Patent ID: 7672288

Claim:
A method for providing Internet Protocol-type mobility for a mobile host in a mobile communications system comprising a plurality of mobile hosts, at least two mobile exchanges, at least two Internet Protocol address spaces defining subnetworks in the mobile communication system, a plurality of base stations connected to said mobile exchanges, at least one of the mobile exchanges being arranged to operate as a gateway which interfaces the mobile communications system with external data networks, the method comprising: allocating an Internet Protocol address for a mobile host in a first Internet protocol address space; using a user identity and a data equipment identity for identifying the mobile host in the mobile communications system, wherein the user identity is a mobile subscriber identity and the data equipment identity is a network service point access identifier; defining the location of the mobile host by an identity of a mobile exchange currently serving the mobile host; establishing address information which binds the allocated Internet Protocol address to the user identity and the data equipment identity, and which contains the location of the mobile host; routing Internet Protocol datagrams having the allocated Internet Protocol address in the first Internet protocol address space from a gateway exchange to the serving exchange and further to the respective mobile host according to said address information; updating the location of the mobile host in the address information in a handover from an old mobile exchange in the first Internet Protocol address space to a new mobile exchange in a second Internet Protocol address space, sending a roaming request from the mobile host to the old mobile exchange, sending a roaming request from the old mobile exchange to the new mobile exchange, said roaming request containing said address information, updating the location of the mobile host in said address information at the new mobile exchange, sending an acknowledgement from the new mobile exchange to the old mobile exchange, said acknowledgement containing the updated address information; and routing the Internet Protocol datagrams having the allocated Internet Protocol address in the first Internet Protocol address to the new exchange in the second Internet Protocol address space according to the updated address information.