運用交錯複數導頻分解於濾波器組多載波無線通訊系統之通道估測

正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM) 技術使用在第四代的行動通訊系統中，此技術藉由循環前綴(Cyclic prefix) 解決多路徑的問題，但相對在頻域上造成頻譜使用效益的降低，除此之外，此調變方式的頻譜有過高的旁波瓣。本篇論文提出導頻序列的設計以及在多載波濾波器組系統之下的通道估測方法。多載波濾波器組系統使用偏移正交振幅調變(Offset Quadrature Amplitude Modulation, OQAM)並且在收發器兩端個別利用合成濾波器組(Synthesis Filte Bank, SFB)和分析濾波器組(Analysis Filter Bank, AFB) 取代循環前綴，因此提高頻寬使用率以及維持其正交性。然而，多載波濾波器組因為相鄰子載波重疊的設計，導致此系統產生固有的虛數干擾，換句話說，其僅在實數域中維持其正交性，故將正交分頻多工的通道估測方法直接套用在多載波濾波器組中並非最佳的估測方法。本篇論文藉由原型濾波器(prototype fiter)的特性，在頻域設計一組導頻訊號，並且其排列為實部及虛部交錯傳送的導頻訊號。而在通道估測，為了能夠解決訊號區間必須大於通道最大延遲擴散的條件限制，此篇論文使用時域的通道估測方法。最後，我們的結果顯示此導頻訊號的設計在均方差能夠達到好的表現，除此之外，此導頻訊號亦擁有較低的峰均功率比（Peak-to-Average Power Ratio, PAPR）。

關鍵字

交錯；導頻序列；濾波器組多載波；通道估測

並列摘要

This thesis foucus on how to design the pilot sequence and the channel estimation in Filter Bank-based Multicarrier systems. Filter Bank-based Multicarrier Modulation (FBMC) using Offset Quadrature Amplitude Modulation (OQAM), also named as FBMC/OQAM or OFDM/OQAM. FBMC/OQAM systems remove the Cyclic Prefix (CP), which reduces the spectrum efficiency in Cyclic Prefix-based Orthogonal Frequency Division Multiplexing (CPOFDM). To increase the spectrum efficiency, FBMC/OQAM systems use the synthesis filter bank (SFB) and analysis filter bank (AFB) at transmitter and receiver,respectively, instead of Cyclic Prefix. However, FBMC/OQAM suffers from an inherent (intrinsic) imaginary interference because of the filter bank. In other words, the orthogonality do not hold in the imaginary domain. So, a new channel estimation scheme is needed for FBMC/OQAM for high performance channel estimation. Therefore, in FBMC/OQAM systems, only realvalued symbols can be transmitted, in this paper we propose a new pilot sequence design we called “Interleaved Complex Pilot Decomposition (ICPD)”. ICPD cascades two identical zero-correlation zone (ZCZ) sequences in time domain, and after the fast Fourier transform (FFT) we decompose the complex-value into two real-valued (i.e., real- and imaginary- part). The feature of ICPD is that it interleave the real- and imaginary- part on the subcarriers to reduce the inter-carrier interference (ICI). The ICPD is a pilot sequence in frequency domain, we do the channel estimation in time domain to solve the necessity of the symbol interval is much longer than the maximum channel delay spread. The simulation of the proposedmethod is effective for FBMC/OQAM system. The performance of ICPD is conducted results show in the mean square error (MSE) and peak-to-average power ratio (PAPR).