WO2022038677A1

WO2022038677A1 - Method and device for capturing wireless frame

Info

Publication number: WO2022038677A1
Application number: PCT/JP2020/031139
Authority: WO
Inventors: 正義鍋島; 寛坂本; 智明小川
Original assignee: 日本電信電話株式会社
Priority date: 2020-08-18
Filing date: 2020-08-18
Publication date: 2022-02-24
Also published as: JP7416264B2; JPWO2022038677A1

Abstract

According to the present invention, executed are: a process for scanning beacon frames that are transmitted from a plurality of wireless access devices through different wireless channels; a capturing process for capturing and accumulating a wireless frame having a channel number to be captured; and a determination process for setting the channel number as a channel number to be captured if a beacon frame scanned in the scan process meets a predetermined condition, or setting a new channel number to be captured if the state in which the beacon frame of the channel number to be captured in the capturing process does not meet the predetermined condition has continued for at least a predetermined period of time. Accordingly, it is possible to capture wireless frames that are transmitted and received by a wireless terminal device that moves in a situation where there are a plurality of wireless access devices to be connected.

Description

Wireless frame capture method and capture device

The present invention relates to a technique for capturing wireless frames transmitted and received by a wireless terminal device in order to experientially evaluate the communication quality of the wireless terminal device using the wireless communication system.

Conventionally, as one of the means for confirming the communication quality of network services regardless of whether it is wired communication or wireless communication, the communication quality is evaluated by capturing the transmitted / received frames (or packets). Here, the information obtained from the captured frame is, for example, a received signal strength (RSSI: Received Signal Strength Indicator), a frequency band (channel number), a data rate, a network identifier (SSID: Service Set IDentifier), and the like.

For example, in the case of a wireless LAN (Local Area Network) system, the measurer uses a capture device such as a personal computer equipped with a wireless LAN function between the wireless access device (AP: AccessPoint) and the wireless LAN terminal device. Capture the transmitted and received wireless LAN frames. After the capture is completed, the measurer analyzes the information obtained from the captured wireless LAN frame using evaluation software such as a personal computer, and evaluates the communication quality such as throughput and packet loss rate. For example, in a wireless LAN system such as Wi-Fi (registered trademark), when a problem such as the wireless LAN terminal device cannot connect to the AP occurs, a survey is conducted to capture the wireless LAN frame and identify the cause. (See, for example, Non-Patent Document 1). In addition, a demonstration experiment is being conducted to evaluate the quality of IP (Internet Protocol) broadcasting (see, for example, Non-Patent Document 2).

When there is only one AP to be connected, the capture device only needs to capture the wireless LAN frame transmitted / received by the AP. On the other hand, when there are a plurality of APs to be connected, the wireless LAN terminal device generally connects to the AP whose RSSI is equal to or higher than the threshold value. Therefore, the measurer sets the capture device to capture the wireless LAN frame transmitted / received by the AP whose RSSI is equal to or higher than the threshold value at the measurement point.

Here, the situation may change, for example, fluctuations in obstacles such as people, automatic control functions for radio wave transmission levels, or movement of wireless LAN terminal devices. When the RSSI of the wireless LAN frame received from the connected AP becomes less than the threshold value due to such a change in the situation, the wireless LAN terminal device is used to perform other devices whose RSSI is equal to or higher than the threshold value from the connected AP. Automatically switch to AP.

However, even if the wireless LAN terminal device switches the connection to another AP, the capture device continues to capture the wireless LAN frame transmitted / received by the AP initialized by the measurer, so that the wireless LAN frame of the other AP Cannot be captured.

In this way, the conventional capture device cannot continue to capture the wireless LAN frame by following the wireless LAN terminal device that moves while switching between a plurality of APs, so that the communication quality experienced by the user of the wireless LAN terminal device can be experienced. I can't confirm.

The present invention is a wireless frame capture method and a capture device capable of capturing wireless frames transmitted and received by a wireless terminal device that moves by switching the wireless access device to be connected when there are a plurality of wireless access devices to be connected. The purpose is to provide.

The present invention is a capture method when a wireless frame communicated between a plurality of wireless access devices and a wireless terminal device is captured by the capture device, and the plurality of wireless access devices are used in a plurality of different wireless channels. A reception process in which the radio frame including the transmitted beacon frame is received by at least one receiving unit, and a scan in which the beacon frames of a plurality of the radio channels received by the receiving unit are scanned and the beacon frame information is output. The beacon frame when the processing, the capture process of capturing the wireless frame of the channel number to be captured and accumulating information about the wireless frame, and the beacon frame information output by the scan process match the determination conditions. The channel number of the information is set to the channel number of the capture target, and the state in which the beacon frame information of the channel number of the capture target captured by the capture process does not meet the determination condition continues for a predetermined time or longer. It is characterized in that it executes a determination process for setting a new channel number to be captured.

Further, the present invention is a capture device that captures a wireless frame communicated between a plurality of wireless access devices and a wireless terminal device, and a beacon frame transmitted from the plurality of wireless access devices on a plurality of different wireless channels. At least one receiving unit that receives the radio frame including the above, a scanning unit that scans the beacon frames of a plurality of the radio channels received by the receiving unit and outputs the beacon frame information, and a channel number to be captured. The capture unit that captures the wireless frame and stores information about the wireless frame, and the channel number of the beacon frame information when the beacon frame information output from the scanning unit meets the determination conditions are captured. When the beacon frame information of the channel number of the capture target captured by the capture unit continues for a predetermined time or longer, the channel number of the new capture target is set to the channel number of. It is characterized by having a determination unit for setting.

The wireless frame capture method and the capture device according to the present invention capture the wireless frames transmitted and received by the wireless terminal device that moves by switching the wireless access device to be connected when there are a plurality of wireless access devices to be connected. Can be done.

It is a figure which shows an example of the wireless LAN system and the capture apparatus which concerns on each embodiment. It is a figure which shows an example of RSSI at each point. It is a figure which shows the configuration example of the capture apparatus which concerns on 1st Embodiment. It is a figure which shows an example of the basic process of the capture apparatus which concerns on 1st Embodiment. It is a figure which shows the operation example of the capture apparatus which concerns on 1st Embodiment. It is a figure which shows the processing example of the scan mode of the capture apparatus which concerns on 1st Embodiment. It is a figure which shows the processing example of the normal mode of the capture apparatus which concerns on 1st Embodiment. It is a figure which shows the configuration example of the capture apparatus of the comparative example. It is a figure which shows the configuration example of the capture apparatus which concerns on 2nd Embodiment. It is a figure which shows the processing example of the capture apparatus which concerns on 2nd Embodiment. It is a figure which shows the processing example of the capture apparatus which concerns on 2nd Embodiment. It is a figure which shows the operation example of the capture apparatus which concerns on 2nd Embodiment.

