KR20060036757A - Hand-off method and system of a access terminal between heterogeneous networks - Google Patents

Abstract

The present invention relates to a method and system for handoff between heterogeneous networks for providing a continuous service in a handoff between a cellular mobile communication network and a wireless local access network (WLAN). This is a handoff of a mobile terminal that is connected to a base station from a wireless LAN including an access router providing an IP (Internet Protocol) routing function and moves to a mobile communication network including a packet data service node (PDSN) providing the IP routing function. When the mobile terminal is set to the access router and the access point to perform the movement to the mobile communication network, the mobile terminal transmits information for tunneling between the access router and the PDSN to the PDSN. The present invention is characterized in that, when a tunnel for packet delivery between the PDSN and the access router is established, packets transmitted from a counterpart node through the configured tunnel are delivered to the mobile terminal.

WLAN, cellular, cellular, IP address, Layer 3 access point, handoff, DHCP, PDSN, access router

Description

HAND-OFF METHOD AND SYSTEM OF A ACCESS TERMINAL BETWEEN HETEROGENEOUS NETWORKS             

1 is a flowchart illustrating an IP allocation process of a mobile terminal in a mobile communication network according to the prior art.

2 is a diagram illustrating an IP packet forwarding process when a mobile terminal moves from a WLAN to a mobile communication network according to the related art.

3 is a diagram illustrating an IP packet forwarding process when a mobile terminal moves from a WLAN to a mobile communication network using a mobile IP according to the related art.

4 is a diagram illustrating a configuration of a handoff system from a WLAN to a mobile communication network according to an embodiment of the present invention.

5 is a diagram illustrating a structure of a protocol stack applied to a handoff method from a WLAN to a mobile communication network according to an embodiment of the present invention.

6 is a flowchart illustrating a handoff method from a WLAN to a mobile communication network according to an embodiment of the present invention.

7 is a flowchart illustrating a process of acquiring an IP address through DHCP over PPP by a mobile terminal handed off to a mobile communication network according to an embodiment of the present invention.                 

FIG. 8 is a flowchart illustrating a process of releasing a tunnel between a packet data service node and an access router after a layer 3 access point of a handed-off mobile terminal is changed according to an embodiment of the present invention.

The present invention relates to a handoff method and system for a wireless communication system, and in particular, a heterogeneous network for providing a continuous service during handoff between a cellular mobile communication network and a wireless local access network (WLAN). (Heterogeneous Networks) handoff method and system.

In general, a dual mode (AT) access terminal (AT) capable of accessing a cellular general mobile communication network and a wireless LAN is assigned an IP (Internet Protocol) address after accessing a wireless LAN, and then moves to a mobile communication network. When performing a vertical handoff, the new IP allocated by the mobile communication network is used instead of the existing IP used by the WLAN. For example, the CDMA 2000 1x system uses a method of allocating IP to a terminal using IPCP (IP Control Protocol). The IP allocation method and system will be described below with reference to the accompanying drawings.

1 is a flowchart illustrating an IP allocation process of a mobile terminal in a mobile communication network according to the prior art. Referring to FIG. 1, in step 101, a mobile station (AT) 10 first performs a traffic channel (TCH) setup with a base station system (BSS) 20, and the base station 20 sets a packet. A RP Session (Remote Node-PDSN Session) setup is performed with the Packet Data Service Node (PDSN) 30. The PDSN 30 performs a Point to Point Protocol (PPP) connection and charging / authentication process for a subscriber accessing an IP network through a mobile communication network, and provides a vertical handoff service. In addition, the PDSN 30 may serve as a foreign agent (FA) when supporting a mobile IP.

The mobile terminal 10 and the PDSN 30 perform a link control protocol (LCP) negotiation in step 103, perform a CHAP (Challenge Handshake Authentication Protocol) authentication in step 105, and then perform step 107. In step IPCP (IP Control Protocol) negotiation is performed to allocate the IP address used by the mobile terminal 10. When using such a conventional IP allocation method, a system may not only maintain a session of a higher layer (TCP / UDP layer and application layer) but also may not deliver a packet delivered to a mobile terminal during a handoff process. .

As described above, when a mobile terminal assigned an IP address moves from a WLAN to a mobile communication network, a handoff operation according to the conventional scheme will be described with reference to FIGS. 2 and 3.

