區塊編碼調變是種具有頻寬效益又可以增加數位通訊可靠度的系統。它將區塊編碼部分和調變部分結合。用在加成性白色高斯雜訊通道上的區塊編碼調變，其最小歐基里德平方距離越大越好。 本論文主要是討論差分同調檢測下之區塊編碼調變系統的效能。我們使用區塊對區塊差分和符元對符元差分兩種檢測方式。由於傳統差分同調檢測效能不如同調檢測好，因此利用兩種決定迴授相差檢測的方法，也就是多符元差分檢測來改進系統的效能。 除此之外，若通道影響載波有任意頻率位移的情況考慮在內時，則傳統差分同調檢測之區塊編碼系統會得到較差的效能。因此我們使用雙重差分同調檢測的方式來克服此情況，使系統不易受到頻率的干擾，擁有好的效能。 Block coded modulation (BCM) is a bandwidth efficient scheme which can increase the reliability of digital communications. This system results from the combination of block coding and modulation. It is mostly applied to the additive white Gaussian noise (AWGN) channel, maximizing its minimum squared Euclidean distance (MSED). The thesis studies the use of differentially coherent detection in block coded modulation systems, using block-by-block and symbol-by-symbol approaches. To further improve the error performance of considered systems, two ways of decision feedback differential detection (DFDD)—the multiple-symbol differential detection techniques, have been also considered. Anther topic concentrated in channels that introduce into the carrier a random frequency shift, classical differentially coherent detection for BCM system is not suitable in use. Therefore, we propose double differential detection scheme to overcome this situation and gain good performance without frequency interference.
