Method and apparatus for dormant mode support with paging

• US 7,417,971 B2
• Filed: 06/14/2005
• Issued: 08/26/2008
• Est. Priority Date: 10/04/2002
• Status: Expired due to Fees

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Kawahara, Toshiro, Jeong, Moo Ryong, Watanabe, Fujio
• Primary Examiner(s): Harper; Vincent P.
• Assistant Examiner(s): SHEDRICK, CHARLES TERRELL
• Application Number:
  US11/153,032
• Publication Number:
  US 20050232200A1
• Time in Patent Office: 1,169 Days
• Field of Search: 455/436, 455/450
• US Class Current: 370/331
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 60/04 using triggered events
• CPC Class Codes: H04W 68/00 User notification, e.g. alerting and paging, for incoming communication, change of service or the like
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method and communication system for supporting dormant mode are described. In one embodiment, the communication system comprises a wireless station operable in a power savings mode and group of access points. Each group of access points comprises one or more access points with at least one group of access points having at least two access points. Ranges for the one or more access points in each of the groups define a paging area for each group, wherein one access point uses a paging channel for paging the wireless station when the wireless station is in the power savings mode and is in the paging area associated with the one access point. The wireless station performs a handoff procedure when the one access point is not in the same group of access points as the access point associated with the wireless station prior to the wireless station entering the power savings mode and does not perform a handoff procedure when the one access point is in the same group of access points as the access point associated with the wireless station prior to the wireless station entering the power savings mode.

Claims

1. A wireless station, having established a paging channel with a first access point and having associated with the first access point prior to the wireless station entering the power savings mode, comprising:

a location manager to store information of one or more access points that are in a group of access points with the first access point, the group of access points define a paging area, and the information of each of the one or more access points includes a Basic Service Set Identifier (BSSID) and one or more of the following;

target beacon transmission time (TBTT), TBTT offset, beacon interval, and beacon interval ratio;

a paging message processor to receive a beacon having a paging area identifier, wherein the paging message processor is configured to determine that paging area has not changed when the received beacon is from the first access point, wherein the wireless station performs scanning based on the stored information to receive a beacon or a probe response of a second access point when the beacon from the first access point is not received, wherein the paging message processor is configured to determine that the paging area has not changed when the beacon or the probe response from the one or more access points that are in the group of access points with the first access point is received based on the scanning, and to determine the paging area has changed when the beacon or the probe response from the first access point and the one or more access points in the group of access points is not received based on the scanning, where the wireless station uses the one or more of the TBTT, TBTT offset, beacon interval, and beacon interval ratio when determining the new time for the beacon, and where the wireless station uses BSSID when sending a directed probe reciuest to solicit a probe response; and

a paging controller coupled to the paging message processor,

wherein the paging controller is configured to establish a paging channel with the second access point through a handoff procedure when the paging area has changed, wherein the paging controller is configured to establish the paging channel with the handoff procedure by;

synchronizing to the second access point;

authenticating the wireless station with the second access point; and

associating the wireless station and the second access point; and

wherein the paging controller is configured to establish the paging channel with the second access point without performing the handoff procedure when the paging area has not changed, wherein the paging controller is configured to establish the paging channel with the second access point by

synchronizing to the second access point without authenticating the wireless station with the second access point, and without associating the wireless station and the second access point.

2. The wireless station defined in claim 1, wherein the wireless station performs scanning by selecting one of the access points stored in the location manager, and transmitting a directed probe request frame to the selected access point, wherein the BSSID of the selected access point is included in the destination address field or in the BSSID field of the directed probe request frame.

3. The wireless station defined in claim 1, wherein the wireless station performs scanning by selecting one of the access points stored in the location manager, determining the TBTT of the selected access point based on the stored information, and listening for the beacon of the selected access point at the TBTT of the selected access point.

4. The wireless station defined in claim 1 wherein the paging area identifier of the received beacon is received from a virtual channel.

5. The wireless station defined in claim 4, wherein the paging area identifier of the group of access points distinctly identifies the group of access points to which the first access point belongs.

6. The wireless station defined in claim 1, wherein when the second access point is not in the same group of access points, the paging controller is configured to synchronize to the second access point by adopting the timing information of the second access point, wherein the paging controller is configured to authenticate the wireless station with the second access point by establishing the wireless station'"'"'s identity as a member of a set of stations authorized to associate with the second access point, and wherein the paging controller is configured to associate the wireless station and the second access point by establishing a mapping between the second access point and the wireless station, and wherein when the second access point is in the same group of access points, the paging controller is configured to synchronize to the second access point by adopting the timing information of the second access point.

