WO2016064031A1 - Method for migration of ap of station in order to resolve wireless link failure - Google Patents

Abstract

A system for migration of an access point (AP) of a station in order to resolve a wireless failure which occurs in a wireless LAN environment, according to an embodiment, comprises: a hidden terminal detection unit for detecting a wireless failure which occurs in a plurality of APs connected to a centralized controller; an AP selection unit which, if a wireless failure occurring in the APs is detected, generates an AP list by aligning the ranking of the APs for reconnection in descending order, and provides a migration message including the AP list to a victim station; and an NTP server unit for performing time synchronization by providing reference time to the plurality of APs.

Description

Station Migration Techniques for Overcoming Radio Link Failures

The present invention is a method for solving a wireless link failure that may occur due to channel noise, radio signal fading, etc., including a hidden terminal problem that may occur in a wireless network environment, by using an application installed in a centralized controller, a plurality of APs, and a station. It is about.

In recent wireless environments, the interference between wireless devices has increased due to the exponential spread of smart devices having a wireless network connection, and as a result, the performance of the overall wireless network has been observed. Among the radio disturbances that can occur in a wireless network, particularly hidden terminal problems, can have a performance impact on the station.

Many techniques have been proposed to solve the hidden terminal problem. The most representative method is to implement virtual carrier sensing using RTS / CTS. In this way, frame collisions due to hidden terminal problems can be prevented, but they are not actively used due to their overload. In addition, the hidden terminal problem can be solved by using a time division multiple access (TDMA) mechanism using a centralized server by avoiding a carrier sense multiple access with collision avoidance (CSMA / CA) mechanism in frame transmission. When using the above method, the frames to be transmitted can be scheduled and transmitted in a predetermined order so that a collision does not occur with respect to a frame for which a collision is foreseen. However, there is a disadvantage in that TDMA requires many operations for scheduling or is difficult to use with existing networks. Another solution is to minimize the damage of the hidden terminal problem by modifying the network physical layer of the node where the frame collision occurs due to the hidden terminal problem. The method has a disadvantage in that it is difficult to be applied with a standard that is commercially available due to modification of an existing standard.

The present invention provides a centralized controller, an AP connected to a centralized controller, and other channels that will not suffer from radio disturbances to stations that suffer from radio disturbances such as channel noise, radio signal fading, including hidden terminal problems, and the like, through applications mounted on stations By reconnecting to the AP of the present invention, a system and method are provided to overcome various radio obstacles such as hidden terminal problems without physical movement of the station.

A system for migrating an AP of a station to solve a wireless failure occurring in a wireless LAN environment according to an embodiment may include a hidden terminal detecting a wireless failure occurring from a plurality of APs connected to a centralized controller. Detection unit; An AP selector configured to generate an AP list by sorting the descending ranks of APs for reconnection in descending order, and to provide a migration message including the AP list to a victim station; And an NTP server unit performing time synchronization by providing a reference time to the plurality of APs.

According to one side, the hidden terminal detection unit, comparing the transmission time and period information of each data frame received from the plurality of APs, and among the frames successfully transmitted in the radio link between the plurality of APs and a plurality of stations An overlap ratio indicating the frames in which the periods overlap can be calculated.

According to another aspect, the hidden terminal detection unit, if the overlap ratio exceeds a predetermined overlap ratio, determines that the relationship of the link is not in a carrier sense relationship, and if the overlap ratio is less than the predetermined overlap ratio It may be determined that the link relationship is in a carrier sense relationship.

According to another aspect, the hidden terminal detector, if the link relationship is not in a carrier sense relationship with each other, checks the LIR value, and compares the LIR (Link Interference Ratio) value is a interference by comparing a predetermined LIR value You can judge.

