Methods and systems for reducing MAC layer handoff latency in wireless networks

• US 8,737,351 B2
• Filed: 11/27/2009
• Issued: 05/27/2014
• Est. Priority Date: 03/03/2004
• Status: Expired due to Fees

• Current Assignee: Trustees Of Columbia University In The City Of New York (Columbia University)
• Original Assignee: Trustees Of Columbia University In The City Of New York (Columbia University)
• Inventors: Schulzrinne, Henning G, Shin, Sangho, Forte, Andrea Giuseppe, Rawat, Anshuman S
• Primary Examiner(s): WASHINGTON, ERIKA ALISE
• Application Number:
  US12/626,738
• Publication Number:
  US 20100135252A1
• Time in Patent Office: 1,642 Days
• Field of Search: None
• US Class Current: 370/331
• CPC Class Codes: H04W 36/0016 Hand-off preparation specially adapted for end-to-end data sessions
• CPC Class Codes: H04W 36/0083 Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
• CPC Class Codes: H04W 36/0085 Hand-off measurements
• CPC Class Codes: H04W 36/36 by user or terminal equipment

Abstract

In accordance with the present invention, computer implemented methods and systems are provided for reducing handoff latency in a wireless network. In response to detecting that a handoff is necessary, the present invention uses a selective scanning algorithm that includes the use of a channel mask and/or a caching algorithm for detecting one or more new access points.

Claims

1. A method for reducing handoff latency for a mobile station in a wireless network, the method comprising:

associating with a first access point;

determining whether a handoff is necessary;

performing a selective scan of channels at the mobile station in response to determining that the handoff is necessary, wherein the selective scan comprises accessing a channel mask that is associated with the mobile station, detecting one or more access points using the channel mask, wherein the mobile station receives one or more responses from the one or more access points, and determining a second access point for association by the mobile station based at least in part on the responses from the one or more access points;

associating with the second access point, wherein information that identifies the second access point is stored in the mobile station; and

removing a channel corresponding to the second access point from the channel mask.

2. The method of claim 1, wherein the determining that the handoff is necessary based on any one of signal strength, signal-to-noise ratio, distance from the first access point, and available bandwidth.

3. The method of claim 1, wherein the determining whether the handoff is necessary further comprises determining that the signal-to-noise ratio of the first access point has decreased below a given threshold value.

4. The method of claim 1, further comprising selecting particular channels for inclusion in the channel mask based on type of wireless network.

5. The method of claim 1, wherein the selective scan further comprises:

inverting the channel mask if the mobile station does not detect the one or more access points using the channel mask; and

detecting the one or more access points using the inverted channel mask.

6. The method of claim 1, wherein the selective scan further comprises performing a scan of all channels at the mobile, station in response to not detecting the channel mask.

7. The method of claim 1, further comprising updating the channel mask to remove the channel that is currently being used to connect to the second access point from the channel mask.

8. The method of claim 1, further comprising determining the second access point based on any one of:

signal strength, signal-to-noise ratio, distance from the first access point, and available bandwidth.

9. The method of claim 1, further comprising storing information in the mobile station relating to at least one of the first access point and the second access point, wherein the information comprises at least one of:

SSID, MAC address, IP address, GPS position information, WiFi information, and location information.

10. A system for reducing handoff latency for a mobile station in a wireless network, the method comprising:

a processor that;

associates with a first access point;

determines whether a handoff is necessary;

performs a selective scan of channels at the mobile station in response to determining that the handoff is necessary, wherein the selective scan comprises accessing a channel mask that is associated with the mobile station, detecting one or more access points using the channel mask, wherein the mobile station receives one or more responses from the one or more access points, and determining a second access point for association by the mobile station based at least in part on the responses from the one or more access points;

associates with the second access point, wherein information that identifies the second access point is stored in the mobile station; and

removes a channel corresponding to the second access point from the channel mask.

11. The system of claim 10, wherein the determining that the handoff is necessary based on any one of:

signal strength, signal-to-noise ratio, distance from the first access point, and available bandwidth.

12. The system of claim 10, wherein the processor is further configured to determine that the signal-to-noise ratio of the first access point has decreased below a given threshold value.

13. The system of claim 10, wherein the processor is further configured to select particular channels for inclusion in the channel mask based on type of wireless network.

14. The system of claim 10, wherein the process&

is further configured to;

invert the channel mask if the mobile station does not detect the one or more access points using the channel mask; and

detect the one or more access points using the inverted channel mask.

15. The system of claim 10, wherein the processor is further configured to perform a scan of all channels at the mobile station in response to not detecting the channel mask.

16. The system of claim 10, wherein the processor is further configured to update the channel mask to remove the channel that is currently being used to connect to the second access point from the channel mask.

17. The system of claim 10, wherein the processor is further configured to determine the second access point based on any one of:

signal strength, signal-to-noise ratio, distance from the first access point, and available bandwidth.

18. The system of claim 10, wherein the processor is further configured to store information in the mobile station relating to at least one of the first access point and the second access point, wherein the information comprises at least one of SSID, MAC address, IP address, GPS position information, WiFi information, and location information.

19. A non-transitory computer-readable medium containing computer-executable instructions that, when executed by a processor, cause the processor to perform a method for reducing handoff latency for a mobile station in a wireless network, the method comprising:

associating with a first access point;

determining whether a handoff is necessary;

performing a selective scan of channels at the mobile station in response to determining that the handoff is necessary, wherein the selective scan comprises accessing a channel mask that is associated with the mobile station, detecting one or more access points using the channel mask, wherein the mobile station receives one or more responses from the one or more access points, and determining a second access point for association by the mobile station based at least in part on the responses from the one or more access points;

associating with the second access point, wherein information that identifies the second access point is stored in the mobile station; and

removing a channel corresponding to the second access point from the channel mask.

20. The non-transitory computer-readable medium of claim 19, wherein the determining that the handoff is necessary based on any one of:

signal strength, signal-to-noise ratio, distance from the first access point, and available bandwidth.

21. The non-transitory computer-readable medium of claim 19, wherein the determining whether the handoff is necessary further comprises determining that the signal-to-noise ratio of the first access point has decreased below a given threshold value.

22. The non-transitory, computer-readable medium of claim 19, wherein the method further comprises selecting particular channels for inclusion in the channel mask based on type of wireless network.

23. The non-transitory computer-readable medium of claim 19, wherein the method further comprises:

inverting the channel mask if the mobile station does not detect the one or more access points using the channel mask; and

detecting the one or more access points using the inverted channel mask.

24. The non-transitory computer-readable medium of claim 19, wherein the method further comprises performing a scan of all channels at, the mobile station in response to not detecting the channel mask.

25. The non-transitory computer-readable medium of claim 19, wherein the method further comprises updating the channel mask to remove the channel that is currently being used to connect to the second access point from the channel mask.

26. The non-transitory computer-readable medium of claim 19, wherein the method further comprises determining the second access point based on any one of:

signal strength, signal-to-noise ratio, distance from the first access point, and available bandwidth.

27. The non-transitory computer-readable medium of claim 19, wherein the method further comprises storing information in the mobile station relating to at least one of the first access point and the second access point, wherein the information comprises at least one of:

SSID, MAC address, IP address, GPS position information, WiFi information, and location information.