由於多媒體的應用快速成長，目前的無線通訊的發展．除了以往聲音的傳送外，還有影像或資料等傳輸，因此有不同傳輸速率效能的需求。基於多載波分碼多工較適合在高速傳輸的特性，因此本篇論文主要考慮多速率多載波分碼多工存取(Multi-Rate MC-CDMA)模型，來配合目前多媒體無線通訊系統的需求。分碼多工存取系統一直存在多使用者干擾的情形，因此，本論文的重心是發展有效的接收機來提升多使用者的偵測效能。

基於軟式決策器比硬式決策器可更進一步提升偵測效能，在本論文中我們提出一個交替式的解調方法，使用最小均方誤差法則且結合軟式決策去將這兩種速率的資料群交替來做解調。與傳統的最小均方法則做比較，模擬結果顯示出我們提出的方法較既有的偵測器能有更好的效能，尤其在對抗非常多使用者干擾的情況。

With the rapid growth of wireless multimedia transmission, which in general call for different transmission rates, the multirate multi-carrier code division multiple access (MC-CDMA) systems have been a great promise for next generation wireless communication systems. However, multirate MC-CDMA systems suffer both the multiple access interference (MAI) and the interferences data of different rates. To alleviate the disturbance, various attempts have been to design the multiuser detectors (MUDs) to enhance the performance.

To accommodate the growing demand of multimedia data, this thesis proposes a novel minimum mean squared error (MMSE) MUD for multirate MC-CDMA systems. The data with different transmission data rates has their respective receivers, which are recursively determined with alternating soft interference cancellation to refine the received data in the receiver updating process. Conducted simulations show that the new MUD outperforms previous works in various scenarios, especially in highly loaded systems.

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