空間頻率區塊碼之多輸入多輸出無線正交分頻多工通訊系統中利用跳頻導航符號配置之頻率飄移與通道共同估測研究

Hopping Pilots for Joint CFO and Channel Estimation in Wireless SFBC-Based MIMO-OFDM Communications

李奇恩(Chi-En Li)

指導教授 ： 林容杉

國立暨南國際大學/科技學院/通訊工程研究所/碩士(2009年)

https://doi.org/10.6837/NCNU.2009.00117

摘要

正交分頻多工 (OFDM) 傳輸系統，能夠極為有效地來降低多重路徑干擾下所產生的頻率選擇性衰落效應，同時頻寬資源的使用效率亦可以獲得提昇，是為其最大的特點。多輸入多輸出 (MIMO) 之架構能夠提供多個獨立的無線通道，透過傳送與接收兩端的多根天線來同時收送多個訊號，運用空間分集的技術提昇訊號品質。
在這篇論文裡，我們考慮在多輸入多輸出正交分頻多工 (MIMO-OFDM) 無線傳輸系統的架構下，去對頻率飄移以及通道作共同估測。在下行的傳輸系統中，用戶端在估測頻率飄移時，能夠接收到基地台傳送過來的有誤差的通道狀況資訊 (CSI)。再補償完頻率飄移的問題之後，我們開始做通道估測。
我們提出跳頻導航符號 (hopping pilot) 配置的方式去改善通道估測之系統效能。這個跳頻導航符號配置的方法，能夠獲得更多的通道資訊，以及對抗頻率選擇性衰弱的影響。再此篇論文裡，我們比較兩種導航符號的配置，應用於空間頻率區塊碼之多輸入多輸出正交分頻多工系統 (SFBC-based MIMO OFDM)。 (1) 梳狀(comb-type) 導航符號配置結合虛擬導航符號 (M1) 以及 (2) 跳頻導航符號配置結合虛擬導航符號 (M2)。而方法二 (M2) 錯誤率之表現，不管在哪種環境都優於方法一 (M1)。

關鍵字

正交分頻多工 ； 多輸入多輸出 ； 頻率飄移 ； 通道估測 ； 空間頻率區塊編碼 ； 導航符號配置

並列摘要

Orthogonal frequency division multiplexing (OFDM) schemes are a well-known wireless transmission technique which is effective against frequency selective fading channel and capable of reducing multipath propagation effects very well. Multi-input multi-output (MIMO) architectures can provide multiple artificial uncorrelated channels for transmitting/receiving replicas of the same signals simultaneously to obtain diversity gains.

In this thesis, the problem of joint carrier frequency offset (CFO) and channel estimation is considered for MIMO-OFDM systems. In downlink, the mobile station can receive the imperfect channel state information (CSI) from the base station when we want to estimate the CFO. After compensating the effect of CFO, we do the channel estimation.

A channel estimation technique with hopping pilot pattern is proposed to improve system performance. The hopping pilot method can move the position of pilot to obtain more channel information and resist the frequency selective fading. In this thesis, two kinds of pilot patterns are compared in SFBC-based MIMO-OFDM systems. They are (1) comb-type pilot arrangement with virtual pilots (M1) and (2) hopping pilot estimation with virtual pilots (M2). The BER performance of M2 is always better than that of M1. Finally, joint CFO and channel estimation are given to enhance system performance.

並列關鍵字

OFDM ； MIMO ； CFO ； channel estimation ； SFBC ； pilot assignments

參考文獻

[1] A. R. S. Bahai and B. R. Saltzberg, Multi-carrier Digital Communications Theory and Applications of OFDM, New York, NY: Kluwer Academic, 1999.

[2] J. Bingham, “Multicarrier Modulation for Data Transmission: An Idea Whose Time Has Come,” IEEE Transactions on Communications, vol. 28, pp. 5-14, May 1990.

[3] R. E. Ziemer and R. L. Peterson, Introduction to Digital Communication, Upper Saddle River, NJ: Prentice-Hall, 2001.

[4] C. Langton, “Orthogonal Frequency Division Multiplex Tutorial,” Intuitive Guide to Principles of Communications on www.complextoreal.com, 2004.

[5] J. J. van de Beek, P. O. B‥orjesson, P. ‥Odling, and S. K. Wilson, “Orthogonal Frequency Division Multiplexing,” W. R. Stone (editor), Review of Radio Science, International Union of Radio Science (URSI), Oxford University Press, Sept. 1998.