FPGA SC-LDPC Code Generation for Rate-Adaptive Optical Links
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Solution Overview
Problem
Current LDPC code generation methods are complex and lack universality across various communication systems, particularly in adapting to the changing conditions of optical and wireless communications, leading to early error floors in time-varying channels.
Innovation Solution
The method involves generating quasi-cyclic low-density parity-check (QC-LDPC) codes, assigning them as template codes, introducing irregularity by copying, and shifting on a sub-block basis to create spatially-coupled LDPC (SC-LDPC) codes, which are suitable for forward error correction in communication systems, including optical and wireless communications, using hardware such as FPGAs or ASICs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional LDPC code generation methods are used, then implementation is straightforward, but the systems are complex and lack universality across communication systems
Solution Approach 1:
The patent employs a universal base LDPC code that can serve multiple communication systems (optical, wireless, 5G, 6G) through systematic transformations. The base code is designed with properties that allow it to be adapted to different channel conditions and system requirements via rate-adaptive spatial coupling, eliminating the need for separate code designs for each communication standard.
Solution Approach 2:
The LDPC code is divided into a base code structure and a spatially-coupled structure. The base code contains the fundamental error correction capabilities, while the spatial coupling layer provides adaptability to time-varying channels. This segmentation allows independent optimization of each component and simplifies the overall system design.
2Reliability
If standard LDPC codes are used, then the implementation is simple, but early error floors occur in time-varying channels
Solution Approach 1:
The patent introduces rate-adaptive spatial coupling that dynamically adjusts the coupling rate based on channel conditions. The spatially-coupled structure enables the code to adapt to time-varying channels by modifying the decoding process, thereby eliminating early error floors while maintaining good BER performance across different signal-to-noise ratios.
Solution Approach 2:
The invention changes key code parameters including the coupling length, base code rate, and spatial coupling rate to optimize performance for different communication scenarios. These parameter adjustments allow the same base code to achieve superior reliability in time-varying channels without requiring completely different code structures.
3Reliability
If rate adaptation is implemented for changing channel conditions, then error correction performance improves, but system complexity increases
Solution Approach 1:
The patent pre-configures the spatially-coupled LDPC code with multiple coupling rates and base code rates that can be selected based on channel conditions. This preliminary preparation allows the system to quickly adapt to changing channels by simply switching between pre-designed code configurations rather than dynamically recalculating codes in real-time, thereby reducing hardware complexity.
Solution Approach 2:
The invention uses a base LDPC code as a template that is copied and spatially coupled to generate the final code structure. This copying approach with systematic transformations (shifting, coupling) simplifies the generation process and reduces hardware complexity compared to designing unique codes for each rate adaptation scenario.
Data Source
AI summary
Disclosed are systems, methods, and software for generating spatially-coupled low-density parity-check (SC-LDPC) codes. A method for generating SC-LDPC codes includes generating one or more quasi-cyclic low-density parity-check (QC-LDPC) codes, and also includes assigning at least one of the generated one or more QC-LDPC codes as one or more template codes. The method further includes copying at least a portion of the one or more template codes to introduce irregularity. The method also includes shifting one or more template codes on a sub-block basis to generate at least one SC-LDPC code. As compared to known LDPC code generation modalities, the disclosed invention provides a simplified technique for implementation in streamlined hardware which has more general applicability across both present, and anticipated, communication systems, including those adapted for use with optical communications, wireless communications, and 5G as well as future 6G.