COMPENSATION OF PROPAGATION DELAYS OF WIRELESS SIGNALS

• US 20100190509A1
• Filed: 04/01/2009
• Published: 07/29/2010
• Est. Priority Date: 01/23/2009
• Status: Active Grant

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Inventors: DAVIS, RICHARD W.
• Granted Patent: US 8,326,319 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 56/006 using known positions of transmitter and receiver

Abstract

System(s) and method(s) for compensation of propagation delay offsets of wireless signals. Compensation is accomplished through determination of an effective wireless signal propagation delay that accounts for signal path delay and propagation delay over the air. Such determination is based at least in part on statistical analysis of accurate location estimates of reference positions throughout a coverage sector or cell, and location estimates of the reference positions generated through time-of-flight (TOF) measurements of wireless signals. Determination of propagation or signal path delay offset also is attained iteratively based at least in part on reference location estimates and TOF location estimates. High-accuracy location estimates such as those obtained through global navigation satellite systems are employed as reference location estimates. Position of probes or wireless beacons, deployed throughout a sector or cell, also are employed as reference locations. Compensation of propagation delay offset improves accuracy of conventional TOF location estimates and radio network performance.

Claims

1. A method for correcting radio frequency (RF) signal propagation delay in an operational wireless system, the method comprising:

employing at least a processor that executes code instructions retained in a memory, the code instructions, when executed by at least the processor, carry out the following acts;

receiving a first set of location estimates from a location source;

generating a second set of location estimates through a time-of-flight assessment, wherein the second set of location estimates corresponds to one of the same or nearly the same ground truth for which the first set of location estimates is generated by the location source;

determining the RF signal propagation delay offset based at least in part on the received first set of location estimates and the second set of location estimates; and

calibrating RF signal propagation timing measurements through at least in part the determined RF signal propagation delay offset.

2. The method of claim 1, wherein the location source includes one or more mobile handsets that support reception of global navigation satellite system data and operation or manipulation thereof.

3. The method of claim 1, wherein the location source is a network component that retains known location records of at least one of a set of one or more wireless beacons or a set of one or more probes, the one or more wireless beacons or the set of one or more probes are stationary or pseudo-stationary.

4. The method of claim 1, wherein the one or more wireless beacons or the set of one or more probes are stationary or pseudo-stationary include at least one of one or more Wi-Fi outdoor access points that are part of a public metropolitan network, one or more wireless probes that are part of wireless-enabled utility equipment, or one or more truck-mounted radio or microwave transceivers temporarily stationed in disparate locations throughout a sector.

5. The method of claim 1, wherein determining the RF signal propagation delay based at least in part on the received first set of location estimates and the second set of location estimates includes:

implementing statistical analysis of received and generated location estimates to establish a relationship between the first set of location estimates and the second set of location estimates; and

employing a systematic variance between the first set of location estimates and the second set of location estimates to calculate an accurate estimate of RF signal propagation delay, the systematic variance extracted from the statistical analysis.

6. The method of claim 4, wherein the correlation is established via at least one of Pearson product-moment correlation coefficient, Pearson'"'"'s χ

² test, Spearman'"'"'s rank correlation, or Kendall τ

rank correlation coefficient.

7. The method of claim 1, wherein determining the RF signal propagation delay offset based at least in part on the received first set of location estimates and the second set of location estimates includes determining the RF signal propagation delay iteratively by refining the location estimates in the generated second set of location estimates, wherein the refining comprises iteratively correcting RF signal propagation delay offset to produce timing delay data consistent with the known location records in the first set of location estimates.

8. The method of claim 6, wherein iteratively correcting RF signal propagation delay offset to produce timing delay data consistent with the known location records in the first set of location estimates includes:

specifying a current propagation delay offset;

generating a set of location estimates based on time-of-flight assessment that utilizes the current signal propagation delay offset;

determining a metric that evaluates quality of the specified RF signal propagation delay offset based at least in part on the known location records in the first set of location estimates and the generated set of location estimates;

when the metric does not satisfies or exceeds a quality tolerance, updating the current propagation delay offset and setting the updated delay offset as the current wireless signal propagation delay offset, and continuing to the generating a set of location estimates based on time-of-flight assessment that utilizes the current signal propagation delay offset; and

when the metric satisfies or exceeds the quality tolerance, defining the current propagation delay offset as the RF signal propagation delay offset.