2 is a diagram illustrating a delivery process of an IP packet when a mobile terminal moves from a WLAN to a mobile communication network according to the prior art.                         

Referring to FIG. 2, the IP packet in the wireless LAN region R1 is accessed from an internet router 1 by an access router (AR) 50 and an access point (access point: AP), as shown at 201. It is delivered to the mobile terminal 10 via 40. The access router 50 processes IP routing for the mobile terminal 10 accessing the IP network through the WLAN area R1 and processes vertical handoff. When the access router 50 supports Mobile IP, it may play a role of Foreign Agent (FA). The access point 40 processes the WLAN access protocol with the mobile terminal 10 and serves as a bridge between the WLAN and the wired network.

Meanwhile, when the mobile terminal 10 moves from the wireless LAN area R1 to the cellular area R2 of the mobile communication network, the IP address of the mobile terminal 10 is updated through the process of FIG. 1, and the IP packet is a reference number. As shown in 203, from a correspondent node (CN) 60, which is an external server or host, to the mobile terminal 10 through the PDSN 30 and the base station (BSS) 20 via the Internet 1; Delivered. In the network configuration of FIG. 2, mobile IP may be used to provide upper layer session maintenance and uninterrupted handoff during the vertical handoff process of the mobile terminal 10.

3 is a diagram illustrating an IP packet forwarding process when a mobile terminal moves from a WLAN to a mobile communication network using a mobile IP according to the related art.

Referring to FIG. 3, when the mobile terminal 10 moves from the WLAN area R1 to the cellular area R2 of the mobile communication network, the IP packet is a home agent supporting mobile IP from the counterpart node 60. It is transmitted through the existing IP tunneling path 301 and the new IP tunneling path 303 connected to the mobile communication network through the HA).

In the case of using the mobile IP as described above, the mobile terminal 10 can maintain the same IP address even after the vertical handoff using a home address managed through the HA 70, and the HA 70 moves. Since the packet transmitted to the terminal 10 is intercepted and then transmitted to the mobile terminal 10, a certain level of uninterrupted handoff service can be provided. However, the mobile IP may have a time delay due to mobility determination and signaling delivery, and there is a problem in that traffic is concentrated in the HA 70 because the packet transmitted from the counterpart node 60 to the mobile terminal 10 must be intercepted. .

An object of the present invention is to provide a method and system for handoff between heterogeneous networks that provides an uninterrupted service when a mobile terminal moves from a WLAN to a mobile communication network.

Another object of the present invention is to provide a handoff method and system between heterogeneous networks for transmitting and receiving IP packets using an existing IP address when a mobile terminal moves from a WLAN to a mobile communication network.

Another object of the present invention is to provide a handoff method and system between heterogeneous networks for transmitting and receiving packets of a mobile terminal using DHCP over PPP when moving from a WLAN to a mobile communication network.

Another object of the present invention is to provide a handoff method and system between heterogeneous networks that can reduce packet loss while maintaining a session of a higher layer when a mobile terminal moves from a WLAN to a mobile communication network.

A handoff method between heterogeneous networks according to the present invention for achieving the above object is a packet data service node connected to a base station from a WLAN including an access router providing an IP (Internet Protocol) routing function to provide the IP routing function. A handoff method of a mobile terminal moving to a mobile communication network including a PDSN, the method comprising: detecting a movement to the mobile communication network by the mobile terminal having an access point connected to the access router; Transferring information for tunneling between the access router and the PDSN, and establishing a tunnel for packet transmission between the PDSN and the access router; And transmitting the packets transmitted from the counterpart node through the established tunnel to the mobile terminal.

A handoff system between heterogeneous networks according to the present invention for achieving the above object is a packet data service node connected to a base station from a WLAN including an access router providing an IP (Internet Protocol) routing function to provide the IP routing function. A wireless communication system for performing a handoff of a mobile terminal moving to a mobile communication network including a PDSN, the wireless communication system having a dual mode function connected to the wireless LAN and the mobile communication network, respectively, and having an access router and an access point set In case of moving to the mobile communication network, the mobile station transmits information for tunneling between the access router and the PDSN to the PDSN, and receives the information for tunneling to establish a tunnel for packet transmission with the access router. Transfer from partner node through the established tunnel The packets that are characterized by configured by comprising the PDSN for delivery to the mobile terminal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

First, the basic concept of the present invention will be described. The present invention proposes a method for transmitting and receiving IP packets using an existing IP address when a mobile terminal supporting at least one wireless access technology moves from a WLAN to a mobile communication network.

