WO2011102651A2 - Spectrum sensing control method and apparatus for a station - Google Patents

Abstract

For a WLAN system including a first station for managing a wireless network and at least one station connected to the first station, a spectrum sensing control method according to one embodiment of the present invention comprises: transmitting a first frame to the at least one station, the first frame including a sensing threshold information element; receiving a second frame in response to the first frame, the second frame including a sensing capability information element from the at least one station; determining the length of a quiet period by using the received second frame; and transmitting a third frame to the at least one station, the third frame including information about the above determined length of the quiet period.

Description

Method and apparatus for controlling spectrum sensing of station

The present invention relates to a wireless communication system using a TV white space, and more particularly, to a method and apparatus for controlling spectrum sensing of a station in a wireless LAN system.

Currently, the television broadcasting service is moving from analog broadcasting to digital broadcasting. This is because digital broadcasting can provide high quality video and two-way services and use spectrum more efficiently.

This shift to digital broadcasting provides an idle frequency band that can be used by any one of the VHF (Very High Frequency, 54 MHz to 88 MHz) band and the UHF (Ultra High Frequency, 174 MHz to 698 MHz) band allocated for the conventional analog broadcasting. An example of such an idle frequency band is a TV white space (hereinafter referred to as TVWS).

In other words, the TV white space means an empty frequency band that is not used by broadcasters in the VHF and UHF frequency bands distributed for TV broadcasting, and is an unlicensed frequency band that anyone can use if the conditions for government radio regulations are met. . If a licensed device is not in use in this unlicensed frequency band, it is possible for an unlicensed device to use the band.

For example, on November 4, 2008, the Federal Communications Commission (FCC) approved the frequencies of the VHF and UHF bands used by DTV as unlicensed bands that anyone could use if they met regulatory requirements set by the FCC. In accordance with the US FCC's policy, other countries are developing corresponding policies and regulations on TV white space.

In addition, various wireless communication systems are being developed for using the TVWS, and the IEEE (Institute of Electrical and Electronics Engineers) 802.11 Working Group uses a wireless local area network (WLAN) system using TVWS as an 802.11af standard. The development is in progress.

The present invention provides a method and apparatus for stations operating under a wireless network environment to accurately detect the presence or absence of a primary user using quiet period information.

In addition, the present invention provides a method and apparatus for stations operating under overlapping wireless network environments to accurately detect the presence or absence of a primary user using quiet period information.

The present invention also provides a method and apparatus for sharing the TVWS channel with the primary user in consideration of the current network situation when the primary user is detected in the wireless network using the TVWS channel.

The present invention is a wireless LAN system comprising a first station for managing a wireless network and at least one station connected to the first station, transmitting a first frame including a sensing threshold information element to the at least one station. Wow; Receiving a second frame corresponding to the first frame, the second frame comprising a sensing capability information element from the at least one station; Determining a length of a quiet period using the received second frame; And transmitting a third frame including information on the determined length of the idle interval to the at least one station.

In addition, the present invention is a wireless LAN system comprising a first station for managing a wireless network and at least one station connected to the first station, transmitting a first frame including a sensing threshold information element to the at least one station A transceiver configured to receive a second frame including a sensing capability information element corresponding to the first frame; And a controller configured to determine a length of the idle section by using the received second frame, and to generate a third frame including information on the determined length of the idle section and provide the third frame to the transceiver. Provided is a spectrum sensing control device.

In addition, the present invention provides a method for controlling the spectrum sensing of a station existing in the overlapping network area in a WLAN system in which areas of a plurality of wireless networks overlap each other. Receiving a first frame comprising information about; Receiving a second frame including information on a timing synchronization function (TSF) timer from a neighboring AP station; And generating a third frame for synchronizing transmission stop times of stations belonging to the plurality of wireless networks using the first frame and the second frame, and transmitting the generated third frame to the neighboring AP stations. It provides a spectrum sensing control method comprising the step.

In addition, the present invention is a wireless LAN system in which the areas of a plurality of wireless networks overlap, in the spectrum sensing control apparatus of a station existing in the overlapping network area, a quiet element (quiet element) from the AP station connected to the station A receiving unit for receiving a first frame including information on the second frame including information on a timing synchronization function (TSF) timer from a neighboring AP station; A controller configured to generate a third frame for synchronizing transmission stop times of stations belonging to the plurality of wireless networks by using the first frame and the second frame; And a transmitter configured to transmit the generated third frame to the neighboring AP station.

The present invention enables stations operating under a wireless network environment to perform spectrum sensing while maintaining the same transmission downtime regardless of the type of primary user.

In addition, the present invention can provide more accurate spectrum sensing by synchronizing the transmission stop time for detecting the presence of the primary user by the stations operating in the overlapping wireless network environment.

In addition, the present invention deactivates some stations affected by the primary user in the wireless network using the TVWS channel, so that the remaining stations belonging to the network can continue to use the current channel.

On the other hand various other effects will be disclosed directly or implicitly in the detailed description of the embodiments of the present invention to be described later.

1 is a diagram illustrating a time relationship in which stations constituting a conventional wireless network perform spectrum sensing and data transmission;

2 is a diagram illustrating an example of a wireless LAN system to which the first embodiment of the present invention can be applied;

3 is a diagram illustrating a time relationship between stations performing spectrum sensing and data transmission using a quiet period according to a first embodiment of the present invention;

4 is a diagram illustrating a signaling procedure for stations existing in a wireless network to perform spectrum sensing using idle interval information according to a first embodiment of the present invention;

5 is a diagram illustrating a sensing threshold information element transmitted by a station managing an idle interval according to a first embodiment of the present invention;

FIG. 6 is a diagram illustrating a sensing capability information element transmitted by stations that do not manage an idle section according to a first embodiment of the present invention; FIG.

