Frequency offset estimator

• US 8,457,178 B2
• Filed: 03/25/2008
• Issued: 06/04/2013
• Est. Priority Date: 03/26/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Luo, Tao
• Primary Examiner(s): Liu, Shuwang
• Assistant Examiner(s): MCKIE, GINA M
• Application Number:
  US12/055,087
• Publication Number:
  US 20080260006A1
• Time in Patent Office: 1,897 Days
• Field of Search: 375/149, 375/260, 375/267
• US Class Current: 375/149
• CPC Class Codes: H04B 1/7087 Carrier synchronisation aspects
• CPC Class Codes: H04B 1/7117 Selection, re-selection, allocation or re-allocation of paths to fingers, e.g. timing offset control of allocated fingers
• CPC Class Codes: H04L 2027/0024 at the receiver end
• CPC Class Codes: H04L 2027/0046 Open loops
• CPC Class Codes: H04L 2027/0055 single phase
• CPC Class Codes: H04L 2027/0093 Intermittant signals
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657

Abstract

Determining a frequency offset of a received signal utilizing two or more multipath components of the received signal is provided herein. By way of example, the received signal can be correlated with a synchronization sequence in a time domain or a frequency domain, resulting in separation of the two or more multipath components of the received signal. Analysis of at least one of the multipath components can provide a frequency offset of the received signal. Furthermore, by analyzing the multipath components, estimation of the frequency offset can be improved as compared with single-signal analysis techniques.

Claims

1. A method of wireless communication, comprising:

correlating a received signal with a synchronization sequence comprising a primary synchronization channel (PSC) sequence, a secondary synchronization channel (SSC) sequence, or a combination thereof, wherein a resulting correlated signal comprises two or more separate multipath components;

analyzing at least one of the two or more separate multipath components and obtaining a frequency offset of the received signal from the analysis;

splitting the received signal and the synchronization sequence into a plurality of time segments, wherein the correlating is applied to corresponding time segments of the received signal and synchronization sequence;

obtaining a plurality of correlated time segments for each of the two or more separate multipath components;

applying a differential product to correlated time segments of the at least one of the two or more separate multipath components, wherein the frequency offset of the received signal is obtained at least in part from a result of the differential product;

applying the differential product to correlated time segments of an additional multipath component of the two or more separate multipath components;

summing results of the differential products of the at least one multipath component and the additional multipath component; and

obtaining the frequency offset from a phase of the sum of the results of the differential products.

2. A method of wireless communication, comprising:

correlating a received signal with a synchronization sequence comprising a primary synchronization channel (PSC) sequence, a secondary synchronization channel (SSC) sequence, or a combination thereof, wherein a resulting correlated signal comprises two or more separate multipath components;

analyzing at least one of the two or more separate multipath components and obtaining a frequency offset of the received signal from the analysis;

obtaining an initial frequency offset estimation from at least one multipath signal associated with the received signal;

offsetting at least a portion of the received signal by the initial frequency offset estimation prior to the correlating, wherein the correlating the received signal with the synchronization sequence is accomplished in a frequency domain;

converting the resulting correlated signal to a time domain signal to distinguish the two or more separate multipath components;

correlating at least the offset portion of the received signal with an additional synchronization sequence to obtain a second resulting correlated signal, the additional synchronization sequence is separated in time from the synchronization sequence;

applying a differential product to at least one multipath component of the resulting correlated signal and to at least one multipath component of the second resulting correlated signal; and

obtaining the frequency offset from a result of the differential product(s).

3. The method of claim 2, further comprising employing a despreading function for correlating the received signal with the synchronization sequence.

4. The method of claim 2, further comprising applying the differential product to at least two of the two or more separate multipath components and summing the results of the differential products.

5. The method of claim 4, further comprising obtaining the frequency offset at least in part based on a phase of the sum of the results of the differential products.

6. The method of claim 2, further comprising splitting the received signal and the synchronization sequence into a plurality of time segments, wherein the correlating is applied to corresponding time segments of the received signal and synchronization sequence.

7. The method of claim 6, further comprising;

obtaining a plurality of correlated time segments for each of the two or more separate multipath components.

8. The method of claim 7, further comprising:

applying the differential product to correlated time segments of the at least one of the two or more separate multipath components, wherein the frequency offset of the received signal is obtained at least in part from a result of the differential product.

9. The method of claim 2, further comprising determining a strongest signal path of the received signal.

10. The method of claim 9, further comprising defining a threshold range about the strongest signal path and identifying two or more significant multipath components based on at least one signal parameter.

11. The method of claim 10, further comprising employing at least one of the following as one of the at least one signal parameter:

path signal strength or normalized path signal strength;

a number of discreet paths centered about the strongest signal path;

or

path signal strength or normalized path signal strength in conjunction with a number of discreet paths centered about the strongest signal path.

