具中繼選擇合作式通信系統之極大訊雜比檢測機制

Abstract

合作式通訊系統就目前來說，是一個有用的方法來實現多輸入多輸出天線系統。但是，如何在目的端設計一個理想的接收機，使得此接收機的效能可以好到與以使用最大概似函數的方式設計的接收機的效能一樣是一個主要的議題。因為如此，在解碼與傳送的系統中我們在目的端設計一個接收機，且接收機可以組合接收到的信號。我們所提的架構是使用當中繼點會自行判斷是否要執行解碼與傳送的行為之臨界點選擇的中繼點，並且在目的端使用修正權重來減少因為中繼點決定錯誤的效應。我們也有試著去找尋適合中繼點使用的最佳臨界值在我們所建議的架構中。除此之外，我們有推導出此架構當使用二位元相位數位調變信號的理論位元錯誤率。我們將會發現理論錯誤率將會與模擬結果貼近。我們也有使用高信號雜訊比下的近似方式來簡化理論錯誤率。從這簡化版的理論錯誤率，我們可以得知建議系統的多樣性階數將會是在1.5∼2之間，其結果與前人所做的結論相同。

The cooperative communication is to realize the MIMO system. The optimum receiver is a highly-complex ML receiver. Hence, the major issue is to design a receiver with low complexity at the destination node with comparable performance as that of the ML receiver. Therefore, we design a receiver to combine the received signals at the Destination node under Decode-and-Forward protocol. The proposed scheme uses the threshold-selection Relay and also uses the maximum SNR detection at the Destination node to minimize the effect that Relay made wrong decision. With this proposed scheme, we also try to find out the optimum threshold value of the Relay. Besides, we derive theoretical bit-error-rate (BER) with BPSK signals for the proposed scheme. We also show that the theoretical BER is tight to the simulated results. The high SNR approximation is made to simplify the theoretical BER, from which we could know that the diversity order of the proposed system lies in 1.5~2 which agrees with previous work.