蘇炫榮臺灣大學：電信工程學研究所吳宗晉Wu, Tzung-JinTzung-JinWu2007-11-272018-07-052007-11-272018-07-052006http://ntur.lib.ntu.edu.tw//handle/246246/58659第三代行動通訊系統藉由先進的技術，提供更高的資料傳送速率。目前第三代行動通訊系統，都是基於直序展頻的技術。在寬頻分碼多工系統中，基地台彼此間並不需要同步。每一個基地台都藉由一個獨特的擾亂碼來做確認。而手機端找尋基地台，並且與其擾亂碼同步，這個過程稱之為基地台搜尋。基地台搜尋在下列三種狀況下被執行：剛開機的初始搜尋、待機模式搜尋，以及通話中的主動模式搜尋。在寬頻分碼多工系統中，基地台搜尋被分成五個步驟來執行：訊槽同步、訊框及擾亂碼分組搜尋、擾亂碼確認、頻率偏移校正、以及接收基地台資訊。 在實際的情況，手機端是在一個多基地台的環境下，執行基地台搜尋的任務，在此同時，還會接收到來自許多不同基地台經過通道所傳送的同步信號。在這種情況下，信號在時間上會重疊，並且彼此互相干擾，增加基地台搜尋的困難度。在本篇論文中，提出一個多路徑信號搜尋的方法，藉由結合其他的多路徑信號，來改善基地台搜尋的效能，以及所需搜尋的時間。在本論文中，將可看出提出的方法比傳統的做法有更好的效能表現。The third-generation (3G) cellular systems can provide higher data rate services with improved service quality and capacity. Among the 3G cellular systems, IS-2000 and Wideband Code-Division-Multiple-Access (W-CDMA) are based on direct-sequence code-division multiple-access (DS-CDMA) technology. In W-CDMA systems, synchronization among base stations is not necessary. Each cell is identi ed by its unique downlink primary scrambling code. The process of the mobile station searching for a cell and achieving code and time synchronization to its downlink scrambling code is referred to as cell search. Cell search is performed in three scenarios: initial cell search when a mobile station is switched on, idle mode search when inactive, and active mode search during a call. In W-CDMA, the cell search itself is divided into five acquisition stages: slot synchronization, frame synchronization and scrambling code group identi cation, scrambling code identi cation, frequency acquisition, and cell identi cation. In practical scenarios, a mobile station performs initial cell search in a multicell environment and receives many synchronization channels passed through a fading channel from di erent base stations. In this situation, di erent synchronization channels groups of di erent cells overlap in time and interfere with each other. This increases the di culty of performing cell search. In this thesis, a convenient multipath searching algorithm is proposed to nd a signal replica within a search window. Combining one more path improves the initial search performance and the average acquisition time. It is shown that the proposed approach has a performance improvement compared to the conventional methods.1 Introduction 1 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Thesis Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 Synchronization Channels and Cell Search Algorithms 3 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 Synchronization Channels . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2.1 Primary Synchronization Channel . . . . . . . . . . . . . . . . 4 2.2.2 Secondary Synchronization Channel . . . . . . . . . . . . . . . 5 2.2.3 Common Pilot Channel . . . . . . . . . . . . . . . . . . . . . 5 2.3 Cell Search Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.4 Signal and System Models . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4.1 Signal Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4.2 System Parameters . . . . . . . . . . . . . . . . . . . . . . . . 9 2.5 Algorithms for Code and Time Synchronization . . . . . . . . . . . . 10 2.5.1 Stage 1: Slot Synchronization . . . . . . . . . . . . . . . . . . 10 2.5.2 Stage 2: Frame Synchronization and Code Group Identi cation 12 2.5.3 Stage 3: Scrambling Code Identi cation . . . . . . . . . . . . 14 3 Base Station Search at Cell Boundaries 16 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.2 Proposed Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3 Cell Search Procedure in W-CDMA . . . . . . . . . . . . . . . . . . . 19 3.4 Calculations of Detection and False Alarm Probabilities . . . . . . . . 21 3.4.1 Test Statistic . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.4.2 Detection Probability . . . . . . . . . . . . . . . . . . . . . . . 22 3.4.3 False Alarm Probability . . . . . . . . . . . . . . . . . . . . . 25 3.4.4 PDSCG and PDSC . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4.5 Threshold Setting . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.5 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 4 Conclusion 36 Bibliography 37en-US寬頻分碼多工W-CDMAthesis