Hereinafter, the method of capturing the wireless frame and the embodiment of the capture device according to the present invention will be described with reference to the drawings.

FIG. 1 shows an example of the wireless LAN system 100 and the capture device 103 according to each embodiment.

In FIG. 1, the capture device 103 is a wireless LAN frame transmitted / received by a wireless LAN system 100 including a plurality of wireless access devices (AP101 (1), AP101 (2) and AP101 (3)) and a wireless LAN terminal device 102. To capture. In the example of FIG. 1, the communication quality experienced by the user of the wireless LAN terminal device 102 moving from the point (1) to the point (3) is evaluated.

Here, the operation of intercepting the transmitted / received wireless LAN frame, capturing the target wireless LAN frame, and saving the information obtained from the captured wireless LAN frame in a memory or the like is referred to as capture. The information obtained from the captured wireless LAN frame is, for example, reception time, channel number, RSSI, SSID, data rate, source identifier, destination identifier, communication data, and the like. That is, the capture device 103 has a function of a data logger that stores the wireless LAN frame itself and various information obtained from the wireless LAN frame. Here, the SSID (network identifier) is the name of the configured network and can be set in a plurality of APs. If the same SSID is set for a plurality of AP101s, the wireless LAN terminal device 102 automatically switches to another AP101 when the RSSI of the connected AP101 becomes less than the threshold value due to movement or the like. , You can continue to access the upper network.

The information obtained from the wireless LAN frame captured and accumulated by the capture device 103 is analyzed by evaluation software such as a personal computer, and the communication quality experienced by the user of the wireless LAN terminal device 102 is evaluated. Here, the quality evaluation is performed on basic numerical values related to communication such as throughput, packet loss rate, data error rate, and number of retransmissions. Alternatively, the quality on the application may be evaluated virtually by assuming an application (video communication or the like) used by the wireless LAN terminal device 102.

The capture device 103 does not need to follow the user who uses the specific wireless LAN terminal device 102, but moves a route assuming the wireless LAN terminal device 102 whose communication quality is to be evaluated, and actually transmits and receives. The wireless LAN frame to be captured is captured.

In the example of FIG. 1, the communication quality when the measurer moves the capture device 103 from the point (1) to the point (3) via the point (2) and the virtual wireless LAN terminal device 102 moves on the same route. Capture a wireless LAN frame to evaluate.

Here, the same SSID (“sample” in FIG. 1) is set for AP101 (1) at the point (1), AP101 (2) at the point (2), and AP101 (3) at the point (3). It is assumed that there is. The plurality of AP 101s use radio channels of different frequency bands (channel numbers) predetermined in order to avoid interference. In the example of FIG. 1, the channel number of AP101 (1) is Ch36, the channel number of AP101 (2) is Ch52, and the channel number of AP101 (3) is Ch100.

FIG. 2 shows an example of RSSI at each point. In FIG. 2, the point (1) to the point (3) corresponds to the point (1) to the point (3) shown in FIG. In the case of a wireless LAN frame with channel number = Ch36 transmitted from AP101 (1), RSSI at point (1) is -60 dBm, RSSI at point (2) is -65 dBm, and RSSI at point (3) is-. It is 70 dBm. Further, in the case of a wireless LAN frame having a channel number = Ch52 transmitted from AP101 (2), the RSSI at the point (1) is -65 dBm, the RSSI at the point (2) is -60 dBm, and the RSSI at the point (3) is -65 dBm. It is -65 dBm. Similarly, in the case of a wireless LAN frame having a channel number = Ch100 transmitted from AP101 (3), the RSSI at the point (1) is -70 dBm, the RSSI at the point (2) is -65 dBm, and the point (3). RSSI is -60 dBm.

Here, the threshold value of RSSI for determining whether or not the wireless LAN terminal device 102 switches the connection destination AP101 to another AP101 is set to -60 dBm. In the example of FIG. 2, as shown by the dotted line circle, the RSSI at the point (1) is above the threshold value at Ch36, and at the point (2), the RSSI is at the threshold value or more at Ch52 and the point (3). ), The RSSI is equal to or higher than the threshold value in Ch100. In this case, since the wireless LAN terminal device 102 connects to the AP101 having a channel number whose RSSI is equal to or higher than the threshold value at each point, the wireless LAN terminal device 102 connects to the AP101 (1) of Ch36 at the point (1). Then, as the wireless LAN terminal device 102 moves, it automatically connects to AP101 (2) of Ch52 at the point (2) and AP101 (3) of Ch100 at the point (3). If there are a plurality of wireless channels whose RSSI is equal to or higher than the threshold value, the wireless channel having the maximum RSSI may be connected. Alternatively, the channel numbers may be scanned in order so that the radio channel with RSSI greater than or equal to the threshold is connected to the radio channel with the first channel number found.

[First Embodiment]
FIG. 3 shows a configuration example of the capture device 103 according to the first embodiment. In FIG. 3, the capture device 103 includes a reception unit 201, a setting unit 202, a capture unit 203, a determination unit 204, and a channel scan unit 205.

Here, the capture device 103 according to the first embodiment has a scan mode for searching for a channel number of the AP 101 that transmits a beacon frame that matches a predetermined determination condition among the channel numbers for which the same SSID is set. .. Then, it has a normal mode of capturing a wireless LAN frame having a channel number that matches the determination condition searched in the scan mode. The determination conditions are two conditions: the SSID of the beacon frame is the SSID of the capture target, and the RSSI of the beacon frame is equal to or higher than the threshold value.

The receiving unit 201 includes a wireless LAN interface, and receives wireless LAN frames transmitted from a plurality of AP 101s with different channel numbers in the scan mode and the normal mode (reception processing). Here, the wireless LAN frame includes a control frame for access control such as ACK, a management frame such as a beacon frame for notifying the existence of a network, and a data frame for communicating user data. The receiving unit 201 outputs the received wireless LAN frame to the capture unit 203 or the channel scanning unit 205.

In the setting unit 202, the SSID to be captured is set by the measurer before the operation starts. The set SSID of the capture target is notified to the determination unit 204. Further, when the determination unit 204 notifies the channel number to be captured, the setting unit 202 sets the capture unit 203. The channel number notified from the determination unit 204 is the channel number of the AP 101 that transmits the beacon frame that matches the determination condition described above.

In the normal mode, the capture unit 203 captures the wireless LAN frame of the channel number set by the setting unit 202, and stores the information obtained from the wireless LAN frame in an internal memory or the like (capture processing). After the operation of the capture device 103 is completed, the measurer analyzes the information stored in the memory or the like with an evaluation device such as a personal computer, and evaluates the communication quality or the like experienced by the user of the wireless LAN terminal device 102.

