KR20110008462A - Method for connecting wireless lan using preferred access point - Google Patents

Abstract

PURPOSE: A wireless LAN connecting method using a preferred AP(Access Point) is provided to prevent a ping pong effect by registering a specific AP as a preference AP in wireless LAN system handover. CONSTITUTION: A communication terminal establishes an MAC(Media Access Control) address of a preference AP(S1). The communications terminal radiates the probe request signal to the neighbor APs(S2). If there exists the preference AP among neighboring APs, the communications terminal interlinks the wireless LAN with the selection of the corresponding preference AP(S5,S6). If there is no preference AP, the communications terminal interlinks the wireless LAN to an AP which generates the highest RSSI(Received Signal Strength Indication)(S7).

Description

Wireless LAN access method using preferred AP {METHOD FOR CONNECTING WIRELESS LAN USING PREFERRED ACCESS POINT}

The present invention relates to a wireless LAN system, and more particularly, to a WLAN access method using a preferred AP in which a communication terminal registers a specific AP as a preferred AP and hands over in an environment in which a plurality of APs exist in the WLAN system. It is about.

Currently, IEEE 802.11-based wireless LAN systems use unlicensed frequency bands (2.4 GHz and 5 GHz) to enable effective services at low cost. In addition, it uses a well-designed physical layer and Medium Access Control (MAC) to provide high data rates up to 54Mbps (IEEE 802.11a / g).

The WLAN system includes a plurality of basic service sets (BSSs), and each service set (BSS) includes an access point (AP) connected to a wired network and a plurality of communication terminals.

If the communication terminal is wired through the AP, and the service areas of different BSSs overlap each other, the APs of the BSS use different channels so that even if the communication terminals move, handover between the APs is seamless. You can get services.

At this time, the communication terminal performs a handover when the received signal strength of the currently connected AP (current AP) is less than the set threshold. At this time, in the overlapping region between APs, a ping pong phenomenon may occur in which frequent handovers occur between APs due to a change in signal strength, thereby increasing power consumption of a communication terminal or voice interruption due to delay.

In the case of using a wireless LAN, since accessibility is low, the accessing AP is often limited to a specific AP. In this case, in order to reduce power consumption and voice interruption caused by the ping pong phenomenon in the overlapping area between APs, a technique of accessing a specific AP for a longer time is required. To this end, the communication terminal should register a specific AP as a preferred AP, preferentially access the preferred AP, and maintain the connection to the preferred AP as long as possible.

The present invention provides a method of registering a specific AP desired by a communication terminal as a preferred AP in a WLAN system and a method of accessing a WLAN using a preferred AP to preferentially access the preferred AP during initial access or handover.

The present invention is to provide a wireless LAN access method using a preferred AP that can maintain a long connection to the preferred AP when moving from the preferred AP to another AP.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

Wireless LAN access method using a preferred AP of the present invention for achieving the above object, the communication terminal receives the identification information on a specific AP (Access Point) to set as a preferred AP; A second step of receiving, by the communication terminal, a response signal from neighboring APs when accessing a wireless LAN to obtain identification information, and confirming whether a preferred AP exists from the acquired identification information; And a third step of connecting the WLAN with the preferred AP when the preferred AP exists.

Specifically, the identification information for the preferred AP is characterized in that the MAC address or specific SSID (Service Set IDentification) of the AP.

After connecting with the preferred AP in the third step, the communication terminal periodically measuring the received signal strength of the current AP; If the received signal strength is smaller than a first predetermined threshold, receiving a response signal from neighbor APs and measuring the received signal strength respectively; And if the neighboring APs having the received signal strength greater than the first reference value are present, connecting the AP with the largest received signal strength to the WLAN.

When handing over from the preferred AP to the non-preferred AP, in order to maintain a long connection of the preferred AP, a first threshold value is set low.

In accordance with another aspect of the present invention, there is provided a method for accessing a wireless LAN using a preferred AP, the communication terminal receiving first identification information on a specific AP (Access Point) and setting it as a preferred AP; A second step of receiving, by the communication terminal, a response signal from neighboring APs when accessing a wireless LAN to obtain identification information, and confirming whether a preferred AP exists from the acquired identification information; And a third step of connecting the wireless LAN with a non-preferred AP having the largest received signal strength when the preferred AP does not exist.

