Method and apparatus for supporting user mobility in a communication system

• US 7,907,564 B2
• Filed: 11/12/2002
• Issued: 03/15/2011
• 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
• Primary Examiner(s): Gary; Erika A
• Application Number:
  US10/293,776
• Publication Number:
  US 20040090929A1
• Time in Patent Office: 3,045 Days
• Field of Search: None
• US Class Current: 370/329
• 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, at a wireless device:

identifying a plurality of communication channels;

for each of the communication channels, identifying a signal strength associated with the communication channel;

for each of the communication channels, determining whether the communication channel overlaps with one or more other ones of the communication channels;

for each of the communication channels, identifying a first Service Set Identifier and a first authentication type associated with the communication channel;

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

classifying each of the communication channels into one of a plurality of groups, the plurality of groups comprising one or more of a first group of valid channels, a second group of potential channels, a third group of overlap channels, or a fourth group of incompatible channels, wherein, for each of the communication channels;

the communication channel is classified into the fourth group if the first and second Service Set Identifiers do not match each other or the first and second authentication types do not match each other;

the communication channel is classified into the first group if the signal strength associated with the communication channel exceeds a threshold, the communication channel does not overlap with another one of the communication channels, the first and second Service Set Identifiers, match each other, and the first and second authentication types match each other;

the communication channel is classified into the second group if the signal strength associated with the communication channel does not exceed the threshold, the communication channel does not overlap with another one of the communication channels, the first and second Service Set Identifiers match each other, and the first and second authentication types match each other; and

the communication channel is classified into the third group if the communication channel overlaps with another one of the communication channels, the first and second Service Set Identifiers match each other, and the first and second authentication types match each other;

scanning the communication channels in the groups, the scanning of one or more of the groups being performed at a first frequency and the scanning of one or more other ones of the groups being performed at a second frequency that is different from the first frequency; and

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

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 comprises the first, second, third, and fourth groups; and

scanning the communication channels comprises;

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

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

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

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

determining whether the wireless device is engaged in an active communication session;

actively scanning the communication channels when the wireless device is engaged in an active communication session; and

passively scanning the communication channels when the wireless device is not engaged in an active communication session.

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 communication 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 communication 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.

8. The method of claim 7, wherein:

the full scan comprises a first full scan; and

a second full scan is performed a specified amount of time 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 communication channels from one group to another group based on at least one of the scans.

10. 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 communication channels.

11. The method of claim 10, wherein:

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

a selected communication 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.

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

13. Logic encoded in one or more tangible media for execution and when executed operable to, at a wireless device:

identify a plurality of communication channels;

for each of the communication channels, identify a signal strength associated with the communication channel;

for each of the communication channels, determine whether the communication channel overlaps with one or more other ones of the communication channels;

for each of the communication channels, identify a first Service Set Identifier and a first authentication type associated with the communication channel;

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

classify each of the communication channels into one of a plurality of groups, the plurality of groups comprising one or more of a first group of valid channels, a second group of potential channels, a third group of overlap channels, or a fourth group of incompatible channels, wherein, for each of the communication channels;

the communication channel is classified into the fourth group if the first and second Service Set Identifiers do not match each other or the first and second authentication types do not match each other;

the communication channel is classified into the first group if the signal strength associated with the communication channel exceeds a threshold, the communication channel does not overlap with another one of the communication channels, the first and second Service Set Identifiers, match each other, and the first and second authentication types match each other;

the communication channel is classified into the second group if the signal strength associated with the communication channel does not exceed the threshold, the communication channel does not overlap with another one of the communication channels, the first and second Service Set Identifiers match each other, and the first and second authentication types match each other; and

the communication channel is classified into the third group if the communication channel overlaps with another one of the communication channels, the first and second Service Set Identifiers match each other, and the first and second authentication types match each other;

scan the communication channels in the groups, the scanning of one or more of the groups being performed at a first frequency and the scanning of one or more other ones of the groups being performed at a second frequency that is different from the first frequency; and

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

14. The logic of claim 13, wherein:

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

the logic is operable to scan the communication channels by;

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

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

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

15. The logic of claim 13, wherein the logic is operable to scan the communication channels by:

determining whether the wireless device is engaged in an active communication session;

actively scanning the communication channels when the communication session wireless device is engaged in an active communication session; and

passively scanning the communication channels when the wireless device is not engaged in an active communication session.