The determination unit 204 operates in either the scan mode or the normal mode, and performs the following processing in each mode (determination processing). In the initial state at the start of operation, the determination unit 204 operates in the scan mode. In the scan mode, the determination unit 204 determines whether or not the beacon frame of the channel number scanned by the channel scan unit 205 matches the determination condition. When the determination condition is satisfied, the determination unit 204 notifies the setting unit 202 of the channel number of the beacon frame. If the determination condition is not met, the determination unit 204 waits until the channel scan unit 205 notifies the information of the next beacon frame (referred to as beacon frame information). On the other hand, in the normal mode, the determination unit 204 determines whether or not the beacon frame of the channel number to be captured output from the capture unit 203 matches the determination condition. If the determination condition is met, the determination unit 204 initializes the time counter to 0. Here, the time counter is a counter for measuring the elapsed time from the reception time when the beacon frame finally meets the determination condition. For example, the time counter can be realized by holding the reception time of the beacon frame of the channel number that matches the determination condition. In this case, the difference between the current time and the held reception time is the count value (that is, the elapsed time) of the time counter. In the scan mode, even when the determination condition is met, the time counter is initialized to 0 and the measurement of the elapsed time is started. On the other hand, the determination unit 204 shifts to the scan mode when the beacon frame of the channel number to be captured output from the capture unit 203 does not meet the determination condition or when the elapsed time exceeds a certain time. Here, when the elapsed time exceeds a certain time, it means that the state of not meeting the judgment condition has continued for a certain time or more since the last time when the judgment condition was met.

The channel scan unit 205 acquires a beacon frame among the wireless LAN frames received by the reception unit 201 and notifies the determination unit 204 of the beacon frame information (channel number, SSID, RSSI, etc.) (scan processing). The channel scan unit 205 switches and circulates the channel numbers that may communicate in the wireless LAN system 100 in order at predetermined time intervals, stays at the switched channel numbers for a certain period of time, and stays in the switched channel numbers for a certain period of time, and the beacon frame of the channel number. To receive. For example, in the case of FIG. 1, the channel scanning unit 205 switches the three channel numbers of Ch36, Ch52, and Ch100 in order and circulates, and stays at each channel number for a certain period of time (for example, 100 msec) to receive a beacon frame. Then, when the channel scan unit 205 receives the beacon frame transmitted by the AP 101, the channel scan unit 205 notifies the determination unit 204 of the scanned channel number, the SSID of the beacon frame, and the RSSI information. Specifically, for example, when the determination unit 204 instructs the channel scan unit 205 to scan, the channel scan unit 205 switches the channel numbers in order and receives the beacon frame by the reception unit 201. Then, the channel scan unit 205 notifies the determination unit 204 of the beacon frame information (channel number, SSID, RSSI, etc.) received by the reception unit 201. Here, the plurality of channel numbers to be scanned are preset according to the wireless LAN standard to be used. The determination unit 204 instructs the channel scan unit 205 to scan the beacon frame at a predetermined time interval (for example, 100 msec).

In this way, the capture device 103 according to the first embodiment can scan the beacon frame to determine the channel number that matches the determination condition, and set it in the capture unit 203. As a result, the capture device 103 can capture the wireless LAN frames transmitted and received by the wireless LAN terminal device 102 that moves while switching to the AP 101 having a channel number whose RSSI is equal to or higher than the threshold value.

(Basic processing)
FIG. 4 shows an example of the basic processing of the capture device 103 according to the first embodiment. Here, the process shown in FIG. 4 is executed by each block constituting the capture device 103 described with reference to FIG.

In step S101, the capture device 103 starts the capture operation. Before starting the operation, it is assumed that the measurer sets the threshold values of the SSID and RSSI to be captured in the setting unit 202.

In step S102, the determination unit 204 shifts to the scan mode and instructs the channel scan unit 205 to scan the beacon frame.

In step S103, the channel scan unit 205 receives the beacon frame and outputs the beacon frame information to the determination unit 204. Here, the beacon frame information includes at least the channel number, SSID and RSSI.

In step S104, the determination unit 204 determines whether or not the beacon frame information received from the channel scan unit 205 matches the determination condition. Then, if they match, the process proceeds to step S105, and if they do not match, the process returns to step S102.

In step S105, the determination unit 204 notifies the setting unit 202 of the channel number of the beacon frame that matches the determination condition, and the setting unit 202 sets the channel number in the capture unit 203. Further, the determination unit 204 initializes the time counter to 0. The time counter is a counter for measuring the elapsed time from the reception time when the beacon frame finally meets the determination condition. The time counter can be realized, for example, by holding the reception time of the beacon frame that matches the determination condition. In this case, the difference between the current time and the held reception time is the count value (that is, the elapsed time) of the time counter.

In step S106, the determination unit 204 shifts from the scan mode to the normal mode.

In step S107, the capture unit 203 captures the wireless LAN frame of the channel number set by the setting unit 202, and stores information about the wireless LAN frame in a memory or the like.

In step S108, the determination unit 204 determines whether or not a certain time has elapsed from the time when the beacon frame matching the determination condition was last received. Whether or not a certain time has elapsed is determined by whether or not the difference between the reception time and the current time when the beacon frame last matches the determination condition is a certain time (for example, 250 msec) or more. If the difference is longer than a certain time, the process returns to step S102, and if the difference is less than a certain time, the process proceeds to step S109.

In step S109, the capture unit 203 notifies the determination unit 204 of the information of the beacon frame received by the channel number set in the setting unit 202.

In step S110, the determination unit 204 determines whether or not the beacon frame information received from the channel scan unit 205 matches the determination condition. Then, if they match, the process proceeds to step S111, and if they do not match, the process returns to step S107.

In step S111, the determination unit 204 initializes the time counter to 0 and returns to the process of step S107. As a result, when the beacon frame information matches the determination condition, the capture mode does not shift to the scan mode, and the capture unit 203 can continue to capture the wireless LAN frame of the channel number set in the setting unit 202.

In this way, the capture device 103 according to the first embodiment is a wireless LAN frame transmitted / received between the AP 101 and the wireless LAN terminal device 102 that transmit a beacon frame having a channel number whose beacon frame information matches the determination condition. Can be captured. As a result, in a situation where there are a plurality of AP101s to be connected, it is possible to follow and capture the wireless LAN frames transmitted and received by the wireless LAN terminal device 102 that moves while switching the AP101s.