Specifically, after connecting to the non-preferred AP in the third step, the communication terminal periodically measures the received signal strength of the current AP; If the received signal strength is smaller than a second preset threshold value, receiving a response signal from neighbor APs and determining whether an AP equal to the preset identification information of the preferred AP exists; And if the preferred AP exists, connecting the preferred AP with the WLAN.

After connecting to the non-preferred AP in the third step, the communication terminal periodically measuring the received signal strength of the current AP; If the received signal strength is smaller than a second preset threshold value, receiving a response signal from neighbor APs and determining whether an AP equal to the preset identification information of the preferred AP exists; Measuring received signal strength of neighboring APs based on the received response signal when the preferred AP does not exist; And if the neighboring APs having the received signal strength greater than the second reference value are present, connecting the AP with the largest received signal strength to the wireless LAN.

As described above, according to the present invention, by registering a preferred AP mainly used for handover in a WLAN system, it is possible to prevent the ping-pong phenomenon of repeating the handover in an overlapping area and to reduce battery consumption.

In addition, since there is information on the AP that the communication terminal mainly uses, it is easy to find the failure of the AP through the communication terminal, and even when a plurality of communication terminals access the AP, adjust the number of communication terminals that access the specific AP. There is an advantage that can not be concentrated on a specific AP.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention. Like elements in the figures are denoted by the same reference numerals wherever possible. In addition, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

1 is a block diagram illustrating a general wireless LAN system.

The WLAN system is composed of a plurality of Basic Service Sets (BSS) as shown in FIG. 1, and each of the plurality of Service Sets BSS1 to BSS3 has overlapping service areas.

Each service set includes an access point (AP) connected by a wired network, and a plurality of communication terminals in which a communication channel is formed with each access node (AP). That is, each communication terminal (T1 ~ T5) is connected to the wired network through the AP.

The communication channels of the service sets are formed of different channels from the adjacent service sets.

Each AP of the adjacent service sets uses a different channel, so that when a communication terminal moves a service area or moves to a location where the service areas overlap, a handover between APs may be performed to receive a seamless service. Here, the communication terminal performs a handover when the received signal strength of the currently connected AP (current AP) is less than or equal to the set threshold.

2 to 6b are flowcharts illustrating a wireless LAN access process using a preferred AP of a communication terminal according to an embodiment of the present invention, which will be described with reference to FIG. 1.

First, as shown in FIG. 2, the communication terminal T1 sets and registers a MAC address (Media Access Control Address), which is identification information of a preferred AP selected by a user, in a memory (S1).

Here, when the communication terminal T1 knows the MAC address of the connected AP, the communication terminal T1 may store the MAC address of the connected AP and register it as the preferred AP. At this time, since the connected AP may not be the specific AP desired, it is necessary to confirm whether the connected AP is the desired specific AP. For example, the communication terminal T1 displays a pop-up message to induce the user to move near a desired AP, and uses a flashing light emitting diode (LED) attached to the AP or a specific screen through the LCD screen of the AP. By displaying a message, it is possible to visually check whether a specific AP desired is registered as a preferred AP. That is, when the specific AP is set as the preferred AP, the selected AP is configured to indicate whether the preferred AP is selected by outputting a flashing LED or a message through a display.

As another example, when the MAC address of the AP and the MAC address of the communication terminal T1 are stored correctly in the subscription DB, the AP may be registered by transmitting the MAC address of the AP from the AP to the communication terminal T1. .

When the preferred AP is registered in the communication terminal T1 as described above, when the power of the communication terminal T1 is turned on or the WLAN is operated, the communication terminal T1 is connected to the neighboring APs AP1, AP2, AP3,... Probe (probe) request signal is emitted to (S2).

