KR100728294B1 - Apparatus and method of channel selection in wireless lan - Google Patents

Abstract

A method for selecting a channel of a WLAN(Wireless LAN) system and an apparatus thereof are provided to minimize a time in changing channels by not changing information on a connection between an access point and a terminal when channels of the WLAN system are changed. An apparatus for selecting a channel of a WLAN system comprises terminals(200) and access points(100). The terminals access the WLAN and exchange frames. The access points scan at least one channel, check the number of usages of access points exchanging the frames via each channel, and change a currently set channel to a new channel whose number of usages of the access points is smaller than that of the currently set channel. The access points include interfaces(110,120) and central controllers(140). The interfaces access a network. The central controllers check the number of usages of each channel according to the number of kinds of beacon frame SSID(Service Set ID) received via one and more scanned channels if a channel currently set with each terminal gets in an idle state, select a channel whose number of usages is the least, and exchange frames with each terminal.

Description

Channel selection method and apparatus therefor in wireless LAN system {apparatus and method of channel selection in Wireless LAN}

1 is a block diagram illustrating a wireless LAN system according to a preferred embodiment of the present invention.

2 is a block diagram illustrating a mobile access point in accordance with the present invention.

3 is a block diagram illustrating an access point according to a preferred embodiment of the present invention.

4 is a structural diagram for explaining a frame according to the present invention;

5 is a view for explaining a beacon frame according to a preferred embodiment of the present invention.

6 is a block diagram illustrating a terminal according to a preferred embodiment of the present invention.

7 is a flowchart illustrating a channel selection method of a wireless LAN system according to a preferred embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: access point 110, 120: interface unit

130: storage unit 140: central control unit

150: channel selector 200: terminal

210: wireless interface unit 220: user interface unit

230: central processing unit 240: channel changing unit

The present invention relates to a channel selection method and apparatus thereof for a wireless LAN system.

Subscribers of wireless LAN systems are increasing due to the development of wireless LAN technology and the convenience of wireless LAN.

Such a wireless LAN system is based on the IEEE 802.11 protocol, and can be connected to a mobile station through a wireless LAN, and an access point connected to the terminal through a wireless LAN to exchange frames between the network and the terminal. It includes.

The access point is a component that greatly affects the performance of the WLAN system. The access point has a choice of a terminal and a channel to be set through the WLAN. Such an access point may have a "best channel" option for statically selecting a channel established with the terminal or selecting a channel with less signal interference.

The frequency band of the WLAN system includes a 2.4 GHz band (IEEE802.11 G / B mode) and a 5 GHz band (IEEE802.11 A mode) band, and these frequency bands are divided into channels.

Korea and Europe allow 13 channels from 1 to 13 and only 11 countries like the USA. These bands are located in 2.4GHz or 5GHz band with 22 ~ 26MHz bandwidth per channel in WLAN system. Means that.

In the conventional WLAN system channel selection method, when the access point initially accesses the WLAN system, the entire channel is scanned to select a channel having the least interference, or the administrator directly sets a channel to be used for the access point.

When the channel selection method of the access point of the general wireless LAN system is described for a while, when the access point is initially driven, it is determined whether the channel set among the fixed channel or the best channel is according to the set configuration information.

If it is set as a fixed channel, the fixed channel value set as configuration information is read, and the corresponding channel is selected. If the best channel is set, the channel is scanned to select an optimal channel.

The access point continues to maintain the selected channel until the power is turned off or the administrator changes the setting.

However, due to the increase in the number of subscribers in the current wireless LAN system, in a region where a plurality of access points are provided in a certain area, and a service set overlaps with each other, a plurality of access points use a single channel, thereby causing interference between channels. May occur, but the access point cannot escape channel interference because it does not change the selected channel.

Accordingly, the present invention was devised to solve the above problems, and in order to minimize channel interference that can occur when a plurality of access points use a single channel in a wireless LAN system, the access point is disconnected from the terminal. An object of the present invention is to provide a channel selection method and apparatus for a wireless LAN system that can actively select / change a channel.

In accordance with an aspect of the present invention, a wireless LAN system includes: at least one mobile station for exchanging frames by connecting to a wireless LAN, and scanning at least one or more channels, and frames through each channel. At least one access point for grasping the usage count information of the access point to exchange a new channel having a usage count information less than the usage count information of the currently set channel to change the set channel with each terminal; .