According to another side, the LIR represents a link interference ratio, the LIR is

LIR = (1-I _int ) / (1-I _iso )

I _int = n _ol / n _o

I _iso = (n _l -n _ol ) / (n _p -n _o )

N _p is the total number of frames, n _l is the number of frame loss, n _o is the number of frames overlapping the transmission period, and n _ol may represent the number of frames overlapping the lost transmission period.

According to another aspect, the hidden terminal detection unit may determine the damage station through the overlap ratio and the LIR, and transmit the IP address of the damage station to the AP selector.

According to another aspect, the hidden terminal detector may transmit the overlap ratio and link interference ratio calculated by comparing the transmission time and duration information of each data frame received from the plurality of APs to the AP selector.

According to another aspect, the AP selection unit, except for the AP of the channel, such as the channel in which the victim station operates, if any AP maintains only the carrier sense relationship, the arbitrary AP maintains only the carrier sense relationship And if the arbitrary AP operates independently of a link other than the link, the arbitrary AP does not operate independently of a link other than the link, and the arbitrary AP interferes with or is not connected to the link. If there is a link interfering, the AP list may be generated in order, and the AP list may be sorted in descending order.

According to another aspect, the AP selector, the migration station for generating a migration message for reconnecting to the AP of the channel in which the victim station is not operating, the victim station including the AP list as the IP address of the victim station; You can send a migration message.

According to another aspect, the victim station may receive the migration message and perform the migration by selecting the AP having the lowest probability of occurrence of the radio failure from the AP list excluding the AP that cannot be connected from the AP list. have.

According to an embodiment, a method for migrating an AP of a station in order to solve a wireless failure occurring in a wireless LAN environment may include detecting a wireless failure occurring from a plurality of APs connected to a centralized controller; Generating a list of APs in descending order of APs for reconnection when a wireless failure generated from the APs is detected, and providing a migration message including the AP list to the victim station; And performing time synchronization by providing a reference time to the plurality of APs.

According to one side, detecting a wireless failure generated from a plurality of AP (Access Point) connected to the centralized controller, comparing the transmission time and duration information of each data frame received from the plurality of AP, The method may include calculating an overlap ratio indicating a frame in which transmission periods overlap among frames successfully transmitted in the wireless link between the plurality of APs and the plurality of stations.

According to another aspect of the present invention, the detecting of a wireless failure generated from a plurality of access points (APs) connected to the centralized controller may include checking an LIR value when the link relations are not in a carrier sense relationship with each other. And comparing the link interference ratio (LIR) value with a predetermined LIR value to determine interference.

According to another aspect, if a wireless failure generated from the AP is detected, generating the AP list by sorting the descending order of the AP for reconnection in descending order, and providing a migration message including the AP list to the victim station Excluding an AP of the same channel as the channel in which the victim station operates; And when any AP maintains only a carrier sense relationship, when the arbitrary AP does not maintain only a carrier sense relationship, and when the arbitrary AP operates independently of a link other than the link, the arbitrary AP Generating an AP list in order when there is a link that does not operate independently of a link other than a link and the AP interferes with or interferes with the link, and sorts the AP list in descending order. Can be.

According to another aspect, if a wireless failure generated from the AP is detected, generating the AP list by sorting the descending order of the AP for reconnection in descending order, and providing a migration message including the AP list to the victim station Generating a migration message at the victim station to reconnect with an AP of a channel on which the victim station is not operating; And transmitting the migration message including the AP list to the IP address of the victim station.

The present invention can be solved by reconnecting a station that suffers from various radio disturbances such as a hidden terminal problem that continuously degrades the station performance in a WLAN environment to an AP of another channel. Reconnected stations can be as if they are relocated by changing the channel they are connected to without physically moving, and can intuitively solve the wireless problem. The method can be used while maintaining the CSMA / CA scheme without modifying the existing IEEE 802.11 WLAN standard.

1 is a block diagram showing the configuration of a system for migrating an AP of a station in order to solve a wireless failure occurring in a wireless LAN environment according to an embodiment of the present invention.

