多光源可見光通訊系統應用與探討

Abstract

現今LED已經逐漸廣泛使用於室內與室外照明，由於LED的相較於螢光燈管有較高的頻寬，LED將會是應用在可見光通訊系統(visible light communication, VLC)的趨勢，為了達到均勻的照明環境，LED的擺放設計會導致在環境中有不同的光場空間分布，在VLC中會在不同的LED上載上不同的數據訊號，因為接收器會收到來各自各光源的光訊號，因此會導致嚴重的干擾情形。而我們的研究將探討多光源在可見光通訊的干擾影響，在此之外利用多光源通訊系統發展其應用與定位出使用者位置。 我們的研究為討論多光源在室內可見光通訊系統的探討，此論文主要分為三個部分，第一部分為透過實驗與模擬驗證多光源訊號間的干擾，與將LED光源套入Lambertian分佈的模擬，並且利用其模型模擬出訊號干擾的應用。第二部分為了提升VLC的通訊速度，加入了多輸入多輸出(multiple input multiple output, MIMO)的技術，並且以計算條件值(condition number, CN)值來評估MIMO通道矩陣，提出以旋轉接收器來使通道矩陣得到改善。最後則是將MIMO結合定位系統，兼顧照明、定位與通訊的有效率利用，並且在實驗中證實此定位系統的高精準度。

Nowadays light-emitting diode (LED) is widely used for both indoor and outdoor illumination. Owing to the higher modulation bandwidth than the fluorescent lamp, LED is also promising light source for visible light communication (VLC). For achieving uniform illumination environment, delicate LED setup strategies are typically required for controlling the resulting indoor spatial field distribution. For the VLC application, different LEDs are driven by different data signals; hence each receiver may receive optical signals irradiated from different LEDs, and suffers from serious signal interference. To achieve high data rate VLC, it is crucial to solve the signal interference. Additionally, for indoor VLC application using multiple LEDs, it is possible to identify users’ location. Our researches focus on the applications of indoor VLC using multiple LED light sources. The thesis is mainly divided into three sections. In the first section, a model for our indoor VLC system is built. The interference induced signal performance degradation is analyzed by simulations and experiments. In the second section, multiple input multiple output (MIMO) technology is used in our indoor VLC system in order to increase the transmission capacity. Moreover, we evaluate the channel matrix of MIMO by calculating the condition number (CN), and propose improving the CN of channel matrix by rotating the receiver. Finally, we combine the MIMO system with the position identification scheme to achieve illumination, positioning and communication simultaneously. High positioning accuracy is achieved in experiment.