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題名 | Estimation of Effective Spatial Signatures for Uplink Antenna Array DS/CDMA System Utilizing Long Code=於上鏈Long code直序分碼多工陣列天線系統中估計等效空間特徵波形 |
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作者姓名(中文) | 武維疆; 鄭易文; | 書刊名 | 高雄師大學報 |
卷期 | 15:3 2003.12[民92.12] |
頁次 | 頁705-716 |
分類號 | 448.6 |
關鍵詞 | 直序分碼多工; 等效空間特徵波形; DS/CDMA; Composite steering vector; |
語文 | 英文(English) |
中文摘要 | 本文探討上鏈Long code直序分碼多工陣列天線系統中等效空間特徵波形之估計。在多重路徑衰減環境下,每一個使用者之等效空間特徵波形由不同路徑之steering vector線性組合而成。在基地臺端仰賴每一位使用者的正確等效空間特徵波形以實現多用戶檢測的技術。理論上,原有的maximum likelihood和subspace fitting兩種演算法可以應用於估計不同使用者的等效空間特徵波形。然而,這兩種演算法在多重路徑下其運算量過於龐大。根據子空間與zero-forcing的概念,我們提出blind的演算法來估計出。利用陣列天線及直序分碼多工信號模型中的空時信號特性,我們可以將多用戶多維的參數估計問題轉變為一組個別使用者信號最佳化問題。本文所提出的演算法可以有效的估算等效空間特徵波形且不需要training sequences。另外從模擬數據的結果可驗證此演算法可以抵抗near-far的效應。 |
英文摘要 | In this paper, we investigate the estimation of composite steering vectors in an uplink antenna array DS/CDMA communication system utilizing long (aperiodic) spreading codes. As multipath fading is considered, each user's spatial signature is characterized by the composite steering vector, which is a linear combination of steering vectors corresponding to each path. The basestation relies on accurate information of all the users' spatial signatures so that multiuser detection techniques can be exploited. Theoretically, the claasical maximum likelihood and subspace fitting algorithms can be applied for the estimation of each user's composite steering vector. However, both methods are computationally prohibitive, especially when the total number of paths is enormous. Based on the subspace and zero-forcing concept, we propose a blind algorithm to estimate each user's effective spatial signature. Making use of the space-time characteristics of an antenna-array DS/CDMA model, we convert the multiuser multidimensional parameters' estimation problem into a set of single user optimization problems. The proposed algorithm is computationally efficient and no training sequences are required. More specifically, simulation results demonstrate that the algorithm is near-far resistant. |
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