正交分頻多工無線通訊系統中傳送端具通道資訊之分集技術研究

Abstract

在正交分頻多工無線通訊系統採用多輸入多輸出分集技術中，以往為接收端具通道資訊或是傳送端與接收端都具通道資訊，如Alamouti與傳輸波束成型(Transmit Beamforming)。在本論文中，我們提出最大比例選擇傳輸與最大比例差分傳輸兩種傳輸方式，來解決只有在傳送端具通道資訊的情況時，如何選擇傳送端各天線的權重，使系統效能提升。為了讓傳送端知道通道資訊，系統需要在分時雙功模式下，由接收端傳送訓練序列至傳送端。傳送端利用訓練序列做通道估計之外，還可藉由接收端傳來的控制資訊調整傳送資料之時間長度。最後，我們使用電腦模擬兩種傳輸方式之系統效能。

In MIMO-OFDM systems with conventional diversity techniques, such as Alamouti and the transmit beamforming schemes, either receiver or both receiver and transmitter know CSI. In this thesis, we propose another two schemes, Selective Maximum Ratio Transmission (SMRT) and Differential Maximum Ratio Transmission (DMRT), both of which choose the weights of antennas when the transmitter knows CSI only, to enhance the system performance. In order to make transmitter know CSI, the system should operate in TDD mode, where the receiver sends training sequences to the transmitter. The transmitter not only estimates CSI by training sequences but also adjusts the length of data transmission time according to the control information sent from the receiver. In the end, the system performance of the two proposed schemes is simulated.