Method of and system for estimating a time of arrival of a radio signal

• US 6,675,018 B2
• Filed: 12/21/1999
• Issued: 01/06/2004
• Est. Priority Date: 01/09/1999
• Status: Expired due to Fees

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ludden, Brendan, Lopes, Luis, Villier, Eric
• Primary Examiner(s): Nguyen, Lee
• Assistant Examiner(s): TRAN, TUAN A
• Application Number:
  US09/468,998
• Publication Number:
  US 20030036390A1
• Time in Patent Office: 1,477 Days
• Field of Search: 455/456.1, 455/457, 455/10, 455/25, 455/225, 455/67.11, 455/67.16, 342/457
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/0215 Interference
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• 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

The invention relates to a method for estimating time of arrival of radio signals in particular as used for location determination. A known method of determining the location of a subscriber unit (401) calculates a number of ranges based on the distance from base stations (403,405,407) with known location. The ranges are calculated from time of arrival estimates of the signals from the different base stations but a significant source of error is the multipath signal components typical in for example cellular mobile communication systems. According to the invention, the effect of multipath is mitigated by selecting a subset of signals based on a time of arrival estimate of each of the signals. An averaged time of arrival estimate with improved accuracy is then determined from the selected subset. A typical use of the invention is for location determination in a cellular mobile communication system.

Claims

1. A method for estimating an average dine of arrival of a radio signal in a receiver, comprising:

receiving a plurality of radio signals at the receiver;

estimating a time of arrival for each of the plurality of radio signals received at the receiver;

selecting a subset of the plurality of the radio signals received at the receiver based on the time of arrival estimates;

generating an averaged propagation channel estimate from the subset of radio signals; and

estimating art averaged time of arrival from the averaged propagation channel estimate.

2. The method of claim 1, selecting the subset by selecting radio signals having an estimated time of arrival between a lower percentile and an upper percentile of the time of arrival estimates of the plurality of the radio signals received at the receiver.

3. The method of claim 2, varying at least one of the percentiles in response to at least one parameter of a group comprising:

a variance of the time of arrival estimates;

a signal to noise ratio of at least one of the plurality of signals;

a previous averaged propagation channel estimate;

a propagation channel estimate of at least one of the plurality of signals;

an accuracy of the averaged time of arrival estimate; and

available computational resource.

4. The method of claim 1, selecting the subset by selecting radio signals having time of arrival estimates closest to a time of arrival corresponding to a percentile of the time of arrival estimates of the plurality of the radio signals received at the receiver.

5. The method of claim 4, varying the number of the radio signals in the subset in response to a parameter of a group comprising:

a variance of the time of arrival estimates;

a signal to noise ratio of at least one of the plurality of signals;

a previous averaged propagation channel estimate;

a propagation channel estimate of at least one of the plurality of signals;

an accuracy of the averaged time of arrival estimate, and available computational resource.

6. The method of claim 5, generating an averaged propagation channel estimate from the subset of radio signals by weighting each of the radio signals of the subset based on a parameter chosen from a group comprising:

a signal to noise ratio of the signals;

an estimated propagation channel impulse response energy; and

multipath propagation characteristics for the radio signals.

7. The method of claim 1, generating a propagation channel estimate for each signal of the subset, and generating the averaged propagation channel estimate from the subset of radio signals by averaging the propagation channel estimates.

8. The method of claim 1, estimating a range between the receiver and a radio signal transmitter by estimating the average time of arrival.

9. The method of claim 8, estimating a plurality of ranges between the receiver and a corresponding plurality of radio signal transmitters, weighting each range estimate based on a distribution of time of arrival estimates of the plurality of signals.

10. The method of claim 1, determining a dominant source of error, selecting the subset of the plurality of the radio signals received at the receiver based on the dominant source of error.

11. A method in a mobile wireless communication device, comprising:

receiving a plurality of radio signals at the mobile wireless communication device;

estimating a time of arrival for each of the plurality of radio signals received at the mobile wireless communication device;

selecting a subset of the plurality of the radio signals received at the mobile wireless communication device based on the time of arrival estimates;

generating an averaged propagation channel estimate from the subset of radio signals; and

estimating an averaged time of arrival from the averaged propagation channel estimate.

12. The method of claim 11, selecting the subset by selecting radio signals having an estimated time of arrival between lower and upper percentiles of the time of arrival estimates.

13. The method of claim 11, selecting the subset by selecting radio signals having time of arrival estimates closest to a percentile of the time of arrival estimates.

14. The method of claim 11, generating a propagation channel estimate for each signal of the subset, generating the averaged propagation channel estimate from the subset of radio signals by averaging the propagation channel estimates.

15. The method of claim 11, estimating a range between the mobile wireless communication device and a radio signal transmitter by estimating the average time of arrival.

16. The method of claim 11, estimating a plurality of ranges between the mobile wireless communication device and a corresponding plurality of radio signal transmitters, weighting each range estimate in response a distribution of time of arrival estimates of the plurality of signals.

17. The method of claim 11, determining a dominant source of error, selecting the subset of the plurality of the radio signals received at the mobile wireless communication device in response to the dominant source of error.

18. A mobile wireless communication device, comprising:

a receiver;

processor coupled to the receiver,

the processor having means for means for estimating a time of arrival for each of a plurality of the radio signals received by the receiver,

the processor having means for selecting a subset of the plurality of the radio signals received by the receiver in response to the time of arrival estimates,

the processor having means for generating an averaged propagation channel estimate from the subset of radio signals, and

the processor having means for estimating an averaged time of arrival from the averaged propagation channel estimate.

19. The mobile wireless communication device of claim 18, the processor having means for estimating a range between the mobile wireless communication device and a radio signal transmitter by estimating the average time of arrival.

20. A method in a wireless communications device, comprising:

estimating a time of arrival for each of a plurality of radio signals received at the mobile wireless communication device;

selecting a subset of the plurality of the radio signals received at the mobile wireless communication device based on the time of arrival estimates;

generating an averaged propagation channel estimate from the subset of radio signals selected.

21. The method of claim 20, estimating an averaged time of arrival from the averaged propagation channel estimate.