摘要
直接序列碼域多重存取系統 (DS-CDMA) 通信系統在使用者使用正交的展頻序列碼下，能夠提供比其他目前所已存在的無線通信系統更高的系統容量。但實際上這種優勢並不是總是存在的，這些展頻序列碼彼此間也許不是正交因而造成多重擷取干擾(MAI)的存在。即使是使用正交的展頻序列碼，由傳輸過程通過頻率選擇性衰落的通道也將破壞正交的性質。在這個情況下，MAI和符號間干擾( ISI )將會被產生。這些干擾對於DS-CDMA通信系統造成很嚴重的影響。 由於這個原因我們提出一種盲蔽式的部分多級平行干擾消除(B-PPIC)的方法。這種方法結合盲蔽式的估測與部分多級平行干擾消除(PPIC)的技術，透過Blind的方法為每一個使用者估計通道的參數和衰減的能量，然後用這些訊息來重建這些估測的干涉信號使之能有效的改善多級平行干擾消除系統的效率。最後，我們從收到的信號中減去那些重建的干擾信號，如此便能使接收到的資料更加的精確。

本論文旨在提出一種有效的干擾消除方法使其在最有效率的情況下達到通道參數的估測，並利用此一資訊幫助提昇碼域多重擷取系統的效能。

第一章是簡介。

第二章首先建立基頻的碼域多重擷取系統，其包含有傳輸端、傳輸通道、接收端三大部分。

第三章探討免訓練(追蹤)(Blind)的估測方法，其中有通道參數的估測與衰減能量的估測兩部分。

第四章討論傳統方法的優缺點與我們所提出方法的結構與特性

第五章是以程式模擬的方法，模擬在不同的環境與條件下，傳統方法與新方法能的比較。

第五章是綜合上述幾章的討論與分析做一個總和。

The Direct Sequence Code Division Multiple Access (DS-CDMA) communication systems can offer higher system capacity than other present radio communication systems in existence, if the orthogonal spreading sequences are used for every user within the same cell. In practice, this situation does not always hold. The spreading sequences may not be orthogonal and then multiple access interference (MAI) exists. Even the orthogonal spreading sequences are used, the property of orthogonal will also be destroyed by transmission through frequency selective fading channel. In this situation, the interference of MAI and intersymbol interference (ISI) will be produced. These interferences cause a severe performance degrade for DS-CDMA communication systems. For this reason, we propose a blind partial parallel interference cancellation (B-PPIC) which combines with blind estimation method and PIC\ technique. The proposed B-PPIC aims to improve the systems performance by estimating channel parameters and fading power for each user in blind sense, and then using these information to regenerate estimates of the interfering signals to achieve efficient interference cancellation. Finally, we subtract those reconstructed interference signals from the received signal and recover the transmitted data bits with more accuracy.

1.S. Verdu, ``Minimum probability of error for asynchronous Gaussian multiple-access channels,'' IEEE Trans Inform. Theory, vol . IT-32 pp. 85-96, 1986.
2.A. Klein, G Kaleh, and P. Baier, ''Zero forcing and minimum mean-square-error equalization in cyclostationary interference analysis and subscriber linecalculations,'' IEEE J.Select. Areas Commun., Vor. 9, pp. 931-940. Aug. 1991
3.R. Lupas and S. Verdu, ''linear multiuser detectors for synchronous code-division-multiple-access channels,'' IEEE J. Select. Areas Commun., Vol. 8, pp. 683-690, May 1990.
4.D.B. Williams ``Counting the degrees of freedom when using AIC and MDL to detect signals '' IEEE Transactions, vol. 42,pp3282-3284, Nov. 1994.
5.B. Yang ``Projection Approximation Subspace Tracking'' \IEEE Trans. Signal Processing. vol .43,no. 1, January 1995.
6.X. Wang and H. V. Poor ``Blind Multiuser Detecion: A Subspace Approach'' IEEE Trans. Information Theory. vol. 44, no. 2, March 1998.
7.H. Liu and G. Xu ``A subspace Method for Signature Waveform Estimaiton in Synchronous CDMA systems,'' IEEE Trans. Commun., vol. 44, pp.1346-1354, Oct. 1996.
9.J. Weng, G. Xue, T. Le-Nfoc, and S. Tahar, ``Multistage interference cancellation with diversity reception for asynchronous QPSK DS/CDMA ysstems over multipath fading channes,'' IEEE J. Select. Areas Commun., vol. 17, no.12, pp. 2162-2180, Dec.1999.
10.G. Xue, J. Weng, T. Le-Ngoc, and S. Tahar, ``Adaptive multistage parallel interference cancellation for CDMA,'' IEEE J. Select. Areas Commun., vol. 17, no. 10, pp. 1815-1827, Oct.1999.
11.R. M. Buehrer and s. P. Nicoloso, ``Comments on partial parallel interference cancellation for CDMA,'' IEEE Trans. Commun., vol.47, no. 5, pp. 658-661,May 1999.
12.P. Patel and j. Holtzman, ``Analysis of a simple successive interference cancellation scheme in a DS/CDMA system,'' IEEE J. Select. Areas Commun., vol. 12, no. 5, pp. 796-807, June 1994.