Granted Patent B2

US 12,554,001 · App. 18/513,332 · Granted Feb 17, 2026

Inventors: Babak Azimi-Sadjadi (Redwood City, CA); David Burgess (Redwood City, CA); Philip A. Kratz (Redwood City, CA); Jonathan S. Lu (Redwood City, CA); Raquel Guerreiro Machado (Redwood City, CA); Srdjan Miocinovic (Redwood City, CA); Jedidiah J. Whelan (Redwood City, CA); Siamak Yousefi (Redwood City, CA)

Assignee: Zainar, Inc.

G01S13/08G01S7/0233G01S7/03G01S7/285

Abstract

Claims (163)

1 . A method comprising:

during a first time period:

accessing a first ranging signal transmitted from a transmitter and received by a receiver, the first ranging signal comprising:

a first set of multiplexed sub-signals, each multiplexed sub-signal in the first set of multiplexed sub-signals characterized by a frequency in a set of frequencies;

identifying a first set of sub-signal pairs in the first set of multiplexed sub-signals;

calculating a first set of phase differences of the first set of sub-signal pairs;

based on the first set of phase differences of the first set of sub-signal pairs, calculating a first phase-based time-of-arrival estimate;

recording a first series of time-domain samples representing the first ranging signal;

based on the first series of time-domain samples, calculating a first sample-based time-of-arrival estimate;

based on the first sample-based time-of-arrival estimate and the first phase-based time-of-arrival estimate, calculating a first hybrid time-of-arrival estimate; and

based on the first hybrid time-of-arrival estimate, calculating a first distance between the transmitter and the receiver.

2 . The method of claim 1 :

wherein calculating the first phase-based time-of-arrival estimate comprises:

prior to calculating the first sample-based time-of-arrival estimate, calculating the first phase-based time-of-arrival estimate; and

wherein calculating the first sample-based time-of-arrival estimate comprises:

detecting a set of multipath components characterizing the first ranging signal;

based on the set of multipath components, calculating a multipath metric characteristic of a power ratio between a line-of-sight component and non-line-of-sight components in the set of multipath components characteristic of the first ranging signal; and

in response to the multipath metric falling below a multipath threshold:

detecting strong multipath environment between/surrounding the transmitter and the receiver; and

calculating the first sample-based time-of-arrival estimate.

3 . The method of claim 2 :

further comprising:

during the first time period:

based on a sampling frequency associated with the receiver, calculating a first uncertainty of the first sample-based time-of-arrival estimate;

calculating an upper bound of a sample-based uncertainty interval by adding the first uncertainty to the first sample-based time-of-arrival estimate; and

calculating a lower bound of the sample-based uncertainty interval by subtracting the first uncertainty from the first sample-based time-of-arrival estimate; and

wherein calculating the first hybrid time-of-arrival estimate comprises:

in response to the first phase-based time-of-arrival estimate exceeding the lower bound and falling below the upper bound, setting the first phase-based time-of-arrival estimate as the first hybrid time-of-arrival estimate.

4 . The method of claim 3 , wherein calculating the first hybrid time-of-arrival estimate comprises:

in response to one of the first phase-based time-of-arrival estimates falling below the lower bound and the first phase-based time-of-arrival estimate exceeding the upper bound, setting the first sample-based time-of-arrival estimate as the first hybrid time-of-arrival estimate.

5 . The method of claim 1 :

further comprising:

during the first time period:

computing a correlation between the first ranging signal and a target ranging signal;

identifying a first time associated with a highest correlation peak of the correlation; and

based on the first time, deriving a sub-sample-based time-of-arrival estimate; and

wherein calculating the first hybrid time-of-arrival estimate comprises:

based on the sub-sample-based time-of-arrival estimate, the first sample-based time-of-arrival estimate, and the first phase-based time-of-arrival estimate, calculating the first hybrid time-of-arrival estimate.

6 . The method of claim 5 :

wherein computing the correlation between the first ranging signal and the target ranging signal comprises:

computing the correlation between the first ranging signal and a Zadoff-Chu sequence; and

wherein identifying the first time associated with the highest correlation peak of the correlation comprises:

identifying the first time associated with a Zadoff-Chu peak of the correlation.

7 . The method of claim 1 :

further comprising:

during the first time period:

concurrently:

executing L1-norm regularization to identify a sparse representation of the channel, the sparse representation excluding insignificant multipath components of the first ranging signal; and

based on the first phase-based time-of-arrival estimate, bounding a solution space of the L1-norm regularization; and

based on the sparse representation of the channel, calculating a time-of-arrival estimate for the line-of-sight component of the ranging signal; and

wherein calculating the first hybrid time-of-arrival estimate comprises:

based on the sparse multipath time-of-arrival estimate, the first sample-based time-of-arrival estimate, and the first phase-based time-of-arrival estimate, calculating the first hybrid time-of-arrival estimate.

