| 摘要: | D2D通訊技術被視為在下代行動通訊發展的重要關鍵，但若要在第五代通訊技術採用D2D就須克服許多問題如干擾抑制、模式選擇、裝置收尋、同步…等問題，而為了能夠達到裝置間能夠連結，在眾多問題中同步問題最為重要，由其是頻率同步問題，若有些許誤差子載波間的正交性將會被破壞，產生載波間干擾問題。在INC(裝置皆在同個基地台服務範圍內)的環境中因所有裝置都在基地台內，所有裝置間用戶的同步可以藉由蜂巢搜尋的方式讓裝置皆與基地台聯結來達成裝置間同步，而在3GPP Release 12中明確指出在PNC(裝置在不同基地台服務範圍內)與ONC(裝置皆不在同基地台服務範圍內)環境下，因在不同基地台服務下的裝置中心頻率不同而造成非同步的問題，而在3GPP TSG RAN1 第79期會議開始也已對此問題展開廣泛的討論，包括D2D同步訊號序列的種類，須放在訊框裡的哪個位置、環境設定…等，更廣召大家討論D2D裝置收尋與裝置同步的方法並在未來幾期的會議中進行決策。
本篇論文提出三個步驟：第一步，使用自相關找出時序(frame timing)與D2D主要同步訊號，第二步，以此時續開始做小數點時間與頻率估測，第三步，我們利用匹配濾波器來偵測區段與整數頻率偏移。
此研究所提出的演算法，將對未來D2D通訊有巨大的幫助，在裝置收尋後往往會因為裝置間步同步而導致連線時常中斷，且因未來D2D通訊將會運用付費的頻段上，因此藉由此演算法將可使連線更加穩固，能夠在未來5G能有更多生活上的應用。
;D2D has been a key development of communication in next-generation communication. However, there exist, such as interference management, mode selection, discovery and signal synchronization, occurring in scenario. Among the problems, signal synchronization is the most crucial one, especially the aspect of frequency synchronization. Intercarrier interference(ICI) may result when the orthogonality among subcarriers do not be perfectly maintained. In INC (In-Network Coverage) scenario, DUEs are in the same coverage and can achieve synchronization state via the sector searching mechanism that makes devices connect to the base station. Nonetheless, according to 3GPP Rel-12, asynchronous problems may occur in the PNC (Partial-Network Coverage) and ONC (Out-of-Network Coverage) scenarios because of different central frequencies. This issue has been discussed since 3GPP TSG RAN1 Session #79, including the position of synchronization sequence of D2D and scenario settings. 3GPP is dedicated to discussing D2D discovery methods and synchronization methods. Until now, the outcome has not been well known.
In this thesis, a novel procedure consisting of three steps is proposed. At first, frame timing and primary synchronization signal of D2D is searched for by autocorrelation. Second, fractional frequency offset is estimated by. At last, integer frequency offset is detected by frequency-domain matched filter.
The proposed algorithm may provide accurate timing synchronization and frequency correction for D2D communication. D2D communication will operate on licensed bands in future, and the proposed method can provide connection stability for D2D communication. Therefore, the proposed technique improves the applicability of D2D communication. |
