KR101040436B1 - Method and apparatus for detecting level 3 movement of wireless lan terminal - Google Patents

Abstract

The present application particularly discloses a method and apparatus for determining whether a level 3 movement has occurred using a basic service set (BSS) network table during handoff of a WLAN terminal. The level 3 mobility discovery method of a WLAN terminal includes receiving a network table including level 2 identifiers of a plurality of access points (APs) and level 3 information corresponding to each of them from a network information server, and performing reconnection according to an AP reconnection procedure. Receiving a level 2 identifier of a connected AP and searching level 3 information corresponding to the level 2 identifier of the reconnected AP in the received network table, and determining whether a level 3 movement occurs based on the retrieved level 3 information. It includes a step.

WiFi, network table, SSID, BSSID, IP address

Description

Level 3 movement detection method of wireless terminal and device therefor {METHOD AND APPARATUS FOR DETECTING LEVEL 3 MOVEMENT OF WIRELESS LAN TERMINAL}

1 is a conceptual diagram of a wireless LAN system according to an embodiment of the present invention.

2 is a block diagram of a wireless LAN terminal according to an embodiment of the present invention.

3 is a detailed block diagram of the controller shown in FIG. 2;

4 is a flowchart of an AP reconnection procedure according to an embodiment of the present invention.

5 is a flowchart illustrating a level 3 movement discovery method of a wireless LAN terminal according to an embodiment of the present invention.

6 is a signal flow chart for explaining the operation of the control unit of the wireless LAN terminal according to an embodiment of the present invention.

7 is a signal flow diagram illustrating a level 3 movement discovery method of a wireless LAN terminal according to an embodiment of the present invention.

<Description of main parts of drawing>

100: wireless LAN system 110: wireless LAN terminal

121,122,123,124: AP 130: Router

140: DHCP server 150: SIP proxy server

210: wireless communication unit 220: input unit

230: display unit 240: storage unit

250: control unit 351: driving unit

351a: 802.11 firmware unit 351b: MAC driver unit

353: MUX part 355: WPA part

357: call processing unit 357a: IP unit

357b: SIP / RTP section 357c: DHCP client section

The present invention relates to a handoff of a wireless LAN terminal, and more particularly, to a method and apparatus for determining whether a level 3 movement has occurred using a basic service set (BSS) network table during handoff of a wireless LAN terminal.

As voice over IP (VoIP) and Wireless Fidelity (WiFi) are activated, studies on VoIP mobility in a wireless local area network (WLAN system) have been actively conducted. This mobility may be divided into level 2 mobility associated with the second layer link layer and level 3 mobility associated with the third layer network layer in an open systems interconnection (OSI) network reference model.

For level 2 mobility, the largest delay factor for level 2 handoff delay is known as the Institute of Electrical and Electronics Engineers (IEEE) standard 802.1x (Port Based Network Access Control) authentication process. 802.11i proposes pre-authentication to reduce 802.1x authentication delays. In order to efficiently perform the 802.1x pre-authentication process, a list of frequently accessed handoff regions (APRs) that are frequently moved for each terminal in an extended service set (ESS) in an authentication authorization and accounting (AAA) server is provided. ), And the method for AP to perform pre-authentication for each terminal has been developed.

For level 3 mobility, several methods have been proposed that use mobile IP to support level 3 handoff between networks or subnets. Mobile IP enables communication between home agents (HAs) and foreign agents (FAs) to ensure mobility without changing the parent application. However, level 3 handoff using only mobile IP is not suitable for transmission of real-time data such as voice due to triangle routing and care of address. In order to solve this problem, a method of performing a level 3 handoff using a VoIP protocol, for example, a session initiation protocol (SIP) protocol together with mobile IP, has been proposed. According to this conventional method, when a signal to noise ratio (SNR) with an access point (AP) currently connected to a WLAN terminal by a second layer component of the WLAN terminal falls below a preset threshold, A reassociation from the currently associated AP to another AP is performed by using a service set identifier (SSID) and a basic service set identifier (BSSID).