8 . The method of claim 1 :

further comprising:

during the first time period:

based on a signal classification function, detecting a set of multipath components characteristic of the first ranging signal;

based on the set of multipath components characteristic of the first ranging signal, calculating a phase-amplitude-based time-of-arrival estimate; and

based on the set of multipath components, calculating a multipath metric representing a Rician K-factor of a power ratio between a first arriving component and subsequent components in the set of multipath components characteristic of the first ranging signal; and

wherein calculating the first hybrid time-of-arrival estimate comprises:

based on the multipath metric, the first sample-based time-of-arrival estimate, the first phase-based time-of-arrival estimate, and the phase-amplitude-based time-of-arrival estimate, calculating the first hybrid time-of-arrival estimate.

9 . The method of claim 1 :

further comprising:

during the first time period:

accessing a transmit power of the first ranging signal at the transmitter;

accessing a transmit antenna gain of the transmitter;

accessing a receive antenna gain of the receiver;

based on the transmit power, the transmit antenna gain, and the receive antenna gain, calculating a receive power of the first ranging signal at the receiver; and

based on the receive power, calculating a signal strength-based distance estimate between the transmitter and the receiver; and

wherein calculating the first distance comprises:

based on the first hybrid time-of-arrival estimate and the signal strength-based distance estimate, calculating the first distance.

10 . The method of claim 9 :

further comprising:

during the first time period:

based on the transmit power and the receive power of the first ranging signal, calculating a path loss metric;

accessing a set of path loss functions relating the path loss metric to a distance between the transmitter and the receiver; and

based on the set of path loss functions and the path loss metric, calculating a set of probabilities, each probability in the set of probabilities:

corresponding to a path loss function in the set of path loss functions; and

characterizing a fit of the path loss metric to each path loss function in the set of path loss functions;

based on the set of path loss functions and the path loss metric, calculating a set of range estimates; and

calculating a path-loss-based distance estimate as a weighted average of the set of range estimates weighted by the set of probabilities; and

wherein calculating the first distance comprises:

based on the first hybrid time-of-arrival estimate, the signal strength-based distance estimate, and the path-loss-based distance estimate, calculating the first distance.

11 . The method of claim 1 , further comprising:

at a first time during a second time period:

accessing a second ranging signal transmitted from the transmitter and received by the receiver, the second ranging signal comprising:

a second set of multiplexed sub-signals, each multiplexed sub-signal in the second set of multiplexed sub-signals characterized by a frequency in the set of frequencies;

identifying a second set of sub-signal pairs in the second set of multiplexed sub-signals;

calculating a second set of phase differences of the second set of sub-signal pairs;

based on the second set of phase differences of the second set of sub-signal pairs, calculating a second phase-based time-of-arrival estimate;

detecting a set of multipath components characteristic of the second ranging signal based on a signal classification function;

calculating a phase-amplitude-based time-of-arrival estimate based on the set of multipath components characteristic of the second ranging signal;

computing a correlation between the second ranging signal and a target ranging signal;

identifying a first time associated with a highest correlation peak of the correlation; and

based on the first time, calculating a sub-sample-based time-of-arrival estimate;

based on the second phase-based time-of-arrival estimate, the phase-amplitude-based time-of-arrival estimate, and the sub-sample-based time-of-arrival estimate, calculating a second hybrid time-of-arrival estimate; and

based on the second hybrid time-of-arrival estimate, calculating a second distance between the transmitter and the receiver.

12 . The method of claim 11 , further comprising, at a second time during the second time period:

based on the set of multipath components, calculating a multipath metric characterizing a power ratio between a line-of-sight component and non-line-of-sight components in the set of multipath components of the second ranging signal; and

in response to the multipath metric indicating a strong multipath environment between the transmitter and the receiver:

recording a second series of time-domain samples representing the second ranging signal; and

calculating a second sample-based time-of-arrival estimate based on the second series of time-domain samples.

13 . The method of claim 12 :

further comprising:

at the second time during the second time period:

calculating a first difference between the second sample-based time-of-arrival estimate and the second phase-based time-of-arrival estimate;

calculating a second difference between the second sample-based time-of-arrival estimate and the phase-amplitude-based time-of-arrival estimate; and

calculating a third difference between the second sample-based time-of-arrival estimate and the sub-sample-based time-of-arrival estimate;

wherein calculating the second hybrid time-of-arrival estimate comprises:

in response to the first difference and the third difference exceeding a threshold difference and the second difference falling below the threshold difference:

based on the second sample-based time-of-arrival estimate and the phase-amplitude-based time-of-arrival estimate, calculating the second hybrid time-of-arrival estimate.

