為了因應未來行動裝置快速增加，造成頻寬與資料量需求增加的問題，現階段第四代行動通 訊系統(4G)，如LTE、LTE-Advanced系統，已經無法滿足比目前通訊技術高10-100倍之資料量， 因此許多國際主要通訊研究組織、通訊大廠、電信營運商、及台灣在內之各國政府，紛紛投入相 當龐大的資源來進行第五代行動通訊(5G)技術先期研究與專利布局。依照目前的研究現況，5G 系統可能採用的技術包含了巨量天線（Massive MIMO）、毫米波（Millimeter Wave，mmWave）、 異質網路（Heterogeneous Network，HetNet）及等前瞻技術。雖然巨量天線技術可以有效的提高 頻譜效益(Spectral Efficiency)，但通道估測、領航汙染、預編碼等基頻訊號處理問題也隨之而生。 因此本論文將著重於討論巨量天線基頻(Baseband)訊號處理相關問題與限制， 及未來可能之研究 方向。

Since the number of mobile devices are dramatically growing, high bandwidth and data transmission rate demands become the main problem. Additionally, current 4G systems can not satisfy the future requirements, whose data transmission rate is 10-100 times greater than that of current modern communication systems, such as LTE/LTE-Advanced systems. Therefore, several research institutes, communication operators, communication companies, and governments in the world, including Taiwan, provide large resources to design possible technologies for 5G mobile communication systems. According to current research results, the possible candidates for 5G systems include massive MIMO, millimeter wave（mmWave）, and heterogeneous network（HetNet） technologies. Although the massive MIMO technology can effectively increase the spectral and energy efficiency, related problems, such as channel estimation, pilot contamination, precoding, need to be considered. Therefore, this paper will focus on discussing the problem of baseband signal processing and limitation of massive MIMO systems and future possible research directions.