Two-way ranging with inter-pulse transmission and reception

• US 8,184,038 B2
• Filed: 03/11/2009
• Issued: 05/22/2012
• Est. Priority Date: 08/20/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ekbal, Amal, Julian, David Jonathan, Jia, Zhanfeng
• Primary Examiner(s): SOTOMAYOR, JOHN B
• Application Number:
  US12/402,420
• Publication Number:
  US 20100045508A1
• Time in Patent Office: 1,168 Days
• Field of Search: 342/125, 342/118, 342/109, 342/145, 342/450, 342/451, 342/457, 342/458, 455/404.2, 455/456.1, 455/456.2, 455/456.3, 455/456.5
• US Class Current: 342/109
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder

Abstract

Relatively short turnaround times are provided in conjunction with two-way ranging to, for example, facilitate accurate ranging measurements when the relative clock drift between ranging nodes (e.g., devices) is relatively high. In some aspects, relatively short turnaround times are achieved through the use of a symmetric channel that is defined to enable concurrent transmission of ranging messages between nodes. For example, a symmetric channel may be established by configuring the nodes to receive one or more pulses associated with a received ranging message in between pulse transmissions associated with a transmitted ranging message. In this way, one node may send a ranging timestamp shortly after the other nodes sends its ranging timestamp, thereby mitigating the impact of the clock drift on the ranging measurements. In some aspects the pulses may comprise ultra-wideband pulses. The techniques described herein may be employed to provide two-way ranging in, for example, low power and/or non-coherent wireless devices.

Claims

1. A method of wireless communication, comprising:

transmitting, by a first node, a first set of pulses;

receiving, at the first node, a second set of pulses, wherein at least one pulse of the second set is received after at least one pulse of the first set is transmitted and before at least one other pulse of the first set is transmitted; and

determining a distance between the first node and a second node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein;

the first node receives at least a portion of a ranging preamble associated with the second set of pulses before transmitting an entire ranging preamble associated with the first set of pulses, and

the determination of the distance is further based on the ranging preamble associated with the first set of pulses and the ranging preamble associated with the second set of pulses.

2. The method of claim 1, further comprising determining transmission times for the first set of pulses and reception times for the second set of pulses such that at least a portion of the pulses of the first set are interleaved in time with at least a portion of the pulses of the second set.

3. The method of claim 2, wherein the first node alternates between transmitting a given pulse of the first set and receiving a given pulse of the second set based on the determined transmission times and receptions times.

4. The method of claim 1, further comprising determining ranging message timing such that the first node receives at least a portion of a ranging message associated with the second set of pulses before transmitting an entire ranging message associated with the first set of pulses.

5. The method of claim 1, wherein the first node performs ranging hypothesis testing based on the second set of pulses while transmitting the first set of pulses for the second node to perform ranging hypothesis testing.

6. The method of claim 1, wherein the determination of the distance further comprises:

determining a period of time based on a first timestamp associated with the transmission of the first set of pulses and a second timestamp associated with the receipt of the second set of pulses; and

subtracting a defined delay period from the period of time, wherein the defined delay period specifies a time at which the second node is to transmit a timing indication via the second set of pulses after receiving a timing indication via the first set of pulses.

7. The method of claim 6, wherein the defined delay period is approximately equal to a symbol duration time.

8. The method of claim 6, wherein the defined delay period is specified by a symbol index.

9. The method of claim 1, wherein the determination of the distance further comprises determining a leading edge of the second set of pulses.

10. The method of claim 1, wherein the first node transmits the first set of pulses a defined delay period after transmitting an acquisition message.

11. The method of claim 1, further comprising communicating with the second node to establish transmission timing for at least one ranging message.

12. The method of claim 1, wherein each of the pulses of the first set has a pulse duration of four nanoseconds or less.

13. An apparatus for wireless communication, comprising:

a transmitter configured to transmit a first set of pulses;

a receiver configured to receive a second set of pulses, and further configured to receive at least one pulse of the second set after the transmitter transmits at least one pulse of the first set and before the transmitter transmits at least one other pulse of the first set; and

a distance determiner configured to determine a distance between the apparatus and a node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein the distance determiner is further configured to;

determine timestamp message timing such that the receiver receives at least a portion of a ranging preamble associated with the second set of pulses before the transmitter transmits an entire ranging preamble associated with the first set of pulses, and

determine the distance based on the ranging preamble associated with the first set of pulses and the ranging preamble associated with the second set of pulses.

