陳光禎臺灣大學：電信工程學研究所吳家豪Wu, Jia-HaoJia-HaoWu2007-11-272018-07-052007-11-272018-07-052005http://ntur.lib.ntu.edu.tw//handle/246246/58955我們使用最大概似技術從基礎上來研究多用戶同步化的問題，特別是著重在多用戶頻率偏差的估測。由於最大概似法量測函數曲面形狀的特殊性，因此在單一使用者的情況下提出了包含離散傅立葉轉換粗估以及近域尋找細估這種兩步驟估測方法，並且我們把這種方法延伸到多用戶同步化的情況下。我們也討論了在頻率偏差存在時的多用戶存取干擾。並且從最大概似法的角度出發，提出了接續干擾消除以及平行干擾消除用來改善遠近效應。最後也考慮了使用相位來估測頻率偏差的方法在有多用戶存取干擾情形下的追蹤能力。We investigate multiuser synchronization problems fundamentally by using maximum likelihood estimation techniques. In particular, we put most efforts on multiuser carrier frequency offset estimation. Due to the special contour shape of ML estimation metric function, a two-stage estimation method including DFT coarse search and neighborhood search is described in single-user case and extended to multiuser case. We discuss multiple-access interference (MAI) in the presence of carrier frequency offset. From the maximum likelihood viewpoints, we suggest the successive interference cancellation and the parallel interference cancellation to improve near-far resistance. We also see the tracking capability of phase based CFO estimation method in multiuser environments.摘要 i 誌謝 iii Abstract v Chapter 1 Introduction 1 Chapter 2 Overview of DS-CDMA systems and Signal models 5 2.1 Overview of DS-CDMA systems……………………………5 2.1.1 Basic structure of transmitter and receiver of DS-CDMA systems…………………………………………………5 2.1.2 Spreading Codes…………………………………………6 2.1.3 Carrier Frequency Offset Synchronization problems in DS-CDMA systems……………………………………………7 2.2 Signal models and assumptions…………………………8 2.2.1 Transmitter and Receiver front end…………………8 2.2.2 Matrix form representation……………………………11 Chapter 3 Maximum Likelihood Multiuser Carrier Frequency Offset Synchronization 13 3.1 Single-user Maximum Likelihood Synchronization……13 3.1.1 Timing known, estimate Phase and Carrier Frequency Offset………………………………………………………………14 3.1.2 Jointly estimate Timing, Phase and Carrier Frequency Offset………………………………………………………………22 3.2 Two-user Maximum Likelihood Carrier Frequency Offset Synchronization……………………………………………………28 3.2.1 Timing known, estimate CFO and Phase………………28 3.2.2 Estimate CFO and Phase when Timing is unknown……34 3.3 Multiuser Maximum Likelihood Synchronization………35 3.3.1 General Structure of Optimum Multiuser Synchronization ………………………………………………………………………36 3.3.2 MAI and Near-Far effect…………………………………39 3.4 Interference Cancellation…………………………………42 3.4.1 Successive Interference Cancellation (SIC)………42 3.4.2 Parallel Interference Cancellation (PIC)…………43 3.5 Recursive Maximum Likelihood synchronization………45 3.5.1 Single parameter Newton-Raphson Recursive form…46 3.5.2 Single-user CFO and Phase estimation………………47 3.5.3 Multiuser CFO and Phase estimation…………………52 3.6 Phase based Carrier Frequency Offset Synchronization ………………………………………………………………………54 Chapter 4 Simulation Results 57 4.1 Search Based ML estimation………………………………57 4.1.1 Single-User two-stage ML joint Timing and CFO estimation ………………………………………………………………………57 4.1.2 Two-user two-stage ML CFO estimation………………59 4.1.3 Single-user ML joint Timing and CFO estimation for two-user case……………………………………………………61 4.2 Interference Cancellation………………………………64 4.2.1 SIC…………………………………………………………64 4.2.2 PIC…………………………………………………………67 4.3 Recursive ML…………………………………………………69 4.3.1 Single-user Newton-Raphson ML CFO estimation……69 4.3.2 Single-user single-sample recursive ML estimation ………………………………………………………………………71 4.4 Phase Based CFO estimation………………………………72 4.4.1 Single-user phase based method with different timing jitter………………………………………………………………72 4.4.2 Phase based method in Multiuser case………………74 Chapter 5 Conclusions 79 Appendix Cramer-Rao Lower Bound 83 Bibliography 891343566 bytesapplication/pdfen-US分碼多工頻率偏移同步化多用戶CDMAcarrier frequency offsetCFOsynchronizationmultiusertimingthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/58955/1/ntu-94-R92942025-1.pdf