Digital Coherent Receiver Distortion Compensation Using Replica Signals
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Solution Overview
Problem
In digital coherent transmission systems, high multi-level modulation leads to signal distortion due to transmission element characteristics, which complicates data transmission over long distances, and existing compensation methods require large memory and bandwidth for compensation signals.
Innovation Solution
A reception device with a distortion compensation unit that calculates and updates tap coefficients for an FIR filter using a replica signal and frame signal, allowing for distortion compensation without the need for a separate compensation signal, thereby reducing memory and bandwidth requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-level modulation with high symbol rate is used to increase data transmission capacity, then data transmission rate is improved, but signal distortion increases due to transmission element characteristics
Solution Approach 1:
The patent implements feedback by using the detected frame signal (after error correction) to generate a replica signal, which is then compared with the received signal to calculate updated tap coefficients for the FIR filter. This closed-loop feedback mechanism continuously adapts the compensation filter to minimize signal distortion while maintaining high transmission rates
Solution Approach 2:
The system performs self-service by using its own output (the detected frame signal) to generate the replica signal that serves as reference for calculating compensation coefficients. The reception device independently updates its own filter coefficients without requiring external calibration signals, enabling autonomous distortion compensation
2Reliability
If a compensation signal is used for distortion compensation, then signal distortion is reduced, but memory and bandwidth requirements increase
Solution Approach 1:
Instead of transmitting a separate compensation signal, the patent creates a replica signal by copying and processing the detected frame signal through the same FIR filter. This replica serves as a reference for calculating tap coefficients, eliminating the need for dedicated compensation signal transmission and reducing bandwidth and memory requirements
Solution Approach 2:
The detected frame signal serves multiple functions: it is used for data extraction, error correction, and generating the replica signal for coefficient calculation. This multi-functionality eliminates the need for separate compensation signals, optimizing resource utilization while maintaining effective distortion compensation
Data Source
AI summary
A transmission device includes a receiver configured to receive a frame signal including synchronization data, main signal data, and an error correction code, a compensator configured to compensate for distortion of the frame signal based on a compensation coefficient, a detector configured to detect synchronization timing of the frame signal from the synchronization data; a corrector configured to correct an error of the frame signal after the distortion is compensated, based on the error correction code according to the synchronization timing, a generator configured to generate a replica signal from the frame signal after the error is corrected by the corrector, based on the synchronization timing, the replica signal corresponding to the frame signal before the distortion is compensated, and an update processor configured to update the compensation coefficient based on the replica signal and the frame signal before the distortion is compensated.