MOBILE STATION ASSISTED TIMING SYNCHRONIZATION IN A CDMA COMMUNICATION SYSTEM

• US 20080285539A1
• Filed: 11/13/2007
• Published: 11/20/2008
• Est. Priority Date: 09/19/1997
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiedemann, Edward G. JR., Wheatley III, Charles E.
• Granted Patent: US 8,184,611 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/70753 Partial phase search
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 56/0045 compensating for timing error by altering transmission time
• CPC Class Codes: H04W 92/20 between access points

Abstract

In the present invention, the slave base station attains synchronization with the reference base station through messages transmitted from and received by a mobile station either in the soft handoff region between the reference base station and the slave base station or within a range which allows the mobile station to communicate with the slave base station. When the mobile station is not in communication with both the reference base station and the slave base station, then the round trip delay between the mobile station and the reference base station is measured by the reference base station. The reference base station communicates the PN code used by the mobile station over the reverse link to the slave base station. The slave base station acquires the signal from the mobile station and determines when the signal from the mobile station arrives. The slave base station then makes an estimate as to the length of the delay between transmission of a signal from the mobile station to the slave base station. Based upon these measurements and estimates, the slave base station determines the error which is present in the slave base station system time.

Claims

1. A method for time synchronizing a second base station with a first base station comprising:

measuring a round trip delay interval of transmissions from the first base station to a mobile station in communication with the first base station and back from the mobile station to the first base station;

receiving at the second base station communications transmitted by the mobile station and noting the time of reception;

determining an estimate of a delay which occurs between transmission by the mobile station and reception by the second base station; and

computing a timing correction value in accordance with said estimate of the delay, said noted time of reception, and said measured round trip delay interval.

2. The method of claim 1 further comprising receiving at the second base station a message indicative of the identity of the mobile station to assist the second base station in said receiving communications from the mobile station.

3. The method of claim 2 further comprising sending the message indicative of the identity of the mobile station from the first base station to the second base station.

4. The method of claim 3 wherein said sending the message from the first base station to the second base station comprises:

sending the message from the first base station to the second base station via a base station controller in communication with the first base station and the second base station.

5. The method of claim 3 wherein said sending the message from the first base station to the second base station comprises:

receiving at the first base station communications from a plurality of mobile stations;

selecting a mobile station most likely to be able to communicate with the second base station; and

sending the message indicative of the identity of the mobile station.

6. The method of claim 5 wherein said selecting a mobile station most likely to be able to communicate with the second base station comprises:

selecting a mobile station furthest from the first base station.

7. The method of claim 5 wherein said selecting a mobile station most likely to be able to communicate with the second base station comprises:

selecting a mobile station closest from the first base station.

8. The method of claim 5 wherein said selecting a mobile station most likely to be able to communicate with the second base station comprises:

selecting a mobile station in accordance with the state of a PN spreader in the mobile station.

9. The method of claim 5 wherein said selecting a mobile station most likely to be able to communicate with the second base station comprises:

selecting a mobile station in accordance with the sector of the first base station being used for communication with the mobile station.

10. The method of claim 5 wherein said selecting a mobile station most likely to be able to communicate with the second base station comprises:

selecting a mobile station in accordance with said measured round trip delay interval.

39. The method of claim 36 wherein synchronizing timing of the base station with at least one base station communicating with the mobile station comprises the method as claimed in claim 1.

11. An apparatus for time synchronizing a second base station with a first base station comprising:

a first base station configured to;

measure a round trip delay interval of transmissions from said first base station to a mobile station in communication with said first base station and back from the mobile station to said first base station; and

a second base station configured to;

receive communications transmitted by the mobile station and noting the time of reception;

determine an estimate of a delay which occurs between transmission by the mobile station and reception by said second base station; and

compute a timing correction value based upon the estimate of the delay, the time of reception, and the measured round trip delay interval.

12. The apparatus of claim 11 wherein said second base station is further configured to receive a message indicative of the identity of the mobile station to assist said second base station to receive communications from the mobile station.

13. The apparatus of claim 12 wherein said first base station is further configured to send the message indicative of the identity of the mobile station to said second base station.

14. The apparatus of claim 13 wherein said first base station is further configured to send the message to said second base station via a base station controller in communication with said first base station and said second base station.

15. The apparatus of claim 13 wherein said first base station is further configured to:

receive communications from a plurality of mobile stations; and

select a mobile station most likely to be able to communicate with said second base station.

