Eigenvalue-Space Precoding for Optical Network ISI Mitigation
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Solution Overview
Problem
Conventional optical network systems face challenges in upgrading modulation formats efficiently due to bandwidth and receiver sensitivity limitations, leading to complex and costly implementations of faster-than-Nyquist (FTN) signaling, which results in significant inter-symbol interference (ISI) and increased power consumption.
Innovation Solution
The implementation of eigenvalue-space precoding (EVSP) and blockwise digital signal processing (DSP) techniques that adaptively adjust the baud rate and utilize precoding and decoding methods to mitigate ISI, allowing for maximum system capacity without increasing modulation levels, and employing look-up tables to reduce computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If faster-than-Nyquist (FTN) signaling is implemented to increase data transmission rate, then bandwidth efficiency is improved, but inter-symbol interference (ISI) increases and system complexity increases
Solution Approach 1:
The patent applies pre-cursor equalization and post-cursor equalization techniques to mitigate inter-symbol interference before and after the main signal transmission. By performing equalization operations in advance (pre-cursor) and after (post-cursor) the main detection, the system reduces ISI effects without requiring complete system redesign, thus managing complexity while maintaining high data transmission rates
Solution Approach 2:
The patent adjusts equalization parameters and filtering characteristics to optimize performance for faster-than-Nyquist signaling. By dynamically changing equalization tap coefficients and filter parameters based on channel conditions, the system adapts to reduced bandwidth and increased ISI while maintaining manageable complexity through parameter optimization rather than structural complexity
2Productivity
If FTN signaling is implemented to improve bandwidth efficiency, then transmission capacity increases, but power consumption increases
Solution Approach 1:
The patent applies partial equalization techniques where only the most critical ISI components are compensated for rather than attempting to equalize all interference. By applying pre-cursor equalization for the most significant pre ISI and post-cursor equalization for dominant post ISI, the system achieves adequate performance with reduced computational complexity and lower power consumption compared to full equalization approaches
3Reliability
If conventional equalization methods are used to reduce ISI, then signal quality improves, but receiver sensitivity deteriorates due to bandwidth limitations
Solution Approach 1:
The patent applies pre-cursor equalization to reduce ISI before the main signal detection process. By pre-processing the signal to mitigate interference from previous symbols, the system improves signal quality at the decision point without requiring excessive bandwidth, thus maintaining receiver sensitivity while enhancing signal quality
Solution Approach 2:
The patent introduces equalization filters as intermediary processing elements between the received signal and the decision device. These filters act as mediators that condition the signal by reducing ISI effects before detection, improving signal quality without directly confronting the bandwidth limitation at the receiver input, thus preserving receiver sensitivity
Data Source
AI summary
An optical network includes a transmitter portion configured to (i) precode an input digitized stream of symbols into a precoded symbol stream, (ii) pulse shape the precoded symbol stream with an eigenvalue channel matrix, and (iii) transmit the pulse shaped symbol stream over a digital optical link. The optical network further includes a receiver portion configured to (i) recover the pulse shaped symbol stream from the digital optical link, (ii) decompose eigenvalues of the eigenvalue channel matrix from the recovered symbol stream, and (iii) decode the decomposed symbol stream into an output symbol stream.