臺灣博碩士論文加值系統

隨著LED 的快速普及，可見光科技在近年來進入高速發展階段，
並且極富通訊潛力。藉此，本論文中我們提出一種室內可見光系統，
取名為LiBeamScanner。本系統僅需使用單顆客製化LED 燈配合光感
二極體做為接收端，即可達到極高精度之室內定位。由於僅需一顆燈
泡進行定位，即使在照明設備不密集的室內亦可布置本系統。此外，
系統使用光感二極體而非相機做為接收端，因此有低能耗與低複雜度
之優點，能夠被實做在耗能限制較嚴的系統上。
在傳輸端，我們借鑒了投影機之運作原理，將定位訊號透過液晶螢
幕進行調變而產生非常細微的光束，進而投射到定位平面上。這些光
束幾乎不會互相干擾，因此能夠達到高精度之室內定位。此外，我們
提出一種新穎的設計：將傳送端投影鏡頭改成雙鏡頭，如此我們便可
將接收端與傳送端之距離，亦即高度資訊，編碼在傳輸之光訊號中。
最後的定位結果顯示，在2D 平面上，我們系統的定位誤差中位數小於
2 公分，而若將上述之高度定位加入評估，定位誤差亦小於17 公分。

Benefit from the wide deployment of Light Emitting Diodes (LED), visible light communication technology has become an active research topic full of commercialization potentials. Taking advantage of this recent development, in this thesis, we proposes LiBeamScanner, an indoor positioning system that utilizes only a single custom light bulb and a light sensor to achieve extremely high positioning accuracy. With only a single light bulb as the transmitter, this system can perform extremely accurate positioning in environments without dense deployment of illuminaries. And the system only utilizes a simple light sensor in the receiver rather than a camera, and has low complexity and low energy consumption. This enables our design to be adopted in systems with more stingent constraints such as wearables.
At the transmitting side, we borrow the idea of projectors to send information to corresponding location without interfering neighboring areas by controlling
LCD pixels to generate narrow light beams, enabling fine-grained indoor positioning. Moreover, we propose a novel design utilizing dual lenses in the transmitter to modulate the information of stand-off distance, i.e. the height information, in the transmitted signals. Evaluation results of our prototype show that the error is less than 5 cm in most cases and the median error does not exceed 2 cm for the 2-dimensional position estimation, and 17 cm
for the 3-dimensional position estimation.

誌謝iii
摘要v
Abstract vi
1 Introduction 1
2 Related Work 6
3 LCD Primer 8
3.1 LCD Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2 LCD Types and Characteristics . . . . . . . . . . . . . . . . . . . . . . . 10
4 System Design 12
4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2 LiBeamScanner Transmission . . . . . . . . . . . . . . . . . . . . . . . 15
4.2.1 LED Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2.2 Bit pattern Approach . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2.3 PPM Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2.4 Compound Approach . . . . . . . . . . . . . . . . . . . . . . . . 17
4.2.5 Dual Lens - Stand-off Distance Estimation . . . . . . . . . . . . 17
4.3 LiBeamScanner Reception and Position Estimation . . . . . . . . . . . . 18
4.3.1 Arbitrary Rotation . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3.2 Decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3.3 Stand-off Distance Estimation . . . . . . . . . . . . . . . . . . . 20
5 Implementation 22
6 Evaluation and Results 26
6.1 Benchmark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6.1.1 LCD Response Time: STN and TFT LCD . . . . . . . . . . . . . 27
6.1.2 Interference to Neighboring Tiles: STN and TFT LCD . . . . . . 28
6.1.3 Transmittance: STN and TFT LCD . . . . . . . . . . . . . . . . 32
6.1.4 Dual-lens Design - Pulse difference . . . . . . . . . . . . . . . . 33
6.2 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
6.2.1 Positioning Accuracy: Bit Pattern and PPM . . . . . . . . . . . . 34
6.2.2 Positioning Accuracy: STN and TFT LCD . . . . . . . . . . . . 34
6.2.3 Impact of Receiver Rotation . . . . . . . . . . . . . . . . . . . . 34
6.2.4 Impact of PPM Cycle Duration . . . . . . . . . . . . . . . . . . . 38
6.2.5 Positioning Error: Stand-off Distance and 3D Positioning . . . . 39
7 Conclusion 43
Bibliography 44

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