Demodulation element assignment in a system capable of receiving multiple signals

• US 5,490,165 A
• Filed: 10/28/1993
• Issued: 02/06/1996
• Est. Priority Date: 10/28/1993
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Padovani, Roberto, Blakeney, Robert D. II, Ziv, Noam A., Weaver, Lindsay A. Jr., Williamson, Paul T.
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US08/144,902
• Time in Patent Office: 831 Days
• Field of Search: 375/1, 375/107, 375/205, 375/208, 375/210, 375/267, 455/3.2, 455/65, 455/276.1, 455/279.1
• US Class Current: 370/335
• CPC Class Codes: H04B 1/7087 Carrier synchronisation aspects
• CPC Class Codes: H04B 1/7117 Selection, re-selection, allocation or re-allocation of paths to fingers, e.g. timing offset control of allocated fingers

Abstract

In a receiver having a plurality of demodulation elements, a method of assigning the plurality of demodulation element so a set of available signals. A first method emphasizes diversity of transmitting devices so that power control is optimal. A second method emphasizes the maximum signal strength available to produce aggregate maximum signal strength. Both methods control the number of reassignments so that excessive data is not lost during the reassignment process. The apparatus comprises the plurality of demodulation elements, at least one searcher element, and a controller.

Claims

1. In a receiver having a plurality of demodulation elements, a method of assigning said plurality of demodulation elements to a set of available signals, comprising the steps of:

measuring said available signals and creating electronic representations of a list of survey paths comprised of an arrival time, a signal strength, and a transmitter index of each of said available signals;

matching a list of demodulation paths comprised of an arrival time, a signal strength, and a transmitter index corresponding to signals being demodulated by said receiver to said list of survey paths; and

assigning an un-assigned demodulation element, if said un-assigned demodulation element exists, to a particular survey path having a corresponding transmitter index that is different than every transmitter index in said list of demodulation paths.

2. The method of claim 1 wherein, in said step of assigning said un-assigned demodulation element, said particular survey path corresponds to the survey path having strongest signal strength of any survey path having said corresponding transmitter index.

3. The method of claim 1 further comprising the steps of:

re-assigning a particular demodulation element to said particular survey path if no un-assigned demodulation element exists comprising the steps;

un-assigning said particular demodulation element; and

assigning said particular demodulation element to said particular survey path.

4. The method of claim 3 wherein said particular demodulation element corresponds to the demodulation path having a signal strength that is weaker than the signal strength of any demodulation element.

5. The method of claim 3 wherein said particular demodulation element corresponds to a demodulation path having a signal strength that is weaker than the signal strength of said particular survey path.

6. The method of claim 3 wherein said particular demodulation element is assigned to a demodulation path having a signal strength that is at least a certain ratio weaker than the signal strength of said particular survey path.

7. The method of claim 3 wherein said particular demodulation element is assigned to a demodulation path having a signal strength that is 3 dB weaker than the signal strength of said particular survey path.

8. The method of claim 3 wherein said particular demodulation element is assigned to a particular demodulation path having a transmitter index which is the same as the transmitter index of at least one other demodulation path.

9. The method of claim 8 wherein said particular demodulation path has the weakest signal strength of any such path in said list of demodulation paths.

10. The method of claim 1 wherein said transmitter index represents a base station.

11. The method of claim 1 wherein said transmitter index represents a sector of a base station.

12. The method of claim 1 wherein each transmitter transmits a spread spectrum signal using pseudo noise modulation and wherein said transmitter index represents the code offset of the transmitted spread spectrum signal.

13. The method of claim 1 wherein said step of matching said list of demodulation paths to said list of survey paths causes each entry in said list of demodulation paths to correspond to an entry in said list of survey paths.

14. The method of claim 1 wherein said step of matching said list of demodulation paths to said list of survey paths comprises the steps of:

matching a first demodulation path having a first signal strength to a first survey path;

matching a second demodulation path having a second signal strength to said first survey path wherein said second signal strength is greater than said first signal strength; and

un-assigning a first demodulation element corresponding to said first demodulation path.

15. The method of claim 1, wherein each demodulation element of said plurality of demodulation elements that is assigned to a demodulation path indicates a state of successful or jeopardized demodulation, further comprising the step of un-assigning a particular demodulation element if said particular demodulation element indicates jeopardized demodulation.

