This paper proposes a novel non-Hermitian symmetry 2×2{2 \times 2} MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) system based on fast Hartley transform (FHT) with unipolar encoding (referred to as HU-OFDM) for visible light communications. The new scheme uses FHT instead of FFT (fast Fourier transform) to process the complex-valued signals reducing the computational complexity and hardware cost and employs two LEDs (light-emitting diodes) to transmit the real and imaginary parts of a complex-valued OFDM signal respectively. Unipolar encoding is applied to the transmitted signal from each LED to ensure non-negative. The restrictions of Hermitian symmetry in traditional optical OFDM systems and real constellation mapping in FHT based optical OFDM systems can be removed simultaneously in the proposed system. Compared with MIMO-ACO/DCO-OFDM system, HU-OFDM has significant performance improvement along with a tremendous decrease in hardware cost and computational complexity. Compared with other non-Hermitian symmetry MIMO-OFDM systems, HU-OFDM has significant advantages in terms of power efficiency, system design flexibility, computational complexity, or hardware cost without losing reliability.

中文翻译：

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一种新型的可见光通信非厄米对称正交频分复用系统


本文提出了一种基于单极编码快速Hartley变换（FHT）的新型非厄米对称2×2{2 \times 2} MIMO-OFDM（多输入多输出正交频分复用）系统（简称HU- OFDM）用于可见光通信。新方案使用FHT而不是FFT（快速傅立叶变换）来处理复值信号，降低了计算复杂度和硬件成本，并采用两个LED（发光二极管）来传输复值OFDM的实部和虚部分别发出信号。单极性编码应用于每个 LED 传输的信号，以确保非负数。在所提出的系统中，可以同时消除传统光学 OFDM 系统中埃尔米特对称性和基于 FHT 的光学 OFDM 系统中实星座映射的限制。与MIMO-ACO/DCO-OFDM系统相比，HU-OFDM具有显着的性能提升，同时硬件成本和计算复杂度也大幅降低。与其他非厄米对称MIMO-OFDM系统相比，HU-OFDM在功率效率、系统设计灵活性、计算复杂度或硬件成本方面具有显着优势，同时又不失可靠性。