Optimized Spreading Codes for Satellite Navigation
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Solution Overview
Problem
Current satellite navigation systems, such as GPS, face limitations with Gold codes, including restricted code lengths, adverse impacts from truncation, and suboptimal cross-correlation properties, especially at high bit rates, which affect positioning accuracy and signal acquisition.
Innovation Solution
A method for generating a set of spreading codes through an optimization process that creates bit patterns of arbitrary lengths, ensuring balance, zero auto-correlation side-lobes, and minimizing cross-correlation values, allowing for better signal separation and robustness against interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Gold codes are used for satellite navigation, then code generation is straightforward, but code length is restricted and cross-correlation properties are suboptimal
Solution Approach 1:
The patent changes the fundamental parameter of code generation from mathematical algorithms (Gold codes) to optimization-based random bit patterns. This allows arbitrary code lengths to be achieved while maintaining good correlation properties, resolving the contradiction between generation simplicity and code length flexibility.
Solution Approach 2:
The patent replaces the mathematical/algorithmic mechanism of Gold code generation with an optimization-based mechanism that uses random bit patterns and correlation minimization. This substitution enables greater code length flexibility while maintaining ease of implementation through automated optimization.
2Measurement precision
If spreading code bit rate is increased to improve positioning accuracy, then measurement precision improves, but cross-correlation interference increases
Solution Approach 1:
The patent employs an optimization process that uses feedback from cross-correlation calculations to modify bit patterns. The optimization loop continuously adjusts code patterns based on their correlation characteristics, enabling high bit rates while minimizing cross-correlation interference through iterative improvement.
Solution Approach 2:
The patent changes the code patterns through optimization to achieve a favorable balance between bit rate and cross-correlation properties. By adjusting the bit patterns based on their correlation characteristics, the system can operate at higher bit rates without excessive interference.
3Measurement precision
If spreading code length is increased to reduce ambiguity, then positioning accuracy improves, but signal acquisition time increases
Solution Approach 1:
The patent performs preliminary optimization of code patterns to ensure they have desirable correlation properties from the start. This preliminary action reduces the need for lengthy acquisition processes, as the codes are pre-configured to enable rapid synchronization despite their length.
Solution Approach 2:
The optimization process adjusts code parameters (bit patterns) to achieve a balance between length and acquisition performance. By carefully selecting and optimizing the bit patterns, the system can use longer codes for accuracy while maintaining acceptable acquisition times through improved correlation characteristics.
4Adaptability or versatility
If Gold codes are truncated to achieve desired length, then code length flexibility is improved, but cross-correlation properties deteriorate
Solution Approach 1:
Instead of truncating long Gold codes to achieve desired lengths (the conventional approach), the patent inverts the approach by generating random bit patterns of the exact desired length and then optimizing them. This inversion avoids the degradation of cross-correlation properties that occurs with truncation.
Solution Approach 2:
The patent changes the code generation approach from algorithmic (Gold codes) to optimization-based random patterns. This allows achieving any desired code length while maintaining good cross-correlation properties, as the optimization process ensures desirable correlation characteristics are met regardless of length.
Data Source
AI summary
One embodiment of the present invention provides a method of creating a set of spreading codes for use in a satellite navigation system comprising a constellation of satellites. Each satellite in the constellation is to be allocated a spreading code from the set of spreading codes. The method comprises generating an initial set of bit patterns (105), where each bit pattern represents a potential spreading code, and performing an optimization process on the initial set of bit patterns (110). The optimization process modifies at least some of the bit patterns in the initial set to create a final set of bit patterns for use as the set of spreading codes (115) for the satellite navigation system. Receivers that support the satellite navigation system incorporate the final set of bit patterns for use in signal acquisition and position determination.