第三代合作夥伴計畫長期演進技術(3GPP Long Term Evolution, 3GPP LTE)的基地台搜尋(Cell Search)包含達成訊框(Frame)的時間同步與頻率同步，以及取得基地台識別碼。3GPP LTE系統共使用五百零四個基地台識別碼(Cell Identity, Cell ID)，共分成一百六十八個各自獨立的基地台群組識別(Cell-Identity Group, Cell-ID Group)，而每個碼群中含有三個扇形區域識別碼(Sector Identity, Sector ID)。3GPP LTE標準[1]-[2]提出的基地台搜尋的方法，在行動端在達成訊框的時間同步及頻率同步之後，取得基地台識別碼的步驟頇先在時域上運用三組匹配濾波器(Matched Filter)找出扇形區域識別碼之一，之後在頻域上接收訊號與一百六十八組虛擬隨機雜訊碼(Pseudo Random Noise Sequence, PN Sequence)逐一作同調相關性偵測(Coherent Correlation Detection)，找出Cell-ID Group的索引(Index) [1]-[5]。
LTE標準[1]-[2]所規範之基地台搜尋方法在硬體上的實現需要大量的複數加法器及複數乘法器，且必頇逐一比對所有序列，造成冗長的處理時間(Processing Time)，進而影響到開機延遲、待機時間、能源節省以及製造價格等問題。
為了降低計算複雜度，本論文提出具有特殊結構之完美序列[6]做為前導訊號(Preamble)，此序列是由兩組基底序列(Base Sequence)之線性組合所組成。我們將其放置在主要同步通道(Primary Synchronization Channel, P-SCH)及次要同步通道(Secondary Synchronization Channel, S-SCH)中，以其組成時的四個相位旋轉因子(Phase Rotation Factor)之組合當作Cell ID的索引，取代傳統以序列的索引來代表的Cell ID方式。基於此序列，經由模擬得知多路徑的通道模型下，假設達成時間與頻率完美同步後，並且有通道補償的情況下，本論文提出的基地台搜尋方法之Cell ID偵測成功率在SNR是-8dB為100%，而LTE標準提出之的方法在SNR是-8dB偵測成功率約為98.7%。並且，所提出的方法可不需經過通道補償而達到近似的效能表現，降低實現的複雜度。
關鍵字：基地台搜尋，3GPP長期演進，正交分頻多工，16n完美序列。

Cell search of Third Generation Partnership Project Long Term Evolution (3GPP LTE) includes time synchronization and frequency synchronization of frames, and the acquisition of Cell Identity (Cell ID). The LTE systems use 504 Cell IDs divided into 168 unique Cell-Identity Groups (Cell-ID Groups), and each Cell-ID Group comprises three Sector Identities (Sector IDs). After reaching synchronization of time and frequency between frames, the Cell ID acquisition scheme provided by specification of 3GPP LTE is consisted of two steps, the first step must utilize three matched filters to detect one out of three Sector IDs, and then implement coherent correlation detection between 168 Pseudo Random Noise Sequences (PN sequences) to obtain the index of Cell-ID Group.
So the cell search scheme provided by LTE standard has to detect correlation of all sequences, and computed complexity brings considerable processing time to effect the delay time of services power on, standby time, energy saved, and cost of manufacture. To reduce complexity, we propose a perfect sequence with special structure as preamble, and the sequence is linear combination of two base sequences. We put the sequences within Primary Synchronization Channel (P-SCH) and Secondary Synchronization Channel (S-SCH), and we utilize the phase rotation factors of the sequences as index to generate Cell ID, instead of the current scheme to generate Cell ID with the indexes between sequences and sequences. Based on the sequences in multipath channel model, simulation results verify the detection probability of Cell IDs by proposed scheme is 100% when SNR is -8dB, and it is 98.7% by the scheme in LTE specification after perfect time and frequency compensation. Except that, Cell ID detection performance is similar without channel compensation to reduce implement complexity.
Index Terms- cell search, 3GPP LTE, 16n perfect sequence.