Each access point according to the present invention transmits a still frame to each terminal when a channel state set with each terminal is in an idle state, and temporarily stores a frame to be transmitted to the terminal.

An access point according to the present invention generates a still frame by setting a '0110' bit value in a sub-type field of a management frame.

The access point according to the present invention grasps the usage count information according to the SSID (Service Set ID) type count information of the beacon frame received through each scanned channel.

An access point according to the present invention transmits a change frame including identification information or frequency band information of a channel to one terminal in one field of a frame body field of a beacon frame.

When the terminal according to the present invention receives a frame in which a sub-type field is set to a '0110' bit value from an access point, the terminal temporarily stores a frame generated by setting a stop mode and is included in a beacon frame. The frame is exchanged with the access point through the new channel according to the channel information.

According to another aspect of the present invention, an access point of a wireless LAN system includes at least one interface unit connected to a network, and a beacon frame received through at least one channel being scanned when a channel currently set with each terminal is in an idle state. A central control unit may be configured to determine usage count information of each channel according to SSID type count information, and to select a channel having less usage count information and exchange a frame with each terminal.

When the channel is in the idle state, the central control unit according to the present invention grasps the usage count information for each channel according to the SSID type information of the beacon frame received through each channel to be scanned, and has a channel less than the usage count information of the current channel. And a channel selector for transmitting the beacon frame including the information to each terminal.

The channel selector according to the present invention generates a change frame by including channel identification information or frequency band information in one field of a frame body field of the beacon frame.

The network according to the invention is at least one of LAN, WLAN or Wibro.

According to another aspect of the present invention, a terminal of a wireless LAN system includes a wireless interface unit connecting to an access point through a wireless LAN, and when a still frame is received through the wireless interface unit, temporarily storing the generated frame, and changing the frame. And a central processing unit for exchanging a frame with an access point through a channel corresponding to the new channel information included.

The central processing unit according to the present invention includes a channel changing unit for connecting with the access point through a new channel corresponding to the new channel information included in the change frame by using the access point and the initially set connection information.

The channel changer according to the present invention temporarily stores a frame and, when connected to an access point through a new channel, transmits a request to send (RTS) frame for transmitting the frame through the new channel.

According to another aspect of the present invention, there is provided a channel selection method of a wireless LAN system including at least one access point and a terminal, wherein each access point and each terminal exchange frames through an initially selected channel, and the channel is in an idle state. The access point scans at least one or more channels to determine the usage count information of the access points exchanging frames through each channel, and the new access point information is smaller than the usage count information of the initial channel. Transmitting channel information to each terminal, and exchanging frames through a new channel between the access point and each terminal.

The determining of the usage count information according to the present invention includes receiving a beacon frame through each channel to be scanned, and determining usage count information according to the SSID type number information included in the beacon frame.

In the channel selection method of the wireless LAN system according to the present invention, when the channel is in the idle state, the access point transmits a still frame in which the '0110' bit value is set in the sub-type field of the management frame to each terminal. And when each terminal receives a still frame, temporarily storing the generated frame.

In the transmitting of the new channel information according to the present invention, the access point generates a change frame including identification information or frequency band information of the new channel in one of the frame body fields of the beacon frame to each terminal. send.

In a channel selection method of a wireless LAN system according to the present invention, each terminal accesses an access point through a new channel using initial access information and received channel information, and if there is a temporarily stored frame, an RTS frame is generated. Transmitting to the access point through the new channel, thereby transmitting the frame to the access point.

According to another aspect of the present invention, a method for selecting a channel by an access point of a WLAN system including at least one terminal includes: scanning at least one channel when an initial channel established with each terminal is in an idle state; Determining the usage count information of each channel according to the SSID type count information of the beacon frame received through each of the scanned channels, selecting a new channel having less usage count information than the initial channel usage count information, and The access point connects each terminal to a new channel using the access information of the initial channel, and exchanges frames.

According to another aspect of the present invention, a method of selecting a channel by a terminal of a wireless LAN system includes temporarily storing a generated frame when a still frame is received through an access point and an initial channel set, and a new channel from the access point. When the information is received, connecting to the access point through the new channel using the access information of the initial channel, and transmitting a temporary stored frame by transmitting the RTS frame to the access point through the new channel.