14 . The method of claim 12 :

further comprising:

assigning a first score to the second phase-based time-of-arrival estimate, the first score representing multipath resilience associated with a phase-based time-of-arrival estimation process;

assigning a second score to the phase-amplitude-based time-of-arrival estimate, the second score representing multipath resilience associated with a phase-amplitude time-of-arrival estimation process;

assigning a third score to the sub-sample-based time-of-arrival estimate, the third score representing multipath resilience associated with a sub-sample-base time-of-arrival estimation process; and

assigning a fourth score to the second sample-based time-of-arrival estimate, the fourth score representing multipath resilience associated with a sample-based time-of-arrival estimation process; and

wherein calculating the second hybrid time-of-arrival estimate comprises:

calculating the second hybrid time-of-arrival estimate as a weighted average of the second phase-based time-of-arrival estimate weighted by the first score, the phase-amplitude-based time-of-arrival estimate weighted by the second score, the sub-sample-based time-of-arrival estimate weighted by the third score, and the second sample-based time-of-arrival estimate weighted by the fourth score.

15 . The method of claim 11 , further comprising:

in response to the second distance falling within a target range representing a range of distances associated with precise signal-strength-based range estimation:

accessing a transmit power of the second ranging signal at the transmitter;

based on the transmit power, calculating a receive power of the first ranging signal at the receiver; and

based on the receive power, calculating a signal strength-based distance between the transmitter and the receiver.

16 . The method of claim 15 :

further comprising:

assigning a first score to the second phase-based time-of-arrival estimate, the first score representing ranging precision associated with a phase-based time-of-arrival estimation process;

assigning a second score to the phase-amplitude-based time-of-arrival estimate, the second score representing ranging precision associated with a phase-amplitude-based time-of-arrival estimation process;

assigning a third score to the sub-sample-based time-of-arrival estimate, the third score representing ranging precision associated with a sub-sample-based time-of-arrival estimation process;

based on the signal strength-based distance, calculating a signal strength-based time-of-arrival estimate; and

assigning a fourth score to the signal strength-based time-of-arrival estimate, the fourth score representing ranging precision associated with a signal strength-based time-of-arrival estimation process; and

wherein calculating the second hybrid time-of-arrival estimate comprises:

calculating the second distance as a weighted average of the second phase-based time-of-arrival estimate weighted by the first score, the phase-amplitude-based time-of-arrival estimate weighted by the second score, the sub-sample-based time-of-arrival estimate weighted by the third score, and the signal strength-based time-of-arrival estimate weighted by the fourth score.

17 . The method of claim 1 :

further comprising:

calculating a first uncertainty of the first sample-based time-of-arrival estimate based a sampling frequency associated with the receiver; and

calculating a second uncertainty of the first phase-based time-of-arrival estimate based on a variability measure characteristic of a phase difference of each sub-signal pair in the first set of sub-signal pairs; and

wherein calculating the first hybrid time-of-arrival estimate comprises:

calculating the first hybrid time-of-arrival estimate as a weighted combination of the first sample-based time-of-arrival estimate weighted by the first uncertainty and the first phase-based time-of-arrival estimate weighted by the second uncertainty.

18 . A method comprising:

accessing a ranging signal transmitted from a transmitter and received by a receiver, the ranging signal comprising:

a set of multiplexed sub-signals, each multiplexed sub-signal characterized by a frequency in a set of frequencies;

recording a first series of time-domain samples representing the ranging signal;

calculating a set of phase differences for a set of sub-signal pairs in the set of multiplexed sub-signals;

calculating a first time-of-arrival estimate based on the set of phase differences of the set of sub-signal pairs;

detecting a set of multipath components characteristic of the ranging signal based on a multiple signal classification function;

calculating a second time-of-arrival estimate based on the set of multipath components characteristic of the ranging signal;

characterizing a hybrid time-of-arrival estimate based on a combination of the first time-of-arrival estimate and the second time-of-arrival estimate; and

calculating a distance between the transmitter and the receiver based on the hybrid time-of-arrival estimate.

19 . The method of claim 18 , wherein calculating the first time-of-arrival estimate comprises:

identifying a subset of multiplexed sub-signals, in the set of multiplexed sub-signals, based on a threshold frequency difference, the threshold frequency difference based on a threshold propagation time of the ranging signal from the transmitter to the receiver;

for each sub-signal pair in the subset of multiplexed sub-signals:

calculating a sub-signal pair time-of-arrival estimate based on a phase difference of the sub-signal pair;

calculating a central tendency metric descriptive of the sub-signal pair time-of-arrival estimates for the sub-signal pairs in the set of sub-signal pairs; and

calculating the first time-of-arrival estimate based on the central tendency metric.

20 . A method comprising:

accessing a ranging signal transmitted from a transmitter and received by a receiver, the ranging signal comprising:

a set of multiplexed sub-signals, each multiplexed sub-signal in the set of multiplexed sub-signals characterized by a frequency in a set of frequencies;

recording a first series of time-domain samples representing the ranging signal;

calculating a first time-of-arrival estimate based on the series of time-domain samples;

detecting a set of multipath components characteristic of the ranging signal;

calculating a second time-of-arrival estimate based on the set of multipath components characteristic of the ranging signal;

characterizing a hybrid time-of-arrival estimate based on a combination of the first time-of-arrival estimate and the second time-of-arrival estimate; and

calculating a distance between the transmitter and the receiver based on the hybrid time-of-arrival estimate.

Assignments (1)

Continuity (6)

References Cited (16)