WO2010067960A2

WO2010067960A2 - Fast handover method in a wireless lan, and mobile terminal adopting same

Info

Publication number: WO2010067960A2
Application number: PCT/KR2009/006253
Authority: WO
Inventors: 박종태
Original assignee: 경북대학교 산학협력단
Priority date: 2008-12-12
Filing date: 2009-10-28
Publication date: 2010-06-17
Also published as: WO2010067960A3; KR20100067793A; KR100991169B1

Abstract

The present invention relates to a fast handover method in a wireless LAN, and to a mobile terminal adopting the same. The handover method comprises the steps of (a) determining a handover, and transmitting an authentication request message to a target access point, if the intensity of the signal received from the current access point is lower than a preset first threshold value (T1); (b) determining whether or not to apply a reauthentication request module in accordance with the set user profile; (c) driving a timer, if the reauthentication request module is applied in accordance with the result of the determination of step (b); (d) receiving an authentication response message from the target access point; (e) performing a reauthentication process with the target access point if the time counted by the timer has elapsed past the preset reauthentication request time and the handover has not been carried out; and (f) performing a procedure for reaccess to the target access point if the handover to the target access point is performed within a limited reaccess time. The present invention makes a request for reauthentication if a handover does not occur within the limited reaccess time, thereby providing a fast handover.

Description

Fast Handover Method in Wireless LAN and Mobile Terminal Using the Same

The present invention relates to a fast handover method of a mobile terminal in a wireless LAN and a mobile terminal using the same. More specifically, a handover performance of a mobile terminal in a wireless LAN environment using IEEE 802.11r supporting fast roaming in the same mobility region The present invention relates to a method and system for installing a user profile management module and a reauthentication request timer module to prevent excessive handover when a mobile station moves between basic service sets and providing high-speed mobility. .

Looking at the conventional technology related to the present invention, there is a wireless LAN system based on the existing IEEE 802.11 international standards that are actively installed worldwide. The IEEE 802.11 WLAN system has the advantage of easily accessing various Internet multimedia services at high speed at low cost, but has the disadvantage of weak security. In order to improve this security problem, the IEEE 802.11i working group proposed the IEEE 802.11i standard security protocol. However, the IEEE 802.11i security protocol has a problem that excessive handover authentication delay occurs when the mobile station changes a different WLAN access point. In order to improve the handover authentication delay time, the IEEE 802.11r working group has recently adopted the IEEE 802.11r fast BSS Transition protocol, which can reduce the handover authentication delay. It was established. Hereinafter, a handover method according to the IEEE 802.11 international standard will be described with reference to the accompanying drawings.

1 is a system configuration diagram illustrating a handover according to a general IEEE 802.11r standard. Referring to FIG. 1, the entire system includes a mobile terminal 100, an authentication server 110, and access points (

Access Points

120, 130, and 140), and each access point is included in the same extended service set. Belong to the same mobility domain with the same mobility domain identifier (MDID). If the mobile station performs handover in the same mobility area, the mobile station does not hand over the existing security-based IEEE 802.11 method, but instead of the IEEE 802.11r high-speed basic service with security that supports fast roaming in the mobility area. Handover is performed in a manner according to the Fast BSS Transition protocol.

First, a general initial access procedure will be described with reference to FIG. 2. FIG. 2 is a flowchart illustrating an initial access procedure in which a mobile station first accesses an access point according to IEEE 802.11r in a wireless LAN environment. Referring to FIG. 2, when a mobile terminal first attempts to connect with an access point of any mobility area of a wireless LAN environment, the mobile terminal transmits an Open Authentication Request message to the access point (step 201). Receive an Open Authentication Response message from the server (step 202). Here, the public authentication request and public authentication response process is based on the public authentication method of the IEEE802.11 standard. For reference, the IEEE802.11 standard provides two authentication mechanisms, an open authentication method and a shared key authentication method. In the open authentication scheme, the entire authentication flow is made in clear text, and the client can access the access point without a valid WEP key. In shared-key authentication, a challenge text packet is sent only if the access point encrypts the client with the correct WEP key and returns it to the access point, where authentication fails if the client has an invalid key or does not have a key. Cannot be connected to