7. An access point comprising:

a paging message generator to generate a paging message for a wireless station, the wireless station having a location manager to store a Basic Service Set Identifier (BSSID) and one or more of the following;

target beacon transmission time (TBTT), TBTT offset, beacon interval, beacon interval ratio, and access point identifiers for all access points in a group of access points that includes the access point, the group of access points define a paging area, wherein the location manager allows the wireless station to perform scanning based on the stored information to receive a beacon or a probe response of a second access point; and

a paging controller to send a signal to the wireless station having the BSSID and the one or more of the following;

TBTT, TBTT offset, beacon interval, beacon interval ratio, and access point identifiers for the group of access points to be stored in the location manager of the wireless station, wherein the wireless station is configured to determine that the paging area has changed when the beacon or the probe response is not received from the one or more access points that are in the group of access points with the access point using the stored information, to perform a handoff procedure to establish a paging channel with a second access point when the second access point is not in the same group of access points, and to not perform the handoff procedure to establish the paging channel with the second access point when the second access point is in the same group of access points,

wherein the paging controller is configured to establish the paging channel with the second access point with the handoff procedure by;

synchronizing to the second access point,

authenticating the wireless station with the second access point, and

associating the wireless station and the second access point, and

wherein the paging controller is configured to establish the paging channel with the second access point without the handoff procedure by

synchronizing to the second access point without authenticating the wireless station with the second access point, and without associating the wireless station and the second access point.

8. The access point defined in claim 7 wherein the paging message generator determines in which beacon the paging message for the wireless station is transmitted.

9. The access point defined in claim 7 wherein the wireless station performs scanning by selecting one of the access points in the location manager and executing either active scanning or passive scanning, wherein a directed probe request with the BSSID of the selected access point being included in the destination address field or in the BSSID field is sent to the selected access point when executing active scanning, and the TBTT of the selected access point is determined based on the stored information when executing passive scanning.

10. The access point defined in claim 7 wherein the paging channel is a virtual channel.

11. The access point defined in claim 7 wherein the paging controller uses the paging channel to notify the wireless station that a message has been received for the wireless station when the wireless station was in the power savings mode.

12. The access point defined in claim 11 further comprising a buffer to buffer the message until the wireless station exits the power savings mode and receives the message.

13. The access point defined in claim 7 wherein the paging controller sends a beacon on the paging channel, the beacon containing a paging identifier distinctly identifying the group of access points to which the one access point belongs.

14. The access point defined in claim 7 wherein when the second access point is not in the same group of access points, the paging controller is configured to synchronize to the second access point by adopting the timing information of the second access point, wherein the paging controller is configured to authenticate the wireless station with the second access point by establishing the wireless station'"'"'s identity as a member of a set of stations authorized to associate with the second access point, and wherein the paging controller is configured to associate the wireless station and the second access point by establishing a mapping between the second access point and the wireless station, and wherein when the second access point is in the same group of access points, the paging controller is configured to synchronize to the second access point by adopting the timing information of the second access point.

15. A method comprising:

establishing a paging channel with a first access point;

associating with the first access point prior to the wireless station entering the power savings mode;

storing at the wireless station information of one or more access points that are in the same group of access points with the first access point, the group of access points define a paging area, and the information of each of the one or more access points includes a Basic Service Set Identifier (BSSID) and one or more of the following;

target beacon transmission time (TBTT), TBTT offset, beacon interval, and beacon interval ratio

receiving a beacon having a paging area identifier;

determining whether the paging area identifier has changed, comprising;

determining that the paging area has not changed when the received beacon is from the first access point;

performing scanning based on the stored information to receive a beacon or a probe response of a second access point based on the stored information when the beacon from the first access point is not received;

determining that the paging area has not changed when the beacon or the probe response from the one or more access points that are in the group of access points with the first access point is received based on the scanning;

determining that the paging area has changed when the beacon is or the probe response from the first access point and the one or more access points in the group of access points is not received based on the scanning, wherein the wireless station uses the one or more of the TBTT, TBTT offset, beacon interval, and beacon interval ratio when determining the new time for the beacon, and where the wireless station uses BSSID when sending a directed probe request to solicit a probe response;

establishing a paging channel with the second access point through a handoff procedure when the paging area has changed; and

establishing the paging channel with the second access point without performing the handoff procedure when the paging area has not changed, wherein establishing the paging channel with the handoff procedure comprises;

synchronizing the wireless station to the second access point;

authenticating the wireless station with the second access point; and

associating the wireless station and the second access point, and

wherein establishing the paging channel without performing the handoff procedure comprises synchronizing the wireless station to the second access point without authenticating the wireless station with the second access point, and without associating the wireless station and the second access point.

16. The method defined in claim 15 further comprising the plurality of access points in the access point group exchanging identifiers and traffic indication maps (TIMs) for the plurality of access points with each of the other access points of the access point group.

17. The method defined in claim 15 further comprising at least one access points sending a signal to the wireless station having the TIMs and access point identifiers for all access points in the access point group.