To this end, in the present invention, first, when a mobile station moves from a wireless LAN to a mobile communication network, the PDSN informs the PDSN of an IP address used by the mobile terminal and an access router in the WLAN, thereby delivering IP packets between the PDSN and the access router. Form a tunneling path for Secondly, the present invention proposes a message flow between a mobile station, an access router, and a PDSN for establishing the tunneling path, and an IP packet delivery method through a tunneling path between a PDSN and an access router. Lastly, a method of releasing a tunneling path between an access router and a PDSN configured when the mobile terminal is handed off will be proposed.                     

4 is a diagram illustrating a configuration of a handoff system from a WLAN to a mobile communication network according to an embodiment of the present invention. In FIG. 4, a thick solid line indicates an IP when a terminal moves from a WLAN to a cellular network. It shows the route of packet forwarding. In FIG. 4, the mobile communication network may use a code division multiple access system such as a CDMA 2000 1x system, and the wireless LAN may use, for example, WiFi technology based on IEEE 802.11x. However, the network configuration of FIG. 4 illustrates an embodiment of the present invention, and it should be noted that the present invention can be applied to a cellular mobile communication network and various networks such as IEEE 802.1x and 802.2x based wireless LANs.

Referring to FIG. 4, when the mobile terminal 110, which is connected to the wireless LAN and receives an IP packet from the counterpart node 60, moves to the cellular area R2, the existing IP address is It stays the same. That is, as shown, when the access router 150 receives the IP packet through the existing IP packet forwarding path 401, the mobile terminal 110 is the PDSN 130 of the mobile communication network and the access router 150 of the WLAN IP packets transmitted from the counterpart node 60 are continuously received through the tunneling path 403 established therebetween.

On the contrary, when the mobile terminal 110 transmits an IP packet to the counterpart node 60, the IP packet is delivered to the counterpart node 60 by the routing function of the PDSN 130, or the PDSN 130 transmits an IP packet to the counterpart node 60. The IP packet is transmitted through the tunneling path 403 established up to the access router 150. The tunneling path 403 here acts as a reverse tunnel. The IP packet transmitted from the mobile terminal 110 is delivered to the counterpart node 50 by the routing function of the access router 150.                     

In the present invention, after the vertical handoff of the mobile terminal 110, the mobile terminal 110 uses a Dynamic Host Configuration Protocol (DHCP) to transmit and receive IP packets using an existing IP address. The mobile terminal 110 transmits the existing IP address and tunneling related information used in the WLAN to the PDSN 130 using a DHCP message to be described later. This DHCP message is delivered in the upper layer of PPP after the PPP connection of the mobile terminal 110 to the WLAN is in the form of DHCP over PPP.

As described above, a protocol stack between the mobile terminal 110 moving from the WLAN to the mobile communication network, the PDSN 130 of the mobile communication network, and the access router 150 of the WLAN will be described with reference to FIG. 5.

5 is a diagram illustrating a structure of a protocol stack applied to a handoff method from a WLAN to a mobile communication network according to an embodiment of the present invention.

Referring to FIG. 5, the mobile terminal 110 of the present invention includes a DHCP layer, a UDP layer, an IP layer, a PPP layer, a MAC layer (1X MAC), and a 1x physical layer (1X PHY) in descending order. The base station 120 includes a physical layer (1X PHY), a 1x MAC layer (1X MAC (RLP)), and an L2 relay layer in ascending order on the mobile terminal 110 side, and L2 in descending order on the PDSN 130 side. Relay layer, Generic Routing Encapsulation (GRE) layer, IP layer, 802.3 MAC layer (MAC), 802.3 physical layer (PHY).

The PDSN 130 includes an 802.3 physical layer (PHY), an 802.3 MAC layer, an IP layer, a GRE layer, a PPP layer, a UDP layer, and a DHCP layer in ascending order on the base station side, and toward the access router 150. In descending order, it includes the AP layer, UDP layer, IP layer, 802.3 MAC layer (MAC) and 802.3 physical layer (PHY). Finally, the access router 40 is composed of the 802.3 physical layer (PHY), 802.3 MAC layer (MAC), IP layer, UDP layer and A-P layer in ascending order.

