Seamless roaming among multiple networks

• US 6,091,951 A
• Filed: 09/03/1997
• Issued: 07/18/2000
• Est. Priority Date: 05/14/1997
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Telxon Corporation (Zebra Technologies Corporation)
• Inventors: Clotti, Frank D. Jr., Sturniolo, Emil A., Seshadri, Krishna P.
• Primary Examiner(s): Hunter, Daniel S.
• Assistant Examiner(s): Armstrong, Darnell R.
• Application Number:
  US08/922,709
• Time in Patent Office: 1,049 Days
• Field of Search: 455/436, 455/437, 455/438, 455/428, 455/435, 455/552
• US Class Current: 455/432.2
• CPC Class Codes: H04L 61/4511 using domain name system [DNS]
• CPC Class Codes: H04L 67/14 Session management for real-time applications in data packet communications networks H04L65/1066
• CPC Class Codes: H04L 67/148 Migration or transfer of sessions
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 60/00 Affiliation to network, e.g. registration; Terminating affiliation with the network, e.g. de-registration
• CPC Class Codes: H04W 76/10 Connection setup
• CPC Class Codes: H04W 76/20 Manipulation of established connections
• CPC Class Codes: H04W 8/087 for preserving data network PoA address despite hand-offs
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/16 Gateway arrangements
• CPC Class Codes: H04W 92/02 Inter-networking arrangements

Abstract

The present invention relates to wireless communication systems involving multiple local area networks. A communication system according to the present invention includes a plurality of local area networks (LANs). Each of the LANs includes: a network backbone; and at least one access point coupled to the network backbone which, when a mobile terminal is registered to the access point, enables the mobile terminal to communicate wirelessly with a device on the network backbone via the at least one access point. When the mobile terminal is registered to at least one access point in one of the plurality of LANs the mobile terminal is assigned a first network address, and when the mobile terminal is registered to at least one access point in another of the plurality of LANs the mobile terminal is assigned a second network address in place of the first network address, the second network address being different from the first network address. The mobile communication system also includes a system backbone interconnecting the plurality of LANs for permitting communications between the plurality of LANs. Furthermore, the system includes a gateway controller, operatively coupled to one of the plurality of LANs, for serving as an intermediary for communications between the mobile terminal and a device on one of the system backbones in order that in the event the mobile terminal is assigned a different network address by virtue of registering with an access point in another of the LANs, the device is able to maintain communications with the mobile terminal without requiring knowledge of a change in the network address of the mobile terminal.

Claims

1. A communication system, comprising:

a plurality of local area networks (LANs), each of the LANs including;

a network backbone; and

at least one access point coupled to the network backbone which, when a mobile terminal is registered to the access point, enables the mobile terminal to communicate wirelessly with a device on the network backbone via the at least one access point;

wherein when the mobile terminal is registered to at least one access point in one of the plurality of LANs the mobile terminal is assigned a first network address, and when the mobile terminal is registered to at least one access point in another of the plurality of LANs the mobile terminal is assigned a second network address in place of the first network address, the second network address being different from the first network address;

a system backbone interconnecting the plurality of LANs for permitting communications between the plurality of LANs; and

a gateway controller, operatively coupled to one of the plurality of LANs, for serving as an intermediary for all communications between the mobile terminal and a device on one of the network backbones in order that in the event the mobile terminal is assigned a different network address by virtue of registering with an access point in another of the LANs, the device is able to maintain communications with the mobile terminal without requiring knowledge of a change in the network address of the mobile terminal;

wherein the device initiates communications with the mobile terminal through the gateway controller.

2. The communication system of claim 1, the gateway controller storing information relating to the current network address of the mobile terminal and the current network address of the device, wherein the gateway controller receives communications from the mobile terminal containing information intended for the device and forwards the information to the device, and the gateway controller receives communications from the device containing information intended for the mobile terminal and forwards the information to the mobile terminal.

3. The communication system of claim 1, wherein each of the plurality of LANs includes a gateway controller connected to the system backbone.

4. The communication system of claim 1, wherein the system backbone represents part of a wide area network (WAN).

5. The communication system of claim 1, wherein the mobile terminal comprises at least one of a data terminal, a telephone, and a pager.

6. A method of carrying out communications in a system comprising the steps of:

a device within a network obtaining a virtual address of a mobile terminal from a memory;

the device sending an unsolicited message to the virtual address;

receiving the unsolicited message by a gateway controller;

a mobile terminal informing the gateway controller of a willingness to accept communications initiated by the device;

the gateway controller establishing a virtual circuit connection with the mobile terminal, the gateway controller using the virtual circuit to forward the unsolicited message received from the device to the mobile terminal and to forward information received from the mobile terminal to the device; and

notifying the gateway controller of changes in a network address of the mobile terminal to permit seamless communications between the mobile terminal and the device regardless of a change in the network address of the mobile terminal.

7. The method of claim 6, wherein the mobile terminal communicates with the gateway controller through at least one wireless link.

8. The method of claim 6, wherein the gateway controller provides for a plurality of virtual circuit connections between the mobile terminal and the gateway controller to enable communication between the mobile terminal and a plurality of different devices.

