正交分頻多工(orthogonal frequency-division multiplexing, OFDM)已經是一成熟且應用廣泛的通訊技術，其中同步技術對於通訊演算法又極其關鍵。尤其是對OFDM傳輸技術而言，同步錯誤將會造成嚴重的符元間干擾(inter-symbol interference, ISI)及子載波間干擾(inter-carrier interference, ICI)，而這些干擾將會嚴重影響後續通道等化(equalization)及資料解碼(decoding)的效能。
近年來具特殊自相關特性之格雷序列(Golay sequences)常用來當作封包的前序(preamble)，例如以IEEE 802.15.3c標準為基礎之Wireless HD技術，以及由WiGig聯盟(Wireless Gigabit Alliance)以現存IEEE 802.11標準為基礎所制定之WiGig規範。然而，使用傳統比對濾波器(matched-filter)之同步演算法，無法適用於使用格雷序列作為前序的時間同步器。
據此，本研究利用本實驗室謝沂庭學姊在2013年所設計之時間同步演算法，進行系統的實現，目的在於評估以格雷序列作為前序之OFDM系統中真實環境下的效能表現。首先，為了將此時間同步演算法實現在系統平台上，我們將電路做些許的修改，並在暫存器轉移階層(register transfer level, RTL)建構基頻接收機，用以初步評估接收機時間同步演算法之效能表現，硬體實現層面會採用萊斯大學所開發的無線開放式研究平台(Wireless Open-Access Research Platform, WARP)實現本研究之硬體架構，評估在真實環境下的效能表現。

Synchronization is critical in the design of an OFDM receiver. Large timing offsets result in a loss of orthogonality between subcarriers, ISI, and severe bit error degradation. To minimize this degradation, standards incorporate preambles intended for all OFDM acquisition functions including automatic gain control (AGC) and synchronization. However, the IEEE 802.11 specification adopts Golay sequences as the preambles, which have special autocorrelation properties. Accordingly, conventional synchronization algorithms using the matched filter cannot be applied in Golay sequences. To address this issue, this paper presents a design and implementation on timing synchronizer for Golay sequences. In order to improve the synchronization performances of OFDM systems, we propose a novel and efficient algorithm according to the special autocorrelation properties of Golay sequences. The performance is evaluated by the register-transfer-level (RTL) model which is implemented on FPGA. Finally, the hardware architecture is implemented and verified by Wireless Open-Access Research Platform.

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