| Summary: | 碩士 === 國立中央大學 === 通訊工程研究所 === 99 === Recently, a new differential encoder was proposed, by a look-up table instead of a rule. In this thesis, we present further research results on this subject. We propose some constellations maximizing minimum noncoherent distance. Then we show that differential encoding by a table is equivalent to differential encoding by a trellis, so we use the Viterbi algorithm at the differential detector to improve the error performance. A theorem about the sufficient number of states for various modulations is proposed. Finally, we extend the new differential encoding and detection to differential space time modulation(DSTM). We use a new definition of DSTM, by which the transmitted block is determined according to the previously transmitted block and current data bits. The encoding table that determines the transmitted block can be optimized. We also propose a theorem to reduce the number of states of the decoding trellis.
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