Nonbinary LDPC Coded Modulation for High-Speed Optical Transmission
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Solution Overview
Problem
Current data transmission technologies face challenges in achieving high-speed data transport while maintaining robustness against linear and nonlinear fiber impairments, such as chromatic dispersion and fiber nonlinearities, without increasing bandwidth or implementation complexity.
Innovation Solution
The method employs polarization-division multiplexed discrete-time non-binary low-density parity-check (NB-LDPC) coded modulation, which expands the signal constellation to accommodate parity symbols within the same bandwidth, using two NB-LDPC encoders and a 2b-ary mapper to generate signals, and combines them using a polarization beam combiner for transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bit interleaved LDPC coded modulation is used to achieve excellent BER performance, then reliability is improved, but bandwidth must increase to compensate for information loss due to coding
Solution Approach 1:
The patent transitions from binary LDPC codes to nonbinary LDPC codes, changing the algebraic structure from GF(2) to GF(q). This dimensional change in the code field allows the system to achieve better error correction performance without proportional bandwidth increase, as nonbinary codes can represent multiple bits per symbol more efficiently
Solution Approach 2:
The patent changes the code rate parameter and constellation size parameter simultaneously. By using nonbinary LDPC codes with appropriate code rates and mapping to expanded signal constellations, the system achieves superior BER performance while maintaining spectral efficiency through optimized parameter selection
2Device complexity
If quasi-cyclic LDPC codes are used for easy implementation, then device complexity is reduced, but performance deteriorates due to excessive codeword length requirements
Solution Approach 1:
The patent segments the coding and modulation functions into distinct nonbinary LDPC encoding and constellation mapping stages. This segmentation allows the use of structured nonbinary LDPC codes that maintain implementation feasibility while achieving better performance through the nonbinary field structure
Solution Approach 2:
The patent replaces the mechanical constraint of fixed quasi-cyclic structures with the algebraic flexibility of nonbinary field operations. By substituting the binary field mechanics with nonbinary field arithmetic, the system achieves both implementation feasibility and superior performance
3Productivity
If symbol rate is increased to achieve higher data transport speed, then productivity is improved, but transmission becomes increasingly sensitive to errors due to linear and nonlinear channel impairments
Solution Approach 1:
The patent uses nonbinary LDPC codes that operate in GF(q) instead of GF(2), providing stronger error correction capability that can handle the increased error sensitivity at high symbol rates. The nonbinary structure offers more degrees of freedom in error correction
Solution Approach 2:
The nonbinary LDPC coded modulation system provides multi-functionality by simultaneously achieving high data rates through efficient mapping and robust error correction through nonbinary coding, making the system adaptable to high-speed transmission conditions where traditional binary codes fail
4Area of stationary object
If signal constellation is expanded to avoid bandwidth expansion due to coding, then bandwidth is preserved, but implementation complexity increases
Solution Approach 1:
The patent segments the mapping process into structured stages: nonbinary encoding to produce codeword symbols, followed by deterministic mapping to constellation points. This segmentation manages complexity by breaking down the expanded constellation mapping into manageable, structured operations
Data Source
AI summary
Systems and methods for data transport, comprising encoding one or more streams of input data using nonbinary low density parity check (NB-LDPC) encoders, corresponding to orthogonal polarization states. Receiving one or more streams of input data using a buffer coupled to the encoders, the data written to the buffer bR bits at a time, where R is the code rate. Generating one or more signals using a 2b-ary mapper implemented as a look-up table (LUT) to store coordinates of a corresponding signal constellation, the 2b-ary mapper configured to assign bits of one or more signals to a signal constellation and to associate the bits of the signals with signal constellation points, wherein the constellation is expanded to avoid bandwidth expansion due to coding, generating substantial net coding gains within a same bandwidth. Modulating nonbinary LDPC-coded data streams using in-phase/quadrature (I/Q) modulators and multiplexing the data streams using polarization beam combiner.