Patent ID: 7349390

Claim:
A packet transmission method adapted for a communication system comprising a mobile terminal, a plurality of access routers, each access router forming a cell and configured to perform radio communication with a mobile terminal located in the cell, and a plurality of relay routers connected to a hierarchical structure above the access routers, said packet transmission method being applied when a packet from a packet source is transmitted from an upper layer in the communication system toward a target mobile terminal, said packet transmission method comprising: letting the relay router engaged in relaying the packet from the packet source, multicast a router advertisement with said packet to all access routers forming cells into which said target mobile terminal may move; letting said mobile terminal receive multicast router advertisements from a plurality of neighbor access routers; letting said mobile terminal calculate a difference between reception times of packets from respective access routers, based on information about reception from the plurality of access routers, and specify a relay router that should perform multicasting; letting said mobile terminal transmit to said specified relay router a multicast message containing delay information of a delay to be added to each path in the multicasting by the relay router; and letting said relay router receive the multicast message from the mobile terminal and add the delay to each path in the multicasting on the basis of the delay information.