Patent ID: 8051198

Claim:
A communication system comprising: a communication terminal apparatus comprising a processor; a plurality of access routers that communicate with the communication terminal apparatus; a first mobility anchor point that controls an access router subordinate under the first mobility anchor point among the plurality of access routers, issues a first care-of address and a second care-of address, and transmits the issued first care-of address and the issued second care-of address through a network; a second mobility anchor point that controls another access router subordinate under the second mobility anchor point among the plurality of access routers, wherein the second mobility anchor point is adjacent to the first mobility anchor point and separated by a boundary with the first mobility anchor point; and a home agent that: transmits data, transmitted to a home address of the communication terminal apparatus, to a destination indicated by at least one of the first care-of address and the second care-of address, wherein: the first care-of address can only be used in cells of the first mobility anchor point; the second care-of address can only be used in predetermined cells; wherein the predetermined cells: (i) only include a first cell group, which is part of the cells of the first mobility anchor point, and a second cell group, which is part of the cells of the second mobility anchor point, the second cell group of the second mobility anchor point being adjacent to the first cell group of the first mobility anchor point and separated by the boundary with the first mobility anchor point, and (ii) do not include at least one of (a) a third cell, which is part of the cells of the first mobility anchor point, and (b) a fourth cell, which is part of the cells of the second mobility anchor point; and the home agent registers the home address of the communication terminal apparatus, the first care-of address transmitted through the network and the second care-of address transmitted through the network, wherein: the home address of the communication terminal apparatus, the first care-of address and the second care-of address are associated with each other.