Handoff selection for wireless communication systems

• US 20070287462A1
• Filed: 06/12/2007
• Published: 12/13/2007
• Est. Priority Date: 06/13/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gorokhov, Alexei, Khandekar, Aamod, Prakash, Rajat, Kadous, Tamer, Borran, Mohammad
• Granted Patent: US 8,676,209 B2
• Time in Patent Office: Days
• US Class Current: 455/439
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/26136 Pilot sequence conveying additional information
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 36/36 by user or terminal equipment

Abstract

Techniques for selecting serving sectors and performing handoff for a terminal on the forward and reverse links are described. The terminal may obtain pilot measurements for pilots transmitted on the forward link and may update an active set based on the pilot measurements. The terminal may send a transmission (e.g., for pilot, signaling, etc.) on the reverse link and may receive channel quality information indicative of reverse link channel quality for the terminal at multiple sectors in the active set. The transmission may include pilot, and the channel quality information from each sector may include a pilot carrier-over-thermal ratio (pCoT) determined by that sector based on the pilot. The terminal may select a serving sector based on the channel quality information, interference information, and/or other information and may send a request for handoff (e.g., via a signaling message an/or an access probe) to the selected serving sector.

Claims

1. An apparatus for wireless communication, comprising:

at least one processor configured to receive channel quality information indicative of reverse link channel quality for a terminal at multiple sectors, and to select a serving sector from among the multiple sectors based on the channel quality information; and

a memory coupled to the at least one processor.

2. The apparatus of claim 1, wherein the at least one processor is configured to determine a channel quality value for each of the multiple sectors based on the channel quality information, the channel quality value for each sector being indicative of reverse link channel quality for the terminal at the sector, and to select the serving sector based on channel quality values for the multiple sectors.

3. The apparatus of claim 2, wherein the at least one processor is configured to receive a report with channel quality information from a sector among the multiple sectors, to determine whether the report is decoded correctly or erased, to retain the channel quality value for the sector if the report is erased, and to update the channel quality value for the sector based on a value determined from the report if decoded correctly.

4. The apparatus of claim 3, wherein the at least one processor is configured to set the channel quality value for the sector to a default value if a correctly decoded report is not obtained for the sector within a predetermined number of update intervals.

5. The apparatus of claim 4, wherein the at least one processor is configured to determine the default value based on a configurable parameter.

6. The apparatus of claim 4, wherein the at least one processor is configured to determine the default value based on a channel quality value for a reverse link serving sector and a channel difference between the sector and the reverse link serving sector.

7. The apparatus of claim 1, wherein the at least one processor is configured to obtain pilot measurements for pilots received from the multiple sectors, and to select the serving sector for forward link based on the pilot measurements and the channel quality information.

8. The apparatus of claim 1, wherein the at least one processor is configured to determine reverse link channel quality for the terminal at each of the multiple sectors based on the channel quality information, and to select the serving sector for reverse link based on the reverse link channel quality for the terminal at each of the multiple sectors.

9. The apparatus of claim 1, wherein the at least one processor is configured to determine reverse link channel quality for the terminal at each of the multiple sectors based on the channel quality information, and to select the serving sector having reverse link channel quality that is within a predetermined amount of best reverse link channel quality among the multiple sectors.

10. The apparatus of claim 1, wherein the at least one processor is configured to determine reverse link channel quality for the terminal at each of the multiple sectors based on the channel quality information, and to select a new serving sector if a current serving sector has reverse link channel quality that is more than a predetermined amount worse than best reverse link channel quality among the multiple sectors.

11. The apparatus of claim 1, wherein the at least one processor is configured to obtain interference information indicative of interference at the multiple sectors, and to select the serving sector based on the channel quality information and the interference information.

12. The apparatus of claim 11, wherein the interference information comprises at least one of a rise over thermal ratio (RoT) and an interference over thermal ratio (IoT).

13. The apparatus of claim 1, wherein the at least one processor is configured to obtain pilot measurements for pilots transmitted on forward link and to update an active set for the terminal based on the pilot measurements, the active set including the multiple sectors.

14. The apparatus of claim 1, wherein the at least one processor is configured to send pilot on the reverse link and to receive from each of the multiple sectors channel quality information comprising a pilot carrier-over-thermal ratio (pCoT) determined by the sector based on the pilot sent on the reverse link.