7 is a diagram illustrating an example of a wireless LAN system to which a second embodiment of the present invention can be applied;

FIG. 8 illustrates a signaling procedure for synchronizing transmission downtimes for performing spectrum sensing by stations operating in an overlapped wireless network environment according to the second embodiment of the present invention; FIG.

9 illustrates a Quiet element of a first message according to a second embodiment of the present invention;

FIG. 10 illustrates a Quiet reply element of a third message according to a second embodiment of the present disclosure; FIG.

FIG. 11 illustrates an operation for synchronizing a transmission stop time for performing spectrum sensing with stations existing in another network by stations existing in the overlapped wireless network area according to the second embodiment of the present disclosure; FIG.

12 and 13 illustrate an example of a wireless LAN system to which a third embodiment of the present invention can be applied;

14 is a diagram illustrating a signaling procedure for stations using a TVWS channel to share the TVWS channel with a primary user in consideration of a situation of a wireless network according to a third embodiment of the present disclosure;

15 illustrates a format of a deenablement frame defined in IEEE 802.11y;

FIG. 16 illustrates a Reason Result Code field of a deenablement frame defined in IEEE 802.11y; FIG.

FIG. 17 illustrates a Reason Result Code field of a deenablement frame according to a third embodiment of the present invention; FIG.

18 illustrates an information element representing a condition under which a deactivated station can request return to an activated state according to the third embodiment of the present invention;

19 is a block diagram illustrating a configuration of a non-licensed device in a wireless LAN system in which embodiments of the present invention can be implemented.

In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

In a wireless LAN system using a TV white space, an unlicensed device that wants to initiate a new network must access a geo-location database to obtain TVWS channel list information available in the region. .

Subsequently, when configuring a network between unlicensed devices using the available TVWS channel list information, the unlicensed devices use spectrum sensing to allow a licensed user to use the current TVWS channel. You should check whether there is. Here, the licensed user refers to a user who is authorized to use the TV white space band, and includes a primary user, a licensed device, or an incumbent user. It may also be referred to by name. Such primary users may include digital TV services, analog TV services, wireless microphones (WMs), and supplementary services licensed for various TV services.

As a result of the spectrum sensing, if a primary user exists in a TVWS channel being used (or intended to be used) by the unlicensed device, the unlicensed device moves the network from a current channel to a predetermined backup channel. shall.

However, as shown in FIG. 1, if the timing for spectrum sensing is not synchronized between the unlicensed devices constituting the network, another unlicensed device transmits data while any unlicensed device performs spectrum sensing. Can be. At this time, due to the data propagation of the other unauthorized device, the non-licensed device may not be able to accurately detect the presence or absence of a primary user.

In addition, when a plurality of wireless networks using the same TVWS channel are formed in close proximity to each other, a communication range of the plurality of wireless networks may overlap with each other. If an unauthorized device belonging to a specific wireless network is also present in the area of another wireless network, even if all devices belonging to the specific wireless network stop data transmission at the same time to detect the presence of a primary user. If the unlicensed device continues to communicate in the area of the other wireless network, the unlicensed device may not correctly perform spectrum sensing.

In order to solve the above problems, there is a need for a method for accurately detecting the existence of a primary user by unauthorized devices operating under a single wireless network environment or a superimposed wireless network environment.

Accordingly, the first embodiment of the present invention provides a method for stations operating under a single wireless network environment to accurately detect the presence or absence of a primary user using quiet period information.

In addition, the second embodiment of the present invention provides a method for accurately detecting the presence or absence of a primary user by stations operating in an overlapped wireless network environment using quiet period information.

In addition, the third embodiment of the present invention provides a method for sharing a TVWS channel with the primary user in consideration of the current network situation when the primary user is detected in the wireless network using the TVWS channel.

First embodiment

Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

2 briefly illustrates an example of a wireless LAN system to which the first embodiment of the present invention can be applied.

Referring to FIG. 2, the WLAN system 200 includes at least one basic service set (hereinafter, referred to as a 'BSS') and a distribution system (DS) using a TV white space band. .

The BSS includes at least one non-AP station STA2-associated with an access point STA1 for controlling a corresponding wireless network, and associated with the AP station STA1. STA3). Here, the BSS is a set of stations capable of performing communication while successfully synchronizing, and is not a concept indicating a specific area.

The AP station STA1 is a functional medium that provides access to a distributed system DS via a wireless medium for stations coupled to the corresponding BSS. In the wireless network (BSS), communication between non-AP stations is performed via the AP station. However, when a direct link is established, direct communication between non-AP stations may be performed. .

The AP station STA1 may be referred to as a centralized controller, a base station (BS), a Node-B, a base transceiver system (BTS), or a site controller in addition to a name of an access point. Meanwhile, the non-AP stations STA2 to STA3 may include a terminal, a wireless transmit / receive unit (WTRU), a user terminal (User Equipment, UE), a mobile station (MS), and a portable terminal ( It may be referred to as another name, such as a mobile terminal, or a mobile subscriber unit.

The distributed system (DS) is a mechanism for one AP station to communicate with another AP station, and does not necessarily need to be a network. If the distributed system (DS) can provide a predetermined distributed service defined in IEEE 802.11, there is no restriction on the form none. For example, the distributed system may be a wireless network such as a mesh network or a physical structure that connects AP stations with each other.

Meanwhile, in a wireless LAN system, the term station is any function including a medium access control (MAC) layer conforming to the IEEE 802.11 standard and a physical layer interface to a wireless medium. As a medium, broadly includes both an AP station and a non-AP station. Therefore, in the following description of the present invention, the non-licensed device operating in the wireless LAN system will be uniformly used under the name "Station (STA)" without distinguishing between the AP and the non-AP.

