為了因應下世代行動通訊系統更高的資料率，巨量天線多重輸入多重輸出系統在近年來成為熱門的研究議題。但是巨量天線多重輸入多重輸出系統需耗費大量的硬體元件像是射頻鏈路，如此將消耗極大的功率來運作此系統。因此，提出混合預編碼架構，利用極少於天線數的射頻元件，搭配一個數位基頻帶預編碼器以及一個類比射頻預編碼器進行巨量天線多重輸入多重輸出系統的訊號處理。
在我的研究中，射頻預編碼器之設計主要可以分為兩類。第一類是不對通道矩陣做奇異值分解，因為在巨量天線多重輸入多重輸出系統其運算複雜度相當高。再者，我們並不能夠知道實際傳輸路徑的輻射角及入射角的角度，因此我們從預先定義好的編碼簿挑選出幾個基底作為射頻預編碼器，將訊號盡可能地朝實際傳輸路徑集中能量送出，並且在接收端調整天線接收角度進行最佳接收。第二類是對通道矩陣做奇異值分解，並且直接取最佳預編碼器之相位作為射頻預編碼器，如次可以形成多重波束並且非常接近最佳預編碼器之波束成型之方向。在這領域大部分的研究忽略資料流間干擾，我們利用奇異值分解來設計數位基頻帶預編碼器以避免接收端產生資料流間干擾。因此，如果實際考慮干擾的影響，我們提出的混合預編碼器之設計方法會比別人提出的方法還要更好。

To support the higher data rate in the next generation mobile communication system, massive multiple-input multiple-output (MIMO) systems has attracted a lot of attentions for the past few years. The disadvantage of massive MIMO systems is high power consumption, since large amount of RF chains should be deployed. Hence, hybrid precoding architecture, which splits the traditional baseband precoder into a RF precoder and baseband prcoder, is proposed to implement massive MIMO systems with small amount of RF chains much less than the number of antennas. In this work, the designs of RF precoder are classified into two categories. The one is not to take singular value decomposition (SVD) for channel matrix, since the computational complexity is very high in massive MIMO systems. Therefore, we will choose several bases from a pre-defined codebook as RF precoder, because the angle of departure (AOD) and angle of arrival (AOA) of the propagation paths are assumed to be unknown. The other approach is to take SVD for channel matrix and extract the phase of the optimal precoder as RF precoder which can form a multiple beam pattern. Baseband precoder and combiner are used to avoid inter-stream interference which most of researches ignores. Our methods can achieve an interference-free effect at the receiver. As a result, we can get a better performance than other researches if interference is considered.

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