Thereafter, the mobile terminal transmits an association request message to the access point (step 203), and receives an association response message from the access point (step 204). The mobile station performs an authentication process by an authentication server according to the IEEE 802.1x / EAP protocol (step 205). Through this authentication process, the access point and the mobile station obtain a pairwise master key (PMK) or PMK-related information, and use the EAPOL-Key message to obtain 4 The 4-way handshake process is performed (steps 206, 207, 208, and 209). The mobile terminal then transmits the encrypted information through the access point.

As such, when the mobile terminal first connects to a connection point in an arbitrary mobility region, an initial connection procedure is performed through the above-described process. In addition, when the mobile terminal moves and accesses another target access point, in order to perform handover at high speed in the same mobility region, the IEEE 802.11r standard proposes a fast handover method. FIG. 3 is a flowchart sequentially illustrating a fast transition operation according to a fast basic service aggregation transition protocol of IEEE 802.11r when a mobile terminal performs handover in the same mobility region after initial access. Referring to FIG. 3, when a terminal performing an initial access procedure (step 300) performs a handover in the same mobility region, the terminal predicts a movable access point, sets a target access point, and the mobile terminal performs a handover. The authentication request message is transmitted to the target access point (step 301) before the authentication response message is received from the target access point (step 302).

In this case, the authentication process according to IEEE 802.1x / EAP for the mobile terminal is omitted, and the authentication request message and the response message play a role of the EAPOL-Key 1,2 process in the four-step handshake process upon initial access. Thereafter, a handover occurs and the mobile station transmits a reassociation request message to the target access point (step 303), and receives a reassociation response message from the target access point (step 304). At this time, the reconnection request message and the reconnection response message play a role of the EAPOL-Key 3, 4 process of the 4-step handshake process. Therefore, when the mobile terminal hands over to another access point in the same mobility area, the mobile terminal performs a simplified four-step handshake to complete the handover process at high speed and communicate.

The IEEE 802.11r protocol performs pre-authentication by requesting an authentication request and receiving a response from a target access point belonging to the same mobility region before handover occurs based on the movement prediction of the terminal. This operation procedure is ideally performed immediately before the handover occurs, but it is difficult to accurately predict when the handover occurs in reality. For this reason, conventional techniques generally prepare a handover by predicting handover when the radio wave strength is lower than or equal to a preset first threshold value (T1) through the radio wave strength received by the mobile terminal, and then set a preset If the signal weakens below two thresholds (T2), a handover is performed. However, in a real environment, since the mobility pattern of the user may vary depending on the surrounding situation, the mobile terminal cannot accurately predict a connection point to be connected next.

Therefore, as the mobile terminal moves from the service area of the access point A to the service area of the B, signal attenuation occurs, the signal strength performs a handover preparation process at the T1 point, and the handover occurs at the T2 point. When the signal from the current access point A received by the mobile terminal is attenuated and the signal strength becomes T1, the mobile terminal transmits an authentication request message in preparation for handover to the target access point B. When the authentication request message is transmitted, the reconnection timeout τ is applied from the time α when the message is transmitted. If there is a situation where the mobile station stops moving and stops at a point where the signal strength is less than T1 and more than T2, the handover is delayed because it does not attenuate to less than the signal strength T2. The time τ is exceeded. In this case, there occurs a problem that the authentication information (PTKSA: Pairwise Transient Key Security Association) between the mobile terminal and the target access point B becomes invalid. In this situation, the mobile terminal must pass all initial access procedures including the IEEE 802.1x / EAP procedure in order to abandon the access to the target access point or communicate with the target access point again, resulting in excessive handover delay time.

The technical problem to be achieved by the present invention is to solve the problems of the prior art as described above, the object of the present invention, when the mobile terminal moves in the IEEE 802.11 WLAN, handover occurs later than the predicted time point Even if the re-authentication process is performed, it is possible to prevent excessive handover delay time and to provide a fast handover method capable of supporting fast basic service set transition.

