Combinational PRN Code Generation for CSK Demodulation
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Solution Overview
Problem
Current Global Navigation Satellite System (GNSS) receivers face a computational burden in demodulating Code Shift Keying (CSK) data from signals like the L6 signal, which requires numerous correlators and significant hardware and software resources, making existing methods inefficient.
Innovation Solution
A GNSS receiver generates combinational pseudo-random noise (PRN) codes for different bit positions of the CSK modulated symbol, using chip-by-chip summation of shifted PRN codes to reduce the number of correlators needed, allowing for efficient demodulation of CSK data with fewer resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brute force implementation with 256 different correlators is used, then CSK data demodulation can be performed, but computational burden and hardware resources increase significantly
Solution Approach 1:
The patent combines multiple PRN codes (specifically 8 PRN codes for an 8-bit symbol) into a single composite PRN code through multiplication. This merging approach allows the receiver to process all 8 bit positions simultaneously using one correlator instead of requiring 256 separate correlators, dramatically reducing hardware complexity while maintaining demodulation capability
Solution Approach 2:
The composite PRN code serves multiple functions: it simultaneously represents all 8 bit positions of the CSK modulated symbol and enables parallel processing of all bit positions through a single correlator. This multi-functionality eliminates the need for multiple specialized correlators, reducing device complexity while preserving reliability
2Reliability
If Fourier Transforms and Inverse Fourier Transforms are implemented, then CSK data can be demodulated, but hardware, software, and computational resources are greatly consumed
Solution Approach 1:
The patent extracts the essential demodulation function from complex Fourier Transform operations and implements it through direct correlation with composite PRN codes. This extraction eliminates the need for computationally intensive Fourier Transforms while retaining the core capability to demodulate CSK data, significantly reducing computational resource consumption
Solution Approach 2:
Instead of using complex Fourier Transform algorithms, the patent creates simplified composite PRN codes that directly encode the correlation patterns needed for demodulation. These composite codes serve as simplified copies of the full demodulation functionality, achieving the same result with minimal computational overhead
Data Source
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AI summary
An apparatus comprising a processor coupled to a memory, the processor configured to: generate a combinational code based on a chip-by-chip summation of a first selected number of a plurality of receiver codes and a chip-by-chip subtraction of a second selected number of the plurality of receiver codes, wherein each of the plurality of receiver codes is a different shift in chips to a predetermined code; correlate a received satellite signal with the combinational code to produce a power correlation value, in particular wherein the received satellite signal is a L6 satellite signal received from a Global Navigation Satellite Signal (GNSS) satellite associated with a Quasi-Zenith Satellite System (QZSS); determine that the received satellite signal is present for demodulation in response to the power correlation value being greater than a threshold value; and determine that the received satellite signal is lost in response to the power correlation value being less than or equal to the threshold value.