User terminal parallel searcher

Abstract

The present invention is a method and apparatus for detecting the presence of or acquiring a signal in a data stream, where the signal has been spread using a pseudonoise sequence. The method comprises the steps of delaying a pseudonoise sequence by a plurality of predetermined delays to produce a plurality of delayed pseudonoise sequences, combining each of the delayed pseudonoise sequences with the data stream to produce a plurality of despread data streams, and accumulating each of the despread data streams for a preselected duration to produce a plurality of coherent sums. Each of the coherent sums are accumulated for a further duration to produce a plurality of non-coherent sums. The non-coherent sums are examined to determine the most likely PN offset hypothesis.

1 . A parallel searcher for use in a wireless communications device, comprising: 
 a pseudonoise code generator for generating at least one pseudonoise sequence having a predetermined chip period;    a plurality of slices, each slice including: 
 a delay unit for delaying said pseudonoise sequence by a predetermined chip period,  
 a despreader for operating on a data stream as a function of a pseudonoise sequence, which is a delayed pseudonoise sequence from a previous slice when the slice is not a first slice of said plurality, and  
 at least one coherent accumulator for coherently accumulating an output of said despreader; and  
   a non-coherent accumulator that accumulates the output of each slice non-coherently to produce a non-coherent sum for each slice;    wherein an output from said pseudonoise generator is coupled to an input of the delay unit of a next slice, except when the current slice is the last slice of said plurality;    wherein each slice has an output from the delay unit coupled to an input of the delay unit of a next slice.    
     
     
         2 . The parallel searcher of  claim 1 , further comprising an accumulator controller for sequentially initializing said coherent accumulators and sequentially coupling the outputs of said coherent accumulators to said non-coherent accumulator based on the state of said pseudonoise sequence.  
     
     
         3 . The parallel searcher of  claim 1 , wherein each said coherent accumulator comprises: 
 a multiplier that receives said pseudonoise sequence and said data stream; and    an accumulator that receives the output of said multiplier.    
     
     
         4 - 5 . (Cancelled)  
     
     
         6 . The parallel searcher of  claim 1 , further comprising: 
 a control processor that generates a threshold; and    a threshold detector that receives said non-coherent sum from said non-coherent accumulator and selectively provides the delay associated with said non-coherent sum to said control processor based on said threshold.    
     
     
         7 . (Cancelled)  
     
     
         8 . The parallel searcher of  claim 1 , further comprising: 
 a Walsh code generator that generates a Walsh code; and    a multiplier that combines said Walsh code with said pseudonoise sequence prior to said slices.    
     
     
         9 . (Cancelled)  
     
     
         10 . The parallel searcher of  claim 1  wherein said pseudonoise code generator is programmable for alternative PN codes in response to a selection input allowing searches over different PN codes.  
     
     
         11 . (Cancelled)  
     
     
         12 . A wireless communication device comprising: 
 a parallel searcher, comprising: 
 a pseudonoise code generator for generating a pseudonoise sequence;  
 a plurality of slice processing elements, each slice including: 
 a delay unit for delaying said pseudonoise sequence by a predetermined chip time,  
 a despreader for operating on a data stream as a function of said delayed pseudonoise sequence except for when it is a first despreader, and  
 at least one coherent accumulator for coherently accumulating an output of said despreader; and  
 
   a non-coherent accumulator that accumulates the output of each slice non-coherently to produce a non-coherent sum for each slice;    wherein an output from said pseudonoise generator is coupled to an input of the delay unit of a next slice, except when the current slice is the last slice of said plurality;    wherein each slice has an output from the delay unit coupled to an input of the delay unit of a next slice.    
     
     
         13 . A method for detecting the presence of a signal in a data stream, said signal spread using a pseudonoise sequence, comprising the steps of: 
 delaying a pseudonoise sequence by a plurality of predetermined delays to produce a plurality of delayed pseudonoise sequences;    combining each of said delayed pseudonoise sequences with the data stream to produce a plurality of despread data streams; and    accumulating each of said despread data streams for a duration to produce a plurality of coherent sums.    
     
     
         14 . The method of  claim 13 , further comprising the step of accumulating each of said coherent sums for a further duration to produce a plurality of non-coherent sums.  
     
     
         15 . The method of  claim 14 , further comprising the steps of: 
 comparing each of said non-coherent sums to a threshold; and    selecting a non-coherent sum that exceeds said threshold.    
     
     
         16 . The method of  claim 15 , further comprising the step of despreading said data stream using a delayed version of said pseudonoise sequence, said delayed version produced by delaying said pseudonoise sequence using the one of said plurality of predetermined delays that corresponds to said selected non-coherent sum.  
     
     
         17 . (Cancelled)