余礼苏, 吕欣欣, 钟润, 张鸣莉, 王正海, 王玉皞. 液晶智能超表面辅助的室内可见光通信系统优化设计[J]. 工程科学学报. DOI: 10.13374/j.issn2095-9389.2024.05.21.002
引用本文: 余礼苏, 吕欣欣, 钟润, 张鸣莉, 王正海, 王玉皞. 液晶智能超表面辅助的室内可见光通信系统优化设计[J]. 工程科学学报. DOI: 10.13374/j.issn2095-9389.2024.05.21.002
* 通信作者,E-mail: wangzhenghai@126.com, wangyuhao@ncu.edu.cn.[J]. Chinese Journal of Engineering. DOI: 10.13374/j.issn2095-9389.2024.05.21.002
Citation: * 通信作者,E-mail: wangzhenghai@126.com, wangyuhao@ncu.edu.cn.[J]. Chinese Journal of Engineering. DOI: 10.13374/j.issn2095-9389.2024.05.21.002

液晶智能超表面辅助的室内可见光通信系统优化设计

* 通信作者,E-mail: wangzhenghai@126.com, wangyuhao@ncu.edu.cn.

  • 摘要: 可见光通信(Visible light communication, VLC)作为6G (Sixth generation) 的候选技术,具备访问广阔的免许可频谱、更高的安全级别、避免射频干扰等诸多优势,这些特点使得VLC成为射频通信的有效补充方案。本文设计并优化了一种基于功率域非正交多址 (Power domain non-orthogonal multiple access, PD-NOMA) 技术的室内VLC下行链路通信系统,该系统中包括一块位于信道中间的透射反射智能超表面 (Simultaneous transmitting and reflecting reconfigurable intelligent surface, STAR-RIS) 和一个基于液晶RIS (Liquid crystal RIS, LC-RIS) 的接收器。为了评估所设计的系统性能,本文提出了一个和速率最大化问题,并考虑实际情况下发射机和接收机之间的视距 (Light-of-sight, LoS) 路径存在非用户遮挡因素。由于所提出优化问题的非凸性,首先使用二次变换 (Quadratic transform) 将目标函数转化为一个分式规划问题,其次采用分步优化算法和CVX工具来获得可行解。此外,本文分析了 LED (Light emitting diode) 的数量、入射光波长以及液晶折射率对室内可见光通信系统和速率的影响。数值仿真结果表明:1) 在能量分裂 (Energy splitting, ES) 操作协议下,STAR-RIS和LC-RIS联合辅助的室内VLC系统的和速率明显高于仅有反射RIS和无LC-RIS的VLC系统。2) LED灯数量、入射光波长以及LC折射率均会在一定程度上对系统性能产生影响。这些研究结果为室内可见光通信系统的设计和优化提供了重要参考。

     

    Abstract: Visible Light Communication (VLC), a candidate technology of sixth generation (6G), offers access to a broad license-free spectrum, a higher level of security, and protection from radio frequency (RF) interference, making VLC an effective complementary solution to RF communication. With these features, VLC serves as an effective complement to RF communication. VLC systems are primarily designed for indoor scenarios, with typical transmission distances ranging between 2 and 5 meters. In wireless networks, reconfigurable intelligent surface (RIS) have recently demonstrated a significant impact. This paper introduces indoor power domain non-orthogonal multiple access technology (PD-NOMA)-based VLC downlink communication system, designed and optimized to include a simultaneous transmitting and reflecting RIS (STAR-RIS) in the channel and a liquid crystal (LC) RIS-based receiver with co-assisted composition. That is the STAR-RIS under the energy splitting (ES) protocol is deployed in the transmission channel, and LC-RIS-based VLC receivers are employed at the receiver side, both schemes having the effect of enhancing the optical signal. To evaluate the proposed system's performance, a sum-rate maximization problem is formulated and solved. This maximization problem accounts for practical situations such as the presence of non-user-obscured line-of-sight (LoS) paths between the transmitter and the receiver. A low-complexity algorithm is recommended for the perfect channel state information (CSI) setup. This algorithm obtains the optimal solution for the joint design problem by utilizing the fractional programming (FP) technique and step-by-step optimization scheme. Due to the non-convexity of the objective function, the objective function is first transformed into a multinomial fractional planning problem using the Lagrangian dual transform to make the objective function more tractable. Secondly, the step-by-step optimization scheme and the CVX tool are used to obtain a feasible solution. Additionally, this paper analyzes the effects of the number of light emitting diodes (LEDs), the wavelength of the optical signal, and the refractive index of LC on the performance of indoor visible light communication system. The final numerical simulation results show that the sum rate of the indoor VLC system assisted by the combination of STAR-RIS and LC-RIS is significantly higher than that of the VLC system with only reflective RIS and no LC-RIS under the ES operation protocol, nearly 130% increase in system sum-rate. Additionally, the number of LEDs, the wavelength of the incident light, and the refractive index of the LC all affect the system performance to some extent. These findings provide an important reference for the design and optimization of indoor visible light communication systems.

     

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