在本論文中，提出了一個為了高速移動環境而設計的多重輸入輸出正交多工系統。為了要對抗時變傳輸通道，在系統中使用了空間頻率區塊編碼(SFBC)理論來獲得額外的分集增益，而不需要額外的通訊資源。更甚者，一個低複雜度與具應用彈性的載波間干擾(ICI)消除模組也一併被提出於本論文中。

在高速移動環境中，都普勒效應造成了載波間干擾。載波間干擾破壞了子載波間的正交特性進而降低了系統效能。從另一個角度來看，通道矩陣不再是一個對角矩陣，且通道矩陣之非對角元素將導致載波間干擾，且需要被消除。在本系統中使用了一個線性近似的演算法來進行通道矩陣的估測。為了將載波間干擾消除模組應用於多重輸入輸出系統中，傳統的Zero Forcing(ZF)載波間補償演算法將被本論文提出的方法所取代來消除載波間干擾。要了避免逆矩陣的龐大運算量，我們使用了減法補償理論代替繁複的逆矩陣運算。而在運算複雜度方面，本論文提出的方法從O(N3)降低至O(N)，且該模組可以彈性的運用於單一輸入輸出(SISO)與多重輸入輸出系統上。

本論文所提出之空間頻率區塊編碼正交多工基頻傳送接收機使用SystemC撰寫建構而成。接收機包含了時序同步模組，載波偏移估測補償模組，通道估測模組，具軟輸出(soft output)之空間頻率區塊編碼解碼器，與一低複雜度且具應用彈性之載波間干擾消除模組。為了要模擬高速移動環境，通道環境使用了由3GPP所提出的ITU-VA通道模型與傑克斯(Jakes)模型用來模擬高速移動環境。根據模擬的結果，我們所提出的空間頻率區塊編碼正交多工具載波間消除模組之系統在補償了載波間干擾之後，可以有效的對抗通道效應且獲得3 dB的增益於高速移動環境中。

In this thesis, a MIMO-OFDM system which is designed for high mobility environment is proposed. In order to fight with the time varying channel, the system uses space frequency block coding (SFBC) algorithm to obtain additional diversity gain without any extra communication resource. Furthermore, a flexible and low complexity intercarrier interference (ICI) mitigation module is also proposed in the thesis.

Doppler Effect causes ICI in high mobility environment. The ICI destroys orthogonality between subcarriers and degrades the system performance. In other words, the channel matrix is not a diagonal matrix anymore, non diagonal elements are the equivalent ICI factors and need to be eliminated. The channel matrix estimation uses a linear approximation algorithm. In order to adapt the module to MIMO systems, the proposed method substitutes for ZF ICI compensation algorithm to mitigate the ICI. So as to avoid calculating the inverse matrix, we take subtraction instead of inversion computation. The computational complexity can be reduced from O(N3) to O(N). The module can be applied not only in SISO systems but also in MIMO systems flexibly.

The proposed SFBC-OFDM baseband transceiver is constructed by SystemC language. The receiver includes a timing synchronization module, a carrier frequency offset estimation and compensation module, a channel estimation module, a SFBC decoder with soft output, and a flexible and low complexity ICI mitigation module. In order to model a high mobility environment, ITU-VA channel model, which is constituted by 3GPP, is employed for the simulation. Also, Jakes’ model is added to simulate the high mobility environment. According to the simulation result, the proposed SFBC-OFDM system with ICI mitigation obtains about 3dB gain after ICI compensation in the high mobility environment.

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