Oversampling increases information rates for bandlimited channels with direct detection, but joint detection and decoding (JDD) is often too complex to implement. Two receiver structures are studied to reduce complexity: separate detection and decoding (SDD) and successive interference cancellation (SIC) with multi-level coding. For bipolar modulation, frequency-domain raised-cosine pulse shaping, and fiber-optic channels with chromatic dispersion, SIC achieves rates close to those of JDD, thereby attaining significant energy gains over SDD and classic intensity modulation. Gibbs sampling further reduces the detector complexity and achieves rates close to those of the forward-backward algorithm at low to intermediate signal-to-noise ratio (SNR) but stalls at high SNR. Simulations with polar codes and higher-order modulation confirm the predicted rate and energy gains.

翻译：过采样可提高带限直接检测信道的信息速率，但联合检测与解码（JDD）的实现复杂度通常过高。本文研究了两种降低复杂度的接收机结构：分离检测与解码（SDD）以及结合多级编码的逐次干扰消除（SIC）。针对双极性调制、频域升余弦脉冲成形以及存在色散的光纤信道，SIC所能达到的速率接近JDD，从而在SDD和经典强度调制基础上实现了显著的能耗增益。吉布斯采样进一步降低了检测器复杂度，在低至中等信噪比（SNR）下可达到接近前向-后向算法的速率，但在高SNR下出现停滞。采用极化码和高阶调制的仿真验证了所预测的速率与能耗增益。