Here, in reality, it is not necessary for the measurer to carry the capture device 103 and move with the user of the wireless LAN terminal device 102, and the measurer captures by assuming the movement of the user of the wireless LAN terminal device 102. All you have to do is move the device 103. As a result, the capture device 103 can capture the wireless LAN frame while automatically switching to the AP 101 that matches the determination condition, similarly to the wireless LAN terminal device 102. After the capture is completed, the measurer analyzes the data accumulated by the capture unit 203 of the capture device 103 with evaluation software such as a personal computer, and confirms the communication quality and the like experienced by the user of the wireless LAN terminal device 102. ..

FIG. 5 shows an operation example of the capture device 103 according to the first embodiment. In FIG. 5, the horizontal axis indicates time (msec), and the channel scanning unit 205 patrolls the three channel numbers of Ch36, Ch52, and Ch100 in order at intervals of 100 msec, scans the beacon frame, and determines. It is determined whether or not the unit 204 meets the determination condition. It is assumed that the determination as to whether or not the beacon frame meets the determination condition is executed with a cycle of 100 msec for the beacon frame received by the channel scan unit 205 or the capture unit 203. Further, in the example of FIG. 5, it is assumed that the state shifts to the scan mode when the state that does not meet the determination condition continues for a certain period of time (250 msec) or more in the normal mode. Here, in the following description, a fixed time is referred to as a time-out time.

In FIG. 5, t_cur indicates the current time, t_last indicates the time when the beacon frame matching the determination condition was last received, and (t_cur)-(t_last) indicates the elapsed time. Further, the scan Ch indicates the channel number scanned by the channel scan unit 205, and the capture Ch indicates the channel number of the capture target set in the capture unit 203.

In FIG. 5, the measurer performs the initial setting of the capture device 103, for example, at the point (2) in FIG. 1, and starts the measurement. For example, the SSID = sample and the threshold value of RSSI = -60 dBm to be measured are initially set in the capture device 103. Here, the RSSIs at the points (2) of Ch36 of AP101 (1), Ch52 of AP101 (2) and Ch100 of AP101 (3) in which the same SSID (sample) is set are -65 dBm, -60 dBm, and -70 dBm, respectively. Suppose that Hereinafter, the initial values of t_cur and t_last will be described as 0.

Since the determination unit 204 of the capture device 103 is in the initial state at t_cur = 0 msec, the operation is started in the scan mode, and the channel scan unit 205 is instructed to scan. The channel number that the channel scan unit 205 scans first is Ch36. However, since the scan result of Ch36 (SSID: 〇, RSSI: ×) does not meet the determination condition, the capture Ch is not yet set and the state is in a standby state. Here, 〇 indicates that they match, and × indicates that they do not match. For example, SSID: 〇 indicates that SSID is simple, and SSID: × indicates that SSID is not possible. Similarly, RSSI: 〇 indicates that RSSI is above the threshold value, and RSSI: × indicates that RSSI is below the threshold value. In the example of FIG. 5, since the SSIDs of AP101 (1) to AP101 (3) are all simple, all SSIDs are: 〇, but if there are AP101s with different SSIDs, SSID: ×.

At t_cur = 100 msec, the channel number scanned by the channel scan unit 205 is Ch52, and the scan result of Ch52 (SSID: 〇, RSSI: 〇) matches the determination condition. Therefore, the determination unit 204 notifies the setting unit 202 of Ch52 as the capture Ch, and the setting unit 202 sets Ch52 in the capture unit 203. Further, the determination unit 204 sets the current time t_cur to t_last as the reception time of the Beacon frame of Ch52 that matches the determination condition (t_last = 100 msec). The current time is changing from moment to moment, but here, for the sake of easy understanding, the time 100 msec when the scan is started is set to t_last. Further, the determination unit 204 shifts from the scan mode to the normal mode. In the normal mode, the capture unit 203 operates regardless of the interval of 100 msec, and always captures the wireless LAN frame transmitted / received between the wireless LAN terminal device 102 and the AP 101.

At t_cur = 200 msec, the channel number, SSID, and RSSI of Ch52 received by the capture unit 203 are notified to the determination unit 204. Since the beacon frame matches the determination conditions (SSID: 〇, RSSI: 〇), the determination unit 204 does not change the capture Ch and maintains the current Ch 52. Further, since the beacon frame of Ch52 matches the determination condition, the determination unit 204 sets the current time t_cur to t_last as the reception time of the beacon frame (t_last = 200 msec).

At t_cur = 270 msec, changes in conditions such as fluctuations in obstacles, automatic control functions for radio wave transmission levels, and movement of wireless LAN terminal devices occur. As a result, the RSSIs of Ch36 of AP101 (1), Ch52 of AP101 (2) and Ch100 of AP101 (3) are changed to −60 dBm, −70 dBm and −65 dBm, respectively.

At t_cur = 300 msec, the channel number, SSID, and RSSI of Ch52 received by the capture unit 203 are notified to the determination unit 204. At this time, since RSSI (−70 dBm) of Ch52 is equal to or less than the threshold value, the determination unit 204 determines that the beacon frame does not meet the determination condition (SSID: 〇, RSSI: ×). Further, since (t_cur)-(t_last) is 300-200 = 100 msec, the timeout time is less than T (250 msec), and the determination unit 204 maintains the normal mode.

At t_cur = 400 msec, the channel number, SSID, and RSSI of Ch52 received by the capture unit 203 are notified to the determination unit 204. Since the RSSI (−70 dBm) of Ch52 is equal to or less than the threshold value as in the case of t_cur = 300 msec, the determination unit 204 determines that the beacon frame does not meet the determination conditions (SSID: 〇, RSSI: ×). Further, since (t_cur)-(t_last) is 400-200 = 200 msec, the timeout time is less than T (250 msec), and the determination unit 204 maintains the normal mode.

At t_cur = 500 msec, (t_cur)-(t_last) is 500-200 = 300 msec, so the timeout time is T (250 msec) or more. As a result, the determination unit 204 shifts to the scan mode and commands the channel scan unit 205 to scan. The channel scan unit 205 scans Ch100 with the channel number next to Ch52 that was scanned last time. At this time, the RSSI of Ch100 is −75 dBm, and the scan result (SSID: 〇, RSSI: ×) does not meet the determination condition. The determination unit 204 maintains the scan mode, and the capture Ch is not set.

