於正交多工正交振幅調變系統下利用領航信號之通道估測

Abstract

本論文探討了正交多工振幅調變（orthogonally-multiplexed orthogonal amplitude modulation, OMOAM）系統的通道估測技術。在傳輸過程中由於多路徑衰減（multipath fading）及都卜勒效應（Doppler effect）的影響，使通道估測在無線傳輸系統的同調接收機表現上扮演一個重要的角色，而目前為止尚未有針對正交多工正交振幅調變系統的通道估測研究。在本論文中，我們於特定正交多工正交振幅調變的調變參數限制下利用其特殊的信號結構及快速傅立葉轉換（fast Fourier transform, FFT）實現，提出一種使用領航信號（pilot signal）於通道估測的演算法，其中包含了領航信號之加入方式、子載波偵測（subcarrier detection）、通道估測及二階段次佳化解調（two-stage suboptimum demodulation），並且對子載波偵測的偵測錯誤率及通道估測的均方誤差（mean square error, MSE）做數學分析，再以電腦模擬驗證其結果，最後去觀察及比較各個調變參數下系統的位元錯誤率（bit error probability, BEP）模擬。

In this thesis, the channel estimation technique of orthogonally-multiplexed orthogonal amplitude modulation (OMOAM) systems is investigated. Channel estimation plays an important role in the performance of coherent receivers due to multipath fading and Doppler effect in wireless transmission. In the literature, the channel estimation problem for OMOAM systems has not been researched yet. With the specific constraint of modulation parameter, we exploit the special signal structure and fast Fourier transform realization to propose a novel pilot-assisted channel estimation algorithm for OMOAM systems. This algorithm includes pilot insertion, subcarrier detection, channel estimation and two-stage suboptimum demodulation. The subcarrier detection error probability and MSE of channel estimation are also analyzed and verified by simulation. Finally, the simulation results of sub-optimum demodulation for different modulation parameters are compared and discussed in terms of bit error probability.