Artificial window size interrupt reduction system for CDMA receiver

• US 5,726,982 A
• Filed: 06/06/1995
• Issued: 03/10/1998
• Est. Priority Date: 04/04/1995
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: OKI Telecom, Inc. (OKI Electric Industry Company Limited)
• Inventors: Witter, Robert C.
• Primary Examiner(s): NGUYEN, CHAU T
• Application Number:
  US08/466,074
• Time in Patent Office: 1,008 Days
• Field of Search: 370/69.1, 370/74, 370/95.1, 370/95.3, 370/18, 370/98, 370/100.1, 370/105.4, 370/105.5, 370/310, 370/320, 370/324, 370/335, 370/342, 370/503, 370/491, 370/509 , 370/512, 370/514, 370/515, 370/500, 379/59, 379/60, 375/205, 375/206, 375/354, 375/356, 375/342, 455/33.1, 455/33.2, 455/51.1, 455/67.4
• US Class Current: 370/335
• CPC Class Codes: H04B 1/70753 Partial phase search
• 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 2201/70701 featuring pilot assisted reception

Abstract

A method and an apparatus for searching code division multiple access pilot signal energies includes limiting a pilot signal window size above a lower limit and only analyzing search result data corresponding to an instructed pilot signal window size. A central processing unit instructs a searcher receiver within a mobile station modem application specific integrated circuit to search for pilot signal energies within an instructed pilot signal search window unless the instructed pilot signal window size is smaller than a pilot signal window size lower limit. In such a case, the pilot signal search window size is artificially designated as the pilot signal window size lower limit to prevent excessive search completion interrupts from over utilizing central processing unit resources. The central processing unit analyzes only the middle search results corresponding to the pilot signal window size as instructed from the base station to maintain the ability of effectively searching pilot signal window sizes smaller than the pilot signal window size lower limit.

Claims

1. A mobile station method of searching for a base station pilot signal, said method comprising steps of:

receiving from a base station an instructed pilot signal search window size;

comparing the instructed pilot signal search window size to a pilot signal search window size limit, wherein the pilot signal search window size limit is a lower limit;

generating a resultant pilot signal search window size responsive to the comparing step, wherein the resultant pilot signal search window size is defined to be the pilot signal search window size limit responsive to the instructed pilot signal search window size being lower than the pilot signal search window size limit, and wherein the resultant pilot signal scorch window size is defined to be the instructed pilot signal search window size responsive to the instructed pilot signal search window size being higher than the pilot signal search window size limit;

searching for the pilot signal using the resultant pilot signal search window size, including generating result data corresponding to the resultant pilot signal search window size;

analyzing only a centered middle portion of the result data, wherein the analyzed portion is determined by {((the pilot signal search window size limit)-(the instructed pilot signal search window size))/2} through {((the pilot signal search window size limit)+(the instructed pilot signal search window size))/2-1}; and

assigning a plurality of digital receivers based upon the result data.

2. A mobile station method of searching for a base station pilot signal, said method comprising steps of:

receiving from a base station an instructed pilot signal search window size;

comparing the instructed pilot signal search window size to a pilot signal search window size limit;

generating a resultant pilot signal search window size responsive to the comparing step; and

searching for the pilot signal using the resultant pilot signal search window size;

including generating result data corresponding to the resultant pilot signal search window size; and

analyzing only a portion of the result data.

3. The method as claimed in claim 2, further comprising a step of assigning a plurality of digital receivers based upon the result data.

4. The method as claimed in claim 2, wherein the analyzed portion defines a centered middle portion of the result data.

5. The method as claimed in claim 2, wherein the analyzed portion is determined by

{((the pilot signal search window size limit)-(the instructed pilot signal search window size))/2} through {((the pilot signal search window size limit)+(the instructed pilot signal search window size))/2-1}.

6. The method as claimed in claim 2, wherein the pilot signal search window size limit is a lower limit.

7. The method as claimed in claim 6, wherein the generating step includes defining the resultant pilot signal search window size to be the pilot signal search window size limit responsive to the instructed pilot signal search window size being lower than the pilot signal search window size limit.

8. The method as claimed in claim 7, wherein the generating step includes defining the resultant pilot signal search window size to be the instructed pilot signal search window size responsive to the instructed pilot signal search window size being higher than the pilot signal search window size limit.

9. The method as claimed in claim 6, wherein the pilot signal search window size limit equals at least 60 chips.

10. A mobile station method of searching for a base station pilot signal, the method comprising steps of:

receiving from a base station an instructed pilot signal search window size;

comparing the instructed pilot signal search window size to a pilot signal search window size lower limit; and

searching for the pilot signal using a search window size equal to the pilot signal search window size lower limit responsive to determining the instructed pilot signal search window size to be below the pilot signal search window size lower limit.

11. The method as claimed in claim 10, further comprising steps of generating search result data in search result data memory locations and analyzing only a portion of the search result data.

12. The method as claimed in claim 11, wherein the analyzing step includes analyzing search result data corresponding only to the instructed pilot signal search window size.

13. The method as claimed in claim 11, wherein the analyzing step includes examining a range of search result data memory locations as a function of the pilot signal search window size lower limit and the instructed pilot signal search window size.

14. The method as claimed in claim 13, wherein the range of search result data memory locations define a centered middle portion relative to all of the search result data.

15. The method as claimed in claim 13, wherein the function includes

{((the pilot signal search window size lower limit)-(the instructed pilot signal search window size))/2} through {((the pilot signal search window size lower limit)+(the instructed pilot signal search window size))/2-1}.

16. The method as claimed in claim 10, further comprising a step of assigning digital receivers based upon the search result data.

17. The method as claimed in claim 10, wherein the pilot signal search window size lower limit is based upon mobile station processor availability and speed.