15. The apparatus of claim 1, wherein the at least one processor is configured to send signaling messages on the reverse link to a sector among the multiple sectors, and to receive channel quality information comprising erasure indicators determined by the sector based on the signaling messages sent to the sector.

16. The apparatus of claim 1, wherein the at least one processor is configured to send pilot on the reverse link and to receive channel quality information comprising power control (PC) commands determined by a sector based on the pilot sent on the reverse link.

17. The apparatus of claim 1, wherein the at least one processor is configured to send a request for handoff to the selected serving sector if not a current serving sector.

18. The apparatus of claim 17, wherein the at least one processor is configured to send the request for handoff via an access probe on an access channel to the selected serving sector.

19. A method comprising:

receiving channel quality information indicative of reverse link channel quality for a terminal at multiple sectors; and

selecting a serving sector from among the multiple sectors based on the channel quality information.

20. The method of claim 19, further comprising:

sending pilot on the reverse link, and wherein the receiving channel quality information comprises receiving from each of the multiple sectors channel quality information comprising a pilot carrier-over-thermal ratio (pCoT) determined by the sector based on the pilot sent on the reverse link.

21. The method of claim 19, wherein the selecting the serving sector comprises

obtaining pilot measurements for pilots received from the multiple sectors, and

selecting the serving sector for forward link based on the pilot measurements and the channel quality information.

22. The method of claim 19, wherein the selecting the serving sector comprises

determining reverse link channel quality for the terminal at each of the multiple sectors based on the channel quality information, and

selecting the serving sector for reverse link based on the reverse link channel quality for the terminal at each of the multiple sectors.

23. The method of claim 19, wherein the selecting the serving sector comprises

determining reverse link channel quality for the terminal at each of the multiple sectors based on the channel quality information, and

selecting a new serving sector if a current serving sector has reverse link channel quality that is more than a predetermined amount worse than best reverse link channel quality among the multiple sectors.

24. An apparatus comprising:

means for receiving channel quality information indicative of reverse link channel quality for a terminal at multiple sectors; and

means for selecting a serving sector from among the multiple sectors based on the channel quality information.

25. The apparatus of claim 24, further comprising:

means for sending pilot on the reverse link, and wherein the means for receiving channel quality information comprises means for receiving from each of the multiple sectors channel quality information comprising a pilot carrier-over-thermal ratio (pCoT) determined by the sector based on the pilot sent on the reverse link.

26. The apparatus of claim 24, wherein the means for selecting the serving sector comprises

means for obtaining pilot measurements for pilots received from the multiple sectors, and

means for selecting the serving sector for forward link based on the pilot measurements and the channel quality information.

27. The apparatus of claim 24, wherein the means for selecting the serving sector comprises

means for determining reverse link channel quality for the terminal at each of the multiple sectors based on the channel quality information, and

means for selecting the serving sector for reverse link based on the reverse link channel quality for the terminal at each of the multiple sectors.

28. The apparatus of claim 24, wherein the means for selecting the serving sector comprises

means for determining reverse link channel quality for the terminal at each of the multiple sectors based on the channel quality information, and

means for selecting a new serving sector if a current serving sector has reverse link channel quality that is more than a predetermined amount worse than best reverse link channel quality among the multiple sectors.

29. A processor-readable medium including instructions stored thereon, comprising:

a first instruction set for receiving channel quality information indicative of reverse link channel quality for a terminal at multiple sectors; and

a second instruction set for selecting a serving sector from among the multiple sectors based on the channel quality information.

30. The processor-readable medium of claim 29, wherein the second instruction set comprises

a third instruction set for obtaining pilot measurements for pilots received from the multiple sectors, and

a fourth instruction set for selecting the serving sector for forward link based on the pilot measurements and the channel quality information.

31. The processor-readable medium of claim 29, wherein the second instruction set comprises

a third instruction set for determining reverse link channel quality for the terminal at each of the multiple sectors based on the channel quality information, and

a fourth instruction set for selecting the serving sector for reverse link based on the reverse link channel quality for the terminal at each of the multiple sectors.

32. An apparatus for wireless communication, comprising:

at least one processor configured to send a request for handoff using a first mechanism, and to send the request for handoff using a second mechanism if the first mechanism is unsuccessful; and

a memory coupled to the at least one processor.