16. The method of claim 1, wherein said receiver has at least one searcher element, and wherein said step of conducting a survey of available signals and creating a list of survey paths comprises the steps of:

receiving from said at least one searcher element a local maximum data point having an arrival time, a signal strength, and a transmitter index;

adding said local maximum data point to said list of survey paths if said signal strength of said local maximum data point exceeds a predetermined level.

17. The method of claim 1, wherein said receiver has at least one searcher element, and wherein said step of conducting a survey of available signals and creating a list of survey paths comprises the steps of:

receiving from said at least one searcher element a set of local maximum data points each having an arrival time, a signal strength, and a common transmitter index; and

adding a limited number of said local maximum data points to said list of survey paths if signal strength each of said added limited number of local maximum data points exceeds a predetermined level.

18. The method of claim 17, wherein said limited number of said local maximum data points is equal to the number of demodulation elements of said plurality of demodulation elements.

19. The method of claim 1, wherein said step of matching said list of demodulation paths to said list of survey paths further comprises the steps of:

finding a demodulation path that does not match any survey path of said list of survey paths; and

adding an entry in said list of survey paths corresponding to said unmatched demodulation path.

20. The method of claim 1, wherein each transmitter index in said list of survey paths is the same as a transmitter index in said list of demodulation paths, further comprising the step of assigning an un-assigned demodulation element, if said un-assigned demodulation element exists, to a second particular survey path.

21. The method of claim 20 wherein, in said step of assigning said un-assigned demodulation element, said second particular survey path does not have the same arrival time and transmitter index of any demodulation path on said list of demodulation paths.

22. The method of claim 21 wherein said second particular survey path has the strongest signal strength of any such path.

23. The method of claim 1 further comprising the steps of:

re-assigning a particular demodulation element comprising the steps of;

un-assigning said particular demodulation element assigned to a particular demodulation path; and

assigning said particular demodulation element to a second particular survey path.

24. The method of claim 23 wherein said particular demodulation path has the same transmitter index as said second particular survey path.

25. The method of claim 24 wherein said particular demodulation path has a signal strength that is weaker than the signal strength of said second particular survey path.

26. The method of claim 24 wherein said particular demodulation path has a signal strength that is at least a certain ratio weaker than the signal strength of said second particular survey path.

27. The method of claim 24 wherein said particular demodulation path has a signal strength that is 3 dB weaker than the signal strength of said second particular survey path.

28. The method of claim 23 wherein said particular demodulation path has the same transmitter index as at least one other entry on said list of demodulation paths.

29. The method of claim 23 wherein said particular demodulation path has the weakest signal strength of any demodulation path having the same transmitter index as said particular demodulation path.

30. The method of claim 1 wherein said step of matching said list of demodulation paths to said list of survey paths further comprises the step of matching said arrival time of each demodulation path in said list of demodulation paths to an arrival time of a corresponding entry on said survey paths.

31. The method of claim 1 wherein said step of matching said list of demodulation paths to said list of survey paths further comprises the step of matching within a predetermine time offset said arrival time of each demodulation path in said list of demodulation paths to an arrival time of a corresponding entry on said survey paths.

32. The method of claim 1 wherein each transmitter transmits a pseudo noise modulated signal using a pseudo noise code comprised of a sequence of code values and wherein said arrival time corresponds to a code value offset of said pseudo noise code.

33. The method of claim 1 wherein each transmitter transmits a pseudo noise modulated signal using a pseudo noise code comprised of a sequence of code values and wherein said arrival time corresponds to a window of time around a code value offset of said pseudo noise code.

34. The method of claim 33 wherein each code value of said sequence of code values has a duration and wherein said window of time is one half of said duration.

35. The method of claim 1 wherein each transmitter transmits a common pseudo noise modulated signal using a common pseudo noise code comprised of a sequence of code values and each transmitter transmits at a different time offset than every other of said transmitters and wherein said transmitter index corresponds to said different time offset.

36. The method of claim 1 wherein said step of conducting a survey of said available signals is systematically repeated over time.