Subsequently, the communication terminal T1 receives a response signal for a probe request from adjacent neighbor APs AP1, AP2, AP3, ... (S3). The probe response signal may include MAC addresses of respective APs (AP1, AP2, AP3, ...) and channel information used by each AP. Subsequently, the communication terminal T1 analyzes the response signals received from each AP (AP1, AP2, AP3, ...) to check whether there is an AP identical to the MAC address of the preset preferred AP (S4, S5).

When there is a preset preferred AP among the neighboring APs, the communication terminal T1 selects the corresponding preferred AP and connects the WLAN (S6).

Meanwhile, if there is no preferred AP in the neighboring APs, the communication terminal T1 measures the received signal strength, which is the strength of the signal received from each AP, and selects a non-preferred AP having the largest received signal strength. The LAN is connected (S7).

As such, when the communication terminal T1 moves to another service area while the communication terminal T1 is connected to a specific AP and a wireless LAN, for example, the communication terminal T1 is in the service area of the current AP (for example, AP1). If you move to another service area or move to a nested service area, handover is performed. At this time, the communication terminal T1 has a different handover criterion depending on whether the currently connected AP AP1 is a preferred AP or a non-preferred AP.

Then, a process of handing over from a preferred AP to a non-preferred AP is as shown in FIGS. 3 and 4. That is, as shown in FIG. 3, the communication terminal T1 periodically measures the received signal strength, which is the strength of the signal received from the current AP, while being connected to the current AP (preferred AP) (S10). In general, Received Signal Strength Indication (RSSI) is expressed in dBm.

Subsequently, the communication terminal T1 compares the measured received signal strength with a preset first threshold to determine whether the received signal strength is equal to or less than the first threshold (S11). Here, the first threshold value is preferably set lower than the second threshold value of FIG. 5 to be described later, in order to maintain a connection state with the preferred AP for a longer time.

If the received signal strength is greater than or equal to the first threshold value, the communication terminal T1 continuously forms a communication channel with the current AP (preferred AP) (S12).

On the other hand, if the received signal strength is less than or equal to the first threshold value, the communication terminal T1 emits a probe request signal to the neighboring APs AP2, AP3, ... (S13).

Subsequently, the communication terminal T1 receives a response signal for a probe request from adjacent neighbor APs AP2, AP3, ... (S14). The probe response signal may include MAC addresses of respective APs (AP2, AP3, ...) and channel information used by each AP. Subsequently, the communication terminal T1 obtains received signal strength through response signals received from each AP (AP2, AP3, ...) (S15).

Next, the communication terminal T1 compares the received signal strengths of the respective APs AP2, AP3,... With the preset first reference value and checks whether there are candidate APs whose received signal strength exceeds the first reference value. Extract (S16).

The first reference value is a value obtained by adding up the first threshold value and a preset delta value (threshold value + delta value). For example, if the preset first threshold value is -80 dBm and the delta value is 15 dB, the first reference value is -65 dBm. Since the first reference value is set to -65 dBm, APs having a received signal strength greater than -65 dBm will be candidate APs.

If there are a plurality of candidate APs having a received signal strength exceeding the first reference value, the non-preferred AP having the largest received signal strength is selected to connect the WLAN.

4 illustrates a method of determining a first threshold value and a first reference value to move from the preferred AP to the non-preferred AP in the case of FIG. 3, where the horizontal axis represents distance from the AP and the vertical axis represents signal strength. In general, the communication terminal T1 decreases the received signal strength as the distance from the current AP increases.

As shown in FIG. 4, the communication terminal T1 emits a probe request signal for starting a handover when the received signal strength of the current AP is lowered below the first threshold value, and from the neighboring APs AP2, AP3,... Measure the received signal strength through the response signal. The measured received signal strength and the preset first reference value are compared with each other to check whether there is an AP whose received signal strength exceeds the first reference value, and when there is an AP exceeding the first reference value among neighboring APs, the received signal strength Selects the largest AP to connect to the WLAN. At this time, the first reference value is preferably set slightly higher than the first threshold value.

That is, when moving from the preferred AP to the non-preferred AP, the first threshold value is set low and the first reference value is set high so that handover to the non-preferred AP occurs late.