14. The apparatus of claim 13, further comprising a communication controller configured to determine transmission times for the first set of pulses and reception times for the second set of pulses such that at least a portion of the pulses of the first set are interleaved in time with at least a portion of the pulses of the second set.

15. The apparatus of claim 14, wherein the transmitter and the receiver are further configured to alternate between transmitting a given pulse of the first set and receiving a given pulse of the second set based on the determined transmission times and receptions times.

16. The apparatus of claim 13, wherein the distance determiner is further configured to determine ranging message timing such that the receiver receives at least a portion of a ranging message associated with the second set of pulses before the transmitter transmits an entire ranging message associated with the first set of pulses.

17. The apparatus of claim 13, further comprising a hypothesis processor configured to perform ranging hypothesis testing based on the second set of pulses while the transmitter transmits the first set of pulses for the node to perform ranging hypothesis testing.

18. The apparatus of claim 13, wherein the distance determiner is further configured to determine the distance by:

determining a period of time based on a first timestamp associated with the transmission of the first set of pulses and a second timestamp associated with the receipt of the second set of pulses; and

subtracting a defined delay period from the period of time, wherein the defined delay period specifies a time at which the node is to transmit a timing indication via the second set of pulses after receiving a timing indication via the first set of pulses.

19. The apparatus of claim 18, wherein the defined delay period is approximately equal to a symbol duration time.

20. The apparatus of claim 18, wherein the defined delay period is specified by a symbol index.

21. The apparatus of claim 13, wherein the distance determiner is further configured to determine the distance by determining a leading edge of the second set of pulses.

22. The apparatus of claim 13, wherein the distance determiner is further configured to determine ranging message timing such that the transmitter transmits the first set of pulses a defined delay period after the transmitter transmits an acquisition message.

23. The apparatus of claim 13, further comprising a communication controller configured to communicate with the node to establish transmission timing for at least one ranging message.

24. The apparatus of claim 13, wherein each of the pulses of the first set has a pulse duration of four nanoseconds or less.

25. An apparatus for wireless communication, comprising:

means for transmitting a first set of pulses;

means for receiving a second set of pulses, wherein the means for receiving is configured to receive at least one pulse of the second set after the means for transmitting transmits at least one pulse of the first set and before the means for transmitting transmits at least one other pulse of the first set; and

means for determining a distance between the apparatus and a node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein the means for determining is configured to;

determine timestamp message timing such that the means for receiving receives at least a portion of a ranging preamble associated with the second set of pulses before the means for transmitting transmits an entire ranging preamble associated with the first set of pulses, and

determine the distance based on the ranging preamble associated with the first set of pulses and the ranging preamble associated with the second set of pulses.

26. The apparatus of claim 25, further comprising means for determining transmission times for the first set of pulses and reception times for the second set of pulses such that at least a portion of the pulses of the first set are interleaved in time with at least a portion of the pulses of the second set.

27. The apparatus of claim 26, wherein the means for transmitting and the means for receiving are further configured to alternate between transmitting a given pulse of the first set and receiving a given pulse of the second set based on the determined transmission times and receptions times.

28. The apparatus of claim 25, wherein the means for determining is configured to determine ranging message timing such that the means for receiving receives at least a portion of a ranging message associated with the second set of pulses before the means for transmitting transmits an entire ranging message associated with the first set of pulses.

29. The apparatus of claim 25, further comprising means for performing ranging hypothesis testing based on the second set of pulses while the means for transmitting transmits the first set of pulses for the node to perform ranging hypothesis testing.

30. The apparatus of claim 25, wherein the means for determining is further configured to determine the distance by:

determining a period of time based on a first timestamp associated with the transmission of the first set of pulses and a second timestamp associated with the receipt of the second set of pulses; and

subtracting a defined delay period from the period of time, wherein the defined delay period specifies a time at which the node is to transmit a timing indication via the second set of pulses after receiving a timing indication via the first set of pulses.

31. The apparatus of claim 30, wherein the defined delay period is approximately equal to a symbol duration time.

32. The apparatus of claim 30, wherein the defined delay period is specified by a symbol index.

33. The apparatus of claim 25, wherein the means for determining is configured to determine the distance by determining a leading edge of the second set of pulses.

