本論文主要為提升水下通訊品質之研究，使系統更能克服多重路徑效應造成的干擾，達到大量資料之傳輸。訊號之發射以資料延時平移編碼機制，搭配雙相位鍵移調變技術；接收端則應用等化器之快速自優化最小均方演算法，搭配被動式時間反轉法還原訊號，探討不同編碼機制在通訊距離為1~50公尺對資料錯誤率的影響。被動式時間反轉法是反轉時序上的接收訊號，以虛擬的方式發回聲源端，使訊號可聚焦在原有聲源位置上以提升訊雜比，並降低多重路徑之干擾，所需的通道脈衝響應函數可由快速自優化最小均方演算法估算，此法是將典型最小均方演算法的步階參數於每次疊代時自動調整到最佳值，使其收斂速度遠高於典型的最小均方演算法；當大量資料於水下通道傳遞時，資料延時平移編碼機制可使系統更能適應水下通道的環境變化。實驗於邊界為176公尺×8公尺×4公尺的拖航水槽中進行，傳輸的資料為8位元64×64的圖像，實驗結果顯示所結合的演算法在含有強烈反射的水槽中，位元錯誤率仍可控制在5%內。

The purpose of this study is to increase the quality of the underwater acoustic communication (UAC) and capable to transmitted the large amounts of data under multipath environment. The transmitted binary data is formatted by pattern time delay shift coding regime (PDS) and modulated by binary phase shift-keying (BPSK). At the receiving end, fast self-optimized least mean squares algorithm (FOLMS) of the equalizer and passive time reversal mirror (TRM) are used to recover the transmitted signal. Then, bit error rate (BER) is discussed with analyzed different coding regime from 1m to 50m UAC distance. The process of TRM is to reverse the time sequence of the received signal, then transmit it back to the signal source receiver in a virtual way, so the signal can focus on the original source location. Therefore, the signal to noise ratio (SNR) is increased and the multipath effect is minimized. The channel impulse response (CIR) of the sound path is estimated by use of FOLMS, which adapts its step size automatically of the typical least mean squares algorithm (LMS), and leads to much higher convergence speed. Through the algorithm of PDS, the UAC system can be more adaptable in changing UAC environment when the large amounts of data are transmitted. The UAC experiment is conducted in the 176m×8m×4m towing tank. A 64×64×8bit photo is transmitted, and the experimental result implies that the proposed combined algorithms can decrease BER under 5% even with a strong reverberation environment.

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