Signal acquisition in a wireless communication system

• US 8,027,372 B2
• Filed: 12/22/2004
• Issued: 09/27/2011
• Est. Priority Date: 06/18/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Agrawal, Avneesh, Khandekar, Aamod
• Primary Examiner(s): Ha; Dac
• Assistant Examiner(s): Guarino; Rahel
• Application Number:
  US11/022,482
• Publication Number:
  US 20060209927A1
• Time in Patent Office: 2,470 Days
• Field of Search: 375/130, 375/134, 375/146, 375/135, 375/141, 375/133, 375/137, 370/500, 370/510, 370/350, 370/345, 370/442, 370/508, 370/512, 370/537, 370/320, 370/321, 370/337, 370/344, 370/347, 370/458, 370/294, 370/324, 370/90, 455/102, 455/103, 455/105
• US Class Current: 375/146
• 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: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/03866 using scrambling
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols
• CPC Class Codes: H04L 5/0026 Division using four or more dimensions
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

Each base station transmits a TDM pilot 1 having multiple instances of a pilot-1 sequence generated with a PN1 sequence and a TDM pilot 2 having at least one instance of a pilot-2 sequence generated with a PN2 sequence. Each base station is assigned a specific PN2 sequence that uniquely identifies that base station. A terminal uses TDM pilot 1 to detect for the presence of a signal and uses TDM pilot 2 to identify base stations and obtain accurate timing. For signal detection, the terminal performs delayed correlation on received samples and determines whether a signal is present. If a signal is detected, the terminal performs direct correlation on the received samples with PN1 sequences for K₁ different time offsets and identifies K₂ strongest TDM pilot 1 instances. For time synchronization, the terminal performs direct correlation on the received samples with PN2 sequences to detect for TDM pilot 2.

Claims

1. A method of transmitting pilots in a communication system, comprising:

generating a first time division multiplexed (TDM) pilot;

identifying a pseudo-random number (PN) sequence from a set of possible PN sequences for a second TDM pilot;

generating the second TDM pilot based at least in part on the PN sequence, wherein an identity of a transmitting entity of the first and second TDM pilots is associated with the PN sequence;

transmitting the first TDM pilot in a first portion of each transmission interval for the first and second TDM pilots; and

transmitting the second TDM pilot in a second portion of said each transmission interval.

2. The method of claim 1, wherein the generating the first TDM pilot comprises

generating a pilot sequence, and

generating the first TDM pilot based on at least one instance of the pilot sequence.

3. The method of claim 1, wherein the generating the second TDM pilot comprises

generating a pilot sequence based on the PN sequence, and

generating the second TDM pilot based on at least one instance of the pilot sequence.

4. The method of claim 1, wherein the generating the first TDM pilot comprises generating the first TDM pilot in frequency domain based on a first set of pilot symbols for a first set of subcarriers, and wherein the generating the second TDM pilot comprises generating the second TDM pilot in the frequency domain based on a second set of pilot symbols for a second set of subcarriers.

5. The method of claim 1, wherein the transmitting the second TDM pilot comprises transmitting the second TDM pilot in the second portion, next to the first portion, of said each transmission interval.

6. The method of claim 1, wherein the generating the first TDM pilot comprises

applying a pilot sequence to multiple subcarriers, and

generating the first TDM pilot based on the pilot sequence applied to the multiple subcarriers.

7. The method of claim 6, further comprising:

identifying the pilot sequence, from a set of pilot sequences available for the first TDM pilot, based on the identity of the transmitting entity.

8. The method of claim 6, further comprising:

identifying the pilot sequence and the PN sequence based on the identity of the transmitting entity, the pilot sequence being from a set of pilot sequences available for the first TDM pilot.

9. The method of claim 1, wherein the generating the second TDM pilot comprises

applying the PN sequence to multiple subcarriers, and

generating the second TDM pilot based on the PN sequence applied to the multiple subcarriers.

10. The method of claim 1, wherein the identifying the PN sequence comprises

identifying the PN sequence, from the set of possible PN sequences for the second TDM pilot, based on the identity of the transmitting entity.