16. The logic of claim 13, 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 communication channels; and

waking the access point from the sleep mode.

17. The logic of claim 13, 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 communication channels between receipt of two consecutive datagrams.

18. The logic of claim 13, 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 a specified amount of time after the first full scan.

19. The logic of claim 13, 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 communication channels.

20. The logic of claim 19, wherein:

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

a selected communication 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.

21. An apparatus comprising:

a processor operable to, at a wireless device;

identify a plurality of communication channels;

for each of the communication channels, identify a signal strength associated with the communication channel;

for each of the communication channels, determine whether the communication channel overlaps with one or more other ones of the communication channels;

for each of the communication channels, identify a first Service Set Identifier and a first authentication type associated with the communication channel;

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

classify each of the communication channels into one of a plurality of groups, the plurality of groups comprising one or more of a first group of valid channels, a second group of potential channels, a third group of overlap channels, or a fourth group of incompatible channels, wherein, for each of the communication channels;

the communication channel is classified into the fourth group if the first and second Service Set Identifiers do not match each other or the first and second authentication types do not match each other;

the communication channel is classified into the first group if the signal strength associated with the communication channel exceeds a threshold, the communication channel does not overlap with another one of the communication channels, the first and second Service Set Identifiers, match each other, and the first and second authentication types match each other;

the communication channel is classified into the second group if the signal strength associated with the communication channel does not exceed the threshold, the communication channel does not overlap with another one of the communication channels, the first and second Service Set Identifiers match each other, and the first and second authentication types match each other; and

the communication channel is classified into the third group if the communication channel overlaps with another one of the communication channels, the first and second Service Set Identifiers match each other, and the first and second authentication types match each other;

scan the communication channels in the groups, the scanning of one or more of the groups being performed at a first frequency and the scanning of one or more other ones of the groups being performed at a second frequency that is different from the first frequency; and

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

22. The apparatus of claim 21, wherein:

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

the processor is operable to scan the communication channels by;

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

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

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

23. The apparatus of claim 21, wherein the processor is operable to scan the communication channels by:

determining whether the wireless device is engaged in an active communication session;

actively scanning the communication channels when the wireless device is engaged in an active communication session; and

passively scanning the communication channels when the wireless device is not engaged in an active communication session.

24. The apparatus of claim 21, 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 communication channels; and

waking the access point from the sleep mode.

25. The apparatus of claim 21, 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 communication channels between receipt of two consecutive datagrams.

26. The apparatus of claim 21, 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 after the first full scan.

27. The apparatus of claim 21, 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 communication channels.

28. The apparatus of claim 27, wherein:

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

a selected communication 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.

29. The apparatus of claim 21, wherein the processor and memory form a portion of the wireless device, wherein the wireless device comprises a mobile telephone.

30. A wireless device comprising:

means for identifying a plurality of communication channels;

for each of the communication channels, means for identifying a signal strength associated with the communication channel;

for each of the communication channels, means for determining whether the communication channel overlaps with one or more other ones of the communication channels;

for each of the communication channels, means for identifying a first Service Set Identifier and a first authentication type associated with the communication channel;

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

means for classifying each of the communication channels into one of a plurality of groups, the plurality of groups comprising one or more of a first group of valid channels, a second group of potential channels, a third group of overlap channels, or a fourth group of incompatible channels, wherein, for each of the communication channels;

the communication channel is classified into the fourth group if the first and second Service Set Identifiers do not match each other or the first and second authentication types do not match each other;

the communication channel is classified into the first group if the signal strength associated with the communication channel exceeds a threshold, the communication channel does not overlap with another one of the communication channels, the first and second Service Set Identifiers match each other, and the first and second authentication types match each other;

the communication channel is classified into the second group if the signal strength associated with the communication channel does not exceed the threshold, the communication channel does not overlap with another one of the communication channels, the first and second Service Set Identifiers match each other, and the first and second authentication types match each other; and

the communication channel is classified into the third group if the communication channel overlaps with another one of the communication channels, the first and second Service Set Identifiers match each other, and the first and second authentication types match each other;

means for scanning the communication channels in the groups, the scanning of one or more of the groups being performed at a first frequency and the scanning of one or more other ones of the groups being performed at a second frequency that is different from the first frequency; and

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