Method and system for changing forward traffic channel power allocation during soft handoff

• US 6,307,849 B1
• Filed: 09/08/1997
• Issued: 10/23/2001
• Est. Priority Date: 09/08/1997
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiedemann, Edward G. Jr.
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Nguyen, Steven
• Application Number:
  US08/925,518
• Time in Patent Office: 1,506 Days
• Field of Search: 370/335, 370/331, 370/332, 370/333, 370/342, 375/200, 455/522, 455/69, 455/436, 455/437, 455/438, 455/439, 455/442, 455/67.4, 455/130, 455/140
• US Class Current: 370/335
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• 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 52/40 during macro-diversity or soft handoff
• CPC Class Codes: H04W 72/0473 the resource being transmission power

Abstract

A system and method for adjusting forward traffic channel power allocation in a communications system, wherein signal qualities of pilot channels respectively transmitted by multiple base stations in an active set of a mobile station, are measured by the mobile station, compared to a signal quality standard, and the comparison results reported to a system controller, thereby to indicate which of the pilots at the mobile station surpass the standard. The system controller then adjusts the forward channel power allocation based on the comparison results.

Claims

1. A method for adjusting forward traffic channel power allocation in a communications system, comprising the steps of:

measuring at a mobile station respective signal qualities of pilots respectively transmitted by a plurality of base stations in an Active set of said mobile station;

comparing said respective signal qualities of said pilots to a standard, said standard determined in response to said signal quality of at least one of said pilots in said active set and a delta value of signal quality, wherein said delta value is a representative of a fixed signal level below a strongest pilot signal level of said pilots;

reporting a message to a system controller indicating which of said pilots at said mobile station equal or surpass said standard; and

adjusting said forward traffic channel power allocation based on said message.

2. The method of claim 1, wherein said comparing step comprises:

generating a threshold signal as said standard based on at least one of said pilots having a largest measured signal quality over a predetermined time interval; and

comparing each of said respective signal qualities of said pilots to said threshold signal.

3. The method of claim 2, wherein said reporting step comprises the steps of:

generating a bit vector listing in a predetermined order values representative of respective signal qualities of said pilots; and

including in said bit vector list an index identifying which of said pilots has the largest measured signal quality.

4. The method of claim 3, wherein said reporting step, comprises reporting said bit vector to the system controller at least once every frame of a CDMA IS-95 protocol.

5. The method of claim 3, wherein said reporting step comprises reporting said bit vector to said system controller on at least one of multiples of a frame and fractions of said frame of a CDMA IS-95 protocol.

6. The method of claim 3, wherein said communications system comprises an CDMA IS-95 communications system and said communicating step comprises communicating said bit vector either periodically or a periodically.

7. The method of claim 2, wherein:

said measuring step comprises measuring respective signal to interference ratios for said pilots; and

said generating step comprises generating a threshold signal based on at least one of a largest of said respective signal to interference ratios for said pilots.

8. The method of claim 7, wherein said generating step comprises subtracting from a largest of said respective signal to interference ratios a predetermined level to produce a threshold signal.

9. The method of claim 8, wherein said largest of said respective signal to interference ratios having a minimum, and said comparing step comprises comparing each of said respective signal qualities of said pilots to said minimum of said largest of said signal to interference ratios of said pilots.

10. The method of claim 3, wherein said listing step further comprises the steps of:

receiving a handoff direction message which identifies said base stations in said active set of said mobile station in a predetermined order;

arranging respective data fields of said bit vector to correspond with said order; and

placing respective values in said respective data fields indicative of whether respective ones of said pilots surpass said threshold signal.

11. The method of claim 10, wherein:

said receiving step comprises receiving a set of received direct and multipath signals corresponding to said pilot signals, said set of received direct and multipath signals comprising a subset of N received direct and multipath signals each exhibiting a signal to interference ratio that is greater than each of a subset of signals that are not in said subset of N received direct and multipath signals; and

said placing step places said respective values indicative of respective ones of said pilots surpassing said threshold signal in said respective data fields only if said respective ones of said pilots correspond to at least one of said subset of N received direct and multipath signals.

