Method and system for handoff to a destination base station by measuring signal strength of carrier signals during at least one CSMA-backoff time
View Patent ↗A wireless packet communication system that enables a wireless terminal to move from one wireless LAN to another while maintaining packet communication. The wireless terminal detects the electric field strength of a carrier signal from each base station during at least one back-off period, creates move destination information based on a carrier signal having the greatest electric field strength and the IP address of the currently used base station, and transmits the created Information and IP address to a server. The server writes the IP address of the wireless terminal into an edge router connected to a base station at the move destination in accordance with the information and IP address created by the wireless terminal to ensure that the packet data from a remote party is transmitted from the base station at the move destination.
1. A wireless packet communication method in which a carrier-sense multiple access/collision avoidance (CSMA) technique is used to let a wireless terminal exchange packet data with a plurality of base stations that are respectively connected to core-net routers and different in carrier signal frequency, and said core-net routers are managed and controlled by a server, said method comprising the steps of:
causing said wireless terminal to measure the electric field strength of each carrier signal during a back-off period, to create move destination information in accordance with the measurement result, and to transmit the created move destination information and the base station address currently used for communication to said server; and
causing said server to determine a base station at the move destination for said wireless terminal in accordance with said move destination information and the base station address currently used for communication, to identify a router connected to the determined base station at the move destination, and to exercise management and control to allow the packet data addressed to said wireless terminal to be transmitted to the router from said base station at the move destination in addition to the base station currently used for communication.
2. The wireless packet communication method according to claim 1 , wherein the electric field strength measurement of said carrier signal is made by measuring the carrier signal electric field strength of a base station other than the base station currently used for communication.
3. The wireless packet communication method according to claim 1 , wherein the electric field strength measurement of said carrier signal is made by measuring the electric field strength of each carrier signal during a plurality of back-off periods.
4. The wireless packet communication method according to claim 1 , wherein said move destination information is created in accordance with a carrier signal having the greatest electric field strength that has been measured.
5. A wireless packet communication system in which a carrier-sense multiple access/collision avoidance (CSMA) technique is used let a wireless terminal exchange packet data with a plurality of base stations that are respectively connected to core-net routers and different in carrier signal frequency, and said core-net routers are managed and controlled by a server, wherein said wireless terminal comprises measurement means for measuring the electric field strength of said carrier signal during a back-off period, creation means for creating move destination information in accordance with the measurement result, and transmission means for transmitting the created move destination information and the base station address currently used for communication to said server before the end of the back-off period, and wherein said server determines a base station at the move destination for said wireless terminal in accordance with said move destination information and the base station address currently used for communication, identifies a router connected to the determined base station at the move destination, and exercises management and control to allow the packet data addressed to said wireless terminal to be transmitted to the router from said base station at the move destination in addition to the base station currently used for communication.
6. The wireless packet communication system according to claim 5 , wherein said measurement means measures the carrier signal electric field strength of a base station other than the base station currently used for communication.