改良式LS領導式通道估測應用在UWB通道上正交分頻多工系統之研究

An Improved LS method of Pilot Channel Estimation in OFDM Systems over the UWB Channel

陳佑維(Yo-Wei Chen)

指導教授 ： 呂振森

國立臺北科技大學/電資學院/電機工程系研究所/碩士(2007年)

https://doi.org/10.6841/NTUT.2007.00141

摘要

本論文主要為探討OFDM系統在UWB通道下，領導式通道估測的方法對於不同通道變換下之分析，以及領導訊框個數對於執行效能的影響。領導式通道估測的方法主要包含LS估測法和LMS演算法，在通道參數固定之下，此二方法皆能達到良好的執行效能，且其執行效能還會隨著領導訊框的數量而增加。基本上LS估測法本身並不考量通道變化的，而LMS演算法雖能適應通道的變化，但僅適用於通道參數緩慢變化時。但如果通道的變化造成通道參數大幅改變，LMS演算法無法得到很好的通道參數調適，導致效能不佳，而LS估測法因無法判斷通道變化，只能以單筆的領導符碼來估測通道參數，若通道變換率極為緩慢時，其執行效能並不佳。為了在動態通道之下能夠達到更好的執行效能，本論文提出了改良式LS估測法，在原有LS估測法中加進通道變化點的判斷法則，以期能夠有效的應用領導符號，改善系統效能。最後，將本方法應用於在UWB通道下之OFDM系統，以電腦模擬方式，驗證其結果。

關鍵字

通道估測 ； 領導符碼 ； UWB ； OFDM

並列摘要

This thesis is mainly to research into the performance of methods of pilot channel estimation over the UWB channel. The primary methods of pilot channel estimation include LS method and LMS method. Both of them have good performances under fixed channel, and the system performances increase with the amount of pilot frames. Basically, LS method does not consider the variations of the channel. Although LMS method can adopt the channel variations, it is limited to the case that the channel parameters change slowly. If the channel parameters change extensively, there won’t be any good performances by LMS method. Under this circumstance, we can only use single pilot symbol for the LS method to estimate the channel parameters, which results in the poor performance of systems for slowly changing channels. In order to get better performance in the dynamic changing channel, this thesis proposes an improved LS method by applying the addition rules for predicting the changing points of the channel. This method can effectively use all pilot frames to improve the system performances. At the end of the thesis, we apply our method to the OFDM system in UWB channel to verify its performance.

並列關鍵字

Channel Estimation ； Pilot Symbol ； UWB ； OFDM

參考文獻

[1] Z. Irahhauten, J. Dacuna, G.J.M. Janssen, and H. Nikookar, ”UWB Channel Measurements and Results for Wireless Personal Area Networks Applications, ” The European Conference, Oct. 2005, pp 189-192.

[3] J. A. C. Bingham, "Multi-carrier modulation for data transmission: An idea whose time has come," IEEE Comm. Magazine, pp. 5-14, May 1990.

[5] J. K. Cavers, Mobile channel characteristics, Boston Kluwer, 2000

[7] S. Haykin, Communication Systems, Fourth Edition, Wiley, 2001.

[10] A. Feng, Q. Yin, J. Zhang, and K. Deng, ”Blind Channel Estimation in Synchronous MC-CDMA System with Consideration of Carrier Offset Compensation, ” IEEE 55th Vehicular Technology Conf, vol. 2, no. 7, Spr. 2002, pp 660-664.