窄頻物聯網是由第三代合作夥伴計劃所制定，並用於大規模連接的新蜂窩技術，在增強式覆蓋區域中支持大量使用者裝置的技術。窄頻物聯網與現有的第四代行動網路具有共通性，下行通道傳輸採用正交頻域多工技術，而子載波間隔與長期演進系統相同。而在下行鏈路中，同樣擁有著兩個同步訊號，在窄頻物聯網中分別是窄頻主同步訊號與窄頻輔同步訊號。其中窄頻主同步訊號功用為訊號間同步的過程，窄頻輔同步訊號功用為細胞搜索。而為了與裝置快速達成同步狀態，窄頻主同步訊號利用了扎德奧夫-朱序列與代碼覆蓋。而會挑選扎德奧夫-朱序列是因為其良好的自相關性，代碼覆蓋中的碼則是在經過差分運算後同樣具備良好的自相關特性。因此，在此論文中，我們透過了分析同步序列之特性，提出了全新的同步序列。此外，我們利用格雷互補序列對的自相關函數值互補特性，設計了全新同步訊號架構。我們比較了不同序列做為代碼覆蓋的同步效能評比。模擬結果顯示此論文所提出的同步訊號架構能縮短同步完成時間。

Narrowband Internet of Things (NB-IoT) is a new cellular technology which is used for large coverage [1] and supports a large number of user devices [2]. The NB-IoT downlink channel transmission employs orthogonal frequency division multiplexing technology (OFDM), and the subcarrier spacing is the same as that of the long term evolution system (LTE). In the downlink channel, there are also two synchronization signals. In the NBIoT, they are narrowband primary synchronization signal (NPSS) and narrowband secondary synchronization signal (NSSS). The NPSS is used to estimate symbol timing and carrier frequency offset (CFO) and NSSS is used to detect cell ID and frame number [3]–[6]. In order to quickly achieve synchronization with the User equipment (UE), the NPSS signal uses Zadoff-Chu sequence and code cover because of their good correlation property. Therefore, in this thesis, we focus on synchronization process and the properties of the code cover. After analyzing the algorithm of synchronization and properties of code cover, we proposed a new code cover, called ZC-based II, which needs 760ms to achieve 90% NPSS detection, while the original code cover, 3GPP needs 790ms to achieve the same. It utilizes 30ms to get the same performance. Additionally, we used the correlation property of the Golay complementary pair (GCP) [7] to design a new synchronization signal structure. We compared the synchronization performance of different sequences when they are used as code covers. The simulation results show that the synchronization signal structure proposed in this thesis can shorten the duration of synchronization process. Our proposed structure based on GCP-based sequences needs 700ms to achieve 90% NPSS detection while the 3GPP code cover needs 790ms to achieve the same performance. It reduces 90ms to achieve the same performance.

[1] Y. P. E. Wang, X. Lin, A. Adhikary, A. Grovlen, Y. Sui, Y. Blankenship, J. Bergman, and H. S. Razaghi, “A primer on 3GPP narrowband internet of things,” IEEE Commun. Mag., vol. 55, no. 3, pp. 117–123, Mar. 2017.
[2] A. Adhikary, X. Lin, and Y.-P. E. Wang, “Performance evaluation of NB-IoT coverage,” in Proc. IEEE Veh. Technol. Conf., Montreal, Canada, Mar. 2017, pp. 1–5.
[3] S. Cheepurishetti and Y. Mohana Roopa, “Iot applications in smart cities,” in 2019 International Conference on Communication and Electronics Systems (ICCES), 2019, pp. 917–920.
[4] J. Guo and B. Song and S. Chen and F. R. Yu and X. Du and M. Guizani, “Contextaware object detection for vehicular networks based on edge-cloud cooperation,” IEEE IoT-J, vol. 7, no. 7, pp. 5783–5791, 2020.
[5] S. Chavhan and D. Gupta and B. N. Chandana and A. Khanna and J. J. P. C. Rodrigues, “Iot-based context-aware intelligent public transport system in a metropolitan area,” IEEE IoT-J, vol. 7, no. 7, pp. 6023–6034, 2020.
[6] S.-L. Su, Y.-C. Lin, and Y.-J. Fan, “Joint sector identity and integer part of carrier frequency offset detection by phase-difference in long term evolution cell search process,” IET Commun., vol. 7, no. 10, pp. 950–959, Jul. 2013.
[7] Y.-C. Lin, S.-L. Su, and Y.-J. Fan, “Joint sector ID and ICFO detection by using partial correlation scheme in LTE cell search process,” IEEE Pers. Commun., vol. 70, no. 4, pp. 1603–1621, Aug. 2013.
[8] C.-Y. Chu, I.-W. Lai, Y.-Y. Lan, and T.-D. Chiueh, “Efficient sequential integer CFO and sector identity detection for LTE cell search,” IEEE Commun. Lett., vol. 3, no. 4, pp. 389–392, 2014.
[9] T. Yingming and Z. Guodong, “Time and frequency synchronization for 3GPP long term evolution systems,” in Proc. IEEE Veh. Technol. Conf., Dublin, Ireland, Apr. 2007, pp. 1727–1731.
[10] Y. Tsai, G. Zhang, D. Grieco, F. Ozluturk, and X. Wang, “Cell search in 3GPP long term evolution systems,” IEEE Veh. Technol. Mag., vol. 2, no. 2, pp. 23–29, Jun. 2007.
[11] K. Manolakis, D. M. G. Estevez, V. Jungnickel, W. Xu, and C. Drewes, “A closed concept for synchronization and cell search in 3GPP LTE systems,” in Proc. IEEE Wireless Commun. and Netw. Conf., Icheon, South Korea, Apr. 2009, pp. 1–6.
