Wireless communication system and mobile terminal

• US 20090285184A1
• Filed: 07/23/2009
• Published: 11/19/2009
• Est. Priority Date: 10/01/2003
• Status: Abandoned Application

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Watanabe, Koji, Ishifuji, Tomoaki
• Application Number:
  US12/458,817
• Publication Number:
  US 20090285184A1
• Time in Patent Office: Days
• US Class Current: 370/332
• CPC Class Codes: H04L 12/5692 Selection among different networks

Abstract

The mobile station has a monitor for monitoring the communication qualities of plural wireless interfaces and selecting one of the wireless interfaces to communicate, and a memory for storing the correspondence between the address unique to the selected wireless interface and the network address unique to the mobile station. The mobile station notifies the gateway of the correspondence. The mobile station supplies power to a not operating wireless interface at constant intervals and during a constant time to monitor the communication quality.

Claims

1. A terminal device, having a network address, connected to a public network through a gateway connected to said public network, and through first wireless communication equipment and second wireless communication equipment, said first wireless communication equipment and said second wireless communication being connected to said gateway, said terminal device comprising:

a first wireless interface having a first interface address to communicate with said first wireless communication equipment;

a second wireless interface having a second interface address to communicate with said second wireless communication equipment;

a controller to monitor at least communication quality of said first wireless interface, and select any one of said wireless interfaces for communication on a basis of said monitored communication quality; and

a memory to store a correspondence of any one of said first and second interface addresses with the network address of said terminal device,

wherein said controller associates an interface address of said selected wireless interface with said network address, stores said correspondence in said memory, and updates said correspondence in said memory if the controller selects a wireless interface which is not currently used,

said controller notifies a gateway of said correspondence via said first or second wireless communication equipment,

wherein if the communication quality of said first wireless interface does not meet a predetermined criterion during communication using said first wireless interface, said controller transmits a switching request to said gateway via said first wireless interface, receives a switching response via said first wireless interface, causes said memory to store a correspondence between said second interface address and said network address, and starts communication using said second wireless interface, and

wherein if the communication quality of said first wireless interface meets a predetermined criterion during communication using said second wireless interface, said controller transmits a switching request to said gateway via said second wireless interface, receives a switching response through said second wireless interface, causes said memory to store a correspondence between said first wireless interface address and said network address, and starts communication using said first wireless interface.

2. A terminal device according to claim 1, wherein said first wireless interface is a wireless LAN interface, and said second wireless interface is a cellular phone interface for cellular communication.

3. A terminal device according to claim 1, wherein said unique addresses of said wireless interfaces are MAC (Media Access Control) addresses, and said network address is an IP (Internet Protocol) address.

4. A terminal device according to claim 1, wherein said switching request contains said second wireless interface address.

5. A terminal device according to claim 1, wherein said switching request contains said first wireless interface address.

6. A terminal device according to claim 1, wherein when said second wireless interface is being operated for communication, said controller controls supply of power to said first wireless interface at intervals of a first period of time and during a second period of time that is shorter than said first period and measurement of the quality of communication.

7. A gateway connected to first wireless communication equipment that communicates with a terminal device having a first wireless interface having a first interface address and a second wireless interface having a second interface address through said first wireless interface of the terminal device, to second wireless communication equipment that communicates with said terminal device through said second wireless interface of the terminal device, and to a public network so that said gateway can be used for the communication between said terminal device and said public network, said gateway comprising:

a memory to store an address-correspondence table of a correspondence between a network address uniquely assigned to a communication device with which the gateway can communicate via said first wireless communication equipment, said second wireless communication equipment and said public network and an interface address uniquely assigned to a communication interface of the communication device; and

a transmission controller to determine the interface address of one of said communication devices as a next destination of a received packet by using header information of said packet and information of said address-correspondence table, and to transmit said packet to said determined interface address,

wherein when receiving a switching request from said terminal device during communication through said first wireless interface of said terminal device, said gateway transmits a switching response back to said first wireless interface, makes the interface address of said second wireless interface correspond to the network address of said terminal device to update said correspondence on said address-correspondence table, and starts communication between said second wireless interface and said gateway.

8. A gateway according to claim 7, wherein said first or second wireless interface is a wireless LAN interface.

9. A gateway according to claim 7, wherein said addresses unique to said communication interfaces are MAC (Media Access Control) addresses, and said network address is an IP (Internet Protocol) address.

10. A gateway according to claim 7, wherein said switching request includes the interface address of said second wireless interface.

11. A gateway according to claim 7, wherein said switching request is transmitted on a basis of communication quality at said first or second wireless interface.

12. A communication method used in a wireless communication system having a gateway connected to a public network, a first or second wireless communication equipment connected to said gateway, and a terminal device having first and second wireless interfaces provided to communicate with said first wireless communication equipment and second wireless communication equipment, said method including the steps of:

providing a network address assigned to said terminal device, and first and second interface addresses assigned to said first and second wireless interfaces of said terminal device; and

in said gateway, storing a correspondence between said network address of said terminal device and one of said first and second interface addresses of the wireless interfaces of said terminal device on a basis of a notice received from said terminal device, and indicating which one of said first and second wireless interfaces is used for communication;

in said gateway, when the network address of a packet received from said public network is of said terminal device, transmitting said packet to said first or second interface address according to the correspondence; and

in said gateway, in response to a switching notice from said terminal device during communication, making an interface address specified in the switching notice of said wireless interface correspond to the network address of said terminal device to update said correspondence and starting communication between said wireless interface having the specified interface address and said gateway.

13. A method according to claim 12, wherein said notice is transmitted on a basis of communication quality of said first or second wireless interface measured in said terminal device.

14. A method according to claim 13, wherein said communication quality is measured at intervals of a predetermined period of time.

15. A method according to claim 12, wherein at least one of said first and second wireless interfaces is a wireless LAN interface.

16. A method according to claim 12, wherein when receiving a switching request from said terminal device under a condition that said network address and first wireless interface address of said terminal device are recorded associated with each other, said gateway updates a correspondence between said network address and said first wireless interface address to a correspondence between said network address and said second wireless interface address of said terminal device.

17. A method according to claim 16, wherein said gateway transmits a switching response to said first wireless interface in response to said switching request.

18. A method according to claim 16, wherein said switching request indicates the interface address of said second wireless interface.