Method and apparatus for handoff between mobile communication network and wireless local area network

A method for performing handoff to a mobile communication network by a terminal located in a wireless local area network (WLAN), the method comprises:

• performing association with the WLAN and receiving an Internet protocol (IP) address for a service that the terminal desires to receive, the IP address being allocated from a dynamic host configuration protocol (DHCP) server;
• exchanging data traffics with an Internet network via the WLAN using the IP address;
• determining to perform handoff to the mobile communication network and setting up a call to the mobile communication network;
• transmitting to the DHCP server a message for requesting continuous use of the IP address allocated from the DHCP server and receiving an acknowledgement in response to the request message;
• and
• performing de-association with the WLAN, and exchanging data with the Internet network via the mobile communication network using the IP address.

An apparatus for supporting handoff of a terminal between a mobile communication network and a wireless local area network (WLAN), the apparatus comprises:

• a router connected to a service server of an Internet network, for routing a data traffic to the terminal to the mobile communication network;
• a first node, which is located in the mobile communication network and connected to the router, for receiving a data traffic to the terminal from the router, determining whether any call set up exists for a data traffic from the router, and routing the data traffic according to the determination result;
• a second node, which is located in the mobile communication network and connected to the first node, for transmitting a data traffic received from the first node to a terminal located in the mobile communication network, and transmitting a data traffic from the terminal to the Internet network, to the first node;
• an access router, which is located in the WLAN and connected to the access router and the first node, for transmitting a data traffic received from the first node to a terminal located in the WLAN and transmitting a data traffic from the terminal to the Internet network to the router;
• and
• a dynamic host configuration protocol (DHCP) server located in the WLAN, for allocating a flexible Internet protocol (IP) to the terminal, receiving from the terminal a message for requesting continuous use of an IP address previously allocated before handoff even after the handoff and continuously allocating the IP address to the terminal in response to the request message.