Referring back to FIG. 2, the BSS represents a wireless network area managed by the first station STA1. Here, it is assumed that the first station STA1 is an AP station and is a terminal that can access a geographical location database. It is assumed that the second station and the third station STA2 and STA3 connected to the first station STA1 are non-AP stations and are terminals that cannot access a geographical location database. In addition, it is assumed that all stations STA1, STA2, and STA3 belonging to the wireless network BSS are terminals capable of using a TV white space.

The first station STA1 may exchange data with an external network by accessing the distributed system DS. That is, when a new network BSS is to be initiated, the first station STA1 accesses a geographical location database and provides its location information, and then the TVWS channel available at the location to which it belongs from the geographical location database. List information and other additional information can be retrieved.

Thereafter, the first station STA1 broadcasts the available TVWS channel list information to neighboring stations by including the Supported Channels Information Element or other information element of the beacon message. Here, the beacon message is a signal that is periodically transmitted to the stations belonging to the network in order to transmit system information and status information of the wireless network to other stations in the network.

The second station and the third station STA2 and STA3 may receive the beacon message and analyze the obtained beacon message to obtain TVWS channel list information available at the current location.

In addition, if a network is to be configured between stations operating in the TVWS band, spectrum sensing is required, and the spectrum sensing confirms whether an authorized user (or a primary user) is currently using a channel. shall. At this time, the stations operating in the network should perform periodic spectrum sensing to check whether the primary user intends to use the current channel.

As a result of the spectrum sensing, if the primary user exists, the station STA1 managing spectrum sensing and channel switching should move the corresponding network from the current channel to a predetermined backup channel.

However, if the timing for spectrum sensing is not synchronized between stations constituting the network, another station may transmit data while one station performs spectrum sensing. At this time, due to data propagation of the other station, a problem may occur in that station cannot accurately detect the presence or absence of a primary user.

In order to solve this problem, the first embodiment of the present invention defines a quiet period so that all stations belonging to the network stop data transmission and perform spectrum sensing during the idle period.

For example, as shown in FIG. 3, the first station and the second station may perform more accurate spectrum sensing by stopping data transmission during a predetermined idle period.

Meanwhile, when stations belonging to a wireless network have different primary user sensing periods, if the length of the idle period is arbitrarily determined, the stations do not accurately detect the presence of the primary user. Failure can often occur.

Accordingly, in the first embodiment of the present invention, a spectrum sensing method for synchronizing stations belonging to a wireless network to have the same transmission stop time regardless of the type of primary user will be described.

4 illustrates a signaling procedure for stations belonging to a wireless network to perform spectrum sensing using idle interval information according to the first embodiment of the present invention. For convenience of description, the signaling procedure between the stations will be described by illustrating the apparatus of FIG. 2.

Referring to FIG. 4, it is assumed that the first station STA1 is an AP station and is a terminal that can access a geographical location database. In addition, it is assumed that the first station STA1 is a terminal that manages an idle section or spectrum sensing.

On the other hand, the second station (STA2) and the third station (STA3) is a non-AP station, it is assumed that the terminal can not access the geographic location database. In addition, it is assumed that the second station STA2 and the third station STA3 are terminals that do not manage idle intervals or spectrum sensing. That is, the second station STA2 and the third station STA3 may obtain information on the idle section through management and control of the first station STA1.

First, the first station STA1 managing the idle period transmits a first message (or first frame 410) including a sensing threshold information element to the neighboring stations STA2 and STA3. . The first message 410 may be a beacon message or beacon frame, a probe response message or prove response frame, an association response message or association response frame, or a reassociation response message. (reassociation response message or reassociation response frame), but is not limited thereto.

The sensing threshold information element included in the first message 410 indicates a threshold value used when stations which do not manage idle periods sense the presence of a primary user. This sensing threshold information element may be defined in the relevant Standard and / or Regulation.

For example, FIG. 5 illustrates a sensing threshold information element of a first message 410 transmitted by a first station STA1 managing a quiet period.

Referring to FIG. 5, the sensing threshold information element 500 includes an Element ID field 510, a Length field 520, an Incumbent Type field 530, and a Sensing Threshold field 540. Here, the Incumbent Type field 530 and the Sensing Threshold field 540 may be generated as many as the number of Incumbent Users and inserted into the first message 410.

The Element ID field 510 indicates an identifier (ID) of the corresponding information element, and the Length field 520 indicates the length of the corresponding information element.

The Incumbent Type field 530 indicates the type of primary user for which stations in a wireless network should perform spectrum sensing. For example, the primary user may include a digital TV service, an analog TV service, a wireless microphone (WM), and a supplementary service licensed for various TV services.

The Sensing Threshold field 540 indicates a threshold value used when stations existing in a wireless network sense the presence of a corresponding primary user.

Referring back to FIG. 4, the second station STA2 and the third station STA3 may obtain a sensing threshold according to the type of the primary user through the sensing threshold information element of the received first message 410. have.

The second station STA2 and the third station STA3 configure minimum sensing requirement information according to the type of the primary user by using the sensing threshold information element 500. The second station STA2 and the third station STA3 transmit a second message (or second frame 420) including the Minimum Sensing Requirement information to the first station STA1.

Typically, the second message 420 is transmitted when the second station STA2 and the third station STA3 associate with the first station STA1 and have their own sensing capability ( Information element indicating a sensing capability). Accordingly, the second message 420 may be an association request message or association request frame or a reassociation request message or reassociation request frame.

For example, FIG. 6 illustrates a sensing capability information element of the second message 420 transmitted by the stations STA2 and STA3 that do not manage the quiet period.

Referring to FIG. 6, the sensing capability information element 600 includes an Element ID field 610, a Length field 620, an Incumbent Type field 630, and a Minimum Sensing Requirement field 640. Herein, the Incumbent Type field 630 and the Minimum Sensing Requirement field 640 may be generated and inserted into the second message 420 as many as the number of Incumbent Users.

