單載波分頻通道估測基於調適性頻域滑動式視窗;Channel Estimation Based on Adaptive Frequency Domain Windowing for SC-FDM Communications

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题名:	單載波分頻通道估測基於調適性頻域滑動式視窗;Channel Estimation Based on Adaptive Frequency Domain Windowing for SC-FDM Communications
作者:	何欣芸;Ho,Hsin-Yun
贡献者:	通訊工程研究所
关键词:	頻域最小平方估測;頻域最小均方估測;單載波分頻;通道估測;正交分頻多工;視窗;Window;Channel estimation;FD-MMSE;FD-LS;OFDM;SC-FDM
日期:	2012-08-16
上传时间:	2012-09-11 18:50:14 (UTC+8)
出版者:	國立中央大學
摘要:	近年來，無線通訊系統所需的傳輸資料量越來越高，所需的頻寬也越來越大，在有限的頻寬下，利用這些資源達到最大的傳輸量。由於正交分頻多工具備高速率資料傳輸的能力，加上能有效對抗頻率選擇性衰減，因此廣泛運用在通訊系統中。但正交分頻多工的功率峰均值比過高，且無法抵抗頻率偏移。單載波分頻多工傳送端使用單一載波調變，架構類似於正交分頻多工，因此效能也相似。不同的是，單載波分頻多工為在正交分頻多工前加上離散傅立葉轉換前置編碼的系統。這方法可以降低功率峰均值比，且有效增加傳送功率效率。因此3GPP LTE使用單載波分頻多工為上傳架構。然而，單載波分頻多工像正交分頻多工一樣，容易對震盪器不穩及通道都卜勒效應產生的頻率偏移很敏感，造成子載波間干擾而降低系統效能。為了增進系統的效能，通道估測技術是必須的。實際上，在單載波分頻多工存取系統上用於通道估測的引導信號 (pilot signals)，在傳送端，每隔固定週期時間插入資料符元間。其中一種引導信號的擺放方式為塊狀信號編排(block-type pilot arrangement)。基於此種擺放方式，此篇論文中我們考慮了系統複雜度不高的狀況下，利用了最小平方的通道估測法作改善，為一種最小平方滑動視窗估測技術，來估測通道變化。再進一步根據不同SNR的情況，在接收端選擇最佳的最小平方滑動視窗的大小。與傳統在頻域上最小平方估測和最小均方估測技術和其他較低複雜度的通道估測技術作比較。提出的改善方法在系統複雜度不高的情況下，效能也能做進一步的改善。Nowadays, wireless communications systems transmit data required for increasing the amount of required bandwidth is also growing. In the limited bandwidth, the use of resources achieve maximum throughput. Because the orthogonal frequency division multiplexing is provided with high data rate and effective against frequency selective fading, it is widely used in communication systems. However, the peak to average power ratio (PAPR) of the orthogonal frequency division multiplexing (OFDM) is too high and cannot resist the frequency offset. Single-carrier frequency division multiplexing (SC-FDM) is using a single carrier modulation. Orthogonal frequency division multiplexing architecture is similar to single carrier, so the performance is also similar. The difference is that single carrier frequency division in orthogonal frequency division multiplexing added before discrete Fourier transform pre-coding system. The method can reduce the peak to average power ratio, and effectively increase the transmission power efficiency. Therefore, 3GPP LTE uses single-carrier frequency division multiplexing architecture for the uplink. However, the single-carrier frequency division multiplexing is like the orthogonal frequency division multiplexing, and the oscillator is easy to instability. Doppler frequency shift effect produced is very sensitive, resulting in ICI and reduce system performance.In order to improve system performance, channel estimation is required. In fact, the signal (pilot signals) is used in the single-carrier frequency division multiple access system for channel estimation. In transmission, every symbol insert into a fixed cycle or time. One of the pilot signal display arrangement (block-type pilot arrangement). Based on this arrangement, we use the least-squares channel estimation method for improvement, which is a sliding window least squares channel estimation techniques to estimate the channel states in this paper. Further according to the different signal to noise ratio (SNR), we estimate the SNR in the receiver and select the optimal sliding windowing length for comparison with the traditional frequency domain least squares estimation and minimum mean squares estimation channel estimation techniques and other low complexity channel estimation techniques. The proposed method performance can improve performance and the computational complexity is not too high.
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