基於子系統奇異值分解之有限回饋部分連接毫米波混和式波束成形設計

Limited Feedback Hybrid Beamforming for Partially Connected Millimeter Wave Systems under Sub-System SVD

陳柏儒(Po-Ju Chen)

指導教授 ： 趙啟超

國立清華大學/電機資訊學院/通訊工程研究所/碩士(2019年)

摘要

毫米波(mmWave)頻段是未來5G無線通訊系統中非常重要的一個技術，但因為毫米波的多天線設計功率消耗較大，混合式波束成形(hybrid beamforming)設計便是一個很好的解法，本篇論文即是在探討在毫米波頻帶下正交分頻多工(Orthogonal Frequency Division Multiplexing)系統的混合式波束成形設計，其中在類比端可以分為完全式連接(fully connected)以及部分式連接(partially connected)兩種架構，雖然部分式連接的頻寬效益較差，但是他的功耗以及硬體複雜度較低，較適用於實際狀況。
此外，傳送端在做波束成形時，需要接收端回饋通道資訊，但因為回饋通道的傳輸速率有限，因此需要設計一個接收端及傳送端皆知道的編碼簿(codebook)，編碼簿內有多個可能的預編碼器(precoder)，並設計演算法從中挑選出最佳的預編碼器。
本篇論文考慮部分連接式且具有編碼簿的有限回饋(limited feedback)波束成形設計，首先，是採用基於子系統奇異值分解(sub-system SVD)的演算法得到理想的波束成形矩陣，並且建出編碼簿，再來，我們提出一個適用於部分連接結構的低複雜度演算法讓我們從編碼簿去選擇想要的預編碼器。最後，我們在IEEE 802.15.3c所提出的毫米波通道模型模擬結果，發現我們所提出的演算法跟過去的演算法比起來複雜度較低且有較佳的表現，此外，在功耗上部分連接式架構也比完全式連接更為有效。

關鍵字

混和式波束成形 ； 毫米波 ； 部分連接式 ； 有限回饋

並列摘要

The millimeter wave (mmWave) frequency band has been regarded as playing a pivotal role for future wireless communication systems. Hybrid beamforming architecture is widely considered owing to the low power consumption. For analog beamformers, most prior works have focused on the fully connected structure in which each antenna is connected to all radio-frequency (RF) chains. The partially connected structure is, however, more practical due to high energy efficiency and low hardware complexity. Precoders at the transmitter need information from the receiver to perform beamforming. Since the data rate of the feedback link is limited, the codebook-based design is required for practical applications.
In this thesis, we investigate the codebook-based hybrid beamforming design in new partially connected structures for multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems over mmWave channels. The sub-system singular value decomposition (SVD) algorithm is applied to obtain the beamformer matrices. We then propose the codebook design for analog and digital precoders in the considered partially connected structure. We also develop a low-complexity codeword selection algorithm to choose the desired codeword from the known codebook and reduce the search time. Simulation results show that our algorithm can achieve better performance than previous designs with the conventional partially connected architecture and has lower computational complexity.

並列關鍵字

Hybrid ； Beamforming ； mmWave ； Partially-connected ； Limited ； Feedback

參考文獻

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