KR20070087430A - Scanning method of wireless lan client - Google Patents

Abstract

A scanning method of a wireless LAN(Local Area Network) client is provided to increase the amount of transmitted data by reducing the time of a scanning process for a different time according to quality of a link used for data transmission or obtain more data capable of exactly searching a roaming access point. A scanning method of a wireless LAN(Local Area Network) client comprises: determining quality of a link used for data transmission(S601); selecting scanning time information corresponding to the determined quality of the link among scanning time information differently set according to the quality of the link(S602); and scanning access points of a wireless channels by using the selected scanning time information(S605).

Description

Scanning method of wireless LAN client

1 shows a system in which the present invention is used;

2 is a view provided to explain in more detail the relationship between the quality of the link and the overall scanning time according to the present invention;

3 is a view provided to explain a scanning period according to the present invention;

4 is a view provided to explain in more detail the determination of a WLAN state according to the present invention;

5 is a view provided to explain in more detail the active scanning according to the present invention;

6 is a diagram illustrating a scanning method of a WLAN client according to the present invention.

Explanation of symbols on the main parts of the drawings

100: WLAN client

210 to 240: access point

The present invention relates to a scanning method of a WLAN client that varies the scanning time according to the quality of a link used for data transmission.

Recently, as wireless LANs are widely introduced in corporate environments, the necessity of roaming, which is a service that connects communication even within a service area of different telecommunications providers, is gradually increasing.

Of the time required to perform such roaming, a large occupancy is the time taken to find an optimal access point for roaming by scanning access points using nearby wireless channels.

Typically, in the case of IEEE 802.11b / g wireless LAN, 13 wireless channels are provided in Korea.

The time to use these 13 wireless channels and scan the access points once is relatively long, approximately 0.26 to 1.3 (seconds), during which time data transmission is stopped.

Therefore, if the time required for this scanning becomes long, the transmission of data is delayed.

In addition, the overall roaming time is also long, it is difficult to perform roaming quickly.

Even so, if you reduce the time it takes to scan, you may not be able to get enough data to accurately find the best access point to roam.

The present invention was developed to solve these problems, and according to the quality of the link being used for data transmission, it is possible to increase the amount of data transmitted by scanning for different times or to accurately find an access point to roam. An object of the present invention is to provide a scanning method of a WLAN client to obtain more data.

The present invention according to this object

If the quality of the link being used for data transmission is poor, scanning for a relatively long time allows more data to accurately find the access point to roam.

When the quality of the link used for data transmission is good, the amount of data transmitted can be increased by scanning for a relatively short time.

Specifically, determining the quality of the link used for data transmission, selecting a scanning time corresponding to the quality of the determined link from among scanning times set differently according to the quality of the link, and selecting the selected scanning time. Scanning the access points of the wireless channels using < RTI ID = 0.0 >

In particular, the determining of the quality of the link may include, for example, setting a predetermined number of transmission parameters required to calculate a median value, and setting a median value for transmission parameters for the set number of units in advance. Periodically calculating each time, and comparing the intermediate value of the transmission parameter calculated last at the time of scanning with a preset threshold value and determining the link quality according to the result of the comparison. Characterized in that made.

The transmission parameter used to determine the quality of the link may be at least one selected from among received signal strength, channel rate, frame error rate, noise index, and connection quality factor.

The scanning of the access points may be performed according to a predetermined radio channel order. For example, after scanning from the channel with the lowest frequency, and proceeding to the channel with the highest number, scanning may be performed from the channel with the lowest number again.

The scanning of the access points may be performed periodically in a state in which data transmission is stopped when a predetermined time elapses.

The access points may be scanned using any one selected from an active method and a passive method. In particular, only when the active method is set to be disabled, the access points may be selected using the passive method. You can scan.

Hereinafter, with reference to the accompanying drawings will be described in more detail the present invention.

The system shown in FIG. 1 is a system to which the present invention is applied, and is largely comprised of a WLAN client 100 and a plurality of access points 210 to 240.

The system configured as described above periodically stops data transmission and scans the access points 210 to 240 using other wireless channels while the wireless LAN client 100 transmits data.

In this scanning operation, it should be noted in connection with the present invention that the scanning time is selected differently depending on the quality of the link being used for data transmission, for example, whether it is good or bad, and this time is set in advance. .

The time set as described above includes the entire scanning time.

In the passive mode, the scanning time per channel is additionally included. In addition, in the active mode, the minimum probe response time Min_Probe_Response_Time and the maximum probe response time Max_Probe_Response_Time are additionally included.

