頻域等化之單載波時空編碼技術可以用來抑制因多路徑效應所引起的符元間干擾，而在接收機上可以避免使用複雜度高的時域等化器,並且能夠使傳送的訊號能得到額外的分集增益。
在本論文裡，我們更進一步的發展單載波時空編碼將其應用在一個適用於非同步使用者的直接序列展頻系統上，並且推導出一個適用於此系統的頻域之最小均方差等化機制，此方法既可等化接收到的訊號也可同時將其做解展頻，之後我們應用最小平方的方法於以上兩種系統來對實際的通道環境做估測。而為了要改善頻域等化之單載波時空編碼系統的效能，我們在接收器上運用了遞迴的渦輪等化機制，本論文所介紹的可應用於時空編碼系統的渦輪等化機制，是由一個使用近似機制的最小均方差的頻域等化器與一個通道解碼器所構成，最後在模擬結果中顯示，此結合渦輪等化機制的頻域等化之單載波時空編碼系統的效能在嚴重的符元干擾效應下會隨著遞迴的次數而明顯的改善。

Single carrier frequency-domain equalization technique (SC-FDE) with space-time block coding (STBC) can be applied to suppress inter-symbol interference (ISI) which is caused by multipath effect, avoiding complex time-domain equalization in the receiver and making transmitted signal obtain additional diversity gain.
In this thesis, we further apply SC-FDE with STBC technique to DS-CDMA system which is suitable for asynchronous users and derive a frequency-domain minimum mean-square error (MMSE) equalization for the system to both equalize and despread the received signal. Then, the least-square fitting (LSF) approach is also considered in the mentioned two systems to estimate practical channel response. To improve the performance of SC-FDE with STBC system, we adopt iterative turbo equalization at the receiver. Here, the turbo equalization which is derived for STBC transmission consists of a frequency-domain approximate MMSE equalizer and a channel decoder. Finally, the simulation results show that the performance of the derived system is increasingly improved by iterations in severe ISI effect.

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