KR101486512B1 - Method for selecting a access point and wireless lan terminal therefor - Google Patents

Abstract

A method for selecting an access point based on context information received from an access point in a WLAN terminal and a WLAN terminal for the method are disclosed. A WLAN terminal according to an aspect of the present invention includes: a status information collecting unit for collecting status information including a channel utilization rate from access points; And a connection controller for assigning a weight according to the channel utilization factor to the signal strength of the access points and selecting an access point to be connected based on the weighted signal strength.

Description

METHOD FOR SELECTING ACCESS POINT AND WIRELESS LAN TERMINAL THEREFOR [0002]

The present invention relates to a wireless LAN technology, and more particularly, to a method of selecting an access point providing a wireless LAN service and a wireless LAN terminal for the method.

An IEEE 802.11 wireless LAN network is configured such that an access point (AP) forms one physical cell area, and the wireless LAN terminals located in the cell search for and connect to the access point through a scanning process. The WLAN terminals may be located in various wireless environments within the cell and may be adapted to adaptively control the data transmission rate according to the wireless channel conditions.

FIG. 1 is a diagram illustrating a process of selecting an access point by a wireless LAN terminal in a conventional wireless LAN network. As shown in FIG. 1, the access point 1 130 and the access point 2 150) is present.

Referring to FIG. 1, the WLAN terminal 110 first transmits a probe request to search for a neighboring access point, and the probe request is transmitted to the access point 130 and the access point 150 do. The access point 1 130 and the access point 2 150 receiving the probe request transmit a probe response to the wireless LAN terminal 110 and the wireless LAN terminal 110 receiving the probe response transmits a probe response The access point having the largest strength is selected and a connection is attempted.

However, if the load of the access point selected by the WLAN terminal 110 to attempt connection is severe or the backhaul is obstructed, the normal service may not be received after the connection is completed. Even if access to such an access point is not possible, the WLAN terminal 110 continuously attempts to reconnect to the access point, which results in an increase in battery consumption and a deterioration in service quality.

Korean Patent Laid-Open No. 10-2012-0002087 (2012.01.05)

It is an object of the present invention to provide a method for selecting an access point based on context information received from an access point in a wireless LAN terminal and a wireless LAN terminal for the same.

Other objects and advantages of the present invention will become apparent from the following description, and it will be understood by those skilled in the art that the present invention is not limited thereto. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

According to an aspect of the present invention, there is provided a WLAN terminal including: a status information collecting unit for collecting status information including a channel utilization rate from access points; And a connection controller for assigning a weight according to the channel utilization factor to the signal strength of the access points and selecting an access point to be connected based on the weighted signal strength.

The access control unit may assign a positive weight to an access point having a channel utilization rate lower than a channel utilization rate threshold and a negative weight to an access point having a channel utilization rate higher than the channel utilization rate threshold.

The access control unit may not assign a weight to the access point whose channel utilization rate is the channel utilization rate threshold.

The access control unit may assign a weight to an access point whose signal strength is greater than a reference signal strength in proportion to a signal strength.

The situation information includes state information of the backhaul, and the connection control unit can exclude an access point not connected to the backhaul from the selection based on the state information of the backhaul.

If the signal strength of the access point being connected is smaller than the release reference signal strength and the DNS (Domain Name Service) query fails, the connection control unit can release connection to the access point in connection and select another access point to access .

When the DNS query is successful, the connection control unit may determine whether the connection to the connected access point is released by sequentially lowering the release reference signal strength.

The connection control unit may cancel the connection without determining whether the DNS query is successful if the signal strength of the access point being connected is smaller than the forced release signal strength.

According to another aspect of the present invention, there is provided a method for selecting an access point to be connected in a wireless local area network, comprising: collecting context information including a channel utilization rate from access points; Measuring a signal strength of the access points; Assigning a weight according to the channel utilization factor to the signal strength of the access points; And selecting an access point to be connected based on the weighted signal strength.

The weighting step may assign a positive weight to an access point having a channel utilization rate lower than a channel utilization threshold and a negative weight to an access point having a channel utilization rate higher than the channel utilization threshold.

The weighting step may not assign a weight to an access point whose channel utilization rate is the channel utilization rate threshold.

The weighting may be weighted in proportion to signal strength for an access point whose signal strength is greater than a reference signal strength.

The status information includes status information of the backhaul, and the step of selecting the access point may exclude an access point not connected to the backhaul based on status information of the backhaul from the selection.

The method may further include a step of releasing a connection to the access point when the signal strength of the access point being connected is less than the release reference signal strength and the DNS query fails.

