於本論文中，我們提出混合式最小均方法 (MMSE) 多使用者解調器與動態通道分配技術結合特徵碼最佳化 (signature optimization) 並應用於直接序列展頻分碼多工系統來解調使用者傳輸的信號。

借助於在接收者的天線陣列，我們採用一種簡單的動態通道分配技術來提升頻譜使用效率，我們考慮兩種動態通道分配限制條件;距離限制條件和角度限制條件來分發頻帶。對動態通道分配技術而言，每個細胞 (cell) 被分配適合的通道來避免附近細胞所產生的共同通道干擾;最小均方法多使用者解調器則能透過解除分配通道的相關性來提升用戶的正交性。 透過動態通道分配技術和最小均方法多使用者解調器彼此之間補償的特性來提升系統效能並降低計算複雜性。同時，為了減輕在多使用者中用戶之間的干擾，我們採用特徵碼最佳化的方法來保證在用戶的特徵碼序列彼此之間低的相關性。

混合式最小均方法多使用者解調器與動態通道分配技術結合特徵碼最佳化的方法不僅基於動態通道分配限制條件來分配適合的通道給予每個用戶以提升頻譜使用效率，而且透過特徵碼最佳化來獲得最佳特徵碼序列以降低用戶之間的干擾。不過，這種方法將會造成高計算複雜度。因此，我們採用分群特徵碼最佳化，在不使系統效能降低的前提下來減少計算複雜度。

模擬結果顯示了混合式最小均方法多使用者解調器與動態通道分配技術結合特徵碼最佳化確實改進了一般傳統的多使用者解調器的限制，並且較單獨使用最小均方法多使用者解調器結合動態通道分配技術或是建立在特徵碼最佳化最小均方法多使用者解調器均有著較好的效能以及較低的錯誤率。

In this thesis, a hybrid MMSE multiuser detection (MUD) and dynamic channel assignment with signature optimization is proposed to detect the desired signal in DS-CDMA systems. With the help of antenna arrays at the receiver, we adopt a simple dynamic channel assignment (DCA) strategy to enhance the spectrum efficiency. We consider the DCA constraints such as distance constraint and angle constraint to assign frequency bands. Based on the proposed DCA, each cell is assigned flexible channel adaptively to avoid the co-channel interferences (CCIs) from neighborhood cells. On the other hand, the MMSE MUD can improve the orthogonality of users by decorrelating the assigned channels. The combination of the DCA and the MMSE MUD, which are compensatory to each other, can then enhance the BER performance will be improved in DS-CDMA systems. To further mitigate the interferences among users, the signature optimization approach is
employed to guarantee low correlations among users’ signature sequences.

The approach of a hybrid MMSE MUD and DCA with signature optimization not only assigns the flexible channel to each mobile based on the DCA constraints to enhance the spectrum efficiency, but also suppress the interference among users by employing signature optimization. This approach, however, results in high computational complexity. For thus, a grouping strategy is also utilized to reduce the complexity without substantial performance degradation.

Simulation results show that the proposed hybrid MMSE MUD and DCA with group signature optimization can provide better performance than the combination of MMSE MUD and DCA strategy alone and the MMSE MUD with optimum signature sequences.

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