34. The apparatus of claim 25, wherein the means for determining is configured to determine ranging message timing such that the means for transmitting transmits the first set of pulses a defined delay period after the means for transmitting transmits an acquisition message.

35. The apparatus of claim 25, further comprising means for communicating with the node to establish transmission timing for at least one ranging message.

36. The apparatus of claim 25, wherein each of the pulses of the first set has a pulse duration of four nanoseconds or less.

37. A computer-program product for wireless communication, comprising:

non-transitory computer-readable medium encoded with codes executable to;

transmit, at a first node, a first set of pulses;

receive, at the first node, a second set of pulses, wherein at least one pulse of the second set is received after at least one pulse of the first set is transmitted and before at least one other pulse of the first set is transmitted;

determine a distance between the first node and a second node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein;

the first node receives at least a portion of a ranging preamble associated with the second set of pulses before transmitting an entire ranging preamble associated with the first set of pulses; and

the determination of the distance is further based on the ranging preamble associated with the first set of pulses and the ranging preamble associated with the second set of pulses.

38. A headset, comprising:

a transmitter configured to transmit a first set of pulses;

a receiver configured to receive a second set of pulses, and further configured to receive at least one pulse of the second set after the transmitter transmits at least one pulse of the first set and before the transmitter transmits at least one other pulse of the first set;

a distance determiner configured to determine a distance between the headset and a node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein the distance determiner is further configured to;

determine timestamp message timing such that the receiver receives at least a portion of a ranging preamble associated with the second set of pulses before the transmitter transmits an entire ranging preamble associated with the first set of pulses, and

determine the distance based on the ranging preamble associated with the first set of pulses and the ranging preamble associated with the second set of pulses; and

a transducer configured to provide an indication based on the determined distance.

39. A watch, comprising:

a transmitter configured to transmit a first set of pulses;

a receiver configured to receive a second set of pulses, and further configured to receive at least one pulse of the second set after the transmitter transmits at least one pulse of the first set and before the transmitter transmits at least one other pulse of the first set;

a distance determiner configured to determine a distance between the watch and a node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein the distance determiner is further configured to;

determine timestamp message timing such that the receiver receives at least a portion of a ranging preamble associated with the second set of pulses before the transmitter transmits an entire ranging preamble associated with the first set of pulses, and

determine the distance based on the ranging preamble associated with the first set of pulses and the ranging preamble associated with the second set of pulses; and

a user interface configured to provide an indication based on based on the determined distance.

40. A sensing device, comprising:

a transmitter configured to transmit a first set of pulses;

a receiver configured to receive a second set of pulses, and further configured to receive at least one pulse of the second set after the transmitter transmits at least one pulse of the first set and before the transmitter transmits at least one other pulse of the first set;

a distance determiner configured to determine a distance between the sensing device and a node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein the distance determiner is further configured to;

determine timestamp message timing such that the receiver receives at least a portion of a ranging preamble associated with the second set of pulses before the transmitter transmits an entire ranging preamble associated with the first set of pulses, and

determine the distance based on the ranging preamble associated with the first set of pulses and the ranging preamble associated with the second set of pulses; and

a sensor configured to provide data to be transmitted via the transmitter.

41. A method of wireless communication, comprising:

receiving, at a first node, a first set of pulses associated with a ranging operation; and

transmitting, by the first node, a second set of pulses associated with the ranging operation, wherein;

at least one pulse of the second set is transmitted after at least one pulse of the first set is received and before at least one other pulse of the first set is received,

at least a portion of a ranging preamble associated with the second set of pulses is transmitted before receiving an entire ranging preamble associated with the first set of pulses,

the second set of pulses comprises a timestamped pulse, and

the timestamped pulse is transmitted a defined delay period after receipt of a timing indication associated with the first set of pulses.

42. The method of claim 41, further comprising determining transmission times for the second set of pulses and reception times for the first set of pulses such that at least a portion of the pulses of the first set are interleaved in time with at least a portion of the pulses of the second set.

43. The method of claim 42, wherein the first node alternates between receiving a given pulse of the first set and transmitting a given pulse of the second set as a result of the determined transmission times and receptions times.

