於通道誤差下空時區塊編碼多用戶多輸入多輸出系統之強健式接收機設計

Abstract

空時區塊編碼（Space-Time Block Code, STBC）在多輸入多輸出（Multiple-Input Multiple-Output, MIMO）的無線通訊系統中是一項被廣泛使用與討論的技術，特別是針對於多用戶的狀況下。目前已有許多空時區塊編碼多用戶多輸入多輸出系統線性接收機演算法被提出，以因應該系統中之多重進接干擾（Multi-Access Inference, MAI）。然而，這些接收機設計有一個共同的問題：它們皆基於完善通道估計的假設下。在實際的傳輸狀況，有限的訓練符元或是嚴重的通道衰退現象時常會導致通道估計錯誤發生。在本論文中，吾人基於通道估計不完善的假設前題，提出一種綜合解碼和消除干擾的強健式接收機設計。此強健式接收機設計是基於限制最佳化（Constrained Optimization）線性等化器，其最佳化問題可藉由廣義旁波帶消除（GSC）技巧被轉換為等效的無限制（Unconstrained）問題而求解。吾人利用擾動 (Perturbation)技巧將通道估計錯誤之效應一併考慮進接收機設計中。吾人同時使用連續干擾消除(successive interference cancellation ,SIC)機制進一步增進接收機效能。由模擬結果可以看出，和其他現存的接收機技術相較，吾人的方法確實能提供較強健之表現。

It is well known that space-time block coding (STBC) has emerged as a popular technique in multiple-input multiple-output (MIMO) wireless communication, especially for multi-user cases. Several linear receiver algorithms have been developed for such a system where multi-access inference (MAI) causes a problem. A common shortcoming of all these techniques, however, is that they are all developed based on the perfect channel assumption. Channel estimation errors do happen in practical situations due to the limited training symbols or severe fading channels. In this thesis, new robust linear receivers for joint space-time decoding and interference rejection in orthogonal space-time block coded multi-user MIMO systems are proposed for combating imperfect channel estimation. The proposed receivers are developed based on the constrained optimization design which can be transformed to an equivalent unconstrained one by the generalized sidelobe canceller (GSC) technique. By using the perturbation techniques, the channel estimation error term can be incorporated into the receiver design. We also apply the successive interference cancellation (SIC) mechanism for further performance enhancement. Numerical simulations confirm the robustness of the proposed receiver when compared with the other existing techniques.