In the protocol stack, the 'A-P layer' is responsible for transmitting and receiving messages to be described later for establishing or releasing a tunnel between the PDSN 130 and the access router 150. As shown in the protocol stack of FIG. 5, the mobile terminal 110 uses the 'DHCP layer' when handing off from the WLAN to the mobile communication network and displays information related to tunneling with the existing IP address used in the WLAN. 130).

A detailed operation procedure of the present invention will be described with reference to FIGS. 6 and 7.

First, in order for the mobile terminal 110 to be handed off from a wireless LAN to a mobile communication network using an existing IP address, as shown in FIG. 6, the IP address of the mobile terminal 110 connected to the mobile communication network and the access router 140 of FIG. The PDSN 130 needs to be informed of the IP address.

6 is a flowchart illustrating a handoff method from a WLAN to a mobile communication network according to an exemplary embodiment of the present invention, and FIG. 6 is a mobile terminal 110 and an access router 150 that are handed off from a WLAN to a mobile communication network. ), A message flow between the PDSNs 130 and an IP packet forwarding process. According to the present invention, when the mobile terminal 110, which has received an IP packet from the counterpart node 60 by accessing the wireless LAN, moves to the mobile communication network, it operates in the following procedure.                     

First, the mobile terminal 110 is connected to an access network 150 in a wireless LAN area by three layers and is connected to an IP network, and transmits and receives an IP packet with the counterpart node 60 through the access router 150. In step 601, when the mobile terminal 110 communicating with the access router 150 moves to the cellular area R2 and detects that the mobile terminal 110 moves from the wireless LAN to the mobile communication network, in step 603, the mobile terminal 110 determines that the base station ( 120 establishes a traffic channel, and base station 120 and PDSN 130 establish an RP (RN-PDSN) session.

Thereafter, in step 605, the mobile terminal 110 and the PDSN 130 perform a link control protocol (LCP) negotiation for a PPP session, and in step 607, a CHAP (Challenge) for subscriber authentication in a PPP session. Handshake Authentication Protocol). In step 609, the PDSN 130 performs IPCP protocol negotiation with the mobile station 110. Here, the IPCP is generally a protocol for assigning an IP address to the mobile terminal, but in the present invention, the IPCP is excluded from the 'IP address option' so as not to assign a new IP address to the mobile terminal 110.

In step 611 to step 619 to be described later, the mobile terminal 110 transmits and receives the DHCP messages to be described later with the PDSN 130 to transmit the existing IP address and tunneling-related information used in the WLAN to the PDSN (130).

That is, in step 611, the mobile terminal 110 generates a DHCP discovery (DISCOVER) message as shown in Table 1 below, and delivers it to the PDSN 130 through the PPP link.                     

Herein, the mobile terminal 110 adds a parameter request list option field as shown in Table 2 to the DHCP DISCOVER message of Table 1, and the parameter request list option field is set to the DHCP DISCOVER message. In the data field, for example, an 'AP parameter' option code of '83' is included.

Subsequently, when the PDSN 130 receives the DHCP DISCOVER message through the PPP link in step 613, the PDSN 130 provides the DHCP as shown in <Table 3> to indicate that the mobile terminal 110 supports the vertical handoff. Generates a message and delivers the message to the mobile terminal 110.                     

In order to indicate that it supports vertical handoff from the WLAN to the mobile communication network, the DHCP OFFER message includes an 'A-P parameter' option field as shown in Table 4 according to the present invention.

The data field of Table 4 includes a data field of an 'AP parameter' option as shown in Table 5 below, which includes a 1-byte capability field, a 4-byte serving node IP field, and 1 byte. It consists of a tunnel protocol field.                     

In Table 5, the performance field indicates whether the PDSN 130 supports reverse tunneling and whether it supports IP packet buffering. The serving node IP field indicates an IP address of a serving node used for tunneling between the access router 150 and the PDSN 130. Herein, the serving node refers to a node that becomes an anchor point during handover. For example, when the mobile node moves from the cellular cellular area to the wireless LAN area, the serving node is a PDSN. When the mobile node moves from the wireless LAN area to the mobile communication cellular area, the serving node becomes an access router. The tunnel protocol field indicates types of various protocols used for tunneling.