The Element ID field 610 indicates an identifier (ID) of the corresponding information element, and the Length field 620 indicates the length of the corresponding information element.

The Incumbent Type field 630 indicates the type of primary user that the station can perform spectrum sensing. In addition, the Minimum Sensing Requirement field 640 represents a minimum time required to detect a corresponding primary user in order to satisfy the sensing threshold of FIG. 5.

For example, if the type of the primary user is a TV service and the Minimum Sensing Requirement is 30 msec, the station may perform sensing for at least 30 msec to detect the TV signal to satisfy the sensing threshold of FIG. 5. In addition, when the type of the primary user is a wireless microphone (MW) and the minimum sensing requirement is 60 msec, the corresponding station needs to perform sensing for at least 60 msec to detect the wireless microphone signal to satisfy the sensing threshold of FIG. 5.

Referring back to FIG. 4, the first station STA1 may acquire sensing capabilities of the peripheral stations STA1 and STA2 through the sensing capability information element 600 of the received second message 420.

The first station STA1 managing the idle period may determine a length of a quiet period to be commonly applied to stations belonging to a wireless network based on the sensing capabilities of the peripheral stations STA2 and STA3. . In this case, the length of the quiet period may be determined in consideration of Minimum Sensing Requirement information obtained from the peripheral stations STA1 and STA2.

More specifically, the length of the idle interval is set to be equal to or greater than the largest Minimum Sensing Requirement among the Minimum Sensing Requirements required by the neighboring stations. By doing so, stations belonging to the wireless network can maintain the same transmission stop time regardless of the type of the primary user by using the length of the idle period.

Thereafter, the first station STA1 may configure a Quiet element including information on the length of the idle section and information on time synchronization between stations. Here, the Quiet element may be configured using a Quiet element of IEEE 802.11, or may be configured of other information elements.

The first station STA1 generates a third message (or a third frame 430) including the quiet element and transmits the third message to the neighboring stations STA2 and STA3. Then, the neighbor stations STA2 and STA3 can accurately detect the presence or absence of the primary user by using the idle section length information and the time synchronization information of the received third message 430. Through this process, all stations belonging to the wireless network perform spectrum sensing without transmitting data (or frames) during the same transmission interruption time.

Meanwhile, the third message 430 transmitted by the first station STA1 may be a beacon message or beacon frame or a probe response message or prove response frame, but is not limited thereto. Do not.

As described above, stations according to the first embodiment of the present invention can accurately detect the presence or absence of a primary user by sharing newly defined idle section information.

Second embodiment

Hereinafter, a second embodiment of the present invention will be described in detail with reference to the drawings.

7 briefly illustrates an example of a wireless LAN system to which a second embodiment of the present invention can be applied.

Referring to FIG. 7, the WLAN system 700 includes at least one basic service set BSS1 and BSS2 forming an overlapping wireless network. Here, the BSS1 represents a wireless network area managed by the first station STA-1, and the BSS2 represents a wireless network area managed by the second station STA-2. In addition, it is assumed that wireless devices existing in the BSS1 and BSS2 may use the TV white space band and use the same frequency channel.

The first station STA-1 and the second station STA-2 are AP stations that manage a corresponding network, and are terminals capable of accessing an external geographical location database through a distribution system. Assume

In addition, it is assumed that the station A (STA-A) is a non-AP station and exists in a wireless network area where the BSS1 and BSS2 overlap each other and is associated with the first station STA-1. On the other hand, a plurality of non-AP stations other than the A station (STA-A) may exist in the BSS1 and BSS2, it will be omitted for convenience of description.

Under this overlapping wireless network environment, the first station STA-1 transmits a request relating to a transmission stop time for spectrum sensing to all stations belonging to its network BSS1. That is, the first station STA-1 determines station period information for the spectrum sensing, generates a frame including the determined idle period information, and belongs to its own network BSS1. Send to. Through this process, all stations belonging to the BSS1 may share the idle section information, thereby promising a transmission stop time for detecting the presence or absence of a primary user.

However, in the case of the stations belonging to the second station STA-2 or the BSS2, the idle section information cannot be received, and the station connected to the second station STA-2 while belonging to the area of the BSS1. In this case, even if the request is received, the request is not sent from the connected BSS2, so the request is not accepted.

Accordingly, there is a possibility that the stations belonging to the second station STA-2 or the BSS2 continue to transmit data during the promised idle period. In addition, data transmission of these stations may interfere with spectrum sensing of the A station STA-A.

In order to solve this problem, in the second embodiment of the present invention, when the first station STA-1 requests the A station STA-A to stop transmitting in a nested wireless network environment, the A station ( The STA-A) provides the idle station information to the second station STA-2 of the BSS2 so that all stations belonging to the BSS1 and the BSS2 can synchronize the transmission stop time.

8 illustrates a signaling procedure for synchronizing transmission downtimes for performing spectrum sensing by stations operating in an overlapped wireless network environment according to the second embodiment of the present invention. For convenience of description, the signaling procedure between the stations will be described by illustrating the apparatuses of FIG. 7.

Referring to FIG. 8, it is assumed that the first station STA-1 and the second station STA-2 are AP stations, and are terminals that manage a quiet period.

In addition, the station A (STA-A) is a non-AP station, it is assumed that the terminal does not directly manage the idle period. That is, the A station STA-A may obtain information on the idle section through management and control of the first station STA1 and the second station STA-2. In addition, it is assumed that the station A (STA-A) exists in a wireless network area where the BSS1 and the BSS2 overlap each other and is in an associated state with the first station STA-1.

The first station STA-1 may transmit a request for a transmission stop time by transmitting a first message (or first frame) 810 including a Quiet element to all stations belonging to the BSS1. have. In this case, the first message 810 may be a beacon message or beacon frame or a probe response message or prove response frame.