At t_cur = 600 msec, the channel scan unit 205 scans Ch36, which is the channel number next to Ch100 that was scanned last time. At this time, the RSSI of Ch36 is −60 dBm, and the scan results (SSID: 〇, RSSI: 〇) meet the determination conditions. Therefore, the determination unit 204 notifies the setting unit 202 of Ch36 as the capture Ch, and the setting unit 202 sets Ch36 in the capture unit 203. Further, the determination unit 204 sets the current time to t_last as the reception time of the Beacon frame of Ch36 that matches the determination condition, t_last = 600 msec, and (t_cur)-(t_last) becomes 600-600 = 0 msec. Further, the determination unit 204 shifts from the scan mode to the normal mode. Then, the capture unit 203 restarts the capture of the wireless LAN frame with the capture Ch set to Ch36.

In this way, the capture device 103 according to the first embodiment can set the channel number whose RSSI is equal to or higher than the threshold value in the capture unit 203 from the AP 101 that transmits the beacon frame of the SSID to be measured. As a result, when there are a plurality of AP101s to be connected, the wireless LAN frames transmitted and received by the wireless LAN terminal device 102 are captured following the wireless LAN terminal device 102 that switches and moves the wireless access device of the connection destination. Can be done.

After the capture is completed, the measurer analyzes the information obtained from the captured wireless LAN frame using evaluation software such as a personal computer, and evaluates the communication quality such as throughput and packet loss rate.

(Scan mode)
FIG. 6 shows a processing example of the scan mode of the capture device 103 according to the first embodiment. The process shown in FIG. 6 corresponds to FIG.

In step S201, the determination unit 204 starts the scan mode.

In step S202, the determination unit 204 instructs the channel scan unit 205 to start scanning the beacon frame.

In step S203, the determination unit 204 acquires the beacon frame information (channel number, SSID, RSSI, etc.) scanned from the channel scan unit 205.

In step S204, the determination unit 204 determines whether or not the SSID and RSSI acquired in step S203 meet the determination conditions. Here, the determination condition is that the SSID is the SSID to be captured and the RSSI of the beacon frame is equal to or higher than the threshold value (TH), as described above. If the determination conditions are met, the process proceeds to step S205, and if the determination conditions are not met, the process returns to step S202.

In step S205, the determination unit 204 instructs the channel scan unit 205 to end the scanning of the beacon frame, and sets t_last to t_cur. Further, the determination unit 204 notifies the setting unit 202 of the channel number of the capture target, and the setting unit 202 sets the channel number of the capture target in the capture unit 203. Then, the determination unit 204 shifts from the scan mode to the normal mode.

In step S206, the determination unit 204 ends the scan mode.

(Normal mode)
FIG. 7 shows a processing example of the normal mode of the capture device 103 according to the first embodiment. The process shown in FIG. 7 corresponds to the operation shown in FIG. Here, in FIG. 7, in the normal mode, the processing of the operation A and the processing of the operation B are executed. First, the process of operation A will be described.

In step S301, the determination unit 204 starts the process of operation A in the normal mode.

In step S302, the determination unit 204 acquires the SSID and RSSI of the beacon frame received by the capture unit 203 at the channel number to be captured.

In step S303, the determination unit 204 determines whether or not the SSID and RSSI of the beacon frame acquired in step S302 meet the determination conditions. The determination conditions are the same as in S204 of FIG. If the determination conditions are met, the process proceeds to step S304, and if the determination conditions are not met, the process returns to step S302.

In step S304, the determination unit 204 sets t_last to t_cur. In the normal mode, the determination unit 204 repeatedly executes the process of operation A from step S302 to step S304.

Next, in FIG. 7, the processing of the operation B in the normal mode will be described.

In step S311, the determination unit 204 starts the process of operation B when the mode shifts to the normal mode.

In step S312, the determination unit 204 determines whether or not a certain time has elapsed. Specifically, the determination unit 204 waits until (t_cur-t_last) becomes equal to or longer than the predetermined timeout time T, and when (t_cur-t_last) ≧ T, proceeds to the process of step S313.

In step S313, the determination unit 204 shifts from the normal mode to the scan mode.

In step S314, the determination unit 204 ends the process of operation B in the normal mode.

As described above, during the normal mode, the processing of the operation A and the processing of the operation B are executed in parallel, and when the normal mode is changed to the scan mode in step S313, both processes are terminated. Further, the process of operation B may be always executed during the normal mode, or may be executed at a fixed cycle such as a 500 msec cycle in order to reduce the processing load.

[Comparison example]
FIG. 8 shows a configuration example of the capture device 803 of the comparative example. In FIG. 8, the capture device 803 has a reception unit 901, a setting unit 902, and a capture unit 903. Here, the receiving unit 901, the setting unit 902, and the capture unit 903 correspond to the receiving unit 201, the setting unit 202, and the capture unit 203 of the capture device 103 according to the first embodiment described with reference to FIG. In the comparative example, the case where the capture unit 903 is used in the wireless LAN system 100 described with reference to FIG. 1 will be described.

The receiving unit 901 includes a wireless LAN interface and receives wireless LAN frames transmitted from a plurality of AP 101s with different channel numbers. The receiving unit 901 outputs the received wireless LAN frame to the capture unit 903.

In the setting unit 902, the SSID to be captured is set by the measurer before the operation starts. At this time, the measurer inputs the channel number used by AP101 whose RSSI is equal to or higher than the threshold value (or maximum) at the time of setting to the setting unit 902 as the channel number to be captured. The setting unit 902 sets the channel number input by the measurer as the capture target channel number in the capture unit 903.

The capture unit 903 captures the wireless LAN frame of the channel number to be captured set by the setting unit 902. The information obtained from the wireless LAN frame captured and accumulated by the capture unit 903 is analyzed by the measurer after the operation of the capture device 803 is completed, and the communication quality and the like are evaluated.

Here, the capture device 803 of the comparative example continues to capture the wireless LAN frame of the channel number set in the measurer. In this case, it is possible to evaluate the communication quality of the wireless LAN terminal device 102 which is fixed at a certain point and is used in a communication situation where the RSSI does not change. However, when the wireless LAN terminal device 102 moves from the point (1) to the point (2) or the point (3), the communication status may change and the RSSI may fluctuate. When the RSSI of the wireless LAN frame of the channel number being connected becomes less than the threshold value, the wireless LAN terminal device 102 automatically switches to the AP101 of the channel number for transmitting the wireless LAN frame of the RSSI of the threshold value or more. To continue communication. However, since the capture device 803 of the comparative example continues to capture the wireless LAN frame of the channel number set by the measurer, it cannot capture the wireless LAN frame of the channel number switched by the wireless LAN terminal device 102.

As described above, the conventional capture device 803 cannot continue to capture the wireless LAN frame following the wireless LAN terminal device 102 that moves while switching between the plurality of AP 101s, and the communication experienced by the user of the wireless LAN terminal device. I can't check the quality.