On the other hand, the mobile terminal 110 receives the DHCP OFFER message including the 'AP parameter' option field in step 615 generates a DHCP notification (INFORM) message as shown in Table 6 below, the mobile terminal 110 is In addition to the IP address used, various information required for establishing a tunnel (hereinafter, referred to as an "AP" tunnel) between the PDSN 130 and the access router 150 is transmitted to the packet data service node (PDSN). The DHCP INFORM message includes the 'A-P tunnel request' option field as shown in Table 7 below to transmit information required for establishing the A-P tunnel to the PDSN 130.

The data field of <Table 7> includes a data field of 'AP tunnel request' option as shown in <Table 8>, which includes a 1-byte capability field and a 4-byte serving node IP field and 1 It consists of a tunnel protocol field of bytes.                     

In Table 8, the capability field indicates whether the mobile station 110 requests the PDSN 130 to establish a reverse tunnel or to release the A-P tunnel. The serving node IP field indicates an IP address of a serving node used for tunneling between the access router 150 and the PDSN 130. In Table 8, the tunnel protocol field indicates types of various protocols used for tunneling.

Subsequently, in step 617, the PDSN 130 receiving the DHCP INFORM message including the 'AP tunnel request' option provides routing information about the IP address used by the mobile station 110 as shown in Table 6 below. Field and the AP tunnel with the access router AR using the 'AP tunnel request' option. In step 619, the PDSN 130, which successfully establishes the A-P tunnel with the access router 150, generates a DHCP acknowledgment (ACK) message as the acknowledgment message and transmits it to the mobile terminal 110. After the vertical handoff from the wireless LAN to the mobile communication network is completed according to the above process, the mobile terminal 110 uses the tunneling path 403 established between the PDSN 130 and the access router 150 to establish a counterpart node 60. ) And continue to send and receive packets to the existing IP address.

Thereafter, when the user traffic state transitions to the idle state in step 621, the mobile terminal 110 changes the layer 3 access point from the access router 150 to the PDSN 130 through the procedure described in FIG. 7.

That is, FIG. 7 is a flowchart illustrating a process of acquiring an IP address through DHCP over PPP by a terminal handed off to a mobile communication network according to an embodiment of the present invention.

First, even after the handoff, the mobile terminal 110 is connected to the access router 150 of the WLAN in three layers. In step 701, the mobile terminal 110 connected to the access router 150 establishes a traffic channel with the base station 120, and the base station 120 and the PDSN 130 establish an RP (RN-PDSN) session. . Thereafter, the mobile terminal 110 and the PDSN 130 perform a link control protocol (LCP) negotiation for a PPP session in step 703, and perform CHAP authentication for subscriber authentication in a PPP session in step 705.

In step 707, the PDSN 130 performs IPCP negotiation with the mobile station 110. The IPCP is generally a protocol for assigning an IP address to a mobile terminal, but the IPCP excludes an 'IP address option' so as not to assign a new IP address to the mobile terminal 110. Thereafter, in step 709, the mobile terminal 110 generates a DHCP DISCOVER message as shown in Table 1 and delivers it to the PDSN 130 through the PPP link. Upon receiving the DHCP DISCOVER message in step 711, the PDSN 130 transmits the IP address and IP configuration information to be allocated to the mobile station 110 in the DHCP OFFER message of Table 3 to the mobile station 110. do.

The mobile terminal 110 receiving the DHCP OFFER message in step 713 transmits a DHCP REQUEST message requesting the use of the assigned IP address from the PDSN 130 to the PDSN 130. After the PDSN (130) receives the DHCP REQUEST message in step 715, the proxy ARP (Proxy) for mapping the routing information for the IP address assigned to the mobile terminal 110 and the IP address and MAC address of the terminal Resolution Protocol) and the like, and delivers a DHCP ACK message to the mobile terminal 110.

FIG. 8 is a diagram illustrating a PDSN 130 and an access router 150 configured in the process of FIG. 6 after a three-layer access point of a mobile terminal handed off is changed from an access router 150 to a PDSN 130 according to an embodiment of the present invention. A flow chart illustrating a process of releasing an AP tunnel between them. When the mobile terminal 110 no longer exchanges IP packets with the counterpart node 60 or when the mobile terminal 110 is powered off, the mobile terminal 110 releases the A-P tunnel according to the following procedure.