第一章 導論...............................................................................................................1
1.0 引言...............................................................................................................1
1.1 研究動機.......................................................................................................2
1.2 論文架構.......................................................................................................2
第二章 正交分頻多工存取技術與LTE標準介紹...................................................4
2.0 引言..............................................................................................................4
2.1 正交分頻多工系統的架構...........................................................................4
2.1.1 正交分頻多工存取技術...................................................................8
2.1.2 循環字首的應用.................................................................................8
2.1.3 反離散傅立葉轉換的應用................................................................10
2.2 3GPP LTE標準中的訊框結構....................................................................12
2.3 3GPP LTE標準中的同步通道....................................................................14
2.4 3GPP LTE標準中的同步訊號....................................................................14
第三章 3GPP LTE系統之基地台搜尋的方法........................................................17
3.0 引言.............................................................................................................17
3.1 常見達成時間同步與頻率同步的方法......................................................17
3.2 3GPP標準中基地台搜尋的方法................................................................21
3.3 Kim與Han提出的LTE基地台搜尋的方法.............................................23
第四章 兩個運用完美序列設計的低複雜度同步訊號..........................................25
4.0 引言.............................................................................................................25
4.1 採用的完美序列的架構..............................................................................25
4.1.1第一類基礎序列................................................................................26
4.1.2第二類基礎序列................................................................................26
4.1.3 16n的完美序列...................................................................................27
4.1.4 運用16n完美序列產生Cell-ID Group的原理.................................28
4.2 提出低複雜度LTE基地台搜尋的方法......................................................30
4.2.1 本論文提出獲得Cell-ID Group的演算法…....................................30
4.2.1.1 主要同步訊號的產生...........................................................30
4.2.1.2次要同步訊號的產生..........................................................31
4.2.1.3 時間同步與頻率同步...........................................................32
4.2.1.4 有通道補償下Cell-ID Group的獲得...................................34
4.2.1.5 無通道補償時Cell-ID Group的獲得...................................39
4.2.1.6獲得完整訊框框架之演算法.................................................41
4.3 提出方法之複雜度分析..............................................................................41
4.3.1 LTE標準Cell ID偵測方法的複雜度分析........................................41
4.3.2 直導式Cell ID偵測方法的複雜度分析...........................................43
第五章 提出方法在各種環境下的效能模擬分析....................................................47
5.0 引言...............................................................................................................48
5.1 模擬Cell ID偵測成功率之效能圖..............................................................48
第六章 結論................................................................................................................51
中英對照表..................................................................................................................52
英文縮寫對照表..........................................................................................................57
參考文獻......................................................................................................................60

[1] Physical channels and modulation (Release 8), 3GPP TSG PAN TS 36.211 V8.3.0., May 2008. Available: http://www.3gpp.org/
[2] LTE physical payer - general description (Release 8), Nov. 2007. 3GPP TSG PAN TS TS 36.201 V8.1.0. Available: http://www.3gpp.org/
[3] Y. M. Tsai, G. D. Zhang, D. N. Grieco, F. Ozluturk, and X. D. Wang, “Cell search in 3GPP long term evolution systems,” IEEE Vehic. Techno. Mag., vol. 2, no. 2, pp. 23-29, Jun. 2007.
[4] I. Kim, Y. Han, Y. H. Kim, and S. C. Bang, “Sequence hopping cell search scheme for OFDM cellular systems,” IEEE Trans. on Wireless Commun., vol. 7, no. 5, pp. 1483-1489, May 2007.
[5] Y. M. Tsai and G. D. Zhang, “Time and frequency synchronization for 3GPP long term evolution systems,” in Proc. IEEE VTC, Dublin, Ireland, Apr. 2007, pp. 1727-1731.
[6] C. P. Li, S. H. Wang, and K. C. Lee, “Integer-valued perfect sequences of length 16n,” submitted to IEEE Trans. Inform. Theory, Jan. 2008.
[7] K. S. Kim, S. W. Kim, Y. S. Cho, and J. Y. Ahn, “Synchronization and cell-search technique using preamble for OFDM cellular systems,” IEEE Trans. Vehic. Techno., vol. 56, no. 6, pp. 3469-3485, Nov. 2007.
[8] F. Berggren and B. M. Popovi´, “A non-hierarchical cell search scheme,” in Proc. IEEE WCNC, Hong Kong, China, Mar. 2007, pp. 2302-2306.
[9] LG Electronics, “Comparison of sequence and structure for P-SCH,” 3GPP Tech. Doc., Tdoc R1-072448, Kobe, Japan, May 2007.
[10] Motorola, “Cell search and initial acquisition for OFDM downlink,” 3GPP Tech. Doc., Tdoc R1-051329, Seoul, Korea, Nov. 2005.
[11] Ericsson, Fujitsu, Mitsubishi Electric Corporation, NEC, NTT DoCoMo, Panasonic, SHARP, Siemens, Toshiba Corporation, “Text proposal on cell search in E-UTRA,” 3GPP Tech. Doc., Tdoc R1-051308, Seoul, Korea, Nov. 2005.