A feature of the present invention for achieving the above-described technical problem relates to a handover method of a mobile terminal in a wireless LAN environment, the handover method, (a) the received signal strength from the current access point is set in advance Determining a handover to the target access point and transmitting an authentication request message to the target access point when falling below one threshold T1; (b) determining whether to apply the reauthentication request module; (c) driving a timer if the reauthentication request module is applied according to the determination of step (b); (d) receiving an authentication response message from the target access point; (e) transmitting a reauthentication request message to the target access point within a preset reconnection time limit when the timer passes a preset reauthentication request time without performing a handover; (f) if the handover is performed to the target access point within the reconnection time limit, performing a reconnection process with the target access point; It is provided.

In the handover method of the mobile terminal having the above-mentioned characteristics, the step (b) is characterized in that it is determined whether to apply the re-authentication request module according to the information set in the user profile of the mobile terminal, The information is preferably information set by the user's selection or information set according to the type of service of the mobile terminal.

In the handover method of the mobile terminal having the above-mentioned feature, the reauthentication request time is preferably set to a time shorter than the reconnection time limit.

In the handover method of the mobile terminal having the above-mentioned characteristics, when the mobile terminal does not transmit the reconnection request message to the target access point in step (e), it is preferable to determine that the mobile terminal has not performed the handover to the target access point. Do.

In the handover method of the mobile terminal having the above-mentioned characteristics, if it is determined in step (b) that the reauthentication request module is not applied, an authentication response message is received from a target access point, and the target access point is within the reconnection time limit. If a handover occurs, the reconnection process is performed with the target access point. If the handover does not occur within the reconnection time limit, the authentication information is invalidated.

In the handover method of the mobile terminal having the above-mentioned characteristic, the reconnection time limit starts from the time when the received signal strength of the current access point is less than or equal to the first threshold value T1, or the received signal strength of the current access point is the first threshold value. It starts at (T1) or less and the received signal strength of the target access point is greater than or equal to the second threshold value T2, and ends when the received signal strength of the current access point is less than or equal to the second threshold value T2.

According to another aspect of the present invention, a mobile terminal includes a key management module for storing authentication related information; A user profile management module for storing and managing a user profile for the mobile terminal; A handover management module for preparing a handover to a target access point or performing a handover to a target access point according to the received signal strength received by the mobile terminal; A timer, determining whether to request reauthentication according to a setting condition of the user profile, and driving the timer when the authentication request message is sent to the target access point by the handover management module, and the driving time of the timer If a handover does not occur even after a predetermined reauthentication request time has elapsed, a reauthentication request module for transmitting a reauthentication request message to a target access point within a preset reconnection time limit; Provides fast handover in LAN environments.

In the mobile terminal having the aforementioned feature, the reauthentication request time is preferably shorter than the reconnection time limit.

In the mobile terminal having the above-mentioned feature, it is preferable that the user profile is set according to the type of service used by the user or whether the application of the re-authentication request module is selected.

As described above, in the IEEE 802.11r environment, the handover method according to the present invention determines the re-authentication request according to the set contents of the user profile management module of the mobile terminal, thereby improving handover performance to ensure high-speed mobility support. Can be.

According to the present invention, when a mobile station moves within the same mobility area in an IEEE 802.11 WLAN, even if a handover occurs later than a handover prediction time, a target access point is used by using a re-authentication request message. Send an authentication request message). As a result, even if the handover occurs after the reassociation deadline time has elapsed, the handover can be prevented from going through the entire initial authentication process, thereby preventing excessive handover delay from occurring and providing a fast basic service set. To support the transition.

1 is a configuration of a wireless LAN system to which a conventional IEEE 802.11r is applied.

2 is a signal flow diagram illustrating an initial access procedure to a wireless access point of a conventional IEEE 802.11r and a mobile terminal to which the present invention is applied.

3 is a message signal flowchart to which the fast movement of the conventional IEEE 802.11r is applied.

