KR102103457B1 - Method for searching access point managing linkage in wireless LAN system - Google Patents

Abstract

The present invention discloses a method in which a wireless LAN terminal searches for an access point secured with a wireless link quality and selects an optimal access point to prevent a problem that may occur due to connection with an unstable link quality access point.
The method for selecting and connecting an access point according to the present invention is a method in which a terminal selects and connects an access point to which a wireless link is to be connected in a wireless LAN system, and the quality parameter that provides information about the quality of the wireless link with the access point Receiving a probe response frame including; A first analysis step of analyzing, by the terminal, quality parameters included in the received probe response frame; And a step in which the terminal selects and connects an access point to be connected to the radio link using the analysis result.

Description

Method for searching access point managing linkage in wireless LAN system

The present invention relates to a wireless LAN technology, and more particularly, to a method of searching for an access point having excellent wireless link quality in a wireless LAN system and a method of maintaining excellent wireless link quality.

In the IEEE 802.11 WLAN network, an access point (AP) forms one physical cell area, and is configured to communicate after WLAN terminals located in the cell locate and connect to the access point through a scan process.

1 is a diagram showing the configuration of a wireless LAN system, as shown in Figure 1, the wireless LAN system is based on a basic service set (BSS: Basic Service Set) in which one or more terminals are wirelessly connected to one access point. Included in the composition. The access point periodically broadcasts a beacon frame including a Service Set ID (SSID) and a Basic Service Set ID (BSSID), or receives a probe request frame from the terminal, and then probes the probe. By transmitting a response frame, the presence of the access point and connection information are provided to the terminals before the wireless LAN connection, and the terminals in the wireless LAN connection state are provided with information about the existence of data to be transmitted to a specific terminal. to provide. A method such as the former in which the access point periodically broadcasts a beacon frame for wireless LAN connection is called a passive access point search method, and when a terminal transmits a probe request frame, the access point receives it and a probe corresponding to the probe request frame The method of transmitting a response frame is called an active access point search method.

Among them, the active access point search method as shown in FIG. 1 is performed by a method in which a terminal transmits a probe request frame, and an access point receiving it transmits a probe response frame. As illustrated in FIG. 1, in general, since there may be one or more access points around the terminal, when a terminal transmits a probe request frame, a plurality of access points that have received the probe request frame correspondingly respond to the probe response frame Will send. The terminal may receive a probe response frame from a plurality of access points, check connection information for each access point from the received probe response frame, and estimate the radio link quality. After completing the access point search step, the terminal selects the optimal access point by comparing the function support information of the access point and the radio link quality with respect to the access points that are the targets of the wireless LAN connection, and performs the connection step.

2 is a diagram illustrating a procedure in which a terminal and an access point are connected in a wireless LAN system. In FIG. 2, after actively searching for an access point, the terminal selects AP1 as an optimal access point and is connected to AP1, and finally accesses through these connection steps including an authentication process and an association process. You will be connected to the point.

Meanwhile, in the conventional access point search step, the terminal generally uses the signal strength of the probe response frame as a parameter for estimating the radio link quality for access point selection. That is, according to the conventional access point search step, when a plurality of access points exist in the vicinity of the terminal, the terminal selects the access point having the largest signal strength of the probe response frame and performs a connection step, and in the vicinity of the terminal. If there is only one access point, the connection step is performed immediately when the signal strength of the probe response frame is higher than a certain level.

However, the conventional access point search method using the signal strength of the probe response frame as a parameter for estimating radio link quality has the following problems.

When the number of radio interference signals around the access point or the terminal is high or the channel usage rate is high by another terminal, the signal strength of the probe response frame is a parameter that can estimate the quality of the radio link and is inaccurate. In addition, since the downlink signal strength transmitted by the access point is usually larger than the uplink signal strength transmitted by the terminal, it is not appropriate to estimate that the overall radio link quality is good simply because the downlink signal strength is strong.

In particular, when a terminal having a separate primary communication device as well as a wireless LAN device such as a cellular phone is automatically connected to an access point having an unstable radio link quality due to incorrect access point selection, normal communication service is performed using the cellular communication device. While receiving the connection is automatically switched to the wireless LAN device, it may cause a serious problem that the communication service is disconnected.

In addition, since wireless channel resources are shared among wireless LAN devices in a wireless LAN system, wireless channel resources can be efficiently used when a specific wireless LAN device can transmit as much data as possible while the wireless channel is occupying a wireless channel. That is, when the access point and the terminals connected to the access point can transmit the access point and data with the highest possible transmission speed, radio channel resources can be efficiently used. If the access point and the terminal are connected to a channel with a low link quality to transmit and receive data, the data transmission speed is lowered. This may cause a problem of deteriorating the link quality of the entire WLAN system as well as the link quality of the corresponding terminal and access point.

The present invention was devised to solve the above problems, and the wireless LAN terminal searches for an access point secured with wireless link quality to prevent problems that may occur due to connection with an unstable link quality access point, and an optimal access point. The purpose is to provide a way to select and connect.

In addition, an object of the present invention is to provide a method of managing access point access to maintain link quality even after being connected to the access point.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by examples of the present invention. In addition, it will be readily understood that the objects and advantages of the present invention can be realized by means and combinations thereof.

A method of selecting and connecting an access point according to an aspect of the present invention for achieving the above object is a method of selecting and connecting an access point to which a terminal connects to a wireless link in a wireless LAN system, wherein the terminal establishes a wireless link with the access point. Receiving a probe response frame including quality parameters that provide quality information; A first analysis step of analyzing, by the terminal, quality parameters included in the received probe response frame; And a step in which the terminal selects and connects an access point to be connected to the radio link using the analysis result.

The quality parameter included in the probe response frame is characterized by including at least one of the number of terminals connected to the access point and the utilization rate of the operating channel.

The probe response frame is characterized by including access criteria for each quality parameter that can satisfy the quality of a radio link to be provided by the access point and status information of a quality parameter that the access point can provide.

The access criterion for each quality parameter includes at least one of a downlink signal strength, an uplink signal strength, a maximum number of allowed access terminals, a maximum allowed channel usage rate, and an access point ambient noise signal strength, and the quality parameter status information includes: Characterized in that it includes at least one of an uplink signal strength measured by the signal strength of the probe request frame transmitted by the terminal, the noise signal strength around the access point, the status information of the backhaul, the number of terminals connected to the access point, and the channel utilization rate. Is done.

The method comprises: the terminal transmitting a standard protocol query; The terminal receiving a standard protocol response to the standard protocol query from the access point; And a second analysis step of analyzing, by the terminal, quality parameters included in the received standard protocol response.