On the other hand, the capture device 103 according to the first embodiment (or the capture device 103a according to the second embodiment described later) can scan and capture the channel number of the beacon frame that matches the determination condition. .. As a result, when there are a plurality of AP101s to be connected, it is possible to capture the wireless LAN frames transmitted and received by the wireless LAN terminal device 102 following the wireless LAN terminal device 102 that switches and moves the connection destination AP101. become.

[Second Embodiment]
FIG. 9 shows a configuration example of the capture device 103a according to the second embodiment. In FIG. 9, the capture device 103a has a scan block 301 and a capture block 302.

The scan block 301 has a function of performing only a scan process for searching for a channel number that matches a predetermined determination condition among beacon frames of a plurality of channel numbers for which the same SSID is set.

The capture block 302 performs a process of capturing a wireless LAN frame having a channel number that matches the determination condition scanned by the scan block 301. Further, the capture block 302 performs a process of setting a channel number that matches the determination condition when the beacon frame of the channel number to be captured does not match the determination condition.

The scan block 301 has a first receiving unit 201a and a channel scanning unit 205a.

The first receiving unit 201a includes a wireless LAN interface, and similarly to the receiving unit 201 of the first embodiment, receives wireless LAN frames transmitted from a plurality of AP 101s with different channel numbers (reception processing). The first receiving unit 201a is different from the receiving unit 201 of the first embodiment in that it is a receiver dedicated to the channel scanning unit 205a. This eliminates the need to switch between the scan mode and the normal mode as in the capture device 103 according to the first embodiment, and the scan process and the capture process can be performed independently in parallel. The first receiving unit 201a outputs the received wireless LAN frame to the channel scanning unit 205a.

The channel scan unit 205a acquires a beacon frame among the wireless LAN frames received by the first reception unit 201a, and notifies the determination unit 204a of the capture block 302 of the beacon frame information (channel number, SSID, RSSI, etc.). (Scan process). The basic operation of the channel scan unit 205a is the same as that of the channel scan unit 205 of the first embodiment. The basic operation is, for example, to cycle through the channel numbers in order at predetermined time intervals, and notify the determination unit 204a of the capture block 302 of the received beacon frame information (channel number, SSID, RSSI, etc.). And so on.

The capture block 302 has a second receiving unit 201b, a setting unit 202, a capture unit 203, and a determination unit 204a.

The second receiving unit 201b includes a wireless LAN interface, and similarly to the receiving unit 201 of the first embodiment, receives wireless LAN frames transmitted from a plurality of AP 101s with different channel numbers (reception processing). The second receiving unit 201b is different from the receiving unit 201 of the first embodiment in that it is a receiver dedicated to the capture unit 203. As a result, it is possible to operate independently of the scan block 301. The second receiving unit 201b outputs the received wireless LAN frame to the capture unit 203.

The setting unit 202 and the capture unit 203 are basically the same blocks as the setting unit 202 of the first embodiment, and operate in the same manner as the first embodiment. However, in the second embodiment, since there is no switching between the normal mode and the scan mode, the capture unit 203 can capture the wireless LAN frame even while the channel scan unit 205a is scanning the beacon frame.

The determination unit 204a operates in the same manner as the determination unit 204 of the first embodiment, but differs from the determination unit 204 in that the scan mode and the normal mode are not switched. In the capture device 103a according to the second embodiment, the channel scan unit 205a having the dedicated first reception unit 201a can always scan the beacon frame independently of the capture unit 203. Therefore, the determination unit 204a does not need to instruct the channel scan unit 205a to scan, and can acquire the beacon frame information from the channel scan unit 205a. The determination unit 204a determines whether or not the beacon frame information acquired from the channel scan unit 205a matches the determination condition, and if the determination condition is met, the channel number of the beacon frame is used as a candidate for the channel number to be captured. Hold. Then, when the state in which the determination condition is not met continues for a certain period of time, the determination unit 204a notifies the setting unit 202 of the candidate of the channel number to be captured and sets the capture unit 203.

Next, the specific processing of the determination unit 204a will be described. The determination unit 204a of the capture device 103a according to the second embodiment performs three processes of operation A, operation B, and operation C in parallel (determination process). In the process of operation A, the beacon frame information is acquired from the channel scan unit 205a and it is determined whether or not the determination condition is satisfied. In the process of operation B, the beacon frame information of the channel number to be captured is acquired from the capture unit 203, and it is determined whether or not the determination condition is satisfied. In the process of operation C, it is determined whether or not the state that does not meet the determination condition continues for a certain period of time. For example, it is determined whether or not the elapsed time from the reception time of the beacon frame when the determination condition is last met is a certain time or more. The process of operation C may be executed all the time, or may be executed at a fixed cycle such as a cycle of 500 msec in order to reduce the processing load.

FIG. 10 shows a processing example of operation A of the determination unit 204a.

In step S401, the determination unit 204a starts the process of operation A when the measurement by the capture device 103a is started.

In step S402, the determination unit 204a acquires the information (channel number, SSID, RSSI, etc.) of the beacon frame scanned from the channel scan unit 205a.

In step S403, the determination unit 204a determines whether or not the SSID and RSSI acquired in step S402 meet the determination conditions. The determination condition is that the SSID is the SSID to be measured and the RSSI is equal to or higher than the threshold value (TH), as in the first embodiment. If the determination condition is met, the process proceeds to step S404, and if the determination condition is not met, the process returns to step S402 and waits for the next beacon frame information.

In step S404, the determination unit 204a holds the channel number of the beacon frame notified from the channel scan unit 205a as a candidate channel number (Next_CH) to be set in the capture unit 203. At the time of initial setting, the channel number to be captured is not set in the capture unit 203. At this point, the determination unit 204a notifies the setting unit 202 of the channel number of Next_CH and sets it in the capture unit 203. .. Further, the determination unit 204a sets the current time (t_cur) to the last reception time (t_last) that matches the determination condition. Alternatively, when a time counter such as a timer is used without using t_last, the time counter is initialized to 0.

After that, the processes from step S402 to step S404 are repeatedly executed.

FIG. 11 shows a processing example of operation B and operation C of the determination unit 204a. First, the process of operation B will be described.

In step S411, the determination unit 204a starts the process of operation B when the measurement by the capture device 103a is started.

In step S412, the determination unit 204a acquires the beacon frame information (channel number, SSID, RSSI, etc.) of the channel number to be captured from the capture unit 203.

In step S413, the determination unit 204a determines whether or not the SSID and RSSI acquired in step S412 meet the determination conditions. The determination conditions are the same as in step S403 of FIG. If the determination condition is met, the process proceeds to step S414, and if the determination condition is not met, the process returns to step S412 and waits for the next beacon frame information.

