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A Study on the Analysis and Modeling of Maritime VHF Wave Propagation- Based on AIS Sea Trials in Coastal Waters of Taiwan
|Authors: ||Wei-Chao Wang|
|Contributors: ||NTOU:Department of Communications Navigation and Control Engineering|
|Issue Date: ||2011-07-04
|Abstract: ||船舶自動識別系統(Automatic Identification System, AIS)結合了通訊與衛星導航系統，已被國際海事組織採納成為強制性的船舶配備之一。AIS相關研究已刻不容緩，AIS的岸基設施等基礎建設的建置規劃更需要充分的研究支援。然而海域（尤其是沿岸）無線通訊的實際場測所需成本相當高，更受到海象、船舶運動或操縱、航行安全等因素影響，在場測航線規劃以及資料量上都比陸上無線通訊受到更多的限制。沿岸陸域地形地物資料庫也往往因地處偏遠以及機密因素等而難以完整取得。 本論文研究重點在於以有限的實測資料以及環境資料庫，利用Matlab數值方法與MapInfo地理資訊系統進行電波傳播模擬與分析，做為AIS基地台規劃之依據。電波傳播模擬採用需要實測資料和實際地形高度當重要參數的Lee模型。研究範圍以台灣北部沿岸與高雄港沿岸為主。電波場強實測部分，是以船舶自動識別系統的基地台與船載台(移動台)進行。環境資料庫則包括數值地形模型、電子海圖、以及內政部陸圖。 經線性回歸分析之比較，實測與模擬結果在台灣北部沿岸衰減率相差約1.3dB/dec，相當於涵蓋距離差約3.7公里，而高雄港沿岸衰減率相差約0.35dB/dec，相當於涵蓋距離差約0.2公里。以高雄港沿岸模擬效果較佳，而台灣北部沿岸因受海象影響，所以模擬效果較差。因此，本論文所提到的方法應可適用於大範圍的預測。|
Automatic Identification System (AIS), which integrates the mobile communication and satellite positioning technologies, has great potential in contributing to navigation safety and maritime security. All vessels subject to the Safety of Life at Sea Convention（SOLAS）are required to be fitted with AIS within a very tight schedule. It is therefore of urgency needs of AIS researches to support the planning and implementations of shore-based AIS facilities and services. However, as compared with the situation on land, field measurements with sea trials are really costly, subject to weather/sea conditions and vessel motions, even restricted in route by the concern about navigation safety. Available database of the coastal land area such as the digital terrain model is also rather incomplete due to either the remoteness or confidential factors. This study focuses on making the most use of limited sea trial measurements and environmental database for the planning of AIS shore-based facilities. Matlab numerical methods and the Mapinfo geographical information system (GIS) are used for the simulation and analysis of AIS signal propagation in the maritime VHF band around 162MHz. Lee Model, which takes field measurement and terrain height data as important parameters, is adopted for the simulation. Research area mainly covers coastal waters of northern Taiwan and the Kaohsiung Harbor, where sea trials are performed by using an AIS base station and a class A AIS mobile station. Comparison between field measurements and simulations by linear regression analysis shows that the difference in path loss slope is about 1.3dB/dec, corresponding to a coverage range difference about 3.7km in the case of northern coastal waters. While the difference in path loss slope is only about 0.35dB/dec, corresponding to a coverage range difference about 0.2km in the case of Kaohsiung Harbor. Considering the fact that measurements were taken at a much worse sea state for the case of northern Taiwan than the case of Kaohsiung Harbor, the simulation fits well with the measurement, especially when in calm sea. Consequently, the mention presented should be applicable to large-scale predictions along the coast of Taiwan with reasonable results.
|Appears in Collections:||[通訊與導航工程學系] 博碩士論文|
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