The standard protocol used for the standard protocol query and the standard protocol response is characterized by being an ANQP of the 802.11u standard.

The ANQP query includes at least one of WAN Metric information, a list of roamable peripheral access points, access criteria for each quality parameter that can satisfy the quality of a wireless link to be provided by the access point, and status information of a quality parameter that the access point can provide. It is characterized by.

The method comprises: the terminal transmitting a link quality measurement request frame; The terminal receiving a link quality measurement response frame for the link quality measurement request frame from the access point; And a third analysis step of analyzing, by the terminal, quality parameters included in the received link quality measurement response frame. Including, the step of transmitting the link quality measurement request frame and the step of receiving the link quality measurement response frame from the access point is characterized in that it is performed alternately one or more times.

The quality parameter included in the link quality measurement response frame is characterized by including the number of received frames and the received signal strength.

The number of received frames and the received signal strength, which are quality parameters included in the link quality measurement request frame, are alternately performed by transmitting the link quality measurement request frame and receiving the link quality measurement response frame. In the process, the number of received frames is cumulatively updated, and the received signal strength is characterized in that the average value of the received signal strength of the received frames is updated.

In the third analysis step, the quality parameter included in the link quality measurement response frame finally received by the terminal is analyzed.

The access point access management method according to another aspect of the present invention for achieving the above object, after the terminal and the access point are connected by a method of selecting and connecting the above-described access point, maintaining the radio link quality; Includes.

The step of maintaining the radio link quality may include: the terminal transmitting a link quality measurement request frame; The terminal receiving a link quality measurement response frame for the link quality measurement request frame from the access point; A fourth analysis step of analyzing, by the terminal, quality parameters included in the received link quality measurement response frame; And determining, by the terminal, whether to maintain a connection state with an access point connected to a radio link using the analysis result; transmitting the link quality measurement request frame and accessing the link quality measurement response frame; The receiving step from the point is characterized in that it is performed alternately more than once.

The step of maintaining the radio link quality may include: the terminal transmitting a link quality information request frame; The terminal receiving a link quality information response frame for the link quality information request frame from the access point; A fifth analysis step of analyzing, by the terminal, quality parameters included in the received link quality information response frame; And determining whether the terminal maintains a connection state with an access point connected to a radio link using the analysis result; wherein the link quality information request frame includes a list of quality parameters that require analysis, and the The link quality information response frame is characterized by providing quality parameter status information for a quality parameter list that requires the analysis.

The access point that has received the link quality information request frame monitors a quality parameter requiring analysis included in the link quality information request frame, and if the quality parameter does not satisfy the quality parameter access criterion, the link quality to the terminal It is characterized by transmitting an information response frame.

According to the present invention, since the quality of the radio link can be evaluated using various quality parameters as well as the signal strength of the probe response frame, it is possible to prevent the terminal from accessing an access point where unstable link quality is expected.

According to an aspect of the present invention, by guiding to the terminal the quality parameter criteria reflecting the wireless environment characteristics of each access point for each access point, the terminal can be provided with more accurate link quality information.

According to another aspect of the present invention, by performing the link quality evaluation step by step, it is possible to more effectively prevent an unstable link quality from accessing an expected access point.

According to another aspect of the present invention, by using the link quality measurement protocol, the terminal can not only receive more accurate link quality information, but also receive link quality information even if some of the frames are lost.

According to another aspect of the present invention, even after the terminal is connected to the access point, by continuously monitoring the link quality, to disconnect the wireless LAN before the link quality is lowered below a certain criterion, or to roam to another access point adjacent to good radio Link quality can be maintained.

The following drawings attached to this specification are intended to illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the detailed description of the invention described below, and thus the present invention is described in such drawings. It is not limited to interpretation.
1 is a view showing the configuration of a wireless LAN system.
2 is a diagram illustrating a procedure in which a terminal and an access point are connected in a wireless LAN system.
3 is a flowchart illustrating an embodiment of a process in which a terminal selects an access point using a probe response frame.
4 is a flowchart illustrating an embodiment of a process for a terminal to select an access point using ANQP.
5 is a diagram illustrating an embodiment of a process of transmitting and receiving a link quality measurement frame according to a link quality measurement protocol.
6 is a view showing another embodiment of a process of transmitting and receiving a link quality measurement frame according to a link quality measurement protocol.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to ordinary or lexical meanings, and the inventor appropriately explains the concept of terms to explain his or her invention in the best way. Based on the principle that it can be defined, it should be interpreted as meanings and concepts consistent with the technical spirit of the present invention.

Therefore, the embodiments shown in the embodiments and the drawings described in this specification are only the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention, and at the time of this application, various alternatives are possible. It should be understood that there may be equivalents and variations.

In addition, in the description of the present invention, when it is determined that detailed descriptions of related well-known structures or functions may obscure the subject matter of the present invention, detailed descriptions thereof will be omitted.

The wireless LAN system according to the present invention includes a terminal and an access point, and the terminal can search for an access point with good radio link quality.

Hereinafter, in this specification, a description will be given based on a wireless LAN system conforming to the IEEE 802.11 standard.

In the step of searching for an access point, the terminal may analyze various quality parameters included in various frames for access point selection.

In the frame used in the present invention, first, a probe request frame and a corresponding probe response frame, second, a standard protocol frame other than the probe request frame and a probe response frame, and third, a link quality measurement request ( Link Quality Measurement request (LQM request) frame and the corresponding Link Quality Measurement response (LQM response) frame, and fourth, Link Quality Information request (LQI request) frame and the corresponding link quality There is a link quality information response (LQI response) frame. Here, the link quality measurement request frame and the corresponding link quality measurement response frame and the link quality information request frame and the corresponding link quality information response frame correspond to the protocol defined in this specification.

The above frames may include various quality parameters that provide information regarding radio link quality. In particular, in the present invention, the quality parameter that provides information on the radio link quality is not limited to the signal strength of the probe response frame. In other words, in the related art, the radio link quality was estimated by measuring the signal strength of the probe response frame. However, the present invention is not limited thereto, and the radio link quality is estimated using various quality parameters. Therefore, the present invention can provide more accurate radio link quality information.

The quality parameters include the number of terminals connected to the access point (station count), channel utilization (channel utilization), assignable medium time (available admission capacity), downlink signal strength, uplink signal strength, access point surroundings Interference / noise signal strength, backhaul state information, and the like, and various parameters that provide information on radio link quality in addition to the listed quality parameters may be included in the quality parameter.

