TIME OF ARRIVAL (TOA) ESTIMATION FOR POSITIONING IN A WIRELESS COMMUNICATION NETWORK

• US 20100279707A1
• Filed: 10/26/2009
• Published: 11/04/2010
• Est. Priority Date: 10/28/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sampath, Ashwin, Bachu, Raja S., Rowitch, Douglas Neal, Fischer, Sven, Agrawal, Avneesh, Amin, Muhammad Awais
• Granted Patent: US 9,037,155 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0221 Receivers
• CPC Class Codes: G01S 5/0226 Transmitters
• CPC Class Codes: G01S 5/0236 Assistance data, e.g. base station almanac
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

Techniques for determining time of arrivals (TOAs) of signals in a wireless communication network are described. Each cell may transmit (i) synchronization signals on a set of contiguous subcarriers in the center portion of the system bandwidth and (ii) reference signals on different sets of non-contiguous subcarriers distributed across the system bandwidth. A UE may determine TOA for a cell based on multiple signals transmitted on different sets of subcarriers. The UE may perform correlation for a first signal (e.g., a synchronization signal) from the cell to obtain first correlation results for different time offsets. The UE may perform correlation for a second signal (e.g., a reference signal) from the cell to obtain second correlation results for different time offsets. The UE may combine the first and second correlation results and may determine the TOA for the cell based on the combined correlation results.

Claims

1. A method of supporting positioning, comprising:

receiving a plurality of signals from each of multiple transmitters at a receiver; and

determining a time of arrival (TOA) of the plurality of signals from each transmitter based on a first signal sent by the transmitter on a first set of subcarriers and a second signal sent by the transmitter on a second set of subcarriers, the plurality of signals comprising the first and second signals.

2. The method of claim 1, wherein the first signal comprises a reference signal sent on the first set of non-contiguous subcarriers, and wherein the second signal comprises a synchronization signal sent on the second set of contiguous subcarriers.

3. The method of claim 2, wherein the first set includes non-contiguous subcarriers distributed across system bandwidth, and wherein the second set includes contiguous subcarriers in a center portion of the system bandwidth.

4. The method of claim 2, wherein the first set includes a configurable number of subcarriers determined by system bandwidth, and wherein the second set includes a fixed number of subcarriers independent of the system bandwidth.

5. The method of claim 1, wherein the first signal comprises a first reference signal sent on the first set of non-contiguous subcarriers, wherein the second signal comprises a second reference signal sent on the second set of non-contiguous subcarriers, and wherein the first and second sets include different subcarriers distributed across system bandwidth.

6. The method of claim 5, wherein the determining the TOA for each transmitter further comprises determining the TOA for each transmitter based further on a synchronization signal sent by the transmitter on a third set of contiguous subcarriers.

7. The method of claim 5, wherein the determining the TOA for each transmitter further comprises determining the TOA for each transmitter based further on a primary synchronization signal and a secondary synchronization signal sent by the transmitter on a third set of contiguous subcarriers.

8. The method of claim 1, wherein the first and second sets overlap partially, and wherein the first and second sets include at least one subcarrier common to both sets.

9. The method of claim 1, wherein the first and second sets are non-overlapping, with each set including subcarriers not included in the other set.

10. The method of claim 1, wherein the determining the TOA of the plurality of signals from each transmitter comprises

performing correlation for the first signal from the transmitter to obtain first correlation results for a plurality of time offsets,

performing correlation for the second signal from the transmitter to obtain second correlation results for the plurality of time offsets,

combining the first and second correlation results to obtain combined correlation results for the transmitter, and

determining the TOA for the transmitter based on the combined correlation results.

11. The method of claim 10, wherein the performing correlation for the first signal comprises

generating a sample sequence with known symbols mapped to the first set of subcarriers used for the first signal, and

correlating received samples at the receiver with the sample sequence at each time offset to obtain the first correlation results for the plurality of time offsets.

12. The method of claim 10, wherein the combining the first and second correlation results comprises coherently combining the first and second correlation results to obtain the combined correlation results for the transmitter.

13. The method of claim 10, wherein the combining the first and second correlation results comprises

coherently combining the first and second correlation results for each time interval to obtain intermediate correlation results for the time interval, and

non-coherently combining the intermediate correlation results across multiple time intervals to obtain the combined correlation results for the transmitter.

14. The method of claim 10, wherein the performing correlation for the first signal from the transmitter comprises

performing correlation for the first signal for each of multiple portions of a signal bandwidth, and

non-coherently combining correlation results for the multiple portions of the signal bandwidth to obtain the first correlation results.

15. The method of claim 10, wherein the combining the first and second correlation results comprises

coherently combining the first and second correlation results for each antenna at the transmitter to obtain intermediate correlation results for the antenna, and

non-coherently combining the intermediate correlation results across multiple antennas at the transmitter to obtain the combined correlation results for the transmitter.

16. The method of claim 10, wherein the determining the TOA for the transmitter based on the combined correlation results comprises

identifying an earliest time offset with a combined correlation result exceeding a threshold, and

determining the TOA for the transmitter based on the identified time offset.

17. The method of claim 10, wherein the determining the TOA for the transmitter based on the combined correlation results comprises

identifying an earliest time offset with a combined correlation result exceeding a threshold,

performing interpolation on at least two combined correlation results, including the combined correlation result for the identified time offset, to obtain an interpolated time offset, and

determining the TOA for the transmitter based on the interpolated time offset.

18. The method of claim 17, wherein the determining the TOA for the transmitter based on the interpolated time offset comprises determining the TOA for the transmitter based further on an adjustment to account for known biases between a transmitted pulse shape and an interpolating function.