9. A communication system, comprising:

a plurality of local area networks (LANs), each of the LANs including;

a network backbone; and

at least one access point coupled to the network backbone which, when a mobile terminal is registered to the access point, enables the mobile terminal to communicate wirelessly with a device on the network backbone via the at least one access point;

wherein when the mobile terminal is registered to at least one access point in one of the plurality of LANs the mobile terminal is assigned a first network address, and when the mobile terminal is registered to at least one access point in another of the plurality of LANs the mobile terminal is assigned a second network address in place of the first network address, the second network address being different from the first network address;

a wide area network (WAN) system backbone interconnecting the plurality of LANs for permitting communications between the plurality of LANs, the WAN system backbone including at least one WAN access point; and

a gateway controller, operatively coupled to one of the plurality of LANs, for serving as an intermediary for communications between the mobile terminal and a device on one of the network backbones in order that in the event the mobile terminal is assigned a different network address by virtue of registering with an access point in another of the LANs or the at least one WAN access point, the device is able to maintain communications with the mobile terminal without requiring knowledge of a change in the network address of the mobile terminal;

wherein the mobile terminal comprises a first wireless transceiver for communicating with the access point with which the mobile terminal is registered, and a second wireless transceiver for communicating directly with a WAN access point.

10. The communication system of claim 9, wherein the mobile terminal is configured to communicate with the gateway controller via the first wireless transceiver and the access point with which the mobile terminal is registered ordinarily, and to communicate with the gateway controller via the second wireless transceiver and the at least one WAN access point in the event the mobile terminal is unable to communicate with the gateway controller via the first wireless transceiver appoint.

11. A communication system, comprising:

a plurality of local area networks (LANs), each of the LANs including a network backbone;

a mobile terminal, wherein when the mobile terminal is coupled to one network backbone the mobile terminal is assigned a first network address, and when the mobile terminal is coupled to another network backbone the mobile terminal is assigned a second network address in place of the first network address, the second network address being different from the first network address;

a system backbone interconnecting the plurality of LANs for permitting communications between the plurality of LANs; and

a gateway controller, operatively coupled to one of the plurality of LANs, for serving as an intermediary for all communications between the mobile terminal and a device on one of the network backbones in order that in the event the mobile terminal is assigned a different network address, the device is able to maintain communications with the mobile terminal without requiring knowledge of a change in the network address of the mobile terminal, wherein the device initiates communications with the mobile terminal through the gateway controller.

12. The communication system of claim 11, wherein the mobile terminal is coupled to the network backbones via a wireless link.

20. The communication system of claim 11, the gateway controller storing information relating to the current network address of the mobile terminal and the current network address of the device, wherein the gateway controller receives communications from the mobile terminal containing information intended for the device and forwards the information to the device, and the gateway controller receives communications from the device containing.

13. A gateway controller for use in a communication system including a plurality of local area networks (LANs), each of the LANs including a network backbone and at least one access point coupled to the network backbone which, when a mobile terminal is registered to the access point of one of the LANs, the mobile terminal is assigned a first network address enabling the mobile terminal to communicate wirelessly with a device on the network backbone via the access point, and when the mobile terminal is registered to the access point of another of the LANs, the mobile terminal is assigned a second network address, the gateway controller comprising:

means for operatively coupling the gateway controller to the network backbone of a selected one of the plurality of LANs;

a gateway address circuit for communicating with a mobile terminal registered with any of the access points for establishing indicia distinguishing the mobile terminal from among other mobile terminals;

means for updating a name resolver coupled to the network backbone with a virtual address selected by the gateway for distinguishing the mobile terminal from among other mobile terminals, the name resolver serving to store the virtual address of the mobile terminal for retrieval by the device; and

a communication circuit for receiving unsolicited communications from the device intended for the mobile terminal, the unsolicited communications including the virtual address of the mobile terminal, and forwarding the received unsolicited communications to the mobile terminal using at least a portion of the indicia, and for receiving communications from the mobile terminal intended for the device and forwarding communications from the mobile terminal to the device, and for serving as an intermediary for all communications between the mobile terminal and the device in order that in the event the network address of the mobile terminal changes from the first network address to the second network address the device is able to maintain communications with the mobile terminal without requiring knowledge of a change in the network address of the mobile terminal.

14. The gateway controller of claim 13 wherein the name resolver is a domain name server.

15. The gateway controller of claim 13, wherein the virtual address represents a unique address utilized in communications involving the gateway controller and the device, but which is not required in communications between the mobile terminal and the gateway controller.

16. The gateway controller of claim 13, wherein the at least a portion of the indicia represents a layer of addressing utilized in communications involving the gateway controller and the mobile terminal but is not required in communications between other devices communicating with the mobile terminal on the network backbone.

17. The gateway controller of claim 13, wherein the communication circuit includes a memory table in which the indicia and the virtual address for a plurality of mobile terminals are stored.

18. A mobile terminal for use in a communication system including a plurality of local area networks (LANs), each of the LANs including a network backbone and at least one access point coupled to the network backbone which, when the mobile terminal is registered to the access point, enables the mobile terminal to communicate wirelessly with a plurality of devices coupled to the network backbone via the at least one access point, the mobile terminal comprising:

means for establishing with a gateway controller coupled to one of the plurality of LANs via the network backbone a unique identifier for use by the gateway controller in transmitting an unsolicited message received from one of the plurality of devices to the mobile terminal; and

a communication circuit for receiving the unsolicited message from the gateway controller together with the unique identifier and for transmitting communications to the one of the plurality of devices via the gateway controller, the transmitted communications including the unique identifier, wherein the unique identifier represents a plurality of layers of addressing utilized in communications involving the mobile terminal and the gateway controller but which are not required in communications between the gateway controller and the one of the plurality of devices and the layer of addressing permits the one of the plurality of devices communicating with the mobile terminal to continue communicating with the mobile terminal through the gateway even if another layer of addressing of the mobile terminal changes unbeknownst to the one of the plurality of devices.

19. The mobile terminal of claim 18, wherein the mobile terminal communication circuit includes a memory table in which the unique identifier is stored.