臺灣博碩士論文加值系統

交通震波為造成道路塞車的原因之一。許多研究指出透過搭載車間 通訊之自動駕駛系統可以有效消除交通震波，然而，此類的解決方法 仍有些許可改進之處，例如，自動駕駛的成本昂貴，短期內難以成為 車輛市場主流。另一方面，車間通訊多以射頻技術為基礎進行開發， 當車流變大時，射頻的干擾增大，造成訊息丟失或是巨大延遲。因此， 我們針對這兩個方向，設計一套針對人類的駕駛速度推薦系統，使駕 駛人能夠更快獲得前方車輛的速度等交通資訊，降低駕駛對前車速度 改變的反應時間，以此減緩交通震波。同時，我們利用車尾燈及感光 元件以正交頻分多工技術 (OFDM) 為基礎研發出可見光通訊系統，作 為車間通訊之傳輸媒介，藉此有效避免車間通訊的信號干擾與降低封 包延遲現象。實驗結果顯示，我們的系統可有效降低至多 54.6% 的駕 駛反應時間，車間的可見光通訊系統可在至遠 45 公尺，獲得穩定的傳 輸品質與速度。

Traffic shockwave is one of the main reasons for reduced road capacity and jammed traffic. Recent studies have shown that traffic shockwave can be mitigated or eliminated using self-driving vehicles with vehicle-to-vehicle (V2V) communication. Several radio frequency (RF) wireless communica- tion methods have been demonstrated in these studies, such as Wi-Fi and Blue- tooth. However, due to the high cost of self-driving vehicles, this technology is still far deployment in our daily life. Also, the high interference between the wireless signals makes RF communication algorithms more difficult to be designed and implemented.
Our work aims to show that traffic shockwave mitigation can also be achieved by human drivers instead of self-driving vehicles and this work ad- dresses the communication challenges faced by existing RF-based solutions with visible light communications (VLCs). In this thesis, we develop a real- time speed advisory system using VLC to provide drivers of the following car with the speed information of the leading car so that drivers can intuitively match the speed. We also implement real-world V2V communications by uti- lizing the LED taillights of the leading car and making use of a light sensor in the following car. Real-world experimental results show that with this speed advisory system, the reaction time of drivers can be reduced by as much as 54.6%. Furthermore, the VLC system can establish a reliable communication link when the two cars are at a distance of 45 meters.

誌謝 iii
摘要 iv
Abstract v
1 Introduction 1
2 Related Work 6
2.1 TrafficShockwaveElimination....................... 6
2.2 Vehicle-to-vehicle Visible Light Communication (V2LC) . . . . . . . . . 7
3 System Design 8
3.1 Overview .................................. 8
3.2 Background:OFDM ............................ 9
3.3 TheAdoptedOFDMScheme........................ 11
3.3.1 PreambleDesign .......................... 11
3.3.2 TransmitterDesign......................... 11
3.3.3 ReceiverDesign .......................... 13
4 Implementation 17
4.1 Overview .................................. 17
4.2 SpeedAdvisoryandUserInterface..................... 19
4.2.1 VehicleSpeedMeasurement .................... 19
4.2.2 SpeedadvisoryandUserInterface................. 19
4.3 VisibleLightCommunication........................ 21
4.3.1 ArchitectureofTransmitter..................... 21
4.3.2 ArchitectureofReceiver ...................... 22
4.3.3 Real-timeVLCdecodingAlgorithm................ 23
4.4 End-to-EndSystemDelay ......................... 24
5 Evaluation 26
5.1 LIDAR–vehiclepositionmeasurement .................. 26
5.2 PerformanceoftheVLCsystem ...................... 27
5.2.1 Throughputperformance...................... 27
5.2.2 BERofdifferentincidenceangles ................. 29
5.2.3 Symbol reception in common driving scenarios . . . . . . . . . . 32
5.3 Performanceofthespeedadvisorysystem................. 34
5.3.1 DrivingRouteandTesingConditions . . . . . . . . . . . . . . . 34
5.3.2 DriverReactionDelayAlgorithm ................. 35
5.4 DriverPerformanceResults......................... 36
6 Conclusion and Future Work ................. 40
Bibliography................. 42

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