Methods and apparatus for improving accuracy of radio timing measurements

• US 20040087269A1
• Filed: 06/13/2003
• Published: 05/06/2004
• Est. Priority Date: 10/31/2002
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Edge, Stephen William, Manohar, Bollapragada V.J.
• Granted Patent: US 7,359,711 B2
• Time in Patent Office: Days
• US Class Current: 455/11.1
• CPC Class Codes: H04B 7/2678 Time synchronisation
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 56/001 Synchronization between nodes

Abstract

A system, method, apparatus, means, and computer program code for improving accuracy of radio timing measurements. According to some embodiments, a wireless terminal or other wireless device can make adjustments to a measurement made from a radio transmission source by adjusting timing measurements using a weighted average and/or synchronizing its timing to the timing of this or some other radio transmission source. The adjusted measurements can be obtained for times other than when the original measurements are made. Measurements for multiple radio transmission sources can then be adjusted to a common time wherein adjustment errors due to unknown timing drift in the radio sources and wireless terminal and Doppler errors due to unknown relative velocities can be reduced or eliminated.

Claims

1. A method for improving the accuracy of a timing measurement made by a terminal, comprising:

making a plurality of sequential radio timing measurements of a first radio transmission source, said first radio transmission source having a timing reference;

determining a timing drift difference between said first radio transmission source and said terminal based, at least in part, on said plurality of sequential radio timing measurements; and

determining an adjustment to a radio timing reference in said terminal based, at least in part, on said timing drift difference.

2. The method of claim 1, wherein said determining an adjustment to a radio timing reference in said terminal includes:

determining a first instant in time according to said timing reference in said terminal;

determining a second instant in time according to said timing reference in said terminal;

determining a first interval of time between said first instant in time and said second instant in time; and

determining a second interval of time between said first instant in time and said second instant in time based, at least in part, on said first interval of time and said timing drift difference between said first radio transmission source and said terminal.

3. The method of claim 2, further comprising:

making a first measurement of radio timing information for a second radio transmission source at said first instant in time; and

determining a second measurement of radio timing information for said second radio transmission source at said second instant in time based, at least in part, on said first measurement and said second interval of time.

4. The method of claim 2, further comprising:

making a third measurement of radio timing information for a second radio transmission source at a third instant in time according to said timing reference for said terminal;

determining a third interval of time between said third instant in time and said second instant in time;

determining a fourth interval of time between said third instant in time and said second instant in time based, at least in part, on said third interval of time and said timing drift difference between said first radio transmission source and said terminal;

determining a fourth measurement of radio timing information for said second radio transmission source at said second instant in time based, at least in part, on said third measurement and said fourth interval of time; and

determining an averaged measurement of radio timing for said second radio transmission source at said second instant in time based, at least in part, on said second and said fourth measurements of radio timing information for said second radio transmission source.

5. The method of claim 1, further comprising:

adjusting said timing reference in said terminal based, at least in part, on said adjustment.

6. The method of claim 1, further comprising:

providing data indicative of said adjustment.

7. The method of claim 1, wherein said making a plurality of sequential timing measurements of said first radio transmission source, said first radio transmission source having a timing reference, includes:

determining sequential radio timing measurements T^s₁, T^s₂, . . . T^s_m (m>

1) for said first radio transmission source.

8. The method of claim 7, wherein said determining a timing drift difference between said first radio transmission source and said terminal based, at least in part, on said plurality of sequential timing measurements, includes:

determining timing references T*₁, T*₂, . . . T*_m for said terminal, wherein T*₁, T*₂, . . . T*_m correspond to said sequential radio timing measurements T^s₁, T^s₂, . . . T^s_m, respectively; and

determining Δ

d_m, wherein Δ

d_m is said timing drift difference obtained, at least in part, from said timing references T*₁, T*₂, . . . T*_m for said terminal and said radio timing measurements T^s₁, T^s₂, . . . T^s_m, for said first radio transmission source.

9. The method of claim 8, wherein said determining said Δ

d_m includes;

determining a weight w with 0<

w<

1;

assigning Δ

d₁=0;

assigning Δ

T^s_i=T^s_i−

T^s<sub>i−

1</sub> and Δ

T*_i=T*_i−

T*<sub>i−

1</sub> (1<

i≦

m) and;

determining Δ

d_i from Δ

d<sub>i−

1</sub> according to Δ

d_i=wΔ

<sub>i−

1</sub>+(1−

w)(Δ

T^s_i−

Δ

T*_i)/Δ

T*_i for each value of i ranging from i=2 to i=m.

10. The method of claim 7, wherein T1* and T2* are, respectively, said first and second instants in time according to said timing reference of said terminal;

Δ

T* and Δ

T** are, respectively, said first and said second intervals of time; and

wherein;

each of said radio timing measurements T^s₁, T^s₂, . . . T^s_m (m>

1) occurred prior to T2*;

Δ

T*=T2*−

T1*; and

Δ

T**=Δ

T*+Δ

d_m Δ

T*.

11. The method of claim 1, wherein said timing reference of said first radio transmission source is more accurate than said timing reference in said terminal.

12. A method for improving the accuracy of a radio timing measurement made by a terminal, comprising:

making a first radio timing measurement for a radio transmission source at a time T*_x according to a timing reference in said terminal;

making a second radio timing measurement for said radio transmission source at a time T*_y according to a timing reference in said terminal;

determining a third radio timing measurement for said radio transmission source at a time T* according to a timing reference in said terminal based, at least in part, on said first radio timing measurement;

determining a fourth radio timing measurement for said radio transmission source at said time T* based, at least in part, on said second radio timing measurement; and

determining a fifth radio timing measurement for said radio transmission source at said time T* based, at least in part, on said third radio timing measurement and said fourth radio timing measurement.