The Quiet element included in the first message 810 may be configured using a Quiet element of IEEE 802.11, or may be configured of other information elements.

For example, as illustrated in FIG. 9, the Quiet element 900 defined in IEEE 802.11 may include an Element ID field 910, a Length field 920, a Quiet Count field 930, and a Quiet Period field 940. , Quiet Duration field 950 and Quiet Offset field 960.

The Element ID field 910 indicates an identifier (ID) of the corresponding information element, and the Length field 920 indicates the length of the corresponding information element.

The Quiet Count field 930 indicates the number of Target Beacon Transmission Times (TBTTs) until the beacon interval during the start of the next quiet interval.

The Quiet Period field 940 indicates the number of beacon intervals between the start and the start of regular quiet intervals defined by the idle element 900.

The Quiet Duration field 950 indicates a duration of the quiet interval, and the Quiet Offset field 960 shows a quiet interval from a TBTT defined in the Quiet Count field 930. Indicates the offset up to the beginning of.

Referring back to FIG. 8, when at least one STA-A of all stations belonging to BSS1 is capable of communicating with another AP station STA-2, the at least one station STA-A The idle period information received from the first station STA-1 may be processed and automatically transmitted to the other AP station STA-2.

In addition, the at least one station STA-A may transmit only when the first station STA-1 requests through the separate method to transmit the idle section information to another AP station STA-2. have. At this time, in order to request the station A-STA (STA-A) to transmit the idle section information, the first station STA-1 is configured such that stations belonging to the BSS1 are located in the network area BSS2 of the other AP station. Be aware that you belong. To this end, the first station STA-1 transmits and receives a measurement request frame and / or a measurement report frame defined in IEEE 802.11 with stations belonging to its network. It can be recognized.

Meanwhile, the idle element 900 received by the A station STA-A from the first station STA-1 is information dependent only on the first station STA-1. For example, the idle element 900 is defined by the TBTT as a reference unit, and this value is a value set and used by the first station STA-1 itself. The TBTT is also used in connection with a Timing Synchronization Function (TSF), which is shared and used only within BSS1.

Therefore, the station A (STA-A) needs to modify and supplement the idle section information so that it can be used by the second station STA-2. More specifically, the station A (STA-A) may use the idle section information of the first message 810 and the Timing Synchronization Function (TSF) timer information of the second message 820 to generate the idle response element (Quiet). You need to pass a reply element.

Here, the second message 820 may be a beacon message or beacon frame or probe response message or prove response frame received from the second station STA2. The second message includes a time stamp value or a TSF timer value operated by the second station STA2.

That is, as shown in FIG. 8, the station A-STA transmits a third message to the second station STA-2 by using the received first message 810 and the second message 820. Send 830. In this case, the third message 830 may include the Quiet reply element.

In addition, the third message 830 may be referred to as a management message or an action message or an action message transmitted by the A station STA-A, but is not limited thereto. Do not.

FIG. 10 illustrates a Quiet reply element of a third message transmitted by a station STA-A existing in an overlapped wireless network area.

Referring to FIG. 10, the dormant response element 1000 includes an Element ID field 1010, a Length field 1020, a Time Stamp Offset field 1030, a Next TBTT field 1040, a Beacon Interval field 1050, and a Quiet. It includes a Count field 1060, a Quiet Period field 1070, a Quiet Duration field 1080, and a Quiet Offset field 1090.

The Element ID field 1010 indicates an identifier (ID) of the corresponding information element, and the Length field 1020 indicates the length of the corresponding information element.

The time stamp offset field 1030 indicates a difference between a timing synchronization function (TSF) timer value of the first station STA-1 and the second station STA-2.

Here, the time stamp offset value may be calculated by comparing the difference between the TSF timer value of the second message 820 received from the second station STA-2 and the TSF timer value of the STA-A. . The TSF timer value that is operated by itself may be set using a time stamp value of a beacon frame or probe response frame previously received from the first station STA-1.

The Next TBTT field 1040 indicates a TSF timer value of an expected next TBTT of the first station STA-1, and the Beacon Interval field 1050 indicates a beacon interval value of BSS1.

In addition, the Quiet Count field 1060, the Quiet Period field 1070, the Quiet Duration field 1080, and the Quiet Offset field 1090, which are the remaining fields except for the fields, are received from the first station STA-1. Same as the information contained in element 900. Accordingly, the Quiet Count field 1060, the Quiet Period field 1070, the Quiet Duration field 1080, and the Quiet Offset field 1090 of the idle response element 1000 use the information of the idle element 900 as it is. If a delay occurs during processing, the delay can be used after compensating for the delay.

Referring back to FIG. 8, the second station STA-2 uses the Time Stamp Offset field 1030, Next TBTT field 1040, and Beacon Interval field 1050 of the idle response element 1000. The idle section information may be converted into its own TSF timer reference value. Accordingly, the second station STA-2 may convert the idle section information dependent on the first station STA-1 into its TSF timer reference.

As described above, through the signaling procedure between the first station STA-1, the A station STA-A, and the second station STA-2, all stations belonging to the BSS1 and the BSS2 are in the same transmission idle state. By sharing the interval, spectrum sensing can be performed at the same timing.

FIG. 11 illustrates an operation for synchronizing a transmission stop time for spectrum sensing with a station STA-A existing in an overlapped wireless network area in another network. For convenience of description, the operation of the station existing in the overlapped wireless network area will be described by illustrating the devices of FIGS. 7 and 8.

Referring to FIG. 11, in operation 1110, the station A (STA-A) existing in the overlapped wireless network area includes a first message 810 including a Quiet element from the first station STA-1. Wait for reception. Here, it is assumed that the station A (STA-A) is connected to the first station STA-1.

In step 1120, when the STA-A receives the first message 810, it moves to the next step, step 1130, otherwise, moves to step 1110 again to receive the first message 810. Keep waiting. Here, the first message 810 may be a beacon message or beacon frame or a probe response message or prove response frame.