[12] M. J. Shim, J. S. Han, H. J. Roh, and H. J. Choi, “A frequency synchronization method for 3GPP LTE OFDMA system in TDD mode,” in Proc. Int. symp. Commun. and Inform. Technol., Icheon, South Korea, Sep. 2009, pp. 864–868.
[13] ZTE, “Remaining issues on PSS and SSS for NB-IoT,” 3GPP TSG RAN WG1 NBAd-Hoc Meeting #2, Tech. Rep. R1-161993, Mar. 2016.
[14] Huawei Inc., “NB-PSS evaluation,” 3GPP TSG RAN WG1 NB-IoT Ad-Hoc Meeting #2, Tech. Rep. R1-161958, Mar. 2016.
[15] LG Electronics, “Synchronization signal design for NB-IoT,” 3GPP TSG RAN WG1 NB- Ad-Hoc Meeting #2, Tech. Rep. R1-161968, Mar. 2016.
[16] Intel Corporation, “Synchronization and cell search in NB-IoT: performance evaluations,” 3GPP TSG RAN WG1 Ad-Hoc Meeting #2, Tech. Rep. R1-161898, Mar. 2016.
[17] Qualcomm Inc., “NB-PSS and NB-SSS design (revised),” 3GPP TSG RAN WG1 NBIoT Ad-Hoc Meeting #2, Tech. Rep. R1-161981, Mar. 2016.
[18] Huawei and HiSilicon, “NB-PSS evaluation,” 3GPP TSG RAN WG1 NB- Ad-Hoc Meeting #2, Tech. Rep. R1-161994, Mar. 2016.
[19] Huawei, HiSilicon, Neul, Ericsson, MediaTek, Spreadtrum, “Summary of evaluation results for NB-PSS,” 3GPP TSG RAN WG1 NB- Ad-Hoc Meeting #2, Tech. Rep. R1-162048, Mar. 2016.
[20] A. Ali, S. Member, W. Hamouda, and S. Member, “On the cell search and initial synchronization for NB-IoT LTE systems,” IEEE Commun. Lett., vol. 21, no. 8, pp. 1843–1846, Aug. 2017.
[21] Intel Corporation, “Receiver algorithms and complexity analyses for NB-IoT synchronization,” 3GPP TSG RAN WG1 NB- Ad-Hoc Meeting #2, Tech. Rep. R1-161897, Mar. 2016.
[22] M. J. E. Golay, “Complementary series,” IRE Trans. Inf. Theory, vol. IT-7, pp. 82–87, Apr. 1961.
[23] 3GPP TS 36.211, “Evolved universal terrestrial radio access (E-UTRA); physical channels and modulation, V14.5.0 , Dec. 2017.
[24] C.-Y. Chen, “The primary synchronization sequences in LTE,” technical report, Dept. of Eng. Sci., National Cheng Kung University, Tainan, Taiwan, May 2018.
[25] F. Schuh, “LTE:der mobilfunk der zukunft synchronization and cell search,” Ausgewahlte Kapitel der Nachrichtentechnik, WS 2009/2010, Feb. 2010.
[26] S. Stefania, B. Matthew, and T. Issam “Synchronization and cell search,” in LTE-the UMTS Long Term Evolution: from theory to practice 2th ed. Wiley, 2011, pp. 151–164.
[27] R. Frank, S. Zadoff, and R. Heimiller, “Phase shift pulse codes with good periodic correlation properties,” IRE Trans. Inf. Theory, vol. IT-8, no. 6, pp. 381–382, Oct. 1962.
[28] D. Chu, “Polyphase codes with good periodic correlation properties,” IEEE Trans. Inf. Theory, vol. IT-18, no. 4, pp. 531–532, Jul. 1972.
[29] H.-Y. Chang, “Low-complexity cell identity detection algorithm by sequences grouping for NB-IoT,” M.S. thesis, Depart. of Eng. Sci., National Cheng Kung University, Tainan, Taiwan, Jun. 2019.
[30] B. M. Popovic and F. Berggren, “Primary synchronization signal in E-UTRA,” in Proc. IEEE Int. Symp. on Spread Spectrum Tech. and Applicat, Bologna, Italy, Aug. 2008, pp. 426–430.
[31] D. Sarwate, “Bounds on crosscorrelation and autocorrelation of sequence,” IEEE Trans. Inf. Theory, vol. IT-25, no. 6, pp. 720–724, Nov. 1979.
[32] B. M. Popovic, “Generalized chirp-like polyphase sequences with optimum correlation properties,” IEEE Trans. Inf. Theory, vol. 38, no. 4, pp. 1406–1409, Jul. 1992.
[33] S. Beyme and C. Leung, “Efficient computation of DFT of Zadoff-Chu sequences,” Electron. Lett., vol. 45, no. 9, pp. 461–462, Apr. 2009.
[34] E. Jorgensen, “Cell acquisition and synchronization for unlicensed NB-IoT,” M.S. thesis, Dept. of Elect. Eng., Linkoping University, Sweden, Feb. 2017.
[35] W. Yang, M. Hua, J. Zhang, T. Xia, J. Zou, C. Jiang, and M. Wang, “Enhanced system acquisition for NB-IoT,” IEEE Access, vol. 5, pp. 13 179–13 191, Jul. 2017.
[36] C.-C. Tseng and C. L. Liu, “Complementary sets of sequences,” IEEE Trans. Inf. Theory, vol. IT-18, pp. 644–652, Sep. 1972.
[37] 3GPP TS 36.104, “Base station (BS) radio transmission and reception,” V8.4.0 , Dec. 2008.