Studies on Cooperative MC-CDMA System

[[abstract]]合作式通訊(Cooperative Communication)是藉由其它的行動裝置分享其單根天線做幫忙傳送之動作，形成一個虛擬的多輸入多輸出(Multiple Input Multiple Output，MIMO)環境，以得到分集增益，而合作式通訊中，解調後轉傳(Decoded and Forward，DF)利用轉傳端具有解調之能力，使系統可以得到良好之錯誤率效能。本篇論文利用合作式通訊的好處運用於多載波分碼多工系統中(Multi Carrier Code Division Multiple Access，MC-CDMA)，在第一部分，我們首先分析在雷利衰減(Rayleigh Fading)通道中，將使用者每兩個做一個配對，利用BPSK調變方式做合作式通訊，在接收端使用最大比例合成接收器(Maximal Ratio Combiner，MRC)解調，並使用一個兩倍子載波的多載波分碼多工系統取代合作式通訊在兩個時槽傳送到目的端的資料，最後推出其分析值。接著在第二部分我們討論兩個多重使用者偵測接收器(Multiple User Detector，MUD)：串列干擾消除(Successive Interference Cancellation，SIC)及並列干擾消除(Parallel Interference Cancellation，PIC)運用於合作式多載波分碼多工系統中之效能，並討論在某些環境下串列干擾消除會比並列干擾消除來的優異，也討論了一階並列干擾消除及二階並列干擾消除的效能，與適合使用二階並列干擾消除的環境。[[abstract]]The formulation of cooperative communications is based on the case that users in the environment nearby share their antenna(s) to relay signals; thus, creating a virtual multiple-input multiple-output (MIMO) system with additional spatial diversity gains. In cooperative communications, the decode-and-forward (DF) protocol can give promising error-rate performance provided that the relay node has the decoding capability. In this thesis, we apply the idea of cooperative communications with DF to the multi-carrier code division multiple access (MC-CDMA) system. In the first part, we analyze the bit-error rate (BER) performance of this cooperative MC-CDMA system. In the cooperation, we consider that the channel is Rayleigh faded, binary-phase shift keying (BPSK) signaling is used, and every two users cooperate with each other in the network. The destination node employs maximal ratio combining (MRC) to combine those received signals. With the idea of MC-CDMA with double number of subcarriers, its BER can be approximated. In the second part, we examine two kinds of multiuser detection (MUD), i.e., successive interference cancelation (SIC) and parallel interference cancelation (PIC), for use in the considered cooperative MC-CDMA system. We discuss the usefulness of these two detectors and show that they are good for different channel environments. In addition, we extend the PIC detector to include more stages to improve the performance. We also give a discussion about under what scenario more stages should be used to enhance the performance.[[note]]碩