在傳統多重輸入輸出系統中,預編碼器的設計大多是以全數位的方式來實現。 而在毫米波 (Millimeter Wave, mmWave) 多重輸入輸出系統中,由於需要使用大 量的天線來克服通道的衰減,因此混合類比與數位之預編碼器近年被提出。這種 預編碼器只使用少數的射頻鏈,可以減少能量消耗也可以減少基頻信號處理的複 雜度。 在 這 些 混 合 類 比 與 數 位 之 預 編 碼 器 中, 大 多 數 的 混 合 結 構 都 是 使 用 全 連 接 (Fully-connected) 結構之預編碼器,需要使用大量的相位偏移器,而使得硬體 的複雜度提高。近年有研究者提出子連接 (Sub-connected) 結構之預編碼器,能夠 大量減少相位偏移器的數量,以及更好的能量效益。 有鑒於這些預編碼器的優缺點,本論文提出一個結合全連接與子連接兩種結 構的方法的新式預編碼器設計。這個方法可以減少全連接結構中射頻中相位偏移 器的數量,降低硬體複雜度,但卻不會大幅降低總和傳輸率。 最後,我們以電腦模擬對於所提出之結構進行比較與討論。 關鍵詞 - 多重輸入輸出,毫米波通訊系統,混合預編碼器,子連接結構,5G 。
In modern multiple-input-multiple-output (MIMO) systems, precoders have been implemented mostly in digital domain. However, due to the massive num- ber of antenna elements in millimeter wave MIMO systems, the cost of adopting conventional fully-digital designs becomes very high and hence may not practical considering today’s semiconductor technology. As a result, hybrid digital-and-analog precoder design have been proposed. Most hybrid precoders are implemented using a fully-connected architecture, and hence a large number of phase shifters have to be used. In more recent years, sub-connected precoders have also been proposed. A much smaller number of phase-shifters is re- quired in the sub-connected precoders which admit lower hardware complexity and higher energy efficiency. In view of the drawbacks of the fully-connected hybrid precoder design, we propose a new hybrid precoder architecture which can reduce the overall hardware complexity without exhibiting significant performance loss. Finally, the performances of the proposed designs are verified and compared via computer simulations. keyword - MIMO, mmWave communications, hybrid precoding, sub-connected, 5G.