在分碼多工存取(CDMA)行動通訊系統中，因為比傳統的分頻多工存取(FDMA)和分時多工存取(TDMA)多了分碼傳輸的技術，在干擾上也增添了多重存取干擾(MAI)，這些干擾會降低系統之效能，因此在解調時需要考量消除干擾的技術。本篇除了運用多載子傳輸搭配正交分頻多工(OFDM)，來降低頻率選擇性衰減通道(frequency-selective fading channel)對系統的影響外，並使用平行干擾消除偵測器（PIC），利用一層層的疊代來減少干擾，進而提高系統的效能。
為了能有效利用平行干擾消除偵測器，還必須知道每個使用者的傳輸振幅，以及通道的增益大小。但是在傳輸訊號的過程當中，受到多重路徑影響的關係，因此接收端在接收訊號時，會收到不同時間延遲、不同通道增益衰減的加成訊號，這會使得估測振幅的工作變的困難。因此本文提出一個能估測出通道和傳輸者振幅之積的方法，並將所估測到的資料，配合原來平行干擾消除偵測器，並利用Direct Combining (DC) 或 Maximum Ratio Combining (MRC) 的技術來還原訊號，以得到一個更合乎實際狀況之接收器。

Code Division Multiple Access (CDMA) mobile communication systems has the code division scheme in comparison with traditional frequency division multiple access (FDMA) and time division multiple access (TDMA). Therefore, the system will have additional interference called multiple access interference (MAI). Because interference will restrain the performance of the system, we should consider the interference cancellation scheme when demodulating. This thesis uses multi-carrier transmission and orthogonal frequency division multiplexing (OFDM) to against the frequency-selective fading channel, and uses the parallel interference cancellation (PIC) scheme to improve the performance of receiver.
By using the PIC scheme efficiently, the transmitting amplitude for every user and channel gain must be known. However, the receiver receives many replicas of the transmitted signals with slightly time difference and channel gain decay because of the multi-path fading during signal transmission. This may cause the difficulty in estimating the amplitude. A method which can estimate the product of amplitude and channel gain is introduced in this thesis. We can use this information together with the PIC scheme, and the technique of direct combining (DC) or maximum ratio combining (MRC) to obtain a more practical communication receiver.

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