Hereinafter, a method of selecting an access point by a terminal using each frame and a method of maintaining radio link quality will be described.

First, a method for selecting an access point using a probe request frame and a probe response frame will be described.

<Selection of access point using probe response frame>

The terminal may search for an access point to be connected to a radio link using a probe request frame and a probe response frame, select an access point having a good radio link quality, and then perform authentication and negotiation processes to access the access point. I can connect.

In particular, in the present invention, the probe response frame may include various quality parameters. For example, the BSS Load Information Element of the probe response frame includes the number of terminals currently connected to the access point (station count), the channel utilization during operation (channel utilization), additionally available medium admission (available admission capacity) information, etc. It may include.

One embodiment of the BSS Load Information Element is shown in Table 1 below.

In addition, the Vendor Specific Information Element of the probe response frame may include access criteria for each quality parameter that can satisfy the radio link quality to be provided by the access point, and current quality parameter status information that the access point can provide. The access criterion for each quality parameter may include downlink signal strength, uplink signal strength, maximum number of allowed access terminals, maximum allowed channel usage rate, interference / noise signal strength around an access point, and the like. The quality parameter status information includes the uplink signal strength measured by the signal strength of the probe request frame transmitted by the terminal, the interference / noise signal strength around the access point, the status information of the backhaul, the number of terminals currently connected to the access point, the current Channel utilization, and the like.

One embodiment of the Vendor Specific Information Element is shown in Table 2 below.

On the other hand, as described above, the probe response frame includes access criteria for each quality parameter and quality parameter status information, so that the criteria of the quality parameters required by each access point can be guided to the terminal. For example, in the case of access point 1, when the maximum number of terminals allowed to access is 100, and the number of terminals currently connected to access point 1 is 100, access point 1 is already in a state where other terminals occupy the access point. However, in the case of access point 2, when the maximum number of terminals allowed to access is 1000 and the number of terminals currently connected to access point 2 is 200, access point 2 is still in a state where 800 more terminals can access. If the access criterion for each quality parameter is not included in the probe response frame, the terminal accesses the access point using the absolute access criterion. That is, in the above example, it means that the terminal attempts to connect to the access point 1 with less absolute value, so that the wireless link quality can be connected to the access point.

According to the present invention, each access point transmits information to the terminal by including information on a current condition and a requirement of a quality parameter suitable for each access point in the probe response frame, so that the terminal can access a more suitable access point. You can.

Preferably, the access point may set a minimum quality criterion capable of providing service when accessing within the coverage of the access point as a quality parameter access criterion. Also, preferably, the access point may set a quality standard of a desired level as a quality parameter access criterion in order to provide radio link quality of a certain level or higher. In addition, these access criteria may be different depending on the installation location or time zone of the access point that provides the service, and are dynamically set based on statistics analyzing the correlation between each item of link quality and access criteria independently for each access point. It may be.

3 is a flowchart illustrating an embodiment of a process in which a terminal selects an access point using a probe response frame.

Referring to FIG. 3, the terminal transmits a probe request frame to search for a nearby access point (S301). The access point around the terminal receiving the probe request frame from the terminal transmits a probe response frame to the terminal. Here, the probe response frame transmitted by the access point includes quality parameters that provide information regarding the quality of the radio link. Subsequently, the terminal receives the probe response frame from the access point around the terminal (S303), extracts information about the quality parameter included in the received probe response frame, and analyzes the quality parameter (S305), thereby accessing the access point around the terminal It is possible to estimate the radio link quality. Here, the quality parameter may be included in the BSS Load Information Element and / or the Vendor Specific Information Element, and the quality parameter and the Vendor Specific Information Element included in the BSS Load Information Element may be partially overlapped. Next, the terminal may remove the access point with poor link quality from the search result list (S307). For example, the terminal compares the access criteria for each quality parameter included in the probe response frame with the status information of the quality parameter provided by the access point and the status information of the quality parameter measured by the terminal, and thus does not satisfy the access criterion. Can be excluded from the search results list. One or more quality parameters to be compared may be present, and conditions for removing an access point from a search result list may be determined as a part or all combinations of quality parameters, and it is also possible to weight each quality parameter. For example, when the backhaul link status of the access point is down, even if other quality parameters satisfy the access criterion, the access point may be excluded from the search result list.

Next, the terminal may wirelessly connect to the access point by selecting an access point having a good radio link quality among access points included in the search result list (S309).

Next, a method of selecting an access point using standard protocol frames other than the probe request frame and the probe response frame will be described.

<Selection of access point using standard protocol frame>

The terminal may select an access point by transmitting and receiving a standard protocol frame other than the probe request frame and the probe response frame with the access point. In particular, the standard protocol frame used in the present invention includes the quality parameters described above. The quality parameters included in the standard protocol frame may overlap with some or all of the quality parameters included in the probe response frame.

On the other hand, in principle, there is no limitation in the standard protocol frame, but it is preferable to use the Access Network Querry Protocol (ANQP) of the 802.11u standard.

On the other hand, the access point selection method using the standard protocol frame may be performed independently, but after the access point having poor link quality is first excluded from the search result list through the quality parameter analysis by the above-described probe response frame, 2 It is preferably used to exclude access points with poor link quality from the search results list.

That is, the terminal analyzes the above-described probe response frame and additionally transmits a standard protocol query to an access point estimated to be a high-quality access point in the first search step, and receives a standard protocol response from the access point, followed by standard A second search step may be performed to analyze quality parameters included in the protocol response. In this way, by analyzing the radio link quality of the access point step by step, the terminal can be connected to an access point with high radio link quality.

Hereinafter, the access point having poor link quality is first excluded using the above-described probe response frame, and then the access point having poor link quality is excluded and the access point having good link quality is selected using ANQP. Let me explain an example.

4 is a flowchart illustrating an embodiment of a process for a terminal to select an access point using ANQP.

The step illustrated in FIG. 4 may be performed as a next step of removing the link quality bad access point of FIG. 3 from the search result list.

Referring to FIG. 4, first, the terminal extracts an access point supporting ANQP (S401). Since the access point may not support the ANQP protocol, it is recommended to first extract the access point supporting ANQP. In this way, an ANQP query is not transmitted to an access point that does not support ANQP, thereby preventing unnecessary waste of radio resources.

Subsequently, the terminal may transmit an ANQP query to an access point supporting ANQP (S403). For example, the ANQP query may include quality parameters in the Generic Query List and Vendor Specific Query List. The Generic Query List may include WAN Metric information. Here, the WAN Metric included in the Generic Query List applies the 802.11u standard as it is, and uses the parameters in the form of [Table 3] and [Table 4] below. You can also use Here, [Table 3] is a table showing the structure of WAN Metric, and [Table 4] is a table showing the structure of the WAN info field of [Table 3].

