Position location using phase-adjusted transmitters

• US 20070069952A1
• Filed: 01/05/2006
• Published: 03/29/2007
• Est. Priority Date: 09/27/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ling, Fuyun, Walker, Gordon, Mukkavilli, Krishna
• Granted Patent: US 9,354,297 B2
• Time in Patent Office: Days
• US Class Current: 342/463
• 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 to adjust position information in a wireless network, comprising:

determining time difference information between a common clock and at least one other clock;

adjusting the phase of at least one transmitter clock in view of the time difference information; and

determining a position for at least one receiver based in part on the adjusted phase of the transmitter clock.

2. The method of claim 1, further comprising generating a signal from at least two transmitters that is advanced or delayed to account for timing differences in a wireless network.

3. The method of claim 1, further comprising advancing or delaying transmitter timing in a Forward Link Only network to regulate an effective channel delay spread as perceived by the receiver.

4. The method of claim 3, further comprising performing a linear convolution of a channel with a transmitted signal that is processed as a cyclic convolution if the delay spread of the channel is less than a cyclic prefix employed by an Orthogonal Frequency Division Multiplexing (OFDM) signal.

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

6. The method of claim 5, 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.

7. The method of claim 6, further comprising 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.

8. The method of claim 7, 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 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.

9. The method of claim 8, 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 transmitter.

10. The method of claim 8, 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)}x_a(n−

d_a)+h_b(n){circle around (x)}x_b(n−

d_b)+w(n),
or
y(n)=h_a(n−

d_a){circle around (x)}x_a(n)+h_b(n−

d_b){circle around (x)}x_b(n)+w(n)

where {circle around (x)} denotes circular convolution.

11. The method of claim 10, further comprising delaying transmissions from transmitters to meet cyclic prefix requirements.

12. The method of claim 10 further comprising employing a long cyclic prefix to enable an estimation of delay from weak transmitters that are far away.

13. The method of claim 12, further comprising undoing an effect of physical delays by a cyclic shift of the positioning signal, where x_a,p(n) is an intended positioning signal from the transmitter A with timing delay d_a, and a transmitter sends a cyclically shifted version given by x_a,p(n+d_a).

15. The method of claim 1, further comprising determining transmitter timing adjustments from an offline network source.

16. The method of claim 15, further comprising measuring pseudo ranges for the transmitter timing.

17. The method of claim 16, further comprising relaying the pseudo ranges to a network almanac.

14. The method of claim 14, further comprising processing the following equation

y(n)=h_a(n){circle around (x)}x_a,p(n)+h_b(n){circle around (x)}x_b,p(n)+w(n),

to mitigate sending transmitter delay information to a receiver.

18. A system to adjust position information in a wireless network, comprising:

means for determining timing differences between at least two transmitters and at least one receiver in a wireless network; and

means for adjusting the transmitters according to a signal phase or a signal frequency in view of the timing differences.

19. The system of claim 18, further comprising means for determining a position at the receiver in view of the adjusted signal phase or signal frequency.

20. A machine readable medium having machine executable instructions stored thereon, comprising:

determining timing differences between a common clock with respect to a subset of transmitter clocks; and

adjusting a phase or a frequency of at least one transmitter clock in view of the determined timing differences.

21. The machine readable medium of claim 20, further comprising determining a location for at least one receiver based on the adjusted phase or frequency of the transmitter.

22. The machine readable medium of claim 20, further comprising employing triangulation techniques with the subset of transmitter clocks to determine the location.

23. The machine readable medium of claim 20, further comprising determining at least one Forward Link Only parameter.

24. The machine readable medium of claim 20, further comprising a layer component having at least one of a physical layer, a stream layer, a medium access layer, and an upper layer.

25. The machine readable medium of claim 24, the physical layer further comprising at least one of a frame field, a pilot field, an overhead information field, a wide area field, and a local area field.

26. The machine readable medium of claim 25, further comprising an error correction field.

27. A wireless communications apparatus, comprising:

a memory that includes a component to determine an adjusted time base between receivers and transmitters over a wireless network; and

a processor that adjusts a signal phase or a frequency in order to determine a location for at least one wireless apparatus.

28. The apparatus of claim 27, further comprising a component to determine a location for the wireless apparatus.

29. The apparatus of claim 27, further comprising one or more components to decode a Forward Link Only data stream.

30. An apparatus for operating base station resources in a wireless network, comprising:

means for determining timing differences for a subset of transmitters and at least one receiver;

means for adjusting the time differences via a signal at the subset of transmitters; and

means for determining a position for the receiver from the signal.

31. The apparatus of claim 30, further comprising means generating the signal from at least two transmitters of the subset that are advanced or delayed to account for timing differences in a wireless network.

32. The apparatus of claim 31, further comprising means for computing a linear convolution of a channel with a transmitted signal.