Satellite Signal Demodulation Error Correction for Weak Field Reception
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Solution Overview
Problem
GPS satellite signal demodulation errors in weak electric field environments lead to inefficiencies in data reception and increased Time to First Fix (TTFF), as existing error detection methods discard data due to single-bit errors, causing inaccuracies in satellite orbit calculations.
Innovation Solution
A method for detecting and correcting demodulated data errors using error detection codes and comparison with prescribed data, determining the adoption of data based on error and inconsistent bits, specifically for word data units containing orbit calculation parameters, and utilizing long-term prediction ephemeris for comparison data generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error detection is performed using parity bits for each word in navigation messages, then demodulation errors can be detected, but the received data is discarded due to demodulation errors causing increased Time to First Fix (TTFF)
Solution Approach 1:
The patent changes the error handling parameter from binary discard/accept to selective correction. By introducing error bit detection that identifies specific incorrect bits rather than treating entire words as invalid, the system transforms the approach from conservative rejection to targeted correction, reducing data loss while maintaining reliability
Solution Approach 2:
Instead of discarding erroneous data words, the patent recovers the correct information by detecting and correcting specific error bits within those words. The error detection code identifies which bits are incorrect, allowing the system to recover the original correct data without needing to request retransmission or discard the entire word
2Reliability
If demodulated data is discarded due to single-bit errors, then error propagation is prevented, but the efficiency of data reception decreases and TTFF increases
Solution Approach 1:
The patent segments the error handling process at the bit level rather than word level. By identifying and correcting individual error bits within data words, the system prevents error propagation while minimizing data loss. This granular approach allows most of the data to be retained and corrected rather than discarding entire words containing errors
Solution Approach 2:
The error detection code provides feedback about which specific bits are erroneous, enabling the system to make informed decisions about correction. This feedback mechanism allows the receiver to identify and correct errors without discarding data, improving reception efficiency while maintaining reliability through targeted error handling
Data Source
AI summary
In a baseband process circuit unit, a demodulation unit demodulates a received satellite signal which carries a navigation message to obtain a demodulated data. Further, an error bit detection unit detects an error bit from among the demodulated data using a parity code included in the demodulated data. An inconsistent bit detection unit detects an inconsistent bit by comparing the demodulated data with prescribed comparison data. An adoption determination unit determines whether or not to adopt the demodulated data, based on a difference between the error bit and the inconsistent bit. In addition, a correction unit corrects the demodulated data, in a case where the demodulated data is determined to be adopted by the adoption determination unit.