電機資訊學院: 資訊工程學研究所指導教授: 蔡欣穆陳艾苓Chen, Ai-LingAi-LingChen2017-03-032018-07-052017-03-032018-07-052016http://ntur.lib.ntu.edu.tw//handle/246246/275458車間通訊日漸蓬勃發展，隨著LED在汽車燈上越來越普遍，想要創造更智能的交通系統，可見光通訊相對於射頻 (RF-based) 將會是一個更有前瞻性的解決方案。利用汽車上現有的LED頭燈做為傳輸端發射光訊號，光電二極管或照相機作為接收端解調光訊號，即使在高密度的車流中，車間可見光通訊系統仍然具有高穩定性以及低成本的特性。然而，很多研究調查了車間射頻通道分析，卻很少有針對動態車間可見光通訊通道衰弱之分析。而在車間可見光通訊通道中，主要會造成衰弱的主因有三項，分別為傳輸接收端的距離、出射角和入射角。在本論文中，我們先利用雷達來收集實際車流精確動向，從這些車流動向，我們可以找出後車 (傳輸端) 與前車 (接收端) 之相對位置進而計算出上述三個參數；接著，我們利用光電二極管來測量實際通道對於車上LED頭燈的接收功率。綜合分析這些數據，我們發現 (1) 兩個局部造成接收功率衰弱產生大幅度變化的原因，一個是車子的震動，會造成高達5 dBm的變化，另一個是轉彎，會造成高達10 dBm的變化 (2) 在車間可見光通訊通道中，快速道路的90%和50%之相干性都比市區高，此外車間可見光通訊通道也比RF好 (3) 衰弱指數跟距離相關性較高，且在較近的距離衰弱指數比較大，但在距離越遠的地方衰弱指數會向4收斂。In the years to come, communication between vehicles is the future trend. With Light Emitting Diode (LED) becoming very common in today''s automotive lights, Vehicular Visible Light Communications (V2LC) will be a promising solution to the intelligent transportation system. Moreover, LED has many advantages, such as long life expectancy, low power consumption, and minimal heat generation lighting. Modulating these existing LED lights to transmit optical signals, and utilizing either a photodiode module or a camera as the receiving component to demodulate the transmitted optical signal, such a typical V2LC system is a intelligent transportation system and requires minimum additional cost. While many existing studies have investigated V2V RF channels, there is very little work characterizing V2V VLC channels in driving scenarios. The path loss of a V2LC channel is dictated by the transmitter-receiver distance, the irradiance angle, and the incidence angle. In this paper, (1) we collected extremely accurate vehicle mobility traces using a 2-dimensional LIDAR mounted on the front bumper of the rear vehicle. From these traces, we can get above parameters of the front vehicle (the receiving vehicle) with respect to the rear vehicle (the transmitting vehicle). (2) we collected optical signal by photodiode mounted on the front vehicle and used OEM LED headlamps as the transmitter mounted on the rear vehicle. Combining the above two sets of data, we found (1) there are two localized factors causing significant variation of the received power. One is vehicle vibration, providing variation up to 5 dBm; and the other is turning at intersections, the variation of which can up to 10 dBm. (2) for both 90\% and 50\% coherence time, the freeway has larger coherence time than urban area in V2LC channels and V2LC has mush slower time variation; the values of the V2LC channel are at least an order of magnitude larger than that of the DSRC channel. (3) the path loss exponent is contributed by the distance rather than the area and the empirical path loss exponent increases at shorter distance, but converges to 4 at larger distance.9571551 bytesapplication/pdf論文公開時間: 2016/8/26論文使用權限: 同意有償授權(權利金給回饋本人)車間可見光通訊可見光通訊車間通訊通道衰弱Vehicular Visible Light CommunicationsVisible Light CommunicationsVehicle-to-Vehicle CommunicationsChannel Fading[SDGs]SDG3[SDGs]SDG11thesis10.6342/NTU201601777http://ntur.lib.ntu.edu.tw/bitstream/246246/275458/1/ntu-105-R03922028-1.pdf