If the DNS query is successful, the releasing step may determine whether the access to the access point is disconnected, while gradually lowering the release reference signal strength.

The releasing may cancel the connection without determining whether the DNS query is successful if the signal strength of the access point being connected is smaller than the forced release signal strength.

According to the present invention, the WLAN terminal can improve service quality by selecting and accessing an optimal access point based on context information.

In addition, according to the present invention, access points are selected according to the signal strength and the channel utilization rate of the access point, so that load between access points can be dispersed so that network resources can be efficiently used.

1 is a diagram illustrating a process of a wireless LAN terminal selecting an access point in a conventional wireless LAN network.
2 is a diagram illustrating a configuration of an access point and a WLAN terminal according to an embodiment of the present invention.
3 is a graph illustrating weights according to channel utilization according to an embodiment of the present invention.
4 is a graph showing an alpha value according to signal intensity according to an embodiment of the present invention.
FIG. 5 is a graph illustrating a signal intensity with a weight according to an exemplary embodiment of the present invention. Referring to FIG.
6 is a flowchart illustrating an access point selection method of a wireless local area network (WLAN) terminal according to an exemplary embodiment of the present invention.
7 is a flowchart illustrating a method of disconnecting an access point from a wireless LAN terminal according to an exemplary embodiment of the present invention.

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, in which: There will be. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating a configuration of an access point and a WLAN terminal according to an embodiment of the present invention.

2, the access point 210 includes a situation information generating unit 211, a situation information transmitting unit 213, and a wireless LAN modem 215. [

The situation information generation unit 211 generates the situation information including the state information of the backhaul to which the access point 210 is connected, the number of connected terminals, the maximum number of connectable terminals, the channel utilization rate, And generates the situation information including the information. The situation information generation unit 211 may be implemented in an application layer. The data included in the situation information is the same as the example of the following [Table 1].

division you Contents example Vendor Specific IE 1 byte dd length 1 byte 1c KT OUI 3 bytes 00 17 c3 Type 1 byte 11 AP Type 1 byte 0: Home AP
1: Zone AP
2: Wibro EGG 01 # of Assoc Devices 1 byte Associated Endpoints 00 # of Active Devices 1 byte Active terminal number 00 Max Assoc Devices 1 byte Maximum Connectable Associate Number of Terminals ff WAN Status 1 byte Wired backhaul status (0: disconnect, 1: connect) 01 WAN Down Throughput 4 bytes WAN interval performance (MB) 42 37 3c 00 WAN Up Throughput 4 bytes WAN interval performance (MB) 42 35 e0 00 Channel Utilization 1 byte Channel Utilization 05 WLAN Down Traffic 4 bytes Last 1 minute wireless DL traffic sum 00 00 00 00 WLAN UP Traffic 4 bytes Sum of wireless UL traffic for the last 1 minute 00 00 00 00 Number of co-channel APs 1 byte AP scan results, number of co-channel APs 00 Number of adjacent channel APs 1 byte Neighboring AP scan result, adjacent channel AP number 00

The situation information transmitting unit 213 transmits the situation information generated by the situation information generating unit 211 to the wireless LAN terminal 230 through the wireless LAN modem 215. [ The context information transmitting unit 213 may be implemented in a device driver layer and send status information to a probe response transmitted in response to a probe request received from the wireless LAN terminal 230. [

2, the wireless LAN terminal 230 includes a wireless LAN modem 231, a status information collecting unit 233, and a connection control unit 235. [

The wireless LAN modem 231 transmits and receives wireless signals according to the IEEE 802.11 standard.

The situation information collecting unit 233 collects context information from peripheral access points through the wireless LAN modem 231. [ Preferably, the situation information collecting unit 233 transmits a probe request through the wireless LAN modem 231 to collect peripheral access points, and in response to the probe response received from nearby access points, Lt; / RTI > The situation information collecting unit 233 is implemented in the device driver layer.

The connection control unit 235 measures the signal strength of the access point based on the probe response as an element of the application layer. Also, the connection control unit 235 selects one of a plurality of neighboring access points based on the status information of peripheral access points collected by the situation information collecting unit 233, and attempts connection. The connection control unit 235 selects one access point based on the backhaul status information and the channel utilization rate included in the context information and attempts connection. Specifically, it is as follows.

The access control unit 235 may select an access point that is not connected to the backhaul (e.g., when the backhaul state is disconnected due to a fault in the backhaul) or an access point whose channel utilization rate is equal to or greater than a predetermined maximum value .

