無線通訊在瑞雷衰減(Rayleigh fading)通道下,通道編碼是改善通訊可靠度的一個重要方法. 若完全已知瑞雷衰減通道的訊息,渦輪(turbo)碼在加成性白色高斯雜訊(additive white Gaussian Noise)和瑞雷衰減通道下已經被證明可達到接近沈農(Shannon)極限.然而,事實上完美通道訊息是不可能得到.因此,一個自然的近似方式就是去估測通道訊息,並且使用這些估測值去計算渦輪解碼器所需求的通道可靠度因子.
　　在渦輪碼的研究中,引導訊號(pilot symbols)只有被使用在得到一個通道估測,以便渦輪解碼可以被完成.在本篇論文,我們利用渦輪編碼器的特性並且在渦輪編碼器之前將引導訊號插入資料中.在此種方法中,引導訊號不只是被使用來估測通道而且也被使用來解碼已接收到的資料.藉由此種方式,我們發現在瑞雷衰減通道下渦輪碼的效能得到改善。

　For wireless applications on the fading channels, the channel coding is an important tool for improving the communication reliability. Turbo codes have been shown to perform near the Shannon limit in both the additive white Gaussian Noise channel and the Rayleigh fading channel with perfect knowledge of channel information. However, in practice, the channel responses are not available. A natural approach is to estimate the channel responses and then use the estimated values to compute the channel reliability factor required by turbo decoder.
　In the researches of the turbo code, the pilot symbols are only used at the receiver to obtain estimates of the channel responses so that the turbo decoding can be performed. In this thesis, we employ the property of turbo encoder and insert the pilot symbols into the data sequences before encoding.For this method, the pilot symbols are used not only to estimate the channel responses but also to decode the received data sequences. By the simulation,we find that this method can improve the performance of turbo code on the Rayleigh fading channel.

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