Hereinafter, a method and a device for selecting a channel of a wireless LAN system according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating a wireless LAN system according to a preferred embodiment of the present invention.

Referring to FIG. 1, there are a plurality of access points (APs) 100-2 provided with overlapping service sets, and a mobile AP (mobile AP: MAP) 100-1.

The access point 100 is connected to a plurality of mobile stations included in its service area through a wireless LAN, transmits a frame received from the terminal to a wired network, and transmits a frame received from the wired network to a wireless LAN. Send to the terminal through.

The mobile access point 100-1 transmits a frame received from the terminal 200 connected to the wireless LAN to the network while supporting mobility, and transmits the frame received from the network to the terminal 200.

2 is a block diagram illustrating a mobile access point according to the present invention.

Referring to FIG. 2, the mobile access point 100-1 according to the present invention connects to a plurality of terminals 200 through a wireless LAN, transmits a frame received from the terminal 200 to a wireless network, and wireless network. The frame received through the wireless LAN to the terminal 200 is transmitted.

The wireless network to which the mobile access point 100-1 is connected may be a wireless network such as a wireless broadband Internet (Wibro) network or the like, or may be connected to another access point 100 through a wireless LAN.

In this case, when the mobile access point 100-1 connects to another access point 100, the mobile access point 100-1 connects to another access point 100 through a channel different from the channel set with the terminal 200.

3 is a block diagram illustrating an access point according to a preferred embodiment of the present invention.

Referring to FIG. 3, the access point 100-2 and the mobile access point 100-1 (hereinafter, collectively referred to as the access point 100) include a plurality of interface units 110 and 120, and a storage unit. 130 and a central control unit 140, the central control unit 140 includes a channel selector 150.

The first interface unit 110 is connected to at least one terminal 200 through a wireless LAN, and exchanges frames with the terminal 200.

The second interface unit 120 is connected to a wired network (for example, a LAN) or a wireless network to which the access point 100 is connected to exchange frames with the wired / wireless network. When the access point 100 is the mobile access point 100-1, the second interface unit 120 may be connected to a Wibro network or may be connected to another access point 100 through a wireless LAN.

The central controller 140 broadcasts a beacon frame including its service area ID (SSID) according to a beacon period and transmits it to each terminal 200 connected to the beacon frame.

In addition, the central control unit 140 converts the format of the frame received through the first interface unit 110 and transmits the converted format through the second interface unit 120 and the frame received through the second interface unit 120. The format is converted and transmitted to the terminal 200 through the first interface unit 110.

If the frame exchange with the connected terminal 200 does not occur for a predetermined time, the central controller 140 switches the channel state to the idle mode.

When the channel state is switched to the idle mode, the channel selector 150 transmits a still frame to each of the connected terminals 200 and sets the channel selection mode.

4 is a structural diagram illustrating a frame according to the present invention.

The frame structure shown in FIG. 4 is a management frame structure of the WLAN system, and detailed description of each field of the frame is omitted since it is defined in 'IEEE 802.11'.

The channel selector 150 generates a still frame by setting a value indicating that the frame exchange is to be paused in a predetermined field of the management frame.

For example, the channel selector 150 generates a still frame by setting a bit value, for example, '0110', which is not defined in a subtype field in a frame control field of a management frame. And multicasting to each connected terminal 200.

In addition, when there is only one terminal 200 connected to a destination address (DA) field of a still frame, the channel selector 150 sets address information of the corresponding terminal 200 and sets at least one terminal ( If 200) is connected, it is set to 01.80.C2.00.00.01, which is a multicast address, and multicasts to each terminal 200.

The channel selector 150 sets the channel selection mode after transmitting the still frame to the terminal 200. In this case, the channel selection mode refers to a mode in which the access point 100 temporarily stores the frames to be transmitted to the terminal 200 and temporarily stores them in the storage unit 130, scans each channel, and changes the channel to the channel with the least interference. do.

The channel selector 150 sets a channel selection mode at every point in time at which the channel state connected to each terminal 200 is switched to the idle mode, or prevents the channel selection mode from being set repeatedly. If the channel state is switched to the idle mode after the time expires, the channel selection mode is set.