2 is a flowchart illustrating a process of detecting a radio failure in a system for migrating an AP of a station according to an embodiment of the present invention.

3 is a flowchart illustrating a process of selecting an AP in a system for migrating an AP of a station according to an embodiment of the present invention.

4 is a diagram illustrating the operation of a system for migrating an AP of a station according to an embodiment of the present invention.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing the configuration of a system for migrating an AP of a station in order to solve a wireless failure occurring in a wireless LAN environment according to an embodiment of the present invention.

The system for migrating the AP of the station is a system for resolving wireless failures occurring in a WLAN environment, and may be performed by a software defined networking controller.

The system for migrating an AP of a station may include a hidden terminal detector 111, an AP selector 112, and an NTP server 113. For example, the wireless failure can be avoided by migrating the AP of the damaged station that is suffering from the wireless failure such as a hidden terminal problem, channel noise, and radio signal fading, which continuously degrades the performance of the station in the WLAN environment. Accordingly, a method for solving a wireless failure occurring in a WLAN environment will be described.

The access point (AP) 120 stores time information related to the transmission frame, the time information collector 121 transmitting the time information record per transmission frame to the centralized controller 110, and an NTP host for time synchronization. 122 may be included. At this time, the time information of the data frame to be stored may consist of 5-tuple, it may be defined as follows.

<AP _ipaddr , STA _ipaddr , StartTime, EndTime, Seq_num, ACK>

The AP _ipaddr and the STA _ipaddr represent IP addresses of the AP 120 and the station capable of defining a radio link. StartTime and EndTime mean a time when a frame is transmitted from a sender and a time received by a receiver, and may indicate a transmission period of a frame through the transmitted time and the received time. In order to calculate the time when the receiver finishes the transmission, the total length of the frame may be divided by the bit rate. At this time, the bit rate is constantly changing according to the network environment and should be observed periodically. Seq_num is the sequential number of frames in the link. The ACK indicates whether the frame is transmitted successfully. For example, if the ACK is 0, the controller may determine that the frame was not successfully transmitted. If the value is 1, the controller may determine that the frame was successfully transmitted. The above time information may be transmitted to the hidden terminal detection unit 111 of the centralized controller 110 when 5-tuple is configured for each frame transmitted by the AP 120.

The hidden terminal detector 111 of the centralized controller 110 compares transmission time and duration information of each data frame received from the plurality of APs 120 and between the plurality of APs 120 and the plurality of stations. An overlap ratio and a link interference ratio (LIR) indicating a frame in which periods overlap among frames successfully transmitted in a wireless link may be calculated. The overlap ratio and the link interference ratio may be used to detect a radio failure, and the process of detecting the radio failure will be described in detail with reference to FIG. 2.

The hidden terminal detector 111 may compare StartTime and EndTime among time information of wireless links between the plurality of APs 120 and the plurality of stations in order to find the interfering link and the interfering link. The hidden terminal detector 111 may calculate an overlap ratio indicating how many frames of the frames successfully transmitted on different links overlap from the result of the comparison. At this time, if the overlap ratio exceeds the predetermined overlap ratio, it is determined that the relationship between the two links is not in the carrier sense relationship. If the overlap ratio is less than the predetermined overlap ratio, it is determined that the relationship between the two links is in the carrier sense relationship. Can be determined. For example, assuming that the overlap ratio is predetermined in advance, and if the overlap ratio exceeds 0.1, the hidden terminal detector 111 determines that the link relationship is not carrier sensed, and if the overlap ratio does not exceed 0.1, In this case, it is possible to determine whether the link relation is carrier sense.

If it is determined that the link relationship is not carrier sense with each other, the hidden terminal detector 111 may check the link interference ratio (LIR) values of the two links. The LIR value may be determined to be interference by comparing with a predetermined LIR value. For example, assuming that the predetermined LIR value is 0.8 and the LIR value is lower than the predetermined LIR value, the hidden terminal detector 111 may determine that one link is interfered with by another link. The hidden terminal detector 111 may detect a station of an interfering link, a station 130 having a wireless failure, and transmit an IP address, an overlap ratio, and an LIR value of the station 130 to the AP selector 112. I can deliver it.

