蘇炫榮臺灣大學：電信工程學研究所闞啟安Kang, Chi-AnnChi-AnnKang2007-11-272018-07-052007-11-272018-07-052004http://ntur.lib.ntu.edu.tw//handle/246246/58528在寬頻分碼多工系統下,不同的基地台之間不需要同步.因此必須要用不同的擾亂碼來區別基地台.基站搜尋所要作的就是要找到能到提供最好的服務品質的基地台.基站搜尋發生在手機剛開機時尋找服務品質最好的基地台,或者是已經維持跟基地台之間的聯繫但是希望能切換到服務品質更好的.此外,低成本的振盪器會造成在手機剛開機的時候有蠻大的一個頻率偏移,這會影響到搜尋基地台的效能.一般而言,搜尋基地台可以分成五個階段,第一階段是訊槽同步,第二階段是訊框同步和找到擾亂碼所在的分組,第三階段是確認擾亂碼,第四階段是掌握到頻率偏移,第五個階段是接收基地台的資訊.在本篇論文中,吾人研究前三個階段,它們遭受到頻率偏移以及都普勒效應.為了避免第一階段的解展頻器受到頻率偏移的影響,吾人考慮將解展頻的展頻碼分成幾個區塊以減少相位翻轉.吾人亦在第一階段使用differential combining 來增加訊雜比,同時可以粗估手機剛開機時遭受到的頻率偏移.第一個階段粗估的頻率偏移可以用到第二和第三階段去抵消掉一部分的相位翻轉,增加偵測效能.此外.為了克服FPC (fast power control) 所造成隨時間改變的干擾,吾人提出了在第一跟第二階段使用weighted combining 的方法.在論文中提到的改進方法都會用電腦模擬在不同的通道底下加以驗證In W-CDMA system, synchronization among base stations is not necessary. Each cell is identified by a unique primary scrambling code. Cell search is the process of the mobile station searching for a best cell and achieving time synchronization to its downlink primary scrambling code. Cell search is performed when 1) the mobile station is just switched on and tries to find a best serving cell (initial cell search) 2) when the mobile station has camped on a cell, and is looking for another that has a better transmission quality to it, in order to switch to (target cell search) or in idle mode. In addition, the low cost oscillator used in the mobile station usually incurs a large frequency offset when the mobile station is switched on. This practical defect further complicates the initial cell search. In general, the cell search process is divided into five stage process:1) slot synchronization 2) frame synchronization and scrambling code group identification 3) scrambling code identification 4) frequency acquisition 5) cell identification . In this thesis, we investigated the first three stages of the initial cell search where large frequency offset and possible Doppler effect are the major obstacles. To avoid the match filtering performance degradation induced by the frequency offset, we considered using a partial correlating match filter which has a length smaller than the coherence time of the channel. Differential combining of the partial correlated segments is then applied to increase the stage 1 signal-to-noise ratio (SNR). The differential technique can also be used to roughly estimate the frequency offset which can be used at stage 2 and stage 3 to correct the phase rotation and improve the detection. In addition, a weighted combining at stage 1, and stage 2 was proposed to overcome the time-varying interference due to fast power control of the traffic and control channels. These proposed enhancements were firstly tested with a single-path Rayleigh fading channel, then applied to the multi-path fading channel models specified in the 3GPP standards. It was shown through simulation that the proposed enhancements improve the initial cell search performance significantly.Contents Chinese Abstract I English Abstract II Acknowledgement IV Contents V List of Figures VII List of Tables IX Acronym Glossary X 1 Introduction 1 2 Synchronization Channels and Cell Search Algorithms in W-CDMA 4 2.1 Introduction to Synchronization Channels in W- CDMA 4 2.2 Primary Synchronization Channel 5 2.3 Secondary Synchronization Channel 8 2.4 Common Pilot Channel 10 2.4.1 Channelization Codes 10 2.4.2 Common Pilot Channel 11 2.5 Cell Search Procedure 11 3 Stage 1 Process 17 3.1 System Model 17 3.2 Slot Synchronization with Noncoherent Combining 19 3.3 Slot Synchronization with Differential Combining23 3.4 Computer Simulations 24 3.5 Slot Synchronization with Weighted Combining under Fast Power Control 28 3.6 Computer Simulations withr Fast Power Control 28 4 Stage2 and Stage3 Process 32 4.1 Frame Synchronization and Scrambling Code Group Identification 32 4.1.1 Noncoherent Detection with 0 Hz Frequency Error 33 4.1.2 Noncoherent Detection with 20 KHz Frequency Error 37 4.1.3 Coherent Detection with 0 Hz Frequency Error 42 4.1.4 Coherent Detection with 20 KHz Frequency Error 42 4.1.5 Computer Simulations 43 4.1.6 Weighted Coherent Combining with Fast Power Control 44 4.1.7 Computer Simulations under with Power Control 45 4.2 Scrambling Code Identification 46 4.2.1 Computer simulations 47 4.3 Average Acquisition