However, in this case, it is not possible to infer the IP address information, which is the level 3 information of the reconnected AP, by the SSID and the BSSID, which are level 2 identifiers. That is, there is a problem that it is not possible to determine whether the level 3 movement has occurred. As a result, even though only the level 2 movement in the same network or subnetwork occurs, the WLAN terminal performs a DHCP discover procedure to perform a DHCP discovery of the AP reconnected from a DHCP server that manages the network address of the WLAN system. New IP addresses belonging to the network or subnetwork must be assigned. This causes unnecessary overhead every time the WLAN terminal performs a handoff and leads to waste of radio resources.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and it is possible to determine whether a level 3 movement has occurred without causing unnecessary overhead each time a WLAN terminal using the VoIP protocol and the mobile IP performs a handoff. To provide a way to do this.

According to an aspect of the present invention, there is provided a level 3 movement detection method of a wireless LAN (wireless LAN) terminal connected to an access point (AP) to perform wireless communication, which method is a level of a plurality of APs from a network information server. Receiving a network table including a second identifier and level 3 information corresponding thereto, receiving a level 2 identifier of a reconnected AP according to an AP reconnection procedure, and corresponding to a level 2 identifier of the reconnected AP Retrieving level 3 information from the received network table, and determining whether a level 3 movement has occurred based on the retrieved level 3 information.

According to another aspect of the present invention, there is provided a wireless LAN terminal, which receives a network table from the network information server, the network table including the level 2 identifiers of the plurality of APs and corresponding level 3 information, respectively, and the AP reconnection procedure According to the wireless communication unit for receiving the level 2 identifier of the reconnected AP and the level 3 information corresponding to the level 2 identifier of the reconnected AP in the received network table, the level 3 moves based on the retrieved level 3 information It includes a control unit for determining whether or not occurrence.

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

1 is a conceptual diagram of a wireless LAN system according to an embodiment of the present invention. Referring to FIG. 1, a wireless LAN system 100 according to an embodiment of the present invention connects or reconnects with a wireless LAN terminal 110 and a wireless LAN terminal 110 to provide a plurality of APs for providing a wireless communication service. (access points) 121-124, a router 130 that performs routing according to a network address that is level 3 information in the WLAN system 100, and assigns the network addresses of the WLAN system 100 components. And a DHCP server (dynamic host configuration protocol server) 140 and a level 2 information of the WLAN system 100, preferably a BSSID and corresponding level 3 information, that is, network information for storing and managing network addresses. A session initiation protocol proxy server 150 that is a server is included.

In general, the WLAN system 100 preferably uses the Institute of Electrical and Electronics Engineers (IEEE) 802.11i protocol to transmit and receive data of a layer corresponding to two layers of an Open Systems Interconnection (OSI) reference network model on a network protocol stack. In this case, the IP protocol may be preferably used to transmit and receive data of a layer corresponding to three layers. The IEEE 802.11i protocol and the IP protocol assign an identifier to each element for management of devices constituting the WLAN system and data exchange between them.

In the IEEE 802.11i protocol, SSID (service set identification) and BSSID (basic SSID) are used. The BSSID is a MAC layer identifier uniquely assigned to each AP 121-124 of the WLAN system 100, and identifies each AP 121-124 of the WLAN system 1 in a module that processes the 802.11i protocol. It is used to SSID is an identifier uniquely assigned to each WLAN system 100 to allow several WLAN systems to operate at the same time and in the same place. In an embodiment of the present invention, only one WLAN system 100 is illustrated and the same SSID is assigned to all components. In the case of the IP protocol, the IP address is used as an identifier. The IP address consists of a network address representing the network and a device number connected to the network. If the network is divided into a plurality of sub-networks, preferably, the network address may be further divided into a network address and a sub-network address. In general, it is not possible to infer information about layer 3, that is, information about an IP address, which is level 3 information, through information about layer 2, that is, level 2 information. Accordingly, in one embodiment of the present invention, it is determined whether the network or sub-network address to which the WLAN terminal 110 belongs is changed using a table including the BSSID and the IP address corresponding thereto.

The WLAN terminal 110 performs an association procedure to perform one of the APs (eg, the second) of the plurality of APs 121-124 having the same service set identification (SSID) as the WLAN terminal 110. An association is made with the AP 122 and wireless communication is performed through the connected second AP 122. The SSID is a level 2 identifier, that is, information about a layer corresponding to a second layer of an OSI network reference model, and includes a plurality of APs (the WLAN terminal 110 constituting the WLAN system 100). 121-124).