11. The method of claim 1, wherein the generating the first TDM pilot comprises generating a first orthogonal frequency division multiplexing (OFDM) symbol comprising the first TDM pilot, and wherein the generating the second TDM pilot comprises generating a second OFDM symbol comprising the second TDM pilot.

12. The method of claim 11, wherein the generating the first OFDM symbol comprises

applying a pilot sequence to multiple subcarriers, and

generating the first OFDM symbol comprising the pilot sequence applied to the multiple subcarriers.

13. The method of claim 11, wherein the generating the second OFDM symbol comprises

applying the PN sequence to multiple subcarriers, and

generating the second OFDM symbol comprising the PN sequence applied to the multiple subcarriers.

14. The method of claim 11, wherein the transmitting the first TDM pilot comprises transmitting the first OFDM symbol in a first symbol period of said each transmission interval, and wherein the transmitting the second TDM pilot comprises transmitting the second OFDM symbol in a second symbol period of said each transmission interval.

15. The method of claim 1, further comprising:

generating a frequency division multiplexed (FDM) pilot; and

transmitting the FDM pilot in a third portion of said each transmission interval.

16. The method of claim 1, wherein the transmitting entity is a base station for a cell.

17. A method of transmitting pilots in a communication system, comprising:

generating a first time division multiplexed (TDM) pilot based at least in part on a first pseudo-random number (PN) sequence in a set of possible first PN sequences for the first TDM pilot;

generating a second TDM pilot based at least in part on a second PN sequence in a set of second PN sequences associated with the first PN sequence;

transmitting the first TDM pilot in a first portion of each transmission interval for the first and second TDM pilots; and

transmitting the second TDM pilot in a second portion of said each transmission interval.

18. The method of claim 17, wherein the generating the first TDM pilot comprises generating the first TDM pilot based on the first PN sequence in time domain, and wherein the generating the second TDM pilot comprises generating the second TDM pilot based on the second PN sequence in time domain.

19. The method of claim 17, wherein the generating the first TDM pilot comprises generating the first TDM pilot in frequency domain based on a first set of pilot symbols for a first set of subcarriers, and wherein the generating the second TDM pilot comprises generating the second TDM pilot in the frequency domain based on a second set of pilot symbols for a second set of subcarriers.

20. The method of claim 17, wherein the generating the first TDM pilot comprises

generating a pilot sequence based on the first PN sequence, and

generating the first TDM pilot based on at least one instance of the pilot sequence.

21. The method of claim 20, wherein the generating the pilot sequence comprises

generating the pilot sequence based on the first PN sequence and having a length equal to the length of the first PN sequence.

22. The method of claim 17, wherein the generating the first TDM pilot comprises

generating the first TDM pilot based on a different first PN sequence for each of a plurality of transmission intervals.

23. The method of claim 17, further comprising:

identifying the first PN sequence from among the set of possible first PN sequences, the first PN sequence corresponding to a code offset selected from among a plurality of possible code offsets.

24. The method of claim 17, wherein the generating the second TDM pilot comprises

generating a pilot sequence based on the second PN sequence, and

generating the second TDM pilot based on at least one instance of the pilot sequence.

25. The method of claim 24, wherein the generating the pilot sequence comprises

generating the pilot sequence based on the second PN sequence and having a length equal to the length of the second PN sequence.

26. The method of claim 24, wherein the generating the pilot sequence comprises

generating the pilot sequence based on the second PN sequence and having a longer length than a pilot sequence for the first TDM pilot.

27. The method of claim 17, further comprising:

generating a third TDM pilot based on a third PN sequence; and

transmitting the third TDM pilot in a third portion of said each transmission interval.

28. The method of claim 17, further comprising:

generating a frequency division multiplexed (FDM) pilot; and

transmitting the FDM pilot in a third portion of said each transmission interval.

29. The method of claim 17, further comprising:

generating a frequency division multiplexed (FDM) pilot based on the second PN sequence; and

transmitting the FDM pilot in a third portion of said each transmission interval.

