METHODS AND APPARATUS FOR IMPROVING TIME OF ARRIVAL DETERMINATION

1 . A method for determining location information associated with a receiver, the method comprising:

receiving information related to at least one of a direct path signal component and one or more multipath signal components associated with a positioning signal received by a receiver from a transmitter; and

determining a distance between the transmitter and the receiver using a first approach, a second approach, or a third approach,

wherein when the first approach is used, the method comprises:

determining a set of times of arrival corresponding to the at least one of the direct path signal component and the one or more multipath signal components;

selecting a time of arrival from the set;

determining a value of a quality metric based on information associated with the selected time of arrival;

determining whether the value corresponding to the selected time of arrival meets a threshold condition;

upon determining that the value meets the threshold condition, determining a distance between the transmitter and receiver using the selected time of arrival; and

upon determining that the value does not meet the threshold condition, determining the distance between the transmitter and receiver using another selected time of arrival corresponding to another value of the quality metric that meets the threshold condition, and

wherein when the second approach is used, the method comprises:

determining an estimated covariance of the positioning signal;

determining a set of eigenvalues of the estimated covariance;

estimating a statistical distribution of the eigenvalues;

separating, based on a threshold determined at least in part from the estimated statistical distribution, the set of eigenvalues into a first subset of eigenvalues corresponding to the at least one of the direct path signal component and the one or more multipath signal components, and a second set of eigenvalues corresponding to noise; and

determining, based at least in part on the separation of the eigenvalues into the two sets, the distance between the transmitter and the receiver, and

wherein when the third approach is used, the method comprises:

determining a statistic of the positioning signal;

determining, if the statistic is within a first range, a first estimated time of arrival of the direct path signal component or one of the one or more multipath signal components using a first method;

determining, if the statistic is within a second range, a second estimated time of arrival of the direct path signal component or one of the one or more multipath signal components using a second method; and

determining, based at least in part on the first or second estimated time of arrival, the distance between the transmitter and the receiver.

2 . The method of claim 1 , wherein the distance is determined using the first approach, and wherein the quality metric is a function of the time of arrival difference between that selected time of arrival and an estimate of the time of arrival of the positioning signal based at least in part upon the location of a time domain cross-correlation peak.

3 . The method of claim 1 , wherein the distance is determined using the first approach, and wherein the method uses a Likelihood MUSIC algorithm to determine a set of early arrival peaks from the pseudo-spectrum.

4 . The method of claim 1 , wherein the distance is determined using the first approach, and wherein the quality metric is determined based on whether a time domain cross-correlation peak associated with the selected time of arrival falls within a signal power versus delay mask, relative to the location and power of the strongest time domain cross-correlation peak.

5 . The method of claim 1 , wherein the distance is determined using the first approach, and wherein the quality metric comprises a measure of the strength of a signal associated with the selected time of arrival relative to a measure of noise.

6 . The method of claim 1 , wherein the distance is determined using the second approach, and wherein one eigenvalue, within the first subset of eigenvalues, and the corresponding eigenvector are associated with the direct path signal component.

7 . The method of claim 1 , wherein the distance is determined using the second approach, and wherein the distance is determined based on a time of arrival of the direct path signal component.

8 . The method of claim 1 , wherein the distance is determined using the second approach, and wherein the method determines an estimated location of the receiver, wherein the estimated location of the receiver is determined based on the distance associated with the transmitter and additional distances associated with two or more additional transmitters.

9 . The method of claim 1 , wherein the distance is determined using the third approach, and wherein one of the first and second methods uses an information theoretic criterion for estimating a number of eigenvalues associated with a positioning signal subspace of the estimated covariance.

10 . The method of claim 1 , wherein the distance is determined using the third approach, and wherein the method determines an estimated covariance of the positioning signal, and wherein one of the first and second methods uses a statistic of the estimated covariance to estimate a number of eigenvalues in a positioning signal subspace of the estimated covariance.

11 . The method of claim 1 , wherein the distance is determined using the third approach, and wherein the statistic is a measure of a signal-to-noise ratio of the positioning signal.

12 . The method of claim 1 , wherein the distance is determined using the first approach, and wherein the method comprises:

receiving information related to at least one of another direct path signal component and one or more other multipath signal components associated with another positioning signal received by the receiver from the transmitter;

determining a statistic of the other positioning signal;

determining, if the statistic is within a first range, a first estimated time of arrival of the other direct path signal component or one of the one or more other multipath signal components using a first method;

determining, if the statistic is within a second range, a second estimated time of arrival of the other direct path signal component or one of the one or more other multipath signal components using a second method; and

determining, based at least in part on the first or second estimated time of arrival, another distance estimate between the receiver and the transmitter.

13 . The method of claim 12 , wherein one of the first and second methods uses an information theoretic criterion for estimating a number of eigenvalues associated with a positioning signal subspace of the estimated covariance.

14 . The method of claim 12 , wherein the method determines an estimated covariance of the positioning signal, and wherein one of the first and second methods uses a statistic of the estimated covariance to estimate a number of eigenvalues in a positioning signal subspace of the estimated covariance.

15 . The method of claim 12 , wherein the statistic is a measure of a signal-to-noise ratio of the positioning signal.

16 . The method of claim 1 , wherein the distance is determined using the first approach, and wherein the method comprises:

receiving information related to at least one of another direct path signal component and one or more other multipath signal components associated with another positioning signal transmitted from the transmitter;

determining an estimated covariance of the other positioning signal;

determining a set of eigenvalues of the estimated covariance;

estimating a statistical distribution of the eigenvalues;

separating, based on a threshold determined at least in part from the estimated statistical distribution, the set of eigenvalues into a first subset of eigenvalues corresponding to the at least one of the other direct path signal component and the one or more other multipath signal components, and a second set of eigenvalues corresponding to noise; and

determining, based at least in part on the separation of the eigenvalues into the two sets, another distance estimate between the receiver and the transmitter.

17 . The method of claim 16 , wherein one eigenvalue, within the first subset of eigenvalues, and the corresponding eigenvector are associated with the other direct path signal component, wherein the distance estimate is determined based on a time of arrival of the other direct path signal component.

18 . The method of claim 16 , wherein the method comprises:

determining an estimated location of the receiver, wherein the estimated location of the receiver is determined based on the other distance estimate and additional distance estimates associated with two or more additional transmitters.

19 . A system comprising one or more processors that perform the method of claim 1 .

20 . A non-transitory machine-readable medium embodying program instructions adapted to be executed to implement the method of claim 1 .