Weak Data Bit Sync in Satellite Positioning Systems
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Solution Overview
Problem
Conventional synchronization schemes for satellite positioning systems are often time-consuming and can lead to position errors due to satellite motion, especially when using approaches like 'Sync Free Nav' that require acquiring signals from five satellites, which is not always possible.
Innovation Solution
A method that speeds up data bit synchronization by allowing a higher probability of false alarm (Pfa) in the bit sync computation and combines signals from multiple satellites for improved sensitivity and speed, enabling successful synchronization with fewer satellites and reducing time offset errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional synchronization schemes are used, then synchronization can be achieved, but the process is time-consuming and leads to position errors due to satellite motion
Solution Approach 1:
The patent applies preliminary action by using coarse time offset estimates from GPS almanac data and other sources to pre-align signals before performing fine synchronization. This preliminary alignment reduces the search space and enables faster convergence to the correct time offset, thereby reducing both synchronization time and position errors caused by satellite motion during the synchronization process.
Solution Approach 2:
The patent merges signals from multiple satellites by combining their power values after time alignment. This combining approach improves the signal-to-noise ratio and enables successful synchronization even when individual satellite signals are weak or unavailable, thereby reducing synchronization time without compromising position accuracy.
2Loss of time
If Sync Free Nav approach is used to reduce synchronization time, then fewer satellites are needed, but position errors increase due to time offsets
Solution Approach 1:
The patent applies preliminary action by using coarse time offset estimates from GPS almanac data and other sources to pre-align signals before performing fine synchronization. This preliminary alignment reduces the search space and enables faster convergence to the correct time offset, thereby reducing both synchronization time and position errors caused by satellite motion during the synchronization process.
Solution Approach 2:
The patent changes the parameter of time offset tolerance by allowing larger initial time offsets (e.g., ±50 milliseconds) during coarse alignment compared to conventional methods. This parameter change enables the system to work with fewer satellites and reduce synchronization time, while subsequent fine synchronization refines the time offset to maintain position accuracy.
3Productivity
If signals from multiple satellites are combined, then synchronization sensitivity and speed improve, but system complexity increases
Solution Approach 1:
The patent segments the synchronization process into distinct stages: coarse time alignment using almanac data, fine time offset search, and signal combination. This segmentation allows each stage to be optimized independently, reducing overall complexity while maintaining high synchronization speed through parallel processing of multiple satellite signals.
Solution Approach 2:
The patent changes the parameter of time offset search range dynamically - using a wide range (±50 milliseconds) during coarse alignment and a narrow range during fine synchronization. This parameter adaptation reduces the computational burden of the fine search stage while maintaining accuracy, thereby improving synchronization speed without proportionally increasing system complexity.
Data Source
AI summary
The present invention is related to location positioning systems, and more particularly, to a method and apparatus of synchronizing to data bits in a positioning system signal. According to a first aspect, the present invention speeds up data bit sync by allowing high Pfa in the overall bit sync computation (e.g. 10−2) for coarse aided case. According to another aspect, the present invention combines and aligns signals from satellites for use in the bit sync computation (e.g. for improved sensitivity and speed).