寬頻分碼多重進接通訊系統中多級平行干擾消除接收器的研究

Abstract

寬頻分碼多重進接(W-CDMA)通訊系統已被廣泛地研究, 同時也已成為第三代行動通訊UMTS/IMT2000的主要標準。本論文首先討論各種符合第三代標準W-CDMA的多級平行干擾消除(PIC)接收器在。多級部分平行干擾消除(PPIC)接收器具有比其它架構的多級平行干擾消除接收器擁有穩健的性能。我們以電腦模擬來達成性能的比較。同時我們也研究在多重路徑衰減通道中用於多級平行干擾消除接收器的導引通道輔助的通道估測技術，並且提出一個多級的通道估測架構以增進通道估測的準確性，這個架構是利用多級平行干擾消除架構去增進通道的估測。我們也同時展示由導引通道輔助信號所導致的多重進接干擾的損害。我們也提出一改進的多級部分平行干擾消除(MPPIC)接收器以降低這個效應。這種接收器是在信號做多級平行干擾消除程序之前先消除導引通道輔助信號。從模擬的結果我們可以得到改進的多級部分平行干擾消除接收器配上多級的通道估測架構將能增進系統性能與增加連結容量。

The wideband direct-sequence code division multiple access (W-CDMA) transmission technique has been widely investigated and also has become to standard of UMTS/IMT2000 for the third generation (3G) mobile communication systems. In this thesis, various parallel interference cancellation (PIC) receivers with 3G standard are studied. The multistage partial PIC (PPIC) receiver is demonstrated to provide more robust performance than other PIC schemes. The performance comparisons are achieved by computer simulations. We also study the pilot-channel-aided channel estimation for the PPIC receiver in multipath fading environment. A multistage channel estimation scheme, which makes use of a multistage PPIC scheme, is proposed to improve the accuracy of the channel estimation. We also show the impairment of the multiple access interference (MAI) due to pilot channel signals. A modified PPIC (MPPIC) receiver, which performs pre-cancellation of the pilot channel signals before parallel interference cancellation processes, is proposed to reduce this effect. From the simulation results, we can show that MPPIC receiver with multistage channel estimation will improve performance and increase link capacity of the wideband CDMA system. English Abstract ………………………………………………………ii Acknowledgement ………………………………………………………iii Contents …………………………………………………………………iv List of Figures …………………………………………………………vi List of Tables …………………………………………………………ix CHAPTER 1 Introduction 1 CHAPTER 2 Wideband CDMA Systems 3 2.1 Introduction 3 2.2 Code Generation and Allocation 5 2.3 Uplink Transmission 10 2.4 Downlink Transmission 11 2.5 Channel Model 12 2.6 Multiuser Detection 14 2.6.1 Maximum-Likelihood Detector 14 2.6.2 Decorrelating Detector 15 2.6.3 Minimum Mean-Square Error (MMSE) Detector 15 2.6.4 Subtractive Interference Cancellation Detector 15 CHAPTER 3 Parallel Interference Cancellation 17 3.1 System Model 17 3.2 Derivation of the Parallel Interference Cancellation Detector 20 3.3 Conventional Multistage Parallel Interference Cancellation 22 3.4 Partial Parallel Interference Cancellation 23 3.5 Adaptive Parallel Interference Cancellation 25 3.6 A low Complexity Parallel Interference Cancellation by Using Tentative Decision Device 26 3.7 Performance Comparison of Parallel Interference Cancellation Detectors 27 CHAPTER 4 Channel Estimation for Parallel Interference Cancellation Detector 34 4.1 Pilot channel assisted channel estimation 35 4.2 Channel estimation for PPIC detector 36 4.3 Multistage Channel Estimation 37 4.4 Simulation 38 CHAPTER 5 Modified Parallel Interference Cancellation Detector 46 5.1 Modified Parallel Interference Cancellation 47 5.2 Simulation 49 CHAPTER 6 Conclusion 58 Bibliography………………………………………………………………60