The wireless LAN terminal 110 performs a DHCP discover procedure and receives an IP address assigned to the wireless LAN terminal 110 through the currently connected second AP 122 from the DHCP server 140. Receive IP address information. The WLAN terminal 110 performs a SIP registration procedure to register the SIP address of the WLAN terminal 110 and IP address information corresponding thereto to the SIP proxy server 150. In this case, the WLAN terminal 110 receives a registration response (for example, 200 OK response of the SIP protocol) from the SIP proxy server 150 through the connected second AP 122. . The 200 OK response includes a basic service set (BSS) network table, and the BSS network table includes BSSIDs and IP address information corresponding to each of the plurality of APs 121-124 having the same SSID. Here, the BSSID is an identifier for identifying each of the plurality of APs 121-124 having the same SSID as the level 2 information. The WLAN terminal 110 may periodically update the BSS network table by performing the SIP registration procedure.

When the WLAN terminal 110 moves, when the signal to noise ratio (SNR) of the wireless signal received from the second AP 122 connected with the WLAN terminal 110 falls below a preset threshold, the WLAN terminal 110 transmits a probe request to APs 121-124 to initiate an AP re-association procedure. The WLAN terminal 110 selects an AP having the largest SNR among the APs 121-124 having the same SSID in response to the probe request and establishes a reconnection. The WLAN terminal 110 receives the BSSID of the reconnected AP while performing the reconnection procedure. The WLAN terminal 110 retrieves IP address information of the reconnected AP from the received BSS network table based on the received BSSID. The wireless LAN terminal 110 determines whether a level 3 movement occurs, that is, whether a network or a subnetwork to which the wireless LAN terminal 110 belongs has changed based on the IP address information of the reconnected AP. That is, it is determined whether the network and / or sub-network address included in the already allocated IP address is different from the network and / or sub-network address included in the IP address of the reconnected AP. When the level 3 movement occurs as a result of the determination, the WLAN terminal 110 performs the DHCP discovery procedure again, receives a new IP address from the DHCP server 140, receives the newly allocated IP address information, and receives the SIP. Perform the handoff signaling procedure.

The router 130 routes data received from the plurality of APs 121-124, the DHCP server 140, and the SIP proxy server 150 according to the IP address information included in the data. The router 130 is a well-known technology, and detailed descriptions thereof will be omitted.

The DHCP server 140 is a server that automatically allocates and manages IP address information necessary for executing IP communication. An AP connected or reconnected to the WLAN terminal 110 according to a request of the WLAN client 110 which is a DHCP client. The new IP address information belonging to the network or subnetwork of the network is allocated to the WLAN terminal 110 and transmitted. The DHCP server 140 is a well-known technology, and detailed descriptions thereof will be omitted.

The SIP proxy server 150 establishes and releases a session and forwards the received SIP message to an appropriate AP 121-124 or another server (not shown). The SIP proxy server 150 stores and manages a BSS network table including BSSIDs of a plurality of preset APs 121-124 and IP address information corresponding thereto. The SIP proxy server 150 receives a SIP registration request from the WLAN terminal 110 according to a SIP registration procedure and transmits a 200 OK response, which is a registration response thereto. The 200 OK response includes the BSS network table.

Hereinafter, with reference to the specific configuration of the wireless LAN terminal 110, the operation of determining whether or not the level 3 movement occurs when performing the hand-off of the wireless LAN terminal 110 will be described in detail.

2 is a block diagram of a wireless LAN terminal according to an embodiment of the present invention. 2, the wireless LAN terminal 110 according to an embodiment of the present invention is provided with a wireless communication unit 210, a letter key, numeric keys and various function keys, the key input corresponding to the key input by the user The input unit 220 generates a signal, for example, a display unit 230 including a liquid crystal display (LCD), a storage unit 240 and a controller 250 in which a control operation program and a system program are stored.

The wireless communication unit 210 is controlled by the control unit 250, converts a signal output from the control unit 250 into a wireless signal and transmits it, and converts a wireless signal received from an antenna (not shown) into a desired signal and controls the control unit 250. ) As the SIP registration procedure is performed, the wireless communication unit 210 generates a BSS network table including BSSIDs of the plurality of APs 121-124 having the same SSID and IP address information corresponding thereto from the SIP proxy server 150. Receive. The wireless communication unit 210 receives the BSSID of the connected or reconnected AP from the connected or reconnected AP according to an AP connection or reconnection procedure.

