Methods and apparatus for performing handoffs in a multi-carrier wireless communications systems

• US 9,485,695 B2
• Filed: 03/02/2007
• Issued: 11/01/2016
• Est. Priority Date: 12/05/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Lane, Frank A.
• Primary Examiner(s): Huynh, Chuck
• Application Number:
  US11/681,522
• Publication Number:
  US 20070173256A1
• Time in Patent Office: 3,532 Days
• Field of Search: 455/437, 455/436, 455/450, 455/442, 455/438, 455/439, 709/224, 370/338
• US Class Current: 1/1
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection

Abstract

A mobile communications device initiates a handoff from its current base station (BS) sector network attachment point to a new BS sector. The mobile sends a handoff request over its current wireless link to the current BS sector, which forwards the request to the new BS sector. The new BS sector processes the request assigning dedicated resources. Information identifying the allocated resources is conveyed from the new BS sector via the current BS sector to the mobile. The mobile determines the time of the allocated dedicated segments based upon a received beacon signal from the new BS sector with known timing relationships to dedicated segments. The mobile breaks the original wireless link just prior to the time of the first assigned dedicated segment. The mobile communicates information on the assigned dedicated segments to perform registration operations establishing a new wireless link.

Claims

1. A wireless terminal comprising:

means for determining a system handoff condition in response to a broadcast signal received from an adjacent network attachment point in at least a portion of a frequency band of an active communication session with a first network attachment point;

means for transmitting, in the frequency band of the active communication session, an access request signal;

means for receiving an assignment of at least one dedicated uplink segment from the adjacent network attachment point, via the active communication session with the first network attachment point, the assigned at least one dedicated uplink segment corresponding to an access channel of the adjacent network attachment point;

means for determining a relative timing between a timing of the broadcast signal within a time slot of the first network attachment point and a timing of the broadcast signal within a time slot of the adjacent network attachment point, wherein the broadcast signal is a beacon signal periodically transmitted into the frequency band of the active communication session by the adjacent network attachment point at least once during an ultraslot that includes a plurality of beacon slots, wherein the time slot of the adjacent network attachment point is one of a plurality of superslots included in each beacon slot of the plurality of beacon slots;

means for determining a time to terminate the active communication session with the first network attachment point based on the relative timing; and

means for establishing a new communication session with the adjacent network attachment point.

2. The wireless terminal of claim 1, wherein the first network attachment point and the adjacent network attachment point operate asynchronously, and the time to terminate the active communication session with the first network attachment point is determined to be prior to a time of an earliest dedicated uplink segment of the assigned at least one dedicated uplink segment.

3. The wireless terminal of claim 1, further comprising means for terminating, at the time to terminate, the active communication session with the first network attachment point.

4. The wireless terminal of claim 1, further comprising means for identifying from the beacon signal at least one of a cell identifier and a sector identifier.

5. The wireless terminal of claim 4, wherein said means for identifying from the beacon signal comprises means for determining from stored information corresponding to the at least one of the cell identifier and the sector identifier, timing of a communication segment to be used during a registration signaling session with the adjacent network attachment point.

6. The wireless terminal of claim 1, wherein the wireless terminal is a mobile node, and the first and adjacent network attachment points are base stations configured to operate in an Orthogonal Frequency Division Multiplexed (OFDM) wireless communications system.

7. The wireless terminal of claim 1, further comprising:

means for receiving, over the active communication session with the first network attachment point, an assigned identifier.

8. The wireless terminal of claim 7, further comprising means for communicating information on the at least one dedicated uplink segment to perform registration operations.

9. The wireless terminal of claim 8, further comprising means for detecting successful registration operations and establishing a new communication link with the adjacent network attachment point to continue the active communication session.

