Time-Tracking for Clustered Demodulation Elements in a Spread Spectrum System

• US 20080260005A1
• Filed: 08/15/2007
• Published: 10/23/2008
• Est. Priority Date: 01/11/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Rick, Roland R., Zhang, Haitao, Patel, Shimman, Saints, Keith
• Granted Patent: US 7,688,882 B2
• Time in Patent Office: Days
• US Class Current: 375/148
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• 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 7/0697 using spatial multiplexing

Abstract

An apparatus, such as a subscriber unit or a base station within a spread spectrum communication system, provides advanced control over the time-tracking of demodulation elements when unresolvable multipath situations arise. The apparatus provides merge protection that prevents clustered demodulation elements from contracting beyond a minimum time span. In addition, the apparatus provides a master/slave feature for synchronizing the time-tracking of the demodulation elements when clustered around a multipath signal.

Claims

1. A wireless communication device comprising:

a searcher that generates a list of paths associated with received signals, each path in the list of paths identified by a corresponding time offset and corresponding signal strength;

a plurality of demodulation elements, each of the plurality of demodulation elements having a corresponding time offset and corresponding signal strength;

a controller that adds a virtual path to the list of paths based on a comparison of the time offsets and the signal strengths of the plurality of demodulation elements with the time offsets and the signal strengths of the list of paths.

2. The device of claim 1, wherein the virtual path is associated with a corresponding time offset and signal strength, which does not correspond to signal peaks detected from received signals.

3. The device of claim 1, wherein the controller replaces a first path from the list of paths with a replacement path having a first time offset and a first signal strength associated with a first demodulation element based on a comparison of the first path and the first demodulation element, and wherein the controller places the virtual path at a second time period and a second signal strength relative to the replacement path.

4. The device of claim 1, wherein the controller identifies a cluster of demodulation elements based a comparison of the corresponding time offsets of the plurality of demodulation units relative to a finger association threshold.

5. The device of claim 1, wherein the controller adds the virtual path if not more than one path from the list of paths is within a determined time period from a cluster of demodulations elements selected from the plurality of demodulation elements.

6. The device of claim 5, wherein the cluster of demodulation elements comprises a single demodulation element.

7. A method for managing a plurality of demodulation units in a wireless communication device, the wireless communication device including a plurality of demodulation elements, each of the plurality of demodulation elements having a corresponding time offset and corresponding signal strength, the method comprising:

generating a list of paths associated with received signals, each path in the list of paths identified by a corresponding time offset and corresponding signal strength;

comparing the time offsets and the signal strengths of the plurality of demodulation elements with the time offsets and the signal strengths of the list of paths;

adding a virtual path to the list of paths based on the comparison.

8. The method of claim 7, wherein the virtual path is associated with a corresponding time offset and signal strength, which does not correspond to signal peaks detected from received signals.

9. The method of claim 7, further comprising:

replacing a first path from the list of paths with a replacement path having a first time offset and a first signal strength associated with a first demodulation element based on a comparison of the first path and the first demodulation element;

placing the virtual path at a second time period and a second signal strength relative to the replacement path.

10. The method of claim 7, further comprising identifying a cluster of demodulation elements based a comparison of the corresponding time offsets of the plurality of demodulation units relative to a finger association threshold.

11. The method of claim 7, wherein the virtual path is added if not more than one path from the list of paths is within a determined time period from a cluster of demodulations elements selected from the plurality of demodulation elements.

12. The method of claim 11, wherein the cluster of demodulation elements comprises a single demodulation element.

13. A wireless communication device comprising:

a plurality of demodulation elements, each of the plurality of demodulation elements having a corresponding time offset and corresponding signal strength;

means for generating a list of paths associated with received signals, each path in the list of paths identified by a corresponding time offset and corresponding signal strength;

means for comparing the time offsets and the signal strengths of the plurality of demodulation elements with the time offsets and the signal strengths of the list of paths;

means for adding a virtual path to the list of paths based on the comparison.

14. The device of claim 13, wherein the virtual path is associated with a corresponding time offset and signal strength, which does not correspond to signal peaks detected from received signals.

15. The device of claim 13, further comprising:

means for replacing a first path from the list of paths with a replacement path having a first time offset and a first signal strength associated with a first demodulation element based on a comparison of the first path and the first demodulation element;

means for placing the virtual path at a second time period and a second signal strength relative to the replacement path.

16. The device of claim 13, further comprising means for identifying a cluster of demodulation elements based a comparison of the corresponding time offsets of the plurality of demodulation units relative to a finger association threshold.

17. The device of claim 13, wherein the virtual path is added if not more than one path from the list of paths is within a determined time period from a cluster of demodulations elements selected from the plurality of demodulation elements.

18. The device of claim 17, wherein the cluster of demodulation elements comprises a single demodulation element.