Coherent Match Filtering with Subcode FFT Signal Acquisition
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently processing large acquisition sequences, leading to high computational complexity and memory usage, especially when coherent match filtering is required, and frequency variations complicate signal acquisition.
Innovation Solution
The approach involves dividing a large acquisition code symbol sequence into smaller subcodes, allowing for reduced computational operations and memory usage by using a subcode structure, and employing frequency domain processing with overlap and save methods to alleviate time aliasing, while maintaining processing gain through differential product calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FFT calculations are performed on large acquisition sequences, then signal acquisition accuracy is improved, but hardware resource usage and memory requirements increase significantly
Solution Approach 1:
The patent divides a large acquisition sequence into multiple smaller subcodes. Instead of performing a single large FFT on the entire sequence, the system performs separate FFT calculations on each subcode. This segmentation reduces the computational complexity and memory requirements of each individual FFT operation while maintaining the overall signal acquisition accuracy through coherent combination of the subcode results.
2Measurement precision
If coherent detection methods are used, then demodulation accuracy is improved, but detection complexity and time consumption increase
Solution Approach 1:
The patent applies segmentation to the coherent detection process by dividing the acquisition sequence into subcodes. This allows the system to perform frequency and phase offset compensation on smaller, more manageable segments. The differential product calculator processes these segmented subcodes, reducing the overall detection complexity while maintaining coherent detection accuracy through the combination of results from all subcodes.
Solution Approach 2:
The patent performs frequency and phase offset compensation (preliminary action) on each subcode before combining the results. By pre-compensating for frequency and phase variations in each segment using the differential product calculator, the system simplifies the subsequent combination process and reduces the overall detection complexity while maintaining accurate coherent detection.
3Productivity
If acquisition sequence size increases, then processing gain is improved, but FFT computational operations and memory usage increase
Solution Approach 1:
The patent segments the large acquisition sequence into smaller subcodes, allowing the system to achieve the necessary processing gain through the coherent combination of multiple subcode FFT results rather than requiring a single large FFT. This approach maintains the processing gain benefits of long sequences while reducing the computational operations and time required for FFT calculations.
Data Source
AI summary
Embodiments include methods and apparatus for verifying the detection of a correlation peak, which may represent an acquisition of a received acquisition code symbol sequence. The method includes determining a series of coherently-aligned peaks from a series of correlation peaks. Determining the plurality of coherently-aligned peaks includes correcting a frequency offset and a phase offset for each of the plurality of correlation peaks. A coherent match filter process is performed on the plurality of coherently-aligned peaks. A detection of the correlation peak may be verified when the match filter result exceeds a threshold.