FEC Bit-Alignment Testing for Faster Framing Lock
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Solution Overview
Problem
Existing communication protocols that employ block-coded forward error correction (FEC) face significant delays in establishing framing due to the need to sequentially test all possible bit alignments, which can take several milliseconds even in error-free conditions, and are further hindered by the overhead of bit alignment changes and potential errors.
Innovation Solution
The proposed method reduces the search time for bit alignment by checking the syndrome at each data word as if it were the last of a FEC code, thereby reducing the number of alignments that need to be probed and allowing for more efficient syndrome evaluation without requiring substantial additional logic, enabling faster code lock acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequential testing of all possible bit alignments is performed, then complete search accuracy is achieved, but search time becomes excessively long (2 milliseconds or more)
Solution Approach 1:
The patent segments the syndrome calculation process into incremental updates. Instead of calculating complete syndromes for each of the 5280 possible alignments independently, the system calculates one syndrome and then segments the search into incremental steps, updating the syndrome calculation efficiently as it tests each subsequent alignment position, thereby reducing redundant computations
Solution Approach 2:
The patent performs preliminary syndrome calculation for the first alignment position, then uses this preliminary result as a basis for efficiently calculating syndromes at subsequent alignment positions. This preliminary action avoids starting from scratch for each alignment test, significantly reducing the total computational time while maintaining complete search accuracy
2Reliability
If all 5280 alignments are tested sequentially, then no alignment is missed, but the number of bits received and processed exceeds 5280*5280 bits
Solution Approach 1:
The patent merges the syndrome calculation operations across different alignment positions. By combining the computational results and using incremental updates, the system avoids independently processing full 5280-bit blocks for each alignment, thereby reducing the total quantity of bits processed while maintaining reliable detection of the correct alignment
Solution Approach 2:
The system performs preliminary processing of the received bit stream to enable efficient syndrome calculations at multiple alignment positions. This preliminary action prepares the data in advance, allowing the system to test all 5280 alignments reliably without having to reprocess the entire bit stream for each alignment position
3Adaptability or versatility
If bit alignment changes are implemented during search, then alignment flexibility is improved, but overhead increases and search complexity grows
Solution Approach 1:
The patent implements dynamic alignment testing where the system can efficiently transition between different alignment positions during the search process. The syndrome calculation mechanism is designed to be dynamic, allowing the search to adapt to different alignment positions without requiring complete reinitialization, thereby maintaining alignment flexibility while controlling search complexity
Data Source
AI summary
Methods and apparatus disclosed herein may be used to establish framing more efficiently in communication protocols with block-coded forward error correction. Such protocols generally involve the check of different bit-alignments searching for positions that yield zero syndromes. The search can be undesirably slow, particularly in the presence of received errors. The presently-disclosed bit-alignment testing technique reduces this search time by checking the syndrome at each data word as if that data word was the last of a code. In other words, the word positions are effectively checked without a prior assumption as to which words are the first and last of the code. This reduces the task to the number of different bit-alignments possible within a single data word, rather than the number of bit-alignments possible in a complete FEC code. In one implementation, the lock time is reduced by approximately 50 times when compared to a straightforward solution.