The total scanning time is a time required for one scanning, that is, the present invention stops data transmission and the scanning for access points using wireless channels once every set time elapses. Is the time required for scanning.

This total scanning time is set for each scanning method according to the quality of the link.

For example, if the quality of the link is in good condition, roaming does not need to be specifically considered, so the overall scanning time suitable for that condition is relatively short, i.e., two or three radio channels can be scanned. Can be set to a relatively short time.

On the other hand, if the quality of the link is poor, roaming needs to be done to find another access point with good link quality, so that the overall scanning time suitable for that condition is relatively long, i. It can be set to a relatively long time such that five or six can be scanned.

Next, the scanning time per channel is a time required for scanning one channel, and is a time specially set when the scanning method is a passive method.

The WLAN client 100 scans access points using a predetermined channel during the scanning time per channel. When the time elapses, the access point using the next channel is scanned according to the preset channel order.

Next, the minimum probe response time Min_Probe_Response_Time and the maximum probe response time Max_Probe_Response_Time are specially set in consideration of the characteristics of the active method.

The minimum probe response time is a time waiting for the WLAN client 100 to receive a probe response packet from an access point using the channel after transmitting a probe request packet using a predetermined channel.

The minimum probe response time is particularly considered that in the IEEE 802.11b / g WLAN, the WLAN client transmits a probe request packet using a predetermined channel for scanning a predetermined channel and uses the channel for scanning a predetermined channel. After receiving the probe response packet from any access point, the scanning operation for the next channel may be performed in a predetermined order.

Therefore, it is possible to wait indefinitely until the probe response data is received. Therefore, in order to prevent a problem or the like caused by this, the above-described response waiting time is set, and if the response waiting time has elapsed even if the probe response data is not received, The scanning operation on the channel may be performed.

The maximum probe response time is a time set for scanning a corresponding channel when a probe response packet is received within the minimum probe response time.

That is, when any one of the access points using the predetermined channel receives the probe response packet transmitted, the access points using the channel are scanned until the maximum probe response time has elapsed.

On the other hand, if the probe response packet is not received during the minimum response wait time, the access points using the next channel are scanned according to a predetermined channel order.

The detailed operation of the WLAN client 100 using these scanning times is as follows.

First, the WLAN client 100 receives a received signal strength (RSI) or a received channel strength indication (RCPI), a channel rate, and a frame error rate for a predetermined packet. : FER), Noise Figure (NF), Link Quality Indication (LQI), etc. One or more parameters are periodically detected and the detected parameters are used to Determine the quality.

For example, when the parameter is one received signal strength (RSSI or RCPI), the determination of the WLAN state is performed as follows.

First, the number of received signal intensities required to calculate a predetermined median value is set.

The intermediate value of the received signal strengths of the set number, that is, the received signal strengths of the packets transmitted through the wireless LAN in use, is periodically calculated and recorded in the memory whenever a predetermined unit time elapses. .

Then, at the time of scanning, the intermediate value of the last received signal strength recorded in the memory is compared with the threshold value of the preset received signal strength, and the quality of the link being used for data transmission is determined according to the comparison result.

That is, when the intermediate value of the received signal strength recorded last in the memory at the time of scanning is larger than the preset threshold value of the received signal strength, it is determined that the quality of the link being used for data transmission is in a good state.

On the other hand, when the intermediate value of the received signal strength recorded last in the memory at the time of scanning is smaller than the preset threshold value of the received signal strength, it is determined that the quality of the link used for data transmission is in a bad state.

The unit time is a time set in advance in order to periodically calculate the median value of the received signal strength, and the WLAN client 100 determines the median value of the received signal strength of the packet transmitted through the WLAN in use. It is calculated every time.

The intermediate value is a representative value representing values of n parameters. For example, when the parameter is a received signal strength and n is 5, the received signal strength is -60 dBM when a predetermined unit time elapses. If the received signal intensity value is -50dBM, -47dBM, -80dBM, or -90dBM recorded at each point in time immediately before the unit time, the median of received signal intensity is -60dBM. Becomes

For example, the threshold is a value used to classify the link quality into a good state or a bad state, and a different value may be set for each parameter such as received signal strength and channel rate.

Next, the WLAN client 100 selects the total scanning time corresponding to the quality of the link being used as determined above, and additionally selects the scanning time per channel in the passive method, and in the active method. Select both minimum probe response time and maximum probe response time.

