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。近年來OFDM技術更被應用於實現60GHz頻段之gigabit級的無線通訊，例如以IEEE 802.15.3c標準為基礎之WirelessHD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。WiGig與目前已廣泛應用之Wi-Fi相容，因此未來發展性相當受業界看好。

一個設計優良的通訊接收機(receiver)，須要有優異的通訊演算法作為其後盾，其中同步技術對於通訊演算法又至為關鍵。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。然而，使用傳統比對濾波器(matched-filter)之同步演算法，無法適用於使用具特殊自相關特性之格雷序列(Golay sequence)作為前序(preamble)之WiGig。

據此，本研究提出一個應用於WiGig之同步器。我們利用格雷序列特殊的自相關特性，提出一套新型且有效率之演算法，目的為改善以格雷序列作為前序之OFDM系統中同步的精準度。除此之外，我們在電路架構上亦有相當的創新，充分利用訊號特性及數學近似方法，可大幅降低複數乘法的運算量。就實現層面而言，本次研究使用TSMC 90奈米的技術實現硬體架構，並在暫存器轉移階層(register transfer level, RTL)評估本架構之效能。此外，亦使用現場可程式化邏輯閘陣列(field-programmable gate array, FPGA)以實現及驗證本研究之硬體架構。

Orthogonal frequency-division multiplexing (OFDM) is a promising technology and has been widely utilized in communication systems. In recent years, OFDM has also been adopted by multi-gigabit wireless communications in the 60 GHz band, such as WirelessHD, which conforms to IEEE 802.15.3c standard. The WiGig (Wireless Gigabit) specification is primarily based on IEEE 802.11 standard. WiGig is compatible with Wi-Fi, which has been widely used. Therefore the industry is optimistic about the future development of WiGig.

For a well-designed communication receiver, an excellent communication algorithm is very important. Besides, the synchronization techniques are critical to the communication algorithms, especially for the OFDM systems. OFDM systems are sensitive to synchronization errors, which will introduce severe inter-symbol interference (ISI) and inter-carrier interference (ICI). These interferences will severely degrade the performance of channel equalization and data decoding. However, WiGig adopts Golay sequences as the preamble, which have special autocorrelation properties. Accordingly, conventional synchronization algorithms using the matched filter cannot be applied in WiGig.

To address this issue, this thesis introduces a timing synchronizer for WiGig. In order to improve the synchronization performance of OFDM system, we propose a novel and efficient algorithm according to the special autocorrelation properties of Golay sequences. Moreover, we reduce the computational complexity in terms of the number of complex multipliers by fully utilizing the signal properties and the mathematical approximation. The performance is evaluated by the register-transfer-level (RTL) model which is implemented with TSMC 90nm silicon technology. Furthermore, the hardware architecture is implemented and verified by field-programmable gate array (FPGA).

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