The controller 250 not only controls the overall operation of the WLAN terminal 110, but also retrieves IP address information corresponding to the BSSID of the reconnected AP from the received BSS network table and based on the retrieved IP address information. It is determined whether the level 3 movement of the IP address of the WLAN terminal 110 is changed. That is, if the network indicated by the retrieved IP address information is different from the network indicated by the IP address information of the WLAN terminal, the controller 250 determines that the level 3 movement has occurred. If it is determined that the level 3 movement has occurred, the controller 250 sets a security setting with the reconnected AP, for example, an 802.11i 4-way handshake and completes the 'portValid' variable to TRUE. Determine whether it is set. When the 'portValid' variable is set to TRUE as a result of the determination, the controller 250 receives the newly allocated IP address information from the DHCP server 140 to the WLAN terminal 110 by performing a DHCP discovery procedure and receives SIP handoff. Perform the procedure. The session currently established in the WLAN terminal 110 by the SIP handoff procedure is changed according to the new IP address, so that another WLAN terminal (session not established) is established through the WLAN terminal 110 and the SIP proxy server 150. SIP message can be forwarded to the WLAN terminal 110. Preferably, the SIP handoff procedure is described in Elin Wedlund et al., "Mobility Support Using SIP", Second ACM / IEEE International Conference on Wireless and Mobile Multimedia Aug 1999, pp. It is possible to follow the SIP handoff procedure disclosed in 76-82, which is a well-known technique and will not be described in detail below.

3 is a detailed block diagram of the controller illustrated in FIG. 2, and FIG. 6 is a signal flowchart illustrating the operation of the controller. 3 and 6, the control unit 250 of the wireless LAN terminal 110 according to an embodiment of the present invention includes a driving unit 351, a MUX unit 353, a WPA unit 355, and a call processing unit 357. ).

Driver 351 is an 802.11 firmware unit (351a) for transmitting the data recorded in the register of the driver 351 to the 802.11 protocol message through the wireless communication unit 210 by the DCF (distribution coordination function) method And a MAC driver unit 351b which provides two channel services, that is, data channel and input / output control (IOCTL) channel service.

The 802.11 firmware unit 351a determines whether the SNR for the currently connected AP is less than or equal to a preset threshold. If the determination result is less than a preset threshold, for example, the level 2 handoff reference value, the 802.11 firmware unit 351a drives the AP reconnection procedure. The 802.11 firmware unit 351a finds the APs 121-124 to be reconnected by an active scan, selects the AP having the largest SNR, and establishes the reconnection. In more detail with respect to the active scan, the 802.11 firmware unit 351a broadcasts a probe request including the SSID of the wireless LAN terminal 110 through the wireless communication unit 210. The 802.11 firmware unit 351a receives a probe response to the probe request from the APs 121-124 having the same SSID as the SSID of the WLAN terminal 110 and responds to the APs 121-124. In step 124, the AP having the largest SNR is selected as an AP to be reconnected, and a first interrupt is generated. The 802.11 firmware unit 351a transmits a re-association request to the selected AP through the wireless communication unit 210 and re-associates a response to the reassociation request from the selected AP. Receive a response. Upon receiving the reconnection response, the 802.11 firmware unit 351a generates a second interrupt thereto. Preferably, the 802.11 firmware unit 351a may be embodied as an EEG gear RF module.

The MAC driver 351b generates a scan event for notifying a result of the probe request while processing the first interrupt when it is generated. The MAC driver 351b generates a link event for notifying that the reconnection with the selected AP is completed while receiving and processing the second interrupt. The MAC driver 351b records the data received from the WPA unit 355 or the call processor 357 in a register of the 802.11 firmware unit 351a.

The MUX unit 353 provides functions of the MAC driver unit 351b to the WPA unit 355 and the call processing unit 357, which are application modules, to serve as an operating system. The functions are provided through a network function table (NFT) including a data transfer function and an input / output control (IOCTL) function of the MAC driver 351b. The MUX unit 353 receives the result values for each event, for example, the BSSID of the reselected AP through the I / O control channel of the MAC driver unit 351b and outputs the I / O control channel of the MUX unit 353. . When the MUX unit 353 receives a signal using the functions from the WPA unit 355 and the call processor 357 using the NFT, the MUX unit 353 converts the signal into a signal suitable for the MAC driver unit 351b of the driver 351. . Preferably, the MUX unit 353 can be implemented using VxWorks.