In step S414, the determination unit 204a sets the current time (t_cur) to t_last as the reception time of the beacon frame notified from the channel scan unit 205a. Alternatively, when using a time counter such as a timer, the time counter is initialized to 0.

After that, the processes from step S412 to step S414 are repeatedly executed.

Next, in FIG. 11, the processing of the operation C of the determination unit 204a will be described.

In step S421, the determination unit 204a starts the process of operation C when the measurement by the capture device 103a is started.

In step S422, the determination unit 204a determines whether or not the difference between the current time (t_cur) and the last reception time (t_last) that matches the determination condition is equal to or greater than the predetermined timeout time T. If the difference is greater than or equal to the timeout time T, the process proceeds to step S423, and if the difference is less than the timeout time T, the process returns to step S422.

In step S423, the determination unit 204a notifies the setting unit 202 of the channel number candidate (Next_CH) held in the process of operation A, and the setting unit 202 sets the channel number in the capture unit 203. Then, the process returns to the process of step S422.

As described above, in the process of operation C, the processes of step S422 and step S423 are repeatedly executed.

In this way, the capture device 103a according to the second embodiment holds the channel number of the beacon frame as a candidate for the channel number to be captured when the beacon frame information acquired from the channel scan unit 205a matches the determination condition. do. Then, when the state in which the determination condition is not met continues for a certain period of time, the determination unit 204a notifies the setting unit 202 of the candidate of the held channel number, and the channel number is set in the capture unit 203. As a result, the capture device 103a according to the second embodiment follows the wireless LAN terminal device 102 that moves by switching the wireless access device of the connection destination when a plurality of AP101s to be connected exist, and the wireless LAN terminal device. It is possible to capture wireless LAN frames transmitted and received by 102.

Further, since the capture device 103a according to the second embodiment has a wireless LAN interface dedicated to the channel scan unit 205a, the time required for channel switching can be shortened as compared with the capture device 103 according to the first embodiment. ..

FIG. 12 shows an operation example of the capture device 103a according to the second embodiment. Note that FIG. 12 shows the operation under the same conditions as in FIG. 5 of the first embodiment.

In FIG. 12, the measurer performs the initial setting of the capture device 103, for example, at the point (2) in FIG. 1, and starts the measurement. For example, the SSID = sample and the threshold value of RSSI = -60 dBm to be measured are initially set in the capture device 103. Here, the RSSIs at the points (2) of Ch36 of AP101 (1), Ch52 of AP101 (2) and Ch100 of AP101 (3) in which the same SSID (sample) is set are -65 dBm, -60 dBm, and -70 dBm, respectively. Suppose that Hereinafter, the initial values of t_cur and t_last will be described as 0.

At t_cur = 0 msec, the channel number first scanned by the channel scan unit 205a is Ch36, but the scan result of Ch36 (SSID: 〇, RSSI: ×) does not meet the determination conditions, so the capture Ch is not yet set.

At t_cur = 100 msec, the channel number scanned by the channel scan unit 205a is Ch52, and the scan result of Ch52 matches the determination conditions (SSID: 〇, RSSI: 〇). In this case, the determination unit 204a holds Ch52 as a candidate (Next_CH) for the channel number to be set in the capture unit 203 next. Here, the processing is slightly different depending on whether or not it is in the initial state. Whether or not it is in the initial state can be determined by whether or not the value of Next_CH before holding Ch52 is the initial value 0. Then, when it is not in the initial state (when the channel number is set in the capture unit 203), the determination unit 204a only holds the candidate channel number (Next_CH). In the initial state (when the channel number is not set in the capture unit 203), the determination unit 204a notifies the setting unit 202 of the channel number candidate (Next_CH), and the setting unit 202 notifies the capture unit 203 of Next_CH (Ch52). ) Is set. Further, the determination unit 204a sets the current time t_cur to t_last as the reception time of the Beacon frame of Ch52 that matches the determination condition (t_last = 100 msec). After that, the capture unit 203 starts capturing the wireless LAN frame transmitted / received between the wireless LAN terminal device 102 and the AP 101 with the set Ch52.

At t_cur = 200 msec, the channel scan unit 205a scans the beacon frame whose channel number is Ch100. In the process of operation A, the determination unit 204a holds Next_CH as Ch52 because the scan result (SSID: 〇, RSSI: ×) of Ch100 acquired from the channel scan unit 205a does not meet the determination condition. On the other hand, the capture unit 203 receives the beacon frame of Ch52 and notifies the determination unit 204a of the channel number, SSID, and RSSI. The determination unit 204a executes the process of operation B, and since the beacon frame of Ch52 matches the determination condition (SSID: 〇, RSSI: 〇), the current time t_cur is set to t_last as the reception time of the beacon frame (SSID: 〇, RSSI: 〇). t_last = 200msec).

At t_cur = 300 msec, the channel scan unit 205a scans the beacon frame whose channel number is Ch36. Here, the RSSI (-60 dBm) of Ch36 is equal to or higher than the threshold value. In the process of operation A, the determination unit 204a newly holds Ch36 in Next_CH because the scan result (SSID: 〇, RSSI: 〇) of Ch36 acquired from the channel scan unit 205a matches the determination condition. On the other hand, the capture unit 203 receives the beacon frame of Ch52 and notifies the determination unit 204a of the channel number, SSID, and RSSI. At this time, the RSSI (−70 dBm) of Ch52 is less than the threshold value. The determination unit 204a determines that the beacon frame of Ch52 does not meet the determination condition (SSID: 〇, RSSI: ×) in the process of operation B. Here, in the process of operation C, the determination unit 204a does not notify the setting unit 202 because (t_cur)-(t_last) is 300-200 = 100 msec and the timeout time is less than T (250 msec), and the capture Ch. Ch 52 is maintained.

At t_cur = 400 msec, the channel scan unit 205a scans the beacon frame whose channel number is Ch52 next to the previously scanned Ch36. Here, the RSSI (-70 dBm) of Ch52 is less than the threshold value. In the process of operation A, the determination unit 204a holds Next_CH as Ch36 because the scan result (SSID: 〇, RSSI: ×) of Ch52 acquired from the channel scan unit 205a does not meet the determination condition. On the other hand, the capture unit 203 receives the beacon frame of Ch52 and notifies the determination unit 204a of the channel number, SSID, and RSSI. Similar to operation A, the RSSI (-70 dBm) of Ch52 is less than the threshold value. The determination unit 204a executes the process of operation B, and determines that the beacon frame of Ch52 does not meet the determination condition (SSID: 〇, RSSI: ×). Here, in the process of operation C, the determination unit 204a does not notify the setting unit 202 because (t_cur)-(t_last) is 400-200 = 200 msec and the timeout time is less than T (250 msec), and the capture Ch. Ch 52 is maintained.