Also, by implementing a function of scanning a channel and selecting a channel only in a specific access point 100 among a plurality of access points 100, resources / services that may be generated by scanning the channel in duplicate of each access point 100. Minimize wasting time.

That is, the channel selector 150 transmits a still frame to the terminal 200 and scans each channel.

In addition, the channel selector 150 determines the number information of the access point 100 using each channel to be scanned.

In this case, the channel selector 150 may grasp the SSID included in the beacon frame received through each channel to be scanned, and determine the number information of the access point 100 using the corresponding channel.

5 is a view for explaining a beacon frame according to a preferred embodiment of the present invention.

As shown in FIG. 5, the beacon frame depends on the type of management frame, and the frame body field includes the SSID field.

The channel selector 150 may determine the number of types of SSIDs of the beacon frames received through the scanned channels to determine the number information of the access points 100 using the respective channels.

The channel selector 150 receives the beacon frame through the corresponding channel as much as the beacon interval information of the beacon frame received through each channel, and grasps the information on the number of access points 100 for each channel. That is, the channel selector 150 receives the beacon frame as much as the beacon interval information through each selection, and grasps the number information of the access point 100 according to the number of types of SSIDs included in the beacon frame.

The channel selector 150 sequentially scans each channel, and stores the number information of the access point 100 for each channel in the storage 130 as shown in Table 1 below.

channel First channel 2nd channel 3rd channel … Count 0 2 2 …

As described in Table 1, the channel selector 150 may manage the number information of the access point 100 for each channel in a table form. Here, the number information of the access point 100 is the same as the type number information of the SSID included in the received beacon frame.

The channel selector 150 selects the channel with the smallest number of access points 100.

For example, if the current channel of the access point 100 is the second channel, two access points 100 are using the scanned third channel, and the access point 100 using the second channel is itself. Since there are three, and there is no access point 100 using the first channel, the first channel is selected.

The channel selector 150 generates a change frame including the band information of the selected channel and multicasts it to each connected terminal 200.

For example, the channel selector 150 selects one field among the optional fields in the frame body field of the beacon frame as shown in FIG. 5 to obtain identification information of the newly selected change channel or frequency band information of the channel. Includes and generates a change frame, and broadcast to each connected terminal (200).

That is, the channel selector 150 does not delete the access information connected to the terminal 200 in order not to go through an authentication process, an association process, and the like again through the connected terminal 200 and the new channel. When the channel selection mode is set, the stationary frame is transmitted to each terminal 200, and frames are exchanged with each terminal 200 through a new channel using existing access information.

Each terminal 200 exchanges a frame with the access point 100 through a new channel by changing the channel according to the identification information or the frequency band information of the channel received from the access point 100.

6 is a block diagram illustrating a terminal according to a preferred embodiment of the present invention.

Referring to FIG. 6, the terminal 200 according to the present invention includes a wireless interface unit 210, a central processing unit 230, and a user interface unit 220, and the central processing unit 230 includes a channel changing unit 240. ).

The wireless interface unit 210 connects to the access point 100 through a wireless LAN and exchanges frames.

The user interface 220 outputs display information or sound information according to the received frame and provides input information according to a user's selection.

The central processing unit 230 transmits a frame according to the input information provided from the user interface unit 220 to the access point 100 through the wireless interface unit 210, and transmits the information according to the received frame to the user interface unit 220. )

In addition, the central processing unit 230 establishes connection information by performing an authentication process and negotiation process with the access point 100 connected through the air interface unit 210, and exchanges frames through the air interface unit 210. .

When the stationary frame is received through the air interface unit 210, that is, whether the frame in which the floating field is set to '0110' is received or not, the channel changer 240 receives the stationary mode. Set it.

Here, the stop mode means a mode in which the terminal 200 temporarily stores a frame without transmitting a request to send (RTP) frame to the access point 100 when a frame to be transmitted to the access point 100 is generated.

The channel changing unit 240 changes the channel connected to the access point 100 according to the channel information (channel identification information or frequency band information) included in the beacon frame received while the stop mode is set, thereby changing the frame. Replace it.

