近年來，在關於未來的4G通訊系統競爭中，IMT-Advanced 提出的長程演進系統(Long Term Evolution, LTE)越來越受到注目。而為了因應使用者在未來對於頻寬的高需求量，並達到 IMT-Advanced所制定的最大下載資料傳輸速率：1Gbps，最大上傳資料傳輸速率：500Mbps，IMT-Advanced進一步提出的LTE的進化版本( LTE-Advanced, LTE-A)，提出了一種新的技術: 頻帶聚合 (Carrier Aggregation, CA)，來滿足使用者對於頻寬的高需求量。 在現有的LTE蜂巢系統下，一個使用者裝置只會與一個基地台做連接。因此，使用者需要快速的與所屬的基地台建立連接，並讓使用者和基地台同步。而LTE及LTE-A在下行鏈路採用的是正交分頻多工存取系統(Orthogonal Frequency Division Multiplexing Access, OFDMA)。而其同步的做法大約可分為以下的步驟：第一步，使用延遲自相關找出訊號時序 (frame timing) 與主要同步訊號 (primary synchronization signal, PSS)，再以此時序開始做小數點時間與小數點頻率估測。第二步，利用匹配濾波器以主要同步訊號來估測整數頻率偏移。 而在此篇論文中，我們因應LTE-A提出的頻帶聚合技術，提出一個可以讓使用者同時和多個基地台建立連接，並快速和多個基地台做到頻率同步的新的架構。 Since the demand of high speed mobile broadband services, the International Telecommunication Union - Radio Communication Sector (ITU-R) has proposed the next generation mobile communication system Long term evolution advanced (LTE-Advanced) which will retain most of the system construction in Long term evolution (LTE) and increase the performance of it. Then, LTE-Advanced proposes carrier aggregation (CA) to aggregate component carriers (CCs) which I belonging to contiguous or non-contiguous frequency bands and it is used to meet the specification of future International Mobile Telecommunication – Advanced (IMT-Advanced) mobile systems: peak data rates up to 1Gbps in downlink and 500Mbps in uplink. In original cellular system in LTE, user equipment (UE) only needs to establish a connection with a best serving evolved-Node B (e-NB). So, UE needs to establish a connection and synchronize with the e-NB. The steps of synchronization are as follows: (1). Using the delay auto-correlation to find frame timing and the P-SCH (primary synchronization signal), and then use the sequence to estimate the symbol timing and the fractional frequency offset. (2). Using the match filter with the P-SCH to estimate the integer frequency offset [1-3]. In the thesis, we propose a new structure for CA to establish the connections between UE and base stations at the same time and the UE can get the frequency offsets and synchronize with the base stations as soon as possible.