When a wireless failure originating from the AP is detected, the AP selector 112 may generate an AP list by sorting the descending order of the APs for reconnection in descending order, and the migration message including the AP list may include a station 130 having a wireless failure. ) Can be provided. Here, the criterion for determining an AP to be reconnected is, 'Does the AP to be reconnected have a high possibility of reoccurring a hidden terminal problem?' For example, if there is more than one AP capable of reconnecting with a station 130 that is experiencing a wireless failure, the station may reconnect by selecting an AP that is less likely to cause a hidden terminal problem.

When the AP selector 112 maintains only the carrier sense relationship, except for the AP of the same channel as the channel in which the station 130 that is experiencing wireless failure operates, the AP selector 112 maintains only the carrier sense relationship. If any AP operates independently of a link other than the link, if any AP does not operate independently from a link other than the link, and if any AP interferes with or interferes with the link You can create APs and sort the AP list in descending order. The process of selecting an AP will be described in detail with reference to FIG. 3.

 The AP selector 112 may configure a migration message including a list of APs to induce reconnection, and transmit the migration message to the IP address of the station 130 suffering from the wireless failure. In this case, the migration message may have the same structure as a general IP packet and may be configured by specifying an AP list in a data field. Since the migration message cannot be delivered to the station 130 directly from the centralized controller 110, the migration message can be delivered to the station 130 through the AP 120.

The station 130 experiencing the wireless failure may be equipped with a migration application 131, receive a migration message using the migration application 131, and access APs that are currently unable to establish a connection in the AP list. The reconnection may be performed by selecting the AP having the highest rank among the remaining APs. In this case, the AP having the highest ranking may be the AP having the lowest probability of occurrence of a wireless failure.

The centralized controller 110 may determine the interference relationship based on the time information. The NTP server unit 113 and the NTP host unit 122 may perform time synchronization by providing a reference time to the plurality of APs. The NTP server unit 113 may provide a reference time to the plurality of NTP host units 122, and the plurality of NTP host units 122 may use the time synchronization network time protocol as a reference time provided by the NTP server unit 113. It can be performed using. The NTP host unit 122 and the NTP server unit 113 are connected by one hop, thereby minimizing time synchronization errors. For example, the NTP host unit 122 may perform time synchronization every 10 minutes.

2 is a flowchart illustrating a process of detecting a radio failure in a system for migrating an AP of a station according to an embodiment of the present invention.

Systems for migrating APs can detect wireless problems such as hidden terminals, channel noise, and the like. The system for migrating the AP may detect the radio failure by the hidden terminal detector. The hidden terminal detector compares the transmission time and duration information of each data frame received from a plurality of APs to find an interfering link and an interfering link, and successfully finds a link in the wireless link between the plurality of APs and the plurality of stations. The overlap ratio indicating a frame in which the period overlaps among the frames transmitted to the second frame may be calculated. In FIG. 2, link i and link k will be described as an example.

The transmission period and time information of the data frames received from the link i and the link k may be compared 210. An overlap ratio indicating how many transmission periods of frames successfully received from the link i and the link k overlap can be calculated. It may be determined whether the overlap ratio is smaller than the predetermined overlap ratio (220). If the overlap ratio is smaller than the predetermined overlap ratio, it may be determined that link i and link k have a carrier sense relationship (230). If the overlap ratio is greater than the predetermined overlap ratio, it may be determined that the link i and the link k are not in a carrier sense relationship with each other (240).

If it is determined that the relationship between the link i and the link k does not carrier sense each other, the hidden terminal detector of the station may calculate the LIR values of the link i and the link k.