37. In a receiver system comprised of a set of receivers, a method of assigning said receivers to a set of existing signals from at least one source:

creating a list of said existing signals, each existing signal of said list of existing signals having a signal strength indication, a time indication, and a corresponding source indication;

comparing said list of said existing signals to a list of signals currently assigned to said receivers, each signal of said list of signals currently assigned to said receivers having a signal strength indication, a time indication, and a corresponding source indication; and

assigning said receivers to said existing signals such that a maximum number of different corresponding source indications is present on said list of signals currently assigned to said receivers.

38. The method of claim 37 further comprises the step of re-assigning a receiver such that said maximum number of different corresponding source indications is present on said list of signals currently assigned to said receivers comprising the steps of:

un-assigning a particular receiver; and

assigning said particular receiver to one of said existing signals of said list of existing signals.

39. The method of claim 37 wherein the rate of occurrence of said steps of re-assigning is limited over time.

40. The method of claim 37 wherein no more than a predetermined number of said steps of re-assigning occurs for each of said step of creating said list of said existing signals.

41. The method of claim 37 wherein said step of creating said list of said existing signals is systematically repeated over time.

42. The method of claim 37 wherein said step of creating said list of said existing signals is systematically repeated over time.

43. The method of claim 37 further comprising the step of making available a first receiver assigned to a first signal wherein a signal strength indication of said first signal is below a predetermined level.

44. The method of claim 43 wherein said available receiver becomes idle.

45. The method of claim 43 wherein said available receiver continues to receive said first signal.

46. The method of claim 43 wherein said available receiver may be assigned a particular existing signal in said step of assigning said receivers to existing signals.

47. The method of claim 37 further comprising the step of making available a first receiver assigned to a first signal wherein the corresponding signal strength indication of said first signal is below a predetermined level for a predetermined period of time.

48. The method of claim 47 wherein said available receiver is idle.

49. The method of claim 47 wherein said available receiver continues to receive said first signal.

50. The method of claim 47 wherein said available receiver may be assigned a particular existing signal in said step of assigning said receivers to existing signals.

51. The method of claim 37 wherein said signal strength indication of said signals assigned to said receivers is generated from an RSSI output on said receivers.

52. The method of claim 51 wherein said RSSI output on said receivers is measured repetitively.

53. The method of claim 37 further comprising the step of making available a first receiver assigned to a first signal wherein the corresponding signal strength indication of said first signal is below a predetermined level for a predetermined number of said measurements.

54. An apparatus for demodulating a signal comprising:

a set of demodulation elements for demodulating a first set of instances of said signal arriving at said apparatus via a set of survey paths, each instance of said signal having an arrival time, signal strength, and transmitter index;

a searcher for determining a second set of instances of said signal arriving at said apparatus, and a corresponding arrival time, signal strength, and transmitter index for each instance;

a control system for matching said first set of instances of said signal with said second set of instances of said signal, and for assigning an un-assigned demodulation element, if said un-assigned demodulation element exists, to a particular instance of said signal from said second set of instances of said signal, said particular instance having a corresponding transmitter index that is different than every transmitter index from said first set of instances of said of signal.

55. The apparatus of claim 54 wherein said signal strength of said particular instance of said signal is greater than any signal strength of any remaining instances of said signal from said first and second set of instances of said signal.

56. The apparatus of claim 55 wherein said control system:

un-assigns a particular demodulation element if no un-assigned demodulation element exists; and

assigns said particular demodulation element to said particular instance of said signal.

57. The method of claim 56 wherein said particular demodulation element was assigned to an instance of said signal having a signal strength that is weaker than the signal strength of any other instance of said signal from said first set of instances of said signal.

58. The method of claim 57 wherein said particular demodulation element corresponds to an instance of said signal having a signal strength that is weaker than said signal strength of said particular instance of said signal.

59. A method for processing a signal during a code division multiple access forward link transmission comprising the steps of:

(a) measuring a series of energy levels of said signal;

(b) generating a series of electronic representations of said signal based on said series of energy levels;

(c) searching said series of electronic representations for a set of forward link signals;

(d) determining a corresponding arrival time, a corresponding signal strength, and a corresponding transmitter for each forward link signal from said set of forward link signals; and

(e) demodulating a sub-set of forward link signals that contains at least one forward link signal for each transmitter, said at least one forward link signal having a greater signal strength than a remaining set of all other forward link signals also associated with said transmitter.