The vendor specific query list may include a roaming possible access point list, quality parameter access criteria, and quality parameter status information. For example, the ANQP Vendor Specific Query List may include quality parameters as shown in [Table 5] below.

Next, the access point around the terminal receiving the ANQP query from the terminal transmits an ANQP response to the terminal. Here, the ANQP response transmitted by the access point may include information corresponding to the quality parameter included in the ANQP query. Subsequently, the terminal receives the ANQP response from the access point around the terminal (S405), extracts information about the quality parameter included in the received ANQP response, and analyzes the quality parameter (S407), thereby wirelessly accessing the access point around the terminal. Link quality can be estimated. Next, the terminal may remove the access point with poor link quality from the search result list (S409). For example, the terminal extracts downlink speed, uplink speed, download amount, upload amount information, and backhaul link status information of the backhaul link from WAN Metric information provided by the access point, and compares this information with the access criterion for access criterion. An access point that does not satisfy can be excluded from the search result list. The terminal does not satisfy the access criterion by comparing not only the WAN Metric information, but also the access criteria for each quality parameter included in the ANQP response, the quality parameter status information provided by the access point, and the quality parameter status information performed by the terminal. You can exclude an access point from the list of search results.

Next, the terminal may wirelessly connect to the access point by selecting an access point having a good radio link quality from among access points included in the search result list (S411).

Next, a method for selecting an access point using a link quality measurement request frame defined in this specification and a link quality measurement response frame corresponding thereto will be described.

<Selection of access point using link quality measurement protocol>

The terminal and the access point may select an access point using a link quality measurement protocol. The link quality measurement protocol is a protocol defined in this specification, and a link quality measurement request frame and a link quality measurement response frame are transmitted and received by a terminal and an access point, and the quality parameters included in these frames are analyzed to improve the quality of the radio link. Make measurement more accurate.

This link quality measurement protocol does not necessarily have to be started at the terminal. That is, the link quality measurement protocol may be initiated at the terminal or at the access point. When the link quality measurement protocol is started at the terminal, the link quality measurement frame transmitted by the terminal becomes the link quality measurement request frame, and the link quality measurement frame transmitted by the access point becomes the link quality measurement response frame. Conversely, when the link quality measurement protocol starts at the access point, the link quality measurement frame transmitted by the access point becomes a link quality measurement request frame, and the link quality measurement frame transmitted by the terminal becomes a link quality measurement response frame.

However, for convenience, in the following, the link quality measurement protocol will be described based on the one started at the terminal. That is, the link quality measurement request frame is a link quality measurement frame transmitted by the terminal to the access point, and the link quality measurement response frame is a link quality measurement frame transmitted by the access point to the terminal in response to the link quality measurement request frame transmitted by the terminal. to be.

The link quality measurement protocol may use a frame defined separately for the link quality measurement frame, and may use a vendor specific type 802.11 action frame (category 126 or 127).

In the link quality measurement protocol, the terminal and the access point repeatedly transmit and receive a link quality measurement request frame and a link quality measurement response frame, but each frame stores update information of the number of frames transmitted and received and / or the average value of quality parameters. By doing so, it is possible not only to provide more accurate quality information of the radio link to the terminal, but also to provide quality information of the radio link to the terminal even if some frames are lost in the transmission / reception process.

Hereinafter, an embodiment of configuring a link quality measurement request frame and a link quality measurement response frame using a Vendor Specific type 802.11 action frame (category 126 or 127) will be described.

Table 6 is a table showing the structure of a link quality measurement request frame according to an embodiment of the present invention, and Table 7 is a table showing the structure of a link quality measurement response frame according to an embodiment of the present invention.

In this embodiment, the Action field is a field that separates the link quality measurement request frame from the link quality measurement response frame, and the Dialog Token field is a field that distinguishes one pair of the request frame and the response frame. And the Mode field is a field indicating start / continue / end of the link quality measurement frame. Since the measurement field includes a quality parameter, in particular, the measurement field stores the quality parameter measured while receiving the link quality measurement frame transmitted by the external device, so that the device transmits the link quality measurement frame to the external device. This quality information can be fed back to the other device while transmitting.

Here, the counterpart device is used to mean a device that transmits a link quality measurement frame among a terminal and an access point. For example, when the terminal transmits a link quality measurement request frame to an access point, the terminal performs a counterpart device. When the access point transmits a link quality response frame, the access point becomes a counterpart device. Here, the device corresponds to the counterpart device. If the counterpart device is a terminal, the device becomes an access point, and when the counterpart device is an access point, the device becomes a terminal.

If the terminal is a counterpart device and the access point is the present device as an example, the device (access point) that has received the link quality measurement frame (link quality measurement request frame) transmitted by the counterpart device (terminal) is the counterpart device. While receiving the link quality measurement frame (link quality measurement request frame) from (terminal), the measured quality parameter is stored in a measurement field of the link quality measurement frame (link quality measurement response frame). Thereafter, the device (access point) transmits a link quality measurement frame (link quality measurement response frame) to the counterpart device (terminal), and receives a link quality measurement frame (link quality measurement response frame) from the device (access point). One counterpart device (terminal) may estimate the quality of data transmission from the counterpart device to the present device through quality parameters included in a measurement field of the link quality measurement frame (link quality measurement response frame).

The quality parameter included in the measurement field may include the average received signal strength and the number of link quality measurement frames for the link quality measurement frames received from the external device since the link quality measurement protocol was started. In the embodiments shown in Table 6 and Table 7, the quality parameters included in the measurement field include the average received signal strength and the link quality measurement frame for the link quality measurement frames received from the external device since the link quality measurement protocol was started. Number is included.

Hereinafter, a process of transmitting and receiving a link quality measurement frame according to a link quality measurement protocol will be described with reference to FIG. 5.

5 is a diagram illustrating an embodiment of a process of transmitting and receiving a link quality measurement frame according to a link quality measurement protocol.

5, in this embodiment, the link quality measurement protocol is started at the terminal. That is, the terminal starts by transmitting a link quality measurement request frame to the access point. In the figure, the box indicated at the top of the arrow shows the structure of the link quality measurement frame including four fields. The first field is the Action field, the second field is the Dialog field, the third field is the Mode field, and the fourth field is the Measurement field, which links to the first item in the fourth field. The average received signal strength for link quality measurement frames received from the external device since the quality measurement protocol was started is recorded, and the second item accumulates the number of link quality measurement frames received from the external device since the link quality measurement protocol was started. One value is recorded.