The WPA unit 355 sets an 802.1x supplicant port access entity (PAE) (not shown) for security authentication (authentication) of the wireless LAN terminal 110 and security settings of a communication channel with the connected or reconnected AP. 802.1i 4-way handshake module (not shown). Preferably, the 802.1x supplicant PAE may be implemented in three state machines (supplicant PAE, key receive, supplicant backend state machine) and one EAP state machine (extensible authentication protocol state machine). Preferably, the 802.1x supplicant PAE is a light weight EAP (LEAP), a Microsoft challenge handshake authentication protocol version 2 (MSPAP2), a protected EAP (PEAP), or TLS in order to generate a pairwise master key (PMK). (transport layer security) and TTLS (tunneled TLS) can be supported. More preferably, the 802.1x supplicant PAE may support PMK caching to reduce PMK generation overhead. The 4-way handshake module derives keys to be used for communication using the generated PMK, sets an 802.1x 'portValid' variable to TRUE, and pairwise pairs the PMKSA with the connected or reconnected AP. master key security association).

When the WPA unit 355 receives a scan event directly from the MAC driver unit 351a of the driver 351, the WPA unit 355 determines whether the BSSID of the selected AP exists in the PMK cache. If the BSSID of the selected AP exists in the PMK cache, the WPA unit 355 performs 802.11i pre-authentication to set the 802.1x 'portValid' variable to TRUE and set the Port Valid Event. Create When the WPA unit 355 receives the direct link event from the MAC driver unit 351a of the driver 351, sets the 'portValid' variable to FALSE, and determines whether the BSSID of the reconnected AP exists in the PMK cache. do. If the BSSID of the selected AP exists in the PMK cache, the WPA unit 355 performs 802.11i pre-authentication to set the 802.1x 'portValid' variable to TRUE and set the Port Valid Event. Create The WPA unit 355 uses a level 2 socket interface when transferring data to the MAC driver unit 351b, which is a lower layer configuration, and uses 0x888E (802.1x authentication) and 0x88c7 (802.11i preauthentication). ) Data is transmitted to the MAC driver 351b.

The call processing unit 357 sets the SNR threshold to be used for the handoff by the WLAN terminal 110 in the 802.11 firmware unit 351a through the input / output control channel, and receives the link event through the input / output control channel. The movement detection function of 353 is driven and a handoff procedure is performed. The call processing unit 357 includes an IP unit 357a, a SIP / RTP unit 357b, and a DHCP client unit 357c for this purpose.

The IP unit 357a is a module for the SIP / RTP unit 357b and the DHCP client unit 357c to communicate with the driver 351, which is a lower layer, in view of the OSI network reference model. Data of LLC protocol type 0x0800 (IP) is transferred to MAC driver 351b of 351. Since the IP unit 357a is a well-known technology, a detailed description thereof will be omitted.

The SIP / RTP unit 158 is a SIP unit (not shown) that processes the SIP protocol for establishing, managing, and releasing voice and video sessions on the wireless LAN system 1, and an RTP protocol that processes the RTP protocol for real-time data transmission. It includes a portion (not shown). The SIP unit performs a SIP registration procedure to notify the SIP proxy server 150 of the SIP address of the WLAN terminal 110 and the IP address corresponding thereto, and simultaneously establishes the BSS network table from the SIP proxy server 150. Receive a 200 OK response that includes. The BSS network table according to an embodiment of the present invention may define a SIP extension header and transmit the message through a 200 OK response. As an embodiment of the present invention, the syntax for the 'BSS-NETWORK' header, which is a SIP extension header indicating information about a BSS network table, is shown below.

<BSS-NETWORK Extension Syntax>

BSS-NETWORK = BSS-value * ("." BSS-value)

// BSS-NETWORK header can have multiple BSS-values, separated by ","

BSS-value = <BSSID ";" IPv4address ";" IPv4NetMask>

// BSS-value consists of BSSID, IP version 4 address, and IP version 4 netmask, separated by ";"

IPv4NetMask = IPv4address

// IP version 4 netmask has the same format as IP version 4 address

BSSID = MACaddress /

/ BSSID has the same format as MAC address, which is layer 2 information

IPv4address = 1 * digit "." 1 * digit "." 1 * digit "." 1 * digit "."