First, in step 801, the mobile station 110 transmits a DHCP Inform message in which the REL field (see <Table 8>) of the 'A-P tunnel request' option is set to the PDSN 130 to start the release procedure of the A-P tunnel. In step 803, the PDSN 130 receiving the DHCP Inform message transmits an AP registration request message having a lifetime set to '0', and the access router 150 receiving the message registers the AP in response. The AP tunnel is released by sending a response message to the PDSN 130. In operation 805, the PPP link between the mobile terminal 110 and the PDSN 130 is also released.                     

As described above, the present invention allocates a new IP address every time a mobile terminal moves from a mobile communication network to a wireless LAN in a conventional method that does not use mobile IP, and thus cannot maintain a session of a higher layer. It is possible to solve the problem that the delivered packets could not be delivered to the terminal. In addition, the present invention can be applied to the handoff from the mobile communication network to the wireless LAN, and even in this case, since the mobile terminal maintains the previously used IP address, it is possible to maintain the session of the upper layer and reduce packet loss. have.

In the conventional method, the mobile terminal, the mobile communication network, and the WLAN must support mobility based on mobile IP. The present invention can support mobility between heterogeneous networks regardless of whether mobile IP is supported. In addition, in order to solve the problem that IP tunneling for delivering IP packets to a home agent is concentrated on a home agent, IP tunneling is distributed from a PDSN to an access router of a WLAN.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention maintains an IP layer previously used by a mobile station when handing off between heterogeneous networks, thereby maintaining a session of a higher layer and reducing packet loss, regardless of whether mobile IP is supported in heterogeneous networks. Mobility support is possible without. In addition, according to the present invention, there is an effect that can solve the problem that the IP tunneling for delivering IP packets to the network where the mobile terminal is located to the home agent.

Claims (12)

A handoff method of a mobile terminal that is connected to a base station from a wireless LAN including an access router providing an IP (Internet Protocol) routing function and moves to a mobile communication network including a packet data service node (PDSN) providing the IP routing function. To Detecting a movement to the mobile communication network by the mobile terminal in which the access router and the access point are set; Transmitting, by the mobile terminal, information for tunneling between the access router and the PDSN to the PDSN; Establishing a tunnel for packet delivery between the PDSN and the access router; And transmitting the packets transmitted from the counterpart node to the mobile terminal through the set tunnel. The method of claim 1, The tunneling information includes the existing IP address used by the mobile station in the WLAN and the IP address of the access router. The method of claim 1, The tunneling information is transmitted through a Dynamic Host Configuration Protocol (DHCP) message exchange between the mobile terminal and the PDSN. The method of claim 3, wherein The DHCP message transmitted from the mobile terminal to the PDSN further includes a field for requesting reverse tunnel establishment from the PDSN to the access router. The method of claim 1, Establishing a reverse tunnel for forwarding packets from the PDSN to the access router; And transmitting the packets transmitted from the mobile terminal to the counterpart node connected to an external IP network through the established reverse tunnel. The method of claim 1, And changing the three-layer access point of the mobile terminal to the PDSN when the mobile station is switched to an idle state after the tunnel is established. The method of claim 6, And releasing a tunnel established between the PDSN and the access router after the three-layer access point is changed. The method according to claim 6 or 7, The step of changing the three-layer access point and the step of releasing the tunnel is performed through a Dynamic Host Configuration Protocol (DHCP) message exchange between the mobile terminal and the PDSN. The method of claim 1, Establishing a tunnel between the access router and the PDSN when the mobile terminal hands off from the mobile communication network to the wireless LAN; And transmitting the packets transmitted from the counterpart node to the mobile terminal through the established tunnel. A handoff of a mobile terminal connected to a base station from a wireless LAN including an access router providing an IP (Internet Protocol) routing function and moving to a mobile communication network including a packet data service node (PDSN) providing the IP routing function is performed. In a wireless communication system to perform, And a dual mode function connected to the wireless LAN and the mobile communication network, respectively, and transfers information for tunneling between the access router and the PDSN to the PDSN when moving to the mobile communication network with the access router and the access point set. With mobile terminal to say, The PDSN configured to receive the information for tunneling, establish a tunnel for packet forwarding with the access router, and deliver packets transmitted from a counterpart node to the mobile terminal through the set tunnel; . The method of claim 10, The system for tunneling includes the existing IP address used by the mobile terminal in the WLAN and the IP address of the access router. The method of claim 10, The tunneling information is transmitted through a Dynamic Host Configuration Protocol (DHCP) message exchange between the mobile terminal and the PDSN.

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