A method of processing a call to an unregistered user in a Wireless Local
Area Network (WLAN)-General Packet Radio Service (GPRS) using a Session
Initiation Protocol (SIP) is provided. The method of connecting a call to
a mobile node present in a GPRS area includes registering location
information of the mobile node to be invited in a Home Subscriber Server
(HSS); when the mobile node uses a Mobile Internet Protocol (MIP),
allocating an Internet Protocol (IP) address to the mobile node and
authenticating the mobile node through MIP registration and setting a SIP
session; and when the mobile node uses a simple IP, allocating an IP
address to the mobile node and authenticating the mobile node through a
Dynamic Host Configuration Protocol (DHCP) procedure and setting a SIP
session.