When reception of the first message 810 is completed, in step 1130, the station A (STA-A) has a difference in TSF timer value between the first station (STA-1) and the second station (STA-2). Check whether you have information about. As a result of the check, if the station A (STA-A) has information on the difference in the TSF timer value, go to step 1160; otherwise, go to step 1140, the next step.

In step 1140, the station A-STA waits for the reception of the second message 820 including a time stamp value or a TSF timer value from the second station STA-2. Here, the second message 820 may be a beacon message or beacon frame or a probe response message or prove response frame.

Thereafter, in step 1150, when the second message 820 is received, the station A-STA (STA-A) moves to step 1160, which is the next step, or moves to step 1140 again to perform step 2140 of the second message 820. Wait for reception.

When receiving the second message 820 in step 1150 or having information on the difference in the TSF timer value in step 1130, the station A-STA performs the operation of step 1160, which is the next step. Perform.

That is, in step 1160, the station A-STA configures the idle response element by using the idle element of the first message 810 and the TSF timer value of the second message 820. The station A-STA transmits a third message 830 including the idle response element to the second station STA-2.

Then, the second station STA-2 converts its TSF timer reference value using the idle response element of the received third message 830 and performs spectrum sensing based on the converted TSF timer reference value. Can be done.

Through the above-described steps, the second embodiment of the present invention provides the advantage that all stations can perform the spectrum sensing at the same timing by sharing the same transmission downtime under the overlapped wireless network environment.

Third embodiment

Hereinafter, a third embodiment of the present invention will be described in detail with reference to the drawings.

12 and 13 briefly illustrate an example of a wireless LAN system to which the third embodiment of the present invention can be applied.

Referring to FIG. 12, the WLAN system 1200 includes at least one basic service set (BSS) and an incumbent user using a TV white space band. The circle 1210 at the top left of FIG. 12 represents a wireless network area managed by the first station STA1, and the circle 1220 at the bottom right represents an interference area generated by the primary user.

The BSS 1210 is connected to an AP (STA1) station STA1 and an AP station STA1 coordinating a corresponding wireless network, and at least one non-AP station operated. (STA2-STA5).

Here, the first station STA1 is a terminal capable of accessing a geographic location database, and the second to fifth stations STA2 to STA5 connected to the first station STA1 may access a geographic location database. Assume that there is no terminal. In addition, it is assumed that all stations STA1 to STA5 existing in the BSS 1210 are terminals capable of using a TV white space.

As shown in FIG. 12, the first station STA1, the second station STA2, the third station STA3, and the fifth station STA5 are subjected to interference of the primary user. In this case, the first station STA1, the second station STA2, the third station STA3, and the fifth station STA5 may detect the presence of the primary user through periodic spectrum sensing.

As a result, the second station STA2, the third station STA3, and the fifth station STA5 transmit a message (or frame) indicating that the primary user has been detected to the first station STA1. Then, the first station STA1 managing spectrum sensing recognizes that most of the stations STA2, STA3, and STA5 belonging to the BSS are affected by the primary user through the received message.

At this time, the first station STA1 must move the wireless network BSS to the available TV white space channel previously designated in the current channel.

However, as shown in FIG. 13, when the primary user affects only some stations STA3 among stations belonging to the BSS 1210, the channel currently used by the first station STA1 may be changed. Moving to a channel can be somewhat inefficient.

Accordingly, in the third embodiment of the present invention, when a primary user is detected in a channel used by (or intending to use) a station operating in a TV white space band, the primary user may be considered in consideration of the current network situation. This section describes how to share a TV white space channel.

FIG. 14 illustrates a signaling procedure for sharing a TV white space channel with a primary user by stations using a TV white space band according to a third embodiment of the present invention in consideration of a situation of a wireless network. For convenience of description, the signaling procedure between the stations will be described by illustrating the apparatuses of FIG. 13.

Referring to FIG. 14, when the third station STA3 detects the presence of the primary user through spectrum sensing, the third station STA3 includes information about the sensing result in order to inform the first station STA1 of this fact. Alternatively, the first frame 1410 is transmitted to the first station STA1.

In addition, the third station STA3 may periodically transmit a first message 1410 including information on the presence or absence of a primary user through periodic spectrum sensing to the first station STA1.

Here, the first message 1410 may be a channel state report message or a sensing report message including information on the spectrum sensing, but is not limited thereto.

Meanwhile, the first station STA1 may analyze the first messages received from the stations STA2 to STA5 belonging to the BSS 1210 to confirm the presence or absence of interference by the primary user.

As a result of the check, when the number of stations that are being interfered by the primary user is greater than or equal to a predetermined threshold, the first station STA1 is configured to use the network BSS as a predetermined available TV white space channel in the channel currently being used. Move).

However, when the number of stations that are being interfered by the primary user is less than a predetermined threshold, the first station STA1 does not attempt to switch channels and performs an operation for sharing the current channel with the primary user. Perform. In this case, to determine whether the channel is switched, the first station STA1 may consider not only the number of stations that are being interfered by the primary user, but also the type of the primary user and the type of the wireless network.

Meanwhile, in order to share a channel with the primary user, the first station STA1 may change a state from an enablement state to a deenablement state to stations that are being interfered with by the primary user. The requesting second message 1420 is transmitted.

That is, if the corresponding station is deactivated by transmitting the second message 1420, the first station STA1 may continue to use the currently used TVWS channel without interference with the primary user. In this case, a deenablement frame 1420 corresponding to the second message may be configured using a deenablement frame defined in IEEE 802.11y.

For example, FIG. 15 and FIG. 16 show a deenablement frame defined in the existing IEEE 802.11y.

