Coherent light fidelity (LiFi) systems which uses coherent detection at the receiver are attracting more and more interest as they provide many advantages over the conventional intensity modulation / direct detection (IM/DD) LiFi systems. Recent efforts to boost the performance of IM/DD LiFi systems include the usage of multiple-input-multiple-output (MIMO) technology, among which spatial multiplexing (SMX) has gained certain attention. This paper combines coherent detection and spatial multiplexing, and proposes a novel scheme called CD SMX (coherent-detection spatial-multiplexing) LiFi systems to improve LiFi performances. Compared with CD single-input-single-output (SISO) LiFi systems and CD spatial modulation (SM) LiFi systems, the proposed scheme provides a spectral efficiency gain. Unlike IM/DD or radio frequency (RF) SMX systems, the proposed CD SMX LiFi system is free from inter-channel interferences (ICI) due to the matching properties of coherent detection. The performance of the proposed CD SMX system is studied via both theoretical analysis and computer simulations. It is reported that the proposed system achieves a large gain over its IM/DD counterpart, and a moderate gain over a coherent system with SM.

中文翻译：

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具有空间复用功能的相干 LiFi 系统


在接收器处使用相干检测的相干光保真 (LiFi) 系统吸引了越来越多的兴趣，因为它们比传统的强度调制/直接检测 (IM/DD) LiFi 系统具有许多优势。最近提高 IM/DD LiFi 系统性能的努力包括使用多输入多输出 (MIMO) 技术，其中空间复用 (SMX) 受到了一定的关注。本文将相干检测和空间复用相结合，提出了一种称为 CD SMX（相干检测空间复用）LiFi 系统的新颖方案，以提高 LiFi 性能。与CD单输入单输出（SISO）LiFi系统和CD空间调制（SM）LiFi系统相比，所提出的方案提供了频谱效率增益。与 IM/DD 或射频 (RF) SMX 系统不同，所提议的 CD SMX LiFi 系统由于相干检测的匹配特性而不受通道间干扰 (ICI) 的影响。通过理论分析和计算机模拟研究了所提出的 CD SMX 系统的性能。据报道，所提出的系统比 IM/DD 系统获得了较大的增益，并且比具有 SM 的相干系统获得了适度的增益。