4 is a module structural diagram of a mobile terminal according to a preferred embodiment of the present invention.

5 is a diagram illustrating an embodiment in which a re-authentication request timer module is applied according to a configuration of a user profile management module for improving handover performance in IEEE 802.11r according to a preferred embodiment of the present invention.

6 is a signal flow diagram of a mobile terminal to which a re-authentication request timer module is applied according to a configuration of a user profile management module for improving handover performance in IEEE 802.11r according to a preferred embodiment of the present invention.

7 is a flowchart sequentially illustrating a fast handover procedure in a mobile terminal according to an embodiment of the present invention.

8 is a system configuration diagram according to another embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to a fast handover method in a mobile terminal in a wireless LAN environment according to a preferred embodiment of the present invention and a mobile terminal applying the same. In the present invention, the term "mobile terminal" refers to equipment that can transmit and receive data through an access point while moving in a wireless LAN environment, such as a wireless communication terminal, PDA, notebook, next-generation laptop or smart phone. The system to which the handover method according to the present invention is applied includes an authentication server, a plurality of access points, and a mobile terminal constituting IEEE 802.11r. The access point belongs to the same extended service set and belongs to the same mobility area using a mobility domain identifier (MDID). When the mobile station performs handover in the same mobility area, the mobile terminal does not hand over the existing security-based IEEE 802.11 method, but instead of performing the handover according to the IEEE 802.11r method with security that supports fast roaming in the mobility area. Do an over.

4 is a block diagram schematically illustrating an internal structure of a mobile terminal 400 performing fast handover according to an exemplary embodiment of the present invention. Referring to FIG. 4, the mobile terminal 400 according to the present invention includes a key management module 410, a handover management module 420, and a fast mobility management module for managing keys in a mobility area. And a re-authentication request module 440 for requesting re-authentication, a user profile management module 450, and a socket interface 460.

The key management module 410 derives PMKR1 and PTK using PMK-R0, R0KH-ID, R1KH-ID, PMKR0Name, and PMKR1Name from S0KH and S1KH. The derived PMKR1 and PTK, together with PMKR0, authenticate the terminal in the authentication and recombination process (steps 301, 302, 303, and 304) for fast handover to another target access point according to IEEE 802.11r. Used to encrypt data exchanged with

The handover management module 420 performs a handover preparation process when the signal falls below the first threshold value T1 according to the signal strength of the radio wave received by the mobile terminal and the signal falls below the second threshold value T2. If it falls, handover to the target AP is performed.

The fast mobility management module 430 manages a policy of handover and mobility areas occurring in the same mobility area, and the policy of the mobility area includes information on a reassociation deadline time.

The user profile management module 450 stores and manages information about a user profile. The user profile stores information on whether the re-authentication request module 440 is applied and the re-authentication request time. The user profile may be newly set, modified, or changed through the user profile management module. The user may directly set whether to apply the reauthentication request module 440 through the input screen of the user profile management module, or may set whether to apply the reauthentication request module according to the type of service applied to the mobile terminal. Since the handover delay sensitivity is different according to the service type of the mobile terminal, the handover delay sensitivity according to each service type may be determined, and accordingly, whether to apply the reauthentication request module may be determined. In addition, the re-authentication request time is set by the user and stored in the user profile management module, or by the system in consideration of the user's policy selection in the user profile, the policy of the mobility area, the type of service being used by the mobile terminal, and the like. It may be set and stored in advance. The reauthentication request time is for transmitting a reauthentication request message to the target access point within the reconnection time limit when the handover does not occur even after a predetermined time has elapsed after transmitting the authentication request message to the target access point. It is set to a few tens to hundreds of milliseconds shorter than Reassociation Deadline Time.

If there is no user profile management module for determining whether to apply the re-authentication request module, if there are a plurality of mobile terminals in a single mobility area, the plurality of mobile terminals apply the re-authentication request module to resend the authentication request message. By reserving resources, communication in the same mobility area may not be smooth because of the overhead. Accordingly, by providing the user profile management module having the above-described configuration, when the service currently being used by the mobile terminal is a service having a high handover delay sensitivity, the mobile terminal provides a high mobility by applying a re-authentication request module. If the service being used is a service having low handover delay sensitivity, only the existing IEEE 802.11r standard may be applied without applying the reauthentication request module.

