水下通訊容易受到多路徑效應的影響產生符元間干擾(Intersymbol interference)進而造成通訊錯誤，若利用移動式載台進行通訊則會因為速度而產生都卜勒效應使得訊號頻率位移，進而造成解調錯誤，此外水下通道中的能量分布特性也會對水下通訊造成影響，受環境作用之能量變化會影響訊號的信雜比(Signal to noise ratio)。因此本文將以多路徑效應、都卜勒效應及能量分布三個參數來進行研究，利用中央氣象局建置於宜蘭外海的海底觀測站做為接收點，以此觀測站為中心並以移動式聲源拍發訊號，討論不同通道中的水平資料傳輸特性，並且研究不同地形之通道差異與變化。最後藉由聲學數值模式進行特徵聲線的模擬用以探討通道預估的可行性。

Underwater acoustic communications are affected by multipath effects which cause inter-symbol interference and result in symbol errors. And if mobile sources or receivers are applied in underwater acoustic communications, the carrier frequency will be fluctuated because of the Doppler effect, which will induce errors in demodulation results. Furthermore, underwater communication performance will be also influenced by the signal to noise ratio which is related to the acoustic propagation characteristics in underwater waveguide. This research use the bottom mounted hydrophone on the MArine Cable Hosted Observatory (MACHO) system, administrated by the Central Weather Bureau, and a mobile source to study the multipath effects, the Doppler effects, and the variation of signal to noise ratio in horizontal communications. The temporal and spatial variations of channel impulse response are studied, and the topographic effects are discussed. Finally, numerical simulation is applied to illustrate the multipath characteristics and to examine the predictability of acoustic field in this waveguide.

審定書…………………………………………………………………………………i
誌謝.......................................................................................................ii
摘要...........................................................................................................iii
Abstract..................................................................................................................iv
目錄..............................................................................................................................v
圖次............................................................................................................................vi
表次...............................................................................................................................ix
第一章 緒論......................................................1
1-1 背景介紹.................................................1
1-2 研究目的.................................................2
1-3 文獻回顧.................................................2
1-4 研究流程.................................................4
1-5 研究結果.................................................6
第二章 研究方法與理論............................................7
2-1 脈衝壓縮.................................................8
2-2 都卜勒效應...............................................9
2-3 聲學模組BELLHOP計算理論..............................11
第三章 實驗與資料分析...........................................14
3-1 實驗....................................................14
3-2 訊號設計................................................18
3-3 環境資料................................................20
3-4 水下通道脈衝響應........................................22
3-5 都卜勒效應..............................................26
3-6 能量變化................................................33
第四章 通道預估……….............................................46
4-1 模擬峽谷測線前段之特徵聲線路徑..............................51
4-2 模擬結果與實驗數據比較...........................................61
第五章 結論與未來工作...........................................65
5-1 結論....................................................65
5-2 未來工作................................................67
參考文獻...........................................................68
附錄A........................................................................70

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