Then, at the start of scanning according to the elapse of the set time, data transmission is stopped and other access points using wireless channels in the vicinity for the selected time are scanned as described above.

For example, if the scanning method is an active method of the IEEE 802.11b / g WLAN, the WLAN client 100 transmits a probe request packet using any one channel according to a preset channel order. .

Then, when any of the access points using a given channel receives a probe response packet transmitted, the access points using the channel are continuously continued until the selected maximum probe response time has elapsed. Scan.

On the other hand, if the probe response packet is not received during the selected minimum response wait time, the access points using the next channel are scanned according to a predetermined channel order, which is performed during the selected total scanning time.

On the other hand, when the scanning method is a passive method of the IEEE 802.11b / g wireless LAN, the wireless LAN client 100 during the selected scanning time per channel, the access point that uses a predetermined channel according to a predetermined channel order Scan.

Then, when the scanning time per selected channel elapses, the access points using the next channel are scanned according to the channel order, and this operation is performed during the selected entire scanning time.

The start point of the scanning is fixedly fixed according to the passage of a preset time, while the end point thereof is variably determined as a point at which a predetermined total scanning time selected according to the state of the WLAN is added to the start point. Accordingly, the number of channels to be scanned is also different.

In this scanning, the WLAN client 100 may scan according to a preset channel order.

For example, the channels may be sequentially scanned in order from low to high, and after progressing to the highest, scanning may be performed again from the lowest.

More specifically, in case of IEEE 802.11b / g wireless LAN having 1 to 13 wireless channels, the access point is sequentially scanned from channel 1 to 13, and channel 1 is performed after proceeding to channel 13. You can start scanning again.

In addition, when scanning of channels 1 and 2 is completed for a predetermined total scanning time, the next scanning may start scanning from channel 3.

The scanning may use any one selected from active scanning and passive scanning, and may use passive scanning only when active scanning is set to be disabled.

That is, the present invention can scan the access points using any one selected from the above-described active method and passive method, and in particular, only when the active method is set to the default mode and is specifically disabled according to a user command. It is desirable to scan the access points using a scheme.

As described above, when the quality of the link used for data transmission is in a good state, the amount of data transmitted can be increased by reducing the time taken for scanning, and the quality of the link used for data transmission is reduced. In this case, you will have enough scanning time to get more data to find exactly the access point to roam.

2 is provided to explain in more detail the relationship between the WLAN state and the total scanning time.

As shown in FIG. 2, the present invention sets a plurality of total scanning times differently according to the quality of a link, and selects a predetermined total scanning time corresponding to the quality of a link used for data transmission. Scanning an access point that is using wireless channels in its vicinity for the selected full scanning time.

For example, if the quality of the link being used for data transmission is in good condition, the WLAN client selects a predetermined total scanning time set to a relatively short time and selects two radios of channels 4 and 5 during the selected total scanning time. Scan access points that are using the channel.

On the other hand, if the quality of the link being used for data transmission is poor, the WLAN client selects a predetermined total scanning time set to a relatively long time and selects five channels from channels 6 to 10 during the selected total scanning time. Scan access points that are using a wireless channel.

The access point is sequentially scanned according to a predetermined channel order during the selected entire scanning time. For example, when scanning the access points using channel 5 during the previous entire scanning time, the next time scanning is performed. In accordance with a preset order, scanning starts from access points using channel 6.

3 is for explaining the period of scanning.

As shown in FIG. 3, the present invention periodically stops data transmission every time a predetermined time elapses during data transmission, and scans access points in the vicinity of using a wireless channel.

And, the start point of the scanning is fixedly fixed according to the passage of a predetermined time, while the end point thereof is variably determined as the point at which the predetermined total scanning time selected according to the state of the WLAN is added to the start point. Therefore, the number of channels to be scanned is also different.

4 is a view provided to explain in more detail the determination of a WLAN state.

According to the present invention, a wireless LAN client selects a scanning time, while transmitting data, receiving signal strength (RSSI or RCPI), channel rate, frame error rate (FER), noise figure (NF), and connection. One or more parameters, such as the quality factor (LQI), are used to periodically determine the quality of the current link.

When the parameter is one received signal strength (RSSI or RCPI), the determination of the WLAN state is performed as follows.

First, the number of received signal intensities required to calculate the median value is set, and the median value of the received signal intensities for the set number is periodically calculated and recorded in the memory whenever the set unit time elapses. .

Then, at the time of scanning, the intermediate value of the last received signal strength recorded in the memory is compared with the threshold value of the preset received signal strength, and the link quality is determined according to the comparison result.