19. The method of claim 1, further comprising:

determining observed time difference of arrivals (OTDOAs) for multiple pairs of transmitters, one OTDOA for each pair of transmitters, each OTDOA being determined based on TOAs for the transmitters in the corresponding pair, and

wherein a location estimate for the receiver is determined based on the OTDOAs for the multiple pairs of transmitters.

20. The method of claim 1, further comprising:

computing a location estimate for the receiver based on TOAs for the multiple transmitters and known locations of the transmitters.

21. The method of claim 20, further comprising:

receiving assistance data for the multiple transmitters, and wherein the location estimate for the receiver is computed using the assistance data.

22. The method of claim 1, further comprising:

sending measurement information comprising TOAs for the multiple transmitters to a network entity; and

receiving a location estimate for the receiver from the network entity, the location estimate being determined based on the TOAs for the multiple transmitters.

23. The method of claim 1, further comprising:

determining relative time differences (RTDs) for multiple pairs of transmitters, one RTD for each pair of transmitters, each RTD being determined based on TOAs and known locations of the transmitters in the corresponding pair and known location of the receiver.

24. The method of claim 1, further comprising:

receiving assistance data for the multiple transmitters, and wherein TOAs for the multiple transmitters are determined using the assistance data.

25. The method of claim 24, wherein the multiple transmitters are for multiple cells, and wherein the assistance data comprises cell identities (IDs) of the cells, locations of the cells, carrier frequency information for the cells, cyclic prefix length for each cell, number of transmit antenna for each cell, relative time differences (RTDs) for the cells, a search window size, or a combination thereof.

26. An apparatus for supporting positioning, comprising:

means for receiving a plurality of signals from each of multiple transmitters at a receiver; and

means for determining a time of arrival (TOA) of the plurality of signals from each transmitter based on a first signal sent by the transmitter on a first set of subcarriers and a second signal sent by the transmitter on a second set of subcarriers, the plurality of signals comprising the first and second signals.

27. The apparatus of claim 26, wherein the first signal comprises a reference signal sent on the first set of non-contiguous subcarriers, and wherein the second signal comprises a synchronization signal sent on the second set of contiguous subcarriers.

28. The apparatus of claim 26, wherein the first signal comprises a first reference signal sent on the first set of non-contiguous subcarriers, wherein the second signal comprises a second reference signal sent on the second set of non-contiguous subcarriers, and wherein the first and second sets include different subcarriers distributed across system bandwidth.

29. The apparatus of claim 26, wherein the means for determining the TOA of the plurality of signals from each transmitter comprises

means for performing correlation for the first signal from the transmitter to obtain first correlation results for a plurality of time offsets,

means for performing correlation for the second signal from the transmitter to obtain second correlation results for the plurality of time offsets,

means for combining the first and second correlation results to obtain combined correlation results for the transmitter, and

means for determining the TOA for the transmitter based on the combined correlation results.

30. The apparatus of claim 29, wherein the means for combining the first and second correlation results comprises

means for coherently combining the first and second correlation results for each time interval to obtain intermediate correlation results for the time interval, and

means for non-coherently combining the intermediate correlation results across multiple time intervals to obtain the combined correlation results for the transmitter.

31. The apparatus of claim 29, wherein the means for combining the first and second correlation results comprises

means for coherently combining the first and second correlation results for each antenna at the transmitter to obtain intermediate correlation results for the antenna, and

means for non-coherently combining the intermediate correlation results across multiple antennas at the transmitter to obtain the combined correlation results for the transmitter.

32. An apparatus for supporting positioning, comprising:

at least one processor configured to receive a plurality of signals from each of multiple transmitters at a receiver, and to determine a time of arrival (TOA) of the plurality of signals from each transmitter based on a first signal sent by the transmitter on a first set of subcarriers and a second signal sent by the transmitter on a second set of subcarriers, the plurality of signals comprising the first and second signals.

33. The apparatus of claim 32, wherein the first signal comprises a reference signal sent on the first set of non-contiguous subcarriers, and wherein the second signal comprises a synchronization signal sent on the second set of contiguous subcarriers.

34. The apparatus of claim 32, wherein the first signal comprises a first reference signal sent on the first set of non-contiguous subcarriers, wherein the second signal comprises a second reference signal sent on the second set of non-contiguous subcarriers, and wherein the first and second sets include different subcarriers distributed across system bandwidth.

35. The apparatus of claim 32, wherein for each transmitter the at least one processor is configured to perform correlation for the first signal from the transmitter to obtain first correlation results for a plurality of time offsets, to perform correlation for the second signal from the transmitter to obtain second correlation results for the plurality of time offsets, to combine the first and second correlation results to obtain combined correlation results for the transmitter, and to determine the TOA for the transmitter based on the combined correlation results.

36. The apparatus of claim 35, wherein for each transmitter the at least one processor is configured to coherently combine the first and second correlation results for each time interval to obtain intermediate correlation results for the time interval, and to non-coherently combine the intermediate correlation results across multiple time intervals to obtain the combined correlation results for the transmitter.

37. The apparatus of claim 35, wherein for each transmitter the at least one processor is configured to coherently combine the first and second correlation results for each antenna at the transmitter to obtain intermediate correlation results for the antenna, and to non-coherently combine the intermediate correlation results across multiple antennas at the transmitter to obtain the combined correlation results for the transmitter.

38. A computer program product, comprising:

a computer-readable medium comprising;

code to cause at least one processor to receive a plurality of signals from each of multiple transmitters at a receiver, and

code to cause the at least one processor to determine a time of arrival (TOA) of the plurality of signals from each transmitter based on a first signal sent by the transmitter on a first set of subcarriers and a second signal sent by the transmitter on a second set of subcarriers, the plurality of signals comprising the first and second signals.