Referring to FIG. 15, the deactivation frame 1500 includes a Category field 1510, an Action Value field 1520, a Requester STA Address field 1530, a Responder STA Address field 1540, and a Reason Result Code field 1550. Include.

The Category field 1510 indicates a category of the corresponding frame, and the Action Value field 1520 indicates that the corresponding frame is an inactive frame.

The Requester STA Address field 1530 indicates a medium access control (MAC) address of a station requesting deactivation processing, and the Responder STA Address field 1540 indicates a MAC address of a station to be deactivated.

The Reason Result Code field 1550 indicates a reason why the deactivation frame 1500 is generated. For example, as shown in FIG. 16, the Reason Result Code field 1550 describes a reason for generating an inactive frame according to the Reason Result Code field value.

Referring back to FIG. 14, the deactivation frame 1420 transmitted by the first station STA1 to the third station STA3 may use the deactivation frame 1500 defined in IEEE 802.11y. Therefore, the Category field and the Action Value field of the deactivation frame 1420 use values defined in IEEE 802.11y.

In addition, the MAC address of the first station STA1 requesting the deactivation process is set in the Requester STA Address field of the deactivation frame 1420, and the third station to be deactivated in the Responder STA Address field of the deactivation frame 1420. The MAC address of STA3) is set.

On the other hand, the Reason Result Code field of the deactivation frame 1420 is used by modifying the Reason Result Code field 1550 defined in IEEE 802.11y.

For example, as shown in FIG. 17, the Reason Result Code field 1700 of the deactivation frame 1420 has a new item "Reason Result Code field value 4-> Deactivation request due to primary user. user) ". Accordingly, the first station STA1 transmits the reason result code field value of the deactivation frame 1420 to 4 to deactivate the third station.

When the deactivation frame 1420 is received, the third station STA3 transmits a third message 1430 in response to the deactivation frame 1420, and then switches to the deactivation state. Accordingly, the remaining stations except for the third station STA3 can continue to use the TVWS channel currently being used with the primary user.

Meanwhile, the third station STA3 may perform periodic spectrum sensing even when the third station STA3 is switched to an inactive state by the request of the first station STA1. Therefore, if the third station STA3 later leaves the interference area of the primary user, this fact can be immediately recognized. And, recognizing this fact, the third station STA3 may request the first station STA1 to return to the activated state.

Before requesting to return to the activated state, the third station STA3 sends a fourth message 1440 to inform the condition for requesting the deactivated station to return to the activated state again. Receive from station STA1.

Here, the fourth message 1440 includes an information element representing a condition for requesting the deactivated station to return to the activated state. In addition, the fourth message 1440 is a beacon message (beacon message or beacon frame), a probe response message (prove response message or prove response frame), the association response message (association response message or) by the first station (STA1) It may be transmitted in the form of an association response frame or a reassociation response message or reassociation response frame.

For example, FIG. 18 illustrates an Enablement Information Element indicating a condition under which the deactivated third station STA3 may request to return to the activated state again.

Referring to FIG. 18, the information element 1800 includes an Element ID field 1810, a Length field 1820, an Incumbent Type field 1830, and a Minimum Sensing Requirement field 1840. Here, the Incumbent Type field 1830 and the Minimum Sensing Requirement field 1840 may be generated and inserted into the fourth message 1440 by the number of primary users.

The Element ID field 1810 indicates an identifier (ID) of the corresponding information element, and the Length field 1820 indicates the length of the corresponding information element.

The Incumbent Type field 1830 indicates the type of primary user to be sensed in order for the deactivated station to return to the activated state. In addition, the Minimum Sensing Requirement field 1840 indicates a minimum time during which the primary user of the type should not be detected.

For example, when the type of the primary user is a TV service and the Minimum Sensing Requirement is 30 msec, the deactivated station STA3 should not detect the TV signal for at least 30 msec to be activated to the first station STA1. May request a return of In addition, when the type of the primary user is a wireless microphone (MW) and the minimum sensing requirement is 60 msec, the deactivated station STA3 should not detect the wireless microphone signal for at least 60 msec to activate the first station STA1. You can request a return to the state.

Referring back to FIG. 14, the third station STA3 may acquire a condition for requesting a switch from the deactivated state to the activated state using the fourth message 1440.

Thereafter, the third station STA3 periodically performs spectrum sensing, and if the result of the execution of the result satisfies the condition, a fifth message 1450 for requesting the first station STA1 to return to activation. ) Can be sent.

When the first station STA1 receives the fifth message 1450, the first station STA1 may switch the third station STA3 from an inactive state to an active state.

As described above, the third embodiment of the present invention deactivates some stations affected by the primary user when the primary user is detected in the wireless network using the TV white space band. Allow belonging stations to share the current channel with the primary user.

19 is a block diagram illustrating a structure of a non-licensed device in a wireless LAN system in which embodiments of the present invention can be implemented.

Referring to FIG. 19, a first station STA1 and 1900 includes a transceiver 1910, a controller 1920, and a memory 1930. The second stations STA2 and 1950 also include a transceiver 1960 and a controller. 1970 and memory 1980. Here, it is assumed that the first station STA1, 1900 is an AP station and is a terminal that can access a geographical location database. On the other hand, the second station (STA2, 1950) is a non-AP station, it is assumed that the terminal can not access the geographic location database.

The transceivers 1910 and 1960 transmit and receive wireless signals, and implement an IEEE 802 physical layer. That is, the transmitters 1910 and 1960 perform forward error correction (FEC) encoding and modulation on data received from the MAC layer, and add a signal such as a preamble and a pilot. And transmits the signal toward the transmitting antenna. At the same time, the receivers 1910 and 1960 perform demodulation, equalization, and FEC decoding on the signals received through the receiving antennas, and perform processing such as removing the added signals from the transmitters and delivering them to the MAC layer. Perform. To this end, the transceivers 1910 and 1960 may include a modulator, a demodulator, an equalizer, an FEC encoder, a FEC decoder, and the like.