44. The method of claim 41, further comprising determining ranging message timing such that the first node transmits at least a portion of a ranging message associated with the second set of pulses before receiving an entire ranging message associated with the first set of pulses.

45. The method of claim 41, wherein the first node performs ranging hypothesis testing based on the first set of pulses while transmitting the second set of pulses for a second node to perform ranging hypothesis testing.

46. The method of claim 41, wherein the defined delay period is approximately equal to a symbol duration time.

47. The method of claim 41, wherein the defined delay period is specified by a symbol index.

48. The method of claim 41, wherein the timestamped pulse is transmitted the defined delay period after receipt of a leading edge of the timing indication.

49. The method of claim 41, wherein the first node transmits the second set of pulses a defined period of time after transmitting an acquisition message.

50. The method of claim 41, further comprising communicating with a second node to establish transmission timing for at least one ranging message.

51. The method of claim 41, wherein each of the pulses of the second set has a pulse duration of four nanoseconds or less.

52. An apparatus for wireless communication, comprising:

a receiver configured to receive a first set of pulses associated with a ranging operation;

a transmitter configured to transmit a second set of pulses associated with the ranging operation, wherein the transmitter is further configured to transmit at least one pulse of the second set after the receiver receives at least one pulse of the first set and before the receiver receives at least one other pulse of the first set, and further wherein the second set of pulses comprises a timestamped pulse; and

a timestamp processor configured to determine timestamp message timing such that the transmitter transmits the timestamped pulse a defined delay period after the receiver receives a timing indication associated with the first set of pulses, wherein the timestamp processor is further configured to determine the timestamp message timing such that the transmitter transmits at least a portion of a ranging preamble associated with the second set of pulses before the receiver receives an entire ranging preamble associated with the first set of pulses.

53. The apparatus of claim 52, further comprising a communication controller configured to determine transmission times for the second set of pulses and reception times for the first set of pulses such that at least a portion of the pulses of the first set are interleaved in time with at least a portion of the pulses of the second set.

54. The apparatus of claim 53, wherein the transmitter and the receiver are further configured to alternate between receiving a given pulse of the first set and transmitting a given pulse of the second set based on the determined transmission times and receptions times.

55. The apparatus of claim 52, wherein the timestamp processor is further configured to determine ranging message timing such that the transmitter transmits at least a portion of a ranging message associated with the second set of pulses before the receiver receives an entire ranging message associated with the first set of pulses.

56. The apparatus of claim 52, further comprising a hypothesis processor configured to perform ranging hypothesis testing based on the first set of pulses while the transmitter transmits the second set of pulses for a node to perform ranging hypothesis testing.

57. The apparatus of claim 52, wherein the defined delay period is approximately equal to a symbol duration time.

58. The apparatus of claim 52, wherein the defined delay period is specified by a symbol index.

59. The apparatus of claim 52, wherein the timestamp processor is further configured to determine timestamp message timing such that the transmitter transmits the timestamped pulse the defined delay period after the receiver receives a leading edge of the timing indication.

60. The apparatus of claim 52, wherein the timestamp processor is further configured to determine ranging message timing such that the transmitter transmits the second set of pulses a defined period of time after the transmitter transmits an acquisition message.

61. The apparatus of claim 52, further comprising a communication controller configured to communicate with a node to establish transmission timing for at least one ranging message.

62. The apparatus of claim 52, wherein each of the pulses of the second set has a pulse duration of four nanoseconds or less.

63. An apparatus for wireless communication, comprising:

means for receiving a first set of pulses associated with a ranging operation;

means for transmitting a second set of pulses associated with the ranging operation, wherein the means for transmitting is configured to transmit at least one pulse of the second set after the means for receiving receives at least one pulse of the first set and before the means for receiving receives at least one other pulse of the first set, and further wherein the second set of pulses comprises a timestamped pulse; and

means for determining timestamp message timing such that the means for transmitting transmits the timestamped pulse a defined delay period after the means for receiving receives a timing indication associated with the first set of pulses, wherein the means for determining is configured to determine the timestamp message timing such that the means for transmitting transmits at least a portion of a ranging preamble associated with the second set of pulses before the means for receiving receives an entire ranging preamble associated with the first set of pulses.