The re-authentication request module 440 includes a timer therein and transmits an authentication request message requesting re-authentication to the target access point within the reconnection time limit according to the setting of the user profile. The reauthentication request module 440 determines whether to request a reauthentication according to the user profile of the user profile management module. When the re-authentication request is determined, the mobile station starts a timer from the time point at which the mobile terminal transmits the authentication request message to the target access point in preparation for handover, from which the re-authentication request time and the re-connection time limit are counted. If the handover does not occur even after the timer operation time has elapsed after the reauthentication request time, the reauthentication request module requests the handover management module to transmit a reauthentication request message to the target access point within the reconnection time limit.

The socket interface 450 is for socket communication between the terminal and the authentication server.

Hereinafter, a process of handover by the mobile terminal having the above-described configuration will be described in detail with reference to FIGS. 5 to 7. FIG. 5 is a diagram showing the overall configuration of a wireless LAN system in which a mobile terminal moves according to a preferred embodiment of the present invention, and a graph showing received signal strengths with access points in the mobile terminal. Referring to FIG. 5, in the wireless LAN environment according to the international standard of IEEE 802.11r according to the present invention,

access points

510 and 520 belonging to the same mobility area as the mobile terminal to which the re-authentication request module is applied according to the setting of the user profile are configured. It is. The access point A 510 is an access point to which the mobile terminal is currently connected, and the access point B 520 is a target access point to which the mobile terminal performs handover. As the mobile terminal moves from the service area of the access point A to the service area of the B, signal attenuation occurs, the handover preparation process is performed at the point where the signal strength is T1, and the handover occurs at the point T2. When the signal from the current access point 510 received by the mobile terminal is attenuated and the signal strength is T1, the mobile terminal transmits an authentication request message to the target access point B 520 as a preparation for handover. From the time α when the authentication request message is transmitted, the timer of the reauthentication request module is driven to count the reconnection timeout and the reauthentication request time. If a situation in which the mobile station stops moving and stops at a point where the received signal strength from the current connection point is less than T1 and more than T2 occurs, handover is delayed because the signal strength is not reduced to less than T2. At this time, if the handover does not occur when the timer driving time passes the reauthentication request time, the reauthentication request message is transmitted to the target access point within the reconnection time limit.

6 is a flowchart illustrating a sequence of data transmitted and received with the access points in order for the mobile terminal to implement a fast handover method according to an embodiment of the present invention. Referring to FIG. 6, the mobile terminal 500 having the above-described structure communicates with the current access point through an initial access process (step 600), and when the signal strength of the received current access point 510 is less than or equal to T1. Determines handover to the target access point 520 and sends an authentication request message to the target access point 520 (step 601). After transmitting the authentication request message, the timer of the reauthentication request module is driven to count the reauthentication request time and the reconnection time limit, and an authentication response message is received from the target access point 520 (step 602).

As such, the mobile terminal drives the timer of the reauthentication request module from the time point at which the authentication request message is transmitted. In this case, as shown in FIG. 5, since the authentication request message is transmitted when the received signal strength from the current access point is less than or equal to the first threshold value T1, the timer is driven. Check whether handover has occurred after the timer run time has passed the reauthentication request time. For example, if the mobile station is stopped at the point where the received signal strength from the current access point is T1, no handover will occur within the reconnection timeout. If no handover occurs after the reauthentication request time slightly shorter than the reconnection time limit, the reauthentication request message is transmitted to the target access point within the reconnection time limit (step 610). The target access point 520 receiving the reauthentication request message transmits a new reauthentication response message (step 612), where a new reconnection timeout is set.

Then, when the mobile terminal passes the point where the received signal strength from the current access point is T2, a handover occurs. Even if the handover occurs later than the expected time in the above manner, the mobile station transmits a reconnection request message (step 620). Communication is made through a procedure of receiving a response message (step 622).

