False channel detection for wireless communication

• US 7,852,971 B2
• Filed: 07/21/2006
• Issued: 12/14/2010
• Est. Priority Date: 07/21/2006
• Status: Active Grant

• Current Assignee: Alveolus, Inc. (Merit Medical Systems, Inc.), Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Chen, Tien-Chien, Riddle, Christopher C.
• Primary Examiner(s): Bayard; Emmanuel
• Application Number:
  US11/491,210
• Publication Number:
  US 20080019427A1
• Time in Patent Office: 1,607 Days
• Field of Search: 375/344, 375/345, 375/326, 375/327
• US Class Current: 375/326
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/70775 Multi-dwell schemes, i.e. multiple accumulation times
• 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: H04B 2001/70706 using a code tracking loop, e.g. a delay locked loop
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657

Abstract

Techniques for detecting acquisition of a false channel in a wireless communication system are described. For false channel detection, a peak corresponding to a signal from a base station is initially detected. Frequency acquisition and time tracking of the peak are then performed. The frequency acquisition attempts to determine and correct downconversion frequency error. The time tracking attempts to follow the peak as it moves due to sample timing error and/or changes in channel conditions. Whether the signal is from a desired frequency channel or a false frequency channel is determined based on the time tracking. If a false channel is acquired, then the sampling timing will be either too slow or too fast, and the peak will move at a fast rate. A false channel may be detected based on the movement of the peak.

Claims

1. An apparatus comprising:

at least one processor configured to detect for a peak corresponding to a signal from a base station, to perform frequency acquisition and time tracking of the peak, and to determine based on movement of the peak whether the signal is from a desired frequency channel or a false frequency channel; and

a memory coupled to the at least one processor.

2. The apparatus of claim 1, wherein the at least one processor is configured to detect the movement of the peak based on the time tracking and to determine whether the signal is from the desired frequency channel or the false frequency channel based on the detected movement of the peak.

3. The apparatus of claim 1, wherein the at least one processor is configured to determine whether the signal is from the desired frequency channel or the false frequency channel based on speed of the peak.

4. The apparatus of claim 1, wherein the at least one processor is configured to determine an initial position of the peak at start of the time tracking, to determine a current position of the peak at a check interval, to determine a distance between the current position and the initial position, and to determine whether the signal is from the desired frequency channel or the false frequency channel based on the distance.

5. The apparatus of claim 4, wherein the at least one processor is configured to declare the signal to be from the false frequency channel if the distance is greater than a distance threshold.

6. The apparatus of claim 5, wherein the at least one processor is configured to determine the distance threshold based on a speed threshold for the peak and an amount of time in which the time tracking is performed.

7. The apparatus of claim 5, wherein the at least one processor is configured to constrain the distance threshold to be greater than or equal to a particular minimum distance.

8. The apparatus of claim 1, wherein the at least one processor is configured to perform frequency acquisition and time tracking for a predetermined time duration, unless the signal is determined to be from the false frequency channel.

9. The apparatus of claim 1, wherein the at least one processor is configured to determine received signal strength of the peak and to discard the peak if the received signal strength is below a received signal strength threshold.

10. The apparatus of claim 1, wherein the at least one processor is configured to detect for frequency lock of the peak and to determine whether the signal is from the desired frequency channel or the false frequency channel after detecting frequency lock.

11. The apparatus of claim 1, wherein the at least one processor is configured to perform frequency acquisition of the peak with a wide automatic frequency control (AFC) loop, to detect for frequency lock with the wide AFC loop, and to perform frequency acquisition of the peak with a narrow AFC loop.

12. The apparatus of claim 1, wherein the at least one processor is configured to perform acquisition for each of multiple frequency bins, each frequency bin covering a different range of frequency error, and to detect for the false frequency channel in selected ones of the multiple frequency bins.

13. The apparatus of claim 12, wherein the at least one processor is configured to detect for the false frequency channel in frequency bins in which false frequency channels are potentially present.

14. The apparatus of claim 1, further comprising:

a receiver configured to perform frequency downconversion with a local oscillator (LO) signal generated from a crystal oscillator (XO) signal; and

at least one analog-to-digital converter (ADC) configured to perform sampling with a sampling clock generated from the XO signal.

15. The apparatus of claim 1, wherein the at least one processor is configured to estimate frequency error of a crystal oscillator (XO) signal based on the frequency acquisition, to generate a digital clock based on the XO signal and a divider ratio determined with the estimated frequency error, and to generate samples with the digital clock, the samples being used for the time tracking.

16. A method comprising:

detecting for a peak corresponding to a signal from a base station;

performing in a processor frequency acquisition and time tracking of the peak; and

determining based on movement of the peak whether the signal is from a desired frequency channel or a false frequency channel.

17. The method of claim 16, wherein the determining whether the signal is from the desired frequency channel or the false frequency channel comprises:

detecting the movement of the peak based on the time tracking, and

determining whether the signal is from the desired frequency channel or the false frequency channel based on the detected movement of the peak.

18. The method of claim 16, wherein the determining whether the signal is from the desired frequency channel or the false frequency channel comprises:

determining an initial position of the peak at start of the time tracking,

determining a current position of the peak at a check interval,

determining a distance between the current position and the initial position, and

determining whether the signal is from the desired frequency channel or the false frequency channel based on the distance.

19. The method of claim 18, wherein the determining whether the signal is from the desired frequency channel or the false frequency channel further comprises:

determining a distance threshold based on a speed threshold for the peak and an amount of time in which the time tracking is performed, and

declaring the signal to be from the false frequency channel if the distance is greater than the distance threshold.

20. The method of claim 16, further comprising:

performing acquisition for each of multiple frequency bins, each frequency bin covering a different range of frequency error; and

detecting for the false frequency channel in selected ones of the multiple frequency bins.

21. An apparatus comprising:

means for detecting for a peak corresponding to a signal from a base station;

means for performing frequency acquisition and time tracking of the peak; and

means for determining based on movement of the peak whether the signal is from a desired frequency channel or a false frequency channel.

22. The apparatus of claim 21, wherein the means for determining whether the signal is from the desired frequency channel or the false frequency channel comprises:

means for detecting the movement of the peak based on the time tracking, and

means for determining whether the signal is from the desired frequency channel or the false frequency channel based on the detected movement of the peak.

23. The apparatus of claim 21, wherein the means for determining whether the signal is from the desired frequency channel or the false frequency channel comprises:

means for determining an initial position of the peak at start of the time tracking,

means for determining a current position of the peak at a check interval,

means for determining a distance between the current position and the initial position, and

means for determining whether the signal is from the desired frequency channel or the false frequency channel based on the distance.

24. The apparatus of claim 23, wherein the means for determining whether the signal is from the desired frequency channel or the false frequency channel further comprises:

means for determining a distance threshold based on a speed threshold for the peak and an amount of time in which the time tracking is performed, and

means for declaring the signal to be from the false frequency channel if the distance is greater than the distance threshold.

25. The apparatus of claim 21, further comprising:

means for performing acquisition for each of multiple frequency bins, each frequency bin covering a different range of frequency error; and

means for detecting for the false frequency channel in selected ones of the multiple frequency bins.

26. A processor readable memory for storing instructions operable in a wireless device to:

detect for a peak corresponding to a signal from a base station;

perform frequency acquisition and time tracking of the peak; and

determine based on movement of the peak whether the signal is from a desired frequency channel or a false frequency channel.

27. The processor readable memory of claim 26, and further for storing instructions operable to:

detect the movement of the peak based on the time tracking; and

determine whether the signal is from the desired frequency channel or the false frequency channel based on the detected movement of the peak.