9. The method of claim 1, wherein determining the RF signal propagation delay based at least in part on the received first set of location estimates and the second set of location estimates further includes determination of propagation delay for specific angles with respect to the centerline between a receiver RL and an emitter FL.

10. The method of claim 1, further comprising mapping sector identification (ID) information extracted from the first set of location estimates to sector ID data obtained from the second set of location estimates.

11. The method of claim 10, further comprising retaining a mapping of nominal sectorization information to effective sectorization data resulting from the mapping act.

12. A system for calibration of wireless signal propagation delay, the system comprising:

a processor configured to execute instructions stored in a memory, the instructions when executed by the processor enable the following components;

a component that receives a first set of location estimates from a location source platform;

a time-of-flight (TOF) component that generates a second set of location estimates through least one of a reverse link (RL) time difference of arrival, a RL time of arrival, cell global identity (CGI) and round trip time, or CGI and timing advance;

an analysis component that establishes a wireless signal propagation delay offset based at least in part on the received first set of location estimates and the second set of location estimates; and

a calibration platform that adjusts wireless signal propagation timing through at least in part the determined wireless signal propagation delay.

13. The system of claim 12, wherein the wireless signal is at least one of a radio frequency signal, a microwave signal, or an infrared signal.

14. The system of claim 12, the location source platform includes at least one of one or more mobile handsets that support reception of global navigation satellite system data and manipulation thereof.

15. The system of claim 12, wherein the location source is a network component that retains known location records of at least one of a set of one or more wireless beacons or a set of one or more probes.

16. The system of claim 12, to establish the wireless signal propagation delay offset based at least in part on the received first set of location estimates and the second set of location estimates, the analysis component computes a correlation between the received first set of location estimates and the second set of location estimates and exploits a systematic variance among the first set and second set.

17. The system of claim 12, to establish the wireless signal propagation delay offset based at least in part on the received first set of location estimates and the second set of location estimates, the analysis component determines at least one of a TA, a RTT, a TOA, or a TDOA and iteratively corrects the determined at least one of the TA, the RTT, the TDOA, or the TDOA based at least in part on the generated second set of location estimates, the analysis component terminates the iteration cycle when magnitude of correction to TA, RTT, TOA, or TDOA is below a configurable threshold.

18. The system of claim 12, wherein the wireless signal propagation delay offset is stochastic, and to establish the wireless signal propagation delay offset based at least in part on the received set of location estimates and the second set of location estimates, the analysis component exploits probabilistic analysis.

19. An apparatus, comprising:

means for receiving a first set of location estimates from a location source;

means for generating a second set of location estimates through a time-of-flight assessment;

means for determining a wireless signal propagation delay offset based at least in part on the received first set of location estimates and the second set of location estimates, wherein the wireless signal includes at least one of a radio frequency (RF) signal, a microwave signal, or an infrared signal; and

means for calibrating RF signal propagation timing through at least in part the determined RF signal propagation delay.

20. The apparatus of claim 19, further comprising:

means for obtaining at least one of simultaneous location estimates or near simultaneous location estimates, for a common ground truth, originating from a high-accuracy location mechanism and a time-of-arrival (TOA) location mechanism;

means for estimating propagation and signal path delay contributions included in a first location mechanism based at least in part on information received from the second location mechanism, wherein the first location mechanism is one of the high-accuracy location mechanism or the TOA location mechanism, and the second mechanism is one of the high-accuracy location mechanism or the TOA location mechanism and excludes the first mechanism;

means for extracting a propagation timing delay error through the estimation of propagation and signal path delay contributions included in the first location method; and

means for storing the extracted delay offset error.

21. The apparatus of claim 19, wherein the high-accuracy location mechanism is a calibrated mechanism.

22. The apparatus of claim 19, wherein the TOA location mechanism includes at least one of reverse link (RL) time difference of arrival, RL-TOA, cell global identity (CGI) and round trip time, or CGI and timing advance.

23. The apparatus of claim 19, further comprising means for conveying the extracted propagation timing delay error to at least one of one or more components in a radio access network, one or more components in a location services network, or one or more components in a utility network.

24. A computer-readable storage medium comprising code instructions stored thereon that, when executed by a processor, cause the processor to carry out the following acts:

receiving a first set of location estimates from a location source;

generating a second set of location estimates through a time-of-flight assessment;

determining radio frequency (RF) signal propagation delay based at least in part on the received first set of location estimates and the second set of location estimates; and

calibrating RF signal propagation timing through at least in part the determined RF signal propagation delay.