12. The method of claim 10, further comprising the step of adding to said message an active set data field in which at least one of a current active set, a past active set, and a future active set are identifiable.

13. The method of claim 1, wherein said measuring step comprises measuring signal qualities of pilots respectively transmitted by at least one sector of a respective one of said plurality of base stations in said active set.

14. The method of claim 1, wherein said adjusting step comprises:

forming a forward traffic channel power allocation control command indicating which of said base stations are to transmit respective code channels to said mobile station and which are not to transmit respective code channels to said mobile station; and

communicating said forward traffic channel power allocation control command to said plurality of base stations in said active set.

15. The method of claim 1, further comprising the steps of:

starting a timing mechanism at said mobile when said message is initially reported from said mobile station; and

observing when a delay time has been reached, said delay time corresponding to a difference in time between when said message is initially reported from said mobile and when said forward traffic channel power has been adjusted.

16. The method of claim 15, further comprising the step of changing a finger allocation of at least one finger of a diversity receiver in said mobile station, said finger allocation corresponding to which of said pilots were reported in said message in said reporting step as equaling or surpassing said standard.

17. The method of claim 14, wherein said forming step forms said forward traffic channel power allocation control command to indicate that not more than N of said base stations are to transmit respective code channels to said mobile station, where N corresponds to a number of fingers in a diversity receiver at said mobile station.

18. The method of claim 1, wherein:

said comparing step comprises determining whether at least one finger of a diversity receiver has been allocated to a code channel signal from a base station; and

said reporting step comprises reporting which of said base stations provide a respective code channel signal that has been allocated to said at least one finger.

19. The method of claim 18, wherein said reporting step comprises the step of generating a bit vector listing in a predetermined order values representative of respective signal qualities of said pilots.

20. The method of claim 19, wherein said reporting step comprises including in said bit vector an index identifying one of said plurality of base stations having at least two fingers assigned thereto.

21. The method of claim 19, wherein said reporting step, comprises reporting said bit vector to the system controller at least once every frame of a CDMA IS-95 protocol.

22. The method of claim 19, wherein said reporting step comprises reporting said bit vector to said system controller on at least one of multiples of said frame and fractions of said frame of a CDMA IS-95 protocol.

23. The method of claim 19, wherein said communications system comprises an CDMA IS-95 communications system and said communicating step comprises communicating said bit vector either periodically or a periodically.

24. The method of claim 18, wherein said generating step further comprises the steps of:

receiving a handoff direction message which identifies said plurality of base stations in said active set in a predetermined order;

arranging respective data fields in said message for each of said plurality of base stations to correspond with said predetermined order; and

placing respective values in said respective data fields indicative of whether said at least one finger of said diversity receiver has been respectively allocated to said plurality of base stations.

25. The method of claim 24, further comprising the step of adding to said message an active set data field in which at least one of a current active set, a past active set, and a future active set are identifiable.

26. The method of claim 1 wherein said pilots are transmitted over a plurality of carrier signals.

27. The method of claim 26 wherein said plurality of carrier signals are transmitted from a corresponding plurality of differently configured antennas.

28. A communications system, comprising:

a plurality of base stations which transmit respective pilots and respective code channels comprising a forward traffic channel;

a system controller communicatively connected to said plurality of base stations;

a mobile station which has said plurality of base stations assigned to an active set thereof, comprising,

a diversity receiver which measures respective signal qualities of said pilots,

a processor which produces a signal quality standard and prepares a message indicating which of said signal qualities of said pilots equal or surpasses said standard, said standard determined in response to said signal quality of at least one of said pilots in said active set and a delta value of signal quality, wherein said delta value is a representative of a fixed signal level below a strongest pilot signal level of said pilots;

a mobile transmitter that transmits said message to said system controller either directly or via said plurality of base stations; and

said system controller adjusting a transmit power level of said forward traffic channel in response to receiving said message.