64. The apparatus of claim 63, further comprising means for determining transmission times for the second set of pulses and reception times for the first set of pulses such that at least a portion of the pulses of the first set are interleaved in time with at least a portion of the pulses of the second set.

65. The apparatus of claim 64, wherein the means for transmitting and the means for receiving are further configured to alternate between receiving a given pulse of the first set and transmitting a given pulse of the second set based on the determined transmission times and receptions times.

66. The apparatus of claim 63, wherein the means for determining is configured to determine ranging message timing such that the means for transmitting transmits at least a portion of a ranging message associated with the second set of pulses before the means for receiving receives an entire ranging message associated with the first set of pulses.

67. The apparatus of claim 63, further comprising means for performing ranging hypothesis testing based on the first set of pulses while the means for transmitting transmits the second set of pulses for a node to perform ranging hypothesis testing.

68. The apparatus of claim 63, wherein the defined delay period is approximately equal to a symbol duration time.

69. The apparatus of claim 63, wherein the defined delay period is specified by a symbol index.

70. The apparatus of claim 63, wherein the means for determining is configured to determine timestamp message timing such that the means for transmitting transmits the timestamped pulse the defined delay period after the means for receiving receives a leading edge of the timing indication.

71. The apparatus of claim 63, wherein the means for determining is configured to determine timestamp message timing such that the means for transmitting transmits the second set of pulses a defined period of time after the means for transmitting transmits an acquisition message.

72. The apparatus of claim 63, further comprising means for communicating with a node to establish transmission timing for at least one ranging message.

73. The apparatus of claim 63, wherein each of the pulses of the second set has a pulse duration of four nanoseconds or less.

74. A computer-program product for wireless communication, comprising:

non-transitory computer-readable medium encoded with codes executable to;

receive, at a first node, a first set of pulses associated with a ranging operation;

transmit, at the first node, a second set of pulses associated with the ranging operation, wherein at least one pulse of the second set is transmitted after at least one pulse of the first set is received and before at least one other pulse of the first set is received, and wherein at least a portion of a ranging preamble associated with the second set of pulses is transmitted before receiving an entire ranging preamble associated with the first set of pulses, and further wherein the second set of pulses comprises a timestamped pulse; and

determine timestamp message timing such that the timestamped pulse is transmitted a defined delay period after receipt of a timing indication associated with the first set of pulses.

75. A headset, comprising:

a receiver configured to receive a first set of pulses associated with a ranging operation;

a transmitter configured to transmit a second set of pulses associated with the ranging operation, wherein the transmitter is further configured to transmit at least one pulse of the second set after the receiver receives at least one pulse of the first set and before the receiver receives at least one other pulse of the first set, and further wherein the second set of pulses comprises a timestamped pulse;

a timestamp processor configured to determine timestamp message timing such that the transmitter transmits the timestamped pulse a defined delay period after the receiver receives a timing indication associated with the first set of pulses, wherein the timestamp processor is further configured to determine the timestamp message timing such that the transmitter transmits at least a portion of a ranging preamble associated with the second set of pulses before the receiver receives an entire ranging preamble associated with the first set of pulses; and

a transducer configured to provide an audio output based on data received via the receiver.

76. A watch, comprising:

a receiver configured to receive a first set of pulses associated with a ranging operation;

a transmitter configured to transmit a second set of pulses associated with the ranging operation, wherein the transmitter is further configured to transmit at least one pulse of the second set after the receiver receives at least one pulse of the first set and before the receiver receives at least one other pulse of the first set, and further wherein the second set of pulses comprises a timestamped pulse;

a timestamp processor configured to determine timestamp message timing such that the transmitter transmits the timestamped pulse a defined delay period after the receiver receives a timing indication associated with the first set of pulses, wherein the timestamp processor is further configured to determine the timestamp message timing such that the transmitter transmits at least a portion of a ranging preamble associated with the second set of pulses before the receiver receives an entire ranging preamble associated with the first set of pulses; and

a user interface configured to provide an indication based on data received via the receiver.

