Light-fidelity (Li-Fi) is a promising solution to provide high-rate, secure, and green communications to be used in the next generation of wireless networks. Since visible or infrared (IR) light-emitting diodes (LEDs) are used as the optical source and have a non-linear transfer function, the transmitted modulated signal can be distorted if the signal has a high peak-to-average power ratio (PAPR). Recently, a new modulation scheme called Hadamard-coded modulation (HCM) is proposed which has no PAPR concern since it produces symbols with discrete levels. In the HCM technique, the symbol levels can be created using multiple LEDs. Therefore, each LED operates in its linear region and just switches on or off. A low-complexity transceiver architecture for the HCM-based communication links is proposed and a complete synchronisation procedure based on the spread-spectrum techniques is presented. Finally, the bit error rate of the system is evaluated by Monte Carlo simulations, and effects of system parameters such as preamble length, fall and rise time of optical devices, and timing jitter on the bit error rate of the link are discussed.

中文翻译：

---

基于 HCM 的室内光无线通信：定时和数据恢复

光保真 (Li-Fi) 是一种很有前途的解决方案，可提供用于下一代无线网络的高速、安全和绿色通信。由于使用可见光或红外 (IR) 发光二极管 (LED) 作为光源并具有非线性传递函数，因此如果信号具有较高的峰均功率比 (峰均利率）。最近，提出了一种称为哈达玛编码调制（HCM）的新调制方案，该方案不存在 PAPR 问题，因为它产生具有离散电平的符号。在 HCM 技术中，可以使用多个 LED 创建符号级别。因此，每个 LED 都在其线性区域内工作并且仅打开或关闭。提出了一种用于基于 HCM 的通信链路的低复杂度收发器架构，并提出了基于扩频技术的完整同步过程。最后，通过蒙特卡罗仿真评估了系统的误码率，讨论了前导码长度、光器件的下降和上升时间、定时抖动等系统参数对链路误码率的影响。