Dynamic frequency selection with recovery for a basic service set network

• US 7,120,138 B2
• Filed: 03/07/2002
• Issued: 10/10/2006
• Est. Priority Date: 07/02/2001
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Choi, Sunghyun, Soomro, Amjad
• Primary Examiner(s): Ngo, Ricky Q.
• Assistant Examiner(s): Wong, Warner
• Application Number:
  US10/093,300
• Publication Number:
  US 20030002456A1
• Time in Patent Office: 1,678 Days
• Field of Search: 370/328, 370/312, 370341-345, 370/349, 370/431, 370/480, 455/161, 455/63
• US Class Current: 370/343
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Dynamic frequency selection for an IEEE 802.11 basic service set network is enabled by a dynamic frequency selection (DFS) element within beacon and probe response frames defining a DFS owner, a DFS interval specifying the time until channel switch in beacon intervals, a DFS count specifying a time in beacon intervals until the DFS owner initiates selection of the next channel frequency from the supported channel set, and a DFS recovery interval specifying a time after the end of the DFS interval when recovery procedures are initiated if no channel switch information was received during that DFS interval. Channel switch information is presented in beacons following the end of the channel selection process, and within beacons during the DFS recovery interval.

Claims

1. A portion of a wireless communications system comprising:

a station wirelessly transmitting a management frame including a dynamic frequency selection element defining a dynamic frequency selection owner, a dynamic frequency selection interval specifying a maximum period that a channel will be employed by stations within the wireless communications system, a dynamic frequency selection count specifying a time remaining until dynamic selection of a next channel is initiated, and a dynamic frequency selection recovery interval specifying a time after an end of the dynamic frequency selection interval when recovery procedures are initiated if no channel switch information is received during the dynamic frequency selection interval, wherein each station within the wireless communications system receiving the management frame transmits subsequent management frames with the dynamic frequency selection element during the dynamic frequency selection interval, and switches to the next channel at an announced channel switch instant.

2. The portion of a wireless communications system according to claim 1, wherein the dynamic frequency selection owner, upon selecting the next channel during the dynamic frequency selection interval, transmits a channel switch announcement identifying the next channel.

3. The portion of a wireless communications system according to claim 2, wherein the dynamic frequency selection owner, upon detecting a beacon without channel switch information following transmission of the channel switch announcement, retransmits the channel switch announcement.

4. The portion of a wireless communications system according to claim 1, wherein a station transmitting a first beacon after moving to a new operational channel becomes the initial dynamic frequency selection owner for a dynamic frequency selection interval.

5. The portion of a wireless communications system according to claim 4, wherein a station transmitting a beacon with the station'"'"'s address in the dynamic frequency selection element, after the first beacon, becomes the dynamic frequency selection owner for a remainder of the dynamic frequency selection interval.

6. The portion of a wireless communications system according to claim 1, wherein, if no channel switch announcement is received during a dynamic frequency selection interval, a first station transmitting a beacon following an end of the dynamic frequency selection interval assumes dynamic frequency selection ownership, sets the dynamic frequency selection count and a channel switch count equal to the dynamic frequency selection interval value, and includes a channel switch announcement and the dynamic frequency selection element in the beacon.

7. The portion of a wireless communications system according to claim 1, wherein stations other than the dynamic frequency selection owner decrement the dynamic frequency selection count and include the dynamic frequency selection element in any beacon transmitted by such station, and include any received channel switch announcement within any beacon transmitted by such station prior to an end of the dynamic frequency selection interval.

8. A wireless communications system comprising:

a plurality of stations,

at least one station within the plurality of stations wirelessly transmitting a management frame including a dynamic frequency selection element defining a dynamic frequency selection owner, a dynamic frequency selection interval specifying a maximum period that a channel will be employed by stations within the wireless communications system, a dynamic frequency selection count specifying a time remaining until dynamic selection of a next channel is initiated, and a dynamic frequency selection recovery interval specifying a time after an end of the dynamic frequency selection interval when recovery procedures are initiated if no channel switch information is received during the dynamic frequency selection interval, wherein each remaining station within the plurality of stations transmits subsequent management frames with the dynamic frequency selection element during the dynamic frequency selection interval, and switches to the next channel at an announced channel switch instant.

9. The wireless communications system according to claim 8, wherein the dynamic frequency selection owner, upon selecting the next channel during the dynamic frequency selection interval, transmits a channel switch announcement identifying the next channel and the channel switch instant.

10. The wireless communications system according to claim 9, wherein the dynamic frequency selection owner, upon detecting a beacon without channel switch information following transmission of the channel switch announcement, retransmits the channel switch announcement.

11. The wireless communications system according to claim 8, wherein a station transmitting a first beacon after moving to a new operational channel becomes the initial dynamic frequency selection owner for a dynamic frequency selection interval.

12. The wireless communications system according to claim 11, wherein a station transmitting a beacon with the station'"'"'s address in the dynamic frequency selection element, after the first beacon, becomes the dynamic frequency selection owner for a remainder of the dynamic frequency selection interval.

13. A method of wireless communications comprising:

wirelessly transmitting a management frame from at least one station within a plurality of stations forming a wireless communications system, the management frame including a dynamic frequency selection element defining a dynamic frequency selection owner, a dynamic frequency selection interval specifying a maximum period that a channel will be employed by stations within the wireless communications system, a dynamic frequency selection count specifying a time remaining until dynamic selection of a next channel is initiated, and a dynamic frequency selection recovery interval specifying a time after an end of the dynamic frequency selection interval when recovery procedures are initiated if no channel switch information is received during the dynamic frequency selection interval;

transmitting subsequent management frames with the dynamic frequency selection element by other stations within the plurality of stations during the dynamic frequency selection interval; and

switching the plurality of stations to the next channel at an announced channel switch time.