77. A sensing device, comprising:

a receiver configured to receive a first set of pulses associated with a ranging operation;

a transmitter configured to transmit a second set of pulses associated with the ranging operation, wherein the transmitter is further configured to transmit at least one pulse of the second set after the receiver receives at least one pulse of the first set and before the receiver receives at least one other pulse of the first set, and further wherein the second set of pulses comprises a timestamped pulse;

a timestamp processor configured to determine timestamp message timing such that the transmitter transmits the timestamped pulse a defined delay period after the receiver receives a timing indication associated with the first set of pulses, wherein the timestamp processor is further configured to determine the timestamp message timing such that the transmitter transmits at least a portion of a ranging preamble associated with the second set of pulses before the receiver receives an entire ranging preamble associated with the first set of pulses; and

a sensor configured to provide data to be transmitted via the transmitter.

78. A method of wireless communication, comprising:

transmitting, by a first node, a first set of pulses;

receiving, at the first node, a second set of pulses, wherein at least one pulse of the second set is received after at least one pulse of the first set is transmitted and before at least one other pulse of the first set is transmitted; and

determining a distance between the first node and a second node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein;

the first node performs ranging hypothesis testing based on the second set of pulses while transmitting the first set of pulses for the second node to perform ranging hypothesis testing.

79. A method of wireless communication, comprising:

transmitting, by a first node, a first set of pulses;

receiving, at the first node, a second set of pulses, wherein at least one pulse of the second set is received after at least one pulse of the first set is transmitted and before at least one other pulse of the first set is transmitted; and

determining a distance between the first node and a second node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein the determination of the distance further comprises;

determining a period of time based on a first timestamp associated with the transmission of the first set of pulses and a second timestamp associated with the receipt of the second set of pulses, and

subtracting a defined delay period from the period of time, wherein the defined delay period specifies a time at which the second node is to transmit a timing indication via the second set of pulses after receiving a timing indication via the first set of pulses.

80. The method of claim 79, wherein the defined delay period is approximately equal to a symbol duration time.

81. The method of claim 79, wherein the defined delay period is specified by a symbol index.

82. An apparatus for wireless communication, comprising:

a transmitter configured to transmit a first set of pulses;

a receiver configured to receive a second set of pulses, and further configured to receive at least one pulse of the second set after the transmitter transmits at least one pulse of the first set and before the transmitter transmits at least one other pulse of the first set;

a distance determiner configured to determine a distance between the apparatus and a node based on at least some of the pulses of the first set and at least some of the pulses of the second set; and

a hypothesis processor configured to perform ranging hypothesis testing based on the second set of pulses while the transmitter transmits the first set of pulses for the node to perform ranging hypothesis testing.

84. The apparatus of claim 82, wherein the defined delay period is approximately equal to a symbol duration time.

83. An apparatus for wireless communication, comprising:

a transmitter configured to transmit a first set of pulses;

a receiver configured to receive a second set of pulses, and further configured to receive at least one pulse of the second set after the transmitter transmits at least one pulse of the first set and before the transmitter transmits at least one other pulse of the first set; and

a distance determiner configured to determine a distance between the apparatus and a node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein the distance determiner is further configured to determine the distance by;

determining a period of time based on a first timestamp associated with the transmission of the first set of pulses and a second timestamp associated with the receipt of the second set of pulses, and

subtracting a defined delay period from the period of time, wherein the defined delay period specifies a time at which the node is to transmit a timing indication via the second set of pulses after receiving a timing indication via the first set of pulses.

85. The apparatus of claim 83, wherein the defined delay period is specified by a symbol index.

86. An apparatus for wireless communication, comprising:

means for transmitting a first set of pulses;

means for receiving a second set of pulses, wherein the means for receiving is configured to receive at least one pulse of the second set after the means for transmitting transmits at least one pulse of the first set and before the means for transmitting transmits at least one other pulse of the first set;

means for determining a distance between the apparatus and a node based on at least some of the pulses of the first set and at least some of the pulses of the second set; and

means for performing ranging hypothesis testing based on the second set of pulses while the means for transmitting transmits the first set of pulses for the node to perform ranging hypothesis testing.

87. An apparatus for wireless communication, comprising:

means for transmitting a first set of pulses;

means for receiving a second set of pulses, wherein the means for receiving is configured to receive at least one pulse of the second set after the means for transmitting transmits at least one pulse of the first set and before the means for transmitting transmits at least one other pulse of the first set; and

means for determining a distance between the apparatus and a node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein the means for determining is further configured to determine the distance by;

determining a period of time based on a first timestamp associated with the transmission of the first set of pulses and a second timestamp associated with the receipt of the second set of pulses, and

subtracting a defined delay period from the period of time, wherein the defined delay period specifies a time at which the node is to transmit a timing indication via the second set of pulses after receiving a timing indication via the first set of pulses.