Meanwhile, a process of handing over from a non-preferred AP to a preferred AP or a non-preferred AP will be described with reference to FIGS. 5 to 6B.

As shown in FIG. 5, the communication terminal T1 periodically measures the received signal strength, which is the strength of the signal received from the current AP, while being connected to the current AP (non-preferred AP) (S20).

Subsequently, the communication terminal T1 compares the measured received signal strength with a preset second threshold to determine whether the received signal strength is less than or equal to the second threshold (S21). If the received signal strength is greater than or equal to the second threshold, the communication terminal T1 continuously forms a communication channel with the current AP (non-preferred AP) (S22).

If the received signal strength is less than or equal to the second threshold value, the communication terminal T1 emits a probe request signal to the neighboring APs AP2, AP3, ... (S23).

Subsequently, the communication terminal T1 receives a response signal for a probe request from adjacent neighbor APs AP2, AP3, ... (S24). The probe response signal may include MAC addresses of respective APs (AP2, AP3, ...) and channel information used by each AP. Subsequently, the communication terminal T1 obtains the received signal strength and the corresponding MAC address through the response signals received from each AP (AP2, AP3, ...).

Subsequently, the communication terminal T1 analyzes the response signals received from the neighbor APs AP2, AP3,..., And confirms whether there is an AP identical to the MAC address of the preset preferred AP (S25, S26).

When there is a preset preferred AP among the neighboring APs, the communication terminal T1 selects the corresponding preferred AP and connects the WLAN (S27).

If there is no preferred AP in the neighboring APs, the communication terminal T1 compares the received signal strengths of the respective APs AP2, AP3, ... with a second preset reference value, and receives the received signal strength as the second reference value. Check whether there are candidate APs exceeding and extracting (S28).

The second reference value is a value obtained by adding up the second threshold value and a preset delta value (threshold value + delta value). For example, if the second preset threshold value is -75 dBm and the delta value is 8 dB, the second reference value is -67 dBm. Since the second reference value is set to -67 dBm, APs having a received signal strength greater than -67 dBm will be candidate APs.

If there are a plurality of candidate APs whose reception signal strength exceeds the second reference value, the non-preferred AP having the largest reception signal strength is selected to connect the WLAN.

6A and 6B illustrate a method of determining a second threshold value and a second reference value to move from the non-preferred AP to the preferred AP in the case of FIG. 5, where the horizontal axis represents distance from the AP and the vertical axis represents signal strength. In general, the communication terminal T1 decreases the received signal strength as the distance from the current AP increases.

As shown in FIG. 6A, the communication terminal T1 emits a probe request signal to start a handover when the received signal strength of the current AP is lowered and falls below a second threshold, and from the neighboring APs AP2, AP3,... The response signal is analyzed to determine whether there is an AP identical to the MAC address of the preset preferred AP.

When there is a preset preferred AP among neighboring APs, the communication terminal T1 selects the corresponding preferred AP regardless of the received signal strength of the preferred AP and connects the WLAN.

However, when there is no preferred AP in the neighboring APs, the communication terminal T1 compares the received signal strengths of the respective APs AP2, AP3, ... and the second preset reference value with each other as shown in FIG. 6B. It checks whether there is an AP whose received signal strength exceeds the second reference value, and selects an AP having the largest received signal strength to connect the WLAN. At this time, the second reference value is preferably set slightly higher than the second threshold value.

And, it is preferable that the second threshold value is set slightly higher than the first threshold value of FIG. 3, and the second reference value is set slightly lower than the first reference value. This is to maintain a connection state with the preferred AP for a long time or to quickly handover to the preferred AP.

That is, when moving from a non-preferred AP to a preferred AP, the second threshold is set high so that a handover to a preferred AP occurs quickly.When a non-preferred AP moves from a non-preferred AP, the received signal strength of neighboring APs is higher than a second reference value, thereby handover. Is performed.

7 and 8 are flowcharts illustrating a wireless LAN access process using a preferred AP of a communication terminal according to another embodiment of the present invention, which will be described with reference to FIG. 1.

