Position location using phase-adjusted transmitters

• US 9,354,297 B2
• Filed: 01/05/2006
• Issued: 05/31/2016
• Est. Priority Date: 09/27/2005
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ling, Fuyun, Walker, Gordon Kent, Mukkavilli, Krishna Kiran
• Primary Examiner(s): Adams, Tashiana
• Assistant Examiner(s): Mull, Fred H
• Application Number:
  US11/326,868
• Publication Number:
  US 20070069952A1
• Time in Patent Office: 3,799 Days
• Field of Search: 342/387, 342463-464, 342/356, 342/458, 342/354
• US Class Current: 1/1
• CPC Class Codes: G01S 1/024 of beacon transmitters
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0226 Transmitters
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Systems and methods are provided for determining position location information in a wireless network. In one embodiment, timing offset information is communicated between multiple transmitters and one or more receivers. Such information enables accurate position or location determinations to be made that account for timing differences throughout the network. In another embodiment, transmitter phase adjustments are made that advance or delay transmissions from the transmitters to account for potential timing differences at receivers. In yet another embodiment, combinations of timing offset communications and/or transmitter phase adjustments can be employed in the wireless network to facilitate position location determinations.

Claims

1. A method of adjusting position information in a wireless network, comprising:

each transmitter of at least three transmitters determining a time difference between a future transmission time of the transmitter and a common clock in the wireless network;

regulating an effective channel delay spread, as perceived by at least one receiver, by advancing or delaying transmission timing of the future transmission of at least one transmitter of the at least three transmitters relative to the common clock;

each transmitter of the at least three transmitters cyclically shifting a signal based on the determined time difference, wherein the signal is cyclically shifted according to a cyclic convolution; and

each of the at least three transmitters transmitting the cyclically shifted signal to the at least one receiver at the transmission time, wherein a position of the at least one receiver is determined based at least on a linear convolution of a channel with the transmitted cyclically shifted signal, from the at least three transmitters, that is processed as the cyclic convolution based on the delay spread of the channel being less than a cyclic prefix employed by the signal.

2. The method of claim 1, further comprising generating at least two timing offsets denoted as d_a and d_b.

3. The method of claim 2, further comprising determining a first parameter τ

′

_a that is an actual delay is perceived by a line of sight propagation component based on a distance between a first transmitter A and the receiver, and determining a second parameter τ

′

_b that is an actual delay that is perceived by a line of sight component from a second transmitter B to the receiver.

4. The method of claim 3, further comprising processing additional delays d_a and d_b at the first and second transmitters based on a delay spread τ

′

_b-τ

′

_a exceeding a cyclic prefix.

5. The method of claim 4, further comprising processing the following equation:

y(n)=h_a(n)*x_a(n−

d_a)+h_b(n)*x_b(n−

d_b)+w(n),

where y(n) represents a signal received at the receiver, h_a(n) and x_a(n) are a channel and a signal with respect to the first transmitter A, * represents a linear convolution operation, w(n) is noise added at the receiver.

6. The method of claim 5, further comprising processing the following equation:

y(n)=h_a(n−

d_a)*x(n)+h_b(n−

d_b)*x(n)+w(n),

where a perceived channel delay spread is given by (τ

′

_b−

d_b)−

(τ

′

_a−

d_a) and controlled by introducing timing offsets at the first transmitter A.

7. The method of claim 5, further comprising determine a cyclic convolution when an effective delay spread is less than a cyclic prefix as in the following equations:

y(n)=h_a(n){circle around (×

)}x_a(n−

d_a)+h_b(n){circle around (×

)}x_b(n−

d_b)+w(n),

or

y(n)=h_a(n−

d_a){circle around (×

)}x_a(n)+h_b(n−

d_b){circle around (×

)}x_b(n)+w(n)

where {circle around (×

)} denotes circular convolution.

8. The method of claim 7, further comprising delaying transmissions from the transmitters thereby meeting length requirements of cyclic prefix.

9. The method of claim 7, further comprising employing a long cyclic prefix to enable an estimation of delay from weak transmitters that are far away.

10. The method of claim 9, further comprising undoing an effect of physical delays by a cyclic shift of a positioning signal, where x_a/p (n) is an intended positioning signal from the first transmitter A with timing delay d_a, and at least one of the transmitters sends a cyclically shifted version given by x_a/p (n+d_a).

11. The method of claim 10, further comprising processing the following equation:

y(n)=h_a(n){circle around (×

)}x_a,p(n)+h_b(n){circle around (×

)}x_b,p(n)+w(n).

12. The method of claim 1, wherein timing information is available offline.

13. The method of claim 12, wherein pseudo ranges are measured.

14. The method of claim 13, further comprising receiving the pseudo ranges.

15. The method of claim 1, wherein a transmission comprises at least one of a frame field, a pilot field, an overhead information field, a wide area field, and a local area field.