10. A wireless terminal comprising:

a receiver configured to receive an assignment of at least one dedicated uplink segment from an adjacent network attachment point via an active communication session with a first network attachment point, the assigned at least one dedicated uplink segment corresponding to an access channel of the adjacent network attachment point;

a transmitter configured to transmit, in a frequency band of the active communication session, an access request signal and establish a new communication session with the adjacent network attachment point; and

a processor configured to;

determine a system handoff condition in response to a broadcast signal received from the adjacent network attachment point in at least a portion of the frequency band of the active communication session with the first network attachment point;

determine a relative timing between a timing of the broadcast signal within a time slot of the first network attachment point and a timing of the broadcast signal within a time slot of the adjacent network attachment point wherein the broadcast signal is a beacon signal periodically transmitted into the frequency band of the active communication session by the adjacent network attachment point at least once during an ultraslot that includes a plurality of beacon slots, wherein the time slot of the adjacent network attachment point is one of a plurality of superslots included in each beacon slot of the plurality of beacon slots; and

determine a time to terminate the active communication session with the first network attachment point based on the relative timing.

11. The wireless terminal of claim 10, wherein the first network attachment point and the adjacent network attachment point operate asynchronously, and the time to terminate the active communication session with the first network attachment point is determined to be prior to a time of an earliest dedicated uplink segment of the assigned at least one dedicated uplink segment.

12. The wireless terminal of claim 10, wherein said processor is further configured to terminate, at the time to terminate, the active communication session with the first network attachment point.

13. The wireless terminal of claim 10, wherein said processor is further configured to identify from the beacon signal at least one of a cell identifier and a sector identifier.

14. The wireless terminal of claim 13, wherein said processor is further configured to determine from stored information corresponding to the at least one of the cell identifier and the sector identifier, timing of a communication segment to be used during a registration signaling session with the adjacent network attachment point associated with the beacon signal.

15. The wireless terminal of claim 10, wherein the wireless terminal is a mobile node, and the first network attachment point and the adjacent network attachment point are base stations configured to operate in an Orthogonal Frequency Division Multiplexed (OFDM) wireless communications system.

16. The wireless terminal of claim 10, wherein:

the receiver is further configured to receive, over the active communication session with the first network attachment point, an assigned identifier.

17. The wireless terminal of claim 16, wherein said transmitter is further configured to communicate information on the at least one dedicated uplink segment to perform registration operations.

18. The wireless terminal of claim 17, wherein said processor is further configured to detect successful registration operations and establish a new communication link with the adjacent network attachment point to continue the active communication session.

19. A method operable by a wireless terminal, the method comprising:

determining a system handoff condition in response to a broadcast signal received from an adjacent network attachment point in at least a portion of a frequency band of an active communication session with a first network attachment point;

transmitting, in the frequency band of the active communication session, an access request signal;

receiving an assignment of at least one dedicated uplink segment from the adjacent network attachment point, via the active communication session with the first network attachment point, the assigned at least one dedicated uplink segment corresponding to an access channel of the adjacent network attachment point;

determining a relative timing between a timing of the broadcast signal within a time slot of the first network attachment point and a timing of the broadcast signal within a time slot of the adjacent network attachment point, wherein the broadcast signal is a beacon signal periodically transmitted into the frequency band of the active communication session by the adjacent network attachment point at least once during an ultraslot that includes a plurality of beacon slots, wherein the time slot of the adjacent network attachment point is one of a plurality of superslots included in each beacon slot of the plurality of beacon slots;

determining a time to terminate the active communication session with the first network attachment point based on the relative timing; and

establishing a new communication session with the adjacent network attachment point.

20. The method of claim 19, wherein the first network attachment point and the adjacent network attachment point operate asynchronously, and the time to terminate the active communication session with the first network attachment point is determined to be prior to a time of an earliest dedicated uplink segment of the assigned at least one dedicated uplink segment.

21. The method of claim 19, further comprising terminating, at the time to terminate, the active communication session with the first network attachment point.

22. The method of claim 19, further comprising identifying from the beacon signal at least one of a cell identifier and a sector identifier.

23. The method of claim 22, wherein said identifying from the beacon signal comprises determining from stored information corresponding to the at least one of the cell identifier and the sector identifier, timing of a communication segment to be used during a registration signaling session with the adjacent network attachment point associated with the beacon signal.