The controllers 1920 and 1970 are connected to the transceivers 1910 and 1960 to implement the IEEE 802 MAC layer. That is, the controllers 1920 and 1970 transfer the data transmitted from the upper layer to the transceivers 1910 and 1960 to control the process necessary for transmission, and process the data transferred from the physical layer to the upper layer. It plays a role. In addition, the controllers 1920 and 1970 are in charge of overall control for performing the aforementioned spectrum sensing method of the station.

The transceivers 1910 and 1960 and / or the controllers 1920 and 1970 may include an application specific integrated circuit (ASIC) circuit, another chip set, a logic circuit, and / or a signal processing device.

The memory 1930 and 1980 may include a read-only memory (ROM), a random access memory (RAM), a flash memory, a memory card, a storage medium, and / or another storage device. When the above-described spectrum sensing method of a station is implemented in software, an embodiment of the present invention may be implemented as a module that performs the method or function. The module may be stored in the memories 1930 and 1980 and executed by the controllers 1920 and 1970.

Also, the memories 1930 and 1980 may be located inside or outside the controllers 1920 and 1970 and may be connected to the controllers 1920 and 1970 by various well-known means.

On the other hand, while the specific embodiments of the present invention have been described, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims below, but also by those equivalent to the claims.

That is, the detailed description of the above-described invention shows an implementation example applied to a wireless LAN system using a TV white space. However, the present invention can be applied to other wireless communication systems using similar technical backgrounds and TV white spaces without departing from the scope of the present invention, which can be determined by those skilled in the art. It will be possible.

Claims (20)

1. In the wireless LAN system comprising a first station for managing a wireless network and at least one station connected to the first station, in the spectrum sensing control method of the first station,

   Transmitting a first frame comprising a sensing threshold information element to the at least one station;

   Receiving a second frame corresponding to the first frame, the second frame comprising a sensing capability information element from the at least one station;

   Determining a length of a quiet period using the received second frame; And

   And transmitting a third frame including information on the determined length of the idle period to the at least one station.
2. The method of claim 1,

   And stations belonging to the wireless network operate in a TV white space band.
3. The method of claim 1,

   The sensing threshold information element includes information on the sensing threshold according to the type of the primary user.
4. The method of claim 1,

   The sensing capability information element includes information on the type of primary user that the at least one station can perform spectrum sensing.
5. The method of claim 4, wherein

   The sensing capability information element further includes information on minimum sensing requirements required for the at least one station to detect a corresponding primary user in order to satisfy the sensing threshold. Way.
6. The method of claim 5,

   The length of the idle period is determined based on the information on the minimum time received from the at least one station.
7. In the wireless LAN system comprising a first station for managing a wireless network and at least one station connected to the first station, the spectrum sensing control apparatus of the first station,

   A transceiver for transmitting a first frame including a sensing threshold information element to the at least one station and receiving a second frame including a sensing capability information element corresponding to the first frame; And

   And a controller configured to determine a length of the idle period by using the received second frame, and to generate a third frame including information on the determined length of the idle period and provide the third frame to the transceiver.
8. The method of claim 7, wherein

   And stations belonging to the wireless network operate in a TV white space band.
9. The method of claim 7, wherein

   The sensing threshold information element includes information on the sensing threshold according to the type of the primary user.
10. The method of claim 7, wherein

    The sensing capability information element includes information on the type of primary user that the at least one station can perform spectrum sensing.
11. The method of claim 10,

    The sensing capability information element further includes information on minimum sensing requirements required for the at least one station to detect a corresponding primary user in order to satisfy the sensing threshold. Device.
12. The method of claim 11,

    And a length of the idle period is determined based on the information on the minimum time received from the at least one station.
13. In a WLAN system in which areas of a plurality of wireless networks partially overlap, a method of controlling spectrum sensing of a station existing in the overlapping network area,

    Receiving a first frame containing information about a quiet element from an AP station connected with the station;

    Receiving a second frame including information on a timing synchronization function (TSF) timer from a neighboring AP station; And

    Generating a third frame for synchronizing transmission stop times of stations belonging to the plurality of wireless networks using the first frame and the second frame, and transmitting the generated third frame to the neighboring AP stations Spectrum sensing control method comprising a.
14. The method of claim 13,

    The information on the idle element is a spectrum sensing control method characterized in that it comprises a period information (quiet period) and synchronization information for performing the spectrum sensing.
15. The method of claim 13,

    The third frame includes information on a quiet reply element,

    And the information on the idle response element includes information on a difference between a TSF timer value of the station and a TSF timer value of the neighboring AP station.
16. The method of claim 15,

    And a TSF timer value of the station is set through a time stamp value of a beacon frame or probe response frame previously received from the AP station.
17. In a WLAN system in which areas of a plurality of wireless networks overlap, the spectrum sensing control apparatus of a station existing in the overlapping network area,

    Receiving unit for receiving a first frame including information on the quiet element (quiet element) from the AP station connected to the station, and receiving a second frame containing information about the Timing Synchronization Function (TSF) timer from the neighboring AP station ;

    A controller configured to generate a third frame for synchronizing transmission stop times of stations belonging to the plurality of wireless networks by using the first frame and the second frame; And

    And a transmitter configured to transmit the generated third frame to the peripheral AP station.
18. The method of claim 17,

    The information on the idle element is a spectrum sensing control device, characterized in that the station for performing the period (quiet period information and synchronization information) for performing the spectrum sensing.
19. The method of claim 17,

    The third frame includes information on a quiet reply element,

    And the information on the idle response element includes information on the difference between the TSF timer value of the station and the TSF timer value of the neighboring AP station.
20. The method of claim 19,

    And a TSF timer value of the station is set through a time stamp value of a beacon frame or probe response frame previously received from the AP station.

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