Method and apparatus for supporting user mobility in a communication system

• US 20040090929A1
• Filed: 11/12/2002
• Published: 05/13/2004
• Est. Priority Date: 11/12/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Toor, Kamaldip, Laux, Carlos V., de Siqueira, Marcio G., Valluru, Sudhakar S., Hayashi, Steven
• Granted Patent: US 7,907,564 B2
• Time in Patent Office: Days
• US Class Current: 370/311
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements

Abstract

A method includes identifying a plurality of communication channels at a wireless device and classifying each of the communication channels into one of a plurality of groups. The method also includes scanning the communication channels in the groups. The communication channels in at least one of the groups are scanned at a different frequency than the communication channels in at least one other of the groups. In addition, the method includes updating one or more of the groups based on the scans.

Claims

1. A method, comprising:

identifying a plurality of communication channels at a wireless device;

classifying each of the communication channels into one of a plurality of groups;

scanning the communication channels in the groups, the communication channels in at least one of the groups scanned at a different frequency than the communication channels in at least one other of the groups; and

updating one or more of the groups based on the scans.

2. The method of claim 1, wherein the communication channels in one group are scanned at a different frequency than the communication channels in all other groups.

3. The method of claim 1, wherein:

the plurality of groups comprise first, second, third, and fourth groups; and

scanning the communication channels comprises;

scanning all channels in the first group for each channel scanned in the second group;

scanning all channels in the second group for each channel scanned in the third group; and

scanning all channels in the third group for each channel scanned in the fourth group.

4. The method of claim 1, wherein scanning the communication channels comprises:

determining if a communication session is active at the wireless device;

actively scanning the communication channels when the communication session is active at the wireless device; and

passively scanning the communication channels when the communication session is not active at the wireless device.

5. The method of claim 1, wherein scanning the communication channels comprises:

placing an access point serving the wireless device in a sleep mode;

scanning one of the channels; and

waking the access point from the sleep mode.

6. The method of claim 1, wherein scanning the communication channels comprises:

receiving a plurality of datagrams from an access point during an active communication session; and

scanning one of the channels between receipt of two consecutive datagrams.

7. The method of claim 1, wherein identifying the plurality of communication channels comprises performing a full scan of all possible communication channels at the wireless device.

8. The method of claim 7, wherein the full scan comprises a first full scan;

and

further comprising performing a second full scan after a specified amount of time elapses after the first full scan.

9. The method of claim 1, wherein updating one or more of the groups based on the scans comprises reclassifying one of the channels from a one group to another group based on at least one of the scans.

10. The method of claim 1, wherein classifying each of the communication channels into one of a plurality of groups comprises:

identifying a first Service Set Identifier and a first authentication type associated with one of the communication channels;

identifying a second Service Set Identifier and a second authentication type associated with the wireless device;

classifying the channel in a first group when at least one of the first and second Service Set Identifiers do not match and the first and second authentication types do not match;

identifying a signal strength associated with the channel;

determining if the channel overlaps with another of the plurality of channels;

classifying the channel in a second group when the signal strength exceeds a threshold, the channel does not overlap with another of the channels, the first and second Service Set Identifiers match, the first and second authentication types match;

classifying the channel in a third group when the signal strength does not exceed a threshold, the channel does not overlap with another of the channels, the first and second Service Set Identifiers match, and the first and second authentication types match; and

classifying the channel in a fourth group when the channel overlaps with another of the channels, the first and second Service Set Identifiers match, and the first and second authentication types match.

11. The method of claim 1, further comprising determining whether to initiate a handoff so that the wireless device may communicate over a selected one of the scanned channels.

12. The method of claim 11, wherein:

a channel currently used by the wireless device comprises a first channel;

the selected channel comprises a second channel; and

determining whether to initiate the handoff comprises;

initiating the handoff when a signal strength of the first channel is less than a signal strength of the second channel by a first amount; and

initiating the handoff when a load associated with the first channel is less than a load associated with the second channel by a second amount.

13. The method of claim 1, wherein the wireless device comprises a mobile telephone.

14. Logic embodied on at least one computer readable medium and operable when executed to:

identify a plurality of communication channels;

classify each of the communication channels into one of a plurality of groups;

scan the communication channels in the groups, the communication channels in at least one of the groups scanned at a different frequency than the communication channels in at least one other of the groups; and

update one or more of the groups based on the scans.

15. The logic of claim 14, wherein:

the plurality of groups comprise first, second, third, and fourth groups; and

the logic is operable to scan the communication channels by;

scanning all channels in the first group for each channel scanned in the second group;

scanning all channels in the second group for each channel scanned in the third group; and

scanning all channels in the third group for each channel scanned in the fourth group.

16. The logic of claim 14, wherein the logic is operable to scan the communication channels by:

determining if a communication session is active at a wireless device;

actively scanning the communication channels when the communication session is active at the wireless device; and

passively scanning the communication channels when the communication session is not active at the wireless device.

17. The logic of claim 14, wherein the logic is operable to scan the communication channels by:

placing an access point serving the wireless device in a sleep mode;

scanning one of the channels; and

waking the access point from the sleep mode.

18. The logic of claim 14, wherein the logic is operable to scan the communication channels by:

receiving a plurality of datagrams from an access point during an active communication session; and

scanning one of the channels between receipt of two consecutive datagrams.

