最近所提出以查表法運用在QAM的相差編碼可以有效降低差分編碼的複雜度與改善其錯誤效能。本篇論文以此做延伸，除了改善並找出16APSK與16TAPSK使用的最佳差分編碼表，更針對由2000年所提出的差分時空調變為其提出一種新的差分編碼方式，利用查表法以避免星座圖上的傳送符號發生擴展問題；此外，查表法的差分編碼等效於籬柵式的差分編碼，在差分檢測器的部分利用維特比演算法，藉由增加限制長度以改善錯誤效能，並提出一定理以降低在差分時空調變籬柵解碼的狀態數量。 Differential encoding by a look-up table for QAM was proposed recently. It can reduce complexity of differential encoding and improve the error performance. In this thesis, we find a better differential encoding table for 16APSK and 16TAPSK; moreover, we propose a new differential encoding method for differential space-time modulation (DSTM), which was proposed in 2000. The new differential encoding method uses a look-up table to avoid the expansion of the constellation of the transmitted signals; we show that, differential encoding by a table is equivalent to differential encoding by a trellis. We use the Viterbi algorithm at the differential detector, and increase truncation length to improve the error performance, and propose a theorem to reduce the number of states of the decoding trellis.