LIR may be calculated by Equation 1. In this case, n _p is the total number of frames, n _l is the number of frame loss, n _o is the number of frames overlapping the transmission period and n _ol may mean the number of frames overlapping the lost transmission period.

Equation 1

LIR = (1-I _int ) / (1-I _iso )

I _int = n _ol / n _o

I _iso = (n _l -n _ol ) / (n _p -n _o )

For example, if the LIR value is lower than the predetermined LIR value of 0.8, it may be determined that one link is interfered with from another link. LIR _{i, k} may indicate the amount of interference that link i receives from link k _, and LIR _{k, i} may mean the amount of interference that link k receives from link i. When comparing link k and time information for link i, if there is a link with an overlap rate higher than a predetermined overlap rate and a LIRi, k value lower than a predetermined LIR value (260), link i is link k and carrier sense. It may be determined that it is not in a relationship, and that interference is received from link k. The link i may determine that the link is damaged from a radio failure such as a hidden terminal.

In addition, if there is a link having an overlap ratio higher than the predetermined overlap ratio and a LIR _{k, i} value lower than the predetermined LIR value (270), the link k is not in a carrier sense relationship with the link i and receives interference from the link i. You can judge that. The link k may determine that the link is damaged from the radio failure. If there is a link having a LIR _{k, i} value higher than a predetermined LIR value, the relationship may be recorded and the next link may be identified, and the steps 210 to 270 may be performed.

The hidden terminal detector can detect a station of a corresponding link or a damaged station that is being damaged due to a radio failure problem, and can transmit the IP address, overlap rate, and LIR value of the damaged station to the AP selector.

3 is a flowchart illustrating a process of selecting an AP in a system for migrating an AP of a station according to an embodiment of the present invention.

In a system for migrating APs, a hidden terminal detector detects a damaged station (eg, S _i ), and then passes the damaged station's IP address, overlap rate, and LIR value to the AP selector, and the AP selector transmits the damaged station. Can receive the IP address, overlap ratio and LIR value. The process of selecting an AP may be performed by the AP selecting unit of the centralized controller.

The AP selector may rank the plurality of APs based on the possibility of the occurrence of a wireless failure, and generate the AP list by sorting them in descending order. The AP list may be provided to select an AP to reconnect to the victim station. The AP selector may generate a migration message for the victim station to reconnect with the AP of the channel in which the victim station is not operating, and transmit a migration message including the AP list to the IP address of the victim station. Accordingly, a method of generating an AP list will be described.

If there are a plurality of APs capable of reconnecting with a damage station that is damaged due to a wireless failure, the damaged station may reconnect to an AP that is less likely to cause a wireless failure among the plurality of APs. First, the system for migrating APs may exclude APs in the same channel as the channel in which the damage station currently suffering from the wireless failure is operating to induce connection to a channel different from the current connection. (310). Systems for migrating APs can be ranked according to the following:

1. If any AP A is detected from other APs, the link containing A will not be damaged from the radio failure problem.

2. If any AP A has neither carrier sense nor interference with other links, then A is unlikely to cause radio disturbance problems.

3. If any AP A is interfering with or interfering with another link, the probability of causing another radio failure problem is relatively high.

In more detail, the AP selector may determine whether any AP maintains only a carrier sense relationship (320). If any AP maintains only the carrier sense, the AP may be ranked first, and if the AP does not maintain only the carrier sense relationship, it may be determined whether the AP operates independently of a link other than the link. (330). If an AP does not maintain only a carrier sense relationship, and an AP operates independently from another link, the AP is ranked second, any AP does not operate independently from another link, and any AP If there is a link that interferes with or interferes with the link, the corresponding AP may be classified into three ranks. If there are remaining APs after sorting the ranks (350), step 350 may be performed at step 320 to examine the next AP, and if there are no remaining APs, then descending order for the ranked APs. In operation 360, the AP list may be sorted.

4 is a diagram illustrating the operation of a system for migrating an AP of a station according to an embodiment of the present invention.

