Reducing memory usage in noncoherent signal processing
View Patent ↗A method for detecting a positioning signal includes (a) correlating a segment of a received positioning signal with a reference signal of a selected code phase and frequency to obtain a correlation value, (b) if the correlation value is less than a predetermined minimum, assigning the correlation value to the predetermined minimum, and (c) accumulating the correlation value in a sum of correlation values obtained using other segments of the received positioning signal. In addition, the correlation value may be reduced by a predetermined value, which is preferably an expected mean value for a noise component in the segment of the received positioning signal.
1. A satellite-based positioning receiver, comprising:
a signal processor configured to process a positioning signal from a satellite, the positioning signal being divided into segments, wherein the signal processor is configured to process the positioning signal using the acts of:
processing each segment in a subset of the segments by:
correlating the segment with a reference signal of a selected code phase and frequency to obtain a complex correlation value;
processing the complex correlation value to provide a non-coherent correlation value;
summing the non-coherent correlation value with a previously-calculated non-coherent integration sum to provide a current non-coherent integration sum;
if the current non-coherent integration sum is less than a predetermined minimum, assigning the current non-coherent integration sum to the predetermined minimum; and
processing the current non-coherent integration sum to determine whether the positioning signal is detected according to the selected code phase and frequency.
2. The receiver of claim 1 , wherein processing the complex correlation value includes obtaining a modulus of the complex correlation value and reducing the modulus by a predetermined value.
3. The receiver of claim 2 , wherein the modulus is reduced by an expected mean value for a noise component in the positioning signal.
4. The receiver of claim 3 , wherein processing the complex correlation value includes quantizing the modulus.
5. The receiver of claim 1 , wherein processing the current non-coherent integration sum includes comparing the current non-coherent integration sum to a predetermined threshold value.
6. The receiver of claim 1 , wherein the subset of segments comprises all of the segments in the positioning signal.
7. The receiver of claim 1 , wherein a size of the subset of segments is less than all of the segments in the positioning signal, the size of the subset being determined by whether the current non-coherent integration sum exceeds a maximum value.