提升可見光通訊傳輸品質之技術

Abstract

隨著無線通訊技術快速發展而且普及，未來不只是人，物與物之間都會有網路連結，將現實世界數位化，應用範圍十分廣泛。為了應對更大量的通訊需求，各式各樣的技術應運而生。其中可見光通訊技術是非常受人關注的，除了傳輸速度更快之外，使用可見光當作傳輸介質可以直接結合未來照明技術，而不用再另外架設基地台，具有高整合性。還有其他優點像安全性，特殊場合應用等，在未來只要有光的地方就有網路。 可以接收光的接收器各式各樣，其中手機是最為而容易取得而且整合上網需求最大的。使用相機影像來接收光訊號，類似應用像快速響應矩陣碼(QR條碼)，就是利用相機掃描二維圖形來達到簡單的資訊傳輸或儲存。首先我們研究整個可見光通訊系統的原理，再利用一系列的影像處理方法讓傳輸品質更穩定，最後使用不同的光源或調變方式來達到更高速的傳輸速度。

In order to satisfy the huge demand in communications, numerous technologies have emerged. Visible light communication (VLC) technology has attracted much attention. Besides the high data rate, using visible light as a transmission medium can be combined with lighting technology directly, achieving cost-effective integration system. VLC can provide higher transmission security (the so-called “what you see is what you send”), and it can provide several unique applications, such as accurate indoor positioning, under-water communications etc. Typical VLC receivers are positive-intrinsic-negative (PIN) photodiode (PD) or avalanche PD (APD). Using mobile-phone camera as VLC receiver can be flexible and reduce the VLC deployment cost. Similar applications like Quick Response (QR) Code which can store the information with a two-dimensional pattern and then retrieved by mobile-phone camera. In this thesis, we proposed and demonstrated different techniques to enhance the performance of VLC. In Chapter 2, we discuss using the rolling-shutter effect of the mobile-phone camera for the VLC. In Chapter 3, we compare different thresholding scheme for defining the logics of the rolling shutter pattern obtained by the mobile phone camera. In Chapter 4, we further discuss different schemes to enhance the transmission data rate of the camera-based VLC, such as using polarization multiplexing (PM), wavelength division multiplexing (WDM), and multiple-input multiple-output (MIMO). Finally, a conclusion and future works are presented in Chapter 5.