In this paper, we proposed a coding scheme based on orthogonal cyclic transpose (OCT) precoding combined with low-density parity check (LDPC) code to improve the transmission performance of 128-quadrature amplitude modulation multiband orthogonal-frequency-division-multiplexing ultrawide band over fiber (128 QAM MB-OFDM UWBoF) system. The proposed scheme could not only improve the performance of the system but also average the signal-to-noise ratio (SNR) of subcarriers and reduce the difference among subchannels in practical application. The simulation results showed that compared with the traditional scheme, the receiver performance of this scheme was improved by 2.7 dB when the LDPC-coding rate was 87.5% through 70 km standard single mode fiber (SSMF) transmission and the bit error rate (BER) was 3.8 × 10−3. Besides, the constellation distribution was more convergent and uniform.

中文翻译：

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128 QAM MB-OFDM UWBoF系统的OCT-预编码结合LDPC-编码方案

本文提出了一种基于正交循环转置（OCT）预编码结合低密度奇偶校验（LDPC）码的编码方案，以提高128正交调幅多频带正交频分复用超宽带的传输性能。光纤（128 QAM MB-OFDM UWBoF）系统。所提出的方案不仅可以提高系统的性能，而且可以在实际应用中平均子载波的信噪比(SNR)，减小子信道之间的差异。仿真结果表明，通过70km标准单模光纤(SSMF)传输和误码率(BER)，该方案在LDPC编码率为87.5%时，与传统方案相比，接收机性能提高了2.7 dB是 3.8 × 10−3。除了，