Patent ID: 7860067

Claim:
A method for a subscriber station to move to a second base station from a first base station and register a mobile IP in a wireless portable Internet system, the method comprising: (a) the second base station and the mobile subscriber station performing a handover; (b) the mobile subscriber station performing a re-registration with the second base station; (c) transmitting a re-registration request message including a flag showing whether to assign an address using a DHCP (Dynamic Host Configuration Protocol) or a mobile IP to the second base station; (d) the mobile subscriber station acquiring a CO A (Care Of Address) from an agent advertisement transmitted from the second base station so as to assign an address using the mobile IP when the flag is set to assign an address using the mobile IP; (e) the mobile subscriber station transmitting a mobile IP registration request message for an IP address allocated from the first base station during a MAC connection establishment; (f) the second base station relaying the mobile IP registration request message to the first base station during the MAC connection establishment; and (g) the first base station transmitting a reply message to the mobile IP registration request message to the mobile subscriber station via the second base station.