Method and system for improving time of arrival (TOA) measurements in a wirless communication network

• US 20070121679A1
• Filed: 11/30/2005
• Published: 05/31/2007
• Est. Priority Date: 11/30/2005
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Strutt, Guenael
• Granted Patent: US 7,653,004 B2
• Time in Patent Office: Days
• US Class Current: 370/516
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging

Abstract

A technique for improving the capability of measuring the distance between nodes of a wireless communication network is provided. Technique (800) includes receiving a measured signal, correlating the measured signal with a reference signal to output a measured correlated function, comparing the correlation function to a predetermined reference correlation function, the reference correlation function being based on a predetermined direct path sequence and an estimation of the phase delay of the measured correlated function. A score is assigned to the measured correlation function based on how close the measured correlation function resembles the predetermined reference correlation function. Technique (800) provides improved location accuracy, even in multipath environments, by indicating the quality of the TOA measurement and enabling the selection of a correction mechanism.

Claims

1. A method of estimating time of arrival (TOA) in an ad-hoc communications network, comprising the steps of:

sending a ranging message from a first node to a second node;

receiving a signal at the second node;

measuring the TOA of the received signal;

correlating the received signal with a reference signal to obtain a measured correlation function;

estimating a phase delay of the received signal utilizing the measured correlation function;

constructing a reference correlation function based on the amplitude and the phase delay of the measured correlation function; and

calculating a score based on similarities between the reference correlation function and the measured correlation function.

2. The method of claim 1, further comprising the steps of:

comparing the calculated score to a predetermined threshold; and

if the score is greater than the predetermined score threshold, then;

correcting the measured TOA according to the estimated phase delay;

if the score does not meet the predetermined score threshold, then;

assuming that the received signal contains multipath.

3. The method of claim 1, wherein the reference correlation function is determined empirically.

4. The method of claim 1, wherein the reference correlation function is determined analytically.

5. The method of claim 1, wherein the calculated score is used as an estimation of signal quality in a communication channel.

6. The method of claim 1, wherein the calculated score is proportional to the inverted sum of the difference between the reference correlation function and the measured correlation function.

7. The method of claim 6, further comprising the step of biasing an error by taking the difference between the reference correlation function and the measured correlation function and multiplying the difference by a power of the amplitude of the highest reference correlation function and the measured correlation function.

8. A method for improving the capability of measuring the distance between nodes of a wireless communication network, comprising the steps of:

receiving a signal at a node;

measuring TOA of the received signal;

correlating the received signal with a reference signal to output a measured correlation function;

comparing the measured correlation function to a reference correlation function, the reference correlation function being based on a predetermined direct path sequence and an estimation of the phase delay of the measured correlated function;

assigning a score to the measured correlation function based on how close the measured correlation function resembles the reference correlation function;

indicating the quality of the TOA measurement based on the assigned score; and

enabling the selection of a correction mechanism for the measured received signal based on the quality.

9. An ad-hoc communication network, comprising a plurality of nodes, at least one operating as a ranger node and another operating as a pinger node, the ranger node using time of arrival (TOA) measurements to generate a measured correlation function, wherein based on estimated phase delay of the measured correlation function, a reference correlation function is constructed and compared to the measured correlation function, and a score is assigned to the measured correlation function in order to provide an indication of direct path and multipath so that a direct path can be used make accurate TOA measurements.

10. The system of claim 9, wherein peaks are analyzed in each TOA measurement and the score represents the likelihood of a peak within the TOA measurement being a single path.