Scanning Methods And Apparatus For System Acquisition

Abstract

A method for searching for a requested CDMA system using a receiver having an AFC circuit is described. A system acquisition scan is performed over a plurality of candidate frequencies. In the scan, a first pilot signal of a first system is detected on one of the frequencies, and information from the first system is decoded. If the first system is different from the requested system, then the first pilot signal is assigned as a first timing reference in the receiver for remaining frequencies. Subsequently, a second pilot signal of a second system is detected on another one of the frequencies, and information from the second system is decoded. If the second system is different from the requested system, and the first pilot signal fails below a predetermined threshold value, then the second pilot signal is selected as a second timing reference in the receiver for remaining frequencies.

1 . A system acquisition method for use in searching for a requested code division multiple access system with use of a receiver having an automatic frequency control (AFC) circuit, the method comprising:
 performing a system acquisition scan over a plurality of candidate frequencies;   in the system acquisition scan:
 detecting a first pilot signal of a first system on one of the candidate frequencies, and decoding information from the first system; 
 if the first system is different from the requested system, then selecting the first pilot signal of the first system as a first timing reference in the receiver for first remaining candidate frequencies in the system acquisition scan; 
 detecting a second pilot signal of a second system on another one of the candidate frequencies, and decoding information from the second system; and 
 if the first pilot signal of the first system fails below a predetermined threshold value of quality, and the second system is different from the requested system, then selecting the second pilot signal of the second system as a second timing reference in the receiver for second remaining candidate frequencies in the system acquisition scan. 
   
     
     
         2 . The system acquisition scanning method of  claim 1 , wherein the acts of selecting the first and the timing references serve to reduce or eliminate an AFC window time for the AFC circuit for converging on a remaining candidate frequency in the system acquisition scan. 
     
     
         3 . The system acquisition scanning method of  claim 1 , further comprising:
 prior to detecting any first pilot signal and decoding any information in the system acquisition scan, employing an initial AFC window time for the AFC circuit; and   wherein the act of selecting the first pilot signal as the first timing reference causes the initial AFC window time for the AFC circuit to be reduced or eliminated.   
     
     
         4 . The system acquisition scanning method of  claim 1 , wherein the act of selecting the first pilot signal is performed based on identifying a successful decoding of the information of the first system. 
     
     
         5 . The system acquisition scanning method of  claim 1 , wherein the information comprises a first system identification of the first system, the method further comprising:
 comparing the first system identification with a predetermined system identification of the requested system for communications;   wherein the requested system comprises one of a registered public land mobile network (RPLMN) or a home public land mobile network (HPLMN); and   wherein the act of selecting the first pilot signal as the first timing reference is performed in response to a mismatch between the first system identification and the predetermined system identification of the RPLMN or HPLMN.   
     
     
         6 . The system acquisition scanning method of  claim 1 , wherein the information comprises a first system identification of the first system, the method further comprising:
 comparing the first system identification with a predetermined system identification of the requested system for communications and, in response to a match:
 terminating the system acquisition scan; and 
 causing the requested system to be acquired for communications. 
   
     
     
         7 . The system acquisition scanning method of  claim 1 , which is performed by a mobile communication device. 
     
     
         8 . The system acquisition scanning method of  claim 1 , wherein the system acquisition scan is a wideband code division multiple access (W-CDMA) system acquisition scan. 
     
     
         9 . A receiver circuitry for a system acquisition scan, comprising:
 an automatic frequency control (AFC) circuit;   a controller configured to operate the receiver circuitry to perform a system acquisition scan over a plurality of candidate frequencies in search for a requested code division multiple access system;   a searcher configured to detect a first pilot signal of a first system on one of the candidate frequencies in the system acquisition scan;   a decoder configured to decode information from the first system in the system acquisition scan;   the controller being further configured to, if the first system is different from the requested system, then select and maintain assignment of the first pilot signal of the first system as a first timing reference in the receiver circuitry for first remaining candidate frequencies in the system acquisition scan;   the searcher being further configured to detect a second pilot signal of a second system on another one of the candidate frequencies in the system acquisition scan;   the decoder being further configured to decode information from the second system in the system acquisition scan; and   the controller being further configured to, if the first pilot signal of the first system fails below a predetermined threshold value of quality, and the second system is different from the requested system, then select and maintain assignment of the second pilot signal of the second system as a second timing reference in the receiver circuitry for second remaining candidate frequencies in the system acquisition scan.   
     
