在無線通訊環境中，接收端必須知道通道資訊才能進行等化和解調，而通道資訊的準確性則會影響到系統效能。在此篇論文我們介紹並分析一種通道估測方法，藉由在時域上插入一組已知訊號來估測通道響應；另一種更普遍的方法是在頻域上擺入已知訊號來估測通道頻域響應，在此簡稱為頻域估測法。
對於通道估測方法，我們可以在資料區塊之前直接傳送一個脈衝，接收端能藉此獲得完整的通道響應資訊以及多路徑的數量，在此簡稱為時域估測法。不同於時域估測法，頻域估測法只能估得位於已知訊號上的部分通道頻域資訊，其他非已知訊號上的通道頻域資訊則必須藉由最小回歸曲線法和線性最小平方誤差法…等方法來估得。在此篇論文，我們將分析比較時域估測法和頻域估測法的效能好壞。
接著我們研究在緩慢的時變通道底下，使用時域估測法的效能好壞，並使用線性內插法來估得資料區塊中，每個取樣點持續變動的通道資訊，最後一個簡單的頻域等化方法將被引用近來，以對抗由於時變通道而產生的載波間互相干擾。

In wireless communication environments, the channel must be estimated for equalization in the receiver. The accuracy of channel information affects the system performance. In this thesis, we will introduce and analyze a simple channel impulse response (CIR) estimation method in which a unit pulse followed by a series of consecutive zeros is inserted ahead of each time domain OFDM block signal. Another more popular method is to estimate the channel frequency response (CFR) in which some pilot symbols are inserted in the frequency-domain signal, and we refer to it as “FD estimation”.
For the CIR estimation method, we can directly transmit one pulse before every data block. In this thesis, we call it “TD estimation”. At the receiver, we can easily obtain the whole instant CIR and decide the path number. Unlike the TD estimation, FD estimation just only estimates the CFR at pilot sub-channels. The CFR at other sub-channels are obtained by interpolation or least-squares fitting, linear minimum mean-squares error and so on. In this thesis, we will compare the performance between TD and FD estimation.
Finally, we study the performance of TD estimation in a slow time-variant multipath channel. We use the linear interpolation method to approximate the variation of CIR. And then a simple frequency-domain equalizer technique is also introduced to compensate the effect of interchannel interference (ICI) due to time-variant channel.

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