88. The apparatus of claim 87, wherein the defined delay period is approximately equal to a symbol duration time.

89. The apparatus of claim 87, wherein the defined delay period is specified by a symbol index.

90. A method of wireless communication, comprising:

receiving, at a first node, a first set of pulses associated with a ranging operation; and

transmitting, by the first node, a second set of pulses associated with the ranging operation, wherein;

at least one pulse of the second set is transmitted after at least one pulse of the first set is received and before at least one other pulse of the first set is received,

the second set of pulses comprises a timestamped pulse,

the timestamped pulse is transmitted a defined delay period after receipt of a timing indication associated with the first set of pulses, and

the first node performs ranging hypothesis testing based on the first set of pulses while transmitting the second set of pulses for a second node to perform ranging hypothesis testing.

91. The method of claim 90 wherein the defined delay period is approximately equal to a symbol duration time.

92. A method of wireless communication, comprising:

receiving, at a first node, a first set of pulses associated with a ranging operation; and

transmitting, by the first node, a second set of pulses associated with the ranging operation, wherein;

at least one pulse of the second set is transmitted after at least one pulse of the first set is received and before at least one other pulse of the first set is received,

the second set of pulses comprises a timestamped pulse,

the timestamped pulse is transmitted a defined delay period after receipt of a timing indication associated with the first set of pulses, and

the defined delay period is specified by a symbol index.

93. An apparatus for wireless communication, comprising:

a receiver configured to receive a first set of pulses associated with a ranging operation;

a transmitter configured to transmit a second set of pulses associated with the ranging operation, wherein the transmitter is further configured to transmit at least one pulse of the second set after the receiver receives at least one pulse of the first set and before the receiver receives at least one other pulse of the first set, and further wherein the second set of pulses comprises a timestamped pulse; and

a timestamp processor configured to determine timestamp message timing such that the transmitter transmits the timestamped pulse a defined delay period after the receiver receives a timing indication associated with the first set of pulses, wherein the timestamp processor is further configured to determine ranging message timing such that the transmitter transmits at least a portion of a ranging message associated with the second set of pulses before the receiver receives an entire ranging message associated with the first set of pulses.

94. An apparatus for wireless communication, comprising:

a receiver configured to receive a first set of pulses associated with a ranging operation;

a transmitter configured to transmit a second set of pulses associated with the ranging operation, wherein the transmitter is further configured to transmit at least one pulse of the second set after the receiver receives at least one pulse of the first set and before the receiver receives at least one other pulse of the first set, and further wherein the second set of pulses comprises a timestamped pulse;

a timestamp processor configured to determine timestamp message timing such that the transmitter transmits the timestamped pulse a defined delay period after the receiver receives a timing indication associated with the first set of pulses; and

a hypothesis processor configured to perform ranging hypothesis testing based on the first set of pulses while the transmitter transmits the second set of pulses for a node to perform ranging hypothesis testing.

95. The apparatus of claim 94, wherein the defined delay period is approximately equal to a symbol duration time.

96. An apparatus for wireless communication, comprising:

a receiver configured to receive a first set of pulses associated with a ranging operation;

a transmitter configured to transmit a second set of pulses associated with the ranging operation, wherein the transmitter is further configured to transmit at least one pulse of the second set after the receiver receives at least one pulse of the first set and before the receiver receives at least one other pulse of the first set, and further wherein the second set of pulses comprises a timestamped pulse; and

a timestamp processor configured to determine timestamp message timing such that the transmitter transmits the timestamped pulse a defined delay period after the receiver receives a timing indication associated with the first set of pulses, wherein the defined delay period is specified by a symbol index.

97. An apparatus for wireless communication, comprising:

means for receiving a first set of pulses associated with a ranging operation;

means for transmitting a second set of pulses associated with the ranging operation, wherein the means for transmitting is configured to transmit at least one pulse of the second set after the means for receiving receives at least one pulse of the first set and before the means for receiving receives at least one other pulse of the first set, and further wherein the second set of pulses comprises a timestamped pulse;

means for determining timestamp message timing such that the means for transmitting transmits the timestamped pulse a defined delay period after the means for receiving receives a timing indication associated with the first set of pulses; and

means for performing ranging hypothesis testing based on the first set of pulses while the means for transmitting transmits the second set of pulses for a node to perform ranging hypothesis testing.

