以分碼多工存取為基礎之可見光通訊應用於室內環境之訊息廣播系統

Abstract

使用可見光進行通訊具有許多優點，例如其所使用之頻帶無須執照、高訊息安全性以及對比於射頻技術較低的健康風險。此外，仰賴於固態照明技術之快速進步，使得我們可使用低廉的成本佈建以及整合固態照明裝置至現有之照明建設。基於以上之特點，使得可見光通訊技術在近年來被廣泛的關注。而整合至照明架構中之可見光通訊網路通常適合用於建構一單向通訊系統，而此網路對於光線之干擾是非常敏感的。因此，同時於同一個可見光通訊頻道傳輸或廣播多種不同的訊息將會導致嚴重的碰撞產生。在本篇論文中，我們提出一基於修改分碼多工存取之室內可見光通訊系統並解決了前述之碰撞問題。經由我們所提出之方法，通訊過程中將免於碰撞之問題，且同一時間於同一頻道中廣播多種訊息將可順利達成。於使用本系統之環境中，使用者接收裝置不需擁有事前之環境參數配置資訊即可運作於本系統中，並且使用者接收裝置只需配置簡單之硬體設備即可運作，例如配置有高解析度光感測器之行動裝置即可作為我們的使用者接收裝置。我們亦提出許多可運作於本系統上之應用及情境，並展示一室內定位應用。系統原型之實作結果驗證了我們所提出系統於真實世界運作之可行性。

Recently, the technology of visible light communication (VLC) has been widely discussed. Communication through visible light has several advantages, such as freedom of license, line-of-sight security, and less health concern compared to radio-based systems. In addition, the rapid progress of light emitting diode (LED) technology by solid-state lighting (SSL) allows VLC to be easily deployed and integrated with existing lighting infrastructure at low costs. However, VLC network, when integrated with lighting infrastructure, is usually for one-way communication and is highly sensitive to external light. Thus, transmitting or broadcasting multiple messages simultaneously over a visible light channel without any preprocessing may result in serious collisions. In this paper, we propose an indoor VLC system based on a modified code division multiple access (CDMA) technique to tackle these problems. Through our approach, communication is immune to collisions and broadcasting multiple messages simultaneously is feasible. By utilizing our technique, a VLC receiver can enter an environment without any prior configuration and can be designed with simple hardware. Even a mobile device with a high-resolution photo diode sensor can be used as a receiver. We also present several feasible applications of the proposed system and demonstrate an example indoor positioning application. The prototyping results verify both the proposed approach and potential future real-world indoor positioning applications.