First, the terminal first transmits a link quality measurement request frame to an access point (S501). Since the link quality measurement frame is a request frame, information called a request frame is stored in the Action field. And, since it is the first frame to measure the link quality, 0 is recorded in the Dialog field and recorded as start in the Mode field. In addition, since the link quality measurement frame is transmitted for the first time, the link quality measurement frame has never been received from the external device, so the measurement field is not yet filled.

Subsequently, the access point receives a first link quality measurement request frame from the terminal. The access point that has received the first link quality measurement request frame measures the received signal strength of the link quality request frame received from the counterpart device. The received signal strength of this link quality request frame is indicated on the side of the arrow in the figure. The average value of the received signal strength of the link quality measurement request frame is determined by using the average of the received signal strength of the measured link quality request frame (-70 dBm) and the received signal strength of the link quality request frame received from the terminal, which is the last device. After the calculation, the calculated average received signal strength is updated in the first field of the Measurement field of the link quality measurement response frame. However, since the current access point has received the first link quality measurement request frame from the terminal, the received signal strength of the received link quality request frame is the average received signal strength. Therefore, -70 dBm is stored in the first field of the Measurement field of the link quality measurement response frame. In addition, the access point that received the first link quality measurement request frame stores the accumulated value of the number of link quality request frames received from the terminal, which is a counterpart device, in the second column of the measurement field of the link quality measurement response frame. Since the current access point has received the first link quality measurement request frame from the terminal, the number of link quality request frames received from the terminal is 1. Therefore, the access point records 1 in the second field of the Measurement field of the link quality measurement response frame.

Next, the access point transmits a link quality measurement response frame to the terminal (S503). Since the link quality measurement frame transmitted by the access point is a response frame, information called a response frame is stored in the Action field. In addition, since the link quality measurement response frame transmitted by the access point is a link quality measurement frame paired with the first link quality measurement request frame, 0 is recorded in the dialog field. In addition, since the link quality measurement response frame transmitted by the access point is the first link quality measurement response frame, information of start is recorded in the Mode field. In addition, in the first field of the measurement field, the average received signal strength of the link quality measurement request frame received by the access point is -70 dBm, and in the second field, the link quality request frame received from the terminal, which is the access point, is accessed. The number of frames, 1, is recorded.

Next, the terminal receives a link quality measurement response frame from the access point. Upon receiving the first link quality measurement response frame, the terminal measures the received signal strength of the link quality response frame received from the access point, which is a counterpart device. Then, the received signal of the link quality measurement request frame using the average value of the received signal strength of the measured link quality response frame (-67 dBm) and the received signal strength of the link quality measurement response frame received from the access point as a partner device up to the last. After calculating the average value of the intensity, the calculated average received signal intensity is stored in the first field of the Measurement field of the link quality measurement request frame. However, since the current terminal has received the first link quality measurement response frame from the access point, the received signal strength of the received link quality response frame is the average received signal strength. Therefore, -67 dBm is stored in the first column of the Measurement field of the link quality measurement request frame. In addition, the terminal that receives the first link quality measurement response frame stores the number of link quality measurement response frames received from the access point, which is a counterpart device, in the second column of the Measurement field. Currently, since the terminal has received the first link quality measurement response frame from the access point, the number of link quality measurement response frames received from the access point is 1. Therefore, the UE records 1 in the second column of the Measurement field of the link quality measurement request frame.

Next, the terminal transmits a link quality measurement request frame to the access point (S505). Since the link quality measurement frame transmitted by the terminal is a request frame, information called a request frame is stored in the Action field. In addition, since the link quality measurement request frame transmitted by the terminal is the second link quality measurement request frame, 1 is recorded in the dialog field. In addition, since the link quality measurement request frame transmitted by the terminal is not the first link quality measurement request frame and is not the last link quality measurement request frame, information of continuity is recorded in the Mode field. In addition, in the first column of the measurement field, the cumulative average received signal strength of the link quality measurement frame received by the terminal is -67 dBm, and in the second column, the terminal of the link quality response frame received from the access point that the terminal is a counterpart device is recorded. The number of frames, 1, is recorded.

Next, the access point receives a link quality measurement request frame from the terminal. The access point receiving the second link quality measurement request frame measures the received signal strength of the link quality measurement request frame received from the terminal, which is a counterpart device. Then, the link quality is measured using the received signal strength (-72 dBm) of the measured link quality measurement request frame and the average value (-70 dbm) of the received signal strength of the link quality measurement request frame received from the access point, which is the last device. After calculating the average value (-71 dBm) of the received signal strength of the request frame, the calculated average received signal strength is updated in the first field of the Measurement field of the link quality measurement response frame. Therefore, -71 dBm is stored in the first field of the Measurement field of the link quality measurement response frame. In addition, the access point receiving the second link quality measurement request frame stores the number of link quality measurement request frames received from the terminal, which is a counterpart device, in the second column of the measurement field of the link quality measurement response frame. Since the current access point has received a second link quality measurement request frame from the terminal, the number of link quality request frames received from the terminal is 2. Therefore, the access point records 2 in the second column of the Measurement field of the link quality measurement response frame. That is, the access point has received two link quality measurement request frames from the terminal since the link quality measurement protocol started, and knows the information that the average value of the received strengths of these two link quality measurement request frames is -71 dBm, and this information is a link. It can be stored in the quality measurement response frame and fed back to the terminal.

Next, the access point transmits a link quality measurement request frame to the terminal (S507). Since the link quality measurement frame transmitted by the access point is a response frame, information called a response frame is stored in the Action field. In addition, since the link quality measurement response frame transmitted by the access point is the second link quality measurement response frame, 2 is recorded in the dialog field. In addition, since the link quality measurement response frame transmitted by the access point is not the first link quality measurement response frame and is not the last link quality measurement response frame, information of continuity is recorded in the Mode field. In addition, in the first field of the Measurement field, the average received signal strength of the link quality measurement request frame received by the access point from the terminal is -71 dBm, and in the second column, the link received from the terminal whose access point is the counterpart device is recorded. The number of frames of the quality measurement request frame 2 is recorded.