The access control unit 235 selects the access point having the largest signal strength among the access points whose backhaul is normal and whose channel utilization rate is lower than the maximum value. At this time, the connection control unit 235 assigns a weight based on the channel utilization factor to the actual signal strength, not the actual signal strength of the access point, and determines the access point having the largest signal strength based on the weighted signal strength Select. The weighting of the signal strength is expressed by the following equation (1).

Where RSSI _weighted is the weighted signal strength, RSSI _orig is the original signal strength, CH.U is the current channel utilization and CH.U _max is the maximum usable channel utilization, 70%, CH.U _thresh is the channel utilization threshold, which is 35% in this embodiment, and? Is a constant.

의 그래프이다. 도 3을 참조하면, 채널 이용율이 35%이면 가중치는 0이 되고, 채널 이용율이 35% 미만이면 가중치는 양(+)의 값으로서 채널 이용율이 낮아질수록 가중치의 값은 증가한다. 반면, 채널 이용율이 35% 초과이면 가중치는 음(-)의 값으로서 채널 이용율이 증가할수록 음의 가중치의 값은 증가한다. FIG. 3 is a graph showing weights according to channel utilization according to an embodiment of the present invention. In Equation 1,

. Referring to FIG. 3, if the channel utilization rate is 35%, the weight value becomes 0. If the channel utilization rate is less than 35%, the weight value is positive, and as the channel utilization rate decreases, the weight value increases. On the other hand, if the channel utilization rate exceeds 35%, the weight value is a negative value, and the value of the negative weight increases as the channel utilization rate increases.

That is, for an access point with a channel utilization of less than 35%, the access control unit 235 assigns a larger amount of weight to the signal strength as the channel utilization is lower, and the channel utilization rate The higher the weight, the larger the negative weight is given to the signal strength. Therefore, even if the signal strength among the plurality of access points is relatively low, the access point having a low channel utilization rate can be selected. On the contrary, the access point having a high channel utilization rate can be excluded from the selection even if the signal strength is relatively good.

In the above-described Equation (1), α is a fixed value as a constant, but α can be subdivided according to signal strength as a variable. That is, according to the original signal strength of the access point,? Can be subdivided as shown in the following Equation (2).

According to Equation (2) above, α is fixed at 10 for an access point with an original signal strength of less than -60 dBm, whereas for an access point whose original signal strength is greater than -60 dBm, ie, signal strength is better than -60 dBm, It increases in proportion to the signal strength. For example, a given to an access point with an original signal strength of -50 dBm is 30, while a given to an access point with an original signal strength of -40 dBm is 50.

FIG. 4 is a graph showing an alpha value according to the signal intensity according to an embodiment of the present invention. Referring to FIG. 4, when the signal intensity is less than -60 dBm, the alpha value is fixed at 10, but the signal intensity is -60 dBm or more The value of [alpha] increases in proportion to the signal intensity. That is, when the signal strength is higher than -60 dBm, since the throughput is guaranteed to a certain level, the weight according to the channel utilization rate is reflected to be high, and when the signal strength is less than -60 dBm, the throughput is reduced so that the weight due to the channel utilization rate is reflected.

FIG. 5 is a graph illustrating a signal intensity in which weights are reflected according to an exemplary embodiment of the present invention, and is a signal intensity in which the weights according to Equations (1) and (2) are reflected. In other words, it is a signal intensity reflecting the weight according to the original signal intensity and the channel utilization ratio. Referring to FIG. 5, when the original signal strength is -60 dBm or more, the signal intensity, i.e., the weighted signal intensity may be lowered to -65 dBm according to the channel utilization, and is greatly affected by the channel utilization ratio.

The connection control unit 235 periodically checks the signal strength of the access point being connected and if the signal strength is lower than the release reference signal strength, the access control unit 235 forcibly releases the current connection and attempts to reconnect to another access point.

At this time, when the signal strength is less than the release reference signal strength, the connection control unit 235 attempts DNS (Domain Name Service) query without releasing the connection immediately, releases the connection when it fails, The mobile station repeats the process of lowering the release reference signal strength by a predetermined value without releasing the connection and then periodically comparing the signal strength of the access point with the release reference signal strength and attempting a DNS query test. Release the connection if the DNS query fails while being less than the release reference signal strength.

6 is a flowchart illustrating an access point selection method of a wireless local area network (WLAN) terminal according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the WLAN terminal 230 receives a WLAN On input signal from a user (S601) and scans surrounding access points accordingly (S603). The wireless LAN terminal 230 scans the neighboring access points in a manner of transmitting a probe request to the surrounding area and receiving a response thereto.