AP 1 and AP 2 operate on channel 1, and AP 3 operates on channel 11. Station 2 suffers a hidden terminal problem due to traffic from AP 1 to station 1, and a system (e.g., a controller) for migrating the AP of the station to resolve the hidden terminal sends a migration message to station 2 It can lead to the migration of stations. In this case, the controller may detect a radio failure as described with reference to FIGS. 1 to 3, and generate a migration message by constructing an AP list through the overlap ratio and the LIR. Description of detecting a radio failure and generating an AP list will be described with reference to FIGS. 1 to 3. The controller may transmit a migration message including the AP list to the IP address of the station 2, and the station 2 receiving the migration message may reconnect with AP 3 operating on a different channel from AP 2.

Similarly, a system for migrating APs can overcome various radio disturbances by applying the same method to affected stations suffering from radio disturbances, allowing stations that are affected by certain problems, such as exposed terminal problems and channel noise, to By re-connecting the operating AP can avoid the problem caused by the radio failure.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the devices and components described in the embodiments may be, for example, processors, controllers, arithmetic logic units (ALUs), digital signal processors, microcomputers, field programmable arrays (FPAs), It may be implemented using one or more general purpose or special purpose computers, such as a programmable logic unit (PLU), microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to the execution of the software. For convenience of explanation, one processing device may be described as being used, but one of ordinary skill in the art will appreciate that the processing device includes a plurality of processing elements and / or a plurality of types of processing elements. It can be seen that it may include. For example, the processing device may include a plurality of processors or one processor and one controller. In addition, other processing configurations are possible, such as parallel processors.

The software may include a computer program, code, instructions, or a combination of one or more of the above, and configure the processing device to operate as desired, or process it independently or collectively. You can command the device. Software and / or data may be any type of machine, component, physical device, virtual equipment, computer storage medium or device in order to be interpreted by or to provide instructions or data to the processing device. Or may be permanently or temporarily embodied in a signal wave to be transmitted. The software may be distributed over networked computer systems so that they may be stored or executed in a distributed manner. Software and data may be stored on one or more computer readable recording media.

The method according to the embodiment may be embodied in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the media may be those specially designed and constructed for the purposes of the embodiments, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

Although the embodiments have been described by the limited embodiments and the drawings as described above, various modifications and variations are possible to those skilled in the art from the above description. For example, the described techniques may be performed in a different order than the described method, and / or components of the described systems, structures, devices, circuits, etc. may be combined or combined in a different form than the described method, or other components. Or even if replaced or substituted by equivalents, an appropriate result can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are within the scope of the claims that follow.

Claims (15)

