Kenya Sugihara

Iteration-Aware LDPC Code Design for Low-Power Optical Communications

Recent low-density parity-check (LDPC) codes have shown capacity-approaching performance for various communications systems. However, their promising performance cannot always be obtained due to practical constraints, such as finite codeword length, finite iteration, finite memory, and finite precision. In this paper, we focus on a practical design method of high-performance LDPC codes under a constraint of finite-iteration decoding for low-power optical communications. We introduce an iteration-aware LDPC code design approach, which is based on decoding trajectory in extrinsic information transfer chart analysis. It is demonstrated that an LDPC code designed by the conventional curve-fitting method exhibits nearly 2 dB of penalty, when the maximum number of iterations is limited. The results suggest that the LDPC code should be adaptively changed, e.g., when the number of decoding iterations is decreased to save power consumption. We also extend our design method to a multi-objective optimization concept by taking average degrees into account, so that the threshold and the computational complexity are minimized at the same time. The proposed Pareto-optimal codes can achieve additional 2-dB gain or 50% complexity reduction at maximum, in low-power decoding scenarios.

A practicable rate-adaptive FEC scheme flexible about capacity and distance in optical transport networks

We propose a practicable rate-adaptive FEC scheme defeating degradation due to high baud rate and increase of circuit complexity. The preferable coding gains of 13.0-17.5 dB are obtained for 25.5-149.5% redundancies.

A study on power-scaling of triple-concatenated FEC for optical transport networks

We studied the power scaling using the measured power consumption and error correction performance of a triple-concatenated FEC. It was confirmed that the triple-concatenated FEC enabled 98% power reduction by controlling the NCG to suit the OSNR of the link.

Bit-interleaved polar-coded OFDM for low-latency M2M wireless communications

Machine-to-machine (M2M) communications play an important role for applications that involve connections between a massive number of heterogeneous devices in home and industrial networks. For M2M networks, realizing low latency and high reliability is of great importance. In this paper, we show the great potential of polar-coded orthogonal frequency-division multiplexing (OFDM) to fulfill those requirements. We show that polar codes with list decoding plus cyclic redundancy check (CRC) can outperform state-of-the-art low-density parity-check (LDPC) codes at short block lengths. In addition, we introduce an efficient interleaver and constellation shaping for polar-coded high-order modulations, where a coded sequence is carefully mapped across subcarriers and modulation bits to exploit non-uniform reliability for higher diversity gains. Through computer simulations, we demonstrate that a significant gain greater than 2 dB can be achieved by quadratic polynomial permutation (QPP) interleaver with optimized parameters in comparison to the conventional random interleaver for high-order 256-ary quadrature-amplitude modulation (QAM) OFDM transmission in frequency-selective wireless channels.

100/150/200 Gb/s real-time demonstration of SD-FEC employing MSSC-LDPC codes for flexible coherent transport

To support forthcoming flexible coherent transport, we demonstrate a multiple-structured spatially-coupled LDPC with BCH codes which offers modulation flexibility, rate-adaptability and pilot-aided cycle-slip mitigation.