System for continuous wave rejection

Abstract

A method for receiving transmitted signals in the presence of CW interference is used in a communication system that determines the presence of a code in a received signal. A detector threshold is compared calculations made in accordance with a sample of a received signal. A first input power value of the received signal is obtained at a first sample time and a second input power value of the received signal is obtained at a second sample time. The first and second power values are compared in order to provide an input sample comparison and the forgoing steps are repeated in order to provide a plurality of input sample comparisons, and the detector threshold is adjusted in accordance with the plurality of sample comparisons. The CW signal can be strongly correlated with a short code used for the acquisition purposes, while avoiding false alarms.

1 . A method for receiving transmitted signals in a CDMA communication system having a detection threshold for comparing with a sample of a received signal in order to determine the presence of CW interference in the received signal, comprising the steps of: 
 (a) obtaining a first sample of the received signal at a first sample time, the first sample including a calculated correlation value between a first input signal and a locally-generated pseudorandom code;    (b) obtaining a second sample of the received signal at a second sample time, the second sample including a calculated correlation value between a second input signal and a locally-generated pseudorandom code;    (c) comparing the first and second samples in order to provide an input sample comparison;    (d) repeating steps (a)-(c) in order to provide a plurality of input sample comparisons; and    (e) adjusting the detection threshold in response to at least one of said input sample comparisons.    
   
   
       2 . The method of  claim 1 , further comprising providing the adjustment of the detection threshold in response to detection of said CW interference.  
   
   
       3 . The method of  claim 1 , further comprising: 
 providing the detection threshold as an upper threshold; and    adjusting the detection threshold upwards in accordance with detection of CW interference.    
   
   
       4 . The method of  claim 2 , further comprising determining whether said first and second samples indicate the presence of CW interference.  
   
   
       5 . The method of  claim 4 , further comprising adjusting the detection threshold in accordance with the CW interference determination.  
   
   
       6 . The method of  claim 2 , wherein said pseudorandom code is a short code.  
   
   
       7 . The method of  claim 1 , wherein said pseudorandom code is a short code.  
   
   
       8 . The method of  claim 1 , further comprising determining an average of the plurality of input sample comparisons.  
   
   
       9 . The method of  claim 1 , wherein the step of comparing said first and second input samples comprises performing a subtraction operation upon said first and second input samples.  
   
   
       10 . The method of  claim 1 , wherein the step of comparing the first and second input samples further includes averaging the first and second input samples.  
   
   
       11 . In a CDMA communication system, a method of receiving transmitted signals in the presence of CW interference comprising: 
 sampling a received signal to generate a plurality of signal samples;    calculating a correlation value between said signal samples and a locally-generated pseudorandom code;    converting each signal sample into a respective power value;    selecting and eliminating a maximum power value from the plurality of power values and said correlation values;    averaging the remaining power values to generate an average power value;    determining an average difference between each power value and the power value of an adjacent sample; and    comparing the average power value to the average difference to adjust a detection threshold in response to said CW interference.    
   
   
       12 . The method of  claim 11 , further comprising providing the adjustment of the detection threshold in response to detection of said CW interference.  
   
   
       13 . The method of  claim 11 , further comprising: 
 providing the detection threshold as an upper threshold; and    adjusting the detection threshold upwards in accordance with detection of CW interference.    
   
   
       14 . The method of  claim 13 , further comprising determining whether said first and second samples indicate the presence of CW interference.  
   
   
       15 . The method of  claim 14 , further comprising adjusting the detection threshold in accordance with the CW interference determination.  
   
   
       16 . The method of  claim 11 , further comprising comparing the first and second input samples to generate the average power value.  
   
   
       17 . A method for a user equipment (UE) to receive transmitted signals in a CDMA communication system having a detection threshold for detecting codes in the received signals in the presence of CW interference in the received signal, characterized by the steps of: 
 (a) obtaining a first sample of the received signal at a first sample time, the first sample including a calculated correlation value between a first input signal and a locally-generated pseudorandom code;    (b) obtaining a second sample of the received signal at a second sample time, the second sample including a calculated correlation value between a first input signal and a locally-generated pseudorandom code;    (c) comparing the first and second samples in order to provide a first correlation; and    (d) adjusting the detection threshold in response to said first correlation.    
   
   
       18 . The method of  claim 17 , further comprising providing the adjustment of the detection threshold in response to detection of said CW interference.  
   
   
       19 . The method of  claim 17 , further comprising the steps of: 
 obtaining at said first sample time a third input sample of the received signal;    obtaining at said second sample time a fourth input sample of the received signal; and    comparing said third and fourth input sample and generating there from a second correlation; whereby a relationship between said first correlation and said second correlation determines the adjustment to said threshold.    
   
   
       20 . The method of  claim 19 , wherein said comparison of said first and second correlations is equivalent to the amount of CW interference present in said received signal.  
   
   
       21 . The method of  claim 19 , wherein: 
 said comparison of said first and second correlations is equivalent to the amount of CW interference present in said received signal; and    said comparison of said third and fourth correlations is equivalent to the amount of background noise present in said received signal.    
   
   
       22 . The method of  claim 21 , further comprising repeating said steps (a)-(c) in order to provide a plurality of first correlations and repeating steps (f)-(h) in order to provide a plurality of second correlations.  
   
   
       23 . The method of  claim 17 , further comprising repeating said steps (a)-(c) in order to provide a plurality of first correlations.  
   
   
       24 . The method of  claim 22 , further comprising averaging said plurality of first correlations and said plurality of second correlations, whereby the relationship between said first correlation and said second correlation provides an adjustment to the detection threshold.