在不具備多根天線的情況下，合作通訊可以有效獲取空間多樣性。而分散式空時碼為一種合作通訊技術，它藉由多個具備一根天線的中繼點相互合作形成虛擬的陣列天線，以獲取空間多樣性，並獲得更好的系統效能。其中，分散式相差空時調變藉由相差編碼，可以使接收端不需要知道通道係數。 在本論文中，我們研究使用相差空時網路編碼的多訊號源合作通訊，它可以避免不完美同步與複雜的通道估測問題。我們提出使用分散式相差空時調變於多訊號源合作通訊中，並比較它與相差空時網路編碼的錯誤效能。由模擬結果顯示，在不考慮同步問題下，我們所提出的分散式相差空時調變架構比使用網路編碼有較好的錯誤效能。 ;Cooperative communications can achieve the spatial diversity effectively without using multi-antennas. Distributed space-time coding, one kind of cooperative communications, uses multiple relays with single antenna to form virtual antenna arrays. By doing so, it acquires spatial diversity and thus improves the system performance. Among them, distributed differential space-time modulation utilizes differential encoding such that the receiver does not need channel coefficients. In this thesis, we study differential space-time network coding for multi-source cooperative communications which overcomes the problems of imperfect synchronization and complicated channel estimation. We propose to use distributed differential space-time modulation for multi-source cooperative communications, and compare its error performance with differential space-time network coding. According to the simulation results, distributed differential space-time modulation scheme which we proposed has better error performance than network coding, irrespective of synchronization issue.
