非同步分碼多工系統之多用戶偵測演算法研究與軟體實現

Research and Software Implement on Multiuser Detection in Asynchronous DS-CDMA System

王旭慶(Shih-Ching Wang)

指導教授 ： 陳逸民

元智大學/工程學院/電機工程學系/碩士(2002年)

摘要

CDMA系統最大的優點就是能夠提升系統容量 , 但隨著使用戶的增加 , 使用戶之間的干擾也越來越強 , 此種干擾稱為多重接取干擾(Multiple Access Interference) ,其主要影響是限制系統的容量與性能。而多用戶偵測演算法(Multiuser Detection)就是改善這種現象的方法之一。其原理為考慮其他使用戶的資訊來提升個別用戶的偵測。
本文所使用的演算法為平行式干擾消除演算法(Parallel Interference Cancellation , PIC) , 我們將PIC中之交互關連性(Cross Correlation)運算獨立出來 , 減少一般PIC重複計算的部分 , 降低系統運算量 , 將決策值(Decision Statistic)模組化 , 方便實現演算法 , 並推導簡化一階模組化通式 , 再將通式推導至簡化二階模組化。其次討論估測部分因子(Partial Factor)方法 , 並選用一組參數進行圖片傳輸驗證 , 最後我們以TI TMS320VC5402數位訊號處理器實現DS-CDMA PIC系統。

關鍵字

分碼多工 ； 多用戶偵測 ； 平行式干擾消除演算法 ； 數位訊號處理 ； 即時系統 ； 非同步系統

並列摘要

The greatest advantage of the DS-CDMA system is the improvement of the system capacity. As the number of the users increase , the interference between the users become larger and larger . The interference so called “Multiple Access Interference , MAI” , and the main influence is the capacity and performance limitation of the system . Multiuser detection(MUD) is one of the methods to improve this kind of phenomenon . The theory of MUD is to enhance the detection of the individual user by considering about the information of the other users.
The MUD algorithm of this thesis is parallel interference cancel- lation(PIC). First , we let the calculation portion of the cross-correlation lonely and thus reduce the repeat calculation portion in PIC . Besides , we module the decision statistic and decrease the operation of the system . In this way , we can implement the algorithm more convenient. Second, we discuss the method of partial factor estimatation , and then choose a set of parameter to implement the transmission experiment of the photograph . At last , we implement the DS-CDMA MUD(PIC) on DSP by using the TI TMS320 VC5402 processor .

並列關鍵字

CDMA ； MUD ； PIC ； DSP ； RTOS ； Asynchronous system

參考文獻

[1]. Jhong Sam Lee,Leonard E.Miller” CDMA Systems Engineerring Handbook, ” Artech House , Inc. 1998

[2]R.Michael Buehrer , Neiyer S. Correal-Mendoza , and Brian D. Woerner , ” A DSP-Based DS-CDMA Multiuser Receiver Employing Partial Parallel Interference Cancellation ” , IEEE Journal On Selected Areas In Communications, VOL. 17,NO.4, APRIL 1999

[3].Tero Ojanpera , Ramjee Prasad, ” Wideband CDMA for Third Generation Mobile Communications ,” Artech House , Inc. 1998

[5]R.Michael Buehrer , Neiyer S. Correal-Mendoza , and Brian D. Woerner , ” A Comparison of Multiuser Receiver for Cellular CDMA” , in Proc. IEEE GLOBECOM , Nov. 1996

[6]. Dariush Divsalar, Marvin K. Simon and Dan Raphaeli, ”Improved Parallel Interference Cancellation for CDMA, ” IEEE Transactions on Communications,Vol. 46 , pp.258-268 , No. 2 , February. 1998.