First, as shown in FIG. 7, the communication terminal T1 sets and registers SSID (Service Set IDentification), which is identification information of a preferred AP selected by a user, in a memory. At this time, the same SSID (Service Set IDentification) as the communication terminal (T1) is also set in the preferred AP (S101).

When the preferred AP is registered in the communication terminal T1 as described above, when the power of the communication terminal T1 is turned on or the WLAN is operated, the communication terminal T1 is connected to the neighboring APs AP1, AP2, AP3,... It emits a probe request signal to the (S102).

Subsequently, the communication terminal T1 receives a response signal for a probe request from adjacent neighbor APs AP1, AP2, AP3, ... (S103). The probe response signal may include SSID of each AP (AP1, AP2, AP3, ...) and channel information used by each AP.

The communication terminal T1 analyzes response signals received from each AP (AP1, AP2, AP3, ...) to determine whether there is an AP identical to the SSID of the preset preferred AP (S104, S105).

When there is a preset preferred AP among the neighboring APs, the communication terminal T1 selects the corresponding preferred AP and connects the WLAN (S106). Here, since the communication terminal T1 connects the WLAN only with an AP having the same SSID, the communication terminal T1 repeatedly emits a probe request signal when the preferred AP does not exist.

As such, when the communication terminal T1 moves to another service area while the communication terminal T1 is connected to the preferred AP and the WLAN, for example, the communication terminal T1 is different from the service area of the current AP AP1. If you move to or move to a nested service area, handover is performed.

That is, the communication terminal T1 periodically measures the received signal strength which is the strength of the signal received from the current AP as shown in FIG. 8 in the state of being connected to the current AP (preferred AP) (S111). In general, Received Signal Strength Indication (RSSI) is expressed in dBm.

Subsequently, the communication terminal T1 compares the measured received signal strength with a preset threshold and determines whether the received signal strength is equal to or less than the threshold (S112). If the received signal strength is greater than or equal to the threshold, the communication terminal T1 continuously forms a communication channel with the current AP (preferred AP) (S113).

In addition, when the received signal strength is less than the threshold value, the communication terminal T1 emits a probe request signal to the neighbor APs AP2, AP3, ... (S114).

Subsequently, the communication terminal T1 receives a response signal for a probe request from adjacent neighbor APs AP2, AP3, ... (S115). The probe response signal may include SSIDs of respective APs (AP2, AP3, ...) and channel information used by each AP. Subsequently, the communication terminal T1 obtains SSIDs of the corresponding APs through response signals received from the respective APs AP2, AP3,...

Subsequently, the communication terminal T1 analyzes the response signals received from the neighbor APs AP2, AP3,..., And confirms whether there is an AP identical to the SSID of the preset preferred AP (S116, S117).

When there is a preset preferred AP among the neighboring APs, the communication terminal T1 selects the corresponding preferred AP and connects the WLAN (S118).

If there is no preferred AP in the neighbor APs, the communication terminal T1 repeatedly emits a probe request signal to the neighbor APs. This is because the communication terminal T1 performs handover only when the neighbor AP and the SSID are the same.

Therefore, in the present invention, when the signal strength is lowered below the threshold value, the probe request signal is emitted to start the handover, and if there is an AP more than the reference value, the AP moves to the AP. When moving from a non-preferred AP to a preferred AP, the second threshold is set high so that handover occurs quickly. If there is no preferred AP, the received signal strength is moved to another non-preferred AP having a higher than the second reference value. Is set slightly higher than the second threshold.

In addition, when moving from the preferred AP to the non-preferred AP, the first threshold value is set very low (for example, the reception signal strength that is barely received), and the first reference value is set high to access the preferred AP for a long time. The probability of handover can be reduced.

By registering a preferred AP to a specific AP mainly used for handover in a WLAN system, it is possible to prevent the ping-pong phenomenon of repeating the handover in the overlapping area and to reduce battery consumption. In addition, since there is information on the AP that the communication terminal mainly uses, it is easy to find the failure of the AP through the communication terminal, and even when a plurality of communication terminals access the AP, adjust the number of communication terminals that access the specific AP. This can prevent you from focusing on a particular AP.