Next, the terminal receives a link quality measurement response frame from the access point. The terminal receiving the second link quality measurement response frame measures the received signal strength of the link quality measurement response frame received from the access point, which is a counterpart device. Then, link quality is measured using the received signal strength (-63 dBm) of the measured link quality measurement response frame and the average value (-67 dbm) of the received signal strength of the link quality measurement response frame received from the access point, which is a counterpart device up to the last. After calculating the average value (-65 dBm) of the received signal strength of the response frame, the calculated average received signal strength is updated in the first column of the Measurement field of the link quality measurement request frame. Therefore, -65 dBm is stored in the first field of the Measurement field of the link quality measurement request frame. In addition, the terminal receiving the second link quality measurement response frame stores the accumulated value of the number of link quality measurement response frames received from the access point, which is a counterpart device, in the second field of the measurement field of the link quality measurement request frame. Since the current terminal has received the second link quality measurement response frame from the access point, the number of link quality measurement response frames received from the access point is 2. Therefore, the UE records 2 in the second column of the Measurement field of the link quality measurement request frame. That is, the terminal has received two link quality measurement response frames from the access point after the link quality measurement protocol is started, and knows the information that the average value of the received strengths of these two link quality measurement response frames is -65 dBm, and this information is a link. It can be stored in the quality measurement request frame and fed back to the access point.

Next, the terminal transmits a third link quality measurement request frame to the access point (S509). However, the access point has not received this third link quality measurement request frame within a certain time. In this case, the terminal repeatedly transmits the fourth link quality request frame after a predetermined time (S511). However, the access point also did not receive the fourth link quality request frame within a predetermined time, and did not continuously receive the subsequent link quality request frame.

However, according to the link quality measurement protocol, even if some of the link quality measurement frames are lost, link quality information can be inferred from the frame received immediately before. That is, the access point receives one link quality measurement response frame from the terminal through the information stored in the second link quality measurement request frame received immediately before, and the average value of the reception strength of the link quality measurement response frame received by the terminal is -67 dBm. Information. In addition, the access point received two link quality request frames from the terminal using the information included in the link quality measurement response frame transmitted to the terminal immediately before, and the average value of the received strengths of the link quality request frames received from the terminal You can see the information of -71dBm. The terminal, like the access point, can know information about uplink quality and downlink quality. In other words, even if some of the link quality measurement frames are lost, the radio link quality may be inferred using the final link quality measurement frame information. In addition, since the link quality measurement frame is repeatedly transmitted and received, there is an advantage that more accurate information about the radio link quality can be obtained.

On the other hand, the terminal has finally transmitted the tenth link quality measurement request frame (S513), the tenth link quality measurement request frame is an end frame. Since the 10th link quality measurement request frame is a request frame and the 10th link quality measurement request frame, request is recorded in the Action field and 9 is recorded in the Dialog field. In addition, since the tenth link quality measurement request frame is an end frame, information of end is recorded in the Mode field. In the case of the measurement field, there is no change, so the same information as the information stored in the previous link quality measurement request frame is recorded.

Next, the access point receives a 10th link quality measurement request frame from the terminal. The access point receiving the 10th link quality measurement request frame measures the received signal strength of the link quality measurement request frame received from the terminal. Then, using the received signal strength of the measured link quality measurement request frame (-78dBm) and the average value (-71dBm) of the received signal strength of the link quality measurement request frame received from the terminal up to the previous reception of the link quality measurement request frame After calculating the average value of signal strength (-73dBm), the calculated average received signal strength is updated in the first field of the Measurement field of the link quality measurement response frame. Therefore, -73 dBm is stored in the first column of the Measurement field of the link quality measurement response frame. In addition, the access point receiving the 10th link quality measurement request frame stores the accumulated value of the number of link quality measurement request frames received from the terminal in the second column of the measurement field of the link quality measurement response frame. Currently, the access point has received the 10th link quality measurement request frame from the terminal, but the number of link quality measurement request frames actually received by the access point is three. Therefore, the access point records 3 in the second column of the Measurement field of the link quality measurement response frame.

Next, the access point transmits a 10th link quality measurement response frame to the terminal (S515). The 10th link quality measurement response frame is a response frame and is an end frame. -73dBm, 3 is stored in the measurement field of the 10th link quality measurement response frame. Through this, the access point has received three link quality measurement request frames from the terminal after the link quality measurement protocol is started, and the information that the average value of the received strengths of these three link quality measurement request frames is -73 dBm can be fed back to the terminal. have. As such, when the access point transmits the last link quality measurement response frame, the link quality measurement protocol ends.

Meanwhile, FIG. 5 shows an embodiment of a link quality measurement protocol in which both a terminal and an access point perform link quality measurement and feed it back to a counterpart device. However, the link quality measurement protocol according to the present invention is not limited to this embodiment, and may be implemented to perform link quality measurement only in one of a terminal or an access point device.

For example, the link quality measurement protocol according to another embodiment of the present invention does not perform link quality measurement in a terminal transmitting a link quality measurement request frame, and only an access point receiving a link measurement request measures the link quality and reports it to the terminal. Can be operated. This embodiment will be described with reference to FIG. 6, but a description overlapping with FIG. 5 will be omitted and the difference will be mainly described.

6 is a view showing another embodiment of a process of transmitting and receiving a link quality measurement frame according to a link quality measurement protocol.

Referring to FIG. 6, a measurement field exists only in a link quality measurement response frame transmitted by an access point. That is, only the access point measures link quality, and the terminal does not measure link quality. In other words, the access point measures the uplink quality from the terminal to the access point, and transmits a link quality measurement response frame to the terminal by including information on the uplink quality in the link quality measurement response frame. In this case, as shown in FIG. 6, the measurement (Measurement) field of the link quality measurement request frame and the mode (Mode) field of the link quality measurement response frame may be omitted.

The access point receives the first link quality measurement request frame from the terminal, measures the received signal strength of the link quality measurement request frame, and stores the average value of the received signal strength in the link quality measurement response frame. As illustrated, the received signal strength of the first link quality measurement request frame is -70 dBm, and since the number of received frames is 1, the average received signal strength is -70 dbm. Therefore, -70 dbm, 1 is recorded in the Measurement field of the link quality measurement response frame transmitted by the access point.

Thereafter, the terminal has transmitted a link quality measurement request frame, but for a period of time, the access point has not received a link quality measurement request frame. Finally, the access point has received the link quality measurement request frame transmitted by the terminal, and the reception strength of this last link quality measurement request frame is -76 dBm. Finally, the number of frames received by the access point is 2, and the average received signal strength is -73 dBm. Accordingly, -73 dBm, 2 is recorded in the measurement field of the link quality measurement response frame transmitted by the access point. The terminal that has received the last link quality measurement response frame from the access point can estimate the uplink quality from the terminal to the access point using the information recorded in the measurement field.