The channel changer 240 transmits the temporarily stored frame after transmitting the request to send (RTS) frame for transmitting the temporarily stored frame to the access point 100 through the changed channel.

At this time, the channel changing unit 240 changes the channel according to the channel information included in the beacon frame without changing the setting information set through the authentication process and negotiation process with the existing access point 100, the access point 100 Replace the frame with.

7 is a flowchart illustrating a channel selection method of a wireless LAN system according to an exemplary embodiment of the present invention.

Referring to FIG. 7, an access point 100 of a wireless LAN system and at least one terminal 200 exchange frames through an initially selected channel (S 100).

If frame exchange with the connected terminal 200 does not occur for a predetermined time, the access point 100 switches the channel state to the idle mode and sets the channel selection mode (S 110).

In this case, the channel selector 150 sets the channel selection mode every time the channel state connected to each terminal 200 is switched to the idle mode, or to prevent the channel selection mode from being repeatedly set. If the channel state is switched to the idle mode after the set timer expires, the channel selection mode is set.

When the channel selection mode is set, the access point 100 multicasts a still frame as described in FIG. 4 to each of the connected terminals 200 (S 120).

According to an example, the access point 200 is connected to each terminal 200 connected to a still frame in which a bit value 0110 is not set in a subtype field in a frame control field of a management frame. Multicast with.

When a stationary frame is received, that is, when a frame having a floating field set to '0110' is received, and a frame to be transmitted to the access point 100 is generated, the terminal 200 transmits a request to send (RTP) frame to the access point ( In operation 100, a stop mode for temporarily storing a frame is set without transmitting the data to the processor 100.

If there is a frame to be transmitted to the terminal 200, the access point 100 temporarily stores and scans each channel (S 140).

The access point 100 receives a beacon message through each channel to be scanned, and grasps information on the number of access points 100 used for each channel (S 150).

The access point 100 determines the number information of the access point 100 according to the type number information of the SSID of the beacon frame received through the channel as much as the beacon interval information of the beacon frame received through each channel, Table 1 Manage as follows.

The access point 100 checks whether there is a channel having less information on the number of access points 100 than the number of access points 100 of the currently selected channel (S 160).

If there is no channel having less information on the number of access points 100 than the current channel, the access point 100 broadcasts a beacon frame including information of the current channel (channel identification information or frequency band information) to each terminal 200. Casting, exchange a frame with each terminal 200 through the current channel (S 170).

Meanwhile, if there is a channel having less information on the number of access points 100 than the current channel, the access point 100 broadcasts a beacon frame including the corresponding channel information to each terminal 200 (S 180).

In addition, the access point 100 and each terminal 200 exchange a frame through a newly selected channel (S 190).

The terminal 200 changes the channel according to the new channel information included in the beacon frame, and if there is a temporarily stored frame, transmits it to the access point 100 through the changed channel, and the frame from the access point 100 through the changed channel. Receive

The access point 100 and the terminal 200 do not change the setting information set through the authentication process and the negotiation process, and change only the channel information to the channel selected by the access point 100 to scan, thereby minimizing the time for changing the channel. do.

In the above detailed description of the present invention, the case in which the access point selects / changes a channel according to the state of a channel connected to each terminal is described. However, when the other mobile access point enters the service area of another access point, the channel is changed. The same applies to the selection / change.

As described above, according to the present invention, in the WLAN system, the access point may actively select / change a channel according to the information on the number of access points of the channel.

And, when changing the channel of the WLAN system, by not changing the connection information between the access point and the terminal, it is possible to minimize the time spent in changing the channel.

Claims (20)

