COMMUNICATION RELAY APPARATUS, WIRELESS TERMINAL AND COMPUTER PROGRAM
In order to continue a communication by performing a handover across or between different communication systems, improvement in redundancy of a communication route and a delay time difference before and after switching the communication system is intended. A bicast entity 21 includes, when a wireless terminal 10 makes a connection and continues a communication across different communication systems 20 X and 20 Y, bicast means for delivering a packet for each communication route via each of the communication systems 20 X and 20 Y before and after switching the communication system to which the above described wireless terminal 10 connects, and control means for completing a relay of the packet when the switching of the communication system to which the above described wireless terminal 10 connects is completed.
1 . A communication relay apparatus for, when a wireless terminal makes a connection and continues a communication across different communication systems, temporarily delivering a packet of said communication, comprising:
bicast means for delivering said packet for each communication route via each communication system before and after switching the communication system to which said wireless terminal connects; and
control means for completing a relay of said packet when the switching of the communication system to which said wireless terminal connects is completed.
2 . The communication relay apparatus according to claim 1 , wherein said bicast means has delay adjustment means for evaluating a delay time in each communication route before and after switching the communication system to which said wireless terminal connects, and adjusting a difference in the delay times.
3 . The communication relay apparatus according to claim 2 , wherein when the adjustment of said difference in the delay times has been completed, said control means reroutes to an optimal communication route via a switch destination communication system for said wireless terminal.
4 . A wireless terminal for making a connection and continuing a communication across different communication systems, comprising:
communication control means for establishing, for each communication route via each communication system before and after switching the communication system, a communication route to and from a communication relay apparatus for delivering a packet,
wherein after the communication via said communication relay apparatus is performed, said communication control means reroutes to an optimal communication route via a switch destination communication system.
5 . A computer program for performing a communication control process when a wireless terminal makes a connection and continues a communication across different communication systems, said computer program causing a computer to realize:
a bicast function of delivering a packet for each communication route via each communication system before and after switching the communication system to which said wireless terminal connects; and
a control function of completing a relay of a packet when the switching of the communication system to which said wireless terminal connects is completed.
6 . The computer program according to claim 5 , further causing the computer to realize a delay adjustment function of evaluating a delay time in each communication route before and after switching the communication system to which said wireless terminal connects, and adjusting a difference in the delay times.
7 . The computer program according to claim 6 , wherein when the adjustment of said difference in the delay times has been completed, said control function reroutes to an optimal communication route via a switch destination communication system for said wireless terminal.