Hereinafter, a quick handover method in a mobile terminal having the above-described structure according to the present invention will be described in detail with reference to FIG. 7. 7 is a flowchart sequentially illustrating a process of performing a fast handover in a WLAN environment by a mobile terminal having the above-described structure according to the present invention.

First, when a mobile terminal to which IEEE 802.11r is applied enters a wireless LAN environment and performs a request for access to an access point for the first time, an initial fully authenticated access procedure is performed (step 700). The initial full authentication access process is the same as that described in FIG. 2 and includes a public authentication request and response process, an access request and response process, a user authentication process to the authentication server, and a four-step handshake process. After this process, the mobile terminal transmits the encrypted information to communicate with the access point (step 710).

Next, if the received signal with the access point is attenuated, the mobile station determines handover to the target access point (step 720). In this case, the handover to the target access point is determined when the received signal strength with the current access point is attenuated below a predetermined first threshold value T1 as shown in FIG. 5.

In response to the handover determination, an Authentication Request message is sent to the target access point (step 730). Next, the mobile terminal reads the setting information of the user profile to determine whether to apply the reauthentication request module (step 740).

If the re-authentication request module is not applied in step 740, an authentication response message is received according to the IEEE 802.11r standard (step 780), and a handover occurs within the reconnection timeout (τ) (step 782). The reconnection request message and the reconnection response message are transmitted and received (steps 770/775) to complete the handover to the target access point. Otherwise, the connection to the target connection point is abandoned and the initial fully authenticated connection procedure is performed again.

If the application of the re-authentication request module is determined in step 740, the timer is driven (step 745). Next, the mobile terminal receives an authentication response message from the target access point (step 750). Next, the mobile terminal determines whether a handover has occurred within a predetermined reauthentication request time at the timer (step 760). At this time, the mobile terminal does not perform the handover unless the received signal strength with the existing access point falls below the second threshold value T2, and the received signal strength with the existing access point falls below the second threshold value T2. When the received signal strength with the target connection point falls below the second threshold value T2, handover is performed to the target connection point. Here, when the mobile terminal transmits the reconnection request message to the target access point, it determines that a handover has occurred.

If a handover occurs within the reauthentication request time in step 760, the handover is completed by sending a reconnection request message to the target access point (step 770) and receiving a reconnection response message from the target access point (step 775).

If the handover does not occur within the reauthentication request time in step 760, the reauthentication request message is transmitted to the target access point within the reconnection time limit to request reauthentication (step 730).

As described above, when the mobile terminal according to the present invention applies the authentication information retransmission request timer module, if the mobile terminal does not perform a handover within a preset reauthentication request time using the timer module, the mobile station authenticates again to the target access point. Send a request message and receive an authentication response message to ensure that authentication to the target access point remains valid and to avoid repeating the initial full authentication access step.

Hereinafter, another embodiment of the fast handover method according to the present invention will be described with reference to FIG. 8. 8 is a system configuration diagram showing another embodiment of the present invention. Referring to FIG. 8,

access points

810 and 820 belonging to the same mobility area as the mobile terminal to which the re-authentication request timer module is applied according to the setting of the user profile management module in the IEEE 802.11r according to the present embodiment are configured. The access point A 810 is an access point to which the mobile terminal is currently connected, and the access point B 820 is a target access point to which the mobile terminal performs handover. As the mobile terminal moves from the service area of the access point A to the service area of the B, a signal attenuation occurs and the signal strength should transmit an authentication request message to perform the handover preparation process at the point T1, but the signal of the target access point B 820 The strength is weaker than T2, so the response message for the authentication request message cannot be transmitted. In this situation, the mobile terminal applying the present invention transmits an authentication request message to the target access point when the signal strength from the current connection point is not more than T1, that is, the signal strength from the current connection point is less than T1 and the signal strength of the target connection point is more than T2. Perform over-preparation. At this time, the reconnection timeout and the reauthentication request time are applied from the time α sent the authentication request message. Therefore, if a handover does not occur even after the reauthentication request time elapses from the time of transmitting the authentication request message, the reauthentication request message is transmitted to the target access point within the reconnection time limit.

