在最近有一個新的相差編碼方法被提出來，它利用查表實現，不像傳統的一樣使用相差編碼規則。本篇論文研究，用於多重符號相差檢測之使用查表相差編碼，此相差編碼根據先前多個時間傳送的符號和目前的資料位元，經由查表獲得目前傳送訊號，用此表所做的相差編碼，其最小非同調距離優於原本相差編碼，模擬結果證實有比較好。此外，我們在相差檢測器利用維特比演算法，以進一步降低錯誤率。

Differential encoding by a look-up table for QAM was proposed recently.
In this thesis, but not by a rule,using differential encoding by a table for multiple- symbol differential detection.The transmitted symbol can be obtained by looking up this read-only table according to the previously transmitted multiple symbol and data bits.Using a table for differential encoding has the advantages of both low complexity and good error performance.The results show that, differential encoding by a table is equivalent to differential encoding by a trellis. Besides Viterbi algorithm to further lower error performance.

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