14. The method according to claim 13, further comprising:

transmitting a channel switch announcement identifying the next channel upon selecting the next channel and the channel switch time during the dynamic frequency selection interval.

15. The method according to claim 14, further comprising:

upon detecting a beacon without channel switch information following transmission of the channel switch announcement, retransmitting the channel switch announcement.

16. The method according to claim 13, wherein a station transmitting a first beacon after moving to a new operational channel becomes the initial dynamic frequency selection owner for a dynamic frequency selection interval.

17. The method according to claim 16, wherein a station transmitting a beacon with the station'"'"'s address in the dynamic frequency selection element, after the first beacon, becomes the dynamic frequency selection owner for a remainder of the dynamic frequency selection interval.

18. The method according to claim 13, further comprising:

if no channel switch announcement is received during a dynamic frequency selection interval, assuming, at a first station transmitting a beacon following an end of the dynamic frequency selection interval, dynamic frequency selection ownership, setting the dynamic frequency selection count and a channel switch count equal to the dynamic frequency selection interval value, and including a channel switch announcement and the dynamic frequency selection element in the beacon.

19. The method according to claim 13, wherein stations other than the dynamic frequency selection owner decrement the dynamic frequency selection count and include the dynamic frequency selection element in any beacon transmitted by such station, and include any received channel switch announcement within any beacon transmitted by such station prior to an end of the dynamic frequency selection interval.

20. A portion of a wireless communications system comprising:

a station wirelessly transmitting a management frame including a dynamic frequency selection element defining a dynamic frequency selection owner, a dynamic frequency selection interval specifying a maximum period that a channel will be employed by stations within the wireless communications system, and a dynamic frequency selection count specifying a time remaining until dynamic selection of a next channel is initiated, wherein each station within the wireless communications system receiving the management frame transmits subsequent management frames with the dynamic frequency selection element during the dynamic frequency selection interval, and switches to the next channel at an announced channel switch instant.

21. The portion of a wireless communications system according to claim 20, wherein the dynamic frequency selection owner, upon selecting the next channel during the dynamic frequency selection interval, transmits a channel switch announcement identifying the next channel and the channel switch time.

22. The portion of a wireless communications system according to claim 21, wherein the dynamic frequency selection owner, upon detecting a beacon without channel switch information following transmission of the channel switch announcement, retransmits the channel switch announcement.

23. The portion of a wireless communications system according to claim 20, wherein a station transmitting a first beacon after moving to the next channel becomes the initial dynamic frequency selection owner for a dynamic frequency selection interval.

24. The portion of a wireless communications system according to claim 23, wherein a station transmitting a beacon after the first beacon with the station'"'"'s address in the dynamic frequency selection element becomes the dynamic frequency selection owner for a remainder of the dynamic frequency selection interval.

25. A wireless communications system comprising:

a plurality of stations,

at least one station within the plurality of stations wirelessly transmitting a management frame including a dynamic frequency selection element defining a dynamic frequency selection owner, a dynamic frequency selection interval specifying a maximum period that a channel will be employed by stations within the wireless communications system, and a dynamic frequency selection count specifying a time remaining until dynamic selection of a next channel is initiated, wherein each remaining station within the plurality of stations transmits subsequent management frames with the dynamic frequency selection element during the dynamic frequency selection interval, and switches to the next channel at an announced channel switch time.

26. The wireless communications system according to claim 25, wherein the dynamic frequency selection owner, upon selecting the next channel during the dynamic frequency selection interval, transmits a channel switch announcement identifying the next channel and the channel switch time.

27. The wireless communications system according to claim 25, wherein the dynamic frequency selection owner, upon detecting a beacon without channel switch information following transmission of the channel switch announcement, retransmits the channel switch announcement.

28. The wireless communications system according to claim 25, wherein a station transmitting a first beacon after moving to the next channel becomes the initial dynamic frequency selection owner for a dynamic frequency selection interval during which the next channel is to be employed by stations within the wireless communications system.

29. The wireless communications system according to claim 28, wherein a station transmitting a beacon after the first beacon with the station'"'"'s address in the dynamic frequency selection element becomes the dynamic frequency selection owner for a remainder of the dynamic frequency selection interval.

30. A method of wireless communications comprising:

wirelessly transmitting a management frame from at least one station within a plurality of stations forming a wireless communications system, the management frame including a dynamic frequency selection element defining a dynamic frequency selection owner, a dynamic frequency selection interval specifying a maximum period that a channel will be employed by stations within the wireless communications system, and a dynamic frequency selection count specifying a time remaining until dynamic selection of a next channel is initiated;

transmitting subsequent management frames with the dynamic frequency selection element by other stations within the plurality of stations during the dynamic frequency selection interval; and

switching the plurality of stations to the next channel at an announced channel switch time.

31. The method according to claim 30, further comprising:

transmitting a channel switch announcement identifying the next channel and the channel switch time upon selecting the next channel during the dynamic frequency selection interval.

32. The method according to claim 31, further comprising:

upon detecting a beacon without channel switch information following transmission of the channel switch announcement, retransmitting the channel switch announcement.

33. The method according to claim 30, wherein a station transmitting a first beacon after moving to the next channel becomes the initial dynamic frequency selection owner for a dynamic frequency selection interval.

34. The method according to claim 33, wherein a station which did not receive the first beacon which transmits a beacon after the first beacon with the station'"'"'s own address in the dynamic frequency selection element becomes the dynamic frequency selection owner for a remainder of the dynamic frequency selection interval.