On the other hand, when the terminal searches for an access point and uses a link quality measurement protocol in the process of being connected to the access point, more accurate information about the quality of the radio link can be obtained and radio link quality information can be obtained even if some frames are lost. Although there is an advantage, the terminal may have a connection delay and power consumption due to additional time required to measure link quality, and the access point may have a problem of consuming radio resources. Therefore, it is desirable to transmit the link quality measurement frame as efficiently as possible. To this end, the terminal may be implemented so as to transmit a link quality measurement request frame a predetermined number of times (for example, 5 times), and not transmit additional link quality measurement request frames when all of the response frames are received or not received at all. When a part of the response frame for the transmitted request frame is received, a link quality measurement request frame may be additionally transmitted to increase measurement accuracy.

In addition, when transmitting a link quality measurement frame, a terminal or an access frame can specify a target data rate, and when transmitting a link quality measurement frame at a specified target data rate, it is possible to check how many frames are successfully received by the receiving side. Yes (the second item in the Measurement field in the example above). Through this, the terminal or the access point can calculate the transmission success rate at a specific data transmission rate. If the transmission success rate at the calculated specific data transmission rate is lower than the access quality criterion suggested by the access point, the access point may be implemented to be excluded from the search list.

Meanwhile, such a link quality measurement protocol has been described as being used to select an access point, but is not limited thereto. That is, the link quality measurement protocol may be used in the step of searching for an access point, or after the terminal is connected to the access point, it may be used to monitor the radio link quality of the terminal and the access point. That is, even after the terminal and the access point are connected, the terminal and the access point can estimate the radio link quality by transmitting and receiving a link quality measurement frame. If the quality of the radio link is lowered below a certain criterion, the terminal may perform roaming to another access point, or disconnect the wireless LAN and perform a connection with the mobile communication network.

In addition, the access point may manage the radio link quality by monitoring the radio link quality with terminals connected to the access point using a link quality measurement protocol.

In addition, it is needless to say that the access point can statistically manage the correlation between the radio link quality and various quality parameters to provide a quality parameter access criterion to the terminal. For example, a quality parameter at a point in time at which a minimum link quality can be guaranteed can be measured and provided to the terminal as a quality parameter access criterion. As another example, quality parameters at a point in time at which link quality at a certain target level can be guaranteed may be measured and provided to the terminal based on the quality parameter access criteria.

After measuring the wireless link quality parameter for each access point using the link quality measurement protocol, the terminal may exclude the access point whose measured quality parameter is lower than the quality parameter access criterion from the connection target access point. The terminal may be implemented to select a priority connection priority by assigning priority or weighting among various quality parameters when multiple access points to be connected are connected, and attempt to connect in order accordingly. Those skilled in the art to which the present invention pertains will be able to analyze the quality parameters in various ways so that the terminal can access an access point having the optimal or family-friendly radio link quality.

On the other hand, the access point selection method using the link quality measurement protocol may be performed independently, but after the access point having poor link quality is first excluded from the search result list through quality parameter analysis by the above-described probe response frame. It is preferable to use the standard protocol frame to exclude the access point having poor link quality from the search result list, and then to use the third link to exclude the access point with poor link quality from the search result list.

Next, the method for maintaining the radio link quality after the access point is connected by using the link quality information request frame defined in this specification and the link quality information response frame corresponding thereto Let's take a look.

<Selection of access point using link quality information frame>

Through the above-described steps, even if the terminal selects an access point having the optimal or family-friendly radio link quality and is connected to the access point, the radio link quality may not be continuously maintained. That is, the quality of the radio link may continuously change according to changes in the radio environment, movement of the terminal, and the like. Accordingly, in order to maintain good radio link quality, the quality of the radio link with the access point is continuously monitored, and if the quality of the radio link of the connected access point deteriorates, attempt to connect with another access point or switch to another communication network, for example, movement It is necessary to attempt to switch to a communication network.

The link quality information protocol is a protocol used to maintain the radio link quality by monitoring the radio link quality after the terminal is connected to the access point.

The link quality information protocol is composed of a link quality information request frame and a link quality information response frame. A device requesting radio link quality information from a terminal or an access point transmits a link quality information request frame to a counterpart device, and a device receiving the link quality information request frame transmits a link quality information response frame correspondingly. That is, the apparatus for transmitting the link quality information request frame may be a terminal or an access point.

The link quality information protocol may use a frame defined separately for the link quality information frame, or a Vendor Specific type of 802.11 action frame (category 126 or 127), the frame communicates with the terminal and the access point to link quality. You can also measure.

Preferably, the terminal is implemented to transmit the link quality information request frame, and the access point is implemented to transmit the link quality information response frame to the terminal in response to the request of the terminal. Hereinafter, an embodiment in which the access point provides radio link quality information at the request of the terminal will be described in detail.

Table 8 is a table showing the structure of a link quality information request frame, and Table 9 is a table showing the structure of a link quality information response frame.

In this embodiment, an 802.11 action frame (category 126 or 127) of Vendor Specific type is used. In this embodiment, the Action field is a field separating the link quality information request frame and the link quality information response frame, and the Dialog field is a field separating a pair of the request frame and the response frame, There is no significant difference from the link quality measurement frame described above.

In the link quality information request frame, the Triggered Bitmap field may provide information regarding a quality parameter list requiring analysis or monitoring among one or more quality parameters. Since the quality parameters used in the link quality information protocol are not limited in principle, various quality parameters can be used. For example, the quality parameters used in the Triggered Bitmap field include uplink signal strength (RSS), access point peripheral interference (Noise) signal strength, downlink frame error rate (FER), channel utilization (channel utilization), etc. This can be included.

The triggered bitmap field is configured in the form of a bitmap. For example, a quality parameter that requires analysis or monitoring among a plurality of parameters is indicated by 1, and a quality parameter that does not require analysis or monitoring is indicated by 0 and analyzed or monitored. It can provide information on a list of quality parameters that require. There are four quality parameters used in the embodiments shown in Tables 8 and 9, uplink signal strength (RSS), access point peripheral interference signal strength (Noise), downlink frame error rate (FER), and channel utilization (CH). .Util). For example, when the terminal requests that the access point monitors for uplink signal strength (RSS), the triggered bitmap may be set to 1 0 0 0. The access point receiving the link quality information request frame may monitor the uplink signal strength (RSS) and transmit the link quality information response frame to the terminal when the uplink signal strength (RSS) does not satisfy the quality parameter access criterion. . On the other hand, since 1 and 0 are not used as bits of an absolute meaning, it is obvious to a person skilled in the art that 1 and 0 can be used in reverse and can be used in other notation methods.