19. The logic of claim 14, wherein:

the logic is operable to identify the plurality of communication channels during a first full scan of all possible communication channels; and

the logic is further operable to perform a second full scan after a specified amount of time elapses after the first full scan.

20. The logic of claim 14, wherein the logic is further operable to determine whether to initiate a handoff so that the wireless device may communicate over a selected one of the scanned channels.

21. The logic of claim 20, wherein:

a channel currently used by the wireless device comprises a first channel;

the selected channel comprises a second channel; and

the logic is operable to determine whether to initiate the handoff by;

initiating the handoff when a signal strength of the first channel is less than a signal strength of the second channel by a first amount; and

initiating the handoff when a load associated with the first channel is less than a load associated with the second channel by a second amount.

22. The logic of claim 14, wherein the logic is operable to classify each of the communication channels into one of a plurality of groups by:

identifying a first Service Set Identifier and a first authentication type associated with one of the communication channels;

identifying a second Service Set Identifier and a second authentication type associated with the wireless device;

classifying the channel in a first group when at least one of the first and second Service Set Identifiers do not match and the first and second authentication types do not match;

identifying a signal strength associated with the channel;

determining if the channel overlaps with another of the plurality of channels;

classifying the channel in a second group when the signal strength exceeds a threshold, the channel does not overlap with another of the channels, the first and second Service Set Identifiers match, the first and second authentication types match;

classifying the channel in a third group when the signal strength does not exceed a threshold, the channel does not overlap with another of the channels, the first and second Service Set Identifiers match, and the first and second authentication types match; and

classifying the channel in a fourth group when the channel overlaps with another of the channels, the first and second Service Set Identifiers match, and the first and second authentication types match.

23. An apparatus, comprising:

a processor operable to;

identify a plurality of communication channels;

classify each of the communication channels into one of a plurality of groups;

scan the communication channels in the groups, the communication channels in at least one of the groups scanned at a different frequency than the communication channels in at least one other of the groups; and

update one or more of the groups based on the scans; and

a memory operable to store the plurality of groups.

24. The apparatus of claim 23, wherein:

the plurality of groups comprise first, second, third, and fourth groups; and

the processor is operable to scan the communication channels by;

scanning all channels in the first group for each channel scanned in the second group;

scanning all channels in the second group for each channel scanned in the third group; and

scanning all channels in the third group for each channel scanned in the fourth group.

25. The apparatus of claim 23, wherein the processor is operable to scan the communication channels by:

determining if a communication session is active at a wireless device;

actively scanning the communication channels when the communication session is active at the wireless device; and

passively scanning the communication channels when the communication session is not active at the wireless device.

26. The apparatus of claim 23, wherein the processor is operable to scan the communication channels by:

placing an access point serving the wireless device in a sleep mode;

scanning one of the channels; and

waking the access point from the sleep mode.

27. The apparatus of claim 23, wherein the processor is operable to scan the communication channels by:

receiving a plurality of datagrams from an access point during an active communication session; and

scanning one of the channels between receipt of two consecutive datagrams.

28. The apparatus of claim 23, wherein:

the processor is operable to identify the plurality of communication channels during a first full scan of all possible communication channels; and

the processor is further operable to perform a second full scan after a specified amount of time elapses after the first full scan.

29. The apparatus of claim 23, wherein the processor is further operable to determine whether to initiate a handoff so that the wireless device may communicate over a selected one of the scanned channels.

30. The apparatus of claim 29, wherein:

a channel currently used by the wireless device comprises a first channel;

the selected channel comprises a second channel; and

the processor is operable to determine whether to initiate the handoff by;

initiating the handoff when a signal strength of the first channel is less than a signal strength of the second channel by a first amount; and

initiating the handoff when a load associated with the first channel is less than a load associated with the second channel by a second amount.

31. The apparatus of claim 23, wherein the processor is operable to classify each of the communication channels into one of a plurality of groups by:

identifying a first Service Set Identifier and a first authentication type associated with one of the communication channels;

identifying a second Service Set Identifier and a second authentication type associated with the wireless device;

classifying the channel in a first group when at least one of the first and second Service Set Identifiers do not match and the first and second authentication types do not match;

identifying a signal strength associated with the channel;

determining if the channel overlaps with another of the plurality of channels;

classifying the channel in a second group when the signal strength exceeds a threshold, the channel does not overlap with another of the channels, the first and second Service Set Identifiers match, the first and second authentication types match;

classifying the channel in a third group when the signal strength does not exceed a threshold, the channel does not overlap with another of the channels, the first and second Service Set Identifiers match, and the first and second authentication types match; and

classifying the channel in a fourth group when the channel overlaps with another of the channels, the first and second Service Set Identifiers match, and the first and second authentication types match.

32. The apparatus of claim 23, wherein the processor and memory form a portion of a mobile telephone.

33. A system, comprising:

means for identifying a plurality of communication channels at a wireless device;

means for classifying each of the communication channels into one of a plurality of groups;

means for scanning the communication channels in the groups, the communication channels in at least one of the groups scanned at a different frequency than the communication channels in at least one other of the groups; and

means for updating one or more of the groups based on the scans.