30. The method of claim 17, further comprising:

generating a frequency division multiplexed (FDM) pilot based on a third PN sequence; and

transmitting the FDM pilot in a third portion of said each transmission interval.

31. The method of claim 17, further comprising:

identifying the first PN sequence from among the set of possible first PN sequences; and

identifying the second PN sequence from among the set of second PN sequences associated with the first PN sequence.

32. The method of claim 17, further comprising:

identifying the second PN sequence assigned to a base station transmitting the first and second TDM pilots, wherein neighboring base stations in the system are assigned different second PN sequences.

33. The method of claim 17, wherein the generating the second TDM pilot comprises

selecting the second PN sequence from among a plurality of second PN sequences assigned to a base station, wherein each of the plurality of second PN sequences corresponds to a different data value.

34. The method of claim 17, further comprising:

identifying the first and second PN sequences based on an identity of a transmitting entity of the first and second TDM pilots.

35. A method of transmitting pilots in a communication system, comprising:

identifying a pseudo-random number (PN) sequence for each of a plurality of time division multiplexed (TDM) pilots from a set of PN sequences available for each TDM pilot;

generating the plurality of TDM pilots based on a plurality of PN sequences identified for the plurality of TDM pilots wherein an identity of a transmitting entity of the plurality of TDM pilots is associated with the plurality of PN sequences; and

transmitting the plurality of TDM pilots in a plurality of time intervals of each transmission interval with TDM pilot transmission.

36. The method of claim 35, wherein the identifying comprises

identifying a first PN sequence for a first TDM pilot from among a set of PN sequences available for the first TDM pilot;

and

for each remaining TDM pilot among the plurality of TDM pilots,

determining a subset of PN sequences associated with at least one PN sequence used for at least one other TDM pilot, and

identifying a PN sequence for the remaining TDM pilot from among the subset of PN sequences.

37. An apparatus in a communication system, comprising:

at least one processor operative to generate a first time division multiplexed (TDM) pilot based at least in part on a first pseudo-random number (PN) sequence in a set of possible first PN sequences for the first TDM pilot, to generate a second TDM pilot based at least in part on a second PN sequence in a set of second PN sequences associated with the first PN sequence,

to multiplex the first TDM pilot in a first portion of each transmission interval for the first and second TDM pilots, and to multiplex the second TDM pilot in a second portion of said each transmission interval.

38. The apparatus of claim 37, wherein the at least one processor is operative to generate a pilot sequence based on the second PN sequence, and to generate the second TDM pilot based on at least one instance of the pilot sequence.

39. The apparatus of claim 37, wherein the at least one processor is operative to identify the first PN sequence from among the set of possible first PN sequences and to identify the second PN sequence from among the set of second PN sequences associated with the first PN sequence.

40. The apparatus of claim 37, further comprising:

a transmitter unit operative to transmit the first and second TDM pilots aligned in time with first and second TDM pilots from at least one other base station.

41. The apparatus of claim 37, further comprising:

a transmitter unit operative to transmit the first and second TDM pilots asynchronously with respect to first and second TDM pilots from at least one other base station.

42. The apparatus of claim 37, further comprising:

a transmitter unit operative to transmit the first and second TDM pilots staggered in time with respect to first and second TDM pilots from at least one other base station.

43. The apparatus of claim 42, wherein the first and second TDM pilots for each base station are transmitted in a time interval assigned to the base station.

44. The apparatus of claim 42, wherein neighboring base stations in the system use the same first PN sequence and the same second PN sequence.

45. The apparatus of claim 37, wherein neighboring base stations in the system are assigned different second PN sequences.

46. The apparatus of claim 37, wherein the communication system utilizes orthogonal frequency division multiplexing (OFDM).

47. The apparatus of claim 37, wherein the at least one processor is operative to identify the first and second PN sequences based on an identity of a transmitting entity of the first and second TDM pilots.

48. An apparatus in a communication system, comprising:

means for generating a first time division multiplexed (TDM) pilot based at least in part on a first pseudo-random number (PN) sequence in a set of possible first PN sequences for the first TDM pilot;

means for generating a second TDM pilot based at least in part on a second PN sequence in a set of second PN sequences associated with the first PN sequence;

means for transmitting the first TDM pilot in a first portion of each transmission interval for the first and second TDM pilots; and

means for transmitting the second TDM pilot in a second portion of said each transmission interval.