At t_cur = 500 msec, the channel scan unit 205a scans the beacon frame of Ch100 with the channel number next to Ch52 that was scanned last time. Here, the RSSI (-65 dBm) of Ch100 is less than the threshold value. In the process of operation A, the determination unit 204a holds Ch36 in Next_CH because the scan result (SSID: 〇, RSSI: ×) of Ch100 acquired from the channel scan unit 205a does not meet the determination condition. On the other hand, the capture unit 203 receives the beacon frame of Ch52 and notifies the determination unit 204a of the channel number, SSID, and RSSI. The determination unit 204a determines that the determination condition (SSID: 〇, RSSI: ×) is not met because the RSSI (-70 dBm) of the Beacon frame of Ch52 acquired from the capture unit 203 is less than the threshold value in the process of the operation B. do. Further, in the process of the operation C, the determination unit 204a has a timeout time T (250 msec) or more because (t_cur) − (t_last) is 500-200 = 300 msec. Therefore, the determination unit 204a notifies the setting unit 202 of the channel number (Ch36) held in Next_CH, and the setting unit 202 sets Ch36 in the capture unit 203. As a result, the channel number of the capture target of the capture unit 203 is changed from Ch52 to Ch36. After that, the capture unit 203 captures the wireless LAN frame transmitted / received by Ch36 with Ch36 as the channel number to be captured.

At t_cur = 600 msec, the channel scan unit 205a scans Ch36, which is the channel number next to Ch100 that was scanned last time. At this time, the RSSI (-60 dBm) of Ch36 is equal to or higher than the threshold value. In the process of operation A, the determination unit 204a holds the Ch36 held in Next_CH as it is because the scan result (SSID: 〇, RSSI: 〇) of Ch36 acquired from the channel scan unit 205a matches the determination condition. To. On the other hand, in the process of operation B, the determination unit 204a sets the current time t_cur to t_last as the reception time of the beacon frame because the beacon frame of Ch36 acquired from the capture unit 203 matches the determination condition (t_last = 600 msec). ). Further, in the process of the operation C, the determination unit 204a has a timeout time T (250 msec) or less because (t_cur) − (t_last) is 600-600 = 0 msec, and the capture Ch is maintained at Ch36.

In this way, the capture device 103a according to the second embodiment can scan the beacon frame of the SSID to be measured and switch to the channel number whose RSSI is equal to or higher than the threshold value. As a result, when there are a plurality of AP101s to be connected, it is possible to capture the wireless LAN frames transmitted and received by the wireless LAN terminal device 102 following the wireless LAN terminal device 102 that switches and moves the connection destination AP101. become.

After the capture is completed, the measurer analyzes the information obtained from the wireless LAN frame captured by the capture device 103a using evaluation software such as a personal computer, and evaluates the communication quality such as throughput and packet loss rate. do.

As described above, as described in each embodiment, the wireless frame capture method and the capture device according to the present invention are wireless devices that switch and move the wireless access device to be connected when there are a plurality of wireless access devices to be connected. It is possible to capture wireless frames sent and received by the terminal device. This makes it possible to continue capturing wireless frames following a wireless terminal device that moves while switching between a plurality of wireless access devices, and it is possible to confirm the communication quality experienced by the user of the wireless terminal device.

100 ... wireless LAN system; 101 ... AP; 102 ... wireless LAN terminal device; 103, 103a, 803 ... capture device; 201, 901 ... receiver; 201a ... first reception Unit; 201b ... Second receiving unit; 202,902 ... Setting unit; 203,903 ... Capture unit; 204,204a ... Judgment unit; 205,205a ... Channel scanning unit

Claims

It is a capture method when a capture device captures a wireless frame communicated between a plurality of wireless access devices and a wireless terminal device.
A reception process in which at least one receiving unit receives the wireless frame including a beacon frame transmitted from the plurality of wireless access devices on a plurality of different wireless channels.
A scanning process that scans the beacon frames of a plurality of the wireless channels received by the receiving unit and outputs the beacon frame information.
A capture process that captures the wireless frame of the channel number to be captured and stores information about the wireless frame,
When the beacon frame information output in the scan process matches the determination condition, the channel number of the beacon frame information is set to the channel number of the capture target, and the channel number of the capture target captured in the capture process is set. A capture method characterized by executing a determination process of setting a new channel number to be captured when the state in which the beacon frame information does not meet the determination condition continues for a predetermined time or longer.
In the capture method according to claim 1,
The beacon frame information includes at least a channel number, a network identifier and a received signal strength.
The determination condition is a capture method characterized in that the network identifier of the beacon frame is the network identifier to be captured and the received signal strength of the beacon frame is equal to or higher than the threshold value.
In the capture method according to claim 1 or 2.
The scan process is a capture method characterized by switching channel numbers in order at predetermined time intervals and scanning a beacon frame received by the receiver.
In the capture method according to any one of claims 1 to 3.
It has two modes, scan mode and normal mode.
In the scan mode, the beacon frame is scanned by the scan process.
A capture method characterized in that, in the case of the normal mode, the capture process captures the radio frame of the channel number to be captured.
In a capture device that captures a wireless frame communicated between multiple wireless access devices and wireless terminal devices.
At least one receiver that receives the radio frame including a beacon frame transmitted from the plurality of radio access devices on a plurality of different radio channels.
A scanning unit that scans the beacon frames of the plurality of wireless channels received by the receiving unit and outputs the beacon frame information.
A capture unit that captures the wireless frame of the channel number to be captured and stores information about the wireless frame,
When the beacon frame information output from the scanning unit matches the determination condition, the channel number of the beacon frame information is set to the channel number of the capture target, and the channel number of the capture target captured by the capture unit is set. A capture device characterized by having a determination unit for setting a new channel number to be captured when the state in which the beacon frame information does not meet the determination condition continues for a predetermined time or longer.
In the capture device according to claim 5,
The beacon frame information includes at least a channel number, a network identifier and a received signal strength.
The determination condition is a capture device characterized in that the network identifier of the beacon frame is the network identifier of the capture target and the received signal strength of the beacon frame is equal to or higher than the threshold value.
In the capture device according to claim 5 or 6.
The scanning unit is a capture device characterized by switching channel numbers in order at predetermined time intervals and scanning a beacon frame received by the receiving unit.
In the capture device according to any one of claims 5 to 7.
It has two modes, scan mode and normal mode.
In the scan mode, the scan unit scans the beacon frame.
A capture device characterized in that, in the case of the normal mode, the capture unit captures the radio frame of the channel number to be captured.