FEC Codeword Alignment Detection for Faster Frame Acquisition
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Solution Overview
Problem
Conventional frame synchronization schemes in digital communication systems face challenges in achieving fast acquisition at lower data rates, as they rely on detecting syncwords, which can result in extended acquisition times due to infrequent sync patterns.
Innovation Solution
Employing a FEC decoder to perform speculative full and partial decoding across multiple possible alignments within a data stream, using techniques like sliding windows or random alignment selection to identify code block borders, thereby accelerating synchronization without relying solely on syncword detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If syncword detection is used for frame synchronization, then the system can identify frame borders, but the acquisition time is extended due to infrequent sync patterns at lower data rates
Solution Approach 1:
The patent applies preliminary action by performing speculative FEC decoding on multiple possible alignment positions simultaneously before final synchronization is established. The decoder proactively attempts to decode codewords at various potential frame borders in advance, rather than waiting for syncword detection to identify the correct position. This allows the system to pre-compute decoding results for multiple hypotheses, significantly reducing the time needed to achieve synchronization at lower data rates where syncwords appear infrequently.
Solution Approach 2:
The patent implements partial action by performing speculative decoding on only a subset of possible alignment positions rather than exhaustively checking every possible position. The system selects a limited number of candidate alignment positions based on probabilistic criteria or heuristics, performs FEC decoding on these candidates, and identifies the correct frame border from this reduced set. This approach achieves fast synchronization without the excessive computational burden of evaluating all possible alignments, balancing speed and complexity effectively.
2Loss of time
If speculative FEC decoding is performed on multiple alignments, then acquisition time is reduced, but decoding complexity increases
Solution Approach 1:
The patent manages decoder complexity by applying partial action - performing speculative FEC decoding on a limited number of candidate alignment positions rather than all possible positions. The system selectively evaluates only those alignments that have a reasonable probability of being correct, based on statistical criteria or heuristic rules. This reduces the computational burden on the decoder while still achieving fast acquisition, as the correct alignment is likely to be among the selected candidates without requiring exhaustive search of every possible position.
Solution Approach 2:
The patent applies segmentation by dividing the decoding process into distinct phases: speculative decoding of multiple candidate alignments, validation of decoding results, and final synchronization establishment. Each phase handles a specific subset of tasks, with the speculative decoding phase focusing only on candidate positions rather than the entire data stream. This segmented approach allows the complex FEC decoding operation to be distributed across multiple independent candidate evaluations, making the overall process more manageable and efficient despite the increased number of operations required for fast acquisition.
Data Source
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AI summary
A forward error correction (FEC) decoder is configured to find an alignment of a code block in a data stream by attempting to fully or partially decode one or more data windows of a predetermined size in the data stream. The predetermined size is a size of each codeword. The FEC decoder selects a first data window of the predetermined size, attempts to decode the first data window based on a particular error control coding method, and determines whether a valid codeword can be identified by attempting to decode the first data window. In response to determining that a valid codeword can be identified, the FEC decoder determines that an alignment of the codeword with the first data window is found. Otherwise, the FEC decoder selects a second data window of the predetermined size and attempts to decode the second data window.