適用於干擾存在環境下多頻帶正交分頻多工系統的適應性頻道估測方法

這篇論文的主要目的在於利用正交分頻多工系統本身的彈性，來提供更好的頻道估測方法。頻道估測的主要目的是估出正確的頻道增益；而頻道增益對於同步解調以及動態資源分配而言，提供了非常重要的資訊。通常，頻道估測估得越準，則整個系統的效能也會更好。對於多頻帶正交分頻多工系統而言，因為頻帶的選擇是由時頻碼所決定，所以系統內同頻的干擾信號是無法避免的。和雜訊相比，干擾信號對估測造成的傷害是嚴重許多的。因此，在這篇論文中，我們把焦點放在消除干擾信號這件事上面。全篇最重要的特性是時域上面的重複特性，利用這個特性，我們提出了一系列的TR估測器。雖然使用了TR估測器，就必須多出內插的動作，但是我們仍然可以從消除干擾信號以及在維持總功率的前提下使得訊雜比變高這兩件事得到助益。此外，因為有接收訊號在時域上的分集，我們可以應用不同的分集合成技術。然而，因為無法避免的內插運算，會引入內插錯誤而影響估測，所以使用TR估測器前必須先衡量。我們提供了數學推導以及模擬驗證來提供一個決定的基準。由推導及模擬的結果，我們可以預期TR估測器能帶來的效能改善。此外，除了多頻道正交分頻多工超寬頻系統外，我們也能期待把它運用在其他正交分頻多工系統能帶來的效能增進。

關鍵字

正交分頻多工；超寬頻；頻道估測；干擾

並列摘要

In this thesis, we exploit the flexibility OFDM provides to improve the performance of channel estimation. Channel gain, which can be obtained by channel estimation, is significant information for coherent demodulation and dynamic resource allocation. It can be assumed that the better the channel estimation, the better the system performance. As for MB-OFDM systems, due to the TFC that governs the selection of available band, interference becomes an unavoidable problem. Compared with thermal noise, the damage interference may cause are much more severe. As a result, we focus on eliminating interference throughout this thesis. The most important property been exploited is the time domain redundancy. With the property, we propose a series of TR estimators. Although interpolation is needed for TR estimators, we can still benefit from the elimination of interference and the enhancement of SNR at the sub-carriers with pilots symbol on it. In addition, with the time domain diversity, we can apply several diversity combining schemes on the received symbol. However, due to the inevitable interpolation and the resulting interpolation error, there exists certain trade-off. We have some numerical derivation to help decide which estimator to use and make some simulation to verify the numerical results. With the simulation and numerical results, we can expect the improvement by using TR estimators. Finally, besides MB-OFDM UWB system, we anticipate better performance in other OFDM systems adopting the TR estimator.

並列關鍵字

OFDM ； UWB ； Channel Estimation ； Interference

參考文獻

[2] A. F. Molisch, J. R. Foerster and M. Pendergrass, “Channel Models for Ultrawideband Personal Area Networks,” IEEE J. Wireless Comm., vol. 10, no. 6, pp. 14-21, Dec. 2003.

[4] H. Minn and V. K. Bhargave, “An Investigation into Time-Domain Approach for OFDM Channel Estimation,” IEEE J. Broadcasting, vol. 46, no. 4, pp. 240-248, Dec. 2000.

[5] A. Jeremic, T. A. Thomas and A. Nehorai, “OFDM Channel Estimation in the Presence of Interference,” IEEE Trans. on Signal Processing, vol. 52, no. 12, pp. 3429-3439, Dec. 2004.

[7] C. Budianu and L. Tong, “Channel Estimation under Asynchronous Packet Interference,” IEEE Trans. on Signal Processing, vol. 53, no. 1, pp. 240-248, Jan. 2005.

[8] P.-Y. Tsai and T.-D. Chiueh, “Frequency-Domain Interpolation-Based Channel Estimation in Pilot-Aided OFDM Systems,” Proceedings of IEEE VTC 2004, vol. 1, pp. 420-424, 2004.

國際替代計量

適用於干擾存在環境下多頻帶正交分頻多工系統的適應性頻道估測方法

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