Multi-stage threshold decoding of high rate convolutional codes for optical communications

Abstract — For 100 Gb/s optical transport network, researchers are searching a suitable error correction coding scheme that can provide coding gain more than 10 dB at the bit error rate less than 10−12, provided that the redundancy does not exceed 20 percent. This paper presents a least complex error correction coding scheme based on iterative threshold decoding called multi-stage threshold decoding with difference register (MTD) for the 100 Gb/s optical transport network. High rate (code rate 0.8) self-orthogonal convolutional codes are considered. The MTD achieves lower bound error performance of maximum likelihood decoding at higher bit energy to noise density ratio. The codes with orthogonal checking 10 and larger satisfy the requirements of 100 Gb/s optical transport network. The bit error rate of MTD with parity check decoding becomes less than 1/100 times in the error floor region compared to ordinary MTD. The MTD based decoding with parity check decoding for the code with orthogonal checking 12 produces 10.60 dB coding gain at the bit error rate 10−15. The coding gain further improves 0.25 dB in the waterfall region by using 2-step decoding. Keywords- threshold decoding, convolutional codes, self-orthogonal codes, optical transport network. I.