Chip Equalizer In Cdma Systems And Turbo Decoder Hardware Implementations

The selective coherent RAKE receiver is the current industry solution for multipath reception of CDMA system. The receiver processes a subset of the strongest paths of the desired user by assigning a finger to each path in the subset. Consequently, the RAKE receiver faces substantial performance degradation in dense multipath environment, when the spreading factor is low. Recently there has been interest in the use of chip equalizers before despreading in order to restore the orthogonality of the transmitted sequences at the receiver.In the first part of this thesis, a modified structure for CDMA receiver in fading channels is presented. The first part is organized as follows. The Griffith algorithm and the LMMSE equalizer are compared with the RAKE receiver in chapter 2. Afterwards the adaptation errors of equalizer caused by some channel conditions are addressed in chapter 3 and a new receiver structure is put forward. In chapter 4 the influence of channel estimation is discussed and the adaptive channel estimation with IIR filter is suggested.The last chapter shows the hardware implementation of Turbo decoder in CDMA2000. A novel high-speed Turbo decoder architecture with optimized memory size and FER performance is presented.