合作式通訊利用了空間多樣性的概念仿效了多輸入多輸出的通訊系統。利用中繼站的協助，使得傳輸資訊更為可靠、傳輸率更高。相較於多輸入多輸出的系統中，更能減少硬體設計上的複雜度及降低所需花費成本。因此，如何在網路中選擇中繼點成為了重要的一個議題。重要的一個議題。本論文中，我們考慮三種不同的中繼站傳送機制並提出在中繼站選擇的最佳化問題。在此分別使用固定式編碼後傳送、選擇性編碼後傳送及放大後傳送等機制。而在中繼站上會依據不同的來源-目的對，並利用已知的狀態通道狀態的資訊得到最大的吞吐量。為了求得最佳解，我們使用了暴力法以求得最佳的結果。雖然此方法能非常簡單地完成，但是電腦的計算複雜度卻會隨著網路中的中繼站數目增加而上升。因此，我們提出了具較低複雜度得次佳化中繼站選擇傳送方法。並且分析我們所提出的中繼站選擇策略。依據模擬的結果，我們得知所提出具較低複雜度的方法與暴力法相較之下有些許的效能改善。 Cooperative communication is a promising technique for the current wireless network systems. In the cooperative wireless network system, the relays can form an antenna array to provide the spatially diversity gain by forwarding the source’s message to the destination similar to the multiple input multiple output (MIMO) technique. Although MIMO can also provide spatially diversity gain, the implementation cost and complexity of the device increase with the number of antennas. Hence, in this thesis, we study the relay selection strategy for the multiple source-destination pairs cooperative wireless networks to provide a reliable high data rate transmission.In the thesis, we consider three different forwarding schemes at relays to discuss the optimization problems with relay selection. The throughput behavior under fixed decode-and-forward (FDF), selective decode-and-forward (SDF), and amplify-and-forward (AF) scheme respectively, is studied. The issue about relay allocation to different source-destination pairs can be optimized based on the channel state information (CSI) under throughput maximization criterion. To obtain the solution of the proposed optimization problems, exhaustive search algorithm can be applied. Although the algorithm is straightforward, the computational complexity increases with the number of relays in the network. Hence, we further propose a low complexity suboptimal relay selection strategy for each forwarding scheme. Based on the simulation results, our proposed suboptimal strategies are proven to be lower complexity than the exhaustive search algorithms with slight performance loss.
