適用於IEEE 802.16e標準之時間與頻率同步系統

此篇論文當中，我們提出了一個適用於IEEE 802.16e標準之時間與頻率同步系統，並可支援在MIMO天線系統下使用。此同步系統依序是由封包偵測、載波頻率位移估測、以及符元時間估測三個部分所整合而成。封包偵測部分是由訊號延遲以及自相關運算，經過正規化之後，和門檻值比較。載波頻率位移是將封包偵測單元中的自相關估計值，取出相位並加以運算。載波頻率位移補償後，會估計符元起始時間，方法則是利用匹配濾波器，將接收到的訊號與前置訊號做匹配。在第一章，我們簡單介紹WiMAX。第二章，我們會介紹模擬的環境。第三章，我們會介紹時間以及頻率同步的演算法。第四章，我們會分析模擬結果。而結論會在第五章提出。本篇論文提出的載波頻率位移估測有三項適合WiMAX的優點。第一、即使在一個低SNR以及有豐富的多重路徑效應下的MIMO環境，估測結果也能展現出令人滿意的效能。第二、載波頻率位移估測在MIMO環境下，會有比SISO環境更佳的效能展現。第三、本篇論文所提出的載波頻率位移估測演算法，效能不會因速度的改變而變差，此項同步特性對於支援行動性（mobility）的IEEE 802.16e平台可說是非常重要。為了驗證此同步系統可以適用於IEEE 802.16e標準。我們會使用本篇論文同步演算法估測到的符元起始時間繼續解調，並算出最終的系統錯誤率。模擬結果顯示，在IEEE 802.16e平台下，無論是何種通道環境，使用本篇論文提供的時間及頻率同步演算法，皆可以得到有效率且正確的結果。

關鍵字

同步；載波頻率偏移；符元時間偏移； 802.16e

並列摘要

In this thesis, we proposed an effective time and frequency synchronization scheme for IEEE 802.16e systems, and this synchronization scheme can be used in MIMO environment. The synchronization is accomplished sequentially by packet detection, CFO estimation, and symbol timing synchronization. The proposed packet detection method is accomplished by delay and correlating the received signal, then normalized the result and compared it with the threshold. We found the phase of the correlation result in the packet detection block, and used the phase to determine the CFO estimation. After compensating the CFO, we will doing the symbol timing synchronization. It can be performed by cross-correlating the received signal and the corresponding transmitted preamble. The proposed CFO estimation has three advantages over WiMAX system. First, the CFO estimation shows satisfactory performance even at a low SNR and rich multi-path MIMO environment. Second, the performance in MIMO channel are much better then those in SISO channel due to the diversity gain. Furthermore, the performance would not down when the speed is change, the characteristic is important to IEEE 802.16e which support mobility. To improve the synchronization system can be used in IEEE 802.16e system, we used the proposed synchronization scheme to determine the receiver BER. As the simulation result shows, no matter we use what kind of MIMO channel environment, the proposed synchronization scheme can provide efficient and accurate result in the IEEE 802.16e system.

並列關鍵字

synchronization ； CFO ； symbol timing ； 802.16e

參考文獻

[4] IEEE Std. 802.16-2004(Revision of IEEE Std. 802.16-2001)”IEEE Standard for Local and Metropolitan Area Networks Part 16:Air Interface for Fixed Broadband Wirless Access Systems”Oct. 2004

[11] Jiao Wang,Yongquan Qiang, Bin Zhang, Daoben Li,”Comparison of Statistical Properties between an Improved Jakes’ Model and the Classical One”, Beijing Univ. of Posts & Telecom,2003

[13] S. M. Alamouti,”A simple transmit diversity scheme for wireless communications”,IEEE J Select. Areas Commun.,vol. 16, pp. 1415-1458, Oct.1998.

[15] Chin-Liang Wang, ”Synchronization Techniques for Multiple Input Multiple Output OFDM systems”, Department of Electrical Engineering and Institute of Communications Engineering ,National Tsing Hua University,2005

[16] En Zhou, Xing Zhang, Hui Zhao, Wenbo Wang, “Synchronization Algorithms for MIMO OFDM Systems”, Center for Wireless Communications of Beijing University,2005

國際替代計量

適用於IEEE 802.16e標準之時間與頻率同步系統

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