Time in Serial Cell Search 48 5 Conclusion 54 Bibliography 56 List of Figures Figure 2.1 Synchronization channels in cell search 5 Figure 2.2 Recursive pruned Golay complementary sequence generator 7 Figure 2.3 Pruned efficient Golay correlator for the generalized hierarchical Golay (GHG) sequence 8 Figure 2.4 Spreading for physical channels 10 Figure 2.5 Code-tree for generation of Orthogonal Variable Spreading Factor (OVSF) codes 11 Figure 2.6 Serial search 13 Figure 2.7 Pipelined search 13 Figure 3.1 System model used for evaluating the performance of the cell search process 17 Figure 3.2 Slot boundary detector 19 Figure 3.3 SNR vs M when the frequency offset is 20 KHz. 21 Figure 3.4 Structure of the hierarchical correlator(64-chip partial correlation) 22 Figure 3.5 Noncoherent combining 22 Figure 3.6 Phase rotation between consecutive 64-chip partial correlations values 23 Figure 3.7 Intra-slot differential combining 24 Figure 3.8 Synchronization probability comparison in 256-chip and 64-chip dispreading (flat fading, 5 km/h synchronization channels) 26 Figure 3.9 Synchronization probability with noncoherent combining 26 Figure 3.10 Synchronization probability with intra-slot differential combining 27 Figure 3.11 Differential vs noncoherent combining 27 Figure 3.12 Intra-cell interference average power variation within one frame interval 30 Figure 3.13 Differential, weighted v.s. conventional combining with flat fading 5 km/h synchronization channels, 30km/h traffic channels 31 Figure 3.14 Synchronization probability with weighted differential combining comparison in 3km/h, 30km/h, and 120km/h traffic channels, flat fading 5 km/h synchronization channels 31 Figure 4.1 The structure of frame synchronization and scrambling code group identification 34 Figure 4.2 Butterfly structure of computing partial correlation 42 Figure 4.3 Frame boundary detection and code group identification performance (flat fading, 5 km/h synchronization channels) 44 Figure 4.4 Stage 2 performance under FPC (30 km/h traffic channels, and 5km/h synchronization channels) 45 Figure 4.5 Synchronization probability with weighted coherent combining comparison in 3km/h, 30km/h, and 120km/h traffic channels, 5km/h synchronization channels 46 Figure 4.6 Miss probability for the scrambling code identification in a flat fading channel with 5 km/h synchronization channels, 48 Figure 4.7 Average acquisition time in a flat fading channel with 5 km/h synchronization channels 49 Figure 4.8 Stage 1 performance in serial cell search (30ms synchronization time) 51 Figure 4.9 Initial frequency offset estimation performance (flat fading, 3km/h synchronization channels) 51 Figure 4.10 Average acquisition time for initial serial cell search in various W-CDMA test channels 52 Figure 4.11 Average acquisition time for initial serial search in Case 2 channel with 20 KHz frequency offset, 30 km/h traffic channels 53 List of Tables Table 2.1 Allocation of SSCs for secondary SCH 14 Table 4.1 Detection threshold 47 Table 4.2 Delay profiles W-CDMA test channels 50 Acronym Glossary 2G The Second Generation 3G The Third Generation 3GPP Third Generation Partnership Project AWGN Additive White Gaussian Noise BS Base Station CDMA Code Division Multiple Access CP Cyclically Permutable CPICH Common Pilot Channel DS-CDMA Direct Sequence-Code Division Multiple Access EGC Efficient Golay Correlator FDD Frequency Division Duplex FHT Fast Hadamard Transform FPC Fast Power Control GHG Generalized Hierarchical Golay GPS Global Position System IEEE Institute of Electrical and Electronics Engineers ML Maximum Likelihood MRC Maximal Ratio Combining MS Mobile Station OVSF Orthogonal Variable Spreading Factor PEGC Pruned Efficient Golay Correlator PFHT Partial Fast Hadamard Transform P-SCH Primary Synchronization Channel PSC Primary Synchronization Codes RS Reed Solomon SCH Synchronization Channel SF Spreading Factor SNR Signal-to-Noise Ratio SSC Secondary Synchronization Code S-SCH Secondary Synchronization Channel W-CDMA Wideband-Code Division Multiple Access1536364 bytesapplication/pdfen-US基站搜尋fast power controlweighted combininingcell searchdifferential combiningthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/58528/1/ntu-93-R91942080-1.pdf