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標題: | 應用於雙向中繼網路之有效能量與頻寬的通道估測法 Energy and Bandwidth-Efficient Channel Estimation in Two-way Relay Networks |
作者: | Jyun-Wei Pu 蒲俊瑋 |
指導教授: | 李學智 |
關鍵字: | 雙向中繼網路,通道估測,審查機制,克拉美-羅下界,中斷機率, Two-way relay networks,channel estimation,censoring rule,Cramer–Rao lower bound,outage probability, |
出版年 : | 2016 |
學位: | 博士 |
摘要: | 本論文考慮在雙向中繼網路(two-way relay networks, TWRNs)之中的通道估測議題,為了有效提升功率使用效率,本論文提出一種藉由審查機制(censoring rule)的通道估測方法。在中繼端(relay node)將部分較不可靠的訊號給拿掉不傳送至來源端(source nodes),藉此提升傳輸功率使用效率,並利用克拉美-羅下界(Cramér–Rao lower bound)來證明所提出的方法有所改善。
先前的文獻之中已提出一種採用訓練式的(training based)通道估測方法,為了有效的提升頻寬使用效率,一種結合式通道估測與資料偵測的方法在本論文的第二部份被提出,利用最大期望值演算法(expectation maximization algorithm)的概念將所欲求解的通道及資料資訊解出。從模擬結果可以發現在高訊雜比(signal to noise ratio)的環境之中,所提出的方法能夠貼近克拉美-羅下界的理論值並且只用少量的領航訊號(pilot signal)。在相同的領航數量之下,所提出的方法能夠勝過訓練式的通道估測方法。 在本論文的第三部份將探討兩種不同的通道資訊對於中繼點選擇所的影響。這兩種通道資訊分別為分離式(separate)及串聯式(cascaded),在分離式的方法中,會利用兩個來源節點到中繼節點個別的通道資訊來進行中繼選擇,而串聯式的方法則是會將訊號所經過的通道合起來考慮,藉此選出想要的中繼點。在分析這兩種方法的中斷機率(outage probability)效能時,均考慮了通道估測錯誤量的影響,在此是採用克拉美-羅下界來建構錯誤量的大小。此外,與先前的文獻相比,在此假設兩個來源節點的通道估測錯誤量是不相同的,從模擬結果可看出若假設兩個來源節點的錯誤量不同將對效能造成很大的影響。 The channel estimation problem in a two-way relay networks (TWRN) is considered in this thesis. To save the transmit power of the system, an energy efficient scheme is proposed by using the concept of censoring rule. The relay node drops the unreliable signals and forwards the reliable signals to source nodes by the designed censoring rule. The Cramér–Rao lower bound (CRLB) for the proposed channel estimation scheme in a TWRN is then derived. Previous studies have designed a training-based channel estimator based on the mean square error to obtain the channel state information. However, this channel estimator may not be efficient for a wireless environment. To improve bandwidth efficiency, a joint data detection and channel estimation scheme based on the expectation-maximization algorithm is proposed in the second part of this thesis. The simulation results show that the performance of the proposed scheme can approach the CRLB at the region with high signal-to-noise ratio. In addition, given the same number of pilots, our results show that the proposed scheme outperforms the training-based scheme proposed in previous study. In the third part of this thesis, the impact of channel estimation errors is investigated in TWRNs with two different channel state information (CSI) estimation schemes, namely separate and cascaded. In the former scheme, the relay node is chosen in accordance with the CSI of the individual channels between the source nodes and the relay node. By contrast, in the latter scheme, relay node selection is performed in accordance with the CSI of the cascaded channel between the two source nodes. For both estimation schemes, the effect of the CSI estimation error on the outage probability is examined by means of the CRLB. Moreover, in contrast to previous studies, the source nodes in the TWRN are assumed to have different estimation errors. The numerical results confirm the validity of the derived expressions and show that the presence of different estimation errors at the two source nodes has a significant effect on the performance of the TWRN. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/51286 |
全文授權: | 有償授權 |
顯示於系所單位: | 電信工程學研究所 |
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