多基地台干擾下IEEE 802.16e系統之初始同步與基地台搜尋方法

Initial Synchronization and Cell Search Schemes for IEEE 802.16e system with Multi-cell Interference

張順雄(Shun-Hsiung Chang)

指導教授 ： 黃正光

元智大學/電機通訊學院/通訊工程學系/碩士(2009年)

摘要

在本論文中，我們首先建構IEEE 802.16e正交分頻多工存取系統之下行線路的前序列碼架構與含有載波頻率偏移的信號模型。為了使之達成真正的初始同步，吾人提出並改進如封包與符碼的時間點同步、頻率域上的頻率同步與基地台ID搜尋等等的方法，並藉由前面所提的前序列碼架構中包含的定理與其推導出的接收信號模型來分析證明這些演算法是否可行。此外當行動通訊裝置接收到有多基地台的前序列碼信號時，這些信號會彼此互相干擾並導致同步錯誤的結果發生。針對這個特殊情況，為了降低多基地台干擾的影響與避免同步錯誤的發生，在進行初始同步之前，吾人也提出了一些有效的多基地台干擾消除的方法分別於頻率域與空間-頻率域下使用。最後經由電腦模擬結果與解析顯示出吾人所提出的初始同步演算法會有高效率的性能表現，使其在實際運作下更為適用。

關鍵字

正交分頻多工存取 ； 下行線路的前序列碼 ； 載波頻率偏移 ； 封包與符碼的時間點同步 ； 頻率同步 ； 基地台ID搜尋 ； 多基地台干擾

並列摘要

In this thesis, we first construct the downlink (DL) preamble structure and signal model with carrier frequency offset (CFO) for IEEE 802.16e orthogonal frequency division multiplexing access (OFDMA) systems. In order to achieve the truly initial synchronization, several methods for packet/symbol timing, frequency synchronization, and cell ID search are introduced, improve, and analyzed by using DL preamble properties and the derived received signal model. In addition, when the mobile device receives the preamble signals from multiple basestations, these signals will cause synchronization errors and interfere with each other which is called multi-cell interference. For this special case, we also propose some effective multi-cell cancellation schemes in frequency domain and in space-frequency domain to mitigate the multi-cell interference and to avoid the synchronization errors before using the proposed initial synchronization algorithms. Finally, from analytic and computer simulation results, we show that the proposed overall initial synchronization algorithm achieves high efficiency and performance, making it suitable for practical applications.

並列關鍵字

orthogonal frequency division multiplexing access (OFDMA) ； downlink (DL) preamble ； carrier frequency offset (CFO) ； packet/symbol timing synchronization ； frequency synchronization ； cell ID search ； multi-cell interference

參考文獻

[1] IEEE std 802.16-2004. IEEE standard for local and metropolitan area networks, -part 16: air interface for fixed broadband wireless access systems, Oct. 2004.

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[6] P. Cheng, Z. Zhang, X. Zhou, J. Li, and P. Qiu, “A study on cell search algorithms for IEEE 802.16e OFDMA systems,” IEEE Wireless Communications and Networking Conference, 2007.

[7] H. Su, J. Zhang, and P. Zhang, “A preamble-based cell search scheme for OFDMA cellular systems,” Proc. of IEEE Conf. ICNICONSMCL, April 2006.

[8] T. M. Schmidl and D. C. Cox, “Robust frequency and timing synchronization for OFDM,” IEEE Trans. Commun., vol. 45, pp. 1613-1621, Dec. 1997.