在正交頻分多工系統中頻域分數間距等化器的效能分析

Abstract

在正交頻分多工系統(OFDM)中，系統的效能對於都卜勒效應或傳送端和接收端的頻率不同所造成的頻率誤差非常敏感。 在此篇論文中，我們提出了一個新的壓抑載波間干擾的技術，為Q-tap的分數間距最小平均平方誤差等化器(Q-tap FSMMSE Equalizer)。在跟傳統的最小平均平方誤差等化器(MMSE Equalizer)的比較下，我們提出方法之計算的複雜度可大幅度的降低而不會犠牲太多的效能。”分數間距”指的是等化器tap之間距為子載波間距的分數倍。此方法之效能對於傳送端與接收端之間中心頻率不同步不敏感。模擬也展示出，在陸地數位電視廣播(DVB-T)的接收端擁有高移動速度的情境下，對相同的Q之下，Q-tap二分之一倍的分數間距最小平均平方誤差等化器比Q-tap最小平均平方誤差等化器有更好的效能。

Orthogonal frequency division multiplexing (OFDM) digital communication system is very sensitive to frequency errors caused by doppler effect or frequency differences between transmitter and receiver local oscillators. In this thesis, we propose a new intercarrier interference (ICI) suppression scheme, Q-tap fractionally spaced MMSE (FSMMSE) equalizer. 'Fractionally spaced' means the spacing of equalizer tap is a fraction of subcarrier spacing. The performance of this method is not sensitive to the unsynchronized center frequency. Simulation also show that Q-tap '1/2' FSMMSE equalizer has better performance than Q-taps MMSE equalizer with the same Q under the scenario of DVB-T receiver with very high mobile speed.