49. The apparatus of claim 48, wherein the means for generating the second TDM pilot comprises

means for generating a pilot sequence based on the second PN sequence and

means for generating the second TDM pilot based on at least one instance of the pilot sequence.

50. The apparatus of claim 48, wherein neighboring base stations in the system are assigned different second PN sequences.

51. The apparatus of claim 48, further comprising:

means for identifying the first and second PN sequences based on an identity of a transmitting entity of the first and second TDM pilots.

52. An apparatus in a communication system, comprising:

means for generating a first time division multiplexed (TDM) pilot;

means for identifying a pseudo-random number (PN) sequence from a set of possible PN sequences for a second TDM pilot;

means for generating the second TDM pilot based at least in part on the PN sequence, wherein an identity of a transmitting entity of the first and second TDM pilots is associated with the PN sequence;

means for transmitting the first TDM pilot in a first portion of each transmission interval for the first and second TDM pilots; and

means for transmitting the second TDM pilot in a second portion of said each transmission interval.

53. The apparatus of claim 52, wherein the means for generating the first TDM pilot comprises

means for generating a pilot sequence, and

means for generating the first TDM pilot based on at least one instance of the pilot sequence.

54. The apparatus of claim 52, wherein the means for generating the second TDM pilot comprises

means for generating a pilot sequence based on the PN sequence, and

means for generating the second TDM pilot based on at least one instance of the pilot sequence.

55. The apparatus of claim 52, wherein the means for generating the first TDM pilot comprises

means for applying a pilot sequence to multiple subcarriers, and

means for generating the first TDM pilot based on the pilot sequence applied to the multiple subcarriers.

56. The apparatus of claim 55, further comprising:

means for identifying the pilot sequence, from a set of pilot sequences available for the first TDM pilot, based on the identity of the transmitting entity.

57. The apparatus of claim 55, further comprising:

means for identifying the pilot sequence and the PN sequence based on the identity of the transmitting entity, the pilot sequence being from a set of pilot sequences available for the first TDM pilot.

58. The apparatus of claim 52, wherein the means for generating the second TDM pilot comprises

means for applying the PN sequence to multiple subcarriers, and

means for generating the second TDM pilot based on the PN sequence applied to the multiple subcarriers.

59. The apparatus of claim 52, wherein the means for identifying the PN sequence comprises

means for identifying the PN sequence, from the set of possible PN sequences for the second TDM pilot, based on the identity of the transmitting entity.

60. The apparatus of claim 52, wherein the means for generating the first TDM pilot comprises means for generating a first orthogonal frequency division multiplexing (OFDM) symbol comprising the first TDM pilot, and wherein the means for generating the second TDM pilot comprises means for generating a second OFDM symbol comprising the second TDM pilot.

61. The apparatus of claim 60, wherein the means for generating the first OFDM symbol comprises

means for applying a pilot sequence to multiple subcarriers, and

means for generating the first OFDM symbol comprising the pilot sequence applied to the multiple subcarriers.

62. The apparatus of claim 60, wherein the means for generating the second OFDM symbol comprises

means for applying the PN sequence to multiple subcarriers, and

means for generating the second OFDM symbol comprising the PN sequence applied to the multiple subcarriers.

63. The apparatus of claim 60, wherein the means for transmitting the first TDM pilot comprises means for transmitting the first OFDM symbol in a first symbol period of said each transmission interval, and wherein the means for transmitting the second TDM pilot comprises means for transmitting the second OFDM symbol in a second symbol period of said each transmission interval.

64. The apparatus of claim 52, further comprising:

means for generating a frequency division multiplexed (FDM) pilot; and

means for transmitting the FDM pilot in a third portion of said each transmission interval.

