Yang Liu, Yang Shuailong, Luo Fengguang, Fu Songnian, Ni Yao, Li Bin, Wang Xiaobo, Liu Deming
Opt Express. 2021 Feb 1;29(3):3067-3080. doi: 10.1364/OE.413161.
Spectral efficient frequency division multiplexing (SEFDM) can greatly increase the spectral efficiency for intensity modulation/direct detection (IM/DD) optical communication systems. The sphere detection algorithm (SD) is the most efficient way to get the maximum likelihood (ML) solution to solve the inter-carrier interference (ICI) induced by the bandwidth compression of SEFDM system. However, SD algorithm is restricted by the numbers of subcarriers for SEFDM system, especially for larger numbers. Therefore, a sorted Gram-Schmidt (SGS) orthogonal decomposition algorithm, which can be applied to any subcarrier numbers, is proposed to overcome this restriction. To the best of our knowledge, the searched paths of FSD are researched for the first time to balance performance and complexity. Based on the analysis, a soft-tree-width sphere detection algorithm (SSD) is proposed and demonstrated by simulation and experiment. The results show that the proposed algorithm can greatly reduce the computational complexity (at least 40%) with the same system performance. The proposed algorithms are a promising candidate for flexible and efficient SEFDM systems. The SEFDM with the proposed detector is significant for the IM/DD optical systems.
频谱高效频分复用（SEFDM）能够极大地提高强度调制/直接检测（IM/DD）光通信系统的频谱效率。球形检测算法（SD）是获得最大似然（ML）解以解决由SEFDM系统带宽压缩引起的载波间干扰（ICI）的最有效方法。然而，SD算法受SEFDM系统子载波数量的限制，特别是对于数量较大的情况。因此，提出了一种可应用于任意子载波数量的排序Gram-Schmidt（SGS）正交分解算法来克服这一限制。据我们所知，首次对FSD的搜索路径进行了研究，以平衡性能和复杂度。在此分析基础上，提出了一种软树宽球形检测算法（SSD），并通过仿真和实验进行了验证。结果表明，所提算法在相同系统性能下能够大幅降低计算复杂度（至少降低40%）。所提算法是灵活高效的SEFDM系统的一个有前景的候选方案。采用所提检测器的SEFDM对IM/DD光系统具有重要意义。
