Signal Processing With Cross-Correlation Peak Shaping for Time Alignment
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Solution Overview
Problem
Existing methods for time alignment in optical communication systems face challenges when the peak of cross-correlation becomes low, leading to a decrease in success rate, particularly in conditions with short pilot signals, large spatial mode dispersion, and high crosstalk, which complicates determining an appropriate threshold.
Innovation Solution
A signal processing system that includes a cross-correlation calculation unit, correlation shaping processing unit, and synchronization processing unit to enhance the peak of the cross-correlation spectrum, using arithmetic processing and shaping parameters to improve time alignment success rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cross-correlation is used for time alignment, then synchronization can be established, but the success rate decreases when the peak of cross-correlation becomes low
Solution Approach 1:
The patent applies preliminary action by performing correlation shaping processing on the cross-correlation spectrum before peak detection. The shaping processing unit pre-enhances the peak characteristics of the cross-correlation spectrum through arithmetic operations, ensuring that even when the original peak is low, the shaped peak will be sufficiently prominent for reliable detection. This preliminary enhancement of the peak structure before the actual peak detection step resolves the contradiction by ensuring reliable time alignment success regardless of the original peak height.
2Ease of operation
If threshold is determined empirically based on Monte Carlo simulation, then synchronization can be established, but it becomes difficult or impossible to determine appropriate threshold under low peak conditions
Solution Approach 1:
The patent applies preliminary action by performing correlation shaping processing on the cross-correlation spectrum before peak detection. The shaping processing unit pre-enhances the peak characteristics of the cross-correlation spectrum through arithmetic operations, ensuring that even when the original peak is low, the shaped peak will be sufficiently prominent for reliable detection. This preliminary enhancement of the peak structure before the actual peak detection step resolves the contradiction by ensuring reliable time alignment success regardless of the original peak height.
3Reliability
If multiple received signals with temporal spread are processed, then comprehensive time alignment can be achieved, but computation complexity increases
Solution Approach 1:
The patent applies merging by combining multiple received signals that have temporal spread and are coupled during propagation into a unified cross-correlation analysis. The correlation shaping processing unit processes the combined cross-correlation spectrum from multiple signals simultaneously, rather than processing each signal separately. This consolidation approach maintains comprehensive time alignment accuracy while reducing overall computational complexity by sharing processing resources across multiple signals.
Data Source
AI summary
A cross-correlation calculation unit calculates a cross-correlation spectrum representing similarity between each of multiple received signals, which have a temporal spread and are coupled to each other during propagation, and a pilot signal included in part of each of the received signals. A correlation shaping processing unit performs arithmetic processing that shapes the peak of the cross-correlation spectrum so that it becomes higher than an original peak. A first peak determination processing unit detects the peak of the cross-correlation spectrum after arithmetic processing. A synchronization processing unit performs time alignment that aligns a time origin to synchronize the pilot signal and the received signal by using the detected peak.