65. The apparatus of claim 52, wherein the transmitting entity is a base station for a cell.

66. An apparatus in a communication system, comprising:

at least one processor configured to generate a first time division multiplexed (TDM) pilot, to identify a pseudo-random number (PN) sequence from a set of possible PN sequences for a second TDM pilot, to generate the second TDM pilot based at least in part on the PN sequence, wherein an identity of a transmitting entity of the first and second TDM pilots is associated with the PN sequence, to send the first TDM pilot in a first portion of each transmission interval for the first and second TDM pilots and to send the second TDM pilot in a second portion of said each transmission interval.

67. The apparatus of claim 66, wherein the at least one processor is configured to generate a pilot sequence and to generate the first TDM pilot based on at least one instance of the pilot sequence.

68. The apparatus of claim 66, wherein the at least one processor is configured to generate a pilot sequence based on the PN sequence and to generate the second TDM pilot based on at least one instance of the pilot sequence.

69. The apparatus of claim 66, wherein the at least one processor is configured to apply a pilot sequence to multiple subcarriers and to generate the first TDM pilot with the pilot sequence applied to the multiple subcarriers.

70. The apparatus of claim 69, wherein the at least one processor is configured to identify the pilot sequence, from a set of pilot sequences available for the first TDM pilot, based on the identity of the transmitting entity.

71. The apparatus of claim 69, wherein the at least one processor is configured to identify the pilot sequence and the PN sequence based on the identity of the transmitting entity, the pilot sequence being from a set of pilot sequences available for the first TDM pilot.

72. The apparatus of claim 66, wherein the at least one processor is configured to apply the PN sequence to multiple subcarriers and to generate the second TDM pilot with the PN sequence applied to the multiple subcarriers.

73. The apparatus of claim 66, wherein the at least one processor is configured to identify the PN sequence, from the set of possible PN sequences for the second TDM pilot, based on the identity of the transmitting entity.

74. The apparatus of claim 66, wherein the at least one processor is configured to generate a first orthogonal frequency division multiplexing (OFDM) symbol comprising the first TDM pilot and to generate a second OFDM symbol comprising the second TDM pilot.

75. The apparatus of claim 74, wherein the at least one processor is configured to apply a pilot sequence to multiple subcarriers and to generate the first OFDM symbol comprising the pilot sequence applied to the multiple subcarriers.

76. The apparatus of claim 74, wherein the at least one processor is configured to apply the PN sequence to multiple subcarriers and to generate the second OFDM symbol comprising the PN sequence applied to the multiple subcarriers.

77. The apparatus of claim 74, wherein the at least one processor is configured to transmit the first OFDM symbol in a first symbol period of said each transmission interval and to transmit the second OFDM symbol in a second symbol period of said each transmission interval.

78. The apparatus of claim 66, wherein the at least one processor is configured to generate a frequency division multiplexed (FDM) pilot and to transmit the FDM pilot in a third portion of said each transmission interval.

79. The apparatus of claim 66, wherein the transmitting entity is a base station for a cell.

80. A computer program product, comprising:

a non-transitory processor-readable medium comprising;

code for causing at least one processor to generate a first time division multiplexed (TDM) pilot,

code for causing the at least one processor to identify a pseudo-random number (PN) sequence from a set of possible PN sequences for a second TDM pilot,

code for causing the at least one processor to generate the second TDM pilot based at least in part on the PN sequence, wherein an identity of a transmitting entity of the first and second TDM pilots is associated with the PN sequence,

code for causing the at least one processor to send the first TDM pilot in a first portion of each transmission interval for the first and second TDM pilots, and

code for causing the at least one processor to send the second TDM pilot in a second portion of said each transmission interval.

81. A computer program product, comprising:

a non-transitory processor-readable medium comprising;

code for causing at least one processor to generate a first time division multiplexed (TDM) pilot based on a first pseudo-random number (PN) sequence in a set of possible first PN sequences for the first TDM pilot,

code for causing the at least one processor to generate a second TDM pilot based on a second PN sequence in a set of second PN sequences associated with the first PN sequence,

code for causing the at least one processor to transmit the first TDM pilot in a first portion of each transmission interval for the first and second TDM pilots, and

code for causing the at least one processor to transmit the second TDM pilot in a second portion of said each transmission interval.