近幾年來，由於相較於分時多工存取系統(TDMA)有較高容量、能抵抗多重路徑之衰減等許多優點之分碼多工存取系統(CDMA)已成為一重要之通訊機制。然而，分碼多工系統中之主要缺點之一為多重存取干擾(MAI)。這是由於在此系統中，多位使用者同時在相同的頻帶上傳送訊息所造成的，通常可利用多用戶偵測器來克服此干擾。
目前已有許多多用戶偵測器架構發表在文獻中。而本論文提出的是一新的架構—利用干擾投影法於CDMA系統之多用戶偵測器。此架構中，首先估計多重存取干擾量的大小，接著，校正接收到的訊號以改善系統的效能，最後利用電腦模擬來估算此架構的效能評比，並與其他文獻中提及的架構比較，其中包含：傳統接收機、最小均方差接收機、最佳化之最大期望值數列接收機與霍菲爾德(Hopfield)類神經網路接收機。

Code Division Multiple Access (CDMA) has become an important access scheme in recent years because of its several advantages such as higher capacity than TDMA system, anti-multipath fading, etc.. However, one of the significant disadvantages of CDMA system is multiple access interference (MAI). This happens because of the multiple users simultaneously using the same frequency band in the CDMA system. In order to overcome the MAI problem, multiuser detector is commonly used.
Several multiuser detection schemes have been proposed in the literatures. In this thesis, a new structure of multiuser detector using interference projection method for CDMA system is constructed. In this approach, the MAI is estimated first. Then, the received signal is modified to improve the performance of the system. The performance (bit error rate) of the proposed receiver is evaluated by computer simulations and compared with other receivers published in literatures, including conventional receiver, minimum mean square error receiver, optimum maximum-likelihood receiver and Hopfield neural network receiver.

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