16. The apparatus of claim 15 wherein said first base station is configured to select the mobile station most likely to be able to communicate with said second base station as a mobile station furthest from said first base station.

17. The apparatus of claim 15 wherein said first base station is configured to select the mobile station most likely to be able to communicate with said second base station as a mobile station closest from said first base station.

18. The apparatus of claim 15 wherein said first base station is configured to select the mobile station most likely to be able to communicate with said second base station in accordance with the state of a PN spreader in the mobile station.

19. The apparatus of claim 15 wherein said first base station is configured to select the mobile station most likely to be able to communicate with said second base station in accordance with the sector of said first base station being used for communication with the mobile station.

20. The apparatus of claim 15 wherein said first base station is configured to select the mobile station most likely to be able to communicate with said second base station in accordance with said measured round trip delay interval.

21. A method for synchronizing a base station with a wireless communication system upon the base station'"'"'s power up, comprising:

disabling a transmission from the base station;

obtaining initial timing at the base station.

22. The method of claim 21 wherein said obtaining initial timing at the base station comprises:

obtaining initial timing at the base station in accordance with a timing signal provided from a base station controller.

23. The method of claim 21 wherein said obtaining initial timing at the base station comprises:

obtaining initial timing at the base station in accordance with a timing signal provided over a backhaul.

24. The method of claim 21 wherein said obtaining initial timing at the base station comprises:

obtaining initial timing at the base station in accordance with a timing signal provided from a WWW receiver.

25. The method of claim 21 wherein said obtaining initial timing at the base station comprises:

obtaining initial timing at the base station in accordance with an intermittent timing signal.

26. The method of claim 21 further comprising:

receiving at the base station signals transmitted from a mobile station; and

adjusting timing of the base station in accordance with said received signals.

27. The method of claim 26 wherein said receiving at the base station signals transmitted from a mobile station comprises:

providing to the base station information about identity of the mobile station;

estimating at the base station distance to the mobile station; and

receiving at the base station signals transmitted from the mobile station in accordance with said provided information and said estimated distance.

28. The method of claim 27 wherein said estimating at the base station distance to the mobile station comprises:

estimating at the base station time delay to the mobile station.

29. The method of claim 27 wherein said estimating at the base station distance to the mobile station comprises:

assuming that the mobile station is located adjacent to the base station

30. The method of claim 27 wherein said estimating at the base station distance to the mobile station comprises:

estimating at the base station distance to the mobile station in accordance with a round trip delay interval of transmissions from a first base station to the mobile station in communication with the first base station and back from the mobile station to said first base station.

31. The method of claim 27 wherein said estimating at the base station distance to the mobile station comprises:

estimating at the base station distance to the mobile station in accordance with;

a first round trip delay interval of transmissions from a first base station to the mobile station in communication with the first base station and back from the mobile station to the first base station; and

a second round trip delay interval of transmissions from a second base station to the mobile station in communication with the second base station and back from the mobile station to the second base station.

32. The method of claim 26 wherein adjusting timing of the base station in accordance with said received signals comprises:

adjusting timing of the base station in accordance with a time offset between an estimated PN offset of the mobile station and an actual PN offset of the mobile station.

33. The method of claim 26 further comprising:

providing the mobile station with an identity of the base station; and

transmitting signals at successively increasing power levels from the base station in accordance with said adjusted timing until the mobile station detects said transmitted signals.

34. The method of claim 33 wherein said providing the mobile station with an identity of the base station comprises:

providing the mobile station with a pilot PN code offset.

35. The method of claim 33 wherein said providing the mobile station with an identity of the base station comprises:

providing the mobile station with a pilot PN code.

36. The method of claim 33 further comprising:

synchronizing timing of the base station with at least one base station communicating with the mobile station.

37. The method of claim 36 wherein said synchronizing timing of the base station with at least one base station communicating with the mobile station comprises:

initiating a communication between the base station and the mobile station;

measuring a first round trip delay interval of transmissions from the base station to the mobile station in communication with the base station and back from the mobile station to the base station;

measuring a second round trip delay interval of transmissions from the at least one base station communicating with the mobile station and back from the mobile station to the at least one base station communicating with the mobile station;

measuring at the mobile station a time difference between the time of receipt of a transmission from the at least one base station communicating with the mobile station and the time of receipt of a transmission from the base station communicating with the mobile station; and

computing a timing correction value based upon, said measured first round trip delay interval, said measured second round trip delay interval, and said measured time difference.