16. The method of claim 15, wherein the transmission further comprising an error correction field.

17. The method of claim 1, wherein the cyclically shifting the signals comprises employing a cyclic shift of an Orthogonal Frequency Division Multiplexing (OFDM) symbol carrying the signal to form a shifted OFDM symbol.

18. The method of claim 17, further comprising forming a cyclic prefix of the OFDM symbol based on the shifted OFDM symbol.

19. The method of claim 17, wherein the OFDM symbol comprises an OFDM symbol carrying pilot positioning signals.

20. The method of claim 1, wherein the cyclically shifted signals comprise fixed timing offset information.

22. The method of claim 1, wherein a clock of at least one of the at least three transmitters is synchronized to a frame boundary of the transmitted cyclically shifted signal.

23. The method of claim 1, further comprising employing triangulation techniques to determine the position for the at least one receiver.

24. The method of claim 1, further comprising determining at least one parameter.

25. The method of claim 1, further comprising decoding a data stream.

26. The method of claim 1, further comprising computing a linear convolution of a channel estimate with the transmitted cyclically shifted signal.

21. The method of claim I, wherein the common clock is synchronized to a signal from a Global Positioning System.

27. A machine readable non-transitory non-volatile storage medium having machine executable instructions stored thereon, which when executed by one or more processor results in performing the steps of:

each transmitter of at least three transmitters determining a time difference between a future transmission time of the transmitter and a common clock in a wireless network;

regulating an effective channel delay spread, as perceived by at least one receiver, by advancing or delaying transmission timing of the future transmission of at least one transmitter of the at least three transmitters relative to the common clock;

each transmitter of the at least three transmitters cyclically shifting a signal based on the determined time difference, wherein the signal is cyclically shifted according to a cyclic convolution; and

each of the at least three transmitters transmitting the cyclically shifted signal to the at least one receiver at the transmission time, wherein a position of the at least one receiver is determined based at least on a linear convolution of a channel with the transmitted cyclically shifted signal, from the at least three transmitters, that is processed as the cyclic convolution based on the delay spread of the channel being less than a cyclic prefix employed by the signal.

28. The machine readable storage medium of claim 27, having machine executable instructions stored thereon, which when executed further perform the steps of:

employing triangulation techniques with the at least three transmitters to determine location.

29. The machine readable storage medium of claim 27, having machine executable instructions stored thereon, which when executed further perform the steps of:

determining at least one parameter.

30. The machine readable storage medium of claim 27, having machine executable instructions stored thereon, which when executed further perform the steps of:

generating at least two timing offsets denoted as d_a and d_b.

31. The machine readable storage medium of claim 30, having machine executable instructions stored thereon, which when executed further perform the steps of determining a first parameter τ

′

_a that is an actual delay perceived by a line of sight propagation component based on a distance between a first transmitter A and a receiver, and determining a second parameter τ

′

_b that is an actual delay that is perceived by a line of sight component from a second transmitter B to the receiver.

32. The machine readable storage medium of claim 31, having machine executable instructions stored thereon, which when executed further performs the steps of processing additional delays d_a and d_b at the first and second transmitters when a delay spread τ

′

_b-τ

′

_a exceeds a cyclic prefix.

33. The machine readable storage medium of claim 32, having machine executable instructions stored thereon, which when executed further perform the steps of processing the following equation:

y(n)=h_a(n)*x_a(n−

d_a)+h_b(n)*x_b(n−

d_b)+w(n),

where y(n) represents a signal received at the receiver, h_a(n) and X_a(n) are a channel and a signal with respect to the first transmitter A, * represents a linear convolution operation, w(n) is noise added at the receiver.

34. The machine readable storage medium of claim 33, having machine executable instructions stored thereon, which when executed further perform the steps of processing the following equation:

y(n)=h_a(n−

d_a)*x(n)+h_b(n−

d_b)*x(n)+w(n),

where a perceived channel delay spread is given by (τ

′

_b−

d_b)−

(τ

′

_a−

d_a) and controlled by introducing timing offsets at the first transmitter A.

35. The machine readable storage medium of claim 33, having machine executable instructions stored thereon, which when executed further perform the steps of determining the cyclic convolution when an effective delay spread is less than a cyclic prefix as in the following equations:

y(n)=h_a(n){circle around (×

)}x_a(n−

d_a)+h_b(n){circle around (×

)}x_b(n−

d_b)+w(n),

or

y(n)=h_a(n−

d_a){circle around (×

)}x_a(n)+h_b(n−

d_b){circle around (×

)}x_b(n)+w(n)

where {circle around (×

)} denotes circular convolution.

36. The machine readable storage medium of claim 35, having machine executable instructions stored thereon, which when executed further perform the steps of delaying transmissions from one or more of the transmitters to meet length requirement of cyclic prefix.

37. The machine readable storage medium of claim 35, having machine executable instructions stored thereon, which when executed further perform the steps of employing a long cyclic prefix to enable an estimation of delay from weak transmitters that are far away.

