FPGA-based rate-adaptive LDPC-coded modulation for the next generation of optical communication systems

Area of Science:

• Digital Communications
• Error Correction Coding
• Field-Programmable Gate Arrays (FPGA)

Background:

• Traditional Forward Error Correction (FEC) schemes often lack adaptability to varying channel conditions.
• Low-Density Parity-Check (LDPC) codes offer powerful error correction capabilities but require efficient implementation for real-time applications.
• Software reconfigurable architectures are crucial for flexible and future-proof digital communication systems.

Purpose of the Study:

• To propose a novel rate-adaptive FEC scheme utilizing LDPC codes.
• To design and emulate a unified software reconfigurable FPGA architecture for the proposed scheme.
• To evaluate the performance of the rate-adaptive LDPC codes across different modulation schemes and error protection strategies.

Main Methods:

• Development of a rate-adaptive LDPC code construction based on shortening.
• Implementation and emulation of a unified, software reconfigurable FPGA architecture.
• Performance evaluation using FPGA emulation for Binary Phase Shift Keying (BPSK) and higher-order modulations (QPSK, 8-QAM, 16-QAM, 32-QAM, 64-QAM).
• Application of unequal error protection by assigning different LDPC codes to different bit positions.

Main Results:

• The proposed rate-adaptive LDPC codes achieved coding gains from 13.08 dB to 14.28 dB at a post-FEC Bit Error Rate (BER) of 10^-15 for BPSK.
• The scheme demonstrated effectiveness with higher-order modulations (QPSK to 64-QAM) across a broad range of signal-to-noise ratios.
• Unequal error protection yielded an additional 0.5 dB gain for 16-QAM and 64-QAM compared to conventional LDPC coded modulation.

Conclusions:

• The proposed rate-adaptive LDPC coding scheme combined with a unified FPGA architecture offers significant performance improvements and flexibility.
• The system effectively supports a wide range of modulation formats and channel conditions.
• Unequal error protection provides a valuable method for further enhancing system performance in specific applications.