In a wireless LAN system, At least one mobile station for exchanging frames by accessing a wireless LAN; A channel configured with each terminal as a new channel having at least one channel scanned, obtaining usage count information of an access point exchanging frames through the respective channels, and having a usage count information smaller than the usage count information of a currently set channel Wireless LAN system comprising at least one access point (access point) for changing the. The method of claim 1, wherein each of the access points, And transmitting a still frame to each terminal when the channel state set with the respective terminals becomes an idle state, and temporarily storing a frame to be transmitted to the terminal. The method of claim 2, wherein the access point, A WLAN system generating the still frame by setting a '0110' bit value in a sub-type field of a management frame. The method of claim 1, wherein the access point, The WLAN system to determine the usage count information according to the SSID (Service Set ID) type number information of the beacon frame received through each of the scanned channels. The method of claim 1, wherein the access point, A wireless LAN system for transmitting a change frame including the identification information or the frequency band information of the channel in one of the frame body field of the beacon frame to each terminal. The method of claim 1, wherein the terminal, When a frame having a sub-type field set to '0110' bit value is received from the access point, the frame generated by setting the stop mode is temporarily stored, and the new frame is stored according to the channel information included in the beacon frame. WLAN system for exchanging frames with the access point via a channel. In the access point of the wireless LAN system, At least one interface unit connected to a network; When the channel currently set with each terminal is in an idle state, the number of usage information of each channel is determined according to the SSID type number information of the beacon frame received through at least one channel being scanned, and the number of usage information is assumed to be less. An access point of a wireless LAN system including a central control unit for selecting a channel to exchange a frame with each terminal. The method of claim 7, wherein the central control unit, When the channel is in the idle state, the number of usage information for each channel is determined according to the SSID type information of the beacon frame received through each channel to be scanned, and the beacon frame includes less channel information than the number of usage information of the current channel. Access point of a wireless LAN system comprising a channel selection unit for transmitting to each terminal. The method of claim 8, wherein the channel selector, The access point of the wireless LAN system to generate the change frame by including the identification information or the frequency band information of the channel in one of the frame body (Frame Body) field of the beacon frame. The method of claim 8, wherein the network, An access point of a wireless LAN system, which is a network of at least one of LAN, WLAN, or Wibro. In a terminal of a wireless LAN system, A wireless interface unit for connecting to an access point via a wireless LAN; When a still frame is received through the wireless interface unit, a wireless LAN system including a central processing unit for temporarily storing the generated frame, and exchanges the frame with the access point through a channel corresponding to the new channel information including the change frame Terminal. The method of claim 11, wherein the central processing unit, And a channel changer for accessing the access point through a new channel corresponding to the new channel information included in the change frame by using the access point and the initially set access information. The method of claim 12, wherein the channel changing unit, And temporarily storing the frame and, when connected to the access point through the new channel, transmitting a Request To Send (RTS) frame for transmitting the frame through the new channel. In the channel selection method of a wireless LAN system comprising at least one access point and a terminal, Exchanging a frame through the initially selected channel between each access point and each terminal; When the channel is in the idle state, scanning the at least one channel by the access point to determine usage count information of the access points exchanging frames through the respective channels; Transmitting, by the access point, new channel information of usage count information less than the usage count information of the initial channel to each terminal; And exchanging a frame through the new channel between the access point and the respective terminals. The method of claim 14, wherein the determining of the usage count information comprises: Receiving a beacon frame through each of the scanned channels; And determining the usage count information according to the SSID type count information included in the beacon frame. The method of claim 14, When the channel is in an idle state, transmitting, by the access point, a stop frame in which a '0110' bit value is set in a sub-type field of a management frame to each terminal; And when the stationary frame is received by each terminal, temporarily storing the generated frame. The method of claim 14, wherein transmitting the new channel information comprises: The method of claim 1, wherein the access point generates a change frame including the identification information or the frequency band information of the new channel in one field of the frame body field of the beacon frame and transmits it to the respective terminals. The method of claim 14, Connecting each access point to the access point through a new channel using the initially set access information and the received channel information; If there is a temporarily stored frame, transmitting the RTS frame to the access point through the new channel, and transmitting the frame to the access point. In the method of the access point of the wireless LAN system including at least one terminal to select a channel, Scanning at least one channel when the initial channel established with each terminal is in an idle state; Determining usage count information of each channel according to SSID type count information of a beacon frame received through each of the scanned channels; Selecting a new channel of usage count information less than the usage count information of the initial channel; And accessing, by the access point, each terminal with the new channel using the access information of the initial channel, and exchanging a frame. In the method of the terminal of the wireless LAN system to select a channel, Temporarily storing the generated frame when a still frame is received through the access channel and the set initial channel; If new channel information is received from the access point, accessing the access point through the new channel using the access information of the initial channel; And transmitting the temporary stored frame by transmitting an RTS frame to the access point through the new channel.

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