38. The method of claim 36 further comprising:

repeating said synchronizing timing of the base station with at least one base station communicating with the mobile station for all mobile stations within the coverage area of the base station.

40. A apparatus for synchronizing a base station with a wireless communication system upon the base station'"'"'s power up, comprising:

a transmitter;

a processor communicatively coupled to said transmitter; and

a storage medium coupled to said processor and containing a set of instructions executable by said processor to;

disable said transmitter; and

obtain initial timing.

41. The apparatus of claim 40 wherein said processor obtains initial timing by executing a set of instructions to:

obtain initial timing in accordance with a timing signal provided from a base station controller.

42. The apparatus of claim 40 wherein said processor obtains initial timing by executing a set of instructions to:

obtain initial timing in accordance with a timing signal provided over a backhaul.

43. The apparatus of claim 40 wherein said processor obtains initial timing by executing a set of instructions to:

obtain initial timing in accordance with a timing signal provided from a WWW receiver.

44. The apparatus of claim 40 wherein said processor obtains initial timing by executing a set of instructions to:

obtain initial timing in accordance with an intermittent timing signal.

45. The apparatus of claim 40 further comprising:

a receiver, communicatively coupled to said processor, configured to receive signals transmitted from a mobile station; and

wherein

said processor executes a set of instructions to;

adjust timing of the base station in accordance with the received signals.

46. The apparatus of claim 45 wherein said processor further executes a set of instructions to:

obtain information about identity of the mobile station; and

estimate a distance from the base station to the mobile station; and

wherein the receiver is further configured to;

receive signals transmitted from the mobile station in accordance with the provided information and the estimated distance.

47. The apparatus of claim 46 wherein said processor estimates a distance from the base station to the mobile station by executing a set of instructions to:

estimate a time delay between the base station and the mobile station.

48. The apparatus of claim 46 wherein said processor estimates a distance from the base station to the mobile station by executing a set of instructions in accordance with an assumption that the mobile station is located adjacent to the base station.

49. The apparatus of claim 46 wherein said processor estimates a distance from the base station to the mobile station by executing a set of instructions to:

estimate distance from the base station to the mobile station in accordance with a round trip delay interval of transmissions from a first base station to the mobile station in communication with said first base station and back from the mobile station to said first base station.

50. The apparatus of claim 46 wherein said processor estimates a distance from the base station to the mobile station by executing a set of instructions to:

estimate a first round trip delay interval of transmissions from a first base station to the mobile station in communication with said first base station and back from the mobile station to said first base station; and

estimate a second round trip delay interval of transmissions from a second base station to the mobile station in communication with said second base station and back from the mobile station to the second base station.

51. The apparatus of claim 45 wherein said processor adjusts timing of the base station in accordance with said received transmission by executing a set of instructions to:

adjust timing of the base station in accordance with a time offset between an estimated PN offset of the mobile station and an actual PN offset of the mobile station.

52. The apparatus of claim 45 further comprising:

a mobile station configured to obtain information about identity of the base station; and

said transmitter configured to transmit signals at successively increasing power levels from the base station in accordance with the adjusted timing until the mobile station detects the transmitted signals.

53. The apparatus of claim 52 wherein the mobile station is configured to obtain information about a pilot PN code offset of the base station.

54. The apparatus of claim 52 wherein the mobile station is configured to obtain information about a pilot PN code of the base station.

55. The apparatus of claim 45 said processor further executes a set of instructions to synchronize timing of the base station with at least one base station communicating with said mobile.

56. The apparatus of claim 45 wherein said processor synchronizes timing of the base station with at least one base station communicating with the mobile station by executing a set of instructions to:

initiate a communication between the base station and the mobile station;

measure a first round trip delay interval of transmissions from the base station to the mobile station in communication with the base station and back from the mobile station to the base station;

measure a second round trip delay interval of transmissions from the at least one base station communicating with the mobile station and back from the mobile station to the at least one base station communicating with said mobile; and

compute a timing correction value in accordance with the first round trip delay interval, the second round trip delay interval, and a time difference provided by the mobile station; and

wherein

the mobile station is configured to;

measure the time difference between the time of receipt of a transmission from the at least one base station communicating with the mobile station and the time of receipt of a transmission from the base station.

57. The apparatus of claim 54 wherein said processor repeats said synchronizing timing of the base station with at least one base station communicating with the mobile station for all mobile stations within the coverage area of the base station.