Abstract

In this work, we implement a rate-adaptable (RA) prefix-free code distribution matching (PCDM) encoder in a field-programmable gate array (FPGA). The implemented RA-PCDM encoder supports a wide range of information rates from 1.6 to 4.8 bit/symbol with fine granularity of 0.2 bit/symbol in probabilistic constellation shaping (PCS) systems. The shaping performance of the implemented RA-PCDM is within 0.55 dB of the theoretical limit. Massively parallel encoding of RA-PCDM is demonstrated using a sliding window processor, in a universal architecture for all PCDM codebooks. Given that the procedure and complexity of RA-PCDM decoding is almost the same as those of RA-PCDM encoding, it is shown that the RA-PCDM uses substantially less hardware area than a traditional rate adaptation scheme based on low-density parity-check (LDPC) codes, while offering finer rate granularity and shaping gain. The RA-PCDM is therefore a practical PCS technology that enables high-throughput optical communications to approach channel capacity more closely at a lower cost than RA-LDPC.

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

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16-QAM probabilistic constellation shaping by adaptively modifying the distribution of transmitted symbols based on errors at the receiver

Ahmad Fallahpour, Fatemeh Alishahi, Amir Minoofar, Kaiheng Zou, Ahmed Almaiman, Peicheng Liao, Hubin Zhou, Moshe Tur, and Alan E. Willner
Opt. Lett. 45(18) 5283-5286 (2020)