38. The machine readable storage medium of claim 37, having machine executable instructions stored thereon, which when executed further perform the steps of undoing an effect of physical delays by a cyclic shift of a positioning signal, where x_a/p (n) is an intended positioning signal from the first transmitter A with timing delay d_a, and the transmitter A sends a cyclically shifted version given by x_a/p (n+d_a).

39. The machine readable storage medium of claim 38, having machine executable instructions stored thereon, which when executed further performs the steps of processing the following equation

y(n)=h_a(n){circle around (×

)}x_a,p(n)+h_b(n){circle around (×

)}x_b,p(n)+w(n).

40. The machine readable storage medium of claim 27, wherein the cyclically shifted signal comprises fixed timing offset information.

41. The machine readable storage medium of claim 27, wherein the common clock is a clock synchronized to a signal from a Global Positioning System.

42. The machine readable storage medium of claim 27, wherein a clock of at least one transmitter of the at least three transmitters is synchronized to a frame boundary of the transmitted cyclically shifted signal.

43. The machine readable storage medium of claim 27, having machine executable instructions stored thereon, which when executed further perform the steps of decoding a data stream.

44. A system in a wireless network, comprising:

processors, at least one processor in each transmitter of at least three transmitters, that determine a time difference between a future transmission time of the transmitter and a common clock in the wireless network,

wherein at least one processor of at least one of the transmitters regulate an effective channel delay spread, as perceived by at least one receiver, by advancing or delaying transmission timing of the future transmission of at least one transmitter of the at least three transmitters relative to the common clock,

wherein the processors of the at least three transmitters further regulate, each transmitter of the at least three transmitters, cyclically shifting a signal based on the determined time difference, wherein the signal is cyclically shifted according to a cyclic convolution; and

means for, each of the at least three transmitters, transmitting the cyclically shifted signal to the at least one receiver at the transmission time, wherein a position of the at least one receiver is determined based at least on a linear convolution of a channel with the transmitted cyclically shifted signal, from the at least three transmitters, that is processed as the cyclic convolution based on the delay spread of the channel being less than a cyclic prefix employed by the signal.

45. The system of claim 44, further comprising means for generating at least two timing offsets denoted as d_a and d_b.

46. The system of claim 45, further comprising means for determining a first parameter τ

′

_a that is an actual delay perceived by a line of sight propagation component based on a distance between a first transmitter A and the at least one receiver, and determining a second parameter τ

′

_b that is an actual delay that is perceived by a line of sight component from a second transmitter B to the at least one receiver.

47. The system of claim 46, further comprising means for processing additional delays d_a and d_b at the first and second transmitters based on a delay spread τ

′

_b-τ

′

_a exceeding a cyclic prefix.

48. The system of claim 47, further comprising means for processing the following equation:

y(n)=h_a(n)*x_a(n−

d_a)+h_b(n)*x_b(n−

d_b)+w(n),

where y(n) represents a signal received at the receiver, h_a(n) and X_a(n) are a channel and a signal with respect to the first transmitter A, * represents a linear convolution operation, w(n) is noise added at the receiver.

49. The system of claim 48, further comprising means for processing the following equation:

y(n)=h_a(n−

d_a)*x(n)+h_b(n−

d_b)*x(n)+w(n),

where a perceived channel delay spread is given by (τ

′

_b−

d_b)−

(τ

′

_a−

d_a) and controlled by introducing timing offsets at the first transmitter A.

50. The system of claim 48, further comprising means for determining a cyclic convolution based on an effective delay spread being less than a cyclic prefix as in the following equations:

y(n)=h_a(n){circle around (×

)}x_a(n−

d_a)+h_b(n){circle around (×

)}x_b(n−

d_b)+w(n),

or

y(n)=h_a(n−

d_a){circle around (×

)}x_a(n)+h_b(n−

d_b){circle around (×

)}x_b(n)+w(n)

where {circle around (×

)} denotes circular convolution.

51. The system of claim 50, further comprising means for delaying transmissions from the transmitters thereby meeting length requirements of cyclic prefix.

52. The system of claim 50, further comprising means for employing a long cyclic prefix to enable an estimation of delay from weak transmitters that are far away.

53. The system of claim 52, further comprising means for undoing an effect of physical delays by a cyclic shift of a positioning signal, where x_a/p (n) is an intended positioning signal from the transmitter A with timing delay d_a, and the transmitter A sends a cyclically shifted version given by x_a/p (n+d_a).

54. The system of claim 53, further comprising means for processing the following equation:

y(n)=h_a(n){circle around (×

)}x_a,p(n)+h_b(n){circle around (×

)}x_b,p(n)+w(n).

55. The system of claim 45, wherein timing information is available offline.

56. The system of claim 55, wherein pseudo ranges are measured.

57. The system of claim 56, further comprising means for receiving the pseudo ranges.