98. The apparatus of claim 97, wherein the defined delay period is approximately equal to a symbol duration time.

99. An apparatus for wireless communication, comprising:

means for receiving a first set of pulses associated with a ranging operation;

means for transmitting a second set of pulses associated with the ranging operation, wherein the means for transmitting is configured to transmit at least one pulse of the second set after the means for receiving receives at least one pulse of the first set and before the means for receiving receives at least one other pulse of the first set, and further wherein the second set of pulses comprises a timestamped pulse; and

means for determining timestamp message timing such that the means for transmitting transmits the timestamped pulse a defined delay period after the means for receiving receives a timing indication associated with the first set of pulses, wherein the defined delay period is specified by a symbol index.

100. A computer-program product for wireless communication, comprising:

non-transitory computer-readable medium encoded with codes executable to;

transmit, at a first node, a first set of pulses;

receive, at the first node, a second set of pulses, wherein at least one pulse of the second set is received after at least one pulse of the first set is transmitted and before at least one other pulse of the first set is transmitted;

determine a distance between the first node and a second node based on at least some of the pulses of the first set and at least some of the pulses of the second set; and

perform ranging hypothesis testing based on the second set of pulses while transmitting the first set of pulses for the second node to perform ranging hypothesis testing.

101. A computer-program product for wireless communication, comprising:

non-transitory computer-readable medium encoded with codes executable to;

transmit, at a first node, a first set of pulses;

receive, at the first node, a second set of pulses, wherein at least one pulse of the second set is received after at least one pulse of the first set is transmitted and before at least one other pulse of the first set is transmitted; and

determine a distance between the first node and a second node based on at least some of the pulses of the first set and at least some of the pulses of the second set, wherein the determination of the distance further comprises;

determining a period of time based on a first timestamp associated with the transmission of the first set of pulses and a second timestamp associated with the receipt of the second set of pulses, and

subtracting a defined delay period from the period of time, wherein the defined delay period specifies a time at which the second node is to transmit a timing indication via the second set of pulses after receiving a timing indication via the first set of pulses.

102. A computer-program product for wireless communication, comprising:

non-transitory computer-readable medium encoded with codes executable to;

receive, at a first node, a first set of pulses associated with a ranging operation;

transmit, at the first node, a second set of pulses associated with the ranging operation, wherein at least one pulse of the second set is transmitted after at least one pulse of the first set is received and before at least one other pulse of the first set is received, and further wherein the second set of pulses comprises a timestamped pulse;

determine timestamp message timing such that the timestamped pulse is transmitted a defined delay period after receipt of a timing indication associated with the first set of pulses; and

perform ranging hypothesis testing based on the first set of pulses while transmitting the second set of pulses for a second node to perform ranging hypothesis testing.

103. A computer-program product for wireless communication, comprising:

non-transitory computer-readable medium encoded with codes executable to;

receive, at a first node, a first set of pulses associated with a ranging operation;

transmit, at the first node, a second set of pulses associated with the ranging operation, wherein at least one pulse of the second set is transmitted after at least one pulse of the first set is received and before at least one other pulse of the first set is received, and further wherein the second set of pulses comprises a timestamped pulse; and

determine timestamp message timing such that the timestamped pulse is transmitted a defined delay period after receipt of a timing indication associated with the first set of pulses, wherein the defined delay period is specified by a symbol index.

104. A computer-program product for wireless communication, comprising:

non-transitory computer-readable medium encoded with codes executable to;

receive, at a first node, a first set of pulses associated with a ranging operation;

transmit, at the first node, a second set of pulses associated with the ranging operation, wherein at least one pulse of the second set is transmitted after at least one pulse of the first set is received and before at least one other pulse of the first set is received, and further wherein the second set of pulses comprises a timestamped pulse;

determine timestamp message timing such that the timestamped pulse is transmitted a defined delay period after receipt of a timing indication associated with the first set of pulses; and

determine ranging message timing such that at least a portion of a ranging message associated with the second set of pulses is transmitted before receipt of an entire ranging message associated with the first set of pulses.