Coordinating a transition of a roaming client between wireless access points using another client in physical proximity

• US 7,483,995 B2
• Filed: 07/11/2006
• Issued: 01/27/2009
• Est. Priority Date: 04/28/2006
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Shen, Hui, Abhishek, Abhishek, Ruan, Jiandong, Lu, Yi, Chen, Yue, Mandhana, Taroon
• Primary Examiner(s): LIN, WEN TAI
• Application Number:
  US11/484,303
• Publication Number:
  US 20070255834A1
• Time in Patent Office: 931 Days
• Field of Search: None
• US Class Current: 709/230
• CPC Class Codes: H04W 36/0055 Transmission or use of information for re-establishing the radio link
• CPC Class Codes: H04W 88/04 adapted for relaying to or from another terminal or user

Abstract

Systems and methods for handling a transition of a roaming mobile user device (i.e., a roaming client) from one access point (AP) to a target AP, referred to herein as soft inter-AP handoff. This technique involves a second mobile user device that is already connected with the target AP, called a roaming coordinator, assisting in handoff coordination between the APs. This coordination includes assisting the roaming client in establishing a client-to-client connection to relay data traffic during the handoff, while the roaming client establishes a connection with the target AP using traditional techniques. Soft inter-AP handoff allows a faster hand-off between APs than traditional techniques, and may reduce jitter in communications with the roaming device during the transition.

Claims

1. A method of a roaming mobile user device discovering one or more candidates to serve as a roaming coordinator for a transition of the roaming mobile user device from a first wireless access point to a second wireless access point, the method comprising an act of:

(a) transmitting one or more discovery requests across one or more wireless networks, each discovery request requesting candidates to serve as a roaming coordinator, wherein the candidates are mobile user devices that are already connected to the second wireless access point and wherein act (a) comprises including, in the one or more discovery requests, a list of one or more methods of key exchange supported by the roaming mobile user device for establishing a client-to-client connection between the roaming coordinator and the roaming mobile user device and for encrypting data exchanged between the roaming coordinator and the roaming mobile user device.

2. The method of claim 1, wherein the act (a) comprises including, in the one or more discovery requests, one or more identifiers specifying the second wireless access point.

3. The method of claim 2, wherein the act (a) comprises including, in the one or more discovery requests, a basic service set identifier and/or a service set identifier of the second wireless access point.

4. The method of claim 1, further comprising acts of:

(b) receiving at least one response to the one or more discovery requests from at least one other mobile user device in physical proximity to the second wireless access point; and

(c) constructing a candidate list of roaming coordinator candidates, the candidate list listing the at least one other mobile user device.

5. The method of claim 4, wherein the act (c) comprises ordering the at least one other mobile user device on the candidate list according to one or more criteria.

6. The method of claim 5, wherein the act (c) comprises ordering the at least one other mobile user device on the candidate list according to at least one of the following criteria:

strength of one or more signals exchanged between the at least one other mobile user device and the second wireless access point;

quality of one or signals exchanged between the at least one other mobile user device and the second wireless access point;

strength of a key exchange method specified in the at least one response received from the at least one other mobile user device;

strength of an encryption method specified in the at least one response received from the at least one other mobile user device; and

rate of data exchange supported by the at least one other mobile user device.

7. A system for discovering a candidate to serve as a roaming coordinator for a transition of a roaming mobile user device from a first wireless access point to a second wireless access point, the system comprising:

a mobile user device operative to receive from the roaming mobile user device across one or more wireless networks a discovery request requesting one or more candidates to serve as a roaming coordinator for the roaming mobile user device, and operative to send to the roaming mobile user device a response to the discovery request, wherein the candidates are mobile user devices that are already connected to the second wireless access point and wherein the discovery request includes a list of one or more methods of key exchange supported by the roaming mobile user device for establishing a client-to-client connection between the roaming coordinator and the roaming mobile user device and for encrypting data exchanged between the roaming coordinator and the roaming mobile user device, and

wherein the mobile user device is operative to read the list.

8. The system of claim 7, wherein the discovery request includes one or more identifiers specifying the second wireless access point, and

wherein the mobile user device is operative to read the one or more identifiers.

9. The system of claim 8, wherein the discovery request includes a basic service set identifier and/or a service set identifier of the second wireless access point, and

wherein the mobile user device is operative to read the basic service set identifier and/or the service set identifier.

10. The system of claim 7, wherein the mobile user device is operative to maintain a list of roaming user devices for which the mobile user device is a candidate to serve as a roaming coordinator.

11. The system of claim 7, wherein the mobile user device is located in physical proximity to the roaming mobile user device and has an established connection with a wireless access point, and

wherein the mobile user device is operative to transmit and receive communications with the wireless access point and the roaming mobile user device on behalf of the roaming mobile user device during a transition of the roaming user device from another wireless access point to the wireless access point.

12. The system of claim 7, wherein the mobile user device is operative to exchange cryptographic keys with the roaming mobile user device prior to the transition.

13. A computer program product comprising:

a computer-readable storage medium; and

computer-readable signals, stored on the computer-readable storage medium, that define instructions that, as a result of being executed by a computer, control the computer to perform a method of establishing a client-to-client connection between a roaming mobile user device and a second mobile user device that is already connected to a first wireless access point and will serve as a roaming coordinator to coordinate an exchange of data between the roaming mobile user device and the first wireless access point, the method comprising an act of;

(a) selecting, during a transition of the roaming mobile user device from a second wireless access point to the first wireless access point, the second mobile user device from a candidate list listing one or more mobile user devices that are identified as candidates by sending discovery requests to mobile user devices to serve as the roaming coordinator, wherein act (a) comprises including, in the discovery requests, a list of one or more methods of key exchange supported by the roaming mobile user device for establishing a client-to-client connection between the roaming coordinator and the roaming mobile user device and for encrypting data exchanged between the roaming coordinator and the roaming mobile user device.

14. The computer program product of claim 13, wherein the candidate list includes a plurality of mobile user devices that are candidates to serve as the roaming coordinator, and the candidate list is ordered according to one or more criteria, and

wherein the act (a) comprises selecting the second mobile user device from a top of the candidate list.

15. The computer program product of claim 14, wherein the method further comprises:

(b) attempting to establish a connection between the roaming mobile user device and the second mobile user device; and

(c) if the attempt fails, selecting a next mobile user device listed in the candidate list and attempting to establish a connection between the roaming mobile user device and the next mobile user device.

16. The computer program product of claim 13, wherein the method further comprises:

(b) attempting to establish a connection between the roaming mobile user device and the second mobile user device; and

(c) if the attempt fails, selecting another mobile user device listed in the candidate list and attempting to establish a connection between the roaming mobile user device and the other mobile user device.

17. The computer program product of claim 13, wherein the method further comprises:

(b) establishing a connection between the roaming mobile user device and the second mobile user device.