29. The communication system of claim 28, wherein said processor of said mobile station comprises:

a threshold generating mechanism that generates a threshold signal as said standard based on at least one of said pilots having a largest measured signal quality over a predetermined time interval; and

a comparison mechanism that compares said respective signal qualities of said pilots to said threshold signal.

30. The communications system of claim 29, wherein said processor of said mobile station comprises a message formatting mechanism which generates in said message a bit vector comprising a list of values representative of whether respective signal qualities of said pilots equal or surpass said threshold signal and an index which identifies which of said pilots has a largest measured signal quality.

31. The communications system of claim 29, wherein said mobile transmitter transmits said bit vector at least once every frame of a CDMA IS-95 protocol.

32. The communications system of claim 30, wherein said mobile transmitter transmits said bit vector at least multiples of a frame and fractions of a frame of a CDMA IS-95 protocol.

33. The communications system of claim 28, wherein said diversity receiver comprises:

a pilot receiver which measures said respective signal qualities of said pilots; and

N fingers, each of which receives at least one of said code channels via at least one of a direct path and a multipath path from a base station.

34. The communications system of claim 33, wherein said processor comprises:

an assignment mechanism which assigns said N fingers to a subset of N of said at least one of said code channels that exhibit signal to interference ratios greater all other signals corresponding to said code channels; and

a message formatting mechanism which provides a list and an index in said message, said list comprises values representative of whether respective of said pilots correspond to said subset of N of said at least one of said code channels, and said index identifies which of said pilots has a largest measured signal quality.

35. The communications system of claim 28, wherein said plurality of base stations each comprise a plurality of sectors that transmit said respective pilots and said respective code channels into selected geographically distinct regions.

36. The communications system of claim 28, wherein said system controller comprises:

a control processor that determines which of said signal qualities of said pilots indicated in said message as equaling or surpassing said signal quality standard correspond to which subset of said plurality of base stations; and

a control signal formatting mechanism that forms a control signal which is communicated to said plurality of base stations for controlling the forward traffic channel power allocation by controlling code channel power levels of said subset of said plurality of base stations as determined by said control processor.

37. The communications system of claim 30, wherein said message formatting mechanism comprises:

a receiving mechanism that receives a handoff direction message which identifies in a predetermined order said plurality of base stations in said active set; and

an arranging mechanism that arranges respective data fields for each of said plurality of base stations to correspond with said order and places said values in said respective data fields corresponding to said order, said values indicative of whether said signal qualities of said pilots equal or surpass said threshold signal.

38. An apparatus for changing forward traffic channel power allocation, comprising:

a mobile unit comprising,

means for measuring respective signal qualities of signals transmitted by a plurality of base stations,

means for generating a signal quality standard based on said signal qualities measured by said measuring means and a delta value of signal quality, wherein said signals are pilot signals, wherein said delta value is a representative of a fixed signal level below a strongest pilot signal level of said pilot signals,

means for generating a bit vector listing base stations having measured signal qualities not less than said standard, each of said base stations in an active set of said mobile unit,

a transmitter that transmits said bit vector; and

means for adjusting said forward channel power allocation of said plurality of base stations based on said plurality of based stations identified in said bit vector.

39. The apparatus of claim 38, wherein said processor comprises:

a threshold generating mechanism that generates a threshold signal as said signal quality standard based on at least one of said pilots having a largest measured signal quality over a predetermined time interval; and

a comparison mechanism that compares said respective signal qualities of said pilots to said threshold signal.

40. The apparatus of claim 38, wherein:

said means for measuring comprises a diversity receiver having n fingers;

said processor comprises a determining mechanism that determines whether at least one finger of the diversity receiver has been allocated to a code channel signal from a base station; and

said means for generating a bit vector lists base stations providing respective code channel signals which have been allocated to said at least one finger.

41. The apparatus of claim 38 wherein said signals are comprised of a plurality of different carrier signals.

42. The apparatus of claim 41 wherein said plurality of different carrier signals are transmitted from a corresponding plurality of differently configured antennas.