     
         10 . The receiver circuitry of  claim 9 , wherein in maintaining the assignment of the first pilot signal as the first timing reference, the controller operates to reduce an AFC window time of the AFC circuit for convergence on a remaining candidate frequency in the system acquisition scan. 
     
     
         11 . The receiver circuitry of  claim 9 , further comprising:
 the AFC circuit having an initial AFC window time prior to the searcher detecting any first pilot signal and the decoder decoding any information in the system acquisition scan; and   wherein in maintaining assignment of the first pilot signal as the first timing reference, the controller operates to reduce or eliminate the initial AFC window time.   
     
     
         12 . The receiver circuitry of  claim 9 , further comprising:
 the controller being further configured to maintain assignment of the first pilot signal as the first timing reference in response to the successful decoding of the information from the first system by the decoder.   
     
     
         13 . The receiver circuitry of  claim 9 , further comprising:
 the decoder being further configured to decode information comprising a first system identification of the first system.   
     
     
         14 . The receiver circuitry of  claim 9 , further comprising:
 the decoder being further configured to decode information comprising a first system identification of the first system; and   the controller being further configured to maintain assignment of the first pilot signal as the first timing reference in response to the successful decoding of the first system identification of the first system.   
     
     
         15 . The receiver circuitry of  claim 9 , further comprising:
 the decoder being further configured to decode information comprising a first system identification of the first system;   the controller being further configured to compare the first system identification with a predetermined system identification of the requested system for communications; and   the controller being further configured to maintain assignment of the first pilot signal as the first timing reference in response to a mismatch between the first system identification and the predetermined system identification.   
     
     
         16 . The receiver circuitry of  claim 9 , further comprising:
 the decoder being further configured to decode information comprising a first system identification of the first system;   the controller being further configured to compare the first system identification with a predetermined system identification of the first system for communications and, in response to a match:
 terminate the system acquisition scan; and 
 causing the requested system to be acquired for communications. 
   
     
     
         17 . The receiver circuitry of  claim 9 , which is included in a mobile communication device. 
     
     
         18 . The receiver circuitry of  claim 9 , which is operative in accordance with wideband code division multiple access (W-CDMA) standards. 
     
     
         19 . A mobile communication device, comprising:
 one or more processors;   a code divisional multiple access receiver having an automatic frequency control (AFC) circuit;   the one or more processors being configured to operate the receiver to perform a system acquisition scan over a plurality of candidate frequencies in search for a requested system;   a searcher configured to detect a first pilot signal of a first system on one of the candidate frequencies in the system acquisition scan;   a decoder configured to decode information from the first system in the system acquisition scan;   the one or more processors being further configured to, if the system is different from the requested system, then select and maintain assignment of the first pilot signal of the first system as a first timing reference in the receiver for remaining candidate frequencies in the system acquisition scan;   the searcher being further configured to detect a second pilot signal of a second system on another one of the candidate frequencies in the system acquisition scan;   the decoder being further configured to decode information from the second system in the system acquisition scan; and   the one or more processors being further configured to, if the first pilot signal of the first system fails below a predetermined threshold value of quality, and the second system is different from the requested system, then select and maintain assignment of the second pilot signal of the second system as a second timing reference in the receiver circuitry for second remaining candidate frequencies in the system acquisition scan.   
     
     
         20 . The mobile communication device of  claim 19 , wherein in maintaining the assignment of the first pilot signal as the first timing reference, the one or more processors operate to reduce an AFC window time of the AFC circuit for convergence on a remaining candidate frequency in the system acquisition scan. 
     
     
         21 . The mobile communication device of  claim 19 , further comprising:
 the AFC circuit having an initial AFC window time prior to the searcher detecting any first pilot signal and the decoder decoding any information in the system acquisition scan; and   wherein in maintaining assignment of the first pilot signal as the first timing reference, the one or more processors operate to reduce or eliminate the initial AFC window time.   
     
     
         22 . The mobile communication device of  claim 19 , comprising a cellular telephone. 
     
     
         23 . The mobile communication device of  claim 19 , wherein the receiver comprises a wideband code division multiple access (W-CDMA) receiver.