13. The method of claim 12, wherein said time T*_x and said time T*_y occur after said time T*.

14. The method of claim 12, wherein said time T*_x and said time T*_y occur before said time T*.

15. The method of claim 12, wherein said time T* occurs after said time T*_x and before said time T*_y.

16. The method of claim 12, wherein said determining a fifth radio timing measurement for said radio transmission source at said time T* includes determining a weighted average radio timing measurement.

17. The method of claim 12, further comprising:

making radio timing measurements for said radio transmission source at 2M (M>

1) sequential times T*₁, T*₂, . . . , T*_2M according to a timing source in said terminal, wherein said making said first and second radio timing measurements for said radio transmission source at said respective times T*_x and T*_y is part of said making timing measurements for said radio transmission source at said 2M sequential times T*₁, T*₂, . . . , T*₂M.

18. The method of claim 17, further comprising,

determining a radio timing measurement for said radio transmission source at said time T* for each of said 2M timing measurements for said radio transmission source at said 2M sequential times.

19. The method of claim 18, further comprising:

determining a sixth radio timing measurement for said radio transmission source at said time T* based, at least in part, on said 2M radio timing measurements for said radio transmission source at said time T* determined from each of said 2M sequential radio timing measurements at times T*₁, T*₂, . . . , T*_2M.

20. The method of claim 19, wherein said determining a sixth radio timing measurement employs a weighted average of said 2M radio timing measurements for said radio transmission source at said time T* where the weight for any radio timing measurement at said time T* determined from a radio timing measurement at time T*_i, (1≦

i≦

2M) is δ

_i/|T*−

T*_i| where δ

_i=+1 or δ

_i=−

1.

21. The method of claim 20, wherein T* exceeds each of the time values T*_i, T*₂, . . . , T*_m and is less than each of the time values T*_m+1, T*_m+2, . . . , T*_2M where 0≦

m≦

2M and δ

_i(1≦

i≦

2M) is chosen so that;

δ

_i=+1 except as follows;

if m<

M;

δ

_i=−

1 for any (M−

m) indices i in the range (m+1, m+2, . . . 2M) that give Σ

(i=1 to i=2M)δ

_i/|T*_i−

T*|≠

0;

if m>

M;

δ

_i=−

1 for any (m−

M) indices i in the range (1, 2, . . . m) that give Σ

(i=1 to i=2M)δ

_i/|T*_i−

T*|≠

0;

if m=M;

all the values δ

_i are +1.

22. The method of claim 12, further comprising:

determining a timing drift difference between said terminal and a second radio transmission source based, at least in part, on a radio timing measurement for said second radio transmission source at a time T1 and a radio timing measurement for said second radio transmission source at a time T2; and

determining an adjustment to said timing reference in said terminal based, at least in part, on said timing drift difference.

23. An apparatus for improving the accuracy of radio timing measurement information for a terminal, comprising:

a memory;

a communication port; and

a processor connected to said memory and said communication port, said processor being operative to;

make a plurality of sequential radio timing measurements of a first radio transmission source, said first radio transmission source having a timing reference;

determine a timing drift difference between said first radio transmission source and the terminal based, at least in part, on said plurality of sequential radio timing measurements; and

determine an adjustment to a timing reference in the terminal based, at least in part, on said timing drift difference.

24. A computer program product in a computer readable medium for improving the accuracy of a radio timing measurement for a terminal, comprising:

first instructions for making a plurality of sequential radio timing measurements of a first radio transmission source, said first radio transmission source having a timing reference;

second instructions for determining a timing drift difference between said first radio transmission source and the terminal based, at least in part, on said plurality of sequential radio timing measurements; and

third instructions for determining an adjustment to a timing reference in the terminal based, at least in part, on said timing drift difference.

25. An apparatus for improving the accuracy of radio timing measurement information for a terminal, comprising:

a memory;

a communication port; and

a processor connected to said memory and said communication port, said processor being operative to;

make a first radio timing measurement for a radio transmission source at a time T_x according to a timing reference in the terminal;

make a second radio timing measurement for said radio transmission source at a time T*_y according to a timing reference in the terminal;

determine a radio third timing measurement for said radio transmission source at a time T* according to a timing reference in the terminal based, at least in part, on said first radio timing measurement;

determine a fourth radio timing measurement for said radio transmission source at said time T* based, at least in part, on said second radio timing measurement; and

determine a fifth timing measurement for said radio transmission source at said time T* based, at least in part, on said third radio timing measurement and said fourth radio timing measurement.

26. A computer program product in a computer readable medium for improving the accuracy of a radio timing measurement for a terminal, comprising:

first instructions for making a first radio timing measurement for a radio transmission source at a time T*_x according to a timing reference in the terminal;

second instructions for making a second radio timing measurement for said radio transmission source at a time T*_y according to a timing reference in the terminal;

third instructions for determining a third radio timing measurement for said radio transmission source at a time T* according to a timing reference in the terminal based, at least in part, on said first radio timing measurement;

fourth instructions for determining a fourth radio timing measurement for said radio transmission source at said time T* based, at least in part, on said second radio timing measurement; and

fifth instructions for determining a fifth radio timing measurement for said radio transmission source at said time T* based, at least in part, on said third radio timing measurement and said fourth radio timing measurement.