Upon receiving the probe response from the surrounding access point, the WLAN terminal 230 measures the signal strength of the neighboring access point based on the probe response, extracts the identification information (SSID, BSSID, etc.) of the access point from the probe response, Based on the identification information of the access point (S605).

If there is an access point that has recently been accessed, the wireless LAN terminal 230 selects the recently accessed access point and attempts connection (S607, S615).

On the other hand, if there is no access point that has been accessed recently or if connection is unsuccessful, the wireless LAN terminal 230 determines whether there is an access point that the user has set as a favorite among neighboring access points (S609). And can be confirmed using the identification information of the access point. If there is an access point set as a favorite, the wireless LAN terminal 230 selects a corresponding access point and attempts connection (S611, S615). At this time, when the wireless LAN terminal 230 has a plurality of access points set as favorites, it is possible to select an access point having a higher signal strength.

When there is no access point set as a favorite by the user among the neighboring access points or the connection is unsuccessful, the WLAN terminal 230 transmits the status information received from the neighbor access point, specifically, the backhaul status, the channel utilization rate, The access point is selected (S613). Where the context information may be included in the probe response received from the access point.

More specifically, the WLAN terminal 230 determines whether the access point (for example, when the backhaul is disconnected due to a fault in the backhaul) or when the channel utilization rate reaches a predetermined maximum value (for example, 70% ) Are excluded from the selection.

The wireless LAN terminal 230 selects an access point having the largest signal strength among the access points whose backhaul is normal and the channel utilization rate is lower than the maximum value. At this time, the WLAN terminal 230 assigns a weight based on the channel utilization factor to the actual signal strength, rather than the actual signal strength of the access point, and based on the weighted signal strength, . The weighting of the signal strength is expressed by the following equation (1). At this time, the access point without the context information uses the original signal strength without weighting. The wireless LAN terminal 230 can calculate a weight by subdividing? In the above-described Equation (1) as in Equation (2).

In this way, the WLAN terminal 230 accesses the selected access point based on the context information (S615).

In the embodiment of FIG. 6, access points are selected in the order of recent access point -> favorite access point -> access point reflecting situation information. However, this is only an example, It is possible to assign the highest priority to the remaining access points based on the context information, or all of the access points may be given the same priority to select the access point based on the context information.

7 is a flowchart illustrating a method of disconnecting an access point from a wireless LAN terminal according to an exemplary embodiment of the present invention.

As described with reference to FIG. 6, the WLAN terminal 230 connected to the access point by selecting the access point first sets the release reference signal strength as shown in FIG. 7 (S701). At this time, the release reference signal strength may be preset according to the user's selection regardless of the selection of the access point. In this embodiment, -70 dBm is taken as an example of the release reference signal strength.

The wireless LAN terminal 230 connected to the access point periodically checks the signal strength of the access point (S703). In step S705, the WLAN terminal 230 compares the checked current signal strength with the forced release signal strength to determine whether the current signal strength is smaller than the forced release signal strength. Here, the forced release signal strength is a value smaller than the release reference signal strength, for example, -90 dBm in the present embodiment.

If the current signal strength is smaller than the forced release signal strength, the WLAN terminal 230 immediately disconnects the access point and proceeds to the automatic connection process described with reference to FIG. 6 (S713).

On the other hand, if the current signal strength is greater than the forced release signal strength, the WLAN terminal 230 determines whether the current signal strength of the access point is less than the release reference signal strength (S707). If the current signal strength is not less than the release reference signal strength, the WLAN terminal 230 determines that the access to the access point is smooth, periodically checks the signal strength, and repeats the above procedure.

However, if the current signal strength is smaller than the release reference signal strength, the WLAN terminal 230 performs a DNS query through the corresponding access point to determine whether to finally release the connection to the access point, (S709). If the DNS query fails, the WLAN terminal 230 releases the connection to the access point and proceeds to the automatic access process described with reference to FIG. 6 to attempt connection to another access point (S713).

On the other hand, if the current signal strength is smaller than the release reference signal strength but the DNS query is successful, the signal strength of the access point is not good, but the connection is not released because it is determined that normal service is possible. 7, the wireless LAN terminal 230 lowers the release reference signal strength by a predetermined value (S711), periodically checks the signal strength of the access point, and repeats the above-described process. Accordingly, if the signal strength of the currently connected access point is lowered by the existing release reference signal intensity, the WLAN terminal 230 does not determine whether the access point is disconnected, And performs a DNS query process to determine whether or not the connection is released. That is, for an access point that succeeds in a DNS query even if the signal strength is poor, the connection is maintained until the signal strength reaches the forced release signal strength.

