空時編碼和調變藉由多根傳送天線傳送訊號改善了多路徑無線通道的效能。各式各樣的時空編碼方案已經被提出。然而直到目前為止，大多數關於空時編碼的研究，已假設在接收端可得到目前通道衰減情形的完美估測。在某些局勢下，我們可能想要去放棄通道估測，為了去減少系統的複雜度和成本，或者衰減的情形改變的非常快速，以至於通道估測是困難的或需要太多的訓練符號。
　　我們提出了幾個可行的、簡單的差動編碼和解碼傳送方案，探究因為多根傳送天線所造成的分歧。這些新的偵測方案傳送端和接收端都不需要去知道通道狀態資訊，並且可以使用相等能量星座圖而且編碼是簡單的；在接收端，解碼被完成了，並且解碼的複雜度低。

　Space-time coding and modulation exploit the presence of multiple transmit antennas to improve the performance on multipath radio channels. Various space-time coding schemes have been proposed. However so far, most research on space-time coding has assumed that perfect estimates of current channel fading conditions are available at the receiver. However, in certain situations, we may want to forego channel estimation in order to reduce the complexity and cost of the handset, or perhaps fading conditions change so rapidly that channel estimation is difficult or requires too many training symbols.
　The thesis presents several practical, feasible, and simple transmission schemes for exploiting diversity given by multiple transmit antennas when neither the transmitter nor the receiver has access to channel state information. The new detection scheme can use equal energy constellations and encoding is simple. At the receiver, decoding is achieved with low decoding complexity. The transmission requires no channel state side information at the receiver. The schemes can be considered as the extension of differential detection schemes to two transmit antennas.

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