for ID 2 may be added, and TIM information for block ID 3 may be added to a short beacon SB having a short beacon count 3.

Upon receiving the short beacon SB, the STA may determine whether data to be transmitted to the terminal is stored in the AP based on the TIM information included in the short beacon SB. If there is data buffered in the access point (AP), the terminal STA may transmit a PS-Poll frame to the access point (AP) indicating that it is ready to receive data, and then the access point (AP) The data can be received from.

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: Access Point (AP)
20: terminal (STA)

Claims (19)

As a manual search method performed in a terminal,
Receiving a short beacon from an access point;
Recognizing a transmission time of a long beacon transmitted from the access point after the short beacon based on time information included in the short beacon; And
Receiving a long beacon from the access point at the transmission time point,
The short beacon is transmitted within an interval of the long beacon.
The method according to claim 1,
The time information includes:
Manual search method comprising the interval information of the short beacon and the number of the short beacon transmitted until the transmission time of the next long beacon.
The method according to claim 1,
The time information includes:
Manual search method comprising the remaining time information until the next transmission point of the long beacon.
The method according to claim 1,
And the period of the long beacon is an integer multiple of the short beacon period.
The method according to claim 1,
The short beacons,
Manual search method further comprises the traffic (traffic) allocation information for a predefined terminal or a predefined group (group).
The method according to claim 1,
And the terminal operates in a sleep mode until a transmission point of a next long beacon.
As a data receiving method performed in a terminal,
Receiving a short beacon from an access point;
Determining the presence of data buffered for the terminal based on traffic allocation information included in the short beacon; And
Receiving the data from the access point, if there is data for the terminal,
The short beacon is transmitted from the access point within an interval of a long beacon.
The method of claim 7,
The traffic allocation information is,
A data receiving method, characterized in that the presence of data buffered in the access point for a predefined terminal or a predefined group (group).
The method according to claim 8,
The traffic allocation information is,
And receiving data based on count information included in the short beacon.
The method of claim 7,
The period of the long beacon is an integer multiple of the short beacon period.
The method of claim 7,
The short beacons,
And time information used for recognizing a transmission time of a long beacon transmitted from the access point after the short beacon.
The method of claim 11,
The time information includes:
And interval information of the short beacons and information on the number of short beacons transmitted until a transmission point of the next long beacon.
The method of claim 11,
The time information includes:
And remaining time information until the next transmission point of the long beacon.
A beacon transmission method performed at an access point,
Transmitting a long beacon at a preset time point; And
Transmitting, within an interval of the long beacons, a short beacon having a size smaller than the long beacons,
And the short beacon includes time information used to recognize a transmission time of a long beacon transmitted after the short beacon from the access point.
The method according to claim 14,
The time information includes:
Beacon transmission method comprising the interval information of the short beacon and the number of the short beacon transmitted until the transmission time of the next long beacon.
The method according to claim 14,
The time information includes:
Beacon transmission method comprising the remaining time information until the next transmission point of the long beacon.
The method according to claim 14,
And the long beacon period is an integer multiple of the short beacon period.
The method according to claim 14,
The short beacons,
A beacon transmission method, characterized in that it further comprises traffic allocation information for a predefined terminal or a predefined group (group).
19. The method of claim 18,
The traffic allocation information is,
A beacon transmission method, characterized in that the set based on the count (count) information included in the short beacon.
KR1020130080737A 2012-07-11 2013-07-10 Method for passive scanning in wireless local area network system KR20140009040A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2985938A3 (en) * 2014-07-25 2016-05-11 Comcast Cable Communications, LLC Network admission control using a beacon
KR20170087406A (en) * 2016-01-20 2017-07-28 팔로 알토 리서치 센터 인코포레이티드 Methods for fast, secure and privacy-friendly internet connection discovery in wireless networks
US10194374B2 (en) 2016-03-02 2019-01-29 Electronics And Telecommunications Research Institute Network join method and network device using the network join method

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2985938A3 (en) * 2014-07-25 2016-05-11 Comcast Cable Communications, LLC Network admission control using a beacon
US9867117B2 (en) 2014-07-25 2018-01-09 Comcast Cable Communications, Llc Network admission control
US11659472B2 (en) 2014-07-25 2023-05-23 Comcast Cable Communications, Llc Network admission control
KR20170087406A (en) * 2016-01-20 2017-07-28 팔로 알토 리서치 센터 인코포레이티드 Methods for fast, secure and privacy-friendly internet connection discovery in wireless networks
US10194374B2 (en) 2016-03-02 2019-01-29 Electronics And Telecommunications Research Institute Network join method and network device using the network join method

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