// defines the format of the IP version 4 address

Below is a 200 OK response including a BSS-NETWORK header created by the syntax according to an embodiment of the present invention.

<200 OK Example with BSS-NETWORK Header>

SIP / 2.0 200 OK

Via: SIP / 2.0 / UDP 19.31.97.3:5060:branch=z9hG4bKp3wer654363

To: UA1 <sip: UA1@L3HANDOFF.COM>; tag = 251077

From: UA1 <sip: UA1@L3HANDOFF.COM>; tag = 456248

Call-ID: 843817637684230 @ 998sdasdh09

CSeq: 1826 REGISTER

Contact: <sip: UA1@192.0.2.4>

BSS-NETWORK: <00-10-5a-76-4b-28; 150.150.57.128; 255.255.255.0>

BSS-NETWORK: <00-10-5a-76-4b-27; 150.150.60.125; 255.255.255.0>

BSS-NETWORK: <00-10-5a-76-4b-c1; 150.150.57.129; 255.255.255.0>

In the illustrated 200 OK response, the BSS-NETWORK header declares that the BSS network table is about the BSS network table. In the above example, information about three APs is shown. From the IP address information, it can be seen that two of the three APs belong to the 150.150.57.0 subnetwork, and the other one belongs to the 150.150.60.0 network.

The SIP unit may periodically update the BSS network table by performing the SIP registration procedure with the SIP proxy server 150. The SIP unit performs a SIP handoff signaling procedure when the DHCP client unit 357c generates a SIP handoff signaling event by receiving a new IP address from the DHCP server 140. The SIP handoff procedure changes the currently established session by reflecting the changed IP address of the WLAN terminal 110. Accordingly, the SIP proxy server 150 properly forwards the SIP message transmitted by the WLAN terminal 110 and another WLAN terminal (not shown) to which the current session is established, so that the WLAN terminal 110 can receive the SIP message. .

The DHCP client unit 357c receives the scan event from the MAC driver unit 351b and obtains the input / output control channel for the BSSID of the AP to be selected and re-associated by the 802.11 firmware unit 351a. When the DHCP client unit 357c receives the link event notifying that the reconnection with the selected AP is completed from the MAC driver unit 351b through the input / output control channel, the BSS network received through the SIP registration procedure. Retrieve IP address information corresponding to the BSSID of the reconnected AP in a table. The DHCP client 357c moves to level 3 if the network indicated by the retrieved IP address information, for example, the sub network number is different from the network indicated by the IP address information of the WLAN terminal 110, for example, the sub network number. Is determined, and it is determined whether or not the port valid event for notifying that the 'portValid' variable is set to TRUE is received. This is because the 802.11i four-way handshake is completed and the portValid 'variable must be set to TRUE to communicate with the DHCP server 150 through the reconnected AP. The DHCP client unit 357c performs a DHCP discovery procedure to receive a new IP address from the WLAN terminal 110 when the port valid event is received as a result of the determination. That is, the DHCP client unit 357c requests IP address information of the WLAN terminal 110 from the DHCP server 150 and newly allocated IP belonging to the sub-network to which the reconnected AP belongs from the DHCP server 150. Receive address information. Upon receiving the newly assigned IP address information by the DHCP server 150, the DHCP client unit 357c generates a SIP handoff signaling event instructing to start the SIP handoff signaling procedure.

Hereinafter, a method of determining whether a level 3 movement occurs when performing the handoff of the WLAN terminal 110 will be described in detail. 4 is a flowchart illustrating an AP reconnection procedure of a wireless LAN terminal according to an embodiment of the present invention. 4, the 802.11 firmware unit 110a of the wireless LAN terminal 110 according to an embodiment of the present invention determines whether the SNR for the currently connected AP is less than or equal to a preset threshold (S400). As a result of determining the S400 step, when the SNR of the currently connected AP is less than or equal to a preset threshold, the 802.11 firmware 110a broadcasts a probe request including the SSID of the WLAN terminal 110 to the WLAN network (S410). Thereafter, the 802.11 firmware unit 110a receives a probe response including the BSSID of each AP from the APs 121-124 having the same SSID as the SSID of the WLAN terminal 110 (S420).

