Pre-equalization by Virtual-user Introduction on Downlink MC-CDMA Systems

在多載波分碼多重進接系統的下傳路線上一種引入虛擬用戶的預等化法

李樹鴻(Shu-Hong Lee) ； 洪珨隆(Ho-Lung Hung)

《建國科大學報》 26卷3期 (2007/04) Pp. 85-93

https://doi.org/10.6995/JCTU.200704.0085

摘要

對多載波分碼多重進接(MC-CDMA)系統的下傳路線而言，由於頻率選擇性衰變(frequency selective fading)使得展頻碼的正交性遭到破壞，導致多重進接干擾(MAI)的產生，而該干擾將嚴重地降低系統的效能。已經有很多的研究以行動台接收器為主體，針對多重進接干擾的問題提出改善的方法。本篇論文則提出一種在基地台發射器上引入虛擬用戶的預等化方法，該方法對所有使用中的用戶都能有效降地低多重進接干擾對接收信號品質的影響。在系統的展頻碼以及由所有使用中用戶送來的個別通道訊息已知的情況下，我們提出一具封閉式(closed-form)的預等化器，同時也對該預等化器的最佳化問題加以探討。電腦的模擬結果顯示，所提出的方法，從位元錯誤率(BER)的角度看，比一些用在行動台接收器上的典型方法，如正交性復原結合法(ORC)、等增益結合法(EQC)及最小均方誤差結合法(MMSEC)等有較好的效能表現。

關鍵字

多載波分碼多重進接 ； 預等化 ； 多重進接干擾

並列摘要

The loss of orthogonality of spreading codes due to the frequency selective fading on downlink MC-CDMA systems causes multiple access interference (MAI), which considerably degrades system performance. A great deal of effort has been made on tackling that problem at the receiver of mobile station. This paper proposes a pre-equalization method based on virtual user introduction to mitigate MAT for all active users at the transmitter of base station. A closed-form pre-equalizer is presented based on known transmitted data, spreading codes, and the channel information derived from all active users. In addition, optimization problem on the pre-equalizer is also discussed. Simulation results show that the proposed method offers a better performance in terms of bit error rate (BER) than that of several typical methods (such as ORC, MRC, EQC and MMSEC) adopted at the receiver of mobile stations.

並列關鍵字

MC-CDMA ； Pre-equalization ； MAI