FAST ACQUISITION OF A PILOT SIGNAL IN A WIRELESS COMMUNICATION DEVICE

• US 20070223566A1
• Filed: 05/29/2007
• Published: 09/27/2007
• Est. Priority Date: 03/31/2000
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Hughes, Robbin, Yao, De-Gang, Glazko, Serguei
• Granted Patent: US 7,684,470 B2
• Time in Patent Office: Days
• US Class Current: 375/147
• CPC Class Codes: H04B 1/70751 using partial detection H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/70754 Setting of search window, i.e. range of code offsets to be searched H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/70775 Multi-dwell schemes, i.e. multiple accumulation times
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects

Abstract

In a remote unit of a wireless communication system, the speed of acquisition, or reacquisition, of a pilot signal by a search engine is increased. PN space is divided into segments and a coarse search of each segment is performed using a set of “fast” search parameters. A set of peak signal strengths, along with their corresponding PN offsets, is saved for each segment of PN space. Following the search of all segments of PN space, the peak signal strengths which were saved during the coarse acquisition are evaluated. Coarse acquisition search results are used by the remote unit to determine fine search window parameters for subsequent searches performed by the remote unit search engine. The fine search parameters concentrate searching efforts on portions of PN space most likely to contain a viable base station pilot signal.

Claims

1. A wireless communication system comprising:

a plurality of base stations, each configured to transmit a PN encoded pilot signal at a different time offset than other base stations; and

at least one remote unit configured to perform a coarse search of a entire PN space using course search parameters and to perform a fine search of a select portion of the entire PN space based on the coarse search using fine search parameters.

2. The wireless communication system of claim 1 wherein a first number of non-coherent passes during the course search is less than a second number of non-coherent passes during the fine search.

3. The wireless communication system of claim 1 wherein a first integration interval during the course search is less than a second integration interval during the fine search.

4. The wireless communication system of claim 1 wherein the at least one remote unit is further configured to divide the entire PN space into a plurality of segments, the course search performed over each of the plurality of segments, the fine search performed over less than each of the plurality of segments.

5. A remote unit in a wireless communication system comprising:

a search engine configured to receive course search parameters, to perform a coarse search of an entire PN space using the course search parameters, to output search results of the course search, to receive fine search parameters including a select portion of the entire PN space to conduct a fine search, to perform a fine search of the select portion of the entire PN space using the fine search parameters;

a memory configured to receive and store the search results of the search engine; and

a controller configured to receive the course search results from the memory, to determine the select portion of the entire PN space based on the coarse search results, and to transmit the fine and course search parameters the search engine.

6. The remote unit of claim 5 wherein a first number of non-coherent passes during the course search is less than a second number of non-coherent passes during the fine search.

7. The remote unit of claim 5 wherein a first integration interval during the course search is less than a second integration interval during the fine search.

8. The remote unit of claim 5 wherein the controller is further configured to divide the entire PN space into a plurality of segments, the course search performed over each of the plurality of segments, the fine search performed over less than each of the plurality of segments.

9. A method of initially acquiring a base station by a wireless remote unit, the method comprising:

performing a course search of an entire PN space for a pilot signal according using coarse search parameters;

determining a select portion of the entire PN space to conduct a fine search based on the course search; and

performing a fine search of the select portions of the entire PN space using fine search parameters.

10. The method of claim 9 wherein a first number of non-coherent passes during the course search is less than a second number of non-coherent passes during the fine search.

11. The method of claim 9 wherein a first integration interval during the course search is less than a second integration interval during the fine search.

12. The method of claim 9 further comprising dividing the entire PN space into a plurality of segments, the course search performed over each of the plurality of segments, the fine search performed over less than each of the plurality of segments.

13. The method of claim 9 further comprising storing all measured signal levels identified during the coarse search which exceed a threshold level and a corresponding PN offsets.

14. A remote unit in a wireless communication system configured to perform a search for a pilot signal, the remote unit comprising:

means for performing a course search of an entire PN space for a pilot signal according using coarse search parameters;

means for determining a select portion of the entire PN space to conduct a fine search based on the course search; and

means for performing a fine search of the select portions of the entire PN space using fine search parameters.