In step S430, the 802.11 firmware unit 110a selects an AP having the largest SNR among the APs 121-124 that have received the probe response as an AP to be reconnected, generates a scan event, and generates a call processor 357 and a WPA unit. Output to 355. Thereafter, the 802.11 firmware unit 110a outputs the BSSID of the selected AP to the call processing unit 357 and the WPA unit 355 through an input / output control channel at the request of the call processing unit 357 and the WPA unit 355. (S440). In step S450, the 802.11 firmware unit 110a transmits a reconnection request to the selected AP. Thereafter, the 802.11 firmware unit 110a receives a reconnection response to the reconnection request from the selected AP (S460), generates a link event indicating that reassociation with the selected AP is completed, and generates a call processing unit ( 357) and the output to the WPA unit 355 (S470) to terminate the procedure. Subsequent to the reconnection procedure shown in FIG. 4, the WPA unit 355 receives the link event from the 802.11 firmware unit 110a, performs the 802.1x signaling procedure, generates a PMK cache entry, and generates the 802.11. i Perform the 4-way handshake procedure to ensure that the 'portValid' variable is set to TRUE.

5 is a flowchart illustrating a level 3 movement discovery method of a WLAN terminal according to an embodiment of the present invention, and FIG. 7 is a signal illustrating a level 3 movement discovery method of a WLAN terminal according to an embodiment of the present invention. It is a flow chart. First, the WLAN terminal 110 periodically performs a SIP registration procedure through the SIP / RTP unit 357b of the WLAN terminal 110 to access APs 121 having the same SSID as the SSID of the WLAN terminal 110. And receives the BSS network table including the BSSID and IP address information corresponding thereto, and stores the received BSS network table. The BSS network table may be updated by periodically performing the SIP registration procedure as shown in FIG. 7. 5 and 7, the DHCP client unit 357c of the wireless LAN terminal 110 according to an embodiment of the present invention receives a scan event notifying that an AP to be reconnected has been selected from the MAC driver 110b. The BSSID of the AP to be reconnected through the input / output control channel is obtained by inquiring the MAC driver 110b (S500). Thereafter, as illustrated in FIG. 7, the DHCP client unit 357c receives a link event indicating that the reassociation procedure is completed from the MAC driver 110b (S510).

In operation S520, the DHCP client unit 357c searches for IP address information corresponding to the BSSID of the reassociated AP in the BSS network table. Thereafter, the DHCP client unit 357c determines whether the network indicated by the retrieved IP address information is different from the network to which the WLAN terminal 110 belongs, that is, whether level 3 movement has occurred (S530). If the network indicated by the searched IP address information is different from the network to which the wireless LAN terminal 110 belongs, in step S530, the DHCP client unit 357c receives a port valid event that notifies that the 'portValid' variable is set to TRUE. It is determined whether or not, that is, whether or not it can communicate with the DHCP server 150 through the reconnected AP (S540).

When the port valid event is received in step S540, the DHCP client unit 357c transmits an IP address allocation request to the DHCP server 150 (S550), and the IP for the IP address allocation request from the DHCP server 150. An address assignment response is received (S560). Thereafter, the DHCP client unit 357c generates a SIP handoff signaling event for initiating the SIP handoff procedure, outputs it to the SIP unit of the SIP / RTP unit 357c (S570), and terminates the procedure.

On the other hand, if the network indicated by the searched IP address information is not different from the network to which the wireless LAN terminal 110 belongs, step S530, the procedure ends. On the other hand, if the port valid event notifying that the 'portValid' variable is set to TRUE is not received in step S540, the process moves to step S540.

In the description of the present invention, the wireless LAN terminal has described the configuration of receiving and updating the BSS network table from the SIP proxy server using the SIP protocol. However, the present invention is directed to receiving the BSS network table from the AAA server using the EAP protocol. The invention can be implemented. As described in Arthur Hecker et al., "Pre-Authenticated Signaling in Wireless LANs using 802.1x Access Control," IEEE Globecom 2004, the EAP protocol can be used as a protocol for transmitting general signaling data as well as authentication. The EAP method can be added between the WLAN terminal and the AAA server without any modification to the AP to provide the application with the necessary information, so that the AAA server can extend the existing EAP method or define a new EAP method to provide level 3 information. Can be provided. That is, as the network information server, the BSS network table is set in the AAA server, not the SIP proxy server, and after the 802.1x authentication process of the WLAN terminal is completed, the BSS network table using the EAP protocol, not the SIP registration procedure of the SIP protocol. The present invention can be implemented so that the WLAN terminal receives and updates from the AAA server. The WLAN terminal receiving the BSS network table from the AAA server may determine whether a level 3 movement has occurred according to the BSS network table.

