長程演進上鏈通訊單載波分頻多工之通道估測技術; Channel Estimation Techniques of SC-FDM in LTE Uplink Communications

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Title:	長程演進上鏈通訊單載波分頻多工之通道估測技術;Channel Estimation Techniques of SC-FDM in LTE Uplink Communications
Authors:	黃士展;Shih-Chan Huang
Contributors:	通訊工程研究所
Keywords:	功率峰均比;頻域最小均方誤差估測;頻域最小平方估測;塊狀引導信號編排;正交分頻多重存取;單載波分頻多重存取;PAPR;block-type pilot arrangement;SC-FDMA;FD-LMMSE;FDLS;OFDMA
Date:	2009-07-01
Issue Date:	2009-09-22 11:22:48 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	近來，由於單載波多重存取(SC-FDMA)技術具有較低的功率峰均比，長程演進(LTE)規格已將單載波分頻多重存取制訂成下一代行動通訊系統上鏈傳輸之多重存取技術。單載波分頻多重存取系統可視為正交分頻多重存取(OFDMA)系統的預先編碼版本，作法是將其資料先行經過離散傅利葉轉換(DFT)編碼。此預先編碼的動作有助於降低功率峰均比，進而達到節省行動傳輸工具電力。然而，像正交分頻多重存取系統所遭遇的問題一樣，單載波分頻多重存取對震盪器不穩及通道都卜勒頻移產生的頻率偏移敏感，此現象將造成子載波間干擾而使得系統效能降低。為了增進系統效能及降低子載波干擾，通道估測技術是必須的。實際上，在單載波分頻多重存取系統上用於通道估測的引導信號(pilot signals)是在固定週期時間插入資料符元之間，此種編排技術被稱為塊狀引導信號編排(block-type pilot arrangement)。因此，基於此種引導信號編排方式，此篇論文提出一種頻域滑窗最小平方(FDLS)估測技術來估測通道變化。此提出的估測技術將與傳統的頻域最小平方估測和頻域最小均方誤差估測技術(FD-LMMSE)在高都卜勒頻移通道下做性能上的比較。此外，時域估測技術及其時域等化器也會在此篇論文中研究並且與頻域估測技術相互比較。 Recently, Single Carrier Frequency Division Multiple Access (SC-FDMA) has been considered as a promising uplink transmission scheme for next generation mobile communication in LTE specification due to its low peak to average power ratio (PAPR). SC-FDMA system is a pre-coding scheme of OFDMA system, and its data signals are pre-coded by DFT. The pre-coding operation will reduce the PAPR, and it has benefit for mobile transmitters. However, similar to OFDMA, SC-FDMA is highly sensitive to frequency offsets caused by oscillator inaccuracies and the Doppler shift, which inevitably result in inter-carrier-interference (ICI), and will degrade the system performance. In order to enhance system performance and mitigate ICI in SC-FDM, channel estimation techniques are necessary. In practice, the pilot signals for channel estimation in SC-FDMA systems are inserted to all subcarriers periodically in time, which is called block-type pilot arrangement. Therefore, based on the block-type pilot arrangement, we propose a frequency domain least-square (FDLS) with a redundant sliding rectangular window estimator to track the channel variations. The proposed method will be compared with conventional FDLS estimators and frequency-domain linear minimum mean-square-error (FD-LMMSE) estimators in high Doppler spread channels. Also, time domain estimators with associated equalizers are investigated and compared in this thesis.
Appears in Collections:	[Graduate Institute of Communication Engineering] Electronic Thesis & Dissertation

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