Pre-filtering Technique for MAI Cancellation in Multi-Code MC-CDMA Systems

[[abstract]]中文摘要 在無線通訊中,多載波傳輸與分碼多重接取系統是兩個常見的技術. 在多載波分碼多重接取系統中；有別於時域上的展頻技術, 展頻技術是被應用於頻域上. 在頻域上每一個子載波之間是維持正交的. 在移動的時變通道中, 我們使用彼此間有良好正交性的展頻碼. 在同步的環境中, 接收端使用單一試用者檢測的通訊品質會受到多重使用者的干擾而變差. 在本論文中, 我們將預率波技術利用於複碼多載波分碼多重接取系統中, 其目的是用於降低因多路徑衰減通道所照成的多重接取干擾. 為了滿足不同使用者通訊品質要求, 我們利用數學運算的方式, 分配不同的功率給不同的子載波進行傳輸. 在同步的環境中, 所有使用者訊號是同時在傳送端被送出. 除了不同的通訊品質要求之外, 藉由使用預濾波技術, 計算複雜度可以同時被降低.[[abstract]]Abstract Multi-carrier (MC) multiplexing and code division multiple access (CDMA) are two common signaling technologies in wireless communications. In MC-CDMA system, instead of applying spreading sequences in time domain, we can apply them in frequency domain. The resulting spectrum of each sub-carrier can satisfy the orthogonality condition with the minimum frequency separation. In a (synchronous) down-link mobile radio communication channel, we can use Hadamard Walsh codes as an optimum orthogonal set. In down-link, the performance of single-user detectors becomes worse due to multiple access interference (MAI) disturbances. In this thesis, we consider the use of transmitter filters to reduce the MAI in Multi-code (MC) MC-CDMA systems over a multi-path fading channel. To satisfy different quality of service (QoS), we can assign different power for every sub-carrier by least-square solution. In down-link, total virtual user signals are transmitted simultaneously. In addition to QoS, the computational complexity is easy to be reduced by using pre-filtering technique at the same time.[[note]]碩