高速移動環境下多天線正交分頻多工之通道估測與等化

Channel Estimation and Equalization for multiple antennas OFDM System in High-mobility Environment

徐華璘(Hua-Lin Hsu)

指導教授 ： 陳逸民

國立中央大學/資訊電機學院/通訊工程學系/碩士(2008年)

摘要

DVB-T是採用正交分頻多工（OFDM）的技術來傳送，OFDM系統具有抵抗多重路徑干擾及頻譜使用效率高等優異特性，其中抵抗多重路徑干擾是藉由前置循環字首（Cyclic prefix）及多載波之特性以達到免除碼字間干擾（ISI），而頻譜使用效率高則是運用多載波正交特性達到的。在高速移動環境下，DVB-T訊號經過時變的通道，接收到的訊號會有都普勒擴展(Doppler Spread)的現象，破壞了子載波間的正交性，而引起載波間干擾(ICI)，使得最高容許的接收速度下降。為了克服高速移動所引起的載波間干擾(ICI)，本論文將前人方法加以改良，介紹了一套適合高速移動接收的通道估測與等化的方法。
　　在此論文中，我們參考DVB-T系統，且進一步的修改使其更合適於高速移動下的環境。我們運用多天線分集多工與ICI估測與消除，並比較了三種不同的通道與ICI估測方法(FD-LS、PN-code、Group Pilot)。
　　在DVB-T在8K模式、16QAM、編碼率為1/2的條件下，利用此改良的方法可以使單天線DVB-T系統達到250km/h，多天線系可達到300km/h。最後，若引入Group pilot估測技術則單天線系統更可達到300km/h。

關鍵字

載波間干擾 ； 歐規數位電視地面廣播 ； 高速移動

並列摘要

DVB-T is an OFDM system, which exhibits outstanding characteristics in terms of simplicity in combating multi-path transmission and efficiency in spectral utilization. The ISI effect results from the multi-path interference could be successfully eliminated by the insertion of cyclic-prefix and the use of multi-carriers. In high-mobility environment, DVB-T signals pass the time-varying channel, and a loss of sub-carrier orthogonality due to Doppler spread of received signals leads to inter-carrier interference (ICI).This ICI effect degrades the maximum allowed velocity of reception. For eliminating this ICI effect due to high-mobility reception, this thesis modifies other’s methods and introduces a method about channel estimation and equalization, which is suitable high-mobility reception.
In this thesis, we refer to the DVB-T standard, and further make it suitability for high mobility environment.We use multiple antennas technique and ICI cancellation,compares three different scheme for channel and ICI estimation.
This thesis proposed method improve the maximum allowed velocity as high as 250km/h for DVB-T receiver with SISO in 8K mode、16QAM、code-rate=1/2,and multiple antennas DVB-T reception improve the maximum allowed velocity more then 300km/h.Finally, reception use group pilot estimation technique SISO-DVB-T-like can work as 300km/h.

並列關鍵字

DVB-T ； ICI ； High-mobility

參考文獻

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