33. The apparatus of claim 32, wherein for the first mechanism the at least one processor is configured to send the request for handoff to a desired serving sector by setting a designated bit in a message sent to the desired serving sector.

34. The apparatus of claim 32, wherein for the first mechanism the at least one processor is configured to send the request for handoff to a desired serving sector by sending a resource request to the desired serving sector instead of a current serving sector.

35. The apparatus of claim 32, wherein for the second mechanism the at least one processor is configured to send the request for handoff to a desired serving sector by sending an access probe for handoff to the desired serving sector.

36. The apparatus of claim 35, wherein the access probe for handoff identifies the desired serving sector as only a desired forward link serving sector, or only a desired reverse link serving sector, or both the desired forward link serving sector and the desired reverse link serving sector.

37. A method comprising:

sending a request for handoff using a first mechanism; and

sending the request for handoff using a second mechanism if the first mechanism is unsuccessful.

38. The method of claim 37, wherein the sending the request for handoff using the first mechanism comprises

sending the request for handoff to a desired serving sector by setting a designated bit in a message sent to the desired serving sector.

39. The method of claim 37, wherein the sending the request for handoff using the first mechanism comprises

sending the request for handoff to a desired serving sector by sending a resource request to the desired serving sector instead of a current serving sector.

40. The method of claim 37, wherein the sending the request for handoff using the second mechanism comprises

sending the request for handoff to a desired serving sector by sending an access probe for handoff to the desired serving sector.

41. An apparatus comprising:

means for sending a request for handoff using a first mechanism; and

means for sending the request for handoff using a second mechanism if the first mechanism is unsuccessful.

42. The apparatus of claim 41, wherein the means for sending the request for handoff using the second mechanism comprises

means for sending the request for handoff to a desired serving sector by sending an access probe for handoff to the desired serving sector.

43. An apparatus for wireless communication, comprising:

at least one processor configured to receive a transmission from a terminal at a first sector, to determine reverse link channel quality for the terminal at the first sector based on the received transmission, to send channel quality information indicative of the reverse link channel quality for the terminal at the first sector, and to receive a request for handoff of the terminal from a second sector to the first sector, the first sector being selected as a new serving sector for the terminal based on the channel quality information; and

a memory coupled to the at least one processor.

44. The apparatus of claim 43, wherein the at least one processor is configured to receive pilot from the terminal, to determine a pilot carrier-over-thermal ratio (pCoT) based on the received pilot, and to send the channel quality information comprising the pCoT.

45. The apparatus of claim 43, wherein the at least one processor is configured to estimate interference at the first sector, and to send interference information indicative of the estimated interference at the first sector, and wherein the first sector is selected further based on the interference information.

46. A method comprising:

receiving a transmission from a terminal at a first sector;

determining reverse link channel quality for the terminal at the first sector based on the received transmission;

sending channel quality information indicative of the reverse link channel quality for the terminal at the first sector; and

receiving a request for handoff of the terminal from a second sector to the first sector, the first sector being selected as a new serving sector for the terminal based on the channel quality information.

47. The method of claim 46, wherein the transmission comprises pilot and the channel quality information comprises a pilot carrier-over-thermal ratio (pCoT) determined based on the received pilot.

48. The method of claim 46, further comprising:

estimating interference at the first sector, and

sending interference information indicative of the estimated interference at the first sector, and wherein the first sector is selected further based on the interference information.

49. An apparatus comprising:

means for receiving a transmission from a terminal at a first sector;

means for determining reverse link channel quality for the terminal at the first sector based on the received transmission;

means for sending channel quality information indicative of the reverse link channel quality for the terminal at the first sector; and

means for receiving a request for handoff of the terminal from a second sector to the first sector, the first sector being selected as a new serving sector for the terminal based on the channel quality information.

50. The apparatus of claim 49, wherein the transmission comprises pilot and the channel quality information comprises a pilot carrier-over-thermal ratio (pCoT) determined based on the received pilot.

51. The apparatus of claim 49, further comprising:

means for estimating interference at the first sector, and

means for sending interference information indicative of the estimated interference at the first sector, and wherein the first sector is selected further based on the interference information.