寬頻分碼多工系統中二維犁耙式接收機與多用戶偵測器結合之研究

Abstract

CDMA是一種熱門的多重進接方式，在一般CDMA系統的應用中，多用戶偵測技術能降低來自其他用戶的訊號干擾，在系統容量上可提供顯著的提昇。此外，智慧型天線技術的使用，能抑制來自不同方向的訊號干擾，同樣提供接收機性能上的改善。基於上述優勢，本論文針對以陣列天線接收的二維犁耙式接收機，結合平行多用戶干擾消去偵測技術，以期系統性能會有更好的提昇。接收機的基本架構為一個多層級平行多用戶接收機，每一層級使用以快速傅立葉轉換為基礎之時空（二維）匹配濾波器來實現資料偵測、訊號重建及通道估計等功能。在每一層級中，消除由上一層級所重建之資料訊號，因而可減少用戶與用戶間的干擾，進而提高系統容量。又此接收機架構具有時空匹配濾波器，可將接收訊號以空間及時間的最大比例合併，而得到時空訊號處理增益。最後，將透過電腦進行接收機性能模擬。

Code-division multiple access (CDMA) is a promising wireless technology. For CDMA systems, the multiuser detection techniques can reduce the interference from other users and provide significant enhancement in system capacity. On the other hand, the smart antenna techniques, which can suppress the interference from different angles, is another approach to improve the system performance. In this thesis, we propose an integration of a parallel interference cancellation (PIC) multiuser detector with a 2D RAKE receiver to obtain further improvement. This receiver architecture is based on a space-time matched filter with additional interference cancellation by multi-stage decision. To reduce the computation complexity, the signal processing is done in the space-frequency domain. The receiver can obtain a space-time processing gain through the maximum ration combining (MRC) and increase the system capacity by MAI cancellation. The performance of this receiver are demonstrated by computer simulation.