12. The method of claim 10, further comprising applying the differential product to the significant multipath components and obtaining the frequency offset at least in part on results of the differential products.

13. An apparatus that provides wireless communication, comprising:

a processing module that correlates a received signal with a synchronization sequence comprising a primary synchronization channel (PSC) sequence, a secondary synchronization channel (SSC) sequence, or a combination thereof, wherein a resulting correlated signal comprises two or more separate multipath components;

a multipath analysis module that evaluates at least one of the two or more separate multipath components and obtains a frequency offset of the received signal;

a logic module that applies a differential product to significant multipath components, wherein the multipath analysis module obtains the frequency offset at least in part on results of the differential products;

a signal modifier that offsets at least a portion of the received signal by the initial frequency offset estimation prior to the correlation by the processing module, wherein the processing module correlates the received signal with the synchronization sequence in a frequency domain; and

a frequency inverter that converts the resulting correlated signal to a time domain to distinguish the two or more separate multipath components;

wherein, the processing module correlates at least the offset portion of the received signal with an additional synchronization sequence to obtain a second resulting correlated signal, the additional synchronization sequence is separated in time from the synchronization sequence;

a logic module applies a differential product to at least one multipath component of the resulting correlated signal and to at least one multipath component of the second resulting correlated signal; and

the multipath analysis module obtains the frequency offset from a result of the differential product(s).

14. The apparatus of claim 13, wherein the processing module employs a despreading function to correlate the received signal with the synchronization sequence.

15. The apparatus of claim 13, further comprising a compilation module that sums results of two or more differential products, the logic module applies the differential product to at least two of the two or more separate multipath components and the compilation module sums the results of the differential products.

16. The apparatus of claim 15, further comprising a phase estimator that determines a phase of the sum of the results of the differential products, the multipath analysis module utilizes the phase, at least in part, to obtain the frequency offset of the received signal.

17. The apparatus of claim 15, further comprising a timing module that splits the received signal and the synchronization sequence into a plurality of time segments, the processing module correlates corresponding time segments of the received signal and the synchronization sequence.

18. The apparatus of claim 17, wherein:

the timing module obtains a plurality of correlated time segments for each of the two or more separate multipath components.

19. The method of claim 18, wherein the logic module applies a differential product to correlated time segments of the at least one of the two or more separate multipath components, wherein the frequency offset of the received signal is obtained at least in part from a result of the differential product.

20. The apparatus of claim 13, further comprising a signal comparator that determines a strongest signal path of the received signal.

21. The apparatus of claim 20, further comprising a filtering module that defines a threshold range about the strongest signal path and identifies two or more significant multipath components based on at least one signal parameter.

22. The apparatus of claim 21, wherein the filtering module employs at least one of the following as one of the at least one signal parameter:

path signal strength or normalized path signal strength;

a number of discreet paths centered about the strongest signal path;

or

path signal strength or normalized path signal strength in conjunction with a number of discreet paths centered about the strongest signal path.

23. The apparatus of claim 21, further comprising a logic module that applies a differential product to the significant multipath components, wherein the multipath analysis module obtains the frequency offset at least in part on results of the differential products.

24. An apparatus that provides wireless communication, comprising:

means for correlating a received signal with a synchronization sequence comprising a primary synchronization channel (PSC) sequence, a secondary synchronization channel (SSC) sequence, or a combination thereof, wherein a resulting correlated signal comprises two or more separate multipath components;

means for analyzing at least one of the two or more separate multipath components and for obtaining a frequency offset of the received signal from the analysis;

means for obtaining an initial frequency offset estimation from at least one multipath signal associated with the received signal;

means for offsetting at least a portion of the received signal by the initial frequency offset estimation prior to the correlation by the processing module, wherein the processing module correlates the received signal with the synchronization sequence in a frequency domain; and

means for converting the resulting correlated signal to a time domain to distinguish the two or more separate multipath components;

wherein, the means for correlating correlates at least the offset portion of the received signal with an additional synchronization sequence to obtain a second resulting correlated signal, the additional synchronization sequence is separated in time from the synchronization sequence;

means for applying a differential product to at least one multipath component of the resulting correlated signal and to at least one multipath component of the second resulting correlated signal; and

the means for analyzing obtains the frequency offset from a result of the differential product(s).

25. A computer program product, comprising:

a non-transitory computer-readable medium comprising;

code for correlating a received signal with a synchronization sequence comprising a primary synchronization channel (PSC) sequence, a secondary synchronization channel (SSC) sequence, or a combination thereof, wherein a resulting correlated signal comprises two or more separate multipath components;

code for analyzing at least one of the two or more separate multipath components and obtain a frequency offset of the received signal from the analysis;

code for obtaining an initial frequency offset estimation from at least one multipath signal associated with the received signal;

code for offsetting at least a portion of the received signal by the initial frequency offset estimation prior to the correlating, wherein the correlating the received signal with the synchronization sequence is accomplished in a frequency domain;

code for converting the resulting correlated signal to a time domain signal to distinguish the two or more separate multipath components;

code for correlating at least the offset portion of the received signal with an additional synchronization sequence to obtain a second resulting correlated signal, the additional synchronization sequence is separated in time from the synchronization sequence;

code for applying a differential product to at least one multipath component of the resulting correlated signal and to at least one multipath component of the second resulting correlated signal; and

code for obtaining the frequency offset from a result of the differential product(s).