24. The method of claim 19, wherein the wireless terminal is a mobile node, and the first network attachment point and the adjacent network attachment point are base stations configured to operate in an Orthogonal Frequency Division Multiplexed (OFDM) wireless communications system.

25. The method of claim 19, further comprising:

receiving, over the active communication session with the first network attachment point, an assigned identifier.

26. The method of claim 25, further comprising communicating information on the at least one dedicated uplink segment to perform registration operations.

27. The method of claim 26, further comprising detecting successful registration operations and establishing a new communication link with the adjacent network attachment point to continue the active communication session.

28. The method of claim 19, wherein each superslot in the plurality of superslots includes a fixed positive number of OFDM symbol times.

29. The method of claim 19, wherein the beacon signal is transmitted by the adjacent network attachment point at a fixed predetermined time within the time slot of each of the plurality of beacon slots.

30. The method of claim 29, wherein the beacon signal is transmitted by the adjacent network attachment point according to a sequence, and wherein a beacon signal of one beacon slot uses a different tone than a beacon signal transmitted in another beacon slot according to the sequence.

31. A non-transitory computer-readable medium, wherein the non-transitory computer-readable medium includes executable instructions for causing a processor of a wireless terminal to:

determine a system handoff condition in response to a broadcast signal received from an adjacent network attachment point in at least a portion of a frequency band of an active communication session with a first network attachment point;

transmit, in the frequency band of the active communication session, an access request signal;

receive an assignment of at least one dedicated uplink segment from the adjacent network attachment point via the active communication session with the first network attachment point, the assigned at least one dedicated uplink segment corresponding to an access channel of the adjacent network attachment point;

determine a relative timing between a timing of the broadcast signal within a time slot of the first network attachment point and a timing of the broadcast signal within a time slot of the adjacent network attachment point, wherein the broadcast signal is a beacon signal periodically transmitted into the frequency band of the active communication session by the adjacent network attachment point at least once during an ultraslot that includes a plurality of beacon slots, wherein the time slot of the adjacent network attachment point is one of a plurality of superslots included in each beacon slot of the plurality of beacon slots;

determine a time to terminate the active communication session with the first network attachment point based on the relative timing; and

establish a new communication session with the adjacent network attachment point.

32. The non-transitory computer-readable medium of claim 31, wherein the first network attachment point and the adjacent network attachment point operate asynchronously, and the time to terminate the active communication session with the first network attachment point is determined to be prior to a time of an earliest dedicated uplink segment of the assigned at least one dedicated uplink segment.

33. The non-transitory computer-readable medium of claim 31, further comprising executable instructions for causing the processor of the wireless terminal to terminate, at the time to terminate, the active communication session with the first network attachment point.

34. The non-transitory computer-readable medium of claim 31, further comprising executable instructions for causing the processor of the wireless terminal to identify from the beacon signal at least one of a cell identifier and a sector identifier.

35. The non-transitory computer-readable medium of claim 34, further comprising executable instructions for causing the processor of the wireless terminal to determine from stored information corresponding to the at least one of the cell identifier and the sector identifier, timing of a communication segment to be used during a registration signaling session with the adjacent network attachment point associated with the beacon signal.

36. The non-transitory computer-readable medium of claim 31, wherein the wireless terminal is a mobile node, and the first network attachment point and the adjacent network attachment point are base stations configured to operate in an Orthogonal Frequency Division Multiplexed (OFDM) wireless communications system.

37. The non-transitory computer-readable medium of claim 31, further comprising executable instructions for causing the processor of the wireless terminal to:

receive, over the active communication session with the first network attachment point, an assigned identifier.

38. The non-transitory computer-readable medium of claim 37, further comprising executable instructions for causing the processor of the wireless terminal to communicate information on the at least one dedicated uplink segment to perform registration operations.

39. The non-transitory computer-readable medium of claim 38, further comprising executable instructions for causing the processor of the wireless terminal to detect successful registration operations and establish a new communication link with the adjacent network attachment point to continue the active communication session.