Correlator Bank for Preamble Detection with Frequency Offset
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Solution Overview
Problem
Existing methods for detecting a known preamble waveform in the presence of frequency offset are computationally complex and require significant resources due to the need for complex correlations and large silicon areas.
Innovation Solution
A method and apparatus for detecting a preamble waveform by dividing the correlation into sub-correlations and approximating complex oscillations over piece-wise intervals, reducing computational complexity and silicon area requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex correlation is used for preamble detection in the presence of frequency offset, then detection accuracy is improved, but computational complexity and silicon area increase significantly
Solution Approach 1:
The patent divides the complex correlation operation into multiple sub-correlations of shorter sequences. Instead of performing one large complex correlation across the entire preamble, the method segments the preamble into smaller blocks and performs separate correlations on each block, then combines the results. This segmentation reduces the computational burden and silicon area required while maintaining detection accuracy through proper combination of sub-correlation results.
Solution Approach 2:
The patent changes the correlation length parameter by using shorter sub-correlation sequences instead of the full preamble length. By adjusting this parameter to use shorter blocks (e.g., dividing a 64-sample preamble into multiple 16-sample sub-correlations), the computational complexity is reduced while the overall detection performance is preserved through the combination strategy.
2Reliability
If autocorrelation is performed on the received signal to detect preamble with frequency offset, then detection capability is improved, but the number of multiplications and processing time increase
Solution Approach 1:
The patent segments the autocorrelation process into multiple shorter sub-correlations performed in parallel or sequence on divided blocks of the received signal. This segmentation reduces the time required for each individual correlation operation while the combination of results maintains overall detection reliability.
Solution Approach 2:
The patent employs periodic sub-correlations at different time offsets and frequency hypotheses. By performing multiple shorter periodic correlation operations at different stages rather than one long continuous correlation, the processing time is reduced while maintaining detection capability through the periodic sampling of the signal characteristics.
3Adaptability or versatility
If complex correlation is used to handle frequency offset in preamble detection, then detection accuracy over frequency offset range is improved, but silicon area requirements increase
Solution Approach 1:
The patent divides the frequency offset handling into multiple sub-correlations that can be performed with simpler hardware. Instead of implementing a full complex correlation engine that handles the entire frequency offset range in one operation, the method segments the frequency space and uses multiple shorter sub-correlations, reducing the silicon area required for each correlation unit while maintaining overall frequency offset tolerance.
Solution Approach 2:
The patent creates a universal correlator structure that can handle multiple frequency offset scenarios through the sub-correlation approach. The same simplified correlation hardware is reused across different frequency hypotheses and time blocks, making the silicon area more efficiently utilized while maintaining adaptability to various frequency offset conditions.
Data Source
AI summary
A method for detecting a preamble waveform of a received signal is described. The method includes dividing a correlation into a plurality of sub-correlations, for a plurality of frequency offset indices, k, covering a range of frequency offsets. The correlation has a correlation length equal to N, and a plurality of sub-correlations has a sub-correlations quantity equal to I, each sub-correlation of the plurality of sub-correlations has a sub-correlation length equal to M. A complex oscillation for a template frequency offset associated with k is approximated, the approximation is to be constant over an M-sample interval and is a piece-wise approximation. The approximated complex oscillation has length I. A quantity I of sub-correlations at each k is assembled using the approximated complex oscillation of length I. The method further includes determining that the received signal comprises the preamble based on the assembled sub-correlations and a correlation threshold.