利用虛擬隨機前後置碼於多輸入多輸出正交分頻多工系統之通道估測

Channel Estimation for MIMO-OFDM Systems Using the Pseudo-Random-Prefix / Postfix Codes

彭子洋(Tzu-Yang Peng)

指導教授 ： 曾德樟

國立臺北科技大學/電資學院/電腦與通訊研究所/碩士(2013年)

摘要

一般而言利用領航訊號的通道估測方法，可以提升估測效能，但也因此降低了頻寬使用效率。為了在MIMO-OFDM系統下進一步提升通道估測品質及頻寬使用效率，本論文以空時區塊編碼(Space-Time Block Coding, STBC)結合虛擬隨機後置碼正交分頻多工系統(Pseudo-Random-Postfix, PRP-OFDM) 為基礎，並採用半盲式通道估測法來進行通道估測。PRP-OFDM系統是將資料經反傅利葉(IFFT)轉換到時域時，將已知的虛擬隨機序列加在資料串之後傳送，稱為虛擬隨機後置碼；如此可以避免符碼間干擾(Inter-Symbol Interference, ISI)和區塊間干擾(Inter-Block Interference, IBI)，同時又克服了通道零點(Channel Zero Location)問題。另外，在PRP-OFDM系統之符碼前加入虛擬隨機前置碼，一方面可以避免載波間的干擾(Inter-Carrier Interference, ICI)，又可利用前後的虛擬隨機序列碼來增加通道估測的次數，並以通道響應的平均值來消除雜訊對通道估測的干擾，進而增加通道估測的準確性。由模擬結果顯示，本文所提估測方法能有效對抗雜訊干擾，其效能優於原有的PRP-OFDM估測方法。

關鍵字

多輸入多輸出 ； 正交分頻多工 ； 半盲式通道估測

並列摘要

In general, the pilot-aided channel estimation can improve the performance of channel estimate. However, it also degrades the spectral efficiency of the system. In this thesis, a semi-blind channel estimation is applied to the pseudo-random-postfix orthogonal frequency division multiplexing (PRP-OFDM) system combined with space-time block coding (STBC) to gain the system bandwidth efficiency.
The known pseudo random sequences called the pseudo-random-postfix are added to the last part of the time-domain data streams in the PRP-OFDM system. The use of the pseudo-random-postfix is to overcome the inter-symbol interference (ISI) and the inter-block interference (IBI) and conquer the channel zero location problem. In addition, we propose a method that the known pseudo-random-prefix is set in front of the time-domain data streams in the PRP-OFDM system, which not only avoids the inter-carrier interference (ICI) but also increases the number of channel estimate. To increase the accuracy of the channel estimation, the average effect of the channel impulse response is obtained to eliminate the noise interference.
Experimental results show that the proposed method can effectively against the noise interference and achieve better performance than the original PRP-OFDM system.

並列關鍵字

MIMO ； OFDM ； Semi-blind channel estimation

參考文獻

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