Coherent LiFi System With Spatial Multiplexing
Yinzhou Tan, Harald Haas
Abstract
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.