Through this process, even if the reconnection timeout has elapsed without being handed over to the target access point, a quick handover can be performed by performing the reauthentication request process after the reauthentication request time has elapsed before the reconnection timeout has elapsed. do.

Although the present invention has been described above with reference to preferred embodiments thereof, it is only an example and is not intended to limit the present invention, and those skilled in the art do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications which are not illustrated above in the scope are possible. And differences relating to such modifications and applications should be construed as being included in the scope of the invention defined in the appended claims.

The present invention can be widely used to provide fast handover in a local area network (LAN) environment, and in particular, 802.11r-Amendment 2: Fast, which is a standard document of the IEEE 802.11r working group. The basic service set (BSS) transition can be applied to a method that can support fast roaming in the same mobility area when handover of a user terminal. In addition, the present invention provides a re-authentication request timer module according to the configuration of the user profile management module when the mobile terminal hands over to a service area of a new target access point belonging to the same mobility area in a WLAN-based mobile environment. By applying this, it is possible to provide a fast handover method.

Claims

In a handover method of a mobile terminal in a wireless LAN environment,

(a) determining the handover to the target access point and transmitting an authentication request message to the target access point when the received signal strength from the current access point falls below a preset first threshold value T1;

(b) determining whether to apply the reauthentication request module;

(c) driving a timer if the reauthentication request module is applied according to the determination of step (b);

(d) receiving an authentication response message from the target access point;

(e) transmitting a reauthentication request message to the target access point within a preset reconnection time limit when the timer passes a preset reauthentication request time without performing a handover;

(f) if the handover is performed to the target access point within the reconnection time limit, performing a reconnection process with the target access point;

Fast handover method of a mobile terminal in a wireless LAN environment comprising a.
The method of claim 1, wherein the step (b) determines whether to apply the reauthentication request module according to the information set in the user profile of the mobile terminal, wherein the information set in the user profile is set by the user's selection. Or information set according to the type of service of the mobile terminal.
The method of claim 1, wherein the reauthentication request time is set to a time shorter than the reconnection time limit.
The fast handover of the mobile terminal according to claim 1, wherein if the mobile terminal does not transmit the reconnection request message to the target access point in step (e), it is determined that the mobile terminal has not performed the handover to the target access point. Way.
The target access point of claim 1, wherein when it is determined in step (b) that the re-authentication request module is not applied, an authentication response message is received from the target access point, and if a handover occurs to the target access point within the reconnection time limit, the target access point is detected. And performing a reconnection process, and invalidating the authentication information if a handover does not occur within the target access point within the reconnection time limit.
The method of claim 1, wherein the reconnection timeout starts at a time when the received signal strength of the current access point is less than or equal to the first threshold value T1, or the received signal strength of the current access point is less than or equal to the first threshold value T1. A method for fast handover of a mobile terminal, characterized in that it starts at a time when the received signal strength is greater than or equal to the second threshold value (T2) and ends at a time when the received signal strength of the current access point is less than or equal to the second threshold value (T2).
A key management module for storing authentication related information;

A user profile management module for storing and managing a user profile for the mobile terminal;

A handover management module for preparing a handover to a target access point or performing a handover to a target access point according to the received signal strength received by the mobile terminal;

A timer, determining whether to request reauthentication according to a setting condition of the user profile, and driving the timer when the authentication request message is sent to the target access point by the handover management module, and the driving time of the timer A re-authentication request module for transmitting a re-authentication request message to a target access point within a preset reconnection time limit if a handover does not occur even after a predetermined re-authentication request time elapses;

Mobile terminal providing a fast handover in a wireless LAN environment having a plurality of access points.
8. The mobile terminal of claim 7, wherein the reauthentication request time is shorter than the reconnection time limit.
The mobile terminal of claim 7, wherein the user profile is set according to a user's selection of the application of the reauthentication request module or according to a type of service used by the mobile terminal. .