由於全雙工通訊系統擁有同時同頻帶傳送和接收的能力，理論上與傳統半雙工系統相比可使頻譜效率加倍。然而全雙工收發器的效能表現因自干擾而有所限制，如何克服自干擾問題將是個挑戰。 此篇論文中，吾人提出包含隨機梯度下降法和遞迴最小平方法兩種最小化功率數位自干擾消除演算法之數學模型與模擬，將可應用於全雙工中繼解碼轉發系統。演算法模擬結果顯示其效果可適應性地估計出多路徑自干擾通道狀態並消除自干擾訊號。 接著，吾人使用 Zynq-7000 + AD9361 軟體定義無線電平台實現基於 LTE 下行標準之全雙工中繼系統原型。此外，在中繼端類比射頻部分使用方向天線做被動抑制和兩種最小化功率演算法做數位自干擾消除。所提出的方法總體自干擾消除效果可達 55 dB。此篇論文中的研究與應用可作為全雙工中繼解碼轉發通訊系統之原型實例。;Due to the capability of transmitting and receiving signals at the same time on the same frequency band, full-duplex communication systems can theoretically double the spectral efficiency, as compared with the conventional half-duplex systems. However, the performance of a full-duplex transceiver is limited by the inherent self-interference. Thus, how to overcome the self-interference problem becomes a challenging issue in successfully realizing the full-duplex communication systems. In this thesis, we first present the mathematical system models for full-duplex relay communications with the decode-and-forward protocol, and design two digital self-interference cancellation algorithms, including stochastic gradient descent and recursive least square, based on the idea of minimizing the average received power after the self-interference. The resultant algorithms can adaptively estimate the self-interference channel with multipaths and successfully cancel the self-interference signals to a sufficiently low level. Next, we use a Zynq-7000 + AD9361 software-defined radio platform to implement the full-duplex relay system prototype based on the long-term evolution (LTE) downlink standard. In addition, directional antennas are used at the relay node for passive self-interference suppression in the RF analog part, and the two proposed digital self-interference cancellation algorithms are implemented at the relay node. Throughout real experiments, it demonstrates that the proposed scheme can achieve the self-interference cancellation up to 55 dB in total. The proposed design methodology in this thesis could be served as a prototype for the development of full-duplex decode-and-forward relay communications.