In the system for migrating the AP of the station in order to solve the wireless failure occurring in the WLAN environment, Hidden terminal detection unit for detecting a wireless failure generated from a plurality of AP (Access Point) connected to the centralized controller; An AP selector configured to generate an AP list by sorting the descending ranks of APs for reconnection in descending order, and to provide a migration message including the AP list to a victim station; And NTP server unit performing time synchronization by providing a reference time to the plurality of APs System for migrating the AP of the station comprising a. The method of claim 1, The hidden terminal detector, The transmission time and duration information of each data frame received from the plurality of APs are compared, and an overlap ratio indicating a frame in which the period overlaps among the frames successfully transmitted in the radio link between the plurality of APs and the plurality of stations is compared. To calculate System for migrating APs of stations. The method of claim 2, The hidden terminal detector, If the overlap ratio exceeds a predetermined overlap ratio, it is determined that the relationship of the link is not in a carrier sense relationship. If the overlap ratio is less than the predetermined overlap ratio, it is determined that the relationship of the link is in a carrier sense relationship. Discriminating System for migrating APs of stations. The method of claim 3, The hidden terminal detector, When the link relationship is not in a carrier sense relationship with each other, the LIR (Link Interference Ratio) value is inspected, and the LIR value is compared with a predetermined LIR value to determine interference. System for migrating APs of stations. The method of claim 4, wherein The LIR represents a link interference ratio, the LIR is calculated as in Equation 1, n _p is the total number of frames, n _l is the number of frame losses, n _o is the number of frames with overlapping transmission periods, and n _ol is the number of frames with overlapping transmission periods. Equation 1: LIR = (1-I _int ) / (1-I _iso ) I _int = n _ol / n _o I _iso = (n _l -n _ol ) / (n _p -n _o ) System for migrating APs of stations. The method of claim 1, The hidden terminal detector, Determining the damaged station through the overlap ratio and LIR, and transmitting the IP address of the damaged station to the AP selector System for migrating APs of stations. The method of claim 1, The hidden terminal detector, Comparing the transmission time and period information of each data frame received from the plurality of AP to transmit the overlap ratio and link interference ratio calculated to the AP selector System for migrating APs of stations. The method of claim 1, The AP selector, Except for the AP of the channel, such as the channel in which the victim station operates, When any AP maintains only a carrier sense relationship, when the arbitrary AP does not maintain only a carrier sense relationship, and when the arbitrary AP operates independently of a link other than the link, the arbitrary AP operates on the link. If the AP does not operate independently from other links and there is a link that interferes with or interferes with the link, the AP list is generated in order, and the AP list is sorted in descending order. System for migrating APs of stations. The method of claim 8, The AP selector, Generating a migration message for reconnecting the AP with the AP of the channel where the victim station is not operating and transmitting the migration message including the AP list to the IP address of the victim station; System for migrating APs of stations. The method of claim 1, The damage station, Receiving the migration message, performing the migration by selecting the AP having the lowest probability of occurrence of the radio failure from the AP list excluding the AP that can not be connected from the AP list System for migrating APs of stations. In the method for migrating the AP of the station in order to solve the wireless failure occurring in the WLAN environment, Detecting a wireless failure occurring from a plurality of access points connected to a centralized controller; Generating a list of APs in descending order of APs for reconnection when a wireless failure generated from the APs is detected, and providing a migration message including the AP list to the victim station; And Performing time synchronization by providing a reference time to the plurality of APs The method for migrating the AP of the station comprising a. The method of claim 11, Detecting a wireless failure generated from a plurality of AP (Access Point) connected to the centralized controller, The transmission time and duration information of each data frame received from the plurality of APs are compared, and an overlap ratio indicating a frame in which transmission periods overlap among frames successfully transmitted in a wireless link between the plurality of APs and the plurality of stations is compared. Calculation step The method for migrating the AP of the station comprising a. The method of claim 12, Detecting a wireless failure generated from a plurality of AP (Access Point) connected to the centralized controller, If the link relationship is not in a carrier sense relationship with each other, inspecting a link interference ratio (LIR) value and comparing the LIR value with a predetermined LIR value to determine interference The method for migrating the AP of the station comprising a. The method of claim 11, When a wireless failure generated from the AP is detected, generating the AP list by sorting the descending order of the APs for reconnection in descending order, and providing the migration message including the AP list to the victim station, Excluding an AP of the same channel as the channel in which the victim station operates; And When any AP maintains only a carrier sense relationship, when the arbitrary AP does not maintain only a carrier sense relationship, and when the arbitrary AP operates independently of a link other than the link, the arbitrary AP operates on the link. Generating a list of APs in order when there is a link that does not operate independently from other links and the APs interfere with or interfere with the links, and sort the AP list in descending order The method for migrating the AP of the station comprising a. The method of claim 14, When a wireless failure generated from the AP is detected, generating the AP list by sorting the descending order of the APs for reconnection in descending order, and providing the migration message including the AP list to the victim station, Generating a migration message at the victim station to reconnect with an AP of a channel on which the victim station is not operating; And Transmitting the migration message including the AP list to the IP address of the victim station The method for migrating the AP of the station comprising a.

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