這篇論文提出一個低複雜度的向量投影輔助向量擾動預編碼器（vector perturbation precoder）。在多天線廣播通訊系統中，向量擾動預編碼器是一個著名的預編碼方法，向量擾動技術可以抑制雜訊放大，改善通訊容量（capacity）。最佳的擾動向量是由球面編碼 (sphere encoding) 而得，其複雜度和傳送天線數量成指數關係，為了降低複雜度，運用晶格縮減 (lattice reduction) 方法可以找出次佳的擾動向量。這篇論文中，我們提議利用低複雜度的向量投影技術計算擾動向量，為了得到更好的擾動向量，我們提出兩段式向量擾動預編碼器，結合向量投影技術和現有尋找擾動向量的方法，用些微增加的複雜度換取更好的傳送品質。此外，我們將向量擾動的想法應用在天線的使用與安排上，藉由閒置天線傳送向量投影所得的擾動訊號以抑制雜訊放大，模擬結果顯示此方法成效顯著。最後，我們將向量擾動技術與晶格縮減輔助預編碼方法 (lattice-reduction-aided vector precoding) 作結合，我們發現當預編碼矩陣已晶格縮減化時，就無法再運用晶格縮減方法尋找擾動向量，因此向量投影技術可以取代晶格縮減作為低複雜度尋找次佳擾動向量的方法。

Low complexity vector-projection-aided vector perturbation precoding is proposed. Vector perturbation is a well-known precoding approach for near-capacity multiantenna multiuser communication. The optimal perturbation vectors are obtained using the sphere encoder. A suboptimal lattice reduction algorithm (Babai's approximation) is applied to reduce the complexity. In this thesis, we propose to use vector projection technique to find the perturbation vector. Furthermore, to obtain a much better perturbation vector, we propose two-stage vector perturbation scheme which perturbs the data twice with a little more complexity. Moreover, we try to perturb the signal vector instead of perturbing the data vector in use of idle antennas via vector projection. Simulation results show that two-stage vector perturbation is slightly better. Besides, vector-projection-aided vector perturbation can apply to a reduced precoding scheme (lattice reduction aided vector precoding) which is not suitable for the use of Babai' approximation. Simulation results show that our proposed method is a great substitute for sphere encoding.

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