多色μLED可见光通信传输理论研究

Commercial multicolor LEDs have narrow modulation bandwidth and few available colors, while multicolor μLEDs are broadband micro-size LED chips with custom-defined wavelength. They will provide plenty of resources in spectra, space reuse, and modulation bandwidth for multicolor visible light communications (MC-VLC). The MC-VLC transceiver design should fully consider the increase of multicolor wavelength-division multiplexing (MC-WDM) channels and the massive multicolor μLED deployment. In the scenario of single user communication, this project will firstly investigate the optimal transceiver design subject to the quality of illumination. And next, to support the mobility of receiver, we will focus on the robust design of optical filters in terms of the central wavelength (CWL) and bandwidth to mitigate the short shift of CWL with the increase of angle of incident (AoI). We further investigate the jointly robust design of optical filters and transceiver. Last, in the scenario of massive multicolor μLEDs deployment, the project will consider the jointly optimal multiuser scheduling and resource allocations. Our research will invoke the latest results from advanced optimization theories such as convex optimization, robust optimization, distributed optimization and game theory to design the MC-VLC system. This project aims to revealing the tradeoff between illuminations and communications, and ultimately reducing the cost of optical systems in MC-VLC by modern digital signal processing and finally providing technical solutions to future MC-VLC networks.

现有商用多色LED调制带宽窄且颜色品种少，而新型微尺寸多色μLED的调制带宽宽且颜色丰富。它将为多色可见光通信提供丰富的光谱、空间和调制带宽资源。为充分发挥该器件的优势，现有多色可见光通信传输机制需要充分考虑由该器件引起的多色波分复用数目增加以及大规模部署所带来的影响。本课题将首先在单用户场景下研究兼顾照明质量的信号多维传输机制。随后课题针对接收滤光系统进行角度鲁棒性设计来缓解滤光通带的中心波长跟随入射光角度变化这一现象对用户的移动性造成的影响，并进一步研究角度鲁棒性的最优传输理论。最后，课题在多色μLED大规模部署下开展多用户资源分配与调度机制的研究。课题将采用凸优化、鲁棒性优化、分布式优化、博弈论等前沿优化理论，力图揭示多色可见光通信中传输与照明的内在制衡关系，并最大程度地利用先进高效的信号处理手段来降低传输对光学器件苛刻指标的依赖，为未来多色可见光通信网络的发展提供技术支撑。

本项目研究以多色μLED作为发射器件的可见光通信系统，围绕密集波分复用多色滤光片设计、针对发送器件的非线性信道建模预均衡以及先进收发系统设计等各个方面展开研究。项目的整体目标是为新型多色μLED 器件在多色可见光通信系统中的应用进行前沿技术的探索。.经过四年研究，针对多色μLED发射器信道的上下限幅问题，在DCO-OFDM系统中给出了预均衡和后均衡的可达速率的性能分析，并证明了预均衡的优越性。据此项目还对多色光DCO-OFDM系统中各色光直流偏置和交流功率以照明亮度、色温约束下完成了系统和速率最大的设计。进一步针对非线性信道，项目提出了基于深度学习网络DNN、CNN的建模和均衡方法，可实现不同偏置电流下的信道输出预测与均衡，比现有基于Volterra建模更小的复杂度、更强的鲁棒性、更低的预测均方误差等。依据所提出的深度学习信道模型，还在DOC-OFDM系统中进行了发送信号的概率和幅度整形的自动编码器设计，从信息论角度获得了比传统M-QAM更适应可见光信道传输的符号设计。针对多色μLED作为发射器件所引发的密集波分复用，项目完整地给出了在固定入射角度基于实测发射光谱模型依据接收SINR以及MSE的滤光片设计方案。而后进一步考虑用户随机移动场景下基于统计平均以及最差情况下的滤光片设计方案。为了彻底解决移动环境下多色可见光系统滤光片蓝移问题，还提出了新型重叠覆盖滤光片组的设计。它能够无差别捕获各个入射角度多色光从而高效实现系统的鲁棒性。据此项目还设计了基于重叠覆盖滤光器组的收发信机的联合设计。上述研究推动了未来宽色域可见光高速传输系统的设计和网络部署提供技术支撑。