For example, if the number of received signal intensities required to calculate the median value is 5, initially, the values of the four received signal intensities measured sequentially instead of the intermediate values are stored in the range of N to N + 3. Write to cell.

Then, in the fifth recording, the median value of the measured value of the received signal strength at that point and the values of the four received signal strengths previously recorded is calculated and recorded in the cell of N + 4.

In the sixth recording, the received signal strength at that time and the four received signal strengths immediately before that time, that is, the received signal strengths recorded in the cells of N + 1 to N + 4. The median value is calculated and recorded in the cell at N + 5.

In this way, the information to be used to determine the quality of the link being used, that is, the intermediate value of the received signal strength of the packet received through the wireless LAN used for data transmission is continuously recorded periodically.

In this state, the WLAN client compares the median value of the received signal strength last recorded in the memory with the threshold value of the preset received signal strength at the time of scanning and determines the quality of the link according to the comparison result.

That is, the WLAN client determines that the quality of the link being used is in a good state when the intermediate value of the received signal strength recorded in the memory at the time of scanning is larger than the preset threshold value of the received signal strength.

On the other hand, if the intermediate value of the received signal intensity recorded last in the memory at the predetermined time to be scanned is smaller than the preset threshold value of the received signal strength, it is determined that the quality of the link being used is in a bad state.

5 is a view provided to explain the active method in more detail.

When the scanning method is the active method, according to the present invention, the WLAN client transmits the probe request packet 510 using any one channel according to a preset channel order.

Then, within the predetermined minimum probe response time selected according to the quality of the link being used, if a probe response packet 520 transmitted by any of the access points using the channel is received, acknowledge character) packet 530 and continues to scan other access points using that channel until the maximum probe response time has elapsed.

On the other hand, if the probe response packet is not received within the minimum probe response, the access point using the next channel is scanned according to a preset channel order, which is performed during the selected entire scanning time.

The start point of the scanning is fixedly fixed according to the passage of a preset time, while the end point thereof is variably determined as a point at which a predetermined total scanning time selected according to the state of the WLAN is added to the start point. Accordingly, the number of channels to be scanned is also different.

The minimum probe response time is a time waiting for the WLAN client to receive a probe response packet from any access point using the channel after transmitting a probe request packet using a predetermined channel, and the maximum probe response time. Is a time set for scanning a corresponding channel when a probe response packet is received within a minimum probe response time, as described above.

6 is provided to explain a scanning method of a WLAN client according to the present invention.

First, as illustrated in FIG. 6, the WLAN client may receive a received signal strength (RSSI or RCPI), a channel rate, a frame error rate (FER), a noise figure (NF), and a connection for a received packet. One or two or more parameters such as the quality factor (LQI) are periodically detected (S600), and the quality of the link currently being used for data transmission is determined using the detected parameters (S601).

For example, when the parameter is one received signal strength (RSSI or RCPI), the determination of the WLAN state is performed as follows.

That is, the number of received signal intensities required to calculate a predetermined median value is set, and the received signal intensities corresponding to the set number, that is, the received signal intensities of the packet transmitted through the currently used WLAN. The median value for is periodically calculated and recorded in the memory whenever a predetermined unit time elapses.

Then, the intermediate value of the last received signal strength recorded in the memory at the time of scanning is compared with the threshold value of the preset received signal strength, and the link quality is determined according to the comparison result.

That is, when the intermediate value of the received signal strength recorded last in the memory at the time of scanning is larger than the preset threshold value of the received signal strength, it is determined that the quality of the link being used for data transmission is in good condition.

On the other hand, if the intermediate value of the received signal strength recorded in the memory at the time of scanning is smaller than the preset threshold value of the received signal strength, it is determined that the quality of the link currently being used for data transmission is poor.

The unit time is a time set in advance in order to periodically calculate an intermediate value of the received signal strength, and the WLAN client stores the median value of the received signal strengths of the packet transmitted through the WLAN in use. Each time elapses, the calculation is made.

The median value is a representative value representing the values of n parameters. For example, if the parameter is the received signal strength and n is 5, the received signal strength at the time when a predetermined unit time has elapsed is -60 dBM, and at each time point when the unit time has elapsed immediately before the time point. If the recorded received signal strength is -50dBM, -47dBM, -80dBM, or -90dBM, the median of received signal strength is -60dBM at that point.

For example, the threshold is a value used to classify the link quality into a good state or a bad state, and a different value may be set for each parameter such as received signal strength and channel rate.

