晶格縮減演算法及編碼簿設計應用於有限回饋多天線通訊系統之研究

A Research on Lattice Reduction Algorithm and Codebook Design for Limited Feedback MIMO Systems

蔡崇鴻(Chung-Hung Tsai)

指導教授 ： 陳喬恩

國立中正大學/工學院/通訊工程學系/碩士(2013年)

摘要

近年來由於無線區域網路的蓬勃發展，多輸入多輸出(MIMO)系統已經成為無線區域網路發展的主流趨勢，許多相關通訊技術亦不斷地被提出。其中有限回饋(limited feedback)多天線技術及晶格縮減(lattice reduction)技術是本論文探討的重點。
以編碼簿為基礎之有限回饋多天線技術在傳送端與接收端皆儲存相同的編碼簿，接收端利用得到的通道資訊，挑出最合適的碼字之編號回傳至傳送端做為預編碼矩陣。此技術對於分頻多工(FDD)的通訊環境尤其重要。晶格縮減技術則是被用來提高在多輸入多輸出系統下的通訊效能，其中最被廣泛使用的晶格縮減演算法為LLL演算法。在本篇論文中，我們將針對整數預編碼(integer precding)多輸入多輸出系統，開發晶格縮減輔助有限回饋多天線技術，著重於有限回饋多天線技術之新型的編碼簿及晶格縮減技術。
我們所提出之系統使用論文中所提出的編碼簿，將晶格縮減技術中所使用到的行運算矩陣分解，並獲得完全單模矩陣(totally unimodular matrix)。我們將此矩陣設定為編碼簿的碼字(codeword)，並透過傳遞碼字之編號進行預編碼矩陣資訊的傳遞。論文接著提出的改良之LLL 演算法，優先執行可以使正交性質最顯著的運算動作。此演算法搭配所提出的編碼簿應用於整數預編碼多輸入多輸出系統時，可以在低回饋量的情況下，獲得比其他LLL 演算法更正交的矩陣。
最後我們模擬出各種演算法並加以比較，模擬結果顯示我們的演算法在低回饋量時能得到更優越的錯誤率效能。

關鍵字

晶格縮減 ； 有限回饋 ； 多重輸入輸出 ； 單模矩陣

並列摘要

In recent years, Multiple-Input-Multiple-Output (MIMO) communication has become a key technique due to rapid development of wireless services. Among a number of MIMO techniques, precoding with limited feedback has played an important role in acquiring closed-loop gain, and is especially important in a Frequency-Division Duplexing (FDD) system. In codebook-based limited feedback techniques, the receiver uses the channel state information to choose a codeword from a pre-defined codebook, and send back the index of the codeword to the transmitter to construct the precoding matrix. Another important MIMO technique is the lattice-reduction-aided precoding which precodes the signal on a reduced channel matrix and thus improves the error rate performance.
In this thesis, we proposed a new codebook-based lattice reduction aided precoding scheme for the recent proposed integer-precoded system. A new codebook consisting of total unimodular matrices as codewords have been proposed, and a modified LLL algorithm has been presented. We show by simulation that the proposed algorithm can construct the most orthogonal matrix among all the existing variants of LLL algorithms under the same amount of feedback information.

並列關鍵字

Lattice reduction ； Limited feedback ； MIMO ； Unimodular matrix

參考文獻

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