由於正交分頻多工系統(OFDM)在多路徑環境下十分穩固，且在頻域等化的複雜度低，使得OFDM經常應用在無線通訊。在OFDM系統，為了達到更高的通道使用率和資料傳輸量，我們使用盲式偵測來取代原有的引導訊號偵測。
本篇論文我們提出振幅正規化之盲式OFDM信號偵測。其中使用通道脈衝響應(CIR)來模擬OFDM系統子頻道的通道響應(CR)變化。配合使用branch-and-bound原理來解決非線性的整數規劃問題。透過使用本篇論文提出的方法，可以有效的降低拜訪點數。同時利用多項式來近似每個子通道的時變通道響應，且透過預測得到一個更佳的起始資料串做為branch-and-bound演算法的初始值。模擬結果證明使用振幅正規化能有效的降低樹狀搜尋的複雜度。

For wireless communications, the orthogonal frequency division multiplexing (OFDM) system is frequently applied due to its robustness to the multipath environment and its low-complexity frequency-domain equalization. In order to enhance the channel utilization and increase the data throughput, we can use the blind method instead of the pilot-based method for the signal detection in OFDM systems.
In this thesis, we propose a blind detection algorithm based on Normalized Amplitudes for the OFDM system. We use channel impulse response (CIR) instead of the polynomial to model the channel response (CR) variation across sub-channels. Then we apply the branch-and-bound principle to solve the non-linear integer programming problem in the blind detection algorithm.
Comparing with the previous algorithm, the proposed blind detection algorithm can effectively reduce the number of visiting nodes in tree search process for the integer programming. We also model the time-variation of CRs in each sub-channel as a polynomial, and use the predicted CRs to obtain a better initial data sequence in the tree search process. A better initial data sequence can further reduce the number of visiting nodes and system complexity. Simulation results verify the effectiveness of our algorithm.

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