The invention being thus described, it will be obvious that the same way may be varied in many ways. Such modifications are intended to be within the spirit and scope of the invention as defined by the appended claims.

According to the present invention as described above, there is an effect that it is possible to determine whether the level 3 movement occurs using the network table of the network information server when performing the handoff of the wireless LAN terminal using the VoIP protocol and mobile IP.

In addition, according to the present invention as described above it is possible to determine whether the level 3 movement occurs by removing the unnecessary overhead caused by performing the level 3 handoff signaling whenever the WLAN terminal performs the handoff. There is also.

Claims (16)

A level 3 movement detection method of a wireless LAN terminal connected to an access point (AP) to perform wireless communication. Receiving, from a network information server, a network table including level 2 identifiers of the plurality of APs and level 3 information corresponding to each of the plurality of APs; Receiving a level 2 identifier of the connected or reconnected AP according to an AP connection or reconnection procedure, and Retrieving level 3 information corresponding to the level 2 identifier of the connected or reconnected AP from the received network table and determining whether a level 3 movement occurs based on the retrieved level 3 information Level 3 movement detection method of a WLAN terminal comprising a. The method of claim 1, Determining whether or not the level 3 movement occurs And determining that the level 3 movement has occurred if the network indicated by the retrieved level 3 information is different from the network indicated by the level 3 information of the WLAN terminal. The method of claim 1, In determining whether the level 3 movement occurs If it is determined that the level 3 movement has occurred, further comprising requesting a level 3 information about the WLAN terminal to a dynamic host configuration protocol (DHCP) server. The method of claim 3, wherein The requesting step And requesting a level 3 information about the WLAN terminal from a DHCP server after the security settings of the reconnected AP and the WLAN terminal are completed. The method of claim 1, And the network information server is a session initiation protocol proxy server. The method of claim 5, In the receiving of the network table, the network table is received through a 200 OK response according to a SIP registration procedure. And the SIP response message includes the network table. The method of claim 1, The network information server is an AAA server (authentication authorization and accounting server), the level 3 movement detection method of a wireless LAN terminal. The method of claim 7, wherein And receiving the network table comprises receiving the network table via an extensible authentication protocol (EAP) protocol. A wireless communication unit for receiving a network table including level 2 identifiers of a plurality of APs and level 3 information corresponding thereto from a network information server, and receiving level 2 identifiers of reconnected APs according to an AP reconnection procedure; A control unit for retrieving level 3 information corresponding to the level 2 identifier of the reconnected AP from the received network table and determining whether a level 3 movement occurs based on the retrieved level 3 information WiFi terminal comprising a. The method of claim 9, The control unit A driver configured to reconnect with a new AP and generate a link event by performing the AP reconnection procedure according to a predetermined rule; and When the link event is received, level 3 information corresponding to the level 2 identifier of the reconnected AP is searched in the received network table, and the level 3 information of the WLAN terminal is indicated by a network indicated by the retrieved level 3 information. A call processor that determines that the level 3 movement has occurred Including, WiFi terminal. 11. The method of claim 10, The call processor requests the DHCP server for level 3 information about the WLAN terminal when it is determined that the level 3 movement has occurred. 11. The method of claim 10, The control unit further includes a security unit that performs security processing of a communication channel connected to the reconnected AP, The call processing unit requests a level 3 information about the WLAN terminal to a DHCP server after security settings of the reconnected AP and the WLAN terminal are completed. The method of claim 9, And said network information server is a SIP proxy server. The method of claim 13, The wireless communication unit receives the network table via a SIP response message according to a SIP registration procedure, wherein the SIP response message includes the network table. The method of claim 9, The network information server is a wireless LAN terminal, AAA server. The method of claim 15, The wireless communication unit receives the network table via the EAP protocol.

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