Handoff selection for wireless communication systems

• US 8,676,209 B2
• Filed: 06/12/2007
• Issued: 03/18/2014
• Est. Priority Date: 06/13/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gorokhov, Alexei, Khandekar, Aamod, Kadous, Tamer, Borran, Mohammad J., Prakash, Rajat
• Primary Examiner(s): Georgewill, Opiribo
• Application Number:
  US11/761,790
• Publication Number:
  US 20070287462A1
• Time in Patent Office: 2,471 Days
• Field of Search: 370/331, 370/430, 370/208, 370/332, 455/439, 455/436, 455/437
• 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 36/302 due to low signal strength
• CPC Class Codes: H04W 36/36 by user or terminal equipment
• CPC Class Codes: H04W 36/362 Conditional handover

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 a reverse link channel quality for a terminal at multiple sectors, wherein the channel quality information includes a pilot carrier-over-thermal ratio determined selectively based upon a transmitted pilot and a predetermined value,

determine a channel quality value for each of the multiple sectors to indicate the reverse link channel quality for the terminal based on the channel quality information,

select a serving sector from among the multiple sectors based on channel quality values for the multiple sectors,

determine a default value of the channel quality value for a sector among the multiple sectors based on a configurable parameter, and

set the channel quality value for the sector to the default if a correctly decoded report including the channel quality information is not obtained from the sector within a predetermined number of update intervals; 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 receive the report with the channel quality information from the 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 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 a forward link based on the pilot measurements and the channel quality information.

5. The apparatus of claim 1, wherein the at least one processor is configured to determine the 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 a reverse link based on the reverse link channel quality for the terminal at each of the multiple sectors.

6. The apparatus of claim 1, wherein the at least one processor is configured to determine the 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 a reverse link channel quality that is within a predetermined amount of a best reverse link channel quality among the multiple sectors.

7. The apparatus of claim 1, wherein the at least one processor is configured to determine the 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 a reverse link channel quality that is more than a predetermined amount worse than a best reverse link channel quality among the multiple sectors.

8. 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.

9. The apparatus of claim 8, wherein the interference information comprises at least one of a rise over thermal ratio (RoT) and an interference over thermal ratio (IoT).

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

11. 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 the channel quality information comprising the pilot carrier-over-thermal ratio (pCoT) determined by the sector based on the pilot sent on the reverse link.

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

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

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

15. The apparatus of claim 14, 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.

3. An apparatus for wireless communication, comprising:

at least one processor configured to;

receive channel quality information indicative of a reverse link channel quality for a terminal at multiple sectors, wherein the channel quality information includes a pilot carrier-over-thermal ratio determined selectively based upon a transmitted pilot and a predetermined value,

determine a channel quality value for each of the multiple sectors to indicate the reverse link channel quality for the terminal based on the channel quality information,

select a serving sector from among the multiple sectors based on channel quality values for the multiple sectors,

determined a default value for a sector among the multiple sectors 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, and

set the channel quality value for the sector to the default value if a correctly decoded report including the channel quality information is not obtained from the sector within a predetermined number of update intervals; and

a memory coupled to the at least one processor.

16. A method, comprising:

receiving channel quality information indicative of a reverse link channel quality for a terminal at multiple sectors, wherein the channel quality information includes a pilot carrier-over-thermal ratio determined selectively based upon a transmitted pilot and a predetermined value;

determining a channel quality value for each of the multiple sectors to indicate the reverse link channel quality for the terminal based on the channel quality information;

selecting a serving sector from among the multiple sectors based on channel quality values for the multiple sectors;

determining a default value of the channel quality value for a sector among the multiple sectors based on a configurable parameter; and

setting the channel quality value for the sector to the default value if a correctly decoded report including the channel quality information is not obtained from the sector within a predetermined number of update intervals.

17. The method of claim 16, further comprising:

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

18. The method of claim 16, wherein the selecting the serving sector comprises:

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

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

19. The method of claim 16, wherein the selecting the serving sector comprises:

determining the 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.

20. The method of claim 16, wherein the selecting the serving sector comprises;

determining the 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 a reverse link channel quality that is more than a predetermined amount worse than a best reverse link channel quality among the multiple sectors.

21. An apparatus, comprising:

means for receiving channel quality information indicative of a reverse link channel quality for a terminal at multiple sectors, wherein the channel quality information includes a pilot carrier-over-thermal ratio determined selectively based upon a transmitted pilot and a predetermined value;

means for determining a channel quality value for each of the multiple sectors to indicate the reverse link channel quality for the terminal based on the channel quality information;

means for selecting a serving sector from among the multiple sectors based on channel quality values for the multiple sectors;

means for determining a default value of the channel quality value for a sector among the multiple sectors based on a configurable parameter; and

means for setting the channel quality value for the sector to the default value if a correctly decoded report including the channel quality information is not obtained from the sector within a predetermined number of update intervals.

22. The apparatus of claim 21, further comprising:

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

23. The apparatus of claim 21, 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 a forward link based on the pilot measurements and the channel quality information.

24. The apparatus of claim 21, wherein the means for selecting the serving sector comprises:

means for determining the 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.

25. The apparatus of claim 21, wherein the means for selecting the serving sector comprises:

means for determining the 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 a reverse link channel quality that is more than a predetermined amount worse than a best reverse link channel quality among the multiple sectors.

26. A non-transitory processor-readable medium including instructions stored thereon, comprising:

a first instruction set for receiving channel quality information indicative of a reverse link channel quality for a terminal at multiple sectors, wherein the channel quality information includes a pilot carrier-over-thermal ratio determined selectively based upon a transmitted pilot and a predetermined value;

a second instruction set for determining a channel quality value for each of the multiple sectors to indicate the reverse link channel quality or the terminal based on the channel quality information;

a third instruction set for selecting a serving sector from among the multiple sectors based on channel quality values for the multiple sectors;

a fourth instruction set for determining a default value of the channel quality value for a sector among the multiple sectors based on a configurable parameter; and

a fifth instruction set for setting the channel quality value for the sector to the default value if a correctly decoded report including the channel quality information is not obtained from the sector within a predetermined number of update intervals.

27. The non-transitory processor-readable medium of claim 26, wherein selecting the serving sector comprises:

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

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

28. The non-transitory processor-readable medium of claim 26, wherein selecting the serving sector comprises:

determining the 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 a reverse link based on the reverse link channel quality for the terminal at each of the multiple sectors.