臺灣博碩士論文加值系統

本論文利用實作可見光通訊於機車尾燈上，來實際測試可見光用於
機車通訊上之可行性，並且用於比對理論上的可見光通訊模型。由於
發光二極體逐漸取代傳燈泡，利用可見光來做無線通訊順勢興起。可
見光通訊同時包含了照明以及溝通的功能，由於是使用既有的LED 來
作為通訊的媒介，成本也相對較小。而且有別於傳統的無線射頻技術，
可見光通訊包含了高指向性、高保密性以及高頻寬等等的特性。我們
的發想是利用可見光通訊的高遮蔽性的特性，利用車輛上原本就存在
的LED 燈來作可見光通訊，一方面將資料傳送給最接近本車(也就是
最重要的對象)，並且在道路擁塞時，不會像傳統無線射頻一樣有嚴重
的互相干擾情況。我們利用軟體的方式搭配Software Defined Radio 來
實作可見光通訊於真實的機車上，並且騎到真實道路上收送資料以驗
證可見光通訊的可行性，以期待未來可以廣泛應用於車間通訊。

This thesis evaluates the feasibility of the VLC(visible light communication)
used in scooter V2V networks scenario by implementing a VLC system
which uses the scooter’s tail light as the transmitting component, and we develop
a theoretical BER model of our scooter VLC system based on the collected
real world data. VLC is a wireless communication technology using
the optical signal to carry digital information by controlling the LED’s light
intensity in free space. It obtains the opportunities raised by the increasing
trends on the usage of LEDs. VLC has several advantages compared to traditional
RF; first, VLC is more secure than RF because it requires line-of-sight
for transmission. Second, VLC is a low cost solution, as LEDs are already
commonly available in the cars. Third, VLC is safer than RF because it operates
in visible light spectrum. Fourth, VLC is more scalable also because
of the line-of-sight transmission requirement. In our work, we apply Gnuradio
and SDR (software defined radio) to be our core development tools to
implement the VLC scooter system. We use the scooter’s tail light as our
transmitting component and a amplified photodiode module as our receiving
component. We have some experiment results by using this VLC system and
build a theoretical model of our scooter VLC system.

誌謝ii
摘要iii
Abstract iv
1 Introduction 1
2 Related Work 4
3 System Architecture and Components 6
3.1 Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2 System Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2.1 Software Defined Radio . . . . . . . . . . . . . . . . . . . . . . 7
3.2.2 GNU Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2.3 VLC Frontend Board . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2.4 Photodiode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3 Prototype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4 Physical Layer Design 12
4.1 Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1.1 Pulse Position Modulation . . . . . . . . . . . . . . . . . . . . . 13
4.2 Packet Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.3 Adjustable Threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.4 Reed-Solomon FEC Code . . . . . . . . . . . . . . . . . . . . . . . . . . 16
v
5 Experimental Results 19
5.1 Static Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.2 Dynamic Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
6 Theoretical Model 30
6.1 Basic LED Light Channel . . . . . . . . . . . . . . . . . . . . . . . . . . 30
7 Conclusion and Future Work 38
7.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
vi

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