Preferred embodiments of the present invention are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit of the present invention. Therefore, such modifications, changes and additions should be determined not only by the claims below, but also by equivalents to those claims.

1 is a block diagram illustrating a general wireless LAN system.

2 is a flowchart illustrating a WLAN access procedure using a preferred AP of a communication terminal according to an embodiment of the present invention.

3 and 4 are flowcharts illustrating a handover process from the preferred AP of FIG. 2 to the non-preferred AP.

5 through 6B are flowcharts illustrating a handover process from the non-preferred AP of FIG. 2 to the preferred AP or the non-preferred AP.

7 and 8 are flowcharts illustrating a WLAN access procedure using a preferred AP of a communication terminal according to another embodiment of the present invention.

Claims (14)

A first step of receiving, by the communication terminal, identification information on a specific access point (AP) and setting it as a preferred AP; A second step of receiving, by the communication terminal, a response signal from neighboring APs when accessing a wireless LAN to obtain identification information, and confirming whether a preferred AP exists from the acquired identification information; And And a third step of connecting the WLAN with the preferred AP when the preferred AP exists. The method of claim 1, Identification information for the preferred AP is a MAC address of the AP, WLAN access method using a preferred AP. The method of claim 1, The identification information on the preferred AP is a specific SSID (Service Set IDentification), and the SSID is stored in the communication terminal and the AP, respectively, WLAN access method using a preferred AP. The method of claim 1, After accessing the preferred AP in the third step, The communication terminal periodically measuring the received signal strength of the current AP; If the received signal strength is smaller than a first predetermined threshold, receiving a response signal from neighbor APs and measuring the received signal strength respectively; And And connecting the wireless LAN to the AP having the largest received signal strength when there are neighboring APs having the received signal strength greater than the first reference value. The method of claim 4, wherein The first reference value is set to be higher than the first threshold value WLAN access method using a preferred AP. The method of claim 4, wherein When handing over from the preferred AP to the non-preferred AP, in order to maintain a long connection of the preferred AP, a first threshold value is set low. The method of claim 1, Wireless LAN access method using a preferred AP, characterized in that when setting the preferred AP, the MAC address of the AP having the largest received signal strength. The method of claim 1, If the specific AP is set as a preferred AP, the selected AP is a wireless LAN access method using a preferred AP, characterized in that indicating whether or not by selecting a flashing LED or outputting a message through the display. A first step of receiving, by the communication terminal, identification information on a specific access point (AP) and setting it as a preferred AP; A second step of receiving, by the communication terminal, a response signal from neighboring APs when accessing a wireless LAN to obtain identification information, and confirming whether a preferred AP exists from the acquired identification information; And And a third step of connecting the wireless LAN with a non-preferred AP having the largest received signal strength when the preferred AP does not exist. The method of claim 9, Identification information for the preferred AP is a MAC address of the AP, WLAN access method using a preferred AP. The method of claim 9, After connecting with the non-preferred AP in the third step, The communication terminal periodically measuring the received signal strength of the current AP; If the received signal strength is smaller than a second preset threshold value, receiving a response signal from neighbor APs and determining whether an AP equal to the preset identification information of the preferred AP exists; And Connecting the WLAN with the preferred AP when the preferred AP exists; and a WLAN access method using the preferred AP. The method of claim 9, After connecting with the non-preferred AP in the third step, The communication terminal periodically measuring the received signal strength of the current AP; If the received signal strength is smaller than a second preset threshold value, receiving a response signal from neighbor APs and determining whether an AP equal to the preset identification information of the preferred AP exists; Measuring received signal strength of neighboring APs based on the received response signal when the preferred AP does not exist; And And connecting the wireless LAN to the AP having the largest received signal strength when there are neighboring APs having the received signal strength greater than a second preset reference value. 13. The method of claim 12, And the second reference value is set higher than a second threshold. 13. The method of claim 12, When handing over from the non-preferred AP to the preferred AP, a second threshold value is set to be high in order to quickly handover to the preferred AP.

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