Frame Synchronization Apparatus for Coherent Optical Communication
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Solution Overview
Problem
Conventional frame synchronization methods fail to accurately determine synchronization states and detect synchronization loss, especially when the error rate of received symbols is high, leading to erroneous synchronization determination and multi-frame synchronization issues.
Innovation Solution
A frame synchronization apparatus that multiplies the received signal by an inverse complex number or a code of the synchronization pattern, performs addition averaging, and determines synchronization based on coincidence with a predetermined signal point, effectively reducing noise and phase slip impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional frame synchronization methods are used, then the system can operate with simple comparison logic, but synchronization accuracy deteriorates when error rate is high
Solution Approach 1:
The patent performs preliminary actions by calculating correlation values between the received signal and synchronization patterns before making synchronization determination. This preliminary correlation calculation allows the system to assess signal similarity metrics before committing to a synchronization state decision, thereby improving accuracy in high error rate environments where direct comparison would fail.
Solution Approach 2:
The patent introduces correlation value calculation as an intermediary mechanism between signal reception and synchronization determination. Instead of directly comparing received symbols with synchronization patterns, the system uses correlation analysis as a mediator to evaluate the degree of match, providing a more robust basis for synchronization decisions under noisy conditions.
2Device complexity
If bit stream comparison method is used, then the device complexity remains low, but measurement precision of synchronization pattern detection decreases under high error conditions
Solution Approach 1:
The patent replaces the mechanical bit-by-bit comparison system with a correlation-based detection system. Instead of mechanically comparing each bit position between received signal and synchronization pattern, the system uses correlation analysis that inherently handles errors by measuring overall signal similarity, thereby maintaining low complexity while improving detection precision.
3Speed
If synchronization determination is based on hard decision bit information, then the processing speed is fast, but reliability of multi-frame synchronization detection deteriorates
Solution Approach 1:
The patent performs preliminary correlation analysis before making hard decisions on synchronization state. By first calculating correlation values and comparing them against thresholds, the system ensures that subsequent hard decisions are based on more reliable metrics, thereby maintaining processing speed while improving multi-frame synchronization detection reliability.
4Ease of operation
If conventional synchronization methods are used, then the system can maintain simple operation, but synchronization state stability deteriorates under phase slip conditions
Solution Approach 1:
The patent uses correlation value calculation as an intermediary that naturally handles phase variations. The correlation-based approach serves as a mediator that is insensitive to phase slips, allowing the simple operational framework to maintain stability even when phase changes occur in the received signal.
Data Source
AI summary
A frame synchronization apparatus (10) according to this invention includes a multiplication unit (11) configured to multiply a received signal by an inverse complex number of a predetermined synchronization pattern with respect to a predetermined signal point on a complex space diagram for each of a plurality of symbols of the received signal, an addition average unit (12) configured to perform addition averaging of outputs from the multiplication unit for the plurality of symbols of the received signal, and a synchronization determination unit (13) configured to perform coincidence determination of whether an output from the addition average unit (12) falls within a predetermined coincidence determination range of the predetermined signal point, and determine a synchronization state of the frame synchronization based on a result of the coincidence determination. According to this invention, it is possible to provide a frame synchronization apparatus that correctly determines a synchronization state even if an error rate of received symbols is high.