Context block leasing for fast handoffs

• US 20040203781A1
• Filed: 08/29/2002
• Published: 10/14/2004
• Est. Priority Date: 03/14/2002
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Lefkowitz, Martin
• Granted Patent: US 6,990,343 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04W 12/069 using certificates or pre-shared keys
• CPC Class Codes: H04W 36/0038 of security context information
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

The roaming of a wireless device 115 extends the effective range of a wireless network 100 by passing a device 115 between access points as the device leaves the coverage area of one and enters another. Roaming can be slow and problematic if an old link is disconnected prior to establishing a new link, especially if authentication and security is required. The present invention speeds up roaming by using existing mechanisms to initiate a new link with a new access point 120 prior to disconnecting the old link with an old access point 110.

Claims

1. A fast handoff method comprising:

receiving an authentication message;

scanning for an alternate wireless access point (WAP);

if the alternate WAP was found;

sending a message to a current WAP;

receiving a response message from the current WAP;

if the response message is an affirmative;

disassociating with the current WAP; and

reassociating with the alternate WAP.

2. The method of claim 1, wherein the scanning step comprises:

searching for an identifier message from the alternate WAP; and

sending a probe request message to the alternate WAP after finding the identifier message.

3. The method of claim 2, wherein the searching step may find more than one alternate WAP, and a probe request message is sent to each alternate WAP found.

4. The method of claim 2 further comprising the step of receiving an acknowledgment message for the probe request message.

5. The method of claim 1, the sending step comprises sending a message with an address of the alternate WAP to the current WAP.

6. The method of claim 5, wherein the message further contains a duration of a context block lease.

7. The method of claim 1 further comprising the step of returning to normal operating mode after the sending step.

8. The method of claim 1, wherein a plurality of alternate WAPs were found and a plurality of response messages were received from the current WAP, and the method further comprises the step of selecting a preferred alternate WAP from the plurality of alternate WAPs.

9. The method of claim 1, wherein each response message from the current WAP contains a response from a different alternate WAP, and the preferred alternate WAP is selected from a set of alternate WAPs responding affirmatively.

10. The method of claim 9, wherein the preferred alternate WAP had a strongest signal level.

11. The method of claim 9, wherein the preferred alternate WAP had a minimum number of wireless communications devices already associated with it.

12. The method of claim 1 further comprising the step of notifying a distributed system after the disassociating step.

13. The method of claim 1, wherein the disassociating step comprises the step of transmitting a disassociate message to the current WAP.

14. The method of claim 1 further comprising the step of notifying a distributed system after the reassociating step.

15. The method of claim 1, wherein the reassociating step comprises the step of transmitting a reassociate message to the alternate WAP.

16. The method of claim 1, wherein there is a plurality of alternate WAPs and one selected alternate WAP, and the reassociating step comprises the step of transmitting a reassociate message to the selected alternate WAP.

17. The method of claim 1 further comprising the step of continuing to scan for the alternate WAP if the first scanning step fails.

18. A method for reducing authentication latency comprising:

at a first wireless access point (WAP);

transmitting an authentication message to a wireless communications device (WCD);

forwarding a context lease request to an alternate WAP;

returning a context lease response to the WCD;

at the WCD;

receiving an authentication message;

scanning for an alternate wireless access point (WAP);

if the alternate WAP was found;

sending a message to a current WAP;

receiving a response message from the current WAP;

if the response message is an affirmative;

disassociating with the current WAP;

reassociating with the alternate WAP;

at the alternate WAP;

receiving the context lease request from the first WAP;

authenticating the WCD;

returning an affirmative response message if authentication succeeds, else return a negative response message; and

reassociating with the WCD if authentication succeeds.

19. The method of claim 18, wherein the forwarding step comprises:

receiving the context lease request from the WCD; and

transmitting the context lease request to the alternate WAP.

20. The method of claim 18, wherein the first returning step comprises:

receiving the context lease response from the alternate WAP; and

transmitting the context lease response to the WCD.

21. The method of claim 18, wherein the authenticating step comprises the step of using information in the context lease request to verify the authenticity of the WCD.

22. The method of claim 21, wherein the contents of the response message is dependent upon the success of the authenticating step.

23. The method of claim 18 further comprising the step at the WCD of continuing to scan for the alternate WAP if the scanning step fails.

24. The method of claim 18, wherein while the alternate WAP is authenticating the WCD, the WCD is continuing normal operations.