正交分頻多工(Orthogonal Frequency Division Multiplexing，OFDM) 的技術已經被廣泛地使用在許多的通訊系統應用上面。然而，在現今的科技時代中，我們所使用的通訊傳輸系統都被使用在高速移動的環境之下。然而，在高速移動的行動通訊環境中，通道的變化會符合時間選擇通道模型(Time-selective Channel Model)。在此通道模型之下，會產生載波間相互干擾(Inter-carrier Interference，ICI)，此效應會使得子載波產生偏移，而使得子載波之間失去正交性，若不補償此一效應的話，則會降低系統的良率。
球面解碼(Sphere Decoding，SD)是一種非常接近最大概似法(Maximum Likelihood，ML)的一種信號偵測方法，雖然球面解碼本身對於抵抗載波間相互干擾就有不錯的抵抗能力，但是在偵測的過程當中，一次去解一個完整的正交分頻多工符元，同時也必須考慮到整個頻率通道響應，如此一來，球面解碼的複雜度是非常地高的。
在此論文中，我們將一個正交分頻多工符元去分成許多小的區塊，如此一來在使用球面解碼時，我們也相對的不必去考慮完整的頻率通道響應，利用這種方法，將會大大的降低球面解碼的運算複雜度。但是，單純使用這種方法，我們卻會沒有考慮到一些載波間相互干擾的效應，使得我們的錯誤率在在一定的程度之後會到達極限。因此，我們把載波間干擾的概念推廣到區塊間相互干擾(Inter-block interference，IBI)，當我們將區塊間干擾的效應去除之後，在使用球面解碼去偵測我們收到的信號，如此一來，不但可以大大的降低運算複雜度，也可以使得良率有不錯的表現。

The channel variation due to vehicle mobility produces time-selective fading among OFDM symbols. As a result, an OFDM symbol suffers inter-carrier interference (ICI) that severely degrades the performance in high vehicle mobility environment. To reduce the problem, an ICI cancellation method that takes the advantage of the ICI power distribution which applies sphere decoding is proposed. At the receiver, an OFDM symbol is partitioned into several blocks, each block uses Sphere Decoding (SD) to generate and pass the message information to other blocks for ICI cancellation. We don’t need to consider the whole channel frequency response matrix.

Index Terms — orthogonal frequency division multiplexing (OFDM), inter-carrier interference (ICI), sphere decoding (SD).

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