26. A method of wireless communication, comprising:

transmitting a wireless signal and a synchronization sequence comprising a primary synchronization channel (PSC) sequence, a secondary synchronization channel (SSC) sequence, or a combination thereof;

receiving a replica of the wireless signal, the replica comprises at least two multipath components;

correlating the replica of the wireless signal with the synchronization sequence, wherein a resulting correlated signal comprises at least two distinct multipath components; and

determining a frequency offset between the wireless signal and the replica of the wireless signal from one or more of the at least two distinct multipath components;

correlating the replica of the wireless signal with a second synchronization sequence to obtain a second resulting correlated signal, the correlating with the synchronization sequence and the second synchronization sequence are implemented in a frequency domain;

converting the resulting correlated signal and the second resulting correlated signal to a time domain; and

applying a differential product to corresponding multipath components of the resulting correlated signal and the second resulting correlated signal to obtain the frequency offset.

27. The method of claim 26, further comprising transmitting the frequency offset to a mobile device.

28. The method of claim 26, further comprising employing a despreading function to correlate the replica of the wireless signal with the synchronization sequence.

29. An apparatus that facilitates wireless communication, comprising:

a transmitter that sends a wireless signal and a synchronization sequence comprising a primary synchronization channel (PSC) sequence, a secondary synchronization channel (SSC) sequence, or a combination thereof;

a receiver that obtains a replica of the wireless signal, the replica comprises at least two multipath components;

a signal processor that correlates the replica of the wireless signal with the synchronization sequence, wherein a resulting correlated signal comprises at least two distinct multipath components; and

an analysis module that determines a frequency offset between the wireless signal and the replica of the wireless signal from one or more of the at least two distinct multipath components, wherein the signal processor correlates the replica of the wireless signal with a second synchronization sequence to obtain a second resulting correlated signal, the correlating with the synchronization sequence and the second synchronization sequence are implemented in a frequency domain; and

a frequency converter that transforms the resulting correlated signal and second resulting correlated signal to a time domain;

wherein the analysis module applies a differential product to corresponding multipath components of the resulting signal and the second resulting signal to obtain the frequency offset.

30. The apparatus of claim 29, wherein the transmitter sends the frequency offset to a mobile device.

31. The apparatus of claim 29, further comprising a logic module that employs a despreading function to correlate the replica of the wireless signal with the synchronization sequence.

32. An apparatus that provides wireless communication, comprising:

means for transmitting a wireless signal and a synchronization sequence comprising a primary synchronization channel (PSC) sequence, a secondary synchronization channel (SSC) sequence, or a combination thereof;

means for receiving from a replica of the wireless signal, the replica comprises at least two multipath components;

means for correlating the replica of the wireless signal with the synchronization sequence, wherein a resulting correlated signal comprises at least two distinct multipath components;

means for determining a frequency offset between the wireless signal and the replica of the wireless signal from one or more of the at least two distinct multipath components, wherein the means for correlating correlates the replica of the wireless signal with a second synchronization sequence to obtain a second resulting correlated signal, the correlating with the synchronization sequence and the second synchronization sequence are implemented in a frequency domain; and

means for transforming the resulting correlated signal and the second resulting correlated signal to a time domain, wherein the means for determining applies a differential product to corresponding multipath components of the resulting correlated signal and the second resulting correlated signal to obtain the frequency offset.

33. A non-transitory computer-readable medium, comprising:

computer-readable instructions configured to provide wireless communication, the instructions are executable by at least one computer to;

transmit a wireless signal and a synchronization sequence comprising a primary synchronization channel (PSC) sequence, a secondary synchronization channel (SSC) sequence, or a combination thereof;

receive a replica of the wireless signal, the replica comprises at least two multipath components;

correlate the replica of the wireless signal with the synchronization sequence, wherein a resulting correlated signal comprises at least two distinct multipath components;

determine a frequency offset between the wireless signal and the replica of the wireless signal from one or more of the at least two distinct multipath components;

correlate the replica of the wireless signal with a second synchronization sequence to obtain a second resulting correlated signal, the correlating with the synchronization sequence and the second synchronization sequence are implemented in a frequency domain;

convert the resulting correlated signal and the second resulting correlated signal to a time domain; and

apply a differential product to corresponding multipath components of the resulting correlated signal and the second resulting correlated signal to obtain the frequency offset.