In the link quality information response frame, the triggered bitmap field is set to the same value as the triggered bitmap field included in the link quality information request frame. Accordingly, the access point continuously monitors the quality parameter requested by the terminal to transmit a link quality information response frame to the terminal when the quality parameter does not satisfy the quality parameter access criterion.

At this time, status information of the quality parameter is stored in the link quality information field included in the link quality information response frame. In the above example, the access point monitoring the uplink signal strength (RSS) records the uplink signal strength (RSS) being monitored in the link quality information field when the uplink signal strength (RSS) does not satisfy the access criterion. And transmit the link quality information response frame to the terminal. In this case, the access point may record the status information for other quality parameters (in the above embodiment, Noise, FER, CH.Util) in the link quality information field, and transmit the link quality information response frame to the terminal. .

Preferably, since it is not certain whether the link quality information response frame transmitted by the access point will be received by the terminal, the access point periodically transmits the link quality information response frame when the quality parameter being monitored does not satisfy the access criterion. May be implemented.

Upon receiving the link quality information response frame transmitted from the access point, the terminal may roam to another access point or switch the interface to the mobile communication network by referring to the Triggered Bitmap field and the link quality information field.

Features described in individual embodiments herein may be implemented in combination in a single embodiment. Conversely, various features that are described in this specification in a single embodiment may be individually implemented in various embodiments, or may be implemented in appropriate subcombinations.

Although the operations in the drawings have been described in a specific order, it is not to be understood that such operations are performed in a specific order as shown, or a series of sequences, or all described actions are performed to obtain a desired result. . In some environments, multitasking and parallel processing can be advantageous. In addition, it should be understood that the division of various system components in the above-described embodiment does not require such division in all embodiments. The program components and systems described above may be implemented in a package in a single software product or multiple software products.

The present invention described above, since it is possible for a person having ordinary skill in the art to which the present invention pertains, various substitutions, modifications and changes are possible within the scope of the technical spirit of the present invention, and the above-described embodiment and the attached It is not limited by the drawings.

100: terminal
200, 200a, 200b, 200c: access point

Claims (15)

In the wireless LAN system, the terminal selects and connects an access point to connect to a wireless link,
Receiving, by the terminal, a probe response frame including quality parameters that provide information regarding the quality of the radio link with the access point;
A first analysis step of analyzing, by the terminal, quality parameters included in the received probe response frame; And
Including the step of selecting and connecting the access point to the radio link to the terminal using the analysis result;
The probe response frame is a method of selecting and connecting an access point including connection information for each quality parameter that can satisfy the quality of a radio link to be provided by the access point and status information of a quality parameter that the access point can provide. According to claim 1,
A method of selecting and connecting an access point, wherein the quality parameter included in the probe response frame includes at least one of the number of terminals connected to the access point and the utilization rate of the operating channel. delete According to claim 1,
The access criterion for each quality parameter includes at least one of a downlink signal strength, an uplink signal strength, a maximum number of allowed access terminals, a maximum allowed channel usage rate, and a noise signal strength around an access point.
The status information of the quality parameter includes the uplink signal strength measured by the signal strength of the probe request frame transmitted by the terminal, the noise signal strength around the access point, the status information of the backhaul, the number of terminals connected to the access point, and the channel. A method of selecting and connecting an access point, characterized in that it comprises at least one of usage rates. According to claim 1,
The terminal transmitting a standard protocol query;
The terminal receiving a standard protocol response to the standard protocol query from the access point; And
A second analysis step of analyzing the quality parameter included in the received standard protocol response by the terminal;
How to select and connect to the access point, characterized in that it further comprises. The method of claim 5,
A method of selecting and connecting an access point, characterized in that the standard protocol used for the standard protocol query and the standard protocol response is ANQP of the 802.11u standard. The method of claim 6,
The ANQP query includes at least one of WAN Metric information, a list of roamable peripheral access points, access criteria for each quality parameter that can satisfy the quality of a wireless link to be provided by the access point, and status information of a quality parameter that the access point can provide. How to select and connect to the access point, characterized in that. The method of claim 5,
The terminal transmitting a link quality measurement request frame;
The terminal receiving a link quality measurement response frame for the link quality measurement request frame from the access point; And
A third analysis step of analyzing, by the terminal, quality parameters included in the received link quality measurement response frame;
A method of selecting and connecting an access point, comprising: transmitting the link quality measurement request frame and receiving the link quality measurement response frame from the access point are performed alternately one or more times. . The method of claim 8,
Quality parameters included in the link quality measurement response frame,
A method of selecting and connecting an access point, characterized by including the number of received frames and the received signal strength. The method of claim 9,
The number of received frames and the received signal strength, which are quality parameters included in the link quality measurement request frame, are alternately performed by transmitting the link quality measurement request frame and receiving the link quality measurement response frame. Updated in the process,
The number of received frames is cumulatively updated.
Method of selecting and connecting an access point, characterized in that the average value of the received signal strength of the received frame of the received frame is updated. The method of claim 10,
The third analysis step is a method of selecting and connecting an access point, characterized in that the quality parameter included in the link quality measurement response frame finally received by the terminal is analyzed. After the terminal and the access point are connected by a method of selecting and connecting the access point according to any one of claims 1, 2, 4 to 11,
Maintaining radio link quality;
Access point access management method comprising a. The method of claim 12,
Maintaining the radio link quality,
The terminal transmitting a link quality measurement request frame;
The terminal receiving a link quality measurement response frame for the link quality measurement request frame from the access point;
A fourth analysis step of analyzing, by the terminal, quality parameters included in the received link quality measurement response frame; And
Determining whether the terminal maintains a connection state with an access point connected to a radio link using the analysis result;
The method of claim 1, wherein the transmitting of the link quality measurement request frame and the receiving of the link quality measurement response frame from the access point are performed alternately one or more times. The method of claim 12,
Maintaining the radio link quality,
The terminal transmitting a link quality information request frame;
The terminal receiving a link quality information response frame for the link quality information request frame from the access point;
A fifth analysis step of analyzing, by the terminal, quality parameters included in the received link quality information response frame; And
Determining whether the terminal maintains a connection state with an access point connected to a radio link using the analysis result;
Including, but, the link quality information request frame includes a list of quality parameters that require analysis, and the link quality information response frame provides quality parameter status information for the quality parameter list that requires the analysis. How to manage access point access. The method of claim 14,
The access point that has received the link quality information request frame monitors a quality parameter requiring analysis included in the link quality information request frame, and if the quality parameter does not satisfy the quality parameter access criterion, the link quality to the terminal A method for managing access point access, characterized by transmitting an information response frame.

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