[12] ZTE, “Comparing of two downlink synchronization channel schemes for E-UTRA,” 3GPP Tech. Doc., Tdoc R1-051357, Seoul, Korea, Nov. 2005.
[13] Nokia, “Cell search procedure for initial synchronization and neighbor cell identification,” 3GPP Tech. Doc., Tdoc R1-051549, Seoul, Korea, Nov. 2005.
[14] Sharp, “Comparison of P-SCH and S-SCH sequence design options,” 3GPP Tech. Doc., Tdoc R1-072049, Kobe, Japan, May 2007.
[15] ETRI, “Performance evaluation of two types of concatenated S-SCH,” 3GPP Tech. Doc., Tdoc R1-072124, Kobe, Japan, May 2007.
[16] Texas Instruments, “P-SCH design and performance,” 3GPP Tech. Doc., Tdoc R1-072190, Kobe, Japan, Mar. 2007.
[17] NTT DoCoMo, Mitsubishi Electric, Sharp, Toshiba Corporation, “S-SCH structure for E-UTRA downlink,” 3GPP Tech. Doc., Tdoc R1-072190, Kobe, Japan, Mar. 2007.
[18] Motorola, “ZC sequence based P-SCH design using no-repetitive structure,” 3GPP Tech. Doc., Tdoc R1-072130, Kobe, Japan, May 2007.
[19] Motorola, “Effect of RS hopping on or off on the number of cell group IDs and SCH performance,” 3GPP Tech. Doc., Tdoc R1-072154, Kobe, Japan, May 2007.
[20] Texas Instruments, “Views on remaining issues on SCH design,” 3GPP Tech. Doc., Tdoc R1-072189, Mar. 2007.
[21] Huawei, “P-SCH sequences,” 3GPP Tech. Doc., Tdoc R1-072321, Kobe, Japan, May 2007.
[22] B. M. Popovic, “Generalized chirp-like poly-phase sequences with optimal correlation properties,” IEEE Trans. Inform. Theory, vol. 38, pp. 1406-1409, Jul. 1992.
[23] F. Z. Khaled and K. S. Stefan, Multi-carrier and spread spectrum systems: from OFDM and MC-CDMA to LTE and WiMAX, 2nd ed. U. K. Wiley, 2008.
[24] G. Faria, J. A. Henriksson, E. Stare, and P. Talmola, “DVB-H: digital broadcast services to handheld devices,” in Proc. IEEE, vol. 94, no. 1, pp. 194-209, Jan. 2006.
[25] Digital video broadcasting (DVB): Framing structure, channel coding and modulation for digital terrestrial television, ETSI, EN 300 744, 1.3.1 ed., 2000.
[26] P. Cheng, Z. Zhang, J. Li, and P. Qiu, “A study on cell search algorithms for IEEE 802.16e OFDMA systems,” in Proc. IEEE WCNC, Hong Kong, Mar. 2007, pp. 1850-1855.
[27] J. J. Sánchez, D. Morales-Jiménez, G. Gómez, and J. T. Enbrambasaguas, “Physical layer performance of long term evolution cellular technology,” in Proc. IEEE ISTMWC, Budapest, Hungary, Jul. 2007, pp. 1-5.
[28] B. Park, H. Cheon, C. Kang, and D. Hong, “A novel timing estimation method for OFDM systems,” IEEE Commun. Lett., vol. 7, no. 5, pp. 239-241, May 2003.
[29] T. M. Schmidl and D. C. Cox, “Robust frequency and timing synchronization for OFDM,” IEEE Trans. Commun., vol. 45, no. 12, pp. 1613-1621, Dec. 1997.
[30] K. S. Kim, K. H. Chang, S. W. Kim, and Y. S. Cho, “A preamble-based cell search technique for OFDM cellular systems,” in Proc. IEEE VTC, Orlando, FL, Oct. 2003, pp. 2471-2475.
[31] O. Edfors, M. Sandell, J. J. van de Beek, and S. K. Wilson, “OFDM channel estimation by singular value decomposition,” IEEE Trans. on Commun., vol. 46, no. 7, pp. 931-939, Jul. 1998.
[32] Base Station (BS) radio transmission and reception (Release 8), 3GPP TSG PAN TS 36.211 V8.5.0., Mar. 2009. Available: http://www.3gpp.org/