Meanwhile, as described above, in a state where information about a quality of a link currently being used for data transmission is continuously recorded in a memory, the WLAN client may perform a scanning method and a state of a wireless LAN last recorded in the memory at the time of scanning. In step S602, a total scanning time is selected.

In the passive method, the scanning time per channel is additionally selected, and in the active method, the minimum probe response time and the maximum probe response time are selected together.

The total scanning time is a time required for one scanning, that is, the present invention stops data transmission and the scanning of access points using wireless channels is performed once every set time elapses. This is the time required for one scan.

And, the scanning time per channel is a time required for scanning one channel.

The minimum probe response time is a time waiting for the WLAN client 100 to receive a probe response packet from any access point using the channel after transmitting a probe request packet using a predetermined channel. The probe response time is a time set for scanning a corresponding channel when a probe response packet is received within a minimum probe response time, as described above.

Next, when it is time to start scanning according to the elapse of the set time (S603), the WLAN client stops data transmission (S604) and the access point using the wireless channels in the vicinity for the selected time according to step S602. Scanning them (S605 to S607).

For example, when the scanning method is an active method, the WLAN client transmits a probe request packet using any one channel according to a preset channel order.

Then, when any of the access points using a given channel receives a probe response packet transmitted, the access points using the channel are continuously continued until the selected maximum probe response time has elapsed. Scan.

On the other hand, if the probe response packet is not received during the selected minimum response wait time, the access points using the next channel are scanned according to a predetermined channel order, which is performed during the selected total scanning time.

Meanwhile, when the scanning method is a passive method, the WLAN client scans access points using a predetermined channel according to a preset channel order during the selected scanning time per channel.

Then, when the scanning time per selected channel elapses, the access points using the next channel are scanned according to the channel order, and this operation is performed during the selected entire scanning time.

In addition, during the scanning, the WLAN client scans according to a preset channel order. For example, the WLAN clients sequentially scan the channels in order from the lowest to the highest, and then proceed from the lowest to the highest. You can scan again.

Specifically, in the case of IEEE 802.11b / g wireless LAN having 1 to 13 wireless channels, access points are sequentially scanned from channels 1 to 13, and after channel 13, channels 1 again. You can scan.

In addition, when scanning of channels 1 and 2 is completed for a predetermined total scanning time, the next scanning may start scanning from channel 3.

In addition, the present invention can scan the access points using any one selected from the above-described active method and passive method, in particular, only when the active method is set to the default mode and is specifically disabled according to a user command. It is desirable to scan the access points using a scheme.

As described in detail above, the present invention, when the quality of the link used for data transmission is in a poor state, the scanning time is increased to obtain more data that can accurately find the access point to roam, so that the roaming time is reduced. If the quality of the link used for data transmission is in a good state at the time of scanning, the amount of data transmitted can be increased by reducing the time taken for scanning. In addition, since the existing access point is used as it is and only the operating method of the WLAN client needs to be updated, it can be easily applied.

Claims (8)

Determining a quality of a link being used for data transmission; Selecting scanning time information corresponding to the determined link quality from among scanning time information differently set according to link quality; Scanning access points of wireless channels using the selected scanning time information. The method of claim 1, Determining the quality of the link, Setting a predetermined number of transmission parameters required to calculate a median value, and periodically calculating a median value for transmission parameters for the set number every time a predetermined unit time elapses; And comparing the intermediate value of the transmission parameter calculated last at the time of scanning with a preset threshold value and determining a link quality according to the result of the comparison. The method of claim 2, The transmission parameter is, Scanning method of a wireless LAN client, characterized in that at least one selected from the received signal strength, channel rate, frame error rate, noise index, connection quality factor. The method of claim 1, Scanning the access points, A scanning method of a WLAN client, characterized in that scanning according to a predetermined wireless channel order. The method of claim 1, Scanning the access points, And scanning from the channel with the lowest frequency and scanning from the channel with the lowest frequency after scanning to the channel with the highest frequency. The method of claim 1, Scanning the access points, Scanning method of a wireless LAN client, characterized in that is made periodically when the set time elapses. The method of claim 1, Scanning the access points, Scanning the access points using any one selected from an active method and a passive method, and scanning the access points using the passive method only when the active method is set to be disabled. . The method of claim 1, The scanning time information, The scanning method of the WLAN client, characterized in that it comprises one or more selected from the scanning time information per channel, the total scanning time information, the minimum probe response time (Min_Probe_Response_Time) information, the maximum probe response time (Max_Probe_Response_Time) information.

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