18. The method defined in claim 15 further comprising receiving the beacon on a virtual channel.

19. The method defined in claim 15 notifying the wireless station that a message has been received for the wireless station when the wireless station was in the power savings mode.

20. The method defined in claim 15 wherein the beacon contains a paging identifier distinctly identifying the access point group to which the first access point belongs.

21. The method defined in claim 15 wherein synchronizing comprises adopting the timing information of the second access point, wherein authenticating comprises the wireless station'"'"'s identity as a member of a set of stations authorized to associate with the second access point, and wherein associating comprises establishing a mapping between the second access point and the wireless station.

22. A communication system comprising:

a wireless station operable in a power savings mode, having a location manager to store information including identifiers, traffic identification maps, and one or more of the following;

target beacon transmission time (TBTT), TBTT offset, beacon interval, and beacon interval ratio; and

a plurality of groups of access points, wherein each group of access points comprises one or more access points with at least one group of access points having at least two access points, wherein ranges for the one or more access points in each of the plurality of groups define a paging area for said each group, and wherein access points in each group of access points exchange identifiers, traffic identification maps, and the one or more of the following;

TBTT, TBTT offset, beacon interval, and beacon interval ratio for the access points with the access points in their group,

wherein at least one access point of the at least one group of access points sends a signal to the wireless station having the TIMs, the access point identifiers, and the one or more of the following;

TBTT, TBTT offset, beacon interval, and beacon interval ratio for all access points in the at least one group of access points to be stored in the location manager of the wireless station to allow the wireless station to perform scanning based on the stored information to receive a beacon or a probe response from a new access point,

wherein a first access point uses a paging channel for paging the wireless station when the wireless station is in the power savings mode and is in the paging area associated with the first access point, the wireless station performing a handoff procedure when the first access point is not in the same group of access points as a second access point having an established paging channel with the wireless station prior to the wireless station entering the power savings mode and not performing a handoff procedure when the first access point is in the same group of access points as the second access point having the established paging channel with the wireless station prior to the wireless station entering the power savings mode, wherein when the first access point is not in the same group of access points as the second access point, the paging controller is configured to establish the paging channel with the first access point by synchronizing to the first access point, authenticating the wireless station with the first access point, and associating the wireless station and the first access point, and wherein when the first access point is in the same group of access point as the second access point, the paging controller configured to establish the paging channel with the first access point by synchronizing to the first access point without authenticating the wireless station with the first access point, and without associating the wireless station and the first access point.

23. The communication system defined in claim 22 wherein the paging channel is a virtual channel.

24. The communication system defined in claim 22 wherein the first access point uses the paging channel to notify the wireless station that a message has been received for the wireless station when the wireless station was in the power savings mode.

25. The communication system defined in claim 24 wherein the first access point buffers the message until the wireless station exits the power savings mode and receives the message.

26. The communication system defined in claim 22 wherein the first access point sends a beacon on the paging channel, the beacon containing a paging identifier distinctly identifying the group of access points to which the first access point belongs.

27. A communication system comprising

a plurality of groups of access points, wherein each group of access points comprises one or more access points with at least one group of access points having at least two access points, each access point in each group uses a paging area identifier to define a paging area of the group, the paging area identifier being unique to the group when broadcasting in the paging area for each group as part of paging by access points in each group, wherein access points in each group of access points exchange identifiers, traffic indication maps (TIMs), and one or more of the following:

target beacon transmission time (TBTT), TBTT offset, beacon interval, and beacon interval ratio for the access points with the access points in their group, wherein at least one access point of the at least one group of access points sends a signal to a wireless station having the TIMs, access point identifiers and the one or more of the following;

TBTT, TBTT offset, beacon interval, and beacon interval ratio for all access points in the at least one group of access points to be stored in a location manager of the wireless station, wherein the wireless station is configured to perform scanning to receive a beacon or a probe response of a new access point for establishing a paging channel with the new access point without performing a complete handoff procedure when the new access point is one of the access points in the same group.

28. The communication system defined in claim 27 wherein access points in a each group use a paging channel to notify that a message has been received for a wireless station when the wireless station was in the power savings mode, wherein the paging channel is a virtual channel.

29. The communication system as claimed in claim 27 wherein the unique paging identifier comprises a unique paging area identification number.

30. The communication system as claimed in claim 27 wherein the unique paging area identification number is included in a beacon packet broadcast by the one or more access points in its corresponding group of access points.

31. The communication system as claimed in claim 27 further comprising a wireless station.

32. The communication system defined in claim 27 further comprising a wireless station operable in a power savings mode, wherein at least one access point uses paging when the wireless station is in the power savings mode and is in the paging area associated with the at least one access point to notify the wireless unit that a message has been received for the wireless station.