When the signal strength of the currently connected access point reaches the forced release signal strength, the WLAN terminal 230 forcibly releases the connection of the corresponding access point regardless of the success or failure of the DNS query, attempts to connect to another access point, For an access point not reaching the release signal strength, the connection is maintained while gradually lowering the release reference signal strength to the forced release signal strength when the DNS query is successful. However, if the DNS query fails while reaching the release reference signal strength, the WLAN terminal 230 immediately disconnects the currently connected access point without lowering the release reference signal strength and scans another access point to attempt connection.

The method of the present invention as described above may be embodied as a program and stored in a computer-readable recording medium (such as a CD-ROM, a RAM, a ROM, a floppy disk, a hard disk, or a magneto-optical disk).

While the specification contains many features, such features should not be construed as limiting the scope of the invention or the scope of the claims. In addition, the features described in the individual embodiments herein may be combined and implemented in a single embodiment. Conversely, various features described herein in a single embodiment may be implemented in various embodiments individually or in a suitable subcombination.

It is to be understood that, although the operations have been described in a particular order in the figures, it should be understood that such operations are performed in a particular order as shown, or that a series of sequential orders, or all described operations, . In some circumstances, multitasking and parallel processing may be advantageous. It should also be understood that the division of various system components in the above embodiments does not require such distinction in all embodiments. The above-described program components and systems can generally be implemented as a single software product or as a package in multiple software products.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. The present invention is not limited to the drawings.

210: access point 230: wireless LAN terminal
211: situation information generating unit 213: situation information transmitting unit
215, 231: Wireless LAN modem 233: Situation information collecting section
235:

Claims (16)

A wireless LAN terminal for selecting an access point to be connected,
A situation information collecting unit for collecting the situation information including the channel utilization rate from the access points; And
Assigning a weight according to the channel utilization rate to the signal strength of the access points, weighting the access point with a signal strength greater than the reference signal strength in proportion to the signal strength, and assigning a weight to the access point to be connected based on the weighted signal strength And a connection control unit to select the wireless LAN terminal. The method according to claim 1,
The connection control unit,
Wherein a positive weight is assigned to an access point having a channel utilization ratio lower than a channel utilization threshold and a negative weight is assigned to an access point having a channel utilization ratio higher than the channel utilization ratio threshold. 3. The method of claim 2,
The connection control unit,
And does not assign a weight to access points whose channel utilization ratios are the channel utilization ratios. delete 4. The method according to any one of claims 1 to 3,
The status information includes status information of the backhaul,
The connection control unit,
And the access point not connected to the backhaul is excluded from the selection based on the status information of the backhaul. 4. The method according to any one of claims 1 to 3,
The connection control unit,
When the signal strength of the access point being connected is lower than the release reference signal strength and the DNS query fails, the connection to the access point being connected is released and another access point is selected and connected. The method according to claim 6,
The connection control unit,
When the DNS query is successful, decides whether to drop the connection to the access point being connected, while gradually lowering the release reference signal strength. 8. The method of claim 7,
The connection control unit,
If the signal strength of the access point being connected is lower than the strength of the forced release signal, disconnecting the wireless LAN terminal without determining the success or failure of the DNS query. A method for selecting an access point to be connected in a wireless LAN terminal,
Collecting status information including the channel utilization rate from the access points;
Measuring a signal strength of the access points;
Assigning a weight according to the channel utilization rate to the signal strength of the access points, and weighting the access point with a signal strength in proportion to the signal strength; And
And selecting an access point to connect based on the weighted signal strength. 10. The method of claim 9,
Wherein the weighting step comprises:
Wherein a positive weight is assigned to an access point having a channel utilization ratio lower than a channel utilization threshold and a negative weight is assigned to an access point having a channel utilization ratio higher than the channel utilization ratio threshold. 11. The method of claim 10,
Wherein the weighting step comprises:
And does not assign a weight to an access point whose channel utilization rate is the channel utilization threshold. delete 12. The method according to any one of claims 9 to 11,
The status information includes status information of the backhaul,
Wherein the selecting of the access point comprises:
And the access point not connected to the backhaul is excluded from the selection based on the state information of the backhaul. 12. The method according to any one of claims 9 to 11,
And canceling a connection to the access point when the signal strength of the access point is less than the release reference signal strength and the DNS query fails. 15. The method of claim 14,
Wherein the step of releasing comprises:
And when the DNS query is successful, deciding whether or not the access point is disconnected from the access point while decreasing the release reference signal strength in order. 16. The method of claim 15,
Wherein the step of releasing comprises:
If the signal strength of the access point being connected is smaller than the strength of the forced release signal, disconnecting the access point without determining whether the DNS query is successful.

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